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Sample records for chemical vapour deposited

  1. Biocompatibility of chemical-vapour-deposited diamond.

    Tang, L; Tsai, C; Gerberich, W W; Kruckeberg, L; Kania, D R

    1995-04-01

    The biocompatibility of chemical-vapour-deposited (CVD) diamond surfaces has been assessed. Our results indicate that CVD diamond is as biocompatible as titanium (Ti) and 316 stainless steel (SS). First, the amount of adsorbed and 'denatured' fibrinogen on CVD diamond was very close to that of Ti and SS. Second, both in vitro and in vivo there appears to be less cellular adhesion and activation on the surface of CVD diamond surfaces compared to Ti and SS. This evident biocompatibility, coupled with the corrosion resistance and notable mechanical integrity of CVD diamond, suggests that diamond-coated surfaces may be highly desirable in a number of biomedical applications. PMID:7654876

  2. Chemical Vapour Deposition of Large Area Graphene

    Larsen, Martin Benjamin Barbour Spanget; Bøggild, Peter; Booth, Tim; Jørgensen, Anders Michael

    2015-01-01

    Chemical Vapor Deposition (CVD) is a viable technique for fabrication of large areas of graphene. CVD fabrication is the most prominent and common way of fabricating graphene in industry. In this thesis I have attempted to optimize a growth recipe and catalyst layer for CVD fabrication of uniform, single layer, and high carrier mobility large area graphene. The main goals of this work are; (1) explore the graphene growth mechanics in a low pressure cold-wall CVD system on a copper substrate, ...

  3. Chemical Vapour Deposition of Large Area Graphene

    Larsen, Martin Benjamin Barbour Spanget

    Chemical Vapor Deposition (CVD) is a viable technique for fabrication of large areas of graphene. CVD fabrication is the most prominent and common way of fabricating graphene in industry. In this thesis I have attempted to optimize a growth recipe and catalyst layer for CVD fabrication of uniform......, single layer, and high carrier mobility large area graphene. The main goals of this work are; (1) explore the graphene growth mechanics in a low pressure cold-wall CVD system on a copper substrate, and (2) optimize the process of growing high quality graphene in terms of carrier mobility, and crystal...... structure. Optimization of a process for graphene growth on commercially available copper foil is limited by the number of aluminium oxide particles on the surface of the catalyst. By replacing the copper foil with a thin deposited copper film on a SiO2/Si or c-plane sapphire wafer the particles can...

  4. Chemical vapour deposition of metal oxides and phosphides.

    Binions, R.

    2006-01-01

    This thesis investigates the deposition of thin films of main group metal phosphide and main group metal oxide compounds on glass substrates by the use of dual source atmospheric pressure chemical vapour deposition. Binary phosphide systems with tin, germanium, silicon, antimony, copper or boron have been examined. Binary oxide systems of gallium, antimony, tin or niobium have also been investigated. Additionally these systems were deposited on gas sensor substrates and evaluated as metal oxi...

  5. IR Laser-induced Chemical Vapour Deposition of Polyselenocarbosilane Films

    Santos, M.; Díaz, L.; Pola, Josef

    - : -, 2006, s. 1-2. [Reunión Nacional de Espectroscopia (RNE) y IV Congresso Ibérico de Espectroscopia (CIE) /20./. Ciúdad Real (ES), 10.09.2006-14.09.2006] Institutional research plan: CEZ:AV0Z40720504 Keywords : chemical vapour deposition Subject RIV: CH - Nuclear ; Quantum Chemistry

  6. Chemical vapour deposition of zeolitic imidazolate framework thin films

    Stassen, Ivo; Styles, Mark; Grenci, Gianluca; Gorp, Hans Van; Vanderlinden, Willem; Feyter, Steven De; Falcaro, Paolo; Vos, Dirk De; Vereecken, Philippe; Ameloot, Rob

    2016-03-01

    Integrating metal-organic frameworks (MOFs) in microelectronics has disruptive potential because of the unique properties of these microporous crystalline materials. Suitable film deposition methods are crucial to leverage MOFs in this field. Conventional solvent-based procedures, typically adapted from powder preparation routes, are incompatible with nanofabrication because of corrosion and contamination risks. We demonstrate a chemical vapour deposition process (MOF-CVD) that enables high-quality films of ZIF-8, a prototypical MOF material, with a uniform and controlled thickness, even on high-aspect-ratio features. Furthermore, we demonstrate how MOF-CVD enables previously inaccessible routes such as lift-off patterning and depositing MOF films on fragile features. The compatibility of MOF-CVD with existing infrastructure, both in research and production facilities, will greatly facilitate MOF integration in microelectronics. MOF-CVD is the first vapour-phase deposition method for any type of microporous crystalline network solid and marks a milestone in processing such materials.

  7. Chemical vapour deposition synthetic diamond: materials, technology and applications

    Balmer, R. S.; Brandon, J R; Clewes, S L; Dhillon, H. K.; Dodson, J M; Friel, I.; Inglis, P. N.; Madgwick, T D; Markham, M. L.; Mollart, T P; Perkins, N.; Scarsbrook, G. A.; Twitchen, D. J.; Whitehead, A J; Wilman, J J

    2009-01-01

    Substantial developments have been achieved in the synthesis of chemical vapour deposition (CVD) diamond in recent years, providing engineers and designers with access to a large range of new diamond materials. CVD diamond has a number of outstanding material properties that can enable exceptional performance in applications as diverse as medical diagnostics, water treatment, radiation detection, high power electronics, consumer audio, magnetometry and novel lasers. Often the material is synt...

  8. Dry-transfer of chemical vapour deposited nanocarbon thin films

    Cole, Matthew Thomas

    2012-01-01

    This thesis presents the development of chemical vapour deposited (CVD) graphene and multi-walled carbon nanotubes (MWCNTs) as enabling technologies for flexible transparent conductors offering enhanced functionality. The technologies developed could be employed as thin film field emission sources, optical sensors and substrate-free wideband optical polarisers. Detailed studies were performed on CVD Fe and Ni catalysed carbon nanotubes and nanofibres on indium tin oxide, alu...

  9. Microscopic characterisation of suspended graphene grown by chemical vapour deposition

    Bignardi, Luca; van Dorp, Willem F; Gottardi, Stefano; Ivashenko, Oleksii; Dudin, Pavel; Barinov, Alexei; de Hosson, Jeff Th. M.; Stöhr, Meike; Rudolf, Petra

    2013-01-01

    We present a multi-technique characterisation of graphene grown by chemical vapour deposition (CVD) and thereafter transferred to and suspended on a grid for transmission electron microscopy (TEM). The properties of the electronic band structure are investigated by angle-resolved photoelectron spectromicroscopy, while the structural and crystalline properties are studied by TEM and Raman spectroscopy. We demonstrate that the suspended graphene membrane locally shows electronic properties comp...

  10. Laser-Induced Chemical Vapour Deposition of Silicon Carbonitride

    Besling, W.; van der Put, P.; Schoonman, J.

    1995-01-01

    Laser-induced Chemical Vapour Deposition of silicon carbonitride coatings and powders has been investigated using hexamethyldisilazane (HMDS) and ammonia as reactants. An industrial CW CO2-laser in parallel configuration has been used to heat up the reactant gases. HMDS dissociates in the laser beam and reactive radicals are formed which increase rapidly in molecular weight by an addition mechanism. Dense polymer-like silicon carbonitride thin films and nanosized powders are formed depending ...

  11. Light-induced chemical vapour deposition painting with titanium dioxide

    Halary-Wagner, E.; Bret, T.; Hoffmann, P

    2003-03-15

    Light-induced chemical vapour deposits of titanium dioxide are obtained from titanium tetra-isopropoxide (TTIP) in an oxygen and nitrogen atmosphere with a long pulse (250 ns) 308 nm XeCl excimer laser using a mask projection set-up. The demonstrated advantages of this technique are: (i) selective area deposition, (ii) precise control of the deposited thickness and (iii) low temperature deposition, enabling to use a wide range of substrates. A revolving mask system enables, in a single reactor load, to deposit shapes of controlled heights, which overlap to build up a complex pattern. Interferential multi-coloured deposits are achieved, and the process limitations (available colours and resolution) are discussed.

  12. Light-induced chemical vapour deposition painting with titanium dioxide

    Halary-Wagner, E.; Bret, T.; Hoffmann, P.

    2003-03-01

    Light-induced chemical vapour deposits of titanium dioxide are obtained from titanium tetra-isopropoxide (TTIP) in an oxygen and nitrogen atmosphere with a long pulse (250 ns) 308 nm XeCl excimer laser using a mask projection set-up. The demonstrated advantages of this technique are: (i) selective area deposition, (ii) precise control of the deposited thickness and (iii) low temperature deposition, enabling to use a wide range of substrates. A revolving mask system enables, in a single reactor load, to deposit shapes of controlled heights, which overlap to build up a complex pattern. Interferential multi-coloured deposits are achieved, and the process limitations (available colours and resolution) are discussed.

  13. Chemical vapour deposited diamonds for dosimetry of radiotherapeutical beams

    Bucciolini, M.; Mazzocchi, S. [Firenze Univ., Firenze (Italy). Dipartimento di Fisiopatologia Clinica; INFN, Firenze (Italy); Borchi, E.; Bruzzi, M.; Pini, S.; Sciortino, S. [Firenze Univ., Firenze (Italy). Dipartimento di Energetica; INFN, Firenze (Italy); Cirrone, G.A.P.; Guttone, G.; Raffaele, L.; Sabini, M.G. [INFN, Catania (Italy). Laboratori Nazionali del Sud

    2002-07-01

    This paper deals with the application of synthetic diamond detectors to the clinical dosimetry of photon and electron beams. It has been developed in the frame of INFN CANDIDO project and MURST Cofin. Diamonds grown with CVD (Chemical Vapour Deposition) technique have been studied; some of them are commercial samples while others have been locally synthesised. Experiments have been formed using both on-line and off-line approaches. For the off-line measurements, TL (thermoluminescent) and TSC (thermally stimulated current) techniques have been used.

  14. Microscopic characterisation of suspended graphene grown by chemical vapour deposition

    Bignardi, Luca; van Dorp, Willem F.; Gottardi, Stefano; Ivashenko, Oleksii; Dudin, Pavel; Barinov, Alexei; de Hosson, Jeff Th. M.; Stöhr, Meike; Rudolf, Petra

    2013-09-01

    We present a multi-technique characterisation of graphene grown by chemical vapour deposition (CVD) and thereafter transferred to and suspended on a grid for transmission electron microscopy (TEM). The properties of the electronic band structure are investigated by angle-resolved photoelectron spectromicroscopy, while the structural and crystalline properties are studied by TEM and Raman spectroscopy. We demonstrate that the suspended graphene membrane locally shows electronic properties comparable with those of samples prepared by micromechanical cleaving of graphite. Measurements show that the area of high quality suspended graphene is limited by the folding of the graphene during the transfer.

  15. Microscopic characterisation of suspended graphene grown by chemical vapour deposition.

    Bignardi, Luca; van Dorp, Willem F; Gottardi, Stefano; Ivashenko, Oleksii; Dudin, Pavel; Barinov, Alexei; De Hosson, Jeff Th M; Stöhr, Meike; Rudolf, Petra

    2013-10-01

    We present a multi-technique characterisation of graphene grown by chemical vapour deposition (CVD) and thereafter transferred to and suspended on a grid for transmission electron microscopy (TEM). The properties of the electronic band structure are investigated by angle-resolved photoelectron spectromicroscopy, while the structural and crystalline properties are studied by TEM and Raman spectroscopy. We demonstrate that the suspended graphene membrane locally shows electronic properties comparable with those of samples prepared by micromechanical cleaving of graphite. Measurements show that the area of high quality suspended graphene is limited by the folding of the graphene during the transfer. PMID:23945527

  16. Chemical vapour deposited diamonds for dosimetry of radiotherapeutical beams

    This paper deals with the application of synthetic diamond detectors to the clinical dosimetry of photon and electron beams. It has been developed in the frame of INFN CANDIDO project and MURST Cofin. Diamonds grown with CVD (Chemical Vapour Deposition) technique have been studied; some of them are commercial samples while others have been locally synthesised. Experiments have been formed using both on-line and off-line approaches. For the off-line measurements, TL (thermoluminescent) and TSC (thermally stimulated current) techniques have been used

  17. Physical properties of chemical vapour deposited nanostructured carbon thin films

    Mahadik, D.B.; Shinde, S.S.; Bhosale, C.H. [Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur, Maharashtra 416004 (India); Rajpure, K.Y., E-mail: rajpure@yahoo.com [Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur, Maharashtra 416004 (India)

    2011-02-03

    Research highlights: In the present paper, nanostructured carbon films are grown using a natural precursor 'turpentine oil (C{sub 10}H{sub 16})' as a carbon source in the simple thermal chemical vapour deposition method. The influence of substrate surface topography (viz. stainless steel, fluorine doped tin oxide coated quartz) and temperature on the evolution of carbon allotropes surfaces topography/microstructural and structural properties are investigated and discussed. - Abstract: A simple thermal chemical vapour deposition technique is employed for the deposition of carbon films by pyrolysing the natural precursor 'turpentine oil' on to the stainless steel (SS) and FTO coated quartz substrates at higher temperatures (700-1100 deg. C). In this work, we have studied the influence of substrate and deposition temperature on the evolution of structural and morphological properties of nanostructured carbon films. The films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle measurements, Fourier transform infrared (FTIR) and Raman spectroscopy techniques. XRD study reveals that the films are polycrystalline exhibiting hexagonal and face-centered cubic structures on SS and FTO coated glass substrates respectively. SEM images show the porous and agglomerated surface of the films. Deposited carbon films show the hydrophobic nature. FTIR study displays C-H and O-H stretching vibration modes in the films. Raman analysis shows that, high ID/IG for FTO substrate confirms the dominance of sp{sup 3} bonds with diamond phase and less for SS shows graphitization effect with dominant sp{sup 2} bonds. It reveals the difference in local microstructure of carbon deposits leading to variation in contact angle and hardness, which is ascribed to difference in the packing density of carbon films, as observed also by Raman.

  18. The atmospheric chemical vapour deposition of coatings on glass

    Sanderson, K D

    1996-01-01

    The deposition of thin films of indium oxide, tin doped indium oxide (ITO) and titanium nitride for solar control applications have been investigated by Atmospheric Chemical Vapour Deposition (APCVD). Experimental details of the deposition system and the techniques used to characterise the films are presented. Results from investigations into the deposition parameters, the film microstructure and film material properties are discussed. A range of precursors were investigated for the deposition of indium oxide. The effect of pro-mixing the vaporised precursor with an oxidant source and the deposition temperature has been studied. Polycrystalline In sub 2 O sub 3 films with a resistivity of 1.1 - 3x10 sup - sup 3 OMEGA cm were obtained with ln(thd) sub 3 , oxygen and nitrogen. The growth of ITO films from ln(thd) sub 3 , oxygen and a range of tin dopants is also presented. The effect of the dopant precursor, the doping concentration, deposition temperature and the effect of additives on film growth and microstr...

  19. Chemical Vapour Deposition of Gas Sensitive Metal Oxides

    Stella Vallejos

    2016-03-01

    Full Text Available This article presents a review of recent research efforts and developments for the fabrication of metal-oxide gas sensors using chemical vapour deposition (CVD, presenting its potential advantages as a materials synthesis technique for gas sensors along with a discussion of their sensing performance. Thin films typically have poorer gas sensing performance compared to traditional screen printed equivalents, attributed to reduced porosity, but the ability to integrate materials directly with the sensor platform provides important process benefits compared to competing synthetic techniques. We conclude that these advantages are likely to drive increased interest in the use of CVD for gas sensor materials over the next decade, whilst the ability to manipulate deposition conditions to alter microstructure can help mitigate the potentially reduced performance in thin films, hence the current prospects for use of CVD in this field look excellent.

  20. Surface chemical studies of chemical vapour deposited diamond thin films

    Polycrystalime diamond grown by low pressure chemical vapour deposition (CVD) techniques has emerged in recent years as a new material with applications in such areas as optics, electronics, radiation detectors, chemical sensors and electrochemistry. A main aim of this thesis has been to advance current knowledge of the surface chemical properties of CVD diamond to underpin the development of our understanding of the properties and potential applications of this material. Cl2 is found to adsorb dissociatively on the clean, hydrogen-free diamond surface up to sub-monolayer coverage with a sticking probability of ∼1.2x10-3. Adsorption is a non-activated process, and the sticking probability and extent of coverage decreased with increasing temperature. This was shown to contrast with the behaviour found for the interaction of chlorine with the hydrogenated diamond surface where increased sticking probabilities and saturation surface coverages were observed, and where the reactivity also increased with temperature. Thermal desorption of atomic Cl occurred over a broad temperature range m both chemisorption systems, indicating the presence of more than one binding state. Atomic hydrogen was successful in efficiently etching the bound Cl from the surface. XeF2 was found to adsorb dissociatively onto the clean diamond surface to give up to monolayer coverages of F, which formed two distinct binding states. The first state, populated at low coverage, was predominantly covalent in character, while the second state, occurring at high surface coverages, had more ionic bonding character. Pre-hydrogenation of the diamond surface increased the reactive sticking probability observed, but decreased the extent of coverage by blocking reactive sites. The semi-ionic F was readily etched by atomic hydrogen, and underwent thermal desorption at temperatures as low as 300 deg C. The covalent form was more stable, being seemingly resistant to etching and persistent to high temperatures

  1. Chemical vapour deposition synthetic diamond: materials, technology and applications

    Balmer, R. S.; Brandon, J. R.; Clewes, S. L.; Dhillon, H. K.; Dodson, J. M.; Friel, I.; Inglis, P. N.; Madgwick, T. D.; Markham, M. L.; Mollart, T. P.; Perkins, N.; Scarsbrook, G. A.; Twitchen, D. J.; Whitehead, A. J.; Wilman, J. J.; Woollard, S. M.

    2009-09-01

    Substantial developments have been achieved in the synthesis of chemical vapour deposition (CVD) diamond in recent years, providing engineers and designers with access to a large range of new diamond materials. CVD diamond has a number of outstanding material properties that can enable exceptional performance in applications as diverse as medical diagnostics, water treatment, radiation detection, high power electronics, consumer audio, magnetometry and novel lasers. Often the material is synthesized in planar form; however, non-planar geometries are also possible and enable a number of key applications. This paper reviews the material properties and characteristics of single crystal and polycrystalline CVD diamond, and how these can be utilized, focusing particularly on optics, electronics and electrochemistry. It also summarizes how CVD diamond can be tailored for specific applications, on the basis of the ability to synthesize a consistent and engineered high performance product.

  2. Thermoluminescence characterisation of chemical vapour deposited diamond films

    Mazzocchi, S; Bucciolini, M; Cuttone, G; Pini, S; Sabini, M G; Sciortino, S

    2002-01-01

    The thermoluminescence (TL) characteristics of a set of six chemical vapour deposited diamond films have been studied with regard to their use as off-line dosimeters in radiotherapy. The structural characterisation has been performed by means of Raman spectroscopy. Their TL responses have been tested with radiotherapy beams ( sup 6 sup 0 Co photons, photons and electrons from a linear accelerator (Linac), 26 MeV protons from a TANDEM accelerator) in the dose range 0.1-7 Gy. The dosimetric characterisation has yielded a very good reproducibility, a very low dependence of the TL response on the type of particle and independence of the radiation energy. The TL signal is not influenced by the dose rate and exhibits a very low thermal fading. Moreover, the sensitivity of the diamond samples compares favourably with that of standard TLD100 dosimeters.

  3. Plasma Enhanced Chemical Vapour Deposition of Horizontally Aligned Carbon Nanotubes

    Matthew T. Cole

    2013-05-01

    Full Text Available A plasma-enhanced chemical vapour deposition reactor has been developed to synthesis horizontally aligned carbon nanotubes. The width of the aligning sheath was modelled based on a collisionless, quasi-neutral, Child’s law ion sheath where these estimates were empirically validated by direct Langmuir probe measurements, thereby confirming the proposed reactors ability to extend the existing sheath fields by up to 7 mm. A 7 mbar growth atmosphere combined with a 25 W plasma permitted the concurrent growth and alignment of carbon nanotubes with electric fields of the order of 0.04 V μm−1 with linear packing densities of up to ~5 × 104 cm−1. These results open up the potential for multi-directional in situ alignment of carbon nanotubes providing one viable route to the fabrication of many novel optoelectronic devices.

  4. Plasma assisted chemical vapour deposition for optical coatings

    Full text: Plasma assisted chemical vapour deposition (PECVD) is commonly used in semiconductor fabrication plants for depositing layers of dielectric materials. Reactive gasses are admitted to a chamber at low pressure and applying an electric field, usually a RF field, generates a plasma. The gasses react to form a solid material on the walls of the chamber and substrates. In this project we are exploring the possibility of applying this method to the growth of multilayer optical thin films. A small prototype system was constructed and optical multi layers of up to 24 layers were deposited over a diameter of 90 mm. The system uses 13.56 MHz RF to generate the plasma in a simple capacitive plate chamber. The gasses used were silane, oxygen and nitrogen. This allows SiO2 (RI 1.45) and Si3N4 (RI 1.93) to be deposited. Multilayer coatings were designed using these materials on TFCalc. The required thickness for the various layers were tabulated and fed into a computer controlling the gas flow during deposition. In this way the structures were deposited semi-automatically. The growing films were monitored using a spectrometer looking at light reflected from the growing film over a range from 400 - 800 nm simultaneously. This data was then used to reconstruct the deposition and analyze deviations from the design. An SEM micrograph of the cross-section of the multilayers was used to obtain relative thicknesses of the individual layers. Other structures deposited include rugate notch filters, coloured filters and broad band anti-reflection layers. Running the prototype has proved the concept and the project has moved to a scale up stage in which a larger version is being constructed at Avtronics Pty Ltd. This aims to coat uniformly over a diameter of 600 mm. Initially, the same materials will be used to produce coatings but fixture work will increase the refractive index range of materials which can be deposited and fully automate the coating process. (authors)

  5. Chemical vapour deposition of diamond coatings onto molybdenum dental tools

    The growth of polycrystalline diamond films onto molybdenum rods and dental burrs by using a new hot filament chemical vapour deposition (CVD) system has been investigated. Negative dc bias voltage relative to the filament was applied to the molybdenum substrate prior to deposition. This led to much improved film adhesion and increased nucleation density. There was a factor of four improvement in the adhesive force from 20 to 80 N when a bias voltage of -300 V was employed to the substrate. The CVD coated molybdenum dental burr was found to give much improved performance and lifetime compared to the conventional sintered diamond burr. The CVD diamond burr showed no signs of deterioration even after 1000 operations whereas the conventional sintered diamond burrs were ineffective after between 30 and 60 operations. This represents a 30-fold improvement when CVD is applied. CVD diamond growth onto dental burrs has the potential for replacing exciting technology by achieving better performance and lifetime in a cost-effective manner

  6. Laser diagnostics of chemical vapour deposition of diamond films

    Wills, J B

    2002-01-01

    Cavity ring down spectroscopy (CRDS) has been used to make diagnostic measurements of chemically activated CH sub 4 / H sub 2 gas mixtures during the chemical vapour deposition (CVD) of thin diamond films. Absolute absorbances, concentrations and temperatures are presented for CH sub 3 , NH and C sub 2 H sub 2 in a hot filament (HF) activated gas mixture and CH, C sub 2 and C sub 2 H sub 2 in a DC arc plasma jet activated mixture. Measurements of the radical species were made using a pulsed dye laser system to generate tuneable visible and UV wavelengths. These species have greatest concentration in the hottest, activated regions of the reactors. Spatial profiling of the number densities of CH sub 3 and NH radicals have been used as stringent tests of predictions of radical absorbance and number densities made by 3-D numerical simulations, with near quantitative agreement. O sub 2 has been shown to reside in the activated region of the Bristol DC arc jet at concentrations (approx 10 sup 1 sup 3 molecules / cm...

  7. Photo Initiated Chemical Vapour Deposition To Increase Polymer Hydrophobicity.

    Bérard, Ariane; Patience, Gregory S; Chouinard, Gérald; Tavares, Jason R

    2016-01-01

    Apple growers face new challenges to produce organic apples and now many cover orchards with high-density polyethylene (HDPE) nets to exclude insects, rather than spraying insecticides. However, rainwater- associated wetness favours the development of apple scabs, Venturia inaequalis, whose lesions accumulate on the leaves and fruit causing unsightly spots. Treating the nets with a superhydrophobic coating should reduce the amount of water that passes through the net. Here we treat HDPE and polyethylene terephthalate using photo-initiated chemical vapour deposition (PICVD). We placed polymer samples in a quartz tube and passed a mixture of H2 and CO through it while a UVC lamp (254 nm) illuminated the surface. After the treatment, the contact angle between water droplets and the surface increased by an average of 20°. The contact angle of samples placed 70 cm from the entrance of the tube was higher than those at 45 cm and 20 cm. The PICVD-treated HDPE achieved a contact angle of 124°. Nets spray coated with a solvent-based commercial product achieved 180° but water ingress was, surprisingly, higher than that for nets with a lower contact angle. PMID:27531048

  8. SYNTHESIS OF CARBON NANOSTRUCTURES BY PLASMA ENHANCED CHEMICAL VAPOUR DEPOSITION AT ATMOSPHERIC PRESSURE

    Jašek Ondřej; Synek Petr; Zajíčková Lenka; Eliáš Marek; Kudrle Vít

    2010-01-01

    Carbon nanostructures present leading field in nanotechnology research. Wide range of chemical and physical methods was used for carbon nanostructures synthesis including arc discharges, laser ablation and chemical vapour deposition. Plasma enhanced chemical vapour deposition (PECVD) with its application in modern microelectronics industry became soon target of research in carbon nanostructures synthesis. The selection of the ideal growth process depends on the application. Most of PECVD tech...

  9. Simplified Monte Carlo simulations of chemical vapour deposition diamond growth

    A simple one-dimensional Monte Carlo model has been developed to simulate the chemical vapour deposition (CVD) of a diamond (100) surface. The model considers adsorption, etching/desorption, lattice incorporation, and surface migration along and across the dimer rows. The top of a step-edge is considered to have an infinite Ehrlich-Schwoebel potential barrier, so that mobile surface species cannot migrate off the edge. The reaction probabilities are taken from experimental or calculated literature values for standard CVD diamond conditions. The criterion used for the critical nucleus needed to form a new layer is considered to be two surface carbon species bonded together, which forms an immobile, unetchable step on the surface. This nucleus can arise from two migrating species meeting, or from direct adsorption of a carbon species next to a migrating species. The analysis includes film growth rate, surface roughness, and the evolving film morphology as a function of varying reaction probabilities. Using standard CVD diamond parameters, the simulations reveal that a smooth film is produced with apparent step-edge growth, with growth rates (∼1 μm h-1) consistent with experiment. The β-scission reaction was incorporated into the model, but was found to have very little effect upon growth rates or film morphology. Renucleation events believed to be due to reactive adsorbates, such as C atoms or CN groups, were modelled by creating random surface defects which form another type of critical nucleus upon which to nucleate a new layer. These were found to increase the growth rate by a factor of ∼10 when the conditions were such that the rate-limiting step for growth was new layer formation. For other conditions these surface defects led to layered 'wedding cake' structures or to rough irregular surfaces resembling those seen experimentally during CVD of nanocrystalline diamond.

  10. Carbon Nanotubes/Nanofibers by Plasma Enhanced Chemical Vapour Deposition

    Teo, K. B. K.; Hash, D. B.; Bell, M. S.; Chhowalla, M.; Cruden, B. A.; Amaratunga, G. A. J.; Meyyappan, M.; Milne, W. I.

    2005-01-01

    Plasma enhanced chemical vapour deposition (PECVD) has been recently used for the production of vertically aligned carbon nanotubedfibers (CN) directly on substrates. These structures are potentially important technologically as electron field emitters (e.g. microguns, microwave amplifiers, displays), nanoelectrodes for sensors, filter media, superhydrophobic surfaces and thermal interface materials for microelectronics. A parametric study on the growth of CN grown by glow discharge dc-PECVD is presented. In this technique, a substrate containing thin film Ni catalyst is exposed to C2H2 and NH3 gases at 700 C. Without plasma, this process is essentially thermal CVD which produces curly spaghetti-like CN as seen in Fig. 1 (a). With the plasma generated by biasing the substrate at -6OOV, we observed that the CN align vertically during growth as shown in Fig. l(b), and that the magnitude of the applied substrate bias affects the degree of alignment. The thickness of the thin film Ni catalyst was found to determine the average diameter and inversely the length of the CN. The yield and density of the CN were controlled by the use of different diffusion barrier materials under the Ni catalyst. Patterned CN growth [Fig. l(c)], with la variation in CN diameter of 4.1% and 6.3% respectively, is achieved by lithographically defining the Ni thin film prior to growth. The shape of the structures could be varied from very straight nanotube-like to conical tip-like nanofibers by increasing the ratio of C2H2 in the gas flow. Due to the plasma decomposition of C2H2, amorphous carbon (a-C) is an undesirable byproduct which could coat the substrate during CN growth. Using a combination of depth profiled Auger electron spectroscopy to study the substrate and in-situ mass spectroscopy to examine gas phase neutrals and ions, the optimal conditions for a-C free growth of CN is determined.

  11. Current understanding of the growth of carbon nanotubes in catalytic chemical vapour deposition

    Jourdain, Vincent; Bichara, Christophe

    2013-01-01

    Due to its higher degree of control and its scalability, catalytic chemical vapour deposition is now the prevailing synthesis method of carbon nanotubes. Catalytic chemical vapour deposition implies the catalytic conversion of a gaseous precursor into a solid material at the surface of reactive particles or of a continuous catalyst film acting as a template for the growing material. Significant progress has been made in the field of nanotube synthesis by this method although nanotube samples ...

  12. Deposition of diamond and boron nitride films by plasma chemical vapour deposition

    Albella, J.M. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.; Gomez-Aleixandre, C. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.; Sanchez-Garrido, O. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.; Vazquez, L. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.; Martinez-Duart, J.M. [Universidad Autonoma, CSIC, Madrid (Spain). Inst. of Mater. Sci.

    1995-01-01

    The deposition problems of diamond and cubic boron nitride (c-BN) by chemical vapour deposition techniques are reviewed, with major emphasis on the nucleation and reaction mechanisms. A discussion is made of the main deposition parameters (i.e. gas mixture, substrate conditioning, plasma discharges etc.) which favour the formation of the cubic phase. Most of the work is devoted to diamond owing to the large progress attained in this material. In fact, the use of diamond as a hard protective coating is now on a commercial scale. By contrast, the preparation of c-BN layers with good characteristics still needs of further research. ((orig.))

  13. Laser diagnostics of chemical vapour deposition of diamond films

    Cavity ring down spectroscopy (CRDS) has been used to make diagnostic measurements of chemically activated CH4 / H2 gas mixtures during the chemical vapour deposition (CVD) of thin diamond films. Absolute absorbances, concentrations and temperatures are presented for CH3, NH and C2H2 in a hot filament (HF) activated gas mixture and CH, C2 and C2H2 in a DC arc plasma jet activated mixture. Measurements of the radical species were made using a pulsed dye laser system to generate tuneable visible and UV wavelengths. These species have greatest concentration in the hottest, activated regions of the reactors. Spatial profiling of the number densities of CH3 and NH radicals have been used as stringent tests of predictions of radical absorbance and number densities made by 3-D numerical simulations, with near quantitative agreement. O2 has been shown to reside in the activated region of the Bristol DC arc jet at concentrations (∼1013 molecules / cm3) sufficient for it to play an important role in the diamond film growth, with CH approximately equivalent in abundance. The average gas temperatures of both C2 and CH radicals in the DC arc jet are found to be 3200 ± 300 K in the free flowing plasma plume, as measured from Boltzmann plots and Doppler line widths. Both number densities and gas temperatures rise significantly within 5 mm of the substrate surface in what is termed the boundary layer. Temperatures rise to 4800 ± 400 K within 1 mm from the substrate surface where the average C2 and CH concentrations are a factor of approximately four greater than in the free flowing plume. The effects of changing process parameters such as methane fraction in the feed gas and activation input power on number densities and temperatures have also been investigated. In addition to these advances in our understanding of the diamond CVD process, a new spectroscopic technique, continuous wave cavity ring down spectroscopy (cw CRDS) using tuneable, continuous wave diode lasers, has

  14. Properties of alumina films by atmospheric pressure metal-organic chemical vapour deposition

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

    1994-01-01

    Thin alumina films were deposited at low temperatures (290–420°C) on stainless steel, type AISI 304. The deposition process was carried out in nitrogen by metal-organic chemical vapour deposition using aluminum tri-sec-butoxide. The film properties including the protection of the underlying substrat

  15. Deposition of indium tin oxide by atmospheric pressure chemical vapour deposition

    We report the deposition of indium tin oxide (ITO) by atmospheric pressure chemical vapour deposition (APCVD). This process is potentially scalable for high throughput, large area production. We utilised a previously unreported precursor combination; dimethylindium acetylacetonate, [Me2In(acac)] and monobutyltintrichloride, MBTC. [Me2In(acac)] is a volatile solid. It is more stable and easier to handle than traditional indium oxide precursors such as pyrophoric trialkylindium compounds. Monobutyltintrichloride (MBTC) is also easily handled and can be readily vaporised. It is compatible with the process conditions required for using [Me2In(acac)]. Cubic ITO was deposited at a substrate temperature of 550 °C with growth rates exceeding 15 nm/s and growth efficiencies of between 20 and 30%. Resistivity was 3.5 × 10−4 Ω cm and transmission for a 200 nm film was > 85% with less than 2% haze.

  16. Deposition of fluorine doped indium oxide by atmospheric pressure chemical vapour deposition

    We report the deposition of fluorine doped indium oxide by atmospheric pressure chemical vapour deposition (APCVD) using a previously unreported precursor combination; dimethylindium acetylacetonate, [Me2In(acac)] and trifluoroacetic acid (TFA). This process is potentially scalable for high throughput, large area production. [Me2In(acac)] is a volatile solid. It is more stable and easier to handle than traditional indium oxide precursors such as pyrophoric trialkylindium compounds. Cubic fluorine doped indium oxide (F.In2O3) was deposited at a substrate temperature of 550 °C with growth rates exceeding 8 nm/s. Resistivity was 8 × 10−4 Ω cm and transmission for a 200 nm film was > 80% with less than 1% haze.

  17. Characterization of Thin Films Deposited with Precursor Ferrocene by Plasma Enhanced Chemical Vapour Deposition

    YAO Kailun; ZHENG Jianwan; LIU Zuli; JIA Lihui

    2007-01-01

    In this paper,the characterization of thin films,deposited with the precursor ferrocene(FcH)by the plasma enhanced chemical vapour deposition(PECVD)technique,was investigated.The films were measured by Scanning Electronic Microscopy(SEM),Atomic Force Microscopy(AFM),Electron Spectroscopy for Chemical Analysis(ESCA),and superconducting Quantum Interference Device(SQUID).It was observed that the film's layer is homogeneous in thickness and has a dense morphology without cracks.The surface roughness is about 36 nm.From the results of ESCA,it can be inferred that the film mainly contains the compound FeOOH,and carbon is combined with oxygen in different forms under different supply-powers.The hysteresis loops indicate that the film is of soft magnetism.

  18. Low resistance polycrystalline diamond thin films deposited by hot filament chemical vapour deposition

    Mahtab Ullah; Ejaz Ahmed; Abdelbary Elhissi; Waqar Ahmed

    2014-05-01

    Polycrystalline diamond thin films with outgrowing diamond (OGD) grains were deposited onto silicon wafers using a hydrocarbon gas (CH4) highly diluted with H2 at low pressure in a hot filament chemical vapour deposition (HFCVD) reactor with a range of gas flow rates. X-ray diffraction (XRD) and SEM showed polycrystalline diamond structure with a random orientation. Polycrystalline diamond films with various textures were grown and (111) facets were dominant with sharp grain boundaries. Outgrowth was observed in flowerish character at high gas flow rates. Isolated single crystals with little openings appeared at various stages at low gas flow rates. Thus, changing gas flow rates had a beneficial influence on the grain size, growth rate and electrical resistivity. CVD diamond films gave an excellent performance for medium film thickness with relatively low electrical resistivity and making them potentially useful in many industrial applications.

  19. Thermoluminescence Characteristics of a New Production of Chemical Vapour Deposition Diamond

    Furetta, C.; Kitis, G.; Brambilla, A.; Jany, C.; Bergonzo, P.; Foulon, F

    1999-07-01

    The dosimetric properties are presented of a recent production of chemical vapour deposition diamond growth. Experimental data concerning the TL response as a function of dose, the energy response and fading behaviour are reported. Very preliminary results suggest that diamond can be used in TL mode as well as an activation detector. (author)

  20. Control of tin oxide film morphology by addition of hydrocarbons to the chemical vapour deposition process

    Yates, H.M.; Evans, P.; Sheel, D.W.; Remeš, Zdeněk; Vaněček, Milan

    2010-01-01

    Roč. 519, č. 4 (2010), s. 1334-1340. ISSN 0040-6090 EU Projects: European Commission(XE) 214134 - N2P; European Commission(XE) 38885 - SE-POWERFOIL Institutional research plan: CEZ:AV0Z10100521 Keywords : alcohol * chemical vapour deposition * morphology * tin oxide Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.909, year: 2010

  1. Characterisation of TiO 2 deposited by photo-induced chemical vapour deposition

    Kaliwoh, Never; Zhang, Jun-Ying; Boyd, Ian W.

    2002-01-01

    We report the deposition of thin TiO 2 films on crystalline Si and quartz by photo-induced chemical vapour deposition (CVD) using UV excimer lamps employing a dielectric barrier discharge in krypton chloride (KrCl ∗) to provide intense narrow band radiation at λ=222 nm. The precursor used was titanium isopropoxide (TTIP). Films from around 20-510 nm in thickness with refractive indices from 2.20 to 2.54 were grown at temperatures between 50 and 350 °C. The higher refractive index values compare favourably with the value of 2.58 recorded for the bulk material. The measured deposition rate was around 50 nm/min at 350 °C. Fourier transform infrared spectroscopy (FTIR) revealed the presence of TiO 2 through the observation of a Ti-O absorption peak and the absence of OH in films deposited at 250-350 °C indicated relatively good quality films. The phase of films deposited at 200-350 °C was anatase as determined by X-ray diffraction.

  2. Selective light induced chemical vapour deposition of titanium dioxide thin films

    Wagner, Estelle; Hoffmann, Patrik

    2005-01-01

    Light Induced Chemical Vapour Deposition (LICVD) of titanium dioxide thin films is studied in this work. It is shown that this technique enables to deposit locally and selectively a chosen crystalline phase with a precise controlled thickness at low substrate temperature, allowing even the use of polymer substrates. A home made LICVD reactor was set up, consisting of a main chamber in which the substrate was placed on a temperature controlled plate and could be irradiated perpendicularly thro...

  3. Selective light induced chemical vapour deposition of titanium dioxide thin films

    Wagner, Estelle

    2003-01-01

    Light Induced Chemical Vapour Deposition (LICVD) of titanium dioxide thin films is studied in this work. It is shown that this technique enables to deposit locally and selectively a chosen crystalline phase with a precise controlled thickness at low substrate temperature, allowing even the use of polymer substrates. A home made LICVD reactor was set up, consisting of a main chamber in which the substrate was placed on a temperature controlled plate and could be irradiated perpendicularly thro...

  4. Laser induced chemical vapour deposition of TiN coatings at atmospheric pressure

    Croonen, Y.; Verspui, G.

    1993-01-01

    Laser induced Chemical Vapour Deposition of a wide variety of materials has been studied extensively at reduced pressures. However, for this technique to be economically and industrially applicable, processes at atmospheric pressure are preferred. A model study was made on the substrate-coating system molybdenum-titaniumnitride focussing on the feasibility to deposit TiN films locally at atmospheric pressure. The results of this study turned out to be very promising. A Nd-YAG laser beam ([MAT...

  5. Green electroluminescence from ZnO/n-InP heterostructure fabricated by metalorganic chemical vapour deposition

    Vertically aligned ZnO films were deposited on n-InP by metalorganic chemical vapour deposition. X-ray diffraction, field emission scanning electron microscopy and photoluminescence measurements demonstrated that the ZnO films had good quality. By evaporating AuZn electrodes on both ZnO and InP surfaces, a ZnO-based light emitting device was fabricated. Under forward voltage, weak green emissions can be observed in darkness

  6. Green electroluminescence from ZnO/n-InP heterostructure fabricated by metalorganic chemical vapour deposition

    Zhu Huichao [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Zhang Baolin [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Li Xiangping [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Dong Xin [State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Department of Physics, Dalian University of Technology, Dalian 116023 (China); Li Wancheng [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Guan Hesong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Cui Yongguo [State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Department of Physics, Dalian University of Technology, Dalian 116023 (China); Xia Xiaochuan [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Yang Tianpeng [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Chang Yuchun [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China); Du Guotong [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China)

    2007-09-07

    Vertically aligned ZnO films were deposited on n-InP by metalorganic chemical vapour deposition. X-ray diffraction, field emission scanning electron microscopy and photoluminescence measurements demonstrated that the ZnO films had good quality. By evaporating AuZn electrodes on both ZnO and InP surfaces, a ZnO-based light emitting device was fabricated. Under forward voltage, weak green emissions can be observed in darkness.

  7. Remote Microwave Plasma Enhanced Chemical Vapour Deposition of SiO2 Films : Oxygen Plasma Diagnostic

    Regnier, C.; Desmaison, J.; Tristant, P.; Merle, D.

    1995-01-01

    Silicon oxide is deposited by remote microwave plasma enhanced chemical vapour deposition (RMPECVD). The silica films are produced by exciting oxygen in a microwave discharge while a mixture of 5% of silane diluted in argon is introduced downstream. In the afterglow, double Langmuir probe measurements and rotational temperatures deduced from optical emission spectroscopy (OES), show that the electron energy is transferred to the gas when the pressure increases (19 - 26 Pa). Therefore the elec...

  8. Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition

    Zhu, Wenjuan; Low, Tony; Lee, Yi-Hsien; Wang, Han; Farmer, Damon B.; Kong, Jing; Xia, Fengnian; Avouris, Phaedon

    2013-01-01

    Layered transition metal dichalcogenides display a wide range of attractive physical and chemical properties and are potentially important for various device applications. Here we report the electronic transport and device properties of monolayer molybdenum disulphide (MoS2) grown by chemical vapour deposition (CVD). We show that these devices have the potential to suppress short channel effects and have high critical breakdown electric field. However, our study reveals that the electronic pr...

  9. Structural properties of zinc oxide deposited using atmospheric pressure combustion chemical vapour deposition

    In this study the deposition of thin zinc oxide (ZnO) films under atmospheric pressure conditions was investigated. The deposition technique applied was combustion chemical vapour deposition (CCVD), at which a propane–air mixture was combusted in a burner. Dissolved zinc nitrate was used as precursor, which was guided as aerosol droplets by the processing gas flow directly into the reaction zone. Fundamental investigations were performed to form undoped ZnO. The structural properties of the films were analysed in dependence of the substrate temperature during the coating process. The presence of crystalline ZnO structures was proved and differences in film growth and crystallite sizes are revealed. Additionally, the particles generated by the CCVD-flame are characterised. The thin films showed a slight excess of Zn and several states of binding energy could be observed by fitting the core level spectra. Scanning and transmission electron microscopy also indicated ordered structures and additionally different orientations of crystallites were observed. - Highlights: • Columnar growth structures of ZnO by CCVD were observed. • The presence of polycrystalline ZnO with (002) as main orientation was confirmed. • Initial particles significantly differ from crystallite sizes of the resulting films. • The films show an excess of Zn with a Zn-to-O ratio of around 1.7

  10. Characterisation of silicon carbide films deposited by plasma-enhanced chemical vapour deposition

    The paper presents a characterisation of amorphous silicon carbide films deposited in plasma-enhanced chemical vapour deposition (PECVD) reactors for MEMS applications. The main parameter was optimised in order to achieve a low stress and high deposition rate. We noticed that the high frequency mode (13.56 MHz) gives a low stress value which can be tuned from tensile to compressive by selecting the correct power. The low frequency mode (380 kHz) generates high compressive stress (around 500 MPa) due to ion bombardment and, as a result, densification of the layer achieved. Temperature can decrease the compressive value of the stress (due to annealing effect). A low etching rate of the amorphous silicon carbide layer was noticed for wet etching in KOH 30% at 80 oC (around 13 A/min) while in HF 49% the layer is practically inert. A very slow etching rate of amorphous silicon carbide layer in XeF2 -7 A/min- was observed. The paper presents an example of this application: PECVD-amorphous silicon carbide cantilevers fabricated using surface micromachining by dry-released technique in XeF2

  11. Chemical vapour deposition of thermochromic vanadium dioxide thin films for energy efficient glazing

    Warwick, Michael E.A. [Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London, WC1H 0AJ (United Kingdom); UCL Energy Institute, Central House, 14 Upper Woburn Place, London, WC1H 0NN (United Kingdom); Binions, Russell, E-mail: r.binions@qmul.ac.uk [School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 4NS (United Kingdom)

    2014-06-01

    Vanadium dioxide is a thermochromic material that undergoes a semiconductor to metal transitions at a critical temperature of 68 °C. This phase change from a low temperature monoclinic structure to a higher temperature rutile structure is accompanied by a marked change in infrared reflectivity and change in resistivity. This ability to have a temperature-modulated film that can limit solar heat gain makes vanadium dioxide an ideal candidate for thermochromic energy efficient glazing. In this review we detail the current challenges to such glazing becoming a commercial reality and describe the key chemical vapour deposition technologies being employed in the latest research. - Graphical abstract: Schematic demonstration of the effect of thermochromic glazing on solar radiation (red arrow represents IR radiation, black arrow represents all other solar radiation). - Highlights: • Vanadium dioxide thin films for energy efficient glazing. • Reviews chemical vapour deposition techniques. • Latest results for thin film deposition for vanadium dioxide.

  12. Aluminium nitride coatings preparation using a chemical vapour deposition process

    Armas, B.; Combescure, C.; Icaza Herrera, M. de; Sibieude, F. [Centre National de la Recherche Scientifique (CNRS), 66 - Font-Romeu (France). Inst. de Science et du Genie des Materiaux et des Procedes

    2000-07-01

    Aluminium nitride was obtained in a cold wall reactor using AlCl{sub 3} and NH{sub 3} as precursors and N{sub 2} as a carrier gas. AlCl{sub 3} was synthesized << in situ >> by means of an original method based on the reaction of SiCl{sub 4(g)} with Al{sub (S)}. The substrate used was a cylinder of graphite coated with SiC and heated by high frequency induction. The deposition rate was studied as a function of temperature in the range 900 - 1500 C, the total pressure varying from 2 to 180 hPa. At low temperatures an Arrhenius type representation of the kinetics for several pressures indicated a thermally activated process with an apparent activation energy of about 80 kJ.mol{sup -1}. At high deposition temperatures, the deposition rate was almost constant, indicating that the growth was controlled by a diffusion process. The influence of gas composition and total AlCl{sub 3} flow rate was also discussed. The different layers were characterised particularly by means of X-ray diffraction and SEM. The influence of temperature and total pressure on crystallization and morphology was studied. (orig.)

  13. The Chemical Vapour Deposition of Tantalum - in long narrow channels

    Mugabi, James Atwoki

    protective layers of tantalum because of the process’ ability to coat complex geometries and its relative ease to control. This work focuses on studying the CVD of tantalum in long narrow channels with the view that the knowledge gained during the project can be used to optimise the commercial coating...... that there is a major change in morphology between 850 – 900 °C. The effects of system pressure and precursor partial pressure are also studied, and were found to have relevance to the tantalum distribution along the substrates but little effect on the structural morphology of the deposited layer. In...

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

    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 deg. 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

  15. Control of surface and bulk crystalline quality in single crystal diamond grown by chemical vapour deposition

    Friel, I.; Clewes, S L; Dhillon, H. K.; Perkins, N.; Twitchen, D. J.; Scarsbrook, G. A.

    2009-01-01

    In order to improve the performance of existing technologies based on single crystal diamond grown by chemical vapour deposition (CVD), and to open up new technologies in fields such as quantum computing or solid state and semiconductor disc lasers, control over surface and bulk crystalline quality is of great importance. Inductively coupled plasma (ICP) etching using an Ar/Cl gas mixture is demonstrated to remove sub-surface damage of mechanically processed surfaces, whilst maintaining macro...

  16. Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration

    Sung-Jin Chang; Moon Seop Hyun; Sung Myung; Min-A Kang; Jung Ho Yoo; Lee, Kyoung G.; Bong Gill Choi; Youngji Cho; Gaehang Lee; Tae Jung Park

    2016-01-01

    Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from R...

  17. Fundamental Studies of the Chemical Vapour Deposition of Graphene on Copper

    Lewis, Amanda

    2014-01-01

    The chemical vapour deposition (CVD) of graphene is the most promising route for production of large-area graphene films. However there are still major challenges faced by the field, including control of the graphene coverage, quality, and the number of layers. These challenges can be overcome by developing a fundamental understanding of the graphene growth process. This thesis contributes to the growing body of work on graphene CVD by uniquely exploring the gas phas...

  18. Purification of Single-walled Carbon Nanotubes Grown by a Chemical Vapour Deposition (CVD) Method

    2002-01-01

    A procedure for purification of single-walled carbon nanotubes(SWNTs) grown by the chemical vapour deposition (CVD) of carbon monooxide has been developed. Based on the result from TGA/DTA of as-prepared sample, the oxidation temperature was determined. The process included sonication, oxidation and acid washing steps. The purity and yield after purification were determined and estimated by TEM. Moreover, for the first time, a loop structure for CVD SWNTs has been observed.

  19. Evaluation of niobium dimethylamino-ethoxide for chemical vapour deposition of niobium oxide thin films

    Chemical vapour deposition (CVD) processes depend on the availability of suitable precursors. Precursors that deliver a stable vapour pressure are favourable in classical CVD processes, as they ensure process reproducibility. In high vacuum CVD (HV-CVD) process vapour pressure stability of the precursor is of particular importance, since no carrier gas assisted transport can be used. The dimeric Nb2(OEt)10 does not fulfil this requirement since it partially dissociates upon heating. Dimethylamino functionalization of an ethoxy ligand of Nb(OEt)5 acts as an octahedral field completing entity and leads to Nb(OEt)4(dmae). We show that Nb(OEt)4(dmae) evaporates as monomeric molecule and ensures a stable vapour pressure and, consequently, stable flow. A set of HV-CVD experiments were conducted using this precursor by projecting a graded molecular beam of the precursor onto the substrate at deposition temperatures from 320 °C to 650 °C. Film growth rates ranging from 8 nm·h−1 to values larger than 400 nm·h−1 can be obtained in this system illustrating the high level of control available over the film growth process. Classical CVD limiting conditions along with the recently reported adsorption–reaction limited conditions are observed and the chemical composition, and microstructural and optical properties of the films are related to the corresponding growth regime. Nb(OEt)4(dmae) provides a large process window of deposition temperatures and precursor fluxes over which carbon-free and polycrystalline niobium oxide films with growth rates proportional to precursor flux are obtained. This feature makes Nb(OEt)4(dmae) an attractive precursor for combinatorial CVD of niobium containing complex oxide films that are finding an increasing interest in photonics and photoelectrochemical water splitting applications. The adsorption–reaction limited conditions provide extremely small growth rates comparable to an atomic layer deposition (ALD) process indicating that HV

  20. The pyrolytic decomposition of ATSB during chemical vapour deposition of thin alumina films

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

    1994-01-01

    The effect of the deposition temperature and the partial pressure of water on the thermal decomposition chemistry of aluminium-tri-sec-butoxide (ATSB) during metal organic chemical vapour deposition (MOCVD) is reported. The MOCVD experiments were performed in nitrogen at atmospheric pressure. The partial pressure of ATSB was 0.026 kPa (0.20 mmHg) and that of water was between 0 and 0.026 kPa (0–0.20 mmHg). The pyrolytic decomposition chemistry of ATSB was studied by mass spectrometry at tempe...

  1. Laser diagnostics of a diamond depositing chemical vapour deposition gas-phase environment

    Studies have been carried out to understand the gas-phase chemistry underpinning diamond deposition in hot filament and DC-arcjet chemical vapour deposition (CVD) systems. Resonance enhanced Multiphoton lonisation (REMPI) techniques were used to measure the relative H atom and CH3 radical number densities and local gas temperatures prevalent in a hot filament reactor, operating on Ch4/H2 and C2H2/H2 gas mixtures. These results were compared to a 3D-computer simulation, and hence provided an insight into the nature of the gas-phase chemistry with particular reference to C2→C1 species conversion. Similar experimental and theoretical studies were also carried out to explain the chemistry involved in NH3/CH4/H2 and N2/CH4/H2 gas mixtures. It was demonstrated that the reactive nature of the filament surface was dependent on the addition of NH3, influencing atomic hydrogen production, and thus the H/C/N gas-phase chemistry. Studies of the DC-arcjet diamond CVD reactor consisted of optical emission spectroscopic studies of the plume during deposition from an Ar/H2/CH4/N2 gas mixture. Spatially resolved species emission intensity maps were obtained for C2(d→a), CN(B→X) and Hβ from Abel-inverted datasets. The C2(d→a) and CN(B→X) emission intensity maps both show local maxima near the substrate surface. SEM and Laser Raman analyses indicate that N2 additions lead to a reduction in film quality and growth rate. Photoluminescence and SIMS analyses of the grown films provide conclusive evidence of nitrogen incorporation (as chemically bonded CN). Absolute column densities of C2(a) in a DC-arcjet reactor operating on an Ar/H2/CH4 gas mixture, were measured using Cavity ring down spectroscopy. Simulations of the measured C2(v=0) transition revealed a rotational temperature of ∼3300 K. This gas temperature is similar to that deduced from optical emission spectroscopy studies of the C2(d→a) transition. (author)

  2. Structural Evolution of SiC Films During Plasma-Assisted Chemical Vapour Deposition

    Evolution of chemical bonding configurations for the films deposited from hexamethyldisiloxane (HMDSO) diluted with H2 during plasma assisted chemical vapour deposition is investigated. In the experiment a small amount of CH4 was added to adjust the plasma environment and modify the structure of the deposited films. The measurements of Raman spectroscopy and X-ray diffraction (XRD) revealed the production of 6H-SiC embedded in the amorphous matrix without the input of CH4. As CH4 was introduced into the deposition reaction, the transition of 6H-SiC to cubic SiC in the films took place, and also the film surfaces changed from a structure of ellipsoids to cauliflower-like shapes. With a further increase of CH4 in the flow ratio, the obtained films varied from Si-C bonding dominant to a sp2/sp3 carbon-rich composition. (low temperature plasma)

  3. Thin-Film Deposition of Metal Oxides by Aerosol-Assisted Chemical Vapour Deposition: Evaluation of Film Crystallinity

    Takeuchi, Masahiro; Maki, Kunisuke

    2007-12-01

    Sn-doped In2O3 (ITO) thin films are deposited on glass substrates using 0.2 M aqueous and methanol solutions of InCl3(4H2O) with 5 mol % SnCl2(2H2O) by aerosol-assisted chemical vapour deposition under positive and negative temperature gradient conditions. The film crystallinity is evaluated by determining the film thickness dependence of X-ray diffraction peak height. When using aqueous solution, the ITO films grow with the same crystallinity during the deposition, but when using methanol solution, the preferred orientation of ITO changes during the deposition.

  4. Characterization of Si:O:C:H films fabricated using electron emission enhanced chemical vapour deposition

    Silicon-based polymers and oxides may be formed when vapours of oxygen-containing organosilicone compounds are exposed to energetic electrons drawn from a hot filament by a bias potential applied to a second electrode in a controlled atmosphere in a vacuum chamber. As little deposition occurs in the absence of the bias potential, electron impact fragmentation is the key mechanism in film fabrication using electron-emission enhanced chemical vapour deposition (EEECVD). The feasibility of depositing amorphous hydrogenated carbon films also containing silicon from plasmas of tetramethylsilane or hexamethyldisiloxane has already been shown. In this work, we report the deposition of diverse films from plasmas of tetraethoxysilane (TEOS)-argon mixtures and the characterization of the materials obtained. The effects of changes in the substrate holder bias (VS) and of the proportion of TEOS in the mixture (XT) on the chemical structure of the films are examined by infrared-reflection absorption spectroscopy (IRRAS) at near-normal and oblique incidence using unpolarised and p-polarised, light, respectively. The latter is particularly useful in detecting vibrational modes not observed when using conventional near-normal incidence. Elemental analyses of the film were carried out by X-ray photoelectron spectroscopy (XPS), which was also useful in complementary structural investigations. In addition, the dependencies of the deposition rate on VS and XT are presented

  5. Electric field assisted aerosol assisted chemical vapour deposition of nanostructured metal oxide thin films

    Nanostructured thin films of tungsten, vanadium and titanium oxides were deposited on gas sensor substrates from the electric field assisted chemical vapour deposition reaction of tungsten hexaphenoxide, vanadyl acetylacetonate and titanium tetraisopropoxide respectively. The electric fields were generated by applying a potential difference between the inter-digitated electrodes of the gas sensor substrates during the deposition. The deposited films were characterised using scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The application of an electric field, encouraged the formation of interesting and unusual nanostructured morphologies, with a change in scale length and island packing. It was also noted that crystallographic orientation of the films could be controlled as a function of electric field type and strength. The gas sensor properties of the films were also examined; it was found that a two to three fold enhancement in the gas response could be observed from sensors with enhanced morphologies compared to control sensors grown without application of an electric field. - Highlights: • Electric field assisted chemical vapour deposition method • Ability to create high surface area film architectures • Can produce enhanced sensor response • Good control over film properties

  6. Electric field assisted aerosol assisted chemical vapour deposition of nanostructured metal oxide thin films

    Naik, Anupriya J.T.; Bowman, Christopher; Panjwani, Naitik [Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London WC1H OAJ (United Kingdom); Warwick, Michael E.A. [Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London WC1H OAJ (United Kingdom); UCL Energy Institute, Central House, 14 Upper Woburn Place, London WC1H 0HY (United Kingdom); Binions, Russell, E-mail: r.binions@qmul.ac.uk [Department of Chemistry, University College London, Christopher Ingold Laboratories, 20 Gordon Street, London WC1H OAJ (United Kingdom); School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

    2013-10-01

    Nanostructured thin films of tungsten, vanadium and titanium oxides were deposited on gas sensor substrates from the electric field assisted chemical vapour deposition reaction of tungsten hexaphenoxide, vanadyl acetylacetonate and titanium tetraisopropoxide respectively. The electric fields were generated by applying a potential difference between the inter-digitated electrodes of the gas sensor substrates during the deposition. The deposited films were characterised using scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The application of an electric field, encouraged the formation of interesting and unusual nanostructured morphologies, with a change in scale length and island packing. It was also noted that crystallographic orientation of the films could be controlled as a function of electric field type and strength. The gas sensor properties of the films were also examined; it was found that a two to three fold enhancement in the gas response could be observed from sensors with enhanced morphologies compared to control sensors grown without application of an electric field. - Highlights: • Electric field assisted chemical vapour deposition method • Ability to create high surface area film architectures • Can produce enhanced sensor response • Good control over film properties.

  7. Chemical vapour deposition diamond coating on tungsten carbide dental cutting tools

    Diamond coatings on Co cemented tungsten carbide (WC-Co) hard metal tools are widely used for cutting non-ferrous metals. It is difficult to deposit diamond onto cutting tools, which generally have a complex geometry, using a single step growth process. This paper focuses on the deposition of polycrystalline diamond films onto dental tools, which possess 3D complex or cylindrical shape, employing a novel single step chemical vapour deposition (CVD) growth process. The diamond deposition is carried out in a hot filament chemical vapour deposition (HFCVD) reactor with a modified filament arrangement. The filament is mounted vertically with the drill held concentrically in between the filament coils, as opposed to the commonly used horizontal arrangement. This is a simple and inexpensive filament arrangement. In addition, the problems associated with adhesion of diamond films on WC-Co substrates are amplified in dental tools due to the very sharp edges and unpredictable cutting forces. The presence of Co, used as a binder in hard metals, generally causes poor adhesion. The amount of metallic Co on the surface can be reduced using a two step pre-treatment employing Murakami etching followed by an acid treatment. Diamond films are examined in terms of their growth rate, morphology, adhesion and cutting efficiency. We found that in the diamond coated dental tool the wear rate was reduced by a factor of three as compared to the uncoated tool

  8. Synthesis of low leakage current chemical vapour deposited (CVD) diamond films for particle detection

    We report on synthesis of diamond films by direct current glow discharge chemical vapour deposition (CVD) prepared at different deposition conditions, for application in high energy physics. The synthesis apparatus is briefly described. Continuous undoped diamond samples have been grown onto Mo substrates with a deposition area up to 1 cm2 and an electrical resistivity as high as 1013 Ωcm. The deposition parameters are related to the material properties of the diamonds, investigated by optical spectroscopy, electron microscopy and diffraction analysis. Decreasing the linear growth rate results in good quality films with small remnants of graphite-like phases. The high crystalline quality and phase purity of the films are related to very low values of leakage currents. The particle induced conductivity of these samples is also studied and preliminary results on charge collection efficiency are presented. (orig.)

  9. Plasma Assisted Chemical Vapour Deposition – Technological Design Of Functional Coatings

    Januś M.

    2015-06-01

    Full Text Available Plasma Assisted Chemical Vapour Deposition (PA CVD method allows to deposit of homogeneous, well-adhesive coatings at lower temperature on different substrates. Plasmochemical treatment significantly impacts on physicochemical parameters of modified surfaces. In this study we present the overview of the possibilities of plasma processes for the deposition of diamond-like carbon coatings doped Si and/or N atoms on the Ti Grade2, aluminum-zinc alloy and polyetherketone substrate. Depending on the type of modified substrate had improved the corrosion properties including biocompatibility of titanium surface, increase of surface hardness with deposition of good adhesion and fine-grained coatings (in the case of Al-Zn alloy and improving of the wear resistance (in the case of PEEK substrate.

  10. Pulsed injection metal organic chemical vapour deposition and characterisation of thin CaO films

    Thin films of CaO were grown on silicon (Si) and lanthanum aluminate (LaAlO3) substrates by pulsed injection metal-organic chemical vapour deposition in a vertical injection MOCVD system. Growth parameters were systematically varied to study their effect on film growth and quality and to determine the optimal growth conditions for this material. Film quality and growth rate were evaluated by atomic force microscopy, X-ray diffraction and Rutherford Backscattering Spectroscopy measurements. Optimised conditions allowed growing transparent, single phase films textured along the (0 0 l) direction.

