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Sample records for deposition mocvd technique

  1. Synthesis, structure, vapour pressure and deposition of ZnO thin film by plasma assisted MOCVD technique using a novel precursor bis[(pentylnitrilomethylidine) (pentylnitrilomethylidine-μ-phenalato)]dizinc(II)

    Science.gov (United States)

    Chandrakala, C.; Sravanthi, P.; Raj Bharath, S.; Arockiasamy, S.; George Johnson, M.; Nagaraja, K. S.; Jeyaraj, B.

    2017-02-01

    A novel binuclear zinc schiff's base complex bis[(pentylnitrilomethylidine)(pentylnitrilomethylidine-μ-phenalato)]dizinc(II) (hereafter referred as ZSP) was prepared and used as a precursor for the deposition of ZnO thin film by MOCVD. The dynamic TG run of ZSP showed sufficient volatility and good thermal stability. The temperature dependence of vapour pressure measured by transpiration technique yielded a value of 55.8 ± 2.3 kJ mol-1 for the enthalpy of sublimation (ΔH°sub) in the temperature range of 423-503 K. The crystal structure of ZSP was solved by single crystal XRD which exhibits triclinic crystal system with the space group of Pī. The molecular mass of ZSP was determined by mass spectrometry which yielded the m/z value of 891 and 445 Da corresponding to its dimeric as well as monomeric form. The complex ZSP was further characterized by FT-IR and NMR. The demonstration of ZnO thin film deposition was carried out by using plasma assisted MOCVD. The thin film XRD confirmed the highly oriented (002) ZnO thin films on Si(100) substrate. The uniformity and composition of the thin film were analyzed by SEM/EDX. The band gap of ZnO thin film measurement indicated the blue shift with the value of 3.79 eV.

  2. In-situ deposition of YBCO high-Tc superconducting thin films by MOCVD and PE-MOCVD

    Science.gov (United States)

    Zhao, J.; Noh, D. W.; Chern, C.; Li, Y. Q.; Norris, P. E.; Kear, B.; Gallois, B.

    1991-01-01

    Metal-Organic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T(sub c) greater than 90 K and J(sub c) of approximately 10(exp 4) A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology.

  3. In Situ deposition of YBCO high-T(sub c) superconducting thin films by MOCVD and PE-MOCVD

    Science.gov (United States)

    Zhao, J.; Noh, D. W.; Chern, C.; Li, Y. Q.; Norris, P.; Gallois, B.; Kear, B.

    1990-01-01

    Metalorganic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T( sub c) greater than 90 K and Jc approx. 10 to the 4th power A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metalorganic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology.

  4. MOCVD of Cobalt Oxide Using Co-Actylacetonate As Precursor: Thin Film Deposition and Study of Physical Properties

    Directory of Open Access Journals (Sweden)

    S.M. Jogade

    2011-01-01

    Full Text Available Metal Organic Chemical Vapor Deposition (MOCVD is the deposition method of choice for achieving conformal uniform (composition and thickness continuous thin films over the micron geometry topology necessary for implementing advanced devices. Thin films of cobalt oxide were prepared by MOCVD technique on alumina substrate using a cobalt acetylacetonate as precursor. The thin films of cobalt oxide were deposited on alumina substrate by MOCVD at four different temperatures viz 490 °C, 515 °C, 535 °C, 565 °C. The as deposited samples are uniform and well adherent to the substrate. Thickness of the cobalt oxide film is maximum at temperature 535 °C. The crystalline and phase composition of films were examined by X-ray diffraction. The XRD reveals the crystalline nature with cubic in structure for all the samples. The surface morphology of the films were studied by scanning electron microscopy. The SEM image shows well defined closely packed grains for all the samples. The hexagonal shape of grains are observed for sample at temperature 515 °C. Raman spectroscopy shows Fm3m, 225 space groups for cobalt oxide thin films deposited on alumina substrate.

  5. Carbonaceous alumina films deposited by MOCVD from aluminium acetylacetonate: a spectroscopic ellipsometry study

    Indian Academy of Sciences (India)

    M P Singh; G Raghavan; A K Tyagi; S A Shivashankar

    2002-04-01

    Spectroscopic ellipsometry was used to characterize carbonaceous, crystalline aluminium oxide films grown on Si(100) by low-pressure metal organic chemical vapour deposition, using aluminium acetylacetonate as the precursor. The presence of carbon in the films, attribured to the use of a metalorganic precursor for the deposition of films, was identified and analysed by secondary ion mass spectroscopy and X-ray photoelectron sectroscopy, for the elemental distribution and the chemical nature of the carbon in the films, respectively. Ellipsometry measurments over the photon energy range 1.5-5 eV were used to derive the pseudo-dielectric function of the aluminium oxide-containing films. Multi-layer modelling using linear regression techniques and the effective medium approximation were carried out to extract the structural details of the specimens. The excellent fit between the simulated and experimental optical data validates the empirical model for alumina-containing coatings grown by MOCVD.

  6. Semiconductor Laser Diode Arrays by MOCVD (Metalorganic Chemical Vapor Deposition)

    Science.gov (United States)

    1987-09-01

    Roberts. N. J1. Mason. and M. Robinson, J. Cryst. Growth 68, 422 (1984). ’M. R. Leys. C. van Opdorp. M. P. A. .’iegers, and H. J. Talen -van der Mheen...geometry effects is and superlattices has been dominated obtained by including one measured by the MOCVD growth technology . data point in the analysis...Dapkus, Gallium : Arsenide Technology , D.K. Ferry, Ed., tices i Howard W. Sams and Co., Indianapolis, hetero- 1985, p. 79. s is nec- G . 4. G. Costrini and

  7. Friction and wear behavior of nitrogen-doped ZnO thin films deposited via MOCVD under dry contact

    Directory of Open Access Journals (Sweden)

    U.S. Mbamara

    2016-06-01

    Full Text Available Most researches on doped ZnO thin films are tilted toward their applications in optoelectronics and semiconductor devices. Research on their tribological properties is still unfolding. In this work, nitrogen-doped ZnO thin films were deposited on 304 L stainless steel substrate from a combination of zinc acetate and ammonium acetate precursor by MOCVD technique. Compositional and structural studies of the films were done using Rutherford Backscattering Spectroscopy (RBS and X-ray Diffraction (XRD. The frictional behavior of the thin film coatings was evaluated using a ball-on-flat configuration in reciprocating sliding under dry contact condition. After friction test, the flat and ball counter-face surfaces were examined to assess the wear dimension and failure mechanism. Both friction behavior and wear (in the ball counter-face were observed to be dependent on the crystallinity and thickness of the thin film coatings.

  8. MOCVD and ALD of rare earth containing multifunctional materials. From precursor chemistry to thin film deposition and applications

    Energy Technology Data Exchange (ETDEWEB)

    Milanov, Andrian Petrov

    2010-03-26

    The present thesis deals with the development of metal-organic complexes of rare elements. They should be used as novel precursors for the production of rare earth thin films by metal-organic chemical vapor deposition (MOCVD) and Atomic Layer Deposition (ALD). Within the work two precursor classes were examined, the tris-Malonato-complexes as well as the tris-Guanidinato-complexes of a series of rare earth metals. The latter showed excellent properties regarding to their volatility, their thermal stability, the defined decomposition and high reactivity towards water. They have been successfully used as precursors for the MOCVD of rare earth oxide layers. By using of a gadolinium guanidinate it could also be shown that the rare earth guanidinates are promising precursors for ALD of rare earth oxide and MOCVD of rare earth nitride layers. [German] Die vorliegende Dissertation beschaeftigt sich mit der Entwicklung von metallorganischen Komplexen der Seltenerd-Elemente. Diese sollten als neuartigen Precursoren fuer die Erzeugung von seltenerdhaltigen Duennschichten mittels Metallorganischer Chemischer Dampfabscheidung (MOCVD) und Atomic Layer Deposition (ALD) eingesetzt werden. Innerhalb der Arbeit wurden zwei Precursorklassen untersucht, die Tris-Malonato-Komplexe sowie die Tris-Gunanidinato-Komplexe einer Reihe von Seltenerdmetallen. Letztere zeigten hervorragende Eigenschaften bezueglich ihrer Fluechtigkeit, ihrer thermischen Stabilitaet, der definierten Zersetzung und der hohen Reaktivitaet gegenueber Wasser. Sie wurden erfolgreich als Precursoren fuer die MOCVD von Seltenerd-Oxid-Schichten eingesetzt. Unter Verwendung eines Gadolinium Guanidinats konnte ausserdem gezeigt werden, dass die Seltenerd-Guanidinate vielversprechende Precursoren fuer die ALD von Seltenerd-Oxid-Schichten sowie die MOCVD von Seltenerd-Nitrid-Schichten darstellen.

  9. Characterisation of titanium nitride films obtained by metalorganic chemical vapor deposition (MOCVD); Caracterizacao de filmes de nitreto de titanio obtidos por MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Pillis, M.F., E-mail: mfpillis@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais; Franco, A.C. [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica; Araujo, E.G. de [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Sacilotti, M. [Universidade Federal de Pernambuco (IF/UFPE), Recife, PE (Brazil). Inst. de Fisica; Fundacao de Amparo a Ciencia e Tecnologia de Pernambuco (FACEPE), Recife, PE (Brazil)

    2009-07-01

    Ceramic coatings have been widely used as protective coating to improve the life of cutting tools, for corrosion protection and in microelectronics, optical and medical areas. Transition metals nitrides are of special interest due to its high hardness and thermal stability. In this work thin films of titanium nitride were obtained by MOCVD (metalorganic chemical vapor deposition) process. The tests were carried out for 1h at 700 deg C under 80 and 100 mbar of pressure. The characterization was made by using scanning electron microscopy coupled with dispersive energy analysis, and X-ray diffraction. Preliminary results suggested that Ti{sub 2}N phase was formed and that the growth rate varied between 4 and 13 nm/min according to the process parameter considered. (author)

  10. Electrical and deep levels characteristics of ZnO/Si heterostructure by MOCVD deposition

    Institute of Scientific and Technical Information of China (English)

    Liu Ci-Hui; Liu Bing-Ce; Fu Zhu-Xi

    2008-01-01

    ZnO films have been prepared on p-type Si substrates by metal-organic chemical vapour deposition (MOCVD) at different total gas flow rates. The current versus voltage and temperature (I - V - T) characteristics, the deep-level transient spectroscopy (DLTS) and the photoluminescence (PL) spectra of the samples were measured. DLTS shows two deep-level centres of E1 (EC-0.13±0.02 eV) and E2 (EC-0.43±0.05eV) in sample 1202a, which has a ZnO/p-Si heterostructure. A deep level at EC-0.13±0.01 eV was also obtained from the I -T characteristics. It was considered to be the same as E1 obtained from DLTS measurement. The emission related to this deep level center was detected by PL spectra. In addition, the energy location and the relative trap density of E1 was varied when the total gas flow rate was changed.

  11. Nonlinear optical characterization of GaN layers grown by MOCVD on sapphire[Metal Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tiginyanu, I.M.; Kravetsky, I.V.; Pavlidis, D.; Eisenbach, A.; Hildebrandt, R.; Marowsky, G.; Hartnagel, H.L.

    2000-07-01

    Optical second and third harmonic generation measurements were carried out on GaN layers grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. The measured d{sub 33} is 33 times the d{sub 11} of quartz. The angular dependence of second-harmonic intensity as well as the measured ratios d{sub 33}/d{sub 15} = {minus}2.02 and d{sub 33}/d{sub 31} = {minus}2.03 confirm the wurzite structure of the studied GaN layers with the optical c-axis oriented perpendicular to the sample surface. Fine oscillations were observed in the measured second and third harmonic angular dependencies. A simple model based on the interference of the fundamental beam in the sample was used to explain these oscillations.

  12. Effect of deposition conditions on the growth rate and electrical properties of ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Roro, K.T.; Botha, J.R.; Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2008-07-01

    ZnO thin films have been grown on glass substrates by MOCVD. The effect of deposition conditions such as VI/II molar ratio, DEZn flow rate and total reactor pressure on the growth rate and electrical properties of the films was studied. It is found that the growth rate decreases with an increase in the VI/II molar ratio. This behaviour is ascribed to the competitive adsorption of reactant species on the growth surface. The growth rate increases with an increase in DEZn flow rate, as expected. It is shown that the carrier concentration is independent of the DEZn flow rate. An increase in the total reactor pressure yields a decrease in growth rate. This phenomenon is attributed to the depletion of the gas phase due to parasitic prereactions between zinc and oxygen species at high pressure. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Three-dimensional modelling of horizontal chemical vapor deposition. I - MOCVD at atmospheric pressure

    Science.gov (United States)

    Ouazzani, Jalil; Rosenberger, Franz

    1990-01-01

    A systematic numerical study of the MOCVD of GaAs from trimethylgallium and arsine in hydrogen or nitrogen carrier gas at atmospheric pressure is reported. Three-dimensional effects are explored for CVD reactors with large and small cross-sectional aspect ratios, and the effects on growth rate uniformity of tilting the susceptor are investigated for various input flow rates. It is found that, for light carrier gases, thermal diffusion must be included in the model. Buoyancy-driven three-dimensional flow effects can greatly influence the growth rate distribution through the reactor. The importance of the proper design of the lateral thermal boundary conditions for obtaining layers of uniform thickness is emphasized.

  14. Model Research On Deposition Of Pure Aluminium Oxide Layers By MOCVD Method

    Directory of Open Access Journals (Sweden)

    Sawka A.

    2015-06-01

    Full Text Available The purpose of this research is to develop an optimal method for synthesizing of nanocrystalline Al2O3 monolayers at high growth rates on cemented carbides coated with an intermediate layer of pre-Al2O3-C (composite layers Al2O3-C/Al2O3. The use of quartz glass substrate allows for obtaining information about the quality of the layers such the thickness and density, because of its high transparency. The Al2O3 layers that do not containing carbon were synthesized on quartz glass by MOCVD using aluminum acetylacetonate and air as the reactants at temperatures of 700-1000°C. Argon was also a carrier gas. The resulting layers were transparent, as homogeneous nucleation did not occur during the synthesis process. The layers synthesized at lower temperatures were subjected to a crystallization process at temperatures above 900°C. The crystallization process was studied as a function of time and temperature. The obtained layers were characterized by their nanocrystalline microstructure.

  15. Highly conformal and high-ionic conductivity thin-film electrolyte for 3D-structured micro batteries: Characterization of LiPON film deposited by MOCVD method

    Science.gov (United States)

    Fujibayashi, Takashi; Kubota, Yusuke; Iwabuchi, Katsuhiko; Yoshii, Naoki

    2017-08-01

    This paper reports a lithium phosphorus oxynitride (LiPON) thin-film electrolyte deposited using a metalorganic-chemical vapor deposition (MOCVD) method for 3D-structured micro batteries. It is shown that the MOCVD-LiPON film has both highly-conformal step coverage on a patterned substrate with line/space=2μm/2μm and aspect ratio=1 (51±3 nm) and high-ionic conductivity for very thin films deposited at 4.7 nm/min (5.9×10-6 S/cm for 190 nm and 5.3×10-6 S/cm for 95 nm). Detailed material characterization attributes the enhancement in ionic conductivity to a decrease in nanocrystallite size and improvement in chemical-composition uniformity in the film. In addition, electrochemical characterization of an all-solid-state thin-film battery fabricated with the 190 nm-thick LiPON film (Si substrate/Ti/Pt/LiCoO2/LiPON/a-Si:H/Cu) demonstrates that the LiPON film can successfully act as the electrolyte for lithium-ion batteries. Therefore, the MOCVD-LiPON film is a promising candidate material to realize 3D-structured micro batteries in the near future.

  16. Highly conformal and high-ionic conductivity thin-film electrolyte for 3D-structured micro batteries: Characterization of LiPON film deposited by MOCVD method

    Directory of Open Access Journals (Sweden)

    Takashi Fujibayashi

    2017-08-01

    Full Text Available This paper reports a lithium phosphorus oxynitride (LiPON thin-film electrolyte deposited using a metalorganic-chemical vapor deposition (MOCVD method for 3D-structured micro batteries. It is shown that the MOCVD-LiPON film has both highly-conformal step coverage on a patterned substrate with line/space=2μm/2μm and aspect ratio=1 (51±3 nm and high-ionic conductivity for very thin films deposited at 4.7 nm/min (5.9×10-6 S/cm for 190 nm and 5.3×10-6 S/cm for 95 nm. Detailed material characterization attributes the enhancement in ionic conductivity to a decrease in nanocrystallite size and improvement in chemical-composition uniformity in the film. In addition, electrochemical characterization of an all-solid-state thin-film battery fabricated with the 190 nm-thick LiPON film (Si substrate/Ti/Pt/LiCoO2/LiPON/a-Si:H/Cu demonstrates that the LiPON film can successfully act as the electrolyte for lithium-ion batteries. Therefore, the MOCVD-LiPON film is a promising candidate material to realize 3D-structured micro batteries in the near future.

  17. Développement de conducteurs à base d'YBaCuO
    sur des substrats flexibles par MOCVD

    OpenAIRE

    CAROFF, Tristan

    2008-01-01

    The stake of this study was to realize low cost superconducting wires for current transport and current limitation, using original and inexpensive processes like rolling for the elaboration of the substrate, and chemical deposition methods MOD (metal organic decomposition) and MOCVD (metal organic chemical vapor deposition) for the different layers (buffer layers and superconducting film).Pulsed injection MOCVD technique is well adapted for coated conductor processing: it allows obtaining rep...

  18. The biocompatibility of titanium in a buffer solution: compared effects of a thin film of TiO2 deposited by MOCVD and of collagen deposited from a gel.

    Science.gov (United States)

    Popescu, Simona; Demetrescu, Ioana; Sarantopoulos, Christos; Gleizes, Alain N; Iordachescu, Dana

    2007-10-01

    This study aims at evaluating the biocompatibility of titanium surfaces modified according two different ways: (i) deposition of a bio-inert, thin film of rutile TiO(2) by chemical vapour deposition (MOCVD), and (ii) biochemical treatment with collagen gel, in order to obtain a bio-interactive coating. Behind the comparison is the idea that either the bio-inert or the bio-active coating has specific advantages when applied to implant treatment, such as the low price of the collagen treatment for instance. The stability in buffer solution was evaluated by open circuit potential (OCP) for medium time and cyclic voltametry. The OCP stabilized after 5.10(4) min for all the specimens except the collagen treated sample which presented a stable OCP from the first minutes. MOCVD treated samples stabilized to more electropositive values. Numeric results were statistically analysed to obtain the regression equations for long time predictable evolution. The corrosion parameters determined from cyclic curves revealed that the MOCVD treatment is an efficient way to improve corrosion resistance. Human dermal fibroblasts were selected for cell culture tests, taking into account that these cells are present in all bio-interfaces, being the main cellular type of connective tissue. The cells grew on either type of surface without phenotype modification. From the reduction of yellow, water-soluble 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT cytotoxicity test), MOCVD treated samples offer better viability than mechanically polished Ti and collagen treated samples as well. Cell spreading, as evaluated from microscope images processed by the program Sigma Scan, showed also enhancement upon surface modification. Depending on the experimental conditions, MOCVD deposited TiO(2) exhibits different nanostructures that may influence biological behaviour. The results demonstrate the capacity of integration in simulated physiologic liquids for an implant pretreated by

  19. Thermodynamic analysis of the deposition of GaAs epitaxial layers prepared by the MOCVD method

    Energy Technology Data Exchange (ETDEWEB)

    Leitner, J.; Mikulec, J. (Dept. of Materials for Electronics, Prague Inst. of Chemical Tech. (Czechoslovakia)); Vonka, P. (Dept. of Physical Chemistry, Prague Inst. of Chemical Tech. (Czechoslovakia)); Stejskal, J.; Hladina, R.; Klima, P. (TESLA Research Inst. of Radiocommunication, Prague (Czechoslovakia))

    1991-06-01

    On the basis of a detailed thermodynamic analysis of the Ga-As-C-H system, the initial conditions have been determined, under which the reaction of trimethylgallium (TMGa) and arsine in a hydrogen atmosphere produces a single condensed phase - solid GaAs. Liquid gallium with a small amount of dissolved arsenic is formed simultaneously when the initial ratio of the elements is B{sup V}/A{sup III}<1, whereas solid graphite is simultaneously deposited at a high initial concentration of TMGa, especially at an elevated temperature and a decreased pressure. The equilibrium concentrations of the gaseous substances are strongly influenced by the initial B{sup V}/A{sup III} ratio. As{sub 2}, As{sub 4}, and CH{sub 4} are the dominant species if B{sup V}/A{sup III}>1, while CH{sub 4}, GaCH{sub 3}, GaH and GaH{sub 2} are the most abundant if B{sup V}/A{sup III} < 1. The calculated deposition diagrams are in good qualitative agreement with experimental results published in the literature. A comparison of the calculated composition of the gaseous phase and the results of experiments under the conditions used for the deposition of GaAs epitaxial layers leads to the conclusion that the course and results of the deposition process are significantly affected by transport and kinetic phenomena. (orig.).

  20. Structure, morphology and Raman and optical spectroscopic analysis of In1-xCuxP thin films grown by MOCVD technique for solar cell applications

    Science.gov (United States)

    Alshahrie, Ahmed; Juodkazis, S.; Al-Ghamdi, A. A.; Hafez, M.; Bronstein, L. M.

    2017-10-01

    Nanocrystalline In1-xCuxP thin films (0 ≤ x ≤ 0.5) have been deposited on quartz substrates by a Metal-Organic Chemical Vapor Deposition (MOCVD) technique. The effect of the copper ion content on the structural crystal lattice, morphology and optical behavior of the InP thin films was assessed using X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectroscopy and spectrophotometry. All films exhibited a crystalline cubic zinc blende structure, inferring the solubility of the Cu atoms in the InP crystal structure. The XRD patterns demonstrated that the inclusion of Cu atoms into the InP films forced the nanoparticles in the films to grow along the (1 1 1) direction. The AFM topography showed that the Cu ions reduce the surface roughness of deposited films. The Raman spectra of the deposited films contain the first and second order anti-stoke ΓTO, ΓLO, ΧLO + ΧTO, 2ΓTO, and ΓLO + ΓTO bands which are characteristic of the InP crystalline structure. The intensities of these bands decreased with increasing the content of the Cu atoms in the InP crystals implying the creation of a stacking fault density in the InP crystal structure. The In1-xCuxP thin films have shown high optical transparency of 90%. An increase of the optical band gap from 1.38 eV to 1.6 eV was assigned to the increase of the amount of Cu ions in the InP films. The In0.5Cu0.5P thin film exhibited remarkable optical conductivity with very low dissipation factor which makes it a promising buffer window for solar energy applications.

  1. EXAFS study on yttrium oxide thin films deposited by RF plasma enhanced MOCVD under the influence of varying RF self-bias

    Energy Technology Data Exchange (ETDEWEB)

    Chopade, S.S. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Nayak, C.; Bhattacharyya, D.; Jha, S.N.; Tokas, R.B.; Sahoo, N.K. [Atomic and Molecular Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Patil, D.S., E-mail: dspatil@barc.gov.in [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2014-09-30

    Highlights: • Local structure and surface morphology of Y{sub 2}O{sub 3} thin films deposited by RF plasma MOCVD at different RF self-bias level investigated by EXAFS and AFM. • Bond length and oxygen coordination changes with bias. • Films are nanostructured with structural distortion at higher bias. • Surface morphology of films changes with bias. • Changes observed in local structural parameters are correlated with observed properties of films. • EXAFS study on Y{sub 2}O{sub 3} films deposited under different RF self-bias levels is not been reported so far. - Abstract: Extended X-ray absorption fine structure (EXAFS) and atomic force microscopy (AFM) studies are carried out on yttrium oxide (Y{sub 2}O{sub 3}) thin films deposited by radio frequency plasma assisted metalorganic chemical vapor deposition (MOCVD) process at different RF self-bias (−50 V to −175 V with a step of −25 V) on silicon substrates. A (2,2,6,6-tetramethyl-3,5-heptanedionate) yttrium (commonly known as Y(thd){sub 3}) precursor is used in a plasma of argon and oxygen gases at a substrate temperature of 350 °C for deposition. To gain profound understanding about influence of RF self-bias on the properties of the deposited Y{sub 2}O{sub 3} thin films, the films are characterized by EXAFS and AFM measurements. From the EXAFS measurements it is observed that oxygen co-ordination is high for the film deposited at the lowest self bias (−50 V) which is due to presence of higher amount of hydroxyl group in the sample. Oxygen coordination however decrease to lower values for the films deposited at self bias of −75 V. Y-O bond length decreases gradually with increase in self bias indicating reduction in hydroxyl content. However there is reduction in bond length for the film deposited at −100 V as compared to other films resulting from structural changes. The disorder factor obtained from EXAFS measurement increases for films deposited at voltages beyond −125 V due to

  2. High-quality uniaxial In(x)Ga(1-x)N/GaN multiple quantum well (MQW) nanowires (NWs) on Si(111) grown by metal-organic chemical vapor deposition (MOCVD) and light-emitting diode (LED) fabrication.

    Science.gov (United States)

    Ra, Yong-Ho; Navamathavan, R; Park, Ji-Hyeon; Lee, Cheul-Ro

    2013-03-01

    This article describes the growth and device characteristics of vertically aligned high-quality uniaxial p-GaN/InxGa1-xN/GaN multiple quantum wells (MQW)/n-GaN nanowires (NWs) on Si(111) substrates grown by metal-organic chemical vapor deposition (MOCVD) technique. The resultant nanowires (NWs), with a diameter of 200-250 nm, have an average length of 2 μm. The feasibility of growing high-quality NWs with well-controlled indium composition MQW structure is demonstrated. These resultant NWs grown on Si(111) substrates were utilized for fabricating vertical-type light-emitting diodes (LEDs). The steep and intense photoluminescence (PL) and cathodoluminescence (CL) spectra are observed, based on the strain-free NWs on Si(111) substrates. High-resolution transmission electron microscopy (HR-TEM) analysis revealed that the MQW NWs are grown along the c-plane with uniform thickness. The current-voltage (I-V) characteristics of these NWs exhibited typical p-n junction LEDs and showed a sharp onset voltage at 2.75 V in the forward bias. The output power is linearly increased with increasing current. The result indicates that the pulsed MOCVD technique is an effective method to grow uniaxial p-GaN/InxGa1-xN/GaN MQW/n-GaN NWs on Si(111), which is more advantageous than other growth techniques, such as molecular beam epitaxy. These results suggest the uniaxial NWs are promising to allow flat-band quantum structures, which can enhance the efficiency of LEDs.

  3. Growth and characterization of germanium epitaxial film on silicon (001 with germane precursor in metal organic chemical vapour deposition (MOCVD chamber

    Directory of Open Access Journals (Sweden)

    Kwang Hong Lee

    2013-09-01

    Full Text Available The quality of germanium (Ge epitaxial film grown directly on a silicon (Si (001 substrate with 6° off-cut using conventional germane precursor in a metal organic chemical vapour deposition (MOCVD system is studied. The growth sequence consists of several steps at low temperature (LT at 400 °C, intermediate temperature ramp (LT-HT of ∼10 °C/min and high temperature (HT at 600 °C. This is followed by post-growth annealing in hydrogen at temperature ranging from 650 to 825 °C. The Ge epitaxial film of thickness ∼ 1 μm experiences thermally induced tensile strain of 0.11 % with a treading dislocation density (TDD of ∼107/cm2 and the root-mean-square (RMS roughness of ∼ 0.75 nm. The benefit of growing Ge epitaxial film using MOCVD is that the subsequent III-V materials can be grown in-situ without the need of breaking the vacuum hence it is manufacturing worthy.

  4. a Dlts Study of the EL2 Deep Level in Epitaxial Layers of GALLIUM(1-X) Indium(x) Arsenide Deposited by Mocvd

    Science.gov (United States)

    Lang, Rick

    1990-01-01

    The EL2 deep level is the dominant naturally occurring electron trapping level in metal organic chemical vapour deposited (MOCVD) GaAs. It is also present in ternary alloys such as Ga_{1-x} Al_{x}As, GaAs_{rm 1-x}P _{x} and Ga_ {1-x}In_{ x}As where the changing composition of the crystal lattice alters the local environment of the deep levels. This can influence the properties of the deep level wave functions due to their sensitivity to their immediate environment. In the present work Deep Level Transient Spectroscopy (DLTS) has been employed to measure the thermal activation energy of the EL2 deep level in Ga_{ 1-x}In_{x}As epilayers deposited by low pressure MOCVD onto degenerately doped GaAs substrates. To perform these measurements Au Schottky barrier diodes were fabricated on the epilayers and characterized by Current-Voltage (I -V) and Capacitance-Voltage (C-V) measurements. For some of the samples investigated, the results of these measurements and the DLTS measurements performed using various biasing conditions revealed either back-to-back diode behaviour, or large temperature dependencies for the calculated depletion region widths, or severe bias-sensitive variations in the DLTS spectra. Such behaviours are related to conditions at the Schottky interface and denote that the DLTS results are distorted and unreliable. After elimination of these distorted results, two different dependences of the EL2 thermal activation energy on the indium concentration of the epilayer were apparent. The dependences differed for epilayers deposited using different substrate orientations and V/III reagent ratios during epilayer deposition. For both cases the thermal activation energy decreased with increasing indium concentration in the epilayers. Investigations of the DLTS measurement conditions were made to determine if the differences in the thermal activation energy dependences on the indium concentrations were caused by conditions which are known to influence the

  5. High mobility, large linear magnetoresistance, and quantum transport phenomena in Bi2Te3 films grown by metallo-organic chemical vapor deposition (MOCVD).

    Science.gov (United States)

    Jin, Hyunwoo; Kim, Kwang-Chon; Seo, Juhee; Kim, Seong Keun; Cheong, Byung-Ki; Kim, Jin-Sang; Lee, Suyoun

    2015-11-07

    We investigated the magnetotransport properties of Bi2Te3 films grown on GaAs (001) substrate by a cost-effective metallo-organic chemical vapor deposition (MOCVD). We observed the remarkably high carrier mobility and the giant linear magnetoresistance (carrier mobility ∼ 22 000 cm(2) V(-1) s(-1), magnetoresistance ∼ 750% at 1.8 K and 9 T for a 100 nm thick film) that depends on the film thickness. In addition, the Shubnikov-de Haas oscillation was observed, from which the effective mass was calculated to be consistent with the known value. From the thickness dependence of the Shubnikov-de Haas oscillation, it was found that a two dimensional electron gas with the conventional electron nature coexists with the topological Dirac fermion states and dominates the carrier transport in the Bi2Te3 film with thickness higher than 300 nm. These results are attributed to the intrinsic nature of Bi2Te3 in the high-mobility transport regime obtained by a deliberate choice of the substrate and the growth conditions.

  6. RF plasma enhanced MOCVD of yttria stabilized zirconia thin films using octanedionate precursors and their characterization

    Energy Technology Data Exchange (ETDEWEB)

    Chopade, S.S. [Laser and Plasma Technology Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India); Nayak, C.; Bhattacharyya, D.; Jha, S.N.; Tokas, R.B.; Sahoo, N.K. [Atomic & Molecular Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India); Deo, M.N. [High Pressure & Synchrotron Radiation Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India); Biswas, A. [Atomic & Molecular Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India); Rai, Sanjay [Indus Synchrotron Utilization Division, RRCAT, Indore 452013 (India); Thulasi Raman, K.H.; Rao, G.M. [Department of Instrumentation and Applied Physics, Indian Institute of Science, Bangalore 560012 (India); Kumar, Niranjan [Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Patil, D.S., E-mail: dspatil@iitb.ac.in [Laser and Plasma Technology Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India)

    2015-11-15

    Highlights: • YSZ films are deposited by RF plasma MOCVD using Zr(tod){sub 4} and Y(tod){sub 3} precursors. • Films are deposited under the influence of RF self-bias on the substrates. • Films are characterized by different techniques. • Films properties are dependent on yttria content and film structure. - Abstract: Yttria stabilized zirconia thin films have been deposited by RF plasma enhanced MOCVD technique on silicon substrates at substrate temperature of 400 °C. Plasma of precursor vapors of (2,7,7-trimethyl-3,5-octanedionate) yttrium (known as Y(tod){sub 3}), (2,7,7-trimethyl-3,5-octanedionate) zirconium (known as Zr(tod){sub 4}), oxygen and argon gases is used for deposition. To the best of our knowledge, plasma assisted MOCVD of YSZ films using octanediaonate precursors have not been reported in the literature so far. The deposited films have been characterized by GIXRD, FTIR, XPS, FESEM, AFM, XANES, EXAFS, EDAX and spectroscopic ellipsometry. Thickness of the films has been measured by stylus profilometer while tribological property measurement has been done to study mechanical behavior of the coatings. Characterization by different techniques indicates that properties of the films are dependent on the yttria content as well as on the structure of the films.

  7. MOCVD ZnO/Screen Printed Ag Back Reflector for Flexible Thin Film Silicon Solar Cell Application

    Directory of Open Access Journals (Sweden)

    Amornrat Limmanee

    2014-01-01

    Full Text Available We have prepared Ag back electrode by screen printing technique and developed MOCVD ZnO/screen printed Ag back reflector for flexible thin film silicon solar cell application. A discontinuity and poor contact interface between the MOCVD ZnO and screen printed Ag layers caused poor open circuit voltage (Voc and low fill factor (FF; however, an insertion of a thin sputtered ZnO layer at the interface could solve this problem. The n type hydrogenated amorphous silicon (a-Si:H film is preferable for the deposition on the surface of MOCVD ZnO film rather than the microcrystalline film due to its less sensitivity to textured surface, and this allowed an improvement in the FF. The n-i-p flexible amorphous silicon solar cell using the MOCVD ZnO/screen printed Ag back reflector showed an initial efficiency of 6.2% with Voc=0.86 V, Jsc=12.4 mA/cm2, and FF = 0.58 (1 cm2. The identical quantum efficiency and comparable performance to the cells using conventional sputtered Ag back electrode have verified the potential of the MOCVD ZnO/screen printed Ag back reflector and possible opportunity to use the screen printed Ag thick film for flexible thin film silicon solar cells.

  8. Thin Film Deposition Techniques (PVD)

    Science.gov (United States)

    Steinbeiss, E.

    The most interesting materials for spin electronic devices are thin films of magnetic transition metals and magnetic perovskites, mainly the doped La-manganites [1] as well as several oxides and metals for passivating and contacting the magnetic films. The most suitable methods for the preparation of such films are the physical vapor deposition methods (PVD). Therefore this report will be restricted to these deposition methods.

  9. MOCVD growth of GaBN on 6H-SiC (0001) substrates[Metal Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wei, C.H.; Xie, Z.Y.; Edgar, J.H.; Zeng, K.C.; Lin, J.Y.; Jiang, H.X.; Chaudhuri, J.; Ignatiev, C.; Braski, D.N.

    2000-04-01

    B{sub x}Ga{sub 1{minus}x}N films were deposited on 6H-SiC (0001) substrates at 1,000 C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. The presence of boron was detected by Auger scanning microprobe, the shift of the (00.2) x-ray diffraction peak, and low-temperature photoluminescence. A single-phase B{sub x}Ga{sub 1{minus}x}N alloy with x = 1.5% was produced at the gas phase B/Ga ratio of 0.005. Phase separation into wurtzite BGaN and the B-rich phase occurred for a B/Ga ratio in the 0.01--0.2 range. Only BN was formed by B/Ga > 0.2. The B-rich phase was identified as h-BN with sp{sup 2} bonding based on the results of Fourier transform infrared spectroscopy. As the diborane flow exceeds the threshold concentration, the growth rate of GBaN decreases sharply, because the growth of GaN is poisoned by the formation of the slow growing BN phase. The band edge emission of B{sub x}Ga{sub 1{minus}x}N varies from 3.451 eV for x = 0% with FWHM of 39.2 meV to 3.465 eV for x = 1.5% with FWHM of 35.1 meV. The narrower FWHM indicates that the quality of GaN epilayer is improved with a small amount of boron incorporation. The PL line widths become broader as more boron is introduced into the solid solution.

  10. Structural characterization of one-dimensional ZnO-based nanostructures grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Sallet, Vincent; Falyouni, Farid; Marzouki, Ali; Haneche, Nadia; Sartel, Corinne; Lusson, Alain; Galtier, Pierre [Groupe d' Etude de la Matiere Condensee (GEMAC), CNRS-Universite de Versailles St-Quentin, Meudon (France); Agouram, Said [SCSIE, Universitat de Valencia, Burjassot (Spain); Enouz-Vedrenne, Shaima [Thales Research and Technology France, Palaiseau (France); Munoz-Sanjose, Vicente [Departamento de Fisica Aplicada y Electromagnetismo, Universitat de Valencia, Burjassot (Spain)

    2010-07-15

    Various one-dimensional (1D) ZnO-based nanostructures, including ZnO nano-wires (NWs) grown using vapour-liquid-solid (VLS) process, ZnO/ZnSe core/shell, nitrogen-doped ZnO and ZnMgO NWs were grown by metalorganic chemical vapour deposition (MOCVD). Transmission electron microscopy (TEM) analysis is presented. For all the samples, a high crystalline quality is observed. Some features are emphasized such as the gold contamination of ZnO wires grown under the metal droplets in the VLS process. It is concluded that MOCVD is a suitable technique for the realization of original ZnO nanodevices. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  11. Photoreflectance for in-situ characterization of MOCVD growth of semiconductors under micro-gravity conditions

    Science.gov (United States)

    Pollak, Fred H.

    1990-01-01

    A contactless electromodulation technique of photoreflectance (PR) was developed for in-situ monitoring of metal-organic chemical vapor deposition (MOCVD) semiconductor growth for micro-gravity applications. PR can be employed in a real MOCVD reactor including rotating substrate (approximately 500 rev/min) in flowing gases and through a diffuser plate. Measurements on GaAs and Ga(0.82)Al(0.18)As were made up to 690 C. The direct band gaps of In(x)Ga(1-x)As (x = 0.07 and 0.16) were evaluated up to 600 C. In order to address the question of real time measurement, the spectra of the direct gap of GaAs at 650 C was obtained in 30 seconds and 15 seconds seems feasible.

  12. Study of TiO{sub 2} nanomembranes obtained by an induction heated MOCVD reactor

    Energy Technology Data Exchange (ETDEWEB)

    Crisbasan, A., E-mail: andreea.crisbasan@yahoo.com [NANOFORM Group, ICB, Université de Bourgogne, BP 47 870, 21078 Dijon (France); Chaumont, D. [NANOFORM Group, ICB, Université de Bourgogne, BP 47 870, 21078 Dijon (France); Sacilotti, M. [NANOFORM Group, ICB, Université de Bourgogne, BP 47 870, 21078 Dijon (France); Departamento de Fisica – Universidade Federal de Pernambuco, Recife (Brazil); Crisan, A.; Lazar, A.M.; Ciobanu, I. [Science and Materials Engineering Faculty, University of Transilvania, Brasov (Romania); Lacroute, Y.; Chassagnon, R. [Université de Bourgogne, BP 47 870, 21078 Dijon (France)

    2015-12-15

    Highlights: • The TiO{sub 2} structures have been obtained by the MOCVD technique using ferrocene, cobalt layer (annealed at 350 °C) and Ti(OC{sub 3}H{sub 7}){sub 4}. • The TiO{sub 2} growth at 550 °C, during 20 min on the cobalt layer (obtained by electron beam evaporation method) on soda-lime glass has as result TiO{sub 2} nanomembranes. • The TiO{sub 2} nanomembranes grow on the cobalt nuclei. • The TiO{sub 2} nanomembranes are polycrystalline, built from TiO{sub 2} anatase and rutile crystals. - Abstract: Nanostructures of TiO{sub 2} were grown using the metal oxide chemical vapor deposition (MOCVD) technique. The procedure used induction heating on a graphite susceptor. This specific feature and the use of cobalt and ferrocene catalysts resulted in nanomembranes never obtained by common MOCVD reactors. The present study discusses the preparation of TiO{sub 2} nanomembranes and the dependence of nanomembrane structure and morphology on growth parameters.

  13. Sputtering. [as deposition technique in mechanical engineering

    Science.gov (United States)

    Spalvins, T.

    1976-01-01

    This paper primarily reviews the potential of using the sputtering process as a deposition technique; however, the manufacturing and sputter etching aspects are also discussed. Since sputtering is not regulated by classical thermodynamics, new multicomponent materials can be developed in any possible chemical composition. The basic mechanism for dc and rf sputtering is described. Sputter-deposition is described in terms of the unique advantageous features it offers such as versatility, momentum transfer, stoichiometry, sputter-etching, target geometry (coating complex surfaces), precise controls, flexibility, ecology, and sputtering rates. Sputtered film characteristics, such as strong adherence and coherence and film morphology, are briefly evaluated in terms of varying the sputtering parameters. Also described are some of the specific industrial areas which are turning to sputter-deposition techniques.

  14. Sputtering. [as deposition technique in mechanical engineering

    Science.gov (United States)

    Spalvins, T.

    1976-01-01

    This paper primarily reviews the potential of using the sputtering process as a deposition technique; however, the manufacturing and sputter etching aspects are also discussed. Since sputtering is not regulated by classical thermodynamics, new multicomponent materials can be developed in any possible chemical composition. The basic mechanism for dc and rf sputtering is described. Sputter-deposition is described in terms of the unique advantageous features it offers such as versatility, momentum transfer, stoichiometry, sputter-etching, target geometry (coating complex surfaces), precise controls, flexibility, ecology, and sputtering rates. Sputtered film characteristics, such as strong adherence and coherence and film morphology, are briefly evaluated in terms of varying the sputtering parameters. Also described are some of the specific industrial areas which are turning to sputter-deposition techniques.

  15. The MOCVD challenge a survey of GaInAsp-InP and GaInAsp-GaAs for photonic and electronic device applications

    CERN Document Server

    Razeghi, Manijeh

    2010-01-01

    Introduction to Semiconductor Compounds III-V semiconductor alloys III-V semiconductor devices Technology of multilayer growth Growth Technology Metalorganic chemical vapor deposition New non-equilibrium growth techniques In situ Characterization during MOCVD Reflectance anisotropy and ellipsometry Optimization of the growth of III-V binaries by RDS RDS investigation of III-V lattice-matched heterojunctions RDS investigation of III-V lattice-mismatched structures Insights on the growt

  16. Vacuum MOCVD fabrication of high efficience cells

    Science.gov (United States)

    Partain, L. D.; Fraas, L. M.; Mcleod, P. S.; Cape, J. A.

    1985-01-01

    Vacuum metal-organic-chemical-vapor-deposition (MOCVD) is a new fabrication process with improved safety and easier scalability due to its metal rather than glass construction and its uniform multiport gas injection system. It uses source materials more efficiently than other methods because the vacuum molecular flow conditions allow the high sticking coefficient reactants to reach the substrates as undeflected molecular beams and the hot chamber walls cause the low sticking coefficient reactants to bounce off the walls and interact with the substrates many times. This high source utilization reduces the materials costs power device and substantially decreases the amounts of toxic materials that must be handled as process effluents. The molecular beams allow precise growth control. With improved source purifications, vacuum MOCVD has provided p GaAs layers with 10-micron minority carrier diffusion lengths and GaAs and GaAsSb solar cells with 20% AMO efficiencies at 59X and 99X sunlight concentration ratios. Mechanical stacking has been identified as the quickest, most direct and logical path to stacked multiple-junction solar cells that perform better than the best single-junction devices. The mechanical stack is configured for immediate use in solar arrays and allows interconnections that improve the system end-of-life performance in space.

  17. Isotropic metal deposition technique for metamaterials fabrication

    DEFF Research Database (Denmark)

    Malureanu, Radu; Andryieuski, Andrei; Lavrinenko, Andrei

    2009-01-01

    In this work we will present the first steps taken towards isotropic deposition of thin metallic layers on dielectric substrates. The deposition takes place in aqueous environment thus making it both cheap and easy to be implemented....

  18. Isotropic metal deposition technique for metamaterials fabrication

    DEFF Research Database (Denmark)

    Malureanu, Radu; Andryieuski, Andrei; Lavrinenko, Andrei

    2009-01-01

    In this work we will present the first steps taken towards isotropic deposition of thin metallic layers on dielectric substrates. The deposition takes place in aqueous environment thus making it both cheap and easy to be implemented....

  19. Synthesis of TiO2 supported on activated carbon by MOCVD:operation parameters study

    Institute of Scientific and Technical Information of China (English)

    张兴旺; 周明华; 雷乐成; 徐甦

    2004-01-01

    A novel metallo-organic chemical vapor deposition (MOCVD) technique has been applied to the preparation of the photocatalytic titanium dioxide supported on activated carbon. The effects of various condition parameters such as carrier gas flow rate, source temperature and deposition temperature on the deposition rate were investigated. The maximum deposition rate of 8.2 mg/(g.h) was obtained under conditions of carrier gas flow rate of 400 ml/min, source temperature of 423 K and deposition temperature of 913 K. The deposition rate followed Arrhenius behavior at temperature of 753 K to 913 K, corresponding to activation energy Ea of 51.09 kJ/mol. TiO2 existed only in anatase phase when the deposition temperature was 773 K to 973 K. With increase of deposition temperature from 1073 K to 1273 K, the rutile content sharply increased from 7% to 70%. It was found that a deposition temperature of 773 K and a higher source temperature of 448 K resulted in finely dispersed TiO2 particles, which were mainly in the range of 10-20 nm.

  20. Platinum-Iridium Alloy Films Prepared by MOCVD

    Institute of Scientific and Technical Information of China (English)

    WEI Yan; CHEN Li; CAI Hongzhong; ZHENG Xu; YANG Xiya; HU Changyi

    2012-01-01

    Platinum-Iridium alloy films were prepared by MOCVD on Mo substrate using metal-acetylacetonate precursors.Effects of deposition conditions on composition,microstructure and mechanical properties were determined.In these experimental conditions,the purities of films are high and more than 99.0%.The films are homogeneous and monophase solid solution of Pt and Ir.Weight percentage of platinum are much higher than iridium in the alloy.Lattice constant of the alloy changes with the platinum composition.Iridium composition showing an up-down-up trend at the precursor temperature of 190~230℃ and the deposition temperature at 400~550℃.The hardness of Pt-Ir alloys prepared by MOCVD is three times more than the alloys prepared by casting.

  1. Optimization of Strontium Titanate (SrTiO3) Thin Films Fabricated by Metal Organic Chemical Vapor Deposition (MOCVD) for Microwave-Tunable Devices

    Science.gov (United States)

    2015-12-01

    maintained near 250 °C to prevent condensates. Solid-state β–Diketonate complex precursors Bis(2,2,6,6-tetramethyl-3,5- heptanedionato), purchased from Strem...and Titanium(IV) diisopropoxidebis(2,2,6,6-tetramethyl-3,5-heptanedionate), purchased from Sigma-Alrich, were used in all depositions. The Sr...Physics. 2005;38:2446–2451. 66. Hofman W, Hoffmann S, Waser, R. Dopant influence on dielectric losses, leakage behaviour , and resistance

  2. Effects of ZnO Buffer Layer Thickness on Properties of MgxZn1-xO Thin Films Deposited by MOCVD

    Institute of Scientific and Technical Information of China (English)

    DONG Xin; LIU Da-li; DU Guo-tong; ZHANG Yuan-tao; ZHU Hui-chao; YAN Xiao-long; GAO Zhong-min

    2005-01-01

    High-quality MgxZn1-xO thin films were grown on sapphire(0001) substrates with a ZnO buffer layer of different thicknesses by means of metal-organic chemical vapor deposition. Diethyl zinc, bis-cyclopentadienyl-Mg and oxygen were used as the precursor materials. The crystalline quality, surface morphologies and optical properties of the MgxZn1-xO films were investigated by X-ray diffraction, atomic force microscopy and photoluminescence spectrometry. It was shown that the quality of the MgxZn1-xO thin films depends on the thickness of the ZnO buffer layer and an MgxZn1-xO thin film with a ZnO buffer layer whose thickness was 20 nm exhibited the best crystal-quality, optical properties and a flat and dense surface.

  3. Malonate complexes of dysprosium: synthesis, characterization and application for LI-MOCVD of dysprosium containing thin films.

    Science.gov (United States)

    Milanov, Andrian P; Seidel, Rüdiger W; Barreca, Davide; Gasparotto, Alberto; Winter, Manuela; Feydt, Jürgen; Irsen, Stephan; Becker, Hans-Werner; Devi, Anjana

    2011-01-07

    A series of malonate complexes of dysprosium were synthesized as potential metalorganic precursors for Dy containing oxide thin films using chemical vapor deposition (CVD) related techniques. The steric bulkiness of the dialkylmalonato ligand employed was systematically varied and its influence on the resulting structural and physico-chemical properties that is relevant for MOCVD was studied. Single crystal X-ray diffraction analysis revealed that the five homoleptic tris-malonato Dy complexes (1-5) are dimers with distorted square-face bicapped trigonal-prismatic geometry and a coordination number of eight. In an attempt to decrease the nuclearity and increase the solubility of the complexes in various solvents, the focus was to react these dimeric complexes with Lewis bases such as 2,2'-biypridyl and pyridine (6-9). This resulted in monomeric tris-malonato mono Lewis base adduct complexes with improved thermal properties. Finally considering the ease of synthesis, the monomeric nature and promising thermal characteristics, the silymalonate adduct complex [Dy(dsml)(3)bipy] (8) was selected as single source precursor for growing DySi(x)O(y) thin films by liquid injection metalorganic chemical vapor deposition (LI-MOCVD) process. The as-deposited films were analyzed for their morphology and composition by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Rutherford backscattering (RBS) analysis and X-ray photoelectron spectroscopy.

  4. Comparison of different experimental techniques used for wax deposition testing

    Energy Technology Data Exchange (ETDEWEB)

    Allenson, Stephen; Johnston, Angela [Nalco Energy Services, Sugar Land, TX (United States)

    2008-07-01

    Crude oils consist of various fractions of hydrocarbons, including n-paraffins. The paraffins precipitate out of oil below the temperature called WAT (wax appearance temperature) and accumulate in flow lines and pipelines causing major transport problems. Prediction of paraffin deposition is, therefore, a key element of flow assurance programs. The purpose of this study was to develop a general and reliable approach to prediction of wax deposition based on a critical comparison of several practical lab techniques. Wax deposition study was conducted on five separate crude oils by using a varying protocols and equipment. One experimental technique was a cold stress test of wax deposition combined with ketone precipitation of waxy paraffin crystals. Another set of experiments were carried out for wax deposits formed on the surface of U-tubes and cold fingers of different designs. A comparison of the effectiveness of several wax inhibitors was conducted for these crude oils by using the selected deposition techniques. In each test method the amount of precipitated wax was recorded and compared. The deposits were characterized by melting point, qualitative and quantitative analysis of the wax components using DSC, SARA and HTGC analyses. Efficiency of paraffin inhibitors was correlated with a profile of n-paraffins distribution in the deposits. The limitations and advantages of different deposition techniques were analyzed and discussed. (author)

  5. Characterization of wax deposition by different experimental techniques - a comparison

    Energy Technology Data Exchange (ETDEWEB)

    Lindeman, Olga; Allenson, Steve

    2006-03-15

    Crude oils consist of various fractions of hydrocarbons, including n-paraffins. The paraffins precipitate out of oil below the temperature called WAT (wax appearance temperature) and accumulate in flow lines causing major transport problems. Prediction of paraffin deposition is, therefore, a key element of flow assurance programs. The purpose of this study was to develop a general and reliable approach to prediction of wax deposition based on a critical comparison of several practical lab techniques. Wax deposition study was conducted on multiple crude oils using various testing protocols and equipment. One experimental technique was a cold stress test of wax deposition combined with ketone precipitation of waxy paraffin crystals. Another set of experiments was carried out for wax deposits formed on the surface of U-tubes and cold fingers of different designs. A comparison of the effectiveness of several wax inhibitors was conducted for these crude oils by using the selected deposition techniques. In each test method the amount of precipitated wax was recorded and compared. The deposits were characterized by melting point, qualitative and quantitative analysis of the wax components using DSC, SARA and HTGC analyses. Efficiency of paraffin inhibitors was correlated with a profile of n-paraffins distribution in the deposits. The limitations and advantages of different deposition techniques were analyzed and discussed. A new test design designated ''cold tube'' is proposed. (Author) (tk)

  6. Photocatalysis in the visible range of sub-stoichiometric anatase films prepared by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Justicia, I. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Garcia, G. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain)]. E-mail: gemma@icmab.es; Battiston, G.A. [ICIS/CNR, Corso Stati Uniti 4, 35127 Padova (Italy); Gerbasi, R. [ICIS/CNR, Corso Stati Uniti 4, 35127 Padova (Italy); Ager, F. [CNA/CSIC Parque Tecnologico Cartuja 93, Avda Thomas A, Edison, 41092 Sevilla (Spain); Guerra, M. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Caixach, J. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Pardo, J.A. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Rivera, J. [IIQAB/CSIC Jordi Girona, 18 08034 Barcelona (Spain); Figueras, A. [ICMAB/CSIC, Campus UAB, 08193 Bellaterra (Spain); Instituto de Fisica, UNAM, Campus UNAM Juriquilla, 76230 Queretaro (Mexico)

    2005-08-25

    Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2 eV) it is not viable to use sunlight as an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380 nm is required. This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO{sub 2} thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters.

  7. Two to six compound thin films by MOCVD for tandem solar cells

    Science.gov (United States)

    Britt, Jeffrey Scott

    Polycrystalline Cd(1-x)Zn(x)S and Hg(x)Zn(1-x)Te films have been deposited on a variety of substrates by MOCVD. Deposition conditions have been adjusted based on measurements of the material properties. Heterojunction solar cells have been formed from these materials and their potential application as the upper member of a tandem solar cell has been examined. The evaluation and optimization of a high efficiency CdTe/CdS solar cell has also been accomplished. Polycrystalline Cd(1-x)Zn(x)S films were deposited at 350-425 C by the reaction between DMCd, DEZn, and the novel source, propanethiol (PM) in a H2 flow. The growth rate and bandgap energy are strongly dependent on the growth temperature, DMCd/DEZn molar ratio, and the II/VI molar ratio. TMAl and octyl-chloride have been introduced into the reaction mixture to lower resistivities to values suitable for device operation. Polycrystalline ZnTe films have been deposited at 270-400 C by the reaction between DIPTe and DMZn or DEZn in a H2 flow. ZnTe films have been deposited by photoenhanced and conventional MOCVD. Polycrystalline Hg(x)Zn(1-x)Te films have been deposited at 350-410 C by the reaction between elemental Hg, DIPTe, and DMZn in a H2 flow. AsH3 was introduced to the reaction mixture to control the resistivity. Heterojunctions have been formed with Cd(1-x)Zn(x)S and ZnSe. The films and junctions have been characterized by x-ray, optical transmission, low temperature photoluminescence, SEM, and electrical measurements. The evaluation and optimization of a CSS CdTe/CdS solar cell has been formed. A technique for the formation of low-resistance contacts to CdTe with HgTe has also been developed. A pre-deposition heat treatment of CdS in H2 has been demonstrated beneficial to the photovoltaic characteristics of the junction. A post-deposition CdCl2 treatment has been shown to have a profound influence on the electrical characteristics of CSS CdTe/CdS junctions. The identification of optical losses in CSS Cd

  8. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    Energy Technology Data Exchange (ETDEWEB)

    Aronne, Antonio [Department of Chemical Engineering, Materials and Industrial Production, University of Naples “Federico II”, Napoli (Italy); Bloisi, Francesco, E-mail: bloisi@na.infn.it [SPIN – CNR, Naples (Italy); Department of Physics, University of Naples “Federico II”, Napoli (Italy); Calabria, Raffaela; Califano, Valeria [Istituto Motori – CNR, Naples (Italy); Depero, Laura E. [Department of Mechanical and Industrial Engineering, University of Brescia, Brescia (Italy); Fanelli, Esther [Department of Chemical Engineering, Materials and Industrial Production, University of Naples “Federico II”, Napoli (Italy); Federici, Stefania [Department of Mechanical and Industrial Engineering, University of Brescia, Brescia (Italy); Massoli, Patrizio [Istituto Motori – CNR, Naples (Italy); Vicari, Luciano R.M. [SPIN – CNR, Naples (Italy); Department of Physics, University of Naples “Federico II”, Napoli (Italy)

    2015-05-01

    Highlights: • A lipase film was deposited with Matrix Assisted Pulsed Laser Evaporation technique. • FTIR spectra show that laser irradiation do not damage lipase molecule. • Laser fluence controls the characteristics of complex structure generated by MAPLE. - Abstract: Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence.

  9. The mechanical properties of thin alumina film deposited by metal-organic chemical vapour deposition

    NARCIS (Netherlands)

    Haanappel, V.A.C.; Gellings, P.J.; Vendel, van de D.; Metselaar, H.S.C.; Corbach, van H.D.; Fransen, T.

    1995-01-01

    Amorphous alumina films were deposited by metal-organic chemical vapour deposition (MOCVD) on stainless steel, type AISI 304. The MOCVD experiments were performed in nitrogen at low and atmospheric pressures. The effects of deposition temperature, growth rate and film thickness on the mechanical pro

  10. SnS thin films deposited by chemical bath deposition, dip coating and SILAR techniques

    Science.gov (United States)

    Chaki, Sunil H.; Chaudhary, Mahesh D.; Deshpande, M. P.

    2016-05-01

    The SnS thin films were synthesized by chemical bath deposition (CBD), dip coating and successive ionic layer adsorption and reaction (SILAR) techniques. In them, the CBD thin films were deposited at two temperatures: ambient and 70 °C. The energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and optical spectroscopy techniques were used to characterize the thin films. The electrical transport properties studies on the as-deposited thin films were done by measuring the I-V characteristics, DC electrical resistivity variation with temperature and the room temperature Hall effect. The obtained results are deliberated in this paper.

  11. 3D CFD Simulations of MOCVD Synthesis System of Titanium Dioxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    Siti Hajar Othman

    2013-01-01

    Full Text Available This paper presents the 3-dimensional (3D computational fluid dynamics (CFD simulation study of metal organic chemical vapor deposition (MOCVD producing photocatalytic titanium dioxide (TiO2 nanoparticles. It aims to provide better understanding of the MOCVD synthesis system especially of deposition process of TiO2 nanoparticles as well as fluid dynamics inside the reactor. The simulated model predicts temperature, velocity, gas streamline, mass fraction of reactants and products, kinetic rate of reaction, and surface deposition rate profiles. It was found that temperature distribution, flow pattern, and thermophoretic force considerably affected the deposition behavior of TiO2 nanoparticles. Good mixing of nitrogen (N2 carrier gas and oxygen (O2 feed gas is important to ensure uniform deposition and the quality of the nanoparticles produced. Simulation results are verified by experiment where possible due to limited available experimental data. Good agreement between experimental and simulation results supports the reliability of simulation work.

  12. Gas phase depletion and flow dynamics in horizontal MOCVD reactors

    Science.gov (United States)

    Van de Ven, J.; Rutten, G. M. J.; Raaijmakers, M. J.; Giling, L. J.

    1986-08-01

    Growth rates of GaAs in the MOCVD process have been studied as a function of both lateral and axial position in horizontal reactor cells with rectangular cross-sections. A model to describe growth rates in laminar flow systems on the basis of concentration profiles under diffusion controlled conditions has been developed. The derivation of the growth rate equations includes the definition of an entrance length for the concentration profile to developed. In this region, growth rates appear to decrease with the 1/3 power of the axial position. Beyond this region, an exponential decrease is found. For low Rayleigh number conditions, the present experimental results show a very satisfactory agreement with the model without parameter fitting for both rectangular and tapered cells, and with both H 2 and N 2 as carrier gases. Theory also predicts that uniform deposition can be obtained over large areas in the flow direction for tapered cells, which has indeed been achieved experimentally. The influence of top-cooling in the present MOCVD system has been considered in more detail. From the experimental results, conclusions could be drawn concerning the flow characteristics. For low Rayleigh numbers (present study ≲ 700) it follows that growth rate distributions correspond with forced laminar flow characteristics. For relatively high Rayleigh numbers (present work 1700-2800), free convective effects with vortex formation are important. These conclusions are not specific for the present system, but apply to horizontal cold-wall reactors in general. On the basis of the present observations, recommendations for a cell design to obtain large area homogeneous deposition have been formulated. In addition, this work supports the conclusion that the final decomposition of trimethylgallium in the MOCVD process mainly takes place at the hot substrate and susceptor and not in the gas phase.

  13. MOCVD of thin film photovoltaic solar cells—Next-generation production technology?

    Science.gov (United States)

    Irvine, S. J. C.; Barrioz, V.; Lamb, D.; Jones, E. W.; Rowlands-Jones, R. L.

    2008-11-01

    This paper will review the chalcogenide thin film photovoltaic (PV) solar cells, based on cadmium telluride (CdTe) and copper indium diselenide (CIS) and discuss the potential for metalorganic chemical vapour deposition (MOCVD) to enable more advanced devices in the second generation of CdTe module production. The current generation of production methods is based on physical vapour deposition (PVD) or close-spaced sublimation (CSS). This paper concentrates on the less well-known topic of MOCVD of thin film chalcogenide cells, and in particular that of CdTe. Efficient CdTe PV solar cells (>10% AM1.5) have been demonstrated from deposition of the CdS, CdTe and CdCl 2 films in a single MOCVD chamber. The CdTe layer was doped with As and an additional high As concentration CdTe layer provides effective low resistance contacting without the need for wet etching the surface. The high level of flexibility in using MOCVD has been demonstrated where the CdS window layer has been alloyed with Zn to improve the blue response of the PV device and improve AM1.5 efficiency to 13.3%.

  14. Lipase biofilm deposited by Matrix Assisted Pulsed Laser Evaporation technique

    Science.gov (United States)

    Aronne, Antonio; Bloisi, Francesco; Calabria, Raffaela; Califano, Valeria; Depero, Laura E.; Fanelli, Esther; Federici, Stefania; Massoli, Patrizio; Vicari, Luciano R. M.

    2015-05-01

    Lipase is an enzyme that finds application in biodiesel production and for detection of esters and triglycerides in biosensors. Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique derived from Pulsed Laser Deposition (PLD) for deposition of undamaged biomolecules or polymers, is characterized by the use of a frozen target obtained from a solution/suspension of the guest material (to be deposited) in a volatile matrix (solvent). The presence of the solvent avoids or at least reduces the potential damage of guest molecules by laser radiation but only the guest material reaches the substrate in an essentially solvent-free deposition. MAPLE can be used for enzymes immobilization, essential for industrial application, allowing the development of continuous processes, an easier separation of products, the reuse of the catalyst and, in some cases, enhancing enzyme properties (pH, temperature stability, etc.) and catalytic activity in non-aqueous media. Here we show that MAPLE technique can be used to deposit undamaged lipase and that the complex structure (due to droplets generated during extraction from target) of the deposited material can be controlled by changing the laser beam fluence.

  15. Characterization of copper selenide thin films deposited by chemical bath deposition technique

    Science.gov (United States)

    Al-Mamun; Islam, A. B. M. O.

    2004-11-01

    A low-cost chemical bath deposition (CBD) technique has been used for the preparation of Cu2-xSe thin films onto glass substrates and deposited films were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and UV-vis spectrophotometry. Good quality thin films of smooth surface of copper selenide thin films were deposited using sodium selenosulfate as a source of selenide ions. The structural and optical behaviour of the films are discussed in the light of the observed data.

  16. Fused Deposition Technique for Continuous Fiber Reinforced Thermoplastic

    Science.gov (United States)

    Bettini, Paolo; Alitta, Gianluca; Sala, Giuseppe; Di Landro, Luca

    2017-02-01

    A simple technique for the production of continuous fiber reinforced thermoplastic by fused deposition modeling, which involves a common 3D printer with quite limited modifications, is presented. An adequate setting of processing parameters and deposition path allows to obtain components with well-enhanced mechanical characteristics compared to conventional 3D printed items. The most relevant problems related to the simultaneous feeding of fibers and polymer are discussed. The properties of obtained aramid fiber reinforced polylactic acid (PLA) in terms of impregnation quality and of mechanical response are measured.

  17. Fused Deposition Technique for Continuous Fiber Reinforced Thermoplastic

    Science.gov (United States)

    Bettini, Paolo; Alitta, Gianluca; Sala, Giuseppe; Di Landro, Luca

    2016-12-01

    A simple technique for the production of continuous fiber reinforced thermoplastic by fused deposition modeling, which involves a common 3D printer with quite limited modifications, is presented. An adequate setting of processing parameters and deposition path allows to obtain components with well-enhanced mechanical characteristics compared to conventional 3D printed items. The most relevant problems related to the simultaneous feeding of fibers and polymer are discussed. The properties of obtained aramid fiber reinforced polylactic acid (PLA) in terms of impregnation quality and of mechanical response are measured.

  18. The crystal morphology effect of Iridium tris-acetylacetonate on MOCVD iridium coatings

    Science.gov (United States)

    Shi, Jing; Hao, Yupeng; Yu, Xiaodong; Tan, Chengwen

    2017-07-01

    Iridium tris-acetylacetonate is the most commonly used precursor for the metal organic chemical vapour deposition (MOCVD) of iridium coating. In this paper, the crystal morphology effect of iridium tris-acetylacetonate on iridium coatings prepared by MOCVD was studied. Two kinds of Ir(acac)3 crystalline powder were prepared. A precursor sublimation experiment in a fixed bed reactor and an iridium deposition experiment in a cold-wall atmospheric CVD reactor were designed. It is found that the volatility of the hexagonal columnar crystals is better than that of the tetragonal flake crystals under the experimental conditions. It’s due to the hexagonal columnar crystals exposed more crystal faces than the tetragonal flake crystals, increasing its contact area with the transport gas. An adequate supply of iridium tris-acetylacetonate during the pre-deposition period contributed to obtain an iridium coating with a smooth and uniform continuity surface.

  19. Nucleation and Growth of MOCVD Grown (Cr, Zn)O Films – Uniform Doping vs. Secondary Phase Formation

    Energy Technology Data Exchange (ETDEWEB)

    Saraf, Laxmikant V.; Engelhard, Mark H.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Wang, Chong M.; Heald, Steve M.; McCready, David E.; Lea, Alan S.; Baer, Donald R.; Chambers, Scott A.

    2007-01-17

    We report a detailed study of chromium solubility and secondary phase formation in MOCVD grown (Cr, Zn)O-based films on silicon (100). Simultaneous deposition of 0.15M Cr(TMHD) and 0.025M Zn(TMHD) based precursors in an oxidizing environment with a flow ratio of 1:10 resulted in secondary phase formation rather than uniform Cr doping. Based on several surface and micro-structural techniques, we have identified nano-crystalline ZnCr2O4 and disordered Cr2O3 as the secondary Cr-containing phases that nucleate. Analysis suggests that ZnCr2O4 crystallites are dispersed throughout the film and that disordered Cr2O3 layer may form at the interface. These results reveal a strong tendency for Cr to exist in octahedral, rather than tetrahedral coordination.

  20. Microwave characterization of normal and superconducting states of MOCVD made YBCO tapes

    Science.gov (United States)

    Wosik, Jarek; Krupka, Jerzy; Qin, Kuang; Ketharnath, Dhivya; Galstyan, Eduard; Selvamanickam, Venkat

    2017-03-01

    We have used a microwave, non-contact, non-destructive, dielectric resonator (DR) technique to characterize complex conductivity of different quality YBCO/Hastelloy tapes for the purpose of exploring such a technique as a potential quality control method for fabrication of YBCO tapes. The tapes were deposited at different temperatures on Hastelloy-supported oxide buffer layers using the MOCVD technique. The buffer stack consisted of aluminum oxide (Al2O3), yttrium oxide (Y2O3), and textured ion beam assisted deposition-MgO and LaMnO3 layers. Two dielectric resonators (DRs), the single post DR, consisting of high-permittivity barium zirconium titanate ceramic operating at 13 GHz in quasi-TE01δ mode, and the rod DR, consisting of rutile single crystal disk operating at 9.4 GHz in-TE011 mode, were designed to meet sensitivity requirements for characterization of conductivity of the superconductor at normal and superconducting states, respectively. For calculations of complex conductivity from experimental data of Q-factor and resonant frequency shift, a commercial electromagnetic simulator HFSS, based on finite elements analysis, was used. The theoretical Q-factor and resonant frequency on conductivity functions obtained from full wave numerical simulations of microwave fields were matched with the experimental data to determine conductivity of the YBCO tapes in both normal and superconducting states. In addition, for comparison purposes, 280 nm thick high-quality YBCO epitaxial film deposited on a dielectric substrate was also characterized, including frequency dependence of the complex conductivity. Discussion about feasibility of using DR microwave techniques as a quality control tool via measurements of conductivity versus temperature slope of the YBCO/Hastelloy tape in normal state is included. Also, microwave conductivity values of Hastelloy substrate as a function of temperature are reported.

  1. ZnO Nanostructures Grown on AlN/Sapphire Substrates by MOCVD

    Institute of Scientific and Technical Information of China (English)

    WEI Hong-Yuan; HU Wei-Guo; ZHANG Pan-Feng; LIU Xiang-Lin; ZHU Qin-Sheng; WANG Zhan-Guo

    2007-01-01

    ZnO nanorods and nanotubes are successful synthesized on AlN/sapphire substrates by metal-organic chemical vapour deposition (MOCVD). The different morphology and structure properties of ZnO nanorods and nanotubes are found to be affected by the A1N under-layer. The photoluminescence spectra show the optical properties of the ZnO nanorods and nanotubes, in which a blueshift of UV emission is observed and is attributed to the surface effect.

  2. MOCVD manifold switching effects on growth and characterization

    Science.gov (United States)

    Clark, Ivan O.; Fripp, Archibald L.; Jesser, William A.

    1991-01-01

    A combined modeling and experimental approach is used to quantify the effects of various manifold components on the switching speed in metalorganic chemical vapor deposition (MOCVD). In particular, two alternative vent-run high-speed switching manifold designs suitable for either continuous or interrupted growth have been investigated. Both designs are incorporated in a common manifold, instrumented with a mass spectrometer. The experiments have been performed using nitrogen as the transport gas and argon as the simulated source gas. The advantages and limitations of two designs are discussed. It is found that while constant flow manifold switching systems may have fluid dynamic advantages, care must be taken to minimize sections of the supply manifold with low flow rates if rapid changes in alloy composition are required.

  3. Silicon doping techniques using chemical vapor dopant deposition

    Energy Technology Data Exchange (ETDEWEB)

    Popadic, M.

    2009-11-12

    Ultrashallow junctions are essential for the achievement of superior transistor performance, both in MOSFET and bipolar transistors. The stringent demands require state-of-the-art fabrication techniques. At the same time, in a different context, the accurate fabrication of various n type doping profiles by low-temperature Si epitaxy is a challenge due to autodoping. In this thesis, these two, apparently unrelated, problems are both addressed as the layer of CVD surface-deposited dopant atoms is used as a doping source. It is demonstrated that a layer of dopants deposited on the Si surface can be used as a doping source by either thermal or laser drive-in for the fabrication of both deep and ultrashallow defect-free junctions. In low-temperature CVD epitaxy, autodoping is a consequence of dopant surface segregation and doping from the surface layer. This process has been characterized, and consequently excellent controllability is achieved. In addition, new results related to the CVD of dopants itself are obtained, and two theoretical achievements are made: the analytical model of arbitrarily shallow junctions is derived, and a new C-V profiling technique suitable for the characterization of ultrashallow junctions is developed.

  4. Study of indium tin oxide thin films deposited on acrylics substrates by Ion beam assisted deposition technique

    OpenAIRE

    Meng Lijian; Liang Erjun; Gao Jinsong; Teixeira, Vasco M. P.; Santos, M. P. dos

    2009-01-01

    Indium tin oxide (ITO) thin films have been deposited onto acrylics (PMMA) substrates by ion beam assisted deposition technique at different oxygen flows. The structural, optical and electrical properties of the deposited films have been characterized by X-ray diffraction, transmittance, FTIR, ellipometry and Hall effect measurements. The optical constants of the deposited films have been calculated by fitting the ellipsometric spectra. The effects of the oxygen flow on the properties of the ...

  5. Investigations of chemical vapor deposition of GaN using synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, C.; Stephenson, G. B.; Eastman, J. A.; Munkholm, A.; Auciello, O.; Murty, M. V. R.; Fini, P.; DenBaars, S. P.; Speck, J. S.

    2000-05-25

    The authors apply synchrotron x-ray analysis techniques to probe the surface structure of GaN films during synthesis by metal-organic chemical vapor deposition (MOCVD). Their approach is to observe the evolution of surface structure and morphology in real time using grazing incidence x-ray scattering (GIXS). This technique combines the ability of x-rays to penetrate the chemical vapor deposition environment for in situ measurements, with the sensitivity of GIXS to atomic scale structure. In this paper they present examples from some of their studies of growth modes and surface evolution as a function of process conditions that illustrate the capabilities of synchrotron x-ray analysis during MOCVD growth. They focus on studies of the homoepitaxial growth mode, island coarsening dynamics, and effects of impurities.

  6. Stoichiometry, thickness and crystallinity of MOCVD grown Hg{sub 1x-y}Cd{sub x}Mn{sub y}Te determined by nuclear techniques of analysis

    Energy Technology Data Exchange (ETDEWEB)

    Studd, W.B.; Johnston, P.N.; Bubb, I.F. [Royal Melbourne Inst. of Tech., VIC (Australia); Leech, P.W. [Applied Research and Developement, Telecom Australia, Clayton, VIC (Australia)

    1993-12-31

    The quaternary semi-conductor Hg{sub 1-x-y}Cd{sub x}Mn{sub y}Te has been grown by Metal Organic Chemical Vapour Deposition using the Interdiffused Multi-layer Process. The layers have been analysed by Ion beam (PIXE, RBS, channeling) and related analytical techniques (EDXRF, XRD, RHEED) to obtain stoichiometric and structural information. The analysis shows that all four elements are present throughout the layer and that the elemental concentrations and thickness of the layer vary considerably over the film. Channeling, XRD and RHEED have been combined to show that the layer is polycrystalline. 14 refs., 3 figs.

  7. Study of nickel silicide formation by physical vapor deposition techniques

    Science.gov (United States)

    Pancharatnam, Shanti

    Metal silicides are used as contacts to the highly n-doped emitter in photovoltaic devices. Thin films of nickel silicide (NiSi) are of particular interest for Si-based solar cells, as they form at lower temperature and consume less silicon. However, interfacial oxide limits the reduction in sheet resistance. Hence, different diffusion barriers were investigated with regard to optimizing the conductivity and thermal stability. The formation of NiSi, and if it can be doped to have good contact with the n-side of a p-n junction were studied. Reduction of the interfacial oxide by the interfacial Ti layer to allow the formation of NiSi was observed. Silicon was treated in dilute hydrofluoric acid for removing the surface oxide layer. Ni and a Ti diffusion barrier were deposited on Si by physical vapor deposition (PVD) methods - electron beam evaporation and sputtering. The annealing temperature and time were varied to observe the stability of the deposited film. The films were then etched to observe the retention of the silicide. Characterization was done using scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and Rutherford back scattering (RBS). Sheet resistance was measured using the four-point probe technique. Annealing temperatures from 300°C showed films began to agglomerate indicating some diffusion between Ni and Si in the Ti layer, also supported by the compositional analysis in the Auger spectra. Films obtained by evaporation and sputtering were of high quality in terms of coverage over substrate area and uniformity. Thicknesses of Ni and Ti were optimized to 20 nm and 10 nm respectively. Resistivity was low at these thicknesses, and reduced by about half post annealing at 300°C for 8 hours. Thus a low resistivity contact was obtained at optimized thicknesses of the metal layers. It was also shown that some silicide formation occurs at temperatures starting from 300°C and can thus be used to make good silicide contacts.

