WorldWideScience

Sample records for plasma chemical vapor

  1. Review: Plasma-enhanced chemical vapor deposition of nanocrystalline diamond

    Directory of Open Access Journals (Sweden)

    Katsuyuki Okada

    2007-01-01

    Full Text Available Nanocrystalline diamond films have attracted considerable attention because they have a low coefficient of friction and a low electron emission threshold voltage. In this paper, the author reviews the plasma-enhanced chemical vapor deposition (PE-CVD of nanocrystalline diamond and mainly focuses on the growth of nanocrystalline diamond by low-pressure PE-CVD. Nanocrystalline diamond particles of 200–700 nm diameter have been prepared in a 13.56 MHz low-pressure inductively coupled CH4/CO/H2 plasma. The bonding state of carbon atoms was investigated by ultraviolet-excited Raman spectroscopy. Electron energy loss spectroscopy identified sp2-bonded carbons around the 20–50 nm subgrains of nanocrystalline diamond particles. Plasma diagnostics using a Langmuir probe and the comparison with plasma simulation are also reviewed. The electron energy distribution functions are discussed by considering different inelastic interaction channels between electrons and heavy particles in a molecular CH4/H2 plasma.

  2. A mathematical model and simulation results of plasma enhanced chemical vapor deposition of silicon nitride films

    NARCIS (Netherlands)

    Konakov, S.A.; Krzhizhanovskaya, V.V.

    2015-01-01

    We developed a mathematical model of Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon nitride thin films from SiH4-NH3-N2-Ar mixture, an important application in modern materials science. Our multiphysics model describes gas dynamics, chemical physics, plasma physics and electrodynamics.

  3. Plasma-Enhanced Chemical Vapor Deposition as a Method for the Deposition of Peptide Nanotubes

    Science.gov (United States)

    2013-09-17

    peptide nanotubes, plasma-enhanced chemical vapor deposition, nano assembly 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18...Using physical vapor deposition ( PVD ) well-ordered assemblies of peptide nanotubes (PNTs) composed of dipeptide subunits are obtained on various...for the deposition of thin films (Figure 1b). A. B. Figure 1. (a) Illustration of physical vapor deposition ( PVD ) process of diphenylalanine

  4. Plasma environment during hot cathode direct current discharge plasma chemical vapor deposition of diamond films

    Institute of Scientific and Technical Information of China (English)

    朱晓东; 詹如娟; 周海洋; 胡敏; 温晓辉; 周贵恩; 李凡庆

    1999-01-01

    The plasma characteristics have been investigated in situ by using optical emission spectroscopy (OES) and the Langmuir probe during hot cathode direct current discharge plasma chemical vapor deposition of diamond films. The changes of atomic H and CH radical in the ground state have been calculated quantitatively according to the results of OES and the Langmuir probe measurement as discharge current density varied. It is shown that atomic H and CH radicals both in the ground state and in the excited state increase with the enhancement of the discharge current density in the plasma. The electron density and CH emission intensity increase linearly with the enhancement of discharge current densities. The generation of different carbon-containing radicals is related to the elevation of electron temperature. Combining the growth process of diamond films and the diagnostic results, it is shown that atomic H in the excited state may improve the diamond growth efficiently, and the increase of electron temperat

  5. Plasma-enhanced Chemical Vapor Deposition of Aluminum Oxide Using Ultrashort Precursor Injection Pulses

    NARCIS (Netherlands)

    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

  6. Diagnostic for Plasma Enhanced Chemical Vapor Deposition and Etch Systems

    Science.gov (United States)

    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

  7. Simulation of low-temperature, atmospheric-pressure plasma enhanced chemical vapor deposition reactors

    OpenAIRE

    Lorant, Christophe; Descamps, Pierre; De Wilde, Juray; 1st BeLux workshop on “Coating, Materials, surfaces and Interfaces

    2014-01-01

    The simulation of low-temperature, atmospheric-pressure plasma enhanced chemical vapor deposition reactors is challenging due to the coupling of the fluid dynamics, the chemical reactions and the electric field and the stiffness of the resulting mathematical system. The model equations and the rigorous model reduction to reduce the stiffness are addressed in this paper. Considering pure nitrogen plasma, simulations with two configurations are discussed.

  8. Oxygen Barrier Coating Deposited by Novel Plasma-enhanced Chemical Vapor Deposition

    DEFF Research Database (Denmark)

    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......, and it increased the barrier property of the modified low-density polyethylene, polyethylene terephthalate, and polylactide by 96.48%, 99.69%, and 99.25%, respectively....

  9. Electroluminescence and photoluminescence of conjugated polymer films prepared by plasma enhanced chemical vapor deposition of naphthalene

    CERN Document Server

    Rajabi, Mojtaaba; Firouzjah, Marzieh Abbasi; Hosseini, Seyed Iman; Shokri, Babak

    2012-01-01

    Polymer light-emitting devices were fabricated utilizing plasma polymerized thin films as emissive layers. These conjugated polymer films were prepared by RF Plasma Enhanced Chemical Vapor Deposition (PECVD) using naphthalene as monomer. The effect of different applied powers on the chemical structure and optical properties of the conjugated polymers was investigated. The fabricated devices with structure of ITO/PEDOT:PSS/ plasma polymerized Naphthalene/Alq3/Al showed broadband Electroluminescence (EL) emission peaks with center at 535-550 nm. Using different structural and optical tests, connection between polymers chemical structure and optical properties under different plasma powers has been studied. Fourier transform infrared (FTIR) and Raman spectroscopies confirmed that a conjugated polymer film with a 3-D cross-linked network was developed. By increasing the power, products tended to form as highly cross-linked polymer films. Photoluminescence (PL) spectra of plasma polymers showed different excimerc ...

  10. Carbon nanofiber growth in plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Denysenko, I.; Ostrikov, K.; Cvelbar, U.; Mozetic, M.; Azarenkov, N. A.

    2008-10-01

    A theoretical model to describe the plasma-assisted growth of carbon nanofibers (CNFs) is proposed. Using the model, the plasma-related effects on the nanofiber growth parameters, such as the growth rate due to surface and bulk diffusion, the effective carbon flux to the catalyst surface, the characteristic residence time and diffusion length of carbon atoms on the catalyst surface, and the surface coverages, have been studied. The dependence of these parameters on the catalyst surface temperature and ion and etching gas fluxes to the catalyst surface is quantified. The optimum conditions under which a low-temperature plasma environment can benefit the CNF growth are formulated. These results are in good agreement with the available experimental data on CNF growth and can be used for optimizing synthesis of related nanoassemblies in low-temperature plasma-assisted nanofabrication.

  11. Shape correction of optical surfaces using plasma chemical vaporization machining with a hemispherical tip electrode.

    Science.gov (United States)

    Takino, Hideo; Yamamura, Kazuya; Sano, Yasuhisa; Mori, Yuzo

    2012-01-20

    We propose a plasma chemical vaporization machining device with a hemispherical tip electrode for optical fabrication. Radio-frequency plasma is generated close to the electrode under atmospheric conditions, and a workpiece is scanned relative to the stationary electrode under three-axis motion control to remove target areas on a workpiece surface. Experimental results demonstrate that surface removal progresses although process gas is not forcibly supplied to the plasma. The correction of shape errors on conventionally polished spheres is performed. As a result, highly accurate smooth surfaces with the desired rms shape accuracy of 3 nm are successfully obtained, which confirms that the device is effective for the fabrication of optics.

  12. Growth of Aligned Carbon Nanotubes through Microwave Plasma Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    王升高; 汪建华; 马志斌; 王传新; 满卫东

    2005-01-01

    Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 ℃. The experimental results show that both the self-bias potential and the density of the catalyst particles are responsible for the alignment of CNTs. When the catalyst particle density is high enough, strong interactions among the CNTs can inhibit CNTs from growing randomly and result in parallel alignment.

  13. High quality plasma-enhanced chemical vapor deposited silicon nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Cotler, T.J.; Chapple-Sokol, J. (IBM General Technology Division, Hopewell Junction, NY (United States))

    1993-07-01

    The qualities of plasma-enhanced chemical vapor deposited (PECVD) silicon nitride films can be improved by increasing the deposition temperature. This report compares PECVD silicon nitride films to low pressure chemical vapor deposited (LPCVD) films. The dependence of the film properties on process parameters, specifically power and temperature, are investigated. The stress is shown to shift from tensile to compressive with increasing temperature and power. The deposition rate, uniformity, wet etch rate, index of refraction, composition, stress, hydrogen content, and conformality are considered to evaluate the film properties. Temperature affects the hydrogen content in the films by causing decreased incorporation of N-H containing species whereas the dependence on power is due to changes in the gas-phase precursors. All PECVD film properties, with the exception of conformality, are comparable to those of LPCVD films.

  14. Ti-doped hydrogenated diamond like carbon coating deposited by hybrid physical vapor deposition and plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Lee, Na Rae; Sle Jun, Yee; Moon, Kyoung Il; Sunyong Lee, Caroline

    2017-03-01

    Diamond-like carbon films containing titanium and hydrogen (Ti-doped DLC:H) were synthesized using a hybrid technique based on physical vapor deposition (PVD) and plasma enhanced chemical vapor deposition (PECVD). The film was deposited under a mixture of argon (Ar) and acetylene gas (C2H2). The amount of Ti in the Ti-doped DLC:H film was controlled by varying the DC power of the Ti sputtering target ranging from 0 to 240 W. The composition, microstructure, mechanical and chemical properties of Ti-doped DLC:H films with varying Ti concentrations, were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nano indentation, a ball-on-disk tribometer, a four-point probe system and dynamic anodic testing. As a result, the optimum composition of Ti in Ti-doped DLC:H film using our hybrid method was found to be a Ti content of 18 at. %, having superior electrical conductivity and high corrosion resistance, suitable for bipolar plates. Its hardness value was measured to be 25.6 GPa with a low friction factor.

  15. Control of interface nanoscale structure created by plasma-enhanced chemical vapor deposition.

    Science.gov (United States)

    Peri, Someswara R; Akgun, Bulent; Satija, Sushil K; Jiang, Hao; Enlow, Jesse; Bunning, Timothy J; Foster, Mark D

    2011-09-01

    Tailoring the structure of films deposited by plasma-enhanced chemical vapor deposition (PECVD) to specific applications requires a depth-resolved understanding of how the interface structures in such films are impacted by variations in deposition parameters such as feed position and plasma power. Analysis of complementary X-ray and neutron reflectivity (XR, NR) data provide a rich picture of changes in structure with feed position and plasma power, with those changes resolved on the nanoscale. For plasma-polymerized octafluorocyclobutane (PP-OFCB) films, a region of distinct chemical composition and lower cross-link density is found at the substrate interface for the range of processing conditions studied and a surface layer of lower cross-link density also appears when plasma power exceeds 40 W. Varying the distance of the feed from the plasma impacts the degree of cross-linking in the film center, thickness of the surface layer, and thickness of the transition region at the substrate. Deposition at the highest power, 65 W, both enhances cross-linking and creates loose fragments with fluorine content higher than the average. The thickness of the low cross-link density region at the air interface plays an important role in determining the width of the interface built with a layer subsequently deposited atop the first.

  16. Plasma-enhanced chemical vapor deposition of amorphous Si on graphene

    Science.gov (United States)

    Lupina, G.; Strobel, C.; Dabrowski, J.; Lippert, G.; Kitzmann, J.; Krause, H. M.; Wenger, Ch.; Lukosius, M.; Wolff, A.; Albert, M.; Bartha, J. W.

    2016-05-01

    Plasma-enhanced chemical vapor deposition of thin a-Si:H layers on transferred large area graphene is investigated. Radio frequency (RF, 13.56 MHz) and very high frequency (VHF, 140 MHz) plasma processes are compared. Both methods provide conformal coating of graphene with Si layers as thin as 20 nm without any additional seed layer. The RF plasma process results in amorphization of the graphene layer. In contrast, the VHF process keeps the high crystalline quality of the graphene layer almost intact. Correlation analysis of Raman 2D and G band positions indicates that Si deposition induces reduction of the initial doping in graphene and an increase of compressive strain. Upon rapid thermal annealing, the amorphous Si layer undergoes dehydrogenation and transformation into a polycrystalline film, whereby a high crystalline quality of graphene is preserved.

  17. Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Well-aligned carbon nitrogen nanotube films have been synthesized successfully on mesoporous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1-xNx (x=0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds covalently with nitrogen in all the carbon nitrogen nanotube films.

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

    Science.gov (United States)

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

    2016-05-01

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

  19. Synthesis of carbon nanotube array using corona discharge plasma-enhanced chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A corona discharge plasma-enhanced chemical vapor deposition with the features of atmospheric pressure and low temperature has been developed to synthesize the carbon nanotube array. The array was synthesized from methane and hydrogen mixture in anodic aluminum oxide template channels in that cobalt was electrodeposited at the bottom. The characterization results by the scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy indicate that the array consists of carbon nanotubes with the diameter of about 40 nm and the length of more than 4 -m, and the carbon nanotubes are mainly restrained within the channels of templates.

  20. A mathematical model and simulation results of plasma enhanced chemical vapor deposition of silicon nitride films

    Science.gov (United States)

    Konakov, S. A.; Krzhizhanovskaya, V. V.

    2015-01-01

    We developed a mathematical model of Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon nitride thin films from SiH4-NH3-N2-Ar mixture, an important application in modern materials science. Our multiphysics model describes gas dynamics, chemical physics, plasma physics and electrodynamics. The PECVD technology is inherently multiscale, from macroscale processes in the chemical reactor to atomic-scale surface chemistry. Our macroscale model is based on Navier-Stokes equations for a transient laminar flow of a compressible chemically reacting gas mixture, together with the mass transfer and energy balance equations, Poisson equation for electric potential, electrons and ions balance equations. The chemical kinetics model includes 24 species and 58 reactions: 37 in the gas phase and 21 on the surface. A deposition model consists of three stages: adsorption to the surface, diffusion along the surface and embedding of products into the substrate. A new model has been validated on experimental results obtained with the "Plasmalab System 100" reactor. We present the mathematical model and simulation results investigating the influence of flow rate and source gas proportion on silicon nitride film growth rate and chemical composition.

  1. Deposition of electrochromic tungsten oxide thin films by plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Henley, W.B.; Sacks, G.J. [Univ. of South Florida, Tampa, FL (United States). Center of Microelectronics

    1997-03-01

    Use of plasma-enhanced chemical vapor deposition (PECVD) for electrochromic WO{sub 3} film deposition is investigated. Oxygen, hydrogen, and tungsten hexafluoride were used as source gases. Reactant gas flow was investigated to determine the effect on film characteristics. High quality optical films were obtained at deposition rates on the order of 100 {angstrom}/s. Higher deposition rates were attainable but film quality and optical coherence degraded. Atomic emission spectroscopy (AES), was used to provide an in situ assessment of the plasma deposition chemistry. Through AES, it is shown that the hydrogen gas flow is essential to the deposition of the WO{sub 3} film. Oxygen gas flow and tungsten hexafluoride gas flow must be approximately equal for high quality films.

  2. Behavior of incorporated nitrogen in plasma-nitrided silicon oxide formed by chemical vapor deposition

    Science.gov (United States)

    Shinoda, Nao; Itokawa, Hiroshi; Fujitsuka, Ryota; Sekine, Katsuyuki; Onoue, Seiji; Tonotani, Junichi

    2016-04-01

    The behavior of nitrogen (N) atoms in plasma-nitrided silicon oxide (SiO2) formed by chemical vapor deposition (CVD) was characterized by physical analysis and from electrical properties. The changes in the chemical bonding and distribution of N in plasma-nitrided SiO2 were investigated for different subsequent processes. N-Si3, N-Si2O, and N2 are formed in a SiO2 film by plasma nitridation. N2 molecules diffuse out during annealing at temperatures higher than 900 °C. NH species are generated from N2 molecules and H in the SiO2 film with subsequent oxide deposition using O3 as an oxidant. The capacitance-voltage (C-V) curves of metal-oxide-semiconductor (MOS) capacitors are obtained. The negative shift of the C-V curve is caused by the increase in the density of positive fix charge traps in CVD-SiO2 induced by plasma nitridation. The C-V curve of plasma-nitrided SiO2 subjected to annealing shifts to the positive direction and that subjected to the subsequent oxide deposition shifts markedly to the negative direction. It is clarified that the density of positive charge fixed traps in plasma-nitrided SiO2 films decrease because the amount of N2 molecules is decreased by annealing, and that the density of traps increases because NH species are generated and move to the interface between SiO2 and the Si substrate with the subsequent oxide deposition.

  3. MICROSTRUCTURE OF SiOx:H FILMS PREPARED BY PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION

    Institute of Scientific and Technical Information of China (English)

    MA ZHI-XUN; LIAO XIAN-BO; KONG GUANG-LIN; CHU JUN-HAO

    2000-01-01

    The micro-Raman spectroscopy and infrared (IR) spectroscopy have been performed for the study of the microstructure of amorphous hydrogenated oxidized silicon (a-SiOx:H) films prepared by Plasma Enhanced Chemical Vapor Deposition technique. It is found that a-SiOx :H consists of two phases: an amorphous silicon-rich phase and an oxygen-rich phase mainly comprised of HSi-SiO2 and HSi-O3. The Raman scattering results exhibit that the frequency of TO-like mode of amorphous silicon red-shifts with decreasing size of silicon-rich region. This is related to the quantum confinement effects, similar to the nanocrystalline silicon.

  4. Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    马旭村; 徐贵昌; 王恩哥

    2000-01-01

    Well-aligned carbon nitrogen nanotube films have been synthesized successfully on meso-porous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1-xNx( x = 0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds cova-lently with nitrogen in all the carbon nitrogen nanotube films.

  5. Low temperature metal free growth of graphene on insulating substrates by plasma assisted chemical vapor deposition

    Science.gov (United States)

    Muñoz, R.; Munuera, C.; Martínez, J. I.; Azpeitia, J.; Gómez-Aleixandre, C.; García-Hernández, M.

    2017-03-01

    Direct growth of graphene films on dielectric substrates (quartz and silica) is reported, by means of remote electron cyclotron resonance plasma assisted chemical vapor deposition r-(ECR-CVD) at low temperature (650 °C). Using a two step deposition process- nucleation and growth- by changing the partial pressure of the gas precursors at constant temperature, mostly monolayer continuous films, with grain sizes up to 500 nm are grown, exhibiting transmittance larger than 92% and sheet resistance as low as 900 Ω sq-1. The grain size and nucleation density of the resulting graphene sheets can be controlled varying the deposition time and pressure. In additon, first-principles DFT-based calculations have been carried out in order to rationalize the oxygen reduction in the quartz surface experimentally observed. This method is easily scalable and avoids damaging and expensive transfer steps of graphene films, improving compatibility with current fabrication technologies.

  6. Surface modification of silicon-containing fluorocarbon films prepared by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Jin, Yoonyoung; Desta, Yohannes; Goettert, Jost; Lee, G. S.; Ajmera, P. K.

    2005-07-01

    Surface modification of silicon-containing fluorocarbon (SiCF) films achieved by wet chemical treatments and through x-ray irradiation is examined. The SiCF films were prepared by plasma-enhanced chemical vapor deposition, using gas precursors of tetrafluoromethane and disilane. As-deposited SiCF film composition was analyzed by x-ray photoelectron spectroscopy. Surface modification of SiCF films utilizing n-lithiodiaminoethane wet chemical treatment is discussed. Sessile water-drop contact angle changed from 95°+/-2° before treatment to 32°+/-2° after treatment, indicating a change in the film surface characteristics from hydrophobic to hydrophilic. For x-ray irradiation on the SiCF film with a dose of 27.4 kJ/cm3, the contact angle of the sessile water drop changed from 95°+/-2° before radiation to 39°+/-3° after x-ray exposure. The effect of x-ray exposure on chemical bond structure of SiCF films is studied using Fourier transform infrared measurements. Electroless Cu deposition was performed to test the applicability of the surface modified films. The x-ray irradiation method offers a unique advantage in making possible surface modification in a localized area of high-aspect-ratio microstructures. Fabrication of a Ti-membrane x-ray mask is introduced here for selective surface modification using x-ray irradiation.

  7. Plasma-enhanced chemical vapor deposited silicon oxynitride films for optical waveguide bridges for use in mechanical sensors

    DEFF Research Database (Denmark)

    Storgaard-Larsen, Torben; Leistiko, Otto

    1997-01-01

    In this paper the influence of RF power, ammonia flow, annealing temperature, and annealing time on the optical and mechanical properties of plasma-enhanced chemically vapor deposited silicon oxynitride films, is presented. A low refractive index (1.47 to 1.48) film having tensile stress has been...

  8. Practical silicon deposition rules derived from silane monitoring during plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hemawan, Kadek W.; Gou, Huiyang; Hemley, Russell J. [Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd., NW, Washington, DC 20015 (United States)

    2015-11-02

    Polycrystalline diamond has been synthesized on silicon substrates at atmospheric pressure, using a microwave capillary plasma chemical vapor deposition technique. The CH{sub 4}/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H{sub 2} into the deposition gas chemistry. Electronically excited species of CN, C{sub 2}, Ar, N{sub 2}, CH, H{sub β}, and H{sub α} were observed in the emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T{sub 2g} phonon at 1333 cm{sup −1} peak relative to the Raman features of graphitic carbon. Field emission scanning electron microscopy images reveal that, depending on the growth conditions, the carbon microstructures of grown films exhibit “coral” and “cauliflower-like” morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.

  10. Conformal encapsulation of three-dimensional, bioresorbable polymeric scaffolds using plasma-enhanced chemical vapor deposition.

    Science.gov (United States)

    Hawker, Morgan J; Pegalajar-Jurado, Adoracion; Fisher, Ellen R

    2014-10-21

    Bioresorbable polymers such as poly(ε-caprolactone) (PCL) have a multitude of potential biomaterial applications such as controlled-release drug delivery and regenerative tissue engineering. For such biological applications, the fabrication of porous three-dimensional bioresorbable materials with tunable surface chemistry is critical to maximize their surface-to-volume ratio, mimic the extracellular matrix, and increase drug-loading capacity. Here, two different fluorocarbon (FC) precursors (octofluoropropane (C3F8) and hexafluoropropylene oxide (HFPO)) were used to deposit FC films on PCL scaffolds using plasma-enhanced chemical vapor deposition (PECVD). These two coating systems were chosen with the intent of modifying the scaffold surfaces to be bio-nonreactive while maintaining desirable bulk properties of the scaffold. X-ray photoelectron spectroscopy showed high-CF2 content films were deposited on both the exterior and interior of PCL scaffolds and that deposition behavior is PECVD system specific. Scanning electron microscopy data confirmed that FC film deposition yielded conformal rather than blanket coatings as the porous scaffold structure was maintained after plasma treatment. Treated scaffolds seeded with human dermal fibroblasts (HDF) demonstrate that the cells do not attach after 72 h and that the scaffolds are noncytotoxic to HDF. This work demonstrates conformal FC coatings can be deposited on 3D polymeric scaffolds using PECVD to fabricate 3D bio-nonreactive materials.

  11. Mechanical and piezoresistive properties of thin silicon films deposited by plasma-enhanced chemical vapor deposition and hot-wire chemical vapor deposition at low substrate temperatures

    Science.gov (United States)

    Gaspar, J.; Gualdino, A.; Lemke, B.; Paul, O.; Chu, V.; Conde, J. P.

    2012-07-01

    This paper reports on the mechanical and piezoresistance characterization of hydrogenated amorphous and nanocrystalline silicon thin films deposited by hot-wire chemical vapor deposition (HWCVD) and radio-frequency plasma-enhanced chemical vapor deposition (PECVD) using substrate temperatures between 100 and 250 °C. The microtensile technique is used to determine film properties such as Young's modulus, fracture strength and Weibull parameters, and linear and quadratic piezoresistance coefficients obtained at large applied stresses. The 95%-confidence interval for the elastic constant of the films characterized, 85.9 ± 0.3 GPa, does not depend significantly on the deposition method or on film structure. In contrast, mean fracture strength values range between 256 ± 8 MPa and 600 ± 32 MPa: nanocrystalline layers are slightly stronger than their amorphous counterparts and a pronounced increase in strength is observed for films deposited using HWCVD when compared to those grown by PECVD. Extracted Weibull moduli are below 10. In terms of piezoresistance, n-doped radio-frequency nanocrystalline silicon films deposited at 250 °C present longitudinal piezoresistive coefficients as large as -(2.57 ± 0.03) × 10-10 Pa-1 with marginally nonlinear response. Such values approach those of crystalline silicon and of polysilicon layers deposited at much higher temperatures.

  12. Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition

    Science.gov (United States)

    Liu, Dan; Gou, Li; Ran, Junguo; Zhu, Hong; Zhang, Xiang

    2015-07-01

    Boron-doped nanocrystalline diamond (NCD) exhibits extraordinary mechanical properties and chemical stability, making it highly suitable for biomedical applications. For implant materials, the impact of boron-doped NCD films on the character of cell growth (i.e., adhesion, proliferation) is very important. Boron-doped NCD films with resistivity of 10-2 Ω·cm were grown on Si substrates by the microwave plasma chemical vapor deposition (MPCVD) process with H2 bubbled B2O3. The crystal structure, diamond character, surface morphology, and surface roughness of the boron-doped NCD films were analyzed using different characterization methods, such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope (SKFM). The cytotoxicity of films was studied by in vitro tests, including fluorescence microscopy, SEM and MTT assay. Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates. MG-63 cells adhered well and exhibited a significant growth on the surface of films, suggesting that the boron-doped NCD films were non-toxic to cells. supported by the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices (University of Electronic Science and Technology of China) (No. KFJJ201313)

  13. Plasma Enhanced Chemical Vapor Deposition Nanocrystalline Tungsten Carbide Thin Film and Its Electro-catalytic Activity

    Institute of Scientific and Technical Information of China (English)

    Huajun ZHENG; Chunan MA; Jianguo HUANG; Guohua LI

    2005-01-01

    Nanocrystalline tungsten carbide thin films were fabricated on graphite substrates by plasma enhanced chemical vapor deposition (PECVD) at H2 and Ar atmosphere, using WF6 and CH4 as precursors. The crystal phase, structure and chemical components of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS), respectively. The results show that the film prepared at CH4/WF6concentration ratio of 20 and at 800℃ is composed of spherical particles with a diameter of 20~35 nm. Electrochemical investigations show that the electrochemical real surface area of electrode of the film is large, and the electrode of the film exhibits higher electro-catalytic activity in the reaction of methanol oxidation. The designated constant current of the film catalyst is 123.6 mA/cm2 in the mixture solution of H2SO4 and CH3OH at the concentration of 0.5 and 2.0 mol/L at 70℃, and the designated constant potential is only 0.306 V (vs SCE).

  14. Organo-Functionalization of Silicon Nanocrystals Synthesized by Inductively Coupled Plasma Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Don-Sung; Choe, Dong-Hoe; Jeong, Hyun-Dam [Chonnam National University, Gwangju (Korea, Republic of); Yoo, Seung-Wan; Kim, Jung-Hyung [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2016-05-15

    Octadecyl-terminated silicon nanocrystals (ODE-Si NCs) are obtained via a surface-initiated thermal hydrosilylation reaction on hydride-terminated Si NCs (H-Si NCs). Pristine Si NCs were synthesized at the gram scale by using inductively coupled plasma chemical vapor deposition (ICP-CVD) . The H-Si NCs were produced through a chemical etching process with hydrofluoric acid (HF), ethanol (EtOH), and distilled water (d-H{sub 2}O). The results obtained from X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) indicate that the synthesized Si NCs obtained via ICP-CVD have diamond cubic-structured silicon with a grain size of 10 nm and a densely packed Si NC array consisting of individual NCs. Organo-functionalized Si NCs, i.e., ODE-Si NCs, are well soluble in organic solvent whereas pristine Si NCs synthesized through ICP-CVD are not. The surface chemistry of the ODE-Si NCs was confirmed via Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy ({sup 1}H-NMR), and field emission transmission electron microscopy (FE-TEM). Thereby, these newly synthesized and scalable organo-functionalized Si NCs are applicable as raw materials for practical use in devices by tuning the surface chemistry with various capping molecules.

  15. The relationship between chemical structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Hao [Materials Sci and Tech Applications, LLC, 409 Maple Springs Drive, Dayton OH 45458 (United States)]. E-mail: hao.jiang@wpafb.af.mil; Hong Lianggou [Materials Sci and Tech Applications, LLC, 409 Maple Springs Drive, Dayton OH 45458 (United States); Venkatasubramanian, N. [Research Institute, University of Dayton, 300 College Park, Dayton, OH 45469-0168 (United States); Grant, John T. [Research Institute, University of Dayton, 300 College Park, Dayton, OH 45469-0168 (United States); Eyink, Kurt [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States); Wiacek, Kevin [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson Air Force Base, OH 45433-7251 (United States); Fries-Carr, Sandra [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson Air Force Base, OH 45433-7251 (United States); Enlow, Jesse [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States); Bunning, Timothy J. [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States)

    2007-02-26

    Polymer dielectric films fabricated by plasma enhanced chemical vapor deposition (PECVD) have unique properties due to their dense crosslinked bulk structure. These spatially uniform films exhibit good adhesion to a variety of substrates, excellent chemical inertness, high thermal resistance, and are formed from an inexpensive, solvent-free, room temperature process. In this work, we studied the dielectric properties of plasma polymerized (PP) carbon-based polymer thin films prepared from two precursors, benzene and octafluorocyclobutane. Two different monomer feed locations, directly in the plasma zone or in the downstream region (DS) and two different pressures, 80 Pa (high pressure) or 6.7 Pa (low pressure), were used. The chemical structure of the PECVD films was examined by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The dielectric constant ({epsilon} {sub r}) and dielectric loss (tan {delta}) of the films were investigated over a range of frequencies up to 1 MHz and the dielectric strength (breakdown voltage) (F {sub b}) was characterized by the current-voltage method. Spectroscopic ellipsometry was performed to determine the film thickness and refractive index. Good dielectric properties were exhibited, as PP-benzene films formed in the high pressure, DS region showed a F{sub b} of 610 V/{mu}m, an {epsilon} {sub r} of 3.07, and a tan {delta} of 7.0 x 10{sup -3} at 1 kHz. The PECVD processing pressure has a significant effect on final film structure and the film's physical density has a strong impact on dielectric breakdown strength. Also noted was that the residual oxygen content in the PP-benzene films significantly affected the frequency dependences of the dielectric constant and loss.

  16. Method of plasma enhanced chemical vapor deposition of diamond using methanol-based solutions

    Science.gov (United States)

    Tzeng, Yonhua (Inventor)

    2009-01-01

    Briefly described, methods of forming diamond are described. A representative method, among others, includes: providing a substrate in a reaction chamber in a non-magnetic-field microwave plasma system; introducing, in the absence of a gas stream, a liquid precursor substantially free of water and containing methanol and at least one carbon and oxygen containing compound having a carbon to oxygen ratio greater than one, into an inlet of the reaction chamber; vaporizing the liquid precursor; and subjecting the vaporized precursor, in the absence of a carrier gas and in the absence in a reactive gas, to a plasma under conditions effective to disassociate the vaporized precursor and promote diamond growth on the substrate in a pressure range from about 70 to 130 Torr.

  17. Microwave Plasma Chemical Vapor Deposition of Diamond Films on Silicon From Ethanol and Hydrogen

    Institute of Scientific and Technical Information of China (English)

    马志斌; 汪建华; 王传新; 满卫东

    2003-01-01

    Diamond films with very smooth surface and good optical quality have been deposited onto silicon substrate using microwave plasma chemical vapor deposition (MPCVD) from a gas mixture of ethanol and hydrogen at a low substrate temperature of 450 ℃. The effects of the substrate temperature on the diamond nucleation and the morphology of the diamond film have been investigated and observed with scanning electron microscopy (SEM). The microstructure and the phase of the film have been characterized using Raman spectroscopy and X-ray diffraction (XRD). The diamond nucleation density significantly decreases with the increasing of the substrate temperature. There are only sparse nuclei when the substrate temperature is higher than 800 ℃ although the ethanol concentration in hydrogen is very high. That the characteristic diamond peak in the Raman spectrum of a diamond film prepared at a low substrate temperature of 450 ℃ extends into broadband indicates that the film is of nanophase. No graphite peak appeared in the XRD pattern confirms that the film is mainly composed of SP3 carbon. The diamond peak in the XRD pattern also broadens due to the nanocrystalline of the film.

  18. Characterization of diamond-like nanocomposite thin films grown by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Santra, T. S.; Liu, C. H.; Bhattacharyya, T. K.; Patel, P.; Barik, T. K.

    2010-06-01

    Diamond-like nanocomposite (DLN) thin films, comprising the networks of a-C:H and a-Si:O were deposited on pyrex glass or silicon substrate using gas precursors (e.g., hexamethyldisilane, hexamethyldisiloxane, hexamethyldisilazane, or their different combinations) mixed with argon gas, by plasma enhanced chemical vapor deposition technique. Surface morphology of DLN films was analyzed by atomic force microscopy. High-resolution transmission electron microscopic result shows that the films contain nanoparticles within the amorphous structure. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to determine the structural change within the DLN films. The hardness and friction coefficient of the films were measured by nanoindentation and scratch test techniques, respectively. FTIR and XPS studies show the presence of CC, CH, SiC, and SiH bonds in the a-C:H and a-Si:O networks. Using Raman spectroscopy, we also found that the hardness of the DLN films varies with the intensity ratio ID/IG. Finally, we observed that the DLN films has a better performance compared to DLC, when it comes to properties like high hardness, high modulus of elasticity, low surface roughness and low friction coefficient. These characteristics are the critical components in microelectromechanical systems (MEMS) and emerging nanoelectromechanical systems (NEMS).

  19. Electrical transport properties of graphene nanowalls grown at low temperature using plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Zhao, Rong; Ahktar, Meysam; Alruqi, Adel; Dharmasena, Ruchira; Jasinski, Jacek B.; Thantirige, Rukshan M.; Sumanasekera, Gamini U.

    2017-05-01

    In this work, we report the electrical transport properties of uniform and vertically oriented graphene (graphene nanowalls) directly synthesized on multiple substrates including glass, Si/SiO2 wafers, and copper foils using radio-frequency plasma enhanced chemical vapor deposition (PECVD) with methane (CH4) as the precursor at relatively low temperatures. The temperature for optimum growth was established with the aid of transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. This approach offers means for low-cost graphene nanowalls growth on an arbitrary substrate with the added advantage of transfer-free device fabrication. The temperature dependence of the electrical transport properties (resistivity and thermopower) were studied in the temperature range, 30-300 K and analyzed with a combination of 2D-variable range hopping (VRH) and thermally activated (TA) conduction mechanisms. An anomalous temperature dependence of the thermopower was observed for all the samples and explained with a combination of a diffusion term having a linear temperature dependence plus a term with an inverse temperature dependence.

  20. FTIR Characterization of Fluorine Doped Silicon Dioxide Thin Films Deposited by Plasma Enhanced Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    WANG Peng-Fei; DING Shi-Jin; ZHANG Wei; ZHANG Jian-Yun; WANGJi-Tao; WEI William Lee

    2000-01-01

    Fluorine doped silicon dioxide (SiOF) thin films have been prepared by plasma enhanced chemical vapor depo sition. The Fourier transform infrared spectrometry (FTIR) spectra of SiOF films are deliberated to reveal the structure change of SiO2 and the mechanism of dielectric constant reduction after doping fluorine. When F is doped in SiO2 films, the Si-O stretching absorption peak will have a blue-shift due to increase of the partial charge of the O atom. The FTIR spectra indicate that some Si-OH components in the thin film can be removed after doping fluorine. These changes reduce the ionic and orientational polarization, and result in the reduction in dielectric constant of the film. According to Gaussian fitting, it is found that the Si-F2 bonds will appear in the SiOF film with increase of the fluorine content. The Si-F2 structures are liable to react with water, and cause the same increase of absorbed moisture in the film.

  1. Chain Assemblies from Nanoparticles Synthesized by Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition: The Computational View.

    Science.gov (United States)

    Mishin, Maxim V; Zamotin, Kirill Y; Protopopova, Vera S; Alexandrov, Sergey E

    2015-12-01

    This article refers to the computational study of nanoparticle self-organization on the solid-state substrate surface with consideration of the experimental results, when nanoparticles were synthesised during atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD). The experimental study of silicon dioxide nanoparticle synthesis by AP-PECVD demonstrated that all deposit volume consists of tangled chains of nanoparticles. In certain cases, micron-sized fractals are formed from tangled chains due to deposit rearrangement. This work is focused on the study of tangled chain formation only. In order to reveal their formation mechanism, a physico-mathematical model was developed. The suggested model was based on the motion equation solution for charged and neutral nanoparticles in the potential fields with the use of the empirical interaction potentials. In addition, the computational simulation was carried out based on the suggested model. As a result, the influence of such experimental parameters as deposition duration, particle charge, gas flow velocity, and angle of gas flow was found. It was demonstrated that electrical charges carried by nanoparticles from the discharge area are not responsible for the formation of tangled chains from nanoparticles, whereas nanoparticle kinetic energy plays a crucial role in deposit morphology and density. The computational results were consistent with experimental results.

  2. Growth of nanocrystalline silicon carbide thin films by plasma enhanced chemical vapor deposition

    CERN Document Server

    Lee, S W; Moon, J Y; Ahn, S S; Kim, H Y; Shin, D H

    1999-01-01

    Nanocrystalline silicon carbide thin films have been deposited by plasma enhanced chemical vapor deposition (PECVD) using SiH sub 4 , CH sub 4 , and H sub 2 gases. The effects of gas mixing ratio (CH sub 4 /SiH sub 4), deposition temperature, and RF power on the film properties have been studied. The growth rate, refractive index, and the optical energy gap depends critically on the growth conditions. The dependence of the growth rate on the gas flow ratio is quite different from the results obtained for the growth using C sub 2 H sub 2 gas instead of CH sub 4. As the deposition temperature is increased from 300 .deg. C to 600 .deg. C, hydrogen and carbon content in the film decreases and as a result the optical gap decreases. At the deposition temperature of 600 .deg. C and RF power of 150 W, the film structure si nanocrystalline, As the result of the nanocrystallization the dark conductivity is greatly improved. The nanocrystalline silicon carbide thin films may be used for large area optoelectronic devices...