  11. Fluidization and coating of very dense powders by fluidized bed chemical vapour deposition

    Rodriguez, Philippe; Caussat, Brigitte; Ablitzer, Carine; Iltis, Xavière; Brothier, Méryl

    2013-01-01

    The hydrodynamic behaviour of a very dense tungsten powder, 75 µm in median diameter and 19,300 kg/m3 in grain density, has been studied in a fluidized bed at room temperature using nitrogen and argon as carrier gas. Even if fluidization was achieved, the small bed expansion indicated that it was imperfect. Then, the fluidization was studied at 400 °C in order to investigate the feasibility of coating this powder by Fluidized Bed Chemical Vapour Deposition (FBCVD). In particular, the influenc...

  12. Chemically vapour deposited diamond coatings on cemented tungsten carbides: Substrate pretreatments, adhesion and cutting performance

    Chemical vapour deposition (CVD) of diamond films onto Co-cemented tungsten carbide (WC-Co) tools and wear parts presents several problems due to interfacial graphitization induced by the binder phase and thermal expansion mismatch of diamond and WC-Co. Methods used to improve diamond film adhesion include substrate-modification processes that create a three-dimensional compositionally graded interface. This paper reviews substrate pretreatments and adhesion issues of chemically vapour deposited diamond films on WC-Co. The combined effect of pretreatments and substrate microstructure on the adhesive toughness and wear rate of CVD diamond in dry machining of highly abrasive materials was analyzed. The role of diamond film surface morphology on chip evacuation in dry milling of ceramics was also investigated by comparing feed forces of coated and uncoated mills. The overall tribological performance of diamond coated mills depended on coating microstructure and smoothness. The use of smother films did allow to reduce cutting forces by facilitating chip evacuation

  13. Zinc oxide nanostructures by chemical vapour deposition as anodes for Li-ion batteries

    Highlights: • ZnO nanostructures are grown by simple chemical vapour deposition. • Polycrystalline nanostructured porous thin film is obtained. • Film exhibits stable specific capacity (∼400 mA h g−1) after prolonged cycling. • CVD-grown ZnO nanostructures show promising prospects as Li-ion battery anode. - Abstract: ZnO nanostructures are grown by a simple chemical vapour deposition method directly on a stainless steel disc current collector and successfully tested in lithium cells. The structural/morphological characterization points out the presence of well-defined polycrystalline nanostructures having different shapes and a preferential orientation along the c-axis direction. In addition, the high active surface of the ZnO nanostructures, which accounts for a large electrode/electrolyte contact area, and the complete wetting with the electrolyte solution are considered to be responsible for the good electrical transport properties and the adequate electrochemical behaviour, as confirmed by cyclic voltammetry and galvanostatic charge/discharge cycling. Indeed, despite no binder or conducting additives are used, when galvanostatically tested in lithium cells, after an initial decay, the ZnO nanostructures can provide a rather stable specific capacity approaching 70 μA h cm−2 (i.e., around 400 mA h g−1) after prolonged cycling at 1 C, with very high Coulombic efficiency and an overall capacity retention exceeding 62%

  14. Zinc oxide nanostructures by chemical vapour deposition as anodes for Li-ion batteries

    Laurenti, M., E-mail: marco.laurenti@iit.it [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Department of Applied Science and Technology – DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin (Italy); Garino, N. [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Porro, S.; Fontana, M. [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Department of Applied Science and Technology – DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin (Italy); Gerbaldi, C., E-mail: claudio.gerbaldi@polito.it [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento, 21, 10129 Turin (Italy); Department of Applied Science and Technology – DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin (Italy)

    2015-08-15

    Highlights: • ZnO nanostructures are grown by simple chemical vapour deposition. • Polycrystalline nanostructured porous thin film is obtained. • Film exhibits stable specific capacity (∼400 mA h g{sup −1}) after prolonged cycling. • CVD-grown ZnO nanostructures show promising prospects as Li-ion battery anode. - Abstract: ZnO nanostructures are grown by a simple chemical vapour deposition method directly on a stainless steel disc current collector and successfully tested in lithium cells. The structural/morphological characterization points out the presence of well-defined polycrystalline nanostructures having different shapes and a preferential orientation along the c-axis direction. In addition, the high active surface of the ZnO nanostructures, which accounts for a large electrode/electrolyte contact area, and the complete wetting with the electrolyte solution are considered to be responsible for the good electrical transport properties and the adequate electrochemical behaviour, as confirmed by cyclic voltammetry and galvanostatic charge/discharge cycling. Indeed, despite no binder or conducting additives are used, when galvanostatically tested in lithium cells, after an initial decay, the ZnO nanostructures can provide a rather stable specific capacity approaching 70 μA h cm{sup −2} (i.e., around 400 mA h g{sup −1}) after prolonged cycling at 1 C, with very high Coulombic efficiency and an overall capacity retention exceeding 62%.

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

    Highlights: • Carbon nitride films were prepared by using radio frequency plasma enhanced chemical vapour deposition system by altering the electrode distance. • The effect of electrode distance on surface morphology, surface roughness, chemical bonding and hydrophobic behaviour has been studied. • Hydrophobic behaviour were studied by measuring contact angle and calculating surface energy. • CNx nanostructures show super-hydrophobic behaviour. • We report a tunable transition of hydrophilic to super-hydrophobic behaviour of film as electrode distance is reduced. - Abstract: 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 C=N to C=C and N−H to O−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

  16. Electron behaviour in CH4/H2 gas mixture in electron-assisted chemical vapour deposition

    Dong Li-Fang; Ma Bo-Qin; Wang Zhi-Jun

    2004-01-01

    The behaviour of electrons in CH4/H2 gas mixture in electron-assisted chemical vapour deposition of diamond is investigated using Monte Carlo simulation. The electron drift velocity in gas mixture is obtained over a wide range of E/P (the ratio of the electric field to gas pressure) from 1500 to 300000 (V/m kPa-1). The electron energy distribution and average energy under different gas pressure (0.1-20kPa) and CH4 concentration (0.5%-10.0%) are calculated. Their effects on the diamond growth are also discussed. It is believed that these results will be helpful to the selection of optimum experimental conditions for high quality diamond film deposition.

  17. Functional ZnO/polymer core-shell nanowires fabricated by oxidative chemical vapour deposition

    Functional ZnO-nanowire/polymer core-shell heterostructures were realized using oxidative chemical vapour deposition (oCVD). This dry and versatile technique allows uniform coating of semiconductor nanowires with polymers and simultaneous doping control of the shell. Here, 100 nm thick, p-doped shells of poly(3,4-ethylenedioxythiophene) (PEDOT) were deposited around n-conductive ZnO nanowires. Energy-dispersive x-ray spectroscopy confirms the incorporation of Br dopants into the PEDOT shell, and the resulting p-conductivity of the polymer shell is demonstrated by electrical measurements on nanowire arrays. Photoluminescence spectroscopy points to reactions of Br with the ZnO surface but proves that the nanowires show only little degradation of their optical properties. (paper)

  18. Scalable route to CH3NH3PbI3 perovskite thin films by aerosol assisted chemical vapour deposition

    Bhachu, D. S.; Scanlon, D. O.; Saban, E. J.; Bronstein, H.; Parkin, I. P.; Carmalt, C. J.; Palgrave, R. G.

    2015-01-01

    Methyl-ammonium lead iodide is the archetypal perovskite solar cell material. Phase pure, compositionally uniform methyl-ammonium lead iodide thin films on large glass substrates were deposited using ambient pressure aerosol assisted chemical vapour deposition. This opens up a route to efficient scale up of hybrid perovskite film growth towards industrial deployment.

  19. High quality plasma enhanced chemical vapour deposited silicon oxide gas barrier coatings on polyester films

    Silicon oxide barrier coatings fabricated by a plasma enhanced chemical vapour deposition roll-to-roll process on polyester film have demonstrated impressive properties as a barrier to water vapour permeation. This study highlights the influence of the substrate on these coatings as we find that heat stabilised poly(ethylene terephthalate) (PET), with or without an additional acrylate primer layer, and poly(ethylene naphthalate) (PEN) produce superior composites than untreated PET film in terms of gas barrier. The barrier layers on PET and filled PET substrates, for which the barrier performance is within the detectable range of our measurement, have an activation energy to water permeation that increases with the thickness of the silica. For the thickest silica this is an increase of 26 kJ mol-1 over that from the uncoated substrate. We attribute this to the creation of highly tortuous, size-hindered pathways and the decoupling of defects as the coating is deposited in multiple passes. Using a more sensitive detection technique we measure a water vapour transmission rate value as low as 2 x 10-4 g m-2 day-1 for 1 μm thick coatings on PEN. Such a good barrier is observed for these thick coatings due to the high degree of carbon detected in the films that makes them less brittle than pure SiO2 layers. Substrate surface roughness is found to influence the morphology of the SiOx films but does not seem to adversely affect the barrier performance of the composites

  20. Characterization of doped hydrogenated nanocrystalline silicon films prepared by plasma enhanced chemical vapour deposition

    Wang Jin-Liang; Wu Er-Xing

    2007-01-01

    The B-and P-doped hydrogenated nanocrystalline silicon films (nc-Si:H) are prepared by plasma-enhanced chemical vapour deposition (PECVD) .The microstructures of doped nc-Si:H films are carefully and systematically char acterized by using high resolution electron microscopy (HREM) ,Raman scattering,x-ray diffraction (XRD) ,Auger electron spectroscopy (AES) ,and resonant nucleus reaction (RNR) .The results show that as the doping concentration of PH3 increases,the average grain size (d) tends to decrease and the crystalline volume percentage (Xc) increases simultaneously.For the B-doped samples,as the doping concentration of B2H6 increases,no obvious change in the value of d is observed,but the value of Xc is found to decrease.This is especially apparent in the case of heavy B2H6 doped samples,where the films change from nanocrystalline to amorphous.

  1. Magnetic and cytotoxic properties of hot-filament chemical vapour deposited diamond

    Zanin, Hudson, E-mail: hudsonzanin@gmail.com [Faculdade de Engenharia Eletrica e Computacao, Departamento de Semicondutores, Instrumentos e Fotonica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N.400, CEP 13 083-852 Campinas, Sao Paulo (Brazil); Peterlevitz, Alfredo Carlos; Ceragioli, Helder Jose [Faculdade de Engenharia Eletrica e Computacao, Departamento de Semicondutores, Instrumentos e Fotonica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N.400, CEP 13 083-852 Campinas, Sao Paulo (Brazil); Rodrigues, Ana Amelia; Belangero, William Dias [Laboratorio de Biomateriais em Ortopedia, Faculdade de Ciencias Medicas, Universidade Estadual de Campinas, Rua Cinco de Junho 350 CEP 13083970, Campinas, Sao Paulo (Brazil); Baranauskas, Vitor [Faculdade de Engenharia Eletrica e Computacao, Departamento de Semicondutores, Instrumentos e Fotonica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N.400, CEP 13 083-852 Campinas, Sao Paulo (Brazil)

    2012-12-01

    Microcrystalline (MCD) and nanocrystalline (NCD) magnetic diamond samples were produced by hot-filament chemical vapour deposition (HFCVD) on AISI 316 substrates. Energy Dispersive X-ray Spectroscopy (EDS) measurements indicated the presence of Fe, Cr and Ni in the MCD and NCD samples, and all samples showed similar magnetisation properties. Cell viability tests were realised using Vero cells, a type of fibroblastic cell line. Polystyrene was used as a negative control for toxicity (NCT). The cells were cultured under standard cell culture conditions. The proliferation indicated that these magnetic diamond samples were not cytotoxic. - Highlights: Black-Right-Pointing-Pointer Polycrystalline diamonds doped with Fe, Cr and Ni acquire ferromagnetic properties. Black-Right-Pointing-Pointer CVD diamonds have been prepared with magnetic and semiconductor properties. Black-Right-Pointing-Pointer Micro/nanocrystalline diamonds show good cell viability with fibroblast proliferation.

  2. Elaboration of Bi 2Se 3 by metalorganic chemical vapour deposition

    Giani, A.; Al Bayaz, A.; Foucaran, A.; Pascal-Delannoy, F.; Boyer, A.

    2002-03-01

    For the first time, Bi 2Se 3 thin films were elaborated by metalorganic chemical vapour deposition (MOCVD) using trimethylbismuth (TMBi) and diethylselenium (DESe) as metalorganic sources. The MOCVD elaboration of Bi 2Se 3 was carried out in a horizontal reactor for a substrate temperature ( Tg) varying from 450°C to 500°C, a total hydrogen flow rate DT=3 l min -1, RVI/V ratio >14 and TMBi partial pressure lower than 1.10 -4 atm. By X-ray diffraction and SEM observation, we noticed the polycrystalline structure of the layers typical preferential c-orientation and confirm the hexagonal structure. The microprobe data indicate that the best stoichiometry of Bi 2Se 3 was achieved. These films always displayed n-type conduction, and the maximum value of thermoelectric power α was found to be close to -120 μV/K.

  3. Microwave plasma-enhanced chemical vapour deposition growth of carbon nanostructures

    Shivan R. Singh

    2010-05-01

    Full Text Available The effect of various input parameters on the production of carbon nanostructures using a simple microwave plasma-enhanced chemical vapour deposition technique has been investigated. The technique utilises a conventional microwave oven as the microwave energy source. The developed apparatus is inexpensive and easy to install and is suitable for use as a carbon nanostructure source for potential laboratory-based research of the bulk properties of carbon nanostructures. A result of this investigation is the reproducibility of specific nanostructures with the variation of input parameters, such as carbon-containing precursor and support gas flow rate. It was shown that the yield and quality of the carbon products is directly controlled by input parameters. Transmission electron microscopy and scanning electron microscopy were used to analyse the carbon products; these were found to be amorphous, nanotubes and onion-like nanostructures.

  4. Optimization of process parameter for synthesis of silicon quantum dots using low pressure chemical vapour deposition

    Dipika Barbadikar; Rashmi Gautam; Sanjay Sahare; Rajendra Patrikar; Jatin Bhatt

    2013-06-01

    Si quantum dots-based structures are studied recently for performance enhancement in electronic devices. This paper presents an attempt to get high density quantum dots (QDs) by low pressure chemical vapour deposition (LPCVD) on SiO2 substrate. Surface treatment, annealing and rapid thermal processing (RTP) are performed to study their effect on size and density of QDs. The samples are also studied using Fourier transformation infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and photoluminescence study (PL). The influence of Si–OH bonds formed due to surface treatment on the density of QDs is discussed. Present study also discusses the influence of surface treatment and annealing on QD formation.

  5. In situ doping of ZnO nanowires using aerosol-assisted chemical vapour deposition

    Pung, Swee-Yong; Choy, Kwang-Leong; Hou Xianghui; Dinsdale, Keith, E-mail: Kwang-leong.Choy@nottingham.ac.uk [Faculty of Engineering, Energy and Sustainability Research Division, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2010-08-27

    An in situ doping approach of producing Al-doped ZnO NWs was demonstrated using an aerosol-assisted chemical vapour deposition (AA-CVD) technique. In this technique, Zn precursor was kept in the middle of a horizontal tube furnace whereas the dopant solution was kept in an aerosol generator, which was located outside the furnace. The Al aerosol was flowed into the reactor during the growth of NWs in order to achieve in situ doping. Al-doped ZnO NWs were synthesized as verified by the combination of XRD, TEM/EDS and TOF-SIMS analysis. Highly (00.2) oriented ZnO seed layers were used to promote vertically aligned growth of Al-doped ZnO NWs. Lastly, a growth mechanism of vertically aligned Al-doped ZnO NWs was discussed.

  6. Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration

    Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A.; Yoo, Jung Ho; Lee, Kyoung G.; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

    2016-03-01

    Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties.

  7. Graphene growth from reduced graphene oxide by chemical vapour deposition: seeded growth accompanied by restoration

    Chang, Sung-Jin; Hyun, Moon Seop; Myung, Sung; Kang, Min-A; Yoo, Jung Ho; Lee, Kyoung G.; Choi, Bong Gill; Cho, Youngji; Lee, Gaehang; Park, Tae Jung

    2016-01-01

    Understanding the underlying mechanisms involved in graphene growth via chemical vapour deposition (CVD) is critical for precise control of the characteristics of graphene. Despite much effort, the actual processes behind graphene synthesis still remain to be elucidated in a large number of aspects. Herein, we report the evolution of graphene properties during in-plane growth of graphene from reduced graphene oxide (RGO) on copper (Cu) via methane CVD. While graphene is laterally grown from RGO flakes on Cu foils up to a few hundred nanometres during CVD process, it shows appreciable improvement in structural quality. The monotonous enhancement of the structural quality of the graphene with increasing length of the graphene growth from RGO suggests that seeded CVD growth of graphene from RGO on Cu surface is accompanied by the restoration of graphitic structure. The finding provides insight into graphene growth and defect reconstruction useful for the production of tailored carbon nanostructures with required properties. PMID:26961409

  8. Chemical vapour deposition of tungsten and tungsten silicide layers for applications in novel silicon technology

    Li, F X

    2002-01-01

    This work was a detailed investigation into the Chemical Vapour Deposition (CVD) of tungsten and tungsten silicide for potential applications in integrated circuit (IC) and other microelectronic devices. These materials may find novel applications in contact schemes for transistors in advanced ICs, buried high conductivity layers in novel Silicon-On-Insulator (SOI) technology and in power electronic devices. The CVD techniques developed may also be used for metal coating of recessed or enclosed features which may occur in novel electronic or electromechanical devices. CVD of tungsten was investigated using the silicon reduction reaction of WF sub 6. W layers with an optimum self-limiting thickness of 100 nm and resistivity 20 mu OMEGA centre dot cm were produced self-aligned to silicon. A hydrogen passivation technique was developed as part of the wafer pre-clean schedule and proved essential in achieving optimum layer thickness. Layers produced by this approach are ideal for intimate contact to shallow junct...

  9. Al-Induced Crystallization Growth of Si Films by Inductively Coupled Plasma Chemical Vapour Deposition

    LI Jun-Shuai; WANG Jin-Xiao; YIN Min; GAO Ping-Qi; HE De-Yan

    2006-01-01

    Polycrystalline Si (poly-Si) films are in situ grown on Al-coated glass substrates by inductively coupled plasma chemical vapour deposition at a temperature as low as 350 C. Compared to the traditional annealing crystallization of amorphous Si/Al-layer structures, no layer exchange is observed and the resultant poly-Si film is much thicker than Al layer. By analysing the depth profiles of the elemental composition, no remains of Al atoms are detected in Si layer within the limit (< 0.01 at. %) of the used evaluations. It is indicated that the poly-Si material obtained by Al-induced crystallization growth has more potential applications than that prepared by annealing the amorphous Si/Al-layer structures.

  10. Magnetic and cytotoxic properties of hot-filament chemical vapour deposited diamond

    Microcrystalline (MCD) and nanocrystalline (NCD) magnetic diamond samples were produced by hot-filament chemical vapour deposition (HFCVD) on AISI 316 substrates. Energy Dispersive X-ray Spectroscopy (EDS) measurements indicated the presence of Fe, Cr and Ni in the MCD and NCD samples, and all samples showed similar magnetisation properties. Cell viability tests were realised using Vero cells, a type of fibroblastic cell line. Polystyrene was used as a negative control for toxicity (NCT). The cells were cultured under standard cell culture conditions. The proliferation indicated that these magnetic diamond samples were not cytotoxic. - Highlights: ► Polycrystalline diamonds doped with Fe, Cr and Ni acquire ferromagnetic properties. ► CVD diamonds have been prepared with magnetic and semiconductor properties. ► Micro/nanocrystalline diamonds show good cell viability with fibroblast proliferation.

  11. Nanocomposite Coatings Codeposited with Nanoparticles Using Aerosol-Assisted Chemical Vapour Deposition

    Xianghui Hou

    2013-01-01

    Full Text Available Incorporating nanoscale materials into suitable matrices is an effective route to produce nanocomposites with unique properties for practical applications. Due to the flexibility in precursor atomization and delivery, aerosol-assisted chemical vapour deposition (AACVD process is a promising way to synthesize desired nanocomposite coatings incorporating with preformed nanoscale materials. The presence of nanoscale materials in AACVD process would significantly influence deposition mechanism and thus affect microstructure and properties of the nanocomposites. In the present work, inorganic fullerene-like tungsten disulfide (IF-WS2 has been codeposited with Cr2O3 coatings using AACVD. In order to understand the codeposition process for the nanocomposite coatings, chemical reactions of the precursor and the deposition mechanism have been studied. The correlation between microstructure of the nanocomposite coatings and the codeposition mechanism in the AACVD process has been investigated. The heterogeneous reaction on the surface of IF-WS2 nanoparticles, before reaching the substrate surface, is the key feature of the codeposition in the AACVD process. The agglomeration of nanoparticles in the nanocomposite coatings is also discussed.

  12. Chemical vapour deposition of praseodymium oxide films on silicon: influence of temperature and oxygen pressure

    Metal-organic chemical vapour deposition (MOCVD) of various phases in PrOx system has been studied in relation with deposition temperature (450-750 deg. C) and oxygen partial pressure (0.027-100 Pa or 0.2-750 mTorr). Depositions were carried out by pulsed liquid injection MOCVD using Pr(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) precursor dissolved in toluene or monoglyme. By varying deposition temperature and oxygen partial pressure amorphous films or various crystalline PrOx phases (Pr2O3, Pr7O12, Pr6O11) and their mixtures can be grown. The pure crystalline Pr2O3 phase grows only in a narrow range of partial oxygen pressure and temperature, while high oxygen pressure (40-100 Pa) always leads to the most stable Pr6O11 phase. The influence of annealing under vacuum at 750 deg. C on film phase composition was also studied. Near 90% step coverage conformity was achieved for PrOx films on structured silicon substrates with aspect ratio 1:10. In air degradation of Pr2O3 films with transformation to Pr(OH)3 was observed in contrast to Pr6O11 films

  13. Synthesis of Tin Nitride Sn x N y Nanowires by Chemical Vapour Deposition

    Zervos, Matthew; Othonos, Andreas

    2009-09-01

    Tin nitride (Sn x N y ) nanowires have been grown for the first time by chemical vapour deposition on n-type Si(111) and in particular by nitridation of Sn containing NH4Cl at 450 °C under a steady flow of NH3. The Sn x N y nanowires have an average diameter of 200 nm and lengths ≥5 μm and were grown on Si(111) coated with a few nm’s of Au. Nitridation of Sn alone, under a flow of NH3 is not effective and leads to the deposition of Sn droplets on the Au/Si(111) surface which impedes one-dimensional growth over a wide temperature range i.e. 300-800 °C. This was overcome by the addition of ammonium chloride (NH4Cl) which undergoes sublimation at 338 °C thereby releasing NH3 and HCl which act as dispersants thereby enhancing the vapour pressure of Sn and the one-dimensional growth of Sn x N y nanowires. In addition to the action of dispersion, Sn reacts with HCl giving SnCl2 which in turn reacts with NH3 leading to the formation of Sn x N y NWs. A first estimate of the band-gap of the Sn x N y nanowires grown on Si(111) was obtained from optical reflection measurements and found to be ≈2.6 eV. Finally, intricate assemblies of nanowires were also obtained at lower growth temperatures.

  14. Structural and Luminescent Properties of ZnO Thin Films Deposited by Atmospheric Pressure Chemical Vapour Deposition

    ZHAO Guo-Liang; LIN Bi-Xia; HONG Liang; MENG Xiang-Dong; FU Zhu-Xi

    2004-01-01

    ZnO thin films were successfully deposited on Si (100) substrates by chemical vapour deposition (CVD) at atmospheric pressure (1 atm). The only solid source used here is zinc acetate, (CHsCOO)2Zn, and the carrier gas is nitrogen. The sample, which was prepared at 550℃ during growth and then annealed in air at 900℃ , has only a ZnO (002) diffraction peak at 34.6° with its FWHM of 0.23° in the XRD pattern. The room-temperature PL spectrum shows a strong ultraviolet emission with the peak centred at 380nm. We analysed the effects of many factors, such as the source, substrates, growth and annealing temperatures, and annealing ambience, on the structural and optical properties of our prepared ZnO films.

  15. Conductive zinc oxide thin film coatings by combustion chemical vapour deposition at atmospheric pressure

    We have established a combustion chemical vapour deposition (C-CVD) system for the deposition of zinc oxide (ZnO) at atmospheric pressure. This C-CVD process has the advantage of a short exposure of the substrates to the flame. It is also potentially applicable as an inline coating system. Fundamental studies were performed on undoped ZnO. The specific resistivity of these layers strongly depends on the film thickness and decreases with increasing thickness. As the lowest resistivities, values of about 2.0 · 10−1 Ωcm are achieved. Ultra-violet photoemission spectra show the valence band structure of the deposited ZnO. The work function and valence band edge were determined. UV–vis spectra were taken to investigate the transmission of the coated glass samples. From these spectra the band gap energy was obtained. Raman spectroscopy as well as infrared spectroscopy confirmed the presence of ordered ZnO crystallites. The X-ray diffraction verified this result and illustrates the hexagonal structure. In the mid-infrared range precursor deposits were detected for low substrate temperatures. - Highlights: ► Zinc oxide (ZnO) films are conductive in the range of 2.0 · 10−1 Ωcm. ► X-ray diffraction, Raman and infrared spectroscopy indicate crystalline ZnO films. ► Precursor deposits were proved within the films for low growing temperatures. ► Band gap energy changes are achieved due to different growing temperatures

  16. Chemical Vapour Deposition Graphene Radio-Frequency Field-Effect Transistors

    We report the dc and rf performance of graphene rf field-effect transistors, where the graphene films are grown on copper by using the chemical vapour deposition (CVD) method and transferred to SiO2/Si substrates. Composite materials, benzocyclobutene and atomic layer deposition Al2O3 are used as the gate dielectrics. The observation of n- and p-type transitions verifies the ambipolar characteristics in the graphene layers. While the intrinsic carrier mobility of CVD graphene is extracted to be 1200 cm2/V·s, the parasitic series resistances are demonstrated to have a serious impact on device performance. With a gate length of 1 μm and an extrinsic transconductance of 72 mS/mm, a cutoff frequency of 6.6 GHz and a maximum oscillation frequency of 8.8 GHz are measured for the transistors, illustrating the potential of the CVD graphene for rf applications. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  17. Hybrid chemical vapour and nanoceramic aerosol assisted deposition for multifunctional nanocomposite thin films

    Warwick, Michael E.A.; Dunnill, Charles W.; Goodall, Josie; Darr, Jawwad A.; Binions, Russell, E-mail: uccarbi@ucl.ac.uk

    2011-07-01

    Hybrid atmospheric pressure chemical vapour and aerosol assisted deposition via the reaction of vanadium acetylacetonate and a suspension of preformed titanium dioxide or cerium dioxide nanoparticles, led to the production of vanadium dioxide nanocomposite thin films on glass substrates. The preformed nanoparticle oxides used for the aerosol were synthesised using a continuous hydrothermal flow synthesis route involving the rapid reaction of a metal salt solution with a flow of supercritical water in a flow reactor. Multifunctional nanocomposite thin films from the hybrid deposition process were characterised using scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The functional properties of the films were evaluated using variable temperature optical measurements to assess thermochromic behaviour and methylene blue photodecolourisation experiments to assess photocatalytic activity. The tests show that the films are multifunctional in that they are thermochromic (having a large change in infra-red reflectivity upon exceeding the thermochromic transition temperature) and have significant photocatalytic activity under irradiation with 254 nm light.

  18. In-line silicon epitaxy for photovoltaics using a continous chemical vapour deposition reactor.

    Keller, Martin; Reber, Stefan; Schillinger, Norbert; Pocza, David; Arnold, Martin

    2011-09-01

    Thin film solar cell techniques can effectively reduce the costs for photovoltaic solar power. However, most of these techniques still have the disadvantage of a comparatively low efficiency. One way to realize a thin film solar cell concept with high efficiency potential is the crystalline silicon thin-film (cSiTF) concept. Following the high-temperature approach, this concept is based on a silicon epitaxy process. This paper reports the current status of the development of a high throughput epitaxy tool at Fraunhofer ISE and presents first results. Also presented is the development of a simulation tool which is a virtual image of the real setup in order to forecast save deposition conditions. The presented epitaxy tool is the ConCVD (Continuous Chemical Vapour Deposition), in which an improved reactor setup has been installed, based on the experience gained so far. To provide insight into upcoming further advances, the industrial scale epitaxy tool ProConCVD is presented as well. PMID:22097523

  19. Development and characterization of Undoped Silicon Glass (USG using chemical vapour deposition

    Jagadeesha T

    2011-02-01

    Full Text Available Sub atmospheric chemical vapour deposition (SACVD is a widely used technique in semiconductor integrated circuit (IC manufacturing, especially to form inter-metal silicon (IMD dioxide thin films. It was designed for commercially available tools in order to satisfy the gap filling requirements necessary for 0.18 and 0.15 lm technology ICs, but it has been successfully extended also for 0.13 lm technological node and over. SACVD technique has a potential impact on device electrical characteristics and metallurgy compatibility, according to process conditions, such as mass flow rate of TEOS, Gasflows, RF power. Present work focuses on development and characterisation of undoped silicate glass that can be used for Flash memory and Logic devices. It is shown that new process yield deposition rate improvement of 51% and throughput improvement of 13%.. Qualitative yield comparison and wafer map to map comparison work is also presented for various technology nodes. Device parameters comparison with the standard process is also included in the present work.

  20. Characterization of chemical vapour deposited diamond films: correlation between hydrogen incorporation and film morphology and quality

    In order to tailor diamond synthesized through chemical vapour deposition (CVD) for different applications, many diamond films of different colours and variable quality were deposited by a 5 kW microwave plasma CVD reactor under different growth conditions. The morphology, quality and hydrogen incorporation of these films were characterized using scanning electron microscopy (SEM), Raman and Fourier-transform infrared (FTIR) spectroscopy, respectively. From this study, a general trend between hydrogen incorporation and film colour, morphology and quality was found. That is, as the films sorted by colour gradually become darker, ranging from white through grey to black, high magnification SEM images illustrate that the smoothness of the well defined crystalline facet gradually decreases and second nucleation starts to appear on it, indicating gradual degradation of the crystalline quality. Correspondingly, Raman spectra evidence that the diamond Raman peak at 1332 cm-1 becomes broader and the non-diamond carbon band around 1500 cm-1 starts to appear and becomes stronger, confirming increase of the non-diamond component and decrease of the phase purity of the film, while FTIR spectra show that the CH stretching band and the two CVD diamond specific peaks around 2830 cm-1 rise rapidly, and this indicates that the total amount of hydrogen incorporated into the film increases significantly

  1. Methyldichloroborane evidenced as an intermediate in the chemical vapour deposition synthesis of boron carbide.

    Reinisch, G; Patel, S; Chollon, G; Leyssale, J-M; Alotta, D; Bertrand, N; Vignoles, G L

    2011-09-01

    The most recent ceramic-matrix composites (CMC) considered for long-life applications as thermostructural parts in aerospace propulsion contain, among others, boron-rich phases like boron carbide. This compound is prepared by thermal Chemical Vapour Infiltration (CVI), starting from precursors like boron halides and hydrocarbons. We present a study aiming at a precise knowledge of the gas-phase composition in a hot-zone LPCVD reactor fed with BCl3, CH4 and H2, which combines experimental and theoretical approaches. This work has brought strong evidences of the presence of Methydichloroborane (MDB, BCl2CH3) in the process. It is demonstrated that this intermediate, the presence of which had never been formally proved before, appears for processing temperatures slightly lower than the deposition temperature of boron carbide. The study features quantum chemical computations, which provide several pieces of information like thermochemical and kinetic data, as well as vibration and rotation frequencies, reaction kinetics computations, and experimental gas-phase characterization of several species by FTIR, for several processing parameter sets. The main results are presented, and the place of MDB in the reaction scheme is discussed. PMID:22097577

  2. Synthesis of few layer single crystal graphene grains on platinum by chemical vapour deposition

    S. Karamat; S. Sonuşen; Ü. Çelik; Y. Uysallı; E. Özgönül; A. Oral

    2015-01-01

    The present competition of graphene electronics demands an efficient route which produces high quality and large area graphene. Chemical vapour deposition technique, where hydrocarbons dissociate in to active carbon species and form graphene layer on the desired metal catalyst via nucleation is considered as the most suitable method. In this study, single layer graphene with the presence of few layer single crystal graphene grains were grown on Pt foil via chemical vapour deposition. The higher growth temperature changes the surface morphology of the Pt foil so a delicate process of hydrogen bubbling was used to peel off graphene from Pt foil samples with the mechanical support of photoresist and further transferred to SiO2/Si substrates for analysis. Optical microscopy of the graphene transferred samples showed the regions of single layer along with different oriented graphene domains. Two type of interlayer stacking sequences, Bernal and twisted, were observed in the graphene grains. The presence of different stacking sequences in the graphene layers influence the electronic and optical properties;in Bernal stacking the band gap can be tunable and in twisted stacking the overall sheet resistance can be reduced. Grain boundaries of Pt provides low energy sites to the carbon species, therefore the nucleation of grains are more at the boundaries. The stacking order and the number of layers in grains were seen more clearly with scanning electron microscopy. Raman spectroscopy showed high quality graphene samples due to very small D peak. 2D Raman peak for single layer graphene showed full width half maximum (FWHM) value of 30 cm ? 1. At points A, B and C, Bernal stacked grain showed FWHM values of 51.22, 58.45 and 64.72 cm ? 1, while twisted stacked grain showed the FWHM values of 27.26, 28.83 and 20.99 cm ? 1, respectively. FWHM values of 2D peak of Bernal stacked grain showed an increase of 20–30 cm ? 1 as compare to single layer graphene which showed its

  3. Synthesis of few layer single crystal graphene grains on platinum by chemical vapour deposition

    S. Karamat

    2015-08-01

    Full Text Available The present competition of graphene electronics demands an efficient route which produces high quality and large area graphene. Chemical vapour deposition technique, where hydrocarbons dissociate in to active carbon species and form graphene layer on the desired metal catalyst via nucleation is considered as the most suitable method. In this study, single layer graphene with the presence of few layer single crystal graphene grains were grown on Pt foil via chemical vapour deposition. The higher growth temperature changes the surface morphology of the Pt foil so a delicate process of hydrogen bubbling was used to peel off graphene from Pt foil samples with the mechanical support of photoresist and further transferred to SiO2/Si substrates for analysis. Optical microscopy of the graphene transferred samples showed the regions of single layer along with different oriented graphene domains. Two type of interlayer stacking sequences, Bernal and twisted, were observed in the graphene grains. The presence of different stacking sequences in the graphene layers influence the electronic and optical properties; in Bernal stacking the band gap can be tunable and in twisted stacking the overall sheet resistance can be reduced. Grain boundaries of Pt provides low energy sites to the carbon species, therefore the nucleation of grains are more at the boundaries. The stacking order and the number of layers in grains were seen more clearly with scanning electron microscopy. Raman spectroscopy showed high quality graphene samples due to very small D peak. 2D Raman peak for single layer graphene showed full width half maximum (FWHM value of 30 cm−1. At points A, B and C, Bernal stacked grain showed FWHM values of 51.22, 58.45 and 64.72 cm−1, while twisted stacked grain showed the FWHM values of 27.26, 28.83 and 20.99 cm−1, respectively. FWHM values of 2D peak of Bernal stacked grain showed an increase of 20–30 cm−1 as compare to single layer graphene

  4. Interface study between nanostructured tantalum nitride films and carbon nanotubes grown by chemical vapour deposition

    Highlights: • Our paper deals with the understanding of the carbon nanotubes growth parameters following the use of specific thin nitride buffer films. • For a large choice of buffer, we use ultra thin films elaborated by the very new method: high power pulsed magnetron sputtering; it allows a larger nitrogen incorporation in the films and lead to out of equilibrium phase formation. • Then by a multiscale investigation, developing a structural, a chemical and a morphology approach, we lead to some conclusion on the correlation between the phase transition for the buffer and morphology transition for the CNTs. • That is a new and deep approach. - Abstract: We present the role of nitrogen content in tantalum nitride ultra-thin buffers, on the carbon nanotubes (CNTs) growth by chemical vapour deposition at 850 °C, assisted by ferrocene as catalyst source. Tantalum nitride (TaNx) films with a very large range of concentration x = [0, 1.8] and various nanostructures, from amorphous Ta(N) to Ta3N5, were deposited by Highly Pulsed Plasma Magnetron Sputtering. The buffer films are characterized after heat treatment at 850 °C, and after the CNT growth, by wide angle X-ray scattering in grazing incidence and scanning electron microscopy. The CNT diameter explored by transition electron microscopy shows an all-out value for under stoichiometric thin films (Ta1-N1−δ, Ta3-N5−δ) and a minimum value just above the stoichiometric phases (Ta1-N1+δ, Ta3-N5+δ). Firstly one shows that the buffer films under the heat treatment present surface modification highly dependent on their initial state, which influences the catalyst particles diffusion. Secondly at the stoichiometric TaN phase we show that a specific ternary phase FeTa2O6 is formed at the interface CNT/buffer, not present in the other cases, leading to a special CNT growth condition

  5. Growth mechanism of planar or nanorod structured tungsten oxide thin films deposited via aerosol assisted chemical vapour deposition (AACVD)

    Ling, Min; Blackman, Chris [Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom)

    2015-07-15

    Aerosol assisted chemical vapour deposition (AACVD) is used to deposit tungsten oxide thin films from tungsten hexacarbonyl (W(CO){sub 6}) at 339 to 358 C on quartz substrate. The morphologies of as-deposited thin films, which are comprised of two phases (W{sub 25}O{sub 73} and W{sub 17}O{sub 47}), vary from planar to nanorod (NR) structures as the distance from the inlet towards the outlet of the reactor is traversed. This is related to variation of the actual temperature on the substrate surface (ΔT = 19 C), which result in a change in growth mode due to competition between growth rate (perpendicular to substrate) and nucleation rate (parallel to substrate). When the ratio of perpendicular growth rate to growth rate contributed by nucleation is higher than 7.1, the as-deposited tungsten oxide thin film forms as NR. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Kinetically controlled InN nucleation on GaN templates by metalorganic chemical vapour deposition

    This paper presents a study on the nucleation and initial growth kinetics of InN on GaN, especially their dependence on metalorganic chemical vapour deposition conditions. It is found that the density and size of separated InN nano-scale islands can be adjusted and well controlled by changing the V/III ratio and growth temperature. InN nuclei density increases for several orders of magnitude with decreasing growth temperature between 525 and 375 0C. At lower growth temperatures, InN thin films take the form of small and closely packed islands with diameters less than 100 nm, whereas at elevated temperatures the InN islands grow larger and become well separated, approaching an equilibrium hexagonal shape due to enhanced surface diffusion of adatoms. The temperature dependence of InN island density gives two activation energies of InN nucleation behaviour, which is attributed to two different kinetic processes related to In adatom surface diffusion and desorption, respectively.

  7. Chemical Vapour Deposition of Graphene with Re-useable Pt and Cu substrates for Flexible Electronics

    Karamat, Shumaila; Sonusen, Selda; Celik, Umit; Uysalli, Yigit; Oral, Ahmet

    2015-03-01

    Graphene has gained the attention of scientific world due to its outstanding physical properties. The future demand of flexible electronics such as solar cells, light emitting diodes, photo-detectors and touch screen technology requires more exploration of graphene properties on flexible substrates. The most interesting application of graphene is in organic light emitting diodes (OLED) where efforts are in progress to replace brittle indium tin oxide (ITO) electrode with a flexible graphene electrode because ITO raw materials are becoming increasingly expensive, and its brittle nature makes it unsuitable for flexible devices. In this work, we grow graphene on Pt and Cu substrates using chemical vapour deposition (CVD) and transferred it to a polymer material (PVA) using lamination technique. We used hydrogen bubbling method for separating graphene from Pt and Cu catalyst to reuse the substrates many times. After successful transfer of graphene on polymer samples, we checked the resistivity values of the graphene sheet which varies with growth conditions. Furthermore, Raman, atomic force microscopy (AFM), I-V and Force-displacement measurements will be presented for these samples.

  8. Synthesis of thick diamond films by direct current hot-cathode plasma chemical vapour deposition

    Jin Zeng Sun; Bai Yi Zhen; Lu Xian Yi

    2002-01-01

    The method of direct current hot-cathode plasma chemical vapour deposition has been established. A long-time stable glow discharge at large discharge current and high gas pressure has been achieved by using a hot cathode in the temperature range from 1100 degree C to 1500 degree C and non-symmetrical configuration of the poles, in which the diameter of the cathode is larger than that of anode. High-quality thick diamond films, with a diameter of 40-50 mm and thickness of 0.5-4.2 mm, have been synthesized by this method. Transparent thick diamond films were grown over a range of growth rates between 5-10 mu m/h. Most of the thick diamond films have thermal conductivities of 10-12 W/K centre dot cm. The thick diamond films with high thermal conductivity can be used as a heat sink of semiconducting laser diode array and as a heat spreading and isolation substrate of multichip modules. The performance can be obviously improved

  9. Nano sized bismuth oxy chloride by metal organic chemical vapour deposition

    Jagdale, Pravin, E-mail: pravin.jagdale@polito.it [Department of Applied Science and Technology (DISAT), Politecnico di Torino, 10129 (Italy); Castellino, Micaela [Center for Space Human Robotics, Istituto Italiano di Tecnologia, Corso Trento 21, 10129 Torino (Italy); Marrec, Françoise [Laboratory of Condensed Matter Physics, University of Picardie Jules Verne (UPJV), Amiens 80039 (France); Rodil, Sandra E. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexicom (UNAM), Mexico D.F. 04510 (Mexico); Tagliaferro, Alberto [Department of Applied Science and Technology (DISAT), Politecnico di Torino, 10129 (Italy)

    2014-06-01

    Metal organic chemical vapour deposition (MOCVD) method was used to prepare thin films of bismuth based nano particles starting from bismuth salts. Nano sized bismuth oxy chloride (BiOCl) crystals were synthesized from solution containing bismuth chloride (BiCl{sub 3}) in acetone (CH{sub 3}-CO-CH{sub 3}). Self-assembly of nano sized BiOCl crystals were observed on the surface of silicon, fused silica, copper, carbon nanotubes and aluminium substrates. Various synthesis parameters and their significant impact onto the formation of self-assembled nano-crystalline BiOCl were investigated. BiOCl nano particles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and Micro-Raman spectroscopy. These analyses confirm that bismuth nanometer-sized crystal structures showing a single tetragonal phase were indeed bismuth oxy chloride (BiOCl) square platelets 18–250 nm thick and a few micrometres wide.

  10. Controlled n-doping in chemical vapour deposition grown graphene by antimony

    We have studied the effects of antimony (Sb) doping on graphene grown by chemical vapour deposition without any significant change in its electrical properties. By increasing the metal thickness from 1 to 5 nm, we found a shift in the wave numbers of Raman G and two-dimensional (2D) peaks consistent with n-doping and a change in the Fermi level of the graphene into the conduction band. The relative intensity of the D peak to the G peak did not show a significant change and that of the 2D peak to the G peak remained at a large enough number as a function of metal thickness, implying little degradation by the metal dopants. Transport measurements also confirm the n-doping of graphene through a shift of Dirac point in the transfer characteristics and the quality preservation with little changes in mobility. We also report on the formation of a p–n junction by metal doping on selected areas of the graphene and their electrical properties with transfer characteristics and Hall measurements. (paper)

  11. Control and characterization of individual grains and grain boundaries in graphene grown by chemical vapour deposition

    Yu, Qingkai; Jauregui, Luis A.; Wu, Wei; Colby, Robert; Tian, Jifa; Su, Zhihua; Cao, Helin; Liu, Zhihong; Pandey, Deepak; Wei, Dongguang; Chung, Ting Fung; Peng, Peng; Guisinger, Nathan P.; Stach, Eric A.; Bao, Jiming; Pei, Shin-Shem; Chen, Yong P.

    2011-06-01

    The strong interest in graphene has motivated the scalable production of high-quality graphene and graphene devices. As the large-scale graphene films synthesized so far are typically polycrystalline, it is important to characterize and control grain boundaries, generally believed to degrade graphene quality. Here we study single-crystal graphene grains synthesized by ambient chemical vapour deposition on polycrystalline Cu, and show how individual boundaries between coalescing grains affect graphene’s electronic properties. The graphene grains show no definite epitaxial relationship with the Cu substrate, and can cross Cu grain boundaries. The edges of these grains are found to be predominantly parallel to zigzag directions. We show that grain boundaries give a significant Raman ‘D’ peak, impede electrical transport, and induce prominent weak localization indicative of intervalley scattering in graphene. Finally, we demonstrate an approach using pre-patterned growth seeds to control graphene nucleation, opening a route towards scalable fabrication of single-crystal graphene devices without grain boundaries.

  12. Investigation of the nucleation process of chemical vapour deposited diamond films

    The primary aim of this work was to contribute to the understanding of the bias enhanced nucleation (BEN) process during the chemical vapour deposition (CVD) of diamond on silicon. The investigation of both the gas phase environment above the substrate surface, by in situ mass selective energy analysis of ions, and of the surface composition and structure by in vacuo surface analytic methods (XPS, EELS) have been carried out. In both cases, the implementation of these measurements required the development and construction of special experimental apparatus as well. The secondary aim of this work was to give orientation to our long term goal of growing diamond films with improved quality. For this reason, (1) contaminant levels at the diamond-silicon interface after growth were studied by SIMS, (2) the internal stress distribution of highly oriented free-standing diamond films were studied by Raman spectroscopy, and (3) an attempt was made to produce spatially regular oriented nuclei formation by nucleating on a pattern created by laser treatment on silicon substrates. (orig.)

  13. Deposition and characterization of diamond-like nanocomposite coatings grown by plasma enhanced chemical vapour deposition over different substrate materials

    Awadesh Kr Mallik; Nanadadulal Dandapat; Prajit Ghosh; Utpal Ganguly; Sukhendu Jana; Sayan Das; Kaustav Guha; Garfield Rebello; Samir Kumar Lahiri; Someswar Datta

    2013-04-01

    Diamond-like nanocomposite (DLN) coatings have been deposited over different substrates used for biomedical applications by plasma-enhanced chemical vapour deposition (PECVD). DLN has an interconnecting network of amorphous hydrogenated carbon and quartz-like oxygenated silicon. Raman spectroscopy, Fourier transform–infra red (FT–IR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) have been used for structural characterization. Typical DLN growth rate is about 1 m/h, measured by stylus profilometer. Due to the presence of quartz-like Si:O in the structure, it is found to have very good adhesive property with all the substrates. The adhesion strength found to be as high as 0.6 N on SS 316 L steel substrates by scratch testing method. The Young’s modulus and hardness have found to be 132 GPa and 14.4 GPa, respectively. DLN coatings have wear factor in the order of 1 × 10-7 mm3/N-m. This coating has found to be compatible with all important biomedical substrate materials and has successfully been deposited over Co–Cr alloy based knee implant of complex shape.

  14. Diagnostics of microwave activated novel gas mixtures for diamond chemical vapour deposition

    Microwave plasma enhanced Chemical Vapour Deposition (CVD) has been used to grow diamond films at substrate temperatures as low as 435 deg C using CO2/CH4 gas mixtures. Molecular beam mass spectrometry (MBMS) has been used to measure simultaneously the concentrations of the dominant gas phase species present during growth, for a wide range of plasma gas mixtures (0 - 80% CH4, balance CO2). The CHEMKIN computer package has also been used to simulate the experimental results in order to gain insight into the major reactions occurring within the microwave plasma. The calculated trends for all species agree well with the experimental observations. Using these data, the model for the gas phase chemistry can be reduced to just four overall reactions. Our findings suggest that CH3 radicals are likely to be the key growth species when using CO2/CH4 plasmas and provide a qualitative explanation for the observation that diamond growth occurs within a very narrow concentration window. Diamond films have also been deposited; using both 1% CH4/H2 and 51%CH4/49%CO2 gas mixtures with various levels of H2S addition (100-5000 ppm). The former gas mixture was investigated using both microwave (MW) and hot filament (HF) activation and it was found that these two deposition techniques yield very different results. For both 1% CH4/H2 and 51%CH4/49%CO2 MW activated gas mixtures, scanning electron microscopy (SEM) observations show that the crystal quality of these films reduces with increasing H2S addition. Laser Raman and four point probe measurements showed a corresponding fall in the quality and resistivity of deposited diamond films, respectively. MBMS measurements for these S containing gas mixtures revealed significant concentrations of CS2 and CS in all of the MW plasmas that yield S-doped diamond films, whereas CS was not detected in the gas phase during HF growth. This suggests that CS may be an important intermediary facilitating S incorporation into diamond. All of these

  15. Atmospheric pressure chemical vapour deposition of thermochromic tungsten doped vanadium dioxide thin films for use in architectural glazing

    Blackman, C. S.; Piccirillo, C.; Binions, R.; Parkin, I. P.

    2009-01-01

    Atmospheric pressure chemical vapour deposition of VCl4, WCl6 and water at 550 degrees C lead to the production of high quality tungsten doped vanadium dioxide thin films. Careful control of the gas phase precursors allowed for tungsten doping up to 8 at.%. The transition temperature of the thermochromic switch was tunable in the range 55 degrees C to - 23 degrees C. The films were analysed using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spect...

  16. Antimicrobial activity of novel nanostructured Cu-SiO2 coatings prepared by chemical vapour deposition against hospital related pathogens

    Varghese, Sajnu; ElFakhri, Souad O; Sheel, David W.; Sheel, Paul; Bolton, Frederick J Eric; Foster, Howard A

    2013-01-01

    There is increasing recognition that the healthcare environment acts as an important reservoir for transmission of healthcare acquired infections (HCAI). One method of reducing environmental contamination would be use of antimicrobial materials. The antimicrobial activity of thin silica-copper films prepared by chemical vapour deposition was evaluated against standard strains of bacteria used for disinfectant testing and bacteria of current interest in HCAI. The structure of the coatings was ...

  17. Growth mechanisms of carbon nanotrees with branched carbon nanofibers synthesized by plasma-enhanced chemical vapour deposition

    He, Zhanbing; Maurice, Jean-Luc; Lee, Chang Seok; Cojocaru, Costel Sorin; Pribat, D.

    2014-01-01

    Y- and comb-type carbon nanotrees formed from branched carbon nanofibres grown by plasma-enhanced chemical vapour deposition were studied by transmission electron microscopy. Different growth mechanisms are proposed for the two types of nanotrees based on the observed and reconstituted dynamic transformations of the catalyst particles during synthesis. However, the splitting of the larger catalyst particles is required for both kinds of nanotrees, whatever the involved growth mechanism. The c...

  18. Excimer laser recrystallization of nanocrystalline-Si films deposited by inductively coupled plasma chemical vapour deposition at 150 deg. C

    Polycrystalline silicon thin film transistors (poly-Si TFTs) fabricated at low temperature (under 200 deg. C) have been widely investigated for flexible substrate applications such as a transparent plastic substrate. Unlike the conventional TFT process using glass substrate, the maximum process temperature should be kept less than 200 deg. C in order to avoid thermal damage on flexible substrates. We report the characteristics of nanocrystalline silicon (nc-Si) irradiated by an excimer laser. Nc-Si precursors were deposited on various buffer layers by inductively coupled plasma chemical vapour deposition (ICP-CVD) at 150 deg. C. We employed various buffer layers, such as silicon nitride (SiNX) and silicon dioxide (SiO2), in order to report recrystallization characteristics in connection with a buffer layer of a different thermal conductivity. The dehydrogenation and recrystallization was performed by step-by-step excimer laser annealing (ELA) (XeCl,λ=308 nm) in order to prevent the explosive release of hydrogen atoms. The grain size of the poly-Si film, which was recrystallized on the various buffer layers, was measured by scanning electron microscopy (SEM) at each laser energy density. The process margin of step-by-step ELA employing the SiNX buffer layer is wider than SiO2 and the maximum grain size slightly increased

  19. Excimer laser recrystallization of nanocrystalline-Si films deposited by inductively coupled plasma chemical vapour deposition at 150 deg. C

    Park, Joong-Hyun [School of Electrical Engineering (50), Seoul National University, Shinlim-Dong, Gwanak-Gu, Seoul (Korea, Republic of); Han, Sang-Myeon [School of Electrical Engineering (50), Seoul National University, Shinlim-Dong, Gwanak-Gu, Seoul (Korea, Republic of); Park, Sang-Geun [School of Electrical Engineering (50), Seoul National University, Shinlim-Dong, Gwanak-Gu, Seoul (Korea, Republic of); Han, Min-Koo [School of Electrical Engineering (50), Seoul National University, Shinlim-Dong, Gwanak-Gu, Seoul (Korea, Republic of); Shin, Moon-Young [LTPS Team, AMLCD Business, Samsung Electronics Co., Giheung, Yongin City (Korea, Republic of)

    2006-09-01

    Polycrystalline silicon thin film transistors (poly-Si TFTs) fabricated at low temperature (under 200 deg. C) have been widely investigated for flexible substrate applications such as a transparent plastic substrate. Unlike the conventional TFT process using glass substrate, the maximum process temperature should be kept less than 200 deg. C in order to avoid thermal damage on flexible substrates. We report the characteristics of nanocrystalline silicon (nc-Si) irradiated by an excimer laser. Nc-Si precursors were deposited on various buffer layers by inductively coupled plasma chemical vapour deposition (ICP-CVD) at 150 deg. C. We employed various buffer layers, such as silicon nitride (SiN{sub X}) and silicon dioxide (SiO{sub 2}), in order to report recrystallization characteristics in connection with a buffer layer of a different thermal conductivity. The dehydrogenation and recrystallization was performed by step-by-step excimer laser annealing (ELA) (XeCl,{lambda}=308 nm) in order to prevent the explosive release of hydrogen atoms. The grain size of the poly-Si film, which was recrystallized on the various buffer layers, was measured by scanning electron microscopy (SEM) at each laser energy density. The process margin of step-by-step ELA employing the SiN{sub X} buffer layer is wider than SiO{sub 2} and the maximum grain size slightly increased.

  20. Low-pressure Chemical Vapour Deposition of Silicon Nanoparticles:Synthesis and Characterisation

    A. Kumar

    2008-07-01

    Full Text Available emiconductor nanostructures such as quantum wells, quantum wires or quantum dots exhibit superior properties in comparison to their bulk forms. Quantum dots are described aszero-dimensional electron gas system, as carriers are confined in all the three directions. Densityof states is discrete function of energy. Allowed energy spectrum is discrete like in an atom.Energy band gap is broadened due to carriers confinement. Semiconductor quantum dots exhibittypical coulomb blockade characteristic which is exploited for development of new generationof nanoelectronic devices namely single-electron transistor, memories, etc, whose operationdepends on quantum mechanical tunneling of carriers through energy barriers. Thesesemiconductor nanostructures emit light in visible range upon excitation by optical means. Inrecent years,  research  has been focused on different nano-scale materials; metals (Au, Ag, Fe,Mn, Ni, metal oxides (SnO2, ZnO2, compound semiconductors (GaAs, GaAlAs, CdSe, CdS,GaN, and elemental semiconductors (silicon and germanium. As silicon is the most favouredmaterial in the established integrated circuits manufacturing technology, research is being donefor controlled synthesis and characterisation of Si nanoparticles. The Si nanoparticles havebeen synthesised on oxide and nitride layers over  Si substrate by IC technology compatiblelow-pressure chemical vapour deposition technique. Atomic force microscopy (AFMcharacterisation has been extensively carried out on the samples. It is shown that the tip radiusand shape of tip lead to less accurate estimate of the actual size. The AFM images have been evaluated based on the real surface topography and shape of the tip. Photolumine scence (PL studies have been performed to characterise the samples. The PL measurements showed visiblelight emission from synthesised silicon nanoparticles.Defence Science Journal, 2008, 58(4, pp.550-558, DOI:http://dx.doi.org/10.14429/dsj.58.1676

  1. The Role of Plasma in Plasma Enhanced Chemical Vapour Deposition of Nanostructure Growth

    Hash, David B.; Meyyappan, M.; Teo, Kenneth B. K.; Lacerda, Rodrigo G.; Rupesinghe, Nalin L.

    2004-01-01

    Chemical vapour deposition (CVD) has become the preferred process for high yield growth of carbon nanotubes and nanofibres because of its ability to pattern growth through lithographic positioning of transition metal catalysts on substrates. Many potential applications of nanotubes such as field emitters [1] require not only patterned growth but also vertical alignment. Some degree of ali,ment in thermal CVD processes can be obtained when carbon nanotubes are grown closely together as a result of van der Waals interactions. The ali,onment however is marginal, and the van der Waals prerequisite makes growth of freestanding nanofibres with thermal CVD unrealizable. The application of electric fields as a means of ali,onment has been shown to overcome this limitation [2-5], and highly aligned nanostructures can be grown if electric fields on the order of 0.5 V/microns are employed. Plasma enhanced CVD in various configurations including dc, rf, microwave, inductive and electron cyclotron resonance has been pursued as a means of enabling alignment in the CVD process. However, the sheath fields for the non-dc sources are in general not sufficient for a high degree of ali,pment and an additional dc bias is usually applied to the growth substrate. This begs the question as to the actual role of the plasma. It is clear that the plasma itself is not required for aligned growth as references [3] and [4] employed fields through small applied voltages (3-20 V) across very small electrode spacings (10-100 microns) and thus avoided striking a discharge.

  2. Temporal Stability of Metal-Chloride-Doped Chemical-Vapour-Deposited Graphene.

    Kang, Moon H; Milne, William I; Cole, Matthew T

    2016-08-18

    Graphene has proven to be a promising material for transparent flexible electronics. In this study, we report the development of a transfer and doping scheme of large-area chemical vapour deposited (CVD) graphene. A technique to transfer the as-grown material onto mechanically flexible and optically transparent polymeric substrates using an ultraviolet adhesive (UVA) is outlined, along with the temporal stability of the sheet resistance and optical transparency following chemical doping with various metal chlorides (Mx Cly The sheet resistance (RS ) and 550 nm optical transparency (%T550 ) of the transferred un-doped graphene was 3.5 kΩ sq(-1) (±0.2 kΩ sq(-1) ) and 84.1 % (±2.9 %), respectively. Doping with AuCl3 showed a notable reduction in RS by some 71.4 % (to 0.93 kΩ sq(-1) ) with a corresponding %T550 of 77.0 %. After 200 h exposure to air at standard temperature and pressure, the increase in RS was found to be negligible (ΔRS AuCl3 =0.06 kΩ sq(-1) ), indicating that, of the considered Mx Cly species, AuCl3 doping offered the highest degree of time stability under ambient conditions. There appears a tendency of increasing RS with time for the remaining metal chlorides studied. We attribute the observed temporal shift to desorption of molecular dopants. We find that desorption was most significant in RhCl3 -doped samples whereas, in contrast, after 200 h in ambient conditions, AuCl3 -doped graphene showed only marginal desorption. The results of this study demonstrate that chemical doping of UVA-transferred graphene is a promising means for enhancing large-area CVD graphene in order to realise a viable platform for next-generation optically transparent and mechanically flexible electronics. PMID:27165783

  3. Nanoparticulate cerium dioxide and cerium dioxide-titanium dioxide composite thin films on glass by aerosol assisted chemical vapour deposition

    Two series of composite thin films were deposited on glass by aerosol assisted chemical vapour deposition (AACVD)-nanoparticulate cerium dioxide and nanoparticulate cerium dioxide embedded in a titanium dioxide matrix. The films were analysed by a range of techniques including UV-visible absorption spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive analysis by X-rays. The AACVD prepared films showed the functional properties of photocatalysis and super-hydrophilicity. The CeO2 nanoparticle thin films displaying photocatalysis and photo-induced hydrophilicity almost comparable to that of anatase titania.

  4. Investigation of optical and electronic properties of hafnium aluminate films deposited by Metal-Organic Chemical Vapour Deposition

    Alloying elemental high-k metal oxides (such as HfO2) with other metals is seen as an effective method of controlling the properties of the dielectric based on the concentration of cations in the mixture; in particular, mixing HfO2 with Al2O3, and forming hafnium aluminate layers which will still have a relatively high dielectric constant (typically k ∼ 15) and remain amorphous up to high processing temperatures. This paper summarizes the results of physical and electrical characterisation of hafnium aluminate (HfAl xO y) films prepared by Metal-Organic Chemical Vapour Deposition. We show how, using ultraviolet-visible, single angle ellipsometry, the thickness and composition of the deposited and of the transition/interfacial layers can be extracted, and further used for the estimation of the relative dielectric constant. Moreover, a methodology for extracting the band gap of these materials and its dependence on the aluminium concentration is presented. This has been achieved by using a simple parameterization model (Wemple-Di Domenico) to account for the optical dispersion of the films. Preparing thin films with a relatively high dielectric constant and with an amorphous structure even at high processing temperatures, are not the only requirements to be achieved when such layers are to be used as gate dielectrics. The electrical characteristics - such as leakage current, density of interface states, fixed charge in the oxide - are extremely important. The results obtained through capacitance-voltage and current-voltage measurements show the possibility of adjusting the relative dielectric constant of the layers in a wide range (9-16), when the aluminium concentration varies between 4% and 38%. The minimum leakage current occurs for Al concentrations up to 9%. The thinner films show Fowler-Nordheim conduction even at higher concentrations of Al into the film, while thicker films show a higher hysteresis due to an increased number of slow trapping centres in the

  5. Morphology of carbon nanotubes prepared via chemical vapour deposition technique using acetylene: A small angle neutron scattering investigation

    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.

  6. Nitrogen-Doped Chemical Vapour Deposited Diamond: a New Material for Room-Temperature Solid State Maser

    N. A. Poklonski; N. M. Lapchuk; A. V. Khomich; LU Fan-Xiu; TANG Wei-Zhong; V. G. Ralchenko; I. I. Vlasov; M. V. Chukichev; Sambuu Munkhtsetseg

    2007-01-01

    Electron spin resonance (ESR) in polycrystalline diamond films grown by dc arc-jet and microwave plasma chemical vapour deposition is studied. The films with nitrogen impurity concentration up to 8 × 1018 cm-3 are also characterized by Raman, cathodoluminescence and optical absorption spectra. The ESR signal from P1 centre with g-factor of 2.0024 (nitrogen impurity atom occupying C site in diamond lattice) is found to exhibit an inversion with increasing the microwave power in an H102 resonator. The spin inversion effect could be of interest for further consideration of N-doped diamonds as a medium for masers operated at room temperature.