  8. Multilayer porous structures of HVPE and MOCVD grown GaN for photonic applications

    Science.gov (United States)

    Braniste, T.; Ciers, Joachim; Monaico, Ed.; Martin, D.; Carlin, J.-F.; Ursaki, V. V.; Sergentu, V. V.; Tiginyanu, I. M.; Grandjean, N.

    2017-02-01

    In this paper we report on a comparative study of electrochemical processes for the preparation of multilayer porous structures in hydride vapor phase epitaxy (HVPE) and metal organic chemical vapor phase deposition (MOCVD) grown GaN. It was found that in HVPE-grown GaN, multilayer porous structures are obtained due to self-organization processes leading to a fine modulation of doping during the crystal growth. However, these processes are not totally under control. Multilayer porous structures with a controlled design have been produced by optimizing the technological process of electrochemical etching in MOCVD-grown samples, consisting of five pairs of thin layers with alternating-doping profiles. The samples have been characterized by SEM imaging, photoluminescence spectroscopy, and micro-reflectivity measurements, accompanied by transfer matrix analysis and simulations by a method developed for the calculation of optical reflection spectra. We demonstrate the applicability of the produced structures for the design of Bragg reflectors.

  9. Enhanced Light Scattering by Preferred Orientation Control of Ga Doped ZnO Films Prepared through MOCVD

    Directory of Open Access Journals (Sweden)

    Long Giang Bach

    2016-01-01

    Full Text Available We have explored the effective approach to fabricate GZO/ZnO films that can make the pyramidal surface structures of GZO films for effective light scattering by employing a low temperature ZnO buffer layer prior to high temperature GZO film growth. The GZO thin films exhibit the typical preferred growth orientations along the (002 crystallographic direction at deposition temperature of 400°C and SEM showed that column-like granule structure with planar surface was formed. In contrast, GZO films with a pyramidal texture surface were successfully developed by the control of (110 preferred orientation. We found that the light diffuse transmittance of the film with a GZO (800 nm/ZnO (766 nm exhibited 13% increase at 420 nm wavelength due to the formed large grain size of the pyramidal texture surface. Thus, the obtained GZO films deposited over ZnO buffer layer have high potential for use as front TCO layers in Si-based thin film solar cells. These results could develop the potential way to fabricate TCO based ZnO thin film using MOCVD or sputtering techniques by depositing a low temperature ZnO layer to serve as a template for high temperature GZO film growth. The GZO films exhibited satisfactory optoelectric properties.

  10. Magnesium doped GaN grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Guarneros, C., E-mail: cesyga@yahoo.com.mx [Ingenieria Electrica, Seccion Electronica del Estado Solido, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Av. I.P.N. 2508, San Pedro Zacatenco, 07360 Mexico, D.F. (Mexico); Sanchez, V. [Ingenieria Electrica, Seccion Electronica del Estado Solido, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, Av. I.P.N. 2508, San Pedro Zacatenco, 07360 Mexico, D.F. (Mexico)

    2010-10-25

    We have studied the optical and electrical characteristics of undoped and doped GaN layers. The n- and p-type layers have been prepared by low pressure MOCVD technique. Photoluminescence (PL) studies were carried at low temperature. In the PL spectra of undoped GaN layer, a low intensity band edge emission and a broad yellow emission band were observed. The donor-acceptor pair (DAP) emission and its phonon replicas were observed in Mg lightly doped GaN layer. The dominance of the blue and the yellow emissions increased in the PL spectra as the Mg concentration was increased. The X-ray diffraction was employed to study the structure of the layers. Both the undoped and the doped layers exhibited hexagonal structure. The samples were annealed and significant changes were not observed in Hall Effect and in the PL measurements, so we suggest that there is no need of a thermal annealing for magnesium acceptor activation.

  11. Advanced indium phosphide based monolithic integration using quantum well intermixing and MOCVD regrowth

    Science.gov (United States)

    Raring, James W.

    The proliferation of the internet has fueled the explosive growth of telecommunications over the past three decades. As a result, the demand for communication systems providing increased bandwidth and flexibility at lower cost continues to rise. Lightwave communication systems meet these demands. The integration of multiple optoelectronic components onto a single chip could revolutionize the photonics industry. Photonic integrated circuits (PIC) provide the potential for cost reduction, decreased loss, decreased power consumption, and drastic space savings over conventional fiber optic communication systems comprised of discrete components. For optimal performance, each component within the PIC may require a unique epitaxial layer structure, band-gap energy, and/or waveguide architecture. Conventional integration methods facilitating such flexibility are increasingly complex and often result in decreased device yield, driving fabrication costs upward. It is this trade-off between performance and device yield that has hindered the scaling of photonic circuits. This dissertation presents high-functionality PICs operating at 10 and 40 Gb/s fabricated using novel integration technologies based on a robust quantum-well-intermixing (QWI) method and metal organic chemical vapor deposition (MOCVD) regrowth. We optimize the QWI process for the integration of high-performance quantum well electroabsorption modulators (QW-EAM) with sampled-grating (SG) DBR lasers to demonstrate the first widely-tunable negative chirp 10 and 40 Gb/s EAM based transmitters. Alone, QWI does not afford the integration of high-performance semiconductor optical amplifiers (SOA) and photodetectors with the transmitters. To overcome this limitation, we have developed a novel high-flexibility integration scheme combining MOCVD regrowth with QWI to merge low optical confinement factor SOAs and 40 Gb/s uni-traveling carrier (UTC) photodiodes on the same chip as the QW-EAM based transmitters. These high

  12. MOCVD ZnO/Screen Printed Ag Back Reflector for Flexible Thin Film Silicon Solar Cell Application

    OpenAIRE

    Amornrat Limmanee; Patipan Krudtad; Sasiwimon Songtrai; Suttinan Jaroensathainchok; Taweewat Krajangsang; Jaran Sritharathikhun; Kobsak Sriprapha

    2014-01-01

    We have prepared Ag back electrode by screen printing technique and developed MOCVD ZnO/screen printed Ag back reflector for flexible thin film silicon solar cell application. A discontinuity and poor contact interface between the MOCVD ZnO and screen printed Ag layers caused poor open circuit voltage (Voc) and low fill factor (FF); however, an insertion of a thin sputtered ZnO layer at the interface could solve this problem. The n type hydrogenated amorphous silicon (a-Si:H) film is preferab...

  13. XPS analysis and luminescence properties of thin films deposited by the pulsed laser deposition technique

    Science.gov (United States)

    Dolo, J. J.; Swart, H. C.; Coetsee, E.; Terblans, J. J.; Ntwaeaborwa, O. M.; Dejene, B. F.

    2010-04-01

    This paper presents the effect of substrate temperature and oxygen partial pressure on the photoluminescence (PL) intensity of the Gd2O2S:Tb3 + thin films that were grown by using pulsed laser deposition (PLD). The PL intensity increased with an increase in the oxygen partial pressure and substrate temperature. The thin film deposited at an oxygen pressure of 900 mTorr and substrate temperature of 900°C was found to be the best in terms of the PL intensity of the Gd2O2S:Tb3 + emission. The main emission peak due to the 5D4-7F5 transition of Tb was measured at a wavelength of 545 nm. The stability of these thin films under prolonged electron bombardment was tested with a combination of techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Cathodoluminescence (CL) spectroscopy. It was shown that the main reason for the degradation in luminescence intensity under electron bombardment is the formation of a non-luminescent Gd2O3 layer, with small amounts of Gd2S3, on the surface.

  14. Photocatalytic ability of TiO2 porous film prepared by modified spray pyrolysis deposition technique

    National Research Council Canada - National Science Library

    SUGIYAMA, Osamu; OKUYA, Masayuki; KANEKO, Shoji

    2009-01-01

    In a spray pyrolysis deposition (SPD) technique, deposition of film material and formation of surface structure are simultaneously occur, therefore, it is suitable for the preparation of microstructure-controlled thin films...

  15. Experimental measurements of the thermal conductivity of ash deposits: Part 1. Measurement technique

    Energy Technology Data Exchange (ETDEWEB)

    A. L. Robinson; S. G. Buckley; N. Yang; L. L. Baxter

    2000-04-01

    This paper describes a technique developed to make in situ, time-resolved measurements of the effective thermal conductivity of ash deposits formed under conditions that closely replicate those found in the convective pass of a commercial boiler. Since ash deposit thermal conductivity is thought to be strongly dependent on deposit microstructure, the technique is designed to minimize the disturbance of the natural deposit microstructure. Traditional techniques for measuring deposit thermal conductivity generally do not preserve the sample microstructure. Experiments are described that demonstrate the technique, quantify experimental uncertainty, and determine the thermal conductivity of highly porous, unsintered deposits. The average measured conductivity of loose, unsintered deposits is 0.14 {+-} 0.03 W/(m K), approximately midway between rational theoretical limits for deposit thermal conductivity.

  16. Thermal behavior of MOCVD-grown Cu-clusters on ZnO(1010).

    Science.gov (United States)

    Kroll, Martin; Löber, Thomas; Schott, Vadim; Wöll, Christof; Köhler, Ulrich

    2012-02-01

    Scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS, AES) were used to study MOCVD of Cu-clusters on the mixed terminated ZnO(1010) surface in comparison to MBE Cu-deposition. Both deposition methods result in the same Cu cluster morphology. After annealing to 670 K the amount of Cu visible above the oxide surface is found to decrease substantially, indicating a substantial diffusion of Cu atoms inside the ZnO-bulk. The spectroscopic data do not show any evidence for changes in the Cu oxidation state during thermal treatment up to 770 K.

  17. Design of a three-layer hot-wall horizontal flow MOCVD reactor

    Institute of Scientific and Technical Information of China (English)

    Gu Chengyan; Lee Chengming; Liu Xianglin

    2012-01-01

    A new three-layer hot-wall horizontal flow metal-organic chemical vapor deposition (MOCVD) reactor is proposed.When the susceptor is heated,the temperature of the wall over the susceptor also increases to the same temperature.Furthermore,the flowing speed of the top layer is also increased by up to four times that of the bottom layer.Both methods effectively decrease the convection and make most of the metal organic (MO) gas and the reactive gas distribute at the bottom surface of the reactor.By selecting appropriate shapes,sizes,nozzles array,and heating area of the walls,the source gases are kept in a laminar flow state.Results of the numeric simulation indicate that the nitrogen is a good carrier to reduce the diffusion among the precursors before arriving at the substrate,which leads to the reduction of pre-reaction.To get a good comparison with the conventional MOCVD horizontal reactor,the two-layer horizontal MOCVD reactor is also investigated.The results indicate that a twolayer reactor cannot control the gas flow effectively when its size and shape are the same as that of the three-layer reactor,so that the concentration distributions of the source gases in the susceptor surface are much more uniform in the new design than those in the conventional one.

  18. TiO2 thin film growth using the MOCVD method

    Directory of Open Access Journals (Sweden)

    Bernardi M.I.B.

    2001-01-01

    Full Text Available Titanium oxide (TiO2 thin films were obtained using the MOCVD method. In this report we discuss the properties of a film, produced using a ordinary deposition apparatus, as a function of the deposition time, with constant deposition temperature (90 °C, oxygen flow (7,0 L/min and substrate temperature (400 °C. The films were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, atomic force microscopy (AFM and visible and ultra-violet region spectroscopy (UV-Vis. The films deposited on Si (100 substrates showed the anatase polycrystalline phase, while the films grown on glass substrates showed no crystallinity. Film thickness increased with deposition time as expected, while the transmittance varied from 72 to 91% and the refractive index remained close to 2.6.

  19. ZrN coatings deposited by high power impulse magnetron sputtering and cathodic arc techniques

    Energy Technology Data Exchange (ETDEWEB)

    Purandare, Yashodhan, E-mail: Y.Purandare@shu.ac.uk; Ehiasarian, Arutiun; Hovsepian, Papken [Nanotechnology Centre for PVD Research, Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield S1 1WB (United Kingdom); Santana, Antonio [Ionbond AG Olten, Industriestrasse 211, CH-4600 Olten (Switzerland)

    2014-05-15

    Zirconium nitride (ZrN) coatings were deposited on 1 μm finish high speed steel and 316L stainless steel test coupons. Cathodic Arc (CA) and High Power Impulse Magnetron Sputtering (HIPIMS) + Unbalanced Magnetron Sputtering (UBM) techniques were utilized to deposit coatings. CA plasmas are known to be rich in metal and gas ions of the depositing species as well as macroparticles (droplets) emitted from the arc sports. Combining HIPIMS technique with UBM in the same deposition process facilitated increased ion bombardment on the depositing species during coating growth maintaining high deposition rate. Prior to coating deposition, substrates were pretreated with Zr{sup +} rich plasma, for both arc deposited and HIPIMS deposited coatings, which led to a very high scratch adhesion value (L{sub C2}) of 100 N. Characterization results revealed the overall thickness of the coatings in the range of 2.5 μm with hardness in the range of 30–40 GPa depending on the deposition technique. Cross-sectional transmission electron microscopy and tribological experiments such as dry sliding wear tests and corrosion studies have been utilized to study the effects of ion bombardment on the structure and properties of these coatings. In all the cases, HIPIMS assisted UBM deposited coating fared equal or better than the arc deposited coatings, the reasons being discussed in this paper. Thus H+U coatings provide a good alternative to arc deposited where smooth, dense coatings are required and macrodroplets cannot be tolerated.

  20. Metallization on FDM Parts Using the Chemical Deposition Technique

    Directory of Open Access Journals (Sweden)

    Azhar Equbal

    2014-08-01

    Full Text Available Metallization of ABS (acrylonitrile-butadiene-styrene parts has been studied on flat part surfaces. These parts are fabricated on an FDM (fused deposition modeling machine using the layer-wise deposition principle using ABS as a part material. Electroless copper deposition on ABS parts was performed using two different surface preparation processes, namely ABS parts prepared using chromic acid for etching and ABS parts prepared using a solution mixture of sulphuric acid and hydrogen peroxide (H2SO4/H2O2 for etching. After surface preparations using these routes, copper (Cu is deposited electrolessly using four different acidic baths. The acidic baths used are 5 wt% CuSO4 (copper sulfate with 15 wt% of individual acids, namely HF (hydrofluoric acid, H2SO4 (sulphuric acid, H3PO4 (phosphoric acid and CH3COOH (acetic acid. Cu deposition under different acidic baths used for both the routes is presented and compared based on their electrical performance, scanning electron microscopy (SEM and energy dispersive X-ray spectrometry (EDS. The result shows that chromic acid etched samples show better electrical performance and Cu deposition in comparison to samples etched via H2SO4/H2O2.

  1. Achieving Thin Films with Micro/Nano-Scale Controllable Morphology by Glancing Angle Deposition Technique

    Institute of Scientific and Technical Information of China (English)

    JIANG Shao-Ji; WANG Chao-Yi; TANG Ji-Jia; HU Lin-Xin

    2008-01-01

    @@ We demonstrate that thin films with micro/nanometre controllable morphology can be fabricated by the glancing angle deposition (GLAD) technique which is a physical vapour deposition technique.In this technique, there are parameters which determine the morphology of the thin films: the incident angle, ratio of the deposition rate with respect to the substrate rotation rate, nature of the material being deposited, etc.We fabricate the morphology of column, pillar, helices, zigzag and study the parameters which determine morphology by given some examples of SEM.

  2. Comparison of the properties of Pb thin films deposited on Nb substrate using thermal evaporation and pulsed laser deposition techniques

    Energy Technology Data Exchange (ETDEWEB)

    Perrone, A., E-mail: alessio.perrone@unisalento.it [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); INFN-Istituto Nazionale di Fisica Nucleare e Università del Salento, 73100 Lecce (Italy); Gontad, F. [INFN-Istituto Nazionale di Fisica Nucleare e Università del Salento, 73100 Lecce (Italy); Lorusso, A.; Di Giulio, M. [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Ferrario, M. [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, 00044 Frascati (Italy)

    2013-11-21

    Pb thin films were prepared at room temperature and in high vacuum by thermal evaporation and pulsed laser deposition techniques. Films deposited by both the techniques were investigated by scanning electron microscopy to determine their surface topology. The structure of the films was studied by X-ray diffraction in θ–2θ geometry. The photoelectron performances in terms of quantum efficiency were deduced by a high vacuum photodiode cell before and after laser cleaning procedures. Relatively high quantum efficiency (>10{sup −5}) was obtained for all the deposited films, comparable to that of corresponding bulk. Finally, film to substrate adhesion was also evaluated using the Daimler–Benz Rockwell-C adhesion test method. Weak and strong points of these two competitive techniques are illustrated and discussed. -- Highlights: •Comparison of Pb thin films deposited on Nb substrate by thermal evaporation and pulsed laser deposition (PLD). •Photoelectron performances of Pb thin films. •Good quality of adhesion strength of Pb films deposited by PLD.

  3. Comparison of the properties of Pb thin films deposited on Nb substrate using thermal evaporation and pulsed laser deposition techniques

    Science.gov (United States)

    Perrone, A.; Gontad, F.; Lorusso, A.; Di Giulio, M.; Broitman, E.; Ferrario, M.

    2013-11-01

    Pb thin films were prepared at room temperature and in high vacuum by thermal evaporation and pulsed laser deposition techniques. Films deposited by both the techniques were investigated by scanning electron microscopy to determine their surface topology. The structure of the films was studied by X-ray diffraction in θ-2θ geometry. The photoelectron performances in terms of quantum efficiency were deduced by a high vacuum photodiode cell before and after laser cleaning procedures. Relatively high quantum efficiency (>10-5) was obtained for all the deposited films, comparable to that of corresponding bulk. Finally, film to substrate adhesion was also evaluated using the Daimler-Benz Rockwell-C adhesion test method. Weak and strong points of these two competitive techniques are illustrated and discussed.

  4. Crystalline Indium Sulphide thin film by photo accelerated deposition technique

    Science.gov (United States)

    Dhanya, A. C.; Preetha, K. C.; Deepa, K.; Remadevi, T. L.

    2015-02-01

    Indium sulfide thin films deserve special attention because of its potential application as buffer layers in CIGS based solar cells. Highly transparent indium sulfide (InS) thin films were prepared using a novel method called photo accelerated chemical deposition (PCD). Ultraviolet source of 150 W was used to irradiate the solution. Compared to all other chemical methods, PCD scores its advantage for its low cost, flexible substrate and capable of large area of deposition. Reports on deposition of high quality InS thin films at room temperature are very rare in literature. The precursor solution was initially heated to 90°C for ten minutes and then deposition was carried out at room temperature for two hours. The appearance of the film changed from lemon yellow to bright yellow as the deposition time increased. The sample was characterized for its structural and optical properties. XRD profile showed the polycrystalline behavior of the film with mixed phases having crystallite size of 17 nm. The surface morphology of the films exhibited uniformly distributed honey comb like structures. The film appeared to be smooth and the value of extinction coefficient was negligible. Optical measurements showed that the film has more than 80% transmission in the visible region. The direct band gap energy was 2.47eV. This method is highly suitable for the synthesis of crystalline and transparent indium sulfide thin films and can be used for various photo voltaic applications.

  5. Characterization of GaN Buffer Layers and Its Epitaxial Layers Grown by MOCVD

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Low-pressure MOCVD has been used to investigate the properties of low-temperature buffer layer deposition conditions and their influence on the properties of high-temperature GaN epilayers grown subsequently. It is found that the surface morphology of the as-grown buffer layer after thermal annealing at 1030℃ and 1050℃ depends strongly on the thickness of the buffer layer. In particular when a thick buffer layer is used, large trapezoidal nuclei are formed after annealing.

  6. Surface Science in an MOCVD Environment: Arsenic on Vicinal Ge(100)

    Energy Technology Data Exchange (ETDEWEB)

    McMahon, W. E.; Olson, J. M.

    1998-11-01

    Scanning tunneling microscope (STM) images of arsine-exposed vicinal Ge(100) surfaces show that most As/Ge steps are reconstructed, and that a variety of different step structures exist. The entire family of reconstructed As/Ge steps can be divided into two types, which we have chosen to call ''single-row'' steps and ''double-row'' steps. In this paper we propose a model for a double-row step created by annealing a vicinal Ge(100) substrate under an arsine flux in a metal-organic chemical vapor deposition (MOCVD) chamber.

  7. Analysis and finite element simulation of electromagnetic heating in the nitride MOCVD reactor

    Institute of Scientific and Technical Information of China (English)

    Li Zhi-Ming; Hao Yue; Zhang Jin-Cheng; Xu Sheng-Rui; Ni JinYu

    2009-01-01

    Electromagnetic field distribution in the vertical metal organic chemical vapour deposition (MOCVD) reactor is simulated by using the finite element method (FEM). The effects of alternating current frequency, intensity, coil turn number and the distance between the coil turns on the distribution of the Joule heat are analysed separately, and their relations to the value of Joule heat are also investigated. The temperature distribution on the suseeptor is also obtained. It is observed that the results of the simulation are in good agreement with previous measurements.

  8. Photodegradative properties of TiO{sub 2} films prepared by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Justicia, I.; Ayllon, J.A.; Figueras, A. [Consejo Superior de Investigaciones Cientificas, Barcelona (Spain). Inst. de Ciencia de Materiales; Battiston, G.A.; Gerbasi, R. [Consejo Superior de Investigaciones Cientificas, Barcelona (Spain). Inst. de Ciencia de Materiales; Ist. di Chimica e Tecnologie Inorganiche e dei Materiali Avanzati del CNR, Padova (Italy)

    2001-08-01

    TiO{sub 2} is a well-known photocatalyst for the air-oxydation of organic compounds. This paper deals with the preparation of TiO{sub 2} layers by MOCVD. The photodegradation rate has been studied in the presence of aqueous suspensions (methylene blue) as a function of the film thickness, roughness and crystallite preferred orientation. These results are compared with aqueous suspensions of Degussa P-25 powders. Deposits obtained on fused quartz showed a higher photodegradation rate than those prepared on glass, while Degussa powders exhibited an intermediate value. (orig.)

  9. Thermogravimetric evaluation of the suitability of precursors for MOCVD

    Science.gov (United States)

    Kunte, G. V.; Shivashankar, S. A.; Umarji, A. M.

    2008-02-01

    A method based on the Langmuir equation for the estimation of vapour pressure and enthalpy of sublimation of subliming compounds is described. The variable temperature thermogravimetric/differential thermogravimetric (TG/DTG) curve of benzoic acid is used to arrive at the instrument parameters. Employing these parameters, the vapour pressure-temperature curves are derived for salicylic acid and camphor from their TG/DTG curves. The values match well with vapour pressure data in the literature, obtained by effusion methods. By employing the Clausius-Clapeyron equation, the enthalpy of sublimation could be calculated. Extending the method further, two precursors for metal-organic chemical vapour deposition (MOCVD) of titanium oxide bis-isopropyl bis tert-butyl 2-oxobutanoato titanium, Ti(OiPr)2(tbob)2, and bis-oxo-bis-tertbutyl 2-oxobutanoato titanium, [TiO(tbob)2]2, have been evaluated. The complex Ti(OiPr)2(tbob)2 is found to be a more suitable precursor. This approach can be helpful in quickly screening for the suitability of a compound as a CVD precursor.

  10. Corrosion resistant coatings (Al2O3) produced by metal organic chemical vapour deposition using aluminium-tri-sec-butoxide

    NARCIS (Netherlands)

    Haanappel, V.A.C.; Corbach, van H.D.; Fransen, T.; Gellings, P.J.

    1993-01-01

    The metal organic chemical vapour deposition (MOCVD) of amorphous alumina films on steel was performed in nitrogen at atmospheric pressure. This MOCVD process is based on the thermal decomposition of aluminium-tri-sec-butoxide (ATSB). The effect of the deposition temperature (within the range 290–42

  11. Differential Deposition Technique for Figure Corrections in Grazing Incidence X-ray Optics

    Science.gov (United States)

    Kilaru, Kiranmayee; Ramsey, Brian D.; Gubarev, Mikhail

    2009-01-01

    A differential deposition technique is being developed to correct the low- and mid-spatial-frequency deviations in the axial figure profile of Wolter type grazing incidence X-ray optics. These deviations arise due to various factors in the fabrication process and they degrade the performance of the optics by limiting the achievable angular resolution. In the differential deposition technique, material of varying thickness is selectively deposited along the length of the optic to minimize these deviations, thereby improving the overall figure. High resolution focusing optics being developed at MSFC for small animal radionuclide imaging are being coated to test the differential deposition technique. The required spatial resolution for these optics is 100 m. This base resolution is achievable with the regular electroform-nickel-replication fabrication technique used at MSFC. However, by improving the figure quality of the optics through differential deposition, we aim at significantly improving the resolution beyond this value.

  12. Optoelectronic and structural properties of InGaN nanostructures grown by plasma-assisted MOCVD

    Science.gov (United States)

    Seidlitz, Daniel; Senevirathna, M. K. I.; Abate, Y.; Hoffmann, A.; Dietz, N.

    2015-09-01

    This paper presents optoelectronic and structural layer properties of InN and InGaN epilayers grown on sapphire templates by Migration-Enhanced Plasma Assisted Metal Organic Chemical Vapor Deposition (MEPA-MOCVD). Real-time characterization techniques have been applied during the growth process to gain insight of the plasma-assisted decomposition of the nitrogen precursor and associated growth surface processes. Analyzed Plasma Emission Spectroscopy (PES) and UV Absorption Spectroscopy (UVAS) provide detection and concentrations of plasma generated active species (N*/NH*/NHx*). Various precursors have been used to assess the nitrogen-active fragments that are directed from the hollow cathode plasma tube to the growth surface. The in-situ diagnostics results are supplemented with ex-situ materials structures investigation results of nanoscale structures using Scanning Near-field Optical Microscopy (SNOM). The structural properties have been analyzed by Raman spectroscopy and Fourier transform infrared (FTIR) reflectance. The Optoelectronic and optical properties were extracted by modeling the FTIR reflectance (e.g. free carrier concentration, high frequency dielectric constant, mobility) and optical absorption spectroscopy. The correlation and comparison between the in-situ metrology results with the ex-situ nano-structural and optoelectronic layer properties provides insides into the growth mechanism on how plasma-activated nitrogen-fragments can be utilized as nitrogen precursor for group III-nitride growth. The here assessed growth process parameter focus on the temporal precursor exposure of the growth surface, the reactor pressure, substrate temperature and their effects of the properties of the InN and InGaN epilayers.

  13. Bismuth coatings deposited by the pulsed dc sputtering technique

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, M. F.; Olaya, J. J.; Alfonso, J. E., E-mail: jealfonsoo@unal.edu.co [Universidad Nacional de Colombia, Departamento de Fisica, Grupo de Ciencia de Materiales y Superficies, Carrera 45 No. 26-85, Edif. Uriel Gutierrez, Bogota D. C. (Colombia)

    2013-08-01

    In this work we present the results obtained from the deposition of nano-structured bismuth coatings through Dc pulsed unbalanced magnetron sputtering. The coatings were grown on two substrates: silicon and AISI steel 316 L. The microstructure of the Bi coatings grown on silicon and the corrosion resistance of the Bi coatings grown on AISI steel were evaluated. The microstructure was evaluated by X-ray diffraction and the corrosion resistance was characterized by means of polarization potentiodynamic and electrochemical impedance spectroscopy. Finally the morphology of the coatings was evaluated through scanning electronic microscopy. The X-ray diffraction analysis indicates that the coatings are polycrystalline; the corrosion resistance tests indicate that the films with better corrosion resistance were deposited at 40 khz. Scanning electron microscopy micrographs show that the coatings are grown as granular form. (Author)

  14. Controlling nucleation of monolayer WSe2 during metal-organic chemical vapor deposition growth

    Science.gov (United States)

    Eichfeld, Sarah M.; Oliveros Colon, Víctor; Nie, Yifan; Cho, Kyeongjae; Robinson, Joshua A.

    2016-06-01

    Tungsten diselenide (WSe2) is a semiconducting, two-dimensional (2D) material that has gained interest in the device community recently due to its electronic properties. The synthesis of atomically thin WSe2, however, is still in its infancy. In this work we elucidate the requirements for large selenium/tungsten precursor ratios and explain the effect of nucleation temperature on the synthesis of WSe2 via metal-organic chemical vapor deposition (MOCVD). The introduction of a nucleation-step prior to growth demonstrates that increasing nucleation temperature leads to a transition from a Volmer-Weber to Frank-van der Merwe growth mode. Additionally, the nucleation step prior to growth leads to an improvement of WSe2 layer coverage on the substrate. Finally, we note that the development of this two-step technique may allow for improved control and quality of 2D layers grown via CVD and MOCVD processes.

  15. A new pulsed laser deposition technique: scanning multi-component pulsed laser deposition method.

    Science.gov (United States)

    Fischer, D; de la Fuente, G F; Jansen, M

    2012-04-01

    The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 °C.

  16. Optical and Structural Properties of Microcrystalline GaN on an Amorphous Substrate Prepared by a Combination of Molecular Beam Epitaxy and Metal-Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Min, Jung-Wook; Hwang, Hyeong-Yong; Kang, Eun-Kyu; Park, Kwangwook; Kim, Ci-Hyun; Lee, Dong-Seon; Jho, Young-Dahl; Bae, Si-Young; Lee, Yong-Tak

    2016-05-01

    Microscale platelet-shaped GaN grains were grown on amorphous substrates by a combined epitaxial growth method of molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). First, MBE GaN was grown on an amorphous substrate as a pre-orienting layer and its structural properties were investigated. Second, MOCVD grown GaN samples using the different growth techniques of planar and selective area growth (SAG) were comparatively investigated by transmission electron microscopy (TEM), cathodoluminescence (CL), and photoluminescence (PL). In MOCVD planar GaN, strong bound exciton peaks dominated despite the high density of the threading dislocations (TDs). In MOCVD SAG GaN, on the other hand, TDs were clearly reduced with bending, but basal stacking fault (BSF) PL peaks were observed at 3.42 eV. The combined epitaxial method not only provides a deep understanding of the growth behavior but also suggests an alternative approach for the growth of GaN on amorphous substances.

  17. Effect of Different Catalyst Deposition Technique on Aligned Multiwalled Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Mohamed Shuaib Mohamed Saheed

    2014-01-01

    Full Text Available The paper reported the investigation of the substrate preparation technique involving deposition of iron catalyst by electron beam evaporation and ferrocene vaporization in order to produce vertically aligned multiwalled carbon nanotubes array needed for fabrication of tailored devices. Prior to the growth at 700°C in ethylene, silicon dioxide coated silicon substrate was prepared by depositing alumina followed by iron using two different methods as described earlier. Characterization analysis revealed that aligned multiwalled carbon nanotubes array of 107.9 µm thickness grown by thermal chemical vapor deposition technique can only be achieved for the sample with iron deposited using ferrocene vaporization. The thick layer of partially oxidized iron film can prevent the deactivation of catalyst and thus is able to sustain the growth. It also increases the rate of permeation of the hydrocarbon gas into the catalyst particles and prevents agglomeration at the growth temperature. Combination of alumina-iron layer provides an efficient growth of high density multiwalled carbon nanotubes array with the steady growth rate of 3.6 µm per minute for the first 12 minutes and dropped by half after 40 minutes. Thicker and uniform iron catalyst film obtained from ferrocene vaporization is attributed to the multidirectional deposition of particles in the gaseous form.

  18. Growth and characterization of AP-MOCVD iron doped titanium dioxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gauthier, V.; Bourgeois, S. [Bourgogne Univ., Dijon (France). Lab. de Recherches sur la Reactivite des Solides; Sibillot, P.; Maglione, M.; Sacilotti, M. [Laboratoire de Physique de l`Universite de Bourgogne, UPRESA 5027 CNRS, BP 400, F 21011, Dijon Cedex (France)

    1999-02-26

    Atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD) was used to prepare iron doped titanium dioxide thin films. Thin films, between 40 and 150 nm thick, were deposited on Si, SiO{sub 2} and Al{sub 2}O{sub 3} substrates using titanium tetra isopropoxide and ferrocene as metal organic precursors. TiO{sub 2} iron doping was achieved in the range of 1-4 at.%. The film morphology and thickness, polycrystalline texture and doping content were studied using respectively scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of growth temperature, deposition time, substrate type and dopant partial pressure were studied. Electrical characterizations of the films were also performed. (orig.) 30 refs.

  19. Investigation of the optimal annealing temperature for the enhanced thermoelectric properties of MOCVD-grown ZnO films

    Science.gov (United States)

    Mahmood, K.; Ali, A.; Arshad, M. I.; Ajaz un Nabi, M.; Amin, N.; Faraz Murtaza, S.; Rabia, S.; Azhar Khan, M.

    2017-04-01

    In this study, we demonstrate the optimization of the annealing temperature for enhanced thermoelectric properties of ZnO. Thin films of ZnO are grown on a sapphire substrate using the metal organic chemical Vapor Deposition (MOCVD) technique. The grown films are annealed in an oxygen environment at 600-1000°C, with a step of 100°C for one hour. Seebeck measurements at room temperature revealed that the Seebeck coefficient of the sample that was not annealed was 152 μV/K, having a carrier concentration of N D 1.46 × 1018 cm-3. The Seebeck coefficient of the annealed films increased from 212 to 415 μV/K up to 900°C and then decreased at 1000°C. The power factor is calculated and found to have an increasing trend with the annealing temperature. This observation is explained by the theory of Johnson and Lark-Horovitz that thermoelectric properties are enhanced by improving the structure of ZnO thin films. The Hall measurements and PL data strongly justify the proposed argument.

  20. Optical and X-ray studies of MOCVD-grown InGaN epilayers with low indium concentration

    Science.gov (United States)

    Park, Gil; Hwang, Seon-Ju; Shee, Sang-Kee; Sugahara, Tomoya; Lam, Jack; Gainer, Gordon; Song, Jin-Joo; Sakai, S.

    2001-03-01

    Optical and X-ray studies of MOCVD-grown InGaN epilayers with low indium concentration G. H. Park, S. J. Hwang, S. K. Shee, T. Sugahara, J. B. Lam, G. H. Gainer and J. J. Song, Center for Laser and Photonics Research and Department of Physics, Oklahoma State University, Stillwater, OK 74078, USA; S. Sakai, Electrical and Electronic Department, University of Tokushima, Tokushima, Japan. In_xGa_1-xN epilayers with low indium concentration (x < 5%) were grown by low pressure metalorganic chemical vapor deposition on (0001) sapphire. These samples were characterized by optical techniques and high-resolution X-ray diffraction. Photoluminescence (PL) and stimulated emission (SE) were measured. The PL intensity of the InGaN epilayers is much higher than that of GaN, even for very small indium concentrations. The PL peaks show the S-shaped temperature dependence, and the stimulated emission threshold is also temperature dependent. The PL and SE also vary greatly with indium concentration. These observations indicate that the way indium incorporates into GaN varies with In concentration. The structural characteristics will be discussed in light of their possible relation to the optical characteristics. This work is supported by ONR, BMDO, and AFOSR.

  1. Influence of vacuum-annealing on the diffusion barrier properties of MOCVD TiN for Cu metallization

    CERN Document Server

    Lee, J G; Lee, E G; Lee, J Y; Kim, K B; Lee, J M

    1999-01-01

    We have investigated the effects of vacuum annealing of TDMAT-sourced TiN on the film qualities, as well as on the properties of the barrier against Cu diffusion. Vacuum annealing at 550 .deg. C to 1000 .deg. C achieved a significant densification of the TiN films with the interaction of Ti in the TiN prepared by metalorganic chemical-vapor deposition (MOCVD TiN) and Si at the interface. This interaction produced a stable interface between TiN and Si. In addition, annealing of the films at 1000 .deg. C transformed the amorphous TiN(C) films into crystalline TiNC solid solutions. About 10 at % silicon diffused into the TiN film from the Si substrate, and oxygen in the as-deposited TiN film was expelled to the surface after annealing at 1000 .deg. C. The barrier failure mechanism of MOCVD TiN in Cu metallization included the indiffusion of Cu and the accompanying outdiffusion of silicon through the barrier layer. The annealing of MOCVD TiN in vacuum improved the diffusion barrier properties, partly due to the d...

  2. The Development of a Differential Deposition Technique for Figure Correction in Grazing Incidence Optics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose the development of a physical-vapor-deposition coating technique to correct residual figure errors in grazing-incidence optics. The process involves...

  3. Temperature coefficients and radiation induced DLTS spectra of MOCVD grown n(+)p InP solar cells

    Science.gov (United States)

    Walters, Robert J.; Statler, Richard L.; Summers, Geoffrey P.

    1991-01-01

    The effects of temperature and radiation on n(+)p InP solar cells and mesa diodes grown by metallorganic chemical vapor deposition (MOCVD) were studied. It was shown that MOCVD is capable of consistently producing good quality InP solar cells with Eff greater than 19 percent which display excellent radiation resistance due to minority carrier injection and thermal annealing. It was also shown that universal predictions of InP device performance based on measurements of a small group of test samples can be expected to be quite accurate, and that the degradation of an InP device due to any incident particle spectrum should be predictable from a measurement following a single low energy proton irradiation.

  4. Preparation of platinum-iridium nanoparticles on titania nanotubes by MOCVD and their catalytic evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Colindres, S. Capula [National Polytechnic Institute, Department of Metallurgical Eng., Mexico 07300 D.F., AP 75-874 (Mexico); Garcia, J.R. Vargas, E-mail: rvargasga@ipn.m [National Polytechnic Institute, Department of Metallurgical Eng., Mexico 07300 D.F., AP 75-874 (Mexico); Antonio, J.A. Toledo; Chavez, C. Angeles [Petroleum Mexican Institute, Eje Central Lazaro Cardenas No.152, Mexico 07730 D.F. (Mexico)

    2009-08-26

    Pt based catalysts are commonly used in several industrial processes involving hydrogenation and dehydrogenation reactions. New deposition methods as well as support materials are being investigated to generate new catalysts with superior catalytic activity. In this work, platinum-iridium (Pt-Ir) nanoparticles of about 5 nm in size were supported on titania (TiO{sub 2}) nanotubes by metal organic chemical vapor deposition (MOCVD). The TiO{sub 2} nanotubes were prepared by an alkali hydrothermal method using sodium hydroxide solution at 100 deg. C, during 64.8 ks. Pt-Ir nanoparticles were obtained by controlling the MOCVD conditions at 400 deg. C and 66.6 kPa. Textural properties and particle size were investigated by nitrogen physisorption (BET method), X-ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy. Catalytic activity was measured in cyclohexene disproportion as the test molecule for hydrogenation/dehydrogenation reactions. The TiO{sub 2} nanotubes exhibit a considerable high surface area of about 425,000 m{sup 2}/kg, however, after calcination at 400 deg. C their nanotubular morphology was partially transformed. In spite of this change, the 5 nm Pt-Ir nanoparticles supported on TiO{sub 2} nanotubes were more active in the cyclohexene disproportion reaction than conventional Pt-Ir/alumina catalysts in the whole range of temperatures investigated (50-250 deg. C). Hydrogenation reactions (high selectivity to cyclohexane) predominate at temperatures below 150 deg. C.

  5. Nanophotonic Fabrication Self-Assembly and Deposition Techniques

    CERN Document Server

    Yatsui, Takashi

    2012-01-01

    Nanophotonics, a novel optical technology, utilizes the local interaction between nanometric particles via optical near fields. The optical near fields are the elementary surface excitations on nanometric particles, i.e. dressed photons that carry material energy. Of the variety of qualitative innovations in optical technology realized by nanophotonics, this books focuses on fabrication. To fabricate nano-scale photonic devices with nanometer-scale controllability in size and position, we developed a self-assembly method for size- and position-controlled ultra-long nanodot chains using a novel effect of near-field optical desorption. A novel deposition and etching scheme under nonresonant conditions is also demonstrated and its origin is reviewed.

  6. Note: Large area deposition of Rh single and Rh/W/Cu multilayer thin films on stainless steel substrate by pulsed laser deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Mostako, A. T. T.; Khare, Alika, E-mail: alika@iitg.ernet.in [Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039 (India)

    2014-04-15

    Mirror like thin films of single layer Rh and multilayer Rh/W/Cu are deposited on highly polished 50 mm diameter stainless steel substrate by Pulsed Laser Deposition (PLD) technique for first mirror application in fusion reactors. For this, the conventional PLD technique has been modified by incorporating substrate rastering stage for large area deposition via PLD. Process optimization to achieve uniformity of deposition as estimated from fringe visibility and thickness is also discussed.

  7. Comparison of hafnium silicate thin films on silicon (1 0 0) deposited using thermal and plasma enhanced metal organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Rangarajan, Vishwanathan; Bhandari, Harish; Klein, Tonya M

    2002-11-01

    Hafnium silicate thin films were deposited by metal organic chemical vapor deposition (MOCVD) on Si at 400 deg. C using hafnium (IV) t-butoxide. Films annealed in O{sub 2} were compared to as-deposited films using X-ray photoelectron spectroscopy and X-ray diffraction. Hafnium silicate films were deposited by both thermal and plasma enhanced MOCVD using 2% SiH{sub 4} in He as the Si precursor. An O{sub 2} plasma increased Si content to as much as {approx}26 at.% Si. Both thermal and plasma deposited Hf silicates are amorphous as deposited, however, thermal films exhibit crystallinity after anneal. Surface roughness as measured by atomic force microscopy was found to be 1.1 and 5.1 nm for MOCVD hafnium silicate and plasma enhanced MOCVD hafnium silicate, respectively.

  8. A hybrid sequential deposition fabrication technique for micro fuel cells

    Science.gov (United States)

    Stanley, Kevin G.; Czyzewska, Eva K.; Vanderhoek, Tom P. K.; Fan, Lilian L. Y.; Abel, Keith A.; Wu, Q. M. Jonathan; Parameswaran, M. Ash

    2005-10-01

    Micro fuel cell systems have elicited significant interest due to their promise for instantly rechargeable, longer duration and portable power. Most micro fuel cell systems are either built as miniaturized plate-and-frame or silicon-based microelectromechanical systems (MEMS). Plate-and-frame systems are difficult to fabricate smaller than 20 cm3. Existing micro fuel cell designs cannot meet the cost, scale and power requirements of some portable power markets. Traditional MEMS scaling advantages do not apply to fuel cells because the minimum area for the fuel cell is fixed by the catalyst area required for a given power output, and minimum volume set by mass transport limitations. We have developed a new hybrid technique that borrows from both micro and macro machining techniques to create fuel cells in the 1-20 cm3 range, suitable for cell phones, PDAs and smaller devices.

  9. Influence of growth pressure of a GaN buffer layer on the properties of MOCVD GaN

    Institute of Scientific and Technical Information of China (English)

    CHEN; Jun(陈俊); ZHANG; Shuming(张书明); ZHANG; Baoshun(张宝顺); ZHU; Jianjun(朱建军); FENG; Gan(冯淦); DUAN; Lihong(段俐宏); WANG; Yutian(王玉田); YANG; Hui(杨辉); ZHENG; Wenchen(郑文琛)

    2003-01-01

    The influence of growth pressure of GaN buffer layer on the properties of MOCVD GaN on α-Al2O3 has been investigated with the aid of a home-made in situ laser reflectometry measurement system. The results obtained with in situ measurements and scanning electron microscope show that with the increase in deposition pressure of buffer layer, the nuclei increase in size, which roughens the surface, and delays the coalescence of GaN nuclei. The optical and crystalline quality of GaN epilayer was improved when buffer layer was deposited at high pressure.

  10. Structural and photocatalytic properties of TiO2 films fabricated on silicon substrates by MOCVD method

    Institute of Scientific and Technical Information of China (English)

    YANG Jia-long; LI Ying; WANG Fu; ZUO Liang; Gu-Chul Yi; Wong Yong Choi

    2005-01-01

    Silicon(111) and Silicon(100) were employed for fabrication of TiO2 films by metal organic chemical vapor deposition(MOCVD).Titanium(Ⅳ) isopropoxide(Ti[O(C3H7)4]) was used as a precursor. The as-deposited TiO2 films were characterized with FE-SEM, XRD and AFM. The photocatalytic properties were investigated by decomposition of aqueous Orange Ⅱ. And UV-VIS photospectrometer was used for checking the absorption characteristics and photocatalytic degradation activity. The crystalline and structural properties of TiO2 film had crucial influences on the photodegradation efficiency. For MOCVD in-situ deposited films on Si substrates, the photoactivities varied following a shape of "M": at lower(350℃), middle(500℃) and higher(800℃) temperature of deposition, relative lower photodegradation activities were observed. At 400℃ and 700℃ of deposition, relative higher efficiencies of degradation were obtained, because one predominant crystallite orientation could be obtained as deposition at the temperature of two levels, especially a single anatase crystalline TiO2 film could be obtained at 700℃.

  11. A review of basic phenomena and techniques for sputter-deposition of high temperature superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Auciello, O. (Microelectronics Center of North Carolina, Research Triangle Park, NC (USA) North Carolina State Univ., Raleigh, NC (USA). Dept. of Materials Science and Engineering); Ameen, M.S.; Kingon, A.I.; Lichtenwalner, D.J. (North Carolina State Univ., Raleigh, NC (USA). Dept. of Materials Science and Engineering); Krauss, A.R. (Argonne National Lab., IL (USA))

    1990-01-01

    The processes involved in plasma and ion beam sputter-deposition of high temperature superconducting thin films are critically reviewed. Recent advances in the development of these techniques are discussed in relation to basic physical phenomena, specific to each technique, which must be understood before high quality films can be produced. Control of film composition is a major issue in sputter-deposition of multicomponent materials. Low temperature processing of films is a common goal for each technique, particularly in relation to integrating high temperature superconducting films with the current microelectronics technology. It has been understood for some time that for Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} deposition, the most intensely studied high-{Tc} compound, incorporation of sufficient oxygen into the film during deposition is necessary to produce as-deposited superconducting films at relatively substrate temperatures. Recent results have shown that with the use of suitable buffer layers, high quality Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} sputtered films can be obtained on Si substrates without the need for post-deposition anneal processing. This review is mainly focussed on issues related to sputter-deposition of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} thin films, although representative results concerning the bismuth and thallium based compounds are included. 143 refs., 11 figs.

  12. Thermodynamic modeling to analyse composition of carbonaceous coatings of MnO and other oxides of manganese grown by MOCVD

    Indian Academy of Sciences (India)

    Sukanya Dhar; A Varade; S A Shivashankar

    2011-02-01

    Equilibrium thermodynamic analysis has been applied to the low-pressure MOCVD process using manganese acetylacetonate as the precursor. ``CVD phase stability diagrams” have been constructed separately for the processes carried out in argon and oxygen ambient, depicting the compositions of the resulting films as functions of CVD parameters. For the process conduced in argon ambient, the analysis predicts the simultaneous deposition of MnO and elemental carbon in 1:3 molar proportion, over a range of temperatures. The analysis predicts also that, if CVD is carried out in oxygen ambient, even a very low flow of oxygen leads to the complete absence of carbon in the film deposited oxygen, with greater oxygen flow resulting in the simultaneous deposition of two different manganese oxides under certain conditions. The results of thermodynamic modeling have been verified quantitatively for lowpressure CVD conducted in argon ambient. Indeed, the large excess of carbon in the deposit is found to constitute a MnO/C nanocomposite, the associated cauliflower-like morphology making it a promising candidate for electrode material in supercapacitors. CVD carried out in oxygen flow, under specific conditions, leads to the deposition of more than one manganese oxide, as expected from thermodynamic analysis (and forming an oxide–oxide nanocomposite). These results together demonstrate that thermodynamic analysis of the MOCVD process can be employed to synthesize thin films in a predictive manner, thus avoiding the inefficient trial-and-error method usually associated with MOCVD process development. The prospect of developing thin films of novel compositions and characteristics in a predictive manner, through the appropriate choice of CVD precursors and process conditions, emerges from the present work.

  13. Three-Step Growth Optimization of A1N Epilayers by MOCVD

    Institute of Scientific and Technical Information of China (English)

    PENG Ming-Zeng; ZHOU Jun-Ming; GUO Li-Wei; ZHANG Jie; YU Nai-Sen; ZHU Xue-Liang; YAN Jian-Feng; GE Bin-Hui; JIA Hai-Qiang; CHEN Hong

    2008-01-01

    A three-step growth process is developed for depositing high-quality aluminium-nitride (AIN) epilayers on (001) sapphire by low pressure metalorganic chemical vapour deposition (LP-MOCVD). We adopt a low temperature (LT) AIN nucleation layer (NL), and two high temperature (HT) AIN layers with different Ⅴ/Ⅲ ratios. Our results reveal that the optimal NL temperature is 840-880℃, and there exists a proper growth switching from low to high Ⅴ/Ⅲ ratio for further reducing threading dislocations (TDs). The screw-type TD density of the optimized AIN film is just 7.86×106 cm-2, about three orders lower than its edge-type one of 2×109 cm-2 estimated by high-resolution x-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (TEM).

  14. Growth of AlN nanostructure on GaN using MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Loganathan, R.; Ramesh, R.; Jayasakthi, M.; Prabakaran, K.; Kuppulingam, B.; Sankaranarayanan, M.; Balaji, M.; Arivazhagan, P.; Singh, Subra; Baskar, K., E-mail: drbaskar2009@gmail.com [Crystal Growth Centre, Anna University, Chennai-600025 (India)

    2015-06-24

    Aluminum nitride (AlN) nanowalls have been epitaxially grown on dislocation assisted GaN/Al{sub 2}O{sub 3} template by metal organic chemical vapor deposition (MOCVD) without any help of metal catalysts. A large number of nanowalls with thicknesses of 1.5-2.0 µm and height 400 nm have been deposited. The AlN nanowalls were found to have a preferred c-axis oriented with a hexagonal crystal structure. The AlN nanowalls and GaN/Al{sub 2}O{sub 3} template have been characterize at room temperature photoluminescence (PL) and high resolution X-ray diffraction (HRXRD)

  15. Effects of CdTe growth conditions and techniques on the efficiency limiting defects and mechanisms in CdTe solar cells

    Science.gov (United States)

    Rohatgi, A.; Chou, H. C.; Jokerst, N. M.; Thomas, E. W.; Ferekides, C.; Kamra, S.; Feng, Z. C.; Dugan, K. M.

    1996-01-01

    CdTe solar cells were fabricated by depositing CdTe films on CdS/SnO2/glass substrates using close-spaced sublimation (CSS) and metalorganic chemical vapor deposition (MOCVD). Te/Cd mole ratio was varied in the range of 0.02 to 6 in the MOCVD growth ambient in an attempt to vary the native defect concentration. Polycrystalline CdTe layers grown by MOCVD and CSS both showed average grain size of about 2 μm. However, the CdTe films grown by CSS were found to be less faceted and more dense compared to the CdTe grown by MOCVD. CdTe growth techniques and conditions had a significant impact on the electrical characteristics of the cells. The CdTe solar cells grown by MOCVD in the Te-rich growth condition and by the CSS technique gave high cell efficiencies of 11.5% and 12.4%, respectively, compared to 6.6% efficient MOCVD cells grown in Cd-rich conditions. This large difference in efficiency is explained on the basis of (a) XRD measurements which showed a higher degree of atomic interdiffusion at the CdS/CdTe interface in high performance devices, (b) Raman measurements which endorsed more uniform and preferred grain orientation by revealing a sharp CdTe TO mode in the high efficiency cells, and (c) carrier transport mechanism which switched from tunneling/interface recombination to depletion region recombination in the high efficiency cells. In this study, Cu/Au layers were evaporated on CdTe for the back contact. Lower efficiency of the Te-rich MOCVD cells, compared to the CSS cells, was attributed to contact related additional loss mechanisms, such as Cd pile-up near Cu/CdTe interface which can give rise to Cd-vacancy defects in the bulk, and higher Cu concentration in the CdTe layer which can cause shunts in the device. Finally, SIMS measurements on the CdTe films of different crystallinity and grain size confirmed that grain boundaries are the main conduits for Cu migration into the CdTe film. Thus larger CdTe grain size or lower grain boundary area per unit volume

  16. Kinetic Study of MOCVD Ⅲ-Ⅴ Quaternary Antimonides

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The kinetics of MOCVD GaInAsSb and AlGaAsSb was studied by the growth rate as a function of growth temperature and partial pressure of Ⅲ and Ⅴ MO species. The diffusion theory was used to explain the mass transport processes in MOCVD Ⅲ-Ⅴ quaternary antimonides. On the basis of the discussion about their growth kinetics and epilayer properties, the good quality multi-epilayers of these two quaternary antimonides and their photodetectors and arrays with wavelength of 1.8~2.3 μm and detectivities of D*>109 cm Hz1/2 W-1 were obtained.

  17. Process in manufacturing high efficiency AlGaAs/GaAs solar cells by MO-CVD

    Science.gov (United States)

    Yeh, Y. C. M.; Chang, K. I.; Tandon, J.

    1984-01-01

    Manufacturing technology for mass producing high efficiency GaAs solar cells is discussed. A progress using a high throughput MO-CVD reactor to produce high efficiency GaAs solar cells is discussed. Thickness and doping concentration uniformity of metal oxide chemical vapor deposition (MO-CVD) GaAs and AlGaAs layer growth are discussed. In addition, new tooling designs are given which increase the throughput of solar cell processing. To date, 2cm x 2cm AlGaAs/GaAs solar cells with efficiency up to 16.5% were produced. In order to meet throughput goals for mass producing GaAs solar cells, a large MO-CVD system (Cambridge Instrument Model MR-200) with a susceptor which was initially capable of processing 20 wafers (up to 75 mm diameter) during a single growth run was installed. In the MR-200, the sequencing of the gases and the heating power are controlled by a microprocessor-based programmable control console. Hence, operator errors can be reduced, leading to a more reproducible production sequence.

  18. DLTS and PL study of defects in InAlAs/InP heterojunctions grown by metal organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Bouzgarrou, S. [Laboratoire de Microelectronique et Instrumentation (UR 03/13-04), Faculte des Sciences de Monastir, Avenue de l' Environnement, 5000 Monastir (Tunisia); Ben Salem, M.M. [Laboratoire de Physique des Semiconducteurs et des Composants Electroniques (LA-MA-06), Faculte des Sciences de Monastir, Avenue de l' Environnement, 5000 Monastir (Tunisia)]. E-mail: mongi.bensalem@fsm.rnu.tn; Hassen, F. [Laboratoire de Physique des Semiconducteurs et des Composants Electroniques (LA-MA-06), Faculte des Sciences de Monastir, Avenue de l' Environnement, 5000 Monastir (Tunisia); Kalboussi, A. [Laboratoire de Microelectronique et Instrumentation (UR 03/13-04), Faculte des Sciences de Monastir, Avenue de l' Environnement, 5000 Monastir (Tunisia); Souifi, A. [Laboratoire de Physique de la Matiere (UMR CNRS 5511), INSA de Lyon, Ba-hat t. 502, 20 Avenue Albert Einstein, 69621 Villeurbanne Cedex (France)

    2005-01-25

    Deep level transient spectroscopy (DLTS) and photoluminescence (PL) techniques are used to study the defects present in InAlAs/InP layers grown by metal organic chemical vapor deposition (MOCVD). In DLTS technique, different reverse bias and different heights and widths of the filling pulse are applied to the samples; the measurements have revealed the presence of four defects labelled A-D, which are found to be in a good agreement with the results of the photoluminescence (PL) technique. In fact, a detailed study of the defect (D) by photoluminescence (PL) technique has led to the same results as those determined by DLTS.

  19. Characterisation of Pb thin films prepared by the nanosecond pulsed laser deposition technique for photocathode application

    OpenAIRE

    Lorusso, Antonella; Gontad, F.; Broitman, Esteban; Chiadroni, E.; Perrone, Walter

    2015-01-01

    Pb thin films were prepared by the nanosecond pulsed laser deposition technique on Si (100) and polycrystalline Nb substrates for photocathode application. As the photoemission performances of a cathode are strongly affected by its surface characteristics, the Pb films were grown at different substrate temperatures with the aim of modifying the morphology and structure of thin films. An evident morphological modification in the deposited films with the formation of spherical grains at higher ...

  20. A novel electron beam evaporation technique for the deposition of superconducting thin films

    Science.gov (United States)

    Krishna, M. G.; Muralidhar, G. K.; Rao, K. N.; Rao, G. M.; Mohan, S.

    1991-05-01

    Superconducting thin films of BiSrCaCuO have been deposited using a novel electron beam evaporation technique. In this technique the crucible has a groove around its circumference and rotates continuously during deposition. The source material is loaded in the form of pellets of the composite. Both oxides as well as flourides have been used in the starting material and a comparison of the film properties has been made. The best film was obtained on a MgO(100) substrate with a Tc onset at 85 K and Tc zero at 77 K using calcium flouride in the source material.

  1. PZT thin film deposition techniques, properties and its application in ultrasonic MEMS sensors: a review

    Science.gov (United States)

    Shilpa, G. D.; Sreelakshmi, K.; Ananthaprasad, M. G.

    2016-09-01

    This paper describes an overview of the state of art in PbZrxTi1-xO3 (PZT)ferroelectric thin films and its applications in Micro Electro Mechanical Systems (MEMS). First, the deposition techniques and then the important properties of PZT films such as surface morphology polarization and ferroelectric properties are reviewed. Two major deposition techniques such as sol-gel and Magnetron sputtering are given and compared for the film surface morphology and ferroelectric properties. Finally, the application of PZT thin film in MEMS ultrasonic sensors is discussed.

  2. Composition and microstructure of beryllium carbide films prepared by thermal MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    He, Yu-dan; Luo, Jiang-shan; Li, Jia; Meng, Ling-biao; Luo, Bing-chi; Zhang, Ji-qiang; Zeng, Yong; Wu, Wei-dong, E-mail: wuweidongding@163.com

    2016-02-15

    Highlights: • Non-columnar-crystal Be{sub 2}C films were firstly prepared by thermal MOCVD. • Beryllium carbide was always the dominant phase in the films. • α-Be and carbon existed in films deposited below and beyond 400 °C, respectively. • Morphology evolved with temperatures and no columnar grains were characterized. • The preferred substrate temperature for depositing high quality Be{sub 2}C films was 400 °C. - Abstract: Beryllium carbide films without columnar-crystal microstructures were prepared on the Si (1 0 0) substrate by thermal metal organic chemical vapor deposition using diethylberyllium as precursor. The influence of the substrate temperature on composition and microstructure of beryllium carbide films was systematically studied. Crystalline beryllium carbide is always the dominant phase according to XRD analysis. Meanwhile, a small amount of α-Be phase exists in films when the substrate temperature is below 400 °C, and hydrocarbon or amorphous carbon exists when the temperature is beyond 400 °C. Surfaces morphology shows transition from domes to cylinders, to humps, and to tetraquetrous crystalline needles with the increase of substrate temperature. No columnar grains are characterized throughout the thickness as revealed from the cross-section views. The average densities of these films are determined to be 2.04–2.17 g/cm{sup 3}. The findings indicate the substrate temperature has great influences on the composition and microstructure of the Be{sub 2}C films grown by thermal MOCVD.

  3. Handbook of thin film deposition processes and techniques principles, methods, equipment and applications

    CERN Document Server

    Seshan, Krishna

    2002-01-01

    New second edition of the popular book on deposition (first edition by Klaus Schruegraf) for engineers, technicians, and plant personnel in the semiconductor and related industries. This book traces the technology behind the spectacular growth in the silicon semiconductor industry and the continued trend in miniaturization over the last 20 years. This growth has been fueled in large part by improved thin film deposition techniques and the development of highly specialized equipment to enable this deposition. The book includes much cutting-edge material. Entirely new chapters on contamination and contamination control describe the basics and the issues-as feature sizes shrink to sub-micron dimensions, cleanliness and particle elimination has to keep pace. A new chapter on metrology explains the growth of sophisticated, automatic tools capable of measuring thickness and spacing of sub-micron dimensions. The book also covers PVD, laser and e-beam assisted deposition, MBE, and ion beam methods to bring together a...

  4. Atomic layer deposition (ALD): A versatile technique for plasmonics and nanobiotechnology.

    Science.gov (United States)

    Im, Hyungsoon; Wittenberg, Nathan J; Lindquist, Nathan C; Oh, Sang-Hyun

    2012-02-28

    While atomic layer deposition (ALD) has been used for many years as an industrial manufacturing method for microprocessors and displays, this versatile technique is finding increased use in the emerging fields of plasmonics and nanobiotechnology. In particular, ALD coatings can modify metallic surfaces to tune their optical and plasmonic properties, to protect them against unwanted oxidation and contamination, or to create biocompatible surfaces. Furthermore, ALD is unique among thin-film deposition techniques in its ability to meet the processing demands for engineering nanoplasmonic devices, offering conformal deposition of dense and ultra-thin films on high-aspect-ratio nanostructures at temperatures below 100 °C. In this review, we present key features of ALD and describe how it could benefit future applications in plasmonics, nanosciences, and biotechnology.

  5. STRUCTURAL PROPERTIES INVESTIGATION ON MICROCRYSTALLINE SILICON FILMS DEPOSITED WITH VHF-PECVD TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    H.D. Yang

    2005-01-01

    Raman scattering spectroscopy and scanning electron microscopy (SEM) techniques were used to determine the structural properties of two typical series of microcrystalline silicon(μc-Si:H) films deposited at different VHF plasma power and different working gas pressure by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique. Raman spectra measurements show that both crystalline volume fraction Xc and average grain size d of μc-Si: H films are strongly affected by the two deposition conditions and are more sensitive to working gas pressure than VHF plasma power. SEM characterizations have further confirmed that VHF plasma power and working gas pressure could clearly enhance the surface roughness of μc-Si: H films ascribing to polymerization reactions, which is also more sensitive to working gas pressure than VHF plasma power.

  6. Pulsed-source MOCVD of high-k dielectric thin films with in situ monitoring by spectroscopic ellipsometry

    CERN Document Server

    Tsuchiya, Y; Tung, R T; Oda, S; Kurosawa, M; Hattori, T

    2003-01-01

    The formation of high-k thin films by pulsed-source metal-organic chemical vapor deposition (MOCVD) has been investigated with in situ spectroscopic ellipsometry. It is demonstrated that spectroscopic ellipsometry is an effective method for in situ monitoring of the fabrication of high-k dielectric thin films with thicknesses of several nm's. Thin yttrium oxide films with average roughnesses smaller than the thickness of a single molecular layer, and with a capacitance equivalent thickness approx 1.7 nm were obtained. Thicknesses and optical properties of each individual layer were also extracted from spectroscopic ellipsometry, by fitting to appropriate structural models. (author)

  7. Stress, structural and electrical properties of Si-doped GaN film grown by MOCVD

    Institute of Scientific and Technical Information of China (English)

    Xu Zhihao; Zhang Jincheng; Duan Huantao; Zhang Zhongfen; Zhu Qingwei; Xu Hao; Hao Yue

    2009-01-01

    The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metalorganic chemical vapor deposition (MOCVD) are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples.

  8. Room-temperature ferromagnetism in V-doped GaN thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Souissi, M.; El Jani, B. [Unite de Recherche sur les Hetero-Epitaxies et Applications, Faculte des Sciences de Monastir, 5000 Monastir (Tunisia); Schmerber, G.; Derory, A. [Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), UMR7504 CNRS-UDS, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2 (France)

    2010-09-15

    V-doped GaN thin films were grown on c-sapphire substrate by metal organic chemical vapour deposition method (MOCVD). We have used vanadium tetrachloride (VCl{sub 4}) to intentionally incorporate vanadium (V) during the crystal growth of GaN. X-ray diffraction measurements revealed no secondary phase in the samples. Magnetic experiments using superconducting quantum interference device (SQUID) showed clear hysteresis loop in magnetization versus applied field (M -H) curves for V-doped GaN films. The ferromagnetic behavior was evidenced at 300 K, implying the Curie temperature to be over 300 K. Strong and broad blue-luminescent band (centered at 2.6 eV) is induced by the V doping in GaN. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Growth and Characterization of InN Thin Films on Sapphire by MOCVD

    Institute of Scientific and Technical Information of China (English)

    XIE Zi-Li; ZHANG Rong; XIU Xiang-Qian; LIU Bin; LI Liang; HAN Ping; GU Shu-Lin; SHI Yi; ZHENG You-Dou

    2007-01-01

    Indium nitride thin films are grown on sapphire substrates by metal-organic chemical vapour deposition(MOCVD).By employing three-step layer buffers,the mirror-like layers on two-inch sapphire wafers have been obtained.The structural,optical and electrical characteristics of InN are investigated by x-ray diffraction,scanning electron microscopy,atomic force microscopy,photoluminescence and infrared optical absorpton.The photoluminescence and the absorption studies of the materials reveal a marked energy bandgap structure around 0.70 eV at room temperature.The room-temperature Hall mobility and carrier concentration of the film are typically 939 cm2/Vs,and 3.9×1018cm-3,respectively.

  10. Stress, structural and electrical properties of Si-doped GaN film grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Xu Zhihao; Zhang Jincheng; Duan Huantao; Zhang Zhongfen; Zhu Qingwei; Xu Hao; Hao Yue, E-mail: forman1115@163.co [Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China)

    2009-12-15

    The stresses, structural and electrical properties of n-type Si-doped GaN films grown by metalorganic chemical vapor deposition (MOCVD) are systemically studied. It is suggested that the main stress relaxation is induced by bending dislocations in low doping samples. But for higher doping samples, as the Si doping concentration increases, the in-plane stresses in the grown films are quickly relaxed due to the rapid increase of the edge dislocation densities. Hall effect measurements reveal that the carrier mobility first increases rapidly and then decreases with increasing Si doping concentration. This phenomenon is attributed to the interaction between various scattering process. It is suggested that the dominant scattering process is defect scattering for low doping samples and ionized impurity scattering for high doping samples. (semiconductor materials)

  11. Synthesis and Characterization of Pr(DPM)3 Served as Precursor for MOCVD

    Institute of Scientific and Technical Information of China (English)

    LIU Ming-fei; HU Yong-xing; JIANG Yin-zhu; GAO Jian-feng; WANG Yan-yan; MENG Guang-yao

    2007-01-01

    Praseodymium β-diketone chelate, Pr(DPM) 3 [DPM=2,2,6,6-tetramethyl-3,5-heptanedionato], was successfully synthesized from the inorganic salt praseodymium chloride and HDPM(2,2,6,6-tetramethyl-3,5-heptane-dione) in an ethanol/aqueous solution followed distillation at low pressure and recrystallization from toluene. The physical and thermal properties of the chelate, including volatility, stability, and thermal decomposition, were investigated by elemental analyses, 1H NMR spectroscopy, XRD, TG/DTG/DTA analysis, infrared spectroscopy, and mass spectroscopy. The chelate with high purity prepared by the authors of this study also shows sufficient volatility and stability in inert gases, which could be used as the precursor for metal-organic chemical vapor deposition(MOCVD).

  12. Effect of oxygen content on the structural and optical properties of ZnO films grown by atmospheric pressure MOCVD

    Institute of Scientific and Technical Information of China (English)

    Sajjad Hussain; Yaqoob Khan; Volodymyr Khranovskyy; Riaz Muhammad; Rositza Yakimova

    2013-01-01

    Atmospheric pressure MOCVD was used to deposit ZnO layers on sapphire and homoepitaxial template under different oxygen flow rates. Oxygen content affects the lattice constant value and texture coefficient of the films as evidenced by the y-2y peaks position and their intensity. Films deposited at lower oxygen flow rate possess higher value of strain and stresses. ZnO films deposited at high oxygen flow rates show intense UV emissions while samples prepared under oxygen deficient conditions exhibited defect related emission along with UV luminescence. The results are compared to the ZnO films deposited homoepitaxially on annealed ZnO samples. The data obtained suggest that ZnO stoichiometry is responsible for the structural and optical quality of ZnO films.

  13. ZnO films deposited by optimized PLD technique with bias voltages

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, Hiroyuki; Shitara, Tamae; Komiyama, Takao; Chonan, Yasunori; Aoyama, Takashi [Department of Electronics and Information Systems, Akita Prefectural University, 84-4 Tsuchiya Ebinokuchi, 015-0055 Yuri-Honjo (Japan)

    2010-02-15

    The pulsed laser deposition (PLD) technique with bias voltage application for formation of high quality ZnO films was investigated. Oxygen ambient in the PLD chamber significantly decreased the photoluminescence (PL) intensity of near band edge (NBE) emission. Then, instead of using oxygen ambient, the PLD technique with bias voltage application was optimized to attain the stoichiometric composition of the ZnO films. As the deposition temperature was increased, the X-ray spectrum width diffracted from the (0002) planes was decreased and it showed a minimum value at 700 C. The PL intensity of the NBE emission also had its maximum value for the film deposited at 700 C. For the ZnO films deposited at 700 C, the X-ray spectrum width showed the minimum value under a bias voltage of -50 V. The PL intensity of the NBE emission also had a maximum value under the same bias voltage. Thus, ZnO films deposited under a bias voltage of -50 V at 700 C had strong NBE emission intensities. These results could be explained not only by attaining the stoichiometric composition of the ZnO film but also by decreasing the number of high energy O{sup 2-} ions which caused non-radiative recombination centers in the film. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. A comparative study of CdS thin films deposited by different techniques

    Energy Technology Data Exchange (ETDEWEB)

    Pérez-Hernández, G., E-mail: german.perez@ujat.mx [Universidad Juárez Autónoma de Tabasco, Avenida Universidad s/n, Col. Magisterial, Villahermosa, Tabasco 86040 (Mexico); Pantoja-Enríquez, J. [Centro de Investigación y Desarrollo Tecnológico en Energías Renovables, UNICACH, Libramiento Norte No 1150, Tuxtla Gutiérrez, Chiapas 29039 (Mexico); Escobar-Morales, B. [Instituto Tecnológico de Cancún, Avenida Kábah Km 3, Cancún, Quintana Roo 77500 (Mexico); Martinez-Hernández, D.; Díaz-Flores, L.L.; Ricardez-Jiménez, C. [Universidad Juárez Autónoma de Tabasco, Avenida Universidad s/n, Col. Magisterial, Villahermosa, Tabasco 86040 (Mexico); Mathews, N.R.; Mathew, X. [Centro de Investigación en Energía, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico)

    2013-05-01

    Cadmium sulfide thin-films were deposited on glass slides and SnO{sub 2}:F coated glass substrates by chemical bath deposition, sputtering and close-spaced sublimation techniques. The films were studied for the structural and opto-electronic properties after annealing in an ambient identical to that employed in the fabrication of CdTe/CdS devices. Quantum efficiency of the CdTe/CdS solar cells fabricated with CdS buffer films prepared by the three methods were investigated to understand the role of CdS film preparation method on the blue response of the devices. The higher blue response observed for the devices fabricated with chemical bath deposited CdS film is discussed. - Highlights: ► CdS films were prepared by different techniques. ► Role of CdS on the blue response of device was studied. ► Structural and optical properties of CdS were analyzed. ► Chemically deposited CdS has high blue transmittance. ► CdS deposition method influences diffusion of S and Te.

  15. Characterisation of Pb thin films prepared by the nanosecond pulsed laser deposition technique for photocathode application

    Energy Technology Data Exchange (ETDEWEB)

    Lorusso, A., E-mail: antonella.lorusso@le.infn.it [Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, Università del Salento, Lecce 73100 (Italy); Gontad, F. [Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, Università del Salento, Lecce 73100 (Italy); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE-581 83 (Sweden); Chiadroni, E. [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, Frascati 00044 (Italy); Perrone, A. [Dipartimento di Matematica e Fisica “E. De Giorgi” and Istituto Nazionale di Fisica Nucleare, Università del Salento, Lecce 73100 (Italy)

    2015-03-31

    Pb thin films were prepared by the nanosecond pulsed laser deposition technique on Si (100) and polycrystalline Nb substrates for photocathode application. As the photoemission performances of a cathode are strongly affected by its surface characteristics, the Pb films were grown at different substrate temperatures with the aim of modifying the morphology and structure of thin films. An evident morphological modification in the deposited films with the formation of spherical grains at higher temperatures has been observed. X-ray diffraction measurements showed that a preferred orientation of Pb (111) normal to the substrate was achieved at 30 °C while the Pb (200) plane became strongly pronounced with the increase in the substrate temperature. Finally, a Pb thin film deposited on Nb substrate at 30 °C and tested as the photocathode showed interesting results for the application of such a device in superconducting radio frequency guns. - Highlights: • Pb thin films obtained by the nanosecond pulsed laser deposition technique at different substrate temperature. • The substrate temperature modifies the morphology and structure of Pb films. • Pb thin film was deposited at room temperature for photocathode application. • The Pb thin film photocathode was tested and the quantum efficiency of the device improved after laser cleaning treatment of the film surface.

  16. Differential deposition technique for figure corrections in grazing-incidence x-ray optics

    Science.gov (United States)

    Kilaru, Kiranmayee; Ramsey, Brian D.; Gubarev, Mikhail V.; Gregory, Don A.

    2011-10-01

    A differential deposition technique was investigated as a way to minimize axial figure errors in full-shell, grazing-incidence, reflective x-ray optics. These types of optics use a combination of off-axis conic segments--hyperbolic, parabolic, and/or elliptical, to reflect and image x-rays. Several such mirrors or ``shells'' of decreasing diameter are typically concentrically nested to form a single focusing unit. Individual mirrors are currently produced at Marshall Space Flight Center using an electroforming technique, in which the shells are replicated off figured and superpolished mandrels. Several factors in this fabrication process lead to low- and mid-spatial frequency deviations in the surface profile of the shell that degrade the imaging quality of the optics. A differential deposition technique, discussed in this paper, seeks to improve the achievable resolution of the optics by correcting the surface profile deviations of the shells after fabrication. As a proof of concept, the technique was implemented on small-animal radionuclide-imaging x-ray optics being considered for medical applications. This paper discusses the deposition technique, its implementation, and the experimental results obtained to date.

  17. SUBSTRATE EFFECT ON HYDROGENATED MICROCRYSTALLINE SILICON FILMS DEPOSITED WITH VHF-PECVD TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    H.D. Yang

    2006-01-01

    Raman spectra and scanning electron microscope (SEM) techniques were used to determine the structural properties of microcrystalline silicon (μc-Si:H) films deposited on different substrates with the very high frequency plasma-enhanced chemical vapor deposition ( VHF-PECVD )technique. Using the Raman spectra, the values of crystalline volume fraction Xc and average grain size d are 86%, 12.3nm; 65%, 5.45nm; and 38%, 4.05nm, for single crystalline silicon wafer,corning 7059 glass, and general optical glass substrates, respectively. The SEM images further demonstrate the substrate effect on the film surface roughness. For the single crystalline silicon wafer and Corning 7059 glass, the surfaces of the μc-Si:H films are fairly smooth because of the homogenous growth or little lattice mismatch. But for general optical glass, the surface of the μc-Si:H film is very rough, thus the growing surface roughness affects the crystallization process and determines the average grain size of the deposited material. Moreover, with the measurements of thickness, photo and dark conductivity, photosensitivity and activation energy, the substrate effect on the deposition rate, optical and electrical properties of the μc-Si:H thin films have also been investigated. On the basis of the above results, it can be concluded that the substrates affect the initial growing layers acting as a seed for the formation of a crystalline-like material, and then the deposition rates, optical and electrical properties are also strongly influenced, hence,deposition parameter optimization is the key method that can be used to obtain a good initial growing layer, to realize the deposition of μc-Si:H films with device-grade quality on cheap substrates such as general glass.

  18. Development of plasma assisted thermal vapor deposition technique for high-quality thin film

    Science.gov (United States)

    Lee, Kang-Il; Choi, Yong Sup; Park, Hyun Jae

    2016-12-01

    The novel technique of Plasma-Assisted Vapor Deposition (PAVD) is developed as a new deposition method for thin metal films. The PAVD technique yields a high-quality thin film without any heating of the substrate because evaporated particles acquire energy from plasma that is confined to the inside of the evaporation source. Experiments of silver thin film deposition have been carried out in conditions of pressure lower than 10-3 Pa. Pure silver plasma generation is verified by the measurement of the Ag-I peak using optical emission spectroscopy. A four point probe and a UV-VIS spectrophotometer are used to measure the electrical and optical properties of the silver film that is deposited by PAVD. For an ultra-thin silver film with a thickness of 6.5 nm, we obtain the result of high-performance silver film properties, including a sheet resistance 75%. The PAVD-film properties show a low sheet resistance of 30% and the same transmittance with conventional thermal evaporation film. In the PAVD source, highly energetic particles and UV from plasma do not reach the substrate because the plasma is completely shielded by the optimized nozzle of the crucible. This new PAVD technique could be a realistic solution to improve the qualities of transparent electrodes for organic light emission device fabrication without causing damage to the organic layers.