  3. Boron nitride nanowalls: low-temperature plasma-enhanced chemical vapor deposition synthesis and optical properties

    Science.gov (United States)

    Merenkov, Ivan S.; Kosinova, Marina L.; Maximovskii, Eugene A.

    2017-05-01

    Hexagonal boron nitride (h-BN) nanowalls (BNNWs) were synthesized by plasma-enhanced chemical vapor deposition (PECVD) from a borazine (B3N3H6) and ammonia (NH3) gas mixture at a low temperature range of 400 °C-600 °C on GaAs(100) substrates. The effect of the synthesis temperature on the structure and surface morphology of h-BN films was investigated. The length and thickness of the h-BN nanowalls were in the ranges of 50-200 nm and 15-30 nm, respectively. Transmission electron microscope images showed the obtained BNNWs were composed of layered non-equiaxed h-BN nanocrystallites 5-10 nm in size. The parallel-aligned h-BN layers as an interfacial layer were observed between the film and GaAs(100) substrate. BNNWs demonstrate strong blue light emission, high transparency (>90%) both in visible and infrared spectral regions and are promising for optical applications. The present results enable a convenient growth of BNNWs at low temperatures.

  4. Stress control of silicon nitride films deposited by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Li, Dong-ling; Feng, Xiao-fei; Wen, Zhi-yu; Shang, Zheng-guo; She, Yin

    2016-07-01

    Stress controllable silicon nitride (SiNx) films deposited by plasma enhanced chemical vapor deposition (PECVD) are reported. Low stress SiNx films were deposited in both high frequency (HF) mode and dual frequency (HF/LF) mode. By optimizing process parameters, stress free (-0.27 MPa) SiNx films were obtained with the deposition rate of 45.5 nm/min and the refractive index of 2.06. Furthermore, at HF/LF mode, the stress is significantly influenced by LF ratio and LF power, and can be controlled to be 10 MPa with the LF ratio of 17% and LF power of 150 W. However, LF power has a little effect on the deposition rate due to the interaction between HF power and LF power. The deposited SiNx films have good mechanical and optical properties, low deposition temperature and controllable stress, and can be widely used in integrated circuit (IC), micro-electro-mechanical systems (MEMS) and bio-MEMS.

  5. Plasma enhanced chemical vapor deposition of iron doped thin dioxide films, their structure and photowetting effect

    Energy Technology Data Exchange (ETDEWEB)

    Sobczyk-Guzenda, A., E-mail: anna.sobczyk-guzenda@p.lodz.pl [Institute of Materials Science and Engineering, Lodz University of Technology, Stefanowskiego 1/15, 90-924 Lodz (Poland); Owczarek, S.; Szymanowski, H. [Institute of Materials Science and Engineering, Lodz University of Technology, Stefanowskiego 1/15, 90-924 Lodz (Poland); Wypych-Puszkarz, A. [Department of Molecular Physics, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz (Poland); Volesky, L. [Technical University of Liberec, Institute for Nanomaterials, Advanced Technologies and Innovation, Studentska 1402/2, 461 17 Liberec 1 (Czech Republic); Gazicki-Lipman, M. [Institute of Materials Science and Engineering, Lodz University of Technology, Stefanowskiego 1/15, 90-924 Lodz (Poland)

    2015-08-31

    Radio frequency plasma enhanced chemical vapor deposition (RF PECVD) technique was applied for the purpose of deposition of iron doped titanium dioxide coatings from a gaseous mixture of oxygen with titanium (IV) chloride and iron (0) pentacarbonyl. Glass slides and silicon wafers were used as substrates. The coatings morphology was investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Their elemental and chemical composition was studied with the help of X-ray energy dispersive spectroscopy (EDS) and Fourier transform infrared (FTIR) spectroscopy, respectively, while their phase composition was analyzed with the Raman spectroscopy. For the determination of the film optical properties, ultraviolet (UV–Vis) spectroscopy techniques were used. Iron content in the range of 0.07 to 11.5 at.% was found in the coatings. FTIR studies showed that iron was built-in in the structure of TiO{sub 2} matrix. Surface roughness, assessed with the SEM and AFM techniques, increases with an increasing content of this element. Trace amounts of iron resulted in a lowering of an absorption threshold of the films and their optical gap, but the tendency was reversed for high concentrations of that element. The effect of iron doping on UV photowettability of the films was also studied and, for coatings containing up to 5% of iron, it was stronger than that exhibited by pure TiO{sub 2}. - Highlights: • Iron doped TiO{sub 2} films were deposited with the PECVD method. • Differences of surface morphology of the films with different iron content were shown. • Depending on the iron content, the film structure is either amorphous or crystalline. • A parabolic character of the optical gap dependence on the concentration of iron was observed. • Up to a concentration of 5% of iron, doped TiO{sub 2} films exhibit a super-hydrophilic effect.

  6. Evaluation of chemical and structural properties of germanium-carbon coatings deposited by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Microwave processing of epoxy resins and synthesis of carbon nanotubes by microwave plasma chemical vapor deposition

    Science.gov (United States)

    Zong, Liming

    Microwave processing of advanced materials has been studied as an attractive alternative to conventional thermal processing. In this dissertation, work was preformed in four sections. The first section is a review on research status of microwave processing of polymer materials. The second section is investigation of the microwave curing kinetics of epoxy resins. The curing of diglycidyl ether of bisphenol A (DGEBA) and 3, 3'-diaminodiphenyl sulfone (DDS) system under microwave radiation at 145 °C was governed by an autocatalyzed reaction mechanism. A kinetic model was used to describe the curing progress. The third section is a study on dielectric properties of four reacting epoxy resins over a temperature range at 2.45 GHz. The epoxy resin was DGEBA. The four curing agents were DDS, Jeffamine D-230, m-phenylenediamine, and diethyltoluenediamine. The mixtures of DGEBA and the four curing agents were stoichiometric. The four reacting systems were heated under microwave irradiation to certain cure temperatures. Measurements of temperature and dielectric properties were made during free convective cooling of the samples. The cooled samples were analyzed with a Differential Scanning Calorimeter to determine the extents of cure. The Davidson-Cole model can be used to describe the dielectric data. A simplified Davidson-Cole expression was proposed to calculate the parameters in the Davidson-Cole model and describe the dielectric properties of the DGEBA/DDS system and part of the dielectric data of the other three systems. A single relaxation model was used with the Arrhenius expression for temperature dependence to model the results. The evolution of all parameters in the models during cure was related to the decreasing number of the epoxy and amine groups in the reactants and the increasing viscosity of the reacting systems. The last section is synthesis of carbon nanotubes (CNTs) on silicon substrate by microwave plasma chemical vapor deposition of a gas mixture of

  8. Plasma-enhanced chemical vapor deposition of graphene on copper substrates

    Directory of Open Access Journals (Sweden)

    Nicolas Woehrl

    2014-04-01

    Full Text Available A plasma enhanced vapor deposition process is used to synthesize graphene from a hydrogen/methane gas mixture on copper samples. The graphene samples were transferred onto SiO2 substrates and characterized by Raman spectroscopic mapping and atomic force microscope topographical mapping. Analysis of the Raman bands shows that the deposited graphene is clearly SLG and that the sheets are deposited on large areas of several mm2. The defect density in the graphene sheets is calculated using Raman measurements and the influence of the process pressure on the defect density is measured. Furthermore the origin of these defects is discussed with respect to the process parameters and hence the plasma environment.

  9. Microwave Plasma-Activated Chemical Vapor Deposition of Nitrogen-Doped Diamond. II: CH4/N2/H2 Plasmas.

    Science.gov (United States)

    Truscott, Benjamin S; Kelly, Mark W; Potter, Katie J; Ashfold, Michael N R; Mankelevich, Yuri A

    2016-11-03

    We report a combined experimental and modeling study of microwave-activated dilute CH4/N2/H2 plasmas, as used for chemical vapor deposition (CVD) of diamond, under very similar conditions to previous studies of CH4/H2, CH4/H2/Ar, and N2/H2 gas mixtures. Using cavity ring-down spectroscopy, absolute column densities of CH(X, v = 0), CN(X, v = 0), and NH(X, v = 0) radicals in the hot plasma have been determined as functions of height, z, source gas mixing ratio, total gas pressure, p, and input power, P. Optical emission spectroscopy has been used to investigate, with respect to the same variables, the relative number densities of electronically excited species, namely, H atoms, CH, C2, CN, and NH radicals and triplet N2 molecules. The measurements have been reproduced and rationalized from first-principles by 2-D (r, z) coupled kinetic and transport modeling, and comparison between experiment and simulation has afforded a detailed understanding of C/N/H plasma-chemical reactivity and variations with process conditions and with location within the reactor. The experimentally validated simulations have been extended to much lower N2 input fractions and higher microwave powers than were probed experimentally, providing predictions for the gas-phase chemistry adjacent to the diamond surface and its variation across a wide range of conditions employed in practical diamond-growing CVD processes. The strongly bound N2 molecule is very resistant to dissociation at the input MW powers and pressures prevailing in typical diamond CVD reactors, but its chemical reactivity is boosted through energy pooling in its lowest-lying (metastable) triplet state and subsequent reactions with H atoms. For a CH4 input mole fraction of 4%, with N2 present at 1-6000 ppm, at pressure p = 150 Torr, and with applied microwave power P = 1.5 kW, the near-substrate gas-phase N atom concentration, [N]ns, scales linearly with the N2 input mole fraction and exceeds the concentrations [NH]ns, [NH2]ns

  10. Raman spectra investigation of the defects of chemical vapor deposited multilayer graphene and modified by oxygen plasma treatment

    Science.gov (United States)

    Li, Zongyao; Xu, Yu; Cao, Bing; Qi, Lin; He, Shunyu; Wang, Chinhua; Zhang, Jicai; Wang, Jianfeng; Xu, Ke

    2016-11-01

    Graphene, a two dimensional material, can be modified its properties by defects engineering. Here, we present Raman spectra studies of the multilayer graphene (MLG) fabricated by low-pressure chemical vapor deposition over copper foil, and report that the defects of MLG can be controlled by adjusting methane concentration. Moreover, MLG can be changed from metallic to semiconductoring properties by using oxygen plasma treatment, and we investigate the defects evolution of the graphene after exposing to oxygen plasma by Raman spectra. Our results indicate that the amount of defects in graphene can be changed by regulating the methane concentration and oxygen plasma exposure times, but the primary type of defect in MLG is still boundary-like defect. It is valuable for understanding the physics of defects evolution through artificially generated defects, and such defect engineering will greatly open up the future application of the novel material.

  11. Selective adhesion of intestinal epithelial cells on patterned films with amine functionalities formed by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung Seop; Choi, Changrok; Kim, Soo Heon; Choi, Kun oh [Department of Physics, Brain Korea 21 Physics Research Division and Institute of Basic Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Jeong Min [Department of Molecular Biology and Institute of Nanosensor and Biotechnology, BK21 Graduate Program for RNA Biology, Dankook University, Yongin 448-701 (Korea, Republic of); Kim, Hong Ja [Department of Internal Medicine, Dankook University College of Medicine, Cheonan 330-715 (Korea, Republic of); Yeo, Sanghak [R and D Center, ELBIO Incorporation, 426-5 Gasan-dong Geumchun-gu, Seoul (Korea, Republic of); Park, Heonyong [Department of Molecular Biology and Institute of Nanosensor and Biotechnology, BK21 Graduate Program for RNA Biology, Dankook University, Yongin 448-701 (Korea, Republic of); Jung, Donggeun, E-mail: djung@skku.ac.kr [Department of Physics, Brain Korea 21 Physics Research Division and Institute of Basic Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2010-11-01

    Control of cell adhesion to surfaces is important to develop analytical tools in the areas of biomedical engineering. To control cell adhesiveness of the surface, we constructed a variety of plasma polymerized hexamethyldisiloxane (PPHMDSO) thin films deposited at the plasma power range of 10-100 W by plasma enhanced chemical vapor deposition (PECVD). The PPHMDSO film that was formed at 10 W was revealed to be resistant to cell adhesion. The resistance to cell adhesion is closely related to physicochemical properties of the film. Atomic force microscopic data show an increase in surface roughness from 0.52 nm to 0.74 nm with increasing plasma power. From Fourier transform infrared (FT-IR) absorption spectroscopy data, it was also determined that the methyl (-CH{sub 3}) peak intensity increases with increasing plasma power, whereas the hydroxyl (-OH) peak decreases. X-ray photoelectron spectroscopy data reveal an increase in C-O bonding with increasing plasma power. These results suggest that C-O bonding and hydroxyl (-OH) and methyl (-CH{sub 3}) functional groups play a critical part in cell adhesion. Furthermore, to enhance a diversity of film surface, we accumulated the patterned plasma polymerized ethylenediamine (PPEDA) thin film on the top of the PPHMDSO thin film. The PPEDA film is established to be strongly cell-adherent. This patterned two-layer film stacking method can be used to form the selectively limited cell-adhesive PPEDA spots over the adhesion-resistant surface.

  12. Electrochromic Devices Deposited on Low-Temperature Plastics by Plasma-Enhanced Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Robbins, Joshua; Seman, Michael

    2005-09-20

    Electrochromic windows have been identified by the Basic energy Sciences Advisory committee as an important technology for the reduction of energy spent on heating and cooling in residential and commercial buildings. Electrochromic devices have the ability to reversibly alter their optical properties in response to a small electric field. By blocking ultraviolet and infrared radiation, while modulating the incoming visible radiation, electrochromics could reduce energy consumption by several Quads per year. This amounts to several percent of the total annual national energy expenditures. The purpose of this project was to demonstrate proof of concept for using plasma-enhanced chemical vapor deposition (PECVD) for depositing all five layers necessary for full electrochromic devices, as an alternative to sputtering techniques. The overall goal is to produce electrochromic devices on flexible polymer substrates using PECVD to significantly reduce the cost of the final product. We have successfully deposited all of the films necessary for a complete electrochromic devices using PECVD. The electrochromic layer, WO3, displayed excellent change in visible transmission with good switching times. The storage layer, V2O5, exhibited a high storage capacity and good clear state transmission. The electrolyte, Ta2O5, was shown to functional with good electrical resistivity to go along with the ability to transfer Li ions. There were issues with leakage over larger areas, which can be address with further process development. We developed a process to deposit ZnO:Ga with a sheet resistance of < 50 W/sq. with > 90% transmission. Although we were not able to deposit on polymers due to the temperatures required in combination with the inverted position of our substrates. Two types of full devices were produced. Devices with Ta2O5 were shown to be functional using small aluminum dots as the top contact. The polymer electrolyte devices were shown to have a clear state transmission of

  13. Optical and electrical characteristics of plasma enhanced chemical vapor deposition boron carbonitride thin films derived from N-trimethylborazine precursor

    Energy Technology Data Exchange (ETDEWEB)

    Sulyaeva, Veronica S., E-mail: veronica@niic.nsc.ru [Department of Functional Materials Chemistry, Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Kosinova, Marina L.; Rumyantsev, Yurii M.; Kuznetsov, Fedor A. [Department of Functional Materials Chemistry, Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Kesler, Valerii G. [Laboratory of Physical Principles for Integrated Microelectronics, Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090 (Russian Federation); Kirienko, Viktor V. [Laboratory of Nonequilibrium Semiconductors Systems, Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090 (Russian Federation)

    2014-05-02

    Thin BC{sub x}N{sub y} films have been obtained by plasma enhanced chemical vapor deposition using N-trimethylborazine as a precursor. The films were deposited on Si(100) and fused silica substrates. The grown films were characterized by ellipsometry, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, spectrophotometry, capacitance–voltage and current–voltage measurements. The deposition parameters, such as substrate temperature (373–973 K) and gas phase composition were varied. Low temperature BC{sub x}N{sub y} films were found to be high optical transparent layers in the range of 300–2000 nm, the transmittance as high as 93% has been achieved. BC{sub x}N{sub y} layers are dielectrics with dielectric constant k = 2.2–8.9 depending on the synthesis conditions. - Highlights: • Thin BC{sub x}N{sub y} films have been obtained by plasma enhanced chemical vapor deposition. • N-trimethylborazine was used as a precursor. • Low temperature BC{sub x}N{sub y} films were found to be high optical transparent layers (93%). • BC{sub x}N{sub y} layers are dielectrics with dielectric constant k = 2.2–8.9.

  14. Characterization of Plasma Enhanced Chemical Vapor Deposition-Physical Vapor Deposition transparent deposits on textiles to trigger various antimicrobial properties to food industry textiles

    Energy Technology Data Exchange (ETDEWEB)

    Brunon, Celine [Universite de Lyon, Universite Lyon 1, Laboratoire des Sciences Analytiques (LSA), CNRS, UMR 5180, Bat. J. Raulin 5eme etage, F-69622 Villeurbanne Cedex (France); Chadeau, Elise; Oulahal, Nadia [Universite de Lyon, Universite Lyon 1, Laboratoire de Recherche en Genie Industriel Alimentaire (LRGIA, E.A. 3733), Rue Henri de Boissieu, F-01000 Bourg en Bresse (France); Grossiord, Carol [Science et Surface, 64, Chemin des Mouilles, F-69130 Ecully (France); Dubost, Laurent [HEF, ZI SUD, Rue Benoit Fourneyron, F-42166 Andrezieux Boutheon (France); Bessueille, Francois [Universite de Lyon, Universite Lyon 1, Laboratoire des Sciences Analytiques (LSA), CNRS, UMR 5180, Bat. J. Raulin 5eme etage, F-69622 Villeurbanne Cedex (France); Simon, Farida [TDV Industrie, 43 Rue du Bas des Bois, BP 121, F-53012 Laval Cedex (France); Degraeve, Pascal [Universite de Lyon, Universite Lyon 1, Laboratoire de Recherche en Genie Industriel Alimentaire (LRGIA, E.A. 3733), Rue Henri de Boissieu, F-01000 Bourg en Bresse (France); Leonard, Didier, E-mail: didier.leonard@univ-lyon1.fr [Universite de Lyon, Universite Lyon 1, Laboratoire des Sciences Analytiques (LSA), CNRS, UMR 5180, Bat. J. Raulin 5eme etage, F-69622 Villeurbanne Cedex (France)

    2011-07-01

    Textiles for the food industry were treated with an original deposition technique based on a combination of Plasma Enhanced Chemical Vapor Deposition and Physical Vapor Deposition to obtain nanometer size silver clusters incorporated into a SiOCH matrix. The optimization of plasma deposition parameters (gas mixture, pressure, and power) was focused on textile transparency and antimicrobial properties and was based on the study of both surface and depth composition (X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), as well as Transmission Electron Microscopy, Atomic Force Microscopy, SIMS depth profiling and XPS depth profiling on treated glass slides). Deposition conditions were identified in order to obtain a variable and controlled quantity of {approx} 10 nm size silver particles at the surface and inside of coatings exhibiting acceptable transparency properties. Microbiological characterization indicated that the surface variable silver content as calculated from XPS and ToF-SIMS data directly influences the level of antimicrobial activity.

  15. High rate deposition of microcrystalline silicon films by high-pressure radio frequency plasma enhanced chemical vapor deposition (PECVD)

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Hydrogenated microcrystalline silicon (μc-Si:H) thin films were prepared by high- pressure radio-frequency (13.56 MHz) plasma enhanced chemical vapor deposition (rf-PECVD) with a screened plasma. The deposition rate and crystallinity varying with the deposition pressure, rf power, hydrogen dilution ratio and electrodes distance were systematically studied. By optimizing the deposition parameters the device quality μc-Si:H films have been achieved with a high deposition rate of 7.8 /s at a high pressure. The Voc of 560 mV and the FF of 0.70 have been achieved for a single-junction μc-Si:H p-i-n solar cell at a deposition rate of 7.8 /s.

  16. Characteristics of silicon nitride deposited by VHF (162 MHz)-plasma enhanced chemical vapor deposition using a multi-tile push-pull plasma source

    Science.gov (United States)

    Kim, Ki Seok; Sirse, Nishant; Kim, Ki Hyun; Rogers Ellingboe, Albert; Kim, Kyong Nam; Yeom, Geun Young

    2016-10-01

    To prevent moisture and oxygen permeation into flexible organic electronic devices formed on substrates, the deposition of an inorganic diffusion barrier material such as SiN x is important for thin film encapsulation. In this study, by a very high frequency (162 MHz) plasma-enhanced chemical vapor deposition (VHF-PECVD) using a multi-tile push-pull plasma source, SiN x layers were deposited with a gas mixture of NH3/SiH4 with/without N2 and the characteristics of the plasma and the deposited SiN x film as the thin film barrier were investigated. Compared to a lower frequency (60 MHz) plasma, the VHF (162 MHz) multi-tile push-pull plasma showed a lower electron temperature, a higher vibrational temperature, and higher N2 dissociation for an N2 plasma. When a SiN x layer was deposited with a mixture of NH3/SiH4 with N2 at a low temperature of 100 °C, a stoichiometric amorphous Si3N4 layer with very low Si-H bonding could be deposited. The 300 nm thick SiN x film exhibited a low water vapor transmission rate of 1.18  ×  10-4 g (m2 · d)-1, in addition to an optical transmittance of higher than 90%.

  17. Resolving the nanostructure of plasma-enhanced chemical vapor deposited nanocrystalline SiOx layers for application in solar cells

    Science.gov (United States)

    Klingsporn, M.; Kirner, S.; Villringer, C.; Abou-Ras, D.; Costina, I.; Lehmann, M.; Stannowski, B.

    2016-06-01

    Nanocrystalline silicon suboxides (nc-SiOx) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO0.8:H fabricated by plasma-enhanced chemical vapor deposition. The nanostructure was varied through the sample series by changing the deposition pressure from 533 to 1067 Pa. The samples were then characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy, selected-area electron diffraction, and a specialized plasmon imaging method. We found that the material changed with increasing pressure from predominantly amorphous silicon monoxide to silicon dioxide containing nanocrystalline silicon. The nanostructure changed from amorphous silicon filaments to nanocrystalline silicon filaments, which were found to cause anisotropic electron transport.

  18. A solid-state nuclear magnetic resonance study of post-plasma reactions in organosilicone microwave plasma-enhanced chemical vapor deposition (PECVD) coatings.

    Science.gov (United States)

    Hall, Colin J; Ponnusamy, Thirunavukkarasu; Murphy, Peter J; Lindberg, Mats; Antzutkin, Oleg N; Griesser, Hans J

    2014-06-11

    Plasma-polymerized organosilicone coatings can be used to impart abrasion resistance and barrier properties to plastic substrates such as polycarbonate. Coating rates suitable for industrial-scale deposition, up to 100 nm/s, can be achieved through the use of microwave plasma-enhanced chemical vapor deposition (PECVD), with optimal process vapors such as tetramethyldisiloxane (TMDSO) and oxygen. However, it has been found that under certain deposition conditions, such coatings are subject to post-plasma changes; crazing or cracking can occur anytime from days to months after deposition. To understand the cause of the crazing and its dependence on processing plasma parameters, the effects of post-plasma reactions on the chemical bonding structure of coatings deposited with varying TMDSO-to-O2 ratios was studied with (29)Si and (13)C solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) using both single-pulse and cross-polarization techniques. The coatings showed complex chemical compositions significantly altered from the parent monomer. (29)Si MAS NMR spectra revealed four main groups of resonance lines, which correspond to four siloxane moieties (i.e., mono (M), di (D), tri (T), and quaternary (Q)) and how they are bound to oxygen. Quantitative measurements showed that the ratio of TMDSO to oxygen could shift the chemical structure of the coating from 39% to 55% in Q-type bonds and from 28% to 16% for D-type bonds. Post-plasma reactions were found to produce changes in relative intensities of (29)Si resonance lines. The NMR data were complemented by Fourier transform infrared (FTIR) spectroscopy. Together, these techniques have shown that the bonding environment of Si is drastically altered by varying the TMDSO-to-O2 ratio during PECVD, and that post-plasma reactions increase the cross-link density of the silicon-oxygen network. It appears that Si-H and Si-OH chemical groups are the most susceptible to post-plasma reactions. Coatings produced at a

  19. Characterization of low temperature graphene synthesis in inductively coupled plasma chemical vapor deposition process with optical emission spectroscopy.

    Science.gov (United States)

    Ma, Yifei; Kim, Daekyoung; Jang, Haegyu; Cho, Sung Min; Chae, Heeyeop

    2014-12-01

    Low-temperature graphene was synthesized at 400 degrees C with inductively coupled plasma chemical vapor deposition (PECVD) process. The effects of plasma power and flow rate of various carbon containing precursors and hydrogen on graphene properties were investigated with optical emission spectroscopy (OES). Various radicals monitored by OES were correlated with graphene film properties such as sheet resistance, I(D)/I(G) ratio of Raman spectra and transparency. C2H2 was used as a main precursor and the increase of plasma power enhanced intensity of carbon (C2) radical OES intensity in plasma, reduced sheet resistance and increased transparency of graphene films. The reduced flow rate of C2H2 decreased sheet resistance and increased transparency of graphene films in the range of this study. H2 addition was found to increase sheet resistance, transparency and attributed to reduction of graphene grain and etching graphene layers. OES analysis showed that C2 radicals contribute to graphite networking and sheet resistance reduction. TEM and AFM were applied to provide credible information that graphene had been successfully grown at low temperature.

  20. Highly Uniform Wafer-scale Synthesis of α-MoOsub>3sub> by Plasma Enhanced Chemical Vapor Deposition.

    Science.gov (United States)

    Kim, HyeongU; Son, Juhyun; Kulkarni, Atul; Ahn, Chisung; Kim, Ki Seok; Shin, Dongjoo; Yeom, Geun; Kim, Taesung

    2017-03-20

    Molybdenum oxide (MoOsub>3sub>) has gained immense attention because of its high electron mobility, wide band gap, and excellent optical and catalytic properties. However, the synthesis of uniform and large-area MoOsub>3sub> is challenging. Here, we report the synthesis of wafer-scale α-MoO3 by plasma oxidation of Mo-deposited on Si/SiOsub>2sub>. Mo was oxidized by Osub>2sub> plasma in a plasma enhanced chemical vapor deposition (PECVD) system at 150 °C. Mo was oxidized by Osub>2sub> plasma in a PECVD system at 150 °C. It was found that the synthesized α-MoOsub>3sub> had a highly uniform crystalline structure. For the as-synthesized α-MoOsub>3sub> sensor, we observed a current change when the relative humidity was increased from 11% to 95%. The sensor was exposed to different humidity levels with fast recovery time of about 8 s. Hence this feasibility study shows that MoOsub>3sub> synthesized at low temperature can be utilized for the gas sensing applications by adopting flexible device technology.

  1. Remote plasma enhanced chemical vapor deposition of GaP with in situ generation of phosphine precursors

    Science.gov (United States)

    Choi, S. W.; Lucovsky, G.; Bachmann, K. J.

    1992-01-01

    Thin homoepitaxial films of gallium phosphide (GaP) have been grown by remote plasma enhanced chemical vapor deposition utilizing in situ-generated phosphine precursors. The GaP forming reaction is kinetically controlled with an activation energy of 0.65 eV. The increase of the growth rate with increasing radio frequency (RF) power between 20 and 100 W is due to the combined effects of increasingly complete excitation and the spatial extension of the glow discharge toward the substrate; however, the saturation of the growth rate at even higher RF power indicates the saturation of the generation rate of phosphine precursors at this condition. Slight interdiffusion of P into Si and Si into GaP is indicated from GaP/Si heterostructures grown under similar conditions as the GaP homojunctions.

  2. Remote plasma enhanced chemical vapor deposition of GaP with in situ generation of phosphine precursors

    Science.gov (United States)

    Choi, S. W.; Lucovsky, G.; Bachmann, Klaus J.

    1993-01-01

    Thin homoepitaxial films of gallium phosphide (GaP) were grown by remote plasma enhanced chemical vapor deposition utilizing in situ generated phosphine precursors. The GaP forming reaction is kinetically controlled with an activation energy of 0.65 eV. The increase of the growth rate with increasing radio frequency (rf) power between 20 and 100 W is due to the combined effects of increasingly complete excitation and the spatial extension of the glow discharge toward the substrate, however, the saturation of the growth rate at even higher rf power indicates the saturation of the generation rate of phosphine precursors at this condition. Slight interdiffusion of P into Si and Si into GaP is indicated from GaP/Si heterostructures grown under similar conditions as the GaP homojunctions.

  3. Highly efficient shrinkage of inverted-pyramid silicon nanopores by plasma-enhanced chemical vapor deposition technology

    Science.gov (United States)

    Wang, Yifan; Deng, Tao; Chen, Qi; Liang, Feng; Liu, Zewen

    2016-06-01

    Solid-state nanopore-based analysis systems are currently one of the most attractive and promising platforms in sensing fields. This work presents a highly efficient method to shrink inverted-pyramid silicon nanopores using plasma-enhanced chemical vapor deposition (PECVD) technology by the deposition of SiN x onto the surface of the nanopore. The contraction of the inverted-pyramid silicon nanopores when subjected to the PECVD process has been modeled and carefully analyzed, and the modeling data are in good agreement with the experimental results within a specific PECVD shrinkage period (˜0-600 s). Silicon nanopores within a 50-400 nm size range contract to sub-10 nm dimensions. Additionally, the inner structure of the nanopores after the PECVD process has been analyzed by focused ion beam cutting process. The results show an inner structure morphology change from inverted-pyramid to hourglass, which may enhance the spatial resolution of sensing devices.

  4. Microstructural modification of nc-Si/SiO{sub x} films during plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X.W. [State Key Laboratory of Silicon Materials Science, Zhejiang University, Hangzhou 310027 (China)

    2005-07-01

    Nanocrystalline-silicon embedded silicon oxide films are prepared by plasma-enhanced chemical vapor deposition (PECVD) at 300 C without post-heat treatment. Measurements of XPS, IR, XRD, and HREM are performed. Microstructural modifications are found occurring throughout the film deposition. The silica network with a high oxide state is suggested to be formed directly under the abduction of the former deposited layer, rather than processing repeatedly from the original low-oxide state of silica. Nanocrystalline silicon particles with a size of 6-10 nm are embedded in the SiO{sub x} film matrix, indicating the potential application in Si-based optoelectronic integrity. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Highly efficient shrinkage of inverted-pyramid silicon nanopores by plasma-enhanced chemical vapor deposition technology.

    Science.gov (United States)

    Wang, Yifan; Deng, Tao; Chen, Qi; Liang, Feng; Liu, Zewen

    2016-06-24

    Solid-state nanopore-based analysis systems are currently one of the most attractive and promising platforms in sensing fields. This work presents a highly efficient method to shrink inverted-pyramid silicon nanopores using plasma-enhanced chemical vapor deposition (PECVD) technology by the deposition of SiN x onto the surface of the nanopore. The contraction of the inverted-pyramid silicon nanopores when subjected to the PECVD process has been modeled and carefully analyzed, and the modeling data are in good agreement with the experimental results within a specific PECVD shrinkage period (∼0-600 s). Silicon nanopores within a 50-400 nm size range contract to sub-10 nm dimensions. Additionally, the inner structure of the nanopores after the PECVD process has been analyzed by focused ion beam cutting process. The results show an inner structure morphology change from inverted-pyramid to hourglass, which may enhance the spatial resolution of sensing devices.

  6. Stress relief patterns of hydrogenated amorphous carbon films grown by dc-pulse plasma chemical vapor deposition

    Science.gov (United States)

    Wang, Qi; Wang, Chengbing; Wang, Zhou; Zhang, Junyan; He, Deyan

    2008-12-01

    Hydrogenated amorphous carbon films were prepared on Si (1 0 0) substrates by dc-pulse plasma chemical vapor deposition. The nature of the deposited films was characterized by Raman spectra and the stress relief patterns were observed by scanning electron microscope. Besides the well-known sinusoidal type and flower type patterns, etc., two different stress relief patterns, ring type and peg-top shape with exiguous tine on the top, were observed. The ring type in this paper was a clear ridge-cracked buckle and unusual. Two competing buckle delamination morphologies ring and sinusoidal buckling coexist. The ridge-cracked buckle in ring type was narrower than the sinusoidal buckling. Meanwhile peg-top shape with exiguous tine on the top in this paper was unusual. These different patterns supported the approach in which the stress relief forms have been analyzed using the theory of plate buckling.

  7. Properties of Erbium Doped Hydrogenated Amorphous Carbon Layers Fabricated by Sputtering and Plasma Assisted Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    V. Prajzler

    2008-01-01

    Full Text Available We report about properties of carbon layers doped with Er3+ ions fabricated by Plasma Assisted Chemical Vapor Deposition (PACVD and by sputtering on silicon or glass substrates. The structure of the samples was characterized by X-ray diffraction and their composition was determined by Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analysis. The Absorbance spectrum was taken in the spectral range from 400 nm to 600 nm. Photoluminescence spectra were obtained using two types of Ar laser (λex=514.5 nm, lex=488 nm and also using a semiconductor laser (λex=980 nm. Samples fabricated by magnetron sputtering exhibited typical emission at 1530 nm when pumped at 514.5 nm. 

  8. Effect of plasma parameters on characteristics of silicon nitride film deposited by single and dual frequency plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Sahu, B. B.; Yin, Yongyi; Han, Jeon G.

    2016-03-01

    This work investigates the deposition of hydrogenated amorphous silicon nitride films using various low-temperature plasmas. Utilizing radio-frequency (RF, 13.56 MHz) and ultra-high frequency (UHF, 320 MHz) powers, different plasma enhanced chemical vapor deposition processes are conducted in the mixture of reactive N2/NH3/SiH4 gases. The processes are extensively characterized using different plasma diagnostic tools to study their plasma and radical generation capabilities. A typical transition of the electron energy distribution function from single- to bi-Maxwellian type is achieved by combining RF and ultra-high powers. Data analysis revealed that the RF/UHF dual frequency power enhances the plasma surface heating and produces hot electron population with relatively low electron temperature and high plasma density. Using various film analysis methods, we have investigated the role of plasma parameters on the compositional, structural, and optical properties of the deposited films to optimize the process conditions. The presented results show that the dual frequency power is effective for enhancing dissociation and ionization of neutrals, which in turn helps in enabling high deposition rate and improving film properties.

  9. Growth of graphene on Cu foils by microwave plasma chemical vapor deposition: The effect of in-situ hydrogen plasma post-treatment

    Science.gov (United States)

    Fang, Liping; Yuan, Wen; Wang, Bing; Xiong, Ying

    2016-10-01

    Microwave plasma chemical vapor deposition (MPCVD) is a promising method for the large-scale production of high-quality graphene. The aim of this work is to investigate the effect of in-situ hydrogen plasma post-treatment on the MPCVD-grown graphene films. By simply varying the duration time of in-situ hydrogen plasma, surface morphology, number of layers and defect density of as-grown graphene films can be manipulated. The role of hydrogen plasma can be proposed from our observations, promoting to further grow graphene films in the early stage and consequently acting as an etching agent to thin graphene films in the later stage. On the basis of above mechanism, monolayer graphene films with low defect density and smooth surface can be grown by adjusting the times of the growing step and the plasma post-treatment step. This additional in-situ hydrogen plasma post-treatment may be significant for growing well-defined graphene films with controllable defects and number of layers.

  10. Plasma-enhanced chemical vapor deposition of low- loss as-grown germanosilicate layers for optical waveguides

    Science.gov (United States)

    Ay, Feridun; Agan, Sedat; Aydinli, Atilla

    2004-08-01

    We report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguides. Plasma enhanced chemical vapor deposition (PECVD) technique was used to grow the films using silane, germane and nitrous oxide as precursor gases. Chemical composition was monitored by Fourier transform infrared (FTIR) spectroscopy. N-H bond concentration of the films decreased from 0.43x1022 cm-3 down to below 0.06x1022 cm-3, by a factor of seven as the GeH4 flow rate increased from 0 to 70 sccm. A simultaneous decrease of O-H related bonds was also observed by a factor of 10 in the same germane flow range. The measured TE rate increased from 5 to 50 sccm, respectively. In contrast, the propagation loss values for TE polarization at λ=632.8 nm were found to increase from are 0.20 +/- 0.02 to 6.46 +/- 0.04 dB/cm as the germane flow rate increased from 5 to 50 sccm, respectively. In contrast, the propagation loss values for TE polarization at λ=1550 nm were found to decrease from 0.32 +/- 0.03 down to 0.14 +/- 0.06 dB/cm for the same samples leading to the lowest values reported so far in the literature, eliminating the need for high temperature annealing as is usually done for these materials to be used in waveguide devices.

  11. Plasma-enhanced chemical vapor deposition of ortho-carborane: structural insights and interaction with Cu overlayers.

    Science.gov (United States)

    James, Robinson; Pasquale, Frank L; Kelber, Jeffry A

    2013-09-01

    X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS) are used to investigate the chemical and electronic structure of boron carbide films deposited from ortho-carborane precursors using plasma-enhanced chemical vapor deposition (PECVD), and the reactivity of PECVD films toward sputter-deposited Cu overlayers. The XPS data provide clear evidence of enhanced ortho-carborane reactivity with the substrate, and of extra-icosahedral boron and carbon species; these results differ from results for films formed by condensation and electron beam induced cross-linking of ortho-carborane (EBIC films). The UPS data show that the valence band maximum for PECVD films is ∼1.5 eV closer to the Fermi level than for EBIC films. The XPS data also indicate that PECVD films are resistant to thermally-stimulated diffusion of Cu at temperatures up to 1000 K in UHV, in direct contrast to recently reported results, but important for applications in neutron detection and in microelectronics.