  7. Inkjet printing of catalyst-Inks on Si wafers and the subsequent synthesis of carbon nanotubes by chemical vapour deposition

    The production of substrates coated with carbon nano tubes (CNTs) in well-defined patterns is desirable for sensor applications. In the present work, nickel based catalytic inks were prepared and printed on silicon substrates using ink jet delivery. Subsequently, the substrates were subjected to calcination and chemical vapour deposition for the growth of aligned CNTs. Scanning electron microscopy, transmission electron microscopy and Raman spectroscopy were used to characterize the CNTs. Various concentrations and formulations of ink preparations were studied to investigate the effect of these parameters on the growth and structure of the CNTs. (author)

  8. Inline atmospheric pressure metal-organic chemical vapour deposition for thin film CdTe solar cells

    A detailed study has been undertaken to assess the deposition of CdTe for thin film devices via an inline atmospheric pressure metal-organic chemical vapour deposition (AP-MOCVD) reactor. The precursors for CdTe synthesis were released from a showerhead assembly normal to a transparent conductive oxide (TCO)/glass substrate, previously coated with a CdZnS window layer using a conventional batch AP-MOCVD reactor with horizontal flow delivery. Under a simulated illumination with air mass coefficient 1.5 (AM1.5), the initial best cell conversion efficiency (11.2%) for such hybrid cells was comparable to a reference device efficiency (∼ 13%), grown entirely in the AP-MOCVD batch reactor. The performance and structure of the hybrid and conventional devices are compared for spectral response, CdTe grain morphology and crystal structure. These preliminary results reported on the transfer from a batch to an inline AP-MOCVD reactor which holds a good potential for the large-scale production of thin film photovoltaics devices and related materials. - Highlights: • Inline metal-organic chemical vapour deposition (MOCVD) used to grow CdTe films • Desired dopant profiles in CdTe:As achieved with inline MOCVD reactor • Initial conversion efficiency of 11.2% was comparable to batch devices (∼ 13%). • Inline MOCVD holds a good potential for large-scale thin film photovoltaics production

  9. Aerosol assisted chemical vapour deposition of germanium thin films using organogermanium carboxylates as precursors and formation of germania films

    Alpa Y Shah; Amey Wadawale; Vijaykumar S Sagoria; Vimal K Jain; C A Betty; S Bhattacharya

    2012-06-01

    Diethyl germanium bis-picolinate, [Et2Ge(O2CC5H4N)2], and trimethyl germanium quinaldate, [Me3Ge(O2CC9H6N)], have been used as precursors for deposition of thin films of germanium by aerosol assisted chemical vapour deposition (AACVD). The thermogravimetric analysis revealed complete volatilization of complexes under nitrogen atmosphere. Germanium thin films were deposited on silicon wafers at 700°C employing AACVD method. These films on oxidation under an oxygen atmosphere at 600°C yield GeO2. Both Ge and GeO2 films were characterized by XRD, SEM and EDS measurements. Their electrical properties were assessed by current–voltage (–) characterization.

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

    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.

  11. Substrate and material transfer effects on the surface chemistry and texture of diamond-like carbon deposited by plasma-enhanced chemical vapour deposition

    Jones, Benjamin; Ojeda, J. J.

    2012-01-01

    Diamond-like carbon (DLC), a thin amorphous carbon film, has many uses in tribological systems. Exploiting alternative substrates and interlayers can enable the control of the hardness and modulus of the multilayer system and improve wear or friction properties. We used XPS and atomic force microscopy to examine DLC that had been concurrently coated on an epoxy interlayer and a steel substrate by plasma-enhanced chemical vapour deposition. sp2/sp3 ratios were calculated both by the deconvolut...

  12. Chemical vapour deposition enhanced by atmospheric microwave plasmas: a large-scale industrial process or the next nanomanufacturing tool?

    Belmonte, T.; Gries, T.; Cardoso, R. P.; Arnoult, G.; Kosior, F.; Henrion, G.

    2011-04-01

    This paper describes several specific aspects of atmospheric plasma deposition carried out with a microwave resonant cavity. Deposition over a wide substrate is first studied. We show that high deposition rates (several hundreds of μm h-1) are due to localization of fluxes on the substrate by convection when slightly turbulent flows are used. Next, we describe possible routes to localize deposition over a nanometre-sized area. Scaling down atmospheric plasma deposition is possible and two strategies to reach nanometre scales are described. Finally, we study self-organization of SiO2 nanodots deposited by chemical vapour deposition at atmospheric pressure enhanced by an Ar-O2 micro-afterglow operating at high temperature (>1200 K). When the film being deposited is thin enough (~500 nm) nanodots are obtained and they can be assembled into threads to create patterned surfaces. When the coating becomes thicker (~1 µm), and for relatively high content in HMDSO, SiO2 walls forming hexagonal cells are obtained.

  13. Characterization of thin TiO2 films prepared by plasma enhanced chemical vapour deposition for optical and photocatalytic applications

    Thin titanium oxide films were deposited using a radio frequency (RF) plasma enhanced chemical vapour deposition method. Their optical properties and thickness were determined by means of ultraviolet-visible absorption spectrophotometry. Films of the optical parameters very close to those of titanium dioxide have been obtained at the high RF power input. Their optical quality is high enough to allow for their use in a construction of stack interference optical filters. At the same time, these materials exhibit strong photocatalytic effects. The results of structural analysis, carried out by Raman Shift Spectroscopy, show that the coatings posses amorphous structure. However, Raman spectra of the same films subjected to thermal annealing at 450 oC disclose an appearance of a crystalline form, namely that of anatase. Surface morphology of the films has also been characterized by Atomic Force Microscopy revealing granular, broccoli-like topography of the films.

  14. Growth of aligned single-walled carbon nanotubes under ac electric fields through floating catalyst chemical vapour deposition

    Dou Xin-Yuan; Luo Shu-Dong; Zhang Zeng-Xing; Liu Dong-Fang; Wang Jian-Xiong; Gao Yan; Zhou Wei-Ya; Wang Gang; Zhou Zhen-Ping; Tan Ping-Heng; Zhou Jian-Jun; Song Li; Sun Lian-Feng; Jiang Peng; Liu Li-Feng; Zhao Xiao-Wei

    2005-01-01

    Through floating catalyst chemical vapour deposition(CVD) method, well-aligned isolated single-walled carbon nanotubes (SWCNTs) and their bundles were deposited on the metal electrodes patterned on the SiO2/Si surface under ac electric fields at relatively low temperature(280℃). It was indicated that SWCNTs were effectively aligned under ac electric fields after they had just grown in the furnace. The time for a SWCNT to be aligned in the electric field and the effect of gas flow were estimated. Polarized Raman scattering was performed to characterize the aligned structure of SWCNTs. This method would be very useful for the controlled fabrication and preparation of SWCNTs in practical applications.

  15. Perfluorodecyltrichlorosilane-based seed-layer for improved chemical vapour deposition of ultrathin hafnium dioxide films on graphene

    Kitzmann, Julia; Göritz, Alexander; Fraschke, Mirko; Lukosius, Mindaugas; Wenger, Christian; Wolff, Andre; Lupina, Grzegorz

    2016-01-01

    We investigate the use of perfluorodecyltrichlorosilane-based self-assembled monolayer as seeding layer for chemical vapour deposition of HfO2 on large area CVD graphene. The deposition and evolution of the FDTS-based seed layer is investigated by X-ray photoelectron spectroscopy, Auger electron spectroscopy, and transmission electron microscopy. Crystalline quality of graphene transferred from Cu is monitored during formation of the seed layer as well as the HfO2 growth using Raman spectroscopy. We demonstrate that FDTS-based seed layer significantly improves nucleation of HfO2 layers so that graphene can be coated in a conformal way with HfO2 layers as thin as 10 nm. Proof-of-concept experiments on 200 mm wafers presented here validate applicability of the proposed approach to wafer scale graphene device fabrication. PMID:27381715

  16. Properties of MgB2 films grown at various temperatures by hybrid physical chemical vapour deposition

    Chen, Ke; Veldhorst, Menno; Lee, Che-Hui; Lamborn, Daniel R.; DeFrain, Raymond; Redwing, Joan M.; Li, Qi; Xi, X. X.

    2008-09-01

    A hybrid physical-chemical vapour deposition (HPCVD) system consisting of separately controlled Mg-source heater and substrate heater is used to grow MgB2 thin films and thick films at various temperatures. We are able to grow superconducting MgB2 thin films at temperatures as low as 350 °C with a Tc0 of 35.5 K. MgB2 films up to 4 µm in thickness grown at 550 °C have Jc over 106 A cm-2 at 5 K and zero applied field. The low deposition temperature of MgB2 films is desirable for all-MgB2 tunnel junctions and MgB2 thick films are important for applications in coated conductors.

  17. Properties of MgB{sub 2} films grown at various temperatures by hybrid physical-chemical vapour deposition

    Chen, Ke; Veldhorst, Menno; Li, Qi; Xi, X X [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States); Lee, Che-Hui; Lamborn, Daniel R; DeFrain, Raymond; Redwing, Joan M [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)

    2008-09-15

    A hybrid physical-chemical vapour deposition (HPCVD) system consisting of separately controlled Mg-source heater and substrate heater is used to grow MgB{sub 2} thin films and thick films at various temperatures. We are able to grow superconducting MgB{sub 2} thin films at temperatures as low as 350 deg. C with a T{sub c0} of 35.5 K. MgB{sub 2} films up to 4 {mu}m in thickness grown at 550 deg. C have J{sub c} over 10{sup 6} A cm{sup -2} at 5 K and zero applied field. The low deposition temperature of MgB{sub 2} films is desirable for all-MgB{sub 2} tunnel junctions and MgB{sub 2} thick films are important for applications in coated conductors.

  18. Properties of MgB2 films grown at various temperatures by hybrid physical-chemical vapour deposition

    A hybrid physical-chemical vapour deposition (HPCVD) system consisting of separately controlled Mg-source heater and substrate heater is used to grow MgB2 thin films and thick films at various temperatures. We are able to grow superconducting MgB2 thin films at temperatures as low as 350 deg. C with a Tc0 of 35.5 K. MgB2 films up to 4 μm in thickness grown at 550 deg. C have Jc over 106 A cm-2 at 5 K and zero applied field. The low deposition temperature of MgB2 films is desirable for all-MgB2 tunnel junctions and MgB2 thick films are important for applications in coated conductors

  19. Perfluorodecyltrichlorosilane-based seed-layer for improved chemical vapour deposition of ultrathin hafnium dioxide films on graphene.

    Kitzmann, Julia; Göritz, Alexander; Fraschke, Mirko; Lukosius, Mindaugas; Wenger, Christian; Wolff, Andre; Lupina, Grzegorz

    2016-01-01

    We investigate the use of perfluorodecyltrichlorosilane-based self-assembled monolayer as seeding layer for chemical vapour deposition of HfO2 on large area CVD graphene. The deposition and evolution of the FDTS-based seed layer is investigated by X-ray photoelectron spectroscopy, Auger electron spectroscopy, and transmission electron microscopy. Crystalline quality of graphene transferred from Cu is monitored during formation of the seed layer as well as the HfO2 growth using Raman spectroscopy. We demonstrate that FDTS-based seed layer significantly improves nucleation of HfO2 layers so that graphene can be coated in a conformal way with HfO2 layers as thin as 10 nm. Proof-of-concept experiments on 200 mm wafers presented here validate applicability of the proposed approach to wafer scale graphene device fabrication. PMID:27381715

  20. Amorphous silicon thin film solar cells deposited entirely by Hot-Wire Chemical Vapour Deposition at low temperature (<150 ºC)

    Villar, Fernando; Antony, Aldrin; Escarré i Palou, Jordi; Ibarz, D.; Roldán, Rubén; Stella, Marco; Muñoz Ramos, David; Asensi López, José Miguel; Bertomeu i Balagueró, Joan

    2009-01-01

    Amorphous silicon n-i-p solar cells have been fabricated entirely by Hot-Wire Chemical Vapour Deposition (HW-CVD) at low process temperature < 150 °C. A textured-Ag/ZnO back reflector deposited on Corning 1737F by rf magnetron sputtering was used as the substrate. Doped layers with very good conductivity and a very less defective intrinsic a-Si:H layer were used for the cell fabrication. A double n-layer (μc-Si:H/a-Si:H) and μc-Si:H p-layer were used for the cell. In this paper, we report the...

  1. Role of Duty Ratio in Diamond Growth by Pulsed DC-Bias Enhanced Hot Filament Chemical Vapour Deposition

    In this study, the role of the pulse duty ratio was investigated during the deposition of diamond films in a hot filament chemical vapour deposition reactor with a pulsed-dc biased substrate positively relative to the hot filaments. The voltage-current characteristics showed that the discharge current rose with the increase of biasing voltage, which was modified by the duty ratio. Before deposition, two approaches were adopted for the pre-treatment of the silicon substrates, respectively, and the substrates were scratched by diamond paste or seeded by diamond powders using the so-called 'soft dry polished' technique. Diamond films were deposited under a fixed discharge power by changing the duty ratios. In the first group with scratched substrates, it was found that under a high duty ratio the diamond grew slowly with quite poor nucleation, while in the second case a high duty ratio induced a high deposition rate and good diamond quality. Reactive hydrocarbon species with high energy are essential for the initial nucleation process, which is more effectively achieved at a high biasing voltage in the condition of a low duty ratio. In the film growth process, the large discharge current at a high duty ratio represents an increased concentration of electrons and reactive species as well, promoting the growth of diamond films

  2. Structural and optical properties of hydrogenated amorphous silicon carbide films by helicon wave plasma-enhanced chemical vapour deposition

    Hydrogenated amorphous silicon carbide (a-Si1-xCx : H) films with different carbon concentrations have been deposited using the helicon wave plasma-enhanced chemical vapour deposition technique under the condition of strong hydrogen dilution. The a-Si1-xCx:H films with carbon content x up to 0.64 have been deposited. Their structural and optical properties are investigated using Fourier transform infrared spectroscopy, Raman scattering, ultraviolet-visible transmittance spectroscopy and x-ray photoelectron spectroscopy. The deposition rate, optical band gap and B factor related to structural disorder are found to monotonically change in the investigated range with methane-silane gas flow ratios. It is found that the deposited films exist with the structure of Si-like clusters and Si-C networks when silicon content is high, while they consist mainly of C-like clusters and Si-C networks for carbon-rich samples. A large optical band gap is obtained in high carbon concentration samples, which is attributed to the high density characteristic of helicon wave plasmas and the strong hydrogen dilution condition

  3. Growth of large size diamond single crystals by plasma assisted chemical vapour deposition: Recent achievements and remaining challenges

    Tallaire, Alexandre; Achard, Jocelyn; Silva, François; Brinza, Ovidiu; Gicquel, Alix

    2013-02-01

    Diamond is a material with outstanding properties making it particularly suited for high added-value applications such as optical windows, power electronics, radiation detection, quantum information, bio-sensing and many others. Tremendous progresses in its synthesis by microwave plasma assisted chemical vapour deposition have allowed obtaining single crystal optical-grade material with thicknesses of up to a few millimetres. However the requirements in terms of size, purity and crystalline quality are getting more and more difficult to achieve with respect to the forecasted applications, thus pushing the synthesis method to its scientific and technological limits. In this paper, after a short description of the operating principles of the growth technique, the challenges of increasing crystal dimensions both laterally and vertically, decreasing and controlling point and extended defects as well as modulating crystal conductivity by an efficient doping will be detailed before offering some insights into ways to overcome them.

  4. Low Density Self-Assembled InAs/GaAs Quantum Dots Grown by Metal Organic Chemical Vapour Deposition

    LI Lin; LIU Guo-Jun; WANG Xiao-Hua; LI Mei; LI Zhan-Guo; WAN Chun-Ming

    2008-01-01

    The serf-assembled InAs quantum dots (QDs) on GaAs substrates with low density (5×108cm-2) are achieved using relatively higher growth temperature and low InAs coverage by low-pressure metal-organic chemical vapour deposition.The macro-PL spectra exhibit three emission peaks at 1361,1280 and 1204nm,corresponding to the ground level (GS),the first excited state (ES1) and the second excited state (ES2) of the QDs,respectively,which are obtained when the GaAs capping layer/s grown using triethylgallium and tertiallybutylarsine.As a result of micro-PL,only a few peaks from individual dots have been observed.The exciton-biexciton behaviour was clearly observed at low temperature.

  5. Atmospheric pressure chemical vapour deposition of thermochromic tungsten doped vanadium dioxide thin films for use in architectural glazing

    Atmospheric pressure chemical vapour deposition of VCl4, WCl6 and water at 550 oC lead to the production of high quality tungsten doped vanadium dioxide thin films. Careful control of the gas phase precursors allowed for tungsten doping up to 8 at.%. The transition temperature of the thermochromic switch was tunable in the range 55 oC to - 23 oC. The films were analysed using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Their optical properties were examined using variable-temperature transmission and reflectance spectroscopy. It was found that incorporation of tungsten into the films led to an improvement in the colour from yellow/brown to green/blue depending on the level of tungsten incorporation. The films were optimized for optical transmission, thermochromic switching temperature, magnitude of the switching behaviour and colour to produce films that are suitable for use as an energy saving environmental glass product.

  6. Monte Carlo simulation of the behaviour of electrons during electron-assisted chemical vapour deposition of diamond

    董丽芳; 陈俊英; 董国义; 尚勇

    2002-01-01

    The behaviour of electrons during electron-assisted chemical vapour deposition of diamond is investigated using Monte Carlo simulation. The electron energy distribution and velocity distribution are obtained over a wide range of reduced field E/N (the ratio of the electric field to gas molecule density) from 100 to 2000 in units of 1Td=10-17Vcm2.Their effects on the diamond growth are also discussed. Themain results obtained are as follows. (1) The velocity profile is asymmetric for the component parallel to the field.Ihe velocity distribution has a peak shift in the field direction. Most electrons possess non-zero velocity parallel to the substrate. (2) The number of atomic H is a function of E/N. (3) High-quality diamond can be obtained under the condition of E/N from 50 to 800Td due to sufficient atomic H and electron bombardment.

  7. Atmospheric pressure chemical vapour deposition of NbSe2-TiSe2 composite thin films

    Atmospheric pressure chemical vapour deposition of titanium tetrachloride and niobium pentachloride with di-tert-butyl selenide at 550 deg. C was investigated for different precursors' flow rates. Scanning electron microscopy of the films showed that they were composed of two different kinds of plate-like crystallites. Point wavelength dispersive X-ray (WDX) analyses of the crystallites revealed that they either had the NbSe2 or the TiSe2 composition. The presence of the two phases was confirmed by X-ray diffraction (XRD) and the calculated cell parameters indicate that niobium or titanium was not incorporated into each others' lattice. WDX and XRD analyses highlighted how the NbSe2:TiSe2 ratio in the composite films could be controlled by precursor flow rate.

  8. Growth and characterization of nitrogen-doped single-walled carbon nanotubes by water-plasma chemical vapour deposition

    Nitrogen-doped single-walled carbon nanotubes (N-SWNTs) are directly grown on SiO2/Si substrates at 450 deg. C with methane and ammonia gases by water-plasma chemical vapour deposition. The strongest radial breathing mode peak in Raman spectra of the grown N-SWNTs, probed with a 633 nm laser excitation, was assigned to (7, 5) semiconducting nanotubes with a diameter of 0.83 nm. As the doped nitrogen content increases, the D-band to G-band ratio in Raman spectra, indicating the imperfection of nanotubes, gradually increases and saturates at around 4%. X-ray photoelectron spectroscopy shows that nitrogen atoms are doped with a pyridine-like configuration in the N-SWNTs

  9. Room-Temperature Ferromagnetic ZnMnO Thin Films Synthesized by Plasma Enhanced Chemical Vapour Deposition Method

    LIN Ying-Bin; ZHANG Feng-Ming; DU You-Wei; HUANG Zhi-Gao; ZHENG Jian-Guo; LU Zhi-Hai; ZOU Wen-Qin; LU Zhong-Lin; XU Jian-Ping; JI Jian-Ti; LIU Xing-Chong; WANG Jian-Feng; LV Li-Ya

    2007-01-01

    Room-temperature ferromagnetic Mn-doped ZnO films are grown on Si (001) substrates by plasma enhanced chemical vapour deposition (PECVD). X-ray diffraction measurements reveal that the Zn1-xMnxO films have the single-phase wurtzite structure. X-ray photoelectron spectroscopy indicates the existence of Mn2+ ions in Mndoped ZnO films. Furthermore, the decreasing additional Raman peak with increasing Mn-doping is considered to relate to the substitution of Mn ions for the Zn ions in ZnO lattice. Superconducting quantum interference device (SQUID) measurements demonstrate that Mn-doped ZnO films have ferromagnetic behaviour at room temperature.

  10. The properties of GaMnN films grown by metalorganic chemical vapour deposition using Raman spectroscopy

    Xing Hai-Ying; Niu Ping-Juan; Xie Yu-Xin

    2012-01-01

    An investigation of room-temperature Raman scattering is carried out on ferromagnetic semiconductor GaMnN films grown by metalorganic chemical vapour deposition with different Mn content values.New bands around 300 and 669 cm-1,that are not observed in undoped GaN,are found.They are assigned to disorder-activated mode and local vibration mode (LVM),respectively.After annealing,the intensity ratio between the LVM and E2(high) mode,i.e.,ILVM/IE2(high),increases.The LO phonon-plasmon coupled (LOPC) mode is found in GaMnN,and the frequency of the LOPC mode of GaMnN shifting toward higher side is observed with the increase in the Mn doping in GaN.The ferromagnetic character and the carrier density of our GaMnN sample are discussed.

  11. Titania Coated Mica via Chemical Vapour Deposition, Post N-doped by Liquid Ammonia Treatment

    Powell, Michael J.; Parkin, Ivan P.

    TiO2 films were successfully grown on synthetic mica powders via Chemical Vapor Deposition (CVD). The CVD rig is a cold-walled design that allows surface coverage of a powder to be successfully achieved. The TiO2 was produced by the reaction between TiCl4 and Ethyl Acetate. The powder produced could be successfully N-doped using post liquid ammonia treatment. The TiO2 powder produced could have potential applications in self-cleaning surfaces or antimicrobial paints.

  12. Metal organic chemical vapour deposition of SrRuO3 thin films on SrTiO3

    SrRuO3 with pseudo-cubic crystalline structure (a=0.393 nm) appears to be one of the most suitable conductive oxides to be used as bottom electrode for the oxide-based electronic devices, due to its high conductivity and low lattice misfit with many functional perovskite transition metal oxides. Furthermore, this electrode has a lower density of defects (oxygen vacancies, dislocations, dead layer) compared with metal electrodes (Pt,Ru,Ir). A vertical liquid-delivery metal-organic chemical vapour deposition (MO-CVD) reactor was used to deposit (100)-oriented SrRuO3 films on vicinal SrTiO3(100) substrates. In order to grow epitaxial thin films with low defect density and high electrical conductivity and to optimise the deposition parameters, the influence of deposition temperature (500-700 C), argon/oxygen ratio (1.6-3.3), total gas flow (4875-8125 sccm) and reactor pressure (12 mbar-40 mbar) was investigated. Composition of the films was identified by GDOES technique. Raman and XRD were used to determine film orientation and the surface morphology and roughness was analysed by AFM and SEM microscopy

  13. Effect of plasma composition on nanocrystalline diamond layers deposited by a microwave linear antenna plasma-enhanced chemical vapour deposition system

    Taylor, Andrew; Ashcheulov, Petr; Čada, Martin; Fekete, Ladislav; Hubík, Pavel; Klimša, Ladislav; Olejníček, Jiří; Remeš, Zdeněk; Jirka, Ivan; Janíček, P.; Bedel-Pereira, E.; Kopeček, Jaromír; Mistrík, J.; Mortet, Vincent

    2015-01-01

    Roč. 212, č. 11 (2015), s. 2418-2423. ISSN 1862-6300 R&D Projects: GA ČR GA13-31783S; GA MŠk LO1409 Grant ostatní: FUNBIO(XE) CZ.2.16/3.1.00/21568 Institutional support: RVO:68378271 ; RVO:61388955 Keywords : diamond * electrical conductivity * nanocrystalline materials * optical emission spectroscopy * plasma enhanced chemical vapour deposition * SiC Subject RIV: BM - Solid Matter Physics ; Magnetism; CF - Physical ; Theoretical Chemistry (UFCH-W) Impact factor: 1.616, year: 2014

  14. Nanofabrication using home-made RF plasma coupled chemical vapour deposition system

    Zinc oxide, ZnO, a popular semiconductor material with a wide band gap (3.37 eV) and high binding energy of the exciton (60 meV), has numerous applications such as in optoelectronics, chemical/biological sensors, and drug delivery. This project aims to (i) optimize the operating conditions for growth of ZnO nanostructures using the chemical vapor deposition (CVD) method, and (ii) investigate the effects of coupling radiofrequency (RF) plasma to the CVD method on the quality of ZnO nanostructures. First, ZnO nanowires were synthesized using a home-made reaction setup on gold-coated and non-coated Si (100) substrates at 950 °C. XRD, SEM, EDX, and PL measurements were used for characterizations and it was found that a deposition duration of 10 minutes produced the most well-defined ZnO nanowires. SEM analysis revealed that the nanowires had diameters ranging from 30-100 mm and lengths ranging from 1-4 µm. In addition, PL analysis showed strong UV emission at 380 nm, making it suitable for UV lasing. Next, RF plasma was introduced for 30 minutes. Both remote and in situ RF plasma produced less satisfactory ZnO nanostructures with poorer crystalline structure, surface morphology, and optical properties due to etching effect of energetic ions produced from plasma. However, a reduction in plasma discharge duration to 10 minutes produced thicker and shorter ZnO nanostructures. Based on experimentation conducted, it is insufficient to conclude that RF plasma cannot aid in producing well-defined ZnO nanostructures. It can be deduced that the etching effect of energetic ions outweighed the increased oxygen radical production in RF plasma nanofabrication. (author)

  15. Metal-organic chemical vapour deposition of lithium manganese oxide thin films via single solid source precursor

    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.

  16. Charge effect of superparamagnetic iron oxide nanoparticles on their surface functionalization by photo-initiated chemical vapour deposition

    Diverse applications of superparamagnetic iron oxide nanoparticles (SPIONs) in the chemical and biomedical industry depend on their surface properties. In this paper, we investigate the effect of initial surface charge (bare, positively and negatively charged SPIONs) on the resulting physicochemical properties of the particles following treatment through photo-initiated chemical vapour deposition (PICVD). Transmission electron microscopy shows a nanometric polymer coating on the SPIONs and contact angle measurements with water demonstrate that their surface became non-polar following functionalization using PICVD. FTIR and XPS data confirm the change in the chemical composition of the treated SPIONs. Indeed, XPS data reveal an initial charge-dependent increase in the surface oxygen content in the case of treated SPIONs. The O/C percentage ratios of the bare SPIONs increase from 1.7 to 1.9 after PICVD treatment, and decrease from 1.7 to 0.7 in the case of negatively charged SPIONs. The ratio remains unchanged for positively charged SPIONs (1.7). This indicates that bare and negatively charged SPIONs showed opposite preference for the oxygen or carbon attachment to their surface during their surface treatment. These results reveal that both the surface charge and stereochemical effects have determinant roles in the polymeric coating of SPIONs with PICVD. Our findings suggest that this technique is appropriate for the treatment of nanoparticles.Graphical Abstract

  17. Charge effect of superparamagnetic iron oxide nanoparticles on their surface functionalization by photo-initiated chemical vapour deposition

    Javanbakht, Taraneh [Ecole Polytechnique of Montreal, Department of Chemical Engineering (Canada); Laurent, Sophie; Stanicki, Dimitri [University of Mons, Laboratory of NMR and Molecular Imaging (Belgium); Raphael, Wendell; Tavares, Jason Robert, E-mail: jason.tavares@polymtl.ca [Ecole Polytechnique of Montreal, Department of Chemical Engineering (Canada)

    2015-12-15

    Diverse applications of superparamagnetic iron oxide nanoparticles (SPIONs) in the chemical and biomedical industry depend on their surface properties. In this paper, we investigate the effect of initial surface charge (bare, positively and negatively charged SPIONs) on the resulting physicochemical properties of the particles following treatment through photo-initiated chemical vapour deposition (PICVD). Transmission electron microscopy shows a nanometric polymer coating on the SPIONs and contact angle measurements with water demonstrate that their surface became non-polar following functionalization using PICVD. FTIR and XPS data confirm the change in the chemical composition of the treated SPIONs. Indeed, XPS data reveal an initial charge-dependent increase in the surface oxygen content in the case of treated SPIONs. The O/C percentage ratios of the bare SPIONs increase from 1.7 to 1.9 after PICVD treatment, and decrease from 1.7 to 0.7 in the case of negatively charged SPIONs. The ratio remains unchanged for positively charged SPIONs (1.7). This indicates that bare and negatively charged SPIONs showed opposite preference for the oxygen or carbon attachment to their surface during their surface treatment. These results reveal that both the surface charge and stereochemical effects have determinant roles in the polymeric coating of SPIONs with PICVD. Our findings suggest that this technique is appropriate for the treatment of nanoparticles.Graphical Abstract.

  18. In situ high temperature XRD studies of ZnO nanopowder prepared via cost effective ultrasonic mist chemical vapour deposition

    Preetam Singh; Ashvani Kumar; Ajay Kaushal; Davinder Kaur; Ashish Pandey; R N Goyal

    2008-06-01

    Ultrasonic mist chemical vapour deposition (UM–CVD) system has been developed to prepare ZnO nanopowder. This is a promising method for large area deposition at low temperature inspite of being simple, inexpensive and safe. The particle size, lattice parameters and crystal structure of ZnO nanopowder are characterized by in situ high temperature X-ray diffraction (XRD). Surface morphology of powder was studied using transmission electron microscopy (TEM) and field emission electron microscope (FESEM). The optical properties are observed using UV-visible spectrophotometer. The influence of high temperature vacuum annealing on XRD pattern is systematically studied. Results of high temperature XRD showed prominent 100, 002 and 101 reflections among which 101 is of highest intensity. With increase in temperature, a systematic shift in peak positions towards lower 2 values has been observed, which may be due to change in lattice parameters. Temperature dependence of lattice constants under vacuum shows linear increase in their values. Diffraction patterns obtained from TEM are also in agreement with the XRD data. The synthesized powder exhibited the estimated direct bandgap (g) of 3.43 eV. The optical bandgap calculated from Tauc’s relation and the bandgap calculated from the particle size inferred from XRD were in agreement with each other.

  19. Fabrication and gas sensing properties of pure and au-functionalised W03 nanoneedle-like structures, synthesised via aerosol assisted chemical vapour deposition method

    Stoycheva, Toni

    2011-01-01

    In this doctoral thesis, it has been investigated and developed the Aerosol Assisted Chemical Vapour Deposition (AACVD) method for direct in-situ growth of intrinsic and Au-functionalised nanostructured WO3, as well as SnO2-based devices for gas sensing applications. The nanostructured material synthesis, device fabrication and their gas sensing properties have been studied. AACVD method was used for synthesis and direct deposition of sensing films onto classical alumina and microhotplat...

  20. PENGARUH KATALIS Co DAN Fe TERHADAP KARAKTERISTIK CARBON NANOTUBES DARI GAS ASETILENA DENGAN MENGGUNAKAN PROSES CATALYTIC CHEMICAL VAPOUR DEPOSITION (CCVD

    Tutuk Djoko Kusworo

    2013-11-01

    Full Text Available EFFECT OF Co AND Fe ON CARBON NANOTUBES CHARACTERISTICS FROM ACETYLENE USING CATALYTIC CHEMICAL VAPOUR DEPOSITION (CCVD PROCESS. Carbon Nanotubes (CNTs is one of the most well known nano-technology applications which the most of attracting the attention of researchers, because it has more advantages than other materials. The application of the CNT has extended into various aspects, such as electronics, materials, biology and chemistry. This research uses a system of Catalytic Chemical Vapour Deposition (CCVD, which aims to determine the influence of Co and Fe as a catalyst and zeolite 4A as a support catalyst with acetylene gas (C2H2 as carbon source in the synthesis of Carbon Nanotubes (CNTs. In this experiment, used the ratio of acetylene gas and flow rate of N2 gas is 1:1 by weight of the catalyst Co/Zeolite and Fe/Zeolite amounted to 0.5 grams at the operating temperature of 700oC for 20 minutes. N2 gas serves to minimize the occurrence of oxidation reaction (explosion when operating. From analysis result by Scanning Electron Microscopy (SEM shows the CNTs formed a type of MWNT with different of diameter size and product weight, depending on the size of the active component concentration on the catalyst. The larger of active components produced CNTs with larger diameter, whereas product weight syntheses result smaller. Use of the catalyst Fe/Zeolite produce CNTs with a diameter larger than the catalyst Co/Zeolite.  Carbon Nanotubes (CNTs merupakan salah satu aplikasi nanoteknologi yang paling terkenal dan banyak menarik perhatian para peneliti, karena memiliki beberapa kelebihan daripada material lainnya. Aplikasi dari CNT telah merambah ke berbagai aspek, seperti bidang elektronika, material, biologi dan kimia. Penelitian ini menggunakan sistem Catalytic Chemical Vapour Deposition (CCVD yang bertujuan untuk mengetahui pengaruh variasi Cobalt (Co dan Ferrum (Fe sebagai katalis dan zeolit tipe 4A sebagai penyangga katalis dengan gas

  1. Chemical vapour deposition of very thin coatings on carbon fibre bundles

    Stumm, T.; Fitzer, E.; Wahl, G

    1992-01-01

    The continuous deposition of thin coatings of refractory materials on carbon fibre rovings is considered as the impregnation of a endless cylinder with slit-like pores in the direction parallel with the cylinder axis. From such a model, the limits of process parameters for the simultaneous coating of all individual monofilaments are derived. In detail a correlation between the deposition parameters and the resulting layer thickness is discussed for a deposition with high and low conversion re...

  2. Modification of electrical properties induced by annealing of ZnO:B thin films deposited by chemical vapour deposition: Kinetic investigation of evolution

    David, C., E-mail: Clement.david@univ-poitiers.fr [Inventux Technologies AG, Wolfener Straße 23, 12681 Berlin (Germany); Institut Pprime, Département de Physique et Mécanique des Matériaux, CNRS – Université de Poitiers, F-86962 Futuroscope Chasseneuil Cedex (France); Paumier, F. [Institut Pprime, Département de Physique et Mécanique des Matériaux, CNRS – Université de Poitiers, F-86962 Futuroscope Chasseneuil Cedex (France); Tinkham, B.P. [Inventux Technologies AG, Wolfener Straße 23, 12681 Berlin (Germany); Eyidi, D.; Marteau, M.; Guérin, P.; Girardeau, T. [Institut Pprime, Département de Physique et Mécanique des Matériaux, CNRS – Université de Poitiers, F-86962 Futuroscope Chasseneuil Cedex (France)

    2013-05-15

    In this study temperature dependent Hall effect measurements combined with Fourier Transformed Infra-Red (FTIR) spectroscopy measurements is used to determine the evolution of the scattering mechanisms ascribable to in-grain and grain boundaries on Boron doped ZnO thin films deposited by Low Pressure Chemical Vapour Deposition (LPCVD). Through Hall effect measurements during in situ isothermal annealing, changes in electrical characteristics of zinc oxide could be followed in real time. Whereas only degradation is observed in air, an improvement of layer conductivity could be achieved at low temperatures by annealing under argon atmosphere. A study of the conductivity during isothermal annealing offers the possibility to extract activation energies, which have been compared to migration energies of the different intrinsic defects in ZnO.

  3. Modification of electrical properties induced by annealing of ZnO:B thin films deposited by chemical vapour deposition: Kinetic investigation of evolution

    In this study temperature dependent Hall effect measurements combined with Fourier Transformed Infra-Red (FTIR) spectroscopy measurements is used to determine the evolution of the scattering mechanisms ascribable to in-grain and grain boundaries on Boron doped ZnO thin films deposited by Low Pressure Chemical Vapour Deposition (LPCVD). Through Hall effect measurements during in situ isothermal annealing, changes in electrical characteristics of zinc oxide could be followed in real time. Whereas only degradation is observed in air, an improvement of layer conductivity could be achieved at low temperatures by annealing under argon atmosphere. A study of the conductivity during isothermal annealing offers the possibility to extract activation energies, which have been compared to migration energies of the different intrinsic defects in ZnO

  4. Surface transformations of carbon (graphene, graphite, diamond, carbide), deposited on polycrystalline nickel by hot filaments chemical vapour deposition

    The deposition of carbon has been studied at high temperature on polycrystalline nickel by hot filaments activated chemical vapor deposition (HFCVD). The sequences of carbon deposition are studied by surface analyses: Auger electron spectroscopy (AES), electron loss spectroscopy (ELS), X-ray photoelectron spectroscopy (XPS) in a chamber directly connected to the growth chamber. A general scale law of the (C/Ni) intensity lines is obtained with a reduced time. Both, shape analysis of the AES C KVV line and the C1s relative intensity suggest a three-step process: first formation of graphene and a highly graphitic layer, then multiphase formation with graphitic, carbidic and diamond-like carbon and finally at a critical temperature that strongly depends on the pretreatment of the polycrystalline nickel surface, a rapid transition to diamond island formation. Whatever the substrate diamond is always the final product and some graphene layers the initial product. Moreover it is possible to stabilize a few graphene layers at the initial sequences of carbon deposition. The duration of this stabilization step is strongly depending however on the pre-treatment of the Ni surface.

  5. ECWR plasma enhanced chemical vapour deposition of microcrystalline silicon thin films

    An ECWR plasma source was used in order to deposit microcrystalline silicon thin films. The effect of input power and silane content on the deposition rate and the materials properties was investigated. Deposition rates, up to 25Å/sec, and high crystallinity degree were achieved using high silane content which is in contrast to the conventional CCP method. The amorphous to crystalline transition zone was determined revealing that in ECWR discharges microcrystalline silicon growth is favoured in a wide range of experimental conditions

  6. Low-pressure chemical vapour deposition growth of high-quality ZnO films on epi-GaN/α-Al2O3

    We present the first results on (0001) ZnO/(0001) epi-GaN/(0001) α-Al2O3 heterostructure fabrication combining metal-organic vapour phase epitaxy and low-pressure chemical vapour deposition methods. The surface morphologies of the films were studied, and x-ray and reflection high-energy electron diffraction measurements were made, which showed a high degree of structural perfection of the ZnO films, with crystallite misorientation as low as 21'. The measured photoluminescence spectra of the films featured prevailingly emission within the excitonic region. (author). Letter-to-the-editor

  7. Chemical vapour deposition of amorphous Ru(P) thin films from Ru trialkylphosphite hydride complexes.

    McCarty, W Jeffrey; Yang, Xiaoping; DePue Anderson, Lauren J; Jones, Richard A

    2012-11-21

    The ruthenium phosphite hydride complexes H(2)Ru(P(OR)(3))(4) (R = Me (1), Et (2), (i)Pr (3)) were used as CVD precursors for the deposition of films of amorphous ruthenium-phosphorus alloys. The as-deposited films were X-ray amorphous and XPS analysis revealed that they were predominantly comprised of Ru and P in zero oxidation states. XPS analysis also showed the presence of small amounts of oxidized ruthenium and phosphorus. The composition of the films was found to depend on ligand chemistry as well as the deposition conditions. The use of H(2) as the carrier gas had the effect of increasing the relative concentrations of P and O for all films. Annealing films to 700 °C under vacuum produced films of polycrystalline hcp Ru while a flowing stream of H(2) resulted in polycrystalline hcp RuP. PMID:23018487

  8. Evaluation of freestanding boron-doped diamond grown by chemical vapour deposition as substrates for vertical power electronic devices

    Issaoui, R.; Achard, J.; Tallaire, A.; Silva, F.; Gicquel, A. [LSPM-CNRS (formerly LIMHP), Universite Paris 13, 99, Avenue Jean-Baptiste Clement, 93430 Villetaneuse (France); Bisaro, R.; Servet, B.; Garry, G. [Thales Research and Technology France, Campus de Polytechnique, 1 Avenue Augustin Fresnel, F-91767 Palaiseau Cedex (France); Barjon, J. [GEMaC-CNRS, Universite de Versailles Saint Quentin Batiment Fermat, 45 Avenue des Etats-Unis, 78035 Versailles Cedex (France)

    2012-03-19

    In this study, 4 x 4 mm{sup 2} freestanding boron-doped diamond single crystals with thickness up to 260 {mu}m have been fabricated by plasma assisted chemical vapour deposition. The boron concentrations measured by secondary ion mass spectroscopy were 10{sup 18} to 10{sup 20} cm{sup -3} which is in a good agreement with the values calculated from Fourier transform infrared spectroscopy analysis, thus indicating that almost all incorporated boron is electrically active. The dependence of lattice parameters and crystal mosaicity on boron concentrations have also been extracted from high resolution x-ray diffraction experiments on (004) planes. The widths of x-ray rocking curves have globally shown the high quality of the material despite a substantial broadening of the peak, indicating a decrease of structural quality with increasing boron doping levels. Finally, the suitability of these crystals for the development of vertical power electronic devices has been confirmed by four-point probe measurements from which electrical resistivities as low as 0.26 {Omega} cm have been obtained.

  9. Surface and Compositional Study of Graphene grown on Lithium Niobate (LiNbO3) substrates by Chemical Vapour Deposition

    Karamat, Shumaila; Celik, Umit; Oral, Ahmet

    The diversity required in the designing of electronic devices motivated the community to always attempt for new functional materials and device structures. Graphene is considered as one of the most promising candidate materials for future electronics and carbon based devices. It is very exciting to combine graphene with new dielectric materials which exhibit multifunctional properties. Lithium Niobate exhibits ferro-, pyro-, and piezoelectric properties with large electro-optic, acousto-optic, and photoelastic coefficients as well as strong photorefractive and photovoltaic effects which made it one of the most extensively studied materials over the last 50 years. We used ambient pressure chemical vapour deposition to grow graphene on LiNbO3 substrates without any catalyst. The growth was carried out in presence of methane, argon and hydrogen. AFM imaging showed very unique structures on the surface which contains triangular domains. X-ray photoelectron spectroscopy (XPS) was used to get information about the presence of necessary elements, their bonding with LiNbO3 substrates. Detailed characterization is under process which will be presented later.

  10. Evaluation of freestanding boron-doped diamond grown by chemical vapour deposition as substrates for vertical power electronic devices

    In this study, 4 x 4 mm2 freestanding boron-doped diamond single crystals with thickness up to 260 μm have been fabricated by plasma assisted chemical vapour deposition. The boron concentrations measured by secondary ion mass spectroscopy were 1018 to 1020 cm-3 which is in a good agreement with the values calculated from Fourier transform infrared spectroscopy analysis, thus indicating that almost all incorporated boron is electrically active. The dependence of lattice parameters and crystal mosaicity on boron concentrations have also been extracted from high resolution x-ray diffraction experiments on (004) planes. The widths of x-ray rocking curves have globally shown the high quality of the material despite a substantial broadening of the peak, indicating a decrease of structural quality with increasing boron doping levels. Finally, the suitability of these crystals for the development of vertical power electronic devices has been confirmed by four-point probe measurements from which electrical resistivities as low as 0.26 Ω cm have been obtained.

  11. Evaluation of freestanding boron-doped diamond grown by chemical vapour deposition as substrates for vertical power electronic devices

    Issaoui, R.; Achard, J.; Tallaire, A.; Silva, F.; Gicquel, A.; Bisaro, R.; Servet, B.; Garry, G.; Barjon, J.

    2012-03-01

    In this study, 4 × 4 mm2 freestanding boron-doped diamond single crystals with thickness up to 260 μm have been fabricated by plasma assisted chemical vapour deposition. The boron concentrations measured by secondary ion mass spectroscopy were 1018 to 1020 cm-3 which is in a good agreement with the values calculated from Fourier transform infrared spectroscopy analysis, thus indicating that almost all incorporated boron is electrically active. The dependence of lattice parameters and crystal mosaicity on boron concentrations have also been extracted from high resolution x-ray diffraction experiments on (004) planes. The widths of x-ray rocking curves have globally shown the high quality of the material despite a substantial broadening of the peak, indicating a decrease of structural quality with increasing boron doping levels. Finally, the suitability of these crystals for the development of vertical power electronic devices has been confirmed by four-point probe measurements from which electrical resistivities as low as 0.26 Ω cm have been obtained.

  12. Atmospheric pressure chemical vapour deposition of thermochromic tungsten doped vanadium dioxide thin films for use in architectural glazing

    Blackman, Christopher S., E-mail: c.blackman@ucl.ac.u [Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ (United Kingdom); Piccirillo, C.; Binions, R.; Parkin, Ivan P. [Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ (United Kingdom)

    2009-06-30

    Atmospheric pressure chemical vapour deposition of VCl{sub 4}, WCl{sub 6} and water at 550 {sup o}C lead to the production of high quality tungsten doped vanadium dioxide thin films. Careful control of the gas phase precursors allowed for tungsten doping up to 8 at.%. The transition temperature of the thermochromic switch was tunable in the range 55 {sup o}C to - 23 {sup o}C. The films were analysed using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Their optical properties were examined using variable-temperature transmission and reflectance spectroscopy. It was found that incorporation of tungsten into the films led to an improvement in the colour from yellow/brown to green/blue depending on the level of tungsten incorporation. The films were optimized for optical transmission, thermochromic switching temperature, magnitude of the switching behaviour and colour to produce films that are suitable for use as an energy saving environmental glass product.

  13. InGa1−N fibres grown on Au/SiO2 by chemical vapour deposition

    A Ramos-Carrazco; R García; M Barboza-Flores; R Rangel

    2014-12-01

    The growth of InGa1−N films ( = 0.1 and = 0.2) on a thin gold layer (Au/SiO2) by chemical vapour deposition (CVD) at 650 °C is reported. As a novelty, the use of a Ga–In metallic alloy to improve the indium incorporation in the InGa1−N is proposed. The results of high quality InGa1−N films with a thickness of three micrometres and the formation of microfibres on the surface are presented. A morphological comparison between the InGa1−N and GaN films is shown as a function of the indium incorporation. The highest crystalline InGa1−N films structure was obtained with an indium composition of = 0.20. Also, the preferential growth on the (002) plane over In0.2Ga0.8N was observed by means of X-ray diffraction. The thermoluminescence (TL) of the InGa1−N films after beta radiation exposure was measured indicating the presence of charge trapping levels responsible for a broad TL glow curve with a maximum intensity around 150 °C. The TL intensity was found to depend on composition being higher for = 0.1 and increases as radiation dose increases.

  14. Photoluminescence and lasing properties of InAs/GaAs quantum dots grown by metal-organic chemical vapour deposition

    Liang Song; Wang Wei; Zhu Hong-Liang; Pan Jiao-Qing; Zhao Ling-Juan; Wang Lu-Feng; Zhou Fan; Shu Hui-Yun; Bian Jing; An Xin

    2008-01-01

    Photoluminescence (PL) and lasing properties of InAs/GaAs quantum dots (QDs) with different growth procedures prepared by metalorganic chemical vapour deposition are studied.PL measurements show that the low growth rate QD sample has a larger PL intensity and a narrower PL line width than the high growth rate sample.During rapid thermal annealing,however,the low growth rate sample shows a greater blueshift of PL peak wavelength.This is caused by the larger InAs layer thickness which results from the larger 2-3 dimensional transition critical layer thickness for the QDs in the low-growth-rate sample.A growth technique including growth interruption and in-situ annealing,named indium flush method,is used during the growth of GaAs cap layer,which can flatten the GaAs surface effectively.Though the method results in a blueshift of PL peak wavelength and a broadening of PL line width,it is essential for the fabrication of room temperature working QD lasers.

  15. Temperature-dependent Hall effect studies of ZnO thin films grown by metalorganic chemical vapour deposition

    The electrical properties of zinc oxide (ZnO) thin films of various thicknesses (0.3–4.4 µm) grown by metalorganic chemical vapour deposition on glass substrates have been studied by using temperature-dependent Hall-effect (TDH) measurements in the 18–300 K range. The high quality of the layers has been confirmed with x-ray diffraction, transmission electron microscopy, scanning electron microscopy and photoluminescence techniques. TDH measurements indicate the presence of a degenerate layer which significantly influences the low-temperature data. It is found that the measured mobility generally increases with increasing layer thickness, reaching a value of 120 cm2 V−1 s−1 at room temperature for the 4.4 µm thick sample. The lateral grain size of the layers is also found to increase with thickness indicating a clear correlation between the size of the surface grains and the electrical properties of corresponding films. Theoretical fits to the Hall data suggest that the bulk conduction of the layers is dominated by a weakly compensated donor with activation energy in the 33–41 meV range and concentration of the order of 1017 cm−3, as well as a total acceptor concentration of mid-1015 cm−3. Grain boundary scattering is found to be an important limiting factor of the mobility throughout the temperature range considered

  16. Silicon nanocrystal growth in the long diffusion length regime using high density plasma chemical vapour deposited silicon rich oxides

    In this study, silicon nanocrystal (Si-nc) growth is studied in a relatively long thermal budget regime, 3 h at 1100-1200 deg. C, to examine large diameter nanocrystals (i.e. average diameters greater than 5 nm). Morphology, defects within the nanocrystals and size dependence as a function of thickness in the oxide are exaggerated in this regime and are more readily characterized in the longer diffusion length regime. In particular, nearby surfaces, the silicon substrate and oxide surface, appear to deplete the excess silicon in the oxide, leading to a strong nanocrystal size dependence with position in the oxide. To pursue this work, silicon naocrystals were formed through a combination of high density plasma enhanced chemical vapour deposition (HDP-CVD) of silicon rich oxides (SRO) followed by phase separation of the SRO into Si-ncs and stoichiometric oxide (SiO2). Details of the characterization of the as-grown HDP-CVD SROs are included, and differences in the Si-O-Si stretch mode peak position dependence on [O] between HDP-CVD and previously reported plasma enhanced CVD are discussed

  17. Study of Metal Organic Chemical Vapour Deposition (MOCVD) semiconductors III-V hyperstructures with Secondary Ion Mass Spectrometry (SIMS)

    One of the most promising technologies in high efficiency solar cells is based on quaternary structures grown by epitaxial techniques as Metal Organic Chemical Vapour deposition (MOCVD). The semiconductors III-V structures are elaborated under tailored parameters, allowing the use of a broader area of the solar spectrum. Analytical techniques capable of providing accurate and precise information in cross sections about the composition and thickness of the layers are demanded. Secondary Ion Mass Spectrometry (SIMS) has been used for characterization of these structures due to its high depth resolution and sensitivity, stability and reproducibility. It was detected the diffusion process of Al and In across the cell interfaces and the layer diffusion over GaAs substrates. The Al diffusion was associated at incorrect incorporation of elements during growth process and the layer diffusion was associated at changes of manufacturing parameters. Such studies show the SIMS ability to diagnose of faults during the growth process, detection of impurities and incorrect diffusion of dopants that may affect the layer properties and the structure functionality

  18. Structural and Compositional Study of Graphene grown on SrTiO3 by Chemical Vapour Deposition

    Karamat, Shumaila; Celik, Umit; Oral, Ahmet

    Graphene, a monolayer of sp2 bonded carbon atom, is considered as one of the most promising candidate materials for future electronics. The most critical step in graphene research is its transfer from the growth catalyst to the dielectric substrate, many unavoidable issues in the transfer process are: contamination from etchants, photoresist residues, wrinkles, and mechanical breakage. The direct growth of graphene on the substrates without using catalyst offer new opportunities in device fabrication without any transfer process. But till now, the field of direct graphene growth on dielectrics or insulating substrates is not mature like growth on metallic catalysts using CVD. We used chemical vapour deposition to grow graphene on SrTiO3 (110) substrates. The growth was carried out in presence of methane, argon and hydrogen. Raman Spectrum clearly showed the D and G peaks which were absent in bare substrate. XPS was used to get information about the presence of necessary elements, their bonding with STO substrates. AFM imaging clearly showed graphene island formation on substrates.

  19. Metal-organic chemical vapour deposition of polycrystalline tetragonal indium sulphide (InS) thin films

    Macinnes, Andrew N.; Cleaver, William M.; Barron, Andrew R.; Power, Michael B.; Hepp, Aloysius F.

    1992-01-01

    The dimeric indium thiolate /(t Bu)2In(mu-S sup t Bu)/2 has been used as a single-source precursor for the MOCVD of InS thin films. The dimeric In2S2 core is proposed to account for the formation of the nonequilibrium high-pressure tetragonal phase in the deposited films. Analysis of the deposited films has been obtained by TEM, with associated energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy.

  20. XMCD studies of Co{sub x}Pt{sub 100-x} nanoparticles prepared by vapour deposition and chemical synthesis

    Imperia, P. [Universitaet Hamburg, Institut fuer Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg (Germany); ANSTO, Institute of Materials and Engineering, New Illawarra Road, Lucas Heights, Sydney, NSW (Australia); Glaser, L.; Martins, M.; Wurth, W. [Universitaet Hamburg, Institut fuer Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg (Germany); Andreazza, P.; Penuelas, J.; Andreazza-Vignolle, C. [Centre de Recherce sur la Matiere Divisee, UMR6619, CNRS-University of Orleans, 1B rue de la Ferollerie, 45071 Orleans Cedex 2 (France); Alessandrovic, V.; Weller, H. [Universitaet Hamburg, Institut fuer Physikalische Chemie, Grindelallee 117, 20146 Hamburg (Germany)

    2008-05-15

    An almost linear relation between the Pt amount and the orbital to spin moment ratio ({mu}{sub l}/{mu}{sub s}) has been found in Co{sub x}Pt{sub 100-x} nanoparticles prepared by vapour deposition and possessing a well defined chemically disordered crystallographic structure. X-ray magnetic circular dichroism (XMCD) measurements done at the L{sub 2,3}Co edges show that a 4.0 nm, x=100 Co reference sample has a ratio {mu}{sub l}/{mu}{sub s}=0.097, comparable to values found for Co thin layers. An increase of the amount of Pt increases the {mu}{sub l}/{mu}{sub s} value: {mu}{sub l}/{mu}{sub s}=0.11 for x=78, {mu}{sub l}/{mu}{sub s}=0.12 when x=74 and finally, for x=38 it becomes {mu}{sub l}/{mu}{sub s}=0.140. Nanoparticles prepared by chemical synthesis with size proportional to changes of the stoichiometric ratio, from Co{sub 25}Pt{sub 75} to Co{sub 50}Pt{sub 50}, show values of the orbital to spin moment ratio compatible with the trend found for the former ones. The samples prepared by chemical synthesis in a diameter range from 4 nm to 8 nm are characterized by a sharp size distribution of 10%. In contrast to the in situ prepared nanoparticles that are oxide free, however, they show a varying degree of surface oxidation depending on the ambient conditions they are exposed to. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Corrosion resistance of amorphous hydrogenated SiC and diamond-like coatings deposited by r.f.-plasma-enhanced chemical vapour deposition

    This paper reports on the properties and corrosion resistance of amorphous hydrogenated carbon and amorphous hydrogenated SiC films deposited by r.f.-plasma-enhanced chemical vapour deposition at low temperatures (below 200 C). SiC coatings were prepared from SiH4-CH4 gas mixtures. Hydrogenated diamond-like coatings were deposited from classical CH4-H2 mixtures. The influence of various deposition parameters was investigated. Microstructural and mechanical properties of the films were studied (density, hydrogen content, nanohardness, internal stress, critical load and friction coefficient). Two examples of corrosion resistance are given: (1) the corrosion resistance and biocompatibility of SiC and diamond-like coatings deposited on metal implants (Ti alloy) (the corrosion resistance is evaluated through potentiodynamic polarization tests in biological media; the biocompatibility of coated and uncoated metals is compared using differentiated human cell cultures); and (2) the corrosion resistance of SiC-coated magnesium in chloride-containing boric borate buffer at pH = 9.3 evaluated from anodic polarization curves and scanning electron microscopy studies. (orig.)

  2. Remote plasma-enhanced chemical vapour deposition of silicon nitride at atmospheric pressure

    Silicon nitride films were deposited using an atmospheric pressure plasma source. The discharge was produced by flowing nitrogen and helium through two perforated metal electrodes that were driven by 13.56 MHz radio frequency power. Deposition occurred by mixing the plasma effluent with silane and directing the flow onto a rotating silicon wafer heated to between 100 deg. C and 500 deg. C. Film growth rates ranged from 90±10 to 1300±130 A min-1. Varying the N2/SiH4 feed ratio from 55.0 to 5.5 caused the film stoichiometry to shift from SiN1.45 to SiN1.2. Minimum impurity concentrations of 0.04% carbon, 3.6% oxygen and 13.6% hydrogen were achieved at 500 deg. C, and an N2/SiH4 feed ratio of 22.0. The growth rate increased with increasing silane and nitrogen partial pressures, but was invariant with respect to substrate temperature and rotational speed. The deposition rate also decreased sharply with distance from the plasma. These results combined with emission spectra taken of the afterglow suggest that gas-phase reactions between nitrogen atoms and silane play an important role in this process

  3. Optical and passivating properties of hydrogenated amorphous silicon nitride deposited by plasma enhanced chemical vapour deposition for application on silicon solar cells

    Wight, Daniel Nilsen

    2008-07-01

    Within this thesis, several important subjects related to the use of amorphous silicon nitride made by plasma enhanced chemical vapour deposition as an anti-reflective coating on silicon solar cells are presented. The first part of the thesis covers optical simulations to optimise single and double layer anti-reflective coatings with respect to optical performance when situated on a silicon solar cell. The second part investigates the relationship between important physical properties of silicon nitride films when deposited under different conditions. The optical simulations were either based on minimising the reflectance off a silicon nitride/silicon wafer stack or maximising the transmittance through the silicon nitride into the silicon wafer. The former method allowed consideration of the reflectance off the back surface of the wafer, which occurs typically at wavelengths above 1000 nm due to the transparency of silicon at these wavelengths. However, this method does not take into consideration the absorption occurring in the silicon nitride, which is negligible at low refractive indexes but quite significant when the refractive index increases above 2.1. For high-index silicon nitride films, the latter method is more accurate as it considers both reflectance and absorbance in the film to calculate the transmittance into the Si wafer. Both methods reach similar values for film thickness and refractive index for optimised single layer anti-reflective coatings, due to the negligible absorption occurring in these films. For double layer coatings, though, the reflectance based simulations overestimated the optimum refractive index for the bottom layer, which would have lead to excessive absorption if applied to real anti-reflective coatings. The experimental study on physical properties for silicon nitride films deposited under varying conditions concentrated on the estimation of properties important for its applications, such as optical properties, passivation

  4. Chemical vapour deposition of nitrogen-doped titanium dioxide thin films.

    Alexandrov, S E; Baryshnikova, M V; Filatov, L A; Shahmin, A L; Andreeva, V D

    2011-09-01

    Nitrogen-doped titanium dioxide is often considered as a promising nanomaterial for photocatalytic applications. Here we report the first results of a study of APCVD of N-doped TiO2 thin films prepared with the use of ammonia as a source of nitrogen and titanium tetraisopropoxide (TTIP) as a source of Ti and O atoms. The obtained films were analyzed with X-ray diffraction, infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, UV-Vis spectroscopy, and ellipsometry. It was found that the film growth rate in the TTIP-NH3-Ar reaction system varied insignificantly with substrate temperature in the range of 450,..., 750 degrees C and did not exceed 4.4 nm/min. Yellow and orange layers with nitrogen content of about 7.6% were formed at the deposition temperature higher than 600 degrees C. The results of the structure analysis of the deposited films showed that addition of ammonia led to stabilization of the amorphous phase in the films. The effect of ammonia on optical and photocatalytic properties was also considered. PMID:22097568

  5. Adsorption and surface diffusion of silicon growth species in silicon carbide chemical vapour deposition processes studied by quantum-chemical computations

    Kalered, Emil; Pedersen, Henrik; Janzén, Erik; Ojamäe, Lars

    2013-01-01

    The effect chlorine addition to the gas mixture has on the surface chemistry in the chemical vapour deposition (CVD) process for silicon carbide (SiC) epitaxial layers is studied by quantum-chemical calculations of the adsorption and diffusion of SiH2 and SiCl2 on the (000-1) 4H–SiC surface. SiH2 was found to bind more strongly to the surface than SiCl2 by approximately 100 kJ mol−1 and to have a 50 kJ mol−1 lower energy barrier for diffusion on the fully hydrogen-terminated surface. On a bar...

  6. CdTe thin film solar cells produced using a chamberless inline process via metalorganic chemical vapour deposition

    Cd1−xZnxS and CdTe:As thin films were deposited using a recently developed chamberless inline process via metalorganic chemical vapour deposition (MOCVD) at atmospheric pressure and assessed for fabrication of CdTe photovoltaic (PV) solar cells. Initially, CdS and Cd1−xZnxS coatings were applied onto 15 × 15 cm2 float glass substrates, characterised for their optical properties, and then used as the window layer in CdTe solar cells which were completed in a conventional MOCVD (batch) reactor. Such devices provided best conversion efficiency of 13.6% for Cd0.36Zn0.64S and 10% for CdS which compare favourably to the existing baseline MOCVD (batch reactor) devices. Next, sequential deposition of Cd0.36Zn0.64S and CdTe:As films was realised by the chamberless inline process. The chemical composition of a 1 μm CdTe:As/150 nm Cd0.36Zn0.64S bi-layer was observed via secondary ions mass spectroscopy, which showed that the key elements are uniformly distributed and the As doping level is suitable for CdTe device applications. CdTe solar cells formed using this structure provided a best efficiency of 11.8% which is promising for a reduced absorber thickness of 1.25 μm. The chamberless inline process is non-vacuum, flexible to implement and inherits from the legacy of MOCVD towards doping/alloying and low temperature operation. Thus, MOCVD enabled by the chamberless inline process is shown to be an attractive route for thin film PV applications. - Highlights: • CdS, CdZnS and CdTe thin films grown by a chamberless inline process • The inline films assessed for fabricating CdTe solar cells • 13.6% conversion efficiency obtained for CdZnS/CdTe cells

  7. Physical and tribological properties of a-Si1-xCx:H coatings prepared by r.f. plama-assisted chemical vapour deposition

    A-Si1-xCx:H films deposited by r.f. plasma-assisted chemical vapour deposition were studied as a function of their composition. The friction and wear properties were investigated with the help of a conventional ball-on-disc apparatus. These results are correlated with chemical (Si/C atomic ratio) and structural (Raman and infrared spectroscopy) properties. The friction coefficient in a humid ambient atmosphere changes markedly with the carbon fraction and reaches a value as low as 0.05 for coatings with 70 to 90 at.% C. The carbon-rich films consist of diamond-like carbon with silicon. (orig.)