  19. Synthesis of carbon nanotubes using the cobalt nanocatalyst by thermal chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Madani, S.S. [Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Zare, K. [Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Department of Chemistry, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Ghoranneviss, M. [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Salar Elahi, A., E-mail: Salari_phy@yahoo.com [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

    2015-11-05

    The three main synthesis methods of Carbon nanotubes (CNTs) are the arc discharge, the laser ablation and the chemical vapour deposition (CVD) with a special regard to the latter one. CNTs were produced on a silicon wafer by Thermal Chemical Vapor Deposition (TCVD) using acetylene as a carbon source, cobalt as a catalyst and ammonia as a reactive gas. The DC-sputtering system was used to prepare cobalt thin films on Si substrates. A series of experiments was carried out to investigate the effects of reaction temperature and deposition time on the synthesis of the nanotubes. The deposition time was selected as 15 and 25 min for all growth temperatures. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the Co nanocatalyst deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface topography of the Co nanocatalyst deposited on Si substrates. The as-grown CNTs were characterized under Field Emission Scanning Electron Microscopy (FESEM) to study the morphological properties of CNTs. Also, the grown CNTs have been investigated by High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results demonstrated that increasing the temperature leads to increasing the diameter of CNTs. The ideal reaction temperature was 850 °C and the deposition time was 15 min. - Graphical abstract: FESEM images of CNTs grown on the cobalt catalyst at growth temperatures of (a) 850 °C, (b) 900 °C, (c) 950 °C and (d) 1000 °C during the deposition time of 15 min. - Highlights: • Carbon nanotubes (CNTs) were produced on a silicon wafer by TCVD technique. • EDX and AFM were used to investigate the elemental composition and surface topography. • FESEM was used to study the morphological properties of CNTs. • The grown CNTs have been investigated by HRTEM and Raman spectroscopy.

  20. Rectifying properties of ZnO thin films deposited on FTO by electrodeposition technique

    Science.gov (United States)

    Lv, Jianguo; Sun, Yue; Zhao, Min; Cao, Li; Xu, Jiayuan; He, Gang; Zhang, Miao; Sun, Zhaoqi

    2016-03-01

    ZnO thin films were successfully grown on fluorine-doped tin oxide glass by electrodeposition technique. The crystal structure, surface morphology and optical properties of the thin films were investigated. The average crystallite size and intensity of A1(LO) mode increase with improving the absolute value of deposition potential. The best preferential orientation along c-axis and the richest oxygen interstitial defects have been observed in the sample deposited at -0.8 V. A heterojunction device consisting of ZnO thin film and n-type fluorine-doped tin oxide was fabricated. The current-voltage (I-V) characteristic of the p-n heterojunction device deposited at -0.8 V shows the best rectifying diode behavior. The p-type conductivity of the ZnO thin film could be attributed to complex defect of unintentional impurity and interstitial oxygen.

  1. Thin Film Formation of Gallium Nitride Using Plasma-Sputter Deposition Technique

    Directory of Open Access Journals (Sweden)

    R. Flauta

    2003-06-01

    Full Text Available The formation of gallium nitride (GaN thin film using plasma-sputter deposition technique has beenconfirmed. The GaN film deposited on a glass substrate at an optimum plasma condition has shown x-raydiffraction (XRD peaks at angles corresponding to that of (002 and (101 reflections of GaN. The remainingmaterial on the sputtering target exhibited XRD reflections corresponding to that of bulk GaN powder. Toimprove the system’s base pressure, a new UHV compatible system is being developed to minimize theimpurities in residual gases during deposition. The sputtering target configuration was altered to allow themonitoring of target temperature using a molybdenum (Mo holder, which is more stable against Gaamalgam formation than stainless steel.

  2. Study of SnS2 thin film deposited by spin coating technique

    Science.gov (United States)

    Chaki, Sunil H.; Joshi, Hardikkumar J.; Tailor, Jiten P.; Deshpande, M. P.

    2017-07-01

    Thin film deposition of SnS2 was done by spin coating technique at ambient temperature. Deposition was done for different spin speed and spin time. The film thickness dependence on spin speed and spin time was studied. The spin speed was varied from 1000 rpm to 2000 rpm and spin time from 2 s to 6 s for constant speed of 1000 rpm. The elemental composition and crystal structure along with the phase of the as-deposited thin film was determined by the energy dispersive analysis of x-ray (EDAX) and x-ray diffraction (XRD) techniques respectively. The as-deposited thin film was found to be near stoichiometric and possess hexagonal crystal structure with determined lattice parameters in good agreement with the reported values. The crystallite size calculated from the XRD data using Scherrer’s formula and Hall-Williamson relation came out to be 9.77 nm and 6.49 nm, respectively. The transmission electron microscopy (TEM) study of spin deposited thin films showed the film to be continuous. Surface study of the as-deposited thin film was done by simple optical microscope and scanning electron microscope (SEM). The study showed that the deposited thin film to be flat and uniform without visible cracks and pores. The optical spectroscopy study of the as-deposited thin film showed that the optical bandgap value decreases with increase in film thickness. The d.c. electrical resistivity variation with temperature for spin coating as-deposited SnS2 film showed that the resistivity decreases with increase in temperature corroborating the semiconducting nature. The resistivity variation plot possesses two slopes. The temperature ranges showing two slopes lay between 300 to 383 K and 384 to 423 K having activation energy values for the two temperature ranges as 0.072 eV and 0.633 eV, respectively. The achieved results are deliberated in details.

  3. Thin films and coatings deposited by vacuum techniques; Capas delgadas y recubrimientos obtenidos mediante tecnicas de vacio

    Energy Technology Data Exchange (ETDEWEB)

    Albella, J. M.; Endrino, J. L.

    2010-07-01

    This paper gives an overview of the various aspects associated with the development of coatings and thin films in all its aspects, from the preparation techniques to the technological applications. It addresses such important issues, such as the comparison of some techniques with others, or the choice of a deposition method to achieve certain characteristics in the deposited layer. (Author) 8 refs.

  4. Influence of CdS deposition technique for CdS/CdTe solar cells applications

    Science.gov (United States)

    Rubio, Sandra; Plaza, José Luis; Diéguez, Ernesto

    2014-09-01

    The manufacturing of an optimal window layer is essential for a high efficiency solar cell. CdS thin films were deposited on FTO commercial substrates by two different techniques: Chemical Bath Deposition (CBD), and Closed Space Sublimation (CSS) using SiC rods as electrical heating elements. The composition, morphology, and crystalline structure of the CdS thin films were analyzed by Energy Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscope (SEM), and X-Ray Diffraction (XRD). CdS layers obtained by CSS have shown good stoichiometries of 51.07(Cd at %), and 48.93(S at %), with the presence of disordered microrods of hexagonal shape. The CdS films obtained by CBD exhibited certain contamination from the bath chemical components and a poor defined structure. In conclusion, the layers deposited by electric heating based CSS present a better morphology and crystal structure than the layers deposited by CBD. The CdTe absorber layer deposited by CSS electric heating also shows good cubic structure and morphology.

  5. Lipase immobilization for catalytic applications obtained using fumed silica deposited with MAPLE technique

    Science.gov (United States)

    Bloisi, Francesco; Califano, Valeria; Perretta, Giuseppe; Nasti, Libera; Aronne, Antonio; Di Girolamo, Rocco; Auriemma, Finizia; De Rosa, Claudio; Vicari, Luciano R. M.

    2016-06-01

    Lipases are enzymes used for catalyzing reactions of acylglycerides in biodiesel production from lipids, where enzyme immobilization on a substrate is required. Silica nanoparticles in different morphologies and configurations are currently used in conjunction with biological molecules for drug delivery and catalysis applications, but up to date their use for triglycerides has been limited by the large size of long-chain lipid molecules. Matrix assisted pulsed laser evaporation (MAPLE), a laser deposition technique using a frozen solution/suspension as a target, is widely used for deposition of biomaterials and other delicate molecules. We have carried out a MAPLE deposition starting from a frozen mixture containing fumed silica and lipase in water. Deposition parameters were chosen in order to increase surface roughness and to promote the formation of complex structures. Both the target (a frozen thickened mixture of nanoparticles/catalyst in water) and the deposition configuration (a small target to substrate distance) are unusual and have been adopted in order to increase surface contact of catalyst and to facilitate access to long-chain molecules. The resulting innovative film morphology (fumed silica/lipase cluster level aggregation) and the lipase functionality (for catalytic biodiesel production) have been studied by FESEM, FTIR and transesterification tests.

  6. Status of Plasma Physics Techniques for the Deposition of Tribological Coatings

    Science.gov (United States)

    Spalvins, T.

    1984-01-01

    The plasma physics deposition techniques of sputtering and ion-plating are reviewed. Their characteristics and potentials are discussed in terms of synthesis or deposition of tribological coatings. Since the glow discharge or plasma generated in the conventional sputtering and ion-plating techniques has a low ionization efficiency, rapid advances have been made in equipment design to further increase the ionization efficiency. The enhanced ionization favorably affects the nucleation and growth sequence of the coating. This leads to improved adherence and coherence, higher density, favorable morphological growth, and reduced internal stresses in the coatings. As a result, desirable coating characteristics can be precision tailored. Tribological coating characteristics of sputtered solid film lubricants such as MoS2, ion-plated soft gold and lead metallic films, and sputtered and ion-plated wear-resistant refractory compound films such as nitrides and carbides are discussed.

  7. Synthesis of nanocrystalline silicon thin films using the increase of the deposition pressure in the hot-wire chemical vapour deposition technique

    Directory of Open Access Journals (Sweden)

    J.K. Rath

    2010-01-01

    Full Text Available Nanostructured thin silicon-based films have been deposited using the hot-wire chemical vapour deposition (HWCVD technique at the University of the Western Cape. A variety of techniques including optical and infrared spectroscopy, Raman scattering spectroscopy, X-rays diffraction (XRD and transmission electron microscopy (TEM have been used for characterisation of the films. The electrical measurements show that the films have good values of photoresponse, and the photocurrent remains stable after several hours of light soaking. This contribution will discuss the characteristics of the hydrogenated nanocrystalline silicon thin films deposited using increased process chamber pressure at a fixed hydrogen dilution ratio in monosilane gas.

  8. Effect of deposition technique of Ni on the perpendicular magnetic anisotropy in Co/Ni multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Akbulut, S., E-mail: sakbulut@gtu.edu.tr [Gebze Technical University, Physics Department, Istanbul Cad, PK 41400 Gebze/Kocaeli (Turkey); Akbulut, A. [Gebze Technical University, Physics Department, Istanbul Cad, PK 41400 Gebze/Kocaeli (Turkey); Özdemir, M. [Marmara University, Physics Department, Göztepe, Istanbul (Turkey); Yildiz, F., E-mail: fyildiz@gtu.edu.tr [Gebze Technical University, Physics Department, Istanbul Cad, PK 41400 Gebze/Kocaeli (Turkey)

    2015-09-15

    The perpendicular magnetic anisotropy (PMA) of Si/Pt 3.5/(Co 0.3/Ni 0.6){sub n} /Co 0.3/ Pt 3 (all thicknesses are nm) multilayers were investigated for two different sample sets by using ferromagnetic resonance (FMR) and magnetooptic Kerr effect (MOKE) techniques. In the first sample set all layers (buffer, cap, Co and Ni) were grown by magnetron sputtering technique while in the second sample set Ni sub-layers were grown by molecular beam epitaxy (MBE) at high vacuum. Apart from deposition technique of Ni, all other parameters like thicknesses and growth rates of each layers are same for both sample sets. Multilayers in these two sample sets display PMA in the as grown state until a certain value of bilayer repetition (n) and the strength of PMA decreases with increasing n. Magnetic easy axis's of the multilayered samples switched from film normal to the film plane when n is 9 and 5 for the first and second sample sets, respectively. The reason for that, PMA was decreased due to increasing roughness with increasing n. This was confirmed by X Ray Reflectivity (XRR) measurements for both sample sets. Moreover, in the first sample set coercive field values are smaller than the second sample set, which means magnetic anisotropy is lower than the latter one. This stronger PMA is arising due to existence of stronger Pt (111) and Co/Ni (111) textures in the second sample set. - Highlights: • Effect of deposition techniques for Ni sub-layers on magnetic properties in [Co/Ni]{sub n} multilayered films was studied. • Ni sub-layers were deposited by two different techniques, molecular beam epitaxy (MBE) and magnetron sputtering. • Spin reorientation thickness and magnitude of the anisotropy are strongly depending on growing techniques.

  9. Impact of photoluminescence temperature and growth parameter on the exciton localized in BxGa1-xAs/GaAs epilayers grown by MOCVD

    Science.gov (United States)

    Hidouri, Tarek; Saidi, Faouzi; Maaref, Hassen; Rodriguez, Philippe; Auvray, Laurent

    2016-10-01

    In this work, BxGa1-xAs/GaAs epilayers with three different boron compositions were elaborated by metal organic chemical vapor deposition (MOCVD) on GaAs (001) substrate. Structural study using High resolution X-ray diffraction (HRXRD) spectroscopy and Atomic Force Microscopy (AFM) have been used to estimate the boron fraction. The luminescence keys were carried out as functions of temperature in the range 10-300 K, by the techniques of photoluminescence (PL). The low PL temperature has shown an abnormal emission appeared at low energy side witch attributed to the recombination through the deep levels. In all samples, the PL peak energy and the full width at half maximum (FWHM), present an anomalous behavior as a result of the competition process between localized and delocalized carriers. We propose the Localized-state Ensemble model to explain the unusual photoluminescence behaviors. Electrical carriers generation, thermal escape, recapture, radiative and non-radiative lifetime are taken into account. The temperature-dependent photoluminescence measurements were found to be in reasonable agreement with the model of localized states. We controlled the evolution of such parameters versus composition by varying the V/III ratio to have a quantitative and qualitative understanding of the recombination mechanisms. At high temperature, the model can be approximated to the band-tail-state emission.

  10. Facile Route to NiO Nanostructured Electrode Grown by Oblique Angle Deposition Technique for Supercapacitors.

    Science.gov (United States)

    Kannan, Vasudevan; Inamdar, Akbar I; Pawar, Sambaji M; Kim, Hyun-Seok; Park, Hyun-Chang; Kim, Hyungsang; Im, Hyunsik; Chae, Yeon Sik

    2016-07-13

    We report an efficient method for growing NiO nanostructures by oblique angle deposition (OAD) technique in an e-beam evaporator for supercapacitor applications. This facile physical vapor deposition technique combined with OAD presents a unique, direct, and economical route for obtaining high width-to-height ratio nanorods for supercapacitor electrodes. The NiO nanostructure essentially consists of nanorods with varying dimensions. The sample deposited at OAD 75° showed highest supercapacitance value of 344 F/g. NiO nanorod electrodes exhibits excellent electrochemical stability with no degradation in capacitance after 5000 charge-discharge cycles. The nanostructured film adhered well to the substrate and had 131% capacity retention. Peak energy density and power density of the NiO nanorods were 8.78 Wh/kg and 2.5 kW/kg, respectively. This technique has potential to be expanded for growing nanostructured films of other interesting metal/metal oxide candidates for supercapacitor applications.

  11. Nano-yttria dispersed stainless steel composites composed by the 3 dimensional fiber deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Verhiest, K., E-mail: Katelijne.Verhiest@ArcelorMittal.com [ArcelorMittal Gent, Hot Strip Mill Department, J. Kennedylaan 51, 9042 Ghent (Belgium); Belgian Nuclear Research Centre, SCK-CEN, Boeretang 200, 2400 Mol (Belgium); Ghent University, UGent, Department of Materials Science and Engineering (DMSE), Technologiepark 903, 9052 Ghent (Belgium); Mullens, S. [Flemish Institute for Technological Research, VITO, Materials Technology, Boeretang 200, 2400 Mol (Belgium); De Wispelaere, N.; Claessens, S. [ArcelorMittal Research Industry Gent, OCAS, J. Kennedylaan 3, 9060 Zelzate (Belgium); DeBremaecker, A. [Belgian Nuclear Research Centre, SCK-CEN, Boeretang 200, 2400 Mol (Belgium); Verbeken, K. [Ghent University, UGent, Department of Materials Science and Engineering (DMSE), Technologiepark 903, 9052 Ghent (Belgium)

    2012-09-15

    In this study, oxide dispersion strengthened (ODS) 316L steel samples were manufactured by the 3 dimensional fiber deposition (3DFD) technique. The performance of 3DFD as colloidal consolidation technique to obtain porous green bodies based on yttria (Y{sub 2}O{sub 3}) nano-slurries or paste, is discussed within this experimental work. The influence of the sintering temperature and time on sample densification and grain growth was investigated in this study. Hot consolidation was performed to obtain final product quality in terms of residual porosity reduction and final dispersion homogeneity.

  12. Studies on non-oxide coating on carbon fibers using plasma enhanced chemical vapor deposition technique

    Science.gov (United States)

    Patel, R. H.; Sharma, S.; Prajapati, K. K.; Vyas, M. M.; Batra, N. M.

    2016-05-01

    A new way of improving the oxidative behavior of carbon fibers coated with SiC through Plasma Enhanced Chemical Vapor Deposition technique. The complete study includes coating of SiC on glass slab and Stainless steel specimen as a starting test subjects but the major focus was to increase the oxidation temperature of carbon fibers by PECVD technique. This method uses relatively lower substrate temperature and guarantees better stoichiometry than other coating methods and hence the substrate shows higher resistance towards mechanical and thermal stresses along with increase in oxidation temperature.

  13. Effects of LP-MOCVD prepared TiO{sub 2} thin films on the in vitro behavior of gingival fibroblasts

    Energy Technology Data Exchange (ETDEWEB)

    Cimpean, Anisoara [Department of Biochemistry and Molecular Biology, University of Bucharest, Bucharest (Romania); Popescu, Simona [Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Polizu, Bucharest (Romania); Centre Interuniversitaire de Recherche et d' Ingenierie des Materiaux (CIRIMAT), CNRS-INPT/ENSIACET, University of Toulouse, Toulouse (France); Ciofrangeanu, Cristina M. [Department of Biochemistry and Molecular Biology, University of Bucharest, Bucharest (Romania); Gleizes, Alain N., E-mail: alain.gleizes@ensiacet.fr [Centre Interuniversitaire de Recherche et d' Ingenierie des Materiaux (CIRIMAT), CNRS-INPT/ENSIACET, University of Toulouse, Toulouse (France)

    2011-02-15

    We report on the in vitro response of human gingival fibroblasts (HGF-1 cell line) to various thin films of titanium dioxide (TiO{sub 2}) deposited on titanium (Ti) substrates by low pressure metal-organic chemical vapor deposition (LP-MOCVD). The aim was to study the influence of film structural parameters on the cell behavior comparatively with a native-oxide covered titanium specimen, this objective being topical and interesting for materials applications in implantology. HGF-1 cells were cultured on three LP-MOCVD prepared thin films of TiO{sub 2} differentiated by their thickness, roughness, transversal morphology, allotropic composition and wettability, and on a native-oxide covered Ti substrate. Besides traditional tests of cell viability and morphology, the biocompatibility of these materials was evaluated by fibronectin immunostaining, assessment of cell proliferation status and the zymographic evaluation of gelatinolytic activities specific to matrix metalloproteinases secreted by cells grown in contact with studied specimens. The analyzed surfaces proved to influence fibronectin fibril assembly, cell proliferation and capacity to degrade extracellular matrix without considerably affecting cell viability and morphology. The MOCVD of TiO{sub 2} proved effective in positively modifying titanium surface for medical applications. Surface properties playing a crucial role for cell behavior were the wettability and, secondarily, the roughness, HGF-1 cells preferring a moderately rough and wettable TiO{sub 2} coating.

  14. HiPIMS: a New Generation of Film Deposition Techniques for SRF Applications

    Energy Technology Data Exchange (ETDEWEB)

    Valente-Feliciano, Anne-Marie [JLAB

    2013-09-01

    Over the years, Nb/Cu technology, despite its shortcomings due to the commonly used magnetron sputtering, has positioned itself as an alternative route for the future of accelerator superconducting structures. Avenues for the production of thin films tailored for Superconducting RF (SRF) applications are showing promise with recent developments in ionized PVD coating techniques, i.e. vacuum deposition techniques using energetic ions. Among these techniques, High power impulse magnetron sputtering (HiPIMS) is a promising emerging technique which combines magnetron sputtering with a pulsed power approach. This contribution describes the benefits of energetic condensation for SRF films and the characteristics of the HiPIMS technology. It describes the on-going efforts pursued in different institutions to exploit the potential of this technology to produce bulk-like Nb films and go beyond Nb performance with the development of film systems, based on other superconducting materials and multilayer structures.

  15. Monolithic Integration of Sampled Grating DBR with Electroabsorption Modulator by Combining Selective-Area-Growth MOCVD and Quantum-Well Intermixing

    Science.gov (United States)

    Liu, Hong-Bo; Zhao, Ling-Juan; Pan, Jiao-Qing; Zhu, Hong-Liang; Zhou, Fan; Wang, Bao-Jun; Wang, Wei

    2008-10-01

    We present the monolithic integration of a sampled-grating distributed Bragg reflector (SG-DBR) laser with a quantum-well electroabsorption modulator (QW-EAM) by combining ultra-low-pressure (55mbar) selective-area-growth (SAG) metal-organic chemical vapour deposition (MOCVD) and quantum-well intermixing (QWI) for the first time. The QW-EAM and the gain section can be grown simultaneously by using SAG MOCVD technology. Meanwhile, the QWI technology offers an abrupt band-gap change between two functional sections, which reduces internal absorption loss. The experimental results show that the threshold current Ith = 62 mA, and output power reaches 3.6mW. The wavelength tuning range covers 30nm, and all the corresponding side mode suppression ratios are over 30 dB. The extinction ratios at available wavelength channels can reach more than 14 dB with bias of -5 V.

  16. Monolithic Integration of Sampled Grating DBR with Electroabsorption Modulator by Combining Selective-Area-Growth MOCVD and Quantum-Well Intermixing

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-Bo; ZHAO Ling-Juan; PAN Jiao-Qing; ZHU Hong-Liang; ZHOU Fan; WANG Bao-Jun; WANG Wei

    2008-01-01

    We present the monolithic integration of a sampled-grating distributed Bragg reflector (SG-DBR) laser with a quantum-well eleetroabsorption modulator (QW-EAM) by combining ultra-low-pressure (55mbar) selectivearea-growth (SAG) metal-organic chemical vapour deposition (MOCVD) and quantum-well intermixing (QWI)for the first time. The QW-EAM and the gain section can be grown simultaneously by using SAG MOCVD technology. Meanwhile, the QWI technology offers an abrupt band-gap change between two functional sections,which reduces internal absorption loss. The experimental results show that the threshold current Ith=62 mA,and output power reaches 3.6 roW. The wavelength tuning range covers 3Ohm, and all the corresponding side mode suppression ratios are over 30 dB. The extinction ratios at available wavelength channels can reach more than 14dB with bias of -5 V.

  17. MOCVD growth of GaN-based materials on ZnO substrates

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shen-Jie; Li, Nola; Park, Eun-Hyun; Kane, Matthew [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250 (United States); Feng, Zhe Chuan [Graduate Institute of Electro-Optical Engineering, National Taiwan University, Taipei, Taiwan 106-17 (China); Valencia, Adriana; Nause, Jeff [CERMET Inc., 1019 Collier Road, Atlanta, Georgia 30318 (United States); Summers, Chris [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250 (United States); Ferguson, Ian [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250 (United States)

    2008-07-01

    The metalorganic chemical vapor deposition (MOCVD) growth of GaN based materials on ZnO substrates has numerous technical issues that need to be investigated and resolved. These include the thermal stability of ZnO, out-diffusion of Zn/O from the ZnO into the epilayers, and H{sub 2} back etching into the ZnO all of which can cause poor film quality. Cracks and pinholes were seen in the epilayers, leading to the epilayer peeling off. In this study, good quality InGaN films with a wide range of indium incorporation have been grown on (0001) ZnO substrates by MOCVD. No indium droplets and phase separation were observed even at high indium concentrations. The optical microscopy and field-emission scanning electron microscopy revealed a mirror-like InGaN surface with no evidence of indium droplets on the surface. Photoluminescence (PL) showed broad InGaN-related emissions with peak energy lower than the calculated InGaN band gap, possibly due to Zn/O impurities diffused into InGaN from the ZnO substrate. More recently, Al{sub 2}O{sub 3} coated ZnO substrates have been employed for growth to limit Zn diffusion as well as assist epilayer growth. HRXRD result shows that a single crystal InGaN film has been successfully grown on an annealed Al{sub 2}O{sub 3} coated ZnO substrate. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. DFT study on adduct reaction paths of GaN MOCVD growth

    Institute of Scientific and Technical Information of China (English)

    SHI; JunCao; ZUO; Ran; MENG; SuCi

    2013-01-01

    The adduct reaction paths for GaN growth by metal organic chemical vapor deposition (MOCVD) were studied by quantum chemical calculations employing density functional theory (DFT). Five possible adduct reaction paths with or without the ex-cess NH3were proposed and the corresponding potential energy surfaces were calculated. From the calculation results, it is concluded that after the formation of DMGNH2from TMG:NH3, the further decomposition paths have very slim probability because of the high energy barriers; whereas the oligomerization pathway to form oligomers [DMGNH2]x(x=2, 3) is probable,because of zero energy barrier. Since the oligomers tend to further polymerize, the nanoparticles are easily formed through this path. When NH3is in excess, TMG:NH3 tends to combine with the second NH3to form two new complexes: the coordination-bonded compound H3N:TMG:NH3and the hydrogen-bonded compound TMG:NH3 NH3. The formation of hydrogen-bonded compound TMG:NH3 NH3 will be more probable because of the lower energy than H3N:TMG:NH3. By comparing the potential energy surfaces in five adduct reaction paths, we postulate that, under the growth conditions of GaN MOCVD, the formation of hydrogen-bonded compound TMG:NH3 NH3 followed by the reversible decomposition may be the main reaction path for GaN thin film growth; while the adduct oligomerization path to generate oligomers [DMGNH2]2 and [DMGNH2]3might be the main reaction path for nanoparticles formation.

  19. A lithium depth-marker technique for rapid erosion and deposition measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, R.M., E-mail: rsulli@psfc.mit.edu; Pang, A.; Martinez-Sanchez, M.; Whyte, D.G.

    2014-01-15

    Highlights: • Rutherford backscattering spectrometry (RBS) to determine the change in depth. • Rutherford backscattering spectrometry (RBS) to determine the change in depth. • Rutherford backscattering spectrometry (RBS) to determine the change in depth. -- Abstract: A novel, high-resolution technique has been developed for the measurement of erosion and deposition in solid material surfaces. The technique uses a combination of nuclear reaction analysis (NRA) and Rutherford backscattering spectrometry (RBS) to determine the change in depth of a previously implanted marker layer consisting of {sup 7}Li. A scoping study shows that {sup 7}Li is an ideal marker candidate due to a high Q (∼18 MeV) nuclear reaction, {sup 7}Li(p,α){sup 4}He. Net erosion or deposition is measured by NRA of modified alpha energy passing through the bulk material. The reaction’s high cross-section provides for the fast time resolution needed to measure erosion from high flux plasmas, and a highly penetrating proton beam provides for a large range of erosion/deposition measurements. Additionally, the implantation of low-Z Li leads to relatively low vacancy concentrations in the solid material due to implantation. This technique thus provides greater assurance that the measured erosion rate is indicative of the solid material: due to both the low vacancy production and the fact that no films or deposits are involved. Validation was performed by comparing the measured and predicted amount of erosion based on previously measured sputtering yields; the two were found to agree, within the uncertainty of the experiment. The depth resolution of the techniques is ∼60 nm at a net erosion depth of about 1 μm. The benefits of this technique are summarized as: short time scales (minutes) to obtain results, the marker layer can be used in any solid material, greater assurance that the measured erosion is indicative of the unperturbed solid material, and the continuous monitoring of the

  20. Synthesis of Colloidal ZnO Nanoparticles and Deposit of Thin Films by Spin Coating Technique

    Directory of Open Access Journals (Sweden)

    Jose Alberto Alvarado

    2013-01-01

    Full Text Available ZnO colloidal nanoparticles were synthesized, the average size of these nanoparticles is around 25 nm with hexagonal form. It was noted that stabilization depends directly on the purifying process; in this work we do not change the nature of the solution as a difference from Meulekamp's method, and we do not use any alkanes to remove the byproducts; only a centrifuge to remove those ones was used, thereby the stabilization increases up to 24 days. It is observed from the results that only three times of washing is enough to prevent the rapid aging process. The effect of annealing process on the composition, size, and geometrical shape of ZnO nanoparticles was studied in order to know whether the annealing process affects the crystallization and growth of the nanoparticles. After the synthesis, the colloidal nanoparticles were deposited by spin coating technique showing that the formed nanoparticles have no uniformly deposition pattern. But is possible to deposit those ones in glass substrates. A possible deposition process of the nanoparticles is proposed.

  1. The multiscale simulation of metal organic chemical vapor deposition growth dynamics of GaInP thin film

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    As a Group III–V compound, GaInP is a high-efficiency luminous material. Metal organic chemical vapor deposition (MOCVD) technology is a very efficient way to uniformly grow multi-chip, multilayer and large-area thin film. By combining the computational fluid dynamics (CFD) and the kinetic Monte Carlo (KMC) methods with virtual reality (VR) technology, this paper presents a multiscale simulation of fluid dynamics, thermodynamics, and molecular dynamics to study the growth process of GaInP thin film in a vertical MOCVD reactor. The results of visualization truly and intuitively not only display the distributional properties of the gas’ thermal and flow fields in a MOCVD reactor but also display the process of GaInP thin film growth in a MOCVD reactor. The simulation thus provides us with a fundamental guideline for optimizing GaInP MOCVD growth.

  2. Comparative study of deep levels in HVPE and MOCVD GaN by combining O-DLTS and pulsed photo-ionization spectroscopy

    Science.gov (United States)

    Pavlov, J.; Čeponis, T.; Gaubas, E.; Meskauskaite, D.; Reklaitis, I.; Vaitkus, J.; Grigonis, R.; Sirutkaitis, V.

    2015-12-01

    Operational characteristics of sensors made of GaN significantly depend on technologically introduced defects acting as rapid traps of excess carriers which reduce charge collection efficiency of detectors. In order to reveal the prevailing defects in HVPE and MOCVD grown GaN, the carrier lifetime and photo-ionization spectra have been simultaneously measured by using microwave probed photo-conductivity transient technique. Several traps ascribed to impurities as well as vacancy and anti-site type defects have been identified in HVPE GaN material samples by combining photo-ionization and electron spin resonance spectroscopy. The optical deep level transient spectroscopy technique has been applied for spectroscopy of the parameters of thermal emission from the traps ascribed to technological defects in the Schottky barrier terrace structures fabricated on MOCVD GaN.

  3. Magnetic and optical properties of the nickel thin film deposited by GLAD technique

    Directory of Open Access Journals (Sweden)

    Potočnik Jelena M.

    2014-01-01

    Full Text Available In this work, nickel thin film was deposited on glass sample using Glancing Angle Deposition (GLAD technique, to a thickness of 1 μm. Glass sample was positioned 15 degrees with respect to the nickel vapor flux. The nickel thin film was characterized by Atomic Force Microscopy (AFM, Magneto- Optical Kerr effect Microscopy and Spectroscopic Ellipsometry. According to an AFM cross-section imaging, it was found that the nickel thin film has a columnar structure. The values of the coercively, obtained from the magnetic hysteresis loops, were analyzed as a function of the sample rotation in the magnetic field. It was found that the direction of magnetization easy axis lies toward the structure growth. Optical properties of the nickel thin film were studied at the wavelength of 455 nm. From the shape of the refractive index and the extinction coefficient diagrams could be concluded that the nickel thin film has an optical anisotropy.

  4. Multifunctional thin films of lactoferrin for biochemical use deposited by MAPLE technique

    Science.gov (United States)

    Constantinescu, Catalin; Palla-Papavlu, Alexandra; Rotaru, Andrei; Florian, Paula; Chelu, Florica; Icriverzi, Madalina; Nedelcea, Anca; Dinca, Valentina; Roseanu, Anca; Dinescu, Maria

    2009-03-01

    Lactoferrin (Lf) is an iron-binding glycoprotein present in almost all mammalian secretions which plays an important role in host defense against microbial and viral infections. The protein has been reported to also have anti-inflammatory activity and antitumoral effects in vitro and in vivo. Thin films of Lf were deposited on silicon, quartz and Thermanox plastic coverslip substrates by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique, using a Nd:YAG laser working at 266 nm, at different laser fluences (0.1-0.8 J cm -2). The deposited layers have been characterized by Fourier Transformed Infra-Red spectroscopy (FTIR), and the morphology of the various substrates was investigated by Atomic Force Microscopy (AFM). The biocompatibility of lactoferrin thin films was evaluated for each substrate, by in vitro biochemical tests.

  5. Modulating the Optoelectronic Properties of Silver Nanowires Films: Effect of Capping Agent and Deposition Technique

    Directory of Open Access Journals (Sweden)

    D. Lopez-Diaz

    2015-11-01

    Full Text Available Silver nanowires 90 nm in diameter and 9 µm in length have been synthesized using different capping agents: polyvinyl pyrrolidone (PVP and alkyl thiol of different chain lengths. The nanowire structure is not influenced by the displacement of PVP by alkyl thiols, although alkyl thiols modify the lateral aggregation of nanowires. We examined the effect of the capping agent and the deposition method on the optical and electrical properties of films prepared by Spray and the Langmuir-Schaefer methodologies. Our results revealed that nanowires capped with PVP and C8-thiol present the best optoelectronic properties. By using different deposition techniques and by modifying the nanowire surface density, we can modulate the optoelectronic properties of films. This strategy allows obtaining films with the optoelectronic properties required to manufacture touch screens and electromagnetic shielding.

  6. Factors affecting the superconductivity in the process of depositing Nd1.85Ce0.15CuO4-δ by the pulsed electron deposition technique

    Institute of Scientific and Technical Information of China (English)

    GUO; YanFeng

    2007-01-01

    On SrTiO3 single crystal substrate, by using the pulsed electron deposition technique, the high-quality electron doped Nd1.85Ce0.15CuO4-δsuperconducting film was successfully fabricated. After careful study on the R-T curves of the obtained samples deposited with different substrate temperatures, thicknesses, annealing methods and pulse frequencies, the effects of them on the superconductivity of the films were found, and the reasons were also analyzed. Additionally, by using the same model of the pulsed laser deposition technique, the relation between the target-to-substrate distance and the deposition pressure was drawn out as a quantitative one.  ……

  7. Synthesis of conductive semi-transparent silver films deposited by a Pneumatically-Assisted Ultrasonic Spray Pyrolysis Technique

    Energy Technology Data Exchange (ETDEWEB)

    Zaleta-Alejandre, E.; Balderas-Xicoténcatl, R. [Centro de Investigación y de Estudios Avanzados-IPN, Departamento de Física, , Apdo. Postal 14-470, Del, Gustavo A. Madero, C.P. 07000, México, D.F. (Mexico); Arrieta, M.L. Pérez [Universidad Autónoma de Zacatecas, Unidad Académica de Física, Calzada Solidaridad esq. Paseo, La Bufa s/n, C.P. 98060, Zacatecas, México (Mexico); Meza-Rocha, A.N.; Rivera-Álvarez, Z. [Centro de Investigación y de Estudios Avanzados-IPN, Departamento de Física, , Apdo. Postal 14-470, Del, Gustavo A. Madero, C.P. 07000, México, D.F. (Mexico); Falcony, C., E-mail: cfalcony@fis.cinvestav.mx [Centro de Investigación y de Estudios Avanzados-IPN, Departamento de Física, , Apdo. Postal 14-470, Del, Gustavo A. Madero, C.P. 07000, México, D.F. (Mexico)

    2013-10-01

    Highlights: • We deposited metallic silver films without post-deposition annealing. • The spray pyrolysis technique is of low cost and scalable for industrial applications. • We obtained deposition rate of 60 nm min{sup −1} at 300 °C. • The average resistivity was 1E−7 Ω m. • Semi-transparent silver films were obtained at 350 °C and deposition time of 45 s. -- Abstract: The synthesis and characterization of nanostructured silver films deposited on corning glass by a deposition technique called Pneumatically-Assisted Ultrasonic Spray Pyrolysis are reported. Silver nitrate and triethanolamine were used as silver precursor and reducer agent, respectively. The substrate temperatures during deposition were in the range of 300–450 °C and the deposition times from 30 to 240 s. The deposited films are polycrystalline with cubic face-centered structure, and crystalline grain size less than 30 nm. Deposition rates up to 600 Å min{sup −1} were obtained at substrate temperature as low as 300 °C. The electrical, optical, and morphological properties of these films are also reported. Semi-transparent conductive silver films were obtained at 350 °C with a deposition time of 45 s.

  8. Detection of Atmospheric Water Deposits in Porous Media Using the TDR Technique

    Directory of Open Access Journals (Sweden)

    Anna Nakonieczna

    2015-04-01

    Full Text Available Investigating the intensity of atmospheric water deposition and its diurnal distribution is essential from the ecological perspective, especially regarding dry geographic regions. It is also important in the context of monitoring the amount of moisture present within building materials in order to protect them from excessive humidity. The objective of this study was to test a constructed sensor and determine whether it could detect and track changes in the intensity of atmospheric water deposition. An operating principle of the device is based on the time-domain reflectometry technique. Two sensors of different plate volumes were manufactured. They were calibrated at several temperatures and tested during field measurements. The calibration turned out to be temperature independent. The outdoor measurements indicated that the upper limits of the measurement ranges of the sensors depended on the volumes of the plates and were equal to 1:2 and 2:8 mm H2O. The respective sensitivities were equal to 3.2 x 10-3 and 7.5 x 10-3 g∙ps-1. The conducted experiments showed that the construction of the designed device and the time-domain reflectometry technique were appropriate for detecting and tracing the dynamics of atmospheric water deposition. The obtained outcomes were also collated with the readings taken in an actual soil sample. For this purpose, an open container sensor, which allows investigating atmospheric water deposition in soil, was manufactured. It turned out that the readings taken by the porous ceramic plate sensor reflected the outcomes of the measurements performed in a soil sample.

  9. Ground state lasing at 1.30 microm from InAs/GaAs quantum dot lasers grown by metal-organic chemical vapor deposition.

    Science.gov (United States)

    Guimard, Denis; Ishida, Mitsuru; Bordel, Damien; Li, Lin; Nishioka, Masao; Tanaka, Yu; Ekawa, Mitsuru; Sudo, Hisao; Yamamoto, Tsuyoshi; Kondo, Hayato; Sugawara, Mitsuru; Arakawa, Yasuhiko

    2010-03-12

    We investigated the effects of post-growth annealing on the photoluminescence (PL) characteristics of InAs/GaAs quantum dots (QDs) grown by metal-organic chemical vapor deposition (MOCVD). The onset temperature at which both the peak linewidth and the PL intensity degraded and the blueshift of the ground state emission wavelength occurred was found to depend on both the QD density and the In composition of the capping layer. This behavior is particularly important in view of QD integration in photonic devices. From the knowledge of the dependences of the PL characteristics after annealing on the QD and capping growth conditions, ground state lasing at 1.30 microm could be demonstrated from InAs/GaAs QDs grown by MOCVD. Finally, we compared the laser characteristics of InAs/GaAs QDs with those of InAs/Sb:GaAs QDs, grown according to the antimony-mediated growth technique, and showed that InAs/Sb:GaAs QDs are more appropriate for laser fabrication at 1.3 microm by MOCVD.

  10. Ground state lasing at 1.30 {mu}m from InAs/GaAs quantum dot lasers grown by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Guimard, Denis; Ishida, Mitsuru; Bordel, Damien; Li Lin; Nishioka, Masao; Arakawa, Yasuhiko [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Tanaka, Yu; Kondo, Hayato; Sugawara, Mitsuru [QD Laser Inc., 1-8-1 Ohtemachi, Chyoda-ku, Tokyo 100-0004 (Japan); Ekawa, Mitsuru; Sudo, Hisao; Yamamoto, Tsuyoshi, E-mail: dguimard@iis.u-tokyo.ac.jp [Fujitsu Laboratories Limited, 10-1 Morinosato-Wakamiya, Atsugi 243-0197 (Japan)

    2010-03-12

    We investigated the effects of post-growth annealing on the photoluminescence (PL) characteristics of InAs/GaAs quantum dots (QDs) grown by metal-organic chemical vapor deposition (MOCVD). The onset temperature at which both the peak linewidth and the PL intensity degraded and the blueshift of the ground state emission wavelength occurred was found to depend on both the QD density and the In composition of the capping layer. This behavior is particularly important in view of QD integration in photonic devices. From the knowledge of the dependences of the PL characteristics after annealing on the QD and capping growth conditions, ground state lasing at 1.30 {mu}m could be demonstrated from InAs/GaAs QDs grown by MOCVD. Finally, we compared the laser characteristics of InAs/GaAs QDs with those of InAs/Sb:GaAs QDs, grown according to the antimony-mediated growth technique, and showed that InAs/Sb:GaAs QDs are more appropriate for laser fabrication at 1.3 {mu}m by MOCVD.

  11. The "Hoover" (vacuum cleaner) technique for calcifying tendonitis deposits excision and removal of the calcific debris.

    Science.gov (United States)

    Ehud, Atoun; Ehud, Rath; Alexander, Van Tongel; Ali, Narvani; Giusseppe, Sforza; Ofer, Levy

    2012-07-01

    A new technical tip for the improvement of the arthroscopic treatment of symptomatic calcifying tendinitis is described. Arthroscopic excision of calcifying tendonitis may result with multiple minute calcific debris in the subacromial bursa, causing severe post operative pain due to chemical irritation of the bursa. We suggest the use of a bladeless shaver barrel as a "Hoover" (vacuum cleaner) for arthroscopic clearance of these miniature calcific debris from the subacromial space after resection of the major deposits. The use of this technique resulted in good clinical outcome with improved post operative pain.

  12. High T(sub c) superconductors fabricated by plasma aerosol mist deposition technique

    Science.gov (United States)

    Wang, X. W.; Vuong, K. D.; Leone, A.; Shen, C. Q.; Williams, J.; Coy, M.

    1995-01-01

    We report new results on high T(sub c) superconductors fabricated by a plasma aerosol mist deposition technique, in atmospheric environment. Materials fabricated are YBaCuO, BiPbSrCaCuO, BaCaCuO precursor films for TlBaCaCuO, and other buffers such as YSZ. Depending on processing conditions, sizes of crystallites and/or particles are between dozens of nano-meters and several micrometers. Superconductive properties and other material characteristics can also be tailored.

  13. The "Hoover" (vacuum cleaner technique for calcifying tendonitis deposits excision and removal of the calcific debris

    Directory of Open Access Journals (Sweden)

    Atoun Ehud

    2012-01-01

    Full Text Available A new technical tip for the improvement of the arthroscopic treatment of symptomatic calcifying tendinitis is described. Arthroscopic excision of calcifying tendonitis may result with multiple minute calcific debris in the subacromial bursa, causing severe post operative pain due to chemical irritation of the bursa. We suggest the use of a bladeless shaver barrel as a "Hoover" (vacuum cleaner for arthroscopic clearance of these miniature calcific debris from the subacromial space after resection of the major deposits. The use of this technique resulted in good clinical outcome with improved post operative pain.

  14. Application of silver nanodendrites deposited on silicon in SERS technique for the trace analysis of paraquat

    Science.gov (United States)

    Cao Dao, Tran; Quynh Ngan Luong, Truc; Cao, Tuan Anh; Kieu, Ngoc Minh; Le, Van Vu

    2016-03-01

    In order to detect trace concentrations of organic or biological molecules by surface-enhanced Raman scattering (SERS) technique, the SERS-active substrates with high enhancement factor are required. The silver nanodendrites (AgNDs) are a growing class of such SERS-active substrates. This report presents the preliminary results of the trace detection of paraquat (PQ), a commonly used herbicide, with the use of SERS-active substrates, which have been made from AgNDs deposited on silicon. The AgNDs were produced either by electroless deposition, or by electrodeposition onto a silicon wafer, using aqueous solution of HF and AgNO3. It was observed that the silver dendrites are formed only when AgNO3 concentration is high enough. Next, it was found that with the additional assistance of an electric potential in the electrodeposition, the dendrites have grown up with the more perfect ramification. The AgNDs with more perfect branching gave the Raman spectrum of PQ with higher enhancement factor. More specifically, while the SERS-active substrates prepared from electrodeposited AgNDs were able to detect PQ with concentration as low as 0.01 ppm, the ones made from electroless deposited AgNDs could only detect PQ at concentration of hundreds times higher.

  15. Effect of thickness on optical properties of nickel vertical posts deposited by GLAD technique

    Science.gov (United States)

    Potočnik, J.; Nenadović, M.; Bundaleski, N.; Popović, M.; Rakočević, Z.

    2016-12-01

    Nickel (Ni) thin films of different thicknesses (25 nm to 150 nm) were deposited on glass substrates using Glancing Angle Deposition technique. Characterization of obtained Ni films was performed by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry and by four-point probe method. Variations in optical parameters with thickness correlated with structural, chemical and electrical properties of nanostructured nickel thin films were studied. The results showed that deposit is porous and consists of nano-scaled columns, which grow perpendicular to the substrate. It was found that the size of the columns and the surface roughness change with film thickness. Spectroscopic ellipsometry revealed that the refractive index and extinction coefficient varied with thickness, which can be correlated with changes in microstructure of Ni films. Additionally, the relationship between the film microstructure and its resistivity was also analyzed. It was found that the variations in Ni films resistivity could be attributed to the changes in the width of the columns. The increasing of layer thickness leads to overall decrease of optical resistivity of nickel thin films.

  16. Strengthening of 3D printed fused deposition manufactured parts using the fill compositing technique.

    Directory of Open Access Journals (Sweden)

    Joseph T Belter

    Full Text Available In this paper, we present a technique for increasing the strength of thermoplastic fused deposition manufactured printed parts while retaining the benefits of the process such as ease, speed of implementation, and complex part geometries. By carefully placing voids in the printed parts and filling them with high-strength resins, we can improve the overall part strength and stiffness by up to 45% and 25%, respectively. We discuss the process parameters necessary to use this strengthening technique and the theoretically possible strength improvements to bending beam members. We then show three-point bend testing data comparing solid printed ABS samples with those strengthened through the fill compositing process, as well as examples of 3D printed parts used in real-world applications.

  17. Detecting salt deposition on a wind turbine blade using laser induced breakdown spectroscopy technique

    Science.gov (United States)

    Sathiesh Kumar, V.; Vasa, Nilesh J.; Sarathi, R.

    2013-07-01

    The study of pollution performance on a wind turbine blade due to lightning is important, as it can cause major damage to wind turbine blades. In the present work, optical emission spectroscopy (OES) technique is used to understand the influence of pollutant deposited on a wind turbine blade in an off-shore environment. A methodical experimental study was carried out by adopting IEC 60507 standards, and it was observed that the lightning discharge propagates at the interface between the pollutant and the glass fiber reinforced plastic (Material used in manufacturing of wind turbine blades). In addition, as a diagnostic condition monitoring technique, laser-induced breakdown spectroscopy (LIBS) is proposed and demonstrated to rank the severity of pollutant on the wind turbine blades from a remote area. Optical emission spectra observed during surface discharge process induced by lightning impulse voltage is in agreement with the spectra observed during LIBS.

  18. Processing and properties of lead zirconate titanate thin films on gallium nitride and ruthenium by sol-gel and chemical vapor deposition

    Science.gov (United States)

    Cao, Wei

    The Pb(ZrxTi1-x)O3 (PZT) thin films are potential candidates for ferroelectric random access memory (FeRAM) devices and components for microelectromechanical systems (MEMS). For example, the PZT/GaN system is being explored as RF MEMS devices for insertion in RF communication systems. A reproducible sol-gel process was developed for the deposition of PZT films on wurtzite (0001) GaN/sapphire substrates. The composition, crystallography, and interfacial nanochemistry were evaluated by various characterization techniques. The PZT/GaN heterostructure exhibited a chemically sharp interface with insignificant interdiffusion between PZT and GaN layers. However, PZT in metal -ferroelectric -semiconductor (MFS) configuration showed lower capacitance and asymmetrical polarization hysteresis compared to PZT in metal-ferroelectric-metal configuration. Such a deviation was attributed to the high depolarization field (Edepol) within PZT. To mitigate this issue, a two-pronged approach was used. First, the calculated spatial distribution of the electric field and potential, which stem from all the charge densities within the MFS configuration, demonstrated that by adjusting controllable parameters, one can minimize Edepol and maximize polarization. Second, a robust metal-organic chemical vapor deposition (MOCVD) process was developed to fabricate high quality PZT thin films on GaN. In this experimental approach, phase-pure and highly (111) oriented PZT films were deposited on GaN/sapphire substrates by MOCVD. The orientation relationships of PZT/GaN system were determined using x-ray pole figure and high-resolution transmission electron microscopy (TEM). The nanochemistry of the PZT/GaN interface, studied using analytical TEM, indicated a chemically sharp interface with interdiffusion limited to a region below 5 nm. The properties of MOCVD-PZT on GaN are briefly compared with PZT by sol-gel processing, rf sputtering, and pulsed laser deposition. Additionally, a preliminary study

  19. Thin alumina and silica films by chemical vapor deposition (CVD)

    NARCIS (Netherlands)

    Hofman, R.; Morssinkhof, R.W.J.; Fransen, T.; Westheim, J.G.F.; Gellings, P.J.

    1993-01-01

    Alumina and silica coatings have been deposited by MOCVD (Metal Organic Chemical Vapor Deposition) on alloys to protect them against high temperature corrosion. Aluminium Tri-lsopropoxide (ATI) and DiAcetoxyDitertiaryButoxySilane (DAOBS) have been used as metal organic precursors to prepare these ce

  20. Status of HgCdTe Barrier Infrared Detectors Grown by MOCVD in Military University of Technology

    Science.gov (United States)

    Kopytko, M.; Jóźwikowski, K.; Martyniuk, P.; Gawron, W.; Madejczyk, P.; Kowalewski, A.; Markowska, O.; Rogalski, A.; Rutkowski, J.

    2016-09-01

    In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor /acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07" and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley-Read-Hall, Auger, and tunneling currents.

  1. Transport phenomena and the effects of reactor geometry for epitaxial GaN growth in a vertical MOCVD reactor

    Science.gov (United States)

    Tseng, Chien-Fu; Tsai, Tsung-Yen; Huang, Yen-Hsiu; Lee, Ming-Tsang; Horng, Ray-Hua

    2015-12-01

    In this study a numerical simulation was carried out to analyze the transport phenomena in a vertical type metal organic chemical vapor deposition (MOCVD) reactor for Gallium Nitride (GaN) growth. The simulated results were compared and validated by experiment. The effects of showerhead design and chamber height are investigated and discussed. It was found that, by properly adjusting the height of the chamber, both the growth rate and film uniformity could be significantly improved. This is attributed to the suppression of the thermal and mass transfer boundary layers by the injection flow of reacting gas mixtures, as well as the confined vertical vortices caused by the geometry of the reduced space. However, inappropriate design of the distance between the showerhead and the susceptor can result in uneven distribution of the organic source in the vicinity of the substrate surface resulting in an uneven growth rate of the GaN film. Consequently, there exists an optimal chamber height that will give the best growth rate and uniformity to the GaN film as discussed in this study. This study provides comprehensive insight into the transport phenomena of GaN growth that includes coupled heat and mass transfer as well as chemical reactions. The results provide important information in a succinct format and enable decisions to be made about the showerhead and the geometrical design and size of a vertical MOCVD reactor.

  2. 3D fibre deposition and stereolithography techniques for the design of multifunctional nanocomposite magnetic scaffolds.

    Science.gov (United States)

    De Santis, Roberto; D'Amora, Ugo; Russo, Teresa; Ronca, Alfredo; Gloria, Antonio; Ambrosio, Luigi

    2015-10-01

    Magnetic nanocomposite scaffolds based on poly(ε-caprolactone) and poly(ethylene glycol) were fabricated by 3D fibre deposition modelling (FDM) and stereolithography techniques. In addition, hybrid coaxial and bilayer magnetic scaffolds were produced by combining such techniques. The aim of the current research was to analyse some structural and functional features of 3D magnetic scaffolds obtained by the 3D fibre deposition technique and by stereolithography as well as features of multimaterial scaffolds in the form of coaxial and bilayer structures obtained by the proper integration of such methods. The compressive mechanical behaviour of these scaffolds was investigated in a wet environment at 37 °C, and the morphological features were analysed through scanning electron microscopy (SEM) and X-ray micro-computed tomography. The capability of a magnetic scaffold to absorb magnetic nanoparticles (MNPs) in water solution was also assessed. confocal laser scanning microscopy was used to assess the in vitro biological behaviour of human mesenchymal stem cells (hMSCs) seeded on 3D structures. Results showed that a wide range of mechanical properties, covering those spanning hard and soft tissues, can be obtained by 3D FDM and stereolithography techniques. 3D virtual reconstruction and SEM showed the precision with which the scaffolds were fabricated, and a good-quality interface between poly(ε-caprolactone) and poly(ethylene glycol) based scaffolds was observed for bilayer and coaxial scaffolds. Magnetised scaffolds are capable of absorbing water solution of MNPs, and a preliminary information on cell adhesion and spreading of hMSCs was obtained without the application of an external magnetic field.

  3. Application of different techniques to obtain spatial estimates of debris flows erosion and deposition depths

    Science.gov (United States)

    Boreggio, Mauro; Gregoretti, Carlo; Degetto, Massimo; Bernard, Martino

    2016-04-01

    In Alpine regions, debris flows endanger settlements and human life. Danger mitigation strategies based on the preparation of hazard maps are necessary tools for the current land planning. To date, hazard maps are obtained by using one- or two-dimensional numerical models that are able to forecast the potential inundated areas, after careful calibration of those input parameters that directly affect the flow motion and its interaction with the ground surface (sediments entrainment or deposition). In principle, the reliability of these numerical models can be tested by flume experiments in laboratory using, for example, particles and water mixtures. However, for more realistic materials including coarse particles, the scaling effects are still difficult to account for. In some cases, where there are enough data (for example, point measures of flow depths and velocities or spatial estimation of erosion and deposition depths), these models can be tested against field observations. As it regards the spatial estimates of debris flows erosion and deposition depths, different approaches can be followed to obtain them, mainly depending on both the type and accuracy of the available initial data. In this work, we explain the methods that have been employed to obtain the maps of erosion and deposition depths for three occurred debris flows in the Dolomites area (North-Eastern Italian Alps). The three events are those occurred at Rio Lazer (Trento) on the 4th of November 1966, at Fiames (Belluno) on the 5th of July 2006 and at Rio Val Molinara (Trento) on the 15th of August 2010. For each case study, we present the available initial data and the related problems, the techniques that have been used to overcome them and finally the results obtained.

  4. Structural and optical properties of anatase TiO2 heteroepitaxial films prepared by MOCVD

    Science.gov (United States)

    Zhao, Wei; Feng, Xianjin; Xiao, Hongdi; Luan, Caina; Ma, Jin

    2016-11-01

    High-quality single-crystal anatase TiO2(a-TiO2) thin films have been obtained on SrTiO3 (STO) substrates using the metalorganic chemical vapor deposition (MOCVD) method. The optimal preparation process was explored. The lattice structure and epitaxial relationship were investigated by X-ray diffraction (XRD, both θ-2θ and Φ scans) and transmission electron microscopy (TEM). The results indicated that the film prepared at 550 °C with the Ti precursor molar flow rate of 4×10-7 mol/min had the best single crystalline quality, for which a clear epitaxial relationship of a-TiO2 (001)||STO (100) with a-TiO2 [100]||STO [001bar] could be inferred. The elemental composition and proportion were studied by the X-ray photoelectron spectroscopy (XPS) method, which proved the deposited film approximated stoichiometric TiO2. The samples showed high transparency of 70-80% in the visible range.

  5. CaCu{sub 3}Ti{sub 4}O{sub 12} thin films on conductive oxide electrode: A comparative study between chemical and physical vapor deposition routes

    Energy Technology Data Exchange (ETDEWEB)

    Catalano, Maria R.; Malandrino, Graziella [Dipartimento di Scienze Chimiche, Universita di Catania, and INSTM, UdR Catania, Viale A. Doria 6, 95125 Catania (Italy); Bongiorno, Corrado [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy); Toro, Roberta G. [Istituto per lo Studio dei Materiali Nanostrutturati, ISMN-CNR, Via dei Taurini, 19, 00185 Roma (Italy); Fiorenza, Patrick [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy); Bodeux, Romain [Laboratoire LEMA, UMR 6157 CNRS/CEA, Universite F. Rabelais, Parc de Grandmont, 37200 Tours (France); STMicroelectronics, R and D, Rue Pierre et Marie Curie, 37000 Tours (France); Wolfman, Jerome; Gervais, Monique; Lambert, Cecile Autret; Gervais, Francois [Laboratoire LEMA, UMR 6157 CNRS/CEA, Universite F. Rabelais, Parc de Grandmont, 37200 Tours (France); Lo Nigro, Raffaella, E-mail: raffaella.lonigro@imm.cnr.it [Istituto per la Microelettronica e Microsistemi, IMM-CNR, Strada VIII 5, 95121 Catania (Italy)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Dielectrics growth and characterization is one of the most hot topics of materials science and microelectronics. Black-Right-Pointing-Pointer CaCu{sub 3}Ti{sub 4}O{sub 12} perovskite, recently, demonstrated to possess peculiar dielectric properties (Science, 2001, 293, 673-676). Black-Right-Pointing-Pointer To date no deep discussion on the growth processes, properties and perspective of CCTO thin films has been proposed. Black-Right-Pointing-Pointer Our paper is an effective example of interdisciplinarity, since the comparison between PLD and MOCVD has been addressed. Black-Right-Pointing-Pointer Great attention has been paid to CaCu{sub 3}Ti{sub 4}O{sub 12} film/substrate interfaces since dielectric properties are strongly affected. - Abstract: Metal Organic Chemical Vapor Deposition (MOCVD) and Pulsed Laser Deposition (PLD) techniques have been used for the growth of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) thin films on La{sub 0.9}Sr{sub 1.1}NiO{sub 4}/LaAlO{sub 3} (LSNO/LAO) stack. (1 0 0) oriented CCTO films have been formed through both deposition routes and film complete structural and morphological characterizations have been carried out using several techniques (X-ray diffraction, scanning electron microscopy, energy-filtered transmission electron microscopy). The comparative study demonstrated some differences at the CCTO/LSNO interfaces depending on the adopted deposition technique. Chemical/structural modification of the LSNO electrode probably occurred as a function of the different oxygen partial pressure used in the PLD and MOCVD processes.

  6. Designed nanostructured pt film for electrocatalytic activities by underpotential deposition combined chemical replacement techniques.

    Science.gov (United States)

    Huang, Minghua; Jin, Yongdong; Jiang, Heqing; Sun, Xuping; Chen, Hongjun; Liu, Baifeng; Wang, Erkang; Dong, Shaojun

    2005-08-18

    Multiple-deposited Pt overlayer modified Pt nanoparticle (MD-Pt overlayer/PtNPs) films were deliberately constructed on glassy carbon electrodes through alternately multiple underpotential deposition (UPD) of Ag followed redox replacement reaction by Pt (II) cations. The linear and regular growth of the films characterized by cyclic voltammetry was observed. Atomic force spectroscopy (AFM) provides the surface morphology of the nanostructured Pt films. Rotating disk electrode (RDE) voltammetry and rotating ring-disk electrode (RRDE) voltammetry demonstrate that the MD-Pt overlayer/PtNPs films can catalyze an almost four-electron reduction of O(2) to H(2)O in air-saturated 0.1 M H(2)SO(4). Thus-prepared Pt films behave as novel nanostructured electrocatalysts for dioxygen reduction and hydrogen evolution reaction (HER) with enhanced electrocatalytic activities, in terms of both reduction peak potential and peak current, when compared to that of the bulk polycrystalline Pt electrode. Additionally, it is noted that after multiple replacement cycles, the electrocatalytic activities improved remarkably, although the increased amount of Pt is very low in comparison to that of pre-modified PtNPs due to the intrinsic feature of the UPD-redox replacement technique. In other words, the electrocatalytic activities could be improved markedly without using very much Pt by the technique of tailoring the catalytic surface. These features may provide an interesting way to produce Pt catalysts with a reliable catalytic performance as well as a reduction in cost.

  7. Surface characterization of III-V MOCVD films from heterocyclic single-source precursors; Oberflaechencharakterisierung von III-V MOCVD-Filmen aus heterozyklischen Single Source Precursoren

    Energy Technology Data Exchange (ETDEWEB)

    Seemayer, Andreas

    2009-07-13

    In the present thesis the sublimation and evaporation properties of heterocyclic gallium and antimony containing single-source precursors as well as the chemical composition and morphology of the films fabricated from this were studied. The single-source precursors available by a new synthesis route were characterized concerning their evaporation properties and the obtained films studied surface-physically. By this way the process parameters were optimized and the applicability of the single-source precursors in HV-MOCVD processes studied. By evaporation experiments in the UHV it could be shown that thereby lighter ligands like ethyl- and methyl-groups lead to a lower contamination of the reaction space with carbon containing molecules. Furthermore it was expected that the 6-rings synthetized with short ligands exhibit a high stability. This however could not be confirmed. By unwanted parasitary reactions in the gaseous phase respectively dissociative sublimation in the gaseous phase a deposition of GaSb with these precursors was not possible. The 4-ring stabilized with tertiary-butyl and ethyl-groups caused in the evaporation the largest contamination of the gaseous phase, becauselonger-chain hydrocarbons exhibil only a bad pump cross section. By parasitary reactions originating elementary antimony is detectable in the gaseous phase. The films were studied concerning their chemical composition and their transport- respectively storage-conditioned surface contamination. Furthermore it has become clear that not only a purely synthetized precursor substance but also the reactor design is deciding for a successful deposition and a high film quality. First by successive optimization of the evaporation geometry it was possible to reduce the roughness of the produced GaSb films down to about 10 nm-30 nm.

  8. Experimental techniques to determine salt formation and deposition in supercritical water oxidation reactors

    Energy Technology Data Exchange (ETDEWEB)

    Chan, J.P.C.; LaJeunesse, C.A.; Rice, S.F.

    1994-08-01

    Supercritical Water Oxidation (SCWO) is an emerging technology for destroying aqueous organic waste. Feed material, containing organic waste at concentrations typically less than 10 wt % in water, is pressurized and heated to conditions above water`s critical point where the ability of water to dissolve hydrocarbons and other organic chemicals is greatly enhanced. An oxidizer, is then added to the feed. Given adequate residence time and reaction temperature, the SCWO process rapidly produces innocuous combustion products. Organic carbon and nitrogen in the feed emerge as CO{sub 2} and N{sub 2}; metals, heteroatoms, and halides appear in the effluent as inorganic salts and acids. The oxidation of organic material containing heteroatoms, such as sulfur or phosphorous, forms acid anions. In the presence of metal ions, salts are formed and precipitate out of the supercritical fluid. In a tubular configured reactor, these salts agglomerate, adhere to the reactor wall, and eventually interfere by causing a flow restriction in the reactor leading to an increase in pressure. This rapid precipitation is due to an extreme drop in salt solubility that occurs as the feed stream becomes supercritical. To design a system that can accommodate the formation of these salts, it is important to understand the deposition process quantitatively. A phenomenological model is developed in this paper to predict the time that reactor pressure begins to rise as a function of the fluid axial temperature profile and effective solubility curve. The experimental techniques used to generate effective solubility curves for one salt of interest, Na{sub 2}SO{sub 4}, are described, and data is generated for comparison. Good correlation between the model and experiment is shown. An operational technique is also discussed that allows the deposited salt to be redissolved in a single phase and removed from the affected portion of the reactor. This technique is demonstrated experimentally.

  9. Investigation on vanadium oxide thin films deposited by spray pyrolysis technique

    Energy Technology Data Exchange (ETDEWEB)

    Margoni, Mudaliar Mahesh; Mathuri, S.; Ramamurthi, K., E-mail: krmurthin@yahoo.co.in, E-mail: ramamurthi.k@ktr.srmuniv.ac.in [Crystal Growth and Thin Film Laboratory, Department of Physics and Nanotechnology, Faculty of Engineering and Technology, SRM University, Kattankulathur – 603 203, Kancheepuram Dt., Tamil Nadu (India); Babu, R. Ramesh [Crystal Growth and Thin Film Laboratory, School of Physics, Bharathidasan University, Tiruchirappalli – 620024, Tamil Nadu (India); Sethuraman, K. [School of Physics, Madurai Kamaraj University, Madurai – 625 021, Tamil Nadu (India)

    2016-05-06

    Vanadium oxide thin films were deposited at 400 °C by spray pyrolysis technique using 0.1 M aqueous precursor solution of ammonium meta vanadate (AMV) with two different pH values. X-ray diffraction results showed that the film prepared using aqueous precursor AMV solution (solution A; pH 7) is amorphous in nature and the film prepared by adding HNO{sub 3} in the AMV aqua solution A (solution B; pH 3) is polycrystalline in nature. Vanadium oxide film prepared from the precursor solution B is in the mixed phases of V{sub 2}O{sub 5} and V{sub 4}O{sub 7}. Crystallinity is improved for the film prepared using solution B when compared to film prepared from solution A. Crystallite size, strain and dislocation density calculated for the film prepared from solution B is respectively 72.1 nm, 0.4554 × 10{sup −3} lin.{sup −2}m{sup −4} and 1.7263 × 10{sup 14} lin.m{sup −2}. Morphology study revealed that the size of the flakes formed on the surface of the films is influenced by the pH of the precursor solution. Average Visible Transmittance and maximum transmittance of the deposited films exceed 70% and the direct optical band gap value calculated for the films deposited from A and B solution is 1.91 eV and 2.08 eV respectively.

  10. Using 137Cs Tracer Technique to Evaluate Erosion and Deposition of Black Soil in Northeast China

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Soil and water losses through erosion have been serious in the black soil region of Northeast China. Therefore, a sloping cultivated land in Songnen Plain was selected as a case study to: 1) determine the 137Cs reference inventory in the study area; 2) calculate erosion and deposition rates of black soil on different slope locations; 3) conduct a sensitivity analysis of some model parameters; and 4) compare overall outputs using four different models. Three transects were set in the field with five slope locations for each transect, including summit, shoulder-slope, back-slope, foot-slope, and toe-slope. Field measurements and model simulation were used to estimate a bomb-derived 137Cs reference inventory in the study area.Soil erosion and deposition rates were estimated using four 137Cs models and percentage of 137Cs loss/gain. The 137Cs reference value in the study area was 2 232.8 Bq m-2 with 137Cs showing a clear topographic pattern, decreasing from the summit to shoulder-slope, then increasing again at the foot-slope and reaching a maximum at the toe-slope. Predicted soil redistribution rates for different slope locations varied. Among models, the Yang Model (YANG-M) overestimated erosion loss but underestimated deposition. However, the standard mass balance model (MBM1) gave predictions similar to a mass balance model incorporating soil movement by tillage (MBM2). Sensitivity analysis of the proportion factor γand distribution pattern of 137Cs in the surface layer demonstrated the impact of 137Cs enrichment on calculation of the soil erosion rate. Factors influencing the redistribution of fallout 137Cs in landscape should be fully considered as calculating soil redistribution rate using 137Cs technique.

  11. Thermodynamic analysis of growth of iron oxide films by MOCVD using tris(-butyl-3-oxo-butanoato)iron(III) as precursor

    Indian Academy of Sciences (India)

    Sukanya Dhar; K Shalini; S A Shivashankar

    2008-10-01

    Thermodynamic calculations, using the criterion of minimization of total Gibbs free energy of the system, have been carried out for the metalorganic chemical vapour deposition (MOCVD) process involving the -ketoesterate complex of iron [tris(-butyl-3-oxo-butanoato)iron(III) or Fe(tbob)3] and molecular oxygen. The calculations predict, under different CVD conditions such as temperature and pressure, the deposition of carbon-free pure Fe3O4, mixtures of different proportions of Fe3O4 and Fe2O3, and pure Fe2O3. The regimes of these thermodynamic CVD parameters required for the deposition of these pure and mixed phases have been depicted in a `CVD phase stability diagram’. In attempts at verification of the thermodynamic calculations, it has been found by XRD and SEM analysis that, under different conditions, MOCVD results in the deposition of films comprising pure and mixed phases of iron oxide, with no carbonaceous impurities. This is consistent with the calculations.

  12. Thickness effect on properties of titanium film deposited by d.c. magnetron sputtering and electron beam evaporation techniques

    Indian Academy of Sciences (India)

    Nishat Arshi; Junqing Lu; Chan Gyu Lee; Jae Hong Yoon; Bon Heun Koo; Faheem Ahmed

    2013-10-01

    This paper reports effect of thickness on the properties of titanium (Ti) film deposited on Si/SiO2 (100) substrate using two different methods: d.c. magnetron sputtering and electron beam (e-beam) evaporation technique. The structural and morphological characterization of Ti film were performed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). XRD pattern revealed that the films deposited using d.c. magnetron sputtering have HCP symmetry with preferred orientation along (002) plane, while those deposited with e-beam evaporation possessed fcc symmetry with preferred orientation along (200) plane. The presence of metallic Ti was also confirmed by XPS analysis. FESEM images depicted that the finite sized grains were uniformly distributed on the surface and AFM micrographs revealed roughness of the film. The electrical resistivity measured using four-point probe showed that the film deposited using d.c. magnetron sputtering has lower resistivity of ∼13 cm than the film deposited using e-beam evaporation technique, i.e. ∼60 cm. The hardness of Ti films deposited using d.c. magnetron sputtering has lower value (∼7.9 GPa) than the film deposited using e-beam technique (∼9.4 GPa).

  13. Recent advances in controlled synthesis of two-dimensional transition metal dichalcogenides via vapour deposition techniques

    KAUST Repository

    Shi, Yumeng

    2014-10-20

    In recent years there have been many breakthroughs in two-dimensional (2D) nanomaterials, among which the transition metal dichalcogenides (TMDs) attract significant attention owing to their unusual properties associated with their strictly defined dimensionalities. TMD materials with a generalized formula of MX2, where M is a transition metal and X is a chalcogen, represent a diverse and largely untapped source of 2D systems. Semiconducting TMD monolayers such as MoS2, MoSe2, WSe2 and WS2 have been demonstrated to be feasible for future electronics and optoelectronics. The exotic electronic properties and high specific surface areas of 2D TMDs offer unlimited potential in various fields including sensing, catalysis, and energy storage applications. Very recently, the chemical vapour deposition technique (CVD) has shown great promise to generate high-quality TMD layers with a scalable size, controllable thickness and excellent electronic properties. Wafer-scale deposition of mono to few layer TMD films has been obtained. Despite the initial success in the CVD synthesis of TMDs, substantial research studies on extending the methodology open up a new way for substitution doping, formation of monolayer alloys and producing TMD stacking structures or superlattices. In this tutorial review, we will introduce the latest development of the synthesis of monolayer TMDs by CVD approaches.

  14. [An investigation of HAP/organic polymer composite coatings prepared by electrochemical co-deposition technique].

    Science.gov (United States)

    Hu, Haobing; Lin, Changjian; Leng, Yang

    2003-03-01

    An electrochemical co-deposition technique has been developed to prepare a hydroxyapatite (HAP)/organic polymer composite coatings on Ti surface as new biomaterial of hard tissue. The composite coating of organic polymer and calcium phosphate is formed by adding a water soluble polymer of the ethylene series to NH4H2PO4-Ca (NO3)2 solution when conducting an appropriate electrochemical co-deposition experiment. The XRD, SEM, XPS, SIMS and nano indent measurements were performed to characterize the morphology, composition, structure and surface stiffness of the composite coating. It was found that the morphology and surface hardness of the coatings showed a remarkable modification when introducing a minor polymer to HAP coating, and the bonding force between the coating and metal substrate was distinctly increased. The incorporation of minor organic polymer into the HAP compound at molecular level will improve the mechanical properties and morphology of the composite coatings, and this may be helpful to raising its bio-activity.

  15. Kinetics of niobium carbide coating produced on AISI 1040 steel by thermo-reactive deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Ugur

    2004-07-15

    There are a lot of technologically interesting characteristics of niobium carbide coating deposited by pack method which is the production of hard, wear-resistant, oxidation and corrosion resistant coating layer on the steel substrates. In the present study, the growth kinetics of niobium carbide layer deposited by thermo-reactive diffusion techniques in a solid medium on steel samples was reported. Niobium carbide coating treatment was performed on AISI 1040 steels in the powder mixture consisting of ferro-niobium, ammonium chloride and alumina at 1073, 1173 and 1273 K for 1-4 h. The presence of NbC and Nb{sub 2}C phases formed on the surface of the steel substrates was confirmed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analyses. Niobium carbide layer thickness ranges from 3.42{+-}0.52 to 11.78{+-}2.29 {mu}m depending upon the treatment time and temperature. Layer growth kinetics was analyzed by measuring the depth of niobium carbide layer as a function of time and temperature. The kinetics of niobium carbide coating by pack method shows a parabolic relationship between carbide layer thickness and treatment time, and the activation energy for the process is estimated to be 91.257 kJ mol{sup -1}. Moreover, an attempt was made to investigate the possibility of predicting the contour diagram of niobium carbide layer variation and to establish some empirical relationships between process parameters and niobium carbide layer thickness.

  16. Polyethylene-Carbon Nanotube Composite Film Deposited by Cold Spray Technique

    Science.gov (United States)

    Ata, Nobuhisa; Ohtake, Naoto; Akasaka, Hiroki

    2017-08-01

    Carbon nanotubes (CNTs) are high-performance materials because of their superior electrical conductivity, thermal conductivity, and self-lubrication, and they have been studied for application to polymer composite materials as fillers. However, the methods of fabricating polymer composites with CNTs, such as injection molding, are too complicated for industrial applications. We propose a simple cold spray (CS) technique to obtain a polymer composite of polyethylene (PE) and CNTs. The composite films were deposited by CS on polypropylene and nano-porous structured aluminum substrates. The maximum thickness of the composite film was approximately 1 mm. Peaks at G and D bands were observed in the Raman spectra of the films. Scanning electron microscopy images of the film surface revealed that PE particles were melted by the acceleration gas and CNTs were attached with melted PE. The PE particles solidified after contact with the substrate. These results indicate that PE-CNT composite films were successfully deposited on polypropylene and nano-porous structured aluminum substrates by CS.

  17. Carbon nanotubes for supercapacitors: Consideration of cost and chemical vapor deposition techniques

    Institute of Scientific and Technical Information of China (English)

    Chao Zheng; Weizhong Qian; Chaojie Cui; Guanghui Xu; Mengqiang Zhao; Guili Tian; Fei Wei

    2012-01-01

    In this topic,we first discussed the requirement and performance of supercapacitors using carbon nanotubes (CNTs) as the electrode,including specific surface area,purity and cost.Then we reviewed the preparation technique of single walled CNTs (SWNTs) in relatively large scale by chemical vapor deposition method.Its catalysis on the decomposition of methane and other carbon source,the reactor type and the process control strategies were discussed.Special focus was concentrated on how to increase the yield,selectivity,and purity of SWNTs and how to inhibit the formation of impurities,including amorphous carbon,multiwalled CNTs and the carbon encapsulated metal particles,since these impurities seriously influenced the performance of SWNTs in supercapacitors.Wish it be helpful to further decrease its product cost and for the commercial use in supercapacitors.