  12. Low-temperature synthesis of diamond films by photoemission-assisted plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kawata, Mayuri, E-mail: kawata@mail.tagen.tohoku.ac.jp; Ojiro, Yoshihiro; Ogawa, Shuichi; Takakuwa, Yuji [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Masuzawa, Tomoaki; Okano, Ken [International Christian University, 3-10-2 Osawa, Mitaka 181-8585 (Japan)

    2014-03-15

    Photoemission-assisted plasma-enhanced chemical vapor deposition (PA-PECVD), a process in which photoelectrons emitted from a substrate irradiated with ultraviolet light are utilized as a trigger for DC discharge, was investigated in this study; specifically, the DC discharge characteristics of PA-PECVD were examined for an Si substrate deposited in advance through hot-filament chemical vapor deposition with a nitrogen-doped diamond layer of thickness ∼1 μm. Using a commercially available Xe excimer lamp (hν = 7.2 eV) to illuminate the diamond surface with and without hydrogen termination, the photocurrents were found to be 3.17 × 10{sup 12} and 2.11 × 10{sup 11} electrons/cm{sup 2}/s, respectively. The 15-fold increase in photocurrent was ascribed to negative electron affinity (NEA) caused by hydrogen termination on the diamond surfaces. The DC discharge characteristics revealed that a transition bias voltage from a Townsend-to-glow discharge was considerably decreased because of NEA (from 490 to 373 V for H{sub 2} gas and from 330 to 200 V for Ar gas), enabling a reduction in electric power consumption needed to synthesize diamond films through PA-PECVD. In fact, the authors have succeeded in growing high-quality diamond films of area 2.0 cm{sup 2} at 540 °C with a discharge power of only 1.8 W, plasma voltage of 156.4 V, and discharge current of 11.7 mA under the glow discharge of CH{sub 4}/H{sub 2}/Ar mixed gases. In addition to having only negligible amounts of graphite and amorphous carbon, the diamond films exhibit a relatively high diamond growth rate of 0.5 μm/h at temperatures as low as 540 °C, which is attributed to Ar{sup +} ions impinging on the diamond surface, and causing the removal of hydrogen atoms from the surface through sputtering. This process leads to enhanced CH{sub x} radical adsorption, because the sample was applied with a negative potential to accelerate photoelectrons in PA-PECVD.

  13. Growth of carbon nanofibers in plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Denysenko, Igor; Ostrikov, Kostya; Tam, Eugene

    2008-10-01

    A theoretical model describing the plasma-assisted growth of carbon nanofibers with metal catalyst particles on top is proposed. Using the model, the plasma-related effects on the nanofiber growth parameters such us the surface diffusion growth rate, the effective carbon flux to the catalyst surface, the characteristic residence time and diffusion length of carbon on the catalyst surface, and the surface coverages, have been studied. It has been found how these parameters depend on the catalyst surface temperature and ion and etching gas fluxes to the catalyst surface. The optimum conditions under which a low-temperature plasma environment can benefit the carbon nanofiber growth are formulated. It has been also found how the plasma environment affects the temperature distribution over the length of the carbon nanofibers. Conditions when the temperature of the catalyst nanoparticles is higher than the temperature of the substrate holder are determined. The results here are in a good agreement with the available experimental data on the carbon nanofiber growth and can be used for optimizing synthesis of nanoassemblies in low-temperature plasma-assisted nanofabrication.

  14. Tribological and thermal stability study of nanoporous amorphous boron carbide films prepared by pulsed plasma chemical vapor deposition

    Science.gov (United States)

    Liza, Shahira; Ohtake, Naoto; Akasaka, Hiroki; Munoz-Guijosa, Juan M.

    2015-06-01

    In this work, the thermal stability and the oxidation and tribological behavior of nanoporous a-BC:H films are studied and compared with those in conventional diamond-like carbon (DLC) films. a-BC:H films were deposited by pulsed plasma chemical vapor deposition using B(CH3)3 gas as the boron source. A DLC interlayer was used to prevent the a-BC:H film delamination produced by oxidation. Thermal stability of a-BC:H films, with no delamination signs after annealing at 500 °C for 1 h, is better than that of the DLC films, which completely disappeared under the same conditions. Tribological test results indicate that the a-BC:H films, even with lower nanoindentation hardness than the DLC films, show an excellent boundary oil lubricated behavior, with lower friction coefficient and reduce the wear rate of counter materials than those on the DLC film. The good materials properties such as low modulus of elasticity and the formation of micropores from the original nanopores during boundary regimes explain this better performance. Results show that porous a-BC:H films may be an alternative for segmented DLC films in applications where severe tribological conditions and complex shapes exist, so surface patterning is unfeasible.

  15. Plasma-enhanced chemical vapor deposition of low-loss SiON optical waveguides at 15-microm wavelength.

    Science.gov (United States)

    Bruno, F; Guidice, M D; Recca, R; Testa, F

    1991-11-01

    Good optical-quality SiON layers deposited upon a SiO(2) buffer layer placed upon silicon wafers have been obtained by using plasma-enhanced chemical vapor deposition from SiH(4), NH(3), and N(2)O. Optical planar waveguides with a thickness of 5 microm and a refractive index of 1.470 have been deposited and investigated in the wavelength region of 1.3-1.6 microm. Three absorption bands at 1.40, 1.48, and 1.54 microm have been detected and interpreted as Si-OH, N-H, and Si-H vibrational modes, respectively. Absorption losses of 3.8 dB/cm at 1.4 microm and 3.2 dB/cm at 1.51 microm have been measured. A mild annealing at approximately 800 degrees C completely removes the band at 1.40 microm, whereas strong reduction of absorption at 1.51 microm requires 3 h of annealing at 1100 degrees C. As a result, propagation losses of 0.36 to 0.54 dB/cm have been measured at 1.54-microm wavelength.

  16. A new perspective on structural and morphological properties of carbon nanotubes synthesized by Plasma Enhanced Chemical Vapor Deposition technique

    Science.gov (United States)

    Salar Elahi, A.; Agah, K. Mikaili; Ghoranneviss, M.

    CNTs were produced on a silicon wafer by Plasma Enhanced Chemical Vapor Deposition (PECVD) using acetylene as a carbon source, cobalt as a catalyst and ammonia as a reactive gas. The DC-sputtering system was used to prepare cobalt thin films on Si substrates. A series of experiments was carried out to investigate the effects of reaction temperature and deposition time on the synthesis of the nanotubes. The deposition time was selected as 15 and 25 min for all growth temperatures. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the Co nanocatalyst deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface topography of the Co nanocatalyst deposited on Si substrates. The as-grown CNTs were characterized under Field Emission Scanning Electron Microscopy (FESEM) to study the morphological properties of CNTs. Also, the grown CNTs have been investigated by High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results demonstrated that increasing the temperature leads to increasing the diameter of CNTs.

  17. Morphology and Structure Properties of Boron-doped Diamond Films Prepared by Hot Cathode Direct Current Plasma Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Mengmei PAN

    2016-05-01

    Full Text Available Boron-doped diamond (BDD films were deposited by hot cathode direct current plasma chemical vapor deposition (HCDC-PCVD according to various mixture ratios of CH4/H2/B(OCH33 gas. The Raman performances and surface morphologies of the BDD films were then characterized by Raman spectroscopy and scanning electron microscopy (SEM. Results indicated that the flow rate of B(OCH33 had marked effects on the growth characteristics of the produced boron-doped diamond films. The presence and concentration of the doped boron atoms significantly altered both the surface morphologies and structures of the diamond films. With increasing flow rate of B(OCH33, the crystal grain surfaces became smooth as visible under SEM. The B-doping levels in these films increased from 1.75×1019cm-3 to a maximum of 2.4×1021cm-3, estimated from the Raman spectra. DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12923

  18. Glutamate biosensor based on carbon nanowalls grown using plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Tomatsu, Masakazu; Hiramatsu, Mineo; Kondo, Hiroki; Hori, Masaru

    2015-09-01

    Carbon nanowalls (CNWs) are composed of few-layer graphene standing almost vertically on the substrate. Due to the large surface area of vertical nanographene network, CNWs draw attention as platform for electrochemical sensing, biosensing and energy conversion applications. In this work, CNWs were grown on nickel substrate using inductively coupled plasma with methane/Ar mixture. After the CNW growth, the surface of CNWs was oxidized using Ar atmospheric pressure plasma to obtain super-hydrophilic surface. For the biosensing application, the surface of CNWs was decorated with platinum (Pt) nanoparticles by the reduction of hydrogen hexachloroplatinate (IV) solution. The resultant Pt particle size was estimated to be 3-4 nm. From the XPS analysis, pure Pt existed without being oxidized on the CNW surface. Electrochemical surface area of the Pt catalyst was evaluated by cyclic voltammetry. Pt-decorated CNWs will be used as an electrode for electrochemical glutamate biosensing. L-glutamate is one of the most important in the mammalian central nervous system, playing a vital role in many physiological processes. Nanoplatform based on vertical nanographene offers great promise for providing a new class of nanostructured electrodes for electrochemical sensing.

  19. Microwave plasma assisted chemical vapor deposition of ultra-nanocrystalline diamond films

    Science.gov (United States)

    Huang, Wen-Shin

    Microwave plasma assisted ultra-nanocrystalline diamond film deposition was investigated using hydrogen deficient, carbon containing argon plasma chemistries with MSU-developed microwave plasma reactors. Ultra-nanocrystalline diamond film deposition on mechanically scratched silicon wafers was experimentally explored over the following input variables: (1) pressure: 60--240Torr, (2) total gas flow rate: 101--642 sccm, (3) input microwave power 732--1518W, (4) substrate temperature: 500°C--770°C, (5) deposition time: 2--48 hours, and (6) N2 impurities 5--2500 ppm. H2 concentrations were less than 9%, while CH 4 concentration was 0.17--1.85%. It was desired to grow films uniformly over 3″ diameter substrates and to minimize the grain size. Large, uniform, intense, and greenish-white discharges were sustained in contact with three inch silicon substrates over a 60--240 Torr pressure regime. At a given operating pressure, film uniformity was controlled by adjusting substrate holder geometry, substrate position, input microwave power, gas chemistries, and total gas flow rates. Film ultra-nanocrystallinity and smoothness required high purity deposition conditions. Uniform ultra-nanocrystalline films were synthesized in low leak-rate system with crystal sizes ranging from 3--30 nm. Films with 11--50 nm RMS roughness and respective thickness values of 1--23 mum were synthesized over 3″ wafers under a wide range of different deposition conditions. Film RMS roughness 7 nm was synthesized with thickness of 430 nm. Film uniformities of almost 100% were achieved over three inch silicon wafers. UV Raman and XRD characterization results indicated the presence of diamond in the synthesized films. Optical Emission Spectroscopy measurements showed that the discharge gas temperature was in excess of 2000 K. The synthesized films are uniformly smooth and the as grown ultra-nanocrystalline diamond can be used for a high frequency SAW device substrate material. IR measurements

  20. Cell proliferation on modified DLC thin films prepared by plasma enhanced chemical vapor deposition.

    Science.gov (United States)

    Stoica, Adrian; Manakhov, Anton; Polčák, Josef; Ondračka, Pavel; Buršíková, Vilma; Zajíčková, Renata; Medalová, Jiřina; Zajíčková, Lenka

    2015-06-12

    Recently, diamondlike carbon (DLC) thin films have gained interest for biological applications, such as hip and dental prostheses or heart valves and coronary stents, thanks to their high strength and stability. However, the biocompatibility of the DLC is still questionable due to its low wettability and possible mechanical failure (delamination). In this work, DLC:N:O and DLC: SiOx thin films were comparatively investigated with respect to cell proliferation. Thin DLC films with an addition of N, O, and Si were prepared by plasma enhanced CVD from mixtures of methane, hydrogen, and hexamethyldisiloxane. The films were optically characterized by infrared spectroscopy and ellipsometry in UV-visible spectrum. The thickness and the optical properties were obtained from the ellipsometric measurements. Atomic composition of the films was determined by Rutherford backscattering spectroscopy combined with elastic recoil detection analysis and by x-ray photoelectron spectroscopy. The mechanical properties of the films were studied by depth sensing indentation technique. The number of cells that proliferate on the surface of the prepared DLC films and on control culture dishes were compared and correlated with the properties of as-deposited and aged films. The authors found that the level of cell proliferation on the coated dishes was high, comparable to the untreated (control) samples. The prepared DLC films were stable and no decrease of the biocompatibility was observed for the samples aged at ambient conditions.

  1. Comparison of diamond growth with different gas mixtures in microwave plasma asssited chemical vapor deposition (MWCVD

    Directory of Open Access Journals (Sweden)

    Corat Evaldo J.

    2003-01-01

    Full Text Available In this work we study the influence of oxygen addition to several halocarbon-hydrogen gas systems. Diamond growth have been performed in a high power density MWCVD reactor built in our laboratory. The growth experiments are monitored by argon actinometry as a reference to plasma temperature and atomic hydrogen production, and by mass spectrometry to compare the exhaust gas composition. Atomic hydrogen actinometry revealed that the halogen presence in the gas phase is responsible for a considerable increase of atomic hydrogen concentration in the gas phase. Mass spectrometry shows similar results for all gas mixtures tested. Growth studies with oxygen addition to CF4/H2, CCl4/H2, CCl2F2/H2 and CH3Cl/H2 reveals that oxygen increases the carbon solubility in the gas phase but no better diamond growth conditions were found. Halogens are not, per se, eligible for diamond growth. All the possible advantages, as the higher production of atomic hydrogen, have been suppressed by the low carbon solubility in the gas phase, even when oxygen is added. The diamond growth with small amount of CF4 added to CH4/H2 mixture is not aggressive to the apparatus but brings several advantages to the process.

  2. Growth and characterization of large, high quality single crystal diamond substrates via microwave plasma assisted chemical vapor deposition

    Science.gov (United States)

    Nad, Shreya

    Single crystal diamond (SCD) substrates can be utilized in a wide range of applications. Important issues in the chemical vapor deposition (CVD) of such substrates include: shrinking of the SCD substrate area, stress and cracking, high defect density and hence low electronic quality and low optical quality due to high nitrogen impurities. The primary objective of this thesis is to begin to address these issues and to find possible solutions for enhancing the substrate dimensions and simultaneously improving the quality of the grown substrates. The deposition of SCD substrates is carried out in a microwave cavity plasma reactor via the microwave plasma assisted chemical vapor deposition technique. The operation of the reactor was first optimized to determine the safe and efficient operating regime. By adjusting the matching of the reactor cavity with the help of four internal tuning length variables, the system was further matched to operate at a maximum overall microwave coupling efficiency of ˜ 98%. Even with adjustments in the substrate holder position, the reactor remains well matched with a coupling efficiency of ˜ 95% indicating good experimental performance over a wide range of operating conditions. SCD substrates were synthesized at a high pressure of 240 Torr and with a high absorbed power density of 500 W/cm3. To counter the issue of shrinking substrate size during growth, the effect of different substrate holder designs was studied. An increase in the substrate dimensions (1.23 -- 2.5 times) after growth was achieved when the sides of the seeds were shielded from the intense microwave electromagnetic fields in a pocket holder design. Using such pocket holders, high growth rates of 16 -- 32 mum/hr were obtained for growth times of 8 -- 72 hours. The polycrystalline diamond rim deposition was minimized/eliminated from these growth runs, hence successfully enlarging the substrate size. Several synthesized CVD SCD substrates were laser cut and separated

  3. A comparative study of nitrogen plasma effect on field emission characteristics of single wall carbon nanotubes synthesized by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

    2014-12-01

    Vertically aligned single wall carbon nanotubes (SWCNTs) with large scale control of diameter, length and alignment have successfully been grown by plasma enhanced chemical vapor deposition (PECVD) system. The nickel (Ni) as catalyst deposited on silicon (Si) substrate was used to grow the SWCNTs. Field emission (FE) characteristics of the as grown SWCNTs were measured using indigenously designed setup in which a diode is configured in such a way that by applying negative voltage on the copper plate (cathode) with respect to stainless steel anode plate, current density can be recorded. To measure the FE characteristics, SWCNTs film pasted on the copper plate with silver epoxy was used as electron emitter source. The effective area of anode was ∼78.5 mm2 for field emission measurements. The emission measurements were carried out under high vacuum pressure of the order of 10-6 Torr to minimize the electron scattering and degradation of the emitters. The distance between anode and cathode was kept 500 μm (constant) during entire field emission studies. The grown SWCNTs are excellent field emitters, having emission current density higher than 25 mA/cm2 at turn-on field 1.3 V/μm. In order to enhance the field emission characteristics, the as grown SWCNTs have been treated under nitrogen (N2) plasma for 5 min and again field emission characteristics have been measured. The N2 plasma treated SWCNTs show a good enhancement in the field emission properties with emission current density 81.5 mA/cm2 at turn on field 1.2 V/μm. The as-grown and N2 plasma treated SWCNTs were also characterized by field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), Raman spectrometer, Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS).

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2002-11-01

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

  5. Single liquid-source plasma enhanced metalorganic chemical vapor deposition of YBa sub 2 Cu sub 3 O sub 7-x thin films. Technical report

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J.; Gardiner, R.; Kirlin, P.S.; Boerstler, R.W.; Steinbeck, J.

    1992-07-29

    High quality YBa2Cu3O7-x films were grown in-situ on LaAlO3 (100) by a novel single liquid source plasma-enhanced metalorganic chemical vapor deposition process. The metalorganic complexes M(thd)n, (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate; M = Y, Ba, Cu) were dissolved in an organic solution and injected into a vaporizer immediately upstream of the reactor inlet The single liquid source technique dramatically simplifies current CVD processing and can significantly improve the process reproducibility. X-ray diffraction. measurements indicated that single phase, highly c-axis oriented YBa2Cu3O7-x was formed in-situ at a substrate temperature 680 degC. The as-deposited films exhibited a mirror-like surface, had transition temperature Tc = 89 K, Delta Tc < 1K, and Jc(77K) = 106 A/cm2. Plasma enhanced metalorganic chemical vapor deposition, YBCO, superconductors.

  6. Speciation analysis of mercury in cereals by liquid chromatography chemical vapor generation inductively coupled plasma-mass spectrometry.

    Science.gov (United States)

    Lin, Liang-Yen; Chang, Lan-Fang; Jiang, Shiuh-Jen

    2008-08-27

    A simple and rapid procedure for the separation and determination of inorganic, methyl, and ethyl mercury compounds was described using liquid chromatography (LC) followed by vapor generation inductively coupled plasma-mass spectrometry (VG-ICP-MS). Well resolved chromatograms were obtained within 5 min by reversed-phase liquid chromatography with a C8 column as the stationary phase and a pH 4.7 solution containing 0.5% v/v 2-mercaptoethanol and 5% v/v methanol as the mobile phase. The separated mercury compounds were converted to mercury vapors by an in situ nebulizer/vapor generation system for their introduction into ICP. The concentrations of NaBH4 and HNO3 required for vapor generation were also optimized. The method was applied for the speciation of mercury in reference materials NIST SRM 1568a Rice Flour and NIST SRM 1567a Wheat Flour and also rice flour and wheat flour samples purchased locally. The accuracy of the procedure was verified by analyzing the certified reference material NRCC DOLT-3 Dogfish Liver for methyl mercury. Precision between sample replicates was better than 13% for all the determinations. The detection limits of the mercury compounds studied were in the range 0.003-0.006 ng Hg mL(-1) in the injected solutions, which correspond to 0.02-0.06 ng g(-1) in original flour samples. A microwave-assisted extraction procedure was adopted for the extraction of mercury compounds from rice flour, wheat flour, and fish samples using a mobile phase solution.

  7. Synthesis of thin films in boron-carbon-nitrogen ternary system by microwave plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Kukreja, Ratandeep Singh

    The Boron Carbon Nitorgen (B-C-N) ternary system includes materials with exceptional properties such as wide band gap, excellent thermal conductivity, high bulk modulus, extreme hardness and transparency in the optical and UV range that find application in most fields ranging from micro-electronics, bio-sensors, and cutting tools to materials for space age technology. Interesting materials that belong to the B-C-N ternary system include Carbon nano-tubes, Boron Carbide, Boron Carbon Nitride (B-CN), hexagonal Boron Nitride ( h-BN), cubic Boron Nitride (c-BN), Diamond and beta Carbon Nitride (beta-C3N4). Synthesis of these materials requires precisely controlled and energetically favorable conditions. Chemical vapor deposition is widely used technique for deposition of thin films of ceramics, metals and metal-organic compounds. Microwave plasma enhanced chemical vapor deposition (MPECVD) is especially interesting because of its ability to deposit materials that are meta-stable under the deposition conditions, for e.g. diamond. In the present study, attempt has been made to synthesize beta-carbon nitride (beta-C3N4) and cubic-Boron Nitride (c-BN) thin films by MPECVD. Also included is the investigation of dependence of residual stress and thermal conductivity of the diamond thin films, deposited by MPECVD, on substrate pre-treatment and deposition temperature. Si incorporated CNx thin films are synthesized and characterized while attempting to deposit beta-C3N4 thin films on Si substrates using Methane (CH4), Nitrogen (N2), and Hydrogen (H2). It is shown that the composition and morphology of Si incorporated CNx thin film can be tailored by controlling the sequence of introduction of the precursor gases in the plasma chamber. Greater than 100mum size hexagonal crystals of N-Si-C are deposited when Nitrogen precursor is introduced first while agglomerates of nano-meter range graphitic needles of C-Si-N are deposited when Carbon precursor is introduced first in the

  8. Direct Fabrication of Carbon Nanotubes STM Tips by Liquid Catalyst-Assisted Microwave Plasma-Enhanced Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Fa-Kuei Tung

    2009-01-01

    Full Text Available Direct and facile method to make carbon nanotube (CNT tips for scanning tunneling microscopy (STM is presented. Cobalt (Co particles, as catalysts, are electrochemically deposited on the apex of tungsten (W STM tip for CNT growth. It is found that the quantity of Co particles is well controlled by applied DC voltage, concentration of catalyst solution, and deposition time. Using optimum growth condition, CNTs are successfully synthesized on the tip apex by catalyst-assisted microwave-enhanced chemical vapor deposition (CA-MPECVD. A HOPG surface is clearly observed at an atomic scale using the present CNT-STM tip.

  9. Simple Chemical Vapor Deposition Experiment

    Science.gov (United States)

    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…

  10. Electron energy-loss spectroscopy analysis of low-temperature plasma-enhanced chemically vapor deposited a-C:H films

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A.J.; Benson, D.K.; Tracy, C.E.; Kazmerski, L.L.; Wager, J.F.

    1989-05-01

    Electron energy-loss spectroscopy (EELS) has been applied to the analysis of a-C:H films grown on various substrates by a unique low-temperature (<100 /sup 0/C) plasma-enhanced chemical vapor deposition (PECVD) process using ethylene and hydrogen gases. EELS data are used to characterize the relative amounts of fourfold coordinated sp/sup 3/ carbon bonding to threefold coordinated sp/sup 2/ carbon bonding as well as the relative order/disorder due to substrate effects. Ellipsometric and transmission measurements provide optical constants for the PECVD a-C:H films.

  11. Synthesis of few-layer graphene on a Ni substrate by using DC plasma enhanced chemical vapor deposition (PE-CVD)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong Hyuk; Castro, Edward Joseph; Hwang, Yong Gyoo; Lee, Choong Hun [Wonkwang University, Iksan (Korea, Republic of)

    2011-01-15

    In this work, few-layer graphene (FLG) was successfully grown on polycrystalline Ni a large scale by using DC plasma enhanced chemical vapor deposition (DC PE-CVD), which may serve as an alternative route in large-scale graphene synthesis. The synthesis time had an effect on the quality of the graphene produced. The applied DC voltage, on the other hand, influenced the minimization of the defect densities in the graphene grown. We also present a method of producing a free-standing polymethyl methacrylate (PMMA)/graphene membrane on a FeCl{sub 3(aq)} solution, which could then be transferred to the desired substrate.

  12. Atmospheric pressure plasma-initiated chemical vapor deposition (AP-PiCVD) of poly(diethylallylphosphate) coating: a char-forming protective coating for cellulosic textile.

    Science.gov (United States)

    Hilt, Florian; Boscher, Nicolas D; Duday, David; Desbenoit, Nicolas; Levalois-Grützmacher, Joëlle; Choquet, Patrick

    2014-01-01

    An innovative atmospheric pressure chemical vapor deposition method toward the deposition of polymeric layers has been developed. This latter involves the use of a nanopulsed plasma discharge to initiate the free-radical polymerization of an allyl monomer containing phosphorus (diethylallylphosphate, DEAP) at atmospheric pressure. The polymeric structure of the film is evidence by mass spectrometry. The method, highly suitable for the treatment of natural biopolymer substrate, has been carried out on cotton textile to perform the deposition of an efficient and conformal protective coating.

  13. Sub-micro a-C:H patterning of silicon surfaces assisted by atmospheric-pressure plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Boileau, Alexis; Gries, Thomas; Noël, Cédric; Perito Cardoso, Rodrigo; Belmonte, Thierry

    2016-11-01

    Micro and nano-patterning of surfaces is an increasingly popular challenge in the field of the miniaturization of devices assembled via top-down approaches. This study demonstrates the possibility of depositing sub-micrometric localized coatings—spots, lines or even more complex shapes—made of amorphous hydrogenated carbon (a-C:H) thanks to a moving XY stage. Deposition was performed on silicon substrates using chemical vapor deposition assisted by an argon atmospheric-pressure plasma jet. Acetylene was injected into the post-discharge region as a precursor by means of a glass capillary with a sub-micrometric diameter. A parametric study was carried out to study the influence of the geometric configurations (capillary diameter and capillary-plasma distance) on the deposited coating. Thus, the patterns formed were investigated by scanning electron microscopy and atomic force microscopy. Furthermore, the chemical composition of large coated areas was investigated by Fourier transform infrared spectroscopy according to the chosen atmospheric environment. The observed chemical bonds show that reactions of the gaseous precursor in the discharge region and both chemical and morphological stability of the patterns after treatment are strongly dependent on the surrounding gas. Various sub-micrometric a-C:H shapes were successfully deposited under controlled atmospheric conditions using argon as inerting gas. Overall, this new process of micro-scale additive manufacturing by atmospheric plasma offers unusually high-resolution at low cost.

  14. Temperature-dependent electrical and photo-sensing properties of horizontally-oriented carbon nanotube networks synthesized by sandwich-growth microwave plasma chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Teng, I-Ju [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Hsu, Hui-Lin [Department of Electrical and Computer Engineering, University of Toronto, Toronto M5S 3G4 (Canada); Jian, Sheng-Rui, E-mail: srjian@gmail.com [Department of Materials Science and Engineering, I-Shou University, Kaohsiung 84041, Taiwan (China); Wang, Li-Chun; Chen, Kai-Ling [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Kuo, Cheng-Tzu, E-mail: kurt.kuotw@gmail.com [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Pan, Fu-Ming [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Wang, Wei-Hsiang [Teraxtal Technology Corporation, Hsinchu 30075, Taiwan (China); Juang, Jenh-Yih [Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

    2013-02-01

    The electrical and photo-sensing properties of horizontally-oriented interconnected carbon nanotube networks (CNT-NWs) prepared by means of a microwave plasma chemical vapor deposition sandwich-growth process are investigated. The temperature-dependent dark and illuminated current–voltage and transfer characteristics of CNT-NW-assisted devices are measured. Results show that the current–voltage characteristics of the devices exhibit nonlinear behavior, and the current can be further modulated by a gate voltage, revealing p-type semiconducting behavior with a device mobility of ∼ 14.5 cm{sup 2}/V·s and an on-off current ratio of ∼ 10{sup 3}. Moreover, when the CNT-NW-assisted devices are irradiated with 1.25–25 μm infrared (IR) from 300 to 11 K, the photo currents increase approximately 1.1- to 2.7-fold compared to the dark currents at ± 2 V bias voltage. Such results demonstrate that the presented CNT-NWs have high potential for IR photo-sensor applications. - Highlights: ► Horizontally-oriented interconnected carbon nanotube networks (CNT-NWs) were grown. ► A microwave plasma chemical vapor deposition sandwich-growth process was employed. ► Temperature-dependent electrical and photo-sensing properties were investigated. ► Devices based on CNT-NWs exhibit promising transistor characteristics. ► CNT-NWs are capable to detect light in the infrared wavelength range.

  15. Development of speckle-free channel-cut crystal optics using plasma chemical vaporization machining for coherent x-ray applications.

    Science.gov (United States)

    Hirano, Takashi; Osaka, Taito; Sano, Yasuhisa; Inubushi, Yuichi; Matsuyama, Satoshi; Tono, Kensuke; Ishikawa, Tetsuya; Yabashi, Makina; Yamauchi, Kazuto

    2016-06-01

    We have developed a method of fabricating speckle-free channel-cut crystal optics with plasma chemical vaporization machining, an etching method using atmospheric-pressure plasma, for coherent X-ray applications. We investigated the etching characteristics to silicon crystals and achieved a small surface roughness of less than 1 nm rms at a removal depth of >10 μm, which satisfies the requirements for eliminating subsurface damage while suppressing diffuse scattering from rough surfaces. We applied this method for fabricating channel-cut Si(220) crystals for a hard X-ray split-and-delay optical system and confirmed that the crystals provided speckle-free reflection profiles under coherent X-ray illumination.

  16. Development of speckle-free channel-cut crystal optics using plasma chemical vaporization machining for coherent x-ray applications

    Science.gov (United States)

    Hirano, Takashi; Osaka, Taito; Sano, Yasuhisa; Inubushi, Yuichi; Matsuyama, Satoshi; Tono, Kensuke; Ishikawa, Tetsuya; Yabashi, Makina; Yamauchi, Kazuto

    2016-06-01

    We have developed a method of fabricating speckle-free channel-cut crystal optics with plasma chemical vaporization machining, an etching method using atmospheric-pressure plasma, for coherent X-ray applications. We investigated the etching characteristics to silicon crystals and achieved a small surface roughness of less than 1 nm rms at a removal depth of >10 μm, which satisfies the requirements for eliminating subsurface damage while suppressing diffuse scattering from rough surfaces. We applied this method for fabricating channel-cut Si(220) crystals for a hard X-ray split-and-delay optical system and confirmed that the crystals provided speckle-free reflection profiles under coherent X-ray illumination.

  17. Direct fabrication of 3D graphene on nanoporous anodic alumina by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    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.

  18. Atmospheric pressure plasma chemical vapor deposition reactor for 100 mm wafers, optimized for minimum contamination at low gas flow rates

    Energy Technology Data Exchange (ETDEWEB)

    Anand, Venu, E-mail: venuanand@cense.iisc.ernet.in, E-mail: venuanand83@gmail.com; Shivashankar, S. A. [Centre for Nano Science and Engineering (CeNSE), Indian Institute of Science (IISc), Bangalore 560012 (India); Nair, Aswathi R.; Mohan Rao, G. [Department of Instrumentation and Applied Physics (IAP), Indian Institute of Science (IISc), Bangalore 560012 (India)

    2015-08-31

    Gas discharge plasmas used for thinfilm deposition by plasma-enhanced chemical vapor deposition (PECVD) must be devoid of contaminants, like dust or active species which disturb the intended chemical reaction. In atmospheric pressure plasma systems employing an inert gas, the main source of such contamination is the residual air inside the system. To enable the construction of an atmospheric pressure plasma (APP) system with minimal contamination, we have carried out fluid dynamic simulation of the APP chamber into which an inert gas is injected at different mass flow rates. On the basis of the simulation results, we have designed and built a simple, scaled APP system, which is capable of holding a 100 mm substrate wafer, so that the presence of air (contamination) in the APP chamber is minimized with as low a flow rate of argon as possible. This is examined systematically by examining optical emission from the plasma as a function of inert gas flow rate. It is found that optical emission from the plasma shows the presence of atmospheric air, if the inlet argon flow rate is lowered below 300 sccm. That there is minimal contamination of the APP reactor built here, was verified by conducting an atmospheric pressure PECVD process under acetylene flow, combined with argon flow at 100 sccm and 500 sccm. The deposition of a polymer coating is confirmed by infrared spectroscopy. X-ray photoelectron spectroscopy shows that the polymer coating contains only 5% of oxygen, which is comparable to the oxygen content in polymer deposits obtained in low-pressure PECVD systems.

  19. Determination of Se in biological samples by axial view inductively coupled plasma optical emission spectrometry after digestion with aqua regia and on-line chemical vapor generation

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Eder Jose dos [Instituto de Tecnologia do Parana (TECPAR), 81350-010 Curitiba, PR (Brazil)], E-mail: eder@tecpar.br; Herrmann, Amanda Beatriz; Kulik de Caires, Suzete [Instituto de Tecnologia do Parana (TECPAR), 81350-010 Curitiba, PR (Brazil); Azzolin Frescura, Vera Lucia; Curtius, Adilson Jose [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), 880400-900 Florianopolis, SC (Brazil)

    2009-06-15

    A simple and fast method for the determination of Se in biological samples, including food, by axial view inductively coupled plasma optical emission spectrometry using on-line chemical vapor generation (CVG-ICP OES) is proposed. The concentrations of HCl and NaBH{sub 4}, used in the chemical vapor generation were optimized by factorial analysis. Six certified materials (non-fat milk powder, lobster hepatopancreas, human hair, whole egg powder, oyster tissue, and lyophilised pig kidney) were treated with 10 mL of aqua regia in a microwave system under reflux for 15 min followed by additional 15 min in an ultrasonic bath. The solutions were transferred to a 100 mL volumetric flask and the final volume was made up with water. The Se was determined directly in these solutions by CVG-ICP OES, using the analytical line at 196.026 nm. Calibration against aqueous standards in 10% v/v aqua regia in the concentration range of 0.5-10.0 {mu}g L{sup -} {sup 1} Se(IV) was used for the analysis. The quantification limit, considering a 0.5 g sample weight in a final volume of 100 mL{sup -} {sup 1} was 0.10 {mu}g g{sup -} {sup 1}. The obtained concentration values were in agreement with the total certified concentrations, according to the t-test for a 95% confidence level.

  20. Preparation of Aligned Ultra-long and Diameter-controlled Silicon Oxide Nanotubes by Plasma Enhanced Chemical Vapor Deposition Using Electrospun PVP Nanofiber Template

    Directory of Open Access Journals (Sweden)

    Zhou Ming

    2009-01-01

    Full Text Available Abstract Well-aligned and suspended polyvinyl pyrrolidone (PVP nanofibers with 8 mm in length were obtained by electrospinning. Using the aligned suspended PVP nanofibers array as template, aligned ultra-long silicon oxide (SiOx nanotubes with very high aspect ratios have been prepared by plasma-enhanced chemical vapor deposition (PECVD process. The inner diameter (20–200 nm and wall thickness (12–90 nm of tubes were controlled, respectively, by baking the electrospun nanofibers and by coating time without sacrificing the orientation degree and the length of arrays. The micro-PL spectrum of SiOx nanotubes shows a strong blue–green emission with a peak at about 514 nm accompanied by two shoulders around 415 and 624 nm. The blue–green emission is caused by the defects in the nanotubes.

  1. Microwave Plasma Chemical Vapor Deposition of Nano-Structured Sn/C Composite Thin-Film Anodes for Li-ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, Cynthia; Marcinek, M.; Hardwick, L.J.; Richardson, T.J.; Song, X.; Kostecki, R.

    2008-02-01

    In this paper we report results of a novel synthesis method of thin-film composite Sn/C anodes for lithium batteries. Thin layers of graphitic carbon decorated with uniformly distributed Sn nanoparticles were synthesized from a solid organic precursor Sn(IV) tert-butoxide by a one step microwave plasma chemical vapor deposition (MPCVD). The thin-film Sn/C electrodes were electrochemically tested in lithium half cells and produced a reversible capacity of 440 and 297 mAhg{sup -1} at C/25 and 5C discharge rates, respectively. A long term cycling of the Sn/C nanocomposite anodes showed 40% capacity loss after 500 cycles at 1C rate.

  2. Deposition and Characterization of Nanocrystalline Diamond Films on Mirror-Polished Si Substrate by Biased Enhanced Microwave Plasma Chemical Vapor Deposition

    Science.gov (United States)

    Soga, T.; Sharda, T.; Jimbo, T.; Umeno, M.

    Hard and smooth nanocrystalline diamond (NCD) thin films were deposited on polished silicon substrates by biased enhanced growth in microwave plasma chemical vapor deposition. The films deposited with varying the methane concentration and biasing voltage were characterized by Raman spectroscopy, nano-indenter, x-ray diffraction and atomic force microscopy. Stress in the films increases with decreasing methane concentration in the gas-phase and with increasing biasing. The adhesion between NCD film and Si substrate is very strong sustaining the compressive stress as high as high as 85 GPa. It was hypothesized that hydrogen content of the films and graphitic content of the films are responsible in generating stress. The hardness is well correlated with the Raman peak intensity ratio of NCD peak to G peak.

  3. Plasma assisted metal-organic chemical vapor deposition of hard chromium nitride thin film coatings using chromium(III) acetylacetonate as the precursor

    Energy Technology Data Exchange (ETDEWEB)

    Dasgupta, Arup; Kuppusami, P.; Lawrence, Falix; Raghunathan, V.S.; Antony Premkumar, P.; Nagaraja, K.S

    2004-06-15

    A new technique has been developed for depositing hard nanocrystalline chromium nitride (CrN) thin films on metallic and ceramic substrates using plasma assisted metal-organic chemical vapor deposition (PAMOCVD) technique. In this low temperature and environment-friendly process, a volatile mixture of chromium(III) acetylacetonate and either ammonium iodide or ammonium bifluoride were used as precursors. Nitrogen and hydrogen have been used as the gas precursors. By optimizing the processing conditions, a maximum deposition rate of {approx}0.9 {mu}m/h was obtained. A comprehensive characterization of the CrN films was carried out using X-ray diffraction (XRD), microhardness, and microscopy. The microstructure of the CrN films deposited on well-polished stainless steel (SS) showed globular particles, while a relatively smooth surface morphology was observed for coatings deposited on polished yittria-stabilized zirconia (YSZ)

  4. Tensile test of a silicon microstructure fully coated with submicrometer-thick diamond like carbon film using plasma enhanced chemical vapor deposition method

    Science.gov (United States)

    Zhang, Wenlei; Uesugi, Akio; Hirai, Yoshikazu; Tsuchiya, Toshiyuki; Tabata, Osamu

    2017-06-01

    This paper reports the tensile properties of single-crystal silicon (SCS) microstructures fully coated with sub-micrometer thick diamond like carbon (DLC) film using plasma enhanced chemical vapor deposition (PECVD). To minimize the deformations or damages caused by non-uniform coating of DLC, which has high compression residual stress, released SCS specimens with the dimensions of 120 µm long, 4 µm wide, and 5 µm thick were coated from the top and bottom side simultaneously. The thickness of DLC coating is around 150 nm and three different bias voltages were used for deposition. The tensile strength improved from 13.4 to 53.5% with the increasing of negative bias voltage. In addition, the deviation in strength also reduced significantly compared to bare SCS sample.