  8. Optical visualization of individual ultralong carbon nanotubes by chemical vapour deposition of titanium dioxide nanoparticles.

    Zhang, Rufan; Zhang, Yingying; Zhang, Qiang; Xie, Huanhuan; Wang, Haidong; Nie, Jingqi; Wen, Qian; Wei, Fei

    2013-01-01

    Direct visualization and manipulation of individual carbon nanotubes in ambient conditions is of great significance for their characterizations and applications. However, the observation of individual carbon nanotubes usually requires electron microscopes under high vacuum. Optical microscopes are much more convenient to be used, yet their resolution is low. Here we realize the visualization and manipulation of individual ultralong carbon nanotubes under optical microscopes by deposition of TiO2 nanoparticles on them. The strong scattering of TiO2 nanoparticles to visible light renders them visible by optical microscopes. Micro-Raman-spectroscopy measurement of individual carbon nanotubes is greatly facilitated by their optical visualization. With the assistance of TiO2 nanoparticles, individual carbon nanotubes can be easily manipulated under an optical microscope at macroscopic scale and in ambient conditions. Based on our approach, various manipulation of ultralong carbon nanotubes, including cutting, transfer, fabrication of structures/devices and pulling out inner shells of multiwalled carbon nanotubes, are demonstrated. PMID:23591894

  9. Atmospheric pressure chemical vapour deposition of vanadium arsenide thin films via the reaction of VCl4 or VOCl3 with tBuAsH2

    Thin films of vanadium arsenide were deposited via the dual-source atmospheric pressure chemical vapour deposition reactions of VCl4 or VOCl3 with tBuAsH2. Using the vanadium precursor VCl4, films were deposited at substrate temperatures of 550–600 °C, which were black-gold in appearance and were found to be metal-rich with high levels of chlorine incorporation. The use of VOCl3 as the vanadium source resulted in films being deposited between 450 and 600 °C and, unlike when using VCl4, were silver in appearance. The films deposited using VOCl3 demonstrated vanadium to arsenic ratios close to 1:1, and negligible chlorine incorporation. Films deposited using either vanadium precursor were identified as VAs using powder X-ray diffraction and possessed borderline metallic/semiconductor resistivities. - Highlights: • Formation of VAs films via atmospheric pressure chemical vapour deposition. • Films formed using VCl4 or VOCl3 and tBuAsH2. • Powder X-ray diffraction showed that crystalline VAs films were deposited. • Films from VOCl3 had a V:As ratio close to 1 with negligible Cl incorporation. • Films were silver and possessed borderline metallic/semiconductor resistivities

  10. Optical monitoring of surface processes relevant to thin film growth by chemical vapour deposition

    This thesis reports on the investigation of the use of reflectance anisotropy spectroscopy (RAS) as an in-situ monitor for the preparation and oxidation of GaAs(100) c(4x4) surfaces using a CVD 2000 MOCVD reactor. These surfaces were oxidised using air. It was found that it was possible to follow surface degradation using RA transients at 2.6eV and 4eV. From this data it was possible to speculate on the nature of the surface oxidation process. A study was performed into the rate of surface degradation under different concentrations of air, it was found that the relation between the air concentration and the surface degradation was complicated but that the behaviour of the first third of the degradation approximated a first order behaviour. An estimation of the activation energy of the process was then made, and an assessment of the potential use of the glove-box for STM studies which is an integral part of the MOCVD equipment was also made. Following this, a description is given of the construction of an interferometer for monitoring thin film growth. An investigation is also described into two techniques designed to evaluate the changes in reflected intensity as measured by an interferometer. The first technique uses an iteration procedure to determine the film thickness from the reflection data. This is done using a Taylor series expansion of the thin film reflection function to iterate for the thickness. Problems were found with the iteration when applied to noisy data, these were solved by using a least squares fit to smooth the data. Problems were also found with the iteration at the turning points these were solved using the derivative of the function and by anticipating the position of the turning points. The second procedure uses the virtual interface method to determine the optical constants of the topmost deposited material, the virtual substrate, and the growth rate. This method is applied by using a Taylor series expansion of the thin film reflection

  11. Low-temperature synthesis and characterization of helical carbon fibers by one-step chemical vapour deposition

    Graphical abstract: - Highlights: • HCNFs were synthesized by one-step CVD using cupric tartrate as a catalyst at temperature below 500 °C. • The synthesis of HCNFs is highly temperature-dependent at the synthesis temperature of 280–480 °C. • The addition of HCNFs makes a noticeable contribution to the reinforcement of NR/CB system. - Abstract: Helical carbon fibers (HCNFs) were synthesized by one-step chemical vapour deposition using cupric tartrate as a catalyst at temperature below 500 °C. The bound rubber of natural rubber (NR)/HCNFs were also prepared in this study. The results of thermogravimetry–differential scanning calorimetry (TG/DSC) for cupric tartrate nanoparticles show that the transformation of C4H4CuO6 → Cu reaction occurs at ∼250–310 °C. The characterization of scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Raman spectrum for the synthesized products confirms that the synthesis of HCNFs is highly temperature-dependent. The straight fibers with the fiber diameter of 100–400 nm are obtained at 280 °C and HCNFs can be synthesized at higher temperature, with the coil diameter of 0.5–1 μm and fiber diameter of 100–200 nm at 380 °C, and the coil diameter of ∼100 nm and fiber diameter of ∼80 nm at 480 °C. The maximum of the bound-rubber content (37%) can be obtained with the addition of 100 wt.% HCNFs in NR, which indicates that the coiled configuration of HCNFs makes a noticeable contribution to the reinforcement of NR/CB system

  12. Growth of AlGaSb Compound Semiconductors on GaAs Substrate by Metalorganic Chemical Vapour Deposition

    A. H. Ramelan

    2010-01-01

    Full Text Available Epitaxial AlxGa1-xSb layers on GaAs substrate have been grown by atmospheric pressure metalorganic chemical vapour deposition using TMAl, TMGa, and TMSb. We report the effect of V/III flux ratio and growth temperature on growth rate, surface morphology, electrical properties, and composition analysis. A growth rate activation energy of 0.73 eV was found. For layers grown on GaAs at 580∘C and 600∘C with a V/III ratio of 3 a high quality surface morphology is typical, with a mirror-like surface and good composition control. It was found that a suitable growth temperature and V/III flux ratio was beneficial for producing good AlGaSb layers. Undoped AlGaSb grown at 580∘C with a V/III flux ratio of 3 at the rate of 3.5 μm/hour shows p-type conductivity with smooth surface morphology and its hole mobility and carrier concentration are equal to 237 cm2/V.s and 4.6 × 1017 cm-3, respectively, at 77 K. The net hole concentration of unintentionally doped AlGaSb was found to be significantly decreased with the increased of aluminium concentration. All samples investigated show oxide layers (Al2O3, Sb2O3, and Ga2O5 on their surfaces. In particular the percentage of aluminium-oxide was very high compared with a small percentage of AlSb. Carbon content on the surface was also very high.

  13. Low-temperature synthesis and characterization of helical carbon fibers by one-step chemical vapour deposition

    Jin, Yongzhong [Department of Materials and Chemistry Engineering, Sichuan University of Science and Engineering, 643000 Zigong, Sichuan (China); Chen, Jian, E-mail: wuhangzs@163.com [Department of Materials and Chemistry Engineering, Sichuan University of Science and Engineering, 643000 Zigong, Sichuan (China); Fu, Qingshan [Department of Materials and Chemistry Engineering, Sichuan University of Science and Engineering, 643000 Zigong, Sichuan (China); Li, Binghong [China Rubber Group Carbon Black Industry Research and Design Institute, 643000 Zigong, Sichuan (China); Zhang, Huazhi; Gong, Yong [Department of Materials and Chemistry Engineering, Sichuan University of Science and Engineering, 643000 Zigong, Sichuan (China)

    2015-01-01

    Graphical abstract: - Highlights: • HCNFs were synthesized by one-step CVD using cupric tartrate as a catalyst at temperature below 500 °C. • The synthesis of HCNFs is highly temperature-dependent at the synthesis temperature of 280–480 °C. • The addition of HCNFs makes a noticeable contribution to the reinforcement of NR/CB system. - Abstract: Helical carbon fibers (HCNFs) were synthesized by one-step chemical vapour deposition using cupric tartrate as a catalyst at temperature below 500 °C. The bound rubber of natural rubber (NR)/HCNFs were also prepared in this study. The results of thermogravimetry–differential scanning calorimetry (TG/DSC) for cupric tartrate nanoparticles show that the transformation of C{sub 4}H{sub 4}CuO{sub 6} → Cu reaction occurs at ∼250–310 °C. The characterization of scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Raman spectrum for the synthesized products confirms that the synthesis of HCNFs is highly temperature-dependent. The straight fibers with the fiber diameter of 100–400 nm are obtained at 280 °C and HCNFs can be synthesized at higher temperature, with the coil diameter of 0.5–1 μm and fiber diameter of 100–200 nm at 380 °C, and the coil diameter of ∼100 nm and fiber diameter of ∼80 nm at 480 °C. The maximum of the bound-rubber content (37%) can be obtained with the addition of 100 wt.% HCNFs in NR, which indicates that the coiled configuration of HCNFs makes a noticeable contribution to the reinforcement of NR/CB system.

  14. Antimicrobial activity of novel nanostructured Cu-SiO2 coatings prepared by chemical vapour deposition against hospital related pathogens.

    Varghese, Sajnu; Elfakhri, Souad O; Sheel, David W; Sheel, Paul; Bolton, Frederick J Eric; Foster, Howard A

    2013-01-01

    There is increasing recognition that the healthcare environment acts as an important reservoir for transmission of healthcare acquired infections (HCAI). One method of reducing environmental contamination would be use of antimicrobial materials. The antimicrobial activity of thin silica-copper films prepared by chemical vapour deposition was evaluated against standard strains of bacteria used for disinfectant testing and bacteria of current interest in HCAI. The structure of the coatings was determined using Scanning Electron Microscopy and their hardness and adhesion to the substrate determined. Antimicrobial activity was tested using a method based on BS ISO 22196:2007. The coatings had a pale green-brown colour and had a similar hardness to steel. SEM showed nano-structured aggregates of Cu within a silica matrix. A log10 reduction in viability of >5 could be obtained within 4 h for the disinfectant test strains and within 6 h for producing Acinetobacter baumannii, Klebsiella pneumoniae and Stenotrophomonas maltophilia. Activity against the other hospital isolates was slower but still gave log10 reduction factors of >5 for extended spectrum β-lactamase producing Escherichia coli and >3 for vancomycin resistant Enterococcus faecium, methicillin resistant Staphylococcus aureus and Pseudomonas aeruginosa within 24 h. The results demonstrate the importance of testing antimicrobial materials destined for healthcare use against isolates of current interest in hospitals as well as standard test strains. The coatings used here can also be applied to substrates such as metals and ceramics and have potential applications where reduction of microbial environmental contamination is desirable. PMID:24007899

  15. Evolution of Structural Defects in SiOx Films Fabricated by Electron Cyclotron Resonance Plasma Chemical Vapour Deposition upon Annealing Treatment

    HAO Xiao-Peng; WANG Bao-Yi; Yu Run-Sheng; WEI Long; WANG Hui; ZHAO De-Gang; HAO Wei-Chang

    2008-01-01

    @@ We study the structural defects in the SiOx film prepared by electron cyclotron resonance plasma chemical vapour deposition and annealing recovery evolution.The photoluminescence property is observed in the as-deposited and annealed samples.[-SiO3]2- defects are the luminescence centres of the ultraviolet photoluminescence(PL)from the Fourier transform infrared spectroscopy and PL measurements.[-SiO3]2- is observed by positron annihilation spectroscopy,and this defect can make the S parameters increase.After 1000℃ annealing,[-SiO3]2- defects still exist in the films.

  16. Thermal Modification of a-SiC:H Films Deposited by Plasma Enhanced Chemical Vapour Deposition from CH4+SiH4 Mixtures

    刘玉学; 王宁会; 刘益春; 申德振; 范希武; 李灵燮

    2001-01-01

    The effects of thermal annealing on photoluminescence (PL) and structural properties of a-Si1-xCx :H films deposited by plasma enhanced chemical vapour deposition from CH4+SiH4 mixtures are studied by using infrared, PL and transmittance-reflectance spectra. In a-SiC:H network, high-temperature annealing gives rise to the effusion of hydrogen from strongly bonded hydrogen in SiH, SiH2, (SiH2)n, SiCHn and CHn configurations and the break of weak C-C, Si-Si and C-Si bonds. A structural rearrangement will occur, which causes a significant correlation of the position and intensity of the PL signal with the annealing temperature. The redshift of the PL peak is related to the destruction of the confining power of barriers. However, the PL intensity does not have a significant correlation with the annealing temperature for a C-rich a-SiC:H network, which refers to the formation of π-bond cluster as increasing carbon content. It is indicated that the thermal stability of C-rich a-Si1-xCx:H films is better than that of Si-like a-Si1-xCx :H films.

  17. Low pressure chemical vapour deposition of ZnO layers for thin-film solar cells. Temperature-induced morphological changes

    Fay, S.; Kroll, U.; Bucher, C.; Vallat-Sauvain, E.; Shah, A. [Institut de Microtechnique IMT, Thin-film Silicon and Photovoltaics Laboratory, Rue A.-L. Breguet 2, 2000 Neuchatel (Switzerland)

    2005-03-31

    Zinc oxide (ZnO) is now often used as a transparent conductive oxide for contacts in thin-film silicon solar cells. This paper presents a study of ZnO material deposited by the low-pressure chemical vapour deposition technique, in a pressure range below the pressures usually applied for the deposition of this kind of material. A temperature series has been deposited, showing a morphological transition around 150{sup o}C. ZnO samples deposited with temperatures just higher than this transition are constituted of large grains highly oriented along a single crystallographic orientation. These 'monocrystals' lead to low resistivity values, showing a clear correlation between the size of the surface grains and the electrical performance of corresponding films. Additionally, these large grains also yield ZnO layers with high transparency and high light-scattering power, specially suitable for solar cell technology based on thin-film silicon.

  18. Growth kinetics of nc-Si:H deposited at 200 deg. C by hot-wire chemical vapour deposition

    We report on the growth kinetics of hydrogenated nanocrystalline silicon, with specific focus on the effects of the deposition time and hydrogen dilution on the nano-structural properties. The growth in the crystallite size, attributed to the agglomeration of smaller nano-crystallites, is accompanied by a reduction in the compressive strain within the crystalline region and an improved ordering and reduction in the tensile stress in the amorphous network. These changes are intimately related to the absorption characteristics of the material. Surface diffusion determines the growth in the amorphous regime, whereas competing reactions between silicon etching by atomic hydrogen and precursor deposition govern the film growth at the high-dilution regime. The diffusion of hydrogen within the film controls the growth during the transition from amorphous to nanocrystalline silicon.

  19. a Study of Volatile Precursors for the Growth of Cadmium Sulphide and Cadmium Selenide by Metal Organic Chemical Vapour Deposition.

    Beer, Michael P.

    Available from UMI in association with The British Library. The wide-band-gap semiconductors, cadmium sulphide and cadmium selenide, may be grown by Metal Organic Chemical Vapour Deposition (MOCVD). This method typically involves the reaction of gaseous streams of Me_2 Cd and H_2Y (Y = S, Se) over a heated substrate (usually gallium arsenide) on which the desired compound is grown as an epitaxial layer. Unfortunately, the precursors start to react in the cold zone of the reactor, that is before they reach the heated substrate. This problem is known as prereaction. The problem of prereaction is partially reduced by the use of adducts of dimethyl cadmium in place of the free dialkyl compound although the mechanism by which such adducts block prereaction is unknown. Accordingly, a study of adducts of dimethyl cadmium was undertaken with a view to determining their properties in all phases. The adduct of Me_2Cd with 2,2^ '-bipyridyl was found to be monomeric in the solid state while that with 1,4-dioxane, a volatile compound used for prereaction reduction, was found to be polymeric. A study of adducts in the gas phase using mass spectrometry and gas phase Fourier transform infrared spectroscopy gave no evidence to suggest there is any gas phase association between 1,4-dioxane and dimethyl cadmium. With the 2,2 ^'-bipyridyl adduct some evidence for partial retention of coordinate bonds upon sublimation was obtained. The solid adduct of Me _2Cd with N,N,N^' ,N^'-tetramethylethylenediamine (TMEDA) was prepared as it was hoped that the flexibility of the aliphatic Lewis base would permit the formation of an adduct containing strong co-ordinate bonds which would remain intact upon sublimation. Using gas phase electron diffraction, the structure of the adduct of Me_2Cd and TMEDA was determined. It was shown to exist in the gas phase purely as the associated monomeric species. The adduct was then employed for the growth of CdS and CdSe in an industrial MOCVD apparatus. The

  20. On titanium dioxide thin films growth from the direct current electric field assisted chemical vapour deposition of titanium (IV) chloride in toluene

    Titanium dioxide thin films were deposited from the aerosol assisted chemical vapour deposition reaction of titanium tetrachloride in toluene (1 M) at 600 °C and 5 L min−1. Direct current electric fields were applied and increased in a range of 0 to 30 V during the reaction. Changes in particle size, agglomeration and particle shape were observed. Raman spectroscopy analysis revealed different composition of anatase and rutile and crystal phase depending on the field strength applied. The photocatalytic activity was calculated from the half-life or time needed by the films to degrade 50% Resazurin dye-ink initial concentration. High photocatalytic performance with high anatase content (98.3%) was observed with half-life values of 3.9 min. Deposited films with pure content in rutile showed better photocatalytic performance than films with mix of crystal phases with anatase content below 40%. - Highlights: • Electric field assisted chemical vapour deposition used to synthesis titania thin films. • Significant alterations to crystallographic orientation and microstructure observed • Order of magnitude reduction in half life of dye degradation obtainable

  1. Effect of surfactants on the morphology of FeSe films fabricated from a single source precursor by aerosol assisted chemical vapour deposition

    Raja Azadar Hussain; Amin Badshah; Naghma Haider; Malik Dilshad Khan; Bhajan Lal

    2015-03-01

    This article presents the fabrication of FeSe thin films from a single source precursor namely (1-(2-fluorobenzoyl)-3-(4-ferrocenyl-3-methylphenyl)selenourea (MeP2F)) by aerosol assisted chemical vapour deposition (AACVD). All the films were prepared via similar experimental conditions (temperature, flow rate, concentration, solvent system and reactor type) except the use of three different concentrations of two different surfactants i.e., triton and span. Seven thin films were characterized with PXRD, SEM, AFM, EDS and EDS mapping. The mechanism of the interaction of surfactant with MeP2F was determined with cyclic voltammetry (CV) and UV-Vis spectroscopy.

  2. Growth and electro-optical properties of Ga-doped ZnO films prepared by aerosol assisted chemical vapour deposition

    Transparent conductive Ga-doped ZnO thin films were deposited onto glass substrates by a low-cost aerosol assisted chemical vapour deposition technique and the effect of gallium content on the ZnO film growth behaviour and opto-electronic properties was systematically investigated. It is found that, upon increasing Ga addition, the ZnO film crystallinity exhibits a continuous reduction in quality associated with the preferential orientation transformed from (002) to (102). The (002) oriented samples had a microstructure of parallel columnar grains while the (102) oriented coating was thickened by overlapping particles. The ZnO:Ga coatings exhibit high carrier concentration (up to 4.1 × 1020 cm−3) but low carrier mobility (up to 0.8 cm2 V−1 s−1), resulting in a minimum resistivity value of 2.3 × 10−2 Ω cm. The inferior carrier mobility performance could result from a profound ionized and neutral impurity scattering effect. Good visible transmittance (≈ 70–80%) is observed in these ZnO:Ga films and samples with higher carrier density present better infrared reflection performance (up to 37.2% at 2500 nm). - Highlights: • Aerosol assisted chemical vapour deposition of doped zinc oxide thin films • Gallium doping and opto-electronic properties systemically investigated • Growth mechanism changed by % gallium incorporation

  3. Growth and electro-optical properties of Ga-doped ZnO films prepared by aerosol assisted chemical vapour deposition

    Chen, Shuqun [School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Carraro, Giorgio [Department of Chemistry and INSTM, Padova University, Padova 35131 (Italy); Barreca, Davide [CNR-IENI and INSTM, Department of Chemistry, Padova University, Padova 35131 (Italy); Binions, Russell [School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

    2015-06-01

    Transparent conductive Ga-doped ZnO thin films were deposited onto glass substrates by a low-cost aerosol assisted chemical vapour deposition technique and the effect of gallium content on the ZnO film growth behaviour and opto-electronic properties was systematically investigated. It is found that, upon increasing Ga addition, the ZnO film crystallinity exhibits a continuous reduction in quality associated with the preferential orientation transformed from (002) to (102). The (002) oriented samples had a microstructure of parallel columnar grains while the (102) oriented coating was thickened by overlapping particles. The ZnO:Ga coatings exhibit high carrier concentration (up to 4.1 × 10{sup 20} cm{sup −3}) but low carrier mobility (up to 0.8 cm{sup 2} V{sup −1} s{sup −1}), resulting in a minimum resistivity value of 2.3 × 10{sup −2} Ω cm. The inferior carrier mobility performance could result from a profound ionized and neutral impurity scattering effect. Good visible transmittance (≈ 70–80%) is observed in these ZnO:Ga films and samples with higher carrier density present better infrared reflection performance (up to 37.2% at 2500 nm). - Highlights: • Aerosol assisted chemical vapour deposition of doped zinc oxide thin films • Gallium doping and opto-electronic properties systemically investigated • Growth mechanism changed by % gallium incorporation.

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

    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.

  5. Autonomous Chemical Vapour Detection by Micro UAV

    Kent Rosser; Karl Pavey; Nicholas FitzGerald; Anselm Fatiaki; Daniel Neumann; David Carr; Brian Hanlon; Javaan Chahl

    2015-01-01

    The ability to remotely detect and map chemical vapour clouds in open air environments is a topic of significant interest to both defence and civilian communities. In this study, we integrate a prototype miniature colorimetric chemical sensor developed for methyl salicylate (MeS), as a model chemical vapour, into a micro unmanned aerial vehicle (UAV), and perform flights through a raised MeS vapour cloud. Our results show that that the system is capable of detecting MeS vapours at low ppm con...

  6. Ellipsometric and Rutherford Back scattering Spectrometry studies of SiO(X)N(Y) films elaborated by plasma-enhanced chemical vapour deposition technique.

    Mahamdi, R; Boulesbaa, M; Saci, L; Mansour, F; Molliet, C; Collet, M; Temple-Boyer, P

    2011-10-01

    Silicon oxynitride (SiO(X)N(Y)) thin films were deposited by plasma-enhanced chemical vapour deposition technique (PECVD) from silane (SiH4), nitrous oxide (N2O), ammonia (NH3) and nitrogen (N2) mixture. Spectroscopic ellipsometry (SE), in the range of wavelengths 450-900 nm, was used to define the film thickness and therefore the deposition rate, as well as the refractive index as a function of the N2O gaseous flow. While considering the (Si3N4, SiO2, H2 or void) heterogeneous mixture, Maxwell Garnett (MG) theory allows to fit the SE measurements and to define the volume fraction of the different phases. Finally, Rutherford Backscattering Spectrometry (RBS) results showed that x = O/Si ratio increases gradually with increasing the N2O flow, allowing the correlation of the SiO(X)N(Y) films main parameters. PMID:22400311

  7. Thin films of tin(II) sulphide (SnS) by aerosol-assisted chemical vapour deposition (AACVD) using tin(II) dithiocarbamates as single-source precursors

    Kevin, Punarja; Lewis, David J.; Raftery, James; Azad Malik, M.; O'Brien, Paul

    2015-04-01

    The synthesis of the asymmetric dithiocarbamates of tin(II) with the formula [Sn(S2CNRR')2] (where R=Et, R'=n-Bu (1); R=Me, R'=n-Bu (2); R=R'=Et (3)) and their use for the deposition of SnS thin films by aerosol-assisted chemical vapour deposition (AACVD) is described. The effects of temperature and the concentration of the precursors on deposition were investigated. The stoichiometry of SnS was best at higher concentrations of precursors (250 mM) and at 450 °C. The direct electronic band gap of the SnS produced by this method was estimated from optical absorbance measurements as 1.2 eV. The composition of films was confirmed by powder X-ray diffraction (p-XRD) and energy dispersive analysis of X-rays (EDAX) spectroscopy.

  8. An investigation into the optimum thickness of titanium dioxide thin films synthesized by using atmospheric pressure chemical vapour deposition for use in photocatalytic water oxidation.

    Hyett, Geoffrey; Darr, Jawwad A; Mills, Andrew; Parkin, Ivan P

    2010-09-10

    Twenty eight films of titanium dioxide of varying thickness were synthesised by using atmospheric pressure chemical vapour deposition (CVD) of titanium(IV) chloride and ethyl acetate onto glass and titanium substrates. Fixed reaction conditions at a substrate temperature of 660 °C were used for all depositions, with varying deposition times of 5-60 seconds used to control the thickness of the samples. A sacrificial electron acceptor system composed of alkaline sodium persulfate was used to determine the rate at which these films could photo-oxidise water in the presence of 365 nm light. The results of this work showed that the optimum thickness for CVD films on titanium substrates for the purposes of water oxidation was ≈200 nm, and that a platinum coating on the reverse of such samples leads to a five-fold increase in the observed rate of water oxidation. PMID:20645333

  9. Preparation of high-quality hydrogenated amorphous silicon film with a new microwave electron cyclotron resonance chemical vapour deposition system assisted with hot wire

    Zhu Xiu-Hong; Chen Guang-Hua; Yin Sheng-Yi; Rong Yan-Dong; Zhang Wen-Li; Hu Yue-Hui

    2005-01-01

    The preparation of high-quality hydrogenated amorphous silicon (a-Si:H) film with a new microwave electron cyclotron resonance-chemical vapour deposition (MWECR-CVD) system assisted with hot wire is presented. In this system the hot wire plays an important role in perfecting the microstructure as well as improving the stability and the optoelectronic properties of the a-Si:H film. The experimental results indicate that in the microstructure of the a-Si:H film, the concentration of dihydride is decreased and a trace of microcrystalline occurs, which is useful to improve its stability, and that in the optoelectronic properties of the a-Si:H film, the deposition rate reaches above 2.0nm/s and the photosensitivity increases up to 4.71× 105.

  10. Growth of beta barium borate (β-BaB2O4) thin films by injection metal organic chemical vapour deposition

    Thin films containing beta barium borate (β-BaB2O4 so called β-BBO) were grown on silicon (100) substrates by injection metal organic chemical vapour deposition for different deposition temperatures. The films were characterized by optical microscopy, micro-Raman spectroscopy and X-ray photoelectron Spectroscopy (XPS). The micro-Raman spectra show an intense peak at 637 cm-1 that is the fingerprint of β-BBO. Our XPS analysis permits the measurement of the Ba, B and O core levels, which are reported here for the first time for β-BBO thin films. The formation of a new spectral component appearing with lower growth temperatures has been observed as well

  11. The physics of plasma-enhanced chemical vapour deposition for large-area coating: industrial application to flat panel displays and solar cells

    Designing plasma-enhanced chemical vapour deposition (PECVD) reactors to coat large-area glass plates (∼1 m2) for flat panel display or solar cell manufacturing raises challenging issues in physics and chemistry as well as mechanical, thermal, and electrical engineering, and material science. In such reactive glow discharge plasma slabs, excited at RF frequency (from 13.56 MHz up to ∼100 MHz), the thin-film deposition uniformity is determined by the gas flow distribution, as well as the RF voltage distribution along the electrodes, and by local plasma perturbations at the reactor boundaries. All these aspects can be approached by analytical and numerical modelling. Moreover, the film properties are largely determined by the plasma chemistry involving the neutral radicals contributing to film growth, the effect of ion bombardment, and the formation and trapping of dust triggered by homogeneous nucleation. This paper will review progress in this field, with particular emphasis on modelling developments. (author)

  12. The physics of plasma-enhanced chemical vapour deposition for large-area coating: industrial application to flat panel displays and solar cells

    Perrin, Jerome [Unaxis-Balzers A.G., Central R and D, PO Box 1000, FL-9496 Balzers (Liechtenstein); Schmitt, Jacques [Unaxis-France S.A., Display Technology, 5 rue Leon Blum, F-91120, Palaiseau (France); Hollenstein, Christoph; Howling, Alan; Sansonnens, Laurent [Centre de Recherche en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne, PPH Ecublens, CH - 1015 Lausanne (Switzerland)

    2000-12-01

    Designing plasma-enhanced chemical vapour deposition (PECVD) reactors to coat large-area glass plates ({approx}1 m{sup 2}) for flat panel display or solar cell manufacturing raises challenging issues in physics and chemistry as well as mechanical, thermal, and electrical engineering, and material science. In such reactive glow discharge plasma slabs, excited at RF frequency (from 13.56 MHz up to {approx}100 MHz), the thin-film deposition uniformity is determined by the gas flow distribution, as well as the RF voltage distribution along the electrodes, and by local plasma perturbations at the reactor boundaries. All these aspects can be approached by analytical and numerical modelling. Moreover, the film properties are largely determined by the plasma chemistry involving the neutral radicals contributing to film growth, the effect of ion bombardment, and the formation and trapping of dust triggered by homogeneous nucleation. This paper will review progress in this field, with particular emphasis on modelling developments. (author)

  13. Characterization of thin TiO{sub 2} films prepared by plasma enhanced chemical vapour deposition for optical and photocatalytic applications

    Sobczyk-Guzenda, A., E-mail: asobczyk@p.lodz.p [Institute of Materials Science and Engineering, Technical University of Lodz, Stefanowskiego 1, 90-924 Lodz (Poland); Gazicki-Lipman, M.; Szymanowski, H.; Kowalski, J. [Institute of Materials Science and Engineering, Technical University of Lodz, Stefanowskiego 1, 90-924 Lodz (Poland); Wojciechowski, P.; Halamus, T. [Department of Molecular Physics, Technical University of Lodz, Stefanowskiego 1, 90-924 Lodz (Poland); Tracz, A. [Centre for Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Lodz (Poland)

    2009-07-31

    Thin titanium oxide films were deposited using a radio frequency (RF) plasma enhanced chemical vapour deposition method. Their optical properties and thickness were determined by means of ultraviolet-visible absorption spectrophotometry. Films of the optical parameters very close to those of titanium dioxide have been obtained at the high RF power input. Their optical quality is high enough to allow for their use in a construction of stack interference optical filters. At the same time, these materials exhibit strong photocatalytic effects. The results of structural analysis, carried out by Raman Shift Spectroscopy, show that the coatings posses amorphous structure. However, Raman spectra of the same films subjected to thermal annealing at 450 {sup o}C disclose an appearance of a crystalline form, namely that of anatase. Surface morphology of the films has also been characterized by Atomic Force Microscopy revealing granular, broccoli-like topography of the films.

  14. Modified DLC coatings prepared in a large-scale reactor by dual microwave/pulsed-DC plasma-activated chemical vapour deposition

    Diamond-Like Carbon (DLC) films find abundant applications as hard and protective coatings due to their excellent mechanical and tribological performances. The addition of new elements to the amorphous DLC matrix tunes the properties of this material, leading to an extension of its scope of applications. In order to scale up their production to a large plasma reactor, DLC films modified by silicon and oxygen additions have been grown in an industrial plant of 1m3 by means of pulsed-DC plasma-activated chemical vapour deposition (PACVD). The use of an additional microwave (MW) source has intensified the glow discharge, partly by electron cyclotron resonance (ECR), accelerating therefore the deposition process. Hence, acetylene, tetramethylsilane (TMS) and hexamethyldisiloxane (HMDSO) constituted the respective gas precursors for the deposition of a-C:H (DLC), a-C:H:Si and a-C:H:Si:O films by dual MW/pulsed-DC PACVD. This work presents systematic studies of the deposition rate, hardness, adhesion, abrasive wear and water contact angle aimed to optimize the technological parameters of deposition: gas pressure, relative gas flow of the monomers and input power. This study has been completed with measures of the atomic composition of the samples. Deposition rates around 1 μm/h, typical for standard processes held in the large reactor, were increased about by a factor 10 when the ionization source has been operated in ECR mode

  15. Effect of Postdeposition Heat Treatment on the Crystallinity, Size, and Photocatalytic Activity of TiO2 Nanoparticles Produced via Chemical Vapour Deposition

    Siti Hajar Othman

    2010-01-01

    Full Text Available Titanium dioxide (TiO2 nanoparticles were produced using chemical vapour deposition (CVD at different deposition temperatures (300–700°C. All the samples were heat treated at their respective deposition temperatures and at a fixed temperature of 400°C. A scanning electron microscope (SEM, a transmission electron microscope (TEM, and X-ray diffraction (XRD were used to characterize the nanoparticles in terms of size and crystallinity. The photocatalytic activity was investigated via degradation of methylene blue under UV light. The effects of post deposition heat treatment are discussed in terms of crystallinity, nanoparticle size as well as photocatalytic activity. Crystallinity was found to have a much larger impact on photocatalytic activity compared to nanoparticle size. Samples having a higher degree of crystallinity were more photocatalytically active despite being relatively larger in size. Surprisingly, the photocatalytic activity of the samples reduced when heat treated at temperatures lower than the deposition temperature despite showing an improvement in crystallinity.

  16. Raman Spectroscopic Study of Carbon Nanotubes Prepared Using Fe/ZnO-Palm Olein-Chemical Vapour Deposition

    Syazwan Afif Mohd Zobir

    2012-01-01

    Full Text Available Multiwalled carbon nanotubes (MWCNTs were synthesized using Fe/ZnO catalyst by a dual-furnace thermal chemical vapor deposition (CVD method at 800–1000°C using nitrogen gas with a constant flow rate of 150 sccm/min as a gas carrier. Palm olein (PO, ferrocene in the presence of 0.05 M zinc nitrate, and a p-type silicon wafer were used as carbon source, catalyst precursor, and sample target, respectively. D, G, and G′ bands were observed at 1336–1364, 1559–1680, and 2667–2682 cm-1, respectively. Carbon nanotubes (CNTs with the highest degree of crystallinity were obtained at around 8000°C, and the smallest diameter of about 2 nm was deposited on the silicon substrate at 1000°C.

  17. Influence of double AlN buffer layers on the qualities of GaN films prepared by metal-organic chemical vapour deposition

    Lin Zhi-Yu; Hao Yue; Zhang Jin-Cheng; Zhou Hao; Li Xiao-Gang; Meng Fan-Na; Zhang Lin-Xia; Ai Shan; Xu Sheng-Rui; Zhao Yi

    2012-01-01

    In this paper we report that the GaN thin film is grown by metal-organic chemical vapour deposition on a sapphire (0001) substrate with double AlN buffer layers.The buffer layer consists of a low-temperature (LT) AlN layer and a high-temperature (HT) AlN layer that are grown at 600 ℃ and 1000 ℃,respectively.It is observed that the thickness of the LT-AlN layer drastically influences the quality of GaN thin film,and that the optimized 4.25-min-LT-AlN layer minimizes the dislocation density of GaN thin film.The reason for the improved properties is discussed in this paper.

  18. Effect of Al Doping in the InGaN/GaN Multiple Quantum Well Light Emitting Diodes Grown by Metalorganic Chemical Vapour Deposition

    LU Yu; YANG Zhi-Jian; PAN Yao-Bo; XU Ke; HU Xiao-Dong; ZHANG Bei; ZHANG Guo-Yi

    2006-01-01

    The effect of Al doping in the GaN layer of InGaN/GaN multiple quantum-well light emitting diodes (LEDs) grown by metalorganic chemical vapour deposition is investigated by using photoluminescence (PL) and high-resolution x-ray diffraction. The full width at half maximum of PL of Al doped LEDs is measured to be about 12nm. The band edge photoluminescence emission intensity is enhanced significantly. In addition, the in-plane compressive strain in the Al-doped LEDs is improved significantly and measured by reciprocal space map. The output power of Al-doped LEDs is 130mW in the case of the induced current of 200mA.

  19. Synthesis, structural characterization and optical properties of multilayered Yttria-stabilized ZrO2 thin films obtained by aerosol assisted chemical vapour deposition

    Multilayered Yttria-stabilized zirconium (YSZ) oxide thin films were synthesized by aerosol assisted chemical vapour deposition onto borosilicate glass substrate. The film consisted of a periodic stack of several YSZ layer pairs. Each pair was composed of layers, a few nanometers thick, of the same composition but different density. Optically the multilayered microstructure correspond to alternating layers of high (dense layer) and low (porous layer) refraction index. The microstructure was analysed by electron and atomic force microscopy. Optical properties were evaluated by reflectance spectroscopy, and associated with the cross sectional microstructure of the films. The measured effective refractive index of the films deviates from bulk value. The discrepancy can be explained by the multilayered structure of the film

  20. Investigation of chemical vapour deposition diamond detectors by X- ray micro-beam induced current and X-ray micro-beam induced luminescence techniques

    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. Growth of MgB2 Thin Films by Chemical Vapour Deposition Using B2H6 as a boron Source

    王淑芳; 朱亚彬; 刘震; 周岳亮; 张芹; 陈正豪; 吕惠宾; 杨国桢

    2003-01-01

    Superconducting MgB2 thin films were grown on single crystal Al2O3 (0001) by chemical vapour deposition using B2H6 as a boron source. MgB2 film was then accomplished by annealing the boron precursor films in the presence of high-purity magnesium bulk at 890℃ in vacuum. The as-grown MgB2 films are smooth and c-axis-oriented.The films exhibit a zero-resistance transition of about 38K with a narrow transition width of 0.2 K. Magnetic hysteresis measurements yield the critical current density of 1.9 × 107 A/cm2 at 10 K in zero field.

  2. Heterocyclic dithiocarbamato-iron(III) complexes: single-source precursors for aerosol-assisted chemical vapour deposition (AACVD) of iron sulfide thin films.

    Mlowe, Sixberth; Lewis, David J; Malik, Mohammad Azad; Raftery, James; Mubofu, Egid B; O'Brien, Paul; Revaprasadu, Neerish

    2016-02-14

    Tris-(piperidinedithiocarbamato)iron(III) (1) and tris-(tetrahydroquinolinedithiocarbamato)iron(iii) (2) complexes have been synthesized and their single-crystal X-ray structures were determined. Thermogravimetric analysis (TGA) of the complexes showed decomposition to iron sulfide. Both complexes were then used as single-source precursors for the deposition of iron sulfide thin films by aerosol-assisted chemical vapour deposition (AACVD). Energy-dispersive X-ray (EDX) spectroscopy confirmed the formation of iron sulfide films. The addition of tert-butyl thiol almost doubled the sulfur content in the deposited films. Scanning electron microscopy (SEM) images of the iron sulfide films from both complexes showed flakes/leaves/sheets, spherical granules and nanofibres. The sizes and shapes of these crystallites depended on the nature of the precursor, temperature, solvent and the amount of tert-butyl thiol used. The observed optical properties are dependent upon the variation of reaction parameters such as temperature and solvent. Powder X-ray diffraction (p-XRD) studies revealed that pyrrhotite, hexagonal (Fe0.975S), marcasite and smythite (Fe3S4) phases were differently deposited. PMID:26732865

  3. Autonomous Chemical Vapour Detection by Micro UAV

    Kent Rosser

    2015-12-01

    Full Text Available The ability to remotely detect and map chemical vapour clouds in open air environments is a topic of significant interest to both defence and civilian communities. In this study, we integrate a prototype miniature colorimetric chemical sensor developed for methyl salicylate (MeS, as a model chemical vapour, into a micro unmanned aerial vehicle (UAV, and perform flights through a raised MeS vapour cloud. Our results show that that the system is capable of detecting MeS vapours at low ppm concentration in real-time flight and rapidly sending this information to users by on-board telemetry. Further, the results also indicate that the sensor is capable of distinguishing “clean” air from “dirty”, multiple times per flight, allowing us to look towards autonomous cloud mapping and source localization applications. Further development will focus on a broader range of integrated sensors, increased autonomy of detection and improved engineering of the system.

  4. Hot wire chemical vapour deposition (HWCVD) of boron carbide thin films from ortho-carborane for neutron detection application

    Detection of neutrons is possible if suitable converters such as Li, LiF or 10B in the form of thin films are used along with the semiconductor device. The use of boron (10B) in some host matrix as a neutron detector is attractive due to its large neutron capture cross-section. Boron carbide (BC) films are deposited on silicon substrates by HWCVD technique using solid ortho-carborane (o-C2B10H12) precursor with argon as carrier gas. The films contain 10B required for neutron detection as confirmed by the Secondary Ion Mass Spectroscopy. Variations in its structure as well as the chemical bonding configurations using Fourier Transform Infra-Red, Raman and X-ray diffraction spectroscopy have been studied.

  5. Broadband antireflection for a high-index substrate using SiNx/SiO2 by inductively coupled plasma chemical vapour deposition

    This paper presents the development of broadband antireflection coating for a high-index substrate such as Si using SiNx/SiO2 by inductively coupled plasma chemical vapour deposition (ICP-CVD). The thin-film design employs a simulated annealing method for a minimal average reflectance over the wavelength range and incidence angles involved, which gives the optimized refractive index and thickness of each layer of the thin-film stack under different layer numbers. Using ICP-CVD, the SiNx material system is optimized by tuning the SiH4/N2 gas ratio. The corresponding thin-film characterization shows the precise refractive index/film thickness control in deposition, and the deposited film also has a low absorption coefficient and smooth surface. The double-layer SiNx/SiO2 coating with the optimized refractive index and thickness for broadband antireflection is demonstrated experimentally. The average reflectance of the Si surface is reduced from ∼32% to ∼3.17% at normal incidence for a wavelength range from 400 to 1100 nm. (paper)

  6. The study and the realization of radiation detectors made from polycrystalline diamond films grown by microwave plasma enhanced chemical vapour deposition technique

    The aim of this work was to develop radiation detectors made from polycrystalline diamond films grown by microwave plasma enhanced chemical vapour deposition technique. The influence of surface treatments, contact technology and diamond growth parameters on the diamond detectors characteristics was investigated in order to optimise the detector response to alpha particles. The first part of the study focused on the electrical behaviour of as-deposited diamond surface, showing a p type conduction and its influence on the leakage current of the device. A surface preparation process was established in order to reduce the leakage current of the device by surface dehydrogenation using an oxidising step. Several methods to form and treat electrical contacts were also investigated showing that the collection efficiency of the device decreases after contact annealing. In the second part, we reported the influence of the diamond deposition parameters on the characteristics of the detectors. The increase of the deposition temperature and/or methane concentration was shown to lead η to decrease. In contrast, η was found to increase with the micro-wave power. The evolution of the diamond detector characteristics results from the variation in sp2 phases incorporation and in the crystallography quality of the films. These defects increase the leakage current and reduce the carrier mobility and lifetime. Measurements carried out on detectors with different thicknesses showed that the physical properties varies along the growth direction, improving with the film thickness. Finally, the addition of nitrogen (> 10 ppm) in the gas mixture during diamond deposition was found to strongly reduce the collection efficiency of the detectors. To conclude the study, we fabricated and characterised diamond devices which were used for thermal neutron detection and for the intensity and shape measurement of VUV and soft X-ray pulses. (author)

  7. Effects of Surface Modification of Nanodiamond Particles for Nucleation Enhancement during Its Film Growth by Microwave Plasma Jet Chemical Vapour Deposition Technique

    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.

  8. Chemical, morphological and nano-mechanical characterizations of Al2O3 thin films deposited by metal organic chemical vapour deposition on AISI 304 stainless steel

    Amorphous alumina coatings of different thickness have been deposited on AISI 304 stainless steel substrates by MOCVD in a hot wall reactor at 380 deg. C under O2/H2O atmosphere. The used aluminium precursor was the high volatile and easy to prepare dimethyl-aluminum-isopropoxide. Selected films were annealed in N2 and O2 atmosphere at 500 and 700 deg. C to evaluate the effects of the thermal treatments on the morphology and on the nano-mechanical properties of the coatings. X-ray diffraction and Rutherford backscattering spectroscopy measurements indicated that both the as grown and annealed films were amorphous and very pure with the correct Al2O3 stoichiometry. The surface morphology, investigated by atomic force microscopy, was free of cracks with a roughness of the films that increases with deposition time and with annealing in oxygen atmosphere. The hardness and the elastic modulus of the films and of the AISI 304 stainless steel substrate were measured by load-depth nano-indentation tests. The results highlighted a significant increase in the Berkovich hardness of the coated samples compared to that of the bulk AISI 304 stainless steel

  9. Surface morphological and photoelectrochemical studies of ZnS thin films developed from single source precursors by aerosol assisted chemical vapour deposition

    Ehsan, Muhammad Ali [Faculty of Science, Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Peiris, T.A. Nirmal; Wijayantha, K.G. Upul [Department of Chemistry, Loughborough University, Loughborough, LE11 3TU (United Kingdom); Khaledi, Hamid [Faculty of Science, Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Ming, Huang Nay [Faculty of Science, Department of Physics, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Misran, Misni; Arifin, Zainudin [Faculty of Science, Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Mazhar, Muhammad, E-mail: mazhar42pk@yahoo.com [Faculty of Science, Department of Chemistry, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia)

    2013-07-01

    Zinc sulphide (ZnS) thin films have been deposited on fluorine-doped tin oxide-coated conducting glass substrates at 375, 425 and 475 °C temperatures from single source adduct precursors [Zn(S{sub 2}CNCy{sub 2}){sub 2}(py)] (1) [where, Cy = cyclohexyl, py = pyridine] and [Zn{S_2CN(CH_2Ph)(Me)}{sub 2}(py)] (2) [where, Ph = Phenyl, Me = Methyl] using aerosol assisted chemical vapour deposition (AACVD). The precursor complexes have been characterized by microanalysis, infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, X-ray single crystal and thermogravimetric analysis. Thermal analysis showed that both precursors (1) and (2) undergo thermal decomposition at 375 °C to produce ZnS residues. The deposited ZnS films have been characterized by X-ray diffraction and energy dispersive X-ray spectroscopy. Scanning electron microscopic studies indicated that the surface morphology of ZnS films strongly depends on the nature of the precursor and the deposition temperature, regardless of marginal variation in thermal stability of the precursors. Direct band gap energies of 3.36 and 3.40 eV have been estimated from the ultraviolet–visible spectroscopy for the ZnS films fabricated from precursors (1) and (2), respectively. The current–voltage characteristics recorded under air mass 1.5 illumination confirmed that the deposited ZnS thin films are photoactive under anodic bias conditions. Furthermore, the photoelectrochemical (PEC) results indicate that these synthesised single source precursors are suitable for obtaining ZnS thin films by AACVD method. The ZnS thin film electrode prepared in this study are very promising for solar energy conversion and optoelectronic applications. The PEC properties of ZnS electrodes prepared from (2) are superior to that of the ZnS electrode prepared from precursor (1). - Highlights: • Synthesis and characterization of zinc dithiocarbamate pyridine adducts. • ZnS photo electrodes have been fabricated using aerosol

  10. Surface morphological and photoelectrochemical studies of ZnS thin films developed from single source precursors by aerosol assisted chemical vapour deposition

    Zinc sulphide (ZnS) thin films have been deposited on fluorine-doped tin oxide-coated conducting glass substrates at 375, 425 and 475 °C temperatures from single source adduct precursors [Zn(S2CNCy2)2(py)] (1) [where, Cy = cyclohexyl, py = pyridine] and [Zn{S2CN(CH2Ph)(Me)}2(py)] (2) [where, Ph = Phenyl, Me = Methyl] using aerosol assisted chemical vapour deposition (AACVD). The precursor complexes have been characterized by microanalysis, infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, X-ray single crystal and thermogravimetric analysis. Thermal analysis showed that both precursors (1) and (2) undergo thermal decomposition at 375 °C to produce ZnS residues. The deposited ZnS films have been characterized by X-ray diffraction and energy dispersive X-ray spectroscopy. Scanning electron microscopic studies indicated that the surface morphology of ZnS films strongly depends on the nature of the precursor and the deposition temperature, regardless of marginal variation in thermal stability of the precursors. Direct band gap energies of 3.36 and 3.40 eV have been estimated from the ultraviolet–visible spectroscopy for the ZnS films fabricated from precursors (1) and (2), respectively. The current–voltage characteristics recorded under air mass 1.5 illumination confirmed that the deposited ZnS thin films are photoactive under anodic bias conditions. Furthermore, the photoelectrochemical (PEC) results indicate that these synthesised single source precursors are suitable for obtaining ZnS thin films by AACVD method. The ZnS thin film electrode prepared in this study are very promising for solar energy conversion and optoelectronic applications. The PEC properties of ZnS electrodes prepared from (2) are superior to that of the ZnS electrode prepared from precursor (1). - Highlights: • Synthesis and characterization of zinc dithiocarbamate pyridine adducts. • ZnS photo electrodes have been fabricated using aerosol-assisted chemical vapor

  11. Fabrication of 160-nm T-gate metamorphic AlInAs/GaInAs HEMTs on GaAs substrates by metal organic chemical vapour deposition

    Li, Hai-Ou; Huang, Wei; Tang Chak, Wah; Deng, Xiao-Fang; Lau Kei, May

    2011-06-01

    The fabrication and performance of 160-nm gate-length metamorphic AlInAs/GaInAs high electron mobility transistors (mHEMTs) grown on GaAs substrate by metal organic chemical vapour deposition (MOCVD) are reported. By using a novel combined optical and e-beam photolithography technology, submicron mHEMTs devices have been achieved. The devices exhibit good DC and RF performance. The maximum current density was 817 mA/mm and the maximum transconductance was 828 mS/mm. The non-alloyed Ohmic contact resistance Rc was as low as 0.02 Ω-mm. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) were 146 GHz and 189 GHz, respectively. This device has the highest fT yet reported for a 160-nm gate-length HEMTs grown by MOCVD. The output conductance is 28.9 mS/mm, which results in a large voltage gain of 28.6. Also, an input capacitance to gate-drain feedback capacitance ratio, Cgs/Cgd, of 4.3 is obtained in the device.

  12. Fabrication of 160-nm T-gate metamorphic AlInAs/GaInAs HEMTs on GaAs substrates by metal organic chemical vapour deposition

    The fabrication and performance of 160-nm gate-length metamorphic AlInAs/GaInAs high electron mobility transistors (mHEMTs) grown on GaAs substrate by metal organic chemical vapour deposition (MOCVD) are reported. By using a novel combined optical and e-beam photolithography technology, submicron mHEMTs devices have been achieved. The devices exhibit good DC and RF performance. The maximum current density was 817 mA/mm and the maximum transconductance was 828 mS/mm. The non-alloyed Ohmic contact resistance Rc was as low as 0.02 Ω-mm. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) were 146 GHz and 189 GHz, respectively. This device has the highest fT yet reported for a 160-nm gate-length HEMTs grown by MOCVD. The output conductance is 28.9 mS/mm, which results in a large voltage gain of 28.6. Also, an input capacitance to gate-drain feedback capacitance ratio, Cgs/Cgd, of 4.3 is obtained in the device. (interdisciplinary physics and related areas of science and technology)

  13. Polyethylene Oxide Films Polymerized by Radio Frequency Plasma-Enhanced Chemical Vapour Phase Deposition and Its Adsorption Behaviour of Platelet-Rich Plasma

    HU Wen-Juan; XIE Fen-Yan; CHEN Qiang; WENG Jing

    2008-01-01

    We present polyethylene oxide (PEO) functional films polymerized by rf plasma-enhanced vapour chemical deposition (rf-PECVD) on p-Si (100) surface with precursor ethylene glycol dimethyl ether (EGDME) and diluted Ar in pulsed plasma mode. The influences of discharge parameters on the film properties and compounds are investigated. The film structure is analysed by Fourier transform infrared (FTIR) spectroscopy. The water contact angle measurement and atomic force microscope (AFM) are employed to examine the surface polarity and to detect surface morphology, respectively. It is concluded that the smaller duty cycle in pulsed plasma mode contributes to the rich C-O-C (EO) group on the surfaces. As an application, the adsorption behaviour of platelet-rich plasma on plasma polymerization films performed in-vitro is explored. The shapes of attached cells are studied in detail by an optic invert microscope, which clarifies that high-density C-O-C groups on surfaces are responsible for non-fouling adsorption behaviour of the PEO films.

  14. A Simple Route of Morphology Control and Structural and Optical Properties of ZnO Grown by Metal-Organic Chemical Vapour Deposition

    FAN Hai-Bo; YANG Shao-Yan; ZHANG Pan-Feng; WEI Hong-Yuan; LIU Xiang-Lin; JIAO Chun-Mei; ZHU Qin-Sheng; CHEN Yong-Hai; WANG Zhan-Guo

    2008-01-01

    @@ Employing the metal-organic chemical vapour deposition (MOCVD) technique, we prepare ZnO samples with different morphologies from the film to nanorods through conveniently changing the bubbled diethylzinc flux (BDF) and the carrier gas flux of oxygen (OCGF). The scanning electron microscope images indicate that small BDF and OCGF induce two-dimensional growth while the large ones avail quasi-one-dimensional growth. X-ray diffraction (XRD) and Raman scattering analyses show that all of the morphology-dependent ZnO samples are of high crystal quality with a c-axis orientation. From the precise shifts of the 20 locations of ZnO (002) face in the XRD patterns and the E2 (high) locations in the Raman spectra, we deduce that the compressive stress forms in the ZnO samples and is strengthened with the increasing BDF and OCGF. Photoluminescence spectroscopyresults show all the samples have a sharp ultraviolet luminescent band without any defects-related emission.Upon the experiments a possible growth mechanism is proposed.

  15. Structural and optical investigation of nonpolar a-plane GaN grown by metal-organic chemical vapour deposition on r-plane sapphire by neutron irradiation

    Xu Sheng-Rui; Zhang Jin-Feng; Gu Wen-Ping; Hao Yue; Zhang Jin-Cheng; Zhou Xiao-Wei; Lin Zhi-Yu; Mao Wei

    2012-01-01

    Nonpolar (11(2)0) a-plane GaN films are grown by metal-organic chemical vapour deposition (MOCVD) on r-plane (1(1)02) sapphire.The samples are irradiated with neutrons under a dose of 1 × 1015 cm-2.The surface morphology,the crystal defects and the optical properties of the samples before and after irradiation are analysed using atomic force microscopy (AFM),high resolution X-ray diffraction (HRXRD) and photoluminescence (PL).The AFM result shows deteriorated sample surface after the irradiation.Careful fitting of the XRD rocking curve is carried out to obtain the Lorentzian weight fraction.Broadening due to Lorentzian type is more obvious in the as-grown sample compared with that of the irradiated sample,indicating that more point defects appear in the irradiated sample.The variations of line width and intensity of the PL band edge emission peak are consistent with the XRD results.The activation energy decreases from 82.5 meV to 29.9 meV after irradiation by neutron.

  16. Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Harsh [Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi 110025 (India); Husain, Mushahid, E-mail: mush-reslab@rediffmail.com [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi 110025 (India)

    2014-02-28

    Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm{sup 2} at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5 min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm{sup 2} at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O{sub 2} plasma treatment and the findings are being reported in this paper.

  17. Fabrication of 160-nm T-gate metamorphic AlInAs/GaInAs HEMTs on GaAs substrates by metal organic chemical vapour deposition

    Li Hai-Ou; Huang Wei; Tang Chak Wah; Deng Xiao-Fang; Lau Kei May

    2011-01-01

    The fabrication and performance of 160-nm gate-length metamorphic AlInAs/GaInAs high electron mobility transistors (mHEMTs) grown on GaAs substrate by metal organic chemical vapour deposition (MOCVD) are reported.By using a novel combined optical and e-beam photolithography technology, submicron mHEMTs devices have been achieved. The devices exhibit good DC and RF performance. The maximum current density was 817 mA/mm and the maximum transconductance was 828 mS/mm. The non-alloyed Ohmic contact resistance Rc was as low as 0.02 Ω-mm. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) were 146 GHz and 189 GHz, respectively. This device has the highest fT yet reported for a 160-nm gate-length HEMTs grown by MOCVD.The output conductance is 28.9 mS/mm, which results in a large voltage gain of 28.6. Also, an input capacitance to gate-drain feedback capacitance ratio, Cgs/Cgd, of 4.3 is obtained in the device.

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

    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.

  19. Fine-tuning of catalytic tin nanoparticles by the reverse micelle method for direct deposition of silicon nanowires by a plasma-enhanced chemical vapour technique.

    Poinern, Gérrard E J; Ng, Yan-Jing; Fawcett, Derek

    2010-12-15

    The reverse micelle method was used for the reduction of a tin (Sn) salt solution to produce metallic Sn nanoparticles ranging from 85 nm to 140 nm in diameter. The reverse micellar system used in this process was hexane-butanol-cetyl trimethylammonium bromide (CTAB). The diameters of the Sn nanoparticles were proportional to the concentration of the aqueous Sn salt solution. Thus, the size of the Sn nanoparticles can easily be controlled, enabling a simple, reproducible mechanism for the growth of silicon nanowires (SiNWs) using plasma-enhanced chemical vapour deposition (PECVD). Both the Sn nanoparticles and silicon nanowires were characterised using field-emission scanning electron microscopy (FE-SEM). Further characterisations of the SiNW's were made using transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy. In addition, dynamic light scattering (DLS) was used to investigate particle size distributions. This procedure demonstrates an economical route for manufacturing reproducible silicon nanowires using fine-tuned Sn nanoparticles for possible solar cell applications. PMID:20887996

  20. Origin of the 2.45 eV luminescence band observed in ZnO epitaxial layers grown on c-plane sapphire by chemical vapour deposition

    Zinc oxide epitaxial layers have been grown on c-plane sapphire substrates by the chemical vapour deposition (CVD) technique. A structural study shows (0001)-oriented films with good crystalline quality. The temperature and excitation power dependence of the photoluminescence (PL) characteristics of these layers is studied as a function of various growth parameters, such as the growth temperature, oxygen flow rate and Zn flux, which suggest that the origin of the broad visible luminescence (VL), which peaks at 2.45 eV, is the transition between the conduction band and the Zn vacancy acceptor states. A bound excitonic transition observed at 3.32 eV in low temperature PL has been identified as an exciton bound to the neutral Zn vacancy. Our study also reveals the involvement of two activation processes in the dynamics of VL, which has been explained in terms of the fluctuation of the capture barrier height for the holes trapped in Zn vacancy acceptors. The fluctuation, which might be a result of the inhomogeneous distribution of Zn vacancies, is found to be associated with an average height of 7 and 90 meV, respectively, for the local and global maxima. (paper)

  1. Characterization of GaN/AlGaN epitaxial layers grown by metalorganic chemical vapour deposition for high electron mobility transistor applications

    Bhubesh Chander Joshi; Manish Mathew; B C Joshi; D Kumar; C Dhanavantri

    2010-01-01

    GaN and AlGaN epitaxial layers are grown by a metalorganic chemical vapour deposition (MOCVD) system. The crystalline quality of these epitaxially grown layers is studied by different characterization techniques. PL measurements indicate band edge emission peak at 363.8 nm and 312 nm for GaN and AlGaN layers respectively. High resolution XRD (HRXRD) peaks show FWHM of 272 and 296 arcsec for the (0 0 0 2) plane of GaN and GaN in GaN/AlGaN respectively. For GaN buffer layer, the Hall mobility is 346 cm2/V-s and carrier concentration is 4.5 × 1016 /cm3. AFM studies on GaN buffer layer show a dislocation density of 2 × 108/cm2 by wet etching in hot phosphoric acid. The refractive indices of GaN buffer layer on sapphire at 633 nm are 2.3544 and 2.1515 for TE and TM modes respectively.

  2. Nanocrystalline silicon and silicon quantum dots formation within amorphous silicon carbide by plasma enhanced chemical vapour deposition method controlling the Argon dilution of the process gases

    Structural and optical properties of the amorphous silicon carbide (a-SiC:H) thin films deposited by radio frequency plasma enhanced chemical vapour deposition method from a mixture of silane (SiH4) and methane (CH4) diluted in argon (Ar) have been studied with variation of Ar dilution from 94% to 98.4%. It is observed that nanocrystalline silicon starts to form within the a-SiC:H matrix by increasing the dilution to 96%. With further increase in Ar dilution to 98% formation of the silicon nanocrystals (nc-Si) with variable size is enhanced. The optical band gap (Eg) of the a-SiC:H film decreases from 2.0 eV to 1.9 eV with increase in Ar dilution from 96% to 98% as the a-SiC:H films gradually become Si rich. On increasing the Ar dilution further to 98.4% leads to the appearance of crystalline silicon quantum dots (c-Si q-dots) of nearly uniform size of 3.5 nm. The quantum confinement effect is apparent from the sharp increase in the Eg value to 2.6 eV. The phase transformation phenomenon from nc-Si within the a-SiC:H films to Si q-dot were further studied by high resolution transmission electron microscopy and the grazing angle X-ray diffraction spectra. A relaxation in the lattice strain has been observed with the formation of Si q-dots.

  3. ZT thin films produced by metal organic-chemical vapour deposition to be used as high-k dielectrics

    In this work the synthesis and characterisation of ZrxTi1-xO2 (ZT) grown via a non conventional MOCVD apparatus on both silicon and platinum coated substrates are described. The samples have been chemically, morphologically and structurally characterised by AFM, XRD, SEM + FEG and XPS. Also high and low frequencies electrical characterisation has been performed to evaluate a possible application of such materials as high-k dielectrics

  4. A dilute Cu(Ni) alloy for synthesis of large-area Bernal stacked bilayer graphene using atmospheric pressure chemical vapour deposition

    A bilayer graphene film obtained on copper (Cu) foil is known to have a significant fraction of non-Bernal (AB) stacking and on copper/nickel (Cu/Ni) thin films is known to grow over a large-area with AB stacking. In this study, annealed Cu foils for graphene growth were doped with small concentrations of Ni to obtain dilute Cu(Ni) alloys in which the hydrocarbon decomposition rate of Cu will be enhanced by Ni during synthesis of large-area AB-stacked bilayer graphene using atmospheric pressure chemical vapour deposition. The Ni doped concentration and the Ni homogeneous distribution in Cu foil were confirmed with inductively coupled plasma optical emission spectrometry and proton-induced X-ray emission. An electron backscatter diffraction map showed that Cu foils have a single (001) surface orientation which leads to a uniform growth rate on Cu surface in early stages of graphene growth and also leads to a uniform Ni surface concentration distribution through segregation kinetics. The increase in Ni surface concentration in foils was investigated with time-of-flight secondary ion mass spectrometry. The quality of graphene, the number of graphene layers, and the layers stacking order in synthesized bilayer graphene films were confirmed by Raman and electron diffraction measurements. A four point probe station was used to measure the sheet resistance of graphene films. As compared to Cu foil, the prepared dilute Cu(Ni) alloy demonstrated the good capability of growing large-area AB-stacked bilayer graphene film by increasing Ni content in Cu surface layer

  5. A dilute Cu(Ni) alloy for synthesis of large-area Bernal stacked bilayer graphene using atmospheric pressure chemical vapour deposition

    Madito, M. J.; Bello, A.; Dangbegnon, J. K.; Oliphant, C. J.; Jordaan, W. A.; Momodu, D. Y.; Masikhwa, T. M.; Barzegar, F.; Fabiane, M.; Manyala, N.