  18. Depositing nanoparticles on a silicon substrate using a freeze drying technique

    Science.gov (United States)

    Sigehuzi, Tomoo

    2017-08-01

    For the microscopic observation of nanoparticles, an adequate sample preparation is an essential part of this task. Much research has been performed for usable preparation methods that will yield aggregate-free samples. A freeze drying technique, which only requires a -80 °C freezer and a freeze dryer, is shown to provide an on-substrate dispersion of mostly isolated nanoparticles. The particle density could be made sufficiently high for efficient observations using atomic force microscopy. Since this sandwich method is purely physical, it could be applied to deposit various nanoparticles independent of their surface chemical properties. Suspension film thickness, or the dimensionality of the suspension film, was shown to be crucial for the isolation of the particles. Silica nanoparticles were dispersed on a silicon substrate using this method and the sample properties were examined using atomic force microscopy.

  19. Tight comparison of Mg and Y thin film photocathodes obtained by the pulsed laser deposition technique

    Science.gov (United States)

    Lorusso, A.; Gontad, F.; Solombrino, L.; Chiadroni, E.; Broitman, E.; Perrone, A.

    2016-11-01

    In this work Magnesium (Mg) and Yttrium (Y) thin films have been deposited on Copper (Cu) polycrystalline substrates by the pulsed laser ablation technique for photocathode application. Such metallic materials are studied for their interesting photoemission properties and are proposed as a good alternative to the Cu photocathode, which is generally used in radio-frequency guns. Mg and Y films were uniform with no substantial differences in morphology; a polycrystalline structure was found for both of them. Photoemission measurements of such cathodes based on thin films were performed, revealing a quantum efficiency higher than Cu bulk. Photoemission theory according to the three-step model of Spicer is invoked to explain the superior photoemission performance of Mg with respect to Y.

  20. Optical characteristics of transparent samarium oxide thin films deposited by the radio-frequency sputtering technique

    Indian Academy of Sciences (India)

    A A ATTA; M M EL-NAHASS; KHALED M ELSABAWY; M M ABD EL-RAHEEM; A M HASSANIEN; A ALHUTHALI; ALI BADAWI; AMAR MERAZGA

    2016-11-01

    Transparent metal oxide thin films of samarium oxide (Sm$_2$O$_3$) were prepared on pre-cleaned fused optically flat quartz substrates by radio-frequency (RF) sputtering technique. The as-deposited thin films were annealed at different temperatures (873, 973 and 1073 K) for 4 h in air under normal atmospheric pressure. The topological morphology of the film surface was characterized by using atomic force microscopy (AFM). The optical properties of the as-prepared and annealed thin films were studied using their reflectance and transmittance spectra at nearly normal incident light. The estimated direct optical band gap energy (E$^{d}_{g}$ ) values were found to increase by increasing the annealing temperatures. The dispersion curves of the refractive index of Sm$_2$O$_3$ thin films were found to obey the single oscillator model.

  1. Structural and optical properties of CdO thin films deposited by RF magnetron sputtering technique

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, G. Anil, E-mail: anilhcu@gmail.com; Reddy, M. V. Ramana, E-mail: anilhcu@gmail.com [Department of Physics, Osmania University, Hyderabad-500007 (India); Reddy, Katta Narasimha, E-mail: anilhcu@gmail.com [Department of Physics, Mahatma Gandhi University, Nalgonda-508003 (India)

    2014-04-24

    Cadmium oxide (CdO) thin films were deposited on glass substrate by r.f. magnetron sputtering technique using a high purity (99.99%) Cd target of 2-inch diameter and 3 mm thickness in an Argon and oxygen mixed atmosphere with sputtering power of 50W and sputtering pressure of 2×10{sup −2} mbar. The prepared films were characterized by X-ray diffraction (XRD), optical spectroscopy and scanning electron microscopy (SEM). The XRD analysis reveals that the films were polycrystalline with cubic structure. The visible range transmittance was found to be over 70%. The optical band gap increased from 2.7 eV to2.84 eV with decrease of film thickness.

  2. Thin alumina and silica films by chemical vapor deposition (CVD)

    OpenAIRE

    Hofman, R.; Morssinkhof, R.W.J.; Fransen, T.; Westheim, J.G.F.; Gellings, P.J.

    1993-01-01

    Alumina and silica coatings have been deposited by MOCVD (Metal Organic Chemical Vapor Deposition) on alloys to protect them against high temperature corrosion. Aluminium Tri-lsopropoxide (ATI) and DiAcetoxyDitertiaryButoxySilane (DAOBS) have been used as metal organic precursors to prepare these ceramic coatings. The influence of several process steps on the deposition rate and surface morphology is discussed. The deposition of SiO2 at atmospheric pressure is kinetically limited below 833 K ...

  3. Synthesis of designed materials by laser-based direct metal deposition technique: Experimental and theoretical approaches

    Science.gov (United States)

    Qi, Huan

    Direct metal deposition (DMD), a laser-cladding based solid freeform fabrication technique, is capable of depositing multiple materials at desired composition which makes this technique a flexible method to fabricate heterogeneous components or functionally-graded structures. The inherently rapid cooling rate associated with the laser cladding process enables extended solid solubility in nonequilibrium phases, offering the possibility of tailoring new materials with advanced properties. This technical advantage opens the area of synthesizing a new class of materials designed by topology optimization method which have performance-based material properties. For better understanding of the fundamental phenomena occurring in multi-material laser cladding with coaxial powder injection, a self-consistent 3-D transient model was developed. Physical phenomena including laser-powder interaction, heat transfer, melting, solidification, mass addition, liquid metal flow, and species transportation were modeled and solved with a controlled-volume finite difference method. Level-set method was used to track the evolution of liquid free surface. The distribution of species concentration in cladding layer was obtained using a nonequilibrium partition coefficient model. Simulation results were compared with experimental observations and found to be reasonably matched. Multi-phase material microstructures which have negative coefficients of thermal expansion were studied for their DMD manufacturability. The pixel-based topology-optimal designs are boundary-smoothed by Bezier functions to facilitate toolpath design. It is found that the inevitable diffusion interface between different material-phases degrades the negative thermal expansion property of the whole microstructure. A new design method is proposed for DMD manufacturing. Experimental approaches include identification of laser beam characteristics during different laser-powder-substrate interaction conditions, an

  4. Processing of CuInSe{sub 2}-based solar cells: Characterization of deposition processes in terms of chemical reaction analyses. Phase 2 Annual Report, 6 May 1996--5 May 1997

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, T.

    1999-10-20

    This report describes research performed by the University of Florida during Phase 2 of this subcontract. First, to study CIGS, researchers adapted a contactless, nondestructive technique previously developed for measuring photogenerated excess carrier lifetimes in SOI wafers. This dual-beam optical modulation (DBOM) technique was used to investigate the differences between three alternative methods of depositing CdS (conventional chemical-bath deposition [CBD], metal-organic chemical vapor deposition [MOCVD], and sputtering). Second, a critical assessment of the Cu-In-Se thermochemical and phase diagram data using standard CALPHAD procedures is being performed. The outcome of this research will produce useful information on equilibrium vapor compositions (required annealing ambients, Sex fluxes from effusion cells), phase diagrams (conditions for melt-assisted growth), chemical potentials (driving forces for diffusion and chemical reactions), and consistent solution models (extents of solid solutions and extending phase diagrams). Third, an integrated facility to fabricate CIS PV devices was established that includes migration-enhanced epitaxy (MEE) for deposition of CIS, a rapid thermal processing furnace for absorber film formation, sputtering of ZnO, CBD or MOCVD of CdS, metallization, and pattern definition.

  5. Investigation of H2/CH4 mixed gas plasma post-etching process for ZnO:B front contacts grown by LP-MOCVD method in silicon-based thin-film solar cells

    Science.gov (United States)

    Wang, Li; Zhang, Xiaodan; Zhao, Ying; Yamada, Takuto; Naito, Yusuke

    2014-10-01

    A new plasma post-etching method, H2/CH4 mixed gas plasma, is introduced to modify ZnO:B films grown by LP-MOCVD technique, successfully relaxing the double trade-offs, i.e., transparency/conductivity trade-off and surface texture/Voc and FF trade-off. To deeply evaluate the post-etching process, optical emission spectroscopy technique is applied to diagnose the plasma condition. Upon different etching power, three distinct possible etching mechanisms are identified by analyzing the evolution of Hα*, Hβ*, CH* emission species in the plasma space. It is demonstrated that Hβ* and CH* species are responsible for the physical etching process and chemical etching process, respectively, from which a new “soft” surface morphology is formed with a combination of micro- and nano-sized texture. Additionally, Hα* species can bond with ZnO and also passivate the grains boundaries, thereby making both the carrier concentration and hall mobility increase. This process is defined as chemical bonding process. Finally, pin-type a-Si:H single-junction solar cells with an optimized device structure is grown on the etched ZnO:B substrate. The corresponding electrical parameters, such as Jsc, Voc and FF, are simultaneously improved compared with the solar cell deposited on as-grown ZnO:B substrate with the same fabrication process. As a consequence, a noteworthy 8.85% conversion-efficiency is achieved with an absorber layer thickness only 160 nm.

  6. Regular growth combined with lateral etching in diamond deposited over silicon substrate by using hot filament chemical vapor deposition technique

    Science.gov (United States)

    Ali, M.; Ürgen, M.

    2013-05-01

    Hot filament chemical vapor deposition has proved to be an attractive method for growing diamond films with good quality and higher growth rate. Diamond films were produced at deposition parameters under which, it is possible to have regular growth combined with lateral etching (RGCLE). Fracture cross-section SEM images showed that RGCLE initiated over polycrystalline diamond film and proceeded by the growth of consecutive steps in each crystallite, which terminated with square/rectangle shaped facets. All the diamond films exhibit RGCLE but with different type of growth behavior. Present work discusses the cyclic formation of the steps in diamond crystallites and RGCLE modes. RGCLE in diamond film may find important applications where heat absorption and dissipation are key issues.

  7. Optical and Magnetic Properties of Fe-Doped GaN Diluted Magnetic Semiconductors Prepared by MOCVD Method

    Institute of Scientific and Technical Information of China (English)

    TAG Zhi-Kuo; ZHANG Rong; CUI Xu-Gao; XIU Xiang-Qian; ZHANG Guo-Yu; XIE Zi-Li; GU Shu-Lin; SHI Yi; ZHENG You-Dou

    2008-01-01

    @@ Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method (MOCVD).Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measurements.There are no detectable second phases formed during growth and no significant degradation in crystalline quality as Fe ions are doped. Fe-related optical transitions are observed in photoluminescence spectra. Magnetic measurements reveal that the films show room-temperature ferromagnetic behaviour. The ferromagnetism may originate from carrier-mediated Fe-doped CaN diluted magnetic semiconductors or nanoscale iron dusters and Fe-N compounds which we have not detected.

  8. Structural and morphological characterizations of ZnO films grown on GaAs substrates by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Agouram, S.; Zuniga Perez, J.; Munoz-Sanjose, V. [Universitat de Valencia, Departamento de Fisica Aplicada y Electromagnetismo, Burjassot (Spain)

    2007-07-15

    ZnO films were grown on GaAs(100), GaAs(111)A and GaAs(111)B substrates by metal organic chemical vapour deposition (MOCVD). Diethylzinc (DEZn) and tertiarybutanol (t-butanol) were used as Zn and O precursors, respectively. The influence of the growth temperature and GaAs substrate orientation on the crystalline orientation and morphology of the ZnO grown films has been analysed. Crystallinity of grown films was studied by X-ray diffraction (XRD); thickness and morphology of ZnO films were investigated by scanning electron microscopy (SEM). SEM results reveal significant differences between morphologies depending on growth temperature but not significant differences were detected on the texture of grown films. (orig.)

  9. Species transport and chemical reaction in a MOCVD reactor and their influence on the GaN growth uniformity

    Science.gov (United States)

    Zhang, Zhi; Fang, Haisheng; Yao, Qingxia; Yan, Han; Gan, Zhiyin

    2016-11-01

    Fluid flow, heat transfer, and species transport with chemical reactions have been investigated for gallium nitride (GaN) growth in a commercial metal-organic chemical vapor deposition (MOCVD) reactor. Both the growth rate and the growth uniformity are investigated zone by zone, as the wafers are divided into three zones/groups according to their distances to the susceptor center. The results show that species transport in the reactor is affected by the inlet conditions, i.e., the premixed or non-premixed inlet, the inlet temperature, the total gas flow rate, and the V/III component ratio, and reveal that the premixed inlet condition is preferred for uniform growth. Especially, a large total flow rate or a low V/III ratio results in both increase of the growth rate and improvement of the growth uniformity.

  10. Fe-Doped TiO2 Nanoparticles Produced via MOCVD: Synthesis, Characterization, and Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Siti Hajar Othman

    2011-01-01

    Full Text Available Iron (Fe-doped titanium dioxide (TiO2 nanoparticles were produced via the metallorganic chemical vapour deposition (MOCVD method at 700∘C. Different amounts of ferrocene as the Fe dopant source (0.001–0.05 g were introduced inside the reactor together with the titanium precursor in order to synthesize different Fe dopant concentrations of TiO2 nanoparticles. Nitrogen (N2 adsorption results showed that increasing the Fe dopant concentration caused a slight increase in the surface area of the nanoparticles due to the decrease in nanoparticle size. The UV-diffuse reflectance spectra demonstrated an absorption shift in Fe-doped TiO2 nanoparticles to longer wavelengths, thus showing an enhancement of the absorption in the visible spectrum. Bandgap energy values determined from the UV-diffuse reflectance spectra data decreased with an increase in the Fe dopant concentrations. The photocatalytic activity of Fe-doped TiO2 nanoparticles was investigated via degradation of methylene blue under UV and fluorescent light. It was found that Fe doping reduced the photocatalytic activity of the samples. Based on X-ray photoelectron spectroscopy (XPS results, it is believed that this is due to the unfavourable location of Fe3+ inside the interior matrix of the TiO2 nanoparticles rather than on the exterior surface, which would affect photocatalytic behaviour.

  11. Effect of silicon doping in InGaN/GaN heterostructure grown by MOCVD

    Science.gov (United States)

    Surender, S.; Pradeep, S.; Prabakaran, K.; Singh, Shubra; Baskar, K.

    2017-05-01

    In this work the effect of Si doped InGaN/GaN heterostructure is systematically studied. The n-InGaN /GaN heterostructure are grown on c-plane sapphire substrate by horizontal flow Metal Organic Chemical Vapor Deposition (MOCVD). The heterostructure samples are investigated by structural, optical, morphological and electrical studies using High Resolution X-ray diffraction (HRXRD), room temperature Photoluminescence (PL), Atomic Force Microscopy (AFM) and Hall measurement respectively. The composition of indium in n-InGaN/GaN heterostructure was calculated as 15.9% using epitaxy smooth fit software. The energy band gap (Eg) of the InGaN epilayer has been calculated as 2.78 eV using vigard's law. PL emission obtained at 446 nm for n-InGaN epilayer. AFM results indicate that the Si doped InGaN/GaN heterostructure has the root mean square (rms) roughness of about 0.59 nm for a scan area of 5×5 µm2 which has island like growth. Moreover, Hall measurements results shows that Si doped InGaN/GaN heterostructure possess carrier concentration of 4.2 × 1018cm-3 and mobility of 257 cm2/V s at room temperature.

  12. Variable Energy Positron Annihilation Spectroscopy of GaN Grown on Sapphire Substrates with MOCVD

    Institute of Scientific and Technical Information of China (English)

    HU Yi-Fan; C.D. Beling; S. Fung

    2005-01-01

    @@ Depth profiled Doppler broadening of positron annihilation spectroscopy (DBPAS), which is also called the variable energy positron annihilation spectroscopy (VEPAS), is used in characterization of GaN grown on sapphire substrates with metal-organic chemical vapour deposition (MOCVD). The GaN film and the film/substrate interface are investigated. The VEPFIT (variable energy positron fit) software was used for analysing the data,and the positron diffusion length of the sapphire is obtained. The results suggest that there is a highly defected region near the GaN/sapphire interface. This thin dislocated region is generated at the film/substrate interface to relieve the strain. Effects of implantation dose on defect formation, for the GaN/Sapphire samples, which implanted by Al+ ions, are also investigated. Studies on Al+ implanted GaN films (not including the interface and sapphire) have revealed that there are two different regions of implantation damage. For the low Al+ implantation dose samples, in the region close to the surface, defects are mainly composed of vacancy pairs with small amount of vacancy clusters, and in the interior region of the film the positron traps are vacancy clusters without micro-voids. For the highest dose sample, however, some positron trap centres are in the form of micro-voids in the second region.

  13. Heavy Metals and Trace Elements Atmospheric Deposition Studies in Tula Region Using Moss Biomonitors Technique

    CERN Document Server

    Ermakova, E V; Steinnes, E

    2002-01-01

    For the first time the moss biomonitors technique was used in air pollution studies in Tula Region (Central Russia), applying NAA, AAS. Moss samples were collected at 83 sites in accordance with the sampling strategy adopted in European projects on biomonitoring atmospheric deposition. A wide set of trace elements in mosses was determined. The method of epithermal neutron activation at IBR-2 reactor of FLNP JINR has made it possible to identify 33 elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, As, Br, Rb, Sr, Mo, Sb, I, Cs, Ba, La, Ce, Sm, Tb, Yb, Hf, Ta, W, Th, U) in the large-scale concentration range - from 10000 ppm for K to 0,001 ppm for Tb and Ta. Cu, Cd and Pb were determined by the flame AAS in the Norwegian Institute of Science and Technology. Using the graphical technique and principal component analysis allowed to separate plant, crustal and general pollution components in the moss. The obtained data will be used for constructing coloured maps of the distribution of elements over t...

  14. A review of hydroxyapatite-based coating techniques: Sol-gel and electrochemical depositions on biocompatible metals.

    Science.gov (United States)

    Asri, R I M; Harun, W S W; Hassan, M A; Ghani, S A C; Buyong, Z

    2016-04-01

    New promising techniques for depositing biocompatible hydroxyapatite-based coatings on biocompatible metal substrates for biomedical applications have continuously been exploited for more than two decades. Currently, various experimental deposition processes have been employed. In this review, the two most frequently used deposition processes will be discussed: a sol-gel dip coating and an electrochemical deposition. This study deliberates the surface morphologies and chemical composition, mechanical performance and biological responses of sol-gel dip coating as well as the electrochemical deposition for two different sample conditions, with and without coating. The review shows that sol-gel dip coatings and electrochemical deposition were able to obtain the uniform and homogeneous coating thickness and high adherent biocompatible coatings even in complex shapes. It has been accepted that both coating techniques improve bone strength and initial osseointegration rate. The main advantages and limitations of those techniques of hydroxyapatite-based coatings are presented. Furthermore, the most significant challenges and critical issues are also highlighted.

  15. Processing of PbTiO{sub 3} and Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} thin films by novel single-solid-source metalorganic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lu, P.; Li, H.; Sun, S. [New Mexico Inst. of Mining and Technology, Socorro, NM (United States). Dept. of Materials Science and Engineering; Tuttle, B. [Sandia National Labs., Albuquerque, NM (United States)

    1997-06-01

    Ferroelectric PbTiO{sub 3} (PT) and Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT) thin films have been deposited on (100) MgO and (111) Pt/SiO{sub 2}/(100)Si substrates by using a novel single-solid-source metalorganic chemical vapor deposition (MOCVD) technique. The new technique uses a powder delivery system to deliver the mixed precursor powders directly into a hot vaporizer from room temperature, therefore, avoiding any problems associated with polymerization or decomposition of the precursors before evaporation. The technique simplifies MOCVD processing significantly and can improve process reliability and reproducibility. The deposited PT and PZT films have a perovskite structure and are highly oriented with respect to the substrate. With improvement of process control, systematic studies of film evolution under various growth conditions have been carried out. Effects of substrate, substrate temperature, system vacuum, and precursor ratios in the mixture on film microstructure and properties will be presented in this paper.

  16. Synthesis, characterization, and thermal properties of homoleptic rare-earth guanidinates: promising precursors for MOCVD and ALD of rare-earth oxide thin films.

    Science.gov (United States)

    Milanov, Andrian P; Fischer, Roland A; Devi, Anjana

    2008-12-01

    Eight novel homoleptic tris-guanidinato complexes M[(N(i)Pr)(2)CNR(2)](3) [M = Y (a), Gd (b), Dy (c) and R = Me (1), Et (2), (i)Pr (3)] have been synthesized and characterized by NMR, CHN-analysis, mass spectrometry and infrared spectroscopy. Single crystal structure analysis revealed that all the compounds are monomers with the rare-earth metal center coordinated to six nitrogen atoms of the three chelating guanidinato ligands in a distorted trigonal prism geometry. With the use of TGA/DTA and isothermal TGA analysis, the thermal characteristics of all the complexes were studied in detail to evaluate their suitability as precursors for thin film deposition by MOCVD and ALD. The (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) showed excellent thermal characteristics in terms of thermal stability and volatility. Additionally, the thermal stability of the (i)Pr-Me(2)N-guanidinates of Y and Dy (1a, c) in solution was investigated by carrying out NMR decomposition experiments and both the compounds were found to be remarkably stable. All these studies indicate that (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) have the prerequisites for MOCVD and ALD applications which were confirmed by the successful deposition of Gd(2)O(3) and Dy(2)O(3) thin films on Si(100) substrates. The MOCVD grown films of Gd(2)O(3) and Dy(2)O(3) were highly oriented in the cubic phase, while the ALD grown films were amorphous.

  17. Investigation of defects in ultra-thin Al{sub 2}O{sub 3} films deposited on pure copper by the atomic layer deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Chang, M.L.; Wang, L.C. [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (China); Lin, H.C., E-mail: hclinntu@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (China); Chen, M.J., E-mail: mjchen@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (China); Lin, K.M. [Department of Materials Science and Engineering, Feng Chia University, No. 100, Wenhwa Road, Seatwen, Taichung 40724, Taiwan (China)

    2015-12-30

    Graphical abstract: Some residual OH ligands originating from incomplete reaction between TMA and surface species of OH* during ALD process induce the defects in deposited Al{sub 2}O{sub 3} films. Three possible types of defects are suggested. The analytic results indicate the defects are Type-I and/or Type-II but do not directly expose the substrate, like pinholes (Type-III). - Highlights: • Oxidation trials were conducted to investigate the defects in ultra-thin Al{sub 2}O{sub 3} films deposited ALD technique on pure copper. • The residual OH ligands in the deposited Al{sub 2}O{sub 3} films induce looser micro-structure which has worse oxidation resistance. • Superficial contamination particles on substrate surface are confirmed to be one of nucleation sites of the defects. - Abstract: Al{sub 2}O{sub 3} films with various thicknesses were deposited by the atomic layer deposition (ALD) technique on pure copper at temperatures of 100–200 °C. Oxidation trials were conducted in air at 200 °C to investigate the defects in these films. The analytic results show that the defects have a looser micro-structure compared to their surroundings, but do not directly expose the substrate, like pinholes. The film's crystallinity, mechanical properties and oxidation resistance could also be affected by these defects. Superficial contamination particles on the substrate surface are confirmed to be nucleation sites of the defects. A model for the mechanism of defect formation is proposed in this study.

  18. CdTe deposition by successive ionic layer adsorption and reaction (SILAR) technique onto ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Salazar, Raul; Delamoreanu, Alexandru; Saidi, Bilel; Ivanova, Valentina [CEA, LETI, MINATEC Campus, 17 Rue des Martyrs, 38054, Grenoble (France); Levy-Clement, Claude [CNRS, Institut de Chimie et des Materiaux de Paris-Est, 94320, Thiais (France)

    2014-09-15

    In this study is reported CdTe deposition by Successive Ionic Layer Adsorption and reaction (SILAR) at room temperature onto ZnO nanowires (NWs). The as-deposited CdTe layer exhibits poor crystalline quality and not well defined optical transition which is probably result of its amorphous nature. The implementation of an annealing step and chemical treatment by CdCl{sub 2} to the classical SILAR technique improved significantly the CdTe film quality. The XRD analysis showed that the as treated layers are crystallized in the cubic zinc blende structure. The full coverage of ZnO nanowires and thickness of the CdTe shell, composed of small crystallites, was confirmed by STEM and TEM analysis. The layer thickness could be controlled by the number of SILAR cycles. The sharper optical transitions for the annealed and CdCl{sub 2} treated heterostructures additionally proves the enhancement of the layer crystalline quality. For comparison CdTe was also deposited by close space sublimation (CSS) method onto ZnO nanowires. It is shown that the SILAR deposited CdTe exhibits equal crystalline and optical properties to that prepared by CSS. These results demonstrate that SILAR technique is more suitable for conformal thin film deposition on nanostructures. CdTe extremely thin film deposited by SILAR method onto ZnO nanowire. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Organo-layered double hydroxides composite thin films deposited by laser techniques

    Energy Technology Data Exchange (ETDEWEB)

    Birjega, R. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest-Magurele (Romania); Vlad, A., E-mail: angela.vlad@gmail.com [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest-Magurele (Romania); Matei, A.; Dumitru, M.; Stokker-Cheregi, F.; Dinescu, M. [National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest-Magurele (Romania); Zavoianu, R. [University of Bucharest, Faculty of Chemistry, Department of Chemical Technology and Catalysis, 4-12 Regina Elisabeta Bd., Bucharest 030018 (Romania); Raditoiu, V.; Corobea, M.C. [National R.& D. Institute for Chemistry and Petrochemistry, ICECHIM, 202 Splaiul Independentei Str., CP-35-274, 060021 Bucharest (Romania)

    2016-06-30

    Highlights: • PLD and MAPLE was successfully used to produce organo-layered double hydroxides. • The organic anions (dodecyl sulfate-DS) were intercalated in co-precipitation step. • Zn2.5Al-LDH (Zn/Al = 2.5) and Zn2.5Al-DS thin films obtained in this work could be suitable for further applications as hydrophobic surfaces. - Abstract: We used laser techniques to create hydrophobic thin films of layered double hydroxides (LDHs) and organo-modified LDHs. A LDH based on Zn-Al with Zn{sup 2+}/Al{sup 3+} ratio of 2.5 was used as host material, while dodecyl sulfate (DS), which is an organic surfactant, acted as guest material. Pulsed laser deposition (PLD) and matrix assisted pulsed laser evaporation (MAPLE) were employed for the growth of the films. The organic anions were intercalated in co-precipitation step. The powders were subsequently used either as materials for MAPLE, or they were pressed and used as targets for PLD. The surface topography of the thin films was investigated by atomic force microscopy (AFM), the crystallographic structure of the powders and films was checked by X-ray diffraction. FTIR spectroscopy was used to evidence DS interlayer intercalation, both for powders and the derived films. Contact angle measurements were performed in order to establish the wettability properties of the as-prepared thin films, in view of functionalization applications as hydrophobic surfaces, owing to the effect of DS intercalation.

  20. Characterizations of multilayer ZnO thin films deposited by sol-gel spin coating technique

    Science.gov (United States)

    Khan, M. I.; Bhatti, K. A.; Qindeel, Rabia; Alonizan, Norah; Althobaiti, Hayat Saeed

    In this work, zinc oxide (ZnO) multilayer thin films are deposited on glass substrate using sol-gel spin coating technique and the effect of these multilayer films on optical, electrical and structural properties are investigated. It is observed that these multilayer films have great impact on the properties of ZnO. X-ray Diffraction (XRD) confirms that ZnO has hexagonal wurtzite structure. Scanning Electron Microscopy (SEM) showed the crack-free films which have uniformly distributed grains structures. Both micro and nano particles of ZnO are present on thin films. Four point probe measured the electrical properties showed the decreasing trend between the average resistivity and the number of layers. The optical absorption spectra measured using UV-Vis. showed the average transmittance in the visible region of all films is 80% which is good for solar spectra. The performance of the multilayer as transparent conducting material is better than the single layer of ZnO. This work provides a low cost, environment friendly and well abandoned material for solar cells applications.

  1. Preparation and properties of ZnO thin films deposited by sol-gel technique

    Institute of Scientific and Technical Information of China (English)

    LAN Wei; PENG Xingping; LIU Xueqin; HE Zhiwei; WANG Yinyue

    2007-01-01

    Zinc oxide (ZnO) thin films were deposited on (100) Si substrates by sol-gel technique.Zinc acetate was used as the precursor material.The effect of different anneal-ing atmospheres and annealing temperatures on composition, structural and optical properties of ZnO thin films was inves-tigated by using Fourier transform infrared spectroscopy, X-ray diffraction,atomic force microscopy and photolumi-nescence (PL),respectively.At an annealing temperature of 400℃ in N2 for 2 h,dried gel films were propitious to undergo structural relaxation and grow ZnO grains.ZnO thin film annealed at 400℃ in N2 for 2 h exhibited the optimal structure and PL property,and the grain size and the lattice constants of the film were calculated (41.6 nm,a = 3.253 A and c=5.210A).Moreover,a green emission around 495 nm was observed in the PL spectra owing to the oxygen vacancies located at the surface of ZnO grains.With increas- ing annealing temperature,both the amount of the grown ZnO and the specific surface area of the grains decrease,which jointly weaken the green emission.

  2. Organo-layered double hydroxides composite thin films deposited by laser techniques

    Science.gov (United States)

    Birjega, R.; Vlad, A.; Matei, A.; Dumitru, M.; Stokker-Cheregi, F.; Dinescu, M.; Zavoianu, R.; Raditoiu, V.; Corobea, M. C.

    2016-06-01

    We used laser techniques to create hydrophobic thin films of layered double hydroxides (LDHs) and organo-modified LDHs. A LDH based on Zn-Al with Zn2+/Al3+ ratio of 2.5 was used as host material, while dodecyl sulfate (DS), which is an organic surfactant, acted as guest material. Pulsed laser deposition (PLD) and matrix assisted pulsed laser evaporation (MAPLE) were employed for the growth of the films. The organic anions were intercalated in co-precipitation step. The powders were subsequently used either as materials for MAPLE, or they were pressed and used as targets for PLD. The surface topography of the thin films was investigated by atomic force microscopy (AFM), the crystallographic structure of the powders and films was checked by X-ray diffraction. FTIR spectroscopy was used to evidence DS interlayer intercalation, both for powders and the derived films. Contact angle measurements were performed in order to establish the wettability properties of the as-prepared thin films, in view of functionalization applications as hydrophobic surfaces, owing to the effect of DS intercalation.

  3. Optical and Surface Characteristics of Mg-Doped GaAs Nanocrystalline Thin Film Deposited by Thermionic Vacuum Arc Technique

    Science.gov (United States)

    Pat, Suat; Özen, Soner; Şenay, Volkan; Korkmaz, Şadan

    2017-01-01

    Magnesium (Mg) is the most promising p-type dopant for gallium arsenide (GaAs) semiconductor technology. Mg-doped GaAs nanocrystalline thin film has been deposited at room temperature by the thermionic vacuum arc technique, a rapid deposition method for production of doped GaAs material. The microstructure and surface and optical properties of the deposited sample were investigated by x-ray diffraction analysis, scanning electron microscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, ultraviolet-visible spectrophotometry, and interferometry. The crystalline direction of the deposited sample was determined to be (220) plane and (331) plane at 44.53° and 72.30°, respectively. The Mg-doped GaAs nanocrystalline sample showed high transmittance.

  4. Yb2Si2O7 Environmental Barrier Coatings Deposited by Various Thermal Spray Techniques: A Preliminary Comparative Study

    Science.gov (United States)

    Bakan, Emine; Marcano, Diana; Zhou, Dapeng; Sohn, Yoo Jung; Mauer, Georg; Vaßen, Robert

    2017-06-01

    Dense, crack-free, uniform, and well-adhered environmental barrier coatings (EBCs) are required to enhance the environmental durability of silicon (Si)-based ceramic matrix composites in high pressure, high gas velocity combustion atmospheres. This paper represents an assessment of different thermal spray techniques for the deposition of Yb2Si2O7 EBCs. The Yb2Si2O7 coatings were deposited by means of atmospheric plasma spraying (APS), high-velocity oxygen fuel spraying (HVOF), suspension plasma spraying (SPS), and very low-pressure plasma spraying (VLPPS) techniques. The initial feedstock, as well as the deposited coatings, were characterized and compared in terms of their phase composition. The as-sprayed amorphous content, microstructure, and porosity of the coatings were further analyzed. Based on this preliminary investigation, the HVOF process stood out from the other techniques as it enabled the production of vertical crack-free coatings with higher crystallinity in comparison with the APS and SPS techniques in atmospheric conditions. Nevertheless, VLPPS was found to be the preferred process for the deposition of Yb2Si2O7 coatings with desired characteristics in a controlled-atmosphere chamber.

  5. Yb2Si2O7 Environmental Barrier Coatings Deposited by Various Thermal Spray Techniques: A Preliminary Comparative Study

    Science.gov (United States)

    Bakan, Emine; Marcano, Diana; Zhou, Dapeng; Sohn, Yoo Jung; Mauer, Georg; Vaßen, Robert

    2017-08-01

    Dense, crack-free, uniform, and well-adhered environmental barrier coatings (EBCs) are required to enhance the environmental durability of silicon (Si)-based ceramic matrix composites in high pressure, high gas velocity combustion atmospheres. This paper represents an assessment of different thermal spray techniques for the deposition of Yb2Si2O7 EBCs. The Yb2Si2O7 coatings were deposited by means of atmospheric plasma spraying (APS), high-velocity oxygen fuel spraying (HVOF), suspension plasma spraying (SPS), and very low-pressure plasma spraying (VLPPS) techniques. The initial feedstock, as well as the deposited coatings, were characterized and compared in terms of their phase composition. The as-sprayed amorphous content, microstructure, and porosity of the coatings were further analyzed. Based on this preliminary investigation, the HVOF process stood out from the other techniques as it enabled the production of vertical crack-free coatings with higher crystallinity in comparison with the APS and SPS techniques in atmospheric conditions. Nevertheless, VLPPS was found to be the preferred process for the deposition of Yb2Si2O7 coatings with desired characteristics in a controlled-atmosphere chamber.

  6. Progress in the development of deposition prevention and cleaning techniques of in-vessel optics in ITER

    Science.gov (United States)

    Mukhin, E.; Vukolov, K.; Semenov, V.; Tolstyakov, S.; Kochergin, M.; Kurskiev, G.; Podushnikova, K.; Razdobarin, A.; Gorodetsky, A.; Zalavutdinov, R.; Bukhovets, V.; Zakharov, A.; Bulovich, S.; Veiko, V.; Shakshno, E.

    2009-08-01

    The lifetime of front optical components unprotected from reactor grade plasmas may be very short due to intensive contamination with carbon and beryllium-based materials eroded by the plasma from beryllium walls and carbon tiles. Deposits result in a significant reduction and spectral alterations of optical transmission. In addition, even rather thin and transparent deposits can dramatically change the shape of reflectance spectra, especially for mirrors with rather low reflectivity, such as W or Mo. The distortion of data obtained with various optical diagnostics may affect the safe operation of ITER. Therefore, the development of optics-cleaning and deposition-mitigating techniques is a key factor in the construction and operation of optical diagnostics in ITER. The problem is of particular concern for optical elements positioned in the divertor region. The latest achievements in protection of in-vessel optics are presented using the example of deposition prevention/cleaning techniques for in-machine components of the Thomson scattering system in the divertor. Careful consideration of well-known and novel protection approaches shows that neither of them alone provides guaranteed survivability of the first in-vessel optics in the divertor. Only a set of complementary prevention/cleaning techniques, which include special materials for mirrors and inhibition additives for plasma, is able to manage the challenging task. The essential issue, which needs to be addressed in the immediate future, is an extensive development of techniques tested under experimental conditions (exposure time and contamination fluxes) similar to those expected in ITER.

  7. Dependence of InN properties on MOCVD growth parameters

    Energy Technology Data Exchange (ETDEWEB)

    Tuna, Oe.; Giesen, C. [AIXTRON AG, Kaiserstr. 98, 52134 Herzogenrath (Germany); Behmenburg, H.; Kalisch, H.; Jansen, R.H. [Chair of Electromagnetic Theory, RWTH Aachen University, Kackertstr. 15-17, 52072 Aachen (Germany); Yablonskii, G.P. [Stepanov Institute of Physics, National Academy of Sciences of Belarus, Independence Ave. 68, Minsk 220072 (Belarus); Heuken, M. [AIXTRON AG, Kaiserstr. 98, 52134 Herzogenrath (Germany); Chair of Electromagnetic Theory, RWTH Aachen University, Kackertstr. 15-17, 52072 Aachen (Germany)

    2011-07-15

    In order to optimize the growth conditions, the effect of the most important growth parameters such as growth temperature, pressure and V/III ratio on MOCVD-grown InN was investigated. A series of samples were grown by changing the growth temperature from 500 C to 550 C at fixed growth pressure of 800 mbar and V/III ratio of 145000. An improvement of electrical properties with temperature increment was noted. The highest mobility of 1200 cm{sup 2}/Vs was achieved at 550 C with a bulk carrier concentration of 4.32 x 10{sup 18} cm{sup -3}. The effect of V/III ratio on In droplet formation and on carrier concentration was also studied. At fixed temperature of 520 C, reactor pressure of 200 mbar and at fixed NH{sub 3} flow of 3 slm, a rising TMIn flow from 1.2 {mu}mol/min to 2.0 {mu}mol/min results in a carrier concentration increment from 6.06 x 10{sup 18} cm{sup -3} to 1.33 x 10{sup 19} cm{sup -3}and a decrement of the mobility from 430 cm{sup 2}/Vs to 348 cm{sup 2}/Vs. X-ray diffraction measurements show that the intensity associated with In droplets on the surface is rising with increasing TMIn flow. The effect of reactor pressure on InN growth was also examined. A high sensitivity to growth pressure for crystalline quality of InN was observed. The full width at half maximum (FWHM) values of InN (0002) reflexes decreased with increasing reactor pressure. With increasing growth pressure above 200 mbar, FWHM of around 275 arcsec of InN (0002) was achieved. This FWHM value is the lowest reported in literature for MOCVD-grown InN so far. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Er{sub 2}O{sub 3} coating synthesized with MOCVD process on the large interior surface of the metal tube

    Energy Technology Data Exchange (ETDEWEB)

    Hishinuma, Yoshimitsu, E-mail: Hishinuma.yoshimitsu@nifs.ac.jp [National Institute for Fusion Science, Toki (Japan); Tanaka, Tsutomu [Toshima MFG Co.,Ltd., Saitama (Japan); Tanaka, Teruya; Nagasaka, Takuya [National Institute for Fusion Science, Toki (Japan); Tasaki, Yuzo [Toshima MFG Co.,Ltd., Saitama (Japan); Sagara, Akio; Muroga, Takeo [National Institute for Fusion Science, Toki (Japan)

    2011-10-15

    The electrical insulating coating on the blanket components such as ducts and walls is an attractive concept for reducing the Magneto Hydrodynamic (MHD) pressure drop. Erbium oxide (Er{sub 2}O{sub 3}) is a promising candidate coating because of its high stability in liquid lithium and high electrical resistivity according to the results of Er{sub 2}O{sub 3} bulk and Physical Vapor Deposition (PVD) thin film. We have investigated the Metal Organic Chemical Vapor Deposition (MOCVD) process for the large area and complicatedly shaped Er{sub 2}O{sub 3} coating. The Er{sub 2}O{sub 3} insulator coating formation on the various metal disk substrates was successfully carried out. The crystallinity of the Er{sub 2}O{sub 3} coating on the metal substrate increased with the decrease in the surface roughness of the metal substrate and, thus, the crystallinity of the coating can be improved by reducing the roughness of the substrate surface. Furthermore, the Er{sub 2}O{sub 3} coating into the interior surface of the honing SUS pipe, whose interior surface was polished by rotating grinding and brush, was formed stably through the MOCVD process.

  9. Studies of CdS/CdTe interface: Comparison of CdS films deposited by close space sublimation and chemical bath deposition techniques

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jun-feng, E-mail: pkuhjf@bit.edu.cn [Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, UMR CNRS 6502, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France); Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Fu, Gan-hua; Krishnakumar, V.; Schimper, Hermann-Josef [Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); Liao, Cheng [Department of Physics, Peking University, Beijing 100871 (China); Jaegermann, Wolfram [Institute of Materials Science, Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt (Germany); Besland, M.P. [Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, UMR CNRS 6502, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France)

    2015-05-01

    The CdS layers were deposited by two different methods, close space sublimation (CSS) and chemical bath deposition (CBD) technique. The CdS/CdTe interface properties were investigated by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM images showed a large CSS-CdS grain size in the range of 70-80 nm. The interface between CSS-CdS and CdTe were clear and sharp, indicating an abrupt hetero-junction. On the other hand, CBD-CdS layer had much smaller grain size in the 5-10 nm range. The interface between CBD-CdS and CdTe was not as clear as CSS-CdS. With the stepwise coverage of CdTe layer, the XPS core levels of Cd 3d and S 2p in CSS-CdS had a sudden shift to lower binding energies, while those core levels shifted gradually in CBD-CdS. In addition, XPS depth profile analyses indicated a strong diffusion in the interface between CBD-CdS and CdTe. The solar cells prepared using CSS-CdS yielded better device performance than the CBD-CdS layer. The relationships between the solar cell performances and properties of CdS/CdTe interfaces were discussed. - Highlights: • Studies of CdS deposited by close space sublimation and chemical bath deposition • An observation of CdS/CdTe interface by transmission electron microscope • A careful investigation of CdS/CdTe interface by X ray photoelectron spectra • An easier diffusion at the chemical bath deposition CdS and CdTe interface.

  10. Parametric investigation of substrate temperatures on the properties of Zinc oxide deposited over a flexible polymeric substrate via spray technique

    Science.gov (United States)

    Rajagopalan, P.; Gagrani, Rohit; Nakamura, Daisuke; Okada, Tatsuo; Singh, Vipul; Palani, I. A.

    2016-09-01

    Here we report the influence of substrate temperature (300-500 °C) on the deposition and growth of ZnO over a Flexible polyimide film. Owing to its simplicity, large area deposition capability and Cost effectivity Spray Pyrolysis technique was used. We have modified the conventional process of Spray pyrolysis by spraying for shorter durations and repeating the process which in turn reduced the Island formation of ZnO. Moreover, this technique helped in maintaining the constant temperature and uniformity during the deposition as prolonged spraying reduces the temperature of the heating plate drastically. Photoluminescence (PL) reveals that at 350 and 400° C the defect have reduced. XRD reveals the crystallinity and Impurities present. FE-SEM reveals the structure morphology changes with the change in the substrate temperature. TGA was done to ensure that substrate does not undergoes dissociation at high temperature. It was observed at the film deposited at 400 °C was found to be more uniform, defect free and crystalline. Hence, IV characterization of the film deposited at 400 °C was done which showed good rectification behaviour of the Schottky diodes.

  11. A lidar technique to quantify surface deposition from atmospheric releases of bulk liquids

    Science.gov (United States)

    Post, Madison J.; Glaes, Thomas; Matta, Joseph; Sommerville, Douglas; Einfeld, Wayne

    We show that a scanning, pulsed lidar can be used to quantify the time history and areal concentration of mass deposited on the ground from an elevated release of bulk liquid. Aircraft measurements, witness car depositions and evaporative modelling crudely support results from analysed lidar data.

  12. Fabrication and Properties of Organic-Inorganic Nanolaminates Using Molecular and Atomic Layer Deposition Techniques

    Science.gov (United States)

    2012-02-01

    55, 1030-1039 (2009).* 2. B.B. Burton, D.N. Goldstein and S.M. George, "Atomic Layer Deposition of MgO Using Bis(ethylcyclopentadienyl) magnesium ...Atomic Layer Deposition Using Tin 2,4-Pentanedionate and Hydrogen Sulfide , J. Phys. Chem. C 114, 17597-17603 (2010).* 28. L.A. Riley, A.S

  13. Ac conductivity and dielectric spectroscopy studies on tin oxide thin films formed by spray deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Barış, Behzad, E-mail: behzadbaris@gmail.com

    2014-04-01

    Au/tin oxide/n-Si (1 0 0) structure has been created by forming a tin oxide (SnO{sub 2}) on n-type Si by using the spray deposition technique. The ac electrical conductivity (σ{sub ac}) and dielectric properties of the structure have been investigated between 30 kHz and 1 MHz at room temperature. The values of ε', ε″, tanδ, σ{sub ac}, M' and M″ were determined as 1.404, 0.357, 0.253, 1.99×10{sup −7} S/cm, 0.665 and 0.168 for 1 MHz and 6.377, 6.411, 1.005, 1.07×10{sup −7} S/cm, 0.077 and 0.078 for 30 kHz at zero bias, respectively. These changes were attributed to variation of the charge carriers from the interface traps located between semiconductor and metal in the band gap. It is concluded that the values of the ε', ε″ and tanδ increase with decreasing frequency while a decrease is seen in σ{sub ac} and the real (M') and imaginary (M″) components of the electrical modulus. The M″ parameter of the structure has a relaxation peak as a function of frequency for each examined voltage. The relaxation time of M″(τ{sub M″}) varies from 0.053 ns to 0.018 ns with increasing voltage. The variation of Cole–Cole plots of the sample shows that there is one relaxation.

  14. Thermal stability and thermal expansion behaviour of ZrO{sub 2}/Y{sub 2}O{sub 3} multilayers deposited by pulsed laser deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Maneesha, E-mail: pkigcar@gmail.com [Materials Synthesis and Structural Characterisation Division, Physical Metallurgy Group, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kuppusami, P. [Centre for Nanoscience and Nanotechnology, Sathyabama University, Chennai, 600119 Tamil Nadu (India); Murugesan, S.; Ghosh, Chanchal; Divakar, R.; Singh, Akash; Mohandas, E. [Materials Synthesis and Structural Characterisation Division, Physical Metallurgy Group, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

    2015-07-15

    Multilayers of ZrO{sub 2}/Y{sub 2}O{sub 3} were prepared by pulsed laser deposition technique with variation in the ZrO{sub 2} layer thickness from 5 to 30 nm keeping the Y{sub 2}O{sub 3} layer thickness constant (∼10 nm). The stability, phase evolution and thermal expansion behaviour of the multilayers were analyzed by high temperature x-ray diffraction technique, in the temperature range of 300–1373 K. Unlike the single layer of ZrO{sub 2} film, which shows a mixture of tetragonal and monoclinic phase, the ZrO{sub 2} layers in multilayers show tetragonal phase in case of all the multilayers investigated in the present work. The values of coefficient of thermal expansion (CTE) decrease with increase in the ZrO{sub 2} layer thickness. The CTE of both ZrO{sub 2} and Y{sub 2}O{sub 3} are found to be influenced by their mutual solubility as well as due to interdiffusion of these oxides taking place along the interfaces of the multilayers, especially during high temperature heat-treatment. - Highlights: • ZrO{sub 2}/Y{sub 2}O{sub 3} multilayers were deposited by pulsed laser deposition technique. • Formation of tetragonal phase of ZrO{sub 2} and cubic phase of Y{sub 2}O{sub 3} were observed. • The multilayers films show good thermal stability upto temperature 1373 K. • The coefficient of thermal expansion (CTE) of t-ZrO{sub 2} decreases with increase in ZrO{sub 2} layer thickness.

  15. Hg1-xCdxTe vapor deposition on CdZnTe substrates by Closed Space Sublimation technique

    Science.gov (United States)

    Rubio, Sandra; Sochinskii, Nikolai V.; Repiso, Eva; Tsybrii, Zinoviia; Sizov, Fiodor; Plaza, Jose Luis; Diéguez, Ernesto

    2017-01-01

    Closed Space Sublimation (CSS) technique has been studied to deposit Hg1-xCdxTe polycrystalline films on CdZnTe substrates at the improved pressure-temperature conditions. The experimental results on film characterization suggest that the CSS optimal conditions are the argon atmospheric pressure (1013 mbar) and the deposition temperature in the range of 500-550 °C. These conditions provide macro-defect free Hg1-xCdxTe films with the uniform size and surface distribution of polycrystals.

  16. In situ pre-growth calibration using reflectance as a control strategy for MOCVD fabrication of device structures

    Energy Technology Data Exchange (ETDEWEB)

    Breiland, W.G.; Hou, H.Q.; Chui, H.C.; Hammons, B.E.

    1996-08-01

    In situ normal incidence reflectance, combined with a virtual interface model, is being used routinely on a commercial MOCVD reactor to measure growth rates of compound semiconductor films. The technique serves as a pre-growth calibration tool analogous to the use of RHEED in MBE as well as a real-time monitor throughout the run. An application of the method to the growth of a vertical cavity surface emitting laser (VCSEL) device structure is presented. All necessary calibration information can be obtained using a single run lasting less than one hour. Working VCSEL devices are obtained on the first try after calibration. Repeated runs have yielded {+-} 0.3% reproducibility of the Fabry-Perot cavity wavelength over the course of more than 100 runs.

  17. Comparative study of CdTe sources used for deposition of CdTe thin films by close spaced sublimation technique

    OpenAIRE

    Pinheiro,Wagner Anacleto; Falcão, Vivienne Denise; Cruz,Leila Rosa de Oliveira; Ferreira,Carlos Luiz

    2006-01-01

    Unlike other thin film deposition techniques, close spaced sublimation (CSS) requires a short source-substrate distance. The kind of source used in this technique strongly affects the control of the deposition parameters, especially the deposition rate. When depositing CdTe thin films by CSS, the most common CdTe sources are: single-crystal or polycrystalline wafers, powders, pellets or pieces, a thick CdTe film deposited onto glass or molybdenum substrate (CdTe source-plate) and a sintered C...

  18. Influence of solution deposition rate on properties of V{sub 2}O{sub 5} thin films deposited by spray pyrolysis technique

    Energy Technology Data Exchange (ETDEWEB)

    Abd–Alghafour, N. M., E-mail: na2013bil@gmail.com [Iraqi Ministry of Education, Anbar (Iraq); Ahmed, Naser M.; Hassan, Zai; Mohammad, Sabah M. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, University Sains Malaysia,11800 Penang (Malaysia)

    2016-07-19

    Vanadium oxide (V{sub 2}O{sub 5}) thin films were deposited on glass substrates by using a cost-efficient spray pyrolysis technique. The films were grown at 350° through thermal decomposition of VCl{sub 3} in deionized water with different solution spray rates. The high resolution X-ray diffraction results revealed the formation of nanocrystalline films having orthorhombic structures with preferential orientation along (101) direction. The spray rate influenced the surface morphology and crystallite size of the films. The crystallite size was found to increase whereas the micro-strain was decreased by increasing the spray deposition rates. The increase in crystallite size and decrease in the macrostrain resulted in an improvement in the films’ crystallinity. The UV-Visible spectroscopy analysis indicated that the average transmittance of all films lies in the range 75-80 %. The band gap of V{sub 2}O{sub 5} film was decreased from 2.65 to 2.46 eV with increase of the spray deposition rate from 5 ml/min to 10 ml/min. first, second, and third level headings (first level heading).

  19. Effect of Annealing Temperature on the Optical Spectra of CdS Thin Films Deposited at Low Solution Concentrations by Chemical Bath Deposition (CBD Technique

    Directory of Open Access Journals (Sweden)

    Zahid Rizwan

    2011-02-01

    Full Text Available Two different concentrations of CdCl2 and (NH22CS were used to prepare CdS thin films, to be deposited on glass substrate by chemical bath deposition (CBD technique. CdCl2 (0.000312 M and 0.000625 M was employed as a source of Cd2+ while (NH22CS (0.00125 M and 0.000625 M for S2− at a constant bath temperature of 70 °C. Adhesion of the deposited films was found to be very good for all the solution concentrations of both reagents. The films were air-annealed at a temperature between 200 °C to 360 °C for one hour. The minimum thickness was observed to be 33.6 nm for film annealed at 320 °C. XRD analyses reveal that the films were cubic along with peaks of hexagonal phase for all film samples. The crystallite size of the films decreased from 41.4 nm to 7.4 nm with the increase of annealing temperature for the CdCl2 (0.000312 M. Optical energy band gap (Eg, Urbach energy (Eu and absorption coefficient (α have been calculated from the transmission spectral data. These parameters have been discussed as a function of annealing temperature and solution concentration. The best transmission (about 97% was obtained for the air-annealed films at higher temperature at CdCl2 (0.000312 M.

  20. Atmospheric deposition of particles at a sensitive alpine lake: Size-segregated daily and annual fluxes from passive sampling techniques.

    Science.gov (United States)

    Tai, Anna Y-C; Chen, L-W Antony; Wang, Xiaoliang; Chow, Judith C; Watson, John G

    2017-02-01

    Lake Tahoe, a North American alpine lake long appreciated for its clear water and geographic setting, has experienced a trend of declining water clarity due to increasing nutrient and particle inputs. Contributions from atmospheric deposition of particulate matter (PM) could be important, yet they are inadequately quantified. This study established a yearlong deposition monitoring network in the northern Lake Tahoe Basin. Dry deposition was quantified on surrogate surfaces while wet deposition was based on particles suspended in precipitation at 24-hour resolution. The particle size ranges by these passive techniques were 1-64μm and 0.5-20μm in diameter for dry and wet deposition, respectively. Dry deposition of submicrometer (0.5-1μm) particles was also estimated by extrapolation of a lognormal size distribution. Higher daily number deposition fluxes (NDFdry and NDFwet) were found at a near-shore site, confirming substantial impacts of commercial and tourist activities. The two more isolated sites indicated a uniform regional background. On average, daily NDFdry is about one order of magnitude lower than daily NDFwet. Dry deposition velocities increased rapidly with particle size, as evidenced by collocated measurements of NDFdry and ambient particle number concentrations, though it seems less so for wet deposition due to different scavenging mechanisms. Despite fewer "wet" days than "dry" days during the monitoring period, wet processes dominated seasonal particle deposition, particularly in winter and spring when most precipitation occurred. Adopting sediment (insoluble, inorganic) particle fraction estimates from the literature, this study reports an annual particle flux of 2.9-5.2×10(10)#m(-2)yr(-1) for sediment particles with 1-20μm diameter and 6.1-11×10(10)#m(-2)yr(-1) for those with 0.5-20μm diameter. Implications of these findings to the current knowledge of atmospheric deposition in the Lake Tahoe Total Maximum Daily Load (TMDL) are discussed

  1. Tandem electroabsorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short pulse generation

    Science.gov (United States)

    Zhao, Q.; Pan, J. Q.; Zhang, J.; Zhou, G. T.; Wu, J.; Wang, L. F.; Wang, W.

    2005-08-01

    A novel device of tandem MQW EAMs monolithically integrated with a DFB laser is fabricated by an ultra-low-pressure (22 mbar) selective area growth MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio when coupled to a single mode fibre. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10 GHz repetition rate pulse with an actual width of 13.7 ps without any compression elements is obtained.

  2. Tandem electro-absorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short-pulse generation

    Science.gov (United States)

    Zhao, Q.; Pan, J. Q.; Zhang, J.; Zhou, G. T.; Wu, J.; Wang, L. F.; Wang, W.

    2005-11-01

    A novel device of tandem multiple quantum wells (MQWs) electroabsorption modulators (EAMs) monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 mbar) selective area growth (SAG) MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio when coupled into a single mode fiber. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10GHz repetition rate pulse with a width of 13.7 ps without any compression elements is obtained.

  3. Evaluation of Co-rich manganese deposits by image analysis and photogrammetric techniques

    Digital Repository Service at National Institute of Oceanography (India)

    Yamazaki, T.; Sharma, R.; Tsurusaki, K.

    Stereo-seabed photographs of Co-rich manganese deposits on a mid-Pacific seamount, were analysed using an image analysis software for coverage estimation and size classification of nodules, and a photogrammetric software for calculation of height...

  4. Investigation of physical vapor deposition techniques of conformal shell coating for core/shell structures by Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Cansizoglu, H., E-mail: hxis@ualr.edu; Yurukcu, M.; Cansizoglu, M.F.; Karabacak, T.

    2015-05-29

    Vertically aligned core/shell nanowire (nanorod) arrays are favorable candidates in many nano-scale devices such as solar cells, detectors, and integrated circuits. The quality of the shell coating around nanowire arrays is as crucial as the quality of the nanowires in device applications. For this reason, we worked on different physical vapor deposition (PVD) techniques and conducted Monte Carlo simulations to estimate the best deposition technique for a conformal shell coating. Our results show that a small angle (≤ 45°) between incoming flux of particles and the substrate surface normal is necessary for PVD techniques with a directional incoming flux (e.g. thermal or e-beam evaporation) for a reasonable conformal coating. On the other hand, PVD techniques with an angular flux distribution (e.g. sputtering) can provide a fairly conformal shell coating around nanowire arrays without a need of small angle deposition. We also studied the shape effect of the arrays on the conformality of the coating and discovered that arrays of the tapered-top nanorods and the pyramids can be coated with a more conformal and thicker coating compared to the coating on the arrays of flat-top nanowires due to their larger openings in between structures. Our results indicate that conventional PVD techniques, which offer low cost and large scale thin film fabrication, can be utilized for highly conformal and uniform shell coating formation in core/shell nanowire device applications. - Highlights: • We examined the shell coating growth in core/shell nanostructures. • We investigated the effect of physical vapor deposition method on the conformality of the shell. • We used Monte Carlo simulations to simulate the shell growth on nanowire templates. • Angular atomic flux (i.e., sputtering at high pressure) leads to conformal and uniform coatings. • A small angle (< 45°) to the directional flux needs to be introduced for conformal coatings.

  5. Antibacterial efficacy of advanced silver-amorphous carbon coatings deposited using the pulsed dual cathodic arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Endrino, J L; Anders, A; Albella, J M; Horton, J A; Horton, T H; Ayyalasomayajula, P R; Allen, M, E-mail: jlendrino@icmm.csic.es

    2010-11-01

    Amorphous carbon (a-C) also referred as diamond-like carbon (DLC) films are well known to be a biocompatible material with good chemical in ertness; this makes it a strong candidate to be used as a matrix that embeds metallic elements with an antimicrobial effect. We have deposited as et of a-C:Ag films using a dual-cathode pulsed filtered cathodic arc source, the arc pulse frequency of the silver and graphite cathodes was controlled in order to obtain samples with various silver contents. In this study, we show the deposition of silver and carbon ions using this technique and analyze the advantages of incorporating silver into a-C by studying the antimicrobial properties against staphylococcus of samples deposited on Ti{sub 6}Al{sub 4}V coupons and evaluated using 24-well tissue culture plates.

  6. Atmospheric Deposition of Trace Elements Around Ulan-Bator City Studied by Moss and Lichen Biomonitoring Technique and INAA

    CERN Document Server

    Ganbold, G; Gundorina, S F; Frontasyeva, M V; Ostrovnaya, T M; Pavlov, S S; Tsendeekhuu, T

    2005-01-01

    For the first time the moss and lichen biomonitoring technique has been applied to air pollution in Mongolia (Ulan-Bator, the capital city). INAA at the IBR-2 reactor has made it possible to determine the content of 35 elements in moss and lichen biomonitors. Samples collected at sites located 10-15 km from the center of Ulan-Bator were analyzed by Instrumental Neutron Activation Analysis (INAA) using epithermal neutrons. The mosses (\\textit{Rhytidium rugosum}, \\textit{Thuidium abietinum}, \\textit{Entodon concinnus}) and lichens (\\textit{Cladonia stellaris}, \\textit{Parmelia separata}) were used to study the atmospheric deposition of trace elements. It was shown that the suggested types of mosses could be used as suitable biomonitors to estimate the concentration levels of heavy metals and trace elements in Ulan-Bator atmospheric deposition. The results are compared to the data of atmospheric deposition of some European countries.

  7. Driving Down HB-LED Costs. Implementation of Process Simulation Tools and Temperature Control Methods of High Yield MOCVD Growth

    Energy Technology Data Exchange (ETDEWEB)

    Quinn, William [Veeco Process Equipment, Inc., Plainview, NY (United States)

    2012-04-30

    . Programmatically, improvements made in Phase I are applied to developments of Phase II when applicable. Phase three is the culmination of the individual tasks from both phases one and two applied to proposed production platforms. We selectively combine previously demonstrated tasks and other options to develop a high-volume production-worthy MOCVD system demonstrating >3x throughput, 1.3x capital efficiency, and 0.7x cost of ownership. In a parallel demonstration we validate the concept of an improved, larger deposition system which utilizes the predictive modeling of chemistry-based flow analysis and extensions of the improvements demonstrated on the current platforms. This validation includes the build and testing of a prototype version of the hardware and demonstration of 69% reduction in the cost of ownership. Also, in this phase we present a stand-alone project to develop a high-temperature system which improves source efficiency by 30% while concurrently increasing growth rate by 1.3x. The material quality is held to the same material quality specifications of our existing baseline processes. The merits of other line item tasks in phase three are discussed for inclusion on next-generation platforms.

  8. Photoluminescence study of ZnO nanostructures grown on silicon by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Biethan, J.-P., E-mail: biethan@hfe.tu-darmstadt.de [Department of High Frequency Electronics, Technische Universitaet Darmstadt, Merckstr. 25, Darmstadt 64283 (Germany); Sirkeli, V.P., E-mail: vsirkeli@yahoo.com [Department of Physics, Moldova State University, A. Mateevici str. 60, MD-2009 Chisinau, Republic of Moldova (Moldova, Republic of); Department of Mathematics and Computer Science, Comrat State University, Galatsan str. 17, MD-3800 Comrat, Republic of Moldova (Moldova, Republic of); Considine, L. [Department of High Frequency Electronics, Technische Universitaet Darmstadt, Merckstr. 25, Darmstadt 64283 (Germany); Nedeoglo, D.D. [Department of Physics, Moldova State University, A. Mateevici str. 60, MD-2009 Chisinau, Republic of Moldova (Moldova, Republic of); Pavlidis, D., E-mail: pavlidis@hfe.tu-darmstadt.de [Department of High Frequency Electronics, Technische Universitaet Darmstadt, Merckstr. 25, Darmstadt 64283 (Germany); Hartnagel, H.L., E-mail: hartnagel@mwe.tu-darmstadt.de [Department of High Frequency Electronics, Technische Universitaet Darmstadt, Merckstr. 25, Darmstadt 64283 (Germany); Department of Microwave Electronics, Technische Universitaet Darmstadt, Merckstr. 25, Darmstadt 64283 (Germany)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer The size and shape of ZnO nanostructures depend on growth temperature. Black-Right-Pointing-Pointer The size reduction of ZnO nanostructures causes a UV shift of the edge-band PL line. Black-Right-Pointing-Pointer A higher growth temperature can decrease the number of deep level defects. Black-Right-Pointing-Pointer Hydrogen appears to be an impurity donor in the ZnO nanostructures. Black-Right-Pointing-Pointer The PL line at 373.7 nm can be attributed to oxygen vacancies. - Abstract: ZnO nanostructures with a size ranging from 20 to 100 nm were successfully deposited on (1 0 0)-Si substrates at different temperatures (500-800 Degree-Sign C) using MOCVD. It could be confirmed that the size of ZnO nanostructures decreased with increasing growth temperature. From photoluminescence (PL) studies it was found, that intensive band-edge PL of ZnO nanostructures consists of emission lines with maxima at 368.6 nm, 370.1 nm, 373.7 nm, 383.9 nm, 391.7 nm, 400.7 nm and 412 nm. These lines can be dedicated to free excitons and impurity donor-bound excitons, where hydrogen acts as donor impurity with an activation energy of about 65 meV. A UV shift of the band-edge PL line with increasing growth temperature of ZnO nanostructures was observed as a result of the quantum confinement effect. The results suggest that an increase of growth temperature leads to increased band-edge PL intensity. Moreover, the ratio of band-edge PL intensity to green- (red-) band intensity also increases, indicating better crystalline quality of ZnO nanostructures with increasing growth temperature.

  9. Controlling the quality of nanocrystalline silicon made by hot-wire chemical vapor deposition by using a reverse H2 profiling technique

    NARCIS (Netherlands)

    Li, H. B. T.; Franken, R.H.; Stolk, R.L.; van der Werf, C.H.M.; Rath, J.K.; Schropp, R.E.I.

    2008-01-01

    Hydrogen profiling, i.e., decreasing the H2 dilution during deposition, is a well-known technique to maintain a proper crystalline ratio of the nanocrystalline (nc-Si:H) absorber layers of plasma-enhanced chemical vapor-deposited (PECVD) thin film solar cells. With this technique a large increase in

  10. Controlling the quality of nanocrystalline silicon made by hot-wire chemical vapor deposition by using a reverse H2 profiling technique

    NARCIS (Netherlands)

    Li, H. B. T.; Franken, R.H.; Stolk, R.L.; van der Werf, C.H.M.; Rath, J.K.; Schropp, R.E.I.

    2008-01-01

    Hydrogen profiling, i.e., decreasing the H2 dilution during deposition, is a well-known technique to maintain a proper crystalline ratio of the nanocrystalline (nc-Si:H) absorber layers of plasma-enhanced chemical vapor-deposited (PECVD) thin film solar cells. With this technique a large increase in

  11. Effect of technique parameters on characteristics of hydrogen-free DLC films deposited by surface wave-sustained plasma

    Science.gov (United States)

    Xu, Junqi; Kousaka, Hiroyuki; Umehara, Noritsugu; Diao, Dongfeng

    2006-01-01

    Hydrogen-free diamond-like carbon (DLC) films were deposited by a new-type surface wave-sustained plasma physical vapor deposition (SWP-PVD) system under various technique conditions. Electron density was measured by a Langmuir probe, while the film thickness and hardness were characterized using a surface profilometer and a nanoindenter, respectively. Surface morphology was investigated by an atomic force microscope (AFM). It was found that the electron density and deposition rate increased following the increase in microwave power, target voltage, or gas pressure. The typical electron density and deposition rate were about 1.87-2.04×10 11 cm -3 and 1.61-14.32 nm/min respectively. AFM images indicated that the grains of films changes as the technique parameters vary. The optical constants, refractive index n and extinction coefficient k, were obtained using an optical ellipsometry. With the increase in microwave power from 150 to 270 W, the extinction coefficient of DLC films increased from 0.05 to 0.27 while the refractive index decreased from 2.31 to 2.18.

  12. Assessment of multiple geophysical techniques for the characterization of municipal waste deposit sites

    Science.gov (United States)

    Gaël, Dumont; Tanguy, Robert; Nicolas, Marck; Frédéric, Nguyen

    2017-10-01

    In this study, we tested the ability of geophysical methods to characterize a large technical landfill installed in a former sand quarry. The geophysical surveys specifically aimed at delimitating the deposit site horizontal extension, at estimating its thickness and at characterizing the waste material composition (the moisture content in the present case). The site delimitation was conducted with electromagnetic (in-phase and out-of-phase) and magnetic (vertical gradient and total field) methods that clearly showed the transition between the waste deposit and the host formation. Regarding waste deposit thickness evaluation, electrical resistivity tomography appeared inefficient on this particularly thick deposit site. Thus, we propose a combination of horizontal to vertical noise spectral ratio (HVNSR) and multichannel analysis of the surface waves (MASW), which successfully determined the approximate waste deposit thickness in our test landfill. However, ERT appeared to be an appropriate tool to characterize the moisture content of the waste, which is of prior information for the organic waste biodegradation process. The global multi-scale and multi-method geophysical survey offers precious information for site rehabilitation studies, water content mitigation processes for enhanced biodegradation or landfill mining operation planning.

  13. Elemental analysis of limestone samples from Obajana and Mfamosing limestone deposits, Nigeria, using nuclear techniques

    Energy Technology Data Exchange (ETDEWEB)

    Akpan, I.O. [Department of Physics, University of Calabar, Calabar, Cross River State (Nigeria); Amodu, A.E. [Science Laboratory Technology Department, Federal Polytechnic, Idah, Kogi State (Nigeria); Akpan, A.E., E-mail: anthonyakpan@yahoo.com [Department of Physics, University of Calabar, Calabar, Cross River State (Nigeria)

    2011-10-15

    Six limestone samples were picked from three different points at the Obajana and Mfamosing limestone deposits. The limestone samples were subjected to elemental analysis by Proton-Induced X-Ray Emission (PIXE) analysis. The samples were irradiated by a 4 mm diameter beam of protons with energy of 2.5 MeV and beam current of 0.2 nA for 0.9 ms. The analysis was carried out with the 1.7 MV Tandem accelerator at the Centre for Energy Research and Development (CERD), Ile-Ife, Osun State, Nigeria. The NIST geology standard NIST 278 was analysed for quality assurance. The elemental composition and concentration of 14 elements were determined in the two locations. Ten elements were found at the Obajana deposit while 13 elements were found at the Mfamosing deposits. The elements: Mg, Al, Ca and Mn do not differ much at both deposits while others differ. The major elements (Ca, Fe, Al, Si and K) present in the limestones were also found in airborne particulate matter studied by earlier researchers. These observations suggest that all particulate emissions and wastes from the Limestone deposit should be closely monitored to reduce their cumulative effects on both health and the environment

  14. Elemental analysis of limestone samples from Obajana and Mfamosing limestone deposits, Nigeria, using nuclear techniques.

    Science.gov (United States)

    Akpan, I O; Amodu, A E; Akpan, A E

    2011-10-01

    Six limestone samples were picked from three different points at the Obajana and Mfamosing limestone deposits. The limestone samples were subjected to elemental analysis by Proton-Induced X-Ray Emission (PIXE) analysis. The samples were irradiated by a 4mm diameter beam of protons with energy of 2.5 MeV and beam current of 0.2nA for 0.9 ms. The analysis was carried out with the 1.7MV Tandem accelerator at the Centre for Energy Research and Development (CERD), Ile-Ife, Osun State, Nigeria. The NIST geology standard NIST 278 was analysed for quality assurance. The elemental composition and concentration of 14 elements were determined in the two locations. Ten elements were found at the Obajana deposit while 13 elements were found at the Mfamosing deposits. The elements: Mg, Al, Ca and Mn do not differ much at both deposits while others differ. The major elements (Ca, Fe, Al, Si and K) present in the limestones were also found in airborne particulate matter studied by earlier researchers. These observations suggest that all particulate emissions and wastes from the Limestone deposit should be closely monitored to reduce their cumulative effects on both health and the environment.

  15. Structural and electrical characterizations of BiFeO{sub 3} capacitors deposited by sol–gel dip coating technique

    Energy Technology Data Exchange (ETDEWEB)

    Cetinkaya, Ali Osman, E-mail: cetinkayaaliosman@gmail.com [Physics Department, Abant Izzet Baysal University, 14280 Bolu (Turkey); Center for Nuclear Radiation Detector Research and Applications, 14280 Bolu (Turkey); Kaya, Senol; Aktag, Aliekber [Physics Department, Abant Izzet Baysal University, 14280 Bolu (Turkey); Center for Nuclear Radiation Detector Research and Applications, 14280 Bolu (Turkey); Budak, Erhan [Chemistry Department, Abant Izzet Baysal University, 14280 Bolu (Turkey); Yilmaz, Ercan [Physics Department, Abant Izzet Baysal University, 14280 Bolu (Turkey); Center for Nuclear Radiation Detector Research and Applications, 14280 Bolu (Turkey)

    2015-09-01

    Bismuth ferrite (BiFeO{sub 3}) thin films were deposited by sol–gel dip coating (SGDC) technique on Si-P(100) and glass substrates to investigate the structural and electrical characteristics. The aluminum (Al) metal contacts were formed on the samples deposited on the Si-P(100) to fabricate metal-oxide-semiconductor (MOS) capacitors. The fabricated MOS structures were characterized electrically by capacitance–voltage (C–V) and conductance–voltage (G/ω–V) measurements. The structural characterizations were performed by X-ray diffraction technique and scanning electron microscopy. The compositions of the films were investigated by energy-dispersive X-ray spectroscopy. The results exhibit that pure rhombohedral perovskite phase films were fabricated without any elemental contamination. Average grain sizes of the BiFeO{sub 3} deposited on silicon and glass wafers were found to be about 34,50 and 30,00 nm, respectively. In addition, while the thin films deposited on glass substrate exhibit porous surface, those deposited on Si-P(100) wafers exhibit dense microstructure with a homogenous surface. Moreover, the C–V and G/ω–V characteristics are sensitive to applied voltage frequency due to frequency dependent charges (N{sub ss}) and series resistance (R{sub s}). The peak values of R{sub s} have been decreased from 2,6 kΩ to 40 Ω, while N{sub ss} is varied from 6,57 × 10{sup 12} to 3,68 × 10{sup 12} eV{sup −1} cm{sup −2} with increasing in frequency. Consequently, pure phase polycrystalline BiFeO{sub 3} thin films were fabricated successfully by SGDC technique and BiFeO{sub 3} dielectric layer exhibits stable insulation characteristics. - Highlights: • Bismuth ferrite thin films were deposited onto silicon and glass substrates by sol–gel. • Structural and electrical properties of fabricated films have been investigated. • Pure rhombohedral perovskite phase films without any contamination were deposited. • Series resistance and interface

  16. Research Update: Large-area deposition, coating, printing, and processing techniques for the upscaling of perovskite solar cell technology

    Science.gov (United States)

    Razza, Stefano; Castro-Hermosa, Sergio; Di Carlo, Aldo; Brown, Thomas M.

    2016-09-01

    To bring perovskite solar cells to the industrial world, performance must be maintained at the photovoltaic module scale. Here we present large-area manufacturing and processing options applicable to large-area cells and modules. Printing and coating techniques, such as blade coating, slot-die coating, spray coating, screen printing, inkjet printing, and gravure printing (as alternatives to spin coating), as well as vacuum or vapor based deposition and laser patterning techniques are being developed for an effective scale-up of the technology. The latter also enables the manufacture of solar modules on flexible substrates, an option beneficial for many applications and for roll-to-roll production.

  17. Synthesis of dense nano cobalt-hydroxyapatite by modified electroless deposition technique

    Science.gov (United States)

    Mohd Zaheruddin, K.; Rahmat, A.; Shamsul, J. B.; Mohd Nazree, B. D.; Aimi Noorliyana, H.

    2016-07-01

    Cobalt-hydroxyapatite (Co-HA) composites was successfully prepared by simple electroless deposition process of Co on the surface of hydroxyapatite (HA) particles. Co deposition was carried out in an alkaline bath with sodium hypophosphite as a reducing agent. The electroless process was carried out without sensitization and activation steps. The deposition of Co onto HA was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The Co-HA composite powder was compacted and sintered at 1250°C. The Co particles were homogeneously dispersed in the HA matrix after sintering and the mechanical properties of composites was enhanced to 100 % with 3 % wt Co and gradually decreased at higher Co content.

  18. Deposition of gold nanoparticles on silica spheres by electroless metal plating technique.

    Science.gov (United States)

    Kobayashi, Yoshio; Tadaki, Yohei; Nagao, Daisuke; Konno, Mikio

    2005-03-15

    A previously proposed method for metal deposition with silver [Kobayashi et al., Chem. Mater. 13 (2001) 1630] was extended to uniform deposition of gold nanoparticles on submicrometer-sized silica spheres. The present method consisted of three steps: (1) the adsorption of Sn(2+) ions took place on surface of silica particles, (2) Ag(+) ions added were reduced and simultaneously adsorbed to the surface, while Sn(2+) was oxidized to Sn(4+), and (3) Au(+) ions added were reduced and deposited on the Ag surface. TEM observation, X-ray diffractometry, and UV-vis absorption spectroscopy revealed that gold metal nanoparticles with an average particle size of 13 nm and a crystal size of 5.1 nm were formed on the silica spheres with a size of 273 nm at an Au concentration of 0.77 M.