  5. Effects of deposition parameters on microstructure and thermal conductivity of diamond films deposited by DC arc plasma jet chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    QU Quan-yan; QIU Wan-qi; ZENG De-chang; LIU Zhong-wu; DAI Ming-jiang; ZHOU Ke-song

    2009-01-01

    The uniform diamond films with 60 mm in diameter were deposited by improved DC arc plasma jet chemical vapor deposition technique. The structure of the film was characterized by scanning electronic microcopy(SEM) and laser Raman spectrometry. The thermal conductivity was measured by a photo thermal deflection technique. The effects of main deposition parameters on microstructure and thermal conductivity of the films were investigated. The results show that high thermal conductivity, 10.0 W/(K-cm), can be obtained at a CH4 concentration of 1.5% (volume fraction) and the substrate temperatures of 880-920 ℃ due to the high density and high purity of the film. A low pressure difference between nozzle and vacuum chamber is also beneficial to the high thermal conductivity.

  6. Effect of residual stresses on the strength, adhesion and wear resistance of SiC coatings obtained by plasma-enhanced chemical vapor deposition on low alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Kattamis, T.Z. (Department of Metallurgy, Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136 (United States)); Chen, M. (Department of Metallurgy, Institute of Materials Science, University of Connecticut, Storrs, CT 06269-3136 (United States)); Skolianos, S. (Aristoteles University, Thessaloniki (Greece)); Chambers, B.V. (Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States))

    1994-11-01

    Amorphous hydrogenated silicon carbide thin coatings were deposited on AISI 4340 low alloy steel wafers and thicker steel specimens by plasma-enhanced chemical vapor deposition. The cohesion of the coating, its adhesion to the substrate and its friction coefficient were evaluated by automatic scratch testing, and its wear resistance by pin-on-disk tribometry. During annealing, the residual stress attributed to hydrogen entrapment during deposition gradually changed from compressive to tensile and its rate of increase decreased with increasing annealing time. The cohesion and adhesion failure loads and the abrasive wear resistance decreased with decreasing residual compressive stress and increasing residual tensile stress. The friction coefficient between the coating surface and a diamond stylus decreased with increasing annealing time. ((orig.))

  7. Amorphous silicon carbon films prepared by hybrid plasma enhanced chemical vapor/sputtering deposition system: Effects of r.f. power

    Energy Technology Data Exchange (ETDEWEB)

    Rashid, Nur Maisarah Abdul, E-mail: nurmaisarahrashid@gmail.com [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ritikos, Richard; Othman, Maisara; Khanis, Noor Hamizah; Gani, Siti Meriam Ab. [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Muhamad, Muhamad Rasat [Chancellery Office, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia); Rahman, Saadah Abdul, E-mail: saadah@um.edu.my [Low Dimensional Materials Research Centre, Department of Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia); Chancellery Office, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia)

    2013-02-01

    Silicon carbon films were deposited using a hybrid radio frequency (r.f.) plasma enhanced chemical vapor deposition (PECVD)/sputtering deposition system at different r.f. powers. This deposition system combines the advantages of r.f. PECVD and sputtering techniques for the deposition of silicon carbon films with the added advantage of eliminating the use of highly toxic silane gas in the deposition process. Silicon (Si) atoms were sputtered from a pure amorphous silicon (a-Si) target by argon (Ar) ions and carbon (C) atoms were incorporated into the film from C based growth radicals generated through the discharge of methane (CH{sub 4}) gas. The effects of r.f. powers of 60, 80, 100, 120 and 150 W applied during the deposition process on the structural and optical properties of the films were investigated. Raman spectroscopic studies showed that the silicon carbon films contain amorphous silicon carbide (SiC) and amorphous carbon (a-C) phases. The r.f. power showed significant influence on the C incorporation in the film structure. The a-C phases became more ordered in films with high C incorporation in the film structure. These films also produced high photoluminescence emission intensity at around 600 nm wavelength as a result of quantum confinement effects from the presence of sp{sup 2} C clusters embedded in the a-SiC and a-C phases in the films. - Highlights: ► Effects of radio frequency (r.f.) power on silicon carbon (SiC) films were studied. ► Hybrid plasma enhanced chemical vapor deposition/sputtering technique was used. ► r.f. power influences C incorporation in the film structure. ► High C incorporation results in higher ordering of the amorphous C phase. ► These films produced high photoluminescence emission intensity.

  8. Morphological and optical properties changes in nanocrystalline Si (nc-Si) deposited on porous aluminum nanostructures by plasma enhanced chemical vapor deposition for Solar energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Ghrib, M., E-mail: mondherghrib@yahoo.fr [Laboratoire de Photovoltaique (L.P.V.), Centre de Recherche et des Technologies de l' Energie, BP 95, Hammam-Lif 2050 (Tunisia); Gaidi, M.; Ghrib, T.; Khedher, N. [Laboratoire de Photovoltaique (L.P.V.), Centre de Recherche et des Technologies de l' Energie, BP 95, Hammam-Lif 2050 (Tunisia); Ben Salam, M. [L3M, Department of Physics, Faculty of Sciences of Bizerte, 7021 Zarzouna (Tunisia); Ezzaouia, H. [Laboratoire de Photovoltaique (L.P.V.), Centre de Recherche et des Technologies de l' Energie, BP 95, Hammam-Lif 2050 (Tunisia)

    2011-08-15

    Photoluminescence (PL) spectroscopy was used to determine the electrical band gap of nanocrystalline silicon (nc-Si) deposited by plasma enhancement chemical vapor deposition (PECVD) on porous alumina structure by fitting the experimental spectra using a model based on the quantum confinement of electrons in Si nanocrystallites having spherical and cylindrical forms. This model permits to correlate the PL spectra to the microstructure of the porous aluminum silicon layer (PASL) structure. The microstructure of aluminum surface layer and nc-Si films was systematically studied by atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray diffraction (XRD). It was found that the structure of the nanocrystalline silicon layer (NSL) is dependent of the porosity (void) of the porous alumina layer (PAL) substrate. This structure was performed in two steps, namely the PAL substrate was prepared using sulfuric acid solution attack on an Al foil and then the silicon was deposited by plasma enhanced chemical vapor deposition (PECVD) on it. The optical constants (n and k as a function of wavelength) of the deposited films were obtained using variable angle spectroscopic ellipsometry (SE) in the UV-vis-NIR regions. The SE spectrum of the porous aluminum silicon layer (PASL) was modeled as a mixture of void, crystalline silicon and aluminum using the Cauchy model approximation. The specific surface area (SSA) was estimated and was found to decrease linearly when porosity increases. Based on this full characterization, it is demonstrated that the optical characteristics of the films are directly correlated to their micro-structural properties.

  9. Impact of Hydrocarbon Control in Ultraviolet-Assisted Restoration Process for Extremely Porous Plasma Enhanced Chemical Vapor Deposition SiOCH Films with k = 2.0

    Science.gov (United States)

    Kimura, Yosuke; Ishikawa, Dai; Nakano, Akinori; Kobayashi, Akiko; Matsushita, Kiyohiro; de Roest, David; Kobayashi, Nobuyoshi

    2012-05-01

    We investigated the effects of UV-assisted restoration on porous plasma-enhanced chemical vapor deposition (PECVD) SiOCH films with k = 2.0 and 2.3 having high porosities. By applying the UV-assisted restoration to O2-plasma-damaged films with k = 2.0 and 2.3, the recovery of the k-value was observed on the k = 2.3 film in proportion to -OH group reduction. However, the k = 2.0 film did not show recovery in spite of -OH group reduction. We found that hydrocarbon content in the k = 2.0 film was significantly increased by the UV-assisted restoration compared with the k = 2.3 film. According to these findings, we optimized the UV-assisted restoration to achieve improved controllability of the hydrocarbon uptake in the k = 2.0 film and confirmed the recovery of the k-value for O2-plasma-damaged film. Thus, adjusting the hydrocarbon uptake was crucial for restoring extremely porous SiOCH film.

  10. Si nanowires grown by Al-catalyzed plasma-enhanced chemical vapor deposition: synthesis conditions, electrical properties and application to lithium battery anodes

    Science.gov (United States)

    Toan, Le Duc; Moyen, Eric; Zamfir, Mihai Robert; Joe, Jemee; Kim, Young Woo; Pribat, Didier

    2016-01-01

    Silicon nanowires have been synhesized using Al as a catalyst. Silane (SiH4) diluted in H2 carrier gas was employed as Si precursor in a plasma enhanced chemical vapor deposition system operated at various temperatures (450 °C and 550 °C). Those growth temperatures, which are lower than the eutectic temperature in the Al-Si system (577 °C) suggests a vapor-solid-solid growth mechanism. Four point resistance measurements and back-gated current-voltage measurements indicated that silicon nanowires were heavily doped (p type), with a doping concentration of a few 1019 cm-3. We have measured hole mobility values of ˜16 cm2 V-1 s-1 at 450 °C and ˜30 cm2 V-1 s-1 at 550 °C. Transmission electron microscope analyses showed that the silicon nanowires were highly twinned even when they grow epitaxially on (111) Si substrates. We have also evaluated the use of those highly doped Si nanowires for lithium-ion battery anodes. We have observed a good cycling behavior during the first 65 charge-discharge cycles, followed by a slow capacity decay. After 150 cycles at a charge-discharge rate of 0.1 C, the electrode capacity was still 1400 mAh g-1. The ageing mechanism seems to be related to the delamination of the SiNWs from the stainless steel substrate on which they were grown.

  11. Single liquid source plasma-enhanced metalorganic chemical vapor deposition of high-quality YBa2Cu3O(7-x) thin films

    Science.gov (United States)

    Zhang, Jiming; Gardiner, Robin A.; Kirlin, Peter S.; Boerstler, Robert W.; Steinbeck, John

    1992-01-01

    High quality YBa2Cu3O(7-x) films were grown in-situ on LaAlO3 (100) by a novel single liquid source plasma-enhanced metalorganic chemical vapor deposition process. The metalorganic complexes M(thd) (sub n), (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate; M = Y, Ba, Cu) were dissolved in an organic solution and injected into a vaporizer immediately upstream of the reactor inlet. The single liquid source technique dramatically simplifies current CVD processing and can significantly improve the process reproducibility. X-ray diffraction measurements indicated that single phase, highly c-axis oriented YBa2Cu3O(7-x) was formed in-situ at substrate temperature 680 C. The as-deposited films exhibited a mirror-like surface, had transition temperature T(sub cO) approximately equal to 89 K, Delta T(sub c) less than 1 K, and Jc (77 K) = 10(exp 6) A/sq cm.

  12. Single liquid source plasma-enhanced metalorganic chemical vapor deposition of high-quality YBa2Cu3O(7-x) thin films

    Science.gov (United States)

    Zhang, Jiming; Gardiner, Robin A.; Kirlin, Peter S.; Boerstler, Robert W.; Steinbeck, John

    1992-01-01

    High quality YBa2Cu3O(7-x) films were grown in-situ on LaAlO3 (100) by a novel single liquid source plasma-enhanced metalorganic chemical vapor deposition process. The metalorganic complexes M(thd) (sub n), (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate; M = Y, Ba, Cu) were dissolved in an organic solution and injected into a vaporizer immediately upstream of the reactor inlet. The single liquid source technique dramatically simplifies current CVD processing and can significantly improve the process reproducibility. X-ray diffraction measurements indicated that single phase, highly c-axis oriented YBa2Cu3O(7-x) was formed in-situ at substrate temperature 680 C. The as-deposited films exhibited a mirror-like surface, had transition temperature T(sub cO) approximately equal to 89 K, Delta T(sub c) less than 1 K, and Jc (77 K) = 10(exp 6) A/sq cm.

  13. Characterization of amorphous hydrogenated carbon formed by low-pressure inductively coupled plasma enhanced chemical vapor deposition using multiple low-inductance antenna units.

    Science.gov (United States)

    Tsuda, Osamu; Ishihara, Masatou; Koga, Yoshinori; Fujiwara, Shuzo; Setsuhara, Yuichi; Sato, Naoyuki

    2005-03-24

    Three-dimensional plasma enhanced chemical vapor deposition (CVD) of hydrogenated amorphous carbon (a-C:H) has been demonstrated using a new type high-density volumetric plasma source with multiple low-inductance antenna system. The plasma density in the volume of phi 200 mm x 100 mm is 5.1 x 10(10) cm(-3) within +/-5% in the lateral directions and 5.2 x 10(10)cm(-3) within +/-10% in the axial direction for argon plasma under the pressure of 0.1 Pa and the total power as low as 400 W. The uniformity of the thickness and refractive index is within +/-3.5% and +/-1%, respectively, for the a-C:H films deposited on the substrates placed on the six side walls, the top of the phi 60 mm x 80 mm hexagonal substrate holder in the pure toluene plasma under the pressure is as low as 0.04 Pa, and the total power is as low as 300 W. It is also found that precisely controlled ion bombardment by pulse biasing led to the explicit observation in Raman and IR spectra of the transition from polymer-like structure to diamond-like structure accompanied by dehydrogenation due to ion bombardment. Moreover, it is also concluded that the pulse biasing technique is effective for stress reduction without a significant degradation of hardness. The stress of 0.6 GPa and the hardness of 15 GPa have been obtained for 2.0 microm thick films deposited with the optimized deposition conditions. The films are durable for the tribology test with a high load of 20 N up to more than 20,000 cycles, showing the specific wear rate and the friction coefficient were 1.2 x 10(-7) mm3/Nm and 0.04, respectively.

  14. Tungsten chemical vapor deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, Kiichi; Takeda, Nobuo.

    1993-07-13

    A tungsten chemical vapor deposition method is described, comprising: a first step of selectively growing a first thin tungsten film of a predetermined thickness in a desired region on the surface of a silicon substrate by reduction of a WF[sub 6] gas introduced into an atmosphere of a predetermined temperature containing said silicon substrate; and a second step of selectively growing a second tungsten film of a predetermined thickness on said first thin tungsten film by reduction of said WF[sub 6] with a silane gas further introduced into said atmosphere, wherein the surface state of said substrate is monitored by a pyrometer and the switching from said first step to said second step is performed when the emissivity of infrared light from the substrate surfaces reaches a predetermined value.

  15. Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) yields better Hydrolytical Stability of Biocompatible SiOx Thin Films on Implant Alumina Ceramics compared to Rapid Thermal Evaporation Physical Vapor Deposition (PVD).

    Science.gov (United States)

    Böke, Frederik; Giner, Ignacio; Keller, Adrian; Grundmeier, Guido; Fischer, Horst

    2016-07-20

    Densely sintered aluminum oxide (α-Al2O3) is chemically and biologically inert. To improve the interaction with biomolecules and cells, its surface has to be modified prior to use in biomedical applications. In this study, we compared two deposition techniques for adhesion promoting SiOx films to facilitate the coupling of stable organosilane monolayers on monolithic α-alumina; physical vapor deposition (PVD) by thermal evaporation and plasma enhanced chemical vapor deposition (PE-CVD). We also investigated the influence of etching on the formation of silanol surface groups using hydrogen peroxide and sulfuric acid solutions. The film characteristics, that is, surface morphology and surface chemistry, as well as the film stability and its adhesion properties under accelerated aging conditions were characterized by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and tensile strength tests. Differences in surface functionalization were investigated via two model organosilanes as well as the cell-cytotoxicity and viability on murine fibroblasts and human mesenchymal stromal cells (hMSC). We found that both SiOx interfaces did not affect the cell viability of both cell types. No significant differences between both films with regard to their interfacial tensile strength were detected, although failure mode analyses revealed a higher interfacial stability of the PE-CVD films compared to the PVD films. Twenty-eight day exposure to simulated body fluid (SBF) at 37 °C revealed a partial delamination of the thermally deposited PVD films whereas the PE-CVD films stayed largely intact. SiOx layers deposited by both PVD and PE-CVD may thus serve as viable adhesion-promoters for subsequent organosilane coupling agent binding to α-alumina. However, PE-CVD appears to be favorable for long-term direct film exposure to aqueous

  16. Properties of silicon nitride thin overlays deposited on optical fibers — Effect of fiber suspension in radio frequency plasma-enhanced chemical vapor deposition reactor

    Energy Technology Data Exchange (ETDEWEB)

    Śmietana, M., E-mail: M.Smietana@elka.pw.edu.pl [Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, Warsaw 00-662 (Poland); Dominik, M.; Myśliwiec, M.; Kwietniewski, N. [Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, Warsaw 00-662 (Poland); Mikulic, P. [Centre de Recherche en Photonique, Université du Québec en Outaouais, 101 rue Saint-Jean-Bosco, Gatineau, J8X 3X7, Québec (Canada); Witkowski, B.S. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, Warsaw 02-666 (Poland); Bock, W.J. [Centre de Recherche en Photonique, Université du Québec en Outaouais, 101 rue Saint-Jean-Bosco, Gatineau, J8X 3X7, Québec (Canada)

    2016-03-31

    This work discusses the effect of sample suspension in radio frequency plasma-enhanced chemical vapor deposition process on properties of the obtained overlays. Silicon nitride (SiN{sub x}) overlays were deposited on flat silicon wafers and cylindrical fused silica optical fibers. The influence of the suspension height and fiber diameter on SiN{sub x} deposition rate is investigated. It has been found that thickness of the SiN{sub x} overlay significantly increases with suspension height, and the deposition rate depends on fiber dimensions. Moreover, the SiN{sub x} overlays were also deposited on long-period gratings (LPGs) induced in optical fiber. Measurements of the LPG spectral response combined with its numerical simulations allowed for a discussion on properties of the deposited overlay. The measurements have proven higher overlay deposition rate on the suspended fiber than on flat Si wafer placed on the electrode. Results of this work are essential for precise tuning of the functional properties of new generations of optical devices such as optical sensors, filters and resonators, which typically are based on optical fibers and require the overlays with well defined properties. - Highlights: • The effect of optical fiber suspension in plasma process is discussed. • The deposition rate of silicon nitride (SiN{sub x}) overlay depends on fiber dimensions. • Thickness of the SiN{sub x} overlay strongly increases with suspension height. • Measurements and simulations of long-period grating confirms experimental results.

  17. Performance Improvement of Microcrystalline p-SiC/i-Si/n-Si Thin Film Solar Cells by Using Laser-Assisted Plasma Enhanced Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Hsin-Ying Lee

    2014-01-01

    Full Text Available The microcrystalline p-SiC/i-Si/n-Si thin film solar cells treated with hydrogen plasma were fabricated at low temperature using a CO2 laser-assisted plasma enhanced chemical vapor deposition (LAPECVD system. According to the micro-Raman results, the i-Si films shifted from 482 cm−1 to 512 cm−1 as the assisting laser power increased from 0 W to 80 W, which indicated a gradual transformation from amorphous to crystalline Si. From X-ray diffraction (XRD results, the microcrystalline i-Si films with (111, (220, and (311 diffraction were obtained. Compared with the Si-based thin film solar cells deposited without laser assistance, the short-circuit current density and the power conversion efficiency of the solar cells with assisting laser power of 80 W were improved from 14.38 mA/cm2 to 18.16 mA/cm2 and from 6.89% to 8.58%, respectively.

  18. Characterization of the SiO2 film deposited by using plasma enhanced chemical vapor deposition (PECVD with TEOS/N2/O2

    Directory of Open Access Journals (Sweden)

    Meysam Zarchi

    2013-12-01

    Full Text Available The purpose of this study was to examine how certain parameters like temperature, pressure, and gas composition affect the characteristics of SiO2 film by Plasma Enhanced Chemical Vapor Deposition (PECVD. We used of low temperature and an inductively coupled plasma (ICP for various with gas mixtures of TEOS/N2/O2 at a given RF power and dc bias voltage. For the gas mixture with 40 sccm of N2 in TEOS, 100 standard cubic centimeters per minute (sccm of N2, and 500 sccm of O2, transparent and scratch-resistant SiO2 could be deposited with a deposition rate of 30 nm/min when RF power of 500 W and a dc-bias voltage of 350V were applied. The characteristics of the deposited SiO2, such as the composition, the binding energy, etc. were compared with the SiO2 deposited by using thermal CVD and evaporation. It was found that the SiO2 deposited by PECVD with TEOS/N2/O2 exhibited properties typical of SiO2 deposited applying thermal CVD and evaporation. The surface roughness of the 100 nm-thick SiO2 deposited by PECVD was similar to that of the substrate.

  19. CHARACTERISTICS OF A FAST RISE TIME POWER SUPPLY FOR A PULSED PLASMA REACTOR FOR CHEMICAL VAPOR DESTRUCTION

    Science.gov (United States)

    Rotating spark gap devices for switching high-voltage direct current (dc) into a corona plasma reactor can achieve pulse rise times in the range of tens of nanoseconds. The fast rise times lead to vigorous plasma generation without sparking at instantaneous applied voltages highe...

  20. Impact of In doping on GeTe phase-change materials thin films obtained by means of an innovative plasma enhanced metalorganic chemical vapor deposition process

    Science.gov (United States)

    Szkutnik, P. D.; Aoukar, M.; Todorova, V.; Angélidès, L.; Pelissier, B.; Jourde, D.; Michallon, P.; Vallée, C.; Noé, P.

    2017-03-01

    We investigated the deposition and the phase-change properties of In-doped GeTe thin films obtained by plasma enhanced metalorganic chemical vapor deposition and doped with indium using a solid delivery system. The sublimated indium precursor flow rate was calculated as a function of sublimation and deposition parameters. Indium related optical emission recorded by means of optical emission spectroscopy during deposition plasma allowed proposing the dissociation mechanisms of the [In(CH3)2N(CH3)2]2 solid precursor. In particular, using an Ar + H2 + NH3 deposition plasma, sublimated indium molecules are completely dissociated and do not induce by-product contamination by addition of nitrogen or carbon in the films. X-ray photoelectron spectroscopy evidences the formation of In-Te bonds in amorphous as-deposited In-doped GeTe films. The formation of an InTe phase after 400 °C annealing is also evidenced by means of X-ray diffraction analysis. The crystallization temperature Tx, deduced from monitoring of optical reflectivity of In-doped GeTe films with doping up to 11 at. % slightly varies as a function of the In dopant level with a decrease of Tx down to a minimum value for an In doping level of about 6-8 at. %. In this In doping range, the structure of crystallized In-GeTe films changes and is dominated by the presence of a crystalline In2Te3 phase. Finally, the Kissinger activation energy for crystallization Ea is showing to monotonically decrease as the indium content in the GeTe film is increased indicating a promising effect of In doping on crystallization speed in memory devices while keeping a good thermal stability for data retention.

  1. Anisotropic growth of single-crystal graphite plates by nickel-assisted microwave-plasma chemical-vapor deposition

    Science.gov (United States)

    Badzian, Teresa; Badzian, Andrzej; Roy, Rustum; Cheng, Shang-Cong

    2000-02-01

    Growth of single-crystal graphite free-standing plates has been achieved by a microwavehydrogen-plasma etching of graphite powder and nickel mesh. The plates resemble a knife blade and grow in the direction with long crystals exceeding 100 μm. Hexagonal growth features at the edges and electron diffraction patterns confirm the single-crystal nature of these ultrathin plates. Electron microprobe and Raman spectroscopy indicate the presence of graphite. Diamond crystals nucleate on these plates and they grow simultaneously. We suggest that the paradoxical growth of graphite in a hydrogen plasma, under conditions in which graphite is usually etched away, is possible because of a protective coating by a Ni-C-H phase. This thin coating allows for transport of carbon atoms from the gas phase to the growing graphite surface.

  2. Optical and morphological properties of SiN{sub x}/Si amorphous multilayer structures grown by Plasma Enhanced Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Santana, G.; Melo, O. de; Monroy, B.M.; Fandino, J.; Ortiz, A.; Alonso, J.C. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Cd. Universitaria, A.P. 70-360, Coyoacan (Mexico); Aguilar-Hernandez, J.; Cruz, F.; Contreras-Puentes, G. [Escuela Superior de Fisica y Matematicas del Instituto Politecnico Nacional; Edificio 9, U.P.A.L.M. (Mexico)

    2005-08-01

    Very thin layers of Si were grown in between silicon nitride layers using Plasma Enhanced Chemical Vapor Deposition (PECVD) technique and SiH{sub 2}Cl{sub 2}/H{sub 2}/NH{sub 3} mixtures. Deposition conditions were selected to favor Si cluster formation. Room Temperature Photoluminescence (RT-PL) and optical transmission in different ranges were used to evaluate the optical and structural properties of the films. Scanning Electron Microscopy (SEM) of the cross section of cleaved samples allowed to observe a clear pattern of Si clusters embedded in the SiN matrix. The UV-VIS absorption spectra present two band edges. We assume that the higher band gap is due to the amorphous Si clusters. RT-PL spectra are characterized by two broad bands: one centered at 1.5 eV and the other at 2.1 eV. The broad luminescence centered at 2.1 eV could be associated with the higher band gap observed in absorption spectrum. After vacuum annealing of the samples at 400 and ordm;C, the band at 2.1 eV disappears. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Growth of Ge nanoparticles on SiO{sub 2}/Si interfaces during annealing of plasma enhanced chemical vapor deposited thin films

    Energy Technology Data Exchange (ETDEWEB)

    Foss, S. [Department of Physics, University of Oslo, PO Box 1048-Blindern, N-0316 (Norway)]. E-mail: stefoss@fys.uio.no; Finstad, T.G. [Department of Physics, University of Oslo, PO Box 1048-Blindern, N-0316 (Norway); Dana, A. [Department of Physics, Bilkent University, 06800 Ankara (Turkey); Aydinli, A. [Department of Physics, Bilkent University, 06800 Ankara (Turkey)

    2007-06-04

    Multilayer germanosilicate (Ge:SiO{sub 2}) films have been grown by plasma enhanced chemical vapor deposition. Each Ge:SiO{sub 2} layer is separated by a pure SiO{sub 2} layer. The samples were heat treated at 900 deg. C for 15 and 45 min. Transmission electron microscopy investigations show precipitation of particles in the layers of highest Ge concentration. Furthermore there is evidence of diffusion between the layers. This paper focuses mainly on observed growth of Ge particles close to the interface, caused by Ge diffusion from the Ge:SiO{sub 2} layer closest to the interface through a pure SiO{sub 2} layer and to the interface. The particles grow as spheres in a direction away from the interface. Particles observed after 15 min anneal time are 4 nm in size and are amorphous, while after 45 min anneal time they are 7 nm in size and have a crystalline diamond type Ge structure.

  4. Formation and characterization of the MgO protecting layer deposited by plasma-enhanced metal-organic chemical-vapor deposition

    CERN Document Server

    Kang, M S; Byun, J C; Kim, D S; Choi, C K; Lee, J Y; Kim, K H

    1999-01-01

    MgO films were prepared on Si(100) and soda-lime glass substrates by using plasma-enhanced metal-organic chemical-vapor deposition. Various ratios of the O sub 2 /CH sub 3 MgO sup t Bu gas mixture and various gas flow rates were tested for the film fabrications. Highly (100)-oriented MgO films with good crystallinity were obtained with a 10 sccm CH sub 3 MgO sup t Bu flow without an O sub 2 gas flow. About 5 % carbon was contained in all the MgO films. The refractive index and the secondary electron emission coefficient for the best quality film were 1.43 and 0.45, respectively. The sputtering rate was about 0.2 nm/min for 10 sup 1 sup 1 cm sup - sup 3 Ar sup + ion density. Annealing at 500 .deg. C in an Ar ambient promoted the grain size without inducing a phase transition.

  5. Nanocrystalline-Si-dot multi-layers fabrication by chemical vapor deposition with H-plasma surface treatment and evaluation of structure and quantum confinement effects

    Directory of Open Access Journals (Sweden)

    Daisuke Kosemura

    2014-01-01

    Full Text Available 100-nm-thick nanocrystalline silicon (nano-Si-dot multi-layers on a Si substrate were fabricated by the sequential repetition of H-plasma surface treatment, chemical vapor deposition, and surface oxidation, for over 120 times. The diameter of the nano-Si dots was 5–6 nm, as confirmed by both the transmission electron microscopy and X-ray diffraction analysis. The annealing process was important to improve the crystallinity of the nano-Si dot. We investigated quantum confinement effects by Raman spectroscopy and photoluminescence (PL measurements. Based on the experimental results, we simulated the Raman spectrum using a phenomenological model. Consequently, the strain induced in the nano-Si dots was estimated by comparing the experimental and simulated results. Taking the estimated strain value into consideration, the band gap modulation was measured, and the diameter of the nano-Si dots was calculated to be 5.6 nm by using PL. The relaxation of the q ∼ 0 selection rule model for the nano-Si dots is believed to be important to explain both the phenomena of peak broadening on the low-wavenumber side observed in Raman spectra and the blue shift observed in PL measurements.

  6. Plasma enhanced chemical vapor deposition of Cr{sub 2}O{sub 3} thin films using chromium hexacarbonyl (Cr(CO){sub 6}) precursor

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jinwen [Center for Materials for Information Technology and Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, AL 35487 (United States)], E-mail: wang006@bama.ua.edu; Gupta, Arunava; Klein, Tonya M. [Center for Materials for Information Technology and Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, AL 35487 (United States)

    2008-09-01

    Chromium oxide (Cr{sub 2}O{sub 3}) thin films have been deposited by plasma enhanced chemical vapor deposition on c-cut sapphire (Al{sub 2}O{sub 3}) and oxidized silicon substrates at temperatures between 250 and 400 deg. C using the precursor chromium hexacarbonyl (Cr(CO){sub 6}). The film growth rate ranges between 5 and 14 A/min, with the growth rate going through a maximum at 300 deg. C before decreasing at higher temperature, suggesting the presence of competing deposition and desorption reaction channels. Scanning electron microscope images indicate that the density of grains and film crystallinity increases with increasing substrate temperatures, while atomic force microscopy shows an overall decrease in film roughness with increasing temperature. Normal {theta} - 2{theta} Bragg X-ray diffraction results show that films deposited on SiO{sub 2} are polycrystalline, while those on sapphire have a preferred (0 0 0 l) orientation. The epitaxial nature of the film growth on Al{sub 2}O{sub 3} has been confirmed from the symmetry of off-axis X-ray scans.

  7. Tribological properties and thermal stability of hydrogenated, silicon/nitrogen-coincorporated diamond-like carbon films prepared by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Nakazawa, Hideki; Okuno, Saori; Magara, Kohei; Nakamura, Kazuki; Miura, Soushi; Enta, Yoshiharu

    2016-12-01

    We have deposited hydrogenated, silicon/nitrogen-incorporated diamond-like carbon (Si-N-DLC) films by plasma-enhanced chemical vapor deposition using hexamethyldisilazane [((CH3)3Si)2NH; HMDS] as the Si and N source, and compared the tribological performance and thermal stability of the Si-N-DLC films with those of hydrogenated, Si-incorporated DLC (Si-DLC) films prepared using dimethylsilane [SiH2(CH3)2] as the Si source. The deposited films were annealed at 723-873 K in air atmosphere. The friction coefficients of hydrogenated DLC films after annealing significantly increased at the initial stages of friction tests. On the other hand, the friction coefficients of the Si-N-DLC films deposited at an HMDS flow ratio [HMDS/(HMDS+CH4)] of 2.27% remained low after the annealing even at 873 K. We found that the wear rate of the Si-N-DLC film deposited at 2.27% and -1000 V remained almost unchanged after the annealing at 873 K, whereas that of the Si-DLC film with a similar Si fraction deposited at -1000 V significantly increased after the annealing at 773 K.

  8. Hydrogenated amorphous carbon-nitride films deposited on Si(100) by direct-current saddle-field plasma-enhanced chemical-vapor deposition

    CERN Document Server

    Jang, H K; Lee, Y S; Whangbo, S W; Whang, C N; Yoo, Y Z; Kim, H G

    1999-01-01

    Hydrogenated amorphous carbon nitride [a-C:H(N)] films were deposited using dc saddle-field plasma-enhanced chemical-vapor deposition. The structural and the compositional changes induced in the films by the different flow-rate ratios of N sub 2 to CH sub 4 (n sub N sub 2 /n sub C sub H sub sub 4) were investigated using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The deposition rate of the films abruptly decreased upon increasing the n sub N sub 2 /n sub C sub H sub sub 4 ratio. However, for n sub N sub 2 /n sub C sub H sub sub 4 >0.5, the deposition rate slightly decreased with increasing n sub N sub 2 /n sub C sub H sub sub 4. The ratio of N to C (N/C) of the films saturated to 0.25 with increasing n sub N sub 2 /n sub C sub H sub sub 4. The numbers of N-H and C ident to N bonds in the films increased with increasing n sub N sub 2 /n sub C sub H sub sub 4 , but the number of C-H bonds decreased. The optical band-gap energy of the films decreased from 2.53 eV to 2.3 eV as t...

  9. Simultaneous synthesis of nanodiamonds and graphene via plasma enhanced chemical vapor deposition (MW PE-CVD) on copper.

    Science.gov (United States)

    Gottlieb, Steven; Wöhrl, Nicolas; Schulz, Stephan; Buck, Volker

    2016-01-01

    The simultaneous growth of both nanodiamonds and graphene on copper samples is described for the first time. A PE-CVD process is used to synthesize graphene layers and nanodiamond clusters from a hydrogen/methane gas mixture as it is typically done successfully in thermal CVD processes for graphene synthesis. However, the standard thermal CVD process is not without problems since the deposition of graphene is affected by the evaporation of a notable amount of copper caused by the slow temperature increase typical for thermal CVD resulting in a long process time. In sharp contrast, the synthesis of graphene by PE-CVD can circumvent this problem by substantially shortening the process time at holding out the prospect of a lower substrate temperature. The reduced thermal load and the possibility to industrially scale-up the PE-CVD process makes it a very attractive alternative to the thermal CVD process with respect to the graphene production in the future. Nanodiamonds are synthesized in PE-CVD reactors for a long time because these processes offer a high degree of control over the film's nanostructure and simultaneously providing a significant high deposition rate. To model the co-deposition process, the three relevant macroscopic parameters (pressure, gas mixture and microwave power) are correlated with three relevant process properties (plasma ball size, substrate temperature and C2/Hα-ratio) and the influence on the quality of the deposited carbon allotropes is investigated. For the evaluation of the graphene as well as the nanodiamond quality, Raman spectroscopy used whereas the plasma properties are measured by optical methods. It is found that the diamond nucleation can be influenced by the C2/Hα-ratio in the plasma, while the graphene quality remains mostly unchanged by this parameter. Moreover it is derived from the experimental data that the direct plasma contact with the copper surface is beneficial for the nucleation of the diamond while the growth and

  10. HANFORD CHEMICAL VAPORS WORKER CONCERNS & EXPOSURE EVALUATION

    Energy Technology Data Exchange (ETDEWEB)

    ANDERSON, T.J.

    2006-12-20

    Chemical vapor emissions from underground hazardous waste storage tanks on the Hanford site in eastern Washington State are a potential concern because workers enter the tank farms on a regular basis for waste retrievals, equipment maintenance, and surveillance. Tank farm contractors are in the process of retrieving all remaining waste from aging single-shell tanks, some of which date to World War II, and transferring it to newer double-shell tanks. During the waste retrieval process, tank farm workers are potentially exposed to fugitive chemical vapors that can escape from tank headspaces and other emission points. The tanks are known to hold more than 1,500 different species of chemicals, in addition to radionuclides. Exposure assessments have fully characterized the hazards from chemical vapors in half of the tank farms. Extensive sampling and analysis has been done to characterize the chemical properties of hazardous waste and to evaluate potential health hazards of vapors at the ground surface, where workers perform maintenance and waste transfer activities. Worker concerns. risk communication, and exposure assessment are discussed, including evaluation of the potential hazards of complex mixtures of chemical vapors. Concentrations of vapors above occupational exposure limits-(OEL) were detected only at exhaust stacks and passive breather filter outlets. Beyond five feet from the sources, vapors disperse rapidly. No vapors have been measured above 50% of their OELs more than five feet from the source. Vapor controls are focused on limited hazard zones around sources. Further evaluations of vapors include analysis of routes of exposure and thorough analysis of nuisance odors.

  11. Effect of nickel oxide seed layers on annealed-amorphous titanium oxide thin films prepared using plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Cheng-Yang; Hong, Shao-Chyang [Institute of Electro-Optical and Materials Science, National Formosa University, Huwei, Yunlin, 63201, Taiwan (China); Hwang, Fu-Tsai [Department of Electro-Optical Engineering, National United University, Miao-Li, 36003, Taiwan (China); Lai, Li-Wen [ITRI South, Industrial Technology Research Institute, Liujia, Tainan, 73445, Taiwan (China); Lin, Tan-Wei [Institute of Electro-Optical and Materials Science, National Formosa University, Huwei, Yunlin, 63201, Taiwan (China); Liu, Day-Shan, E-mail: dsliu@sunws.nfu.edu.tw [Institute of Electro-Optical and Materials Science, National Formosa University, Huwei, Yunlin, 63201, Taiwan (China)

    2011-10-31

    The effect of a nickel oxide (NiO{sub x}) seed layer on the crystallization and photocatalytic activity of the sequentially plasma-enhanced chemical vapor deposited amorphous titanium oxide (TiO{sub x}) thin film processed by a post-annealing process was investigated. The evolution of the crystalline structures, chemical bond configurations, and surface/cross-sectional morphologies of the annealed TiO{sub x} films, with and without a NiO{sub x} seed layer, was examined using X-ray diffractometer, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, atomic force microscopy, and field emission scanning electron microscope measurements. Thermo- and photo-induced hydrophilicity was determined by measuring the contact angle of water droplet. Photocatalytic activity after UV light irradiation was evaluated from the decolorization of a methylene blue solution. The crystallization temperature of the TiO{sub x} film, deposited on a NiO{sub x} seed layer, was found to be lower than that of a pure TiO{sub x} film, further improving the thermo- and photo-induced surface super-hydrophilicity. The TiO{sub x} film deposited onto the NiO{sub x} seed layer, resulting in significant cluster boundaries, showed a rough surface morphology and proved to alleviate the anatase crystal growth by increasing the post-annealing temperature, which yielded a more active surface area and prohibited the recombination of photogenerated electrons and holes. The photocatalytic activity of the NiO{sub x}/TiO{sub x} system with such a textured surface therefore was enhanced and optimized through an adequate post-annealing process.

  12. Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application.

    Science.gov (United States)

    Chao, Chung-Hua; Wei, Da-Hua

    2015-10-03

    In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 (o)C. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 (o)C. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance. For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 (o)C by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application.