    2016-01-01

    A bilayer graphene film obtained on copper (Cu) foil is known to have a significant fraction of non-Bernal (AB) stacking and on copper/nickel (Cu/Ni) thin films is known to grow over a large-area with AB stacking. In this study, annealed Cu foils for graphene growth were doped with small concentrations of Ni to obtain dilute Cu(Ni) alloys in which the hydrocarbon decomposition rate of Cu will be enhanced by Ni during synthesis of large-area AB-stacked bilayer graphene using atmospheric pressure chemical vapour deposition. The Ni doped concentration and the Ni homogeneous distribution in Cu foil were confirmed with inductively coupled plasma optical emission spectrometry and proton-induced X-ray emission. An electron backscatter diffraction map showed that Cu foils have a single (001) surface orientation which leads to a uniform growth rate on Cu surface in early stages of graphene growth and also leads to a uniform Ni surface concentration distribution through segregation kinetics. The increase in Ni surface concentration in foils was investigated with time-of-flight secondary ion mass spectrometry. The quality of graphene, the number of graphene layers, and the layers stacking order in synthesized bilayer graphene films were confirmed by Raman and electron diffraction measurements. A four point probe station was used to measure the sheet resistance of graphene films. As compared to Cu foil, the prepared dilute Cu(Ni) alloy demonstrated the good capability of growing large-area AB-stacked bilayer graphene film by increasing Ni content in Cu surface layer.

  6. A dilute Cu(Ni) alloy for synthesis of large-area Bernal stacked bilayer graphene using atmospheric pressure chemical vapour deposition

    Madito, M. J.; Bello, A.; Dangbegnon, J. K.; Momodu, D. Y.; Masikhwa, T. M.; Barzegar, F.; Manyala, N., E-mail: ncholu.manyala@up.ac.za [Department of Physics, Institute of Applied Materials, SARCHI Chair in Carbon Technology and Materials, University of Pretoria, Pretoria 0028 (South Africa); Oliphant, C. J.; Jordaan, W. A. [National Metrology Institute of South Africa, Private Bag X34, Lynwood Ridge, Pretoria 0040 (South Africa); Fabiane, M. [Department of Physics, Institute of Applied Materials, SARCHI Chair in Carbon Technology and Materials, University of Pretoria, Pretoria 0028 (South Africa); Department of Physics, National University of Lesotho, P.O. Roma 180 (Lesotho)

    2016-01-07

    A bilayer graphene film obtained on copper (Cu) foil is known to have a significant fraction of non-Bernal (AB) stacking and on copper/nickel (Cu/Ni) thin films is known to grow over a large-area with AB stacking. In this study, annealed Cu foils for graphene growth were doped with small concentrations of Ni to obtain dilute Cu(Ni) alloys in which the hydrocarbon decomposition rate of Cu will be enhanced by Ni during synthesis of large-area AB-stacked bilayer graphene using atmospheric pressure chemical vapour deposition. The Ni doped concentration and the Ni homogeneous distribution in Cu foil were confirmed with inductively coupled plasma optical emission spectrometry and proton-induced X-ray emission. An electron backscatter diffraction map showed that Cu foils have a single (001) surface orientation which leads to a uniform growth rate on Cu surface in early stages of graphene growth and also leads to a uniform Ni surface concentration distribution through segregation kinetics. The increase in Ni surface concentration in foils was investigated with time-of-flight secondary ion mass spectrometry. The quality of graphene, the number of graphene layers, and the layers stacking order in synthesized bilayer graphene films were confirmed by Raman and electron diffraction measurements. A four point probe station was used to measure the sheet resistance of graphene films. As compared to Cu foil, the prepared dilute Cu(Ni) alloy demonstrated the good capability of growing large-area AB-stacked bilayer graphene film by increasing Ni content in Cu surface layer.

  7. TPR system: a powerful technique to monitor carbon nanotube formation during chemical vapour deposition; Sistema RTP: uma tecnica poderosa para o monitoramento da formacao de nanotubos de carbono durante o processo por deposicao de vapor quimico

    Tristao, Juliana Cristina; Moura, Flavia Cristina Camilo; Lago, Rochel Montero, E-mail: rochel@ufmg.b [Universidade Federal de Minas Gerais (DQ/UFMG), Belo Horizonte, MG (Brazil). Dept. de Quimica; Sapag, Karim [Universidade Nacional de San Luis (Argentina). Lab. de Ciencias de Superficies y Medios Porosos

    2010-07-01

    In this work, a TPR (Temperature Programmed Reduction) system is used as a powerful tool to monitor carbon nanotubes production during CVD (Chemical Vapour Deposition), The experiments were carried out using catalyst precursors based on Fe-Mo supported on Al{sub 2}O{sub 3} and methane as carbon source. As methane reacts on the Fe metal surface, carbon is deposited and H2 is produced. TPR is very sensitive to the presence of H2 and affords information on the temperature where catalyst is active to form different forms of carbon, the reaction kinetics, the catalyst deactivation and carbon yields. (author)

  8. Technical committee meeting on aerosol formation, vapour deposits and sodium vapour trapping. Summary report

    The papers presented at the LMFBR meeting on aerosol formation covered the following four main topics: theoretical studies on aerosol behaviour and comparison with experimental results; techniques for measurement of aerosols; techniques for trapping sodium vapour and aerosols in gas circuits; design of components having to cope with aerosol deposits. The resulting summaries, conclusions and recommendations which were were agreed upon are presented

  9. Precursor design of vapour deposited cubic boron nitride versus diamond

    The similarities and dissimilarities in the growth of diamond vs. cubic boron nitride (c-BN) were studied using quantum mechanical calculations. Great similarities were observed when considering the surface stabilization by H atoms. Very great similarities were recorded when considering the adsorption of various growth species to these materials. It was found necessary to avoid mixtures of B- and N-containing species in the gas phase during c-BN growth, since they should most probably result in a mixture of these species also on the surfaces. Greater dissimilarities were observed when studying the surface migrations on the diamond and c-BN surfaces and nucleation of the cubic phases on the corresponding hexagonal ones. Nucleation of diamond/c-BN on graphite/h-BN was found to be energetically feasible. This was calculated to be especially the situation for the armchair edge of the basal plane of h-BN and of the zigzag edge of the basal plane of graphite. These theoretical results can be used as guidelines in the strive towards thin film deposition of c-BN using gentle chemical vapour deposition methods like atomic layer deposition. (author)

  10. Epitaxial growth of antiphase boundary free GaAs layer on 300 mm Si(001) substrate by metalorganic chemical vapour deposition with high mobility

    Alcotte, R.; Martin, M.; Moeyaert, J.; Cipro, R.; David, S.; Bassani, F.; Ducroquet, F.; Bogumilowicz, Y.; Sanchez, E.; Ye, Z.; Bao, X. Y.; Pin, J. B.; Baron, T.

    2016-04-01

    Metal organic chemical vapor deposition of GaAs on standard nominal 300 mm Si(001) wafers was studied. Antiphase boundary (APB) free epitaxial GaAs films as thin as 150 nm were obtained. The APB-free films exhibit an improvement of the room temperature photoluminescence signal with an increase of the intensity of almost a factor 2.5. Hall effect measurements show an electron mobility enhancement from 200 to 2000 cm2/V s. The GaAs layers directly grown on industrial platform with no APBs are perfect candidates for being integrated as active layers for nanoelectronic as well as optoelectronic devices in a CMOS environment.

  11. Investigations on the effects of plasma-assisted pre-treatment for plasma-assisted chemical vapour deposition TiN coatings on tool steel

    Gammer, K.; Stoiber, M.; Wagner, J.; Hutter, H.; Kullmer, R.; Mitterer, C

    2004-08-16

    Different mixtures of hydrogen, nitrogen and argon were tested for the cleaning and nitriding of cold-working, high chromium tool steel, prior to TiN deposition with the aim of improving adhesion of the TiN layer. It is well known that the condition of the substrate surface and hardening of the substrate by nitriding have a large influence on the adhesion strength of films. Good adhesion was achieved when nitrogen-hydrogen atmosphere with 40%-80% nitrogen (and 20%-60% hydrogen, respectively) was used, the best adhesion quality values were achieved (HF 1-2) with 40% nitrogen. With higher or lower fractions of nitrogen in the pre-treatment gas, adhesion was reduced. Argon addition also had negative effects on the adhesion strength. The microstructure and chemical composition of the near-interface region of the differently pretreated samples were analysed using secondary ion mass spectrometry, X-ray diffraction and light optical microscopy.

  12. Investigations on the effects of plasma-assisted pre-treatment for plasma-assisted chemical vapour deposition TiN coatings on tool steel

    Different mixtures of hydrogen, nitrogen and argon were tested for the cleaning and nitriding of cold-working, high chromium tool steel, prior to TiN deposition with the aim of improving adhesion of the TiN layer. It is well known that the condition of the substrate surface and hardening of the substrate by nitriding have a large influence on the adhesion strength of films. Good adhesion was achieved when nitrogen-hydrogen atmosphere with 40%-80% nitrogen (and 20%-60% hydrogen, respectively) was used, the best adhesion quality values were achieved (HF 1-2) with 40% nitrogen. With higher or lower fractions of nitrogen in the pre-treatment gas, adhesion was reduced. Argon addition also had negative effects on the adhesion strength. The microstructure and chemical composition of the near-interface region of the differently pretreated samples were analysed using secondary ion mass spectrometry, X-ray diffraction and light optical microscopy

  13. Epitaxial growth of antiphase boundary free GaAs layer on 300 mm Si(001 substrate by metalorganic chemical vapour deposition with high mobility

    R. Alcotte

    2016-04-01

    Full Text Available Metal organic chemical vapor deposition of GaAs on standard nominal 300 mm Si(001 wafers was studied. Antiphase boundary (APB free epitaxial GaAs films as thin as 150 nm were obtained. The APB-free films exhibit an improvement of the room temperature photoluminescence signal with an increase of the intensity of almost a factor 2.5. Hall effect measurements show an electron mobility enhancement from 200 to 2000 cm2/V s. The GaAs layers directly grown on industrial platform with no APBs are perfect candidates for being integrated as active layers for nanoelectronic as well as optoelectronic devices in a CMOS environment.

  14. Porous Silicon & Titanium Dioxide Coatings Prepared by Atmospheric Pressure Plasma Jet Chemical Vapour Deposition Technique-A Novel Coating Technology for Photovoltaic Modules

    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.

  15. A catalyst-free synthesis of germanium nanowires obtained by combined X-ray chemical vapour deposition of GeH$_4$ and low-temperature thermal treatment techniques

    CHIARA DEMARIA; ALDO ARRAIS; PAOLA BENZI; ENRICO BOCCALERI; PAOLA ANTONIOTTI; ROBERTO RABEZZANA; LORENZA OPERTI

    2016-04-01

    A catalyst-free innovative synthesis, by combined X-ray chemical vapour deposition and lowtemperature thermal treatments, which has not been applied since so far to the growth of germanium nanowires (Ge-NWs), produced high yields of the nanoproducts with theGeH4 reactant gas. Nanowires were grown on both surfaces of a conventional deposition quartz substrate. They were featured with high purity and very large aspect ratios (ranging from 100 to 500). Products were characterized by scanning electron microscopy with energy-dispersiveatomic X-ray fluorescence and transmission electron microscopies, X-ray powder diffraction diffractometry, thermogravimetric analysis with differential scanning calorimetry, vibrational infrared and Raman and ultraviolet–visible–near infrared spectroscopies. A quantitative nanowire bundles formation was observed in the lower surface of the quartz substrate positioned over a heating support, whilst spots of nanoflowers constituted by Ge-NWs emerged from a bulk amorphous germanium film matter, deposited on the upper surface of the substrate. Thenanoproducts were characterized by crystalline core morphology, providing semiconductive features and optical band gap of about 0.67 eV. The possible interpretative base-growth mechanisms of the nanowires, stimulated bythe concomitant application of radiant and thermal conditions with no specific added metal catalyst, are hereafter investigated and presented.

  16. Comparative Study of Properties of ZnO/GaN/Al2O3 and ZnO/Al2O3 Films Grown by Low-Pressure Metal Organic Chemical Vapour Deposition

    赵佰军; 杨洪军; 杜国同; 缪国庆; 杨天鹏; 张源涛; 高仲民; 王金忠; 方秀军; 刘大力; 李万成; 马燕; 杨晓天; 刘博阳

    2003-01-01

    ZnO films were deposited by low-pressure metal organic chemical vapour deposition on epi-GaN/Al2O3 films and c-Al2O3 substrates.The structure and optical properties of the ZnO/GaN/Al2O3 and ZnO/Al2O3 films have been investigated to determine the differences between the two substrates.ZnO films on GaN/Al2O3 show very strong emission features associated with exciton transitions,just as ZnO films on Al2O3,while the crystalline structural qualities for ZnO films on GaN/Al2O3 are much better than those for ZnO films directly grown on Al2O3 substrates.Zn and O elements in the deposited ZnO/GaN/Al2O3 and ZnO/Al2O3 films are investigated and compared by x-ray photoelectron spectroscopy.According to the statistical results,the Zn/O ratio changes from Zn-rich for ZnO/Al2O3 films to O-rich for ZnO/GaN/Al2O3 films.

  17. Chemical vapour deposition of graphene on Nk(111) and Co(0001) and intercalation with Au to study Dirac Cone Formation and Rashba splitting

    Sanchez-Barriga, J.; Vescovo, E.; Varykhalov, A.; Scholz, M.R.; Rader, O.; Marchenko, D.; Rybkin, A.

    2010-01-01

    We show in detail monitoring by photoelectron spectroscopy how graphene can be grown by chemical vapor deposition on the transition-metal surfaces Ni(111) and Co(0001) and intercalated by a monoatomic layer of Au. For both systems, a linear E(k) dispersion of massless Dirac fermions appears in the graphene {pi}-band in the vicinity of the Fermi energy. In order to study ferromagnetism and spin-orbit effects by spin- and angle-resolved photoelectron spectroscopy, the sample must be magnetized in remanence. To this end, a W(110) substrate is prepared, its cleanliness verified by photoemission from W(110) surface states and surface core levels, and epitaxial Ni(111) and Co(0001) thin films are grown on top. Spin-resolved photoemission from the {pi}-band shows that the ferromagnetic polarization of graphene/Ni(111) and graphene/Co(0001) is negligible and that graphene on Ni(111) is after intercalation of Au spin-orbit split by the Rashba effect.

  18. Co3O4 protective coatings prepared by Pulsed Injection Metal Organic Chemical Vapour Deposition

    Burriel, M.; Garcia, G.; Santiso, J.;

    2005-01-01

    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...

  19. Mechanism and efficiency of chemical vapour generation of silver

    Matoušek, Tomáš

    Budapešť, 2005. [European Winter Conference on Plasma Spectrochemistry . Budapest (HU), 30.01.2005-03.02.2005] R&D Projects: GA ČR(CZ) GA203/01/0453 Institutional research plan: CEZ:AV0Z40310501 Keywords : silver * chemical vapour generation * ICP-OES Subject RIV: CB - Analytical Chemistry, Separation

  20. SiCN Amorphous Materials Chemical Vapour Deposited Using the Si(CH3)4-NH3-H2 System

    Bendeddouche, A.; Berjoan, R.; Bêche, E.; Schamm, S.; Serin, V.; Carles, R.; Hillel, R.

    1995-01-01

    Elaboration of amorphous SiCN materials was perfomed using a conventional thermaly activated CVD at 1000-1200°C from the TMS-NH3-H2 system. The influence on the deposition rate and the composition was investigated using an experimental design by varying : deposition temperature, pressure and NH3 flow rate. A set of 16 samples SiCxNy with x/y ranged from 0.04 to 1.69 was prepared. Accurate determination of the elemental compositon required EPMA-WDS and XPS and occasionally RBS analyses. The ch...

  1. Process control by optical emission spectroscopy during growth of a-C:H from a CH4 plasma by plasma-enhanced chemical vapour deposition

    Barholm-Hansen, C; Bentzon, MD; Vigild, Martin Etchells; Findeisen, Eberhard; Feidenhans'l, Robert Krarup; Bindslev Hansen, J

    1994-01-01

    various flow rates of CH4. Their thickness, mass density and hydrogen content were determined by a combination of X-ray and neutron reflectivity measurements. Dissociation of the feed gas is determined relatively by monitoring the integrated peak intensity around the CH 431 nm band head as a function of...... the gas flow. Above a certain flow rate the intensity saturates, since the deposition process is limited by the power input. At low flow rates a large fraction of the feed gas is dissociated and the deposition is limited by the supply of feed gas. A relationship was found for the intensity of the CH....... During plasma cleaning, the emission from the OH radical at 306.4 nm indicated that H2O was initially present in the discharge. The OH signal typically vanished during the cleaning cycle, which indicates that it was due to adsorbed water on the inner surfaces of the vacuum chamber and not an impurity in...

  2. Chemical-Engineering Approach for Evaluation of Vapour Permeation Data.

    Sedláková, Zuzana; Morávková, Lenka; Vejražka, Jiří; Izák, Pavel

    Ozarow Mazowiecki: Nobell Compressing sp. z o.o, 2015 - (Kosinsky, K.; Urbanczyk, M.; Žerko, S.), E-026 ISBN N. [Euromembrane Conference 2015. Aachen (DE), 06.09.2015-10.09.2015] R&D Projects: GA MŠk(CZ) LD14094 Institutional support: RVO:67985858 Keywords : organic vapour permeation * membrane separation * chemical-engineering model Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  3. Study of three dimensional germanium islands and ultrathin Si{sub x}Ge{sub 1-x} films grown by chemical vapour deposition on Si(111)-(7 x 7)

    Gopalakrishnan, Selvi

    2005-07-15

    This work probed at the atomic level, processes that occur during the Ge three dimensional island formation and on ultrathin Si{sub x}Ge{sub 1-x} epitaxial growth by chemical vapour deposition on the Si(111)-(7 x 7) substrate with the aid of surface probe techniques such as STM and AFM, XPS, as well as TEM imaging of any 3D island formation. This work could essentially be divided into two parts. The first part studied the growth of the strained Ge on Si system with emphasis on the characterisation of the CVD grown three dimensional germanium islands on a standard Si(111)-(7 x 7) substrate as well as on a surface modified Si(111)-(7 x 7) substrate. The characterisation was carried out using a combination of techniques. XPS was used to calculate the effective coverages of deposited germanium, the STM was used to image the top most layers whenever possible and AFM, cross-sectional TEM and HRTEM to image the three dimensional islands. The possible causes of the surface modification were also examined. In the second part of this work the growth morphologies ultrathin Si{sub x}Ge{sub 1-x} layers grown on the Si(111)-(7 x 7) substrate at 750 K where the hydrogen desorption rate from the Si(111) surface is low and at 850 K which was the temperature at which the rate of hydrogen desorption from the Si(111) surface was a maximum were investigated. In addition modelling of ultrathin layer growth was carried out using two existing growth models. (orig.)

  4. Process control by optical emission spectroscopy during growth of a-C:H from a CH4 plasma by plasma-enhanced chemical vapour deposition

    Barholm-Hansen, C; Bentzon, MD; Vigild, Martin Etchells;

    1994-01-01

    During the growth of a-C:H thin films for tribological applications, the characteristic optical emission from a CH4 plasma was used to estimate growth conditions such as the degree of dissociation of the feed gas, the deposition rate and the presence of impurities. Films were fabricated with....... During plasma cleaning, the emission from the OH radical at 306.4 nm indicated that H2O was initially present in the discharge. The OH signal typically vanished during the cleaning cycle, which indicates that it was due to adsorbed water on the inner surfaces of the vacuum chamber and not an impurity in...... various flow rates of CH4. Their thickness, mass density and hydrogen content were determined by a combination of X-ray and neutron reflectivity measurements. Dissociation of the feed gas is determined relatively by monitoring the integrated peak intensity around the CH 431 nm band head as a function of...

  5. Effect of Silane Flow Rate on Structure and Corrosion Resistance of Ti–Si—N Thin Films Deposited by a Hybrid Cathodic Arc and Chemical Vapour Process

    Ti–Si–N thin films with different silicon contents are deposited by a cathodic arc technique in an Ar+N2 +SiH4 mixture atmosphere. With the increase of silane Bow rate, the content of silicon in the Ti–Si–N films varies from 2.0 at. % to 12.2 at. %. Meanwhile, the cross-sectional morphology of these films changes from an apparent columnar microstructure to a dense fine-grained structure. The x-ray diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS) results show that the Ti–Si–N film consists of TiN crystallites and SiNx amorphous phase. The corrosion resistance is improved with the increase of silane Bow rate. Growth defects in the films produced play a key role in the corrosion process, especially for the local corrosion. The porosity of the films decreases from 0.13% to 0.00032% by introducing silane at the Bow rate of 14sccm. (gases, plasmas, and electric discharges)

  6. Effect of silane flow rate on structure and corrosion resistance of Ti-Si-N thin films deposited by a hybrid cathodic arc and chemical vapour process

    Ti-Si-N thin films with different silicon contents are deposited by a cathodic arc technique in an Ar+N2+SiH4 mixture atmosphere. With the increase of silane flow rate, the content of silicon in the Ti-Si-N films varies from 2.0 at.% to 12.2 at.%. Meanwhile, the cross-sectional morphology of these films changes from an apparent columnar microstructure to a dense fine-grained structure. The x-ray diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS) results show that the Ti-Si-N film consists of TiN crystallites and SiNx amorphous phase. The corrosion resistance is improved with the increase of silane flow rate. Growth defects in the films produced play a key role in the corrosion process, especially for the local corrosion. The porosity of the films decreases from 0.13% to 0.00032% by introducing silane at the flow rate of 14 sccm. (authors)

  7. Self-assembled arrays of peptide nanotubes by vapour deposition.

    Adler-Abramovich, Lihi; Aronov, Daniel; Beker, Peter; Yevnin, Maya; Stempler, Shiri; Buzhansky, Ludmila; Rosenman, Gil; Gazit, Ehud

    2009-12-01

    The use of bionanostructures in real-world applications will require precise control over biomolecular self-assembly and the ability to scale up production of these materials. A significant challenge is to control the formation of large, homogeneous arrays of bionanostructures on macroscopic surfaces. Previously, bionanostructure formation has been based on the spontaneous growth of heterogenic populations in bulk solution. Here, we demonstrate the self-assembly of large arrays of aromatic peptide nanotubes using vapour deposition methods. This approach allows the length and density of the nanotubes to be fine-tuned by carefully controlling the supply of the building blocks from the gas phase. Furthermore, we show that the nanotube arrays can be used to develop high-surface-area electrodes for energy storage applications, highly hydrophobic self-cleaning surfaces and microfluidic chips. PMID:19893524

  8. Sistema RTP: uma técnica poderosa para o monitoramento da formação de nanotubos de carbono durante o processo por deposição de vapor químico TPR system: a powerful technique to monitor carbon nanotube formation during chemical vapour deposition

    Juliana Cristina Tristão

    2010-01-01

    Full Text Available In this work, a TPR (Temperature Programmed Reduction system is used as a powerful tool to monitor carbon nanotubes production during CVD (Chemical Vapour Deposition, The experiments were carried out using catalyst precursors based on Fe-Mo supported on Al2O3 and methane as carbon source. As methane reacts on the Fe metal surface, carbon is deposited and H2 is produced. TPR is very sensitive to the presence of H2 and affords information on the temperature where catalyst is active to form different forms of carbon, the reaction kinetics, the catalyst deactivation and carbon yields.

  9. The metal-organic chemical vapour deposition and optical studies of ZnSe1-xTex and CdS1-xTex epilayers and tellurium doped ZnS/CdS superlattices

    This work sought to achieve efficient room temperature blue photoluminescence (PL) from II-VI superlattices by incorporation of tellurium (Te) exciton traps into the wells. In preparation for this, the growth and optical properties of ZnSe1-xTex and CdS1-xTex dilute alloy epilayers were first investigated. The epilayer and superlattice samples were prepared using atmospheric pressure metal-organic chemical vapour deposition (AP-MOCVD). The dependence of Te concentration (x) on the growth precursors and conditions used was investigated. This led to an understanding of the relative stabilities of the precursors used, as well as the best growth conditions required to control Te concentrations. A diffusion doping technique was also developed for growth of low Te concentration ZnSe:Te and CdS:Te epilayers. The corresponding concentration and PL results for these layers were used to confirm the expected microscopic nature of the Te centres. The low temperature (1.8K) PL emission intensities from ZnSe1-xTex and CdS1-xTex epilayers were intense, but found to decrease rapidly with increasing temperature despite the large exciton trapping energies. A theoretical capture cross section model was thus developed to explain these observations. In addition, application of this model allowed the microscopic size of Te centres to be obtained, thereby explaining the different appearance of corresponding PL bands. In view of the more persistent emissions from CdS1-xTex layers compared with those of ZnSe1-xTex, it was decided to grow Te doped ZnS/CdS:Te superlattices. The ZnS/CdS:Te superlattices were found give the intended blue emission. However, structural disruption in these superlattice samples led to quenching of this emission at room temperature. Finally, it was found that the degree of electron-phonon coupling to Te centres was less in superlattice structures compared to epilayers. (author)

  10. Low Temperature Growth of In2O3and InN Nanocrystals on Si(111 via Chemical Vapour Deposition Based on the Sublimation of NH4Cl in In

    Tsokkou Demetra

    2009-01-01

    Full Text Available Abstract Indium oxide (In2O3 nanocrystals (NCs have been obtained via atmospheric pressure, chemical vapour deposition (APCVD on Si(111 via the direct oxidation of In with Ar:10% O2at 1000 °C but also at temperatures as low as 500 °C by the sublimation of ammonium chloride (NH4Cl which is incorporated into the In under a gas flow of nitrogen (N2. Similarly InN NCs have also been obtained using sublimation of NH4Cl in a gas flow of NH3. During oxidation of In under a flow of O2the transfer of In into the gas stream is inhibited by the formation of In2O3around the In powder which breaks up only at high temperatures, i.e.T > 900 °C, thereby releasing In into the gas stream which can then react with O2leading to a high yield formation of isolated 500 nm In2O3octahedrons but also chains of these nanostructures. No such NCs were obtained by direct oxidation forT G < 900 °C. The incorporation of NH4Cl in the In leads to the sublimation of NH4Cl into NH3and HCl at around 338 °C which in turn produces an efficient dispersion and transfer of the whole In into the gas stream of N2where it reacts with HCl forming primarily InCl. The latter adsorbs onto the Si(111 where it reacts with H2O and O2leading to the formation of In2O3nanopyramids on Si(111. The rest of the InCl is carried downstream, where it solidifies at lower temperatures, and rapidly breaks down into metallic In upon exposure to H2O in the air. Upon carrying out the reaction of In with NH4Cl at 600 °C under NH3as opposed to N2, we obtain InN nanoparticles on Si(111 with an average diameter of 300 nm.

  11. CHEMICAL VAPOUR INFILTRATION (CVI) OF SILICON CARBIDE FIBRE PREFORMS

    Lundberg, R.; Pejryd, L.; LÖÖf, G.

    1991-01-01

    An alternative fabrication technique is proposed for ceramic matrix / ceramic fibre composites involving filling a fibre fabric preform with a Si/Si3 N4 slurry and subsequently reaction bonding. For the first processing step in this process, chemical vapour infiltration (CVI) was evaluated as a means of both biding together and protecting the fibres. SiC (Nicalon) fibre preforms consisting of through-stitched 2D fabrics were infiltrated. The preform thickness was more than 4 mm and a 3 µm TiC...

  12. The exchange reaction between deuterium and water vapour on platinum deposited over a hydrophobic support

    Isotope exchange reaction between deuterium gas and water vapour at room temperature and below on platinum deposited on hydrophobic supports such as polytetrafluoroethylene (PTFE) or Porapak Q (copolymer of styrene and divinylbenzene) was studied and the results were compared with those of the exchange reaction on platinum over hydrophilic support such as alumina. It was demonstrated that the exchange reaction at temperatures below the boiling point of water is markedly retarded by the multilayer adsorption of water over the platinum catalyst deposited on hydrophilic support, whereas the platinum catalyst on hydrophobic support exhibited a high catalytic activity, being not retarded by the water, forming no multilayer of adsorbed water over platinum surface. Therefore in the case of the hydrogen isotope exchange reaction on platinum over hydrophobic support, the chemical exchange rate can be measured even under a saturated vapour pressure of water. The surface area of platinum was estimated by hydrogen chemisorption and hydrogen titration and specific activities of the catalyst were calculated at both room temperature and freezing point of water, which revealed that the specific rate of this reaction does not differ so much over various supports. (orig.)

  13. Photocatalytic property of titanium dioxide thin films deposited by radio frequency magnetron sputtering in argon and water vapour plasma

    Sirghi, L.; Hatanaka, Y.; Sakaguchi, K.

    2015-10-01

    The present work is investigating the photocatalytic activity of TiO2 thin films deposited by radiofrequency magnetron sputtering of a pure TiO2 target in Ar and Ar/H2O (pressure ratio 40/3) plasmas. Optical absorption, structure, surface morphology and chemical structure of the deposited films were comparatively studied. The films were amorphous and included a large amount of hydroxyl groups (about 5% of oxygen atoms were bounded to hydrogen) irrespective of the intentional content of water in the deposition chamber. Incorporation of hydroxyl groups in the film deposited in pure Ar plasma is explained as contamination of the working gas with water molecules desorbed by plasma from the deposition chamber walls. However, intentional input of water vapour into the discharge chamber decreased the deposition speed and roughness of the deposited films. The good photocatalytic activity of the deposited films could be attributed hydroxyl groups in their structures.

  14. The beauty of frost: nano-sulfur assembly via low pressure vapour deposition.

    Wang, Yu; Chen, Lu; Scudiero, Louis; Zhong, Wei-Hong

    2015-11-14

    A low pressure vapour deposition (LPVD) technique is proposed as an environmentally friendly, cost-effective and versatile strategy for fabrication of sulfur nanomaterials. By controlling the characteristics of the deposit substrate for the LPVD, various sulfur-based nanomaterials have been obtained through a substrate-induced self-assembly process. PMID:26383233

  15. Electrochemical vapour deposition of SOFC interconnection materials. Doctoral thesis

    van Dieten, V.

    1995-01-23

    The aim of this thesis is to investigate the synthesis of the SOFC (Solid Oxide Fuel Cells) interconnection material Mg-doped LaCrO3 by means of EVD (electrochemical vapor deposition). Although the EVD process is the key technology for the fabrication of the interconnect of the Westinghouse tubular concept SOFC, very little has been published on this subject. Nearly all publications on EVD are dealing with the synthesis of the electrolyte material YSZ. In Chapter 2 the principle of the EVD process is described, as well as the experimental setups used for the synthesis experiments. In Chapter 3 a thermodynamic analysis of the La-Cr-Mg-O-H-Cl-Ar system is made in order to determine how the EVD process conditions may affect the incorporation of magnesium in LaCrO3, and to predict the range of experimental conditions for the synthesis of Mg-doped LaCrO3 by means of CVD (chemical vapor deposition)/EVD. In Chapter 4 the EVD stage of the growth process is modeled. The experimental results of the synthesis of Mg-doped LaCrO3 on porous and gastight substrates are described in Chapter 5. In Chapter 6 the first results on the synthesis of the perovskite oxide YCrO3, a material resembling LaCrO3, by means of particle-precipitation-aided CVD(PP-CVD) are described, as well as the principles of the process.

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

    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.

  17. Synthesis of Pt nanowires with the participation of physical vapour deposition

    Dobrzański Leszek A.; Szindler Marek; Pawlyta Mirosława; Szindler Magdalena M.; Boryło Paulina; Tomiczek Błazej

    2016-01-01

    The following paper presents the possibility of formation of Pt nanowires, achieved by a three-step method consisting of conformal deposition of a carbon nanotube and conformal coverage with platinum by physical vapour deposition, followed by removal of the carbonaceous template. The characterization of this new nanostructure was carried out through scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD).

  18. Surface chemical studies of chemical vapour deposited diamond thin films

    Proffitt, S

    2001-01-01

    could not easily be correlated to the bulk film properties. It is suggested that electron emission arises from the graphite component of graphite- diamond grain boundaries that are present in the nanocrystalline films. species. The adsorbed O and Cl species are more strongly bound to the K layer than they are to the diamond substrate, so thermal desorption of K from the K/CI/diamond or K/O/diamond surface results also in the simultaneous loss ofO and Cl. The phosphorus precursor trisdimethylaminophosphine (TDMAP) has a negligible reactive sticking probability on the clean diamond surface. This can be increased by thermal cracking of the gas phase precursor by a heated filament, resulting in non-activated adsorption to produce an adlayer containing a mixture of surface-bound ligands and phosphorus containing species. The ligands were readily lost upon heating, leaving P, some of which was lost from the surface at higher temperatures. Pre-hydrogenation of the diamond surface inhibited the uptake of cracked TDMA...

  19. Synthetic Graphene Grown by Chemical Vapor Deposition on Copper Foils

    Chung, Ting Fung; Shen, Tian; Cao, Helin; Jauregui, Luis A.; Wu, Wei; Yu, Qingkai; Newell, David; Chen, Yong P.

    2013-01-01

    The discovery of graphene, a single layer of covalently bonded carbon atoms, has attracted intense interests. Initial studies using mechanically exfoliated graphene unveiled its remarkable electronic, mechanical and thermal properties. There has been a growing need and rapid development in large-area deposition of graphene film and its applications. Chemical vapour deposition on copper has emerged as one of the most promising methods in obtaining large-scale graphene films with quality compar...

  20. Material design of plasma-enhanced chemical vapour deposition SiCH films for low-k cap layers in the further scaling of ultra-large-scale integrated devices-Cu interconnects

    Cap layers for Cu interconnects in ultra-large-scale integrated devices (ULSIs), with a low dielectric constant (k-value) and strong barrier properties against Cu and moisture diffusion, are required for the future further scaling of ULSIs. There is a trade-off, however, between reducing the k-value and maintaining strong barrier properties. Using quantum mechanical simulations and other theoretical computations, we have designed ideal dielectrics: SiCH films with Si–C2H4–Si networks. Such films were estimated to have low porosity and low k; thus they are the key to realizing a cap layer with a low k and strong barrier properties against diffusion. For fabricating these ideal SiCH films, we designed four novel precursors: isobutyl trimethylsilane, diisobutyl dimethylsilane, 1, 1-divinylsilacyclopentane and 5-silaspiro [4,4] noname, based on quantum chemical calculations, because such fabrication is difficult by controlling only the process conditions in plasma-enhanced chemical vapor deposition (PECVD) using conventional precursors. We demonstrated that SiCH films prepared using these newly designed precursors had large amounts of Si–C2H4–Si networks and strong barrier properties. The pore structure of these films was then analyzed by positron annihilation spectroscopy, revealing that these SiCH films actually had low porosity, as we designed. These results validate our material and precursor design concepts for developing a PECVD process capable of fabricating a low-k cap layer. (paper)

  1. Fabrication of Solar Cells by Deposition of Phosphorous Vapour

    This paper shows the fabrication of solar cells by deposition of phosphorous vapor using 10x10 cm2 polycrystalline silicon wafer. The diffusion process for forming p-n junction was carried out in the conveyor furnace at temperature of 860, 875, and 950 oC with belt velocities at 2, 3, 4, 5, 71/2 and 10 inches per minute (Ipm). The emphasize of the research is for understanding the characterization of the doping of phosphorous in order to obtain better performance of solar cells. At this initial research, it was found that solar cell efficiency is still around 7.5 - 8 % with short circuit current ISC in the range of 2.6 - 2.75 A. The current - voltage (I-V) measurement as well as the electrical parameters of solar cell are also discussed here. (author)

  2. Physical vapour deposition of alkyl phosphonic acid on mica and HOPG investigated by NC-AFM

    We investigate the growth of octadecylphosphonic acid (OPA) self-assembly molecules prepared by physical vapour deposition (PVD) on mica and highly oriented pyrolytic graphite (HOPG) under ultrahigh-vacuum conditions. On samples prepared by immersion from diluted solution on mica self-assembled monolayers are formed, whereas by PVD and subsequent annealing we observe the formation of almost perfect self-assembled bilayers slightly tilted with respect to the surface normal. On the non-polar surface of HOPG, the vapour-deposited molecules adsorb in bilayers parallel to the surface, similar to the films produced by spread coating (Fontes and Neves 2005 Langmuir 21 11113). On all samples we deduce the molecular ordering by means of noncontact atomic force microscopy; on HOPG, even submolecular resolution is obtained. A comparison of our vapour-deposited films with samples prepared by other techniques mentioned in the literature demonstrates that PVD yields excellent film quality, and in many applications might be preferred due to its clean, solution-free environment and the possibility for exact dosage, e.g. for multilayer formation with a defined thickness

  3. Hard chrome and molybdenum coatings produced by physical vapour deposition

    Coatings of solid solutions of carbon or nitrogen in chromium or molybdenum were prepared by cathodic magnetron sputtering. Carbon or nitrogen was introduced either through the gas phase by reactive sputtering or by direct sputtering of sintered composite targets. Chemical and structural analyses of films revealed the formation of supersaturated solid solutions for carbon or nitrogen concentrations of up to several weight per cent. The nitride and carbide phases predicted from the binary diagrams were not observed. The Cr-C and Mo-C coatings showed hardnesses of up to 2500 HV. The hardnesses of Mo-N and Cr-N reached 3000 HV. The wear and corrosion resistance of these coatings, which showed a dense structure, was superior to that of electrolytic hard chrome. (Auth.)

  4. The study and the realization of radiation detectors made from polycrystalline diamond films grown by microwave plasma enhanced chemical vapour deposition technique; Etude et realisation de detecteurs de rayonnements a base de films de diamant polycristallin elabores par depot chimique en phase vapeur assiste par plasma micro-onde

    Jany, Ch

    1998-10-29

    The aim of this work was to develop radiation detectors made from polycrystalline diamond films grown by microwave plasma enhanced chemical vapour deposition technique. The influence of surface treatments, contact technology and diamond growth parameters on the diamond detectors characteristics was investigated in order to optimise the detector response to alpha particles. The first part of the study focused on the electrical behaviour of as-deposited diamond surface, showing a p type conduction and its influence on the leakage current of the device. A surface preparation process was established in order to reduce the leakage current of the device by surface dehydrogenation using an oxidising step. Several methods to form and treat electrical contacts were also investigated showing that the collection efficiency of the device decreases after contact annealing. In the second part, we reported the influence of the diamond deposition parameters on the characteristics of the detectors. The increase of the deposition temperature and/or methane concentration was shown to lead {eta} to decrease. In contrast, {eta} was found to increase with the micro-wave power. The evolution of the diamond detector characteristics results from the variation in sp{sup 2} phases incorporation and in the crystallography quality of the films. These defects increase the leakage current and reduce the carrier mobility and lifetime. Measurements carried out on detectors with different thicknesses showed that the physical properties varies along the growth direction, improving with the film thickness. Finally, the addition of nitrogen (> 10 ppm) in the gas mixture during diamond deposition was found to strongly reduce the collection efficiency of the detectors. To conclude the study, we fabricated and characterised diamond devices which were used for thermal neutron detection and for the intensity and shape measurement of VUV and soft X-ray pulses. (author)

  5. Formation and Yield of Multi-Walled Carbon Nanotubes Synthesized via Chemical Vapour Deposition Routes Using Different Metal-Based Catalysts of FeCoNiAl, CoNiAl and FeNiAl-LDH

    Mohd Zobir Hussein

    2014-11-01

    Full Text Available Multi-walled carbon nanotubes (MWCNTs were prepared via chemical vapor deposition (CVD using a series of different catalysts, derived from FeCoNiAl, CoNiAl and FeNiAl layered double hydroxides (LDHs. Catalyst-active particles were obtained by calcination of LDHs at 800 °C for 5 h. Nitrogen and hexane were used as the carrier gas and carbon source respectively, for preparation of MWCNTs using CVD methods at 800 °C. MWCNTs were allowed to grow for 30 min on the catalyst spread on an alumina boat in a quartz tube. The materials were subsequently characterized through X-ray diffraction, Fourier transform infrared spectroscopy, surface area analysis, field emission scanning electron microscopy and transmission electron microscopy. It was determined that size and yield of MWCNTs varied depending on the type of LDH catalyst precursor that is used during synthesis. MWCNTs obtained using CoNiAl-LDH as the catalyst precursor showed smaller diameter and higher yield compared to FeCoNiAl and FeNiAl LDHs.

  6. Characterization of TiO{sub 2} thin films obtained by metal-organic chemical vapour deposition; Caracterizacao de filmes finos de TiO{sub 2} obtidos por deposicao quimica em fase vapor

    Carriel, Rodrigo Crociati

    2015-07-01

    Titanium dioxide (TiO{sub 2}) thin films were grown on silicon substrate (100) by MOCVD process (chemical deposition of organometallic vapor phase). The films were grown at 400, 500, 600 and 700 ° C in a conventional horizontal equipment. Titanium tetraisopropoxide was used as source of both oxygen and titanium. Nitrogen was used as carrier and purge gas. X-ray diffraction technique was used for the characterization of the crystalline structure. Scanning electron microscopy with field emission gun was used to evaluate the morphology and thickness of the films. The films grown at 400 and 500°C presented anatase phase. The film grown at 600ºC presented rutile besides anatase phase, while the film grown at 700°C showed, in addition to anatase and rutile, brookite phase. In order to evaluate the electrochemical behavior of the films cyclic voltammetry technique was used. The tests revealed that the TiO2 films formed exclusively by the anatase phase exhibit strong capacitive character. The anodic current peak is directly proportional to the square root of the scanning rate for films grown at 500ºC, suggesting that linear diffusion is the predominant mechanism of cations transport. It was observed that in the film grown during 60 minutes the Na+ ions intercalation and deintercalation easily. The films grown in the other conditions did not present the anodic current peak, although charge was accumulated in the film. (author)

  7. Chemical vapour generation of silver: reduced palladium as permanent reaction modifier for enhanced performance

    Matoušek, Tomáš; Sturgeon, R. E.

    2004-01-01

    Roč. 19, č. 8 (2004), s. 1014-1017. ISSN 0267-9477 R&D Projects: GA ČR GA203/01/0453 Institutional research plan: CEZ:AV0Z4031919 Keywords : chemical vapour generation * chemical modification * silver Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.926, year: 2004

  8. Review of analytical techniques to determine the chemical forms of vapours and aerosols released from overheated fuel

    A comprehensive review has been undertaken of appropriate analytical techniques to monitor and measure the chemical effects that occur in large-scale tests designed to study severe reactor accidents. Various methods have been developed to determine the chemical forms of the vapours, aerosols and deposits generated during and after such integral experiments. Other specific techniques have the long-term potential to provide some of the desired data in greater detail, although considerable efforts are still required to apply these techniques to the study of radioactive debris. Such in-situ and post-test methods of analysis have been also assessed in terms of their applicability to the analysis of samples from the Phebus-FP tests. The recommended in-situ methods of analysis are gamma-ray spectroscopy, potentiometry, mass spectrometry, and Raman/UV-visible absorption spectroscopy. Vapour/aerosol and deposition samples should also be obtained at well-defined time intervals during each experiment for subsequent post-test analysis. No single technique can provide all the necessary chemical data from these samples, and the most appropriate method of analysis involves a complementary combination of autoradiography, AES, IR, MRS, SEMS/EDS, SIMS/LMIS, XPS and XRD

  9. Controllable growth of vertically aligned zinc oxide nanowires using vapour deposition

    The controllable growth of vertically aligned ZnO nanowires using a simple vapour deposition method system is reported. The growth properties are studied as a function of the thickness of the Au catalyst layer, total pressure, deposition temperature and oxygen partial pressure. The experiments indicate the existence of five main zones of growth. The zone in which the aligned wires grow varies according to the pressure, temperature and oxygen partial pressure. A specific level of low supersaturation of Zn and oxygen vapour are both necessary to ensure the correct rate of growth, which then leads to having thin and densely aligned wires. The growth kinetics are discussed in terms of the interdependent variables. It was found that the diameter and density of the nanowires is controlled mostly by the growth temperature and pressure. The zone with the most aligned nanowires with the highest aspect ratio was found to be at 5 mbar in a temperature range of 860-800 deg. C with a flow of 27 sccm of a N2/O2 mixture

  10. Crystalline gamma-Al2O3 physical vapour deposition-coating for steel thixoforging tools.

    Bobzin, K; Hirt, G; Bagcivan, N; Khizhnyakova, L; Ewering, M

    2011-10-01

    The process of thixoforming, which has been part of many researches during the last decades, combines the advantages of forging and casting for the shaping of metallic components. But due to the high temperatures of semi-solid steel alloys high demands on the tools are requested. To resists the thermal and mechanical loads (wear, friction, thermal and thermomechanical fatigue) protecting thin films are necessary. In this regard crystalline gamma-Al2O3 deposited via Physical Vapour Deposition (PVD) is a promising candidate: It exhibits high thermal stability, high oxidation resistance and high hot hardness. In the present work the application of a (Ti, Al)N/gamma-Al2O3 coating deposited by means of Magnetron Sputter Ion Plating in an industrial coating unit is presented. The coating was analysed by means of Rockwell test, nanoindentation, and Scanning Electron Microscopy (SEM). The coated tool was tested in thixoforging experiments with steel grade X210CrW12 (AlSI D6). The surface of the coated dies was examined with Scanning Electron Microscope (SEM) after 22, 42, 90 and 170 forging cycles. PMID:22400259

  11. The Chemical Vapour Deposition of Tantalum - in long narrow channels

    Mugabi, James Atwoki; Bjerrum, Niels J.; Petrushina, Irina; Christensen, Erik; Eriksen, Søren

    2014-01-01

    Tantals korrosionsbestandighed i varme sure miljøer samt dets overlegne metalliske egenskaber har gjort det til en førsteklasses løsning som konstruktionsmateriale eller som beskyttende belægning til udstyr beregnet til brug under barske kemiske og fysiske forhold. Den høje pris på tantalmetal begrænser imidlertid dets anvendelse som et grundmateriale til procesudstyr. Et billigere alternativ er at fremstille udstyret af stål for derefter at beskytte det med et tyndt, men effektivt lag af tan...

  12. Chemical vapour deposition (CVD) diamond as thermoluminescence (Tl) dosimeter

    Furetta, C. [Physics Department, University of Rome La Sapienza, Piazzale A. Moro 2, 00185 Rome (Italy)

    1999-07-01

    The aim of this paper is to present a review of the most recent experimental data concerning the CVD diamond as a thermoluminescence detector. Batches of different production have been investigated and the most important dosimetric properties are here reported. The kinetics parameters, such as activation energy, E, frequency factor, s, and kinetic order, b, have been also studied and a phenomenological model of the Tl emission is proposed for the supra linearity behavior of some diamond samples. (Author)

  13. Chemical vapour deposition of vanadium oxide thermochromic thin films

    Piccirillo, Clara

    2012-01-01

    Thermochromic materials change optical properties, such as transmittance or reflectance, with a variation in temperature. An ideal intelligent (smart) material will allow solar radiation in through a window in cold conditions, but reflect that radiation in warmer conditions. The variation in the properties is often associated with a phase change, which takes place at a definite temperature, and is normally reversible. Such materials are usually applied to window glass as thi...

  14. Chemical vapour deposition (CVD) diamond as thermoluminescence (Tl) dosimeter

    The aim of this paper is to present a review of the most recent experimental data concerning the CVD diamond as a thermoluminescence detector. Batches of different production have been investigated and the most important dosimetric properties are here reported. The kinetics parameters, such as activation energy, E, frequency factor, s, and kinetic order, b, have been also studied and a phenomenological model of the Tl emission is proposed for the supra linearity behavior of some diamond samples. (Author)

  15. Point and extended defects in chemical vapour deposited diamond

    Homoepitaxially grown single crystal CVD diamond has a dislocation arrangement not seen in natural IIa diamond. Whereas in the latter, dislocations lie on (111) planes along [11-bar 0] directions, dislocations in CVD diamond lie nearly along the [001] growth axis and are arranged in bundles with almost four fold rotational symmetry. Their large strain is easily seen in birefringence and we model the arrangements in the bundle to account for the singular behaviour of the birefringence when the polarisers are rotated with respect to the crystal. The optical absorption spectrum of brown CVD diamond displays a continuum similar to that found in brown IIa natural diamonds but in addition broad point defect induced bands. We investigate the suggestion that the 2.38 eV (560 nm) peak is related to VNH. We suggest that the breadth of these bands is related to the large structural change when the defect is excited.

  16. Chemical vapour deposition: Transition metal carbides go 2D

    Gogotsi, Yury

    2015-11-01

    The unique properties of 2D materials, such as graphene or transition metal dichalcogenides, have been attracting much attention in the past decade. Now, metallically conductive and even superconducting transition metal carbides are entering the game.

  17. Simple Chemical Vapor Deposition Experiment

    Pedersen, Henrik

    2014-01-01

    Chemical vapor deposition (CVD) is a process commonly used for the synthesis of thin films for several important technological applications, for example, microelectronics, hard coatings, and smart windows. Unfortunately, the complexity and prohibitive cost of CVD equipment makes it seldom available for undergraduate chemistry students. Here, a…

  18. Ballistic transport in graphene grown by chemical vapor deposition

    In this letter, we report the observation of ballistic transport on micron length scales in graphene synthesised by chemical vapour deposition (CVD). Transport measurements were done on Hall bar geometries in a liquid He cryostat. Using non-local measurements, we show that electrons can be ballistically directed by a magnetic field (transverse magnetic focussing) over length scales of ∼1 μm. Comparison with atomic force microscope measurements suggests a correlation between the absence of wrinkles and the presence of ballistic transport in CVD graphene

  19. Preparation and physical properties of vapour-deposited carbon-carbon composites

    In its first part, this research thesis reports a bibliographical study on methods of preparation of various types of vapour-deposited (CVD) carbons, and the author notices that only structure and texture properties of these macroscopically homogeneous pyro-carbons have been studied in detail. For a better understanding of the behaviour of carbon-carbon composites, this thesis thus reports the study of the relationships between physical properties, macroscopic texture and microscopic structure. A densification installation and methods of characterisation have been developed. The fabrication process and its installation are presented (oven with its temperature and gas rate controls, study of its thermal gradient, substrate, heat treatments), and the study and characterisation of carbon-carbon composites are reported: structure and texture properties (studied by optic and scanning electronic microscopy, density measurements, and X-ray diffraction), physical properties (electronic paramagnetic resonance, static magnetism, electric and thermal conductivity). In the last part, the author comments and discusses the obtained results: conditions of preparation, existence, physical properties of the different observed microstructures

  20. Fabrication and characterization of kesterite Cu2ZnSnS4 thin films deposited by electrostatic spray assisted vapour deposition method

    J.P. Liu; Choy, Kwang-Leong; Placidi, M.; J. López-García; Saucedo, Edgardo; Colombara, Diego; Robert, Erika

    2014-01-01

    Most of the high efficiency kesterite solar cells are fabricated by vacuum or hydrazine-based solution methods which have drawbacks, such as high cost, high toxicity or explosivity. In our contribution, an alternative non-vacuum and environmental friendly deposition technology called electrostatic spray assisted vapour deposition (ESAVD) has been used for the cost-effective growth of Cu2ZnSnS4 (CZTS) thin films with well controlled structure and composition. CZTS films have been characterized...

  1. The vapour phase deposition of boron on titanium by the reaction between gaseous boron trichloride and titanium metal. Final report

    The reaction, between boron trichloride vapour and titanium has been investigated in the temperature range 200 - 1350 deg. C. It has been found that an initial reaction leads to the formation of titanium tetrachloride and the deposition of boron on titanium, but that except for reactions between 900 and 1000 deg. C, the system is complicated by the formation of lower titanium chlorides due to secondary reactions between the titanium and titanium tetrachloride

  2. Modelling water vapour permeability through atomic layer deposition coated photovoltaic barrier defects

    Elrawemi, Mohamed, E-mail: Mohamed.elrawemi@hud.ac.uk [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom); Blunt, Liam; Fleming, Leigh [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom); Bird, David, E-mail: David.Bird@uk-cpi.com [Centre for Process Innovation Limited, Sedgefield, County Durham (United Kingdom); Robbins, David [Centre for Process Innovation Limited, Sedgefield, County Durham (United Kingdom); Sweeney, Francis [EPSRC Centre for Innovative Manufacturing in Advanced Metrology, School of Computing and Engineering, University of Huddersfield, Huddersfield (United Kingdom)

    2014-11-03

    Transparent barrier films such as Al{sub 2}O{sub 3} used for prevention of oxygen and/or water vapour permeation are the subject of increasing research interest when used for the encapsulation of flexible photovoltaic modules. However, the existence of micro-scale defects in the barrier surface topography has been shown to have the potential to facilitate water vapour ingress, thereby reducing cell efficiency and causing internal electrical shorts. Previous work has shown that small defects (≤ 3 μm lateral dimension) were less significant in determining water vapour ingress. In contrast, larger defects (≥ 3 μm lateral dimension) seem to be more detrimental to the barrier functionality. Experimental results based on surface topography segmentation analysis and a model presented in this paper will be used to test the hypothesis that the major contributing defects to water vapour transmission rate are small numbers of large defects. The model highlighted in this study has the potential to be used for gaining a better understanding of photovoltaic module efficiency and performance. - Highlights: • A model of water vapour permeation through barrier defects is presented. • The effect of the defects on the water vapour permeability is investigated. • Defect density correlates with water vapour permeability. • Large defects may dominate the permeation properties of the barrier film.

  3. Chemical vapour etching-based porous silicon and grooving: Application in silicon solar cells processing

    Ben Rabha, M.; Boujmil, M. F.; Saadoun, M.; Bessaïs, B.

    2005-06-01

    Sponge like porous silicon (PS) was formed by a simple and low cost chemical vapour etching (CVE) method and applied in polycrystalline silicon (mc-Si) solar cells processing. The CVE method consists of exposing Si wafers to HNO3/HF vapours. It was shown that 8 min of HNO3/HF CVE (volume ratio = 1/7) is sufficient to form optimized PS layers on the emitter of mc-Si cells. The CVE-based PS can simultaneously passivate the Si surface and serves as an effective antireflection coating (ARC). As a result, the reflectivity decreases by about 60% of its initial value and the internal quantum efficiency is improved, particularly in the short wavelength region. For acid vapours rich in HNO3 (HNO3/HF >1/4), the CVE method favours the formation of a (NH4)2SiF6 powder, which is highly soluble in water. These findings let us achieve anisotropic grooving that enables to groove mc-Si wafers locally and in depth using an adequate anti-acid mask. The CVE - based grooving technique was used to form buried metallic contacts on the rear and frontal surface of the Si wafer in order to improve the current collection in mc-Si solar cells. No alteration of the spectral response in the long wavelength range was observed in mc-Si cells with rear-buried contacts. Adjustments of theoretical spectral responses to experimental ones show an increase in the effective electron diffusion length (Ln), which was attributed to Al gettering (passivation) at grain boundaries and to the reduction of the effective thickness of the base of the cells.

  4. Chemical vapour etching-based porous silicon and grooving: Application in silicon solar cells processing

    Ben Rabha, M.; Boujmil, M.F.; Saadoun, M.; Bessais, B. [Institut National de Recherche Scientifique et Technique, Laboratoire de Photovoltaique et des Semiconducteurs, BP 95, 2050 Hammam-Lif (Tunisia)

    2005-06-01

    Sponge like porous silicon (PS) was formed by a simple and low cost chemical vapour etching (CVE) method and applied in polycrystalline silicon (mc-Si) solar cells processing. The CVE method consists of exposing Si wafers to HNO{sub 3}/HF vapours. It was shown that 8 min of HNO{sub 3}/HF CVE (volume ratio = 1/7) is sufficient to form optimized PS layers on the emitter of mc-Si cells. The CVE-based PS can simultaneously passivate the Si surface and serves as an effective antireflection coating (ARC). As a result, the reflectivity decreases by about 60% of its initial value and the internal quantum efficiency is improved, particularly in the short wavelength region. For acid vapours rich in HNO{sub 3} (HNO{sub 3}/HF >1/4), the CVE method favours the formation of a (NH{sub 4}){sub 2}SiF{sub 6} powder, which is highly soluble in water. These findings let us achieve anisotropic grooving that enables to groove mc-Si wafers locally and in depth using an adequate anti-acid mask. The CVE - based grooving technique was used to form buried metallic contacts on the rear and frontal surface of the Si wafer in order to improve the current collection in mc-Si solar cells. No alteration of the spectral response in the long wavelength range was observed in mc-Si cells with rear-buried contacts. Adjustments of theoretical spectral responses to experimental ones show an increase in the effective electron diffusion length (Ln), which was attributed to Al gettering (passivation) at grain boundaries and to the reduction of the effective thickness of the base of the cells. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Well-controlled metal co-catalysts synthesised by chemical vapour impregnation for photocatalytic hydrogen production and water purification.

    Su, Ren; Forde, Michael M; He, Qian; Shen, Yanbin; Wang, Xueqin; Dimitratos, Nikolaos; Wendt, Stefan; Huang, Yudong; Iversen, Bo B; Kiely, Christopher J; Besenbacher, Flemming; Hutchings, Graham J

    2014-10-28

    As co-catalyst materials, metal nanoparticles (NPs) play crucial roles in heterogeneous photocatalysis. The photocatalytic performance strongly relies on the physical properties (i.e., composition, microstructure, and surface impurities) of the metal NPs. Here we report a convenient chemical vapour impregnation (CVI) approach for the deposition of monometallic-, alloyed, and core-shell structured metal co-catalysts onto the TiO2 photocatalyst. The as-synthesised metal NPs are highly dispersed on the support and show narrow size distributions, which suit photocatalysis applications. More importantly, the surfaces of the as-synthesised metal NPs are free of protecting ligands, enabling the photocatalysts to be ready to use without further treatment. The effect of the metal identity, the alloy chemical composition, and the microstructure on the photocatalytic performance has been investigated for hydrogen production and phenol decomposition. Whilst the photocatalytic H2 production performance can be greatly enhanced by using the core-shell structured co-catalyst (Pdshell-Aucore and Ptshell-Aucore), the Ptshell-Aucore modified TiO2 yields enhanced quantum efficiency but a reduced effective decomposition of phenol to CO2 compared to that of the monometallic counterparts. We consider the CVI approach provides a feasible and elegant process for the decoration of photocatalyst materials. PMID:24970298

  6. High temperature stability of nanocrystalline anatase powders prepared by chemical vapour synthesis under varying process parameters

    Ahmad, Md. Imteyaz; Fasel, Claudia; Mayer, Thomas; Bhattacharya, S. S.; Hahn, Horst

    2011-05-01

    Systematic variation in the high temperature stability of nanocrystalline anatase powders prepared by chemical vapour synthesis (CVS) using titanium (IV) isopropoxide under varying flow rates of oxygen and helium was obtained by progressively shifting the decomposition product from C 3H 6 to CO 2. The as-synthesised powders were characterised by high temperature X-ray diffraction (HTXRD), simultaneous thermo-gravimetric analyses (STA), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). It was observed that the anatase to rutile transformation temperature progressively increased for samples synthesised at higher O 2/He flow rate ratios. The improved anatase stability was attributed to the presence of incorporated carbon within the titania structure and confirmed by a high temperature carbon desorption peak.

  7. High temperature stability of nanocrystalline anatase powders prepared by chemical vapour synthesis under varying process parameters

    Ahmad, Md. Imteyaz [Materials Testing Facility, Materials Forming Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Joint Research Laboratory Nanomaterials, Technische Universitaet Darmstadt and Forschungszentrum Karlsruhe, 64287 Darmstadt (Germany); Fasel, Claudia [Disperse Feststoffe, Institute of Materials Science, Darmstadt University of Technology, 64287 Darmstadt (Germany); Mayer, Thomas [Oberflaechenforschung, Institute of Materials Science, Darmstadt University of Technology, 64287 Darmstadt (Germany); Bhattacharya, S.S., E-mail: ssb@iitm.ac.in [Materials Testing Facility, Materials Forming Laboratory, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036 (India); Hahn, Horst [Joint Research Laboratory Nanomaterials, Technische Universitaet Darmstadt and Forschungszentrum Karlsruhe, 64287 Darmstadt (Germany)

    2011-05-15

    Systematic variation in the high temperature stability of nanocrystalline anatase powders prepared by chemical vapour synthesis (CVS) using titanium (IV) isopropoxide under varying flow rates of oxygen and helium was obtained by progressively shifting the decomposition product from C{sub 3}H{sub 6} to CO{sub 2}. The as-synthesised powders were characterised by high temperature X-ray diffraction (HTXRD), simultaneous thermo-gravimetric analyses (STA), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). It was observed that the anatase to rutile transformation temperature progressively increased for samples synthesised at higher O{sub 2}/He flow rate ratios. The improved anatase stability was attributed to the presence of incorporated carbon within the titania structure and confirmed by a high temperature carbon desorption peak.

  8. Synthesis, characterization and sintering of nanocrystalline titania powders produced by chemical vapour synthesis

    The chemical vapour synthesis (CVS) route is a versatile process that can be used for the synthesis of nanocrystalline ceramics with very small crystallite sizes having a narrow particle size distribution. In this study, a CVS technique was used to prepare nanocrystalline titania from tetraisopropyl orthotitanate at a processing temperature of 1273 K (1000 deg, C). High resolution transmission electron microscopy, x-ray diffraction and nitrogen adsorption techniques were used for the characterization of the as-synthesized powders. Green bodies were produced by a combination of uniaxial and cold isostatic pressing, which were then sintered. A simple pressureless sintering route was established that led to the production of a dense titania ceramic with a uniform microstructure and an average grain size well in the nanophase regime

  9. Influence of hydrogen on chemical vapour synthesis of different carbon nanostructures using propane as precursor and nickel as catalyst

    R K Sahoo; H Mamgain; C Jacob

    2014-10-01

    The role of hydrogen in the catalytic chemical vapour deposition of carbon nanotubes using sputtered nickel thin film as a catalyst is explained in this work. The growth of different carbon nanostructures with the variation in the precursor gas content was studied by keeping all other process parameters constant and using sputtered Ni thin film as a catalyst. The catalyst granule size, its external morphology and the resulting products were analysed. Carbon nanotubes (CNTs), carbon nanofibres (CNFs) and carbon nanoribbons (CNRs) were observed under different growth conditions. The different conditions of growth leading to form tubes, fibres or ribbons were analysed by varying the flow ratio of propane and hydrogen gas during the high temperature growth. Scanning and transmission electron microscopies confirmed the above structures under different growth conditions. The role of hydrogen on the surface passivation behaviour of the Ni catalyst and its correlative effect on the growth of carbon nanostructures is analysed. This direct approach can, in principle, be used to synthesize different types of carbon nanostructures by tailoring the hydrogen concentration.