  19. Synthesis of dense nano cobalt-hydroxyapatite by modified electroless deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Mohd Zaheruddin, K., E-mail: zaheruddin@unimap.edu.my; Rahmat, A., E-mail: azmirahmat@unimap.edu.my; Shamsul, J. B., E-mail: sbaharin@unimap.edu.my; Mohd Nazree, B. D., E-mail: nazree@unimap.edu.my; Aimi Noorliyana, H., E-mail: aimiliyana@unimap.edu.my [School of Materials Engineering, Universiti Malaysia Perlis, Kompleks Pusat Pengajian Jejawi Universiti Malaysia Perlis, Taman Muhibbah, Jejawi 02600 Arau Perlis (Malaysia)

    2016-07-19

    Cobalt-hydroxyapatite (Co-HA) composites was successfully prepared by simple electroless deposition process of Co on the surface of hydroxyapatite (HA) particles. Co deposition was carried out in an alkaline bath with sodium hypophosphite as a reducing agent. The electroless process was carried out without sensitization and activation steps. The deposition of Co onto HA was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The Co-HA composite powder was compacted and sintered at 1250°C. The Co particles were homogeneously dispersed in the HA matrix after sintering and the mechanical properties of composites was enhanced to 100 % with 3 % wt Co and gradually decreased at higher Co content.

  20. Development of ITER relevant laser techniques for deposited layer characterisation and tritium inventory

    Energy Technology Data Exchange (ETDEWEB)

    Malaquias, A., E-mail: artur.malaquias@jet.efda.org [Associação EURATOM/IST, Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisboa (Portugal); EFDA-CSU, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Philipps, V.; Huber, A. [Institute for Energy Research – Plasma Physics, Forschungszentrum Jülich GmbH, Association EURATOM-FZJ (Germany); Hakola, A.; Likonen, J. [VTT, Association EURATOM-TEKES, P.O. Box 1000, 02044 VTT (Finland); Kolehmainen, J.; Tervakangas, S. [DIARC-Technology Inc., Kattilalaaksontie 1, 02330 Espoo (Finland); Aints, M.; Paris, P.; Laan, M.; Lissovski, A. [Institute of Physics, University of Tartu, Association EURATOM-TEKES, Tahe 4, Tartu 51010 (Estonia); Almaviva, S.; Caneve, L.; Colao, F. [ENEA, UTAPRAD-DIM, C.R. Frascati, P.O. Box 65, 00044 Frascati, Roma (Italy); Maddaluno, G. [Associazione EURATOM-ENEA sulla Fusione, C. R. Frascati, P.O. Box 65, 00044 Frascati, Roma (Italy); Kubkowska, M.; Gasior, P. [Institute of Plasma Physics and Laser Microfusion, Association EURATOM/IPPLM, 00-908 Warsaw, P.O. Box 49, Hery St. 23 (Poland); Meiden, H.J. van der; Lof, A.R.; Zeijlmans van Emmichoven, P.A. [FOM Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, Trilateral Euregio Cluster, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); and others

    2013-07-15

    Laser Induced Breakdown Spectroscopy (LIBS) is a potential candidate to monitor the layer composition and fuel retention during and after plasma shots on specific locations of the main chamber and divertor of ITER. This method is being investigated in a cooperative research programme on plasma devices such as TEXTOR, FTU, MAGNUM-PSI and in other various laboratorial experiments. In this paper LIBS results from targets of D–H-rich carbon films and mixed W–Al–C deposits on bulk tungsten substrates are reported (simulating ITER-like deposits with Al as proxy for Be). Two independent methods, one to determine the relative elemental composition and the other the absolute contents of the target based on the experimental LIBS signals are proposed. The results show that LIBS has the capability to provide the relative concentrations of the elements on the deposited layer when the experimental conditions on the targets surface are identical to the calibration samples.

  1. Deposition of TiN Films by Novel Filter Cathodic Arc Technique

    Institute of Scientific and Technical Information of China (English)

    NIU Er-Wu; FAN Song-Hua; LI Li; L(U) Guo-Hua; FENG Wen-Ran; ZHANG Gu-Ling; YANG Si-Ze

    2006-01-01

    A straight magnetic filtering arc source is used to deposit thin films of titanium nitride.The properties of thefilms depend strongly on the deposition process.TiN films can be deposited directly onto heated substrates in anitrogen atmosphere or onto unbiased substrates by condensing the Ti+ ion beam in about 300 eV N2+ nitrogen ionbombardment.In the latter case.the film stoichiometry is varied from an N:Ti ratio of 0.6-1.1 by controlling thearrival rates of Ti and nitrogen ions.Meanwhile,simple models are used to describe the evolution of compressivestress as function of the arrival ratio and the composition of the ion-assisted TiN films.

  2. Correlation of local structure peculiarities and critical current density of 2G MOCVD YBCO tapes with BaZrO3 nanoinclusions

    Science.gov (United States)

    Menushenkov, A. P.; Ivanov, V. G.; Chepikov, V. N.; Nygaard, R. R.; Soldatenko, A. V.; Rudnev, I. A.; Osipov, M. A.; Mineev, N. A.; Kaul, A. R.; Mathon, O.; Monteseguro, V.

    2017-04-01

    We have studied the influence of BaZrO3 nanoinclusions on the local structure and critical current density of second-generation high temperature superconducting tapes based on YBa2Cu3O7-δ (YBCO) films. The films were made by metal-organic chemical vapor deposition (MOCVD). The crystal and local structure of the materials under study were analysed by x-ray diffraction and x-ray absorption spectroscopy (EXAFS + XANES). We have found that, being added at MOCVD process, Zr forms BaZrO3 nanoinclusions in YBCO matrix. The distance between Zr and the neighboring atoms is shorter than that one in a bulk crystalline BaZrO3, so we conclude that the nanoinclusions are in compressed state. The incorporation of 5 mol% BaZrO3 minimizes the static disorder of Cu-O bonds and maximizes their stiffness in YBCO. We show that the local structure peculiarities correlate well with the observed critical current behavior and consider this to be additional evidence in favor of small amounts of BaZrO3 nanoinclusions as efficient pinning centers.

  3. Vertically p-n-junctioned GaN nano-wire array diode fabricated on Si(111) using MOCVD.

    Science.gov (United States)

    Park, Ji-Hyeon; Kim, Min-Hee; Kissinger, Suthan; Lee, Cheul-Ro

    2013-04-07

    We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method .The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 × 10(7) cm(-2). The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN:Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute).

  4. Physical and structural studies of chemical Vapor deposited lacunar neodymium manganite thin films

    Directory of Open Access Journals (Sweden)

    Oumezzine M.

    2012-06-01

    Full Text Available Lacunar Nd1-xMnO3-δ thin films were successfully deposited by a liquid source metal-organic MOCVD technique on (001 SrTiO3 (STO, LaAlO3 (LAO and Si substrates. Optimal growth conditions are reported. TEM and X-ray diffraction characterisations reveal that the thin films grown on STO and LAO substrates are single crystalline layers epitaxially grown on the top of the substrates. The relationship between the crystallographic orientation of the films and those of the substrates were determined. Magnetic transition temperatures (Tc of the as-grown STO films, deduced from Squid Magnetometer measurements, are compared to the corresponding bulk values (typically 100K. Our magnetic measurements also suggest a complicated magnetic behavior close to the one observed in bulk samples: magnetization curves obtained under different applied magnetic fields indicate a possible reverse of the magnetization sign at low temperatures.

  5. Nanostructured silicon carbon thin films grown by plasma enhanced chemical vapour deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Coscia, U. [Dipartimento di Fisica, Università di Napoli “Federico II” Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); CNISM Unita' di Napoli, Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); Ambrosone, G., E-mail: ambrosone@na.infn.it [Dipartimento di Fisica, Università di Napoli “Federico II” Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); SPIN-CNR, Complesso Universitario MSA, via Cinthia, 80126 Napoli (Italy); Basa, D.K. [Department of Physics, Utkal University, Bhubaneswar 751004 (India); Rigato, V. [INFN Laboratori Nazionali Legnaro, 35020 Legnaro (Padova) (Italy); Ferrero, S.; Virga, A. [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino (Italy)

    2013-09-30

    Nanostructured silicon carbon thin films, composed of Si nanocrystallites embedded in hydrogenated amorphous silicon carbon matrix, have been prepared by varying rf power in ultra high vacuum plasma enhanced chemical vapour deposition system using silane and methane gas mixtures diluted in hydrogen. In this paper we have studied the compositional, structural and electrical properties of these films as a function of rf power. It is shown that with increasing rf power the atomic densities of carbon and hydrogen increase while the atomic density of silicon decreases, resulting in a reduction in the mass density. Further, it is demonstrated that carbon is incorporated into amorphous matrix and it is mainly bonded to silicon. The study has also revealed that the crystalline volume fraction decreases with increase in rf power and that the films deposited with low rf power have a size distribution of large and small crystallites while the films deposited with relatively high power have only small crystallites. Finally, the enhanced transport properties of the nanostructured silicon carbon films, as compared to amorphous counterpart, have been attributed to the presence of Si nanocrystallites. - Highlights: • The mass density of silicon carbon films decreases from 2.3 to 2 g/cm{sup 3}. • Carbon is incorporated in the amorphous phase and it is mainly bonded to silicon. • Nanostructured silicon carbon films are deposited at rf power > 40 W. • Si nanocrystallites in amorphous silicon carbon enhance the electrical properties.

  6. Creating pure nanostructures from electron-beam-induced deposition using purification techniques: a technology perspective

    NARCIS (Netherlands)

    Botman, A.; Mulders, J.J.L.; Hagen, C.W.

    2009-01-01

    The creation of functional nanostructures by electron-beam-induced deposition (EBID) is becoming more widespread. The benefits of the technology include fast ‘point-and-shoot’ creation of three-dimensional nanostructures at predefined locations directly within a scanning electron microscope. One sig

  7. Thermo-Mechanical Properties of Alumina Films Created Using the Atomic Layer Deposition Technique

    Science.gov (United States)

    2010-01-01

    23 (9) (2008) 2443–2457. [32] G.G. Stoney, The tension ofmetallic films deposited by electrolysis , Proc. R. Soc. A82 (553) (1909) 172–175. [33] M...Springer-Verlag, New York, 2006. [37] R.M. Keller, S.P. Baker, E. Arzt, Stress–temperature behavior of unpassivated thin copper films, Acta Mater. 47 (2

  8. Effect of annealing temperature on the optical spectra of CdS thin films deposited at low solution concentrations by Chemical Bath Deposition (CBD) Technique.

    Science.gov (United States)

    Rizwan, Zahid; Zakaria, Azmi; Mohd Ghazali, Mohd Sabri; Jafari, Atefeh; Din, Fasih Ud; Zamiri, Reza

    2011-02-22

    Two different concentrations of CdCl(2) and (NH(2))(2)CS were used to prepare CdS thin films, to be deposited on glass substrate by chemical bath deposition (CBD) technique. CdCl(2) (0.000312 M and 0.000625 M) was employed as a source of Cd(2+) while (NH(2))(2)CS (0.00125 M and 0.000625 M) for S(2-) at a constant bath temperature of 70 °C. Adhesion of the deposited films was found to be very good for all the solution concentrations of both reagents. The films were air-annealed at a temperature between 200 °C to 360 °C for one hour. The minimum thickness was observed to be 33.6 nm for film annealed at 320 °C. XRD analyses reveal that the films were cubic along with peaks of hexagonal phase for all film samples. The crystallite size of the films decreased from 41.4 nm to 7.4 nm with the increase of annealing temperature for the CdCl(2) (0.000312 M). Optical energy band gap (E(g)), Urbach energy (E(u)) and absorption coefficient (α) have been calculated from the transmission spectral data. These parameters have been discussed as a function of annealing temperature and solution concentration. The best transmission (about 97%) was obtained for the air-annealed films at higher temperature at CdCl(2) (0.000312 M).

  9. Fabrication and evaluation of CdS/PbS thin film solar cell by chemical bath deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Saikia, Dulen, E-mail: dulen.s@rediffmail.com; Phukan, Pallabi

    2014-07-01

    A solar cell with the structure glass/SnO{sub 2}/CdS/PbS/HgTe has been fabricated where both window (CdS) and absorber (PbS) layers were deposited by a chemical bath deposition technique which is completely free from any complexing agents. The films were prepared by in-situ thermolysis of precursors confined in polyvinyl alcohol matrix (PVA). As the method is free of any complexing agent, hence no need to control the pH of the solution. The as-prepared films were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and UV–Vis absorption spectroscopy. The surface morphology clearly shows that as synthesized CdS/PVA and PbS/PVA thin films were nanostructured, almost homogeneous, without any pinholes or cracks and covered the substrate well. The photovoltaic parameters of the cell were measured with the Keithley 2400 source meter under one sun illumination and efficiency of the cell was found to be 1.668%. - Highlights: • Polyvinyl alcohol matrix-capped PbS thin film from a complexing agent free system • Fabrication of CdS/PbS solar cell based on chemical bath deposition technique • An efficiency of 1.668% is achieved under one SUN illumination.

  10. Higher lung deposition with Respimat® Soft Mist™ Inhaler than HFA-MDI in COPD patients with poor technique

    Directory of Open Access Journals (Sweden)

    Peter Brand

    2008-08-01

    Full Text Available Peter Brand1, Bettina Hederer2, George Austen3, Helen Dewberry3, Thomas Meyer41RWTH, Aachen, Germany; 2Boehringer Ingelheim, Ingelheim, Germany; 3Boehringer Ingelheim, Bracknell, UK; 4Inamed Research, Gauting, GermanyAbstract: Aerosols delivered by Respimat® Soft Mist™ Inhaler (SMI are slower-moving and longer-lasting than those from pressurized metered-dose inhalers (pMDIs, improving the efficiency of pulmonary drug delivery to patients. In this four-way cross-over study, adults with chronic obstructive pulmonary disease (COPD and with poor pMDI technique received radiolabelled Berodual® (fenoterol hydrobromide 50 µg/ipratropium bromide 20 µg via Respimat® SMI or hydrofluoroalkane (HFA-MDI (randomized order on test days 1 and 2, with no inhaler technique training. The procedure was repeated on test days 3 and 4 after training. Deposition was measured by gamma scintigraphy. All 13 patients entered (9 males, mean age 62 years; FEV1 46% of predicted inhaled too fast at screening (peak inspiratory flow rate [IF]: 69–161 L/min. Whole lung deposition was higher with Respimat® SMI than with pMDI for untrained (37% of delivered dose vs 21% of metered dose and trained patients (53% of delivered vs 21% of metered dose (pSign-Test = 0.15; pANOVA< 0.05. Training also improved inhalation profiles (slower average and peak IF as well as longer breath-hold time. Drug delivery to the lungs with Respimat® SMI is more efficient than with pMDI, even with poor inhaler technique. Teaching patients to hold their breath as well as to inhale slowly and deeply increased further lung deposition using Respimat® SMI.Keywords: chronic obstructive pulmonary disease, drug delivery, inhalation, metered-dose inhaler, poor inhalation technique, training

  11. An economic CVD technique for pure SnO2 thin films deposition: Temperature effects

    Indian Academy of Sciences (India)

    M Maleki; S M Rozati

    2013-04-01

    A modified new method of CVD for formation of pure layers of tin oxide films was developed. This method is very simple and inexpensive and produces films with good electrical properties. The effect of substrate temperature on the sheet resistance, resistivity, mobility, carrier concentration and transparency of the films has been studied. The best sheet resistance obtained at substrate temperature of 500 ◦C was about 27 /cm2. X-ray diffraction showed that the structure of deposited films was polycrystalline with a grain size between 150–300 Å. The preferred orientation was (211) for films deposited at substrate temperature of about 500 °C. FESEM micrographs revealed that substrate temperature is an important factor for increasing grain size and modifies electrical parameters. UV-visible measurement showed reduction of transparency and bandgap of the layers with increasing substrate temperature.

  12. Chalcogenide-based thin film sensors prepared by pulsed laser deposition technique

    Science.gov (United States)

    Schubert, J.; Schöning, M. J.; Schmidt, C.; Siegert, M.; Mesters, St.; Zander, W.; Kordos, P.; Lüth, H.; Legin, A.; Mourzina, Yu. G.; Seleznev, B.; Vlasov, Yu. G.

    One advantage of the pulsed laser deposition (PLD) method is the stoichiometric transfer of multi-component target material to a given substrate. This advantage of the PLD determined the choice to prepare chalco-genide-based thin films with an off-axis geometry PLD. Ag-As-S and Cu-Ag-As-Se-Tetargets were used to deposit thin films on Si substrates for an application as a heavy metal sensing device. The films were characterized by means of Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM), and electrochemical measurements. The same stoichiometry of the films and the targets was confirmed by RBS measurements. We observed a good long-term stability of more than 60 days and a nearly Nernstian sensitivity towards Pb and Cu, which is comparable to bulk sensors.

  13. Optimization of the Automated Spray Layer-by-Layer Technique for Thin Film Deposition

    Science.gov (United States)

    2010-06-01

    she was extremely busy running our household of five, homeschooling our son and volunteering. She amazes me every single day. I know that her... benefit to using solutions in excess of 80 mmol of PAA. However, at concentrations less than 80 mmol for the other standard parameter values it is...maximum film thickness. These results demonstrate that faster film deposition time is not the only benefit of Spray-LbL’s shorter polyelectrolyte to

  14. Thick CrN/NbN multilayer coating deposited by cathodic arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, Juliano Avelar; Tschiptschin, Andre Paulo; Souza, Roberto Martins, E-mail: antschip@usp.br [Universidade de Sao Paulo (USP), SP (Brazil); Lima, Nelson Batista de [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-01-15

    The production of tribological nanoscale multilayer CrN/NbN coatings up to 6 μm thick by Sputtering/HIPIMS has been reported in literature. However, high demanding applications, such as internal combustion engine parts, need thicker coatings (>30 μm). The production of such parts by sputtering would be economically restrictive due to low deposition rates. In this work, nanoscale multilayer CrN/NbN coatings were produced in a high-deposition rate, industrial-size, Cathodic Arc Physical Vapor Deposition (ARC-PVD) chamber, containing three cathodes in alternate positions (Cr/ Nb/Cr). Four 30 μm thick NbN/CrN multilayer coatings with different periodicities (20, 10, 7.5 and 4 nm) were produced. The coatings were characterized by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The multilayer coating system was composed of alternate cubic rock salt CrN and NbN layers, coherently strained due to lattice mismatch. The film grew with columnar morphology through the entire stratified structure. The periodicities adopted were maintained throughout the entire coating. The 20 nm periodicity coating showed separate NbN and CrN peaks in the XRD patterns, while for the lower periodicity (≤10nm) coatings, just one intermediate lattice (d-spacing) was detected. An almost linear increase of hardness with decreasing bilayer period indicates that interfacial effects can dominate the hardening mechanisms. (author)

  15. Adhesion improvement of carbon-based coatings through a high ionization deposition technique

    Science.gov (United States)

    Broitman, E.; Hultman, L.

    2012-06-01

    The deposition of highly adherent carbon nitride (CNx) films using a pretreatment with two high power impulse magnetron sputtering (HIPIMS) power supplies in a master-slave configuration is reviewed. SKF3 (AISI 52100) steel substrates were pretreated in the environment of a high ionized Cr+Ar plasma in order to sputter clean the surface and implant Cr metal ions. CNx films were subsequently deposited at room temperature by DC magnetron sputtering from a high purity C target in a N2/Ar plasma discharge. All processing was done in an industrial-scale CemeCon CC800 coating system. A series of depositions were obtained with samples pretreated at different bias voltages (DC and pulsed). The adhesion of CNx films, evaluated by the Daimler-Benz Rockwell-C test, reaches strength quality HF1. Adhesion results are correlated to high resolution transmission electron microscopy observations confirming the formation of an optimal interfacial mixing layer of Cr and steel. The throwing power increase for HIPIMS coatings is associated to the higher ionization in the plasma discharge.

  16. Wetting behaviour of carbon nitride nanostructures grown by plasma enhanced chemical vapour deposition technique

    Science.gov (United States)

    Ahmad Kamal, Shafarina Azlinda; Ritikos, Richard; Abdul Rahman, Saadah

    2015-02-01

    Tuning the wettability of various coating materials by simply controlling the deposition parameters is essential for various specific applications. In this work, carbon nitride (CNx) films were deposited on silicon (1 1 1) substrates using radio-frequency plasma enhanced chemical vapour deposition employing parallel plate electrode configuration. Effects of varying the electrode distance (DE) on the films' structure and bonding properties were investigated using Field emission scanning electron microscopy, Atomic force microscopy, Fourier transform infrared and X-ray photoemission spectroscopy. The wettability of the films was analyzed using water contact angle measurements. At high DE, the CNx films' surface was smooth and uniform. This changed into fibrous nanostructures when DE was decreased. Surface roughness of the films increased with this morphological transformation. Nitrogen incorporation increased with decrease in DE which manifested the increase in both relative intensities of Cdbnd N to Cdbnd C and Nsbnd H to Osbnd H bonds. sp2-C to sp3-C ratio increased as DE decreased due to greater deformation of sp2 bonded carbon at lower DE. The films' characteristics changed from hydrophilic to super-hydrophobic with the decrease in DE. Roughness ratio, surface porosity and surface energy calculated from contact angle measurements were strongly dependent on the morphology, surface roughness and bonding properties of the films.

  17. N-doped ZnO films grown from hybrid target by the pulsed laser deposition technique

    Science.gov (United States)

    Martín-Tovar, E. A.; Chan y Díaz, E.; Acosta, M.; Castro-Rodríguez, R.; Iribarren, A.

    2016-10-01

    ZnO thin films were grown by the pulsed laser deposition technique on glass substrate using a hybrid target composed of ZnO powder embedded into a poly(ethyl cyanoacrylate) matrix. The resulting thin film presented ZnO wurtzite structure with very low stress and diffractogram very similar to that of the powder pattern. From comparing with ZnO thin films grown from traditional sintered target, it is suggested that the use of this hybrid target with a soft matrix led to ejection of ZnO clusters that conveniently disposed and adhered to substrate and previous deposited layers. Chemical measurements showed the presence of Zn-N bonds, besides Zn-O ones. Optical absorption profile confirmed the presence of low-polymerized zinc oxynitride molecular subunits, besides ZnO.

  18. Solution Layer Deposition: A Technique for the Growth of Ultra-Pure Manganese Oxides on Silica at Room Temperature.

    Science.gov (United States)

    Cure, Jérémy; Piettre, Kilian; Coppel, Yannick; Beche, Eric; Esvan, Jérôme; Collière, Vincent; Chaudret, Bruno; Fau, Pierre

    2016-02-24

    With the ever increasing miniaturization in microelectronic devices, new deposition techniques are required to form high-purity metal oxide layers. Herein, we report a liquid route to specifically produce thin and conformal amorphous manganese oxide layers on silicon substrate, which can be transformed into a manganese silicate layer. The undesired insertion of carbon into the functional layers is avoided through a solution metal-organic chemistry approach named Solution Layer Deposition (SLD). The growth of a pure manganese oxide film by SLD takes place through the decoordination of ligands from a metal-organic complex in mild conditions, and coordination of the resulting metal atoms on a silica surface. The mechanism of this chemical liquid route has been elucidated by solid-state (29) Si MAS NMR, XPS, SIMS, and HRTEM.

  19. CdS thin films obtained by thermal treatment of cadmium(II) complex precursor deposited by MAPLE technique

    Energy Technology Data Exchange (ETDEWEB)

    Rotaru, Andrei [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Mietlarek-Kropidlowska, Anna [Gdansk University of Technology, Chemistry Faculty, 11/12 G. Narutowicza Str., PL-90-233 Gdansk (Poland); Constantinescu, Catalin, E-mail: catalin.constantinescu@inflpr.ro [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Scarisoreanu, Nicu; Dumitru, Marius [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Strankowski, Michal [Gdansk University of Technology, Chemistry Faculty, 11/12 G. Narutowicza Str., PL-90-233 Gdansk (Poland); Rotaru, Petre [University of Craiova, Faculty of Physics, 13 A.I. Cuza St., Craiova RO-200585, Dolj (Romania); Ion, Valentin [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Vasiliu, Cristina [INOE 2000 - National Institute for Optoelectronics, 1 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania); Becker, Barbara [Gdansk University of Technology, Chemistry Faculty, 11/12 G. Narutowicza Str., PL-90-233 Gdansk (Poland); Dinescu, Maria [INFLPR - National Institute for Laser, Plasma and Radiation Physics, PPAM - Lasers Department, 409 Atomistilor Bvd., Magurele RO-077125, Bucharest (Romania)

    2009-05-15

    Thin films of [Cd{l_brace}SSi(O-Bu{sup t}){sub 3}{r_brace}(S{sub 2}CNEt{sub 2})]{sub 2}, precursor for semiconducting CdS layers, were deposited on silicon substrates by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. Structural analysis of the obtained films by Fourier transform infrared spectroscopy (FTIR) confirmed the viability of the procedure. After the deposition of the coordination complex, the layers are manufactured by appropriate thermal treatment of the system (thin film and substrate), according to the thermal analysis of the compound. Surface morphology of the thin films was investigated by atomic force microscopy (AFM) and spectroscopic-ellipsometry (SE) measurements.

  20. Method for Improving Mg Doping During Group-III Nitride MOCVD

    Science.gov (United States)

    Creighton, J. Randall; Wang, George T.

    2008-11-11

    A method for improving Mg doping of Group III-N materials grown by MOCVD preventing condensation in the gas phase or on reactor surfaces of adducts of magnesocene and ammonia by suitably heating reactor surfaces between the location of mixing of the magnesocene and ammonia reactants and the Group III-nitride surface whereon growth is to occur.

  1. Near room-temperature direct encapsulation of organic photovoltaics by plasma-based deposition techniques

    Science.gov (United States)

    Perrotta, Alberto; Fuentes-Hernandez, Canek; Khan, Talha M.; Kippelen, Bernard; Creatore, Mariadriana; Graham, Samuel

    2017-01-01

    Plasma-assisted atomic layer deposition (ALD) is used for the deposition of environmental barriers directly onto organic photovoltaic devices (OPVs) at near room temperature (30 °C). To study the effect of the ALD process on the organic materials forming the device, the precursor diffusion and intermixing at the interface during the growth of different plasma-assisted ALD inorganic barriers (i.e. Al2O3 and TiO2) onto the organic photoactive layer (P3HT:ICBA) was investigated. Depth profile x-ray photoelectron spectroscopy was used to analyze the composition of the organic/inorganic interface to investigate the infiltration of the plasma-assisted ALD precursors into the photoactive layer as a function of the precursor dimension, the process temperature, and organic layer morphology. The free volume in the photoactive layer accessible to the ALD precursor was characterized by means of ellipsometric porosimetry (EP) and spectroscopic ellipsometry as a function of temperature. The organic layer is shown to exhibit free volume broadening at high temperatures, increasing the infiltration depth of the ALD precursor into the photoactive layer. Furthermore, based on previous investigations, the intrinsic permeation properties of the inorganic layers deposited by plasma-assisted ALD were predicted from the nano-porosity content as measured by EP and found to be in the 10-6 gm-2 d-1 range. Insight from our studies was used to design and fabricate multilayer barriers synthesized at near-room temperature by plasma-assisted ALD in combination with plasma-enhanced CVD onto organic photovoltaic (OPVs) devices. Encapsulated OPVs displayed shelf-lifetimes up to 1400 h at ambient conditions.

  2. Investigation of Non-Vacuum Deposition Techniques in Fabrication of Chalcogenide-Based Solar Cell Absorbers

    KAUST Repository

    Alsaggaf, Ahmed

    2015-07-01

    The environmental challenges are increasing, and so is the need for renewable energy. For photovoltaic applications, thin film Cu(In,Ga)(S,Se)2 (CIGS) and CuIn(S,Se)2 (CIS) solar cells are attractive with conversion efficiencies of more than 20%. However, the high-efficiency cells are fabricated using vacuum technologies such as sputtering or thermal co-evaporation, which are very costly and unfeasible at industrial level. The fabrication involves the uses of highly toxic gases such as H2Se, adding complexity to the fabrication process. The work described here focused on non-vacuum deposition methods such as printing. Special attention has been given to printing designed in a moving Roll-to-Roll (R2R) fashion. The results show potential of such technology to replace the vacuum processes. Conversion efficiencies for such non-vacuum deposition of Cu(In,Ga)(S,Se)2 solar cells have exceeded 15% using hazardous chemicals such as hydrazine, which is unsuitable for industrial scale up. In an effort to simplify the process, non-toxic suspensions of Cu(In,Ga)S2 molecular-based precursors achieved efficiencies of ~7-15%. Attempts to further simplify the selenization step, deposition of CuIn(S,Se)2 particulate solutions without the Ga doping and non-toxic suspensions of Cu(In,Ga)Se2 quaternary precursors achieved efficiencies (~1-8%). The contribution of this research was to provide a new method to monitor printed structures through spectral-domain optical coherence tomography SD-OCT in a moving fashion simulating R2R process design at speeds up to 1.05 m/min. The research clarified morphological and compositional impacts of Nd:YAG laser heat-treatment on Cu(In,Ga)Se2 absorber layer to simplify the annealing step in non-vacuum environment compatible to R2R. Finally, the research further simplified development methods for CIGS solar cells based on suspensions of quaternary Cu(In,Ga)Se2 precursors and ternary CuInS2 precursors. The methods consisted of post deposition reactive

  3. Metalorganic chemical vapor deposition of Ti-O-C-N thin films using TBOT as a promising precursor

    Energy Technology Data Exchange (ETDEWEB)

    Fouad, O.A., E-mail: oafouad@yahoo.com [Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan 11421, Helwan (Egypt); Geioushy, R.A.; El-Sheikh, S.M. [Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan 11421, Helwan (Egypt); Khedr, M.H. [Chemistry Department, Faculty of Science, Beni-Suef University, Beni-Suef (Egypt); Ibrahim, I.A. [Central Metallurgical Research and Development Institute (CMRDI), P.O. Box 87, Helwan 11421, Helwan (Egypt)

    2011-05-19

    Graphical abstract: Display Omitted Highlights: > Novel precursor (TBOT) has been used for synthesis of from Ti(O,C,N) thin films via APCVD process. > TiO{sub 2} and TiC compounds deposition were thermodynamically favored as products of metalorganic precursor decomposition in presence of H{sub 2} gas at temperature >500 deg. C. > TiO{sub 2} deposited in the form of spherical-like shape particles, TiC deposited in the form of fiber-like shape structures. > High hardness value was obtained for Ti-O-C-N films at 750 deg. C ({approx}425 HV{sub 50}) due to the formation of stoichiometric TiN phase. - Abstract: Ti-O, Ti-O-C and Ti-O-C-N thin films have been synthesized successfully via metalorganic chemical vapor deposition (MOCVD) technique. Tetrabutyl orthotitanate (TBOT) is used as a precursor in presence of Ar, H{sub 2}, and N{sub 2} as process gases. By controlling deposition temperature and type of process gases, it was possible to control the composition of the deposited films. The deposited films are composed mainly of Ti and O when H{sub 2} is used as a process gas in the temperature range 350-500 deg. C. As the temperature increased up to 600 deg. C, thin films containing anatase (TiO{sub 2}) and titanium carbide (TiC) phases are deposited and confirmed by XRD and EDX analyses. As the temperature increased to 750 deg. C, a transformation from anatase to rutile phase (TiO{sub 2}) is started and clearly observed from XRD patterns. Titanium nitride (Ti{sub 2}N and TiN) phase in addition to TiO{sub 2} and TiC phases are formed at 600-1000 deg. C in presence of nitrogen as a process gas. SEM images for all investigated film samples showed that the films are deposited mainly in the form of spherical particles ranged from few nano- to micrometer in size with some additional special features regardless the type of the process gas. Films containing carbon and nitrogen show higher hardness than that containing only oxygen. The obtained results may help in better

  4. Characterization of ZnO:SnO2 (50:50) thin film deposited by RF magnetron sputtering technique

    Science.gov (United States)

    Cynthia, S. R.; Sivakumar, R.; Sanjeeviraja, C.; Ponmudi, S.

    2016-05-01

    Zinc oxide (ZnO) and tin oxide (SnO2) thin films have attracted significant interest recently for use in optoelectronic application such as solar cells, flat panel displays, photonic devices, laser diodes and gas sensors because of their desirable electrical and optical properties and wide band gap. In the present study, thin films of ZnO:SnO2 (50:50) were deposited on pre-cleaned microscopic glass substrate by RF magnetron sputtering technique. The substrate temperature and RF power induced changes in structural, surface morphological, compositional and optical properties of the films have been studied.

  5. Determination of the optical parameters of a-Si:H thin films deposited by hot wire–chemical vapour deposition technique using transmission spectrum only

    Indian Academy of Sciences (India)

    Nabeel A Bakr; A M Funde; V S Waman; M M Kamble; R R Hawaldar; D P Amalnerkar; S W Gosavi; S R Jadkar

    2011-03-01

    Three demonstration samples of intrinsic hydrogenated amorphous silicon (a-Si:H) films were deposited using hot wire–chemical vapour deposition (HW–CVD) technique. The optical parameters and the thickness were determined from the extremes of the interference fringes of transmission spectrum in the range of 400–2500 nm using the envelope method. The calculated values of the refractive index () were fitted using the two-term Cauchy dispersion relation and the static refractive index values (0) obtained were 2.799, 2.629 and 3.043 which were in the range of the reported values. The calculated thicknesses for all samples were cross-checked with Taly-Step profilometer and found to be almost equal. Detailed analysis was carried out to obtain the optical band gap (g) using Tauc’s method and the estimated values were 1.99, 2.01 and 1.75 eV. The optical band gap values were correlated with the hydrogen content (H) in the samples calculated from Fourier transform infrared (FTIR) analysis. An attempt was made to apply Wemple–DiDomenico single-effective oscillator model to the a-Si:H samples to calculate the optical parameters. The optical band gap obtained by Tauc’s method and the static refractive index calculated from Cauchy fitting are in good agreement with those obtained by the single-effective oscillator model. The real and the imaginary parts of dielectric constant (r, ), and the optical conductivity () were also calculated.

  6. Measurement of LHCD edge power deposition through modulation techniques on Alcator C-Mod

    Energy Technology Data Exchange (ETDEWEB)

    Faust, I. C.; Brunner, D.; LaBombard, B.; Parker, R. R.; Baek, S. G.; Chilenksi, M. A.; Hubbard, A.; Hughes, J. W.; Terry, J. L.; Shiraiwa, S.; Walk, J. R.; Wallace, G. M.; Whyte, D. G. [MIT Plasma Science and Fusion Center, Cambridge, MA USA (United States); Edlund, E. [Princeton Plasma Physics Laboratory, Princeton, NJ USA (United States)

    2015-12-10

    The efficiency of LHCD on Alcator C-Mod drops exponentially with line average density. At reactor relevant densities (> 1 · 1020 [m{sup −3}]) no measurable current is driven. While a number of causes have been suggested, no specific mechanism has been shown to be responsible for the loss of current drive at high density. Fast modulation of the LH power was used to isolate and quantify the LHCD deposition within the plasma. Measurements from these plasmas provide unique evidence for determining a root cause. Modulation of LH power in steady plasmas exhibited no correlated change in the core temperature. A correlated, prompt response in the edge suggests that the loss in efficiency is related to a edge absorption mechanism. This follows previous results which found the generation of n{sub ||}-independent SOL currents. Multiple Langmuir probe array measurements of the conducted heat conclude that the lost power is deposited near the last closed flux surface. The heat flux induced by LH waves onto the outer divertor is calculated. Changes in the neutral pressure, ionization and hard X-ray emission at high density highlight the importance of the active divertor in the loss of efficiency. Results of this study implicate a mechanism which may occur over multiple passes, leading to power absorption near the LCFS.

  7. Diagnostic Techniques Used to Study Chemical-Vapor-Deposited Diamond Films

    Science.gov (United States)

    Miyoshi, Kazuhisa

    2000-01-01

    The advantages and utility of chemical-vapor-deposited (CVD) diamond as an industrial ceramic can only be realized if the price and quality are right. Until recently, this technology was of interest only to the academic and basic research community. However, interest has grown because of advances made by leading CVD diamond suppliers: 1) Reduction of the cost of CVD polycrystalline diamond deposition below $5/carat ($8/sq cm); 2) Installation of production capacity; 3) Epitaxial growth of CVD single-crystal diamond. Thus, CVD diamond applications and business are an industrial reality. At present, CVD diamond is produced in the form of coatings or wafers. CVD diamond film technology offers a broader technological potential than do natural and high-pressure synthetic diamonds because size, geometry, and eventually cost will not be as limiting. Now that they are cost effective, diamond coatings - with their extreme properties - can be used in a variety of applications. Diamond coatings can improve many of the surface properties of engineering substrate materials, including erosion, corrosion, and wear resistance. Examples of actual and potential applications, from microelectromechanical systems to the wear parts of diamond coatings and related superhard coatings are described. For example, diamond coatings can be used as a chemical and mechanical barrier for the space shuttles check valves, particularly on the guide pins and seat assemblies.

  8. Comparison of laser-ablation and hot-wall chemical vapour deposition techniques for nanowire fabrication

    Science.gov (United States)

    Stern, E.; Cheng, G.; Guthrie, S.; Turner-Evans, D.; Broomfield, E.; Lei, B.; Li, C.; Zhang, D.; Zhou, C.; Reed, M. A.

    2006-06-01

    A comparison of the transport properties of populations of single-crystal, In2O3 nanowires (NWs) grown by unassisted hot-wall chemical vapour deposition (CVD) versus NWs grown by laser-ablation-assisted chemical vapour deposition (LA-CVD) is presented. For nominally identical growth conditions across the two systems, NWs fabricated at 850 °C with laser-ablation had significantly higher average mobilities at the 99.9% confidence level, 53.3 ± 5.8 cm2 V-1 s-1 versus 10.2 ± 1.9 cm2 V-1 s-1. It is also observed that increasing growth temperature decreases mobility for LA-CVD NWs. Transmission electron microscopy studies of CVD-fabricated samples indicate the presence of an amorphous In2O3 region surrounding the single-crystal core. Further, low-temperature measurements verify the presence of ionized impurity scattering in low-mobility CVD-grown NWs.

  9. In Situ Synthesis and Characterization of Fe-Based Metallic Glass Coatings by Electrospark Deposition Technique

    Science.gov (United States)

    Burkov, Alexander A.; Pyachin, S. A.; Ermakov, M. A.; Syuy, A. V.

    2017-02-01

    Crystalline FeWMoCrBC electrode materials were prepared by conventional powder metallurgy. Metallic glass (MG) coatings were produced by electrospark deposition onto AISI 1035 steel in argon atmosphere. X-ray diffraction and scanning electron microscopy verified the amorphous structure of the as-deposited coatings. The coatings have a thickness of about 40 microns and a uniform structure. The results of dry sliding wear tests against high-speed steel demonstrated that Fe-based MG coatings had a lower friction coefficient and more than twice the wear resistance for 20 km sliding distance with respect to AISI 1035 steel. High-temperature oxidation treatment of the metal glass coatings at 1073 K in air for 12 h revealed that the oxidation resistance of the best coating was 36 times higher than that for bare AISI 1035 steel. These findings are expected to broaden the applications of electrospark Fe-based MG as highly protective and anticorrosive coatings for mild steel.

  10. Effect of indium doping level on certain physical properties of CdS films deposited using an improved SILAR technique

    Energy Technology Data Exchange (ETDEWEB)

    Ravichandran, K., E-mail: kkr1365@yahoo.com [P.G. and Research Department of Physics, AVVM Sri Pushpam College (Autonomous), Poondi, Thanjavur-613 503, Tamil Nadu (India); Senthamilselvi, V. [P.G. and Research Department of Physics, AVVM Sri Pushpam College (Autonomous), Poondi, Thanjavur-613 503, Tamil Nadu (India); Department of Physics, Kunthavai Naachiyaar Government College for Women (Autonomous), Thanjavur-613 007, Tamil Nadu (India)

    2013-04-01

    The influence of indium (In) doping levels (0, 2, …, 8 at.%) on certain physical properties of cadmium sulphide (CdS) thin films deposited using an improved successive ionic layer adsorption and reaction (ISILAR) method has been studied. In this improved SILAR technique, a fresh anionic solution was introduced after a particular number of dipping cycles in order to achieve good stoichiometry. All the deposited films exhibited cubic phase with (1 1 1) plane as preferential orientation. The calculated crystallite size values are found to be decreased from 54.80 nm to 23.65 nm with the increase in In doping level. The optical study confirmed the good transparency (80%) of the film. A most compact and pinhole free smooth surface was observed for the CdS films with 8 at.% of In doping level. The perceived photoluminescence (PL) bands endorsed the lesser defect crystalline nature of the obtained CdS:In films. The chemical composition analysis (EDAX) showed the near stoichiometric nature of this ISILAR deposited CdS:In films.

  11. Effect of active screen plasma nitriding pretreatment on wear behavior of TiN coating deposited by PACVD technique

    Energy Technology Data Exchange (ETDEWEB)

    Raoufi, M., E-mail: raoufi@iust.ac.ir [School of Metallurgical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Mirdamadi, Sh. [School of Metallurgical Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Mahboubi, F. [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Ahangarani, Sh. [Advanced Materials and Renewable Energies Dep., Iranian Research Organization for Science and Technology (Iran, Islamic Republic of); Mahdipoor, M.S. [Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Elmkhah, H. [Department of Metallurgical Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of)

    2012-08-01

    Titanium based alloys are used extensively for improving wear properties of different parts due to their high hardness contents. Titanium nitride (TiN) is among these coatings which can be deposited on surface using various techniques such as CVD, PVD and PACVD. Their weak interface with substrate is one major drawback which can increase the total wear in spite of favorite wear behavior of TiN. Disc shaped samples from AISI H13 (DIN 1.2344) steel were prepared in this study. Single TiN coating was deposited on some of them while others have experienced a TiN deposition by active screen plasma nitriding (ASPN). Hardness at the surface and depth of samples was measured through Vickers micro hardness test which revealed 1810 Hv hardness as the maximum values for a dual-layered ASPN-TiN. Pin-on-disc wear test was done in order to study the wear mechanism. In this regard, the wear behavior of samples was investigated against pins from 100Cr6 (Din 1.3505) bearing steel and tungsten carbide-cobalt (WC-Co) steel. It was evidenced that the dual-layer ASPN-TiN coating has shown the least weight loss with the best wearing behavior because of its high hardness values, stable interface and acceptable resistance against peeling during wearing period.

  12. Characterization and photocatalytic activity of boron-doped TiO2 thin films prepared by liquid phase deposition technique

    Indian Academy of Sciences (India)

    Noor Shahina Begum; H M Farveez Ahmed; O M Hussain

    2008-10-01

    Boron doped TiO2 thin films have been successfully deposited on glass substrate and silicon wafer at 30°C from an aqueous solution of ammonium hexa-fluoro titanate and boron trifluoride by liquid phase deposition technique. The boric acid was used as an – scavenger. The resultant films were characterized by XRD, EDAX, UV and microstructures by SEM. The result shows the deposited film to be amorphous which becomes crystalline between 400 and 500°C. The EDAX and XRD data confirm the existence of boron atom in TiO2 matrix and a small peak corresponding to rutile phase was also found. Boron doped TiO2 thin films can be used as photocatalyst for the photodegradation of chlorobenzene which is a great environmental hazard. It was found that chlorobenzene undergoes degradation efficiently in presence of boron doped TiO2 thin films by exposing its aqueous solution to visible light. The photocatalytic activity increases with increase in the concentration of boron.

  13. Using wire shaping techniques and holographic optics to optimize deposition characteristics in wire-based laser cladding

    Science.gov (United States)

    Goffin, N. J.; Higginson, R. L.; Tyrer, J. R.

    2016-12-01

    In laser cladding, the potential benefits of wire feeding are considerable. Typical problems with the use of powder, such as gas entrapment, sub-100% material density and low deposition rate are all avoided with the use of wire. However, the use of a powder-based source material is the industry standard, with wire-based deposition generally regarded as an academic curiosity. This is because, although wire-based methods have been shown to be capable of superior quality results, the wire-based process is more difficult to control. In this work, the potential for wire shaping techniques, combined with existing holographic optical element knowledge, is investigated in order to further improve the processing characteristics. Experiments with pre-placed wire showed the ability of shaped wire to provide uniformity of wire melting compared with standard round wire, giving reduced power density requirements and superior control of clad track dilution. When feeding with flat wire, the resulting clad tracks showed a greater level of quality consistency and became less sensitive to alterations in processing conditions. In addition, a 22% increase in deposition rate was achieved. Stacking of multiple layers demonstrated the ability to create fully dense, three-dimensional structures, with directional metallurgical grain growth and uniform chemical structure.

  14. Effects of Thermal Annealing on the Optical Properties of Titanium Oxide Thin Films Prepared by Chemical Bath Deposition Technique

    Directory of Open Access Journals (Sweden)

    H.U. Igwe

    2010-08-01

    Full Text Available A titanium oxide thin film was prepared by chemical bath deposition technique, deposited on glass substrates using TiO2 and NaOH solution with triethanolamine (TEA as the complexing agent. The films w ere subjected to post deposition annealing under various temperatures, 100, 150, 200, 300 and 399ºC. The thermal treatment streamlined the properties of the oxide films. The films are transparent in the entire regions of the electromagnetic spectrum, firmly adhered to the substrate and resistant to chemicals. The transmittance is between 20 and 95% while the reflectance is between 0.95 and 1%. The band gaps obtained under various thermal treatments are between 2.50 and 3.0 ev. The refractive index is between 1.52 and 2.55. The thickness achieved is in the range of 0.12-0.14 :m.These properties of the oxide film make it suitable for application in solar cells: Liquid and solid dye-sensitized photoelectrochemical solar cells, photo induced water splitting, dye synthesized solar cells, environmental purifications, gas sensors, display devices, batteries, as well as, solar cells with an organic or inorganic extremely thin absorber. These thin films are also of interest for the photooxidation of water, photocatalysis, electro chromic devices and other uses.

  15. A Novel Technique for the Deposition of Bismuth Tungstate onto Titania Nanoparticulates for Enhancing the Visible Light Photocatalytic Activity

    Directory of Open Access Journals (Sweden)

    Marina Ratova

    2016-07-01

    Full Text Available A novel powder handling technique was used to allow the deposition of bismuth tungstate coatings onto commercial titanium dioxide photocatalytic nanoparticles. The coatings were deposited by reactive pulsed DC magnetron sputtering in an argon/oxygen atmosphere. The use of an oscillating bowl with rotary particle propagation, positioned beneath two closed-field planar magnetrons, provided uniform coverage of the titania particle surfaces. The bismuth/tungsten atomic ratio of the coatings was controlled by varying the power applied to each target. The resulting materials were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX, Brunauer–Emmett–Teller (BET surface area measurements, transmission electron microscopy (TEM, and UV-visible diffuse reflectance spectroscopy. Photocatalytic properties under visible light irradiation were assessed using an acetone degradation test. It was found that deposition of bismuth tungstate onto titania nanoparticles resulted in significant increases in visible light photocatalytic activity, compared to uncoated titania. Of the coatings studied, the highest photocatalytic activity was measured for the sample with a Bi/W atomic ratio of 2/1.

  16. Evaluation and study of advanced optical contamination, deposition, measurement, and removal techniques. [including computer programs and ultraviolet reflection analysis

    Science.gov (United States)

    Linford, R. M. F.; Allen, T. H.; Dillow, C. F.

    1975-01-01

    A program is described to design, fabricate and install an experimental work chamber assembly (WCA) to provide a wide range of experimental capability. The WCA incorporates several techniques for studying the kinetics of contaminant films and their effect on optical surfaces. It incorporates the capability for depositing both optical and contaminant films on temperature-controlled samples, and for in-situ measurements of the vacuum ultraviolet reflectance. Ellipsometer optics are mounted on the chamber for film thickness determinations, and other features include access ports for radiation sources and instrumentation. Several supporting studies were conducted to define specific chamber requirements, to determine the sensitivity of the measurement techniques to be incorporated in the chamber, and to establish procedures for handling samples prior to their installation in the chamber. A bibliography and literature survey of contamination-related articles is included.

  17. Research Update: Large-area deposition, coating, printing, and processing techniques for the upscaling of perovskite solar cell technology

    Directory of Open Access Journals (Sweden)

    Stefano Razza

    2016-09-01

    Full Text Available To bring perovskite solar cells to the industrial world, performance must be maintained at the photovoltaic module scale. Here we present large-area manufacturing and processing options applicable to large-area cells and modules. Printing and coating techniques, such as blade coating, slot-die coating, spray coating, screen printing, inkjet printing, and gravure printing (as alternatives to spin coating, as well as vacuum or vapor based deposition and laser patterning techniques are being developed for an effective scale-up of the technology. The latter also enables the manufacture of solar modules on flexible substrates, an option beneficial for many applications and for roll-to-roll production.

  18. Effects of Ni doping on photocatalytic activity of TiO2 thin films prepared by liquid phase deposition technique

    Indian Academy of Sciences (India)

    Noor Shahina Begum; H M Farveez Ahmed; K R Gunashekar

    2008-10-01

    The TiO2 thin films doped by Ni uniformly and non-uniformly were prepared on glass substrate from an aqueous solution of ammonium hexa-fluoro titanate and NiF2 by liquid phase deposition technique. The addition of boric acid as an – scavenger will shift the equilibrium to one side and thereby deposition of the film is progressed. The rate of the reaction and the nature of deposition depend on growing time and temperature. The resultant films were characterized by XRD, EDAX, UV and SEM. The result shows that the deposited films have amorphous background, which becomes crystalline at 500°C. The EDAX data confirms the existence of Ni atoms in TiO2 matrix. XRD analysis reveals the peaks corresponding to Ni but no peak of crystalline NiO was found. The transmittance spectra of Ni uniformly and non-uniformly doped TiO2 thin films show `blue shift and red shift’, respectively. Ni-doped TiO2 thin films can be used as photocatalyst for the photodegradation of methyl orange dye. It was found that, organic dye undergoes degradation efficiently in presence of non-uniformly Ni-doped TiO2 thin films when compared to uniformly doped films and pure TiO2 films under visible light. The photocatalytic activity increases with increase in the concentration of Ni in case of nonuniformly doped thin films but decreases with the concentration when uniformly doped thin films were used.

  19. Dry deposition of acidic air pollutants to tree leaves, determined by a modified leaf-washing technique

    Science.gov (United States)

    Watanabe, Mirai; Takamatsu, Takejiro; Koshikawa, Masami K.; Yamamura, Shigeki; Inubushi, Kazuyuki

    Dry deposition fluxes ( FL) of NO 3- and SO 42- to leaf surfaces were measured for Japanese red pine ( Pinus densiflora), Japanese cedar ( Cryptomeria japonica), Japanese cypress ( Chamaecyparis obtusa), and Japanese white oak ( Quercus myrsinaefolia), together with atmospheric concentrations ( CL) of NO x (NO + NO 2), T-NO 3 (gaseous HNO 3 + particulate NO 3-) and SO x (gaseous SO 2 + particulate SO 42-) around the leaves in a suburban area of Japan, using a modified leaf-washing technique. FL of NO 3- and SO 42- decreased as follows: pine >> cedar > cypress ≥ oak and pine >> cedar > oak ≥ cypress, respectively. FL of NO 3- for all tree species fluctuated synchronously with CL of T-NO 3. FL of SO 42- fluctuated with CL of SO x, but the dominant pollutant deposited (SO 2 or SO 42-) appeared to differ for different tree species. Dry deposition conductance ( KL) of T-NO 3 and SO x was derived as an FL/ CL ratio. Seasonal variations of KL likely reflect the gas/particle ratios of T-NO 3 and SO x, which were affected by meteorological conditions such as temperature. Dry deposition velocities ( Vd) of T-NO 3 and SO x were obtained as the mathematical product of annual mean KL and the total leaf surface areas in the forests. The comparison of Vd among tree species indicated that the loads of acidic air pollutants were higher to coniferous forests than broad-leaved forest because of the higher KL and/or larger leaf surface areas.

  20. Dependence of bimodal size distribution on temperature and optical properties of InAs quantum dots grown on vicinal GaAs (100) substrates by using MOCVD

    Institute of Scientific and Technical Information of China (English)

    Liang Song; Zhu Hong-Liang; Pan Jiao-Qing; Wang Wei

    2006-01-01

    Self-assembled InAs quantum dots (QDs) are grown on vicinal GaAs (100) substrates by using metal-organic chemical vapour deposition (MOCVD). An abnormal temperature dependence of bimodal size distribution of InAs quantum dots is found. As the temperature increases, the density of the small dots grows larger while the density of the large dots turns smaller, which is contrary to the evolution of QDs on exact GaAs (100) substrates. This trend is explained by taking into account the presence of multiatomic steps on the substrates. The optical properties of InAs QDs on vicinal GaAs(100) substrates are also studied by photoluminescence (PL) . It is found that dots on a vicinal substrate have a longer emission wavelength, a narrower PL line width and a much larger PL intensity.

  1. Multi-wafer growth of GaInAs photodetectors on 4" InP by MOCVD for SWIR imaging applications

    Science.gov (United States)

    Furlong, Mark J.; Mattingley, Mark; Lim, Sung Wook; Geen, Matthew; Jones, Wynne

    2014-06-01

    Photodiodes based on the GaInAs/InP material system responding in the 1.3-1.7 μm wavelength range are of interest in a wide range of applications, from optical power and channel monitors in telecommunication systems through to advanced night vision imaging using large format focal plane type detectors for defense and security applications. Here we report on our results of GaInAs PIN photo detector structures grown on 2", 3" and 4" InP substrates by low pressure Metalorganic Chemical Vapor Deposition (MOCVD) in both standard and new larger volume format reactor configurations. High quality, lattice matched InP/GaInAs epitaxial layers were grown and we demonstrate that when moving to larger platen configurations, high degree of thickness uniformity (improved performance.

  2. Optical characterization of Al sub x Ga sub 1 sub - sub x N alloys grown by MOCVD

    CERN Document Server

    Kim, H S; Li, J; Lin, J Y; Jiang, H

    2000-01-01

    Al sub x Ga sub 1 sub - sub x N alloys with x varied from 0 to 0.35 have been produced on sapphire substrates with GaN buffer layers by using metalorganic chemical vapor deposition (MOCVD), and the optical properties of the Al sub x Ga sub 1 sub - sub x N alloys have been investigated using picosecond time-resolved photoluminescence (PL) spectroscopy at low temperature (10 K). Our results reveal that the PL intensity decreases with increasing of Al content. On the other hand, the PL decay lifetime increases with Al content. These results can be understood in terms of the effects of tail states in the density of states (DOS) due to alloy fluctuation in the Al sub x Ga sub 1 sub - sub x N alloys. The Al content dependence of the energy tail-state distribution parameter, E sub 0 , which is an important parameter for determining the optical and the electrical properties of the AlGaN alloys, has been obtained experimentally.

  3. Monolithic integration of MQW wavelength tunable DBR lasers with external cavity electroabsorption modulators by selective-area MOCVD

    Science.gov (United States)

    Lammert, Robert M.; Smith, Gary M.; Hughes, J. S.; Osowski, Mark L.; Jones, A. M.; Coleman, James J.

    1997-01-01

    The design and operation of multiple-quantum well (MQW) wavelength tunable distributed Bragg reflector (DBR) lasers with nonabsorbing gratings and monolithically integrated external cavity electroabsorption modulators fabricated by selective-area metal-organic chemical vapor deposition (MOCVD) are presented. Uncoated devices exhibit cw threshold currents as low as 10.5 mA with slope efficiencies of 0.21 W/A from the laser facet and 0.06 W/A from the modulator facet. After the application of facet coatings, slope efficiencies from the modulator facet increase to 0.14 W/A. Wavelength tuning of 7 nm is obtained by injection current heating of the DBR section. These devices exhibit extinction ratios of 18 dB from the modulator facet at a low modulator bias of 1 V, when measured with a broad-area detector. When coupled to a singlemode fiber, these devices exhibit high extinction ratios of 40 dB at a modulator bias of 1.25 V. Photo-generated current versus optical power plots indicate that the extinction ratios are not limited by carrier build- up in the modulator quantum wells.

  4. Structural and Optical Properties of ZnO Films with Different Thicknesses Grown on Sapphire by MOCVD

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    ZnO(002) films with different thicknesses, grown on Al2O3 (006) substrates by metal-organic chemical vapor deposition( MOCVD), were etched by Ar ion beams. The samples were examined by D8 X-ray diffraction, scanning electron microscopy(SEM), and photoluminescence (PL) spectrometry. The structural properties vary with the increasing thickness of the films. When the film thickness is thin, the phi(Φ) scanning curves for ZnO(103) and sapphire(116) substrate show the existence of two kinds of orientation relationships between ZnO films and sapphire,which are ZnO(002)//Al2O3 (006), ZnO(100)//Al2O3 (110) and ZnO(002)//Al2O3 (006), ZnO(110)//Al2O3(110). When the thickness increases to 500 nm there is only one orientation relationship, which is ZnO(002)//Al2O3 (006), ZnO [ 100 ]//Al2O3[ 110 ]. Their photoluminescence (PL) spectra at room temperature show that the optical properties of ZnO films have been greatly improved when increasing the thickness of films is increased.

  5. ELECTRICAL FURNACE FOR PRODUCING CARBIDE COATINGS USING THE THERMOREACTIVE DEPOSITION/DIFFUSION TECHNIQUE

    Directory of Open Access Journals (Sweden)

    FABIO CASTILLEJO

    2011-01-01

    the presence of VC and NbC, and as MEB results clearly show, the formation of regular thickness coatings. The results obtained allow for assessing that the designed and built furnace fulfills the requirements of the TRD technique for obtaining different types of hard coatings.

  6. Comparative study of CdTe sources used for deposition of CdTe thin films by close spaced sublimation technique

    Directory of Open Access Journals (Sweden)

    Wagner Anacleto Pinheiro

    2006-03-01

    Full Text Available Unlike other thin film deposition techniques, close spaced sublimation (CSS requires a short source-substrate distance. The kind of source used in this technique strongly affects the control of the deposition parameters, especially the deposition rate. When depositing CdTe thin films by CSS, the most common CdTe sources are: single-crystal or polycrystalline wafers, powders, pellets or pieces, a thick CdTe film deposited onto glass or molybdenum substrate (CdTe source-plate and a sintered CdTe powder. In this work, CdTe thin films were deposited by CSS technique from different CdTe sources: particles, powder, compact powder, a paste made of CdTe and propylene glycol and source-plates (CdTe/Mo and CdTe/glass. The largest deposition rate was achieved when a paste made of CdTe and propylene glycol was used as the source. CdTe source-plates led to lower rates, probably due to the poor heat transmission, caused by the introduction of the plate substrate. The results also showed that compacting the powder the deposition rate increases due to the better thermal contact between powder particles.

  7. Electric characterization of GaAs deposited on porous silicon by electrodeposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Lajnef, M., E-mail: Mohamed.lajnef@yahoo.fr [Laboratoire de Photovoltaique et de Semi-conducteurs, Centre de Recherche et des Technologies de l' Energie, BP. 95, Hammam-Lif 2050 (Tunisia); Chtourou, R.; Ezzaouia, H. [Laboratoire de Photovoltaique et de Semi-conducteurs, Centre de Recherche et des Technologies de l' Energie, BP. 95, Hammam-Lif 2050 (Tunisia)

    2010-03-01

    GaAs thin films were synthesized on porous Si substrate by the electrodeposition technique. The X-ray diffraction studies showed that the as-grown films were crystallised in mixed phase nature orthorhombic and cubic of GaAs. The GaAs film was then electrically characterized using current-voltage (I-V) and capacitance-voltage (C-V) techniques by the way of Al/GaAs Schottky junctions. The electric analysis allowed us to determine the n factor and the barrier height {phi}{sub b0} parameters of Al/GaAs Schottky junctions. The (C-V) characteristics were recorded at frequency signal 1 MHz in order to identify the effect of the surface states on the behaviour of the capacitance of the device.

  8. Lamellar multilayer hexadecylaniline-modified gold nanoparticle films deposited by the Langmuir-Blodgett technique

    Indian Academy of Sciences (India)

    Anita Swami; Ashavani Kumar; Murali Sastry

    2003-06-01

    Organization of hexadecylaniline (HDA)-modified colloidal gold particles at the air-water interface and the formation thereafter of lamellar, multilayer films of gold nanoparticles by the Langmuir-Blodgett technique is described in this paper. Formation of HDA-capped gold nanoparticles is accomplished by a simple biphasic mixture experiment wherein the molecule hexadecylaniline present in the organic phase leads to electrostatic complexation and reduction of aqueous chloroaurate ions, capping of the gold nanoparticles thus formed and phase transfer of the now hydrophobic particles into the organic phase. Organization of gold nanoparticles at the air-water interface is followed by surface pressure-area isotherm measurements while the formation of multilayer films of the nanoparticles by the Langmuir-Blodgett technique is monitored by quartz crystal microgravimetry, UVVis spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy.

  9. Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique

    Science.gov (United States)

    Ahumada-Lazo, R.; Torres-Martínez, L. M.; Ruíz-Gómez, M. A.; Vega-Becerra, O. E.; Figueroa-Torres, M. Z.

    2014-12-01

    The photocatalytic activity of ZnO thin films with different physicochemical characteristics deposited by RF magnetron sputtering on glass substrate was tested for the decolorization of orange G dye aqueous solution (OG). The crystalline phase, surface morphology, surface roughness and the optical properties of these ZnO films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV-visible spectroscopy (UV-Vis), respectively. The dye photodecolorization process was studied at acid, neutral and basic pH media under UV irradiation of 365 nm. Results showed that ZnO films grow with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a (002) preferential crystalline orientation. A clear relationship between surface morphology and photocatalytic activity was observed for ZnO films. Additionally, the recycling photocatalytic abilities of the films were also evaluated. A promising photocatalytic performance has been found with a very low variation of the decolorization degree after five consecutive cycles at a wide range of pH media.

  10. Hydrocarbon oxidation over catalysts prepared by the molecular layer deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Koltsov, S.I.; Smirnov, V.M.; Postnov, V.N.; Postnova, A.M.; Aleskovskii, V.B.

    1980-01-01

    By depositing consecutive uniform monolayers of phosphorus pentoxide and vanadium pentoxide on a large-surface-area (240 sq m/g) silica gel, active and selective catalysts for hydrocarbon oxidation were obtained. Thus, in piperylene oxidation by air at 330/sup 0/-430/sup 0/C and 2000-18,000/hr space velocity, a productive capacity of 220 g/l./hr with 41 mole % each maleic anhydride yield and selectivity was achieved over a SiO/sub 2/-P/sub 2/O/sub 5//P/sub 2/O/sub 5//V/sub 2/O/sub 5/ catalyst (120 sq cm/g surface area), compared with 80 g/l./hr for a P/sub 2/O/sub 5/-V/sub 2/O/sub 5/ catalyst prepared by impregnation. In benzene oxidation, maleic anhydride yields of 52 and 60% and selectivities of 63 and 79% were achieved over SiO/sub 2/-P/sub 2/O/sub 5//V/sub 2/O/sub 5/ and SiO/sub 2/-P/sub 2/O/sub 5//P/sub 2/O/sub 5//P/sub 2/O/sub 5//V/sub 2/O/sub 5/ catalysts, respectively, compared with a 6% yield and very low selectivity over the impregnated P/sub 2/O/sub 5/-V/sub 2/O/sub 5/ catalyst. The molecular-layer catalysts retained their total activity for 100 hr on stream and permitted to reduce the oxidation temperature by 50/sup 0/-70/sup 0/C.

  11. Photocatalytic efficiency of reusable ZnO thin films deposited by sputtering technique

    Energy Technology Data Exchange (ETDEWEB)

    Ahumada-Lazo, R.; Torres-Martínez, L.M. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Civil, Departamento de Ecomateriales y Energía, Av. Universidad S/N Ciudad Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66450, México (Mexico); Ruíz-Gómez, M.A. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Civil, Departamento de Ecomateriales y Energía, Av. Universidad S/N Ciudad Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66450, México (Mexico); Departmento de Física Aplicada, CINVESTAV-IPN, Antigua Carretera a Progreso km 6, Mérida, Yucatán 97310, México (Mexico); Vega-Becerra, O.E. [Centro de Investigación en Materiales Avanzados S.C, Alianza norte 202, Parque de Investigación e Innovación Tecnológica, C.P. 66600 Apodaca Nuevo León, México (Mexico); and others

    2014-12-15

    Graphical abstract: - Highlights: • Decolorization of Orange G dye using highly c-axis-oriented ZnO thin films. • The flake-shaped film shows superior and stable photoactivity at a wide range of pH. • The highest photodecolorization was achieved at pH of 7. • The exposure of (101) and (100) facets enhanced the photoactivity. • ZnO thin films exhibit a promising performance as recyclable photocatalysts. - Abstract: The photocatalytic activity of ZnO thin films with different physicochemical characteristics deposited by RF magnetron sputtering on glass substrate was tested for the decolorization of orange G dye aqueous solution (OG). The crystalline phase, surface morphology, surface roughness and the optical properties of these ZnO films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and UV–visible spectroscopy (UV–Vis), respectively. The dye photodecolorization process was studied at acid, neutral and basic pH media under UV irradiation of 365 nm. Results showed that ZnO films grow with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a (002) preferential crystalline orientation. A clear relationship between surface morphology and photocatalytic activity was observed for ZnO films. Additionally, the recycling photocatalytic abilities of the films were also evaluated. A promising photocatalytic performance has been found with a very low variation of the decolorization degree after five consecutive cycles at a wide range of pH media.

  12. Design of a safe facility for the metalorganic chemical vapor deposition of high-purity GaAs and AlGaAs

    Science.gov (United States)

    Messham, R. L.; Tucker, W. K.

    1986-09-01

    A metalorganic chemical vapor deposition (MOCVD) facility designed to safely handle highly toxic and pyrophoric growth materials is described. The system concept is based on remote operation, passive flow restriction, and forced air dilution to maintain safe gas concentrations under normal running and catastrophic system failure conditions. MOCVD is a key materials technology for advanced high-frequency optical and microwave devices. At this time, the use of highly toxic arsine as an arsenic source is dictated by critical device purity, reproducibility, and doping control requirements. The handling and use of this gas is a primary feature in the design of any safe facility for MOCVD growth of high-quality GaAs/AlGaAs. After a critical review of presently available effluent treatment techniques, it was concluded that a combination of flow restriction and dilution presented the most reliable treatment. Measured flow rates through orifices from 0.002 to 0.005 inch in diameter were compared to calculated values. A 0.002 inch orifice located in the cylinder valve or CGA fitting, combined with a cylinder of pure liquid arsine (205 psi), limits the maximum gas flow to ≪1 lpm. Such a flow can then be vented through a dedicated exhaust system where an additional forced injection of diluting air reduces the gas concentration to acceptable levels. In the final Westinghouse R&D Center design, the use of low-pressure pure arsine, flow restriction, and stack air injection has reduced the maximum stack exist gas concentration to below 25% of the IDLH level for arsine under total and catastrophic MOCVD facility equipment failure conditions. The elimination of potential problems with purging behind such orifices using carefully designed purging procedures and a microprocessor-controlled purging system are described. The IDLH level is defined by the OSHA and NIOSH standards completion program and represents the maximum level from which one could escape within 30 min without any

  13. Model Research On Deposition Of Pure Aluminium Oxide Layers By MOCVD Method

    National Research Council Canada - National Science Library

    A. Sawka; A. Kwatera

    2015-01-01

    ... (composite layers Al -C/Al ). The use of quartz glass substrate allows for obtaining information about the quality of the layers such the thickness and density, because of its high transparency...

  14. High-performance InGaN/GaN MQW LEDs with Al-doped ZnO transparent conductive layers grown by MOCVD using H2O as an oxidizer

    Science.gov (United States)

    Lin, Jia-Yong; Pei, Yan-Li; Zhuo, Yi; Chen, Zi-Min; Hu, Rui-Qin; Cai, Guang-Shuo; Wang, Gang

    2016-11-01

    In this study, the high performance of InGaN/GaN multiple quantum well light-emitting diodes (LEDs) with Al-doped ZnO (AZO) transparent conductive layers (TCLs) has been demonstrated. The AZO-TCLs were fabricated on the n+-InGaN contact layer by metal organic chemical vapor deposition (MOCVD) using H2O as an oxidizer at temperatures as low as 400 °C without any post-deposition annealing. It shows a high transparency (98%), low resistivity (510-4 Ω·cm), and an epitaxial-like excellent interface on p-GaN with an n+-InGaN contact layer. A forward voltage of 2.82 V @ 20 mA was obtained. Most importantly, the power efficiencies can be markedly improved by 53.8%@20 mA current injection and 39.6%@350 mA current injection compared with conventional LEDs with indium tin oxide TCL (LED-III), and by 28.8%@20 mA current injection and 4.92%@350 mA current injection compared with LEDs with AZO-TCL prepared by MOCVD using O2 as an oxidizer (LED-II), respectively. The results indicate that the AZO-TCL grown by MOCVD using H2O as an oxidizer is a promising TCL for a low-cost and high-efficiency GaN-based LED application. Project supported by the National Natural Science Foundation of China (Grant Nos. 61204091, 61404177, 51402366, and U1201254) and the Science and Technology Planning Project of Guangdong Province, China (Grant No. 2015B010132006).

  15. Chemical Vapor Deposition of Turbine Thermal Barrier Coatings

    Science.gov (United States)

    Haven, Victor E.

    1999-01-01

    Ceramic thermal barrier coatings extend the operating temperature range of actively cooled gas turbine components, therefore increasing thermal efficiency. Performance and lifetime of existing ceram ic coatings are limited by spallation during heating and cooling cycles. Spallation of the ceramic is a function of its microstructure, which is determined by the deposition method. This research is investigating metalorganic chemical vapor deposition (MOCVD) of yttria stabilized zirconia to improve performance and reduce costs relative to electron beam physical vapor deposition. Coatings are deposited in an induction-heated, low-pressure reactor at 10 microns per hour. The coating's composition, structure, and response to the turbine environment will be characterized.

  16. Copper phthalocyanine films deposited by liquid-liquid interface recrystallization technique (LLIRCT).

    Science.gov (United States)

    Patil, K R; Sathaye, S D; Hawaldar, R; Sathe, B R; Mandale, A B; Mitra, A

    2007-11-15

    The simple recrystallization process is innovatively used to obtain the nanoparticles of copper phthalocyanine by a simple method. Liquid-liquid interface recrystallization technique (LLIRCT) has been employed successfully to produce small sized copper phthalocyanine nanoparticles with diameter between 3-5 nm. The TEM-SAED studies revealed the formation of 3-5 nm sized with beta-phase dominated mixture of alpha and beta copper phthalocyanine nanoparticles. The XRD, SEM, and the UV-vis studies were further carried out to confirm the formation of copper phthalocyanine thin films. The cyclic voltametry (CV) studies conclude that redox reaction is totally reversible one electron transfer process. The process is attributed to Cu(II)/Cu(I) redox reaction.

  17. Micro-Structures of Hard Coatings Deposited on Titanium Alloys by Laser Alloying Technique

    Science.gov (United States)

    Li, Wei; Yu, Huijun; Chen, Chuanzhong; Wang, Diangang; Weng, Fei

    2013-01-01

    This work is based on micro-structural performance of the Ti-B4C-C laser alloying coatings on Ti-6Al-4V titanium alloy. The test results indicated that laser alloying of the Ti-B4C-C pre-placed powders on the Ti-6Al-4V alloy substrate can form the ceramics reinforced hard alloying coatings, which increased the micro-hardness and wear resistance of substrate. The test result also indicated that the TiB phase was produced in alloying coating, which corresponded to its (101) crystal plane. In addition, yttria has a refining effect on micro-structures of the laser alloying coating, and its refinement mechanism was analyzed. This research provided essential experimental and theoretical basis to promote the applications of the laser alloying technique in manufacturing and repairing of the aerospace parts.

  18. 3D printing of high-resolution PLA-based structures by hybrid electrohydrodynamic and fused deposition modeling techniques

    Science.gov (United States)

    Zhang, Bin; Seong, Baekhoon; Nguyen, VuDat; Byun, Doyoung

    2016-02-01

    Recently, the three-dimensional (3D) printing technique has received much attention for shape forming and manufacturing. The fused deposition modeling (FDM) printer is one of the various 3D printers available and has become widely used due to its simplicity, low-cost, and easy operation. However, the FDM technique has a limitation whereby its patterning resolution is too low at around 200 μm. In this paper, we first present a hybrid mechanism of electrohydrodynamic jet printing with the FDM technique, which we name E-FDM. We then develop a novel high-resolution 3D printer based on the E-FDM process. To determine the optimal condition for structuring, we also investigated the effect of several printing parameters, such as temperature, applied voltage, working height, printing speed, flow-rate, and acceleration on the patterning results. This method was capable of fabricating both high resolution 2D and 3D structures with the use of polylactic acid (PLA). PLA has been used to fabricate scaffold structures for tissue engineering, which has different hierarchical structure sizes. The fabrication speed was up to 40 mm/s and the pattern resolution could be improved to 10 μm.

  19. Modification of the morphology and optical properties of SnS films using glancing angle deposition technique

    Science.gov (United States)

    Sazideh, M. R.; Dizaji, H. Rezagholipour; Ehsani, M. H.; Moghadam, R. Zarei

    2017-05-01

    Tin sulfide (SnS) films were prepared by thermal evaporation method using Glancing Angle Deposition (GLAD) technique at zero and different oblique incident flux angles (α = 45°, 55°, 65°, 75° and 85°). The physical properties of prepared films were systematically investigated. The X-ray diffraction analysis indicated that the film deposited at α = 0° formed as single phase with an orthorhombic structure. However, the layers became amorphous at α = 45°, 55°, 65°, 75° and 85°. Beside the appearance of amorphous feature in the film prepared at α higher than zero, Sn2S3 phase was also observed. The top and cross-sectional field emission scanning electron microscope (FESEM) images of the samples showed noticeable changes in the structure and morphology of individual nano-plates as a function of incident angle. The band gap and refractive index values of the films were calculated by optical transmission measurements. The optical band-gap values were observed to increase with increasing the incident flux angle. This can be due to presence of Sn2S3 phase observed in the samples produced at α values other than zero. The effective refractive index and porosity exhibit an opposite evolution as the incident angle α rises. At α = 85° the layers show a considerable change in effective refractive index (Δn = 1.7) at near-IR spectral range.

  20. Microstructural, nanomechanical, and microtribological properties of Pb thin films prepared by pulsed laser deposition and thermal evaporation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Broitman, Esteban, E-mail: esbro@ifm.liu.se [Thin Film Physics Division, IFM, Linköping University, SE-581 83 Linköping (Sweden); Flores-Ruiz, Francisco J. [Thin Film Physics Division, IFM, Linköping University, SE-581 83 Linköping, Sweden and Centro de Investigación y de Estudios Avanzados del I.P.N., Unidad Querétaro, Querétaro 76230 (Mexico); Di Giulio, Massimo [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce (Italy); Gontad, Francisco; Lorusso, Antonella; Perrone, Alessio [Università del Salento, Dipartimento di Matematica e Fisica “E. De Giorgi”, 73100 Lecce, Italy and INFN-Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy)

    2016-03-15

    In this work, the authors compare the morphological, structural, nanomechanical, and microtribological properties of Pb films deposited by thermal evaporation (TE) and pulsed laser deposition (PLD) techniques onto Si (111) substrates. Films were investigated by scanning electron microscopy, surface probe microscopy, and x-ray diffraction in θ-2θ geometry to determine their morphology, root-mean-square (RMS) roughness, and microstructure, respectively. TE films showed a percolated morphology with densely packed fibrous grains while PLD films had a granular morphology with a columnar and tightly packed structure in accordance with the zone growth model of Thornton. Moreover, PLD films presented a more polycrystalline structure with respect to TE films, with RMS roughness of 14 and 10 nm, respectively. Hardness and elastic modulus vary from 2.1 to 0.8 GPa and from 14 to 10 GPa for PLD and TE films, respectively. A reciprocal friction test has shown that PLD films have lower friction coefficient and wear rate than TE films. Our study has demonstrated for first time that, at the microscale, Pb films do not show the same simple lubricious properties measured at the macroscale.