  13. Synthesis, structural and field emission properties of multiwall carbon nanotube-graphene-like nanocarbon hybrid films grown by microwave plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chockalingam, Sreekumar, E-mail: sreekuc@nplindia.org [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Bisht, Atul [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Kesarwani, A.K. [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Singh, B.P. [Physics and Engineering of Carbon, Materials Physics and Engineering Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Chand, Jagdish [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Singh, V.N. [Electron and Ion Microscopy, Sophisticated and Analytical Instruments, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India)

    2015-04-15

    Multiwall carbon nanotube (MWCNT)-graphene-like nanocarbon hybrid films were directly deposited on nickel substrate without any pre-treatment in a single-step by microwave plasma enhanced chemical vapor deposition (MW PECVD) technique at 600 °C. The effects of hydrogen partial pressure on the growth of MWCNT-graphene-like nanocarbon hybrid films and their structural, morphological and field emission properties were investigated. High resolution scanning electron microscope revealed MWCNT structure. High resolution transmission electron microscope images and Raman spectra revealed graphene-like nanocarbon film. Raman spectra showed 2D, G, D and D + G peaks at approximately 2690, 1590, 1350 and 2930 cm{sup −1}, respectively. The minimum threshold field for electron emission was found to be 3.6 V/μm corresponding to 1 μA/cm{sup 2} current density for the MWCNT-graphene-like nanocarbon hybrid film deposited at 20 Torr pressure whereas the maximum current density of 0.12 mA/cm{sup 2} and field enhancement factor of ∼3356 was obtained for the sample deposited at 5 Torr pressure. - Highlights: • MWCNT-graphene-like nanocarbon hybrid films were synthesized by MWPECVD technique. • Effect of pressure on the structural and field emission properties has been studied. • FESEM revealed MWCNT and HRTEM revealed graphene-like nanocarbon film structure. • Minimum E{sub T} = 3.6 V/μm with β = 3164 has been obtained in the film deposited at 20 Torr. • Maximum J = 0.12 mA/cm{sup 2} with β = 3356 has been obtained in the film deposited at 5 Torr.

  14. High-temperature degradation in plasma-enhanced chemical vapor deposition Al{sub 2}O{sub 3} surface passivation layers on crystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Kühnhold, Saskia [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, D-79110 Freiburg (Germany); Freiburg Materials Research Center FMF, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Straße 21 (Germany); Saint-Cast, Pierre; Kafle, Bishal; Hofmann, Marc [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, D-79110 Freiburg (Germany); Colonna, Francesco [Freiburg Materials Research Center FMF, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Straße 21 (Germany); Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg (Germany); Zacharias, Margit [Department of Microsystems Engineering IMTEK, Albert-Ludwigs-Universität Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg (Germany)

    2014-08-07

    In this publication, the activation and degradation of the passivation quality of plasma-enhanced chemical vapor deposited aluminum oxide (Al{sub 2}O{sub 3}) layers with different thicknesses (10 nm, 20 nm, and 110 nm) on crystalline silicon (c-Si) during long and high temperature treatments are investigated. As indicated by Fourier Transform Infrared Spectroscopy, the concentration of tetrahedral and octahedral sites within the Al{sub 2}O{sub 3} layer changes during temperature treatments and correlates with the amount of negative fixed charges at the Si/Al{sub 2}O{sub 3} interface, which was detected by Corona Oxide Characterization of Semiconductors. Furthermore, during a temperature treatment at 820 °C for 30 min, the initial amorphous Al{sub 2}O{sub 3} layer crystallize into the γ-Al{sub 2}O{sub 3} structure and was enhanced by additional oxygen as was proven by x-ray diffraction measurements and underlined by Density Functional Theory simulations. The crystallization correlates with the increase of the optical density up to 20% while the final Al{sub 2}O{sub 3} layer thickness decreases at the same time up to 26%. All observations described above were detected to be Al{sub 2}O{sub 3} layer thickness dependent. These observations reveal novel aspects to explain the temperature induced passivation and degradation mechanisms of Al{sub 2}O{sub 3} layers at a molecular level like the origin of the negative fixe charges at the Si/SiO{sub x}/Al{sub 2}O{sub 3} interface or the phenomena of blistering. Moreover, the crystal phase of Al{sub 2}O{sub 3} does not deliver good surface passivation due to a high concentration of octahedral sites leading to a lower concentration of negative fixed charges at the interface.

  15. Nanocrystalline diamond thin films on titanium-6 aluminum-4 vanadium alloy temporomandibular joint prosthesis simulants by microwave plasma chemical vapor deposition

    Science.gov (United States)

    Fries, Marc Douglas

    A course of research has been performed to assess the suitability of nanocrystal-line diamond (NCD) films on Ti-6Al-4V alloy as wear-resistant coatings in biomedical implant use. A series of temporomandibular (TMJ) joint condyle simulants were polished and acid-passivated as per ASTM F86 standard for surface preparation of implants. A 3-mum-thick coating of NCD film was deposited by microwave plasma chemical vapor deposition (MPCVD) over the hemispherical articulation surfaces of the simulants. Plasma chemistry conditions were measured and monitored by optical emission spectroscopy (OES), using hydrogen as a relative standard. The films consist of diamond grains around 20 nm in diameter embedded in an amorphous carbon matrix, free of any detectable film stress gradient. Hardness averages 65 GPa and modulus measures 600 GPa at a depth of 250 nm into the film surface. A diffuse film/substrate boundary produces a minimal film adhesion toughness (GammaC) of 158 J/m2. The mean RMS roughness is 14.6 +/- 4.2 nm, with an average peak roughness of 82.6 +/- 65.9 nm. Examination of the surface morphology reveals a porous, dendritic surface. Wear testing resulted in two failed condylar coatings out of three tests. No macroscopic delamination was found on any sample, but micron-scale film pieces broke away, exposing the substrate. Electrochemical corrosion testing shows a seven-fold reduction in corrosion rate with the application of an NCD coating as opposed to polished, passivated Ti-6Al-4V, producing a corrosion rate comparable to wrought Co-Cr-Mo. In vivo biocompatibility testing indicates that implanted NCD films did not elicit an immune response in the rabbit model, and osteointegration was apparent for both compact and trabecular bone on both NCD film and bare Ti-6Al-4V. Overall, NCD thin film material is reasonably smooth, biocompatible, and very well adhered. Wear testing indicates that this material is unacceptable for use in demanding TMJ applications without

  16. Chemical vapor deposition of mullite coatings

    Science.gov (United States)

    Sarin, Vinod; Mulpuri, Rao

    1998-01-01

    This invention is directed to the creation of crystalline mullite coatings having uniform microstructure by chemical vapor deposition (CVD). The process comprises the steps of establishing a flow of reactants which will yield mullite in a CVD reactor, and depositing a crystalline coating from the reactant flow. The process will yield crystalline coatings which are dense and of uniform thickness.

  17. Making Ceramic Fibers By Chemical Vapor

    Science.gov (United States)

    Revankar, Vithal V. S.; Hlavacek, Vladimir

    1994-01-01

    Research and development of fabrication techniques for chemical vapor deposition (CVD) of ceramic fibers presented in two reports. Fibers of SiC, TiB2, TiC, B4C, and CrB2 intended for use as reinforcements in metal-matrix composite materials. CVD offers important advantages over other processes: fibers purer and stronger and processed at temperatures below melting points of constituent materials.

  18. Laser Velocimetry of Chemical Vapor Deposition Flows

    Science.gov (United States)

    1993-01-01

    Laser velocimetry (LV) is being used to measure the gas flows in chemical vapor deposition (CVD) reactors. These gas flow measurements can be used to improve industrial processes in semiconductor and optical layer deposition and to validate numerical models. Visible in the center of the picture is the graphite susceptor glowing orange-hot at 600 degrees C. It is inductively heated via the copper cool surrounding the glass reactor.

  19. Kinetics of wet sodium vapor complex plasma

    Science.gov (United States)

    Mishra, S. K.; Sodha, M. S.

    2014-04-01

    In this paper, we have investigated the kinetics of wet (partially condensed) Sodium vapor, which comprises of electrons, ions, neutral atoms, and Sodium droplets (i) in thermal equilibrium and (ii) when irradiated by light. The formulation includes the balance of charge over the droplets, number balance of the plasma constituents, and energy balance of the electrons. In order to evaluate the droplet charge, a phenomenon for de-charging of the droplets, viz., evaporation of positive Sodium ions from the surface has been considered in addition to electron emission and electron/ion accretion. The analysis has been utilized to evaluate the steady state parameters of such complex plasmas (i) in thermal equilibrium and (ii) when irradiated; the results have been graphically illustrated. As a significant outcome irradiated, Sodium droplets are seen to acquire large positive potential, with consequent enhancement in the electron density.

  20. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Ni [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Jiang, Shiuh-Jen, E-mail: sjjiang@faculty.nsysu.edu.tw [Department of Chemistry, National Sun Yat-sen University, Kaohsiung 80424, Taiwan (China); Department of Medical Laboratory Science and Biotechnology, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Chen, Yen-Ling [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Sahayam, A.C. [National Centre for Compositional Characterisation of Materials (CCCM), Hyderabad (India)

    2015-02-20

    Highlights: • Determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions in a single run. • Accurate analysis using isotope dilution and standard addition methods. • Vapor generation ICP-MS yielded superior detection limits compared to ETV-ICP-MS. • No sample dissolution increased sample through put. • Analysis of GBW09305 Cosmetic (Cream) reference material for accuracy. - Abstract: A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL{sup −1} Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g{sup −1} for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample.

  1. Thin films of hydrogenated amorphous carbon (a-C:H) obtained through chemical vapor deposition assisted by plasma; Peliculas delgadas de carbono amorfo hidrogenado (a-C:H) obtenidas mediante deposito quimico de vapores asistido por plasma

    Energy Technology Data Exchange (ETDEWEB)

    Mejia H, J.A.; Camps C, E.E.; Escobar A, L.; Romero H, S.; Chirino O, S. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Muhl S, S. [IIM-UNAM, 04510 Mexico D.F. (Mexico)

    2004-07-01

    Films of hydrogenated amorphous carbon (a-C:H) were deposited using one source of microwave plasma with magnetic field (type ECR), using mixtures of H{sub 2}/CH{sub 4} in relationship of 80/20 and 95/05 as precursory gases, with work pressures of 4X10{sup -4} to 6x10{sup -4} Torr and an incident power of the discharge of microwaves with a constant value of 400 W. It was analyzed the influence among the properties of the films, as the deposit rate, the composition and the bonding types, and the deposit conditions, such as the flow rates of the precursory gases and the polarization voltage of the sample holders. (Author)

  2. A nucleation and growth model of vertically-oriented carbon nanofibers or nanotubes by plasma-enhanced catalytic chemical vapor deposition.

    Science.gov (United States)

    Cojocaru, C S; Senger, A; Le Normand, F

    2006-05-01

    Carbon nanofibers are grown by direct current and hot filaments-activated catalytic chemical vapor deposition while varying the power of the hot filaments. Observations of these carbon nanofibers vertically oriented on a SiO2 (8 nm thick)/Si(100) substrate covered with Co nanoparticles (10-15 nm particle size) by Scanning Electron and Transmission Electron Microscopies show the presence of a graphitic "nest" either on the surface of the substrate or at the end of the specific nanofiber that does not encapsulate the catalytic particle. Strictly in our conditions, the activation by hot filaments is required to grow nanofibers with a C2H2 - H2 gas mixture, as large amounts of amorphous carbon cover the surface of the substrate without using hot filaments. From these observations as well as data of the literature, it is proposed that the nucleation of carbon nanofibers occurs through a complex process involving several steps: carbon concentration gradient starting from the catalytic carbon decomposition and diffusion from the surface of the catalytic nanoparticles exposed to the activated gas and promoted by energetic ionic species of the gas phase; subsequent graphitic condensation of a "nest" at the interface of the Co particle and substrate. The large concentration of highly reactive hydrogen radicals mainly provided by activation with hot filaments precludes further spreading out of this interfacial carbon nest over the entire surface of the substrate and thus selectively orientates the growth towards the condensation of graphene over facets that are perpendicular to the surface. Carbon nanofibers can then be grown within the well-known Vapor-Liquid-Solid process. Thus the effect of energetic ions and highly reactive neutrals like atomic hydrogen in the preferential etching of carbon on the edge of graphene shells and on the broadening of the carbon nanofiber is underlined.

  3. Handbook of chemical vapor deposition principles, technology and applications

    CERN Document Server

    Pierson, Hugh O

    1999-01-01

    Turn to this new second edition for an understanding of the latest advances in the chemical vapor deposition (CVD) process. CVD technology has recently grown at a rapid rate, and the number and scope of its applications and their impact on the market have increased considerably. The market is now estimated to be at least double that of a mere seven years ago when the first edition of this book was published. The second edition is an update with a considerably expanded and revised scope. Plasma CVD and metallo-organic CVD are two major factors in this rapid growth. Readers will find the latest

  4. Frequency-dependent capacitance-voltage and conductance-voltage characteristics of low-dielectric-constant SiOC(-H) thin films deposited by using plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang Young; Lee, Heang Seuk; Woo, Jong Kwan; Choi, Chi Kyu; Lee, Kwang Man; Hyun, Myung Taek [Jeju National University, Jeju (Korea, Republic of); Navamathavan, Rangaswamy [Chonbuk National University, Chonju (Korea, Republic of)

    2010-12-15

    We report on the electrical characteristics of the metal-insulator-semiconductor (MIS) structure of low-dielectric-constant SiOC(-H) films. SiOC(-H) thin films were deposited on p-Si(100) substrates by using a plasma-enhanced chemical vapor deposition (PECVD) system. The frequency dependence of the capacitance-voltage (C-V) and the conductance-voltage (G/{omega}-V) characteristics of the A1/SiOC(-H)/p-Si(100)/Al MIS structures was analyzed. C-V and G/{omega}-V measurements were carried out over a frequency range of 1 kHz to 5 MHz. Based on our analysis, the C-V and the G/{omega}-V characteristics confirmed that the surface states and the series resistance were important parameters that strongly influenced the electrical properties of the A1/SiOC(-H)/p-Si(100)/Al MIS structures.

  5. Impacts of light illumination on monocrystalline silicon surfaces passivated by atomic layer deposited Al2O3 capped with plasma-enhanced chemical vapor deposited SiN x

    Science.gov (United States)

    Lin, Fen; Toh, Mei Gi; Thway, Maung; Li, Xinhang; Nandakumar, Naomi; Gay, Xavier; Dielissen, Bas; Raj, Samuel; Aberle, Armin G.

    2017-08-01

    In this work, we investigate the impact of light illumination on crystalline silicon surfaces passivated with inline atomic layer deposited aluminum oxide capped with plasma-enhanced chemical vapor deposited silicon nitride. It is found that, for dedicated n-type lifetime samples under illumination, there is no light induced degradation (LID) but enhanced passivation. The lifetime increase happened with a much faster speed compared to the lifetime decay during dark storage, resulting in the overall lifetime enhancement for actual field application scenarios (sunshine during the day and darkness during the night). In addition, it was found that the lifetime enhancement is spectrally dependent and mainly associated with the visible part of the solar spectrum. Hence, it has negligible impact for such interfaces applied on the rear of the solar cells, for example p-type aluminum local back surface field (Al-LBSF) cells.

  6. SiO{sub 2}/TiO{sub 2} thin films with variable refractive index prepared by ion beam induced and plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gracia, F. [Instituto de Ciencia de Materiales de Sevilla (CSIC-Univ. Sevilla) and Dpt. Q. Inorganica, Avda. Americo Vespucio s/n, 41092 Sevilla (Spain); Yubero, F. [Instituto de Ciencia de Materiales de Sevilla (CSIC-Univ. Sevilla) and Dpt. Q. Inorganica, Avda. Americo Vespucio s/n, 41092 Sevilla (Spain); Holgado, J.P. [Instituto de Ciencia de Materiales de Sevilla (CSIC-Univ. Sevilla) and Dpt. Q. Inorganica, Avda. Americo Vespucio s/n, 41092 Sevilla (Spain); Espinos, J.P. [Instituto de Ciencia de Materiales de Sevilla (CSIC-Univ. Sevilla) and Dpt. Q. Inorganica, Avda. Americo Vespucio s/n, 41092 Sevilla (Spain); Gonzalez-Elipe, A.R. [Instituto de Ciencia de Materiales de Sevilla (CSIC-Univ. Sevilla) and Dpt. Q. Inorganica, Avda. Americo Vespucio s/n, 41092 Sevilla (Spain)]. E-mail: arge@icmse.csic.es; Girardeau, T. [Laboratoire de Metallurgie Physique de Poitiers, UMR 6630 CNRS, Bat SP2MI BP 30179, 86962-Futuroscope-Chasseneuil Cedex (France)

    2006-04-03

    SiO{sub 2}/TiO{sub 2} optical thin films with variable compositions have been prepared by ion beam induced and plasma enhanced chemical vapour deposition (IBICVD and PECVD). While the films obtained by IBICVD were very compact, the PECVD ones with a high content of Ti presented a columnar microstructure. The formation of Si-O-Ti bonds and a change in the environment around titanium from four- to six-coordinated has been proved by vibrational and X-ray absorption spectroscopies. The refractive index increased with the titanium content from 1.45 to 2.46 or 2.09 for, respectively, the IBICVD and PECVD films. Meanwhile, the band gap decreased, first sharply and then more smoothly up to the value of pure TiO{sub 2}. It is concluded that the optical properties of SiO{sub 2}/TiO{sub 2} thin films can be properly tailored by using these two procedures.

  7. Chemical vapor deposition coating for micromachines

    Energy Technology Data Exchange (ETDEWEB)

    MANI,SEETHAMBAL S.; FLEMING,JAMES G.; SNIEGOWSKI,JEFFRY J.; DE BOER,MAARTEN P.; IRWIN,LAWRENCE W.; WALRAVEN,JEREMY A.; TANNER,DANELLE M.; DUGGER,MICHAEL T.

    2000-04-21

    Two major problems associated with Si-based MEMS devices are stiction and wear. Surface modifications are needed to reduce both adhesion and friction in micromechanical structures to solve these problems. In this paper, the authors will present a process used to selectively coat MEMS devices with tungsten using a CVD (Chemical Vapor Deposition) process. The selective W deposition process results in a very conformal coating and can potentially solve both stiction and wear problems confronting MEMS processing. The selective deposition of tungsten is accomplished through silicon reduction of WF{sub 6}, which results in a self-limiting reaction. The selective deposition of W only on polysilicon surfaces prevents electrical shorts. Further, the self-limiting nature of this selective W deposition process ensures the consistency necessary for process control. Selective tungsten is deposited after the removal of the sacrificial oxides to minimize process integration problems. This tungsten coating adheres well and is hard and conducting, requirements for device performance. Furthermore, since the deposited tungsten infiltrates under adhered silicon parts and the volume of W deposited is less than the amount of Si consumed, it appears to be possible to release stuck parts that are contacted over small areas such as dimples. Results from tungsten deposition on MEMS structures with dimples will be presented. The effect of wet and vapor phase cleanings prior to the deposition will be discussed along with other process details. The W coating improved wear by orders of magnitude compared to uncoated parts. Tungsten CVD is used in the integrated-circuit industry, which makes this approach manufacturable.

  8. Surface functionalization of PET fabric with atmospheric pressure plasma enhanced chemical vapor deposition%常压等离子体增强化学气相沉积法表面功能化聚酯织物

    Institute of Scientific and Technical Information of China (English)

    K. H. Kale; S. S. Palaskar; 刘鹏(译); 罗艳(校)

    2012-01-01

    Plasma technology is emerging as a novel and environmentally friendly technology for surface modification of textile materials. It is possible to deposit very thin film with specific functional properties on the surface of textiles. The current study describes a novel approach for surface modification of 100% polyester textiles with plasma enhanced chemical vapor deposition (PECVD). The chemical and structural nature of plasma polymers deposited at the surface of the samples with respect to discharge power was studied with FTIR spectroscopy. The functional property i. e. water repellency imparted was determined with spray test and contact angle measurement.%对于纺织材料的表面改性来说,等离子体技术正成为一种新兴且环境友好的技术。等离子体技术在纺织品表面可沉积具有特殊功能的薄膜。阐述了一种常压等离子体增强化学气相沉积法表面改性100%聚酯织物的新型方法。通过傅里叶变换红外光谱研究了沉积于样品表面上相对于放电功率的等离子体聚合物化学和结构性质。采用雾化试验和接触角测量赋予织物诸如疏水等的功能特性。

  9. Amorphous indium-gallium-zinc-oxide thin-film transistors using organic-inorganic hybrid films deposited by low-temperature plasma-enhanced chemical vapor deposition for all dielectric layers

    Science.gov (United States)

    Hsu, Chao-Jui; Chang, Ching-Hsiang; Chang, Kuei-Ming; Wu, Chung-Chih

    2017-01-01

    We investigated the deposition of high-performance organic-inorganic hybrid dielectric films by low-temperature (close to room temperature) inductively coupled plasma chemical vapor deposition (ICP-CVD) with hexamethyldisiloxane (HMDSO)/O2 precursor gas. The hybrid films exhibited low leakage currents and high breakdown fields, suitable for thin-film transistor (TFT) applications. They were successfully integrated into the gate insulator, the etch-stop layer, and the passivation layer for bottom-gate staggered amorphous In-Ga-Zn-O (a-IGZO) TFTs having the etch-stop configuration. With the double-active-layer configuration having a buffer a-IGZO back-channel layer grown in oxygen-rich atmosphere for better immunity against plasma damage, the etch-stop-type bottom-gate staggered a-IGZO TFTs with good TFT characteristics were successfully demonstrated. The TFTs showed good field-effect mobility (μFE), threshold voltage (V th), subthreshold swing (SS), and on/off ratio (I on/off) of 7.5 cm2 V-1 s-1, 2.38 V, 0.38 V/decade, and 2.2 × 108, respectively, manifesting their usefulness for a-IGZO TFTs.

  10. The Influence of Chemical Composition on LNG Pool Vaporization

    Directory of Open Access Journals (Sweden)

    Yu Zhidong

    2017-01-01

    Full Text Available A model is used to examine the influence of chemical composition on the vaporization rate of LNG during spreading. Calculations have been performed whereby the vaporization rate of the LNG mixtures has been compared to the vaporization of pure methane under the initial conditions. The detailed results indicate that the vaporization rate LNG mixture is different to that of pure methane. LNG as the liquid mixture gets rich in ethane and isobaric latent heat increases rapidly, leading to the rate vaporization of LNG decrease in compared to pure methane.

  11. Chemical vapor deposited fiber coatings and chemical vapor infiltrated ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. Determining the microwave coupling and operational efficiencies of a microwave plasma assisted chemical vapor deposition reactor under high pressure diamond synthesis operating conditions.

    Science.gov (United States)

    Nad, Shreya; Gu, Yajun; Asmussen, Jes

    2015-07-01

    The microwave coupling efficiency of the 2.45 GHz, microwave plasma assisted diamond synthesis process is investigated by experimentally measuring the performance of a specific single mode excited, internally tuned microwave plasma reactor. Plasma reactor coupling efficiencies (η) > 90% are achieved over the entire 100-260 Torr pressure range and 1.5-2.4 kW input power diamond synthesis regime. When operating at a specific experimental operating condition, small additional internal tuning adjustments can be made to achieve η > 98%. When the plasma reactor has low empty cavity losses, i.e., the empty cavity quality factor is >1500, then overall microwave discharge coupling efficiencies (η(coup)) of >94% can be achieved. A large, safe, and efficient experimental operating regime is identified. Both substrate hot spots and the formation of microwave plasmoids are eliminated when operating within this regime. This investigation suggests that both the reactor design and the reactor process operation must be considered when attempting to lower diamond synthesis electrical energy costs while still enabling a very versatile and flexible operation performance.

  13. Controlling the resistivity gradient in chemical vapor deposition-deposited aluminum-doped zinc oxide

    NARCIS (Netherlands)

    Ponomarev, M. V.; Verheijen, M. A.; Keuning, W.; M. C. M. van de Sanden,; Creatore, M.

    2012-01-01

    Aluminum-doped ZnO (ZnO:Al) grown by chemical vapor deposition (CVD) generally exhibit a major drawback, i.e., a gradient in resistivity extending over a large range of film thickness. The present contribution addresses the plasma-enhanced CVD deposition of ZnO: Al layers by focusing on the control

  14. Microwave Plasma Chemical Vapor Deposition of Carbon Coatings on LiNi1/3Co1/3Mn1/3O2 for Li-Ion Battery Composite Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Doeff, M.M.; Kostecki, R.; Marcinek, M.; Wilcoc, J.D.

    2008-12-10

    In this paper, we report results of a novel synthesis method of thin film conductive carbon coatings on LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} cathode active material powders for lithium-ion batteries. Thin layers of graphitic carbon were produced from a solid organic precursor, anthracene, by a one-step microwave plasma chemical vapor deposition (MPCVD) method. The structure and morphology of the carbon coatings were examined using SEM, TEM, and Raman spectroscopy. The composite LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrodes were electrochemically tested in lithium half coin cells. The composite cathodes made of the carbon-coated LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} powder showed superior electrochemical performance and increased capacity compared to standard composite LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrodes.

  15. Formation of size-controlled silicon nanocrystals in plasma enhanced chemical vapor deposition grown SiO{sub x}N{sub y}/SiO{sub 2} superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Hartel, A.M., E-mail: andreas.hartel@imtek.uni-freiburg.de [IMTEK, Faculty of Engineering, Albert-Ludwigs-University Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg (Germany); Hiller, D.; Gutsch, S. [IMTEK, Faculty of Engineering, Albert-Ludwigs-University Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg (Germany); Loeper, P. [Fraunhofer Institute for Solar Energy Systems, Heidenhofstr. 2, 79110 Freiburg (Germany); Estrade, S. [MIND-IN2UB, Departament d' Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); TEM-MAT, SCT- UB, Sole i Sabaris 1, 08028 Barcelona (Spain); Peiro, F.; Garrido, B. [MIND-IN2UB, Departament d' Electronica, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Zacharias, M. [IMTEK, Faculty of Engineering, Albert-Ludwigs-University Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg (Germany)

    2011-10-31

    Size controlled silicon nanocrystals (SiNC) in silicon oxynitride matrix were prepared using plasma enhanced chemical vapor deposition. The as-deposited superlattices (SLs) and the corresponding bulk films were treated by thermal annealing. Hydrogen effusion was performed during the heating up by choosing a sufficiently low heating ramp. The phase separation of the layers into SiNCs and surrounding oxynitride matrix was studied at temperatures of up to 1150 {sup o}C. The influence of the annealing temperature on SiO{sub x}N{sub y}/SiO{sub 2} - SLs with varying SiO{sub x}N{sub y} layer thickness was investigated by several analytical techniques including variable angle spectroscopic ellipsometry, photoluminescence (PL) spectroscopy, x-ray photoelectron spectroscopy, Fourier transform infrared spectrometry (FTIR) and transmission electron microscopy (TEM). Before annealing FTIR investigations show in addition to the expected Si-O bonds also the formation of nitrogen and hydrogen related bonds. The shift of the Si-O-Si stretching vibration to higher wave numbers after annealing indicates phase separation. The disappearance of the hydrogen related bonds indicates the hydrogen effusion. The PL signal is rising significantly with increasing annealing temperature and the PL peak position is strongly related to the thickness of the SiO{sub x}N{sub y} sublayers due to quantum confinement effects. TEM investigations confirm the size-controlled growth of SiNCs within the oxynitride matrix. The role of incorporated nitrogen and hydrogen is discussed.

  16. A geração química de vapor em espectrometria atômica Chemical vapor generation in atomic spectrometry

    Directory of Open Access Journals (Sweden)

    Iracema Takase

    2002-12-01

    Full Text Available The historical development of atomic spectrometry techniques based on chemical vapor generation by both batch and flow injection sampling formats is presented. Detection via atomic absorption spectrometry (AAS, microwave induced plasma optical emission spectrometry (MIP-OES, inductively coupled plasma optical emission spectrometry (ICP-OES , inductively coupled plasma mass spectrometry (ICP-MS and furnace atomic nonthermal excitation spectrometry (FANES are considered. Hydride generation is separately considered in contrast to other methods of generation of volatile derivatives. Hg ¾ CVAAS (cold vapor atomic absorption spectrometry is not considered here. The current state-of-the-art, including extension, advantages and limitations of this approach is discussed.

  17. Chemical Fractionation in the Silicate Vapor Atmosphere of the Earth

    CERN Document Server

    Pahlevan, Kaveh; Eiler, John; 10.1016/j.epsl.2010.10.03

    2010-01-01

    Despite its importance to questions of lunar origin, the chemical composition of the Moon is not precisely known. In recent years, however, the isotopic composition of lunar samples has been determined to high precision and found to be indistinguishable from the terrestrial mantle despite widespread isotopic heterogeneity in the Solar System. In the context of the giant-impact hypothesis, this level of isotopic homogeneity can evolve if the proto-lunar disk and post-impact Earth undergo turbulent mixing into a single uniform reservoir while the system is extensively molten and partially vaporized. In the absence of liquid-vapor separation, such a model leads to the lunar inheritance of the chemical composition of the terrestrial magma ocean. Hence, the turbulent mixing model raises the question of how chemical differences arose between the silicate Earth and Moon. Here we explore the consequences of liquid-vapor separation in one of the settings relevant to the lunar composition: the silicate vapor atmosphere...

  18. Surface chemistry of the preferred (111) and (220) crystal oriented microcrystalline Si films by radio-frequency plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ohba, Daisuke; Koshino, Hideto; Tang, Zeguo; Shirai, Hajime [Graduate School of Science and Engineering, Saitama University, Sakura (Japan)

    2011-10-15

    The surface chemistry of the preferentially (111) and (220) crystal orientated chlorinated hydrogenated microcrystalline silicon ({mu}c-Si:H:Cl) films was studied using a rf PE-CVD of a dichlorosilane (SiH{sub 2}Cl{sub 2}) and H{sub 2} mixture. The growing surface for the preferentially (220) crystal oriented {mu}c-Si:H:Cl films included much voids and dangling bonds, whereas the growing surface with the preferential (111) crystal orientation was chemically stable relatively. These findings suggest that the sticking process of deposition precursors and/or the reconstruction of Si clusters within the sub-surface determine the preferential crystal orientation. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Advances in the chemical vapor deposition (CVD) of Tantalum

    DEFF Research Database (Denmark)

    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...

  20. Characteristics of carbon coatings on optical fibers prepared by radio-frequency plasma enhanced chemical vapor deposition with different H{sub 2}/C{sub 2}H{sub 2} ratios

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Hung-Chien; Yu, Jen-Feng [Department of Materials Science and Engineering, National Chung Hsing University 250 Kuo Kuang Road, Taichung 402, Taiwan (China); Shiue, Sham-Tsong, E-mail: stshiue@dragon.nchu.edu.t [Department of Materials Science and Engineering, National Chung Hsing University 250 Kuo Kuang Road, Taichung 402, Taiwan (China); Lin, Hung-Yi [Mechanical and Systems Research Laboratories, Industrial Technology Research Institute, Hsinchu 310, Taiwan (China)

    2010-10-01

    Characteristics of carbon coatings on optical fibers prepared by radio-frequency plasma enhanced chemical vapor deposition with different H{sub 2}/C{sub 2}H{sub 2} ratios are investigated. Five kinds of carbon coatings are prepared with H{sub 2}/C{sub 2}H{sub 2} ratios of 2, 4, 6, 8, and 10. Experimental results show that the deposition rate and surface roughness of carbon coatings decrease as the H{sub 2}/C{sub 2}H{sub 2} ratio increases. When the H{sub 2}/C{sub 2}H{sub 2} ratio changes from 2 to 8, the increase of H{sub 2}/C{sub 2}H{sub 2} ratios detrimentally yields sp{sup 3} carbon atoms and sp{sup 3}-CH{sub 3} bonds in the carbon coatings. However, when the H{sub 2}/C{sub 2}H{sub 2} ratio exceeds 8, the hydrogen retards the growth of the graphite structure. Moreover, the redundant hydrogen radicals favor bonding with the dangling bonds in the coating surface. Therefore, when the H{sub 2}/C{sub 2}H{sub 2} ratio increases from 8 to 10, the amounts of sp{sup 3} carbon atoms and sp{sup 3}-CH{sub 3} bonds in the carbon coatings increase. At an H{sub 2}/C{sub 2}H{sub 2} ratio of 8, the carbon coating exhibits excellent water-repellency and thermal-loading resistance, and so this ratio is the best for producing a hermetically sealed optical fiber coating.

  1. Chemical vapor deposited silica coatings for solar mirror protection

    Science.gov (United States)

    Gulino, Daniel A.; Dever, Therese M.; Banholzer, William F.

    1988-01-01

    A variety of techniques is available to apply protective coatings to oxidation susceptible spacecraft components, and each has associated advantages and disadvantages. Film applications by means of chemical vapor deposition (CVD) has the advantage of being able to be applied conformally to objects of irregular shape. For this reason, a study was made of the oxygen plasma durability of thin film (less than 5000 A) silicon dioxide coatings applied by CVD. In these experiments, such coatings were applied to silver mirrors, which are strongly subject to oxidation, and which are proposed for use on the space station solar dynamic power system. Results indicate that such coatings can provide adequate protection without affecting the reflectance of the mirror. Scanning electron micrographs indicated that oxidation of the silver layer did occur at stress crack locations, but this did not affect the measured solar reflectances. Oxidation of the silver did not proceed beyond the immediate location of the crack. Such stress cracks did not occur in thinner silica films, and hence such films would be desirable for this application.

  2. Plasma-Powder Feedstock Interaction During Plasma Spray-Physical Vapor Deposition

    Science.gov (United States)

    Anwaar, Aleem; Wei, Lianglinag; Guo, Hongbo; Zhang, Baopeng

    2017-02-01

    Plasma spray-physical vapor deposition is a new process developed to produce coatings from the vapor phase. To achieve deposition from the vapor phase, the plasma-feedstock interaction inside the plasma torch, i.e., from the powder injection point to the nozzle exit, is critical. In this work, the plasma characteristics and the momentum and heat transfer between the plasma and powder feedstock at different torch input power levels were investigated theoretically to optimize the net plasma torch power, among other important factors such as the plasma gas composition, powder feed rate, and carrier gas. The plasma characteristics were calculated using the CEA2 code, and the plasma-feedstock interaction was studied inside the torch nozzle at low-pressure (20-25 kPa) conditions. A particle dynamics model was introduced to compute the particle velocity, coupled with Xi Chen's drag model for nonevaporating particles. The results show that the energy transferred to the particles and the coating morphology are greatly influenced by the plasma gas characteristics and the particle dynamics inside the nozzle. The heat transfer between the plasma gas and feedstock material increased with the net torch power up to an optimum at 64 kW, at which a maximum of 3.4% of the available plasma energy was absorbed by the feedstock powder. Experimental results using agglomerated 7-8 wt.% yttria-stabilized zirconia (YSZ) powder as feedstock material confirmed the theoretical predictions.

  3. Plasma-Powder Feedstock Interaction During Plasma Spray-Physical Vapor Deposition

    Science.gov (United States)

    Anwaar, Aleem; Wei, Lianglinag; Guo, Hongbo; Zhang, Baopeng

    2017-01-01

    Plasma spray-physical vapor deposition is a new process developed to produce coatings from the vapor phase. To achieve deposition from the vapor phase, the plasma-feedstock interaction inside the plasma torch, i.e., from the powder injection point to the nozzle exit, is critical. In this work, the plasma characteristics and the momentum and heat transfer between the plasma and powder feedstock at different torch input power levels were investigated theoretically to optimize the net plasma torch power, among other important factors such as the plasma gas composition, powder feed rate, and carrier gas. The plasma characteristics were calculated using the CEA2 code, and the plasma-feedstock interaction was studied inside the torch nozzle at low-pressure (20-25 kPa) conditions. A particle dynamics model was introduced to compute the particle velocity, coupled with Xi Chen's drag model for nonevaporating particles. The results show that the energy transferred to the particles and the coating morphology are greatly influenced by the plasma gas characteristics and the particle dynamics inside the nozzle. The heat transfer between the plasma gas and feedstock material increased with the net torch power up to an optimum at 64 kW, at which a maximum of 3.4% of the available plasma energy was absorbed by the feedstock powder. Experimental results using agglomerated 7-8 wt.% yttria-stabilized zirconia (YSZ) powder as feedstock material confirmed the theoretical predictions.

  4. Graphene-Based Chemical Vapor Sensors for Electronic Nose Applications

    Science.gov (United States)

    Nallon, Eric C.

    chemiresistor device and used as a chemical sensor, where its resistance is temporarily modified while exposed to chemical compounds. The inherent, broad selective nature of graphene is demonstrated by testing a sensor against a diverse set of volatile organic compounds and also against a set of chemically similar compounds. The sensor exhibits excellent selectivity and is capable of achieving high classification accuracies. The kinetics of the sensor's response are further investigated revealing a relationship between the transient behavior of the response curve and physiochemical properties of the compounds, such as the molar mass and vapor pressure. This kinetic information is also shown to provide important information for further pattern recognition and classification, which is demonstrated by increased classification accuracy of very similar compounds. Covalent modification of the graphene surface is demonstrated by means of plasma treatment and free radical exchange, and sensing performance compared to an unmodified graphene sensor. Finally, the first example of a graphene-based, cross-reactive chemical sensor array is demonstrated by applying various polymers as coatings over an array of graphene sensors. The sensor array is tested against a variety of compounds, including the complex odor of Scotch whiskies, where it is capable of perfect classification of 10 Scotch whiskey variations.

  5. SAW Sensors for Chemical Vapors and Gases.

    Science.gov (United States)

    Devkota, Jagannath; Ohodnicki, Paul R; Greve, David W

    2017-04-08

    Surface acoustic wave (SAW) technology provides a sensitive platform for sensing chemicals in gaseous and fluidic states with the inherent advantages of passive and wireless operation. In this review, we provide a general overview on the fundamental aspects and some major advances of Rayleigh wave-based SAW sensors in sensing chemicals in a gaseous phase. In particular, we review the progress in general understanding of the SAW chemical sensing mechanism, optimization of the sensor characteristics, and the development of the sensors operational at different conditions. Based on previous publications, we suggest some appropriate sensing approaches for particular applications and identify new opportunities and needs for additional research in this area moving into the future.