  10. Study of the physical properties of Bi doped CdTe thin films deposited by close space vapour transport

    Bi doped cadmium telluride (CdTe:Bi) thin films were grown on glass-substrates by the close space vapour transport method. CdTe:Bi crystals grown by the vertical Bridgman method, varying the nominal Bi concentration in the range between 1 x 1017 and 8 x 1018 cm-3, were used in powder form for CdTe:Bi thin film deposition. Dark conductivity and photoconductivity measurements in the 90-300 K temperature range and determination by photoacoustic spectroscopy of the optical-absorption coefficient of the films in the 1.0 to 2.4 eV spectral region were carried out. The influence of Bi doping levels upon the intergrain barrier height and other associated grain boundary parameters of the polycrystalline CdTe:Bi thin films were determined from electrical, optical and morphological characterization

  11. Ambient temperature operated acetaldehyde vapour detection of spray deposited cobalt doped zinc oxide thin film.

    Shalini, S; Balamurugan, D

    2016-03-15

    Undoped and Co-doped ZnO thin films were prepared by a home built spray pyrolysis method. X-ray diffraction results indicate that both undoped and Co-doped ZnO have a polycrystalline nature and a preferential orientation peak in the (002) plane. From a field-emission scanning electron micrographs of annealed films, a uniform distribution of nanoparticles along with nanorods was observed. UV-Visible measurement indicated that all the films are transparent in the visible region. The electrical resistance was also reported. The acetaldehyde sensing behaviour of the prepared undoped and Co-doped ZnO thin films was studied using the chemi-resistive method at ambient temperature (∼30 °C). In the presence of 10 ppm of acetaldehyde vapour, the Co-doped ZnO thin films showed good sensing response of 74% with fast response and recovery time of 3 s and 110 s respectively. PMID:26748067

  12. Fundamental studies of growth mechanisms in physical vapour deposition of aluminium

    Knorr, N J

    2000-01-01

    temperature could be independently controlled due to the low deposition rate of the aluminium. The depositions were performed in a UHV environment to ensure that film growth was not mediated by contamination. The ion energy range used was 10-75eV and the substrate temperature varied from -100 deg C to 200 deg C. The depositions were onto silicon (100) with a native oxide surface, except for a set of depositions which were performed on to silicon with the native oxide surface removed. The cleanliness of the depositions was verified using in-situ XPS analysis and after deposition the structure of the aluminium films was inferred from measurements using SEM, TEM, AFM XRD and Nano-indendation. This information allowed the mechanisms of growth of the aluminium films to be investigated. In addition to the extensive array of IBDR depositions a series of aluminium films were deposited using evaporation and sputtering. These films were grown at substrate temperatures between room temperate and 200 deg C. The use of ev...

  13. Surfactant assisted chemical vapour generation of silver for AAS and ICP-OES: a mechanistic study

    Matoušek, Tomáš; Sturgeon, R. E.

    2003-01-01

    Roč. 18, č. 5 (2003), s. 487-494. ISSN 0267-9477 Institutional research plan: CEZ:AV0Z4031919 Keywords : vapour generation * ICP-OES * silver Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.200, year: 2003

  14. Study of a new hybrid process combining slurry infiltration and Reactive Chemical Vapour Infiltration for the realisation of Ceramic Matrix Composites

    Ceramic matrix composites were originally developed for aerospace,military aeronautics or energy applications thanks to their good properties at high temperature. They are generally made by Chemical Vapor Infiltration (CVI). A new short hybrid process combining fiber preform slurry impregnation of ceramic powders with an innovative Reactive CVI (RCVI) route is proposed to reduce the production time. This route is based on the combination of Reactive Chemical Vapour Deposition (RCVD), which is often used to deposit coatings on fibres, with the Chemical Vapor Infiltration (CVI).In RCVD, the absence of one element of the deposited carbide in the initial gas phase involves the consumption/conversion of the solid substrate. In this work, the RCVD growth and the associated consumption were studied with different parameters in the Ti-H-Cl-C chemical system. The study has been completed with the chemical products analysis, combining XRD, XPS and FTIR. Then, the partial conversion of sub-micrometer carbon powders into titanium carbide and the consolidation of green bodies by RCVI from H2/TiCl4 gaseous infiltration were studied. The residual porosity and the final TiC content were measured in the bulk of the infiltrated powders by image analysis from scanning electron microscopy. Depending on temperature, few hundred micrometers-depth infiltrations are obtained.Finally, the results have been transposed to the RCVI into CMC-type pre-forms. Despite a minimal TiC content of 25% in the overall preform, the results shown a bad homogeneity of the infiltration and a poor cohesion of fibres with RCVI consolidated powder of their environment. (author)

  15. Towards engineered branch placement: Unreal™ match between vapour-liquid-solid glancing angle deposition nanowire growth and simulation

    The vapour-liquid-solid glancing angle deposition (VLS-GLAD) process is capable of producing complex nanotree structures with control over azimuthal branch orientation and height. We have developed a thin film growth simulation including ballistic deposition, simplified surface diffusion, and droplet-mediated cubic crystal growth for the VLS-GLAD process using the UnrealTM Development Kit. The use of a commercial game engine has provided an interactive environment while allowing a custom physics implementation. Our simulation's output is verified against experimental data, including a volumetric film reconstruction produced using focused ion beam and scanning-electron microscopy (SEM), crystallographic texture, and morphological characteristics such as branch orientation. We achieve excellent morphological and texture agreement with experimental data, as well as qualitative agreement with SEM imagery. The simplified physics in our model reproduces the experimental films, indicating that the dominant role flux geometry plays in the VLS-GLAD competitive growth process responsible for azimuthally oriented branches and biaxial crystal texture evolution. The simulation's successful reproduction of experimental data indicates that it should have predictive power in designing novel VLS-GLAD structures

  16. Characteristics of aluminium-scandium alloy thin sheets obtained by physical vapour deposition

    Thin sheets of an age-hardenable aluminium-scandium alloy were deposited by direct current magnetron sputtering. As targets an aluminium-scandium pre-alloy with a scandium content of 2.0 mass% (size 88 x 500 mm) was applied. The substrates to be coated consisted of thin steel sheets which after deposition were dissolved in an oxidizing medium. In this way, free-standing sheets of less than 30 μm thickness of the aluminium-scandium alloy were received. Two deposition temperatures, 37 and 160 oC, were applied. The as-received sheets showed a typical columnar structure. Two post-treatments of the sheets were applied: a cold isostatic pressing and an artificial ageing for 1 h at temperatures between 200 and 400 oC. The strength of the sheets was measured by tensile tests. The employed specimens had a width of 10 mm and were gained from the sheets by cutting. During testing, load and strain were measured by a 1000 N load cell and a video extensometer, respectively. The as-deposited specimens show a tensile strength of 350 MPa. Artificial ageing at 300 oC increases the tensile strength to more than 400 MPa. It could be shown that during tensile tests cracks are initialized at coating defects.

  17. Paraffin wax deposits and chemical inhibitors

    Mendell, J.L.

    1970-01-01

    Solutions to this problem becomes necessary with the advent of extremely deep production, offshore production, and the probability of ocean-floor completions. The reasons for paraffin-wax accumulations are many and difficult to pinpoint. Inhibition of these paraffin deposits appears to be the best solution. Paraffin solvents and inhibitors are as follows: solvents, wetting agents, dispersants, and crystal modifiers. Solvents are effective, but can harm a refinery catalyst and create health hazards. Wetting agents and dispersants comprise the majority of chemicals used as paraffin wax inhibitors. Crystal modifiers are relatively new and may provide the most efficient means of reducing deposition. Evaluations of chemical paraffin inhibitors are outlined. Field test results which consider the various chemicals tested may give satisfactory results in determining which particular chemical can solve the problem of the particular situation. (38 refs.)

  18. Estimation of vapour pressure and partial pressure of subliming compounds by low-pressure thermogravimetry

    G V Kunte; Ujwala Ail; P K Ajikumar; A K Tyagi; S A Shivashankar; A M Umarji

    2011-12-01

    A method for the estimation of vapour pressure and partial pressure of subliming compounds under reduced pressure, using rising temperature thermogravimetry, is described in this paper. The method is based on our recently developed procedure to estimate the vapour pressure from ambient pressure thermogravimetric data using Langmuir equation. Using benzoic acid as the calibration standard, vapour pressure–temperature curves are calculated at 80, 160 and 1000 mbar for salicylic acid and vanadyl bis-2,4-pentanedionate, a precursor used for chemical vapour deposition of vanadium oxides. Using a modification of the Langmuir equation, the partial pressure of these materials at different total pressures is also determined as a function of temperature. Such data can be useful for the deposition of multi-metal oxide thin films or doped thin films by chemical vapour deposition (CVD).

  19. Sodium vapour aerosol formation and sodium deposition current work within the United Kingdom

    The significance to reactor operation of sodium transport through the cover gas of a sodium-cooled fast reactor and its subsequent deposition on cooled reactor surfaces is fully appreciated in the UK. A programme of work is therefore underway designed to understand the mechanism of sodium transport under these conditions. This paper described the work which has so far been completed, discussed the work presently in progress, and outlines future plans. (author)

  20. Determination of electroless deposition by chemical nickeling

    M. Badida

    2013-07-01

    Full Text Available Increasing of technical level and reliability of machine products in compliance with the economical and ecological terms belongs to the main trends of the industrial development. During the utilisation of these products there arise their each other contacts and the interaction with the environment. That is the reason for their surface degradation by wear effect, corrosion and other influences. The chemical nickel-plating allows autocatalytic deposition of nickel from water solutions in the form of coherent, technically very profitable coating without usage of external source of electric current. The research was aimed at evaluating the surface changes after chemical nickel-plating at various changes of technological parameters.

  1. Determination of electroless deposition by chemical nickeling

    Badida, M.; M. Gombár; L. Sobotová; J. Kmec

    2013-01-01

    Increasing of technical level and reliability of machine products in compliance with the economical and ecological terms belongs to the main trends of the industrial development. During the utilisation of these products there arise their each other contacts and the interaction with the environment. That is the reason for their surface degradation by wear effect, corrosion and other influences. The chemical nickel-plating allows autocatalytic deposition of nickel from water solutions in the fo...

  2. Chemical vapour etching of silicon and porous silicon: silicon solar cells and micromachining applications

    Ben Jaballah, A.; Hassen, M.; Hajji, M.; Saadoun, M.; Bessais, B.; Ezzaouia, H. [Institut National de Recherche Scientifique et Technique, Laboratoire de Photovoltaique et des Materiaux Semiconducteurs, PB 95 2050 Hammam lif (Tunisia)

    2005-06-01

    In this work, we used HNO{sub 3}/HF Vapour Etching (VE) of silicon (Si) wafers for the formation of different porous structures. Depending on the volume ratio of the HNO{sub 3}/HF acid mixture, we can obtain Porous Silicon (PS) layers or a (NH{sub 4}){sub 2}SiF{sub 6} like powder phase. These two kind of porous structures may be used in silicon solar cells and in micromachining applications. The VE technique allows producing thick porous layers (>100 {mu}m) in short times. Simple masking films enable to selectively groove Si wafers, leading to the formation of holes and channels of different sizes suitable for their application in micromachining. The various grooving profiles were investigated by Scanning electron microscopy (SEM). (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Quantum Hall resistance standards from graphene grown by chemical vapor deposition on silicon carbide

    Lafont, F.; Ribeiro-Palau, R.; Kazazis, D.; Michon, A.; Couturaud, O.; Consejo, C.; Chassagne, T.; Zielinski, M; Portail, M.; Jouault, B.; F. Schopfer; Poirier, W.

    2014-01-01

    Replacing GaAs by graphene to realize more practical quantum Hall resistance standards (QHRS), accurate to within $10^{-9}$ in relative value, but operating at lower magnetic fields than 10 T, is an ongoing goal in metrology. To date, the required accuracy has been reported, only few times, in graphene grown on SiC by sublimation of Si, under higher magnetic fields. Here, we report on a device made of graphene grown by chemical vapour deposition on SiC which demonstrates such accuracies of th...

  4. Advanced deposition model for thermal activated chemical vapor deposition

    Cai, Dang

    Thermal Activated Chemical Vapor Deposition (TACVD) is defined as the formation of a stable solid product on a heated substrate surface from chemical reactions and/or dissociation of gaseous reactants in an activated environment. It has become an essential process for producing solid film, bulk material, coating, fibers, powders and monolithic components. Global market of CVD products has reached multi billions dollars for each year. In the recent years CVD process has been extensively used to manufacture semiconductors and other electronic components such as polysilicon, AlN and GaN. Extensive research effort has been directed to improve deposition quality and throughput. To obtain fast and high quality deposition, operational conditions such as temperature, pressure, fluid velocity and species concentration and geometry conditions such as source-substrate distance need to be well controlled in a CVD system. This thesis will focus on design of CVD processes through understanding the transport and reaction phenomena in the growth reactor. Since the in situ monitor is almost impossible for CVD reactor, many industrial resources have been expended to determine the optimum design by semi-empirical methods and trial-and-error procedures. This approach has allowed the achievement of improvements in the deposition sequence, but begins to show its limitations, as this method cannot always fulfill the more and more stringent specifications of the industry. To resolve this problem, numerical simulation is widely used in studying the growth techniques. The difficulty of numerical simulation of TACVD crystal growth process lies in the simulation of gas phase and surface reactions, especially the latter one, due to the fact that very limited kinetic information is available in the open literature. In this thesis, an advanced deposition model was developed to study the multi-component fluid flow, homogeneous gas phase reactions inside the reactor chamber, heterogeneous surface

  5. Liquid and vapour-phase antifungal activities of selected essential oils against candida albicans: microscopic observations and chemical characterization of cymbopogon citratus

    Malik Anushree

    2010-11-01

    Full Text Available Abstract Background Use of essential oils for controlling Candida albicans growth has gained significance due to the resistance acquired by pathogens towards a number of widely-used drugs. The aim of this study was to test the antifungal activity of selected essential oils against Candida albicans in liquid and vapour phase and to determine the chemical composition and mechanism of action of most potent essential oil. Methods Minimum Inhibitory concentration (MIC of different essential oils in liquid phase, assayed through agar plate dilution, broth dilution & 96-well micro plate dilution method and vapour phase activity evaluated through disc volatilization method. Reduction of C. albicans cells with vapour exposure was estimated by kill time assay. Morphological alteration in treated/untreated C. albicans cells was observed by the Scanning electron microscopy (SEM/Atomic force microscopy (AFM and chemical analysis of the strongest antifungal agent/essential oil has been done by GC, GC-MS. Results Lemon grass (Cymbopogon citratus essential oil exhibited the strongest antifungal effect followed by mentha (Mentha piperita and eucalyptus (Eucalyptus globulus essential oil. The MIC of lemon grass essential oil in liquid phase (288 mg/l was significantly higher than that in the vapour phase (32.7 mg/l and a 4 h exposure was sufficient to cause 100% loss in viability of C. albicans cells. SEM/AFM of C. albicans cells treated with lemon grass essential oil at MIC level in liquid and vapour phase showed prominent shrinkage and partial degradation, respectively, confirming higher efficacy of vapour phase. GC-MS analysis revealed that lemon grass essential oil was dominated by oxygenated monoterpenes (78.2%; α-citral or geranial (36.2% and β-citral or neral (26.5%, monoterpene hydrocarbons (7.9% and sesquiterpene hydrocarbons (3.8%. Conclusion Lemon grass essential oil is highly effective in vapour phase against C. albicans, leading to deleterious

  6. Applicability of chemical vapour polishing of additive manufactured parts to meet production-quality

    Pedersen, D. B.; Hansen, H. N.; Nielsen, J. S.;

    2014-01-01

    The Fused Deposition Modelling (FDM) method is the most rapidly growing Additive Manufacturing (AM) method[1]. FDM employs a 2.5D deposition scheme which induce a step-ladder shaped surface definition [2], with seams of the individual layers clearly visible[3]. This paper investigate to which...

  7. Chemical Vapor Deposition Of Silicon Carbide

    Powell, J. Anthony; Larkin, David J.; Matus, Lawrence G.; Petit, Jeremy B.

    1993-01-01

    Large single-crystal SiC boules from which wafers of large area cut now being produced commerically. Availability of wafers opens door for development of SiC semiconductor devices. Recently developed chemical vapor deposition (CVD) process produces thin single-crystal SiC films on SiC wafers. Essential step in sequence of steps used to fabricate semiconductor devices. Further development required for specific devices. Some potential high-temperature applications include sensors and control electronics for advanced turbine engines and automobile engines, power electronics for electromechanical actuators for advanced aircraft and for space power systems, and equipment used in drilling of deep wells. High-frequency applications include communication systems, high-speed computers, and microwave power transistors. High-radiation applications include sensors and controls for nuclear reactors.

  8. Chemical characteristics of some major uranium deposits in western USA

    Multi-element chemical analyses of several thousand samples were retrieved from the US Geological Survey's computerized Rock Analysis Storage System and used to estimate the average abundances of various elements in each of several types of uranium deposits, in altered rocks associated with some of these deposits, and in unmineralized parts of the various host rocks. Deposits for which results are presented include the tabular deposits in the Morrison Formation, Ambrosia Lake district, New Mexico; secondary deposits in the Ambrosia Lake district; tabular deposits in the Morrison Formation of the Henry Mountains, Utah; tabular deposits in the Chinle Formation in Utah and Colorado; roll-type deposits in Tertiary rocks from the Texas Gulf district; roll-type deposits in the Tertiary basins of Wyoming; tabular deposits in the Entrada Sandstone in Colorado; and a vein-type deposit in crystalline rocks of the Front Range of Colorado. Statistical treatment of the data identified elements that were notably more or less abundant in the deposits and altered rocks than in the unmineralized parts of the host rocks. Comparisons of the mean abundances of elements in the deposits show that the chemical composition of roll-type deposits varies greatly even among deposits in the same district. By contrast, the chemical characteristics of tabular deposits display little variation; the Ambrosia Lake tabular deposits and those of the Henry Mountains district are particularly similar. The data place some constraints on the geochemical aspects of genetic models and suggest certain elements as potential prospecting guides

  9. Optical and electrical properties of ZrSe3 single crystals grown by chemical vapour transport technique

    Kaushik Patel; Jagdish Prajapati; Rajiv Vaidya; S G Patel

    2005-08-01

    Single crystals of the lamellar compound, ZrSe3, were grown by chemical vapour transport technique using iodine as a transporting agent. The grown crystals were characterized with the help of energy dispersive analysis by X-ray (EDAX), which gave confirmation about the stoichiometry. The optical band gap measurement of as grown crystals was carried out with the help of optical absorption spectra in the range 700–1450 nm. The indirect as well as direct band gap of ZrSe3 were found to be 1.1 eV and 1.47 eV, respectively. The resistivity of the as grown crystals was measured using van der Pauw method. The Hall parameters of the grown crystals were determined at room temperature from Hall effect measurements. Electrical resistivity measurements were performed on this crystal in the temperature range 303–423 K. The crystals were found to exhibit semiconducting nature in this range. The activation energy and anisotropy measurements were carried out for this crystal. Pressure dependence of electrical resistance was studied using Bridgman opposed anvils set up up to 8 GPa. The semiconducting nature of ZrSe3 single crystal was inferred from the graph of resistance vs pressure. The results obtained are discussed in detail.

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

    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.

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

    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

  12. Studying chemical vapor deposition processes with theoretical chemistry

    Pedersen, Henrik; Elliott, Simon D.

    2014-01-01

    In a chemical vapor deposition (CVD) process, a thin film of some material is deposited onto a surface via the chemical reactions of gaseous molecules that contain the atoms needed for the film material. These chemical reactions take place on the surface and in many cases also in the gas phase. To fully understand the chemistry in the process and thereby also have the best starting point for optimizing the process, theoretical chemical modeling is an invaluable tool for providing atomic-scale...

  13. High-performance perovskite CH3NH3PbI3 thin films for solar cells prepared by single-source physical vapour deposition

    Fan, Ping; Gu, Di; Liang, Guang-Xing; Luo, Jing-Ting; Chen, Ju-Long; Zheng, Zhuang-Hao; Zhang, Dong-Ping

    2016-01-01

    In this work, an alternative route to fabricating high-quality CH3NH3PbI3 thin films is proposed. Single-source physical vapour deposition (SSPVD) without a post-heat-treating process was used to prepare CH3NH3PbI3 thin films at room temperature. This new process enabled complete surface coverage and moisture stability in a non-vacuum solution. Moreover, the challenges of simultaneously controlling evaporation processes of the organic and inorganic sources via dual-source vapour evaporation and the heating process required to obtain high crystallization were avoided. Excellent composition with stoichiometry transferred from the powder material, a high level of tetragonal phase-purity, full surface coverage, well-defined grain structure, high crystallization and reproducibility were obtained. A PCE of approximately 10.90% was obtained with a device based on SSPVD CH3NH3PbI3. These initial results suggest that SSPVD is a promising method to significantly optimize perovskite CH3NH3PbI3 solar cell efficiency. PMID:27426686

  14. High-performance perovskite CH3NH3PbI3 thin films for solar cells prepared by single-source physical vapour deposition.

    Fan, Ping; Gu, Di; Liang, Guang-Xing; Luo, Jing-Ting; Chen, Ju-Long; Zheng, Zhuang-Hao; Zhang, Dong-Ping

    2016-01-01

    In this work, an alternative route to fabricating high-quality CH3NH3PbI3 thin films is proposed. Single-source physical vapour deposition (SSPVD) without a post-heat-treating process was used to prepare CH3NH3PbI3 thin films at room temperature. This new process enabled complete surface coverage and moisture stability in a non-vacuum solution. Moreover, the challenges of simultaneously controlling evaporation processes of the organic and inorganic sources via dual-source vapour evaporation and the heating process required to obtain high crystallization were avoided. Excellent composition with stoichiometry transferred from the powder material, a high level of tetragonal phase-purity, full surface coverage, well-defined grain structure, high crystallization and reproducibility were obtained. A PCE of approximately 10.90% was obtained with a device based on SSPVD CH3NH3PbI3. These initial results suggest that SSPVD is a promising method to significantly optimize perovskite CH3NH3PbI3 solar cell efficiency. PMID:27426686

  15. Hard carbon films: Deposition and diagnostics

    Frgala Zdeněk; Kudrle Vít; Janča Jan; Meško Marcel; Eliáš Marek; Buršík Jiří

    2003-01-01

    We studied the growth of microcrystalline diamond films on pre-treated Si and WC-Co substrates by microwave plasma chemical vapour deposition (MPCVD). The pre-treatment was varied and its effect on diamond film was studied.

  16. Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics

    Qi, Junjie

    2015-06-25

    High-performance piezoelectricity in monolayer semiconducting transition metal dichalcogenides is highly desirable for the development of nanosensors, piezotronics and photo-piezotransistors. Here we report the experimental study of the theoretically predicted piezoelectric effect in triangle monolayer MoS2 devices under isotropic mechanical deformation. The experimental observation indicates that the conductivity of MoS2 devices can be actively modulated by the piezoelectric charge polarization-induced built-in electric field under strain variation. These polarization charges alter the Schottky barrier height on both contacts, resulting in a barrier height increase with increasing compressive strain and decrease with increasing tensile strain. The underlying mechanism of strain-induced in-plane charge polarization is proposed and discussed using energy band diagrams. In addition, a new type of MoS2 strain/force sensor built using a monolayer MoS2 triangle is also demonstrated. Our results provide evidence for strain-gating monolayer MoS2 piezotronics, a promising avenue for achieving augmented functionalities in next-generation electronic and mechanical–electronic nanodevices.

  17. Experimental observation of local electrical signature of suspended graphene grown via chemical vapour deposition method

    We employ electrostatic force microscope (EFM) techniques to explore local electrical properties of suspended graphene on Cu foil, SiO2/Si and PET substrate. By using electrical modulation of amplitude in a tapping mode atomic force microscope tip, we can obtain distinguished electrostatic force amplitude mapping of graphene on various substrates. In particular, at nano-valley domains on Cu and a SiO2/Si surface, relatively weaker electrostatic attractive interaction is observed than at nano-peak domains. In SiO2/Si, we find that electrostatic force distribution of graphene still follows the substrate surface morphology. Furthermore, employing EFM to graphene on a PET system can be suggested as a facile tool to investigate electrical performance of graphene. (paper)

  18. SiC fibre by chemical vapour deposition on tungsten filament

    R V Krishnarao; J Subrahmanyam; S Subbarao

    2001-06-01

    A CVD system for the production of continuous SiC fibre was set up. The process of SiC coating on 19 m diameter tungsten substrate was studied. Methyl trichloro silane (CH3SiCl3) and hydrogen reactants were used. Effect of substrate temperature (1300–1500°C) and concentration of reactants on the formation of SiC coating were studied. SiC coatings of negligible thickness were formed at very low flow rates of hydrogen (5 × 10–5 m3/min) and CH3SiCl3 (1.0 × 10–4 m3/min of Ar). Uneven coatings and brittle fibres were formed at very high concentrations of CH3SiCl3 (6 × 10–4 m3/min of Ar). The flow rates of CH3SiCl3 and hydrogen were adjusted to get SiC fibre with smooth surface. The structure and morphology of SiC fibres were evaluated.

  19. Controlled growth of large area multilayer graphene on copper by chemical vapour deposition

    Kaya, Ismet I.; Kasap, Sibel; Khaksaran, Hadi; Celik, Suleyman; Ozkaya, Hasan; Yanik, Cenk; Faculty of Engineering; Natural Sciences Team; Nanotechnology Research; Application Center Team

    2015-03-01

    The growth of multilayer graphene on the surface of a copper foil is studied experimentally. It has been shown that the average film thickness can be controlled by the growth time with a linear trend and the growth can be extended until nearly full coverage of multilayer graphene over the copper surface. It is observed that the impurity particles on the copper surface mediate the multilayer growth. The formation of large multilayer islands is explained by a qualitative model which takes into account the interplay between the length scales governed by the molecular mean free path of gas molecules and the distribution of the impurities.

  20. Metalorganic chemical vapour deposition of junction isolated GaAlAs/GaAs LED structures

    Bradley, R. R.; Ash, R. M.; Forbes, N. W.; Griffiths, R. J. M.; Jebb, D. P.

    1986-09-01

    A low-cost high-radiance Ga(1-x)Al(x)As/GaAs LED has been developed using p-n junction isolation to achieve current confinement in an inverted Burrus LED structure. Using this structure devices with a high internal quantum efficiency of 87 percent which launch up to 1.5 mW into 200-micron, 0.3 nA fiber at 150 mA and have rise and fall times of less than 5 ns, have been fabricated. The LED structure involved a two-stage growth process in which initially an n-type isolation layer was grown on a p-type substrate, followed by infill growth, through contact holes, of the inverted LED structure. This paper will describe in detail the growth and preparation of the optimized junction isolated LED structure, including growth rate and composition control, layer uniformity and deliberate interface grading. Exploration of the use of magnesium doping and triethylaluminum for precise control of active layer doping and composition will be discussed, and finally details of device characteristics and performance are presented.

  1. Structural study of vapour phase deposited 3,4,9,10-perylene tetracarboxylicacid diimide: Comparison between single crystal and ultra thin films grown on Pt(100)

    Structural properties of a single crystal and of a thin film of 3,4,9,10-perylene-tetracarboxylic-acid-diimide are compared. The two samples are both obtained from the vapour phase, the latter being deposited at room temperature, in an ultrahigh vacuum environment, on a clean Pt(100) substrate. In the single crystal we have pointed out interactions between adjacent molecules by overlapping of the π systems in the stacks and by hydrogen bonds between neighbouring stacks. The various surface unit cells of the nanocrystals from the film, identified by means of scanning tunnelling microscopy, are not comparable to those expected from the X-ray diffraction study of the single crystal and to those already published for other substrates. This fact clearly highlights the role played by the type of substrate chosen and/or the substrate-molecule interaction that affects the stacking and crystallinity of the growing crystal on top

  2. Graphene decorated microelectrodes for simultaneous detection of ascorbic, dopamine, and folic acids by means of chemical vapor deposition

    Namdar, N.; Hassanpour Amiri, M.; Dehghan Nayeri, F.; Gholizadeh, A.; Mohajerzadeh, S.

    2015-09-01

    In this paper, high quality and large area graphene layers were synthesized using thermal chemical vapour deposition on copper foil substrates. We use graphene incorporated electrodes to measure simultaneously ascorbic acid, dopamine and folic acid. Cyclic voltammetry and differential pulse voltammetry methods were used to evaluate electrochemical behaviour of the grown graphene layers. The graphene-modified electrode shows large electrochemical potential difference compared to bare gold electrodes with higher current responses. Also our fabricated electrodes configuration can be used easily for microfluidic analysis.

  3. Graphene decorated microelectrodes for simultaneous detection of ascorbic, dopamine, and folic acids by means of chemical vapor deposition

    In this paper, high quality and large area graphene layers were synthesized using thermal chemical vapour deposition on copper foil substrates. We use graphene incorporated electrodes to measure simultaneously ascorbic acid, dopamine and folic acid. Cyclic voltammetry and differential pulse voltammetry methods were used to evaluate electrochemical behaviour of the grown graphene layers. The graphene-modified electrode shows large electrochemical potential difference compared to bare gold electrodes with higher current responses. Also our fabricated electrodes configuration can be used easily for microfluidic analysis. (paper)

  4. Characterisation of Pristine and Recoated electron beam evaporation plasma-assisted physical vapour deposition Cr-N coatings on AISI M2 steel and WC-Co substrates

    This paper is focussed on the characterisation of electron beam evaporation plasma-assisted physical vapour deposition Cr-N coatings deposited on AISI M2 steel and hardmetal (K10) substrates in two different conditions: Pristine (i.e., coated) and Recoated (i.e., stripped and recoated). Analytical methods, including X-ray diffraction (XRD), scanning electron microscopy, scratch adhesion and pin-on-disc tests were used to evaluate several coating properties. XRD analyses indicated that both Pristine and Recoated coatings consisted of a mixture of hexagonal Cr2N and cubic CrN, regardless of substrate type. For the M2 steel substrate, only small differences were found in terms of coating phases, microstructure, adhesion, friction and wear coefficients between Pristine and Recoated. Recoated on WC-Co (K10) exhibited a less dense microstructure and significant inferior adhesion compared to Pristine on WC-Co (K10). The wear coefficient of Recoated on WC-Co was 100 times higher than those exhibited by all other specimens. The results obtained confirm that the stripping process did not adversely affect the Cr-N properties when this coating was deposited onto M2 steel substrates, but it is clear from the unsatisfactory tribological performance of Recoated on WC-Co that the stripping process is unsuitable for hardmetal substrates

  5. Anti corrosion layer for stainless steel in molten carbonate fuel cell - comprises phase vapour deposition of titanium nitride, aluminium nitride or chromium nitride layer then oxidising layer in molten carbonate electrolyte

    2000-01-01

    Forming an anticorrosion protective layer on a stainless steel surface used in a molten carbonate fuel cell (MCFC) - comprises the phase vapour deposition (PVD) of a layer comprising at least one of titanium nitride, aluminium nitride or chromium nitride and then forming a protective layer in situ...... by replacement of the nitride ions with oxide ions in the molten carbonate electrolyte....

  6. Fission product vapour - aerosol interactions in the containment: simulant fuel studies

    Experiments have been conducted in the Falcon facility to study the interaction of fission product vapours released from simulant fuel samples with control rod aerosols. The aerosols generated from both the control rod and fuel sample were chemically distinct and had different deposition characteristics. Extensive interaction was observed between the fission product vapours and the control rod aerosol. The two dominant mechanisms were condensation of the vapours onto the aerosol, and chemical reactions between the two components; sorption phenomena were believed to be only of secondary importance. The interaction of fission product vapours and reactor materials aerosols could have a major impact on the transport characteristics of the radioactive emission from a degrading core. (author)

  7. Chemical vapor deposition of graphene single crystals.

    Yan, Zheng; Peng, Zhiwei; Tour, James M

    2014-04-15

    As a two-dimensional (2D) sp(2)-bonded carbon allotrope, graphene has attracted enormous interest over the past decade due to its unique properties, such as ultrahigh electron mobility, uniform broadband optical absorption and high tensile strength. In the initial research, graphene was isolated from natural graphite, and limited to small sizes and low yields. Recently developed chemical vapor deposition (CVD) techniques have emerged as an important method for the scalable production of large-size and high-quality graphene for various applications. However, CVD-derived graphene is polycrystalline and demonstrates degraded properties induced by grain boundaries. Thus, the next critical step of graphene growth relies on the synthesis of large graphene single crystals. In this Account, we first discuss graphene grain boundaries and their influence on graphene's properties. Mechanical and electrical behaviors of CVD-derived polycrystalline graphene are greatly reduced when compared to that of exfoliated graphene. We then review four representative pathways of pretreating Cu substrates to make millimeter-sized monolayer graphene grains: electrochemical polishing and high-pressure annealing of Cu substrate, adding of additional Cu enclosures, melting and resolidfying Cu substrates, and oxygen-rich Cu substrates. Due to these pretreatments, the nucleation site density on Cu substrates is greatly reduced, resulting in hexagonal-shaped graphene grains that show increased grain domain size and comparable electrical properties as to exfoliated graphene. Also, the properties of graphene can be engineered by its shape, thickness and spatial structure. Thus, we further discuss recently developed methods of making graphene grains with special spatial structures, including snowflakes, six-lobed flowers, pyramids and hexagonal graphene onion rings. The fundamental growth mechanism and practical applications of these well-shaped graphene structures should be interesting topics and

  8. Chemical Vapor Deposition of Silicon from Silane Pyrolysis

    Praturi, A. K.; Lutwack, R.; Hsu, G.

    1977-01-01

    The four basic elements in the chemical vapor deposition (CVD) of silicon from silane are analytically treated from a kinetic standpoint. These elements are mass transport of silane, pyrolysis of silane, nucleation of silicon, and silicon crystal growth. Rate expressions that describe the various steps involved in the chemical vapor deposition of silicon were derived from elementary principles. Applications of the rate expressions for modeling and simulation of the silicon CVD are discussed.

  9. Ultrafast deposition of silicon nitride and semiconductor silicon thin films by Hot Wire Chemical Vapor Deposition

    Schropp, R.E.I.; van der Werf, C.H.M.; Verlaan, V.; J.K. Rath; Li, H. B. T.

    2009-01-01

    The technology of Hot Wire Chemical Vapor Deposition (HWCVD) or Catalytic Chemical Vapor Deposition (Cat-CVD) has made great progress during the last couple of years. This review discusses examples of significant progress. Specifically, silicon nitride deposition by HWCVD (HW-SiNx) is highlighted, as well as thin film silicon single junction and multijunction junction solar cells. The application of HW-SiNx at a deposition rate of 3 nm/s to polycrystalline Si wafer solar cells has led to cell...

  10. Synthetic Graphene Grown by Chemical Vapor Deposition on Copper Foils

    Chung, Ting Fung; Shen, Tian; Cao, Helin; Jauregui, Luis A.; Wu, Wei; Yu, Qingkai; Newell, David; Chen, Yong P.

    2013-04-01

    The discovery of graphene, a single layer of covalently bonded carbon atoms, has attracted intense interest. Initial studies using mechanically exfoliated graphene unveiled its remarkable electronic, mechanical and thermal properties. There has been a growing need and rapid development in large-area deposition of graphene film and its applications. Chemical vapor deposition on copper has emerged as one of the most promising methods in obtaining large-scale graphene films with quality comparable to exfoliated graphene. In this paper, we review the synthesis and characterizations of graphene grown on copper foil substrates by atmospheric pressure chemical vapor deposition. We also discuss potential applications of such large-scale synthetic graphene.

  11. Physical vapour deposition reactive magnetron sputtering for the production and application of dichroics in photovoltaic system with solar spectral splitting

    Raniero, W., E-mail: walter.raniero@unitn.it [Department of Industrial Engineering, University of Trento, Via Sommarive 9, 38123 Trento (Italy); INFN – Legnaro National Laboratories, Viale dell’Università 2, 35020 Legnaro, PD (Italy); Campostrini, M., E-mail: m.campostrini.1@studenti.unitn.it [Department of Industrial Engineering, University of Trento, Via Sommarive 9, 38123 Trento (Italy); Maggioni, G., E-mail: Gianluigi.Maggioni@lnl.infn.it [Department of Physics and Astronomy, University of Padua, Padua (Italy); INFN – Legnaro National Laboratories, Viale dell’Università 2, 35020 Legnaro, PD (Italy); Mea, G. Della, E-mail: dellamea@ing.unitn.it [Department of Industrial Engineering, University of Trento, Via Sommarive 9, 38123 Trento (Italy); INFN – Legnaro National Laboratories, Viale dell’Università 2, 35020 Legnaro, PD (Italy); Quaranta, A., E-mail: quaranta@ing.unitn.it [Department of Industrial Engineering, University of Trento, Via Sommarive 9, 38123 Trento (Italy); INFN – Legnaro National Laboratories, Viale dell’Università 2, 35020 Legnaro, PD (Italy)

    2014-07-01

    This paper aims at designing, producing and characterizing a series of dichroic filters that are made up of a stack of layers with variable nanometer thickness. Such filters are created by PVD reactive magnetron sputtering, obtaining SiO{sub 2} and TiO{sub 2} through an active oxidation during the deposition. The single layers have then been analyzed using different techniques including RBS (Rutherford Backscattering Spectrometry) to determine the stoichiometry, AFM (Atomic Force Microscope) to assess the deposition rate, and UV–vis–NIR spectrophotometric analysis to evaluate the optical response. The application of the dichroic in concentration photovoltaic systems, separates the solar radiation in two optical spectral bands [7], that allows to couple them with a different solar cells which have dedicated external quantum efficiency. The optical separation using dichroic filters allows to combine different photovoltaic cells with an appropriate energy gap, thus optimizing the photovoltaic conversion.

  12. Physical vapour deposition reactive magnetron sputtering for the production and application of dichroics in photovoltaic system with solar spectral splitting

    This paper aims at designing, producing and characterizing a series of dichroic filters that are made up of a stack of layers with variable nanometer thickness. Such filters are created by PVD reactive magnetron sputtering, obtaining SiO2 and TiO2 through an active oxidation during the deposition. The single layers have then been analyzed using different techniques including RBS (Rutherford Backscattering Spectrometry) to determine the stoichiometry, AFM (Atomic Force Microscope) to assess the deposition rate, and UV–vis–NIR spectrophotometric analysis to evaluate the optical response. The application of the dichroic in concentration photovoltaic systems, separates the solar radiation in two optical spectral bands [7], that allows to couple them with a different solar cells which have dedicated external quantum efficiency. The optical separation using dichroic filters allows to combine different photovoltaic cells with an appropriate energy gap, thus optimizing the photovoltaic conversion.

  13. CdS films deposited by chemical bath under rotation

    Oliva-Aviles, A.I., E-mail: aoliva@mda.cinvestav.mx [Centro de Investigacion y de Estudios Avanzados Unidad Merida, Departamento de Fisica Aplicada. A.P. 73-Cordemex, 97310 Merida, Yucatan (Mexico); Patino, R.; Oliva, A.I. [Centro de Investigacion y de Estudios Avanzados Unidad Merida, Departamento de Fisica Aplicada. A.P. 73-Cordemex, 97310 Merida, Yucatan (Mexico)

    2010-08-01

    Cadmium sulfide (CdS) films were deposited on rotating substrates by the chemical bath technique. The effects of the rotation speed on the morphological, optical, and structural properties of the films were discussed. A rotating substrate-holder was fabricated such that substrates can be taken out from the bath during the deposition. CdS films were deposited at different deposition times (10, 20, 30, 40 and 50 min) onto Corning glass substrates at different rotation velocities (150, 300, 450, and 600 rpm) during chemical deposition. The chemical bath was composed by CdCl{sub 2}, KOH, NH{sub 4}NO{sub 3} and CS(NH{sub 2}){sub 2} as chemical reagents and heated at 75 deg. C. The results show no critical effects on the band gap energy and the surface roughness of the CdS films when the rotation speed changes. However, a linear increase on the deposition rate with the rotation energy was observed, meanwhile the stoichiometry was strongly affected by the rotation speed, resulting a better 1:1 Cd/S ratio as speed increases. Rotation effects may be of interest in industrial production of CdTe/CdS solar cells.

  14. CdS films deposited by chemical bath under rotation

    Cadmium sulfide (CdS) films were deposited on rotating substrates by the chemical bath technique. The effects of the rotation speed on the morphological, optical, and structural properties of the films were discussed. A rotating substrate-holder was fabricated such that substrates can be taken out from the bath during the deposition. CdS films were deposited at different deposition times (10, 20, 30, 40 and 50 min) onto Corning glass substrates at different rotation velocities (150, 300, 450, and 600 rpm) during chemical deposition. The chemical bath was composed by CdCl2, KOH, NH4NO3 and CS(NH2)2 as chemical reagents and heated at 75 deg. C. The results show no critical effects on the band gap energy and the surface roughness of the CdS films when the rotation speed changes. However, a linear increase on the deposition rate with the rotation energy was observed, meanwhile the stoichiometry was strongly affected by the rotation speed, resulting a better 1:1 Cd/S ratio as speed increases. Rotation effects may be of interest in industrial production of CdTe/CdS solar cells.

  15. Development of suppression method for deposition of radioactive nuclides after chemical decontamination by platinum deposition treatment

    Noble metal chemical addition (NMCA) technology has been widely adopted for BWR plants in the US as a means to mitigate stress corrosion cracking (SCC). Dose rate of the reactor water recirculation system piping of some BWR plants that apply a combination of NMCA and zinc injection technology have gradually decreased. Chemical decontamination removes 60Co, but also the noble metal from the piping surfaces. Thus, effect of dose rate reduction by NMCA is decreased in the plant operating period after chemical decontamination. We considered that platinum deposition treatment just after chemical decontamination before plant operation would be effective to prevent redeposition of the 60Co. In this platinum deposition treatment process, Sodium hexahydroxyplatinate (IV), hydrazine and ammonia are used as the treatment chemicals. A 60Co deposition reduction effect of 1/2 compared to non-treatment is confirmed for up to 1,000 hours by laboratory experiments. (author)

  16. Optimization of the contact mechanical strength of magnetron-sputtered nitrogen-doped AISI 316L physically vapour deposited coatings

    The reactive magnetron sputtering technique adopted produces perfectly adhering nitrogen-doped AISI 316L coatings on construction and stainless steel substrates (AISI 316L and 4135). Surface mechanical testing was done by indentation and sclerometric, frictional, low cycle fatigue. The major damage parameters adopted were the critical coating cracking loads, track depression and lateral pile-up volumes. It is shown that the detrimental effect of growth defects on coating brittleness can be controlled to some extent by optimizing substrate surface treatment prior to and bias voltage during deposition. (orig.)

  17. Networks of ultra-fine Ag nanocrystals in a Teflon AF (registered) matrix by vapour phase e-beam-assisted deposition

    We have fabricated nanocomposite thin films comprising silver (Ag) nanoparticles dispersed in a Teflon AF (registered) polymer matrix using electron-beam-assisted physical vapour deposition. Four different Ag nanoparticle volume fillings (20%, 35%, 70% and 75%) were achieved by varying the relative metal-polymer evaporation rates with the formation of highly crystalline Ag nanoparticles regardless of the filling ratio. The present fabrication technique allowed full control over dispersion uniformity of nanoparticles in the polymer network. At 20% and 35% metal volume fillings, the nanocomposite film morphology consists of a uniformly dispersed assembly of equiaxed isolated Ag nanoparticles. At higher metal volume fractions the nanocomposite structures displayed two different and unique Ag nanoparticle arrangements within the polymer matrix. In particular, at 70% metal filling, the formation of irregularly shaped clusters of individually assembled nanocrystals was observed. At a slightly higher volume filling (75%), larger irregularly shaped Ag nanocrystals that appeared to be the result of coalescence and grain growth were observed. Finally, a composite theory developed by Tandon and Weng was used to estimate various elastic properties of the nanocomposite films. At high metal filling, the reinforcing effect of the Ag nanoparticles was reflected as approximately a sixfold increase in the elastic modulus compared to the virgin polymer film. Possible applications of such ultra-fine metal nanoparticles networks are discussed

  18. Structural and environmental dependence of superlow friction in ion vapour-deposited a-C : H : Si films for solid lubrication application

    Understanding the tribochemical interaction of water molecules in humid environment with carbonaceous film surfaces, especially hydrophilic surface, is fundamental for applications in tribology and solid lubrication. This paper highlights some experimental evidence to elucidate the structural and environmental dependence of ultralow or even superlow friction in ion vapour-deposited a-C : H : Si films. The results indicate that both surface density of silicon hydroxyl group (Si–OH) and humidity level (RH) determine the frictional performance of a-C : H : Si films. Ultralow friction coefficient μ (∼0.01–0.055) is feasible in a wide range of RH. The dissociative formation of hydrophilic Si–OH surface and the following nanostructure of interfacial water molecules under contact pressure are the origin of ultralow friction for a-C : H : Si films in humid environment. The correlation between contact pressure and friction coefficient derived from Hertzian contact model is not valid in the present case. Under this nanoscale boundary lubrication, the friction coefficient tends to increase as the contact pressure increases. There even exists a contact pressure threshold for the transition from ultralow to superlow friction (μ ∼ 0.007). In comparison, when tribotested in dry N2, the observed superlow friction (μ ∼ 0.004) in the absence of water is correlated with the formation of a low shear strength tribolayer by wear-induced phase transformation. (paper)

  19. Structural and environmental dependence of superlow friction in ion vapour-deposited a-C : H : Si films for solid lubrication application

    Chen, Xinchun; Kato, Takahisa; Kawaguchi, Masahiro; Nosaka, Masataka; Choi, Junho

    2013-06-01

    Understanding the tribochemical interaction of water molecules in humid environment with carbonaceous film surfaces, especially hydrophilic surface, is fundamental for applications in tribology and solid lubrication. This paper highlights some experimental evidence to elucidate the structural and environmental dependence of ultralow or even superlow friction in ion vapour-deposited a-C : H : Si films. The results indicate that both surface density of silicon hydroxyl group (Si-OH) and humidity level (RH) determine the frictional performance of a-C : H : Si films. Ultralow friction coefficient μ (˜0.01-0.055) is feasible in a wide range of RH. The dissociative formation of hydrophilic Si-OH surface and the following nanostructure of interfacial water molecules under contact pressure are the origin of ultralow friction for a-C : H : Si films in humid environment. The correlation between contact pressure and friction coefficient derived from Hertzian contact model is not valid in the present case. Under this nanoscale boundary lubrication, the friction coefficient tends to increase as the contact pressure increases. There even exists a contact pressure threshold for the transition from ultralow to superlow friction (μ ˜ 0.007). In comparison, when tribotested in dry N2, the observed superlow friction (μ ˜ 0.004) in the absence of water is correlated with the formation of a low shear strength tribolayer by wear-induced phase transformation.

  20. Chemical solution deposition: a path towards low cost coated conductors

    The achievement of low cost deposition techniques for high critical current YBa2Cu3O7 coated conductors is one of the major objectives to achieve a widespread use of superconductivity in power applications. Chemical solution deposition techniques are appearing as a very promising methodology to achieve epitaxial oxide thin films at a low cost, so an intense effort is being carried out to develop routes for all chemical coated conductor tapes. In this work recent achievements will be presented towards the goal of combining the deposition of different type of buffer layers on metallic substrates based on metal-organic decomposition with the growth of YBa2Cu3O7 layers using the trifluoroacetate route. The influence of processing parameters on the microstructure and superconducting properties will be stressed. High critical currents are demonstrated in 'all chemical' multilayers

  1. Water Condensation on Zinc Surfaces Treated by Chemical Bath Deposition

    Narhe, R.D. (Ramchandra D.); González-Viñas, W.; Beysens, D.A. (Daniel A.)

    2010-01-01

    Water condensation, a complex and challenging process, is investigated on a metallic (Zn) surface, regularly used as anticorrosive surface. The Zn surface is coated with hydroxide zinc carbonate by chemical bath deposition, a very simple, low-cost and easily applicable process. As the deposition time increases, the surface roughness augments and the contact angle with water can be varied from 75º to 150º , corresponding to changing the surface properties from hydrophobic to ultrahydrophobic a...

  2. Chemical Liquid Phase Deposition of Thin Aluminum Oxide Films

    Sun, Jie; Sun, Yingchun

    2007-01-01

    Thin aluminum oxide films were deposited by a new and simple physicochemical method called chemical liquid phase deposition (CLD) on semiconductor materials. Aluminum sulfate with crystallized water and sodium bicarbonate were used as precursors for film growth, and the control of the system pH value played an important role in this experiment. The growth rate is 12 nm/h at room temperature. Post-growth annealing not only densifies and purifies the films, but results in film crystallization a...

  3. Effects of deposition time in chemically deposited ZnS films in acidic solution

    Haddad, H.; Chelouche, A., E-mail: azeddinechelouche@gmail.com; Talantikite, D.; Merzouk, H.; Boudjouan, F.; Djouadi, D.

    2015-08-31

    We report an experimental study on the synthesis and characterization of zinc sulfide (ZnS) single layer thin films deposited on glass substrates by chemical bath deposition technique in acidic solution. The effect of deposition time on the microstructure, surface morphology, optical absorption, transmittance, and photoluminescence (PL) was investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), UV-Vis–NIR spectrophotometry and photoluminescence (PL) spectroscopy. The results showed that the samples exhibit wurtzite structure and their crystal quality is improved by increasing deposition time. The latter, was found to affect the morphology of the thin films as showed by SEM micrographs. The optical measurements revealed a high transparency in the visible range and a dependence of absorption edge and band gap on deposition time. The room temperature PL spectra indicated that all ZnS grown thin films emit a UV and blue light, while the band intensities are found to be dependent on deposition times. - Highlights: • Single layer ZnS thin films were deposited by CBD in acidic solution at 95 °C. • The effect of deposition time was investigated. • Coexistence of ZnS and ZnO hexagonal structures for time deposition below 2 h • Thicker ZnS films were achieved after monolayer deposition for 5 h. • The highest UV-blue emission observed in thin film deposited at 5 h.

  4. Effects of deposition time in chemically deposited ZnS films in acidic solution

    We report an experimental study on the synthesis and characterization of zinc sulfide (ZnS) single layer thin films deposited on glass substrates by chemical bath deposition technique in acidic solution. The effect of deposition time on the microstructure, surface morphology, optical absorption, transmittance, and photoluminescence (PL) was investigated by X-ray diffraction (XRD), scanning electronic microscopy (SEM), UV-Vis–NIR spectrophotometry and photoluminescence (PL) spectroscopy. The results showed that the samples exhibit wurtzite structure and their crystal quality is improved by increasing deposition time. The latter, was found to affect the morphology of the thin films as showed by SEM micrographs. The optical measurements revealed a high transparency in the visible range and a dependence of absorption edge and band gap on deposition time. The room temperature PL spectra indicated that all ZnS grown thin films emit a UV and blue light, while the band intensities are found to be dependent on deposition times. - Highlights: • Single layer ZnS thin films were deposited by CBD in acidic solution at 95 °C. • The effect of deposition time was investigated. • Coexistence of ZnS and ZnO hexagonal structures for time deposition below 2 h • Thicker ZnS films were achieved after monolayer deposition for 5 h. • The highest UV-blue emission observed in thin film deposited at 5 h

  5. Chemical vapor deposition (CVD) of uranium for alpha spectrometry

    The uranium determination through radiometric techniques as alpha spectrometry requires for its proper analysis, preparation methods of the source to analyze and procedures for the deposit of this on a surface or substrate. Given the characteristics of alpha particles (small penetration distance and great loss of energy during their journey or its interaction with the matter), is important to ensure that the prepared sources are thin, to avoid problems of self-absorption. The routine methods used for this are the cathodic electro deposition and the direct evaporation, among others. In this paper the use of technique of chemical vapor deposition (CVD) for the preparation of uranium sources is investigated; because by this, is possible to obtain thin films (much thinner than those resulting from electro deposition or evaporation) on a substrate and comprises reacting a precursor with a gas, which in turn serves as a carrier of the reaction products to achieve deposition. Preliminary results of the chemical vapor deposition of uranium are presented, synthesizing and using as precursor molecule the uranyl acetylacetonate, using oxygen as carrier gas for the deposition reaction on a glass substrate. The uranium films obtained were found suitable for alpha spectrometry. The variables taken into account were the precursor sublimation temperatures and deposition temperature, the reaction time and the type and flow of carrier gas. Of the investigated conditions, two depositions with encouraging results that can serve as reference for further work to improve the technique presented here were selected. Alpha spectra obtained for these depositions and the characterization of the representative samples by scanning electron microscopy and X-ray diffraction are also presented. (Author)

  6. Preparation of Sm–Ru bimetallic alloy films on Ru(0001) surface by vapour-deposition and annealing

    G Ranga Rao; H Nozoye

    2001-12-01

    Sm–Ru intermetallic surface alloy films were prepared by vacuum deposition and annealing of rare earth Sm on single crystal Ru(0001) surface. The Ru 3 and Sm 3 core level spectra clearly show the formation of surface alloy layers. XPS measurements on surface alloy film revealed an induced peak in the Ru3 region at lower binding energy by 1 eV compared to the bulk Ru (elemental) suggesting an electronic effect of alloying and Sm–Ru bond formation. The Sm 35/2 photoemission peak of Sm film consists of strong features characteristic of Sm(II) with electron configuration 46 (5\\ 6)2 and Sm(III) with electron configuration 46 (5\\ 6)3. It is observed that the Sm(II) feature decreases in intensity upon alloy formation with surface Ru atoms. Oxidation of these films with carbon monoxide indicates alloy breakdown due to the oxidation of Sm atoms selectively. Alloy oxidation also shows a clear shift of Sm 35/2 feature.

  7. Grafting 4f and 3d metal complexes into mesoporous MCM-41 silica by wet impregnation and by chemical vapour infiltration

    Hybrid organic/inorganic materials have been prepared by reacting mesoporous MCM-41 silica with transition metal β-diketonates, either by wet impregnation (WI) or by chemical vapour infiltration (CVI). Compounds obtained from Eu(III) or Gd(III) β-diketonates, both by wet impregnation and by CVI, contain chemisorbed metalorganic species with strong Si-O-Ln bonding. Compounds prepared (by CVI only) from Cu(II) or Mn(III) β-diketonates show a more complex absorption process than the lanthanides, since upon heating under dynamic vacuum they release part of the absorbed metal complex. Eu(thd)3 was more specifically used to prepare luminescent materials. It was used either alone, or with phenanthroline as an additional ligand in order to promote the so called 'antenna effect'

  8. Chemical-vapor deposition of silicon from silane

    Hsu, G. C.; Lutwack, R.; Praturi, A. K.

    1979-01-01

    Report lists tables of standard free-energy change, equilibrium constant, and heat of reaction for chemical vapor deposition (CVD) of silicon from silane over temperature range of 100 to 1000 K. Data indicates silicon CVD may be a commercially economical process for production of silicon for solar arrays and other applications.

  9. Chemical vapor deposition (CVD) growth of graphene films

    Frank, Otakar; Kalbáč, Martin

    Cambridge: Woodhead Publishing, 2014 - (Skákalová, V.; Kaiser, A.), s. 27-49. (Woodhead Publishing Series in Electronic and Optical Materials. 57). ISBN 978-0-85709-508-4 R&D Projects: GA MŠk LL1301 Institutional support: RVO:61388955 Keywords : graphene * chemical vapor deposition (CVD) * isotope labeling Subject RIV: CF - Physical ; Theoretical Chemistry

  10. Chemical Vapor Deposition of Aluminum Oxide Thin Films

    Vohs, Jason K.; Bentz, Amy; Eleamos, Krystal; Poole, John; Fahlman, Bradley D.

    2010-01-01

    Chemical vapor deposition (CVD) is a process routinely used to produce thin films of materials via decomposition of volatile precursor molecules. Unfortunately, the equipment required for a conventional CVD experiment is not practical or affordable for many undergraduate chemistry laboratories, especially at smaller institutions. In an effort to…

  11. Structure and physico-chemical properties of Kumkol petroleum deposit

    Results of study of physico-chemical properties and structure of Kumkol deposit petroleum in Southern Kazakhstan are presented. It is determined, that these petroleums are light, paraffinic, with low sulfur and ash contents, has insignificant concentration of vanadium and nickel, and has not porphyrin complexes. (author)

  12. Oxygen Barrier Coating Deposited by Novel Plasma-enhanced Chemical Vapor Deposition

    Jiang, Juan; Benter, M.; Taboryski, Rafael Jozef;

    2010-01-01

    We report the use of a novel plasma-enhanced chemical vapor deposition chamber with coaxial electrode geometry for the SiOx deposition. This novel plasma setup exploits the diffusion of electrons through the inner most electrode to the interior samples space as the major energy source. This confi...... increased the barrier property of the modified low-density polyethylene, polyethylene terephthalate, and polylactide by 96.48%, 99.69%, and 99.25%, respectively....

  13. ZnSe thin films by chemical bath deposition method

    Lokhande, C.D.; Patil, P.S.; Tributsch, H. [Hahn-Meitner-Institute, Bereich Physikalische Chemie, Abt. CS, Glienicker Strasse-100, D-14109 Berlin (Germany); Ennaoui, A. [Hahn-Meitner-Institute, Bereich Physikalische Chemie, Abt. CG, Glienicker Strasse-100, D-14109 Berlin (Germany)

    1998-09-04

    The ZnSe thin films have been deposited onto glass substrates by the simple chemical bath deposition method using selenourea as a selenide ion source from an aqueous alkaline medium. The effect of Zn ion concentration, bath temperature and deposition time period on the quality and thickness of ZnSe films has been studied. The ZnSe films have been characterized by XRD, TEM, EDAX, TRMC (time-resolved microwave conductivity), optical absorbance and RBS techniques for their structural, compositional, electronic and optical properties. The as-deposited ZnSe films are found to be amorphous, Zn rich with optical band gap, Eg, equal to 2.9 eV

  14. Influence of deposition time on the properties of chemical bath deposited manganese sulfide thin films

    Anuar Kassim

    2010-12-01

    Full Text Available Manganese sulfide thin films were chemically deposited from an aqueous solution containing manganese sulfate, sodium thiosulfate and sodium tartrate. The influence of deposition time (2, 3, 6 and 8 days on the properties of thin films was investigated. The structure and surface morphology of the thin films were studied by X-ray diffraction and atomic force microscopy, respectively. In addition, in order to investigate the optical properties of the thin films, the UV-visible spectrophotometry was used. The XRD results indicated that the deposited MnS2 thin films exhibited a polycrystalline cubic structure. The number of MnS2 peaks on the XRD patterns initially increased from three to six peaks and then decreased to five peaks, as the deposition time was increased from 2 to 8 days. From the AFM measurements, the film thickness and surface roughness were found to be dependent on the deposition time.

  15. Chemically Deposited Thin-Film Solar Cell Materials

    Raffaelle, R.; Junek, W.; Gorse, J.; Thompson, T.; Harris, J.; Hehemann, D.; Hepp, A.; Rybicki, G.

    2005-01-01

    We have been working on the development of thin film photovoltaic solar cell materials that can be produced entirely by wet chemical methods on low-cost flexible substrates. P-type copper indium diselenide (CIS) absorber layers have been deposited via electrochemical deposition. Similar techniques have also allowed us to incorporate both Ga and S into the CIS structure, in order to increase its optical bandgap. The ability to deposit similar absorber layers with a variety of bandgaps is essential to our efforts to develop a multi-junction thin-film solar cell. Chemical bath deposition methods were used to deposit a cadmium sulfide (CdS) buffer layers on our CIS-based absorber layers. Window contacts were made to these CdS/CIS junctions by the electrodeposition of zinc oxide (ZnO). Structural and elemental determinations of the individual ZnO, CdS and CIS-based films via transmission spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy and energy dispersive spectroscopy will be presented. The electrical characterization of the resulting devices will be discussed.

  16. Fundamental studies of chemical vapor deposition diamond growth processes

    We are developing laser spectroscopic techniques to foster a fundamental understanding of diamond film growth by hot filament chemical vapor deposition (CVD). Several spectroscopic techniques are under investigation to identify intermediate species present in the bulk reactor volume, the thin active volume immediately above the growing film, and the actual growing surface. Such a comprehensive examination of the overall deposition process is necessary because a combination of gas phase and surface chemistry is probably operating. Resonantly enhanced multiphoton ionization (REMPI) techniques have been emphasized. A growth rector that permits through-the-substrate gas sampling for REMPI/time-of-flight mass spectroscopy has been developed. 7 refs., 2 figs

  17. An Overview on Thin Films Prepared by Chemical Vapor Deposition

    Chemical vapor deposition, (CVD); involves the formation of a solid thin layer on a heated substrate surface by means of chemical reaction in gas or vapor phase. CVD techniques have expanded continuously and developed into the most important method for producing films for solid-state devices. CVD is considered to be the major technique for preparing most films used in the fabrication of semiconductor devices and integrated circuits. It has advantages such as the versatility, compatibility, quality, simplicity, reproducibility, and low cost. CVD has some disadvantages of; the use of comparatively high temperatures in many processes and chemical hazards caused by toxic, explosive, or corrosive gases. Chemical vapor deposition processes can be classified according to the type of their activation energy into thermally-activated CVD, plasma-enhanced CVD, laser-induced CVD, photochemical CVD, and electron-beam assisted CVD. In this paper an attempt is made to present all aspects of CVD equipment design and the variables affecting the deposition rate. Finally the preparation requirements and the application of CVD films are also summarized. 5 figs

  18. Microstructural characterisation and thermal stability of Mg-2.3% wt Zr alloy synthesised by Physical Vapour Deposition (PVD); Caracterizacion microestructural y estabilidad termica de la aleacion Mg-2,3% Zr sintetizada mediante Deposicion Fisica en Fase Vapor (PVD)

    Garces, G.; Perez, P.; Adeva, P.