  1. Structure and sliding wear behavior of 321 stainless steel/Al composite coating deposited by high velocity arc spraying technique

    Institute of Scientific and Technical Information of China (English)

    CHEN Yong-xiong; XU Bin-shi; LIU Yan; LIANG Xiu-bing; XU Yi

    2008-01-01

    A typical 321 stainless steel/aluminum composite coating (321/Al coating) was prepared by high velocity arc spraying technique (HVAS) with 321 stainless steel wire as the anode and aluminum wire as the cathode.The traditional 321 stainless steel coating was also prepared for comparison.Tribological properties of the coatings were evaluated with the ring-block wear tester under different conditions.The structure and worn surface of the coatings were analyzed by scanning electron microscopy (SEM),X-ray diffractometry (XRD) and energy dispersion spectroscopy (EDS).The results show that,except for aluminum phase addition in tne 321/Al coating,no other phases are created compared with the 321 coating.However,due to the addition of aluminum,the 321/Al coating forms a type of "ductile/hard phases inter-deposited" structure and performs quite different tribological behavior.Under the dry sliding condition,the anti-wear property of 321/Al coating is about 42% lower than that of 321 coating.Butunder the oil lubricated conditions with or without 32h oil-dipping pretreatment,the anti-wear property of 321/Al coating is about 9% and 5% higher than that of 321 coating,respectively.The anti-wear mechanism of the composite coating is mainly relevant to the decrease of oxide impurities and the strengthening action resulted from the "ductile/hard phases inter-deposited" coating structure.

  2. The Characteristics of an Antibacterial TiAgN Thin Film Coated by Physical Vapor Deposition Technique.

    Science.gov (United States)

    Kang, Byeong-Mo; Jeong, Woon-Jo; Park, Gye-Choon; Yoon, Dong-Joo; Ahn, Ho-Geun; Lim, Yeong-Seog

    2015-08-01

    In this work, we found the characteristics of an antibacterial TiAgN thin film coated on the pure titanium specimen via the physical vapor deposition process (PVD). TiAgN thin films were coated using TiAg alloy targets by arc ion plating method. Changing the process parameters, the surface analysis of TiAgN thin film was observed by FE-SEM and the force of adhesion was measured with Scratch Tester. The proliferation of human gingival fibroblast (HGF) cells was examined by XTT test assay and the antibacterial properties were investigated by culturing Streptococus Mutans (KCTC 3065) using paper disk techniques. At the result of experiment, cytotoxic effects were not found and the antibacterial effects against Streptococus Mutans were appeared over 5 wt% TiAgN specimens.

  3. Preparation of Bioactive Calcium Phosphate Coating on Porous C/C Substrate by a Novel Deposition Technique

    Institute of Scientific and Technical Information of China (English)

    XIONG Xinbo; ZENG Xierong; LI Xiaohua; Xie Shenghui; ZOU Chunli

    2008-01-01

    A novel heat substrate technique,high frequency inductive heat deposition(IHD),was introduced to coat porous carbon materials,C/C and carbon felt to improve their bioactivity.The morphologies,composition and microstructure of the resulting coatings were examined by scanning electron microscopy(SEM),energy dispersive spectra(EDS),X-ray diffractometer(XRD)and Fourier transform infrared spectroscopy (FTIR).The results show that,the calcium phosphate consisted of non-stoichiometric,CO3-containing and plate-like octacalcium phosphate(Ca8-xH2(PO4)6,OCP)could uniformly cover the entire porous surfaces of carbon materials.Good adhesion of the coating to carbon material substrates was observed.

  4. Photoluminescence and diode characteristic of ZnO thin films/junctions fabricated by pulsed laser deposition (PLD) technique

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Kazuhiro; Komiyama, Takao; Chonan, Yasunori; Yamaguchi, Hiroyuki; Aoyama, Takashi [Department of Electronics and Information Systems, Akita Prefectural University, 84-4 Ebinokuchi, Tsuchiya, Yuri-honjo, Akita 015-0055 (Japan)

    2010-02-15

    ZnO:Ga and ZnO:P films were grown by a pulsed laser deposition (PLD) technique changing the dopant concentrations, and their photoluminescence (PL) spectra were obtained. Then, ZnO:P/ZnO:Ga junctions were fabricated and their junction characteristics were evaluated. As the Ga concentration increased in the films, the PL intensity was decreased while as the P concentration increased, the PL intensity was increased. The maximum PL intensities were obtained for the films of 0.5%(Ga) and 7.0% (P), respectively. Rectifying junction characteristics were observed only for the combination of 0.5-1.0% (Ga) and 5.0% (P) films. Mutual dopant diffusion is supposed to explain the relation between the PL and the junction characteristics. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Top gate ZnO-Al2O3 thin film transistors fabricated using a chemical bath deposition technique

    Science.gov (United States)

    Gogoi, Paragjyoti; Saikia, Rajib; Changmai, Sanjib

    2015-04-01

    ZnO thin films were prepared by a simple chemical bath deposition technique using an inorganic solution mixture of ZnCl2 and NH3 on glass substrates and then were used as the active material in thin film transistors (TFTs). The TFTs were fabricated in a top gate coplanar electrode structure with high-k Al2O3 as the gate insulator and Al as the source, drain and gate electrodes. The TFTs were annealed in air at 500 °C for 1 h. The TFTs with a 50 μm channel length exhibited a high field-effect mobility of 0.45 cm2/(V·s) and a low threshold voltage of 1.8 V. The sub-threshold swing and drain current ON-OFF ratio were found to be 0.6 V/dec and 106, respectively.

  6. Monomeric malonate precursors for the MOCVD of HfO2 and ZrO2 thin films.

    Science.gov (United States)

    Pothiraja, Ramasamy; Milanov, Andrian; Parala, Harish; Winter, Manuela; Fischer, Roland A; Devi, Anjana

    2009-01-28

    New Hf and Zr malonate complexes have been synthesized by the reaction of metal amides with different malonate ligands (L = dimethyl malonate (Hdmml), diethyl malonate (Hdeml), di-tert-butyl malonate (Hdbml) and bis(trimethylsilyl) malonate (Hbsml)). Homoleptic eight-coordinated monomeric compounds of the type ML4 were obtained for Hf with all the malonate ligands employed. In contrast, for Zr only Hdmml and Hdeml yielded the eight-coordinated monomeric compounds of the type ML4, while using the bulky Hdbml and Hbsml ligands resulted into mixed alkoxo-malonato six-coordinated compounds of the type [ML2(OR)2]. Single crystal X-ray diffraction studies of all the compounds are presented and discussed, and they are found to be monomeric. The complexes are solids and in solution, they retain their monomeric nature as evidenced by NMR measurements. Compared to the classical beta-diketonate complexes, [M(acac)4] and [M(thd)4] (M = Hf, Zr; acac: acetylacetonate; thd: tetramethylheptadione), the new malonate compounds are more volatile, decompose at lower temperatures and have lower melting points. In particular, the homoleptic diethyl malonate complexes of Hf and Zr melt at temperatures as low as 62 degrees C. In addition, the compounds are very stable in air and can be sublimed quantitatively. The promising thermal properties makes these compounds interesting for metal-organic chemical vapor deposition (MOCVD). This was demonstrated by depositing HfO2 and ZrO2 thin films successfully with two representative Hf and Zr complexes.

  7. Annealing effects on the structural and optical properties of vanadium oxide film obtained by the hot-filament metal oxide deposition technique (HFMOD)

    Energy Technology Data Exchange (ETDEWEB)

    Scarminio, Jair; Silva, Paulo Rogerio Catarini da, E-mail: scarmini@uel.br, E-mail: prcsilva@uel.br [Universidade Estadual de Londrina (UEL), PR (Brazil). Departamento de Fisica; Gelamo, Rogerio Valentim, E-mail: rogelamo@gmail.com [Universidade Federal do Triangulo Mineiro (UFTM), Uberaba, MG (Brazil); Moraes, Mario Antonio Bica de, E-mail: bmoraes@mailhost.ifi.unicamp.br [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)

    2017-01-15

    Vanadium oxide films amorphous, nonstoichiometric and highly absorbing in the optical region were deposited on ITO-coated glass and on silicon substrates, by the hot-filament metal oxide deposition technique (HFMOD) and oxidized by ex-situ annealing in a furnace at 200, 300, 400 and 500 deg C, under an atmosphere of argon and rarefied oxygen. X-ray diffraction, Raman and Rutherford backscattering spectroscopy as well as optical transmission were employed to characterize the amorphous and annealed films. When annealed at 200 and 300 deg C the as-deposited opaque films become transparent but still amorphous. Under treatments at 400 and 500 deg C a crystalline nonstoichiometric V{sub 2}O{sub 5} structure is formed. All the annealed films became semiconducting, with their optical absorption coefficients changing with the annealing temperature. An optical gap of 2.25 eV was measured for the films annealed at 400 and 500 deg C. The annealing in rarefied oxygen atmosphere proved to be a useful and simple ex-situ method to modulate the structural and optical properties of vanadium oxide films deposited by HFMOD technique. This technique could be applied to other amorphous and non-absorbing oxide films, replacing the conventional and sometimes expensive method of modulate desirable film properties by controlling the film deposition parameters. Even more, the HFMOD technique can be an inexpensive alternative to deposit metal oxide films. (author)

  8. Progress in MOCVD growth of HgCdTe epilayers for HOT infrared detectors

    Science.gov (United States)

    Kebłowski, A.; Gawron, W.; Martyniuk, P.; Stepień, D.; Kolwas, K.; Piotrowski, J.; Madejczyk, P.; Kopytko, M.; Piotrowski, A.; Rogalski, A.

    2016-05-01

    In this paper we present progress in MOCVD growth of (100) HgCdTe epilayers achieved recently at the Institute of Applied Physics, Military University of Technology and Vigo System S.A. It is shown that MOCVD technology is an excellent tool in fabrication of different HgCdTe detector structures with a wide range of composition, donor/acceptor doping and without post grown annealing. Particular progress has been achieved in the growth of (100) HgCdTe epilayers for long wavelength infrared photoconductors operated in HOT conditions. The (100) HgCdTe photoconductor optimized for 13-μm attain detectivity equal to 6.5x109 Jones and therefore outperform its (111) counterpart. The paper also presents technological progress in fabrication of MOCVD-grown (111) HgCdTe barrier detectors. The barrier device performance is comparable with state-of-the-art of HgCdTe photodiodes. The detectivity of HgCdTe detectors is close to the value marked HgCdTe photodiodes. Dark current densities are close to the values given by "Rule 07".

  9. Raman Spectroscopy of Solid Oxide Fuel Cells: Technique Overview and Application to Carbon Deposition Analysis

    KAUST Repository

    Maher, R. C.

    2013-07-30

    Raman spectroscopy is a powerful characterization tool for improving the understanding of solid oxide fuel cells (SOFCs), capable of providing direct, molecularly specific information regarding the physical and chemical processes occurring within functional SOFCs in real time. In this paper we give a summary of the technique itself and highlight ex situ and in situ studies that are particularly relevant for SOFCs. This is followed by a case study of carbon formation on SOFC Ni-based anodes exposed to carbon monoxide (CO) using both ex situ and in situ Raman spectroscopy combined with computational simulations. In situ measurements clearly show that carbon formation is significantly reduced for polarized SOFCs compared to those held at open circuit potential (OCP). Ex situ Raman mapping of the surfaces showed clear variations in the rate of carbon formation across the surface of polarized anodes. Computational simulations describing the geometry of the cell showed that this is due to variations in gas access. These results demonstrate the ability of Raman spectroscopy in combination with traditional characterization tools, to provide detailed understanding of critical processes occurring within functional SOFCs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. MOCVD of zirconium oxide thin films: Synthesis and characterization

    Science.gov (United States)

    Torres-Huerta, A. M.; Domínguez-Crespo, M. A.; Ramírez-Meneses, E.; Vargas-García, J. R.

    2009-02-01

    The synthesis of thin films of zirconia often produces tetragonal or cubic phases, which are stable at high temperatures, but that can be transformed into the monoclinic form by cooling. In the present study, we report the deposition of thin zirconium dioxide films by metalorganic chemical vapor deposition using zirconium (IV)-acetylacetonate as precursor. Colorless, porous, homogeneous and well adherent ZrO 2 thin films in the cubic phase were obtained within the temperature range going from 873 to 973 K. The deposits presented a preferential orientation towards the (1 1 1) and (2 2 0) planes as the substrate temperature was increased, and a crystal size ranging between 20 and 25 nm. The kinetics is believed to result from film growth involving the deposition and aggregation of nanosized primary particles produced during the CVD process. A mismatch between the experimental results obtained here and the thermodynamic prediction was found, which can be associated with the intrinsic nature of the nanostructured materials, which present a high density of interfaces.

  11. MOCVD of zirconium oxide thin films: Synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Torres-Huerta, A.M., E-mail: atohuer@hotmail.com [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira, Instituto Politecnico Nacional, Km. 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Dominguez-Crespo, M.A.; Ramirez-Meneses, E. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Unidad Altamira, Instituto Politecnico Nacional, Km. 14.5 Carr. Tampico-Puerto Industrial, C.P. 89600, Altamira, Tamaulipas (Mexico); Vargas-Garcia, J.R. [ESIQIE, Departamento de Metalurgia y Materiales, Instituto Politecnico Nacional. A.P. 75-876, 07300 Mexico, D.F. (Mexico)

    2009-02-15

    The synthesis of thin films of zirconia often produces tetragonal or cubic phases, which are stable at high temperatures, but that can be transformed into the monoclinic form by cooling. In the present study, we report the deposition of thin zirconium dioxide films by metalorganic chemical vapor deposition using zirconium (IV)-acetylacetonate as precursor. Colorless, porous, homogeneous and well adherent ZrO{sub 2} thin films in the cubic phase were obtained within the temperature range going from 873 to 973 K. The deposits presented a preferential orientation towards the (1 1 1) and (2 2 0) planes as the substrate temperature was increased, and a crystal size ranging between 20 and 25 nm. The kinetics is believed to result from film growth involving the deposition and aggregation of nanosized primary particles produced during the CVD process. A mismatch between the experimental results obtained here and the thermodynamic prediction was found, which can be associated with the intrinsic nature of the nanostructured materials, which present a high density of interfaces.

  12. pplication of Fractal Technique for Analysis of Geophysical - Geochemical Databases in Tekieh Pb-Zn Ore Deposit (SE of Arak

    Directory of Open Access Journals (Sweden)

    Seyed Reza Mehrnia

    2017-02-01

    Full Text Available Introduction Tekieh Lead-Zinc ore deposit that is located in the Sanandaj-Sirjan structural zone has been recognized as one of the most important mineralized regions in Malayer-Isfahan metallogenic sub-state, south east of Arak (Momenzadeh and Ziseman, 1981. Carbonate host units have been developed along (or across the Vishan-Tekieh anticline as the main structure extended in NW-SE trends (Annells et al, 1985. According to geochemical investigations (Salehi, 2004, the element content of the mineralized regions has originated from Alpine post-volcanisms and subsequently it has migrated toward early Cretaceous formations (dolomitic limestones among several hypogenic stages (Torkashvand et a.2009. Also echelon type structures consisting of folded systems and inversed faulting of structures are the most common features in western and eastern parts of ore deposit regions (Annells et al, 1985. Syngenetic enrichments beside limited (rarely developed epigenetic mineralization have been known as two main phases which are closely relevant to ore forming processes in the massive lenses and vein type occurrences, respectively (Momenzadeh and Ziseman, 1981. Material and Methods In this research, two statistical techniques that consist of classical and fractal equations (Mandelbrot, 2005 were applied in geochemical (Torkashvand et al., 2009 and geophysical (Jafari, 2007 databases for obtaining the linear and nonlinear distributions of geochemical elements (Tekieh Pb-Zn content in association with resistivity variations and induction polarization measurements (Calagari, 2010. According to linear statistical techniques (Torkashvand et al., 2009, the main central parameters such as mean, median and mode in addition to variances and standard deviations as distribution tendencies could be used for obtaining the regression coefficients of the databases. However, in fractal statistics, a reliable regression between geoelectrical - geochemical anomalies should be

  13. Molecular beam epitaxy and metalorganic chemical vapor deposition growth of epitaxial CdTe on (100) GaAs/Si and (111) GaAs/Si substrates

    Science.gov (United States)

    Nouhi, A.; Radhakrishnan, G.; Katz, J.; Koliwad, K.

    1988-01-01

    Epitaxial CdTe has been grown on both (100)GaAs/Si and (111)GaAs/Si substrates. A combination of molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) has been employed for the first time to achieve this growth: the GaAs layers are grown on Si substrates by MBE and the CdTe film is subsequently deposited on GaAs/Si by MOCVD. The grown layers have been characterized by X-ray diffraction, scanning electron microscopy, and photoluminescence.

  14. Characterization of an array of Love-wave gas sensors developed using electrospinning technique to deposit nanofibers as sensitive layers.

    Science.gov (United States)

    Matatagui, D; Fernández, M J; Fontecha, J; Sayago, I; Gràcia, I; Cané, C; Horrillo, M C; Santos, J P

    2014-03-01

    The electrospinning technique has allowed that very different materials are deposited as sensitive layers on Love-wave devices forming a low cost and successful sensor array. Their excellent sensitivity, good linearity and short response time are reported in this paper. Several materials have been used to produce the nanofibers: polymers as Polyvinyl alcohol (PVA), Polyvinylpyrrolidone (PVP) and Polystirene (PS); composites with polymers as PVA+SnCl4; combined polymers as PS+Poly(styrene-alt-maleic anhydride) (PS+PSMA) and metal oxides (SnO2). In order to test the array, well-known chemical warfare agent simulants (CWAs) have been chosen among the volatile organic compounds due to their importance in the security field. Very low concentrations of these compounds have been detected by the array, such as 0.2 ppm of DMMP, a simulant of sarin nerve gas, and 1 ppm of DPGME, a simulant of nitrogen mustard. Additionally, the CWA simulants used in the experiment have been discriminated and classified using pattern recognition techniques, such as principal component analysis and artificial neural networks.

  15. Enhanced optical properties of InAs/InAlGaAs/InP quantum dots grown by metal-organic chemical vapor deposition using a double-cap technique

    Science.gov (United States)

    Shi, Bei; Lau, Kei May

    2016-01-01

    The effects of a double-cap procedure on the optical properties of an InAs/InAlGaAs quantum dots (QDs) system grown by metal-organic chemical vapor deposition (MOCVD) have been investigated by atomic force microscopy (AFM) and room temperature photoluminescence (RT-PL) spectroscopy. An optimized QD growth condition has been achieved, with an areal density of 4.6×1010 cm-2. It was found that the thickness and lattice constant of the high temperature second cap layer (SCL) were crucial for improving the integrated PL intensity and line-width of the 1.55 μm emission from the InAs/InAlGaAs QD system grown on a semi-insulating InP (100) substrate. With fine-tuned SCL thickness and lattice constant, the optical performance of the five-stack QDs was enhanced. The improvements can be attributed to the smooth growth front, observed from the AFM images, and the well-balanced stress engineering.

  16. TiOxNy coatings grown by atmospheric pressure metal organic chemical vapor deposition

    OpenAIRE

    Maury, Francis; Duminica, Florin-Daniel

    2010-01-01

    International audience; Titanium oxynitride coatings were deposited on various substrates by an original atmospheric pressure metal organic chemical vapor deposition (MOCVD) process using titanium tetra-iso-propoxide as titanium and oxygen precursors and hydrazine as a nitrogen source. The films composition was monitored by controlling the N2H4 mole fraction in the initial reactive gas phase. The variation of the N content in the films results in significant changes in morphological, structur...

  17. Pyrolytic deposition of nanostructured titanium carbide coatings on the surface of multiwalled carbon nanotubes

    Science.gov (United States)

    Kremlev, K. V.; Ob"edkov, A. M.; Ketkov, S. Yu.; Kaverin, B. S.; Semenov, N. M.; Gusev, S. A.; Tatarskii, D. A.; Yunin, P. A.

    2016-05-01

    Nanostructured titanium carbide coatings have been deposited on the surface of multiwalled carbon nanotubes (MWCNTs) by the MOCVD method with bis(cyclopentadienyl)titanium dichloride precursor. The obtained TiC/MWCNT hybrid materials were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is established that a TiC coating deposits onto the MWCNT surface with the formation of a core-shell (MWSNT-TiC) type structure.

  18. A Comparative Study of Three Different Chemical Vapor Deposition Techniques of Carbon Nanotube Growth on Diamond Films

    Directory of Open Access Journals (Sweden)

    Betty T. Quinton

    2013-01-01

    Full Text Available This paper compares between the methods of growing carbon nanotubes (CNTs on diamond substrates and evaluates the quality of the CNTs and the interfacial strength. One potential application for these materials is a heat sink/spreader for high-power electronic devices. The CNTs and diamond substrates have a significantly higher specific thermal conductivity than traditional heat sink/spreader materials making them good replacement candidates. Only limited research has been performed on these CNT/diamond structures and their suitability of different growth methods. This study investigates three potential chemical vapor deposition (CVD techniques for growing CNTs on diamond: thermal CVD (T-CVD, microwave plasma-enhanced CVD (MPE-CVD, and floating catalyst thermal CVD (FCT-CVD. Scanning electron microscopy (SEM and high-resolution transmission electron microscopy (TEM were used to analyze the morphology and topology of the CNTs. Raman spectroscopy was used to assess the quality of the CNTs by determining the ID/IG peak intensity ratios. Additionally, the CNT/diamond samples were sonicated for qualitative comparisons of the durability of the CNT forests. T-CVD provided the largest diameter tubes, with catalysts residing mainly at the CNT/diamond interface. The MPE-CVD process yielded non uniform defective CNTs, and FCT-CVD resulted in the smallest diameter CNTs with catalyst particles imbedded throughout the length of the nanotubes.

  19. Structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique.

    Science.gov (United States)

    Ghrairi, Najla; Bouaicha, Mongi

    2012-07-01

    In this work, we report the structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique. The TiO2 film was formed on a doped fluorine tin oxide (SnO2:F, i.e., FTO) layer and used as a photo electrode in a dye solar cell (DSC). Using spectroscopic ellipsometry measurements in the 200 to 800 nm wavelengths domain, we obtain a thickness of the TiO2 film in the range of 70 to 80 nm. Characterizations by X-ray diffraction and atomic force microscopy (AFM) show a polycrystalline film. In addition, AFM investigation shows no cracks in the formed layer. Using an ultraviolet-visible near-infrared spectrophotometer, we found that the transmittance of the TiO2 film in the visible domain reaches 75%. From the measured current-voltage or I-V characteristic under AM1.5 illumination of the formed DSC, we obtain an open circuit voltage Voc = 628 mV and a short circuit current Isc = 22.6 μA, where the surface of the formed cell is 3.14 cm2.

  20. [XPS characterization of TiN layer on bearing steel surface treated by plasma immersion ion implantation and deposition technique].

    Science.gov (United States)

    Liu, Hong-xi; Jiang, Ye-hua; Zhan, Zhao-lin; Tang, Bao-yin

    2009-09-01

    Titanium nitride (TIN) hard protective films were fabricated on AISI52100 bearing steel surface employing plasma immersion ion implantation and deposition (PIIID) technique. The TiN films were characterized using a variety of test methods. Atomic force microscope (AFM) revealed that the titanium nitride film has extremely smooth surface, very high uniformity and efficiency of space filling over large areas. X-ray diffraction (XRD) result indicated that (200) crystal face of titanium nitride phase is the preferred orientation and three kinds of titanium components exist in the surface modified layer. Tailor fitting analysis of X-ray photoelectron spectroscopy (XPS) combined with Ar ion etching proved that Ti2p(1/2) and Ti2p(3/2) have two peaks in the titanium nitride film layer, respectively. It is shown that different chemical state exists in titanium compound. N(1s) bond energy of XPS has also three fitting peaks at 396.51, 397. 22 and 399.01 eV, corresponding to the nitrogen atom in TiNxOy, TiN and N--N, respectively. Combined with the XPS Tailor fitting analysis results of O(1s) bond energy, it was shown that there is a large amount of titanium nitride phase in addition to a small amount of simple substance nitrogen and oxide of titanium in the surface layer. The whole film system is made up of TiN, TiO2, N--N and Ti--O--N compound.

  1. Growth of InAs Quantum Dots on Germanium Substrate Using Metal Organic Chemical Vapor Deposition Technique

    Directory of Open Access Journals (Sweden)

    Tyagi Renu

    2009-01-01

    Full Text Available Abstract Self-assembled InAs quantum dots (QDs were grown on germanium substrates by metal organic chemical vapor deposition technique. Effects of growth temperature and InAs coverage on the size, density, and height of quantum dots were investigated. Growth temperature was varied from 400 to 450 °C and InAs coverage was varied between 1.40 and 2.35 monolayers (MLs. The surface morphology and structural characteristics of the quantum dots analyzed by atomic force microscope revealed that the density of the InAs quantum dots first increased and then decreased with the amount of InAs coverage; whereas density decreased with increase in growth temperature. It was observed that the size and height of InAs quantum dots increased with increase in both temperature and InAs coverage. The density of QDs was effectively controlled by growth temperature and InAs coverage on GaAs buffer layer.

  2. Deposition of LaMO3 (M=Ni,Co,Cr,Al)-Oriented Films by Spray Combustion Flame Technique

    Science.gov (United States)

    Ichinose, Hiromichi; Shiwa, Yuzo; Nagano, Masamitsu

    1994-10-01

    LaMO3 (M=Ni,Co,Cr,Al) films were prepared on sintered alumina, sapphire (001) and MgO(100) at 500 900°C by spraying ultrasonically atomized aqueous solutions of nitrates into a combustion flame (spray combustion flame technique). LaNiO3 and LaCoO3 on MgO(100) crystallized in high-temperature phases (cubic) while LaCrO3 and LaAlO3 crystallized in room-temperature phases. LaMO3 (M=Ni,Co,Cr,Al) films on MgO(100) were highly oriented to (100), (100), (001) and (100), respectively, while the films on sintered alumina and sapphire were not. The electric resistivities of the dense LaMO3 (M=Ni,Co,Cr) films were as low as those of bulk ceramics. LaNiO3 film deposited on MgO above 700°C showed the lowest resistivity of about 6×10-6 Ω m. It was suggested that the reactivities of the constituent metal atoms with OH in the flame are associated with the preferred phase and the morphology of the films.

  3. Preparation of SrIrO{sub 3} thin films by using metal-organic aerosol deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Esser, Sebastian; Schneider, Melanie; Moshnyaga, Vasily; Gegenwart, Philipp [1. Physikalisches Institut, Georg-August-Universitaet Goettingen (Germany)

    2013-07-01

    The interplay between spin-orbit coupling and electronic correlations could lead to interesting novel states in iridium oxide materials. We focus on the perovskite phase of SrIrO{sub 3} because Moon et al. [1] showed by using optical spectroscopy and first-principles calculations that the last member of the Ruddlesden-Popper series Sr{sub n+1}Ir{sub n}O{sub 3n+1} (n = ∞) is close to the Mott transition. By using metal-organic aerosol deposition technique we have grown SrIrO{sub 3} thin films on (111)-oriented SrTiO{sub 3} substrates. The cubic symmetry of the SrTiO{sub 3} substrate ensured that the SrIrO{sub 3} thin film grew in the monoclinic perovskite phase. The X-ray diffraction results suggest that SrIrO{sub 3} thin films in perovskite structure were obtained and these show out of plane epitaxy with monoclinic (002){sub m}-orientation. The temperature dependence of the electrical resistivity of these SrIrO{sub 3} thin films were investigated and metallic behavior was observed down to 50 K.

  4. Oriented growth of thin films of samarium oxide by MOCVD

    Indian Academy of Sciences (India)

    K Shalini; S A Shivashankar

    2005-02-01

    Thin films of Sm2O3 have been grown on Si(100) and fused quartz by low-pressure chemical vapour deposition using an adducted -diketonate precursor. The films on quartz are cubic, with no preferred orientation at lower growth temperatures (∼ 550°C), while they grow with a strong (111) orientation as the temperature is raised (to 625°C). On Si(100), highly oriented films of cubic Sm2O3 at 625°C, and a mixture of monoclinic and cubic polymorphs of Sm2O3 at higher temperatures, are formed. Films grown on either substrate are very smooth and fine-grained. Infrared spectroscopic study reveals that films grown above 600°C are free of carbon.

  5. Nanocauliflower like structure of CdS thin film for solar cell photovoltaic applications: Insitu tin doping by chemical bath deposition technique

    CSIR Research Space (South Africa)

    Wilson, KC

    2014-01-01

    Full Text Available We report on surface morphology changes of in situ tin (Sn) doped cadmium sulphide (CdS) thin film nanostructures prepared on a glass substrate using the chemical bath deposition (CBD) technique. Sn-doping in the presence of triethanolammine (TEOA...

  6. High quality GaN-based LED epitaxial layers grown in a homemade MOCVD system

    Institute of Scientific and Technical Information of China (English)

    Yin Haibo; Wang Xiaoliang; Ran Junxue; Hu Guoxin; Zhang Lu; Xiao Hongling; Li Jing; Li Jinmin

    2011-01-01

    A homemade 7 × 2 inch MOCVD system is presented.With this system,high quality GaN epitaxial layers,InGaN/GaN multi-quantum wells and blue LED structural epitaxial layers have been successfully grown.The non-uniformity of undoped GaN epitaxial layers is as low as 2.86%.Using the LED structural epitaxial layers,blue LED chips with area of 350 × 350μm2 were fabricated.Under 20 mA injection current,the optical output power of the blue LED is 8.62 mW.

  7. Electrical properties of ZnO thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Pagni, O. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Somhlahlo, N.N. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Weichsel, C. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Leitch, A.W.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)]. E-mail: andrew.leitch@nmmu.ac.za

    2006-04-01

    We report on the electrical characterization of ZnO films grown by MOCVD on glass and sapphire substrates. After correcting our temperature variable Hall measurements by applying the standard two-layer model, which takes into account an interfacial layer, scattering mechanisms in the ZnO films were studied as well as donor activation energies determined. ZnO films grown at different oxygen partial pressures indicated the importance of growth conditions on the defect structure by means of their conductivities and conductivity activation energies.

  8. Deposition of cobalt and nickel sulfide thin films from thio- and alkylthio-urea complexes as precursors via the aerosol assisted chemical vapour deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Mgabi, L.P.; Dladla, B.S. [Department of Chemistry, University of Zululand, Private bag X1001 KwaDlangezwa, 3880 (South Africa); Malik, M.A. [School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Garje, Shivram S. [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400098 (India); Akhtar, J. [Nanoscience and Materials Synthesis Lab, Department of Physics, COMSATS, Institute of Information Technology (CIIT), Chak shahzad, Islamabad (Pakistan); Revaprasadu, N., E-mail: RevaprasaduN@unizulu.ac.za [Department of Chemistry, University of Zululand, Private bag X1001 KwaDlangezwa, 3880 (South Africa)

    2014-08-01

    We report the synthesis of Co(II) and Ni(II) thiourea and alkylthiourea complexes by reacting the metal salts (CoCl{sub 2} and NiCl{sub 2}) with the thiourea, phenylthiourea and dicyclohexylthiourea ligands in a 1:2 ratio. The complexes, [CoCl{sub 2}(CS(NH{sub 2}){sub 2}){sub 2}] (I), [CoCl{sub 2}(CSNHC{sub 6}H{sub 5}NH{sub 2}){sub 2} (II) and [CoCI{sub 2}(SC(NHC{sub 6}H{sub 11}){sub 2}){sub 2}] (III), [NiCl{sub 2}(CS(NH{sub 2}){sub 2}){sub 2}] (IV), [NiCl{sub 2}(CSNHC{sub 6}H{sub 5}NH{sub 2}){sub 2}] (V) and [NiCl{sub 2}(SC(NHC{sub 6}H{sub 11}){sub 2}){sub 2}] (VI) were characterized by C, H, N analysis and Fourier transform infrared spectroscopy. Thermogravimetric analysis shows that all complexes undergo a two step decomposition process except for [NiCl{sub 2}(CSNHC{sub 6}H{sub 5}NH{sub 2}){sub 2}] (V) which decomposes in a single step. The complexes were used as single-source precursors for the deposition of cobalt sulfide and nickel sulfide thin films by aerosol assisted chemical vapor deposition at temperatures between 350 an 500 °C. The crystallinity of the films was determined by X-ray diffraction and their morphology was determined by scanning electron microscopy. The morphology of the cobalt sulfide thin films varies from randomly oriented platelets, to granulated spheres and cubes as the precursor and deposition conditions are changed. For nickel sulfide, the [NiCl{sub 2}(CS(NH{sub 2}){sub 2}){sub 2}] (IV) complex gave rods whereas the [NiCl{sub 2}(CSNHC{sub 6}H{sub 5}NH{sub 2}){sub 2}] (V) produced spherical particles. - Highlights: • We report the synthesis of Co(II) and Ni(II) thiourea and alkylthiourea complexes. • C, H, N analysis and Fourier transform infrared spectroscopy characterization • NiS and CoS thin films deposited by aerosol assisted chemical vapor deposition • X-ray diffraction characterization of the phase of the films • Film morphology determined by scanning electron microscopy.

  9. Physical aspects of the pulsed laser deposition technique: The stoichiometric transfer of material from target to film

    DEFF Research Database (Denmark)

    Schou, Jørgen

    2009-01-01

    The physical processes of pulsed laser deposition (PLD) change strongly from the initial light absorption in a target to the final deposition and growth of a film. One of the primary advantages of PLD is the stoichiometric transfer of material from target to a film on a substrate. Even for a stoi...

  10. Thermodynamic investigation of the MOCVD of copper films from bis(2,2,6,6-tetramethyl-3,5-heptadionato)copper(II)

    Indian Academy of Sciences (India)

    Sukanya Mukhopadhyay; K Shalini; Anjana Devi; S A Shivashankar

    2002-10-01

    Equilibrium concentrations of various condensed and gaseous phases have been thermodynamically calculated, using the free energy minimization criterion, for the metalorganic chemical vapour deposition (MOCVD) of copper films using bis(2,2,6,6-tetramethyl-3,5-heptadionato)copper(II) as the precursor material. From among the many chemical species that may possibly result from the CVD process, only those expected on the basis of mass spectrometric analysis and chemical reasoning to be present at equilibrium, under different CVD conditions, are used in the thermodynamic calculations. The study predicts the deposition of pure, carbon-free copper in the inert atmosphere of argon as well as in the reactive hydrogen atmosphere, over a wide range of substrate temperatures and total reactor pressures. Thin films of copper, grown on SiO2/Si(100) substrates from this metalorganic precursor by low pressure CVD have been characterized by XRD and AES. The experimentally determined composition of CVD-grown copper films is in reasonable agreement with that predicted by thermodynamic analysis.

  11. MOCVD growth of GaN on Si through novel substrate modification techniques

    Science.gov (United States)

    Gagnon, Jarod C.

    GaN is a semiconductor material with great potential for use in high power electronics and optoelectronics due to the high electron mobility, high breakdown voltage, high thermal stability, and large direct bandgap of GaN. Si is a desirable substrate material for GaN heteroepitaxy due to the low cost of production, large wafer sizes available, and current widespread use in the electronics industry. The growth of GaN/Si devices suffers from the lattice and CTE mismatches between GaN and Si and therefore multiple methods of strain reduction have been employed to counter these effects. In this work we presented two novel methods of substrate modification to promote the growth of device quality GaN on Si. Initial work focused on the implantation of AlN/Si(111) substrates with N+ ions below the AlN/Si(111) interface. A reduction in the initial compressive stress in GaN films as well as the degree of tensile stress generation during growth was observed on implanted samples. Optical microscopy of the GaN surfaces showed reduced channeling crack density on implanted substrates. Transmission electron microscopy (TEM) studies showed a disordered layer in the Si substrate at the implantation depth which consisted of a mixture of polycrystalline and amorphous Si. Evidence was provided to suggest that the disordered layer at the implantation depth was acting as a compliant layer which decoupled the GaN film from the bulk Si substrate and partially accommodated the tensile stress formed during growth and cooling. A reduction in threading dislocation (TD) density on ion implanted substrates was also observed. Additional studies showed that by increasing the lateral size of AlN islands, the tensile growth stress and TD density in GaN films on ion implanted substrates could be further reduced. XRD studies showed an expansion of the AlN lattice on implanted substrates with larger lateral island sizes. The final tensile growth stress of films on implanted substrates was further reduced by utilizing thinner buffer layers and increasing the implantation depth of N+ ions. Final studies were presented on a method of etching Si(001) substrates in order to fabricate trenches with Si{110} sidewalls. It was shown in these studies that GaN could be preferentially grown on Si{110} sidewalls such that GaN(0002)//Si{110}. The result was non-polar GaN "fins" which vertically overgrew Si(001) ridges. Further studies showed that high V/III, low temperature, and low pressure was required to promote the lateral growth of the GaN(0002) which was necessary to obtain a fully coalesced film.

  12. Performance of Erbium-doped TiO2 thin film grown by physical vapor deposition technique

    Science.gov (United States)

    Lahiri, Rini; Ghosh, Anupam; Dwivedi, Shyam Murli Manohar Dhar; Chakrabartty, Shubhro; Chinnamuthu, P.; Mondal, Aniruddha

    2017-09-01

    Undoped and Erbium-doped TiO2 thin films (Er:TiO2 TFs) were fabricated on the n-type Si substrate using physical vapour deposition technique. Field emission scanning electron microscope showed the morphological change in the structure of Er:TiO2 TF as compared to undoped sample. Energy dispersive X-ray spectroscopy (EDX) confirmed the Er doping in the TiO2 thin film (TF). The XRD and Raman spectrum showed the presence of anatase phase TiO2 and Er2O3 in the Er:TiO2 TF. The Raman scattering depicted additional number of vibrational modes for Er:TiO2 TF due to the presence of Er as compared to the undoped TiO2 TF. The UV-Vis absorption measurement showed that Er:TiO2 TF had approximately 1.2 times more absorption over the undoped TiO2 TF in the range of 300-400 nm. The main band transition, i.e., the transition between the oxygen (2p) state and the Ti (3d) state was obtained at 3.0 eV for undoped TiO2 and at 3.2 eV for Er:TiO2 TF, respectively. The photo responsivity measurement was done on both the detectors, where Er:TiO2 TF detector showed better detectivity ( D *), noise equivalent power and temporal response as compared to undoped detector under ultra-violet illumination.

  13. Widespread calcium deposits, as detected using the alizarin red S technique, in the nervous system of rats treated with dimethyl mercury.

    Science.gov (United States)

    Mori, F; Tanji, K; Wakabayashi, K

    2000-09-01

    It has been reported that the alizarin red S technique may be used to visualize both intracellular and extracellular calcium deposits. Using this method histologic observations of the nervous system were made in rats that were given dimethyl mercury at 5 mg/kg per day for 12 consecutive days, and killed on days 1, 4, 7, 10, 12, 24, 32, 49, 100 and 140 (day 0 was the day that the final dose was administered). Neuronal degeneration with calcium deposition was found in the nervous system from day 4 onward. In the cerebellum alizarin red S-positive granules became gradually larger with time after dimethyl mercury administration, and large calcospherites were observed from day 32 onward. In contrast, the visualization of calcium deposits in the cerebral cortex was restricted to days 10-12. Calcium deposits were found in the ascending axons of the dorsal root ganglion neurons (dorsal fascicles of the spinal cord), but not in their perikarya. These findings suggest that widespread calcium deposition could occur in the nervous system following dimethyl mercury exposure, and that in the rat the mechanism of calcium deposition differs depending upon the brain region.

  14. Effect of substrate bias in nitrogen incorporated amorphous carbon films with embedded nanoparticles deposited by filtered cathodic jet carbon arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Amorphous and Microcrystalline Silicon Solar Cell Group, Physics of Energy Harvesting Division, National Physical Laboratory (C.S.I.R.), Dr. K.S. Krishnan Road, New Delhi-110012 (India); Kumar, Sushil; Ishpal,; Srivastava, A.K.; Chouksey, Abhilasha; Tripathi, R.K.; Basu, A. [Amorphous and Microcrystalline Silicon Solar Cell Group, Physics of Energy Harvesting Division, National Physical Laboratory (C.S.I.R.), Dr. K.S. Krishnan Road, New Delhi-110012 (India)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer a-C: N films having nanoparticles were deposited by filtered cathodic jet carbon arc (FCJCA) technique. Black-Right-Pointing-Pointer The effect of negative substrate bias on the properties of a-C: N films embedded with nanoparticles have been studied. Black-Right-Pointing-Pointer The properties of a-C: N films deposited by FCJCA technique have been compared with ta-C: N films deposited by FCVA process. - Abstract: The properties of nitrogen incorporated amorphous carbon (a-C: N) films with embedded nanoparticles, deposited using a filtered cathodic jet carbon arc technique, are reported. X-ray diffraction, high resolution transmission electron microscope and Raman spectroscopy measurements reveal an amorphous structure, but on closer examination the presence of clusters of nanocarbon single crystals with d-spacing close to diamond cubic-phase have also been identified. The effect of substrate bias on the microstructure, conductivity, activation energy, optical band gap, optical constants, residual stress, hardness, elastic modulus, plastic index parameter, percentage elastic recovery and density of states of a-C: N films have been studied and the properties obtained are found to depend on the substrate bias.

  15. Microstructure, optical and electrical properties of Al-doped ZnO films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Su, Jianfeng, E-mail: sujianfengvy@gmail.com [Department of Mathematics and Physics, Luoyang Institute of Science and Technology, Luoyang 471023 (China); Tang, Chunjuan; Niu, Qiang; Zang, Chunhe; Zhang, Yongsheng [Department of Mathematics and Physics, Luoyang Institute of Science and Technology, Luoyang 471023 (China); Fu, Zhuxi [Department of Physics, University of Science and Technology of China, Hefei 230026 (China)

    2012-09-01

    Highlights: Black-Right-Pointing-Pointer Al-doped ZnO films were grown on quartz substrates by MOCVD. Black-Right-Pointing-Pointer The preferred orientation of ZnO films decreased with the increase of Al content. Black-Right-Pointing-Pointer Decomposition products of TMA bringing down the surface activity of ZnO grains. Black-Right-Pointing-Pointer UV emission peak initially red-shifted and then blue-shifted as increasing Al content. Black-Right-Pointing-Pointer Low electrical resistivity of Al-doped ZnO films was obtained. - Abstract: Al-doped ZnO films were grown on quartz substrates by MOCVD. A systematical and detailed study about the effect of Al content on structural, optical and electrical properties were discussed. XRD measurements revealed that the preferred orientation of ZnO films decreased with the increase of Al content. AFM images indicated that the TMA molecules or their decomposition products bringing down the surface activity of ZnO grains, and so grain growth is inhibited. By the band tail states and the quantum confinement effect, the UV emission peak initially red-shifted and then blue-shifted. All Al-doped samples demonstrated more than 80% of the optical transparency in the visible region. Low electrical resistivity of Al-doped ZnO films was obtained. However, due to defects and grain boundary scattering which caused by Al doping, the hall mobility is increased initially and then decreased.

  16. In situ structural study on underpotential deposition of Ag on Au(111) electrode using surface X-ray scattering technique

    OpenAIRE

    KONDO, Toshihiro; Morita, Jun; Okamura, Masayuki; Saito, Toshiya; Uosaki, Kohei

    2002-01-01

    In situ surface X-ray scattering (SXS) measurements were carried out to study the structure of a Ag layer on a Au(111) electrode formed by underpotential deposition (upd) in sulfuric acid solution. Specular rod profiles showed that a monolayer of Ag was formed at a potential between the second and third upd peaks, and a bilayer of Ag was formed at a potential between the third upd peak and bulk deposition. Non-specular rod profiles demonstrated that electrochemically deposited Ag atoms both i...

  17. Structural and kinetic studies of metal hydride hydrogen storage materials using thin film deposition and characterization techniques

    Science.gov (United States)

    Kelly, Stephen Thomas

    Hydrogen makes an attractive energy carrier for many reasons. It is an abundant chemical fuel that can be produced from a wide variety of sources and stored for very long periods of time. When used in a fuel cell, hydrogen emits only water at the point of use, making it very attractive for mobile applications such as in an automobile. Metal hydrides are promising candidates for on-board reversible hydrogen storage in mobile applications due to their very high volumetric storage capacities---in most cases exceeding even that of liquid hydrogen. The United States Department of Energy (DOE) has set fuel system targets for an automotive hydrogen storage system, but as of yet no single material meets all the requirements. In particular, slow reaction kinetics and/or inappropriate thermodynamics plague many metal hydride hydrogen storage materials. In order to engineer a practical material that meets the DOE targets, we need a detailed understanding of the kinetic and thermodynamic properties of these materials during the phase change. In this work I employed sputter deposited thin films as a platform to study materials with highly controlled chemistry, microstructure and catalyst placement using thin film characterization techniques such as in situ x-ray diffraction (XRD) and neutron reflectivity. I observed kinetic limitations in the destabilized Mg2Si system due to the slow diffusion of the host Mg and Si atoms while forming separate MgH2 and Si phases. Conversely, I observed that the presence of Al in the Mg/Al system inhibits hydrogen diffusion while the host Mg and Al atoms interdiffuse readily, allowing the material to fall into a kinetic and/or thermodynamic trap by forming intermetallic compounds such as Mg17Al 12. By using in situ XRD to analyze epitaxial Mg films grown on (001) oriented Al2O3 substrates I observed hydride growth consistent with a model of a planar hydride layer growing into an existing metal layer. Subsequent film cycling changes the hydrogen

  18. Source investigation of the tar balls deposited along the Gujarat coast, India, using chemical fingerprinting and transport modeling techniques

    Digital Repository Service at National Institute of Oceanography (India)

    Suneel, V.; Vethamony, P.; Naik, B.G.; VinodKumar, K.; Sreenu, L.; Samiksha, S.V.; Tai,Y.; Sudheesh, K.

    Deposition of tar balls (TBs) along the south Gujarat coast, situated on the west coast of India (WCI), commonly occurs during the southwest monsoon season. Several offshore oil fields off the Mumbai-Gujarat coast, and refineries along the coast...

  19. Characterization of 2004 Indian Ocean tsunami induced deposits along the Chennai coast using magnetic and geochemical techniques

    Digital Repository Service at National Institute of Oceanography (India)

    Veerasingam, S.; Venkatachalapathy, R.

    measurements, as a proxy tool to identify tsunami induced deposits in the core sediments from the Chennai coast, India Down core profiles of mass specific magnetic susceptibility (x variable), x variable ARM and SIRM are similar in all sediment cores...

  20. Electrodeposition of zinc-cobalt alloys. Tapping mode AFM technique applied to study the initial stages of deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, E.; Valles, E.; Gorostiza, P.; Servat, J.; Sanz, F. [Univ. de Barcelona (Spain). Dept. de Quimica Fisica

    1995-12-01

    The first stages of electrodeposition of zinc-cobalt alloys on highly oriented pyro-graphite are studied by tapping mode atomic force microscopy (AFM), scanning electron microscopy, and electrochemical analysis. Low Zn(II)/Co(II) ratio (1/9) solutions are selected for this study. Potentiostatic deposition begins through the formation of randomly distributed zinc-rich nuclei on the surface, showing exclusion areas around the larger nuclei and preferential nucleation at the kink sites. At long deposition times an incipient dendritic growth, related to the initiation of pure cobalt deposition is observed. A simple AFM tip deconvolution model is used to obtain the actual dimensions of both the tip itself and the deposited nuclei. The nuclei growth mechanism observes lateral diffusion and aggregation and the formation of emerging nuclei on top of yet consolidated nuclei.

  1. The preparation of high-J c Gd0.5Y0.5Ba2Cu3O7-δ thin films by the MOCVD process

    Science.gov (United States)

    Zhao, R. P.; Zhang, F.; Liu, Q.; Xia, Y. D.; Lu, Y. M.; Cai, C. B.; Tao, B. W.; Li, Y. R.

    2016-06-01

    A home-designed metal organic chemical vapor deposition (MOCVD) system has been employed to prepare high critical current density (J c) Gd0.5Y0.5Ba2Cu3O7-δ (GdYBCO) thin films on LaMnO3/epitaxial MgO/ion beam assisted deposition (IBAD)-MgO/solution deposition planarization (SDP)-Y2O3-buffered Hastelloy tapes; the thin films were directly heated by the Joule effect after applying an heating current (I h ) through the Hastelloy tapes. The effect of the mole ratio of the metal organic sources has been systematically investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses indicated that the GdYBCO films crystallized better and became denser with the increasing of the Cu/Ba ratio from 1.0 to 1.1, yielding a J c at 77 K and 0 T of 200 nm GdYBCO film increasing from 2.5 MA cm-2 to 7 MA cm-2. In addition, SEM and energy dispersive spectrometer (EDS) characterizations revealed that more and more outgrowths appeared and the density of the film was reduced with an increase in the Cu/Ba ratio from 1.1 to 1.2. When the I h was 26.8 A and the mole ratio of Gd(tmhd)3, Y(tmhd)3, Ba(tmhd)2 and Cu(tmhd)2 in the precursor was 0.55:0.55:2:2.2, the critical current (I c) of the deposited 200 nm-thick GdYBCO film reached a 140 A cm-1 width (77 K, 0 T), corresponding to the J c 7 MA cm-2 (77 K, 0 T).

  2. Diamond-like carbon films deposited on three-dimensional shape substrate model by liquid electrochemical technique

    Energy Technology Data Exchange (ETDEWEB)

    He, Y.Y. [Institute of Nano-photonics, School of Physics and Materials Engineering, Dalian Nationalities University, 116600 Dalian (China); Zhang, G.F. [School of Materials Science and Engineering, Dalian University of Technology, 116024, Dalian China (China); Zhao, Y.; Liu, D.D. [Institute of Nano-photonics, School of Physics and Materials Engineering, Dalian Nationalities University, 116600 Dalian (China); Cong, Y., E-mail: congyan@ciomp.ac.cn [Institute of Nano-photonics, School of Physics and Materials Engineering, Dalian Nationalities University, 116600 Dalian (China); Buck, V. [Thin Film Technology Group, Faculty of Physics, University Duisburg-Essen and CeNIDE, 47057 Duisburg (Germany)

    2015-09-01

    Diamond-like carbon (DLC) films were deposited on three-dimensional (3D) shape substrate model by electrolysis of 2-propanol solution at low temperature (60 °C). This 3D shape model was composed of a horizontally aligned stainless steel wafer and vertically aligned stainless steel rods. Morphology and microstructure of the films were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy, respectively. The results suggested there were only differences in film uniformity and thickness for two kinds of samples. The hydrogenated amorphous carbon films deposited on horizontally aligned substrate were smooth and homogeneous. And the film thickness of DLC films gained on the vertical substrates decreased along vertical direction. It is believed that bubble formation could enhance nucleation on the wetted capillary area. This experiment shows that deposition of DLC films by liquid phase deposition on 3D shape conductive substrates is possible. - Highlights: • DLC film is expected to be deposited on complex surface/shape substrate. • DLC film is deposited on 3D shape substrate by liquid electrochemical method. • Horizontal substrate is covered by smooth and homogeneous DLC films. • Film thickness decreases along vertical direction due to boiling effect.

  3. Recycling of metal-organic chemical vapor deposition waste of GaN based power device and LED industry by acidic leaching: Process optimization and kinetics study

    Science.gov (United States)

    Swain, Basudev; Mishra, Chinmayee; Kang, Leeseung; Park, Kyung-Soo; Lee, Chan Gi; Hong, Hyun Seon; Park, Jeung-Jin

    2015-05-01

    Recovery of metal values from GaN, a metal-organic chemical vapor deposition (MOCVD) waste of GaN based power device and LED industry is investigated by acidic leaching. Leaching kinetics of gallium rich MOCVD waste is studied and the process is optimized. The gallium rich waste MOCVD dust is characterized by XRD and ICP-AES analysis followed by aqua regia digestion. Different mineral acids are used to find out the best lixiviant for selective leaching of the gallium and indium. Concentrated HCl is relatively better lixiviant having reasonably faster kinetic and better leaching efficiency. Various leaching process parameters like effect of acidity, pulp density, temperature and concentration of catalyst on the leaching efficiency of gallium and indium are investigated. Reasonably, 4 M HCl, a pulp density of 50 g/L, 100 °C and stirring rate of 400 rpm are the effective optimum condition for quantitative leaching of gallium and indium.

  4. Nitrogen doping for adhesion improvement of DLC film deposited on Si substrate by Filtered Cathodic Vacuum Arc (FCVA) technique

    Energy Technology Data Exchange (ETDEWEB)

    Bootkul, D., E-mail: mo_duangkhae@hotmail.com [Department of General Science, Faculty of Science, Srinakharinwirot University, Bangkok 10110 (Thailand); Supsermpol, B.; Saenphinit, N. [Western Digital Company, Ayutthaya 13160 (Thailand); Aramwit, C. [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50202 (Thailand); Intarasiri, S., E-mail: saweat@gmail.com [Science and Technology Research Institute, Chiang Mai University, Chiang Mai 50202 (Thailand)

    2014-08-15

    Diamond-like carbon (DLC) films have been used in many applications due to their attractive combination of properties including chemical inertness, corrosion protection, biocompatibility, high hardness, and low wear rates. However, they still have some limitations such as high internal stresses and low toughness which lead to poor adhesion of films. Synthesis of nitrogen-doped DLC (N-DLC) offers the possibility of overcoming these limitations. In this study, DLC films, namely tetrahedral amorphous carbon (ta-C) and nitrogen doped tetrahedral amorphous carbon (ta-C:N) were deposited on single crystalline Si wafer substrates using the Filtered Cathodic Vacuum Arc (FCVA) technique. Film characterizations were carried out by Raman spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), triboindenter tester and nano-scratch tester. Measurement results showed that intentionally doping with nitrogen reduced the carbon sp{sup 3} content and increased the surface roughness in comparison with that of pure ta-C films. The hardness measurement confirmed the Raman and AFM analyses that adding nitrogen in ta-C films decreased the hardness, especially with high nitrogen content. However, the nano-scratch test revealed the increasing of the critical load with nitrogen. This work, then, extended its scope to investigate the properties of double-layer ta-C films which were composed of ta-C:N interlayer of various thickness around 10–30 nm and ta-C top-layer with thickness of around 80 nm. Microstructure characterization demonstrated that a ta-C:N interlayer gradually decreased the sp{sup 3} fraction in the films and increased film roughness whenever the ta-C:N interlayer thickness increased. In this structure, the tribological property in terms of adhesion to the Si substrate was significantly improved by about 20–90%, but the mechanical property in terms of hardness was gradually degraded by about 2–10%, compared to pure ta-C film, when the ta

  5. Metal-organic chemical vapour deposition of lithium manganese oxide thin films via single solid source precursor

    Directory of Open Access Journals (Sweden)

    Oyedotun K.O.

    2015-12-01

    Full Text Available Lithium manganese oxide thin films were deposited on sodalime glass substrates by metal organic chemical vapour deposition (MOCVD technique. The films were prepared by pyrolysis of lithium manganese acetylacetonate precursor at a temperature of 420 °C with a flow rate of 2.5 dm3/min for two-hour deposition period. Rutherford backscattering spectroscopy (RBS, UV-Vis spectrophotometry, X-ray diffraction (XRD spectroscopy, atomic force microscopy (AFM and van der Pauw four point probe method were used for characterizations of the film samples. RBS studies of the films revealed fair thickness of 1112.311 (1015 atoms/cm2 and effective stoichiometric relationship of Li0.47Mn0.27O0.26. The films exhibited relatively high transmission (50 % T in the visible and NIR range, with the bandgap energy of 2.55 eV. Broad and diffused X-ray diffraction patterns obtained showed that the film was amorphous in nature, while microstructural studies indicated dense and uniformly distributed layer across the substrate. Resistivity value of 4.9 Ω·cm was obtained for the thin film. Compared with Mn0.2O0.8 thin film, a significant lattice absorption edge shift was observed in the Li0.47Mn0.27O0.26 film.

  6. Growth and characterization of tin disulfide (SnS{sub 2}) thin film deposited by successive ionic layer adsorption and reaction (SILAR) technique

    Energy Technology Data Exchange (ETDEWEB)

    Deshpande, N.G. [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (India); Sagade, A.A. [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (India); Gudage, Y.G. [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (India); Lokhande, C.D. [Thin film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur 416004 (India); Sharma, Ramphal [Thin film and Nanotechnology Laboratory, Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004 (India)]. E-mail: ramphalsharma@yahoo.com

    2007-06-14

    Thin films of tin disulfide (SnS{sub 2}) have been deposited by using low cost successive ionic layer adsorption and reaction (SILAR) technique. The deposition parameters such as SILAR cycles (60), immersion time (20 s), rinsing time (10 s) and deposition temperature (27 {sup o}C) were optimized to obtain good quality of films. Physical investigations were made to study the structural, optical and electrical properties. X-ray diffraction (XRD) patterns reveal that the deposited SnS{sub 2} thin films have hexagonal crystal structure. Energy dispersive X-ray analysis (EDAX) indicated elemental ratio close to those for tin disulfide (SnS{sub (2.02)}). Uniform deposition of the material over the entire glass substrate was revealed by scanning electron microscopy (SEM). Atomic force microscopy (AFM) showed the film is uniform and the substrate surface is well covered with small spherical grains merged in each other. A direct band gap of 2.22 eV was obtained. Photoluminescence (PL) showed two strong peaks corresponding to green and red emission. Ag/SnS{sub 2} junction showed Schottky diode like I-V characteristics. The barrier height calculated was 0.22 eV. Thermoelectric power (TEP) properties showed that tin disulfide exhibits n-type conductivity.

  7. Co3O4 protective coatings prepared by Pulsed Injection Metal Organic Chemical Vapour Deposition

    DEFF Research Database (Denmark)

    Burriel, M.; Garcia, G.; Santiso, J.

    2005-01-01

    Cobalt oxide films were grown by Pulsed Injection Metal Organic Chemical Vapour Deposition (PI-MOCVD) using Co(acac)(3) (acac=acetylacetonate) precursor dissolved in toluene. The structure, morphology and growth rate of the layers deposited on silicon substrates were studied as a function...... of deposition temperature. Pure Co3O4 spinel structure was found for deposition temperatures ranging from 360 to 540 degreesC. The optimum experimental parameters to prepare dense layers with a high growth rate were determined and used to prepare corrosion protective coatings for Fe-22Cr metallic interconnects...

  8. Enhanced performance of CdS/CdTe thin-film devices through temperature profiling techniques applied to close-spaced sublimation deposition

    Energy Technology Data Exchange (ETDEWEB)

    Xiaonan Li; Sheldon, P.; Moutinho, H.; Matson, R. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    The authors describe a methodology developed and applied to the close-spaced sublimation technique for thin-film CdTe deposition. The developed temperature profiles consisted of three discrete temperature segments, which the authors called the nucleation, plugging, and annealing temperatures. They have demonstrated that these temperature profiles can be used to grow large-grain material, plug pinholes, and improve CdS/CdTe photovoltaic device performance by about 15%. The improved material and device properties have been obtained while maintaining deposition temperatures compatible with commercially available substrates. This temperature profiling technique can be easily applied to a manufacturing environment by adjusting the temperature as a function of substrate position instead of time.

  9. Characterization of Pd catalyst-electrodes deposited on YSZ: Influence of the preparation technique and the presence of a ceria interlayer

    Science.gov (United States)

    Jiménez-Borja, Carmen; Matei, Florina; Dorado, Fernando; Valverde, José Luis

    2012-11-01

    Palladium catalyst-electrodes supported on Y2O3-stabilized-ZrO2 (YSZ) prepared either by paste deposition or wet impregnation technique were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found a strong dependence of the catalytic film preparation technique as well as of the presence of a ceria interlayer between the palladium film and the solid electrolyte on the catalytic activity towards methane oxidation. Impregnated palladium films were found to be more active than films prepared by paste deposition. Besides, the addition of ceria allowed stabilizing the palladium active phase for methane oxidation.

  10. A new perspective on structural and morphological properties of carbon nanotubes synthesized by Plasma Enhanced Chemical Vapor Deposition technique

    Science.gov (United States)

    Salar Elahi, A.; Agah, K. Mikaili; Ghoranneviss, M.

    CNTs were produced on a silicon wafer by Plasma Enhanced Chemical Vapor Deposition (PECVD) using acetylene as a carbon source, cobalt as a catalyst and ammonia as a reactive gas. The DC-sputtering system was used to prepare cobalt thin films on Si substrates. A series of experiments was carried out to investigate the effects of reaction temperature and deposition time on the synthesis of the nanotubes. The deposition time was selected as 15 and 25 min for all growth temperatures. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the Co nanocatalyst deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface topography of the Co nanocatalyst deposited on Si substrates. The as-grown CNTs were characterized under Field Emission Scanning Electron Microscopy (FESEM) to study the morphological properties of CNTs. Also, the grown CNTs have been investigated by High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results demonstrated that increasing the temperature leads to increasing the diameter of CNTs.

  11. Structural and optical studied of nano structured lead sulfide thin films prepared by the chemical bath deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Al Din, Nasser Saad, E-mail: nsaadaldin@yahoo.com; Hussain, Nabiha, E-mail: nabihahssin@yahoo.com [Damascus University Faculty of Science, Department of physics, Homs (Syrian Arab Republic); Jandow, Nidhal, E-mail: nidhaljandow@yahoo.com [Al –Mustansiriyah University, College of Education, Department of physics, Baghdad (Iraq)

    2016-07-25

    Lead (II) Sulfide PbS thin films were deposited on glass substrates at 25°C by chemical bath deposition (CBD) method. The structural properties of the films were studied as a function of the concentration of Thiourea (CS (NH{sub 2}){sub 2}) as Source of Sulfide and deposition time. The surface morphology of the films was characterized by X-ray diffraction and SEM. The obtained results showed that the as-deposited films Polycrystalline had cubic crystalline phase that belong to S.G: Fm3m. We found that they have preferred orientation [200]. Also the thickness of thin films decrease with deposition time after certain value and, it observed free sulfide had orthorhombic phase. Optical properties showed that the thin films have high transmission at visible range and low transmission at UV, IR range. The films of PbS have direct band gap (I.68 - 2.32 ev) at 300 K the values of band energy decreases with increases thickness of the Lead (II) Sulfide films.

  12. Development and application of a green-chemistry solution deposition technique for buffer layer coating on cube-textured metal substrates in view of further deposition of rare-earth based superconductors

    DEFF Research Database (Denmark)

    Pallewatta, Pallewatta G A P

    , allowing the epitaxial growth of the superconducting layer. State-of-the-art coated conductor hetero structures are mainly based on CeO2 based buffer stacks that consist of a sequence of several different buffer layers. Buffer layers deposited by continuous chemical deposition techniques, which...... and hazardous chemicals such as 2-methoxyethanol, and trifluroacetic acid (TFA). Therefore, in our research the main focus was on the development of SrTiO3 single buffer layers based on environmentally safe chemicals, to reach the engineering requirements for continuous coating of long substrate tapes. A new......Superconductor based energy production has been thoroughly researched by many scientists all over the world, due to the advantage of zero electric resistance that will contribute to the energy saving capabilities. Recently successful developments have been reported in coated conductor architectures...

  13. Fabrication of ZnO nanoparticles-embedded hydrogenated diamond-like carbon films by electrochemical deposition technique

    Institute of Scientific and Technical Information of China (English)

    Zhang Pei-Zeng; Li Rui-Shan; Pan Xiao-Jun; Xie Er-Qing

    2013-01-01

    ZnO nanoparticles-embedded hydrogenated diamond-like carbon (ZnO-DLC) films have been prepared by electrochemical deposition in ambient conditions.The morphology,composition,and microstructure of the films have been investigated.The results show that the resultant films are hydrogenated diamond-like carbon films embedded with ZnO nanoparticles in wurtzite structure,and the content and size of the ZnO nanoparticles increase with increasing deposition voltage,which are confirmed by X-ray photoelectron spectroscopy (XPS),Raman,and transmission electron microscope (TEM).Furthermore,a possible mechanism used to describe the growth process of ZnO-DLC films by electrochemical deposition is also discussed.

  14. Manipulating microstructures and electrical properties of carbon fiber/reduced graphene oxide/nickel composite textiles with electrochemical deposition techniques

    Science.gov (United States)

    Cheng, Wei-Liang; Zhao, Quan-Liang; Shi, Fei

    2017-04-01

    Since graphene and their composites play significant roles in the catalysts, energy storage, electronics and other fields, where electron transport is highly critical, here, we introduce reduced graphene oxide (RGO) interfaces in the carbon fiber (CF) networks for preparing a novel lightweight carbon fiber/reduced graphene oxide/nickel (CF-RGO-Ni) composite textile. Upon the charaterizations on the microscopic morphologies, electrical and magnetic properties, and density, the presence of RGO nanosheets and nickel nanoparticles would substantially influence the related physical properties in the resulting composite textiles. Furthermore, the key parameters, including RGO loading, deposition time, current density and annealing temperature of carbon matrices, have been studied to understand their effects on the electrochemical deposition of nickel nanoparticles. Implication of the results suggests that the RGO interface is a unique medium for essentially promoting the electrochemical deposition kinetics and active sites for growing nickel nanoparticles, which indicates a universal approach for preparing advanced lightweight composites with the presence of graphene naonstructures.

  15. InP基MOCVD及MBE外延生长HBT的制备与分析%Fabrication and analysis of InP-based HBT by MOCVD and MBE growth

    Institute of Scientific and Technical Information of China (English)

    崔海林; 任晓敏; 黄辉

    2012-01-01

    设计并研制了用于光电集成(OEIC)的InP基异质结双极晶体管(HBT),介绍了工艺流程及器件结构。分别采用金属有机化学气相沉积(MOCVD)及分子束外延(MBE)生长的外延片,并在外延结构、工艺流程相同的条件下,对两种生长机制的HBT直流及高频参数进行和分析。结果表明,采用MOCVD生长的InP基HBT,直流增益为30倍,截止频率约为38GHz;MBE生长的HBT,直流增益达到100倍,截止频率约为40GHz。这表明,MBE生长的HBT外延层质量更高,在相同光刻条件下,所对应的HBT器件的性能更好。%We designed and fabricated the InP-based heterojunction bipolar transistor (HBT) for optoe-lectronic integrated circuit (OEIC). Both metal organic chemical vapor deposition (MOCVD) and molec-ular beam epitax (MBE) growth methods were developed. We compared and analyzed HBTs direct cur-rent (DC) and high frequency parameters by two growth mechanism types under the same epitaxial structure and technique process. The HBT by MOCVD growth exhibits a current gain of 30 and a cut-off frequency of 38 GHz. The HBT by MBE growth has a current gain of 100 and a cut-off frequency of 40 GHz. Based on testing results, the MBE growth epitaxy layer has better quality and in the same lithogra- phy condition,the corresponding HBT device has better performance.

  16. Effects of deposition methods and processing techniques on band gap, interband electronic transitions, and optical absorption in perovskite CH3NH3PbI3 films

    Science.gov (United States)

    Li, Wenwu; Sha, Tingting; Wang, Yan; Yu, Wenlei; Jiang, Kai; Zhou, Hang; Liu, Chuan; Hu, Zhigao; Chu, Junhao

    2017-07-01

    Despite intensive studies on the improvements of conversion efficiencies in solar cells, many questions regarding the effects of deposition techniques on optical properties and electronic band structures of CH3NH3PbI3 (MAPbI3) remain unresolved. Here, perovskite MAPbI3 films were prepared using different deposition methods and processing techniques. The effects of deposition and processing parameters on dielectric functions and optical absorption were investigated by fitting the reflectance spectra in the photon energy range of 0.5-5.16 eV. It is found that the bandgap (Eg) of the films deposited by two-step spinning (1.591 eV) is larger than that prepared by evaporations (1.514 eV), due to different Pb-I orbital hybridization and spin-orbit coupling. Moreover, the Eg value of the films increases from 1.543 eV to 1.591 eV after toluene solution dripping. Five interband electronic transitions ( Ep 1, Ep 2, Ep 3, Ep 4 , and Ep 5 ) are observed, and the origins of Ep 2, Ep 3 , and Ep 4 are assigned to the direct transitions between the highest valence band and the lowest lying conduction band at the R, M, and X symmetry points. Further, the transition energies of the films deposited by evaporation are less than those prepared by two-step spinning. The present results shed light on preparing more reliable and reproducible high performance MAPbI3-based solar cells.

  17. Simultaneous Counter-Ion Co-Deposition a Technique Enabling Matrix Isolation Spectroscopy Studies Using Low-Energy Beams of Mass-Selected Ions

    Science.gov (United States)

    Ludwig, Ryan M.; Moore, David T.

    2014-06-01

    Matrix isolation spectroscopy was first developed in Pimentel's group during the 1950's to facilitate spectroscopic studies of transient species. Cryogenic matrices of condensed rare gases provide an inert chemical environment with facile energy dissipation and are transparent at all wavelengths longer than vacuum UV, making them ideal for studying labile and reactive species such as radicals, weakly bound complexes, and ions. Since frozen rare gases are poor electrolytes, studies of ions require near-equal populations of anions and cations in order to stabilize the number densities required for spectroscopic experiments. Many techniques for generation of ions for using in matrix isolation studies satisfy this criterion intrinsically, however when ion beams generated in external sources are deposited, the counter-ions typically arise via secondary processes that are at best loosely controlled. It has long been recognized that it would be desirable to stabilize deposition of mass-selected ions generated in an external source using simultaneous co-deposition of a beam of counter-ions, however previous attempts to achieve this have been reported as unsuccessful. The Moore group at Lehigh has demonstrated successful experiments of this type, using mass-selected anions generated from a metal cluster source, co-deposited with a balanced current of cations generated in a separate electron ionization source. This talk will focus on the details of the technique, and present some results from proof-of-concept studies on anionic copper carbonyl complexes formed in argon matrices following co-deposition of Cu- with Ar+ or Kr+. Funding support from NSF CAREER Award CHE-0955637 is gratefully acknowledged. Whittle et al., J. Chem. Phys. 22, p.1943 (1954); Becker et al., J. Chem. Phys. 25, p.224 (1956). Godbout et al., J. Chem. Phys. 96, p.2892 (1996). Sabo et al., Appl. Spectrosc. 45, p. 535 (1991).

  18. Synthesis of Si/SiO2/ZnO nanoporous materials using chemical and electrochemical deposition techniques

    Science.gov (United States)

    Dauletbekova, A. K.; Alzhanova, A. Ye.; Akilbekov, A. T.; Mashentseva, A. A.; Zdorovets, M. V.; Balabekov, K. N.

    2016-09-01

    The work represents the results of forming Zn-based nanoprecipitates in nanoporous amorphous silicon dioxide on silicon substrate by the template synthesis method. SEM and AFM images of the surface after chemical and electrochemical deposition of zinc were obtained. The analysis of photoluminescence of the precipitated samples resulted in the assumption of formation of nanoclusters of zinc oxide.

  19. Effect of deposition conditions on the physical properties of SnxSy thin films prepared by the spray pyrolysis technique

    Institute of Scientific and Technical Information of China (English)

    M. R. Fadavieslam; N. Shahtahmasebi; M. Rezaee-Roknabadi; M. M. Bagheri-Mohagheghi

    2011-01-01

    Tin sulfide thin films (SnxSy ) with an atomic ratio of y / x =0.5 have been deposited on a glass substrate by spray pyrolysis.The effects of deposition parameters,such as spray solution rate (R),substrate temperature (Ts) and film thickness (t),on the structural,optical,thermo-electrical and photoconductivity related properties of the films have been studied.The precursor solution was prepared by dissolving tin chloride (SnCl4,5H2O)and thiourea in propanol,and SnxSy thin film was prepared with a mole ratio of y/x =0.5.The prepared films were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM) and UV-vis spectroscopy.It is indicated that the XRD patterns of SnxSy films have amorphous and polycrystalline structures and the size of the grains has been changed from 7 to 16 nm.The optical gap of SnxSy thin films is determined to be about 2.41 to 3.08 eV by a plot of the variation of (ohv)2 versus hv related to the change of deposition conditions.The thermoelectric and photo-conductivity measurement results for the films show that these properties are depend considerably on the deposition parameters.

  20. Annealing behavior of hexagonal phase content in cubic GaN thin films grown on GaAs (001) by MOCVD

    Institute of Scientific and Technical Information of China (English)

    孙小玲; 杨辉; 王玉田; 李国华; 郑联喜; 李建斌; 徐大鹏; 王占国

    1999-01-01

    The annealing behavior of the hexagonal phase content in cubic GaN (c-GaN) thin films grown on GaAs (001) by MOCVD is reported. C-GaN thin films are grown on GaAs (001) substrates by metalorganic chemical vapor deposition (MOCVD). High temperature annealing is employed to treat the as-grown c-GaN thin films. The characterization of the c-GaN films is investigated by photoluminescence (PL) and Raman scattering spectroscopy. The change conditions of the hexagonal phase content in the metastable c-GaN are reported. There is a boundary layer existing in the c-GaN/GaAs film. When being annealed at high temperature, the intensity of the TOB and LOB phonon modes from the boundary layer weakens while that of the E2 phonon mode from the hexagonal phase increases. The content change of hexagonal phase has closer relationship with annealing temperature than with annealing time period.

  1. Photoluminescence Properties of Two-dimensional Planar Layer and Three-dimensional Island Layer for ZnO Films Grown Using MOCVD

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    ZnO(002) films with different thicknesses ranging from 7 to 300 nm were grown on sapphire(006) substrates via metal-organic chemical vapor deposition(MOCVD). The two-dimensional(2D) planar layer and the three-dimensional(3D) island layer were studied by using of X-ray diffraction(XRD) rocking curves and atomic force microscopy(AFM). The room temperature photoluminescence(PL) spectra show a blue shift of the peak positions of the ultraviolet(UV) emission with increasing film thickness. The blue shift is remarkably high(393-380 nm) when an increase in film thickness(7-15 nm) is accompanied by the change of structure from a2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a2D planar layer to a 3D island layer near the2D layer region.

  2. Improved GaN Brown on Si(111 ) substrate using ammonia flow modulation on SiNx mask layer by MOCVD

    Institute of Scientific and Technical Information of China (English)

    YU NaiSen; WANG Yong; WANG Hui; NG KaiWei; LAU KeiMay

    2009-01-01

    In this paper, 1 μm n-GaN was grown by using varied and fixed ammonia flow (NH3) on SiNx mask layer on Si(111) substrate using metal organic chemical vapor deposition (MOCVD). In-situ optical reflectivity traces of GaN growth show that the three- to two-dimensional process has been prolonged by using varied ammonia flow on SiNx mask layer method compared with that grown by fixing ammonia flow. Structural and optical properties were characterized by high-resolution X-ray diffraction and photolu-minescence, and compared with the sample grown by fixing ammonia flow, GaN grown using the varied ammonia flow on SiNx mask layer showed better structure and optical quality. It was assumed that the low NH3 flow in the initial growth stage considerably increased the GaN island density on the nano-porous SiNx layer by enhancing vertical growth. Lateral growth was significantly favored by high NH3 flow in the subsequent step. As a result, the improved crystal and optical quality was achieved utilizing NH3 flow modulation for GaN buffer growth on Si(111) substrate.