  6. Vaporization of a mixed precursors in chemical vapor deposition for YBCO films

    Science.gov (United States)

    Zhou, Gang; Meng, Guangyao; Schneider, Roger L.; Sarma, Bimal K.; Levy, Moises

    1995-01-01

    Single phase YBa2Cu3O7-delta thin films with T(c) values around 90 K are readily obtained by using a single source chemical vapor deposition technique with a normal precursor mass transport. The quality of the films is controlled by adjusting the carrier gas flow rate and the precursor feed rate.

  7. A novel induction heater for chemical vapor deposition

    Science.gov (United States)

    Ong, C. W.; Wong, H. K.; Sin, K. S.; Yip, S. T.; Chik, K. P.

    1989-06-01

    We report how an induction cooker for household use can be modified for heating substrate or heating gases to high temperature in a chemical vapor deposition system. Only minor changes of the cooker are necessary. Stable substrate temperature as high as 900 °C was achieved with input power of about 1150 W.

  8. Chemical Vapor Deposition of Aluminum Oxide Thin Films

    Science.gov (United States)

    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…

  9. Quantitative Infrared Spectra of Vapor Phase Chemical Agents

    Energy Technology Data Exchange (ETDEWEB)

    Sharpe, Steven W.; Johnson, Timothy J.; Chu, P M.; Kleimeyer, J; Rowland, Brad; Gardner, Patrick J.

    2003-04-21

    Quantitative high resolution (0.1 cm -1) infrared spectra have been acquired for a number of pressure broadened (101.3 KPa N2), vapor phase chemicals including: Sarin (GB), Soman (GD), Tabun (GA), Cyclosarin (GF), VX, nitrogen mustard (HN3), sulfur mustard (HD) and Lewisite (L).

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

    NARCIS (Netherlands)

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

    1993-01-01

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

  11. Chemical vapor deposition reactor. [providing uniform film thickness

    Science.gov (United States)

    Chern, S. S.; Maserjian, J. (Inventor)

    1977-01-01

    An improved chemical vapor deposition reactor is characterized by a vapor deposition chamber configured to substantially eliminate non-uniformities in films deposited on substrates by control of gas flow and removing gas phase reaction materials from the chamber. Uniformity in the thickness of films is produced by having reactive gases injected through multiple jets which are placed at uniformally distributed locations. Gas phase reaction materials are removed through an exhaust chimney which is positioned above the centrally located, heated pad or platform on which substrates are placed. A baffle is situated above the heated platform below the mouth of the chimney to prevent downdraft dispersion and scattering of gas phase reactant materials.

  12. Chemical Vapor Deposition of Turbine Thermal Barrier Coatings

    Science.gov (United States)

    Haven, Victor E.

    1999-01-01

    Ceramic thermal barrier coatings extend the operating temperature range of actively cooled gas turbine components, therefore increasing thermal efficiency. Performance and lifetime of existing ceram ic coatings are limited by spallation during heating and cooling cycles. Spallation of the ceramic is a function of its microstructure, which is determined by the deposition method. This research is investigating metalorganic chemical vapor deposition (MOCVD) of yttria stabilized zirconia to improve performance and reduce costs relative to electron beam physical vapor deposition. Coatings are deposited in an induction-heated, low-pressure reactor at 10 microns per hour. The coating's composition, structure, and response to the turbine environment will be characterized.

  13. Copper-vapor-catalyzed chemical vapor deposition of graphene on dielectric substrates

    Science.gov (United States)

    Yang, Chao; Wu, Tianru; Wang, Haomin; Zhang, Xuefu; Shi, Zhiyuan; Xie, Xiaoming

    2017-07-01

    Direct synthesis of high-quality graphene on dielectric substrates is important for its application in electronics. In this work, we report the process of copper-vapor-catalyzed chemical vapor deposition of high-quality and large graphene domains on various dielectric substrates. The copper vapor plays a vital role on the growth of transfer-free graphene. Both single-crystal domains that are much larger than previous reports and high-coverage graphene films can be obtained by adjusting the growth duration. The quality of the obtained graphene was verified to be comparable with that of graphene grown on Cu foil. The progress reported in this work will aid the development of the application of transfer-free graphene in the future.

  14. Plasma and Ion Assistance in Physical Vapor Deposition: AHistorical Perspective

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre

    2007-02-28

    Deposition of films using plasma or plasma-assist can betraced back surprisingly far, namely to the 18th century for arcs and tothe 19th century for sputtering. However, only since the 1960s thecoatings community considered other processes than evaporation for largescale commercial use. Ion Plating was perhaps the first importantprocess, introducing vapor ionization and substrate bias to generate abeam of ions arriving on the surface of the growing film. Ratherindependently, cathodic arc deposition was established as an energeticcondensation process, first in the former Soviet Union in the 1970s, andin the 1980s in the Western Hemisphere. About a dozen various ion-basedcoating technologies evolved in the last decades, all characterized byspecific plasma or ion generation processes. Gridded and gridless ionsources were taken from space propulsion and applied to thin filmdeposition. Modeling and simulation have helped to make plasma and ionseffects to be reasonably well understood. Yet--due to the complex, oftennon-linear and non-equilibrium nature of plasma and surfaceinteractions--there is still a place for the experience plasma"sourcerer."

  15. Chemical vapor deposition coating of fibers using microwave application

    Science.gov (United States)

    Barmatz, Martin B. (Inventor); Hoover, Gordon (Inventor); Jackson, Henry W. (Inventor)

    2000-01-01

    Chemical vapor deposition coating is carried out in a cylindrical cavity. The fibers are heated by a microwave source that is uses a TM0N0 mode, where O is an integer, and produces a field that depends substantially only on radius. The fibers are observed to determine their heating, and their position can be adjusted. Once the fibers are uniformly heated, a CVD reagent is added to process the fibers.

  16. Oxidation Resistance of CVD (Chemical Vapor Deposition) Coatings

    Science.gov (United States)

    1987-02-01

    carbonaceous residuoe were overcome, and dense, iadherent, coat-ings which :ýtop oxidat-ion Of the substrate art! reliably produced. The iridium deposition...flow, pressure and geometry within the reaction chamber, and substrate material. For the coating to have high integrity and adhesion to the substrate...entirely produced by Ultramet using chemical vapor deposition and a novel integrated fabrication technique. Coating the inside of a long chamber presents

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

    OpenAIRE

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

    1993-01-01

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

  18. Combustion chemical vapor desposited coatings for thermal barrier coating systems

    Energy Technology Data Exchange (ETDEWEB)

    Hampikian, J.M.; Carter, W.B. [Georgia Institute of Technology, Atlanta, GA (United States)

    1995-10-01

    The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings.

  19. Research on chemical vapor deposition processes for advanced ceramic coatings

    Science.gov (United States)

    Rosner, Daniel E.

    1993-01-01

    Our interdisciplinary background and fundamentally-oriented studies of the laws governing multi-component chemical vapor deposition (VD), particle deposition (PD), and their interactions, put the Yale University HTCRE Laboratory in a unique position to significantly advance the 'state-of-the-art' of chemical vapor deposition (CVD) R&D. With NASA-Lewis RC financial support, we initiated a program in March of 1988 that has led to the advances described in this report (Section 2) in predicting chemical vapor transport in high temperature systems relevant to the fabrication of refractory ceramic coatings for turbine engine components. This Final Report covers our principal results and activities for the total NASA grant of $190,000. over the 4.67 year period: 1 March 1988-1 November 1992. Since our methods and the technical details are contained in the publications listed (9 Abstracts are given as Appendices) our emphasis here is on broad conclusions/implications and administrative data, including personnel, talks, interactions with industry, and some known applications of our work.

  20. Investigation of opening switch mechanisms based on chemically reactive plasmas

    Science.gov (United States)

    Lapatovich, W. P.; Piejak, R. B.; Proud, J. M.

    1985-11-01

    An investigation of discharge-induced chemical reactions resulting in high-density product vapors containing strongly attaching gases has been conducted to evaluate the feasibility and potential of such reactions in rapid opening plasma switches. This new concept of employing such reactions to limit and/or interrupt large currents on a microsecond time scale was studied in two element (electrodeless and electroded) devices and in three element (electroded) devices. Bimolecular and unimolecular reactions were considered. The plasma reaction between AlCl sub 3 and SiO sub 2 was studied. The electrical properties of one of the reaction products (SiCl sub 4) is reported.

  1. Electrical properties of plasma-deposited silicon oxide clarified by chemical modeling

    NARCIS (Netherlands)

    Kovalgin, A.Y.; Boogaard, A.; Brunets, I.; Aarnink, A.A.I.; Wolters, R.A.M.

    2009-01-01

    Our study is focused on Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon dioxide films at low temperatures (< 150 oC) using Inductively Coupled (IC) High-Density (HD) plasma source. We recently fabricated Thin Film Transistors (TFTs) with high-quality ICPECVD gate oxides, which exhibited

  2. Fabrication of fiber-reinforced composites by chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Besmann, T.M.; McLaughlin, J.C. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Probst, K.J.; Anderson, T.J. [Univ. of Florida, Gainesville, FL (United States). Dept. of Chemical Engineering; Starr, T.L. [Georgia Inst. of Tech., Atlanta, GA (United States). Dept. of Materials Science and Engineering

    1997-12-01

    Silicon carbide-based heat exchanger tubes are of interest to energy production and conversion systems due to their excellent high temperature properties. Fiber-reinforced SiC is of particular importance for these applications since it is substantially tougher than monolithic SiC, and therefore more damage and thermal shock tolerant. This paper reviews a program to develop a scaled-up system for the chemical vapor infiltration of tubular shapes of fiber-reinforced SiC. The efforts include producing a unique furnace design, extensive process and system modeling, and experimental efforts to demonstrate tube fabrication.

  3. Combustion chemical vapor deposited coatings for thermal barrier coating systems

    Energy Technology Data Exchange (ETDEWEB)

    Hampikian, J.M.; Carter, W.B. [Georgia Institute of Technology, Atlanta, GA (United States). School of Materials Science and Engineering

    1995-12-31

    The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings. In this report, the evaluation of alumina and ceria coatings on a nickel-chromium alloy is described.

  4. Fabrication of fiber-reinforced composites by chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Matlin, W.M. [Univ. of Tennessee, Knoxville, TN (United States); Stinton, D.P.; Besmann, T.M. [Oak Ridge National Lab., TN (United States)

    1995-08-01

    A two-step forced chemical vapor infiltration process was developed that reduced infiltration times for 4.45 cm dia. by 1.27 cm thick Nicalon{sup +} fiber preforms by two thirds while maintaining final densities near 90 %. In the first stage of the process, micro-voids within fiber bundles in the cloth were uniformly infiltrated throughout the preform. In the second stage, the deposition rate was increased to more rapidly fill the macro-voids between bundles within the cloth and between layers of cloth. By varying the thermal gradient across the preform uniform infiltration rates were maintained and high final densities achieved.

  5. Combustion chemical vapor deposited coatings for thermal barrier coating systems

    Energy Technology Data Exchange (ETDEWEB)

    Hampikian, J.M.; Carter, W.B. [Georgia Institute of Technology, Atlanta, GA (United States). School of Materials Science and Engineering

    1995-12-31

    The new deposition process, combustion chemical vapor deposition, shows a great deal of promise in the area of thermal barrier coating systems. This technique produces dense, adherent coatings, and does not require a reaction chamber. Coatings can therefore be applied in the open atmosphere. The process is potentially suitable for producing high quality CVD coatings for use as interlayers between the bond coat and thermal barrier coating, and/or as overlayers, on top of thermal barrier coatings. In this report, the evaluation of alumina and ceria coatings on a nickel-chromium alloy is described.

  6. Chemical Vapor Deposited Zinc Sulfide. SPIE Press Monograph

    Energy Technology Data Exchange (ETDEWEB)

    McCloy, John S.; Tustison, Randal W.

    2013-04-22

    Zinc sulfide has shown unequaled utility for infrared windows that require a combination of long-wavelength infrared transparency, mechanical durability, and elevated-temperature performance. This book reviews the physical properties of chemical vapor deposited ZnS and their relationship to the CVD process that produced them. An in-depth look at the material microstructure is included, along with a discussion of the material's optical properties. Finally, because the CVD process itself is central to the development of this material, a brief history is presented.

  7. In-situ preparation of polymer-coated alumina nanopowders by chemical vapor synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Schallehn, M.; Winterer, M.; Weirich, T.E.; Hahn, H. [Inst. of Materials Science, Darmstadt Univ. of Technology, Darmstadt (Germany); Keiderling, U. [Hahn-Meitner-Inst., Berlin (Germany)

    2003-01-01

    Nanocrystalline alumina particles coated with polyethylene have been prepared by a two-step chemical vapor synthesis (CVS) process using a hot-wall reactor to synthesize the nanocrystalline alumina core, and a RF plasma reactor for the subsequent polymer coating. The particle radius is about 4 nm, with the radius of the ceramic core being about 2.5 nm and the coating thickness about 1.5 nm. The powders have been characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), small-angle neutron scattering (SANS), and high-resolution transmission electron microscopy (HRTEM). (orig.)

  8. Time Dependent DD Neutrons Measurement Using a Single Crystal Chemical Vapor Deposition Diamond Detector on EAST

    Science.gov (United States)

    Du, Tengfei; Peng, Xingyu; Chen, Zhongjing; Hu, Zhimeng; Ge, Lijian; Hu, Liqun; Zhong, Guoqiang; Pu, Neng; Chen, Jinxiang; Fan, Tieshuan

    2016-09-01

    A single crystal chemical vapor deposition (scCVD) diamond detector has been successfully employed for neutron measurements in the EAST (Experimental Advanced Superconducting Tokamak) plasmas. The scCVD diamond detector coated with a 5 μm 6LiF (95% 6Li enriched) layer was placed inside a polyethylene moderator to enhance the detection efficiency. The time-dependent neutron emission from deuteron plasmas during neutral beam injection (NBI) heating was obtained. The measured results are compared with that of fission chamber detectors, which always act as standard neutron flux monitors. The scCVD diamond detector exhibits good reliability, stability and the capability to withstand harsh radiation environments despite its low detection efficiency due to the small active volume. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB106004 and 2012GB101003) and National Natural Science Foundation of China (No. 91226102)

  9. Chemical vapor deposition coatings for oxidation protection of titanium alloys

    Science.gov (United States)

    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.

  10. Initiated chemical vapor deposition of antimicrobial polymer coatings.

    Science.gov (United States)

    Martin, T P; Kooi, S E; Chang, S H; Sedransk, K L; Gleason, K K

    2007-02-01

    The vapor phase deposition of polymeric antimicrobial coatings is reported. Initiated chemical vapor deposition (iCVD), a solventless low-temperature process, is used to form thin films of polymers on fragile substrates. For this work, finished nylon fabric is coated by iCVD with no affect on the color or feel of the fabric. Infrared characterization confirms the polymer structure. Coatings of poly(dimethylaminomethyl styrene) of up to 540 microg/cm2 were deposited on the fabric. The antimicrobial properties were tested using standard method ASTM E2149-01. A coating of 40 microg/cm2 of fabric was found to be very effective against gram-negative Escherichia coli, with over a 99.99%, or 4 log, kill in just 2 min continuing to over a 99.9999%, or 6 log, reduction in viable bacteria in 60 min. A coating of 120 microg/cm2 was most effective against the gram-positive Bacillus subtilis. Further tests confirmed that the iCVD polymer did not leach off the fabric.

  11. Synthesis of Aligned Carbon Nanotubes by Thermal Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    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.

  12. Synthesis of mullite coatings by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    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. Quantitative Infrared Spectra of Vapor Phase Chemical Agents

    Energy Technology Data Exchange (ETDEWEB)

    Sharpe, Steven W.; Johnson, Timothy J.; Chu, P. M.; Kleimeyer, J.; Rowland, Brad

    2003-08-01

    Quantitative, moderately high resolution (0.1 cm-1) infrared spectra have been acquired for a number of nitrogen broadened (1 atm N2) vapor phase chemicals including: Sarin (GB), Soman (GD), Tabun (GA), Cyclosarin (GF), VX, Nitrogen Mustard (HN3), Sulfur Mustard (HD), and Lewisite (L). The spectra are acquired using a heated, flow-through White Cell1 of 5.6 meter optical path length. Each reported spectrum represents a statistical fit to Beer’s law, which allows for a rigorous calculation of uncertainty in the absorption coefficients. As part of an ongoing collaboration with the National Institute of Standards and Technology (NIST), cross-laboratory validation is a critical aspect of this work. In order to identify possible errors in the Dugway flow-through system, quantitative spectra of isopropyl alcohol from both NIST and Pacific Northwest National Laboratory (PNNL) are compared to similar data taken at Dugway proving Grounds (DPG).

  14. Field emission properties of chemical vapor deposited individual graphene

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Chemical vapor deposition of amorphous ruthenium-phosphorus alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Shin Jinhong [Texas Materials Institute, University of Texas at Austin, Austin, TX 78750 (United States); Waheed, Abdul [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Winkenwerder, Wyatt A. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Kim, Hyun-Woo [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Agapiou, Kyriacos [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Jones, Richard A. [Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712 (United States); Hwang, Gyeong S. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States); Ekerdt, John G. [Department of Chemical Engineering, University of Texas at Austin, Austin, TX 78712 (United States)]. E-mail: ekerdt@che.utexas.edu

    2007-05-07

    Chemical vapor deposition growth of amorphous ruthenium-phosphorus films on SiO{sub 2} containing {approx} 15% phosphorus is reported. cis-Ruthenium(II)dihydridotetrakis-(trimethylphosphine), cis-RuH{sub 2}(PMe{sub 3}){sub 4} (Me = CH{sub 3}) was used at growth temperatures ranging from 525 to 575 K. Both Ru and P are zero-valent. The films are metastable, becoming increasingly more polycrystalline upon annealing to 775 and 975 K. Surface studies illustrate that demethylation is quite efficient near 560 K. Precursor adsorption at 135 K or 210 K and heating reveal the precursor undergoes a complex decomposition process in which the hydride and trimethylphosphine ligands are lost at temperatures as low at 280 K. Phosphorus and its manner of incorporation appear responsible for the amorphous-like character. Molecular dynamics simulations are presented to suggest the local structure in the films and the causes for phosphorus stabilizing the amorphous phase.

  16. Chemical Vapor Deposition at High Pressure in a Microgravity Environment

    Science.gov (United States)

    McCall, Sonya; Bachmann, Klaus; LeSure, Stacie; Sukidi, Nkadi; Wang, Fuchao

    1999-01-01

    In this paper we present an evaluation of critical requirements of organometallic chemical vapor deposition (OMCVD) at elevated pressure for a channel flow reactor in a microgravity environment. The objective of using high pressure is to maintain single-phase surface composition for materials that have high thermal decomposition pressure at their optimum growth temperature. Access to microgravity is needed to maintain conditions of laminar flow, which is essential for process analysis. Based on ground based observations we present an optimized reactor design for OMCVD at high pressure and reduced gravity. Also, we discuss non-intrusive real-time optical monitoring of flow dynamics coupled to homogeneous gas phase reactions, transport and surface processes. While suborbital flights may suffice for studies of initial stages of heteroepitaxy experiments in space are essential for a complete evaluation of steady-state growth.

  17. Mass transport measurements and modeling for chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Starr, T.L.; Chiang, D.Y.; Fiadzo, O.G.; Hablutzel, N. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering

    1997-12-01

    This project involves experimental and modeling investigation of densification behavior and mass transport in fiber preforms and partially densified composites, and application of these results to chemical vapor infiltration (CVI) process modeling. This supports work on-going at ORNL in process development for fabrication of ceramic matrix composite (CMC) tubes. Tube-shaped composite preforms are fabricated at ORNL with Nextel{trademark} 312 fiber (3M Corporation, St. Paul, MN) by placing and compressing several layers of braided sleeve on a tubular mandrel. In terms of fiber architecture these preforms are significantly different than those made previously with Nicalon{trademark} fiber (Nippon Carbon Corp., Tokyo, Japan) square weave cloth. The authors have made microstructure and permeability measurements on several of these preforms and a few partially densified composites so as to better understand their densification behavior during CVI.

  18. Chemical vapor infiltration of TiB{sub 2} composites

    Energy Technology Data Exchange (ETDEWEB)

    Besmann, T.M. [Oak Ridge National Laboratory, TN (United States)

    1995-05-01

    This program is designed to develop a Hall-Heroult aluminum smelting cathode with substantially improved properties. The carbon cathodes in current use require significant anode-to-cathode spacing in order to prevent shorting, causing significant electrical inefficiencies. This is due to the non-wettability of carbon by aluminum which causes instability in the cathodic aluminum pad. It is suggested that a fiber reinforced-TiB{sub 2} matrix composite would have the requisite wettability, strength, strain-to-failure, cost, and lifetime to solve this problem. The approach selected to fabricate such a cathode material is chemical vapor infiltration (CVI). This program is designed to evaluate potential fiber reinforcements, fabricate test specimens, and test the materials in a static bath and lab-scale Hall cell.

  19. Chemical vapor deposition synthesis of tunable unsubstituted polythiophene.

    Science.gov (United States)

    Nejati, Siamak; Lau, Kenneth K S

    2011-12-20

    Despite having exceptional electroactive properties, applications of unsubstituted polythiophene (PTh) have been limited due to its insolubility. To overcome this challenge, we have employed oxidative chemical vapor deposition (oCVD) as a unique liquid-free technique to enable the oxidative polymerization of PTh using thiophene as the starting monomer and vanadium oxytrichloride as an effective vaporizable oxidant initiator. Vibrational and phototelectron spectroscopy indicated the formation of unsubstituted polythiophene. Cyclic voltammetry revealed its electrochromic behavior in solution. Significantly, polymer conjugation length and electrical conductivity can be tuned by controlling oCVD process variables. Polymerization is found to be adsorption-limited, so by providing sufficient monomer and limiting the amount of initiator at the growth surface, PTh is believed to be formed through α-α thiophene linkages.

  20. Rapid fabrication of ceramic composite tubes using chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Starr, T.L.; Chiang, D. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering; Besmann, T.M.; Stinton, D.P.; McLaughlin, J.C.; Matlin, W.M. [Oak Ridge National Lab., TN (United States)

    1996-06-01

    Ceramic composite tubes can be fabricated with silicon carbide matrix and Nicalon fiber reinforcement using forced flow-thermal gradient chemical vapor infiltration (FCVI). The process model GTCVI is used to design the equipment configuration and to identify conditions for rapid, uniform densification. The initial injector and mandrel design produced radial and longitudinal temperature gradients too large for uniform densification. Improved designs have been evaluated with the model. The most favorable approach utilizes a free-standing preform and an insulated water-cooled gas injector. Selected process conditions are based on the temperature limit of the fiber, matrix stoichiometry and reagent utilization efficiency. Model runs for a tube 12 inches long, 4 inches OD and 1/4 inch wall thickness show uniform densification in approximately 15 hours.

  1. Strain relaxation in graphene grown by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Direct synthesis of large area graphene on insulating substrate by gallium vapor-assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Murakami, Katsuhisa, E-mail: k.murakami@bk.tsukuba.ac.jp; Hiyama, Takaki; Kuwajima, Tomoya; Fujita, Jun-ichi [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573 (Japan); Tsukuba Research Center for Interdisciplinary Materials Science, University of Tsukuba, Tsukuba 305-8573 (Japan); Tanaka, Shunsuke; Hirukawa, Ayaka [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573 (Japan); Kano, Emi [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8573 (Japan); National Institute for Materials Science, Tsukuba 305-0047 (Japan); Takeguchi, Masaki [National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2015-03-02

    A single layer of graphene with dimensions of 20 mm × 20 mm was grown directly on an insulating substrate by chemical vapor deposition using Ga vapor catalysts. The graphene layer showed highly homogeneous crystal quality over a large area on the insulating substrate. The crystal quality of the graphene was measured by Raman spectroscopy and was found to improve with increasing Ga vapor density on the reaction area. High-resolution transmission electron microscopy observations showed that the synthesized graphene had a perfect atomic-scale crystal structure within its grains, which ranged in size from 50 nm to 200 nm.

  3. Conversion Coatings for Aluminum Alloys by Chemical Vapor Deposition Mechanisms

    Science.gov (United States)

    Reye, John T.; McFadden, Lisa S.; Gatica, Jorge E.; Morales, Wilfredo

    2004-01-01

    With the rise of environmental awareness and the renewed importance of environmentally friendly processes, the United States Environmental Protection Agency has targeted surface pre-treatment processes based on chromates. Indeed, this process has been subject to regulations under the Clean Water Act as well as other environmental initiatives, and there is today a marked movement to phase the process out in the near future. Therefore, there is a clear need for new advances in coating technology that could provide practical options for replacing present industrial practices. Depending on the final application, such coatings might be required to be resistant to corrosion, act as chemically resistant coatings, or both. This research examined a chemical vapor deposition (CVD) mechanism to deposit uniform conversion coatings onto aluminum alloy substrates. Robust protocols based on solutions of aryl phosphate ester and multi-oxide conversion coating (submicron) films were successfully grown onto the aluminum alloy samples. These films were characterized by X-ray Photoelectron Spectroscopy (XPS). Preliminary results indicate the potential of this technology to replace aqueous-based chromate processes.

  4. Oxidative chemical vapor deposition of polyaniline thin films.

    Science.gov (United States)

    Smolin, Yuriy Y; Soroush, Masoud; Lau, Kenneth K S

    2017-01-01

    Polyaniline (PANI) is synthesized via oxidative chemical vapor deposition (oCVD) using aniline as monomer and antimony pentachloride as oxidant. Microscopy and spectroscopy indicate that oCVD processing conditions influence the PANI film chemistry, oxidation, and doping level. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) indicate that a substrate temperature of 90 °C is needed to minimize the formation of oligomers during polymerization. Lower substrate temperatures, such as 25 °C, lead to a film that mostly includes oligomers. Increasing the oxidant flowrate to nearly match the monomer flowrate favors the deposition of PANI in the emeraldine state, and varying the oxidant flowrate can directly influence the oxidation state of PANI. Changing the reactor pressure from 700 to 35 mTorr does not have a significant effect on the deposited film chemistry, indicating that the oCVD PANI process is not concentration dependent. This work shows that oCVD can be used for depositing PANI and for effectively controlling the chemical state of PANI.

  5. Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection

    Science.gov (United States)

    Li, Jing; Lu, Yijiang

    2005-01-01

    A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs) and metal oxides nanowires or nanobelts, on a pair of interdigitated electrodes (IDE) processed with a silicon based microfabrication and micromachining technique. The IDE fingers were fabricated using thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to hazardous gases and vapors, such as acetone, benzene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing in our sensor platform can be understood by electron modulation between the nanostructure engineered device and gas molecules. As a result of the electron modulation, the conductance of nanodevice will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost.

  6. Self-organization and nanostructure formation in chemical vapor deposition

    Science.gov (United States)

    Walgraef, Daniel

    2013-10-01

    When thin films are grown on a substrate by chemical vapor deposition, the evolution of the first deposited layers may be described, on mesoscopic scales, by dynamical models of the reaction-diffusion type. For monatomic layers, such models describe the evolution of atomic coverage due to the combined effect of reaction terms representing adsorption-desorption and chemical processes and nonlinear diffusion terms that are of the Cahn-Hilliard type. This combination may lead, below a critical temperature, to the instability of uniform deposited layers. This instability triggers the formation of nanostructures corresponding to regular spatial variations of substrate coverage. Patterns wavelengths and symmetries are selected by dynamical variables and not by variational arguments. According to the balance between reaction- and diffusion-induced nonlinearities, a succession of nanostructures including hexagonal arrays of dots, stripes, and localized structures of various types may be obtained. These structures may initiate different growth mechanisms, including Volmer-Weber and Frank-Van der Merwe types of growth. The relevance of this approach to the study of deposited layers of different species is discussed.

  7. Advanced deposition model for thermal activated chemical vapor deposition

    Science.gov (United States)

    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

  8. Ultrafast deposition of silicon nitride and semiconductor silicon thin films by Hot Wire Chemical Vapor Deposition

    NARCIS (Netherlands)

    Schropp, R.E.I.; van der Werf, C.H.M.; Verlaan, V.; Rath, J.K.; 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, a

  9. Novel Prospects for Plasma Spray-Physical Vapor Deposition of Columnar Thermal Barrier Coatings

    Science.gov (United States)

    Anwaar, Aleem; Wei, Lianglinag; Guo, Qian; Zhang, Baopeng; Guo, Hongbo

    2017-09-01

    Plasma spray-physical vapor deposition (PS-PVD) is an emerging coating technique that can produce columnar thermal barrier coatings from vapor phase. Feedstock treatment at the start of its trajectory in the plasma torch nozzle is important for such vapor-phase deposition. This study describes the effects of the plasma composition (Ar/He) on the plasma characteristics, plasma-particle interaction, and particle dynamics at different points spatially distributed inside the plasma torch nozzle. The results of calculations show that increasing the fraction of argon in the plasma gas mixture enhances the momentum and heat flow between the plasma and injected feedstock. For the plasma gas combination of 45Ar/45He, the total enthalpy transferred to a representative powder particle inside the plasma torch nozzle is highest ( 9828 kJ/kg). Moreover, due to the properties of the plasma, the contribution of the cylindrical throat, i.e., from the feed injection point (FIP) to the start of divergence (SOD), to the total transferred energy is 69%. The carrier gas flow for different plasma gas mixtures was also investigated by optical emission spectroscopy (OES) measurements of zirconium emissions. Yttria-stabilized zirconia (YSZ) coating microstructures were produced when using selected plasma gas compositions and corresponding carrier gas flows; structural morphologies were found to be in good agreement with OES and theoretical predictions. Quasicolumnar microstructure was obtained with porosity of 15% when applying the plasma composition of 45Ar/45He.

  10. Effects of additional vapors on sterilization of microorganism spores with plasma-excited neutral gas

    Science.gov (United States)

    Matsui, Kei; Ikenaga, Noriaki; Sakudo, Noriyuki

    2015-01-01

    Some fundamental experiments are carried out in order to develop a plasma process that will uniformly sterilize both the space and inner wall of the reactor chamber at atmospheric pressure. Air, oxygen, argon, and nitrogen are each used as the plasma source gas to which mixed vapors of water and ethanol at different ratios are added. The reactor chamber is remotely located from the plasma area and a metal mesh for eliminating charged particles is installed between them. Thus, only reactive neutral particles such as plasma-excited gas molecules and radicals are utilized. As a result, adding vapors to the source gas markedly enhances the sterilization effect. In particular, air with water and/or ethanol vapor and oxygen with ethanol vapor show more than 6-log reduction for Geobacillus stearothermophilus spores.

  11. Fundamental aspects of plasma chemical physics Thermodynamics

    CERN Document Server

    Capitelli, Mario; D'Angola, Antonio

    2012-01-01

    Fundamental Aspects of Plasma Chemical Physics - Thermodynamics develops basic and advanced concepts of plasma thermodynamics from both classical and statistical points of view. After a refreshment of classical thermodynamics applied to the dissociation and ionization regimes, the book invites the reader to discover the role of electronic excitation in affecting the properties of plasmas, a topic often overlooked by the thermal plasma community. Particular attention is devoted to the problem of the divergence of the partition function of atomic species and the state-to-state approach for calculating the partition function of diatomic and polyatomic molecules. The limit of ideal gas approximation is also discussed, by introducing Debye-Huckel and virial corrections. Throughout the book, worked examples are given in order to clarify concepts and mathematical approaches. This book is a first of a series of three books to be published by the authors on fundamental aspects of plasma chemical physics.  The next bo...

  12. Experimental investigation of vapor shielding effects induced by ELM-like pulsed plasma loads using the double plasma gun device

    Science.gov (United States)

    Sakuma, I.; Kikuchi, Y.; Kitagawa, Y.; Asai, Y.; Onishi, K.; Fukumoto, N.; Nagata, M.

    2015-08-01

    We have developed a unique experimental device of so-called double plasma gun, which consists of two magnetized coaxial plasma gun (MCPG) devices, in order to clarify effects of vapor shielding on material erosion due to transient events in magnetically confined fusion devices. Two ELM-like pulsed plasmas produced by the two MCPG devices were injected into a target chamber with a variable time difference. For generating ablated plasmas in front of a target material, an aluminum foil sample in the target chamber was exposed to a pulsed plasma produced by the 1st MCPG device. The 2nd pulsed plasma was produced with a time delay of 70 μs. It was found that a surface absorbed energy measured by a calorimeter was reduced to ∼66% of that without the Al foil sample. Thus, the reduction of the incoming plasma energy by the vapor shielding effect was successfully demonstrated in the present experiment.

  13. Experimental investigation of vapor shielding effects induced by ELM-like pulsed plasma loads using the double plasma gun device

    Energy Technology Data Exchange (ETDEWEB)

    Sakuma, I., E-mail: eu13z002@steng.u-hyogo.ac.jp; Kikuchi, Y.; Kitagawa, Y.; Asai, Y.; Onishi, K.; Fukumoto, N.; Nagata, M.

    2015-08-15

    We have developed a unique experimental device of so-called double plasma gun, which consists of two magnetized coaxial plasma gun (MCPG) devices, in order to clarify effects of vapor shielding on material erosion due to transient events in magnetically confined fusion devices. Two ELM-like pulsed plasmas produced by the two MCPG devices were injected into a target chamber with a variable time difference. For generating ablated plasmas in front of a target material, an aluminum foil sample in the target chamber was exposed to a pulsed plasma produced by the 1st MCPG device. The 2nd pulsed plasma was produced with a time delay of 70 μs. It was found that a surface absorbed energy measured by a calorimeter was reduced to ∼66% of that without the Al foil sample. Thus, the reduction of the incoming plasma energy by the vapor shielding effect was successfully demonstrated in the present experiment.

  14. Large improvement of phosphorus incorporation efficiency in n-type chemical vapor deposition of diamond

    Science.gov (United States)

    Ohtani, Ryota; Yamamoto, Takashi; Janssens, Stoffel D.; Yamasaki, Satoshi; Koizumi, Satoshi

    2014-12-01

    Microwave plasma enhanced chemical vapor deposition is a promising way to generate n-type, e.g., phosphorus-doped, diamond layers for the fabrication of electronic components, which can operate at extreme conditions. However, a deeper understanding of the doping process is lacking and low phosphorus incorporation efficiencies are generally observed. In this work, it is shown that systematically changing the internal design of a non-commercial chemical vapor deposition chamber, used to grow diamond layers, leads to a large increase of the phosphorus doping efficiency in diamond, produced in this device, without compromising its electronic properties. Compared to the initial reactor design, the doping efficiency is about 100 times higher, reaching 10%, and for a very broad doping range, the doping efficiency remains highly constant. It is hypothesized that redesigning the deposition chamber generates a higher flow of active phosphorus species towards the substrate, thereby increasing phosphorus incorporation in diamond and reducing deposition of phosphorus species at reactor walls, which additionally reduces undesirable memory effects.

  15. Reactivity of water vapor in an atmospheric argon flowing post-discharge plasma torch

    CERN Document Server

    Collette, S; Reniers, F

    2016-01-01

    The reactivity of water vapor introduced in the flowing post-discharge of an RF atmospheric plasma torch is investigated through electrical characterization, optical emission spectroscopy and mass spectrometry measurements. Due to the technical features of the plasma torch, the post-discharge can be considered as divided into two regions: an inner region (inside the plasma torch device) where the water vapor is injected and an outer region which directly interacts with the ambient air. The main reactions induced by the injection of water vapor are identified as well as those indicative of the influence of the ambient air. Plausible pathways allowing the production of H, OH, O radicals and H2O2 are discussed as well as reactions potentially responsible for inhomogeneities and for a low DC current measured in the flowing post-discharge. Keywords: atmospheric post-discharge, H2O plasma reactivity, RF plasma torch

  16. High surface area graphene foams by chemical vapor deposition

    Science.gov (United States)

    Drieschner, Simon; Weber, Michael; Wohlketzetter, Jörg; Vieten, Josua; Makrygiannis, Evangelos; Blaschke, Benno M.; Morandi, Vittorio; Colombo, Luigi; Bonaccorso, Francesco; Garrido, Jose A.

    2016-12-01

    Three-dimensional (3D) graphene-based structures combine the unique physical properties of graphene with the opportunity to get high electrochemically available surface area per unit of geometric surface area. Several preparation techniques have been reported to fabricate 3D graphene-based macroscopic structures for energy storage applications such as supercapacitors. Although reaserch has been focused so far on achieving either high specific capacitance or high volumetric capacitance, much less attention has been dedicated to obtain high specific and high volumetric capacitance simultaneously. Here, we present a facile technique to fabricate graphene foams (GF) of high crystal quality with tunable pore size grown by chemical vapor deposition. We exploited porous sacrificial templates prepared by sintering nickel and copper metal powders. Tuning the particle size of the metal powders and the growth temperature allow fine control of the resulting pore size of the 3D graphene-based structures smaller than 1 μm. The as-produced 3D graphene structures provide a high volumetric electric double layer capacitance (165 mF cm-3). High specific capacitance (100 Fg-1) is obtained by lowering the number of layers down to single layer graphene. Furthermore, the small pore size increases the stability of these GFs in contrast to the ones that have been grown so far on commercial metal foams. Electrodes based on the as-prepared GFs can be a boost for the development of supercapacitors, where both low volume and mass are required.

  17. Charged impurity-induced scatterings in chemical vapor deposited graphene

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ming-Yang; Tang, Chiu-Chun [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Ling, D. C. [Department of Physics, Tamkang University, Tamsui Dist., New Taipei 25137, Taiwan (China); Li, L. J. [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 11529, Taiwan (China); Chi, C. C.; Chen, Jeng-Chung [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2013-12-21

    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.