    2003-07-01

    The objective of this work has been the study of the microstructure and the thermal stability of the alloy Mg-2,3%Zr grown by Physical Vapour Deposition. This study has been carried out by Differential Scanning Calorimetry and Transmission Electron Microscopy. The alloy in the as-deposited condition consists of a solid solution of zirconium atoms in the magnesium matrix. The microstructure of the alloy is characterised by elongated grains oriented in the growth direction. These grains grow with the (0001) direction parallel to the deposit growth direction. During a continuous heating, the deposit shows three exo thermal transformations which have been associated with a recovery process, the zirconium precipitation in the magnesium matrix and oxidation oat high temperatures. The activation energy for the precipitation reaction calculated from Kissinger analysis is 139 kJmol''1. (Author) 31 refs.

  19. The power source effect on SiOx coating deposition by plasma enhanced chemical vapor deposition

    SiOx coatings were prepared by capacitively coupled plasma enhanced chemical vapor deposition on polyethyleneterephtalate substrates in 23 kHz middle-frequency and radio frequency power supplies, respectively, where hexamethyldisiloxane was used as gas source. The influences of discharge conditions on gas phase intermediate species and active radicals for SiOx formation was investigated by mass spectrometry as real-time in-situ diagnosis. The deposited SiOx coating chemical structures were also analyzed by Fourier transform infrared spectroscopy. Meanwhile, the film barrier property, oxygen transmission rate, was measured at 23 oC and 50% humidity circumstance. The better barrier property was obtained in the MF power source depositing SiOx coated PET.

  20. The versatility of hot-filament activated chemical vapor deposition

    In the field of activated chemical vapor deposition (CVD) of polycrystalline diamond films, hot-filament activation (HF-CVD) is widely used for applications where large deposition areas are needed or three-dimensional substrates have to be coated. We have developed processes for the deposition of conductive, boron-doped diamond films as well as for tribological crystalline diamond coatings on deposition areas up to 50 cm x 100 cm. Such multi-filament processes are used to produce diamond electrodes for advanced electrochemical processes or large batches of diamond-coated tools and parts, respectively. These processes demonstrate the high degree of uniformity and reproducibility of hot-filament CVD. The usability of hot-filament CVD for diamond deposition on three-dimensional substrates is well known for CVD diamond shaft tools. We also develop interior diamond coatings for drawing dies, nozzles, and thread guides. Hot-filament CVD also enables the deposition of diamond film modifications with tailored properties. In order to adjust the surface topography to specific applications, we apply processes for smooth, fine-grained or textured diamond films for cutting tools and tribological applications. Rough diamond is employed for grinding applications. Multilayers of fine-grained and coarse-grained diamond have been developed, showing increased shock resistance due to reduced crack propagation. Hot-filament CVD is also used for in situ deposition of carbide coatings and diamond-carbide composites, and the deposition of non-diamond, silicon-based films. These coatings are suitable as diffusion barriers and are also applied for adhesion and stress engineering and for semiconductor applications, respectively

  1. Coating of metals with titanium diboride by chemical vapor deposition

    This study is an experimental investigation of the chemical vapor deposition of titanium diboride on metallic substrates by the hydrogen reduction of TiCl4 and BCl3 at temperatures between 8500C and 11000C. Kovar, tantalum, and several stainless steels were found to be suitable substrates since they could withstand the deposition temperature, had adequate resistance to HCl, a by-product of the deposition reaction, and had thermal expansion coefficients sufficiently close to that of TiB2 (less than or equal to10 x 10-6/0C). The TiB2 coatings produced were 68.2% Ti and thus near stoichiometry and had very low impurity content. They had Knoop hardnesses averaging 3300 kg/mm2 and exhibited extraordinary erosion resistance

  2. Chemical Liquid Phase Deposition of Thin Aluminum Oxide Films

    SUN,Jie(孙捷); SUN,Ying-Chun(孙迎春)

    2004-01-01

    Thin aluminum oxide films were deposited by a new and simple physicochemical method called chemical liquid phase deposition (CLD) on semiconductor materials. Aluminum sulfate with crystallized water and sodium bicarbonate were used as precursors for film growth, and the control of the system's pH value played an important role in this experiment. The growth rate is 12 nm/h with the deposition at [Al2(SO4)3]=0.0837 mol·L-1, [NaHCO3]=0.214 mol·L-1, 15 ℃. Post-growth annealing not only densifies and purifies the films, but results in film crystallization as well, Excellent quality of A12O3 films in this work is supported by electron dispersion spectroscopy,Fourier transform infrared spectrum, X-ray diffraction spectrum and scanning electron microscopy photograph.

  3. Advances in the chemical vapor deposition (CVD) of Tantalum

    Mugabi, James Atwoki; Eriksen, Søren; Christensen, Erik;

    2014-01-01

    The chemical stability of tantalum in hot acidic media has made it a key material in the protection of industrial equipment from corrosion under such conditions. The Chemical Vapor Deposition of tantalum to achieve such thin corrosion resistant coatings is one of the most widely mentioned examples...... of CVD processes; however very little information on the process and its characteristics can be found. This work presents the state of the art on the CVD of tantalum in long narrow channels and a reaction mechanism is suggested based on a rudimentary model. The effects of the system pressure...

  4. Carbon nanostructures and networks produced by chemical vapor deposition

    Kowlgi, N.K.K.; Koper, G.J.M.; Raalten, R.A.D.

    2012-01-01

    The invention pertains to a method for manufacturing crystalline carbon nanostructures and/or a network of crystalline carbon nanostructures, comprising: (i) providing a bicontinuous micro-emulsion containing metal nanoparticles having an average particle size between 1and 100nm; (ii) bringing said bicontinuous micro-emulsion into contact with a substrate; and (iii) subjecting said metal nanoparticles and a gaseous carbon source to chemical vapor deposition, thus forming carbon nanostructures...

  5. Preparation of potassium tantalate thin films through chemical solution deposition

    Buršík, Josef; Drbohlav, Ivo; Vaněk, Přemysl; Železný, Vladimír

    2004-01-01

    Roč. 24, č. 2 (2004), s. 455-462. ISSN 0955-2219 R&D Projects: GA MŠk LN00A028; GA MŠk OC 528.001; GA ČR GA202/02/0238; GA ČR GA202/00/1245 Institutional research plan: CEZ:AV0Z4032918 Keywords : chemical solution deposition * films * tantalates Subject RIV: CA - Inorganic Chemistry Impact factor: 1.483, year: 2004

  6. Advantages and limitations of employment of high resolution continuum source AAS as detector of chemical generated metallic vapours

    Complete text of publication follows. A method was developed to determine metals after vapour generation, atomization in a heated quartz tube and detection using High Resolution Continuum Source AAS (ContrAA 300R equipment, Analytic Jena, Germany). High resolution continuum source AAS allows sequential analysis of elements with detection limits a factor of five better than those of Line Source AAS. This fact is due to the combined use of higher radiation intensity xenon continuum source, a high resolution monochromator and a CCD array detector. Moreover, important advantages of this technique were relatively low cost, possibility to visualize molecular absorption lines (mainly diatomic species). Modifications on the HS60 (Analytic Jena, Germany) vapor generation system were performed. The system includes three peristaltic pumps, a three channel and a one channel, controlled by software and a external peristaltic pump. Flow rates were selected from the three permitted velocities, in order to provide maximum sensitivity and an adequate operation in the gas-liquid separator. A home-made glass hydrostatic gas-liquid separator was used. A 140 cm length PTFE tube and a small piece of PharmedR tube were included to transfer vapors from the gas-liquid separator to the quartz cell. Regarding the Ar carrier flow, it must be pointed out that ContrAA 300R equipment only has three options for this parameter (6, 25, and 31 L h-1), and this is a difficulty to study possible effects on the liberation of vapors from the aqueous phase or their concentration in the quartz tube. Optimum conditions for the sequential determination of Ag, Cd, Cu, Co, Ni and Zn were obtained and technical limitations of the system are examined. Calibration curves were lineal (r = 0.995 or higher). Method is precise (RSD <10%) and with LODs lower than 20 g/L for studied elements except for Ni and Co. The authors kindly acknowledge the financial support from Xunta de Galicia (ref. PGIDIT07PXIB209034PR).

  7. Synthesis and characterization of Bi1−xNdxFeO3 thin films deposited using a high throughput physical vapour deposition technique

    The high throughput synthesis of BiFeO3 and rare earth doped BiFeO3 films using a modified molecular beam epitaxy technique is reported. Optimum conditions for deposition have been established and compositionally graded Bi(1−x)NdxFeO3 (x = 0.08 to 0.24) thin films have been fabricated on platinised silicon substrate (Si/SiO2/TiO2/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 BiFeO3 end member. For x > 0.20, the structure and symmetry were consistent with the NdFeO3 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 PbZrO3-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

  8. Deposition and characterization of Ru thin films prepared by metallorganic chemical vapor deposition

    Kang, S Y; Lee, S K; Hwang, C S; Kim, H J

    2000-01-01

    Ru thin films were deposited at 300 approx 400 .deg. C by using Ru(C sub 5 H sub 4 C sub 2 H sub 5) sub 2 (Ru(EtCp) sub 2) as a precursor and low-pressure metalorganic chemical vapor deposition. The addition of O sub 2 gas was essential to form Ru thin films. The deposition rates of the films were about 200 A/min. For low oxygen addition and high substrate temperature, RuO sub 2 phases were formed. Also, thermodynamic calculations showed that all the supplied oxygen was consumed to oxidize carbon and hydrogen, cracked from the precursor ligand, rather than Ru. Thus, metal films could be obtained There was an optimum oxygen to precursor ratio at which the pure Ru phase could be obtained with minimum generation of carbon and RuO sub 2

  9. Pengaruh Temperatur, Massa Zink, Substrat Dan Waktu Tahan Terhadap Struktur Dan Morfologi Zno Hasil Sintesis Dengan Metode Chemical Vapour Transport (CVT

    Arisela Distyawan

    2013-09-01

    Full Text Available Normal 0 false false false MicrosoftInternetExplorer4 Material Zink Oksida (ZnO telah berhasil disintesis menggunakan metode Chemical Vapour Transport dengan bahan dasar prekursor berupa serbuk Zn yang dipanaskan hingga mencapai temperatur uap dalam furnace horisontal. Adapun variasi yang diberikan dalam penelitian adalah berupa temperatur pemanasan (850, 900, dan 950oC, massa prekursor Zn (0,15, 0,25, dan 0,35g, lama waktu sputtering substrat (90 dan 180 detik, dan waktu tahan khusus untuk mengetahui initial growth ZnO (10, 20, 30, 40, 50, dan 60 menit. Pembentukan Zink Oksida (ZnO dikonfirmasi melalui data X-RD, dimana telah terbentuk material ZnO dengan struktur hexagonal wurtzite. Berdarsarkan data XRD juga diketahui ukuran kristal pada sampel sputtering 90 detik mengalami penurunan bersamaan penambahan massa Zn. Dari hasil pengamatan SEM didapatkan bahwa morfologi permukaan lapisan tipis ZnO terdiri dari berbagai macam bentuk berupa nanoparticle, nanowires, nanorods, dan nanotetrapod. Lapisan Zno paling tebal sebesar ±350 nm pada sampel 950oC-0,15g sputter 90 detik. Semakin tinggi temperatur operasi berdampak peningkatan ukuran partikel. Pengujian FTIR turut menguatkan terbentuknya lapisan tipis di permukaan substrat Alumina. Hal ini didasarkan terjadinya penyerapan vibrasi yang membentuk lekukan pada kisaran area 509 cm-1 dari masing-masing sampel.

  10. A chemical assessment of the suitability of allyl- iso-propyltelluride as a Te precursor for metal organic vapour phase epitaxy

    Hails, Janet E.; Cole-Hamilton, David J.; Stevenson, John; Bell, William; Foster, Douglas F.; Ellis, David

    2001-04-01

    The chemical studies, which led to the testing of allyl- iso-propyltelluride (allylTePr i) as a Te precursor in metal organic vapour phase epitaxy are presented. The pyrolysis in hydrogen of allylTePr i gave products including 1,5-hexadiene, propane and propene. Co-pyrolysis of dimethylcadmium (Me 2Cd) and allylTePr i gave the hydrocarbons expected from the pyrolysis of the individual precursors plus additional hydrocarbons including 2-methylpropane and 1-butene. Plots of percentage decomposition versus temperature, which proved extremely useful in determining the likely growth temperatures for both CdTe and HgTe, showed that allylTePr i is less stable than both Pr 2iTe (di- iso-propyltelluride) and Me 2Cd. The possible role of Hg in the growth of CdTe is also discussed. The chemistry of allylTePr i is well suited for use as an efficient precursor for epitaxial growth of tellurium containing semiconductors since there is very little formation of other organotellurium compounds on pyrolysis.

  11. Effect of gas flow rates on the anatase-rutile transformation temperature of nanocrystalline TiO2 synthesised by chemical vapour synthesis.

    Ahmad, Md Imteyaz; Bhattacharya, S S; Fasel, Claudia; Hahn, Horst

    2009-09-01

    Of the three crystallographic allotropes of nanocrystalline titania (rutile, anatase and brookite), anatase exhibits the greatest potential for a variety of applications, especially in the area of catalysis and sensors. However, with rutile being thermodynamically the most stable phase, anatase tends to transform into rutile on heating to temperatures in the range of 500 degrees C to 700 degrees C. Efforts made to stabilize the anatase phase at higher temperatures by doping with metal oxides suffer from the problems of having a large amorphous content on synthesis as well as the formation of secondary impurity phases on doping. Recent studies have suggested that the as-synthesised phase composition, crystallite size, initial surface area and processing conditions greatly influence the anatase to rutile transformation temperature. In this study nanocrystalline titania was synthesised in the anatase form bya chemical vapour synthesis (CVS) method using titanium tetra iso-propoxide (TTIP) as a precursor under varying flow rates of oxygen and helium. The anatase to rutile transformation was studied using high temperature X-ray diffraction (HTXRD) and simultaneous thermogravimetric analysis (STA), followed by transmission electron microscopy (TEM). It was demonstrated that the anatase-rutile transformation temperatures were dependent on the oxygen to helium flow rate ratio during CVS and the results are presented and discussed. PMID:19928267

  12. Synthesis of mullite coatings by chemical vapor deposition

    Mulpuri, R.P.; Auger, M.; Sarin, V.K. [Boston Univ., MA (United States)

    1996-08-01

    Formation of mullite on ceramic substrates via chemical vapor deposition was investigated. Mullite is a solid solution of Al{sub 2}O{sub 3} and SiO{sub 2} with a composition of 3Al{sub 2}O{sub 3}{circ}2SiO{sub 2}. Thermodynamic calculations performed on the AlCl{sub 3}-SiCl{sub 4}-CO{sub 2}-H{sub 2} system were used to construct equilibrium CVD phase diagrams. With the aid of these diagrams and consideration of kinetic rate limiting factors, initial process parameters were determined. Through process optimization, crystalline CVD mullite coatings have been successfully grown on SiC and Si{sub 3}N{sub 4} substrates. Results from the thermodynamic analysis, process optimization, and effect of various process parameters on deposition rate and coating morphology are discussed.

  13. Electrospray deposition of isolated chemically synthesized magnetic nanoparticles

    Agostini, Pierre; Meffre, Anca; Lacroix, Lise-Marie; Ugnati, Damien [Université de Toulouse (France); INSA, UPS, CNRS, Laboratoire de Physique et Chimie des Nano-objets (LPCNO) (France); Ondarçuhu, Thierry [Centre d’Elaboration de Matériaux et d’Etudes Structurales (CEMES-CNRS) (France); Respaud, Marc; Lassagne, Benjamin, E-mail: lassagne@insa-toulouse.fr [Université de Toulouse (France); INSA, UPS, CNRS, Laboratoire de Physique et Chimie des Nano-objets (LPCNO) (France)

    2016-01-15

    The deposition of isolated magnetic nanoparticles onto a substrate was performed using electrohydrodynamic spraying. Two kinds of nanoparticles were sprayed, 11 nm CoFe carbide nanospheres and 10.5 nm Fe nanocubes. By studying carefully the evolution of the sprayed charged droplets and the mechanism of nanoparticle dispersion in them, we could optimize the nanoparticle concentration within the initial nanoparticle solution (i) to reduce the magnetic interaction and therefore prevent agglomeration and (ii) to obtain in a relatively short period (1 h) a deposit of isolated magnetic nanoparticles with a density of up to 400 nanoparticles per µm{sup 2}. These results open great perspectives for magnetic measurements on single objects using advanced magnetometry techniques as long as spintronics applications based on single chemically synthesized magnetic nanoparticles.

  14. Bath parameter dependence of chemically deposited Copper Selenide thin film

    In this article, a low cost chemical bath deposition (CBD) technique has been used for the preparation Of Cu2-xSe thin films on to glass substrate. Different thin fms (0.2-0.6/μm) were prepared by adjusting the bath parameter like concentration of ammonia, deposition time, temperature of the solution, and the ratios of the mixing composition between copper and selenium in the reaction bath. From these studies, it reveals that at low concentration of ammonia or TEA, the terminal thicknesses of the films are less, which gradually increases with the increase of concentrations and then drop down at still higher concentrations. It has been found that completing the Cu2+ ions with EA first, and then addition of ammonia yields better results than the reverse process. The film thickness increases with the decrease of value x of Cu2-xSe. (author)

  15. Synthesis of Aligned Carbon Nanotubes by Thermal Chemical Vapor Deposition

    LI Gang; ZHOU Ming; MA Weiwei; CAI Lan

    2009-01-01

    Single crystal silicon was found to be very beneficial to the growth of aligned carbon nanotubes by chemical vapor deposition with C2H2 as carbon source. A thin film of Ni served as catalyst was deposited on the Si substrate by the K575X Peltier Cooled High Resolution Sputter Coater before growth. The growth properties of carbon nanotubes were studied as a function of the Ni catalyst layer thickness. The diameter, growth rate and areal density of the carbon nanotubes were controlled by the initial thickness of the catalyst layer. Steric hindrance between nanotubes forces them to grow in well-aligned manner at an initial stage of growth. Transmission electron microscope analysis revealed that nanotubes grew by a tip growth mechanism.

  16. Kinetics of chemical vapor deposition of boron on molybdenum

    Experimental rate data of chemical vapor deposition of boron by reduction of boron trichloride with hydrogen are analyzed to determine the reaction mechanism. The experiments were conducted at atmospheric pressure. The weight change of the sample was noted by means of a thermobalance. Molybdenum was used as the substrate. It has been found that the outer layer of the deposited film is Mo/sub 2/B/sub 5/ and the inner layer is MoB, and in the stational state of the reaction, the diffusion in the solid state is considered not to be rate controlling. When mass transport limitation was absent, the reaction orders with respect to boron trichloride and hydrogen were one third and one half, respectively. By comparing these orders with those obtained from Langmuir-Hinshelwood type equations, the rate controlling mechanism is identified to be the desorption of hydrogen chloride from the substrate

  17. Coloration efficiency of chemically deposited electrochromic thin films

    Transparent nickel oxide and copper oxide thin films were produced by very simple and economic method of chemical deposition. Those films were deposited onto fluorine doped tin oxide (FTO) coated glass substrates. Electrochromic test device (ECTD) was constructed by using these films as working electrodes, together with the FTO as a counter electrode in alkaline environment (0,1 M NaOH aqueous solution). All the obtained films exhibited electrochromic behavior. Nichel oxide films were transparent for visible light in the reduced state, and displayed a dark brown color in the oxidised state and displayed a very dark brown color in the reduced state. The coloration efficiency (CE) at wavelength λ=670 nm was estimated from the slope of the graphical presentation of the optical density as a function of the charge density, during the charge extraction (nickel oxide films) and charge insertion (copper oxide films). (Author)

  18. Ion beam induced conductivity in chemically vapor deposited diamond films

    Polycrystalline diamond films deposited by the microwave plasma chemical vapor deposition (CVD) technique onto quartz substrates have been irradiated with 100 keV C and 320 keV Xe ions at room temperature and at 200 degree C. The dose dependence of the electrical conductivity measured in situ exhibited complicated, nonmonotonic behavior. High doses were found to induce an increase of up to ten orders of magnitude in the electrical conductivity of the film. The dose dependence of the conductivity for the CVD films was found to be very similar to that measured for natural, type IIa, single-crystal diamonds irradiated under identical conditions. This result suggests that the conduction mechanism in ion beam irradiated polycrystalline CVD diamond films is not dominated by grain boundaries and graphitic impurities as one might have expected, but rather is determined by the intrinsic properties of diamond itself

  19. Plasma-enhanced chemical vapor deposition of multiwalled carbon nanofibers

    Matthews, Kristopher; Cruden, Brett A.; Chen, Bin; Meyyappan, M.; Delzeit, Lance

    2002-01-01

    Plasma-enhanced chemical vapor deposition is used to grow vertically aligned multiwalled carbon nanofibers (MWNFs). The graphite basal planes in these nanofibers are not parallel as in nanotubes; instead they exhibit a small angle resembling a stacked cone arrangement. A parametric study with varying process parameters such as growth temperature, feedstock composition, and substrate power has been conducted, and these parameters are found to influence the growth rate, diameter, and morphology. The well-aligned MWNFs are suitable for fabricating electrode systems in sensor and device development.

  20. Nitrogen-doped graphene by microwave plasma chemical vapor deposition

    Rapid synthesis of nitrogen-doped, few-layer graphene films on Cu foil is achieved by microwave plasma chemical vapor deposition. The films are doped during synthesis by introduction of nitrogen gas in the reactor. Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and scanning tunneling microscopy reveal crystal structure and chemical characteristics. Nitrogen concentrations up to 2 at.% are observed, and the limit is linked to the rigidity of graphene films on copper surfaces that impedes further nitrogen substitutions of carbon atoms. The entire growth process requires only a few minutes without supplemental substrate heating and offers a promising path toward large-scale synthesis of nitrogen-doped graphene films. - Highlights: ► Rapid synthesis of nitrogen doped few layer graphene on Cu foil. ► Defect density increment on 2% nitrogen doping. ► Nitrogen doped graphene is a good protection to the copper metallic surface

  1. Direct fabrication of 3D graphene on nanoporous anodic alumina by plasma-enhanced chemical vapor deposition

    Zhan, Hualin; Garrett, David J.; Apollo, Nicholas V.; Ganesan, Kumaravelu; Lau, Desmond; Prawer, Steven; Cervenka, Jiri

    2016-01-01

    High surface area electrode materials are of interest for a wide range of potential applications such as super-capacitors and electrochemical cells. This paper describes a fabrication method of three-dimensional (3D) graphene conformally coated on nanoporous insulating substrate with uniform nanopore size. 3D graphene films were formed by controlled graphitization of diamond-like amorphous carbon precursor films, deposited by plasma-enhanced chemical vapour deposition (PECVD). Plasma-assisted graphitization was found to produce better quality graphene than a simple thermal graphitization process. The resulting 3D graphene/amorphous carbon/alumina structure has a very high surface area, good electrical conductivity and exhibits excellent chemically stability, providing a good material platform for electrochemical applications. Consequently very large electrochemical capacitance values, as high as 2.1 mF for a sample of 10 mm3, were achieved. The electrochemical capacitance of the material exhibits a dependence on bias voltage, a phenomenon observed by other groups when studying graphene quantum capacitance. The plasma-assisted graphitization, which dominates the graphitization process, is analyzed and discussed in detail.

  2. Liquid and vapour-phase antifungal activities of selected essential oils against candida albicans: microscopic observations and chemical characterization of cymbopogon citratus

    Malik Anushree; Tyagi Amit K

    2010-01-01

    Abstract Background Use of essential oils for controlling Candida albicans growth has gained significance due to the resistance acquired by pathogens towards a number of widely-used drugs. The aim of this study was to test the antifungal activity of selected essential oils against Candida albicans in liquid and vapour phase and to determine the chemical composition and mechanism of action of most potent essential oil. Methods Minimum Inhibitory concentration (MIC) of different essential oils ...

  3. Vapour trap development and operational experience

    Sodium aerosols have the unpleasant characteristic that they deposit at places with low temperature level. This effect can be utilized when sodium aerosols are to be trapped at places which are determined beforehand. Thus vapour traps were developed which can filter sodium vapour from the cover gas. By this means the necessity was eliminated to heat all gas lines and gas systems with trace heaters just as all sodium lines are heated. It was of special interest for the INTERATOM to develop vapour traps which must not be changed or cleaned after a certain limited operating period. The vapour traps were supposed to enable maintenance free operation, i.e. they were to operate 'self cleaning'

  4. Chemical vapor deposition of conformal, functional, and responsive polymer films.

    Alf, Mahriah E; Asatekin, Ayse; Barr, Miles C; Baxamusa, Salmaan H; Chelawat, Hitesh; Ozaydin-Ince, Gozde; Petruczok, Christy D; Sreenivasan, Ramaswamy; Tenhaeff, Wyatt E; Trujillo, Nathan J; Vaddiraju, Sreeram; Xu, Jingjing; Gleason, Karen K

    2010-05-11

    Chemical vapor deposition (CVD) polymerization utilizes the delivery of vapor-phase monomers to form chemically well-defined polymeric films directly on the surface of a substrate. CVD polymers are desirable as conformal surface modification layers exhibiting strong retention of organic functional groups, and, in some cases, are responsive to external stimuli. Traditional wet-chemical chain- and step-growth mechanisms guide the development of new heterogeneous CVD polymerization techniques. Commonality with inorganic CVD methods facilitates the fabrication of hybrid devices. CVD polymers bridge microfabrication technology with chemical, biological, and nanoparticle systems and assembly. Robust interfaces can be achieved through covalent grafting enabling high-resolution (60 nm) patterning, even on flexible substrates. Utilizing only low-energy input to drive selective chemistry, modest vacuum, and room-temperature substrates, CVD polymerization is compatible with thermally sensitive substrates, such as paper, textiles, and plastics. CVD methods are particularly valuable for insoluble and infusible films, including fluoropolymers, electrically conductive polymers, and controllably crosslinked networks and for the potential to reduce environmental, health, and safety impacts associated with solvents. Quantitative models aid the development of large-area and roll-to-roll CVD polymer reactors. Relevant background, fundamental principles, and selected applications are reviewed. PMID:20544886

  5. Neutron detectors made from chemically vapor deposited semiconductors

    In this paper, the authors present the results of investigations on the use of semiconductors deposited by chemical vapor deposition (CVD) for the fabrication of neutron detectors. For this purpose, 20 microm thick hydrogenated amorphous silicon (a-Si:H) pin diodes and 100 microm thick polycrystalline diamond resistive detectors were fabricated. The detectors were coupled to a neutron-charged particle converter: a layer of either gadolinium or boron (isotope 10 enriched) deposited by evaporation. They have demonstrated the capability of such neutron detectors to operate at neutron fluxes ranging from 101 to 106 neutrons/cm2.s. The fabrication of large area detectors for neutron counting or cartography through the use of multichannel reading circuits is discussed. The advantages of these detectors include the ability to produce large area detectors at low cost, radiation hardness (∼ 4 Mrad for a-Si:H and ∼ 100 Mrad for diamond), and for diamond, operation at temperatures up to 500 C. These properties enable the use of these devices for neutron detection in harsh environments. Thermal neutron detection efficiency up to 22% and 3% are expected by coupling a-Si:H diodes and diamond detectors to 3 microm thick gadolinium (isotope 157) and 2 microm thick boron layers, respectively

  6. Coating particles by chemical vapor deposition in fluidized bed reactors

    A technique to deposit a thin, adherent, uniformly dispersed coating onto the individual particles in a batch of granular or powdered material is described. We have been able to apply successfully a number of coatings to a variety of particulate materials using a fluidized-bed chemical vapor deposition (CVD) technique. By means of this technique we used tri-isobutylaluminum to apply adherent coatings of aluminum on powdered mica and powdered nickel. The powdered mica was also coated with titanium in a fluidized bed reactor in which titanium precursors were generated in situ by the reaction between HCl and metallic titanium. Post treatment of the titanium coated mica with ammonia produced agglomerates coated with TiN. These systems demonstrate the potential utility of the fluidized bed reactor for depositing a variety of coatings onto metallic and non-metallic dispersed materials. Preparation of such coated powders is likely to be valuable in a variety of industrial applications, such as the manufacture of composite structures. (orig.)

  7. Solvent-assisted dewetting during chemical vapor deposition.

    Chen, Xichong; Anthamatten, Mitchell

    2009-10-01

    This study examines the use of a nonreactive solvent vapor, tert-butanol, during initiated chemical vapor deposition (iCVD) to promote polymer film dewetting. iCVD is a solventless technique to grow polymer thin films directly from gas phase feeds. Using a custom-built axisymmetric hot-zone reactor, smooth poly(methyl methacrylate) films are grown from methyl methacrylate (MMA) and tert-butyl peroxide (TBPO). When solvent vapor is used, nonequilibrium dewetted structures comprising of randomly distributed polymer droplets are observed. The length scale of observed topographies, determined using power spectral density (PSD) analysis, ranges from 5 to 100 microm and is influenced by deposition conditions, especially the carrier gas and solvent vapor flow rates. The use of a carrier gas leads to faster deposition rates and suppresses thin film dewetting. The use of solvent vapor promotes dewetting and leads to larger length scales of the dewetted features. Control over lateral length scale is demonstrated by preparation of hierarchal "bump on bump" topographies. Vapor-induced dewetting is demonstrated on silicon wafer substrate with a native oxide layer and also on hydrophobically modified substrate prepared using silane coupling. Autophobic dewetting of PMMA from SiOx/Si during iCVD is attributed to a thin film instability driven by both long-range van der Waals forces and short-range polar interactions. PMID:19670895

  8. Structural, electrical and optical properties of copper selenide thin films deposited by chemical bath deposition technique

    A low cost chemical bath deposition (CBD) technique has been used for the preparation of Cu2-xSe thin films on glass substrates. Structural, electrical and optical properties of these films were investigated. X-ray diffraction (XRD) study of the Cu2-xSe films annealed at 523K suggests a cubic structure with a lattice constant of 5.697A. Chemical composition was investigated by X-ray photoelectron spectroscopy (XPS). It reveals that absorbed oxygen in the film decreases remarkably on annealing above 423K. The Cu/Se ratio was observed to be the same in as-deposited and annealed films. Both as- deposited and annealed films show very low resistivity in the range of (0.04- 0.15) x 10-5 Ω-m. Transmittance and Reflectance were found in the range of 5-50% and 2-20% respectively. Optical absorption of the films results from free carrier absorption in the near infrared region with absorption coefficient of ∼108 m-1. The band gap for direct transition, Eg.dir varies in the range of 2.0-2.3eV and that for indirect transition Eg.indir is in the range of 1.25-1.5eV.1. (author)

  9. Thin films of barium fluoride scintillator deposited by chemical vapor deposition

    We have used metal-organic chemical vapor deposition (MOCVD) technology to coat optical substrates with thin (≅ 1-10 μm thick) films of inorganic BaF2 scintillator. Scanning electron microscope (SEM) photographs indicate that high-quality epitaxial crystalline film growth was achieved, with surface defects typically smaller than optical wavelengths. The scintillation light created by the deposition of ionizing radiation in the scintillating films was measured with a photomultiplier and shown to be similar to bulk melt-grown crystals. The results demonstrate the potential of these composite optical materials for planar and fiber scintillation radiation detectors in high energy and nuclear physics, synchrotron radiation research, and in radiation and X-ray imaging and monitoring. (orig.)

  10. The Liquid Vapour Interface

    Als-Nielsen, Jens Aage

    1985-01-01

    In this short review we are concerned with the density variation across the liquid-vapour interface, i.e. from the bulk density of the liquid to the essentially zero density of the vapour phase. This density variation can in principle be determined from the deviation of the reflectivity from...

  11. Organometallic chemical vapor-phase deposition (MOCVD) of oxidic high-ε layers

    The considered materials in this work are (Ba,Sr)TiO3, SrTiO3 and SrTa2O6 and the oxides from the group IVb metals: Ti, Zr and Hf. The films were deposited on Platinum and Silicon substrates in order to evaluate the dielectric properties for applications in metal-insulator-metal (MIM) structures as well as in metal-insulator-semiconductor (MIS) structures. The high-k films were grown by metal organic chemical vapour deposition (MOCVD) and the evaluation and optimisation of the production processes is a major part of this work. Different approaches were investigated: mixing of conventional precursors for the example of (Ba,Sr)TiO3, test of a single source precursor for SrTa2O6 and tests of newly designed precursors for the group IVb-metal oxides, M-(O-I-Pr)2(tbaoac)2. In addition, compatibility tests of the new Titanium precursors with the conventional Strontium precursor are presented for the example of SrTiO3. Most detailed investigations were performed on the nucleation and growth processes of (Ba,Sr)TiO3 on platinum . Details of the nucleation were obtained from the new method of conductivity scans with the AFM. These investigations were combined with XRD, SEM, HRTEM, SPM and XPS and give a consistent picture of development of the structural properties and their dependencies on growth temperature and chemical composition. The electrical properties, especially capacity and leakage current indicate a strong dependency from film thickness, which can be explained by separating the bulk- from the interface capacity. Based on these results the interface layer was optimised by changing the interfacial stoichiometry. Additionally, SrTa2O6 was tested as an alternative material with low tunability and shows promising electrical results. For the example of SrTiO3 on silicon details of the growth kinetics of the interfacial layer were investigated by HRTEM. The first results from group IVb oxides, which are the most promising candidates for gate oxides, are presented. (orig.)

  12. Hydrogen production by ethanol partial oxidation over nano-iron oxide catalysts produced by chemical vapour synthesis

    Ahmed, Wael Ahmed Abou Taleb Sayed

    2011-01-13

    This work presents the experimental results of the synthesis of unsupported and supported SiC iron oxide nanoparticles and their catalytic activity towards ethanol partial oxidation. For comparison, further unsupported iron oxide phases were investigated towards the ethanol partial oxidation. These {gamma}-Fe{sub 2}O{sub 3} and {alpha}/{gamma}-Fe{sub 2}O{sub 3} phase catalysts were prepared by the CVS method using Fe(CO){sub 5} as precursor, supplied by another author. The {alpha}-Fe{sub 2}O{sub 3} and SiC nanoparticles were prepared by the CVS method using a home made hot wall reactor technique at atmospheric pressure. Ferrocene and tetramethylsilane were used as precursor for the production process. Process parameters of precursor evaporation temperature, precursor concentration, gas mixture velocity and gas mixture dilution were investigated and optimised to produce particle sizes in a range of 10 nm. For Fe{sub 2}O{sub 3}/SiC catalyst series production, a new hot wall reactor setup was used. The particles were produced by simultaneous thermal decomposition of ferrocene and tetramethylsilane in one reactor from both sides. The production parameters of inlet tube distance inside the reactor, precursor evaporation temperature and carrier gas flow were investigated to produce a series of samples with different iron oxide content. The prepared catalysts composition, physical and chemical properties were characterized by XRD, EDX, SEM, BET surface area, FTIR, XPS and dynamic light scattering (DLS) techniques. The catalytic activity for the ethanol gas-phase oxidation was investigated in a temperature range from 260 C to 290 C. The product distributions obtained over all catalysts were analysed with mass spectrometry analysis tool. The activity of bulk Fe{sub 2}O{sub 3} and SiC nanoparticles was compared with prepared nano-iron oxide phase catalysts. The reaction parameters, such as reaction temperature and O{sub 2}/ethanol ratio were investigated. The catalysts

  13. Properties of nitrogen doped silicon films deposited by low-pressure chemical vapor deposition from silane and ammonia

    Temple Boyer, Pierre; Jalabert, L.; Masarotto, L.; Alay, Josep Lluís; Morante i Lleonart, Joan Ramon

    2000-01-01

    Nitrogen doped silicon (NIDOS) films have been deposited by low-pressure chemical vapor deposition from silane SiH4 and ammonia NH3 at high temperature (750°C) and the influences of the NH3/SiH4 gas ratio on the films deposition rate, refractive index, stoichiometry, microstructure, electrical conductivity, and thermomechanical stress are studied. The chemical species derived from silylene SiH2 into the gaseous phase are shown to be responsible for the deposition of NIDOS and/or (silicon rich...

  14. Chemical vapour deposition diamond. Charge carrier movement at low temperatures and use in time-critical applications

    Diamond, a wide band gap semiconductor with exceptional electrical properties, has found its way in diverse fields of application reaching from the usage as a sensor material for beam loss monitors at particle accelerator facilities, over laser windows, to UV light sensors in space applications, e.g. for space weather forecasting. Though often used at room temperature, little is known about the charge transport in diamond towards liquid helium temperatures. In this work the method of the transient current technique is employed at temperatures between room temperature and 2 K. The temperature and electric field strength dependence of the pulse shape, the charge carrier transit time, the drift velocity, the saturation velocity, and the low-field mobility is measured in detector-grade scCVD diamond. Furthermore, the usability of diamond in time-critical applications is tested, and the main results are presented.

  15. Chemical Vapour Deposition Diamond - Charge Carrier Movement at Low Temperatures and Use in Time-Critical Applications

    Jansen, Hendrik; Pernegger, Heinz

    Diamond, a wide band gap semiconductor with exceptional electrical properties, has found its way in diverse fields of application reaching from the usage as a sensor material for beam loss monitors at particle accelerator facilities, to laser windows, to UV light sensors in space applications, e.g. for space weather forecasting. Though often used at room temperature, little is known about the charge transport in diamond towards liquid helium temperatures. In this work the method of the transient current technique is employed at temperatures between room temperature and 2 K. The temperature and electric field strength dependence of the pulse shape, the charge carrier transit time, the drift velocity, the saturation velocity, and the low-field mobility is measured in detector-grade scCVD diamond. Furthermore, the usability of diamond in time-critical applications is tested, and the main results are presented.

  16. Dopant Effects on Defects in GaN Films Grown by Metal-Organic Chemical Vapour Deposition

    陆敏; 杨华; 黎子兰; 杨志坚; 李忠辉; 任谦; 金春来; 陆曙; 章蓓; 张国义

    2003-01-01

    The effects of dopants on the defects of GaN films were investigated by using different methods, such as wet,etching of pits, x-ray diffraction and photoluminescence (PL). Three kinds of the samples were prepared with different dopants, that is, nominally undoped, Si-doped and Mg-doped GaN films. It was found that the lowest density of the, etched pit was existed in the nominally undoped GaN, while the highest in the Mg-doped sample.The effects of the dopants on the, etching pits were discussed.

  17. Optical monitoring of surface processes relevant to thin film growth by chemical vapour deposition Oxidation; Surface degradation

    Simcock, M N

    2002-01-01

    This thesis reports on the investigation of the use of reflectance anisotropy spectroscopy (RAS) as an in-situ monitor for the preparation and oxidation of GaAs(100) c(4x4) surfaces using a CVD 2000 MOCVD reactor. These surfaces were oxidised using air. It was found that it was possible to follow surface degradation using RA transients at 2.6eV and 4eV. From this data it was possible to speculate on the nature of the surface oxidation process. A study was performed into the rate of surface degradation under different concentrations of air, it was found that the relation between the air concentration and the surface degradation was complicated but that the behaviour of the first third of the degradation approximated a first order behaviour. An estimation of the activation energy of the process was then made, and an assessment of the potential use of the glove-box for STM studies which is an integral part of the MOCVD equipment was also made. Following this, a description is given of the construction of an inte...

  18. Field emission properties of chemical vapor deposited individual graphene

    Zamri Yusop, Mohd [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, 466-8555 Nagoya (Japan); Department of Materials, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia); Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, 466-8555 Nagoya (Japan); Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, 466-8555 Nagoya (Japan); Yaakob, Yazid; Takahashi, Chisato; Tanemura, Masaki [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, 466-8555 Nagoya (Japan)

    2014-03-03

    Here, we report field emission (FE) properties of a chemical vapor deposited individual graphene investigated by in-situ transmission electron microscopy. Free-standing bilayer graphene is mounted on a cathode microprobe and FE processes are investigated varying the vacuum gap of cathode and anode. The threshold field for 10 nA current were found to be 515, 610, and 870 V/μm for vacuum gap of 400, 300, and 200 nm, respectively. It is observed that the structural stability of a high quality bilayer graphene is considerably stable during emission process. By contacting the nanoprobe with graphene and applying a bias voltage, structural deformation and buckling are observed with significant rise in temperature owing to Joule heating effect. The finding can be significant for practical application of graphene related materials in emitter based devices as well as understanding the contact resistance influence and heating effect.

  19. Thermoluminescence of Zn O thin films deposited by chemical bath

    Full text: Zn O films on Si were synthesized using a deposition method by chemical bath and thermally treated at 900 degrees C for 12 h in air. The morphological characterization by scanning electron microscopy reveals that uniform films were obtained. To investigate the thermoluminescent properties of the films were exposed to irradiation with beta particles with doses in the range from 0.5 to 128 Gy. The brightness curves obtained using a heating rate of 5 degrees C have two peaks, one at 124 and another at 270 degrees C, and a linear dependence of the integrated thermoluminescence as a function of dose. The second maximum reveals the existence of localized trapping states of potential utility in thermoluminescent dosimetry. (Author)

  20. Strain relaxation in graphene grown by chemical vapor deposition

    Troppenz, Gerald V., E-mail: gerald.troppenz@helmholtz-berlin.de; Gluba, Marc A.; Kraft, Marco; Rappich, Jörg; Nickel, Norbert H. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institut für Silizium Photovoltaik, Kekuléstr. 5, D-12489 Berlin (Germany)

    2013-12-07

    The growth of single layer graphene by chemical vapor deposition on polycrystalline Cu substrates induces large internal biaxial compressive strain due to thermal expansion mismatch. Raman backscattering spectroscopy and atomic force microscopy were used to study the strain relaxation during and after the transfer process from Cu foil to SiO{sub 2}. Interestingly, the growth of graphene results in a pronounced ripple structure on the Cu substrate that is indicative of strain relaxation of about 0.76% during the cooling from the growth temperature. Removing graphene from the Cu substrates and transferring it to SiO{sub 2} results in a shift of the 2D phonon line by 27 cm{sup −1} to lower frequencies. This translates into additional strain relaxation. The influence of the processing steps, used etching solution and solvents on strain, is investigated.

  1. Characterization of Carbon Nanotubes Grown by Chemical Vapor Deposition

    Cochrane, J. C.; Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Since the superior properties of multi-wall carbon nanotubes (MWCNT) could improve numerous devices such as electronics and sensors, many efforts have been made in investigating the growth mechanism of MWCNT to synthesize high quality MWCNT. Chemical vapor deposition (CVD) is widely used for MWCNT synthesis, and scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) are useful methods for analyzing the structure, morphology and composition of MWCNT. Temperature and pressure are two important growth parameters for fabricating carbon nanotubes. In MWCNT growth by CVD, the plasma assisted method is normally used for low temperature growth. However a high temperature environment is required for thermal CVD. A systematic study of temperature and pressure-dependence is very helpful to understanding MWCNT growth. Transition metal particles are commonly used as catalysis in carbon nanotube growth. It is also interesting to know how temperature and pressure affect the interface of carbon species and catalyst particles

  2. Chemical vapor deposition coatings for oxidation protection of titanium alloys

    Cunnington, G. R.; Robinson, J. C.; Clark, R. K.

    1991-01-01

    Results of an experimental investigation of the oxidation protection afforded to Ti-14Al-21Nb and Ti-14Al-23Nb-2V titanium aluminides and Ti-17Mo-3Al-3Nb titanium alloy by aluminum-boron-silicon and boron-silicon coatings are presented. These coatings are applied by a combination of physical vapor deposition (PVD) and chemical vapor deposition (CVD) processes. The former is for the application of aluminum, and the latter is for codeposition of boron and silicon. Coating thickness is in the range of 2 to 7 microns, and coating weights are 0.6 to 2.0 mg/sq cm. Oxidation testing was performed in air at temperatures to 1255 K in both static and hypersonic flow environments. The degree of oxidation protection provided by the coatings is determined from weight change measurements made during the testing and post test compositional analyses. Temperature-dependent total normal emittance data are also presented for four coating/substrate combinations. Both types of coatings provided excellent oxidation protection for the exposure conditions of this investigation. Total normal emittances were greater than 0.80 in all cases.

  3. Thirty Gigahertz Optoelectronic Mixing in Chemical Vapor Deposited Graphene.

    Montanaro, Alberto; Mzali, Sana; Mazellier, Jean-Paul; Bezencenet, Odile; Larat, Christian; Molin, Stephanie; Morvan, Loïc; Legagneux, Pierre; Dolfi, Daniel; Dlubak, Bruno; Seneor, Pierre; Martin, Marie-Blandine; Hofmann, Stephan; Robertson, John; Centeno, Alba; Zurutuza, Amaia

    2016-05-11

    The remarkable properties of graphene, such as broadband optical absorption, high carrier mobility, and short photogenerated carrier lifetime, are particularly attractive for high-frequency optoelectronic devices operating at 1.55 μm telecom wavelength. Moreover, the possibility to transfer graphene on a silicon substrate using a complementary metal-oxide-semiconductor-compatible process opens the ability to integrate electronics and optics on a single cost-effective chip. Here, we report an optoelectronic mixer based on chemical vapor-deposited graphene transferred on an oxidized silicon substrate. Our device consists in a coplanar waveguide that integrates a graphene channel, passivated with an atomic layer-deposited Al2O3 film. With this new structure, 30 GHz optoelectronic mixing in commercially available graphene is demonstrated for the first time. In particular, using a 30 GHz intensity-modulated optical signal and a 29.9 GHz electrical signal, we show frequency downconversion to 100 MHz. These results open promising perspectives in the domain of optoelectronics for radar and radio-communication systems. PMID:27043922

  4. Pattern Dependency and Loading Effect of Pure-Boron-Layer Chemical-Vapor Deposition

    Mohammadi, V.; De Boer, W.B.; Scholtes, T.L.M.; Nanver, L.K.

    2012-01-01

    The pattern dependency of pure-boron (PureB) layer chemical-vapor Deposition (CVD) is studied with respect to the correlation between the deposition rate and features like loading effects, deposition parameters and deposition window sizes. It is shown experimentally that the oxide coverage ratio and

  5. Selected area chemical vapor deposition of thin films for conductometric microelectronic chemical sensors

    Majoo, Sanjeev

    Recent advances in microelectronics and silicon processing have been exploited to fabricate miniaturized chemical sensors. Although the capability of chemical sensing technology has grown steadily, it has been outpaced by the increasing demands for more reliable, inexpensive, and selective sensors. The diversity of applications requires the deployment of different sensing materials that have rich interfacial chemistry. However, several promising sensor materials are often incompatible with silicon micromachining and their deposition requires complicated masking steps. The new approach described here is to first micromachine a generic, instrumented, conductometric, microelectronic sensor platform that is fully functional except for the front-end sensing element. This generic platform contains a thin dielectric membrane, an integrated boron-doped silicon heater, and conductance electrodes. The membrane has low thermal mass and excellent thermal isolation. A proprietary selected-area chemical vapor deposition (SACVD) process in a cold-wall reactor at low pressures was then used to achieve maskless, self-lithographic deposition of thin films. The temperature-programmable integrated microheater initiates localized thermal decomposition/reaction of suitable CVD precursors confined to a small heated area (500 mum in diameter), and this creates the active sensing element. Platinum and titania (TiOsb2) films were deposited from pyrolysis of organometallic precursors, tetrakistrifluorophosphine platinum Pt(PFsb3)sb4 and titanium tetraisopropoxide Ti(OCH(CHsb3)sb2rbrack sb4, respectively. Deposition of gold metal films from chlorotriethylphosphine gold (Csb2Hsb5)sb3PAuCl precursor was also attempted but without success. The conductance electrodes permit in situ monitoring of film growth. The as-deposited films were characterized in situ by conductance measurements and optical microscopy and ex situ by electron microscopy and spectroscopy methods. Devices equipped with

  6. Surface chemical states of barium zirconate titanate thin films prepared by chemical solution deposition

    Ba(Zr0.05Ti0.95)O3 (BZT) thin films grown on Pt/Ti/SiO2/Si(1 0 0) substrates were prepared by chemical solution deposition. The structural and surface morphology of BZT thin films has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed that the random oriented BZT thin film grown on Pt/Ti/SiO2/Si(1 0 0) substrate with a perovskite phase. The SEM surface image showed that the BZT thin film was crack-free. And the average grain size and thickness of the BZT film are 35 and 400 nm, respectively. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Ti, and Zr exist mainly in the forms of BZT perovskite structure.

  7. Vertically aligned peptide nanostructures using plasma-enhanced chemical vapor deposition.

    Vasudev, Milana C; Koerner, Hilmar; Singh, Kristi M; Partlow, Benjamin P; Kaplan, David L; Gazit, Ehud; Bunning, Timothy J; Naik, Rajesh R

    2014-02-10

    In this study, we utilize plasma-enhanced chemical vapor deposition (PECVD) for the deposition of nanostructures composed of diphenylalanine. PECVD is a solvent-free approach and allows sublimation of the peptide to form dense, uniform arrays of peptide nanostructures on a variety of substrates. The PECVD deposited d-diphenylalanine nanostructures have a range of chemical and physical properties depending on the specific discharge parameters used during the deposition process. PMID:24400716

  8. Chemical vapor deposited fiber coatings and chemical vapor infiltrated ceramic matrix composites

    Kmetz, M.A.

    1992-01-01

    Conventional Chemical Vapor Deposition (CVD) and Organometallic Chemical Vapor Deposition (MOCVD) were employed to deposit a series of interfacial coatings on SiC and carbon yarn. Molybdenum, tungsten and chromium hexacarbonyls were utilized as precursors in a low temperature (350[degrees]C) MOCVD process to coat SiC yarn with Mo, W and Cr oxycarbides. Annealing studies performed on the MoOC and WOC coated SiC yarns in N[sub 2] to 1,000[degrees]C establish that further decomposition of the oxycarbides occurred, culminating in the formation of the metals. These metals were then found to react with Si to form Mo and W disilicide coatings. In the Cr system, heating in N[sub 2] above 800[degrees]C resulted in the formation of a mixture of carbides and oxides. Convention CVD was also employed to coat SiC and carbon yarn with C, Bn and a new interface designated BC (a carbon-boron alloy). The coated tows were then infiltrated with SiC, TiO[sub 2], SiO[sub 2] and B[sub 4]C by a chemical vapor infiltration process. The B-C coatings were found to provide advantageous interfacial properties over carbon and BN coatings in several different composite systems. The effectiveness of these different coatings to act as a chemically inert barrier layer and their relationship to the degree of interfacial debonding on the mechanical properties of the composites were examined. The effects of thermal stability and strength of the coated fibers and composites were also determined for several difference atmospheres. In addition, a new method for determining the tensile strength of the as-received and coated yarns was also developed. The coated fibers and composites were further characterized by AES, SEM, XPS, IR and X-ray diffraction analysis.

  9. Evaluation of chemical and structural properties of germanium-carbon coatings deposited by plasma enhanced chemical vapor deposition

    Jamali, Hossein, E-mail: h.jamali@mut-es.ac.ir; Mozafarinia, Reza; Eshaghi, Akbar

    2015-10-15

    Germanium-carbon coatings were deposited on silicon and glass substrates by plasma enhanced chemical vapor deposition (PECVD) using three different flow ratios of GeH{sub 4} and CH{sub 4} precursors. Elemental analysis, structural evaluation and microscopic investigation of coatings were performed using laser-induced breakdown spectroscopy (LIBS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. Based on the results, the coatings exhibited a homogeneous and dense structure free of pores with a very good adhesion to substrate. The structural evaluation revealed that the germanium-carbon coatings were a kind of a Ge-rich composite material containing the amorphous and crystalline germanium and amorphous carbon with the mixture of Ge–Ge, Ge–C, C–C, Ge–H and C–H bonds. The result suggested that the amorphisation of the coatings could be increased with raising CH{sub 4}:GeH{sub 4} flow rate ratio and subsequently increasing C amount incorporated into the coating. - Highlights: • Germanium-carbon coatings were prepared by PECVD technique. • The germanium-carbon coatings were a kind of composite material. • The amorphisation of the coatings were increased with raising CH{sub 4}:GeH{sub 4} flow ratio.

  10. Evaluation of chemical and structural properties of germanium-carbon coatings deposited by plasma enhanced chemical vapor deposition

    Germanium-carbon coatings were deposited on silicon and glass substrates by plasma enhanced chemical vapor deposition (PECVD) using three different flow ratios of GeH4 and CH4 precursors. Elemental analysis, structural evaluation and microscopic investigation of coatings were performed using laser-induced breakdown spectroscopy (LIBS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. Based on the results, the coatings exhibited a homogeneous and dense structure free of pores with a very good adhesion to substrate. The structural evaluation revealed that the germanium-carbon coatings were a kind of a Ge-rich composite material containing the amorphous and crystalline germanium and amorphous carbon with the mixture of Ge–Ge, Ge–C, C–C, Ge–H and C–H bonds. The result suggested that the amorphisation of the coatings could be increased with raising CH4:GeH4 flow rate ratio and subsequently increasing C amount incorporated into the coating. - Highlights: • Germanium-carbon coatings were prepared by PECVD technique. • The germanium-carbon coatings were a kind of composite material. • The amorphisation of the coatings were increased with raising CH4:GeH4 flow ratio

  11. The structural properties of CdS deposited by chemical bath deposition and pulsed direct current magnetron sputtering

    Lisco, F., E-mail: F.Lisco@lboro.ac.uk [Centre for Renewable Energy Systems Technology (CREST), School of Electronic, Electrical and Systems Engineering, Loughborough University, Leicestershire, LE11 3TU (United Kingdom); Kaminski, P.M.; Abbas, A.; Bass, K.; Bowers, J.W.; Claudio, G. [Centre for Renewable Energy Systems Technology (CREST), School of Electronic, Electrical and Systems Engineering, Loughborough University, Leicestershire, LE11 3TU (United Kingdom); Losurdo, M. [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, via Orabona 4, 70126 Bari (Italy); Walls, J.M. [Centre for Renewable Energy Systems Technology (CREST), School of Electronic, Electrical and Systems Engineering, Loughborough University, Leicestershire, LE11 3TU (United Kingdom)

    2015-05-01

    Cadmium sulphide (CdS) thin films were deposited by two different processes, chemical bath deposition (CBD), and pulsed DC magnetron sputtering (PDCMS) on fluorine doped-tin oxide coated glass to assess the potential advantages of the pulsed DC magnetron sputtering process. The structural, optical and morphological properties of films obtained by CBD and PDCMS were investigated using X-ray photoelectron spectroscopy, X-ray diffraction, scanning and transmission electron microscopy, spectroscopic ellipsometry and UV-Vis spectrophotometry. The as-grown films were studied and comparisons were drawn between their morphology, uniformity, crystallinity, and the deposition rate of the process. The highest crystallinity is observed for sputtered CdS thin films. The absorption in the visible wavelength increased for PDCMS CdS thin films, due to the higher density of the films. The band gap measured for the as-grown CBD-CdS is 2.38 eV compared to 2.34 eV for PDCMS-CdS, confirming the higher density of the sputtered thin film. The higher deposition rate for PDCMS is a significant advantage of this technique which has potential use for high rate and low cost manufacturing. - Highlights: • Pulsed DC magnetron sputtering (PDCMS) of CdS films • Chemical bath deposition of CdS films • Comparison between CdS thin films deposited by chemical bath and PDCMS techniques • High deposition rate deposition for PDCMS deposition • Uniform, pinhole free CdS thin films.

  12. Photoluminescence properties of poly (p-phenylene vinylene) films deposited by chemical vapor deposition

    Gedelian, Cynthia A. [Department of Physics, Applied Physics, and Astronomy, Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy 12180-3590, NY (United States); Rajanna, K.C., E-mail: kcrajannaou@yahoo.com [Department of Chemistry, Osmania University, Hyderabad 500007, Andhra Pradesh (India); Premerlani, Brian; Lu, Toh-Ming [Department of Physics, Applied Physics, and Astronomy, Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy 12180-3590, NY (United States)

    2014-01-15

    Photoluminescence spectra of PPV at varying thicknesses and temperatures have been studied. A study of the quenching of the polymer film using a modified version of fluorescence spectroscopy reveals interface effects dominating at thicknesses below about 600 Å, while bulk effects dominate at higher thicknesses. The application of the Stern–Volmer equation to solid film is discussed. Stern–Volmer plots were nonlinear with downward deviations at higher thickness of the film which was explained due to self-quenching in films and larger conformational change and increased restriction from change in electron density due to electron transition during excitation in bulk polymer films over 60 nm thick. PPV deposited into porous (∼4 nm in diameter) nanostructured substrate shows a larger 0–0 than 0–1 transition peak intensity and decreased disorder in the films due to structure imposed by substrate matrix. Temperature dependent effects are measured for a film at 500 Å, right on the border between the two areas. PPV films deposited on porous methyl silsesquioxane (MSQ) were also examined in order to compare the flat film to a substrate that allows for the domination of interface effects. The enthalpies of the first two peaks are very similar, but the third peak demonstrates a lower enthalpy and a larger wavelength shift with temperature. Films deposited inside pores show a smaller amount of disorder than flat films. Calculation of the Huang–Rhys factor at varying temperatures for the flat film and film in porous MSQ shows large temperature dependence for the flat film but a smaller amount of disorder in the nanostructured film. -- Highlights: • Poly (p-phenylene vinylene) films deposited by chemical vapor deposition exhibited photoluminescence properties. • Fluorescence spectra of the polymer films revealed interface effects dominating at thicknesses below about 600 Å, while bulk effects dominate at higher thicknesses. • Stern–Volmer plots were

  13. Photoluminescence properties of poly (p-phenylene vinylene) films deposited by chemical vapor deposition

    Photoluminescence spectra of PPV at varying thicknesses and temperatures have been studied. A study of the quenching of the polymer film using a modified version of fluorescence spectroscopy reveals interface effects dominating at thicknesses below about 600 Å, while bulk effects dominate at higher thicknesses. The application of the Stern–Volmer equation to solid film is discussed. Stern–Volmer plots were nonlinear with downward deviations at higher thickness of the film which was explained due to self-quenching in films and larger conformational change and increased restriction from change in electron density due to electron transition during excitation in bulk polymer films over 60 nm thick. PPV deposited into porous (∼4 nm in diameter) nanostructured substrate shows a larger 0–0 than 0–1 transition peak intensity and decreased disorder in the films due to structure imposed by substrate matrix. Temperature dependent effects are measured for a film at 500 Å, right on the border between the two areas. PPV films deposited on porous methyl silsesquioxane (MSQ) were also examined in order to compare the flat film to a substrate that allows for the domination of interface effects. The enthalpies of the first two peaks are very similar, but the third peak demonstrates a lower enthalpy and a larger wavelength shift with temperature. Films deposited inside pores show a smaller amount of disorder than flat films. Calculation of the Huang–Rhys factor at varying temperatures for the flat film and film in porous MSQ shows large temperature dependence for the flat film but a smaller amount of disorder in the nanostructured film. -- Highlights: • Poly (p-phenylene vinylene) films deposited by chemical vapor deposition exhibited photoluminescence properties. • Fluorescence spectra of the polymer films revealed interface effects dominating at thicknesses below about 600 Å, while bulk effects dominate at higher thicknesses. • Stern–Volmer plots were

  14. Preparation and Characterization of SnO2 thin films deposited by Chemical Bath Deposition method

    Yusuf, Gbadebo T.; Raimi, Adepoju M.; Familusi, Timothy O.; Awodugba, Ayodeji O.; Efunwole, Hezekiah O.

    2013-04-01

    SnO2 thin films have been deposited onto the soda lime glass substrates by the chemical bath deposition method. The structural and optical properties of the SnO2 thin films were investigated. Tin chloride solution (SnCl2) and methanol were used as starting materials at substrate temperature 300^oC. The crystal structure and orientation of the SnO2 thin films were investigated by X-ray diffraction (XRD) patterns. The average grain size of the films was calculated using the Scherer formula and was found to be 29.6 nm which increased to 30.04nm after annealing in air at 400^oC. The optical absorbance and transmittance measurements were recorded by using spectrophotometer. The average transmittance of the film was around 80 % at wavelength 550 nm. The optical band gap of the thin films was determined and found to be 3.71eV. The gas sensing properties of tin oxide thin films obtained in this work could be performed for different gases like CO, CH4, H2S, H2 etc.

  15. Deposition of highly (111)-oriented PZT thin films by using metal organic chemical deposition

    Bu, K H; Choi, D K; Seong, W K; Kim, J D

    1999-01-01

    Lead zirconate titanate (PZT) thin films have been grown on Pt/Ta/SiNx/Si substrates by using metal organic chemical vapor deposition with Pb(C sub 2 H sub 5) sub 4 , Zr(O-t-C sub 4 H sub 9) sub 4 , and Ti(O-i-C sub 3 H sub 7) sub 4 as source materials and O sub 2 as an oxidizing gas. The Zr fraction in the thin films was controlled by varying the flow rate of the Zr source material. The crystal structure and the electrical properties were investigated as functions of the composition. X-ray diffraction analysis showed that at a certain range of Zr fraction, highly (111)-oriented PZT thin films with no pyrochlore phases were deposited. On the other hand, at low Zr fractions, there were peaks from Pb-oxide phases. At high Zr fractions, peaks from pyrochlore phase were seen. The films also showed good electrical properties, such as a high dielectric constant of more than 1200 and a low coercive voltage of 1.35 V.

  16. Plasma-enhanced chemical vapor deposition for YBCO film fabrication of superconducting fault-current limiter

    Jun, Byung Hyuk; Kim, Chan Joong

    2006-05-15

    Since the high-temperature superconductor of oxide type was founded, many researches and efforts have been performed for finding its application field. The YBCO superconducting film fabricated on economic metal substrate with uniform critical current density is considered as superconducting fault-current limiter (SFCL). There are physical and chemical processes to fabricate superconductor film, and it is understood that the chemical methods are more economic to deposit large area. Among them, chemical vapor deposition (CVD) is a promising deposition method in obtaining film uniformity. To solve the problems due to the high deposition temperature of thermal CVD, plasma-enhanced chemical vapor deposition (PECVD) is suggested. This report describes the principle and fabrication trend of SFCL, example of YBCO film deposition by PECVD method, and principle of plasma deposition.