  3. Improved GaN grown on Si(111) substrate using ammonia flow modulation on SiN_x mask layer by MOCVD

    Institute of Scientific and Technical Information of China (English)

    NG; KaiWei; LAU; KeiMay

    2009-01-01

    In this paper,1 μm n-GaN was grown by using varied and fixed ammonia flow (NH3) on SiNx mask layer on Si(111) substrate using metal organic chemical vapor deposition (MOCVD). In-situ optical reflectivity traces of GaN growth show that the three-to two-dimensional process has been prolonged by using varied ammonia flow on SiNx mask layer method compared with that grown by fixing ammonia flow. Structural and optical properties were characterized by high-resolution X-ray diffraction and photolu-minescence,and compared with the sample grown by fixing ammonia flow,GaN grown using the varied ammonia flow on SiNx mask layer showed better structure and optical quality. It was assumed that the low NH3 flow in the initial growth stage considerably increased the GaN island density on the nano-porous SiNx layer by enhancing vertical growth. Lateral growth was significantly favored by high NH3 flow in the subsequent step. As a result,the improved crystal and optical quality was achieved utilizing NH3 flow modulation for GaN buffer growth on Si(111) substrate.

  4. Effects of high-temperature annealing on magnetic properties of V-doped GaN thin films grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Souissi, M., E-mail: mnawer.souissi@fsm.rnu.tn [Higher Institute of Computer Sciences and Communication Techniques of Hammam Sousse, Sousse 4011 (Tunisia); Schmerber, G.; Derory, A. [Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS) UMR7504 CNRS-UDS, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2 (France); El Jani, B. [URHEA, Faculte des Sciences de Monastir, Monastir 5000 (Tunisia)

    2012-08-15

    Metal organic chemical vapor deposition (MOCVD) has been used to grow vanadium-doped GaN (GaN:V) on c-sapphire substrate using VCl{sub 4} as the V source. The as-grown GaN:V exhibited a saturated magnetic moment (M{sub s}) of 0.28 emu/cm{sup 3} at room temperature. Upon high-temperature annealing treatment at 1100 Degree-Sign C for 7 min under N{sub 2} ambient, the M{sub s} of the GaN:V increased by 39.28% to 0.39 emu/cm{sup 3}. We found that rapid thermal annealing leads to a remarkable increase in surface roughness of the V-doped GaN as well as the electron concentration. The annealing also leads to a significant increase in the Curie temperature (T{sub C}), we have identified Curie temperatures about 350 K concluded from the difference between the field-cooled and zero-field-cooled magnetizations. Structure characterization by x-ray diffraction indicated that the ferromagnetic properties are not a result of secondary magnetic phases.

  5. Wafer-level MOCVD growth of AlGaN/GaN-on-Si HEMT structures with ultra-high room temperature 2DEG mobility

    Science.gov (United States)

    Xu, Xiaoqing; Zhong, Jiebin; So, Hongyun; Norvilas, Aras; Sommerhalter, Christof; Senesky, Debbie G.; Tang, Mary

    2016-11-01

    In this work, we investigate the influence of growth temperature, impurity concentration, and metal contact structure on the uniformity and two-dimensional electron gas (2DEG) properties of AlGaN/GaN high electron mobility transistor (HEMT) structure grown by metal-organic chemical vapor deposition (MOCVD) on 4-inch Si substrate. High uniformity of 2DEG mobility (standard deviation down to 0.72%) across the radius of the 4-inch wafer has been achieved, and 2DEG mobility up to 1740.3 cm2/Vṡs at room temperature has been realized at low C and O impurity concentrations due to reduced ionized impurity scattering. The 2DEG mobility is further enhanced to 2161.4 cm2/Vṡs which is comparable to the highest value reported to date when the contact structure is switched from a square to a cross pattern due to reduced piezoelectric scattering at lower residual strain. This work provides constructive insights and promising results to the field of wafer-scale fabrication of AlGaN/GaN HEMT on Si.

  6. Wafer-level MOCVD growth of AlGaN/GaN-on-Si HEMT structures with ultra-high room temperature 2DEG mobility

    Directory of Open Access Journals (Sweden)

    Xiaoqing Xu

    2016-11-01

    Full Text Available In this work, we investigate the influence of growth temperature, impurity concentration, and metal contact structure on the uniformity and two-dimensional electron gas (2DEG properties of AlGaN/GaN high electron mobility transistor (HEMT structure grown by metal-organic chemical vapor deposition (MOCVD on 4-inch Si substrate. High uniformity of 2DEG mobility (standard deviation down to 0.72% across the radius of the 4-inch wafer has been achieved, and 2DEG mobility up to 1740.3 cm2/V⋅s at room temperature has been realized at low C and O impurity concentrations due to reduced ionized impurity scattering. The 2DEG mobility is further enhanced to 2161.4 cm2/V⋅s which is comparable to the highest value reported to date when the contact structure is switched from a square to a cross pattern due to reduced piezoelectric scattering at lower residual strain. This work provides constructive insights and promising results to the field of wafer-scale fabrication of AlGaN/GaN HEMT on Si.

  7. Selective-Area MOCVD Growth and Carrier-Transport-Type Control of InAs(Sb)/GaSb Core-Shell Nanowires.

    Science.gov (United States)

    Ji, Xianghai; Yang, Xiaoguang; Du, Wenna; Pan, Huayong; Yang, Tao

    2016-12-14

    We report the first selective-area growth of high quality InAs(Sb)/GaSb core-shell nanowires on Si substrates using metal-organic chemical vapor deposition (MOCVD) without foreign catalysts. Transmission electron microscopy (TEM) analysis reveals that the overgrowth of the GaSb shell is highly uniform and coherent with the InAs(Sb) core without any misfit dislocations. To control the structural properties and reduce the planar defect density in the self-catalyzed InAs core nanowires, a trace amount of Sb was introduced during their growth. As the Sb content increases from 0 to 9.4%, the crystal structure of the nanowires changes from a mixed wurtzite (WZ)/zinc-blende (ZB) structure to a perfect ZB phase. Electrical measurements reveal that both the n-type InAsSb core and p-type GaSb shell can work as active carrier transport channels, and the transport type of core-shell nanowires can be tuned by the GaSb shell thickness and back-gate voltage. This study furthers our understanding of the Sb-induced crystal-phase control of nanowires. Furthermore, the high quality InAs(Sb)/GaSb core-shell nanowire arrays obtained here pave the foundation for the fabrication of the vertical nanowire-based devices on a large scale and for the study of fundamental quantum physics.

  8. Alloying, co-doping, and annealing effects on the magnetic and optical properties of MOCVD-grown Ga{sub 1-x}Mn {sub x}N

    Energy Technology Data Exchange (ETDEWEB)

    Kane, Matthew H. [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30332 (United States); Georgia Institute of Technology, School of Materials Science and Engineering, Atlanta, GA 30332 (United States); Strassburg, Martin [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30332 (United States); Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA 30332 (United States); Asghar, Ali [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30332 (United States); Fenwick, William E. [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30332 (United States); Senawiratne, Jayantha [Georgia State University, Department of Physics and Astronomy, Atlanta, GA 30303 (United States); Song, Qing [Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA 30332 (United States); Summers, Christopher J. [Georgia Institute of Technology, School of Materials Science and Engineering, Atlanta, GA 30332 (United States); Zhang, Z. John [Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA 30332 (United States); Dietz, Nikolaus [Georgia State University, Department of Physics and Astronomy, Atlanta, GA 30303 (United States); Ferguson, Ian T. [Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30332 (United States)]. E-mail: ianf@ece.gatech.edu

    2006-01-25

    Recent theoretical work for Ga{sub 1-x}Mn {sub x}N predicts ferromagnetism in this materials system with Curie temperatures above room temperature. Ferromagnetic behavior observed in Ga{sub 1-x}Mn {sub x}N is still controversial, as there are conflicting experimental reports owing to the disparity in crystalline quality and phase purity of Ga{sub 1-x}Mn {sub x}N produced by different methods. In this work, metal-organic chemical vapor deposition (MOCVD) has been used to grow high-quality epitaxial films of Ga{sub 1-x}Mn {sub x}N of varying thickness and manganese doping levels using Cp{sub 2}Mn as the Mn source. Crystalline quality and phase purity were determined by high-resolution X-ray diffraction, indicating that no macroscopic second phases are formed. Atomic force microscopy revealed MOCVD-like step flow growth patterns and a mean surface roughness of 0.378 nm in optimally grown films, which is close to that from the as-grown template layer of 0.330 nm. No change in the growth mechanism and morphology with Mn incorporation is observed. A uniform Mn concentration in the epitaxial layers is confirmed by secondary ion mass spectroscopy. SQUID measurements showed an apparent room temperature ferromagnetic hysteresis with saturation magnetizations of over 2 {mu}{sub B}/Mn at x = 0.008, which decreases with increasing Mn incorporation. Upon high-temperature annealing, numerous changes are observed in these properties, including an increase in surface roughness due to surface decomposition and a large decrease in the magnetic signature. A similar decrease in the magnetic signature is observed upon co-doping with the shallow donor silicon during the growth process. These results demonstrate the critical importance of controlling the Fermi level relative to the Mn{sup 2+/3+} acceptor level in Ga{sub 1-x}Mn {sub x}N in order to achieve strong ferromagnetism.

  9. Temperature Uniformity of Wafer on a Large-Sized Susceptor for a Nitride Vertical MOCVD Reactor

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-Ming; JIANG Hai-Ying; HAN Yan-Bin; LI Jin-Ping; YIN Jian-Qin; ZHANG Jin-Cheng

    2012-01-01

    The effect of coil location on wafer temperature is analyzed in a vertical MOCVD reactor by induction heating.It is observed that the temperature distribution in the wafer with the coils under the graphite susceptor is more uniform than that with the coils around the outside wall of the reactor.For the case of coils under the susceptor,we find that the thickness of the susceptor,the distance from the coils to the susceptor bottom and the coil turns significantly affect the temperature uniformity of the wafer. An optimization process is executed for a 3-inch susceptor with this kind of structure,resulting in a large improvement in the temperature uniformity.A further optimization demonstrates that the new susceptor structure is also suitable for either multiple wafers or large-sized wafers approaching 6 and 8 inches.

  10. A Kind of Coating Method of GaN-MOCVD Graphite Susceptor

    Directory of Open Access Journals (Sweden)

    Xiao-feng Wu

    2013-01-01

    Full Text Available A novel coating method for the GaN-MOCVD graphite susceptor is proposed in the paper, which means that the upper surface and sides of the graphite susceptor are covered with a low emissivity material coating, and the surface under the susceptor is covered with a high emissivity SiC coating. By using finite element analysis software COMSOL Multiphysics, the temperature field of the susceptors without coating, with common SiC coating, and with improved coating is obtained and compared, which shows that the susceptor with the improved coating not only increases the heating efficiency of the heater, but also improves the temperature uniformity of the substrate, which can be of great benefit to the film growth. In addition, this improved coating for the susceptor has the same heating sensitivity as the common SiC coating.

  11. Appropriate materials and preparation techniques for polycrystalline-thin-film thermophotovoltaic cells

    Science.gov (United States)

    Dhere, Neelkanth G.

    1997-03-01

    techniques have paved the way for obtaining epitaxial Hg1-xCdxTe thin films at substrate temperatures of ~180 °C with the desired crystalline perfection, stoichiometry, and doping without the necessity of further annealing for improving either the crystalline quality or dopant activity. Retaining larger mercury proportions during annealing would require heated enclosures as in isothermal VPE, hot-wall technique, vacuum evaporation, hot-wall MOCVD, or close-space sublimation. Pb1-xCdxTe thin films can be prepared by magnetron sputtering from cooled Pb1-xCdxTe targets on heated substrates. Hot-wall technique is suitable for the deposition of Pb1-xCdxTe thin films. Hg1-xCdxTe and Pb1-xCdxTe TPV cells will benefit from the substantial work on CdTe thin film solar cells. The paper reviews work on thin films of ternary and pseudoternary compounds of interest for TPV conversion and methods of their preparation with a view to choosing the appropriate materials and fabrication techniques for polycrystalline-thin-film TPV cells.

  12. Fabrication of Ag:TiO2 Nanocomposite Thin Films by Sol-Gel Followed by Electron Beam Physical Vapour Deposition Technique

    Directory of Open Access Journals (Sweden)

    Manish Kumar

    2013-01-01

    Full Text Available Ag:TiO2 nanocomposite films have been synthesized by sol-gel method followed by electron beam physical vapour deposition. Targets for this deposition were prepared by a hydraulic press using a powder containing Ag and TiO2 prepared by sol-gel technique. Microstructure, surface, and plasmonic properties of nanocomposite films were studied using glancing angle X-ray diffractometer, atomic force microscopy, field emission secondary electron microscopy, and UV-Vis spectroscopy. Microstructural study reveals that Ag nanoparticles are embedded in TiO2 matrix consisting of mixed phases of anatase and rutile. Size estimation using Scherrer formula reveals that average crystallite size of Ag nanoparticles is 23 nm. Surface morphological studies indicate that deposited films are uniform and intact to the substrate and have very low value of root mean square roughness. Optical studies exhibit a surface plasmon resonance induced absorption band in visible region, which is the characteristic feature of Ag nanoparticles. The intensity of this absorption band is found to increase with the increase in deposition time. Multiple peaks observed in absorption band were explained using the concepts of extended Mie scattering. Preliminary experiments also suggested that these nanocomposite films exhibit promising photocatalytic properties, which can be used for water treatment.

  13. Synthesis of nanocrystalline TiO2 thin films by liquid phase deposition technique and its application for photocatalytic degradation studies

    Indian Academy of Sciences (India)

    Noor Shahina Begum; H M Farveez Ahmed

    2008-02-01

    A transparent, high purity titanium dioxide thin film composed of densely packed nanometer sized grains has been successfully deposited on a glass substrate at 30°C from an aqueous solution of TiO2–HF with the addition of boric acid as a scavenger by liquid phase deposition technique. From X-ray diffraction measurement, the deposited film was found to be amorphous and turns crystalline at 500°C. The deposited film showed excellent adherence to the substrate and was characterized by homogeneous flat surface. TiO2 thin films can be used as a photocatalyst to clean up organohalides, a class of compound in pesticides that pollute the ground water. Photocatalytic degradation experiments show that indanthrene golden orange dye undergoes degradation efficiently in presence of TiO2 thin films by exposing its aqueous solution to ultraviolet light. The suitable surface structure and porosity increases the photocatalytic activity. It was also observed that hemin doped TiO2 thin films break up organohalides at a surprisingly high rate under visible light.

  14. Metal-Organic Vapor Phase Epitaxial Reactor for the Deposition of Infrared Detector Materials

    Science.gov (United States)

    2015-04-09

    ADDRESS (ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park , NC 27709-2211 Epitaxial reactor, MOCVD, Infrared Materials, CdTe and...researchers from First Solar in depositing single crystal solar cell materials. A research contract worth over $150K was awarded to RPI b First Solar based on...Administrative Support Army Contracting Command - APG Research Triangle Park Division TEL: (919) 549-4269 FAX: (919) 549-4388 Table of

  15. High index of refraction films for dielectric mirrors prepared by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Brusasco, R.M.

    1989-01-01

    A wide variety of metal oxides with high index of refraction can be prepared by Metal-Organic Chemical Vapor Deposition. We present some recent optical and laser damage results on oxide films prepared by MOCVD which could be used in a multilayer structure for highly reflecting (HR) dielectric mirror applications. The method of preparation affects both optical properties and laser damage threshold. 10 refs., 8 figs., 4 tabs.

  16. Characterization of Pd catalyst-electrodes deposited on YSZ: Influence of the preparation technique and the presence of a ceria interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Borja, Carmen, E-mail: Carmen.JBorja@uclm.es [Departamento de Ingenieria Quimica, Facultad de Ciencias Quimicas, Universidad de Castilla-La Mancha. Avenida Camilo Jose Cela 12, 13071 Ciudad Real (Spain); Matei, Florina [Department of Petroleum Processing Engineering and Environmental Protection, Petroleum - Gas University of Ploiesti (Romania); Dorado, Fernando; Valverde, Jose Luis [Departamento de Ingenieria Quimica, Facultad de Ciencias Quimicas, Universidad de Castilla-La Mancha. Avenida Camilo Jose Cela 12, 13071 Ciudad Real (Spain)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Impregnation of palladium over YSZ led to more dispersed films. Black-Right-Pointing-Pointer XPS spectra indicated electron deficient Pd{sup 2+} species on the surface of palladium films. Black-Right-Pointing-Pointer Impregnated palladium films were more active than those prepared by paste deposition Black-Right-Pointing-Pointer The addition of a CeO{sub 2} interlayer enhanced the catalytic rate for the impregnated samples. - Abstract: Palladium catalyst-electrodes supported on Y{sub 2}O{sub 3}-stabilized-ZrO{sub 2} (YSZ) prepared either by paste deposition or wet impregnation technique were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found a strong dependence of the catalytic film preparation technique as well as of the presence of a ceria interlayer between the palladium film and the solid electrolyte on the catalytic activity towards methane oxidation. Impregnated palladium films were found to be more active than films prepared by paste deposition. Besides, the addition of ceria allowed stabilizing the palladium active phase for methane oxidation.

  17. Tin sulfide (SnS) nanostructured films deposited by continuous spray pyrolysis (CoSP) technique for dye-sensitized solar cells applications

    Energy Technology Data Exchange (ETDEWEB)

    Alam, Firoz; Dutta, Viresh, E-mail: vdutta@ces.iitd.ac.in

    2015-12-15

    Highlights: • Single phase, perfectly stoichiometric tin sulfide (SnS) films have been deposited by continuous spray pyrolysis technique. • Structural and morphological investigations show the orthorhombic SnS with nanoflakes. • SnS film shows excellent electrochemical stability. • SnS films have been used as a counter electrode (CE) in an I{sub 3}{sup −}/I{sup −} based dye-sensitized solar cells. - Abstract: Tin sulfide (SnS) nanostructured films have been deposited on transparent conducting glass substrate using continuous spray pyrolysis (CoSP) technique using aqueous spray solution of tin chloride and thiourea. Structural, morphological and optical properties of as-synthesized SnS nanostructured films showed the formation of (1 0 1) oriented orthorhombic SnS with nanoflakes having a direct band gap of 1.40 eV. X-ray photoelectron spectroscopy (XPS) analysis confirms the formation of pure SnS with Sn in +2 oxidation state. The SnS nanostructured film has also been characterized using Brunauer–Emmett–Teller (BET) technique to determine the surface area and pore volume which are found to be 11.4 m{sup 2}/g and 0.02 cm{sup 2}/g, respectively. The film has been used as a counter electrode (CE) in a triiodide/iodide (I{sub 3}{sup −}/I{sup −}) based dye-sensitized solar cells (DSSCs). The DSSCs of 0.25 cm{sup 2} area with SnS nanostructured CE exhibits a lower power conversion efficiency (2.0 ± 0.06%) than that for the cell with standard platinum (Pt) CE (4.5 ± 0.13%). However, the usefulness of the CoSP technique for deposition of nanostructures SnS CE film has been established in the present study.

  18. Co-assembly of functional graphene and multiwall carbon nanotubes for supercapacitors by a vertical deposition technique

    Science.gov (United States)

    Zhang, Yanhong; Cao, Xiaojian; Li, Zhenwei; Zhao, Dongmei

    2016-06-01

    Graphene and carbon nanotubes (CNTs) are nanosized carbon materials with large specific surface areas, outstanding electrical conductivities, excellent mechanical properties, and other remarkable characteristics. Preparation of graphene oxide is by a redox method, followed by vertical deposition to prepare graphene oxide/carbon nanotube GO/CNT) composites. Scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterize the morphology and microstructure of the materials. Electrodes were made by deposition of graphene oxide/carbon nanotube composites on an indium tin oxide glass slide, and its electrical properties were characterized by cyclic voltammetry. The GO/CNT composites exhibit excellent energy and power densities and are ideal materials for the preparation of supercapacitor electrodes.

  19. Preparation and characterization of ultra-thin films containing Au and Ag nanoparticles using layer-by-layer deposition technique

    OpenAIRE

    Cönger, Can Pınar

    2009-01-01

    Ankara : The Department of Chemistry and the Institute of Engineering and Sciences of Bilkent University, 2009. Thesis (Master's) -- Bilkent University, 2009. Includes bibliographical references leaves 69-77. The main objective of this thesis is to investigate the layer-by-layer deposited polyelectrolyte and polyelectrolyte/metal nanoparticle films by using X-ray Photoelectron (XPS) and Optical Spectroscopy (UV-Vis). Within this purpose, in the first part of the study, laye...

  20. Investigation of chemical vapour deposition diamond detectors by X- ray micro-beam induced current and X-ray micro-beam induced luminescence techniques

    CERN Document Server

    Olivero, P; Vittone, E; Fizzotti, F; Paolini, C; Lo Giudice, A; Barrett, R; Tucoulou, R

    2004-01-01

    Tracking detectors have become an important ingredient in high-energy physics experiments. In order to survive the harsh detection environment of the Large Hadron Collider (LHC), trackers need to have special properties. They must be radiation hard, provide fast collection of charge, be as thin as possible and remove heat from readout electronics. The unique properties of diamond allow it to fulfill these requirements. In this work we present an investigation of the charge transport and luminescence properties of "detector grade" artificial chemical vapour deposition (CVD) diamond devices developed within the CERN RD42 collaboration, performed by means of X-ray micro-beam induced current collection (XBICC) and X-ray micro- beam induced luminescence (XBIL) techniques. XBICC technique allows quantitative estimates of the transport parameters of the material to be evaluated and mapped with micrometric spatial resolution. In particular, the high resolution and sensitivity of the technique has allowed a quantitati...

  1. Understanding and optimization of InN and high indium containing InGaN alloys by metal organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tuna, Oecal

    2013-07-18

    Among the III-nitride semiconductors (Ga,Al,In)N, InN is the most attractive one due to having the narrowest bandgap of 0.64 eV. The revision in the bandgap of InN makes the InGaN more important since one can cover the whole solar spectrum by only changing In composition in an InGaN layer. The comparison of quality of InN and InGaN layers grown using a metal organic chemical vapor deposition (MOCVD) and a molecular beam epitaxy (MBE) methods indicate that growth with MOCVD is the more challenging, again due to the high dissociation temperature of NH{sub 3} relative to the low decomposition temperature of InN (560-570 C). However, there is significant interest in developing an MOCVD process for InN and InGaN growth since MOCVD technology is the technology currently in use for commercial fabrication of group III nitride thin films. This thesis is therefore focused on a study of MOCVD growth of n- and p-type InN and In-rich InGaN films with the goal of providing new information on the influence of growth conditions on the film properties. Initially, a detailed investigation of MOCVD of InN is given. It is shown that MOCVD growth parameters (growth temperature and V/III ratio) have impacts on the layer properties such as In droplet formation on the surface as well as on its electrical and optical properties. PAS is employed for point defect analyzation. It is shown that In vacancies isolated by nitrogen vacancies are the dominant vacancy-type positron traps in InN. A decrease in the N vacancy concentration in InN is observed as a result of the growth temperature increase from 500 to 550 C. This is an indication of a reduction of N vacancy concentration by enhancing NH{sub 3} dissociation at high growth temperature. Results obtained from optical techniques (Raman and PL) are used to estimate the free carrier concentrations in InN. Electrical characterizations are also carried out using Hall measurements. Carrier concentration values obtained by these three techniques

  2. Effect of Reaction Temperature and Time on the Structural Properties of Cu(In,Ga)Se2 Thin Films Deposited by Sequential Elemental Layer Technique

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Thin films of copper indium gallium selenide Cu(In,Ga)Se2 (CIGS) were prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound formation, and were studied at temperature as high as 1250℃ for the first time. These films were concurrently studied for their structural properties by X-ray diffraction (XRD) technique. The XRD analyses include phase transition studies, grain size variation and microstrain measurements with the reaction temperature and time.It has been observed that there are three distinct regions of variation in all these parameters. These regions belong to three temperature regimes: <450℃, 450-950℃, and >950℃. It is also seen that the compound formation starts at 250℃, with ternary phases appearing at 350℃ or above. Whereas, there is another phase shift at 950℃ without any preference to the quaternary compound.

  3. Interface studies on the tunneling contact of a MOCVD-prepared tandem solar cell; Grenzflaechenuntersuchungen am Tunnelkontakt einer MOCVD-praeparierten Tandemsolarzelle

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, U.

    2007-07-10

    In this thesis a tandem solar cell with a novel tunneling contact was developed. For the development of the monolithic preparation especailly critical hetero-interfaces were studied in the region of the tunneling contact with surface-sensitive measuring method. The tandem solar cell consisted of single solar cells with absorber layers of In{sub 0.53}Ga{sub 0.47}As (E{sub g}=0.73 eV) and In{sub 0.78}Ga{sub 0.22}As{sub 0.491}P{sub 0.51} (E{sub g}=1.03 eV), the serial switching of which was pursued with a tunneling contact (ESAKI diode, which consisted of a very thin n-doped InGaAs and a p-doped GaAsSb layer. The III-V semiconductor layers were prepared by metalorganic gas phase epitaxy (MOCVD) monocrystallinely on an InP(100) substrate lattice-matchedly. Especially the influence of the preparation of InGaAs surfaces on the sharpness of the InGaAs/GaAsSb interface was in-situ studied by reflection-anisotropy spectroscopy and after a contamination-free transfer into the ultrahigh vacuum with photoelectron spectroscopy and with low-energetic electron diffraction (LEED). Thereby for the first time three different reconstructions of the MOCVD-prepared InGaAs surfaces could be observed, which were dependent on the heating temperature under pure hydrogen. The arsenic-rich InGaAs surface was observed for temperatures less than 300 C and showed in the LEED picture a (4 x 3) reconstruction. In the temperature range from 300 C until about 500 C a (2 x 4) reconstruction was observed, above 500 C the InGaAs surface 94 x 2)/c(8 x 2) was reconstructed. Subsequently the study of the growth of thin GaAsSb layers on these three InGaAs surface reconstructions followed. XPS measurements showed that the Sb/As ratio in GaAsSb at the growth on the As-rich (4 x 3) reconstructed surface in the first monolayers was too low. The preparation of the GaAsSb on the two other InGaAs surfaces yielded however in both cases a distinctly higher Sb/As ratio. Finally tandem solar cells with differently

  4. Investigations on alluvial deposits through borehole stratigraphy, radiocarbon dating and passive seismic technique (Carnic Alps, NE Italy)

    Science.gov (United States)

    Viero, Alessia; Marchi, Lorenzo; Cavalli, Marco; Crema, Stefano; Fontana, Alessandro; Mozzi, Paolo; Venturini, Corrado

    2016-04-01

    Alluvial sediment investigations provide fundamental tools to infer the processes that control geomorphological evolution of mountain environments. By analyzing sediment stratigraphy in depth, it is possible to retrieve the source, the geology, the time of deposition, the relative distance travelled by material as well as to distinguish among different type of transport (i.e., gravitational, fluvial or glacial). In this work, we present a combination of log stratigraphy, radiocarbon dating and geophysical surveys carried out on the valley floor of the But River (Carnic Alps, North East Italy). The But River basin drains an area of 326 km2 with a range in elevation from 2769 to 323 m a.s.l.; the bedrock mainly consists of carbonates and quartz arenites with minor inclusions of effusive rocks. After Pleistocene the gravitational deposits from mountain slopes have impounded the But River several times. In particular, we analyzed a sector of the upper portion of the But valley close to the confluence of the Moscardo Torrent, frequently affected by debris flows. A borehole was drilled in the But River floodplain, at the intersection with the Moscardo Torrent alluvial fan, down to a depth of 80 m. The analysis of the core samples allowed discerning three sedimentary levels rich in clay and organic materials, which testify the presence of small dam lakes, originated from the Moscardo debris-flow deposits. Three samples of wood and plant debris were collected from 13, 14 and 23 m of depth, respectively. They were analyzed through radiocarbon dating in order to determine the age of the lakes and, thus, to infer the activity of the debris flows building the Moscardo cone. The calibrated ages of the 3 samples are close to the younger limit of the radiocarbon method indicating a fast aggradation of the valley floor, starting from a period ranging between 1450 - 1632 AD. Historical maps and documents confirm the presence of the lakes until 19th century and they permit to assess

  5. Structural, nanomechanical and variable range hopping conduction behavior of nanocrystalline carbon thin films deposited by the ambient environment assisted filtered cathodic jet carbon arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Rawal, Ishpal; Tripathi, R.K. [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Srivastava, A.K. [Electron and Ion Microscopy, Sophisticated and Analytical Instruments, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Kumar, Mahesh [Ultrafast Opto-Electronics and Tetrahertz Photonics Group, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India)

    2015-04-15

    Highlights: • Nanocrystalline carbon thin films are grown by filtered cathodic jet carbon arc process. • Effect of gaseous environment on the properties of carbon films has been studied. • The structural and nanomechanical properties of carbon thin films have been studied. • The VRH conduction behavior in nanocrystalline carbon thin films has been studied. - Abstract: This paper reports the deposition and characterization of nanocrystalline carbon thin films by filtered cathodic jet carbon arc technique assisted with three different gaseous environments of helium, nitrogen and hydrogen. All the films are nanocrystalline in nature as observed from the high resolution transmission electron microscopic (HRTEM) measurements, which suggests that the nanocrystallites of size ∼10–50 nm are embedded though out the amorphous matrix. X-ray photoelectron spectroscopic studies suggest that the film deposited under the nitrogen gaseous environment has the highest sp{sup 3}/sp{sup 2} ratio accompanied with the highest hardness of ∼18.34 GPa observed from the nanoindentation technique. The film deposited under the helium gaseous environment has the highest ratio of the area under the Raman D peak to G peak (A{sub D}/A{sub G}) and the highest conductivity (∼2.23 S/cm) at room temperature, whereas, the film deposited under the hydrogen environment has the lowest conductivity value (2.27 × 10{sup −7} S/cm). The temperature dependent dc conduction behavior of all the nanocrystalline carbon thin films has been analyzed in the light of Mott’s variable range hopping (VRH) conduction mechanism and observed that all the films obey three dimension VRH conduction mechanism for the charge transport.

  6. Evidence of room temperature ferromagnetism in argon/oxygen annealed TiO{sub 2} thin films deposited by electron beam evaporation technique

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, P. [School of Materials Science and Technology, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Kabiraj, D. [Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110067 (India); Mandal, R.K. [Department of Metallurgical Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Kulriya, P.K. [Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110067 (India); Sinha, A.S.K. [Department of Chemical Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005 (India); Rath, Chandana, E-mail: chandanarath@yahoo.com [School of Materials Science and Technology, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005 (India)

    2014-04-15

    TiO{sub 2} thin films deposited by electron beam evaporation technique annealed in either O{sub 2} or Ar atmosphere showed ferromagnetism at room temperature. The pristine amorphous film demonstrates anatase phase after annealing under Ar/O{sub 2} atmosphere. While the pristine film shows a super-paramagnetic behavior, both O{sub 2} and Ar annealed films display hysteresis at 300 K. X-ray photo emission spectroscopy (XPS), Raman spectroscopy, Rutherford’s backscattering spectroscopy (RBS), cross-sectional transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) were used to refute the possible role of impurities/contaminants in magnetic properties of the films. The saturation magnetization of the O{sub 2} annealed film is found to be higher than the Ar annealed one. It is revealed from shifting of O 1s and Ti 2p core level spectra as well as from the enhancement of high binding energy component of O 1s spectra that the higher magnetic moment is associated with higher oxygen vacancies. In addition, O{sub 2} annealed film demonstrates better crystallinity, uniform deposition and smoother surface than that of the Ar annealed one from glancing angle X-ray diffraction (GAXRD) and atomic force microscopy (AFM). We conclude that although ferromagnetism is due to oxygen vacancies, the higher magnetization in O{sub 2} annealed film could be due to crystallinity, which has been observed earlier in Co doped TiO{sub 2} film deposited by pulsed laser deposition (Mohanty et al., 2012 [10]). - Highlights: • TiO{sub 2} films were deposited by e-beam evaporation technique and post annealed under O{sub 2}/Ar at 500 °C. • The pristine film shows SPM behavior where as O{sub 2} and Ar annealed films demonstrate RTFM. • The presence of magnetic impurities has been discarded by various characterization techniques. • The magnetic moment is found to be higher in O{sub 2} annealed film than the Ar annealed one. • The higher M{sub s} in O{sub 2

  7. Depth determination of the subsurface uranium deposits using CR-39 cylindrical technique in Gneissoic granitic rocks, Abu Rushied area, Southeastern Desert, Egypt

    Directory of Open Access Journals (Sweden)

    Sayed F. Hassan

    2015-10-01

    Full Text Available Using solid state nuclear track detectors and employing CR-39 cylindrical technique, the depth of the subsurface uranium deposits were determined. This techniques depends mainly on the nuclear track detector situated in zigzag form inside a polyethylene cylinder of 65 cm length and 7 cm diameter. This technique was applied on a borehole in a granite mass Abu Rushied area, southeast area desert. The obtained results revealed that, the depth of U -ore deposited reached about 89 m with thickness nearly 24 m. The obtained data for radon concentrations were also used for the determination of the exhalation rates, the measured values for exhalation rate (mBqm−2h−1 varies between 6.14E-03 at h = 50 cm and 4.53E-02 at h = 10 cm, The obtained values are comparable with that recorded for the granite type of rock.

  8. OPTICAL PROPERTIES OF Al:ZnO THIN FILM DEPOSITED BY DIFFERENT SOL-GEL TECHNIQUES: ULTRASONIC SPRAY PYROLYSIS AND DIP-COATING

    Directory of Open Access Journals (Sweden)

    Ebru Gungor

    2016-08-01

    Full Text Available Undoped and Al-doped ZnO polycrystalline thin films have been fabricated on glass substrates by using a computer-controlled dip coating (DC and ultrasonic spray pyrolysis (USP systems. The film deposition parameters of DC process were optimized for the samples. In this technique, the substrate was exposed to temperature gradient using a tube furnace. In the study, the other solvent-based technique was conventional USP. The zinc salt and Al salt concentrations in the solution were kept constant as 0.1 M and 2% of Zn salt’s molarity, respectively. The optical properties were compared for the films deposited two different techniques. The optical transmission of Al:ZnO/Glass/Al:ZnO sample dip coated and  the optical transmission of Al:ZnO/Glass sample ultrasonically sprayed were determined higher than 80% in the visible and near infrared region. Experimental optical transmittance spectra of the films in the forms of FilmA/Glass/FilmA and FilmA/glass were used to determine the optical constants. It was observed that the optical band gaps of Al doped ZnO films onto glass substrate were increases with increase of Al content and the absorption edge shifted to the shorter wavelength (blue shift compared with the undoped ZnO thin film.

  9. Photoluminescence imaging of Eu(III) doped Y{sub 2}O{sub 3} nanorods on a Si substrate deposited by an electrospray technique

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Weon Gyu; Park, Miso; Kim, Jinhyoung [Department of Mechanical Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Joo, Sang Woo [School of Mechanical Engineering, Yeungnam University, Gyeongsan, Gyeongbuk 712-749 (Korea, Republic of); Cho, Insu [Department of Chemistry, Yeungnam University, Gyeongsan, Gyeongbuk 712-749 (Korea, Republic of); Sohn, Youngku, E-mail: youngkusohn@ynu.ac.kr [Department of Chemistry, Yeungnam University, Gyeongsan, Gyeongbuk 712-749 (Korea, Republic of)

    2014-08-28

    Eu(III)-doped Y{sub 2}O{sub 3} nanorods were deposited onto a Si substrate by an electrospray technique and the photoluminescence imaging profiles of the electrospray film and powder form were compared. The electrospray method enabled generation of a uniform monolayer film without much clustering of nanorods. Strong emission peaks were observed between 580 and 730 nm in response to an indirect excitation transition and assigned to {sup 5}D{sub 0} → {sup 7}F{sub J} (J = 0–4) transitions of Eu(III) ions embedded at the C{sub 2} symmetry site in Y{sub 2}O{sub 3}. No emission in response to the direct excitation transition of Eu(III) ions was observed, while light was emitted from the Eu(III)-doped Y{sub 2}O{sub 3} powder. Taken together, these findings indicate that the electrospray technique could be very useful for generating thin films for displays and sensors. - Highlights: • Eu(III)-doped Y{sub 2}O{sub 3} nanorod was synthesized by a hydrothermal method. • Eu(III)-Y{sub 2}O{sub 3} nanorod was deposited onto a Si substrate by electrospray technique. • Photoluminescence (PL) imaging was obtained for electrospray and powder samples. • For electrospray film, PL was only observed by an indirect excitation unlike power. • Interfacial electronic structures were examined before and after annealing.

  10. Characterization of AgGa{sub 0.5}In{sub 0.5}Se{sub 2} thin films deposited by electron-beam technique

    Energy Technology Data Exchange (ETDEWEB)

    Karaagac, H; Parlak, M [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey); Kaleli, M, E-mail: parlak@metu.edu.t [Department of Physics, Sueleyman Demirel University, 32260 Isparta (Turkey)

    2009-08-21

    AgGa{sub 0.5}In{sub 0.5}Se{sub 2} thin films were deposited onto a quartz substrate by the electron-beam technique. For the investigation of the annealing effect on structural, optical and electrical properties of deposited films, samples were annealed in the temperature range 300-775 {sup 0}C. The composition analyses of the deposited films carried out by energy dispersive x-ray analysis measurements have shown that the deposited AgGa{sub 0.5}In{sub 0.5}Se{sub 2} films were indium- and gallium-rich but selenium- and slightly silver-deficient and there was a remarkable change in composition with annealing. As a result of x-ray diffraction measurements, the as-deposited films were found to have an amorphous structure and after annealing at 300 {sup 0}C a polycrystalline structure with different phases was observed. However, subsequent annealing resulted in the formation of single phase AgGa{sub 0.5}In{sub 0.5}Se{sub 2} thin film at about 775 {sup 0}C. The absorption coefficient of the films was determined from the transmission spectra and the band gap values were calculated and found to vary between 1.57 and 2.43 eV following annealing in the temperature range 300-775 {sup 0}C. The refractive index (n) and extinction coefficient (k) of the films were evaluated by applying the envelope method to the transmission spectra. The spectral distributions of these quantities for both as-deposited and annealed films were determined in detail and it was observed that there has been a remarkable influence of annealing on these quantities. The electrical properties of AgGa{sub 0.5}In{sub 0.5}Se{sub 2} thin films were also investigated by means of temperature dependent conductivity measurements in the temperature range 100-460 K. The resistivity of the samples depending on the annealing temperature varied between 6.5 x 10{sup 5} and 16 {Omega} cm. As a result of the hot-probe method it was observed that the as-deposited films have indicated an n-type behaviour, while all the

  11. Morphology of carbon nanotubes prepared via chemical vapour deposition technique using acetylene: A small angle neutron scattering investigation

    Indian Academy of Sciences (India)

    D Sen; K Dasgupta; J Bahadur; S Mazumder; D Sathiyamoorthy

    2008-11-01

    Small angle neutron scattering (SANS) has been utilized to study the morphology of the multi-walled carbon nanotubes prepared by chemical vapour deposition of acetylene. The effects of various synthesis parameters like temperature, catalyst concentration and catalyst support on the size distribution of the nanotubes are investigated. Distribution of nanotube radii in two length scales has been observed. The number density of the smaller diameter tubes was found more in number compared to the bigger one for all the cases studied. No prominent scaling of the structure factor was observed for the different synthesis conditions.

  12. High-efficiency CdTe thin-film solar cells using metalorganic chemical vapor deposition techniques

    Science.gov (United States)

    Nouhi, A.; Stirn, R. J.; Meyers, P. V.; Liu, C. H.

    1989-01-01

    Energy conversion efficiency of metalorganic chemical vapor deposited CdTe as an intrinsic active layer in n-i-p solar cell structures is reported. Small-area devices with efficiencies over 9 percent have been demonstrated. I-V characteristics, photospectral response, and the results of Auger profiling of structural composition for typical devices will be presented. Also presented are preliminary results on similar photovoltaic devices having Cd(0.85)Mn(0.15)Te in place of CdTe as an i layer.

  13. MOCVD方法在Si衬底上低温生长ZnO薄膜%Low -temperature preparation of ZnO films on Si substrates by MOCVD

    Institute of Scientific and Technical Information of China (English)

    沈文娟; 王俊; 王启元; 段垚; 曾一平

    2006-01-01

    ZnO films were deposited on Si(100) substrates at 300℃ by metal -organic chemical vapor deposition(MOGVD). The effect of different ratios of DEZn to N2O on crystal quality was analyzed. It is found that the optimum ratio of DEZn to N2O is 2:1. And in this optimum growth condition, X - ray diffraction (XRD) and scanning probe morphology (SPM) images indicate that the films grow along the c -axis orientation. ZnO film exhibits a strong UV optical absorption near 388 nm..And the optical absorbance is close to zero,that indicates nearly 100% optical transparence. Photoluminescence (PL) spectrum shows only strong near- band -edge emissions with little or no deep -level emission related to defects. The full - width at half - maximum (FWHM) of the ultraviolet emission peak is 80meV. The results indicate that better crystal quality can be obtained.%采用二乙基锌(DEZn)和氧化亚氮(N2O)作为锌源和氧源,在低温300℃,利用金属有机化学气相沉积(MOCVD)的方法在Si(100)衬底上制备了ZnO薄膜.通过优化氧锌比,ZnO薄膜为高度单一c轴方向生长.由光致发光谱和反射谱得知,ZnO薄膜的紫外发光峰位于388nm,具有很好的光透性,且其PL谱半峰宽为80meV.

  14. Analysis of morphological, structural and electrical properties of annealed TiO2 nanowires deposited by GLAD technique

    Science.gov (United States)

    Shougaijam, B.; Swain, R.; Ngangbam, C.; Lenka, T. R.

    2017-06-01

    The effect of annealing on vertically aligned TiO2 NWs deposited by glancing angle deposition (GLAD) method on Si substrate using pressed and sintered TiO2 pellets as source material is studied. The FE-SEM images reveal the retention of vertically aligned NWs on Si substrate after annealing process. The EDS analysis of TiO2 NWs sample annealed at 600 °C in air for 1 h shows the higher weight percentage ratio of ˜2.6 (i.e., 72.27% oxygen and 27.73% titanium). The XRD pattern reveals that the polycrystalline nature of anatase TiO2 dominates the annealed NWs sample. The electrical characteristics of Al/TiO2-NWs/TiO2-TF/p-Si (NW device) and Al/TiO2-TF/p-Si (TF device) based on annealed samples are compared. It is riveting to observe a lower leakage current of ˜1.32 × 10-7 A/cm2 at +1 V with interface trap density of ˜6.71 × 1011 eV-1 cm-2 in NW device compared to ˜2.23 × 10-7 A/cm2 in TF device. The dominant leakage mechanism is investigated to be generally Schottky emission; however Poole-Frenkel emission also takes place during high reverse bias beyond 4 V for NWs and 3 V for TF device.

  15. Chemical vapor deposition of ceramic coatings on metals and ceramic fibers

    Science.gov (United States)

    Nable, Jun Co

    2005-07-01

    The research presented in this study consists of two major parts. The first part is about the development of ceramic coatings on metals by chemical vapor deposition (CVD) and metal-organic chemical vapor deposition (MOCVD). Ceramics such as Al2O3 and Cr2O3, are used as protective coatings for materials used at elevated temperatures (>700°C). These metal oxides either exhibit oxidation resistance or have been used as environmental bond coats. Conventional methods of coating by chemical vapor deposition requires deposition temperatures of >950°C which could damage the substrate material during the coating process. Lower deposition temperatures (400 to 600°C) by MOCVD of these metal oxides were successful on Ni metal substrates. Surface modification such as pre-oxidation and etching were also investigated. In addition, a novel approach for the CVD of TiN on metals was developed. This new approach utilizes ambient pressure conditions which lead to deposition temperatures of 800°C or lower compared to conventional CVD of TiN at 1000°C. Titanium nitride can be used as an abrasive and wear coating on cutting and grinding tools. This nitride can also serve as a diffusion coating in metals. The second major part of this research involves the synthesis of interfacial coatings on ceramic reinforcing fibers for ceramic matrix composites. Aluminum and chromium oxides were deposited onto SiC, and Al2O3-SiO 2 fibers by MOCVD. The effects of the interface coatings on the tensile strength of ceramic fibers are also discussed. New duplex interface coatings consisting of BN or TiN together with Al2O3 or ZrO 2 were also successfully deposited and evaluated on SiC fibers.

  16. The influence of charge effect on the growth of hydrogenated amorphous silicon by the hot-wire chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Q.; Nelson, B.P.; Iwaniczko, E.; Mahan, A.H.; Crandall, R.S.; Benner, J. [National Renewable Energy Lab., Golden, CO (United States)

    1998-09-01

    The authors observe at lower substrate temperatures that the scatter in the dark conductivity on hydrogenated amorphous silicon (a-Si:H) films grown on insulating substrates (e.g., Corning 7059 glass) by the hot-wire chemical vapor deposition technique (HWCVD) can be five orders of magnitude or more. This is especially true at deposition temperatures below 350 C. However, when the authors grow the same materials on substrates with a conductive grid, virtually all of their films have acceptable dark conductivity (< 5 {times} 10{sup {minus}10} S/cm) at all deposition temperatures below 425 C. This is in contrast to only about 20% of the materials grown in this same temperature range on insulating substrates having an acceptable dark conductivity. The authors estimated an average energy of 5 eV electrons reaching the growing surface in vacuum, and did additional experiments to see the influence of both the electron flux and the energy of the electrons on the film growth. Although these effects do not seem to be important for growing a-Si:H by HWCVD on conductive substrates, they help better understand the important parameters for a-Si:H growth, and thus, to optimize these parameters in other applications of HWCVD technology.

  17. Crystalline nanostructured Cu doped ZnO thin films grown at room temperature by pulsed laser deposition technique and their characterization

    Energy Technology Data Exchange (ETDEWEB)

    Drmosh, Qasem A. [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Rao, Saleem G.; Yamani, Zain H. [Laser Research Group, Department of Physics, Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Gondal, Mohammed A., E-mail: magondal@kfupm.edu.sa [Laser Research Group, Department of Physics, Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2013-04-01

    We report structural and optical properties of Cu doped ZnO (ZnO:Cu) thin films deposited on glass substrate at room temperature by pulsed laser deposition (PLD) method without pre and post annealing contrary to all previous reports. For preparation of (ZnO:Cu) composites pure Zn and Cu targets in special geometrical arrangements were exposed to 248 nm radiations generated by KrF exciter laser. The laser energy was 200 mJ with 10 Hz frequency and 20 ns pulse width. The effect of Cu concentration on crystal structure, morphology, and optical properties were investigated by XRD, FESEM and photoluminescence spectrometer respectively. A systematic shift in ZnO (0 0 2) peak with Cu concentration observed in XRD spectra demonstrated that Cu ion has been incorporated in ZnO lattice. Uniform film with narrow size range grains were observed in FESEM images. The photoluminescence (PL) spectra measured at room temperature revealed a systematic red shift in ZnO emission peak and decrease in the band gap with the increase in Cu concentration. These results entail that PLD technique can be realized to deposit high quality crystalline ZnO and ZnO:Cu thin films without pre and post heat treatment which is normally practiced worldwide for such structures.

  18. Optical properties of double layer thin films zinc oxide doping aluminum (ZnO/Al) were deposited on glass substrates by sol gel method spray coating technique

    Science.gov (United States)

    Permatasari, Anes; Sutanto, Heri; Marito Siagian, Sinta

    2017-01-01

    Thin films of double layer of ZnO/Al has succeeded in deposition on a glass substrate using sol-gel method and spray coating techniques. Variations of doping Al as much as 2%, 4%, 6% and 8%. ZnO precursor synthesized using zinc acetate dehydrate (Zn(COOCH3)2.2H2O), isopropanol ((CH3)2CHOH) and monoethanolamine (MEA) were stirred using a magnetic stirrer for 45 minutes. ZnO precursor get homogeneous and then added of aluminum nitrate nonahydrate predetermined doping concentration and stirred again for 15 minutes. Deposition solution is done by the spray on a glass substrate and then heated at a temperature of 450°C. A layer of ZnO/Al deposited over the ZnO to produce a thin layer of a double layer. Optical properties layer of ZnO/Al characterized using UV-Vis spectrophotometer. Based on data from UV-Vis absorbance was determined the value of the energy band gap. Pure and dopped layers has different energy due the Al dopping. For pure ZnO layer has energy band gap of 3.347 eV and decreased to 3.09 eV for ZnO layer with Al dopant.

  19. Influence of annealing in H atmosphere on the electrical properties of Al2O3 layers grown on p-type Si by the atomic layer deposition technique

    Science.gov (United States)

    Kolkovsky, Vl.; Stübner, R.; Langa, S.; Wende, U.; Kaiser, B.; Conrad, H.; Schenk, H.

    2016-09-01

    In the present study the electrical properties of 100 nm and 400 nm alumina films grown by the atomic layer deposition technique on p-type Si before and after a post-deposition annealing at 440 °C and after a dc H plasma treatment at different temperatures are investigated. We show that the density of interface states is below 2 × 1010 cm-2 in these samples and this value is significantly lower compared to that reported previously in thinner alumina layers (below 50 nm). The effective minority carrier lifetime τg,eff and the effective surface recombination velocity seff in untreated p-type Si samples with 100 nm and 400 nm aluminum oxide is comparable with those obtained after thermal oxidation of 90 nm SiO2. Both, a post-deposition annealing in forming gas (nitrogen/hydrogen) at elevated temperatures and a dc H-plasma treatment at temperatures close to room temperature lead to the introduction of negatively charged defects in alumina films. The results obtained in samples annealed in different atmospheres at different temperatures or subjected to a dc H plasma treatment allow us to correlate these centers with H-related defects. By comparing with theory we tentatively assign them to negatively charged interstitial H atoms.

  20. Fabrication of p-type CuO thin films using chemical bath deposition technique and their solar cell applications with Si nanowires

    Science.gov (United States)

    Akgul, Funda Aksoy; Akgul, Guvenc

    2017-02-01

    Recently, CuO has attracted much interest owing to its suitable material properties, inexpensive fabrication cost and potential applications for optoelectronic devices. In this study, CuO thin films were deposited on glass substrates using chemical bath deposition technique and post-deposition annealing effect on the properties of the prepared samples were investigated. p-n heterojunction solar cells were then constructed by coating of p-type CuO films onto the vertically well-aligned n-type Si nanowires synthesized through MACE method. Photovoltaic performance of the fabricated devices were determined with current-voltage (I-V) measurements under AM 1.5 G illumination. The optimal short-circuit current density, open-circuit voltage, fill factor and power conversion efficiency were found to be 3.2 mA/cm-2, 337 mV, 37.9 and 0.45%, respectively. The observed performance clearly indicates that the investigated device structure could be a promising candidate for high-performance low-cost new-generation photovoltaic diodes.

  1. Bi-layer Channel AZO/ZnO Thin Film Transistors Fabricated by Atomic Layer Deposition Technique.

    Science.gov (United States)

    Li, Huijin; Han, Dedong; Liu, Liqiao; Dong, Junchen; Cui, Guodong; Zhang, Shengdong; Zhang, Xing; Wang, Yi

    2017-12-01

    This letter demonstrates bi-layer channel Al-doped ZnO/ZnO thin film transistors (AZO/ZnO TFTs) via atomic layer deposition process at a relatively low temperature. The effects of annealing in oxygen atmosphere at different temperatures have also been investigated. The ALD bi-layer channel AZO/ZnO TFTs annealed in dry O2 at 300 °C exhibit a low leakage current of 2.5 × 10(-13)A, I on/I off ratio of 1.4 × 10(7), subthreshold swing (SS) of 0.23 V/decade, and high transmittance. The enhanced performance obtained from the bi-layer channel AZO/ZnO TFT devices is explained by the inserted AZO front channel layer playing the role of the mobility booster.

  2. Bi-layer Channel AZO/ZnO Thin Film Transistors Fabricated by Atomic Layer Deposition Technique

    Science.gov (United States)

    Li, Huijin; Han, Dedong; Liu, Liqiao; Dong, Junchen; Cui, Guodong; Zhang, Shengdong; Zhang, Xing; Wang, Yi

    2017-03-01

    This letter demonstrates bi-layer channel Al-doped ZnO/ZnO thin film transistors (AZO/ZnO TFTs) via atomic layer deposition process at a relatively low temperature. The effects of annealing in oxygen atmosphere at different temperatures have also been investigated. The ALD bi-layer channel AZO/ZnO TFTs annealed in dry O2 at 300 °C exhibit a low leakage current of 2.5 × 10-13A, I on/ I off ratio of 1.4 × 107, subthreshold swing (SS) of 0.23 V/decade, and high transmittance. The enhanced performance obtained from the bi-layer channel AZO/ZnO TFT devices is explained by the inserted AZO front channel layer playing the role of the mobility booster.

  3. Technique for the estimation of surface temperatures from embedded temperature sensing for rapid, high energy surface deposition.

    Energy Technology Data Exchange (ETDEWEB)

    Watkins, Tyson R.; Schunk, Peter Randall; Roberts, Scott Alan

    2014-07-01

    Temperature histories on the surface of a body that has been subjected to a rapid, highenergy surface deposition process can be di cult to determine, especially if it is impossible to directly observe the surface or attach a temperature sensor to it. In this report, we explore two methods for estimating the temperature history of the surface through the use of a sensor embedded within the body very near to the surface. First, the maximum sensor temperature is directly correlated with the peak surface temperature. However, it is observed that the sensor data is both delayed in time and greatly attenuated in magnitude, making this approach unfeasible. Secondly, we propose an algorithm that involves tting the solution to a one-dimensional instantaneous energy solution problem to both the sensor data and to the results of a one-dimensional CVFEM code. This algorithm is shown to be able to estimate the surface temperature 20 C.

  4. The effect of oxygen flow rate on refractive index of aluminum oxide film deposited by electron beam evaporation technique

    Directory of Open Access Journals (Sweden)

    R Shakouri

    2016-02-01

    Full Text Available The effects of oxygen flow rate on refractive index of aluminum oxide film have been investigated. The Al2O3 films are deposited by electron beam on glass substrate at different oxygen flow rates. The substrate was heated to reach  and the temperature was constant during the thin film growth. The transmittance spectrum of samples was recorded in the wavelength 400-800 nm.  Then, using the maxima and minima of transmittance the refractive index and the extinction coefficient of samples were determined. It has been found that if we reduce the oxygen flow, while the evaporation rate is kept constant, the refractive index of Al2O3 films increases. On the other hand, reduced oxygen pressure causes the Al2O3 films to have some absorption.

  5. Optical and structural properties of ZnO hexagonal rods prepared by thermal chemical vapor deposition technique

    Directory of Open Access Journals (Sweden)

    A Reyhani

    2014-11-01

    Full Text Available In this research, ZnO nanostructure hexagonal pyramid rods with high optical and structural quality were synthesized by the simple thermal chemical vapor deposition of Zn powder without a metal catalyst. Surface morphologies were characterized by scanning electron microscopy (SEM. XRD analyses demonstrated that ZnO hexagonal pyramid rods had a wurtzite structure with the orientation of (002. Investigation of optical properties of samples by photoluminescence spectrum exhibited a sharp UV emission peak at 380nm. The quality and composition of the ZnO pyramid rods were characterized using the Fourier transform infrared spectrum (FTIR at room temperature. In addition, the growth mechanism of ZnO hexagonal rods is also briefly discussed.

  6. Use of a novel double uterine deposition artificial insemination technique using low concentrations of sperm in pigs.

    Science.gov (United States)

    Mozo-Martín, R; Gil, L; Gómez-Rincón, C F; Dahmani, Y; García-Tomás, M; Úbeda, J L; Grandía, J

    2012-07-01

    Currently, the three most important non-surgical artificial insemination systems used in pigs are the conventional, the post-cervical (IUI), and the deep-intrauterine (DIUI) methods. In this study, a new system, termed double uterine deposition insemination (DUDI), which combines aspects of both IUI and DIUI, was evaluated. This method used a thinner, shorter and more flexible catheter than those normally used for DIUI and resulted in the deposition of semen post-cervically, approximately half-way along the uterine horn, thus potentially by-passing the threat of 'unilateral' insemination or pregnancy when using sperm of low concentration. The experiment was carried out over 8 weeks on a group of 166 sows, which were divided into seven groups, inseminated with semen of varying concentration, using the conventional system (control group) or by DUDI. There were no significant differences in fertility at day 35 post-insemination between the controls and the various DUDI sub-groups. Only sows inseminated with 500 million viable spermatozoa in a total of 30 mL of fluid using the DUDI system demonstrated decreased total litter sizes when compared to conventional insemination (Pinsemination normally uses 2.5-3.5 billion sperm, the findings of this study suggest that DUDI can be used under 'field' conditions with sperm concentrations as low as 750 million spermatozoa in 50-30 mL without any detrimental effect on fertility or litter size. DUDI may provide a viable, robust alternative to IUI and DIUI, and has the potential to become incorporated into on-farm insemination systems.

  7. Evaluating the Effect of Surface Roughness on Titanium Dioxide Nanoparticle Deposition using a Combined Quartz Crystal Microbalance with Dissipation (QCM-D) and Generalized Ellipsometry (GE) Technique

    Science.gov (United States)

    Kananizadeh, N.; Lee, J.; Rodenhausen, K. B.; Sekora, D.; Schubert, M.; Schubert, E.; Bartelt-Hunt, S.; Li, Y.

    2016-12-01

    Quantification and characterization of nanoparticles in soils and sediments are very challenging because they will interact not only with soil-water chemistry but also with highly heterogeneous soil and sediment surfaces. In this work, we measured the interaction of Titanium dioxide nanoparticles (nTiO2), the most extensively manufactured engineered materials, with engineered rough surfaces under varied ionic strength conditions. Innovative three-dimensional Silicon nanostructured surfaces, referred to here as slanted columnar thin films (SCTFs), were used to generate surface roughness with controlled heights of 50nm, 100nm, and 200nm. Using atomic layer deposition technique (ALD), surfaces of SCTF were coated with either silicon dioxide or aluminum oxides to represent the most abundant silica aquifer materials and metal oxide impurities, respectively. The interaction between nTiO2 and model rough surfaces was measured using quartz crystal microbalance with dissipation monitoring (QCM-D). The data were analyzed using a model that couples the viscoelastic effect with the surface roughness effect. No nTiO2 deposition was observed on neither flat nor rough silicon dioxide surfaces under ionic strength ranged from 0 to 100 mM NaCl. On the other hand, the deposition of nTiO2 on the aluminum oxides coated surfaces increased as the height of roughness increased. In parallel with QCM-D, a Generalized Ellipsometry (GE) was used to measure the mass of deposited nTiO2. The combination of QCM-D and GE revealed that the properties (i.e. porosity and rigidness) of attached nTiO2 layer on the QCM-D surfaces were dependent on ionic strength and surface roughness.

  8. Characterization of the Micro-Orifice Uniform Deposit Impactor-droplet freezing technique (MOUDI-DFT) for size-resolved quantitative measurements of ice nuclei

    Science.gov (United States)

    Mason, Ryan; Si, Meng; Li, Jixiao; Huffman, J. Alex; McCluskey, Christina; Levin, Ezra; Irish, Victoria; Chou, Cédric; Hill, Thomas; Ladino, Luis; Yakobi, Jacqueline; Schiller, Corinne; Abbatt, Jon; DeMott, Paul; Bertram, Allan

    2014-05-01

    Ice formation within a cloud system can significantly modify its lifetime and radiative forcing. Many current instruments for measuring atmospheric concentrations of ice nuclei (IN) are not capable of providing size-resolved information. Such knowledge is useful in identifying the sources of IN and predicting their transport in the atmosphere. Furthermore, those that use size-discrimination to identify IN typically exclude particles with an aerodynamic diameter greater than 2.5 μm from analysis. Several studies have indicated this may be an important size regime for IN, particularly with those activating at warmer temperatures. The recently developed Micro-Orifice Uniform Deposit Impactor-droplet freezing technique (MOUDI-DFT) addresses these limitations through combining sample collection by a model of cascade impactor with an established immersion freezing apparatus. Here we present a characterization of the MOUDI-DFT and the development of a modified technique which address experimental uncertainties arising from sample deposit inhomogeneity and the droplet freezing method. An intercomparison with a continuous-flow diffusion chamber (CFDC) was performed. We also show preliminary results from a campaign undertaken in a remote coastal region of western Canada. Correlations between atmospheric IN concentrations and the abundance of suspended submicron and supermicron particles, biological aerosols, carbonaceous aerosols, and prevailing meteorological conditions were investigated.

  9. Synthesis and self-assembly of dumbbell shaped ZnO sub-micron structures using low temperature chemical bath deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Borade, P. [National Centre for Nanoscience and Nanotechnology, University of Mumbai, Kalina Campus, Santacruz (E), Mumbai 400098 (India); Joshi, K.U. [Anton-Paar India Pvt. Ltd., Thane (W), 400607 (India); Gokarna, A.; Lerondel, G. [Laboratoire de Nanotechnologie et D' Instrumentation Optique, Institut Charles Delaunay, CNRS UMR 6281, Université de Technologie de Troyes, 12 Rue Marie Curie, BP 2060, 10010 Troyes (France); Walke, P. [National Centre for Nanoscience and Nanotechnology, University of Mumbai, Kalina Campus, Santacruz (E), Mumbai 400098 (India); Late, D. [National Chemical Laboratory (NCL), Pune 400027 (India); Jejurikar, S.M., E-mail: jejusuhas@gmail.com [National Centre for Nanoscience and Nanotechnology, University of Mumbai, Kalina Campus, Santacruz (E), Mumbai 400098 (India)

    2016-02-01

    We report well dispersed horizontal growth of ZnO sub-micron structures using simplest technique ever known i.e. chemical bath deposition (CBD). A set of samples were prepared under two different cases A) dumbbell shaped ZnO grown in CBD bath and B) tubular ZnO structures evolved from dumbbell shaped structures by dissolution mechanism. Single phase wurtzite ZnO formation is confirmed using X-ray diffraction (XRD) technique in both cases. From the morphological investigations performed using scanning electron microscopy (SEM), sample prepared under case A indicate formation of hex bit tool (HBT) shaped ZnO crystals, which observed to self-organize to form dumbbell structures. Further these microstructures are then converted into tubular structures as a fragment of post CBD process. The possible mechanism responsible for the self-assembly of HBT units to form dumbbell structures is discussed. Observed free excitonic peak located at 370 nm in photoluminescence (PL) spectra recorded at 18 K indicate that the micro/nanostructures synthesized using CBD are of high optical quality. - Highlights: • Controlled growth of Dumbbell shaped ZnO using Chemical Bath Deposition (CBD). • Growth mechanism of dumbbell shaped ZnO by self-assembling was discussed. • Quick Transformation of ZnO dumbbell structures in to tubular structures by dissolution. • Sharp UV Emission at 370 nm from both dumbbell and tubular structures.

  10. Deposition of TiN coatings using ACPVD technique on AM60 alloy; Recubrimientos de TiN depositados mediante ACPVD sobre aleaciones de magnesio AM60

    Energy Technology Data Exchange (ETDEWEB)

    Pichel, M.; Candela, N.; Barea, R.; Conejero, G.; Carsi, M.

    2013-06-01

    Magnesium alloys are reaching special interest due to their good specific properties, low cost and good manufacturing properties. However, their low hardness, wear and corrosion resistance limit their applications in certain sectors of industry. These drawbacks can be solved by applying hard ceramic coatings, such as nitrides or metal carbides. TiN is one of the most used coatings due to its high adhesion, hardness, low coefficient of friction and chemical stability. Physical vapor deposition by cathodic arc CAPVD, is a versatile technique, which uses low temperatures and high ionization energies, generating homogeneous coatings. To achieve coatings with high quality, a careful control of the manufacturing parameters is required, such as bias voltage, gas flow or intensity. This paper focuses on magnesium alloys, AM60, coated with TiN using physical vapor deposition cathodic arc technique (CAPVD) at different intensity values (40A and 100A) and surface preparation (grinding up to 4000 grit and polished to 3{mu}m). It was included a final condition with an intermediate Al film. The samples were characterized by X-ray diffraction, roughness, optical microscopy and scanning electron. (Author) 28 refs.

  11. The effect of δ-doping and modulation-doping on Si-doped high Al content n-AlxGa1-xN grown by MOCVD

    Institute of Scientific and Technical Information of China (English)

    Zhu Shaoxin; Yan Jianchang; Zeng Jianping; Zhang Ning; Si Zhao; Dong Peng; Li Jinmin

    2013-01-01

    The effect of periodic delta-doping and modulation-doping on high Al content n-AlxGa1-xN (x =0.55) epilayers grown by MOCVD has been investigated.Measured by XRD,AFM,contactless sheet resistance,and Hall-effect tests,δ-doped and modulation-doped n-AlxGa1-xN have better crystal quality,surface morphology and electrical properties as compared with uniformly-doped n-AlxGa1-xN.These improvements are attributed to the SiNx growth mask induced by δ-doping layers and the dislocation-blocking effect induced by both growth techniques.In addition,due to the broadened doping profile ascribed to enhanced dopant diffusion at high growth temperatures (1150 ℃) of n-Al0.55Ga0.45N,modulation-doped n-Al0.55Ga0.45N has similar properties as δ-doped n-Al0.55Ga0.45N.

  12. Stability increase of fuel clad with zirconium oxynitride thin film by metalorganic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Jee, Seung Hyun [Department of Materials Science and Engineering, Yonsei University, 134 Sinchon Dong, Seoul 120-749 (Korea, Republic of); Materials Research and Education Center, Dept. of Mechanical Engineering, Auburn University, 275 Wilmore Labs, AL 36849-5341 (United States); Kim, Jun Hwan; Baek, Jong Hyuk [Recycled Fuel Development Division, Korea Atomic Energy Research Institute, P.O. Box 105, Yuseong, Daejeon, 305-600 (Korea, Republic of); Kim, Dong-Joo [Materials Research and Education Center, Dept. of Mechanical Engineering, Auburn University, 275 Wilmore Labs, AL 36849-5341 (United States); Kang, Seong Sik [Regulatory Research Division, Korea Institute of Nuclear Safety, 19, Guseong-Dong, Yuseong-Gu, Daejeon, 305-338 (Korea, Republic of); Yoon, Young Soo, E-mail: yoonys@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, 134 Sinchon Dong, Seoul 120-749 (Korea, Republic of)

    2012-06-01

    A zirconium oxynitride (ZON) thin film was deposited onto HT9 steel as a cladding material by a metalorganic chemical vapor deposition (MOCVD) in order to prevent a fuel-clad chemical interaction (FCCI) between a U-10 wt% Zr metal fuel and a clad material. X-ray diffraction spectrums indicated that the mixture of structures of zirconium nitride, oxide and carbide in the MOCVD grown ZON thin films. Also, typical equiaxial grain structures were found in plane and cross sectional images of the as-deposited ZON thin films with a thickness range of 250-500 nm. A depth profile using auger electron microscopy revealed that carbon and oxygen atoms were decreased in the ZON thin film deposited with hydrogen gas flow. Diffusion couple tests at 800 Degree-Sign C for 25 hours showed that the as-deposited ZON thin films had low carbon and oxygen content, confirmed by the Energy Dispersive X-ray Spectroscopy, which showed a barrier behavior for FCCI between the metal fuel and the clad. This result suggested that ZON thin film cladding by MOCVD, even with the thickness below the micro-meter level, has a high possibility as an effective FCCI barrier. - Highlights: Black-Right-Pointing-Pointer Zirconium oxynitride (ZON) deposited by metal organic chemical vapor deposition. Black-Right-Pointing-Pointer Prevention of fuel cladding chemical interaction (FCCI) investigated. Black-Right-Pointing-Pointer Interfusion reduced by between metal fuel (U-10 wt% Zr) and a HT9 cladding material. Black-Right-Pointing-Pointer Hydrogenation of the ZON during growth improved the FCCI barrier performance.

  13. Growth and properties of hafnicone and HfO(2)/hafnicone nanolaminate and alloy films using molecular layer deposition techniques.

    Science.gov (United States)

    Lee, Byoung H; Anderson, Virginia R; George, Steven M

    2014-10-08

    Molecular layer deposition (MLD) of the hafnium alkoxide polymer known as "hafnicone" was grown using sequential exposures of tetrakis(dimethylamido) hafnium (TDMAH) and ethylene glycol (EG) as the reactants. In situ quartz crystal microbalance (QCM) experiments demonstrated self-limiting reactions and linear growth versus the number of TDMAH/EG reaction cycles. Ex situ X-ray reflectivity (XRR) analysis confirmed linear growth and measured the density of the hafnicone films. The hafnicone growth rates were temperature-dependent and decreased from 1.2 Å per cycle at 105 °C to 0.4 Å per cycle at 205 °C. The measured density was ∼3.0 g/cm(3) for the hafnicone films at all temperatures. Transmission electron microscopy images revealed very uniform and conformal hafnicone films. The XRR studies also showed that the hafnicone films were very stable with time. Nanoindentation measurements determined that the elastic modulus and hardness of the hafnicone films were 47 ± 2 and 2.6 ± 0.2 GPa, respectively. HfO2/hafnicone nanolaminate films also were fabricated using HfO2 atomic layer deposition (ALD) and hafnicone MLD at 145 °C. The in situ QCM measurements revealed that HfO2 ALD nucleation on the hafnicone MLD surface required at least 18 TDMAH/H2O cycles. Hafnicone alloys were also fabricated by combining HfO2 ALD and hafnicone MLD at 145 °C. The composition of the hafnicone alloy was varied by adjusting the relative number of TDMAH/H2O ALD cycles and TDMAH/EG MLD cycles in the reaction sequence. The electron density changed continuously from 8.2 × 10(23) e(-)/cm(3) for pure hafnicone MLD films to 2.4 × 10(24) e(-)/cm(3) for pure HfO2 ALD films. These hafnicone films and the HfO2/hafnicone nanolaminates and alloys may be useful for flexible thin-film devices.

  14. Deposition of duplex Al 2O 3/aluminum coatings on steel using a combined technique of arc spraying and plasma electrolytic oxidation

    Science.gov (United States)

    Gu, Weichao; Shen, Dejiu; Wang, Yulin; Chen, Guangliang; Feng, Wenran; Zhang, Guling; Fan, Songhua; Liu, Chizi; Yang, Size

    2006-02-01

    Plasma electrolytic oxidation (PEO) is a cost-effective technique that can be used to prepare ceramic coatings on metals such as Ti, Al, Mg, Nb, etc., and their alloys, but this promising technique cannot be used to modify the surface properties of steels, which are the most widely used materials in engineering. In order to prepare metallurgically bonded ceramic coatings on steels, a combined technique of arc spraying and plasma electrolytic oxidation (PEO) was adopted. In this work, metallurgically bonded ceramic coatings on steels were obtained using this method. We firstly prepared aluminum coatings on steels by arc spraying, and then obtained the metallurgically bonded ceramic coatings on aluminum coatings by PEO. The characteristics of duplex coatings were analyzed by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The corrosion and wear resistance of the ceramic coatings were also studied. The results show that, duplex Al 2O 3/aluminum coatings have been deposited on steel substrate after the combined treatment. The ceramic coatings are mainly composed of α-Al 2O 3, γ-Al 2O 3, θ-Al 2O 3 and some amorphous phase. The duplex coatings show favorable corrosion and wear resistance properties. The investigations indicate that the combination of arc spraying and plasma electrolytic oxidation proves a promising technique for surface modification of steels for protective purposes.

  15. 3D granular deposits on rock avalanches: can the application of different operators and filtering techniques improve our understanding of the phenomena?

    Science.gov (United States)

    Longchamp, Celine; Abellan, Antonio; Derron, Marc-Henri; Jaboyedoff, Michel

    2014-05-01

    Rock avalanches are catastrophic events involving a great volume of material (>106 m3). The flowing mass can reach velocities up to ten meters per second and travel long distances on the order of kilometres, covering an area over 0.1 km2. These extremely destructive and uncontrollable events are very unusual in nature and the use of analogue modelling is of great importance in the understanding of the behaviour of such events. The main objective of this research is to analyse rock avalanche dynamics by means of a detailed structural analysis of the features observed in the avalanche. Data used for this research consist on 3D measurements of mass movements of different magnitudes, from decimetre level scale laboratory experiments to well-studied rock avalanches of several square kilometres magnitude, as follows: (1) Laboratory experiments are performed on a tilting plane in which a well-defined granular material is released, chute down a slope, propagate and finally stop on a horizontal surface. The deposits are then scanned by a 3D digitizer (Konica Minolta vivid 9i micro-LiDAR) in order to get a 3D geometrical model of the mass. Different grainsize (115, 545 and 2605 μm) and substratum roughness (simulate by aluminium and sandpapers with grainsize from 16 to 425 μm) were used in order to understand their influence on the motion of a granular mass; (2) A well know rock avalanche deposit, the Frank slide (Alberta, Canada), was also analysed from the available 3D LiDAR dataset. This deposit consists in a 30× 106 m3 rockslide-avalanche of Palaeozoic limestone that was widely studied by several authors before (e.g. Cruden and Hungr, 1986, Cruden and Krahn, 1973, etc). In order to better understand the fault and folding structures presented in the rock avalanche deposits, we applied a series of linear and non-linear Matlab operators and filtering techniques to the 3D datasets, including differences derivatives ('diff'), numerical gradient ('gradient'), discrete

  16. Review on dust depositing on PV module and cleaning techniques%光伏面板积灰及除尘清洁技术研究综述

    Institute of Scientific and Technical Information of China (English)

    鲍官军; 张林威; 蔡世波; 蒋建东; 胥芳; 贾桂红

    2013-01-01

    Aiming at the problems of PV module dust depositing,affecting factors,the reducing effect on conversion efficiency,the related researches were overviewed and the main researching aspects in the future were proposed.The source and components of dust were introduced.Research documents about the PV module dust depositing process and the PV efficiency decline or solar radiation transmittance decline caused by dust depositing were emphasized and reviewed.The main factors of module angle,wind speed and orientation,dust property,environment humidity,which will influence the dust depositing,PV efficiency and solar radiation transmittance,were analyzed.The dust depositing model and its impacting model on PV efficency from the perspective of dust property,dust falling and raining were summarized.The commonly used PV module cleaning techniques,that is electrode screen dust mitigation and mechanical dust cleaning,were introduced.Finally,the shortages of present research were abstracted and the main research aspects in the future,such as the integrality of the dust depositing experiment,dust characteristics,dust depositing mechanism and PV panel cleaning techniques,were pointed out.%针对光伏面板积灰、影响因素、积灰对面板转换效率的降低效应等问题,综述分析了国内外相关研究成果,总结提出了今后研究的主要方向.介绍了灰尘的来源及组成,着重综述了国内外关于光伏面板积灰形成过程及积灰引起的面板输出效率降低或太阳辐射透过率降低等研究文献,分析了面板倾角、风速风向、灰尘性质、环境湿度等主要因素对光伏面板积灰的形成和面板效率/太阳辐射透过率的影响.总结了基于灰尘性质、降尘、降雨等因素建立的积灰模型及其对面板效率的影响模型.介绍了目前常用的光伏面板清洁技术:电帘除尘和机械除尘.最后,总结了目前研究中存在的不足,并指出了今后应进一步加强积灰实验完

  17. A Comparative Study of Three Different Chemical Vapor Deposition (CVD) Techniques of Carbon Nanotube Growth on Diamond Films

    Science.gov (United States)

    2013-01-01

    a,b , Paul N. Barnes c , Chakrapani V. Varanasi e , Jack Burke d , Bang -Hung Tsao d , and Sharmila M. Mukhopadhyay b a. Air Force Research...catalysts play a big role in the structure and properties of the resulting CNTs. The three different techniques compared here have two different approaches...catalysts at the interface suggests the silica nanolayer keeps them anchored and prevents them from migrating during CNT growth. Figure 5: Cross

  18. Coupling spectroscopic and chromatographic techniques for evaluation of the depositional history of hydrocarbons in a subtropical estuary.