  18. Carbon-assisted chemical vapor deposition of hexagonal boron nitride

    Science.gov (United States)

    Ismach, Ariel; Chou, Harry; Mende, Patrick; Dolocan, Andrei; Addou, Rafik; Aloni, Shaul; Wallace, Robert; Feenstra, Randall; Ruoff, Rodney S.; Colombo, Luigi

    2017-06-01

    We show that in a low-pressure chemical vapor deposition (CVD) system, the residual oxygen and/or air play a crucial role in the mechanism of the growth of hexagonal boron nitride (h-BN) films on Ni foil ‘enclosures’. Hexagonal-BN films grow on the Ni foil surface via the formation of an intermediate boric-oxide (BO x ) phase followed by a thermal reduction of the BO x by a carbon source (either amorphous carbon powder or methane), leading to the formation of single- and bi-layer h-BN. Low energy electron microscopy (LEEM) and diffraction (LEED) were used to map the number of layers over large areas; Raman spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) were used to characterize the structure and physical quality of the ultra-thin h-BN film. The growth procedure reported here leads to a better understanding and control of the synthesis of ultra-thin h-BN films.

  19. Growth of graphene underlayers by chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    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.

  20. Temperature admittance spectroscopy of boron doped chemical vapor deposition diamond

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Thirty Gigahertz Optoelectronic Mixing in Chemical Vapor Deposited Graphene.

    Science.gov (United States)

    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.

  2. Interfacial studies of chemical-vapor-infiltrated ceramic matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Brennan, J.J. (United Technologies Research Center, East Hartford, CT (USA))

    1990-06-15

    The objective of this program was to investigate the fiber-matrix interfacial chemistry in chemical-vapor-infiltrated SiC matrix composites utilizing NICALON SiC and Nextel 400 mullite fibers and how this interface influences composite properties such as strength, toughness and environmental stability. The SiC matrix was deposited using three different reactants: methyldichlorosilane, methyltrichlorosilane and dimethyldichlorosilane. It was found that by varying the reactant gas flow rates, the ratio of carrier gas to reactant gas, the type of carrier gas (hydrogen or argon), the flushing gas used in the reactor prior to deposition (hydrogen or argon) or the type of silane reactant gas used, the composition of the deposited SiC could be varied from very silicon rich (75 at.%) to carbon rich (60%) to almost pure carbon. Stoichiometric SiC was found to bond very strongly to both NICALON and Nextel fibers, resulting in a weak and brittle composite. A thin carbon interfacial layer deposited either deliberately by the decomposition of methane or inadvertently by the introduction of argon into the reactor prior to silane flow resulted in a weakly bonded fiber-matrix interface and strong and tough composites. However, composites with this type of interface were not oxidatively stable. Preliminary results point ot the use of a carbon-rich SiC (mixture of carbon plus SiC) interfacial zone to achieve a relatively weak, crack-deflecting fiber-matrix bond but also exhibiting oxidative stability. (orig.).

  3. Application of chemical vapor composites (CVC) to terrestrial thermionics

    Science.gov (United States)

    Miskolczy, Gabor; Reagan, Peter

    1995-01-01

    Terrestrial flame fired thermionics took a great leap forward in the earlier 1980's with the development of reliable long-lived hot shells. These results were presented by Goodale (1981). The hot shell protects the fractory emitter from oxidizing in the combustion environment. In earlier efforts with supralloys emitters it was found that superalloys were poor thermionic emitters since they operated at too low a temperature for practical and economical use as discussed by Huffman (1978). With the development of Chemical Vapor Deposited (CVD) silicon carbide and CVD tungsten, it became possible to fabricate long-lived thermionic converters. These results were shown by Goodale (1980). Further improvements were achieved with the use of oxygen additives on the electrodes. These developments made thermionics attractive for topping a power plant or as the energy conversion part of a cogeneration plant as described by Miskolczy (1982) and Goodale (1983). The feasibility of a thermonic steam boiler and a thermionic topped gas turbine plant become a possibility, as shown by Miskolczy (1980).

  4. Calculation of transport coefficients of air-water vapor mixtures thermal plasmas used in circuit breakers

    Directory of Open Access Journals (Sweden)

    KOHIO Niéssan

    2014-12-01

    Full Text Available In this paper we calculate the transport coefficients of plasmas formed by air and water vapor mixtures. The calculation, which assume local thermodynamic equilibrium (LTE are performed in the temperature range from 500 to 12000 K. We use the Gibbs free energy minimization method to determine the equilibrium composition of the plasmas, which is necessary to calculate the transport coefficients. We use the Chapman-Enskog method to calculate the transport coefficients. The results are presented and discussed according to the rate of water vapor. The results of the total thermal conductivity and electrical conductivity show in particular that the increasing of the rate of water vapor in air can be interesting for power cut. This could be improve the performance of plasma during current breaking in air contaminate by the water vapor.

  5. The effect of ultrasonic pre-treatment on nucleation density of chemical vapor deposition diamond

    Science.gov (United States)

    Tang, Chi; Ingram, David C.

    1995-11-01

    Using statistical design of experiments, the effect of ultrasonic pre-treatment on the nucleation density of diamond was studied. The parameters investigated included ultrasonic excitation power, concentration of diamond powder in water, duration of ultrasonic excitation, and duration of cleaning with water after ultrasonic excitation. Diamond films were deposited on silicon (100) substrates using microwave assisted plasma chemical vapor deposition. The nucleation density varied from 106 nuclei/cm2 to 109 nuclei/cm2. The results illustrated that the dominant effect in ultrasonic pre-treatment was seeding. Moreover, scratches caused by the seeds during the treatment enabled more seeds to be retained on the surface. Based on these results, an optimized ultrasonic pretreatment has been developed. The new procedure yields a uniform nucleation density of 109 nuclei/cm2 on silicon (100) substrates.

  6. Fundamental aspects of plasma chemical physics transport

    CERN Document Server

    Capitelli, Mario; Laricchiuta, Annarita

    2013-01-01

    Fundamental Aspects of Plasma Chemical Physics: Tranpsort develops basic and advanced concepts of plasma transport to the modern treatment of the Chapman-Enskog method for the solution of the Boltzmann transport equation. The book invites the reader to consider actual problems of the transport of thermal plasmas with particular attention to the derivation of diffusion- and viscosity-type transport cross sections, stressing the role of resonant charge-exchange processes in affecting the diffusion-type collision calculation of viscosity-type collision integrals. A wide range of topics is then discussed including (1) the effect of non-equilibrium vibrational distributions on the transport of vibrational energy, (2) the role of electronically excited states in the transport properties of thermal plasmas, (3) the dependence of transport properties on the multitude of Saha equations for multi-temperature plasmas, and (4) the effect of the magnetic field on transport properties. Throughout the book, worked examples ...

  7. All hot wire chemical vapor deposition low substrate temperature transparent thin film moisture barrier

    NARCIS (Netherlands)

    Spee, D.A.; Schipper, M.R.; van der Werf, C.H.M.; Rath, J.K.; Schropp, R.E.I.

    2013-01-01

    We deposited a silicon nitride/polymer hybrid multilayer moisture barrier for flexible electronics in a hot wire chemical vapor deposition process, entirely below 100 °C. We were able to reach a water vapor transmission rate (WVTR) as low as 5×10−6 g/m2/day at a temperature of 60 °C and a relative h

  8. A new productivity function and stability criterion in chemical vapor transport processes

    NARCIS (Netherlands)

    Klosse, K.

    1975-01-01

    The crystal growth rate in a chemical vapor transport process using a closed system is analyzed on the basis of a one-dimensional configuration. A simplified model of vapor transport enables one to obtain a set of equations yielding the rates of reaction without a complete evaluation of the partial

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

    NARCIS (Netherlands)

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

    2008-01-01

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

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

    NARCIS (Netherlands)

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

    2008-01-01

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

  11. Chemical reaction between water vapor and stressed glass

    Science.gov (United States)

    Soga, N.; Okamoto, T.; Hanada, T.; Kunugi, M.

    1979-01-01

    The crack velocity in soda-lime silicate glass was determined at room temperature at water-vapor pressures of 10 to 0.04 torr using the double torsion technique. A precracked glass specimen (70 x 16 x 1.6 mm) was placed in a vacuum chamber containing a four-point bending test apparatus. The plotted experimental results show that the crack propagation curve in water agrees fairly well with that of Wiederhorn (1967). Attention is given to the effect of water vapor pressure on crack velocity at K(I) = 550,000 N/m to the 3/2 power, with (Wiederhorn's data) or without N2 present. The plotted results reveal that the present crack velocity is about two orders of magnitude higher than that of Wiederhorn at high water-vapor conditions, but the difference decreases as the water-vapor concentration diminishes or the crack velocity slows down.

  12. Chemical Fractionation and Abundances in Coronal Plasma

    CERN Document Server

    Drake, J J

    2003-01-01

    Much of modern astrophysics is grounded on the observed chemical compositions of stars and the diffuse plasma that pervades the space between stars, galaxies and clusters of galaxies. X-ray and EUV spectra of the hot plasma in the outer atmospheres of stars have demonstrated that these environments are subject to chemical fractionation in which the abundances of elements can be enhanced and depleted by an order of magnitude or more. These coronal abundance anomalies are discussed and some of the physical mechanisms that might be responsible for producing them are examined. It is argued that coronal abundances can provide important new diagnostics on physical processes at work in solar and stellar coronae. It seems likely that other hot astrophysical plasmas will be subject to similar effects.

  13. Behavior of vapor/plasma within the keyhole and above the workpiece during CO2 laser penetration welding

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper, a high-speed camera and an optical emission monitor were used to study the behavior of vapor/plasma during CO2 laser welding of SUS304 stainless steel. Results of optical emission from vapor/plasma show that two characteristic frequency bands exist, 100-500 Hz and 1 500-3 500 Hz. At the same time, the changing images of vapor/plasma and bottom pool also confirm that there are two different fluctuation frequency bands. One of the frequency bands represents the characteristic of vapor/plasma within the keyhole, and it is within 167-500 Hz. Another frequency band is within 1 500-3 500 Hz, and it obviously derives from the shielding gas. Some factors may cause these frequency differences between the keyhole plasma and the shielding gas plasma. One of them is that the vapor/plasma pressure within the keyhole will increase slowly.

  14. Industrialization of Hot Wire Chemical Vapor Deposition for thin film applications

    Energy Technology Data Exchange (ETDEWEB)

    Schropp, R.E.I., E-mail: r.e.i.schropp@tue.nl

    2015-11-30

    The consequences of implementing a Hot Wire Chemical Vapor Deposition (HWCVD) chamber into an existing in-line or roll-to-roll reactor are described. The hardware and operation of the HWCVD production reactor is compared to that of existing roll-to-roll reactors based on Plasma Enhanced Chemical Vapor Deposition. The most important consequences are the technical consequences and the economic consequences, which are both discussed. The technical consequences are adaptations needed to the hardware and to the processing sequences due to the different interaction of the HWCVD process with the substrate and already deposited layers. The economic consequences are the reduced investments in radio frequency (RF) supplies and RF components. This is partially offset by investments that have to be made in higher capacity pumping systems. The most mature applications of HWCVD are moisture barrier coatings for thin film flexible devices such as Organic Light Emitting Diodes and Organic Photovoltaics, and passivation layers for multicrystalline Si solar cells, high mobility field effect transistors, and silicon heterojunction cells (also known as heterojunction cells with intrinsic thin film layers). Another example is the use of Si in thin film photovoltaics. The cost perspective per unit of thin film photovoltaic product using HWCVD is estimated at 0.07 €/Wp for the Si thin film component. - Highlights: • Review of consequences of implementing Hot Wire CVD into a manufacturing plant • Aspects of scaling up to large area and continuous manufacturing are discussed • Economic advantage of introducing a HWCVD process in a production system is estimated • Using HWCVD, the cost for the Si layers in photovoltaic products is 0.08 €/Wp.

  15. Laser initiation and decay processes in an organic vapor plasma

    Science.gov (United States)

    Ding, Guowen

    A large volume organic molecular plasma (hundreds of cm3) is created by a 193 nm laser ionizing an organic molecule, Tetrakis-(dimethylamino)-ethylene (TMAE). The plasma is found to be characterized by high electron density (10 13-1011cm-3), low electron temperature (~0.1 eV), fast creation (~10 ns) and rapid decaying (electron-ion recombination coefficient ~10-6 cm3/s). Fast Langmuir probe (LP) techniques are developed for diagnosing this plasma, including a novel probe design and fabrication, a fast detection system, sampling, indirect probe heating, electro-magnetic shielding and dummy probe techniques. Plasma physical processes regarding fast LP diagnostics for different time scales (t> and <100 ns) are studied. A theory for the correction due to a rapidly decaying plasma to LP measurements is developed. The mechanisms responsible for the plasma decay are studied, and a delayed ionization process is found to be important in interpreting the decay processes. It is also found that nitrogen can enhance the delayed emission of a TMAE Rydberg state from the TMAE plasma. This result strongly suggests that a long-lifetime highly-excited state is important in the TMAE plasma decay process. This result supports the delayed ionization mechanism. A model combining electron-ion recombination and delayed ionization processes is developed to calculate the delayed ionization lifetime.

  16. Upstream Density for Plasma Detachment with Conventional and Lithium Vapor-Box Divertors

    Science.gov (United States)

    Goldston, Rj; Schwartz, Ja

    2016-10-01

    Fusion power plants are likely to require detachment of the divertor plasma from material targets. The lithium vapor box divertor is designed to achieve this, while limiting the flux of lithium vapor to the main plasma. We develop a simple model of near-detachment to evaluate the required upstream plasma density, for both conventional and lithium vapor-box divertors, based on particle and dynamic pressure balance between up- and down-stream, at near-detachment conditions. A remarkable general result is found, not just for lithium-induced detachment, that the upstream density divided by the Greenwald-limit density scales as (P 5 / 8 /B 3 / 8) Tdet1 / 2 / (ɛcool + γTdet) , with no explicit size scaling. Tdet is the temperature just before strong pressure loss, 1/2 of the ionization potential of the dominant recycling species, ɛcool is the average plasma energy lost per injected hydrogenic and impurity atom, and γ is the sheath heat transmission factor. A recent 1-D calculation agrees well with this scaling. The implication is that the plasma exhaust problem cannot be solved by increasing R. Instead significant innovation, such as the lithium vapor box divertor, will be required. This work supported by DOE Contract No. DE-AC02-09CH11466.

  17. Polymer-Silicon Flexible Structures for Fast Chemical Vapor Detection

    Science.gov (United States)

    2007-01-01

    Engineering and School of Polymer, Textile and Fiber Engineering Georgia Institute of Technology Atlanta, GA 30332 (USA) E-mail: vladimir@mse.gatech.edu Dr...induce differential stress in a bimaterial cantilever for vapor sensing.[40] However, these coatings, amongst others (such as spin-coating, and inkjet

  18. Fundamental aspects of plasma chemical physics kinetics

    CERN Document Server

    Capitelli, Mario; Colonna, Gianpiero; Esposito, Fabrizio; Gorse, Claudine; Hassouni, Khaled; Laricchiuta, Annarita; Longo, Savino

    2016-01-01

    Describing non-equilibrium "cold" plasmas through a chemical physics approach, this book uses the state-to-state plasma kinetics, which considers each internal state as a new species with its own cross sections. Extended atomic and molecular master equations are coupled with Boltzmann and Monte Carlo methods to solve the electron energy distribution function. Selected examples in different applied fields, such as microelectronics, fusion, and aerospace, are presented and discussed including the self-consistent kinetics in RF parallel plate reactors, the optimization of negative ion sources and the expansion of high enthalpy flows through nozzles of different geometries. The book will cover the main aspects of the state-to-state kinetic approach for the description of nonequilibrium cold plasmas, illustrating the more recent achievements in the development of kinetic models including the self-consistent coupling of master equations and Boltzmann equation for electron dynamics. To give a complete portrayal, the...

  19. Potentiometric detection of chemical vapors using molecularly imprinted polymers as receptors

    Science.gov (United States)

    Liang, Rongning; Chen, Lusi; Qin, Wei

    2015-07-01

    Ion-selective electrode (ISE) based potentiometric gas sensors have shown to be promising analytical tools for detection of chemical vapors. However, such sensors are only capable of detecting those vapors which can be converted into ionic species in solution. This paper describes for the first time a polymer membrane ISE based potentiometric sensing system for sensitive and selective determination of neutral vapors in the gas phase. A molecularly imprinted polymer (MIP) is incorporated into the ISE membrane and used as the receptor for selective adsorption of the analyte vapor from the gas phase into the sensing membrane phase. An indicator ion with a structure similar to that of the vapor molecule is employed to indicate the change in the MIP binding sites in the membrane induced by the molecular recognition of the vapor. The toluene vapor is used as a model and benzoic acid is chosen as its indicator. Coupled to an apparatus manifold for preparation of vapor samples, the proposed ISE can be utilized to determine volatile toluene in the gas phase and allows potentiometric detection down to parts per million levels. This work demonstrates the possibility of developing a general sensing principle for detection of neutral vapors using ISEs.

  20. The Aging Study on Polyethylene Terephthalate with Surface Modification by Water Vapor Plasma

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The aging effects of the contact angle and surface energy on polyethylene tereph thalate (PET) have been investigated with surface modification by water vapor plasma. The experimental results show that the contact angle of water and PET decreases obviously and sur face energy increases. However, with the increase of the aging time, the contact angle and surface energy change back gradually to original state.

  1. Plasma Spray-Physical Vapor Deposition (PS-PVD) of Ceramics for Protective Coatings

    Science.gov (United States)

    Harder, Bryan J.; Zhu, Dongming

    2011-01-01

    In order to generate advanced multilayer thermal and environmental protection systems, a new deposition process is needed to bridge the gap between conventional plasma spray, which produces relatively thick coatings on the order of 125-250 microns, and conventional vapor phase processes such as electron beam physical vapor deposition (EB-PVD) which are limited by relatively slow deposition rates, high investment costs, and coating material vapor pressure requirements. The use of Plasma Spray - Physical Vapor Deposition (PS-PVD) processing fills this gap and allows thin (coatings of less than 100 microns to be generated with the flexibility to tailor microstructures by changing processing conditions. Coatings of yttria-stabilized zirconia (YSZ) were applied to NiCrAlY bond coated superalloy substrates using the PS-PVD coater at NASA Glenn Research Center. A design-of-experiments was used to examine the effects of process variables (Ar/He plasma gas ratio, the total plasma gas flow, and the torch current) on chamber pressure and torch power. Coating thickness, phase and microstructure were evaluated for each set of deposition conditions. Low chamber pressures and high power were shown to increase coating thickness and create columnar-like structures. Likewise, high chamber pressures and low power had lower growth rates, but resulted in flatter, more homogeneous layers

  2. Si Passivation and Chemical Vapor Deposition of Silicon Nitride: Final Technical Report, March 18, 2007

    Energy Technology Data Exchange (ETDEWEB)

    Atwater, H. A.

    2007-11-01

    This report investigated chemical and physical methods for Si surface passivation for application in crystalline Si and thin Si film photovoltaic devices. Overall, our efforts during the project were focused in three areas: i) synthesis of silicon nitride thin films with high hydrogen content by hot-wire chemical vapor deposition; ii) investigation of the role of hydrogen passivation of defects in crystalline Si and Si solar cells by out diffusion from hydrogenated silicon nitride films; iii) investigation of the growth kinetics and passivation of hydrogenated polycrystalline. Silicon nitride films were grown by hot-wire chemical vapor deposition and film properties have been characterized as a function of SiH4/NH3 flow ratio. It was demonstrated that hot-wire chemical vapor deposition leads to growth of SiNx films with controllable stoichiometry and hydrogen.

  3. Industrial Scale Synthesis of Carbon Nanotubes Via Fluidized Bed Chemical Vapor Deposition: A Senior Design Project

    Science.gov (United States)

    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…

  4. MBMS studies of gas-phase kinetics in diamond chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Fox, C.A. [Stanford Univ., CA (United States); McMaster, M.C. [IBM San Jose, CA (United States); Tung, D.M. [Sandia National Labs., Livermore, CA (United States)] [and others

    1995-03-01

    A molecular beam mass spectrometer system (MBMS) has been used to determine the near-surface gaseous composition involved in the low pressure chemical vapor deposition of diamond. With this system, radical and stable species can be detected with a sensitivity better than 10 ppm. Threshold ionization techniques have been employed to distinguish between radical species in the deposition environment from radical species generated by parent molecule cracking. An extensive calibration procedure was used to enable the quantitative determination of H-atom and CH{sub 3} radical mole fractions. Using the MBMS system, the gaseous composition involved in LPCVD of diamond has been measured for a wide variety of deposition conditions, including hot-filament gas activation, microwave-plasma gas activation, and a variety of precursor feed mixtures (ex: CH{sub 4}/H{sub 2}, C{sub 2}H{sub 2}/H{sub 2}). For microwave-plasma activation (MPCVD), the radical concentrations (H-atom and CH{sub 3} radicals) are independent of the identity of the precursor feed gas provided the input carbon mole fraction is constant. However, in hot-filament diamond deposition (HFCVD), the atomic hydrogen concentration decreased by an order of magnitude as the mole fraction of carbon in the precursor mixture is increased to .07; this sharp reduction has been attributed to filament poisoning of the catalytic tungsten surface via hydrocarbon deposition. Additionally, the authors find that the H-atom concentration is independent of the substrate temperature for both hot-filament and microwave plasma deposition; radial H-atom diffusion is invoked to explain this observation.

  5. Synthesis of one-dimensional boron-related nanostructures by chemical vapor deposition

    Science.gov (United States)

    Guo, Li

    in the submicron range were used to synthesize aligned BNNTs. Fine BN nanostructures with a diameter around 10-20 nm and length up to 10 microns were grown and dispersed in the Ni dots. Nanosized Ni dots were suggested for the growth of the vertically aligned BNNTs. Boron nanowires (BNWs) were also grown by the decomposition of diborane using a thermal CVD process at a temperature of 900°C, a pressure of 20 torr, diborane flow rate (5 vol.% in hydrogen) of 5 sccm, and nitrogen flow rate of 55 sccm. These BNWs had diameters in a range of 20-200 nanometers and lengths up to several tens of micrometers. Repeatable Raman spectra indicated icosahedra B12 to be the basic building units forming the B nanowires. Amorphous BNWs with rough surface were obtained without any catalysts on different substrates, such as Si wafer or ZrB2 powders. A vapor-solid (VS) growth was proposed for the amorphous BNWs, in which the solid phase precipitated directly from the vapor phase reactions. The amorphous BNWs were modified for size and composition using a plasma CVD process containing argon, ammonia and hydrogen. The diameters of these BNWs were reduced from 200 nm to several tens of nanometers, and a small amount of N was incorporated into BNWs after the plasma treatment. On the other hand, the metal catalyst proved to be effective for the growth of crystalline BNWs. Tetragonal BNWs with smooth surface were grown on thin Ni film (1 nm) coated Si substrates. Ni attachment was observed at the tip of the BNW for the first time, which indicated that the vapor-liquid-solid (VLS) growth mechanism can be used for synthesis of the BNW. The diameters of these BNWs were strongly dependent on the size of the metal particles encapsulated in the BNWs. In summary, two boron-related nanostructures were synthesized by chemical vapor deposition (CVD) in this work. A new method was successfully developed to decrease the substrate temperature more than 400°C to fabricate boron nitride nanotubes in a

  6. Investigations on the Nature of Ceramic Deposits in Plasma Spray-Physical Vapor Deposition

    Science.gov (United States)

    He, W.; Mauer, G.; Gindrat, M.; Wäger, R.; Vaßen, R.

    2017-01-01

    In Plasma Spray-Physical Vapor Deposition (PS-PVD) process, major fractions of the feedstock powder can be evaporated so that coatings are deposited mainly from the vapor phase. In this work, Computational Fluid Dynamics (CFD) results indicate that such evaporation occurs significantly in the plasma torch nozzle and even nucleation and condensation of zirconia is highly possible there. Experimental work has been performed to investigate the nature of the deposits in the PS-PVD process, in particular coatings from condensate vapor and nano-sized clusters produced at two spraying distances of 1000 mm and 400 mm. At long spraying distance, columns in the coatings have pyramidal tops and very sharp faceted microstructures. When the spraying distance is reduced to 400 mm, the tops of columns become relatively flat and a faceted structure is not recognizable. XRD patterns show obvious preferred orientations of (110) and (002) in the coatings sprayed at 400 mm but only limited texture in the coatings sprayed at 1000 mm. Meanwhile, a non-line of sight coating was also investigated, which gives an example for pure vapor deposition. Based on these analyses, a vapor and cluster depositions are suggested to further explain the formation mechanisms of high-quality columnar-structured PS-PVD thermal barrier coatings which have already shown excellent performance in cyclic lifetime test.

  7. Laser pulse propagation in a meter scale rubidium vapor/plasma cell in AWAKE experiment

    Energy Technology Data Exchange (ETDEWEB)

    Joulaei, A. [Max-Planck Institute for Physics, Munich (Germany); University of Mazandaran (Iran, Islamic Republic of); Moody, J. [Max-Planck Institute for Physics, Munich (Germany); Berti, N.; Kasparian, J. [University of Geneva (Switzerland); Mirzanejhad, S. [University of Mazandaran (Iran, Islamic Republic of); Muggli, P. [Max-Planck Institute for Physics, Munich (Germany)

    2016-09-01

    We present the results of numerical studies of laser pulse propagating in a 3.5 cm Rb vapor cell in the linear dispersion regime by using a 1D model and a 2D code that has been modified for our special case. The 2D simulation finally aimed at finding laser beam parameters suitable to make the Rb vapor fully ionized to obtain a uniform, 10 m-long, at least 1 mm in radius plasma in the next step for the AWAKE experiment. - Highlights: • Discussion the AWAKE plasma source based on photoionization of rubidium vapor with a TW/cm^2 Intensity laser with a spectrum across valence ground state transition resonances. • Examines the propagation of the AWAKE ionization laser through rubidium vapor at design density on a small scale and reduced intensity with a linear numerical model compared to experimental results. • Discusses physics of pulse propagation through the vapor at high intensity regime where strong ionization occurs within the laser pulse.

  8. Characterization of atmospheric pressure plasma treated pure cashmere and wool/cashmere textiles: Treatment in air/water vapor mixture

    Energy Technology Data Exchange (ETDEWEB)

    Zanini, Stefano, E-mail: stefano.zanini@mib.infn.it [Università degli Studi di Milano-Bicocca, Dipartimento di Fisica “G. Occhialini”, p.za della Scienza, 3, I-20126 Milano (Italy); Grimoldi, Elisa [Università degli Studi di Milano-Bicocca, Dipartimento di Fisica “G. Occhialini”, p.za della Scienza, 3, I-20126 Milano (Italy); Citterio, Attilio [Politecnico di Milano, Dipartimento di Chimica, Materiali ed Ingegneria Chimica “G. Natta”, Via Mancinelli 7, I-20131 Milano (Italy); Riccardi, Claudia, E-mail: riccardi@mib.infn.it [Università degli Studi di Milano-Bicocca, Dipartimento di Fisica “G. Occhialini”, p.za della Scienza, 3, I-20126 Milano (Italy)

    2015-09-15

    Highlights: • We treated cashmere and wool/cashmere textiles with atmospheric pressure plasma. • Wettability of the fabrics was increased. • The increment in wettability derived from a surface oxidation of the fibers. • Only minor etching effects were observed with scanning electron microscopy. - Abstract: We performed atmospheric pressure plasma treatments of pure cashmere and wool/cashmere textiles with a dielectric barrier discharge (DBD) in humid air (air/water vapor mixtures). Treatment parameters have been optimized in order to enhance the wettability of the fabrics without changing their bulk properties as well as their touch. A deep characterization has been performed to study the wettability, the surface morphologies, the chemical composition and the mechanical properties of the plasma treated textiles. The chemical properties of the plasma treated samples were investigated with attenuated total reflectance Fourier transform infrared (FTIR/ATR) spectroscopy and X-ray photoelectron microscopy (XPS). The analyses reveal a surface oxidation of the treated fabrics, which enhances their surface wettability. Morphological characterization of the treated fibers with scanning electron microscopy (SEM) reveals minor etching effects, an essential feature for the maintenance of the textile softness.

  9. Porous wall hollow glass microsphere as an optical microresonator for chemical vapor detection

    Science.gov (United States)

    Wang, Hanzheng; Yuan, Lei; Kim, Cheol-Woon; Pienkowski, Edward; Xiao, Hai

    2012-02-01

    Optical microresonators have been proven effective for developing sensitive chemical and biological sensors by monitoring the changes in refractive index or mass near the resonator surface. The rotationally symmetric structures support high quality (Q) whispering gallery modes (WGMs) that interact with the local environment through the evanescent field. The long photon lifetime of the high-Q resonator (thus the long light-material interaction path) is the key reason that a microresonator can achieve very high sensitivity in detection. In this paper, we present our recent research on using porous wall hollow glass microsphere (PW-HGM) as an optical microresonator for chemical vapor detection. The diameter of the PW-HGM ranges from 10μm to 100μm. The wall thickness is about 2μm and the pore size is about 20nm. The Q-factors and free spectrum ranges (FSR) of PW-HGMs were measured by coupling light into the PW-HGM using a single mode fiber taper. Various types of chemical vapors were used to characterize the PW-HGM resonator. The resonant wavelength shift was measured as a function of vapor concentration. Comparisons between a PW-HGM and a solid glass microsphere indicated that a PW-HGM can effectively adsorb vapor molecules into its nanosized pores, providing a direct and long light-material interaction path for significant sensitivity enhancement for chemical vapor detection.

  10. Evaporation and Vapor Shielding of CFC Targets Exposed to Plasma Heat Fluxes Relevant to ITER ELMs

    Energy Technology Data Exchange (ETDEWEB)

    Safronov, V.; Arkhipov, N.I.; Toporkov, D.A.; Zhitlukhin, A.M. [Troitsk Inst. for Innovation and Fusion Research, TRINITI, Kostromskaya, 12A, 79, RU-142092 Troitsk, Moscow Region (Russian Federation); Landman, I. [FZK-Forschungszentrum Karlsruhe, Association Euratom-FZK, Technik und Umwelt, Postfach 3640, D-7602l Karlsruhe (Germany)

    2007-07-01

    Full text of publication follows: Carbon-fibre composite (CFC) is foreseen presently as armour material for the divertor target in ITER. During the transient processes such as instabilities of Edge Localized Modes (ELMs) the target as anticipated will be exposed to the plasma heat loads of a few MJ/m{sup 2} on the time scale of a fraction of ms, which causes an intense evaporation at the target surface and contaminates tokamak plasma by evaporated carbon. The ITER transient loads are not achievable at existing tokamaks therefore for testing divertor armour materials other facilities, in particular plasma guns are employed. In the present work the CFC targets have been tested for ITER at the plasma gun facility MK- 200 UG in Troitsk by ELM relevant heat fluxes. The targets in the applied magnetic field up to 2 T were irradiated by hydrogen plasma streams of diameter 6 - 8 cm, impact ion energy 2 - 3 keV, pulse duration 0.05 ms and energy density varying in the range 0.05 - 1 MJ/m{sup 2}. Primary attention has been focused on the measurement of evaporation threshold and investigation of carbon vapor properties. Fast infrared pyrometer, optical and VUV spectrometers, framing cameras and plasma calorimeters were applied as diagnostics. The paper reports the results obtained on the evaporation threshold of CFC, the evaporation rate of the carbon fibers oriented parallel and perpendicular to the exposed target surface, the velocity of carbon vapor motion along and across the magnetic field lines, and the parameters of carbon plasma such as temperature, density and ionization state measured up to the distance 15 cm at varying plasma load. First experimental results on investigation of the vapor shield onset conditions are presented also. (authors)

  11. Laser pulse propagation in a meter scale rubidium vapor/plasma cell in AWAKE experiment

    Science.gov (United States)

    Joulaei, A.; Moody, J.; Berti, N.; Kasparian, J.; Mirzanejhad, S.; Muggli, P.

    2016-09-01

    We present the results of numerical studies of laser pulse propagating in a 3.5 cm Rb vapor cell in the linear dispersion regime by using a 1D model and a 2D code that has been modified for our special case. The 2D simulation finally aimed at finding laser beam parameters suitable to make the Rb vapor fully ionized to obtain a uniform, 10 m-long, at least 1 mm in radius plasma in the next step for the AWAKE experiment.

  12. Laser pulse propagation in a meter scale rubidium vapor/plasma cell in AWAKE experiment

    CERN Document Server

    Joulaei, Atefeh; Berti, Nicolas; Kasparian, Jerome; Mirzanejhad, Saeed; Muggli, Patric

    2016-01-01

    We present the results of numerical studies of laser pulse propagating in a 3.5 cm Rb vapor cell in the linear dispersion regime by using a 1D model and a 2D code that has been modified for our special case. The 2D simulation finally aimed at finding laser beam parameters suitable to make the Rb vapor fully ionized to obtain a uniform, 10 m-long, at least 1 mm in radius plasma in the next step for the AWAKE experiment.

  13. Assessment and control of chemical risk from organic vapors for attendants in a gas station

    Directory of Open Access Journals (Sweden)

    Stephanie Ehmig Santillán

    2015-12-01

    Full Text Available This research comprises monitoring, assessment and recommendations for chemical risk originating from organic vapors (benzene, toluene and xylene of fuel (super and extra gasoline to which attendants at a gas station are exposed. Given the concentration measured of organic vapors (benzene, toluene and xylene the chemical risk to which attendants are exposed in the supply area is acceptable. Control measures are recommended to ensure healthy working conditions for gas station attendants and also to avoid occurrence of occupational diseases in the medium or long term

  14. Spontaneous oscillations and pattern formation during chemical vapor deposition of metastable InN.

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, F.; Munkholm, A.; Wang, R.-V.; Streiffer, S. K.; Thompson, C.; Fuoss, P. H.; Latifi, K.; Elder, K. R.; Stephenson, G. B.; Philips Lumileds Lighting Co.; Northern Illinois Univ.; Oakland Univ.; Ohio Univ.; Intel Corp.

    2008-01-01

    We report observations of self-sustaining spatiotemporal chemical oscillations during metal-organic chemical vapor deposition of InN onto GaN. Under constant supply of vapor precursors trimethylindium and NH{sub 3}, the condensed-phase cycles between crystalline islands of InN and elemental In droplets. Propagating fronts between regions of InN and In occur with linear, circular, and spiral geometries. The results are described by a model in which the nitrogen activity produced by surface-catalyzed NH{sub 3} decomposition varies with the exposed surface areas of GaN, InN, and In.

  15. Spontaneous oscillations and waves during chemical vapor deposition of InN.

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, F.; Munkholm, A.; Wang, R.-V.; Streiffer, S. K.; Thompson, C.; Fuoss, P. H.; Latifi, K.; Elder, K. R.; Stephenson, G. B.; Philips Lumileds Lighting Co.; Northern Illinois Univ.; Oakland Univ.

    2008-08-22

    We report observations of self-sustaining spatiotemporal chemical oscillations during metal-organic chemical vapor deposition of InN onto GaN. Under constant supply of vapor precursors trimethylindium and NH{sub 3}, the condensed-phase cycles between crystalline islands of InN and elemental In droplets. Propagating fronts between regions of InN and In occur with linear, circular, and spiral geometries. The results are described by a model in which the nitrogen activity produced by surface-catalyzed NH{sub 3} decomposition varies with the exposed surface areas of GaN, InN, and In.

  16. Half-sandwich cobalt complexes in the metal-organic chemical vapor deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Georgi, Colin [Technische Universität Chemnitz, Faculty of Natural Science, Institute of Chemistry, Inorganic Chemistry, Chemnitz 09107 (Germany); Hapke, Marko; Thiel, Indre [Leibniz-Institut für Katalyse e.V. an der Universität Rostock (LIKAT), Albert-Einstein-Straße 29a, Rostock 18059 (Germany); Hildebrandt, Alexander [Technische Universität Chemnitz, Faculty of Natural Science, Institute of Chemistry, Inorganic Chemistry, Chemnitz 09107 (Germany); Waechtler, Thomas; Schulz, Stefan E. [Fraunhofer Institute of Electronic Nano Systems (ENAS), Technologie-Campus 3, Chemnitz 09126 (Germany); Technische Universität Chemnitz, Center for Microtechnologies (ZfM), Chemnitz 09107 (Germany); Lang, Heinrich, E-mail: heinrich.lang@chemie.tu-chemnitz.de [Technische Universität Chemnitz, Faculty of Natural Science, Institute of Chemistry, Inorganic Chemistry, Chemnitz 09107 (Germany)

    2015-03-02

    A series of cobalt half-sandwich complexes of type [Co(η{sup 5}-C{sub 5}H{sub 5})(L)(L′)] (1: L, L′ = 1,5-hexadiene; 2: L = P(OEt){sub 3}, L′ = H{sub 2}C=CHSiMe{sub 3}; 3: L = L′ = P(OEt){sub 3}) has been studied regarding their physical properties such as the vapor pressure, decomposition temperature and applicability within the metal-organic chemical vapor deposition (MOCVD) process, with a focus of the influence of the phosphite ligands. It could be shown that an increasing number of P(OEt){sub 3} ligands increases the vapor pressure and thermal stability of the respective organometallic compound. Complex 3 appeared to be a promising MOCVD precursor with a high vapor pressure and hence was deposited onto Si/SiO{sub 2} (100 nm) substrates. The resulting reflective layer is closed, dense and homogeneous, with a slightly granulated surface morphology. X-ray photoelectron spectroscopy (XPS) studies demonstrated the formation of metallic cobalt, cobalt phosphate, cobalt oxide and cobalt carbide. - Highlights: • Thermal studies and vapor pressure measurements of cobalt half-sandwich complexes was carried out. • Chemical vapor deposition with cobalt half-sandwich complexes is reported. • The use of Co-phosphites results in significant phosphorous-doped metallic layers.

  17. Study of water molecules disociative adsorption in water vapor plasma

    OpenAIRE

    Liudvikas PRANEVIČIUS

    2013-01-01

    Heterogeneous photocatalysis involves the use of a semi-conducting material which can be excited by the absorption of light. The most commonly employed photocatalyst material for research and industrial applications is titanium dioxide (TiO2). This is because it is photostable, chemically stable, photoactive, relatively inexpensive and non-toxic. Previous investigations performed in collaboration with researchers of the Lithuanian Energy Institute and Kaunas University of Technology researche...

  18. A new modular multichamber plasma enhanced chemical vapor deposition system

    Science.gov (United States)

    Madan, A.; Rava, P.; Schropp, R. E. I.; von Roedern, B.