  17. Plasma-enhanced chemical vapor deposition for YBCO film fabrication of superconducting fault-current limiter

    Since the high-temperature superconductor of oxide type was founded, many researches and efforts have been performed for finding its application field. The YBCO superconducting film fabricated on economic metal substrate with uniform critical current density is considered as superconducting fault-current limiter (SFCL). There are physical and chemical processes to fabricate superconductor film, and it is understood that the chemical methods are more economic to deposit large area. Among them, chemical vapor deposition (CVD) is a promising deposition method in obtaining film uniformity. To solve the problems due to the high deposition temperature of thermal CVD, plasma-enhanced chemical vapor deposition (PECVD) is suggested. This report describes the principle and fabrication trend of SFCL, example of YBCO film deposition by PECVD method, and principle of plasma deposition

  18. Grain boundaries in graphene grown by chemical vapor deposition

    The scientific literature on grain boundaries (GBs) in graphene was reviewed. The review focuses mainly on the experimental findings on graphene grown by chemical vapor deposition (CVD) under a very wide range of experimental conditions (temperature, pressure hydrogen/hydrocarbon ratio, gas flow velocity and substrates). Differences were found in the GBs depending on the origin of graphene: in micro-mechanically cleaved graphene (produced using graphite originating from high-temperature, high-pressure synthesis), rows of non-hexagonal rings separating two perfect graphene crystallites are found more frequently, while in graphene produced by CVD—despite the very wide range of growth conditions used in different laboratories—GBs with more pronounced disorder are more frequent. In connection with the observed disorder, the stability of two-dimensional amorphous carbon is discussed and the growth conditions that may impact on the structure of the GBs are reviewed. The most frequently used methods for the atomic scale characterization of the GB structures, their possibilities and limitations and the alterations of the GBs in CVD graphene during the investigation (e.g. under e-beam irradiation) are discussed. The effects of GB disorder on electric and thermal transport are reviewed and the relatively scarce data available on the chemical properties of the GBs are summarized. GBs are complex enough nanoobjects so that it may be unlikely that two experimentally produced GBs of several microns in length could be completely identical in all of their atomic scale details. Despite this, certain generalized conclusions may be formulated, which may be helpful for experimentalists in interpreting the results and in planning new experiments, leading to a more systematic picture of GBs in CVD graphene. (paper)

  19. Charged impurity-induced scatterings in chemical vapor deposited graphene

    Li, Ming-Yang; Tang, Chiu-Chun; Ling, D. C.; Li, L. J.; Chi, C. C.; Chen, Jeng-Chung

    2013-12-01

    We investigate the effects of defect scatterings on the electric transport properties of chemical vapor deposited (CVD) graphene by measuring the carrier density dependence of the magneto-conductivity. To clarify the dominant scattering mechanism, we perform extensive measurements on large-area samples with different mobility to exclude the edge effect. We analyze our data with the major scattering mechanisms such as short-range static scatters, short-range screened Coulomb disorders, and weak-localization (WL). We establish that the charged impurities are the predominant scatters because there is a strong correlation between the mobility and the charge impurity density. Near the charge neutral point (CNP), the electron-hole puddles that are induced by the charged impurities enhance the inter-valley scattering, which is favorable for WL observations. Away from the CNP, the charged-impurity-induced scattering is weak because of the effective screening by the charge carriers. As a result, the local static structural defects govern the charge transport. Our findings provide compelling evidence for understanding the scattering mechanisms in graphene and pave the way for the improvement of fabrication techniques to achieve high-quality CVD graphene.

  20. Structure of chemical vapor deposition titania/silica gel

    Leboda, R.; Gun' ko, V.M.; Marciniak, M.; Malygin, A.A.; Malkin, A.A.; Grzegorczyk, W.; Trznadel, B.J.; Pakhlov, E.M.; Voronin, E.F.

    1999-10-01

    The structure of porous silica gel/titania synthesized using chemical vapor deposition (CVD) of titania via repeated reactions of TiCl{sub 4} with the surface and subsequent hydrolysis of residual Ti-Cl bonds at different temperatures was investigated by means of low-temperature nitrogen adsorption-desorption, X-ray diffraction (XRD), IR spectroscopy, and theoretical methods. A globular model of porous solids with corpuscular structure was applied to estimate the porosity parameters of titania/silica gel adsorbents. The utilization of this model is useful, for example, to predict conditions for synthesis of titania/silica with a specified structure. Analysis of pore parameters and fractal dimension suggests that the porosity and fractality of samples decrease with increasing amount of TiO{sub 2} covering the silica gel surface in a nonuniform layer, which represents small particles embedded in pores and larger particles formed at the outer surface of silica globules. Theoretical simulation shows that the Si-O-Ti linkages between the cover and the substrate can be easily hydrolyzed, which is in agreement with the IR data corresponding to the absence of a band at 950 cm {sup {minus}1} (characteristic of Si-O-Ti bridges) independent of the concentration of CVD-titania.

  1. Temperature admittance spectroscopy of boron doped chemical vapor deposition diamond

    Zubkov, V. I., E-mail: VZubkovspb@mail.ru; Kucherova, O. V.; Zubkova, A. V.; Ilyin, V. A.; Afanas' ev, A. V. [St. Petersburg State Electrotechnical University (LETI), Professor Popov Street 5, 197376 St. Petersburg (Russian Federation); Bogdanov, S. A.; Vikharev, A. L. [Institute of Applied Physics of the Russian Academy of Sciences, Ul' yanov Street 46, 603950 Nizhny Novgorod (Russian Federation); Butler, J. E. [St. Petersburg State Electrotechnical University (LETI), Professor Popov Street 5, 197376 St. Petersburg (Russian Federation); Institute of Applied Physics of the Russian Academy of Sciences, Ul' yanov Street 46, 603950 Nizhny Novgorod (Russian Federation); National Museum of Natural History (NMNH), P.O. Box 37012 Smithsonian Inst., Washington, D.C. 20013-7012 (United States)

    2015-10-14

    Precision admittance spectroscopy measurements over wide temperature and frequency ranges were carried out for chemical vapor deposition epitaxial diamond samples doped with various concentrations of boron. It was found that the experimentally detected boron activation energy in the samples decreased from 314 meV down to 101 meV with an increase of B/C ratio from 600 to 18000 ppm in the gas reactants. For the heavily doped samples, a transition from thermally activated valence band conduction to hopping within the impurity band (with apparent activation energy 20 meV) was detected at temperatures 120–150 K. Numerical simulation was used to estimate the impurity DOS broadening. Accurate determination of continuously altering activation energy, which takes place during the transformation of conduction mechanisms, was proposed by numerical differentiation of the Arrhenius plot. With increase of boron doping level the gradual decreasing of capture cross section from 3 × 10{sup −13} down to 2 × 10{sup −17} cm{sup 2} was noticed. Moreover, for the hopping conduction the capture cross section becomes 4 orders of magnitude less (∼2 × 10{sup −20} cm{sup 2}). At T > T{sub room} in doped samples the birth of the second conductance peak was observed. We attribute it to a defect, related to the boron doping of the material.

  2. Temperature admittance spectroscopy of boron doped chemical vapor deposition diamond

    Zubkov, V. I.; Kucherova, O. V.; Bogdanov, S. A.; Zubkova, A. V.; Butler, J. E.; Ilyin, V. A.; Afanas'ev, A. V.; Vikharev, A. L.

    2015-10-01

    Precision admittance spectroscopy measurements over wide temperature and frequency ranges were carried out for chemical vapor deposition epitaxial diamond samples doped with various concentrations of boron. It was found that the experimentally detected boron activation energy in the samples decreased from 314 meV down to 101 meV with an increase of B/C ratio from 600 to 18000 ppm in the gas reactants. For the heavily doped samples, a transition from thermally activated valence band conduction to hopping within the impurity band (with apparent activation energy 20 meV) was detected at temperatures 120-150 K. Numerical simulation was used to estimate the impurity DOS broadening. Accurate determination of continuously altering activation energy, which takes place during the transformation of conduction mechanisms, was proposed by numerical differentiation of the Arrhenius plot. With increase of boron doping level the gradual decreasing of capture cross section from 3 × 10-13 down to 2 × 10-17 cm2 was noticed. Moreover, for the hopping conduction the capture cross section becomes 4 orders of magnitude less (˜2 × 10-20 cm2). At T > Troom in doped samples the birth of the second conductance peak was observed. We attribute it to a defect, related to the boron doping of the material.

  3. Growth of graphene underlayers by chemical vapor deposition

    Fabiane, Mopeli; Khamlich, Saleh; Bello, Abdulhakeem; Dangbegnon, Julien; Momodu, Damilola; Manyala, Ncholu, E-mail: ncholu.manyala@up.ac.za [Department of Physics, Institute of Applied Materials, SARChI Chair in Carbon Technology and Materials, University of Pretoria, Pretoria 0028 (South Africa); Charlie Johnson, A. T. [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

    2013-11-15

    We present a simple and very convincing approach to visualizing that subsequent layers of graphene grow between the existing monolayer graphene and the copper catalyst in chemical vapor deposition (CVD). Graphene samples were grown by CVD and then transferred onto glass substrates by the bubbling method in two ways, either direct-transfer (DT) to yield poly (methyl methacrylate) (PMMA)/graphene/glass or (2) inverted transfer (IT) to yield graphene/PMMA/glass. Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were used to reveal surface features for both the DT and IT samples. The results from FE-SEM and AFM topographic analyses of the surfaces revealed the underlayer growth of subsequent layers. The subsequent layers in the IT samples are visualized as 3D structures, where the smaller graphene layers lie above the larger layers stacked in a concentric manner. The results support the formation of the so-called “inverted wedding cake” stacking in multilayer graphene growth.

  4. Growth of graphene underlayers by chemical vapor deposition

    Mopeli Fabiane

    2013-11-01

    Full Text Available We present a simple and very convincing approach to visualizing that subsequent layers of graphene grow between the existing monolayer graphene and the copper catalyst in chemical vapor deposition (CVD. Graphene samples were grown by CVD and then transferred onto glass substrates by the bubbling method in two ways, either direct-transfer (DT to yield poly (methyl methacrylate (PMMA/graphene/glass or (2 inverted transfer (IT to yield graphene/PMMA/glass. Field emission scanning electron microscopy (FE-SEM and atomic force microscopy (AFM were used to reveal surface features for both the DT and IT samples. The results from FE-SEM and AFM topographic analyses of the surfaces revealed the underlayer growth of subsequent layers. The subsequent layers in the IT samples are visualized as 3D structures, where the smaller graphene layers lie above the larger layers stacked in a concentric manner. The results support the formation of the so-called “inverted wedding cake” stacking in multilayer graphene growth.

  5. Development of microforming process combined with selective chemical vapor deposition

    Koshimizu Kazushi

    2015-01-01

    Full Text Available Microforming has been received much attention in the recent decades due to the wide use of microparts in electronics and medical purpose. For the further functionalization of these micro devices, high functional surface with noble metals and nanomaterials are strongly required in bio- and medical fields, such as bio-sensors. To realize the efficient manufacturing process, which can deform the submillimeter scale bulk structure and can construct the micro to nanometer scale structures in one process, the present study proposes a combined process of microforming for metal foils with a selective chemical vapor deposition (SCVD on the active surface of work materials. To clarify the availability of this proposed process, the feasibility of SCVD of functional materials to active surface of titanium (Ti was investigated. CVD of iron (Fe and carbon nanotubes (CNTs which construct CNTs on the patterned surface of active Ti and non-active oxidation layer were conducted. Ti thin films on silicon substrate and Fe were used as work materials and functional materials, respectively. CNTs were grown on only Ti surface. Consequently, the selectivity of the active surface of Ti to the synthesis of Fe particles in CVD process was confirmed.

  6. Initiated-chemical vapor deposition of organosilicon layers: Monomer adsorption, bulk growth, and process window definition

    Aresta, G.; Palmans, J.; M. C. M. van de Sanden,; Creatore, M.

    2012-01-01

    Organosilicon layers have been deposited from 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (V3D3) by means of the initiated-chemical vapor deposition (i-CVD) technique in a deposition setup, ad hoc designed for the engineering of multilayer moisture permeation barriers. The application of Fourier

  7. Diagnostic for Plasma Enhanced Chemical Vapor Deposition and Etch Systems

    Cappelli, Mark A.

    1999-01-01

    In order to meet NASA's requirements for the rapid development and validation of future generation electronic devices as well as associated materials and processes, enabling technologies ion the processing of semiconductor materials arising from understanding etch chemistries are being developed through a research collaboration between Stanford University and NASA-Ames Research Center, Although a great deal of laboratory-scale research has been performed on many of materials processing plasmas, little is known about the gas-phase and surface chemical reactions that are critical in many etch and deposition processes, and how these reactions are influenced by the variation in operating conditions. In addition, many plasma-based processes suffer from stability and reliability problems leading to a compromise in performance and a potentially increased cost for the semiconductor manufacturing industry. Such a lack of understanding has hindered the development of process models that can aid in the scaling and improvement of plasma etch and deposition systems. The research described involves the study of plasmas used in semiconductor processes. An inductively coupled plasma (ICP) source in place of the standard upper electrode assembly of the Gaseous Electronics Conference (GEC) radio-frequency (RF) Reference Cell is used to investigate the discharge characteristics and chemistries. This ICP source generates plasmas with higher electron densities (approximately 10(exp 12)/cu cm) and lower operating pressures (approximately 7 mTorr) than obtainable with the original parallel-plate version of the GEC Cell. This expanded operating regime is more relevant to new generations of industrial plasma systems being used by the microelectronics industry. The motivation for this study is to develop an understanding of the physical phenomena involved in plasma processing and to measure much needed fundamental parameters, such as gas-phase and surface reaction rates. species

  8. Improved adhesion and tribological properties of fast-deposited hard graphite-like hydrogenated amorphous carbon films

    Zaharia, T.; Kudlacek, P.; Creatore, M.; Groenen, R.; Persoone, P.; M. C. M. van de Sanden,

    2011-01-01

    Graphite-like hard hydrogenated amorphous carbon (a-C:H) was deposited using an Ar-C(2)H(2) expanding thermal plasma chemical vapour deposition (ETP-CVD) process. The relatively high hardness of the fast deposited a-C:H material leads to high compressive stress resulting in poor adhesion between the

  9. Corrosion deposits removal from Kozloduy NPP VVER-440 steam generator tubing by chemical cleaning

    A strict control of primary and secondary circuits metal equipment corrosion of VVER-440 Kozloduy NPP units has been performed for the whole period of operation. This is carried out following a specific program including visual inspection and chemical analysis of equipment corrosion deposits. During their migration, the corrosion products deposit on the metal surface in the so-called standstill zones. One of these is the steam generator. The process results in: deterioration of thermal exchange; deterioration of corrosion conditions under deposits corrosion, pitting corrosion, etc. Using quantity deposits data and deposits chemical consistence, chemical cleaning of steam generator surfaces is performed. Decision for such chemical treatment of secondary circuit equipment is taken when the amount of deposits on the steam generator tubing is greater than 150 g/m2. This limit is based on operational experience and manufacturer requirements. (R.P.)

  10. Early Stages of the Chemical Vapor Deposition of Pyrolytic Carbon Investigated by Atomic Force Microscopy

    Pfrang, Andreas; WAN Yong-Zhong; Schimmel, Thomas

    2009-01-01

    The early stages of chemical vapor deposition of pyrolytic carbon on planar silicon substrates were studied by the atomic force microscopy-based technique of chemical contrast imaging. Short deposition times were chosen to focus on the early stages of the deposition process, and three different types of nucleation were found: random nucleation of single islands, nucleation of carbon islands along lines and secondary nucleation which corresponds to the nucleation of carbon islands at the edges...

  11. Experimental Data of Vapour Permeation Obtained from New Apparatus

    Morávková, Lenka; Sedláková, Zuzana; Vejražka, Jiří; Izák, Pavel

    Bratislava : Slovak Society of Chemical Engineering, 2015 - (Markoš, J.), s. 71 ISBN 978-80-89475-14-8. [International Conference of Slovak Society of Chemical Engineering /42./. Tatranské Matliare (SK), 25.05.2015-29.05.2015] R&D Projects: GA MŠk(CZ) LD14094 Institutional support: RVO:67985858 Keywords : vapour permeation * evaluation of experimental data * organic vapour removal Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  12. Experimental Data of Vapour Permeation Obtained from New Apparatus

    Morávková, Lenka; Sedláková, Zuzana; Vejražka, Jiří; Izák, Pavel

    Bratislava: Slovak Society of Chemical Engineering, 2015 - (Markoš, J.), s. 71 ISBN 978-80-89475-14-8. [International Conference of Slovak Society of Chemical Engineering /42./. Tatranské Matliare (SK), 25.05.2015-29.05.2015] R&D Projects: GA MŠk(CZ) LD14094 Institutional support: RVO:67985858 Keywords : vapour permeation * evaluation of experimental data * organic vapour removal Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  13. Molecular designing of precursors for chemical vapor deposition

    Both tin oxide and antimony oxide, can act as gas sensing material whose activity/selectivity is enhanced by the incorporation of a second metal. We are interested in the formation of bimetallic and trimetallic carboxylates and alkoxides which can be used as single source precursors for such mixed metal oxides. Sb(dmae)/sub 3/ (dmae=OCH/sub 2/CH/sub 2/(CH/sub 3/)sub 2/ has been prepared from Sb(OC/sub 2/H/sub 5/)/sub 3/ and Hdmae and used to generate the bimetallic materials Sb(dmae)/sub 3/Cd(acac)/sub 2/. Sn(acac)/sub 2/ hydrolyses to yield crystalline cage Sn/sub 4/O/sub 6/(dmae)/sub 4/. Sn(dmae)/sub 2/ can also be used to generate bimetallic materials such as [Sn(dmae)/sub 2/ Cd(acac)/sub 2/]/sub 2/]. Bimetallic and trimetallic carboxylates of general formula [R/sub 3/Ge-CHRCH/sub 2/COO]/sub 4-n/SnRn. [Where R=CH/sub 3/, C/sub 2/H/sub 5/, C/sub 6/H/sub 5/, tolyl, cyclohexyl, (CH/sub 3/)/sub 3/ Si CH/sub 2/-etc.] have been prepared and characterized by various analytic techniques. Chemical vapor deposition using Sb(dmae)/sub 3/ Cd(acac)/sub 2/ and various bimetallic carboxylates yield thin films of Cd/sub 2/Sb/sub 2/O/sub 7/ and SnOGeO respectively. (author)

  14. Review of chemical vapor deposition of graphene and related applications.

    Zhang, Yi; Zhang, Luyao; Zhou, Chongwu

    2013-10-15

    Since its debut in 2004, graphene has attracted enormous interest because of its unique properties. Chemical vapor deposition (CVD) has emerged as an important method for the preparation and production of graphene for various applications since the method was first reported in 2008/2009. In this Account, we review graphene CVD on various metal substrates with an emphasis on Ni and Cu. In addition, we discuss important and representative applications of graphene formed by CVD, including as flexible transparent conductors for organic photovoltaic cells and in field effect transistors. Growth on polycrystalline Ni films leads to both monolayer and few-layer graphene with multiple layers because of the grain boundaries on Ni films. We can greatly increase the percentage of monolayer graphene by using single-crystalline Ni(111) substrates, which have smooth surface and no grain boundaries. Due to the extremely low solubility of carbon in Cu, Cu has emerged as an even better catalyst for the growth of monolayer graphene with a high percentage of single layers. The growth of graphene on Cu is a surface reaction. As a result, only one layer of graphene can form on a Cu surface, in contrast with Ni, where more than one layer can form through carbon segregation and precipitation. We also describe a method for transferring graphene sheets from the metal using polymethyl methacrylate (PMMA). CVD graphene has electronic properties that are potentially valuable in a number of applications. For example, few-layer graphene grown on Ni can function as flexible transparent conductive electrodes for organic photovoltaic cells. In addition, because we can synthesize large-grain graphene on Cu foil, such large-grain graphene has electronic properties suitable for use in field effect transistors. PMID:23480816

  15. Compositional study of silicon oxynitride thin films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition technique

    We have used backscattering spectrometry and 15N(1H,α,γ)12C nuclear reaction analysis techniques to study in detail the variation in the composition of silicon oxynitride films with deposition parameters. The films were deposited using 2.45 GHz electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) technique from mixtures of precursors argon, nitrous oxide, and silane at deposition temperature 90 deg. C. The deposition pressure and nitrous oxide-to-silane gas flow rates ratio have been found to have a pronounced influence on the composition of the films. When the deposition pressure was varied for a given nitrous oxide-to-silane gas flow ratio, the amount of silicon and nitrogen increased with the deposition pressure, while the amount of oxygen decreased. For a given deposition pressure, the amount of incorporated nitrogen and hydrogen decreased while that of oxygen increased with increasing nitrous oxide-to-silane gas flow rates ratio. For nitrous oxide-to-silane gas flow ratio of 5, we obtained films which contained neither chemically bonded nor nonbonded nitrogen atoms as revealed by the results of infrared spectroscopy, backscattering spectrometry, and nuclear reaction analysis. Our results demonstrate the nitrogen-free nearly stoichiometric silicon dioxide films can be prepared from a mixture of precursors argon, nitrous oxide, and silane at low substrate temperature using high-density PECVD technique. This avoids the use of a hazardous and an often forbidden pair of silane and oxygen gases in a plasma reactor

  16. A comparison of the wear and fatigue properties of plasma-assisted physical vapour deposition TiN, CrN and duplex coatings on Ti-6Al-4V

    The study sets out to establish a comparison between duplex systems of plasma nitriding followed by plasma-assisted physical vapour deposition (PAPVD) of TiN deposited on Ti-6Al-4V, compared with PAPVD of TiN and CrN alone. The fatigue resistance has also been examined since conventional surface modifications can often impair fatigue resistance. A rubber-wheel-type abrasion tester and pin-on-disc sliding wear tester were used to examine the wear resistance of the coatings and the load-bearing capacity of the substrate respectively. A Wohler-type rotating tester was used to study the fatigue properties. Using smooth rotating-bending fatigue specimens tested in air at 5700 rev min-1 for 106 cycles or until failure it was found that TiN, CrN and the duplex coating did not impair fatigue resistance but actually improved the S-N curves and increased the endurance limit. From the wear results it was found that, although TiN and CrN do improve the wear resistance of Ti-6Al-4V significantly, it is the duplex coating that has much the greater load-bearing capacity on the titanium substrate and gives a significant improvement on PAPVD TiN or CrN coatings in sliding and abrasive wear conditions. (orig.)

  17. Polyimide (PI) films by chemical vapor deposition (CVD): Novel design, experiments and characterization

    Puig-Pey González, Jaime; Lamure, Alain; Senocq, François

    2007-01-01

    International audience Polyimide (PI) has been deposited by chemical vapor deposition (CVD) under vacuum over the past 20 years. In the early nineties, studies, experiences and characterization were mostly studied as depositions from the co-evaporation of the dianhydride and diamine monomers. Later on, several studies about its different applications due to its interesting mechanical and electrical properties enhanced its development. Nowadays, not many researches around PI deposition are ...

  18. Chemical bath deposition of II-VI compound thin films

    Oladeji, Isaiah Olatunde

    II-VI compounds are direct bandgap semiconductors with great potentials in optoelectronic applications. Solar cells, where these materials are in greater demand, require a low cost production technology that will make the final product more affordable. Chemical bath deposition (CBD) a low cost growth technique capable of producing good quality thin film semiconductors over large area and at low temperature then becomes a suitable technology of choice. Heterogeneous reaction in a basic aqueous solution that is responsible for the II-VI compound film growth in CBD requires a metal complex. We have identified the stability constant (k) of the metal complex compatible with CBD growth mechanism to be about 106.9. This value is low enough to ensure that the substrate adsorbed complex relax for subsequent reaction with the chalcogen precursor to take place. It is also high enough to minimize the metal ion concentration in the bath participating in the precipitation of the bulk compounds. Homogeneous reaction that leads to precipitation in the reaction bath takes place because the solubility products of bulk II-VI compounds are very low. This reaction quickly depletes the bath of reactants, limit the film thickness, and degrade the film quality. While ZnS thin films are still hard to grow by CBD because of lack of suitable complexing agent, the homogeneous reaction still limits quality and thickness of both US and ZnS thin films. In this study, the zinc tetraammine complex ([Zn(NH3) 4]2+) with k = 108.9 has been forced to acquire its unsaturated form [Zn(NH3)3]2+ with a moderate k = 106.6 using hydrazine and nitrilotriacetate ion as complementary complexing agents and we have successfully grown ZnS thin films. We have also, minimized or eliminated the homogeneous reaction by using ammonium salt as a buffer and chemical bath with low reactant concentrations. These have allowed us to increase the saturation thickness of ZnS thin film by about 400% and raise that of US film

  19. Structural and chemical transformations in the products of the interaction of silica gel with vapours of TiCl4 and H2O

    Titanium oxide structures were synthesised by a molecular layering method on the surface of silica (ShSKG, SBET = 270 m2/g, V = 0.94 cm3/g, d = 14 nm). The change in the mass of the sample during the deposition was measured in situ. The samples were characterised by elemental analysis of Ti (photocolorimetry) and Cl (mercurimetry), scanning electron microscopy, and energy-dispersive X-ray spectroscopy. In this study, the effect of the temperature (200 °C, 500 °C) and number of synthesis cycles (1–4) on the distribution of titanium oxide structures over a cross-section of silica was investigated, along with the chemical composition and the microstructure of the modified silica samples. All of the deposition steps carried out at 200 °C and 500 °C were self-limiting. Synthesis at 200 °C provided a uniform distribution of titanium oxide structures over a cross-section of silica, and no traces of phase formation were found by scanning electron microscopy. For the samples synthesised at 500 °C, the titanium concentration in the edge of the granule was 1.5 times higher than in the central regions. Titanium dioxide crystals were found on the external surface of the silica modified by four cycles at 500 °C (its concentration was approximately 3.5 wt% of the total titanium content in the sample). On the surface of this sample, oval agglomerates of a higher titanium concentration were observed. The structure of these agglomerates was globular, similar to the structure of the initial silica.

  20. Comparative X-ray photoelectron spectroscopy study of plasma enhanced chemical vapor deposition and micro pressure chemical vapor deposition of phosphorus silicate glass layers after rapid thermal annealing

    In this paper the bonding state of Phosphorus Silicate Glass (PSG) layers obtained by two different technological approaches, i.e. in two types of reactors: Plasma Enhanced Chemical Vapor Deposition (PECVD) and Micro Pressure Chemical Vapor Deposition (MPCVD) are investigated employing XPS and AES. The PSG layers are deposited at 3800C and 4200C in corresponding reactors. XPS and AES analyses show that Si2p peak recorded from PECVD layers are not as expected at their position characteristics of silicon dioxide but instead they are at the characteristic of elemental silicon. Plasma enhancement during deposition leads to less oxidized and more inhomogeneous layer. After rapid thermal annealing the Si2p peak is situated at position characteristic of silicon dioxide. (authors)

  1. Metallization on FDM Parts Using the Chemical Deposition Technique

    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.

  2. Practical silicon deposition rules derived from silane monitoring during plasma-enhanced chemical vapor deposition

    Bartlome, Richard, E-mail: richard.bartlome@alumni.ethz.ch; De Wolf, Stefaan; Demaurex, Bénédicte; Ballif, Christophe [Ecole Polytechnique Fédérale de Lausanne (EPFL), Institute of Microengineering (IMT), Photovoltaics and Thin-Film Electronics Laboratory, Rue de la Maladière 71b, 2000 Neuchâtel (Switzerland); Amanatides, Eleftherios; Mataras, Dimitrios [University of Patras, Department of Chemical Engineering, Plasma Technology Laboratory, P.O. Box 1407, 26504 Patras (Greece)

    2015-05-28

    We clarify the difference between the SiH{sub 4} consumption efficiency η and the SiH{sub 4} depletion fraction D, as measured in the pumping line and the actual reactor of an industrial plasma-enhanced chemical vapor deposition system. In the absence of significant polysilane and powder formation, η is proportional to the film growth rate. Above a certain powder formation threshold, any additional amount of SiH{sub 4} consumed translates into increased powder formation rather than into a faster growing Si film. In order to discuss a zero-dimensional analytical model and a two-dimensional numerical model, we measure η as a function of the radio frequency (RF) power density coupled into the plasma, the total gas flow rate, the input SiH{sub 4} concentration, and the reactor pressure. The adjunction of a small trimethylboron flow rate increases η and reduces the formation of powder, while the adjunction of a small disilane flow rate decreases η and favors the formation of powder. Unlike η, D is a location-dependent quantity. It is related to the SiH{sub 4} concentration in the plasma c{sub p}, and to the phase of the growing Si film, whether the substrate is glass or a c-Si wafer. In order to investigate transient effects due to the RF matching, the precoating of reactor walls, or the introduction of a purifier in the gas line, we measure the gas residence time and acquire time-resolved SiH{sub 4} density measurements throughout the ignition and the termination of a plasma.

  3. Practical silicon deposition rules derived from silane monitoring during plasma-enhanced chemical vapor deposition

    We clarify the difference between the SiH4 consumption efficiency η and the SiH4 depletion fraction D, as measured in the pumping line and the actual reactor of an industrial plasma-enhanced chemical vapor deposition system. In the absence of significant polysilane and powder formation, η is proportional to the film growth rate. Above a certain powder formation threshold, any additional amount of SiH4 consumed translates into increased powder formation rather than into a faster growing Si film. In order to discuss a zero-dimensional analytical model and a two-dimensional numerical model, we measure η as a function of the radio frequency (RF) power density coupled into the plasma, the total gas flow rate, the input SiH4 concentration, and the reactor pressure. The adjunction of a small trimethylboron flow rate increases η and reduces the formation of powder, while the adjunction of a small disilane flow rate decreases η and favors the formation of powder. Unlike η, D is a location-dependent quantity. It is related to the SiH4 concentration in the plasma cp, and to the phase of the growing Si film, whether the substrate is glass or a c-Si wafer. In order to investigate transient effects due to the RF matching, the precoating of reactor walls, or the introduction of a purifier in the gas line, we measure the gas residence time and acquire time-resolved SiH4 density measurements throughout the ignition and the termination of a plasma

  4. Manufacture of Bi-cuprate thin films on MgO single crystal substrates by chemical solution deposition

    Grivel, Jean-Claude; Bertelsen, Christian Vinther; Andersen, Niels Hessel; Kepa, Katarzyna; Hlásek, T.; Rubešová, K.; Huhtinen, H.; Paturi, P.

    2014-01-01

    Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors dissolved in xylene. Pyrolysis takes place between 200°C and 450°C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c...

  5. Large area deposition of boron doped nano-crystalline diamond films at low temperatures using microwave plasma enhanced chemical vapour deposition with linear antenna delivery

    Taylor, Andrew; Fekete, Ladislav; Hubík, Pavel; Jäger, Aleš; Janíček, P.; Mortet, Vincent; Mistrík, J.; Vacík, Jiří

    2014-01-01

    Roč. 47, AUG (2014), s. 27-34. ISSN 0925-9635 R&D Projects: GA MŠk(CZ) LM2011026; GA MŠk(XE) LM2011019 Institutional support: RVO:68378271 ; RVO:61389005 Keywords : large area * low temperature * boron doped nano-crystalline diamond * linear antenna MW PE CVD Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.919, year: 2014

  6. Deposition and Characterisation of Crystalline Silicon

    Rachow, Thomas

    2014-01-01

    In this thesis, crystalline silicon thin films by atmospheric pressure chemical vapour deposition have been studied. These silicon films can be deposited on silicon wafers or transferred to various substrates for photovoltaic applications. One of the main advantages is the flexibility in thickness and doping concentration which allows the application of the silicon thin films in various solar cell concepts. The combination of these films with an industrial solar cell fabrication process has a...

  7. Influences of deposition temperature on characteristics of B-doped ZnO films deposited by metal–organic chemical vapor deposition

    Boron-doped zinc oxide films were fabricated by metal–organic chemical vapor deposition at deposition temperatures (Td) from 150 to 210 °C. The deposition rate increases abruptly and monotonically with increasing Td. The resistivity also varies drastically, and a minimum resistivity of 1.6 × 10−3Ω cm is obtained at Td = 175 °C. The crystal orientation and surface texture show Td dependence. These characteristics correlate with each other. The dependence of these characteristics on Td is caused by the reactivity of the source materials. - Highlights: • Transparent conducting boron-doped zinc oxide films were deposited and characterized. • Comparing various characteristics, these characteristics correlate each other. • These characteristics were influenced by chemical vapor reactions strongly

  8. Fabrication of Isotropic Pyrocarbon at 1400℃ by Thermal Gradient Chemical Vapor Deposition Apparatus

    GUO Lingjun; ZHANG Dongsheng; LI Kezhi; LI Hejun

    2009-01-01

    An experiment was designed to prepare isotropic pyrocarbon by thermal gradient chemical vapor deposition apparatus.The deposition was performed under ambient atmosphere at 1400℃,with natural gas volume flow of 3.5 m~3/h for 80 h.The results show that the thickness and the bulk density of the deposit are about 1.95 g/cm~3 and 10 mm,respectively.The microstructure of the deposit was examined by polarized light microscopy and scanning electron microscopy,which shows that the deposit is constituted of sphere isotropic pyrocarbon,pebble pyrocarbon and laminar pyrocarbon.

  9. The power source effect on SiO{sub x} coating deposition by plasma enhanced chemical vapor deposition

    Zhang Junfeng [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Daxing, Beijing, 102600 (China); Chen Qiang, E-mail: chenqiang@bigc.edu.c [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Daxing, Beijing, 102600 (China); Zhang Yuefei; Liu Fuping; Liu Zhongwei [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Daxing, Beijing, 102600 (China)

    2009-05-29

    SiOx coatings were prepared by capacitively coupled plasma enhanced chemical vapor deposition on polyethyleneterephtalate substrates in 23 kHz middle-frequency and radio frequency power supplies, respectively, where hexamethyldisiloxane was used as gas source. The influences of discharge conditions on gas phase intermediate species and active radicals for SiOx formation was investigated by mass spectrometry as real-time in-situ diagnosis. The deposited SiOx coating chemical structures were also analyzed by Fourier transform infrared spectroscopy. Meanwhile, the film barrier property, oxygen transmission rate, was measured at 23 {sup o}C and 50% humidity circumstance. The better barrier property was obtained in the MF power source depositing SiOx coated PET.

  10. Effect of deposition temperature on boron-doped carbon coatings deposited from a BCl3-C3H6-H2 mixture using low pressure chemical vapor deposition

    A mixture of propylene, hydrogen and boron trichloride was used to fabricate boron-doped carbon coatings by using low pressure chemical vapor deposition (LPCVD) technique. Effect of deposition temperature on deposition rate, morphologies, compositions and bonding states of boron-doped carbon coatings was investigated. Below 1273 K, the deposition rate is controlled by reaction dynamics. The deposition rate increases with increasing deposition temperature. The activation energy is 208.74 kJ/mol. Above 1273 K, the deposition rate decreases due to smaller critical radius rc and higher nuclei formation rate J with increasing temperature. Scanning electron microscopy shows that the structure changes from glass-like to nano-laminates with increasing deposition temperature. The boron concentration decreases with increasing deposition temperature, corresponding with increasing carbon concentration. The five types of bonding states are B-C, B-sub-C, BC2O, BCO2 and B-O. B-sub-C and BC2O are the main bonding states. The reactions are dominant at all temperatures, in which the B-sub-C and PyC are formed.

  11. Low pressure chemical vapor deposition of niobium coating on silicon carbide

    Nb coatings were prepared on a SiC substrate by low pressure chemical vapor deposition using NbCl5. Thermodynamic calculations were performed to study the effect of temperature and partial pressure of NbCl5 on the final products. The as-deposited coatings were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. The Nb coatings are oriented and grow in the preferred (2 0 0) plane and (2 1 1) plane, at 1173 K and 1223-1423 K, respectively. At 1123-1273 K, the deposition is controlled by the surface kinetic processes. The activation energy is found to be 133 kJ/mol. At 1273-1373 K, the deposition is controlled by the mass transport processes. The activation energy is found to be 46 kJ/mol. The growth mechanism of the chemical vapor deposited Nb is also discussed based on the morphologies and the deposition rates.

  12. Electro-Optical Properties of Carbon Nanotubes Obtained by High Density Plasma Chemical Vapor Deposition

    Ana Paula Mousinho; Ronaldo D. Mansano

    2011-01-01

    In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a new concept of plasma generation: a planar coil is coupled to an RF system for plasma generation. This was used together with an electrostatic shield, for plasma densification, thereby obtaining high-density plasmas. The carbon nanotubes were deposited using pure methane plasmas. T...

  13. Sealing of micromachined cavities using chemical vapor deposition methods: characterization and optimization

    Liu, Chang; Tai, Yu-Chong

    1999-01-01

    This paper presents results of a systematic investigation to characterize the sealing of micromachined cavities using chemical vapor deposition (CVD) methods. We have designed and fabricated a large number and variety of surface-micromachined test structures with different etch-channel dimensions. Each cavity is then subjected to a number of sequential CVD deposition steps with incremental thickness until the cavity is successfully sealed. At etch deposition interval, the sealing status of ev...

  14. Chemical deposition in CdSe thin films using cadmium trithanolamine complex

    Eid, A.H.; Mahmoud, S. (National Research centre, Dokki, Cairo (EG). Dept. of Electron Microscopy and Thin Films)

    1992-07-01

    Thin layers of metal chalcogenides are important for photovoltaic cells, photoconductors and other electro-optical devices. These materials can be obtained in thin-layer form by sputtering, spray pyrolysis, vacuum deposition and sintering. Chemical deposition is the simplest way of obtaining thin layers of high quality and good reproducibility. In the recent work the triethanolamine (TEA) complex of Cd{sup 2+} ion was used for CdSe thin-film deposition. (author).

  15. Plasma enhanced chemical vapor deposition of zirconium nitride thin films

    Depositions of high quality zirconium nitride, (Zr3N4), films using the metal-organic precursor Zr(NEt2)4 were carried out in a microwave argon/ammonia plasma (2.45 GHz). The films were deposited on crystalline silicon wafers and quartz substrates at temperatures of 200--400 C. The transparent yellow films have resistivity values greater than MΩ cm. The stoichiometry is N/Zr = 1.3, with less than 5 atom % carbon and little or no oxygen. The hydrogen content is less than 9 atom %, and it does not vary with deposition temperature. The growth rates range from 600 to 1,200 angstrom/min, depending on the flow rates and precursor bubbler temperature. X-ray diffraction studies show a Zr3N4 film deposited at 400 C is polycrystalline with some (220) orientation. The crystallite size is approximately 30 angstrom. The band gap, as estimated from transmission spectra, is 3.1 eV

  16. Plasma-enhanced Chemical Vapor Deposition of Aluminum Oxide Using Ultrashort Precursor Injection Pulses

    Dingemans, G.; M. C. M. van de Sanden,; Kessels, W. M. M.

    2012-01-01

    An alternative plasma-enhanced chemical vapor deposition (PECVD) method is developed and applied for the deposition of high-quality aluminum oxide (AlOx) films. The PECVD method combines a continuous plasma with ultrashort precursor injection pulses. We demonstrate that the modulation of the precurs

  17. High Pressure Chemical Vapor Deposition of Hydrogenated Amorphous Silicon Films and Solar Cells.

    He, Rongrui; Day, Todd D; Sparks, Justin R; Sullivan, Nichole F; Badding, John V

    2016-07-01

    Thin films of hydrogenated amorphous silicon can be produced at MPa pressures from silane without the use of plasma at temperatures as low as 345 °C. High pressure chemical vapor deposition may open a new way to low cost deposition of amorphous silicon solar cells and other thin film structures over very large areas in very compact, simple reactors. PMID:27174318

  18. Titanium-based coatings on copper by chemical vapor deposition in fluidized bed reactors

    Titanium, TiN and TiOx coatings were deposited on copper and Cu-Ni alloys by chemical vapor deposition in fluidized bed reactors. These coatings provide the copper with a tenfold increase in corrosion resistance in chloride aqueous environments, as determined by a.c. impedance studies. (orig.)

  19. Electron emission from nano-structured carbon films fabricated by hot-filament chemical-vapor deposition and microwave plasma-enhanced chemical vapor deposition

    Park, K H; Lee, K M; Oh, S G; Lee, S I; Koh, K H

    2000-01-01

    The electron-emission characteristics of nano-structured carbon films fabricated by using the HFCVD (hot- filament chemical-vapor deposition) and the MPECVD (microwave plasma-enhanced chemical-vapor deposition) methods with a metal catalyst are presented. According to our observation, neither the formation nor the alignment of nano tubes is absolutely necessary to realize carbon-based electron emitters. However, utilization of chrome as an interlayer between Si substrates and metal catalyst particles results in a great improvement in the emission characteristics and the mechanical stability. Also, fabrication of good electron-emitting carbon films on glass substrates, with sputter-deposited chrome electrodes,at a nominal temperature approx 615 .deg. C was demonstrated.

  20. Experimental setup for producing tungsten coated graphite tiles using plasma enhanced chemical vapor deposition technique for fusion plasma applications

    Plasma wall interaction (PWI) in fusion grade machines puts stringent demands on the choice of materials in terms of high heat load handling capabilities and low sputtering yields. Choice of suitable material still remains a challenge and open topic of research for the PWI community. Carbon fibre composites (CFC), Beryllium (Be), and Tungsten (W) are now being considered as first runners for the first wall components of future fusion machines. Tungsten is considered to be one of the suitable materials for the job because of its superior properties than carbon like low physical sputtering yield and high sputter energy threshold, high melting point, fairly high re-crystallization temperature, low fuel retention capabilities, low chemical sputtering with hydrogen and its isotopes and most importantly the reparability with various plasma techniques both ex-situ and in-situ. Plasma assisted chemical vapour deposition is considered among various techniques as the most preferable technique for fabricating tungsten coated graphite tiles to be used as tokamak first wall and target components. These coated tiles are more favourable compared to pure tungsten due to their light weight and easier machining. A system has been designed, fabricated and installed at SVITS, Indore for producing tungsten coated graphite tiles using Plasma Enhanced Chemical Vapor Deposition (PE-CVD) technique for Fusion plasma applications. The system contains a vacuum chamber, a turbo-molecular pump, two electrodes, vacuum gauges, mass analyzer, mass flow controllers and a RF power supply for producing the plasma using hydrogen gas. The graphite tiles will be put on one of the electrodes and WF6 gas will be inserted in a controlled manner in the hydrogen plasma to achieve the tungsten-coating with WF6 dissociation. The system is integrated at SVITS, Indore and a vacuum of the order of 3*10-6 is achieved and glow discharge plasma has been created to test all the sub-systems. The system design with all

  1. Atmospheric pressure chemical vapor deposition of ZnO: Process modeling and experiments

    Deelen, J. van, E-mail: joop.vandeelen@tno.nl [TNO, Department of Thin Film Technology, De Rondom 1, 5612 AP Eindhoven (Netherlands); Illiberi, A.; Kniknie, B.; Beckers, E.H.A. [TNO, Department of Thin Film Technology, De Rondom 1, 5612 AP Eindhoven (Netherlands); Simons, P.J.P.M.; Lankhorst, A. [Celsian, De Rondom 1, 5612 AP Eindhoven (Netherlands)

    2014-03-31

    The deposition of zinc oxide has been performed by atmospheric pressure chemical vapor deposition and trends in growth rates are compared with the literature. Diethylzinc and tertiary butanol were used as the primary reactants and deposition rates above 800 nm/min were obtained. The reaction kinetics were studied and detailed process modeling based on a reaction mechanism that includes the formation of an alkylzinc alkoxide intermediate product is discussed. This mechanism can explain the temperature dependent variety in deposition profiles observed in the static deposition experiments. The capability of modeling to gain insight in the local process conditions inside a reactor is demonstrated. - Highlights: • ZnO deposition at high rates of 800 nm/min • Modeling based on two step mechanism gives good fit. • Modeling gives insight in the inside of the reactor. • Modeling can even predict static deposition profiles.

  2. Atmospheric pressure chemical vapor deposition of ZnO: Process modeling and experiments

    The deposition of zinc oxide has been performed by atmospheric pressure chemical vapor deposition and trends in growth rates are compared with the literature. Diethylzinc and tertiary butanol were used as the primary reactants and deposition rates above 800 nm/min were obtained. The reaction kinetics were studied and detailed process modeling based on a reaction mechanism that includes the formation of an alkylzinc alkoxide intermediate product is discussed. This mechanism can explain the temperature dependent variety in deposition profiles observed in the static deposition experiments. The capability of modeling to gain insight in the local process conditions inside a reactor is demonstrated. - Highlights: • ZnO deposition at high rates of 800 nm/min • Modeling based on two step mechanism gives good fit. • Modeling gives insight in the inside of the reactor. • Modeling can even predict static deposition profiles

  3. Chemical vapor deposition polymerization the growth and properties of parylene thin films

    Fortin, Jeffrey B

    2004-01-01

    Chemical Vapor Deposition Polymerization - The Growth and Properties of Parylene Thin Films is intended to be valuable to both users and researchers of parylene thin films. It should be particularly useful for those setting up and characterizing their first research deposition system. It provides a good picture of the deposition process and equipment, as well as information on system-to-system variations that is important to consider when designing a deposition system or making modifications to an existing one. Also included are methods to characterizae a deposition system's pumping properties as well as monitor the deposition process via mass spectrometry. There are many references that will lead the reader to further information on the topic being discussed. This text should serve as a useful reference source and handbook for scientists and engineers interested in depositing high quality parylene thin films.

  4. Photocatalytic activity of tin-doped TiO{sub 2} film deposited via aerosol assisted chemical vapor deposition

    Chua, Chin Sheng, E-mail: cschua@simtech.a-star.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Tan, Ooi Kiang; Tse, Man Siu [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Ding, Xingzhao [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore)

    2013-10-01

    Tin-doped TiO{sub 2} films are deposited via aerosol assisted chemical vapor deposition using a precursor mixture composing of titanium tetraisopropoxide and tetrabutyl tin. The amount of tin doping in the deposited films is controlled by the volume % concentration ratio of tetrabutyl tin over titanium tetraisopropoxide in the mixed precursor solution. X-ray diffraction analysis results reveal that the as-deposited films are composed of pure anatase TiO{sub 2} phase. Red-shift in the absorbance spectra is observed attributed to the introduction of Sn{sup 4+} band states below the conduction band of TiO{sub 2}. The effect of tin doping on the photocatalytic property of TiO{sub 2} films is studied through the degradation of stearic acid under UV light illumination. It is found that there is a 10% enhancement on the degradation rate of stearic acid for the film with 3.8% tin doping in comparison with pure TiO{sub 2} film. This improvement of photocatalytic performance with tin incorporation could be ascribed to the reduction of electron-hole recombination rate through charge separation and an increased amount of OH radicals which are crucial for the degradation of stearic acid. Further increase in tin doping results in the formation of recombination site and large anatase grains, which leads to a decrease in the degradation rate. - Highlights: ► Deposition of tin-doped TiO{sub 2} film via aerosol assisted chemical vapor depositionDeposited anatase films show red-shifted in UV–vis spectrum with tin-dopants. ► Photoactivity improves at low tin concentration but reduces at higher concentration. ► Improvement in photoactivity due to bandgap narrowing from Sn{sup 4+} band states ► Maximum photoactivity achieved occurs for films with 3.8% tin doping.

  5. Graphene growth with giant domains using chemical vapor deposition

    Yong, Virginia; Hahn, H. Thomas

    2011-01-01

    We report the first demonstration of the growth of giant graphene domains on platinum (Pt), which results in a uniform bilayer graphene film with domain sizes of millimetre scale. These giant graphene domains are attributed to the giant Pt grains attained in post-deposition annealed Pt thin films that exhibit a strong dependency on the Pt film thickness. Giant grains have been claimed to occur in other metallic materials under appropriate film thicknesses and processing conditions. Our findin...

  6. Physical properties of nitrogen-doped diamond-like amorphous carbon films deposited by supermagnetron plasma chemical vapor deposition

    Diamond-like amorphous carbon films doped with nitrogen (DAC:N) were deposited on Si and glass wafers intermittently using i-C4H10/N2 repetitive supermagnetron plasma chemical vapor deposition. Deposition duration, which is equal to a plasma heating time of wafer, was selected to be 40 or 60 s, and several layers were deposited repetitively to form one thick film. DAC:N films were deposited at a lower-electrode temperature of 100 deg. C as a function of upper- and lower-electrode rf powers (200 W/200 W-1 kW/1 kW) and N2 concentration (0%-80%). With an increase in N2 concentration and rf power, the resistivity and the optical band gap decreased monotonously. With increase of the deposition duration from 40 to 60 s, resistivity decreased to 0.03Ω cm and optical band gap decreased to 0.02 eV (substantially equal to 0 eV within the range of experimental error), at an N2 concentration of 80% and rf power of 1 kW(/1 kW)

  7. Metal organic chemical vapor deposition of environmental barrier coatings for the inhibition of solid deposit formation from heated jet fuel

    Mohan, Arun Ram

    Solid deposit formation from jet fuel compromises the fuel handling system of an aviation turbine engine and increases the maintenance downtime of an aircraft. The deposit formation process depends upon the composition of the fuel, the nature of metal surfaces that come in contact with the heated fuel and the operating conditions of the engine. The objective of the study is to investigate the effect of substrate surfaces on the amount and nature of solid deposits in the intermediate regime where both autoxidation and pyrolysis play an important role in deposit formation. A particular focus has been directed to examining the effectiveness of barrier coatings produced by metal organic chemical vapor deposition (MOCVD) on metal surfaces for inhibiting the solid deposit formation from jet fuel degradation. In the first part of the experimental study, a commercial Jet-A sample was stressed in a flow reactor on seven different metal surfaces: AISI316, AISI 321, AISI 304, AISI 347, Inconel 600, Inconel 718, Inconel 750X and FecrAlloy. Examination of deposits by thermal and microscopic analysis shows that the solid deposit formation is influenced by the interaction of organosulfur compounds and autoxidation products with the metal surfaces. The nature of metal sulfides was predicted by Fe-Ni-S ternary phase diagram. Thermal stressing on uncoated surfaces produced coke deposits with varying degree of structural order. They are hydrogen-rich and structurally disordered deposits, spherulitic deposits, small carbon particles with relatively ordered structures and large platelets of ordered carbon structures formed by metal catalysis. In the second part of the study, environmental barrier coatings were deposited on tube surfaces to inhibit solid deposit formation from the heated fuel. A new CVD system was configured by the proper choice of components for mass flow, pressure and temperature control in the reactor. A bubbler was designed to deliver the precursor into the reactor

  8. Chemical vapor deposition and characterization of titanium dioxide thin films

    Gilmer, David Christopher

    1998-12-01

    The continued drive to decrease the size and increase the speed of micro-electronic Metal-Oxide-Semiconductor (MOS) devices is hampered by some of the properties of the SiOsb2 gate dielectric. This research has focused on the CVD of TiOsb2 thin films to replace SiOsb2 as the gate dielectric in MOS capacitors and transistors. The relationship of CVD parameters and post-deposition anneal treatments to the physical and electrical properties of thin films of TiOsb2 has been studied. Structural and electrical characterization of TiOsb2 films grown from the CVD precursors tetraisopropoxotitanium (IV) (TTIP) and TTIP plus Hsb2O is described in Chapter 3. Both types of deposition produced stoichiometric TiOsb2 films comprised of polycrystalline anatase, but the interface properties were dramatically degraded when water vapor was added. Films grown with TTIP in the presence of Hsb2O contained greater than 50% more hydrogen than films grown using only TTIP and the hydrogen content of films deposited in both wet and dry TTIP environments decreased sharply with a post deposition Osb2 anneal. A significant thickness variation of the dielectric constant was observed which could be explained by an interfacial oxide and the finite accumulation thickness. Fabricated TiOsb2 capacitors exhibited electrically equivalent SiOsb2 gate dielectric thicknesses and leakage current densities as low as 38, and 1×10sp{-8} Amp/cmsp2 respectively. Chapter 4 discusses the low temperature CVD of crystalline TiOsb2 thin films deposited using the precursor tetranitratotitanium (IV), TNT, which produces crystalline TiOsb2 films of the anatase phase in UHV-CVD at temperatures as low as 184sp°C. Fabricated TiOsb2 capacitors exhibited electrically equivalent SiOsb2 gate dielectric thicknesses and leakage current densities as low as 17, and 1×10sp{-8} Amp/cmsp2 respectively. Chapter 5 describes the results of a comparison of physical and electrical properties between TiOsb2 films grown via LPCVD using

  9. Thermodynamic analysis and deposition of refractory materials

    This article does not pretend to be an exhaustive review of all publications in which a thermodynamic analysis has been used to analyse the chemical vapour deposition of refractory materials. It simply covers a certain number of experiments in which the present authors made use of various aspects of this method: overall or partial optimization of a process, determination of the deposition material most suited to fulfilling a given role and approach to mechanisms governing the chemical deposition reaction. A thermodynamic analysis is presented here from a more unusual angle, by examples of localized and varied intervention, in order to demonstrate the multiple uses of the method. (orig.)

  10. Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition

    Liu, C. Y.; Zhang, B. P.; Binh, N. T.; Segawa, Y.

    2004-07-01

    Second harmonic generation (SHG) from ZnO thin films fabricated by metalorganic chemical vapor deposition (MOCVD) technique was carried out. By comparing the second harmonic signal generated in a series of ZnO films with different deposition temperatures, we conclude that a significant part of second harmonic signal is generated at the film deposited with appropriate temperature. The second-order susceptibility tensor χ(2)zzz=9.2 pm/V was deduced for a film deposited at 250 °C.

  11. An in-situ chemical reaction deposition of nanosized wurtzite CdS thin films

    Chu Juan [School of Materials Science and Engineering, Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China); Jin Zhengguo, E-mail: zhgjin@tju.edu.cn [School of Materials Science and Engineering, Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Cai Shu [School of Materials Science and Engineering, Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin 300072 (China); State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Yang Jingxia [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Hong Zhanglian, E-mail: hong_zhanglian@zju.edu.cn [State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2012-01-01

    Nanocrystalline CdS thin films were deposited on glass substrates by an ammonia-free in-situ chemical reaction synthesis technique using cadmium cationic precursor solid films as reaction source and sodium sulfide based solutions as anionic reaction medium. Effects of ethanolamine addition to the cadmium cationic precursor solid films, deposition cycle numbers and annealing treatments in Ar atmosphere on structure, morphology, chemical composition and optical properties of the resultant films were investigated by X-ray diffraction, field emission scanning electron microscope, energy dispersive X-ray analysis and UV-Vis spectra measurements. The results show that CdS thin films deposited by the in-situ chemical reaction synthesis have wurtzite structure with (002) plane preferential orientation and crystallite size is in the range of 16 nm-19 nm. The growth of film thickness is almost constant with deposition cycle numbers and about 96 nm per cycle.

  12. Modification of optical and electrical properties of chemical bath deposited CdS using plasma treatments

    Gonzalez, G. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Krishnan, B. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Avellaneda, D.; Castillo, G. Alan; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); Shaji, S., E-mail: sshajis@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, C.P 66450 (Mexico); CIIDIT, Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

    2011-08-31

    Cadmium sulphide (CdS) is a well known n-type semiconductor that is widely used in solar cells. Here we report preparation and characterization of chemical bath deposited CdS thin films and modification of their optical and electrical properties using plasma treatments. CdS thin films were prepared from a chemical bath containing Cadmium chloride, Triethanolamine and Thiourea under various deposition conditions. Good quality thin films were obtained during deposition times of 5, 10 and 15 min. CdS thin films prepared for 10 min. were treated using a glow discharge plasma having nitrogen and argon carrier gases. The changes in morphology, optical and electrical properties of these plasma treated CdS thin films were analyzed in detail. The results obtained show that plasma treatment is an effective technique in modification of the optical and electrical properties of chemical bath deposited CdS thin films.

  13. Modification of optical and electrical properties of chemical bath deposited CdS using plasma treatments

    Cadmium sulphide (CdS) is a well known n-type semiconductor that is widely used in solar cells. Here we report preparation and characterization of chemical bath deposited CdS thin films and modification of their optical and electrical properties using plasma treatments. CdS thin films were prepared from a chemical bath containing Cadmium chloride, Triethanolamine and Thiourea under various deposition conditions. Good quality thin films were obtained during deposition times of 5, 10 and 15 min. CdS thin films prepared for 10 min. were treated using a glow discharge plasma having nitrogen and argon carrier gases. The changes in morphology, optical and electrical properties of these plasma treated CdS thin films were analyzed in detail. The results obtained show that plasma treatment is an effective technique in modification of the optical and electrical properties of chemical bath deposited CdS thin films.

  14. An in-situ chemical reaction deposition of nanosized wurtzite CdS thin films

    Nanocrystalline CdS thin films were deposited on glass substrates by an ammonia-free in-situ chemical reaction synthesis technique using cadmium cationic precursor solid films as reaction source and sodium sulfide based solutions as anionic reaction medium. Effects of ethanolamine addition to the cadmium cationic precursor solid films, deposition cycle numbers and annealing treatments in Ar atmosphere on structure, morphology, chemical composition and optical properties of the resultant films were investigated by X-ray diffraction, field emission scanning electron microscope, energy dispersive X-ray analysis and UV–Vis spectra measurements. The results show that CdS thin films deposited by the in-situ chemical reaction synthesis have wurtzite structure with (002) plane preferential orientation and crystallite size is in the range of 16 nm–19 nm. The growth of film thickness is almost constant with deposition cycle numbers and about 96 nm per cycle.

  15. Industrial Scale Synthesis of Carbon Nanotubes Via Fluidized Bed Chemical Vapor Deposition: A Senior Design Project

    Smith, York R.; Fuchs, Alan; Meyyappan, M.

    2010-01-01

    Senior year chemical engineering students designed a process to produce 10 000 tonnes per annum of single wall carbon nanotubes (SWNT) and also conducted bench-top experiments to synthesize SWNTs via fluidized bed chemical vapor deposition techniques. This was an excellent pedagogical experience because it related to the type of real world design…

  16. ZnS thin film deposited with chemical bath deposition process directed by different stirring speeds

    In this combined film thickness, scanning electron microscopy (SEM), X-ray diffraction and optical properties study, we explore the effects of different stirring speeds on the growth and optical properties of ZnS film deposited by CBD method. From the disclosed changes of thickness of ZnS film, we conclude that film thickness is independent of the stirring speeds in the heterogeneous process (deposition time less than 40 min), but increases with the stirring speeds and/or deposition time increasing in the homogeneous process. Grazing incident X-ray diffraction (GIXRD) and the study of optical properties disclosed that the ZnS films grown with different stirring speeds show partially crystallized film and exhibit good transmittance (70-88% in the visible region), but the stirring speeds cannot give much effects on the structure and optical properties in the homogeneous process.

  17. Selective epitaxial Si based layers and TiSi 2 deposition by integrated chemical vapor deposition

    Regolini, J. L.; Margail, J.; Bodnar, S.; Maury, D.; Morin, C.

    1996-07-01

    High performance IC manufacturing requirements, such as large diameter wafer uniformity, reproducibility, throughput and reliability can be fulfilled by commercial integrated processing, single wafer cluster tools. This paper presents results obtained on an industrial cluster reactor for 200 mm wafers by combining epitaxial silicon related materials and selective deposition of TiSi 2. Low temperature epitaxial Si and SiGe alloys are studied for buried thin layers used in CMOS and HBT devices. The doping profile abruptness for B and P are within SIMS resolution limits. TheTiSi 2/Si selective deposition is also investigated, sequentially and in situ, as a technique for future salicidedS/D with a reduction in technological steps and interface contamination. Statistical electrical results obtained using 0.35 and 0.25 μm CMOS technologies in which the CVD silicide deposition is tested, are presented and compared with the standard salicide technique.

  18. Characterization of titanium oxynitride films deposited by low pressure chemical vapor deposition using amide Ti precursor

    Song Xuemei; Gopireddy, Deepthi [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Takoudis, Christos G. [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States)], E-mail: takoudis@uic.edu

    2008-07-31

    In this study, we investigate the use of an amide-based Ti-containing precursor, namely tetrakis(diethylamido)titanium (TDEAT), for TiN{sub x}O{sub y} film deposition at low temperature. Traditionally, alkoxide-based Ti-containing precursor, such as titanium tetra-isopropoxide (TTIP), along with NH{sub 3} is used for titanium oxynitride (TiN{sub x}O{sub y}) film deposition. When TTIP is used, at low temperatures it is difficult to form TiN{sub x}O{sub y} films with high N/O ratios. In this study, by using TDEAT, TiN{sub x}O{sub y} films are deposited on H-passivated Si (100) substrates in a cold wall reactor at 300 {sup o}C and 106 Pa. Rutherford backscattering spectroscopy analysis shows nitrogen incorporation in the TiN{sub x}O{sub y} films to be as high as 28 at.%. X-ray photoelectron spectroscopy analysis of as-deposited films confirms the formation of{sub .} TiN{sub x}O{sub y}, while Fourier transform infrared and Raman spectra indicate that the films have amorphous structure. Moreover, there is no detectable bulk carbon impurity and no SiO{sub 2} formation at the TiN{sub x}O{sub y}/Si interface. Upon annealing the as-deposited films in air at 750 deg. C for 30 min, they oxidize to TiO{sub 2} and crystallize to form a rutile structure with a small amount of anatase phase. Based on these results, TDEAT appears to be a promising precursor for both TiN{sub x}O{sub y} and TiO{sub 2} film deposition.

  19. Coating of ceramic powders by chemical vapor deposition techniques (CVD)

    New ceramic materials with selected advanced properties can be designed by coating of ceramic powders prior to sintering. By variation of the core and coating material a large number of various powders and ceramic materials can be produced. Powders which react with the binder phase during sintering can be coated with stable materials. Thermal expansion of the ceramic materials can be adjusted by varying the coating thickness (ratio core/layer). Electrical and wear resistant properties can be optimized for electrical contacts. A fluidized bed reactor will be designed which allow the deposition of various coatings on ceramic powders. (author)

  20. Fabrication and characterization of indium sulfide thin films deposited on SAMs modified substrates surfaces by chemical bath deposition

    In an effort to explore the optoelectronic properties of nanostructured indium sulfide (In2S3) thin films for a wide range of applications, the In2S3 thin films were successfully deposited on the APTS layers (-NH2-terminated) modified ITO glass substrates using the chemical bath deposition technique. The surface morphology, structure and composition of the resultant In2S3 thin films were characterized by FESEM, XRD, and XPS, respectively. Also, the correlations between the optical properties, photocurrent response and the thickness of thin films were established. According to the different deposition mechanisms on the varying SAMs terminational groups, the positive and negative micropatterned In2S3 thin films were successfully fabricated on modified Si substrates surface combining with the ultraviolet lithography process. This offers an attractive opportunity to fabricate patterned In2S3 thin films for controlling the spatial positioning of functional materials in microsystems.