    Science.gov (United States)

    Martins, César C; Doumer, Marta E; Gallice, Wellington C; Dauner, Ana Lúcia L; Cabral, Ana Caroline; Cardoso, Fernanda D; Dolci, Natiely N; Camargo, Luana M; Ferreira, Paulo A L; Figueira, Rubens C L; Mangrich, Antonio S

    2015-10-01

    Spectroscopic and chromatographic techniques can be used together to evaluate hydrocarbon inputs to coastal environments such as the Paranaguá estuarine system (PES), located in the SW Atlantic, Brazil. Historical inputs of aliphatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) were analyzed using two sediment cores from the PES. The AHs were related to the presence of biogenic organic matter and degraded oil residues. The PAHs were associated with mixed sources. The highest hydrocarbon concentrations were related to oil spills, while relatively low levels could be attributed to the decrease in oil usage during the global oil crisis. The results of electron paramagnetic resonance were in agreement with the absolute AHs and PAHs concentrations measured by chromatographic techniques, while near-infrared spectroscopy results were consistent with unresolved complex mixture (UCM)/total n-alkanes ratios. These findings suggest that the use of a combination of techniques can increase the accuracy of assessment of contamination in sediments. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Electrical properties of GaAs metal-oxide-semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal-organic vapor deposition/atomic layer deposition hybrid system

    Science.gov (United States)

    Aoki, Takeshi; Fukuhara, Noboru; Osada, Takenori; Sazawa, Hiroyuki; Hata, Masahiko; Inoue, Takayuki

    2015-08-01

    This paper presents a compressive study on the fabrication and optimization of GaAs metal-oxide-semiconductor (MOS) structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD), with an AlN interfacial passivation layer prepared in situ via metal-organic chemical vapor deposition (MOCVD). The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA) conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance-voltage (C-V) characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit) near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm-2 eV-1. Using a (111)A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  20. Electrical properties of GaAs metal–oxide–semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal–organic vapor deposition/atomic layer deposition hybrid system

    Directory of Open Access Journals (Sweden)

    Takeshi Aoki

    2015-08-01

    Full Text Available This paper presents a compressive study on the fabrication and optimization of GaAs metal–oxide–semiconductor (MOS structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD, with an AlN interfacial passivation layer prepared in situ via metal–organic chemical vapor deposition (MOCVD. The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance–voltage (C–V characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm−2 eV−1. Using a (111A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  1. Atmospheric deposition of rare earth elements in Albania studied by the moss biomonitoring technique, neutron activation analysis and GIS technology.

    Science.gov (United States)

    Allajbeu, Sh; Yushin, N S; Qarri, F; Duliu, O G; Lazo, P; Frontasyeva, M V

    2016-07-01

    Rare earth elements (REEs) are typically conservative elements that are scarcely derived from anthropogenic sources. The mobilization of REEs in the environment requires the monitoring of these elements in environmental matrices, in which they are present at trace level. The determination of 11 REEs in carpet-forming moss species (Hypnum cupressiforme) collected from 44 sampling sites over the whole territory of the country were done by using epithermal neutron activation analysis (ENAA) at IBR-2 fast pulsed reactor in Dubna. This paper is focused on REEs (lanthanides) and Sc. Fe as typical consistent element and Th that appeared good correlations between the elements of lanthanides are included in this paper. Th, Sc, and REEs were never previously determined in the air deposition of Albania. Descriptive statistics were used for data treatment using MINITAB 17 software package. The median values of the elements under investigation were compared with those of the neighboring countries such as Bulgaria, Macedonia, Romania, and Serbia, as well as Norway which is selected as a clean area. Geographical distribution maps of the elements over the sampled territory were constructed using geographic information system (GIS) technology. Geochemical behavior of REEs in moss samples has been studied by using the ternary diagram of Sc-La-Th, Spider diagrams and multivariate analysis. It was revealed that the accumulation of REEs in current mosses is associated with the wind-blowing metal-enriched soils that is pointed out as the main emitting factor of the elements under investigation.

  2. RETRACTED: Ammonia-free method for synthesis of CdS nanocrystalline thin films through chemical bath deposition technique

    Science.gov (United States)

    Karimi, M.; Rabiee, M.; Moztarzadeh, F.; Bodaghi, M.; Tahriri, M.

    2009-11-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief of Solid State Communications as the authors have plagiarized part of a paper that has also appeared in Current Applied Physics: Controlled synthesis, characterization and optical properties of CdS nanocrystalline thin films via chemical bath deposition (CBD) route Meysam Karimi, Mohammad Rabiee, Fathollah Moztarzadeh, Mohammadreza Tahriri and Masoud Bodaghi; Curr. Appl. Phys., 9 (2009) 1263-1268, doi: 10.1016/j.cap.2009.02.006. One of the conditions of submission of a paper for publication is that authors declare explicitly that their work is original and has not appeared in a publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

  3. Optimization of parameters by Taguchi method for controlling purity of carbon nanotubes in chemical vapour deposition technique.

    Science.gov (United States)

    Dasgupta, K; Sen, D; Mazumder, S; Basak, C B; Joshi, J B; Banerjee, S

    2010-06-01

    The process parameters (viz. temperature of synthesis, type of catalyst, concentration of catalyst and type of catalyst-support material) for controlling purity of carbon nanotubes synthesized by catalytic chemical vapour deposition of acetylene have been optimized by analyzing the experimental results using Taguchi method. It has been observed that the catalyst-support material has the maximum (59.4%) and the temperature of synthesis has the minimum effect (2.1%) on purity of the nanotubes. At optimum condition (15% ferrocene supported on carbon black at the synthesis temperature of 700 degrees C) the purity of nanotubes was found out to be 96.2% with yield of 1900%. Thermogravimetry has been used to assess purity of nanotubes. These nantubes have been further characterized by scanning electron microscopy, transmission electron microscopy and Raman Spectroscopy. Small angle neutron scattering has been used to find out their average inner and outer diameter using an appropriate model. The nanotubes are well crystallized but with wide range of diameter varying between 20-150 nm.

  4. Fabricating a pearl/PLGA composite scaffold by the low-temperature deposition manufacturing technique for bone tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Xu Mingen; Li Yanlei; Suo Hairui; Wang Qiujun; Ge Yakun; Xu Ying [Center Laboratory of Biomanufacture and Tissue Engineering, Hang Zhou Dianzi University, Hangzhou 310018 (China); Yan Yongnian; Liu Li, E-mail: xumingen@tsinghua.edu.c, E-mail: xumingen@hdu.edu.c [Key Laboratory for Advanced Materials Processing Technology, Ministry of Education and Center of Organ Manufacturing, Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2010-06-15

    Here we developed a composite scaffold of pearl/poly(lactic-co-glycolic acid) (pearl/PLGA) utilizing the low-temperature deposition manufacturing (LDM). LDM makes it possible to fabricate scaffolds with designed microstructure and macrostructure, while keeping the bioactivity of biomaterials by working at a low temperature. Process optimization was carried out to fabricate a mixture of pearl powder, PLGA and 1,4-dioxane with the designed hierarchical structures, and freeze-dried at a temperature of -40 deg. C. Scaffolds with square and designated bone shape were fabricated by following the 3D model. Marrow stem cells (MSCs) were seeded on the pearl/PLGA scaffold and then cultured in a rotating cell culture system. The adhesion, proliferation and differentiation of MSCs into osteoblasts were determined using scanning electronic microscopy, WST-1 assay, alkaline phosphatase activity assay, immunofluorescence staining and real-time reverse transcription polymerase chain reaction. The results showed that the composite scaffold had high porosity (81.98 +- 3.75%), proper pore size (micropores: <10 mum; macropore: 495 +- 54 mum) and mechanical property (compressive strength: 0.81 +- 0.04 MPa; elastic modulus: 23.14 +- 0.75 MPa). The pearl/PLGA scaffolds exhibited better biocompatibility and osteoconductivity compared with the tricalcium phosphate/PLGA scaffold. All these results indicate that the pearl/PLGA scaffolds fulfill the basic requirements of bone tissue engineering scaffold.

  5. Q-factor of (In,Ga)N containing III-nitride microcavity grown by multiple deposition techniques

    Energy Technology Data Exchange (ETDEWEB)

    Gačević, Ž., E-mail: gacevic@isom.upm.es; Calleja, E. [Universidad Politécnica de Madrid, Avda. Complutense s/n, 28040 Madrid (Spain); Rossbach, G.; Butté, R.; Glauser, M.; Levrat, J.; Cosendey, G.; Carlin, J.-F.; Grandjean, N. [Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Réveret, F. [Institut Pascal, UMR 6602 UBP/CNRS, Clermont Université, 24 Avenue des Landais, F-63177 Aubière Cedex (France)

    2013-12-21

    A 3λ/2 (In,Ga)N/GaN resonant cavity, designed for ∼415 nm operation, is grown by molecular beam epitaxy and is sandwiched between a 39.5-period (In,Al)N/GaN distributed Bragg reflector (DBR), grown on c-plane GaN-on-sapphire pseudo-substrate by metal-organic vapor phase epitaxy and an 8-period SiO{sub 2}/ZrO{sub 2} DBR, deposited by electron beam evaporation. Optical characterization reveals an improvement in the cavity emission spectral purity of approximately one order of magnitude due to resonance effects. The combination of spectrophotometric and micro-reflectivity measurements confirms the strong quality (Q)-factor dependence on the excitation spot size. We derive simple analytical formulas to estimate leak and residual absorption losses and propose a simple approach to model the Q-factor and to give a quantitative estimation of the weight of cavity disorder. The model is in good agreement with both transfer-matrix simulation and the experimental findings. We point out that the realization of high Q-factor (In,Ga)N containing microcavities on GaN pseudo-substrates is likely to be limited by the cavity disorder.

  6. Monolithic integration of an InGaAsP InP strained DFB laser and an electroabsorption modulator by ultra-low-pressure selective-area-growth MOCVD

    Science.gov (United States)

    Zhao, Q.; Pan, J. Q.; Zhou, F.; Wang, B. J.; Wang, L. F.; Wang, W.

    2005-06-01

    The design and basic characteristics of a strained InGaAsP-InP multiple-quantum-well (MQW) DFB laser monolithically integrated with an electroabsorption modulator (EAM) by ultra-low-pressure (22 mbar) selective-area-growth (SAG) MOCVD are presented. A fundamental study of the controllability and the applicability of band-gap energy by using the SAG method is performed. A large band-gap photoluminescence wavelength shift of 88 nm was obtained with a small mask width variation (0-30 µm). The technique is then applied to fabricate a high performance strained MQW EAM integrated with a DFB laser. The threshold current of 26 mA at CW operation of the device with DFB laser length of 300 µm and EAM length of 150 µm has been realized at a modulator bias of 0 V. The devices also exhibit 15 dB on/off ratio at an applied bias voltage of 5 V.

  7. Growth and photoluminescence of Si-SiOx nanowires by catalyst-free chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Yue [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); Luo, Ruiying, E-mail: ryluo@buaa.edu.cn [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China); School of Materials Science and Engineering, Shanxi University of Technology, Hanzhong 723000 (China); Shang, Haidong [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China)

    2016-04-15

    Graphical abstract: - Highlights: • The Si-SiOx NWs were successfully synthesized via a one-step catalyst-free CVD method using TEOS as the precursor. • The Si-SiOx NWs had a core–shell structure with Si as the inner crystalline cores and SiOx as the outer amorphous layer. • The formation of Si-SiOx NWs was implemented by the non-classical crystallization mechanism. • The Si-SiOx NWs spontaneously self-assembled from the building block of charged nanoparticles. • The Si-SiOx NWs showed their potential applications in UV emission and visible light emission devices. - Abstract: We developed a one-step catalyst-free chemical vapor deposition process to synthesize Si-SiOx nanowires using tetraethoxysilane as the precursor. Observations using scanning electron microscopy showed that the Si-SiOx nanowires were 20–50 nm in diameter and tens of microns in length. The high-resolution transmission electron microscope analysis and X-ray diffraction demonstrated that the nanowires consisted of crystal silicon and amorphous SiOx. The Si and O with an atomic ratio of the Si-SiOx NWs were 1:1.2 according to the energy dispersion X-ray spectroscope. A systematic study on the effect of the growth conditions, such as reaction temperature, the reaction time, and the TEOS vapor flow rate was performed. The formation of Si-SiOx nanowires was implemented by the non-classical crystallization mechanism. The charged nanoparticles acting as building blocks self-assembled into nanowires. The photoluminescence measurements were carried out and showed that the Si-SiOx nanowires emitted stable ultraviolet and green luminescence excited by ultraviolet light.

  8. A field technique for rapid lithological discrimination and ore mineral identification: Results from Mamandur Polymetal Deposit, India

    Indian Academy of Sciences (India)

    D Ramakrishnan; M Nithya; K D Singh; Rishikesh Bharti

    2013-02-01

    This work illustrates the efficiency of field spectroscopy for rapid identification of minerals in ore body, alteration zone and host rocks. The adopted procedure involves collection of field spectra, their processing for noise, spectral matching and spectral un-mixing with selected library end-members. Average weighted spectral similarity and effective peak matching techniques were used to draw end-members from library. Constrained linear mixture modelling technique was used to convolve end-member spectra. Linear mixture model was optimized based on root mean square error between field- and modelled-spectra. Estimated minerals and their abundances were subsequently compared with conventional procedures such as petrography, X-ray diffraction and X-ray fluorescence for accuracy assessment. The mineralized zone is found to contain azurite, galena, chalcopyrite, bornite, molybdenite, marcacite, gahnite, hematite, goethite, anglesite and malachite. The alteration zone contains chlorite, kaolinite, actinolite and mica. These mineral assemblages correlate well with the petrographic measurements (2 = 0.89). Subsequently, the bulk chemistry of field samples was compared with spectroscopically derived cumulative weighted mineral chemistry and found to correlate well (2 = 0.91–0.98) at excellent statistical significance levels (90–99%). From this study, it is evident that field spectroscopy can be effectively used for rapid mineral identification and abundance estimation.

  9. Dating Magmatic Hornblende and Biotite and Hydrothermal Sericite by Laser Probe Technique:Constraints on Genesis of Wangershan Gold Deposit, Eastern Shandong Province,China

    Institute of Scientific and Technical Information of China (English)

    Li Jianwei; Vasconcelos P M; Zhou M F; Duzgoren-Aydin N S

    2003-01-01

    The Wangershan gold deposit and spatially related Shangzhuang granite, eastern Shandong Province, have been precisely dated by 40 Ar/39 Ar laser incremental heating technique. Magmatic hornblende and biotite, collected from the Shangzhuang granites, yielded well-defined and reproducible plateau ages at 128. 1-127.5 and 124.4-124. 1 Ma (2σ), measuring the cooling ages of the intrusion at ca. 500 ℃ and 300-350 ℃, respectively. Hydrothermal sericite extracted from auriferous vein gave high-quality plateau ages between (120. 6±0.3) Ma and (120. 0±0. 4) Ma (2σ). Given the similarity of the closure temperature for argon diffusion (300-350 ℃ ) in the sericite mineral to the homogenization temperature of primary fluid inclusions in the quartz from gold ores, and the intergrowth of sericite with native gold, present 40Ar/39 Ar sericite ages can be reliably interpreted in terms of the mineralization age for the Wangershan deposit. 40 Ar/39 Ar hornblende and biotite ages permit an estimate for the cooling rate of the Shangzhuang granite at about 50 ℃/Ma. There are abundant intermediate-mafic dikes in most gold camps of eastern Shandong, whose ages of formation have been previously constrained mainly at 121-119 Ma. The temporal association between the Shangzhuang granite, the Wangershan gold deposit, and the widespread dikes confirms that intrusive activity, gold mineralization, and dike emplacement in this region were broadly coeval, reflecting significant continental lithosphere thinning and resulting crustal extension of Early Cretaceous in eastern China.

  10. An investigation of localised surface plasmon resonance (LSPR) of Ag nanoparticles produced by pulsed laser deposition (PLD) technique

    Science.gov (United States)

    Gezgin, Serap Yiǧit; Kepceoǧlu, Abdullah; Kılıç, Hamdi Şükür

    2017-02-01

    Noble metal nano-structures such as Ag, Cu, Au are used commonly to increase power conversion efficiency of the solar cell by using their surface plasmons. The plasmonic metal nanoparticles of Ag among others that have strong LSPR in near UV range. They increase photon absorbance via embedding in the active semiconductor of the solar cell. Thin films of Ag are grown in the desired particle size and interparticle distance easily and at low cost by PLD technique. Ag nanoparticle thin films were grown on micro slide glass at 25-36 mJ laser pulse energies under by PLD using ns-Nd:YAG laser. The result of this work have been presented by carrying out UV-VIS and AFM analysis. It was concluded that a laser energy increases, the density and size of Ag-NPs arriving on the substrate increases, and the interparticle distance was decreases. Therefore, LSPR wavelength shifts towards to longer wavelength region.

  11. Investigations of the structural, morphological and electrical properties of multilayer ZnO/TiO2 thin films, deposited by sol-gel technique

    Science.gov (United States)

    Khan, M. I.; Bhatti, K. A.; Qindeel, Rabia; Bousiakou, Leda G.; Alonizan, Norah; Fazal-e-Aleem

    Investigations of the structural, morphological and electrical properties of multilayer ZnO/TiO2 thin films deposited by sol-gel technique on glass substrate. Sol-gel is a technique in which compound is dissolved in a liquid in order to bring it back as a solid in a controlled manner. TiO2 solution was obtained by dissolving 0.4 g of TiO2 nano powder in 5 ml ethanol and 5 ml diethylene glycol. ZnO solution was obtained by dissolving 0.88 g zinc acetate in 20 ml of 2-methoxyethanol. X-ray diffraction (XRD) (PW 3050/60 PANalytical X'Pert PRO diffractometer) results showed that the crystallinity is improved when the number of ZnO/TiO2 layers increased. Also it shows the three phases (rutile, anatase and brookite) of TiO2. Surface morphology measured by scanning electron microscopy (SEM) (Quanta 250 fei) revealed that Crakes are present on the surface of ZnO/TiO2 thin films which are decreased when the number of ZnO/TiO2 layers increased. Four point probe (KIETHLEY instrument) technique used to investigate the electrical properties of ZnO/TiO2 showed the average resistivity decreased by increasing the number of ZnO/TiO2 layers. These results indicated that the multilayer thin films improved the quality of film crystallinity and electrical properties as compared to single layer.

  12. Effect of complexing agent TEA: The structural, morphological, topographical and optical properties of Fe{sub x}S{sub x} nano thin films deposited by SILAR technique

    Energy Technology Data Exchange (ETDEWEB)

    Manikandan, K., E-mail: 1984manikandan@gmail.com [Department of Physics, Anna University BIT Campus, Tiruchirappalli 620 024, Tamilnadu (India); Mani, P. [Department of Physics, Anna University BIT Campus, Tiruchirappalli 620 024, Tamilnadu (India); Surendra Dilip, C. [Department of Chemistry, Anna University BIT Campus, Tiruchirappalli 620 024, Tamilnadu (India); Valli, S. [Department of Physics, M.I.E.T. Arts and Science College, Tiruchirappalli 620 007, Tamilnadu (India); Fermi Hilbert Inbaraj, P.; Joseph Prince, J. [Department of Physics, Anna University BIT Campus, Tiruchirappalli 620 024, Tamilnadu (India)

    2014-01-01

    Iron sulfide thin films (Fe{sub x}S{sub x}) (x = 0.05 M, 0.10 M, 0.15 M, 0.20 M and 0.25 M) were deposited by SILAR method from equimolar and equivolume aqueous solutions of ferrous nitrate and sodium sulfide with the addition of complexing agent TEA. The structural, morphological and optical characteristics of the films were derived from X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–vis spectral techniques. The mixed characteristics (crystalline and amorphous) of the deposited films and the increasing crystalline qualities with the concentrations were understood from the XRD analysis. The grain sizes and roughness of the films were decreases with the increasing concentration and also at the higher concentration films are shown by the same images presence of hexagonal like crystallite structure. The influence of complexing agent TEA on the surface roughness and morphological properties are confirmed by the atomic force microscope (AFM) results. The effect of increasing substrate concentration on the absorption and transmission measurements and its impact on the optical band-gap energy were enumerated from the UV–vis analysis.

  13. Development of graded Ni-YSZ composite coating on Alloy 690 by Pulsed Laser Deposition technique to reduce hazardous metallic nuclear waste inventory.

    Science.gov (United States)

    Sengupta, Pranesh; Rogalla, Detlef; Becker, Hans Werner; Dey, Gautam Kumar; Chakraborty, Sumit

    2011-08-15

    Alloy 690 based 'nuclear waste vitrification furnace' components degrade prematurely due to molten glass-alloy interactions at high temperatures and thereby increase the volume of metallic nuclear waste. In order to reduce the waste inventory, compositionally graded Ni-YSZ (Y(2)O(3) stabilized ZrO(2)) composite coating has been developed on Alloy 690 using Pulsed Laser Deposition technique. Five different thin-films starting with Ni80YSZ20 (Ni 80 wt%+YSZ 20 wt%), through Ni60YSZ40 (Ni 60 wt%+YSZ 40 wt%), Ni40YSZ60 (Ni 40 wt%+YSZ 60 wt%), Ni20YSZ80 (Ni 20 wt%+YSZ 80 wt%) and Ni0YSZ100 (Ni 0 wt%+YSZ 100 wt%), were deposited successively on Alloy 690 coupons. Detailed analyses of the thin-films identify them as homogeneous, uniform, pore free and crystalline in nature. A comparative study of coated and uncoated Alloy 690 coupons, exposed to sodium borosilicate melt at 1000°C for 1-6h suggests that the graded composite coating could substantially reduced the chemical interactions between Alloy 690 and borosilicate melt.

  14. Effects of Surface Modification of Nanodiamond Particles for Nucleation Enhancement during Its Film Growth by Microwave Plasma Jet Chemical Vapour Deposition Technique

    Directory of Open Access Journals (Sweden)

    Chii-Ruey Lin

    2014-01-01

    Full Text Available The seedings of the substrate with a suspension of nanodiamond particles (NDPs were widely used as nucleation seeds to enhance the growth of nanostructured diamond films. The formation of agglomerates in the suspension of NDPs, however, may have adverse impact on the initial growth period. Therefore, this paper was aimed at the surface modification of the NDPs to enhance the diamond nucleation for the growth of nanocrystalline diamond films which could be used in photovoltaic applications. Hydrogen plasma, thermal, and surfactant treatment techniques were employed to improve the dispersion characteristics of detonation nanodiamond particles in aqueous media. The seeding of silicon substrate was then carried out with an optimized spin-coating method. The results of both Fourier transform infrared spectroscopy and dynamic light scattering measurements demonstrated that plasma treated diamond nanoparticles possessed polar surface functional groups and attained high dispersion in methanol. The nanocrystalline diamond films deposited by microwave plasma jet chemical vapour deposition exhibited extremely fine grain and high smooth surfaces (~6.4 nm rms on the whole film. These results indeed open up a prospect of nanocrystalline diamond films in solar cell applications.

  15. Anti-microbial surfaces: An approach for deposition of ZnO nanoparticles on PVA-Gelatin composite film by screen printing technique.

    Science.gov (United States)

    Meshram, J V; Koli, V B; Phadatare, M R; Pawar, S H

    2017-04-01

    Initially micro-organisms get exposed to the surfaces, this demands development of anti-microbial surfaces to inhibit their proliferation. Therefore, herein, we attempt screen printing technique for development of PVA-GE/ZnO nanocomposite (PG/ZnO) films. The synthesis of PG/ZnO nanocomposite includes two steps as: (i) Coating of Zinc Oxide nanoparticles (ZnO NPs) by poly ethylene glycol in order to be compatible with organic counterparts. (ii) Deposition of coated nanoparticles on the PG film surface. The results suggest the enhancement in anti-microbial activity of PG/ZnO nanocomposite over pure ZnO NPs against both Gram positive Bacillus subtilis and Gram negative Escherichia coli from zone of inhibition. The uniformity in deposition is further confirmed by scanning electron microscopy (SEM) images. The phase identification of ZnO NPs and formation of PG/ZnO nanocomposite has been confirmed by X-ray diffraction (XRD) analysis and UV-vis spectroscopy (UV-vis). The Attenuated total reflection Spectroscopy (ATR) analysis indicates the ester bond between PVA and gelatin molecules. The thermal stability of nanocomposite is studied by thermogravimetric analysis (TGA) revealing increase in crystallinity due to ZnO NPs which could be utilized to inhibit the growth of micro-organisms. The tensile strength is found to be higher and percent elongation is double of PG/ZnO nanocomposite than PG composite film.

  16. Sn and Cu oxide nanoparticles deposited on TiO{sub 2} nanoflower 3D substrates by Inert Gas Condensation technique

    Energy Technology Data Exchange (ETDEWEB)

    Kusior, A., E-mail: akusior@agh.edu.pl [Faculty of Materials Science and Ceramics, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland); Kollbek, K. [Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland); Kowalski, K. [Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland); Borysiewicz, M. [Institute of Electron Technology, al. Lotnikow 32/46, 02-668 Warszawa (Poland); Wojciechowski, T. [Institute of Physics Polish Academy of Science, al. Lotnikow 32/46, 02-668 Warszawa (Poland); Adamczyk, A.; Trenczek-Zajac, A.; Radecka, M. [Faculty of Materials Science and Ceramics, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland); Zakrzewska, K. [Faculty of Computer Science, Electronics and Telecommunications, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow (Poland)

    2016-09-01

    Graphical abstract: - Highlights: • Inert Gas Condensation method yields non-agglomerated nanoparticles. • The growth of nanoparticles is controllable at the level of deposition. • Electrical conductivity increases with respect to pure nanostructured TiO{sub 2}. - Abstract: Sn and Cu oxide nanoparticles were deposited by Inert Gas Condensation (IGC) technique combined with dc magnetron sputtering onto nanoflower TiO{sub 2} 3D substrates obtained in the oxidation process of Ti-foil in 30% H{sub 2}O{sub 2}. Sputtering parameters such as insertion length and Ar/He flow rates were optimized taking into account the nanostructure morphology. Comparative studies with hydrothermal method were carried out. Surface properties of the synthesized nanomaterials were studied by Scanning Electron Microscopy, SEM, Atomic Force Microscopy, AFM, and X-ray Photoelectron Spectroscopy, XPS. X-ray diffraction, XRD and Raman spectroscopy were performed in order to determine phase composition. Impedance spectroscopy demonstrated the influence of nanoparticles on the electrical conductivity.

  17. Effect of complexing agent TEA: The structural, morphological, topographical and optical properties of FexSx nano thin films deposited by SILAR technique

    Science.gov (United States)

    Manikandan, K.; Mani, P.; Surendra Dilip, C.; Valli, S.; Fermi Hilbert Inbaraj, P.; Joseph Prince, J.

    2014-01-01

    Iron sulfide thin films (FexSx) (x = 0.05 M, 0.10 M, 0.15 M, 0.20 M and 0.25 M) were deposited by SILAR method from equimolar and equivolume aqueous solutions of ferrous nitrate and sodium sulfide with the addition of complexing agent TEA. The structural, morphological and optical characteristics of the films were derived from X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-vis spectral techniques. The mixed characteristics (crystalline and amorphous) of the deposited films and the increasing crystalline qualities with the concentrations were understood from the XRD analysis. The grain sizes and roughness of the films were decreases with the increasing concentration and also at the higher concentration films are shown by the same images presence of hexagonal like crystallite structure. The influence of complexing agent TEA on the surface roughness and morphological properties are confirmed by the atomic force microscope (AFM) results. The effect of increasing substrate concentration on the absorption and transmission measurements and its impact on the optical band-gap energy were enumerated from the UV-vis analysis.

  18. Porous Silicon & Titanium Dioxide Coatings Prepared by Atmospheric Pressure Plasma Jet Chemical Vapour Deposition Technique-A Novel Coating Technology for Photovoltaic Modules

    Directory of Open Access Journals (Sweden)

    S. Bhatt

    2011-01-01

    Full Text Available Atmospheric Pressure Plasma Jet (APPJ is an alternative for wet processes used to make anti reflection coatings and smooth substrate surface for the PV module. It is also an attractive technique because of it’s high growth rate, low power consumption, lower cost and absence of high cost vacuum systems. This work deals with the deposition of silicon oxide from hexamethyldisiloxane (HMDSO thin films and titanium dioxide from tetraisopropyl ortho titanate using an atmospheric pressure plasma jet (APPJ system in open air conditions. A sinusoidal high voltage with a frequency between 19-23 kHz at power up to 1000 W was applied between two tubular electrodes separated by a dielectric material. The jet, characterized by Tg ~ 600-800 K, was mostly laminar (Re ~ 1200 at the nozzle exit and became partially turbulent along the jet axis (Re ~ 3300. The spatially resolved emission spectra showed OH, N2, N2+ and CN molecular bands and O, H, N, Cu and Cr lines as well as the NO2 chemiluminescence continuum (450-800 nm. Thin films with good uniformity on the substrate were obtained at high deposition rate, between 800 -1000 nm.s-1, and AFM results revealed that coatings are relatively smooth (Ra ~ 2 nm. The FTIR and SEM analyses were better used to monitor the chemical composition and the morphology of the films in function of the different experimental conditions.

  19. Preparation and characterization of YBa{sub 2}Cu{sub 3}O{sub 7-x} thick films deposited on silver substrates by the electrophoretic deposition technique for magnetic screening applications

    Energy Technology Data Exchange (ETDEWEB)

    Grenci, G [Politecnico di Torino, Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, 10129 Turin (Italy); Denis, S [SUPRATECS group, Department of Electrical Engineering and Computer Science (B28), University of Liege, Sart-Tilman, 4000 Liege (Belgium); Dusoulier, L [CISS Department, Royal Military Academy, Brussels (Belgium); Pavese, F [CNR, Istituto di Metrologia ' G Colonnetti' , Turin (Italy); Penazzi, N [Politecnico di Torino, Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, 10129 Turin (Italy)

    2006-04-15

    The production of magnetic shields using high-temperature superconductors (HTS) is not straightforward, as these materials are brittle ceramics. In this paper, we report the results of investigations concerning the use of the electrophoretic deposition (EPD) technique to produce magnetic shields of various shapes and with large surface areas, in the form of a thick coating of HTS on a metallic substrate. For the first time, we report shielding characterization of samples prepared by the EPD technique. The most important problems concern the choice of the process parameters and the heat treatment of the coating, in order to obtain a dense and well-connected polycrystalline system. We have used the HTS compound YBa{sub 2}Cu{sub 3}O{sub 7-x} as the coating material and silver as the substrate. An optimized heat treatment, in an atmosphere with poor oxygen content, was chosen following experimental investigations. Different samples were produced in the form of slabs for chemical, structural and electrical characterization. A cylindrical sample was prepared for magnetic shielding measurements at 77 K. With an applied magnetic field parallel to its axis, the cylinder presents a high level of shielding (>80 dB) at low frequencies, for applied inductions lower than 0.1 mT. If the applied induction is higher than 0.25 mT, the magnetic field inside the cylinder strongly increases. This value is close to the field of penetration given by Bean's model, taking a critical current density of 500 A cm{sup -2} measured by the four-probe technique on similar samples.

  20. Optical and local structural study of Gd doped ZrO{sub 2} thin films deposited by RF magnetron sputtering technique

    Energy Technology Data Exchange (ETDEWEB)

    Haque, S. Maidul, E-mail: skmaidulhaque@gmail.com; Shinde, D. D.; Misal, J. S. [Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, VIZAG Centre, Visakhapatnam-530012 (India); Jha, S. N.; Bhattacharyya, D.; Sahoo, N. K. [Atomic & Molecular Physics Division, Bhabha Atomic Research Centre. Mumbai – 400094 (India)

    2015-06-24

    ZrO{sub 2} samples with 0, 7, 9, 11, 13 % Gd doping have been prepared by RF magnetron sputtering deposition technique for solid oxide fuel cell application. The optical properties of the samples have been studied by transmission spectrophotometry and spectroscopic ellipsometry while the local structure surrounding Zr sites has been characterized by extended x-ray absorption fine structure (EXAFS) measurement at Zr K edge with synchrotron radiation. It has been observed that beyond 11% Gd doping, band gap decreases and refractive index increases significantly and also oxygen and Zr coordinations surrounding Zr sites increase which indicates the formation of Gd clustering in ZrO{sub 2} matrix beyond this doping concentration.

  1. Fe3O4/γ-Fe2O3 nanoparticle multilayers deposited by the Langmuir-Blodgett technique for gas sensors application.

    Science.gov (United States)

    Capone, S; Manera, M G; Taurino, A; Siciliano, P; Rella, R; Luby, S; Benkovicova, M; Siffalovic, P; Majkova, E

    2014-02-04

    Fe3O4/γ-Fe2O3 nanoparticles (NPs) based thin films were used as active layers in solid state resistive chemical sensors. NPs were synthesized by high temperature solution phase reaction. Sensing NP monolayers (ML) were deposited by Langmuir-Blodgett (LB) techniques onto chemoresistive transduction platforms. The sensing ML were UV treated to remove NP insulating capping. Sensors surface was characterized by scanning electron microscopy (SEM). Systematic gas sensing tests in controlled atmosphere were carried out toward NO2, CO, and acetone at different concentrations and working temperatures of the sensing layers. The best sensing performance results were obtained for sensors with higher NPs coverage (10 ML), mainly for NO2 gas showing interesting selectivity toward nitrogen oxides. Electrical properties and conduction mechanisms are discussed.

  2. Comparative study of the structure and corrosion behavior of Zr-20%Cr and Zr-20%Ti alloy films deposited by multi-arc ion plating technique

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Farhat, E-mail: ilatahraf@yahoo.com [National Centre for Nanotechnology, Department of Metallurgy and Materials Engineering (DMME), Pakistan Institute of Engineering and Applied Sciences (PIEAS), PO Nilore, Islamabad 45650 (Pakistan); Mehmood, Mazhar, E-mail: mazhar@pieas.edu.pk [National Centre for Nanotechnology, Department of Metallurgy and Materials Engineering (DMME), Pakistan Institute of Engineering and Applied Sciences (PIEAS), PO Nilore, Islamabad 45650 (Pakistan); Qasim, Abdul Mateen; Ahmad, Jamil; Naeem-ur-Rehman [National Centre for Nanotechnology, Department of Metallurgy and Materials Engineering (DMME), Pakistan Institute of Engineering and Applied Sciences (PIEAS), PO Nilore, Islamabad 45650 (Pakistan); Iqbal, Muhammad [Physics Division, Pakistan Institute of Science and Technology (PINSTECH), Islamabad 45650 (Pakistan); Qureshi, Ammad H. [Materials Division, Pakistan Institute of Science and Technology (PINSTECH), Islamabad 45650 (Pakistan)

    2014-08-01

    The primary focus of the present work was to perform comparative study of the structure as well as corrosion behavior of two Zr-rich alloy films, i.e. Zr-20%Cr and Zr-20%Ti, as well as metallic Ti, Cr and Zr films, formed by multi-arc ion plating technique. The required alloy film composition was obtained by co-deposition with proper choice of current for the targets of the constituent metals. The deposited alloy film composition was determined by energy dispersion X-ray spectroscopy, X-ray fluorescence and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) techniques, which were in close agreement with each other. The film thickness lied in the range of 550-620 nm. The crystal structure was studied by X-ray diffraction, which revealed the formation of nanocrystalline and semi-amorphous structures. The corrosion rates of the films were determined through weight loss measurement in 1 M, 6 M and 12 M hydrochloric acid (HCl) by ICP-AES analysis of the solution after immersion for 200-350 h. Anodic (potentiodynamic) polarization was also performed. Zr-20%Cr alloy film exhibited the best corrosion resistance, and its dissolution rate was less than 0.5 μm/year in 6 M HCl and about 4 μm/year in 12 M HCl. - Highlights: • Fine control over the stoichiometry of each alloy film • Development of either nano-crystalline or semi-amorphous alloy films • Development of highly corrosion resistant films.

  3. Effect of Mn doping on the electrical and optical properties of SnO{sub 2} thin films deposited by chemical spray pyrolysis technique

    Energy Technology Data Exchange (ETDEWEB)

    Indira Gandhi, T. [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Ramesh Babu, R., E-mail: rampap2k@yahoo.co.in [Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Ramamurthi, K. [Crystal Growth and Thin Film Laboratory, Department of Physics and Nanotechnology, Faculty of Engineering and Technology, SRM University, Kattankulathur 603 203, Tamil Nadu (India); Arivanandhan, M. [Nanodevices and Nanomaterials Division, Research Institute of Electronics, Shizuoka University, Hamamatsu 432 8011 (Japan)

    2016-01-01

    Manganese doped tin oxide (Mn:SnO{sub 2}) thin films were deposited by spray pyrolysis technique adding various concentrations of manganese acetate (0–8 at.%) in the spray solution of tin chloride. X-ray diffraction studies show the preferred growth along (301) direction for 0.0–2.0 at.% concentration of manganese acetate in the spray solution. Higher doping concentration of manganese acetate (4 and 8 at.%) in the solution shifts the preferred growth direction along (200) plane. Scanning electron microscopic studies reveal the change in the surface morphology of the films due to various levels of Mn doping. X-ray photoelectron spectroscopic analysis shows that in the prepared thin film manganese atoms exist in Mn{sup 3+} state. The sheet resistance of SnO{sub 2} film decreases from ~ 23.5 Ω/□ to 22.8 Ω/□ for 0.4 at.% doping concentration and increases with increasing Mn concentration in the solution. The average optical transmittance of SnO{sub 2} thin film increases from 34% to 55% in the wavelength region of 550–850 nm with increase in Mn concentration. Mn concentration in the films influences the intensity of the photoluminescence emission peak observed for SnO{sub 2} film at 398 nm. - Highlights: • Mn:SnO2 thin films deposited with different doping concentration by spray pyrolysis technique • Structural information confirms that all the films are polycrystalline and tetragonal crystal structure. • XPS studies confirm the oxidation state of Mn (3 +) and Sn (4 +) in Mn:SnO{sub 2} thin film. • 0.4 at.% of Mn:SnO{sub 2} thin film shows lowest sheet resistance 22.8 Ω/□. • Optical band gap of 1.2 at.% Mn:SnO{sub 2} thin film is about 3.70 eV.

  4. Molecular self ordering and charge transport in layer by layer deposited poly (3,3‴-dialkylquarterthiophene) films formed by Langmuir-Schaefer technique

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Rajiv K.; Singh, Arun Kumar; Upadhyay, C.; Prakash, Rajiv, E-mail: rprakash.mst@itbhu.ac.in [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2014-09-07

    The performance of π-conjugated polymer based electronic devices is directly governed by the molecular morphology of polymer aggregation, the extent to which a molecule is electronically coupled (self ordered and interacted) to neighboring molecules, and orientation. The well electronic coupled and crystalline/ordered polymer films have the potential to enhance the charge transport properties up to a benchmark. However, there is insufficient knowledge about the direct formation of large area, oriented, crystalline, and smooth films. In this study, we have presented Langmuir Schaefer technique to obtain the large area, oriented, crystalline, and smooth film of Poly (3,3‴-dialkylquarterthiophene) (PQT-12) polymer. The effect of self ordering and orientation of PQT-12 polymer on optical, morphological, and charge transport properties has been investigated. The prepared films have been characterized by UV-vis spectroscopy, Raman spectroscopy, transmission electron microscopy (TEM), selected area diffractions pattern (SAED), and atomic force microscopy (AFM) techniques. UV-vis spectra, TEM, SAED, and AFM images of monolayer films reveal the formation of well ordered and electronically coupled polymer domains. Layer by layer deposited films reveal the change in the orientation, which is confirmed by Raman spectra. Electronic properties and layer dependent charge transport properties are investigated using sandwiched structure Al/PQT-12/ITO Schottky configuration with perpendicular to the deposited films. It is observed that the charge transport properties and device electronic parameters (ideality factor and turn on voltage) are significantly changing with increasing the number of PQT-12 layers. Our study also demonstrates the charge transport between polymer crystallites and cause of deviation of ideal behavior of organic Schottky diodes. It may be further explored for improving the performance of other organic and optoelectronic devices.

  5. Optimal Materials and Deposition Technique Lead to Cost-Effective Solar Cell with Best-Ever Conversion Efficiency (Fact Sheet)

    Energy Technology Data Exchange (ETDEWEB)

    2012-07-01

    This fact sheet describes how the SJ3 solar cell was invented, explains how the technology works, and why it won an R&D 100 Award. Based on NREL and Solar Junction technology, the commercial SJ3 concentrator solar cell - with 43.5% conversion efficiency at 418 suns - uses a lattice-matched multijunction architecture that has near-term potential for cells with {approx}50% efficiency. Multijunction solar cells have higher conversion efficiencies than any other type of solar cell. But developers of utility-scale and space applications crave even better efficiencies at lower costs to be both cost-effective and able to meet the demand for power. The SJ3 multijunction cell, developed by Solar Junction with assistance from foundational technological advances by the National Renewable Energy Laboratory, has the highest efficiency to date - almost 2% absolute more than the current industry standard multijunction cell-yet at a comparable cost. So what did it take to create this cell having 43.5% efficiency at 418-sun concentration? A combination of materials with carefully designed properties, a manufacturing technique allowing precise control, and an optimized device design.

  6. Valorization of GaN based metal-organic chemical vapor deposition dust a semiconductor power device industry waste through mechanochemical oxidation and leaching: A sustainable green process.

    Science.gov (United States)

    Swain, Basudev; Mishra, Chinmayee; Lee, Chan Gi; Park, Kyung-Soo; Lee, Kun-Jae

    2015-07-01

    Dust generated during metal organic vapor deposition (MOCVD) process of GaN based semiconductor power device industry contains significant amounts of gallium and indium. These semiconductor power device industry wastes contain gallium as GaN and Ga0.97N0.9O0.09 is a concern for the environment which can add value through recycling. In the present study, this waste is recycled through mechanochemical oxidation and leaching. For quantitative recovery of gallium, two different mechanochemical oxidation leaching process flow sheets are proposed. In one process, first the Ga0.97N0.9O0.09 of the MOCVD dust is leached at the optimum condition. Subsequently, the leach residue is mechanochemically treated, followed by oxidative annealing and finally re-leached. In the second process, the MOCVD waste dust is mechanochemically treated, followed by oxidative annealing and finally leached. Both of these treatment processes are competitive with each other, appropriate for gallium leaching and treatment of the waste MOCVD dust. Without mechanochemical oxidation, 40.11 and 1.86 w/w% of gallium and Indium are leached using 4M HCl, 100°C and pulp density of 100 kg/m(3,) respectively. After mechanochemical oxidation, both these processes achieved 90 w/w% of gallium and 1.86 w/w% of indium leaching at their optimum condition.

  7. Structural, morphological and optical properties of Cd doped ZnO film grown on a- and r-plane sapphire substrate by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Fouzri, A., E-mail: Fouzri.Afif@gmail.com [Institut Supérieur des Sciences Appliquées et de Technologie de Sousse, Université de Sousse (Tunisia); Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche, High resolution X-ray diffractometer, Département de Physique, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Boukadhaba, M.A. [Laboratoire Physico-chimie des Matériaux, Unité de Service Commun de Recherche, High resolution X-ray diffractometer, Département de Physique, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Touré, A. [Unité de recherche hétéroepitaxie et ses applications, Département de Physique, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); Sakly, N. [Laboratoire Physico-chimie des Interfaces, Département de Physique, Faculté des Sciences de Monastir, Université de Monastir, Avenue de l’Environnement, 5019 Monastir (Tunisia); and others

    2014-08-30

    Highlights: • Cd doped ZnO films have been grown on (1 1 −20) (a-plane) and (0 1 −1 2) (r-plane) sapphire substrate by MOCVD. • A maximum cadmium incorporation of 8.5% and 11.2% has been, respectively, determined for films deposited on a- and r-plane sapphire. • XRD study revealed that all films had wurtzite phase but solid solution grown on a-plane sapphire are polycrystalline with a preferred orientation along the [0 0 0 1] and a-plane (1 1 −2 0) film are epitaxially grown on r-plane-sapphire. • The near band-edge photoluminescence emission shifts gradually to lower energies as Cd is incorporated and reaches 2.916 eV for the highest Cd content (11.2%) at low temperature (20 K). - Abstract: Cd doped ZnO films have been grown on (1 1 −2 0) (a-plane) and (0 1 −1 2) (r-plane) sapphire substrate by metal organic chemical vapor deposition. A maximum cadmium incorporation of 8.5% and 11.2% has been, respectively, determined for films deposited on a- and r-plane sapphire. The optical transmission spectra and energy band-gap equation established by Makino et al. were used to estimate the cadmium mole fraction in layer. Structural, morphological and optical properties of these films were examined using high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and room and low temperature photoluminescence (Pl) as Cd incorporation and employed substrate. X-ray diffraction study revealed that all films had wurtzite phase but solid solution grown on a-plane sapphire are polycrystalline with a preferred orientation along the [0 0 0 1] direction and a-plane (1 1 −2 0) film are epitaxially grown on r-plane sapphire. AFM image show significant differences between morphologies depending on orientation sapphire substrate but no significant differences on surface roughness have been found. The near band-edge photoluminescence emission shifts gradually to lower energies as Cd is incorporated and reaches 2.916 eV for the highest Cd content (11.2%) at

  8. Epitaxial growth of group III-nitride films by pulsed laser deposition and their use in the development of LED devices

    Science.gov (United States)

    Li, Guoqiang; Wang, Wenliang; Yang, Weijia; Wang, Haiyan

    2015-11-01

    Recently, pulsed laser deposition (PLD) technology makes viable the epitaxial growth of group III-nitrides on thermally active substrates at low temperature. The precursors generated from the pulsed laser ablating the target has enough kinetic energy when arriving at substrates, thereby effectively suppressing the interfacial reactions between the epitaxial films and the substrates, and eventually makes the film growth at low temperature possible. So far, high-quality group III-nitride epitaxial films have been successfully grown on a variety of thermally active substrates by PLD. By combining PLD with other technologies such as laser rastering technique, molecular beam epitaxy (MBE), and metal-organic chemical vapor deposition (MOCVD), III-nitride-based light-emitting diode (LED) structures have been realized on different thermally active substrates, with high-performance LED devices being demonstrated. This review focuses on the epitaxial growth of group III-nitrides on thermally active substrates by PLD and their use in the development of LED devices. The surface morphology, interfacial property between film and substrate, and crystalline quality of as-grown group III-nitride films by PLD, are systematically reviewed. The corresponding solutions for film homogeneity on large size substrates, defect control, and InGaN films growth by PLD are also discussed in depth, together with introductions to some newly developed technologies for PLD in order to realize LED structures, which provides great opportunities for commercialization of LEDs on thermally active substrates.

  9. MOCVD of ZrO2 films from $bis(t$-butyl-3-oxo-butanoato)zirconium(IV): some theoretical (thermodynamic) and experimental aspects

    Indian Academy of Sciences (India)

    Sukanya Dhar; M S Dharmaprakash; S A Shivashankar

    2008-02-01

    The equilibrium concentrations of various condensed and gaseous phases were calculated from thermodynamic modeling of MOCVD of ZrO2 films using a -ketoesterate complex of zirconium as precursor. This leads to the construction of the `CVD phase stability diagram’ for the formation of solid phases. In the reactive ambient of oxygen, the calculations predict carbon-free ZrO2 film over a wide range of process conditions. The thermodynamic yields are in reasonable agreement with experimental observations, though the removal of carbon from the MOCVD grown films is not as complete as the thermodynamic calculations predict.

  10. The novel chamber hardware design to improve the thin film deposition quality in both 12″ (300 mm and 18″ (450 mm wafers with the development of 3D full chamber modeling and experimental visual technique

    Directory of Open Access Journals (Sweden)

    M.-H. Liao

    2013-07-01

    Full Text Available The thin film deposition property and the process difference during the wafer size migration from 12″ (300 mm to 18″ (450 mm in the Chemical Vapor Deposition (CVD equipment is improved and reduced, respectively, when the chamber hardware is designed with the help of 3D full chamber modeling and 3D experimental visual technique developed in this work. The accuracy of 3D chamber simulation model is demonstrated with the experimental visual technique measurement. With the CVD chamber hardware design of placing the inlet position and optimizing the distance between the susceptor edge and the reactor wall, the better thin film deposition property and the larger process compatibility during the wafer size migration from 12″ (300 mm to 18″ (450 mm for the industry cost reduction can be achieved. Non-dimensional Nusselt parameter is also found to be the effective indicator to monitor the thin film deposition property.

  11. Study of carrier recombination transient characteristics in MOCVD grown GaN dependent on layer thickness

    Directory of Open Access Journals (Sweden)

    E. Gaubas

    2013-11-01

    Full Text Available The MOCVD grown GaN epi-layers of different thickness have been examined in order to clarify a role of surface recombination, to separate an impact of radiative and non-radiative recombination and disorder factors. The microwave probed –photoconductivity (MW-PC and spectrally resolved photo-luminescence (PL transients were simultaneously recorded under ultraviolet (UV light 354 nm pulsed 500 ps excitation. The MW-PC transients exhibited the carrier decay components associated with carrier decay within micro-crystals and the disordered structure on the periphery areas surrounding crystalline columns. Three PL bands were resolved within PL spectrum, namely, the exciton ascribed UV-PL band edge for hν>3.3 eV, blue B-PL band for 2.5 < hν < 3.0 eV and yellow Y-PL band with hν < 2.4 eV. It has been obtained that intensity of UV-PL band increases with excitation density, while intensity of B-PL band is nearly invariant. However, intensity of the Y-PL increases with reduction of the excitation density. The Y-PL can be associated with trapping centers. A reduction of UV excitation density leads to a decrease of the relative amplitude of the asymptotic component within the MW-PC transients and to an increase of the amplitude as well as duration of the yellow spectral band (Y-PL asymptotic component. Fractional index α with values 0.5 < α < 0.8 was evaluated for the stretched-exponent component which fits the experimental transients determined by the disordered structure ascribed to the periphery areas surrounding the crystalline columns.

  12. Influence of bias voltage on the optical and structural properties of nc-Si:H films grown by layer-by-layer (LBL) deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Goh Boon, E-mail: boontong77@yahoo.co [Solid State Research Laboratory, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Gani, Siti Meriam Ab.; Muhamad, Muhamad Rasat; Rahman, Saadah Abdul [Solid State Research Laboratory, Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2009-07-01

    The effects of applying a positive bias of 25 to 100 V on the optical, structural and photoluminescence (PL) properties of hydrogenated nanocrystalline silicon (nc-Si:H) films produced by layer-by-layer (LBL) deposition technique has been studied. Optical characterization of the films has been obtained from UV-VIS-NIR spectroscopy measurements. Structural characterization has been performed using X-ray diffraction, micro-Raman spectroscopy and field emission scanning electron microscope (FESEM). PL spectroscopy technique has been used to investigate the PL properties of the films. In general, the films formed shows a mixed phase of silicon (Si) nanocrystallites embedded within an amorphous phase of the Si matrix. The crystalline volume fraction and grain size of the Si nanocrystallites have been shown to be strongly dependent on the applied bias voltage. High applied bias voltage enhances the growth rate of the films but reduces the refractive index and the optical energy gap of the films. Higher crystalline volume fraction of the films prepared at low bias voltages exhibits room temperature PL at around 1.8 eV (700 nm).

  13. Application of the electrophoretic deposition technique for obtaining Yttria-stabilized zirconia tubes; Aplicacao da tecnica de deposicao eletroforetica para a obtencao de tubos ceramicos de zirconia-itria

    Energy Technology Data Exchange (ETDEWEB)

    Caproni, E.; Muccillo, R., E-mail: ecaproni@gmail.com, E-mail: muccillo@usp.br [Centro de Ciencia e Tecnologia de Materiais, Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2012-01-15

    The electrophoretic deposition (EPD) is recognized as the most versatile technique for processing particulate materials, due to low cost, deposition in minutes and forming of pieces with complex geometry shapes. In this work an experimental setup for the simultaneous conformation of 16 ceramic tubes by EPD was built. Bimodal submicron Yttria-stabilized zirconia particles were deposited into graphite electrodes, after suitably adjusting the rheological characteristics of the suspension in isopropanol. After graphite burning and YSZ sintering at 1500 deg C, the ceramic tubes were characterized by X-ray diffraction, scanning probe microscope, impedance spectroscopy and electrical response as a function of oxygen content. Small dense one end-closed ceramic tubes, fully stabilized in the cubic phase, were successfully obtained by the EPD technique, showing the ability of that technique for processing large quantities of tubular solid electrolytes with electrical response to different amounts of oxygen according to the Nernst law (author)

  14. Growth of (Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} thin films by metal-organic chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Aboulfarah, B.; Mzerd, A. [Univ. MedV Agdal, Rabat (Morocco). Dept. de Physique; Giani, A.; Boulouz, A.; Pascal-Delannoy, F.; Foucaran, A.; Boyer, A. [Centre d' Electronique et de Micro-Optoelectronique de Montpellier (CEM 2), UM II UMR 5507 CNRS, Place E. Bataillon, 34095, Montpellier (France)

    2000-01-29

    The effects of VI/V ratio on electrical and thermoelectrical properties of p-type (Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} elaborated by metal-organic chemical vapour deposition (MOCVD) in horizontal quartz reactor are discussed. The deposited layers exhibit a polycrystalline structure and an improvement in the intensity is observed with increasing the VI/V ratio. The quality of the layers is measured by means of the Energy dispersive X-ray (EDX) microanalyser and scanning electron microscopy (SEM). It is observed that the layers are stoichiometric when the VI/V ratio exceeds 3 and the surface texture is improved with increasing this ratio. The electrical properties of the thin films dependent on the VI/V ratio. The measurements of the Seebeck coefficient suggest a significant potential of MOCVD growth for large-scale production of thermoelectric materials. (orig.)

  15. Progress of Research on Underpotential Deposition--II. Research Techniques and Application of Underpotential Deposition%欠电位沉积研究现状--II.欠电位沉积的研究方法及其应用

    Institute of Scientific and Technical Information of China (English)

    许振; 齐东梅; 江莉; 陈宇; 张昭; 张鉴清

    2015-01-01

    总结了主要的欠电位沉积(upd)的原位研究方法,包括电化学研究方法(循环伏安(CV)、计时电流(CHR)和电化学阻抗谱(EIS))、界面分析方法(电化学石英晶体微天平(EQCM)和电化学扫描隧道显微镜/电化学原子力显微镜(ECSTM/ECAFM))及X射线分析技术(X射线吸收谱(XAS)和表面X射线散射(SXS))。根据这些研究方法,总结和探讨了许多体系的upd特征,分析了upd微观特征与宏观的测试结果的对应关系及其原理。此外,探讨了基于这些研究方法得出的关于upd的重要结论,并对比分析了上述研究方法的优缺点。在upd应用领域的研究方面,主要从四个方面进行了概述,涉及功能材料电合成、电分析应用、电化学原子层外延(ECALE)和表征贵金属(或纳米)材料电化学活性面积(ECSA),并简析了上述应用研究中涉及的关于upd过程的原理。最后,总结了upd研究方法和应用研究的现状并展望了其未来发展趋势。%A variety of primary in situ research techniques applied to underpotential deposition (upd) research, including electrochemical (cyclic voltammetry (CV), chronoamperometry (CHR), and electrochemical impedance spectroscopy (EIS)), interfacial (electrochemical quartz crystal microbalance (EQCM) and electrochemical scanning tunneling microscopy/electrochemical atomic force microscopy (ECSTM/ECAFM)) and X-ray based (X-ray absorption spectroscopy (XAS) and surface X-ray scattering (SXS)) analysis techniques, are summarized in this paper. We summarize and discuss the upd characteristics of many electrochemical systems as determined by these research techniques, and analyze the corresponding relationships and principles between the upd microscopic characteristics and macroscopic test results. Some conclusions of vital importance to upd drawn based on these techniques are explicitly discussed. Also, the merits and demerits of the above-mentioned research techniques are

  16. Electrochemical behavior of TiAlSiN hard coatings synthesized by a multi-plasma immersion ion implantation and deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Gengzhu [University of Science and Technology Liaoning, Anshan 114051 (China); Xie, Zhiwen, E-mail: xzw@cigit.ac.cn [University of Science and Technology Liaoning, Anshan 114051 (China); Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122 (China); Chen, Tian [Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122 (China); Chen, Zhenyu [Key Laboratory of Power Sources, Institute of Power Sources, Tianjin 300381 (China); Song, Xiaohang [Shanghai Aerospace Equipments Manufacturer, Shanghai 401122 (China); Gao, Xu; Yu, Xiaoguang; Song, Hua [University of Science and Technology Liaoning, Anshan 114051 (China)

    2015-06-01

    The TiAlSiN coatings are synthesized by a multi-plasma immersion ion implantation and deposition technique. The microstructure and the electrochemical behavior of the as-deposited coatings are investigated by using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and electrochemical tests. These studies reveal that huge lattice distortions and dislocations emerge in the coating after introducing a small amount of Al component. These structural defects can facilitate the corrosion process of the TiAlN coating. The TiAlN coating exhibits a worse corrosion resistance performance than the TiN coating. The TiAlSiN coating has a two phase microstructure, nc-TiAlN/a-Si{sub 3}N{sub 4.} The grain size is greatly reduced after introducing Si component, whereas the portion of the a-Si{sub 3}N{sub 4} phase increases as the amount of Si increases in the coating. The reduced grain size and the increased percentage of the a-Si{sub 3}N{sub 4} phase in the TiAlSiN coatings enhance their ability in corrosion resistance. The TiAlSiN coating with a larger amount of Si shows better corrosion resistance performance. This research provides a comprehensive understanding of the relationship between the microstructure and the electrochemical behavior of the TiAlSiN hard coatings. - Highlights: • Microstructure and electrochemical behavior of TiAlSiN coatings are presented. • Al addition induces serious lattice distortions and dislocations. • Si incorporation induces an obvious grain refinement effect. • TiAlN coating shows a higher corrosion rate than the TiN coating. • TiAlSiN coating with higher Si content shows better corrosion resistance.

  17. Synthesis of core/shell ZnO/ZnSe nanowires using novel low cost two-steps electrochemical deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Ghoul, M., E-mail: ghoulmed2009@yahoo.fr [Laboratoire Photovoltaïque, Centre de Recherches et des Technologies de l' Energie Technopole BorjCedria, Bp 95, Hammammlif 2050 (Tunisia); Braiek, Z. [Laboratoire Photovoltaïque, Centre de Recherches et des Technologies de l' Energie Technopole BorjCedria, Bp 95, Hammammlif 2050 (Tunisia); Brayek, A. [Laboratoire Photovoltaïque, Centre de Recherches et des Technologies de l' Energie Technopole BorjCedria, Bp 95, Hammammlif 2050 (Tunisia); ITODYS, Université Paris Diderot, Sorbonne Paris Cité, CNRS UMR – 7086, 75205 Paris (France); Ben Assaker, I.; Khalifa, N.; Ben Naceur, J.; Souissi, A.; Lamouchi, A. [Laboratoire Photovoltaïque, Centre de Recherches et des Technologies de l' Energie Technopole BorjCedria, Bp 95, Hammammlif 2050 (Tunisia); Ammar, S. [ITODYS, Université Paris Diderot, Sorbonne Paris Cité, CNRS UMR – 7086, 75205 Paris (France); Chtourou, R. [Laboratoire Photovoltaïque, Centre de Recherches et des Technologies de l' Energie Technopole BorjCedria, Bp 95, Hammammlif 2050 (Tunisia)

    2015-10-25

    This work highlights the original use of a two-step electrochemical deposition protocol to grow ZnO/ZnSe core/shell nanowires on a Sn-doped In{sub 2}O{sub 3} (ITO)/glass substrate. The good alignment of the nanowires is verified by the scanning electron microscopy characterization technique in addition to the surface roughness after the ZnSe electrodeposition on the ZnO nanowires lateral facets. The X-ray diffraction patterns and Raman spectra allow estimating that ZnO has grown along the wurtzite (W) structure c-axis. The presence of the type-II interfacial transition between the valence band of ZnSe and the conduction band of ZnO was confirmed by UV–visible spectroscopy. It was proved that the absorbed energy of the developed nanostructures is extended to the near infrared which is well recommended for the photovoltaic applications. - Graphical abstract: Fabrication of the ZnO–ZnSe core–shell nanowires through a solution based all-electrochemical approach, and their application as photoanodes in photoelectrochemical water splitting cells. - Highlights: • Deposition of ZnO/ZnSe nanowires by two steps electrodeposition method. • The morphology studies show the formation of ZnO/ZnSe core/Shell nanowires. • XRD and Raman spectroscopy confirm the presence of the wurtzite ZnO and blende ZnSe junction. • Optical properties demonstrate the evidence type-II interfacial transition between the two semiconductors.

  18. 金属矿地震勘探方法技术研究综述%Reviews of seismic exploration methods and techniques for metallic ore deposits

    Institute of Scientific and Technical Information of China (English)

    阎頔; 敬荣中

    2011-01-01

    系统地总结了国内外金属矿地震勘探技术及其研究与应用现状,其中包括反射波法、折射波法、散射波法等,并就多项实验研究中采用的方法技术及取得的良好地质效果进行了概括总结,认为反射波地震方法在振测沉积层控矿床和控矿构造方面效果较好,而散射波地震方法不但可探测与矿体有关的地下局部不均匀体,而且,结合其它物探资料还可确定隐伏矿体的位置,是未来应用于金属矿地震勘探方法的发展方向.%This paper reviews the researches and applications of seismic techniques in mining exploration in details, including the reflected wave method, refraction method and scattering wave method etc. A seismic methodology for mineral exploration has been introduced and the acquired better geological results are summarized in the paper. It is indicated that the seismic reflection is applicable for delineating strata-bound sedimentary ore deposits and ore-controlling structures, while the seismic scattering waves could be used not only to detect inhomogeneous bodies related with ore bodies but also to locate the concealed orebody combined with other geophysical and geochemical information. It is the development orientation of seismic exploration methods used for metallic ore deposits in the future.

  19. Dating of the late Quaternary volcanic events using Uranium-series technique on travertine deposit: A case study in Ihlara, Central Anatolia Volcanic Province

    Science.gov (United States)

    Karabacak, Volkan; Tonguç Uysal, İ.; Ünal-İmer, Ezgi

    2016-04-01

    Dating of late Quaternary volcanism is crucial to understanding of the recent mechanism of crustal deformation and future volcanic explosivity risk of the region. However, radiometric dating of volcanic products has been a major challenge because of high methodological error rate. In most cases, there are difficulties on discrimination of the volcanic lava flow relations in the field. Furthermore, there would be unrecorded and unpreserved volcanoclastic layers by depositional and erosional processes. We present a new method that allows precise dating of late Quaternary volcanic events (in the time range of 0-500,000 years before present) using the Uranium-series technique on travertine mass, which is thought to be controlled by the young volcanism. Since the high pressure CO2 in the spring waters are mobilized during crustal strain cycles and the carbonates are precipitated in the fissures act as conduit for hot springs, thus, travertine deposits provide important information about crustal deformation. In this study we studied Ihlara fissure ridge travertines in the Central Anatolia Volcanic Province. This region is surrounded by many eruption centers (i.e. Hasandaǧı, Acıgöl and Göllüdaǧı) known as the late Quaternary and their widespread volcanoclastic products. Recent studies have suggested at least 11 events at around Acıgöl Caldera for the last 180 ka and 2 events at Hasandaǧı Stratovolcano for the last 30 ka. Active travertine masses around Ihlara deposited from hotwaters, which rise up through deep-penetrated fissures in volcanoclastic products of surrounding volcanoes. Analyses of the joint systems indicate that these vein structures are controlled by the crustal deformation due to young volcanism in the vicinity. Thus, the geological history of Ihlara travertine mass is regarded as a record of surrounding young volcanism. We dated 9 samples from 5 ridge-type travertine masses around Ihlara region. The age distribution indicates that the crustal

  20. Metallorganic chemical vapor deposition and atomic layer deposition approaches for the growth of hafnium-based thin films from dialkylamide precursors for advanced CMOS gate stack applications

    Science.gov (United States)

    Consiglio, Steven P.

    To continue the rapid progress of the semiconductor industry as described by Moore's Law, the feasibility of new material systems for front end of the line (FEOL) process technologies needs to be investigated, since the currently employed polysilicon/SiO2-based transistor system is reaching its fundamental scaling limits. Revolutionary breakthroughs in complementary-metal-oxide-semiconductor (CMOS) technology were recently announced by Intel Corporation and International Business Machines Corporation (IBM), with both organizations revealing significant progress in the implementation of hafnium-based high-k dielectrics along with metal gates. This announcement was heralded by Gordon Moore as "...the biggest change in transistor technology since the introduction of polysilicon gate MOS transistors in the late 1960s." Accordingly, the study described herein focuses on the growth of Hf-based dielectrics and Hf-based metal gates using chemical vapor-based deposition methods, specifically metallorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD). A family of Hf source complexes that has received much attention recently due to their desirable properties for implementation in wafer scale manufacturing is the Hf dialkylamide precursors. These precursors are room temperature liquids and possess sufficient volatility and desirable decomposition characteristics for both MOCVD and ALD processing. Another benefit of using these sources is the existence of chemically compatible Si dialkylamide sources as co-precursors for use in Hf silicate growth. The first part of this study investigates properties of MOCVD-deposited HfO2 and HfSixOy using dimethylamido Hf and Si precursor sources using a customized MOCVD reactor. The second part of this study involves a study of wet and dry surface pre-treatments for ALD growth of HfO2 using tetrakis(ethylmethylamido)hafnium in a wafer scale manufacturing environment. The third part of this study is an investigation of

  1. Surface morphologies of MOCVD-grown GaN films on sapphire studied by scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, J.; Reddic, J.E.; Sinha, M.; Ricker, W.S.; Karlinsey, J.; Yang, J.-W.; Khan, M.A.; Chen, D.A

    2002-12-30

    The surface morphologies of MOCVD GaN films grown on sapphire substrates have been investigated by scanning tunneling microscopy (STM). High quality STM images could not be obtained prior to cleaning the les in HF, hot HCl or 2 M NaOH. STM images of the GaN films showed that the surfaces consisted of curved step edges and interlocking terraces, which were roughly 224 nm wide. Surface pits approximately 2-5 nm deep and 50-80 nm wide were observed on the GaN films, and these pits were preferentially located at a juncture between two step edges. Previous studies in the literature involving MOCVD-grown GaN on sapphire have demonstrated that the surface pits are associated with screw-component threading dislocations. Therefore, the number of screw-component threading dislocations in these GaN films is estimated as 6.3x10{sup 8} cm{sup -2} from the number surface pits observed in the STM images. X-ray photoelectron studies indicated that the major surface contaminants before cleaning were carbon and oxygen. Treatment in HF or HCl removed oxygen from the surface while treatment in NaOH was more effective at removing surface carbon.

  2. DLTS study of n-type GaN grown by MOCVD on GaN substrates

    Science.gov (United States)

    Tokuda, Y.; Matsuoka, Y.; Ueda, H.; Ishiguro, O.; Soejima, N.; Kachi, T.

    2006-10-01

    Electron traps in n-type GaN layers grown homoepitaxially by MOCVD on free-standing GaN substrates have been characterized using DLTS for vertical Schottky diodes. Two free-standing HVPE GaN substrates (A and B), obtained from two different sources, are used. The Si-doped GaN layers with the thickness of 5 μm are grown on an area of 0.9×0.9 cm 2 of substrate A and on an area of 1×1 cm 2 of substrate B. Two traps labeled B1 (Ec-0.23 eV) and B2 (Ec-0.58 eV) are observed with trap B2 dominant in GaN on both substrates. There exist no dislocation-related traps which have been previously observed in MOCVD GaN on sapphire. This might be correlated to the reduction in dislocation density due to the homoepitaxial growth. However, it is found that there is a large variation, more than an order of magnitude, in trap B2 concentration and that the B2 spatial distributions are different between the two substrates used.

  3. Magnetic and structural characteristics of multiferroic Fe3O4/(Bi3.25Nd0.65Eu0.10)Ti3O12 composite thin films deposited by metalorganic chemical vapor deposition

    Science.gov (United States)

    Kobune, Masafumi; Furotani, Ryosuke; Fujita, Satoshi; Kikuchi, Kazuki; Kikuchi, Takeyuki; Fujisawa, Hironori; Shimizu, Masaru; Fukumuro, Naoki

    2016-10-01

    Ferromagnetic magnetite (Fe3O4) thin films for magnetoelectric multiferroic applications were deposited on (200) (Bi3.25Nd0.65Eu0.10)Ti3O12 (BNEuT)/(101) Nb:TiO2 substrates by metalorganic chemical vapor deposition (MOCVD) using an iron(III) tris(2,2,6,6-tetramethyl-3,5-heptanedionato) precursor as the iron source. The BNEuT film utilized as a ferroelectric template material was in the form of freestanding nanoplates with narrow spaces between them. The effects of deposition conditions such as the deposition time and substrate temperature on the magnetic and structural characteristics of the Fe3O4/BNEuT composite films were investigated. All the films consisted of mostly single-phase Fe3O4 with a cubic inverse-spinel structure. When deposition was carried out at temperatures of 400-420 °C, the filling rates of particles introduced into the narrow spaces between the BNEuT nanoplates exhibited high values of 76-89% including the amorphous phase. This suggested that the deposition in this temperature range made progress according to the growth mechanism of MOCVD in the surface reaction rate determining state. Room-temperature magnetic moment-magnetic field curves for Fe3O4 thin films deposited at 400-500 °C for 60 min exhibited narrow rectangular hysteresis loops, indicating typical soft magnetic characteristics.

  4. GaAsP/InGaP heterojunction bipolar transistors grown by MOCVD

    Science.gov (United States)

    Heidelberger, Christopher; Fitzgerald, Eugene A.

    2017-01-01

    Heterojunction bipolar transistors with GaAsxP1-x bases and collectors and InyGa1-yP emitters were grown on GaAs substrates via metalorganic chemical vapor deposition, fabricated using conventional techniques, and electrically tested. Four different GaAsxP1-x compositions were used, ranging from x = 0.825 to x = 1 (GaAs), while the InyGa1-yP composition was adjusted to remain lattice-matched to the GaAsP. DC gain close to or exceeding 100 is measured for 60 μm diameter devices of all compositions. Physical mechanisms governing base current and therefore current gain are investigated. The collector current is determined not to be affected by the barrier caused by the conduction band offset between the InGaP emitter and GaAsP base. While the collector current for the GaAs/InGaP devices is well-predicted by diffusion of electrons across the quasi-neutral base, the collector current of the GaAsP/InGaP devices exceeds this estimate by an order of magnitude. This results in higher transconductance for GaAsP/InGaP than would be estimated from known material properties.

  5. 1.3 m m InGaAsN/ GaAs Lasers Grown by MOCVD Using TBAs and DMHy Sources

    Institute of Scientific and Technical Information of China (English)

    Gray Lin; C. M. Lu; C. H. Chiou; I. F. Chen; T. D. Lee; J. Y. Chi; D.A. Livshits

    2003-01-01

    We have demonstrated InGaAsN/ GaAs single quantum well (SQW) lasers grown by MOCVD using TBAs and DMHy sources. For un-buffer-strained InGaAsN/ GaAs system, our SQW lasers of 1.3 m m range is among the best in terms of transparency and threshold current density.

  6. Characterization of Al{sub x}Ga{sub 1-x}As/GaAs heterostructures for single quantum wells grown by a solid arsenic MOCVD system

    Energy Technology Data Exchange (ETDEWEB)

    Castillo-Ojeda, R. [Universidad Politecnica de Pachuca, Km. 20, Rancho Luna, Ex-Hacienda de Santa Barbara, Municipio de Zempoala, Hidalgo 43830 (Mexico); Diaz-Reyes, J., E-mail: jdiazr2001@yahoo.co [Instituto Politecnico Nacional, Centro de Investigacion en Biotecnologia Aplicada, CIBA-IPN, Ex Hacienda de San Juan Molino, Km. 1.5. Tepetitla, Tlaxcala 90700 (Mexico); Galvan-Arellano, M.; Pena-Sierra, R. [CINVESTAV-IPN, Depto. de Ing. Electrica, SEES. Apdo. 14-740, Mexico, D.F. 07000 (Mexico)

    2011-06-15

    This work presents the results of the growth and characterization of Al{sub x}Ga{sub 1-x}As/GaAs multilayer structures obtained in a metallic-arsenic-based-MOCVD system. The main goal is to explore the ability of the growth system to grow high quality multilayer structures like quantum wells. The use of metallic arsenic could introduce important differences in the growth process due to the absence of the hydride group V precursor (AsH{sub 3}), which manifests in the electrical and optical characteristics of both GaAs and Al{sub x}Ga{sub 1-x}As layers. The characterization of these epilayers and structures was performed using low-temperature photoluminescence, Hall effect measurements, X-ray diffraction, Raman spectroscopy, secondary ion mass spectroscopy (SIMS) and Atomic Force Microscopy (AFM). - Research highlights: {yields} This work is reported the growth of AlxGa1-xAs/GaAs/AlxGa1-xAs heterostructures by a solid arsenic based MOCVD system. {yields} The results obtained with this system are comparable with those obtained with the traditional arsine based growth system. {yields} The main limitation of the alternative MOCVD system is related to the lack of monoatomic hydrogen on the growth surface that acts modifying the surface kinetics and enhancing the carbon incorporation. {yields} The experimental results indicate that it can be grown AlxGa1-xAs using elemental arsenic by MOCVD, which can be used to optoelectronic devices.

  7. Synthesis and characterization of Bi{sub 1−x}Nd{sub x}FeO{sub 3} thin films deposited using a high throughput physical vapour deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Darby, M.S.B., E-mail: darbymsb@gmail.com [Department of Materials, Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom); Karpinsky, D.V. [Complexo de Laboratórios Tecnológicos, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Pokorny, J. [Department of Materials, Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom); Institute of Physics, Academy of Sciences of the Czech Republic, 182 21 Prague (Czech Republic); Guerin, S. [Ilika Technologies Limited, Kenneth Dibben House, Enterprise Road, University of Southampton Science Park, Chilworth, Southampton, SO16 7NS (United Kingdom); Kholkin, A.L. [Complexo de Laboratórios Tecnológicos, Campus Universitário de Santiago, 3810-193 Aveiro (Portugal); Miao, S. [Department of Materials, Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom); Hayden, B.E. [Ilika Technologies Limited, Kenneth Dibben House, Enterprise Road, University of Southampton Science Park, Chilworth, Southampton, SO16 7NS (United Kingdom); Reaney, I.M. [Department of Materials, Science and Engineering, University of Sheffield, Sheffield, S1 3JD (United Kingdom)

    2013-03-01

    The high throughput synthesis of BiFeO{sub 3} and rare earth doped BiFeO{sub 3} films using a modified molecular beam epitaxy technique is reported. Optimum conditions for deposition have been established and compositionally graded Bi{sub (1−x)}Nd{sub x}FeO{sub 3} (x = 0.08 to 0.24) thin films have been fabricated on platinised silicon substrate (Si/SiO{sub 2}/TiO{sub 2}/Pt) with the aim of finding the optimum Nd dopant concentrations for enhanced piezoelectric properties. For x < 0.12, the structure and symmetry were identical to that of the R3c BiFeO{sub 3} end member. For x > 0.20, the structure and symmetry were consistent with the NdFeO{sub 3} end member (Pnma). For compositions 0.12 < x < 0.2, a gradual transition from R3c to Pnma was observed via a mixed phase region but no compositional interval could be unambiguously identified in which the intermediate PbZrO{sub 3}-like structure, reported by Karimi et al. (2009) [6], existed as a single phase. Piezoresponse force microscopy remanent hysteresis measurements of the film revealed a statistical increase in the piezoelectric response at x ≈ 0.11 within the R3c region adjacent to the mixed phase field. - Highlights: ► High throughput synthesis and characterization of BiFeO3 and Nd-doped BiFeO3 films ► The piezoelectric properties of compositionally graded bismuth ferrite are studied. ► The structure and phase assemblage of Nd-doped bismuth ferrite have been studied.