    1993-06-01

    The present work reports on a new modular UHV multichamber PECVD system with characteristics which prevent both the incorporation of residual impurities and cross contamination between different layers. A wide range of intrinsic and doped hydrogenated amorphous silicon (a-Si:H) materials have been produced and single junction pin solar cells with an efficiency greater than 10% have been readily obtained with little optimization. The system contains three UHV modular process zones (MPZ's); the MPZ's and a load lock chamber are located around a central isolation and transfer zone which contains the transport mechanism consisting of an arm with radial and linear movement. This configuration allows for introduction of the substrate into the MPZ's in any sequence so that any type of multilayer device can be produced. The interelectrode distance in the MPZ's can be adjusted between 1 and 5 cm. This has been found to be an important parameter in the optimisation of the deposition rate and of the uniformity. The multichamber concept also allows individually optimized deposition temperatures and interelectrode distances for the various layers. The system installed in Utrecht will be employed for further optimization of single junction solar cells and for research and development of stable a-Si:H tandem cells.

  19. Selected area chemical vapor deposition of thin films for conductometric microelectronic chemical sensors

    Science.gov (United States)

    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

  20. Evaluation of Chemical Warfare Agent Percutaneous Vapor Toxicity: Derivation of Toxicity Guidelines for Assessing Chemical Protective Ensembles.

    Energy Technology Data Exchange (ETDEWEB)

    Watson, A.P.

    2003-07-24

    Percutaneous vapor toxicity guidelines are provided for assessment and selection of chemical protective ensembles (CPEs) to be used by civilian and military first responders operating in a chemical warfare agent vapor environment. The agents evaluated include the G-series and VX nerve agents, the vesicant sulfur mustard (agent HD) and, to a lesser extent, the vesicant Lewisite (agent L). The focus of this evaluation is percutaneous vapor permeation of CPEs and the resulting skin absorption, as inhalation and ocular exposures are assumed to be largely eliminated through use of SCBA and full-face protective masks. Selection of appropriately protective CPE designs and materials incorporates a variety of test parameters to ensure operability, practicality, and adequacy. One aspect of adequacy assessment should be based on systems tests, which focus on effective protection of the most vulnerable body regions (e.g., the groin area), as identified in this analysis. The toxicity range of agent-specific cumulative exposures (Cts) derived in this analysis can be used as decision guidelines for CPE acceptance, in conjunction with weighting consideration towards more susceptible body regions. This toxicity range is bounded by the percutaneous vapor estimated minimal effect (EME{sub pv}) Ct (as the lower end) and the 1% population threshold effect (ECt{sub 01}) estimate. Assumptions of exposure duration used in CPE certification should consider that each agent-specific percutaneous vapor cumulative exposure Ct for a given endpoint is a constant for exposure durations between 30 min and 2 hours.

  1. Organic, inorganic and total mercury determination in fish by chemical vapor generation with collection on a gold gauze and electrothermal atomic absorption spectrometry

    Science.gov (United States)

    Duarte, Fábio Andrei; Bizzi, Cezar Augusto; Antes, Fabiane Goldschmidt; Dressler, Valderi Luiz; Flores, Érico Marlon de Moraes

    2009-06-01

    A method for organic, inorganic and total mercury determination in fish tissue has been developed using chemical vapor generation and collection of mercury vapor on a gold gauze inside a graphite tube and further atomization by electrothermal atomic absorption spectrometry. After drying and cryogenic grinding, potassium bromide and hydrochloric acid solution (1 mol L - 1 KBr in 6 mol L - 1 HCl) was added to the samples. After centrifugation, total mercury was determined in the supernatant. Organomercury compounds were selectively extracted from KBr solution using chloroform and the resultant solution was back extracted with 1% m/v L-cysteine. This solution was used for organic Hg determination. Inorganic Hg remaining in KBr solution was directly determined by chemical vapor generation electrothermal atomic absorption spectrometry. Mercury vapor generation from extracts was performed using 1 mol L - 1 HCl and 2.5% m/v NaBH 4 solutions and a batch chemical vapor generation system. Mercury vapor was collected on the gold gauze heated resistively at 80 °C and the atomization temperature was set at 650 °C. The selectivity of extraction was evaluated using liquid chromatography coupled to chemical vapor generation and determination by inductively coupled plasma mass spectrometry. The proposed method was applied for mercury analysis in shark, croaker and tuna fish tissues. Certified reference materials were used to check accuracy and the agreement was better than 95%. The characteristic mass was 60 pg and method limits of detection were 5, 1 and 1 ng g - 1 for organic, inorganic and total mercury, respectively. With the proposed method it was possible to analyze up to 2, 2 and 6 samples per hour for organic, inorganic and total Hg determination, respectively.

  2. Organic, inorganic and total mercury determination in fish by chemical vapor generation with collection on a gold gauze and electrothermal atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Duarte, Fabio Andrei; Bizzi, Cezar Augusto; Goldschmidt Antes, Fabiane; Dressler, Valderi Luiz [Departamento de Quimica, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); Flores, Erico Marlon de Moraes [Departamento de Quimica, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil)], E-mail: flores@quimica.ufsm.br

    2009-06-15

    A method for organic, inorganic and total mercury determination in fish tissue has been developed using chemical vapor generation and collection of mercury vapor on a gold gauze inside a graphite tube and further atomization by electrothermal atomic absorption spectrometry. After drying and cryogenic grinding, potassium bromide and hydrochloric acid solution (1 mol L{sup - 1} KBr in 6 mol L{sup - 1} HCl) was added to the samples. After centrifugation, total mercury was determined in the supernatant. Organomercury compounds were selectively extracted from KBr solution using chloroform and the resultant solution was back extracted with 1% m/v L-cysteine. This solution was used for organic Hg determination. Inorganic Hg remaining in KBr solution was directly determined by chemical vapor generation electrothermal atomic absorption spectrometry. Mercury vapor generation from extracts was performed using 1 mol L{sup - 1} HCl and 2.5% m/v NaBH{sub 4} solutions and a batch chemical vapor generation system. Mercury vapor was collected on the gold gauze heated resistively at 80 deg. C and the atomization temperature was set at 650 deg. C. The selectivity of extraction was evaluated using liquid chromatography coupled to chemical vapor generation and determination by inductively coupled plasma mass spectrometry. The proposed method was applied for mercury analysis in shark, croaker and tuna fish tissues. Certified reference materials were used to check accuracy and the agreement was better than 95%. The characteristic mass was 60 pg and method limits of detection were 5, 1 and 1 ng g{sup - 1} for organic, inorganic and total mercury, respectively. With the proposed method it was possible to analyze up to 2, 2 and 6 samples per hour for organic, inorganic and total Hg determination, respectively.

  3. Evaluation of vapor generation for the determination of nickel by inductively coupled plasma-atomic emission spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Marrero, Julieta [Comision Nacional de Energia Atomica, Unidad de Actividad Quimica, Centro Atomico Constituyentes, Av. Gral. Paz 1499, 1650-San Martin, Pcia. de Buenos Aires (Argentina); Smichowski, Patricia [Comision Nacional de Energia Atomica, Unidad Proyectos Especiales de Suministros Nucleares, Av. Libertador 8250, 1429-Buenos Aires (Argentina)

    2002-09-01

    Volatile species of Ni were generated by merging acidified aqueous samples and sodium tetrahydroborate(III) in a continuous flow system. The gaseous analyte was subsequently introduced via a stream of Ar carrier into the inlet tube of the plasma torch. Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used for detection. The operating conditions (chemical and physical parameters) and the concentrations of different acids were evaluated for the efficient generation of Ni vapor. The detection limit (3 {sigma}{sub blank}) was 1.8 ng mL{sup -1}. The precision (RSD) of the determination was 4.2% at a level of 500 ng mL{sup -1} and 7.3% for 20 ng mL{sup -1} (n=10). The efficiency of the generation process was estimated to be 51%. The possible interfering effect of transition metals (Cd, Co, Cu, Cr, Fe, Mn, Zn), hydride forming elements (As, Ge, Pb, Sb, Se, Sn, Te), and Hg on Ni signal was examined. This study has demonstrated that Ni vapor generation is markedly free of interferences. (orig.)

  4. Silicon epitaxy using tetrasilane at low temperatures in ultra-high vacuum chemical vapor deposition

    Science.gov (United States)

    Hazbun, Ramsey; Hart, John; Hickey, Ryan; Ghosh, Ayana; Fernando, Nalin; Zollner, Stefan; Adam, Thomas N.; Kolodzey, James

    2016-06-01

    The deposition of silicon using tetrasilane as a vapor precursor is described for an ultra-high vacuum chemical vapor deposition tool. The growth rates and morphology of the Si epitaxial layers over a range of temperatures and pressures are presented. The layers were characterized using transmission electron microscopy, x-ray diffraction, spectroscopic ellipsometry, Atomic Force Microscopy, and secondary ion mass spectrometry. Based on this characterization, high quality single crystal silicon epitaxy was observed. Tetrasilane was found to produce higher growth rates relative to lower order silanes, with the ability to deposit crystalline Si at low temperatures (T=400 °C), with significant amorphous growth and reactivity measured as low as 325 °C, indicating the suitability of tetrasilane for low temperature chemical vapor deposition such as for SiGeSn alloys.

  5. Physico-chemical mechanism for the vapors sensitivity of photoluminescent InP quantum dots

    Science.gov (United States)

    Prosposito, P.; De Angelis, R.; De Matteis, F.; Hatami, F.; Masselink, W. T.; Zhang, H.; Casalboni, M.

    2016-03-01

    InP/InGaP surface quantum dots are interesting materials for optical chemical sensors since they present an intense emission at room temperature, whose intensity changes rapidly and reversibly depending on the composition of the environmental atmosphere. We present here their emission properties by time resolved photoluminescence spectroscopy investigation and we discuss the physico-chemical mechanism behind their sensitivity to the surrounding atmosphere. Photoluminescence transients in inert atmosphere (N2) and in solvent vapours of methanol, clorophorm, acetone and water were measured. The presence of vapors of clorophorm, acetone and water showed a very weak effect on the transient times, while an increase of up to 15% of the decay time was observed for methanol vapour exposure. On the basis of the vapor molecule nature (polarity, proticity, steric hindrance, etc.) and of the interaction of the vapor molecules with the quantum dots surface a sensing mechanism involving quantum dots non-radiative surface states is proposed.

  6. Density-controlled growth of well-aligned ZnO nanowires using chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Well-aligned ZnO nanowires were grown on Si substrate by chemical vapor deposition.The experimental results showed that the density of nanowires was related to the heating process and growth temperature.High-density ZnO nanowires were obtained under optimal conditions.The growth mechanism of the ZnO nanowires was presented as well.

  7. Tip-based chemical vapor deposition with a scanning nano-heater

    NARCIS (Netherlands)

    Gaitas, A.

    2013-01-01

    In this preliminary effort, a moving nano-heater directs a chemical vapor deposition reaction (nano-CVD) demonstrating a tip-based nanofabrication (TBN) method. Localized nano-CVD of copper (Cu) and copper oxide (CuO) on a silicon (Si) and silicon oxide (SiO2) substrate from gasses, namely sublimate

  8. Silicon nitride at high growth rate using hot wire chemical vapor deposition

    NARCIS (Netherlands)

    Verlaan, V.

    2008-01-01

    Amorphous silicon nitride (SiNx) is a widely studied alloy with many commercial applications. This thesis describes the application of SiNx deposited at high deposition rate using hot wire chemical vapor deposition (HWCVD) for solar cells and thin film transistors (TFTs). The deposition process of H

  9. Chemical Vapor Deposition of Atomically-Thin Molybdenum Disulfide (MoS2)

    Science.gov (United States)

    2015-03-01

    photoluminescence. 15. SUBJECT TERMS Chemical vapor deposition (CVD) Nanotechnology Molybdenum disulfide (MoS2) Raman spectroscopy 16...by ANSI Std. Z39.18 UNCLASSIFIED Approved for public release; distribution is unlimited. i CONTENTS Page Introduction 1...UNCLASSIFIED Approved for public release; distribution is unlimited. 1 INTRODUCTION Recently, an explosion of interest in low-dimensional

  10. Silicon nitride at high growth rate using hot wire chemical vapor deposition

    NARCIS (Netherlands)

    Verlaan, V.

    2008-01-01

    Amorphous silicon nitride (SiNx) is a widely studied alloy with many commercial applications. This thesis describes the application of SiNx deposited at high deposition rate using hot wire chemical vapor deposition (HWCVD) for solar cells and thin film transistors (TFTs). The deposition process of H

  11. Tandem solar cells deposited using hot-wire chemical vapor deposition

    NARCIS (Netherlands)

    Veen, M.K. van

    2003-01-01

    In this thesis, the application of the hot-wire chemical vapor deposition (HWCVD) technique for the deposition of silicon thin films is described. The HWCVD technique is based on the dissociation of silicon-containing gasses at the catalytic surface of a hot filament. Advantages of this technique ar

  12. Low temperature junction growth using hot-wire chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qi; Page, Matthew; Iwaniczko, Eugene; Wang, Tihu; Yan, Yanfa

    2014-02-04

    A system and a process for forming a semi-conductor device, and solar cells (10) formed thereby. The process includes preparing a substrate (12) for deposition of a junction layer (14); forming the junction layer (14) on the substrate (12) using hot wire chemical vapor deposition; and, finishing the semi-conductor device.

  13. Growth Process Conditions of Tungsten Oxide Thin Films Using Hot-Wire Chemical Vapor Deposition

    NARCIS (Netherlands)

    Houweling, Z.S.; Geus, J.W.; de Jong, M.; Harks, P.P.R.M.L.; van der Werf, C.H.M.; Schropp, R.E.I.

    2011-01-01

    We report the growth conditions of nanostructured tungsten oxide (WO3−x) thin films using hot-wire chemical vapor deposition (HWCVD). Two tungsten filaments were resistively heated to various temperatures and exposed to an air flow at various subatmospheric pressures. The oxygen partial pressure was

  14. Kinetic Study of the Chemical Vapor Deposition of Tantalum in Long Narrow Channels

    DEFF Research Database (Denmark)

    Mugabi, James Atwoki; Eriksen, Søren; Petrushina, Irina

    2016-01-01

    A kinetic study of the chemical vapor deposition of tantalum in long narrow channels is done to optimize the industrial process for the manufacture of tantalum coated plate heat exchangers. The developed model fits well at temperatures between 750 and 850 °C, and in the pressure range of25–990 mb...

  15. Initiated-chemical vapor deposition of organosilicon layers: Monomer adsorption, bulk growth, and process window definition

    NARCIS (Netherlands)

    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

  16. Chemical hazards present in liquids and vapors of electronic cigarettes.

    Science.gov (United States)

    Hutzler, Christoph; Paschke, Meike; Kruschinski, Svetlana; Henkler, Frank; Hahn, Jürgen; Luch, Andreas

    2014-07-01

    Electronic (e-)cigarettes have emerged in recent years as putative alternative to conventional tobacco cigarettes. These products do not contain typical carcinogens that are present in tobacco smoke, due to the lack of combustion. However, besides nicotine, hazards can also arise from other constituents of liquids, such as solvents, flavors, additives and contaminants. In this study, we have analyzed 28 liquids of seven manufacturers purchased in Germany. We confirm the presence of a wide range of flavors to enhance palatability. Although glycerol and propylene glycol were detected in all samples, these solvents had been replaced by ethylene glycol as dominant compound in five products. Ethylene glycol is associated with markedly enhanced toxicological hazards when compared to conventionally used glycerol and propylene glycol. Additional additives, such as coumarin and acetamide, that raise concerns for human health were detected in certain samples. Ten out of 28 products had been declared "free-of-nicotine" by the manufacturer. Among these ten, seven liquids were identified containing nicotine in the range of 0.1-15 µg/ml. This suggests that "carry over" of ingredients may occur during the production of cartridges. We have further analyzed the formation of carbonylic compounds in one widely distributed nicotine-free brand. Significant amounts of formaldehyde, acetaldehyde and propionaldehyde were only found at 150 °C by headspace GC-MS analysis. In addition, an enhanced formation of aldehydes was found in defined puff fractions, using an adopted machine smoking protocol. However, this effect was delayed and only observed during the last third of the smoking procedure. In the emissions of these fractions, which represent up to 40 % of total vapor volume, similar levels of formaldehyde were detected when compared to conventional tobacco cigarettes. By contrast, carbonylic compounds were hardly detectable in earlier collected fractions. Our data demonstrate the

  17. Chemical vapor detection using a capacitive micromachined ultrasonic transducer.

    Science.gov (United States)

    Lee, Hyunjoo J; Park, Kwan Kyu; Kupnik, Mario; Oralkan, O; Khuri-Yakub, Butrus T

    2011-12-15

    Distributed sensing of gas-phase chemicals using highly sensitive and inexpensive sensors is of great interest for many defense and consumer applications. In this paper we present ppb-level detection of dimethyl methylphosphonate (DMMP), a common simulant for sarin gas, with a ppt-level resolution using an improved capacitive micromachined ultrasonic transducer (CMUT) as a resonant chemical sensor. The improved CMUT operates at a higher resonant frequency of 47.7 MHz and offers an improved mass sensitivity of 48.8 zg/Hz/μm(2) by a factor of 2.7 compared to the previous CMUT sensors developed. A low-noise oscillator using the CMUT resonant sensor as the frequency-selective device was developed for real-time sensing, which exhibits an Allan deviation of 1.65 Hz (3σ) in the presence of a gas flow; this translates into a mass resolution of 80.5 zg/μm(2). The CMUT resonant sensor is functionalized with a 50-nm thick DKAP polymer developed at Sandia National Laboratory for dimethyl methylphosphonate (DMMP) detection. To demonstrate ppb-level detection of the improved chemical sensor system, the sensor performance was tested at a certified lab (MIT Lincoln Laboratory), which is equipped with an experimental chemical setup that reliably and accurately delivers a wide range of low concentrations down to 10 ppb. We report a high volume sensitivity of 34.5 ± 0.79 pptv/Hz to DMMP and a good selectivity of the polymer to DMMP with respect to dodecane and 1-octanol.

  18. Physical-Chemical Characterization of Nanodispersed Powders Produced by a Plasma-Chemical Technique

    Institute of Scientific and Technical Information of China (English)

    M. GEORGIEVA; G. VISSOKOV; Iv. GRANCHAROV

    2007-01-01

    This article presents a review on the physical-chemical properties and characteristics of plasma-chemically produced nanodispersed powders (NDP), such as metals, oxides, nitrides, carbides, and catalysts. The plasma-chemical preparation of the powders was carried out in thermal plasma (TP) created by means of high-current electric arcs, plasma jets, high-frequency (HF) discharges, etc. We also discuss certain properties and characteristics of the NDPs, which are determined largely by the conditions of preparation.

  19. Processing Research on Chemically Vapor Deposited Silicon Nitride.

    Science.gov (United States)

    1979-12-01

    7 A-A79 328 GENERAL ELECTR IC Co PHILADELPH IA PA RE-ENTRY AND ENV--ETC F/S 3/ PROCESING RESEARCH ON CHEMICALLY VAPR DEPOSITED SILICON HITRI ETCIU) I...NH)2] x-- .Si3N 4 as well as NH 3 2) 3SiCI + 6H --- 3i + 6 HC - Si N 4 2 (V,l1) 3 4 pressure may play a part in shifting the deposition sequence from...hot-wall reactor should be further refined with em- phasis on the formation of figured geometries (hemispherical and ogive shells). As part of this

  20. Chemical vapor deposition (CVD) of uranium for alpha spectrometry; Deposicion quimica de vapor (CVD) de uranio para espectrometria alfa

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez V, M. L.; Rios M, C.; Ramirez O, J.; Davila R, J. I.; Mireles G, F., E-mail: luisalawliet@gmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2015-09-15

    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)

  1. PARTICLE COATING BY CHEMICAL VAPOR DEPOSITION IN A FLUIDI7ED BED REACTOR

    Institute of Scientific and Technical Information of China (English)

    Gregor; Czok; Joachim; Werther

    2005-01-01

    Aluminum coatings were created onto glass beads by chemical vapor deposition in a fluidized bed reactor at different temperatures. Nitrogen was enriched with Triisobutylaluminum (TIBA) vapor and the latter was thermally decomposed inside the fluidized bed to deposit the elemental aluminum. To ensure homogeneous coating on the bed material, the fluidizing conditions necessary to avoid agglomeration were investigated for a broad range of temperatures.The deposition reaction was modeled on the basis of a discrete particle simulation to gain insight into homogeneity and thickness of the coating throughout the bed material. In particular, the take-up of aluminum was traced for selected particles that exhibited a large mass of deposited aluminum.

  2. Rapid synthesis of tantalum oxide dielectric films by microwave microwave-assisted atmospheric chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ndiege, Nicholas [School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801 (United States)], E-mail: ndiege@uiuc.edu; Subramanian, Vaidyanathan [School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801 (United States)], E-mail: ravisv@unr.edu; Shannon, Mark A. [Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green street, Urbana, IL 61801 (United States)], E-mail: mshannon@uiuc.edu; Masel, Richard I. [School of Chemical Sciences, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801 (United States)], E-mail: r-masel@uiuc.edu

    2008-10-01

    Microwave-assisted chemical vapor deposition has been used to generate high quality, high-k dielectric films on silicon at high deposition rates with film thicknesses varying from 50 nm to 110 {mu}m using inexpensive equipment. Characterization of the post deposition products was performed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy and Raman spectroscopy. Film growth was determined to occur via rapid formation and accumulation of tantalum oxide clusters from tantalum (v) ethoxide (Ta(OC{sub 2}H{sub 5}){sub 5}) vapor on the deposition surface.

  3. Synthesis of silicon carbide nanowires by solid phase source chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    NI Jie; LI Zhengcao; ZHANG Zhengjun

    2007-01-01

    In this paper,we report a simple approach to synthesize silicon carbide(SiC)nanowires by solid phase source chemical vapor deposition(CVD) at relatively low temperatures.3C-SiC nanowires covered by an amorphous shell were obtained on a thin film which was first deposited on silicon substrates,and the nanowires are 20-80 am in diameter and several μm in length,with a growth direction of[200].The growth of the nanowires agrees well on vapor-liquid-solid (VLS)process and the film deposited on the substrates plays an important role in the formation of nanowires.

  4. Deoiled asphalt as carbon source for preparation of various carbon materials by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xuguang; Yang, Yongzhen; Lin, Xian; Xu, Bingshe; Zhang, Yan [Key Laboratory of Interface Science and Engineering in Advanced Materials of Taiyuan University of Technology, Ministry of Education, Taiyuan 030024 (China)

    2006-10-15

    Various carbon materials, including vapor grown carbon fibers (VGCFs) and carbon trees, were synthesized by chemical vapor deposition in argon atmosphere, using deoiled asphalt as carbon source and ferrocene as catalyst. Pure carbon microbeads (CMBs) were also obtained by this method in the absence of ferrocene. The influence of different growth parameters, such as ferrocene content, reaction temperature, retention time and argon flow rate, was investigated, with respect to morphology and product yield. The products were characterized by field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and Raman spectroscopy. (author)

  5. A Comparison between Thin-Film Transistors Deposited by Hot-Wire Chemical Vapor Deposition and PECVD

    Directory of Open Access Journals (Sweden)

    Meysam Zarchi

    2015-03-01

    Full Text Available The effect of new growth techniques on the mobility and stability of amorphous silicon (a-Si:H thin film transistors (TFTs has been studied. It was suggested that the key parameter controlling the field-effect mobility and stability is the intrinsic stress in the a-Si:H layer. Amorphous and microcrystalline silicon films were deposited by radiofrequency plasma enhanced chemical vapor deposition (RF-PECVD and hot-wire chemical vapor deposition (HW-CVD at 100 ºC and 25 ºC. Structural properties of these films were measured by Raman Spectroscopy. Electronic properties were measured by dark conductivity, σd, and photoconductivity, σph. For amorphous silicon films deposited by RF-PECVD on PET, photosensitivity's of >105 were obtained at both 100 º C and 25 ºC. For amorphous silicon films deposited by HW-CVD, a photosensitivity of > 105 was obtained at 100 ºC. Microcrystalline silicon films deposited by HW-CVD at 95% hydrogen dilution show σph~ 10-4 Ω-1cm-1, while maintaining a photosensitivity of ~102 at both 100 ºC and 25 ºC. Microcrystalline silicon films with a large crystalline fraction (> 50% can be deposited by HW-CVD all the way down to room temperature.

  6. Discrete formulation of mixed finite element methods for vapor deposition chemical reaction equations

    Institute of Scientific and Technical Information of China (English)

    LUO Zhen-dong; ZHOU Yan-jie; ZHU Jiang

    2007-01-01

    The vapor deposition chemical reaction processes, which are of extremely extensive applications, can be classified as a mathematical modes by the following governing nonlinear partial differential equations containing velocity vector,temperature field,pressure field,and gas mass field.The mixed finite element(MFE)method is employed to study the system of equations for the vapor deposition chemical reaction processes.The semidiscrete and fully discrete MFE formulations are derived.And the existence and convergence(error estimate)of the semidiscrete and fully discrete MFE solutions are deposition chemical reaction processes,the numerical solutions of the velocity vector,the temperature field,the pressure field,and the gas mass field can be found out simultaneonsly.Thus,these researches are not only of important theoretical means,but also of extremely extensive applied vistas.

  7. Tuning the Electrical Properties of Graphene via Nitrogen Plasma-Assisted Chemical Modification.

    Science.gov (United States)

    Jung, Min Wook; Song, Wooseok; Jung, Dae Sung; Lee, Sun Sook; Park, Chong-Yun; An, Ki-Seok

    2016-03-01

    The control in electrical properties of graphene is essentially required in order to realize graphenebased nanoelectronics. In this study, N-doped graphene was successfully obtained via nitrogen plasma treatment. Graphene was synthesized on copper foil using thermal chemical vapor deposition. After N2 plasma treatment, the G-band of the graphene was blueshifted and the intensity ratio of 2D- to G-bands decreased with increasing the plasma power. Pyrrolic-N bonding configuration induced by N2 plasma treatment was studied by X-ray photoelectron spectroscopy. Remarkably, electrical characterization including Hall measurement and I-V characteristics of the N-doped graphene exhibit semiconducting behavior as well as the n-type doping effect.

  8. Oxidation Kinetics of Chemically Vapor-Deposited Silicon Carbide in Wet Oxygen

    Science.gov (United States)

    Opila, Elizabeth J.

    1994-01-01

    The oxidation kinetics of chemically vapor-deposited SiC in dry oxygen and wet oxygen (P(sub H2O) = 0.1 atm) at temperatures between 1200 C and 1400 C were monitored using thermogravimetric analysis. It was found that in a clean environment, 10% water vapor enhanced the oxidation kinetics of SiC only very slightly compared to rates found in dry oxygen. Oxidation kinetics were examined in terms of the Deal and Grove model for oxidation of silicon. It was found that in an environment containing even small amounts of impurities, such as high-purity Al2O3 reaction tubes containing 200 ppm Na, water vapor enhanced the transport of these impurities to the oxidation sample. Oxidation rates increased under these conditions presumably because of the formation of less protective sodium alumino-silicate scales.

  9. Effects of growth pressure on morphology of ZnO nanostructures by chemical vapor transport

    Science.gov (United States)

    Babu, Eadi Sunil; Kim, Sungjin; Song, Jung-Hoon; Hong, Soon-Ku

    2016-08-01

    The effect of growth pressure on the morphology of the ZnO nanostructures in chemical vapor transport by using Zn powder and oxygen as source materials has been investigated. Highly uniform aligned ZnO nanorods or multifaceted tripod structures were grown depending on the growth pressure. The mechanism governing the morphology change was explained by the relative concentration of Zn vapor and supersaturation based on experimental observations. It was concluded that heterogeneous nucleation on the substrate is enhanced at low growth pressure, while homogeneous nucleation from vapor phase is enhanced at high growth pressure. The difference resulted in different morphology of ZnO nanostructures. ZnO nanorods grown at optimized condition were used for the fabrication of gas sensor for the detection of H2 gas.

  10. Self-Catalytic Growth of Tin Oxide Nanowires by Chemical Vapor Deposition Process

    Directory of Open Access Journals (Sweden)

    Bongani S. Thabethe

    2013-01-01

    Full Text Available We report on the synthesis of tin oxide (SnO2 nanowires by a chemical vapor deposition (CVD process. Commercially bought SnO nanopowders were vaporized at 1050°C for 30 minutes with argon gas continuously passing through the system. The as-synthesized products were characterized using UV-visible absorption spectroscopy, X-ray diffraction (XRD, scanning electron microscopy (SEM, and high-resolution transmission electron microscopy (HRTEM. The band gap of the nanowires determined from UV-visible absorption was around 3.7 eV. The SEM micrographs revealed “wool-like” structure which contains nanoribbons and nanowires with liquid droplets at the tips. Nanowires typically have diameter in the range of 50–200 nm and length 10–100 μm. These nanowires followed the vapor-liquid-solid (VLS growth mechanism.

  11. Vibrationally Excited Carbon Monoxide Produced via a Chemical Reaction Between Carbon Vapor and Oxygen

    Science.gov (United States)

    Jans, Elijah R.; Eckert, Zakari; Frederickson, Kraig; Rich, Bill; Adamovich, Igor V.

    2017-06-01

    Measurements of the vibrational distribution function of carbon monoxide produced via a reaction between carbon vapor and molecular oxygen has shown a total population inversion on vibrational levels 4-7. Carbon vapor, produced using an arc discharge to sublimate graphite, is mixed with an argon oxygen flow. The excited carbon monoxide is vibrationally populated up to level v=14, at low temperatures, T=400-450 K, in a collision-dominated environment, 15-20 Torr, with total population inversions between v=4-7. The average vibrational energy per CO molecule formed by the reaction is 0.6-1.2 eV/molecule, which corresponds to 10-20% of the reaction enthalpy. Kinetic modeling of the flow reactor, including state specific vibrational processes, was performed to infer the vibrational distribution of the products of the reaction. The results show viability of developing of a new chemical CO laser from the reaction of carbon vapor and oxygen.

  12. Chemical vapor synthesis of size-selected zinc oxide nanoparticles.

    Science.gov (United States)

    Polarz, Sebastian; Roy, Abhijit; Merz, Michael; Halm, Simon; Schröder, Detlef; Schneider, Lars; Bacher, Gerd; Kruis, Frank E; Driess, Matthias

    2005-05-01

    ZnO can be regarded as one of the most important metal oxide semiconductors for future applications. Similar to silicon in microelectronics, it is not only important to obtain nanoscale building blocks of ZnO, but also extraordinary purity has to be ensured. A new gas-phase approach to obtain size-selected, nanocrystalline ZnO particles is presented. The tetrameric alkyl-alkoxy zinc compound [CH(3)ZnOCH(CH(3))(2)](4) is chemically transformed into ZnO, and the mechanism of gas-phase transformation is studied in detail. Furthermore, the morphological genesis of particles via gas-phase sintering is investigated, and for the first time a detailed model of the gas-phase sintering processes of ZnO is presented. Various analytical techniques (powder XRD, TEM/energy-dispersive X-ray spectroscopy, magic-angle spinning NMR spectroscopy, FTIR spectroscopy, etc.) are used to investigate the structure and purity of the samples. In particular, the defect structure of the ZnO was studied by photoluminescence spectroscopy.

  13. Formation of perfectly aligned nitrogen-vacancy-center ensembles in chemical-vapor-deposition-grown diamond (111)

    Science.gov (United States)

    Ozawa, Hayato; Tahara, Kosuke; Ishiwata, Hitoshi; Hatano, Mutsuko; Iwasaki, Takayuki

    2017-04-01

    Selectively aligning a nitrogen-vacancy (NV) ensemble in diamond is an important technique for obtaining a high-sensitivity magnetic sensor. Nitrogen-doped diamonds were grown on (111) substrates by microwave plasma chemical vapor deposition to perform the selective alignment of high-density NV ensembles, yielding perfectly aligned NV ensembles along the [111] direction with a density greater than 1016 cm‑3 and a spin relaxation time of 2 µs. Such alignment results in a high signal contrast with an optical magnetic resonance close to the typical value reported with an isolated NV center. These results indicate the possibility of achieving a high sensitivity through the selective alignment of NV ensembles.

  14. Growth of aligned ZnO nanowires via modified atmospheric pressure chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yuping; Li, Chengchen [Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Chen, Mingming, E-mail: andychain@live.cn [Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Yu, Xiao; Chang, Yunwei [Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Chen, Anqi [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics & Information Technology, Sun Yat-Sen University, Guangzhou Higher Education Mega Center (University Town), Guangzhou, 510006 (China); Zhu, Hai, E-mail: zhuhai5@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics & Information Technology, Sun Yat-Sen University, Guangzhou Higher Education Mega Center (University Town), Guangzhou, 510006 (China); Tang, Zikang, E-mail: zktang@umac.mo [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics & Information Technology, Sun Yat-Sen University, Guangzhou Higher Education Mega Center (University Town), Guangzhou, 510006 (China); The Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macau (China)

    2016-12-09

    In this work, we report the growth of high-quality aligned ZnO nanowires via a facile atmospheric pressure chemical vapor deposition (CVD) method. The CVD reactor chamber used was more complicated than a conventional one due to the quartz boats loaded with sources (ZnO/C) and substrates being inserted into a semi-open quartz tube, and then placed inside the CVD reactor. The semi-open quartz tube played a very important role in growing the ZnO nanowires, and demonstrated that the transportation properties of Zn and O vapor differ from those in the conventional CVD reactor chamber. Aligned ZnO nanowires were successfully obtained, though they were only found at substrates located upstream. The very high crystalline quality of the obtained ZnO nanowires was demonstrated by high-resolution transmission electron microscopy and room temperature photoluminescence investigations. Such ZnO nanowires with high crystalline quality may provide opportunities for the fabrication of ZnO-based nano-devices in future. - Highlights: • High-quality aligned ZnO nanowires were obtained via modified chemical vapor deposition under atmospheric pressure. • The semi-open quartz tube plays very important roles in growing ZnO nanowires. • The transportation properties of Zn and O vapor differ from those in the conventional CVD reactor chamber.

  15. Low-Temperature Process for Atomic Layer Chemical Vapor Deposition of an Al2O3 Passivation Layer for Organic Photovoltaic Cells.

    Science.gov (United States)

    Kim, Hoonbae; Lee, Jihye; Sohn, Sunyoung; Jung, Donggeun

    2016-05-01

    Flexible organic photovoltaic (OPV) cells have drawn extensive attention due to their light weight, cost efficiency, portability, and so on. However, OPV cells degrade quickly due to organic damage by water vapor or oxygen penetration when the devices are driven in the atmosphere without a passivation layer. In order to prevent damage due to water vapor or oxygen permeation into the devices, passivation layers have been introduced through methods such as sputtering, plasma enhanced chemical vapor deposition, and atomic layer chemical vapor deposition (ALCVD). In this work, the structural and chemical properties of Al2O3 films, deposited via ALCVD at relatively low temperatures of 109 degrees C, 200 degrees C, and 300 degrees C, are analyzed. In our experiment, trimethylaluminum (TMA) and H2O were used as precursors for Al2O3 film deposition via ALCVD. All of the Al2O3 films showed very smooth, featureless surfaces without notable defects. However, we found that the plastic flexible substrate of an OPV device passivated with 300 degrees C deposition temperature was partially bended and melted, indicating that passivation layers for OPV cells on plastic flexible substrates need to be formed at temperatures lower than 300 degrees C. The OPV cells on plastic flexible substrates were passivated by the Al2O3 film deposited at the temperature of 109 degrees C. Thereafter, the photovoltaic properties of passivated OPV cells were investigated as a function of exposure time under the atmosphere.

  16. Surface modification of aramid fiber by plasma induced vapor phase graft polymerization of acrylic acid. I. Influence of plasma conditions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.X., E-mail: cxwang@mail.dhu.edu.cn [College of Textiles and Clothing, Yancheng Institute of Technology, Jiangsu 224003 (China); School of Textile and Clothing, Nantong University, Jiangsu 226019 (China); Du, M. [College of Textiles and Clothing, Yancheng Institute of Industry Technology, Jiangsu 224000 (China); Lv, J.C.; Zhou, Q.Q. [College of Textiles and Clothing, Yancheng Institute of Technology, Jiangsu 224003 (China); Ren, Y. [School of Textile and Clothing, Nantong University, Jiangsu 226019 (China); Liu, G.L.; Gao, D.W. [College of Textiles and Clothing, Yancheng Institute of Technology, Jiangsu 224003 (China); Jin, L.M. [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204 (China)

    2015-09-15

    Highlights: • Aramid fiber surface was modified by PIVPGP of AA to improve wettability, adhesion. • Surface modification effect by PIVPGP of AA increased and then decreased with time. • Surface modification effect increased and then stayed unaltered with output power. • Ar plasma was the most effective in PIVPGP of AA on aramid fiber surface. • In studied range, optimum technology of PIVPGP of AA: Ar plasma, 15 min, 300 W. - Abstract: Plasma induced vapor phase graft polymerization (PIVPGP) method was applied to modify aramid fiber surface. In this study, aramid fibers were pretreated under various plasma conditions such as different treatment times, output powers and working gases to see how these plasma processing parameters influenced the PIVPGP of acrylic acid (AA) on aramid fiber surface and its surface structure and properties. The analysis results of atomic force microscope (AFM) and X-ray photoelectron spectroscope (XPS) showed the increase of surface roughness and the introduction of O=C−OH, which confirmed that the PIVPGP of AA on aramid fiber surface was achieved. The contact angle and interfacial shear strength (IFSS) of the aramid fibers modified by PIVPGP of AA prominently decreased and increased, respectively, indicating the obvious improvements of surface wettability and adhesion between aramid fiber and matrix. The surface modification effects of aramid fiber by PIVPGP of AA firstly increased and then after 15 min slightly decreased with the increasing plasma treatment time, and but firstly increased and then after 300 W nearly remained unchanged with the increasing output power, respectively. Among different working gases, Ar plasma occupied first place, O{sub 2} plasma and N{sub 2} plasma came second and third in the aspect of PIVPGP of AA on aramid fiber surface, respectively. It could be concluded that the PIVPGP of AA on aramid fiber surface could effectively improve surface wettability and adhesion. Plasma conditions had signally

  17. A Study on Medium Temperature Chemical Vapor Deposition (MT-CVD) Technology and Super Coating Materials

    Institute of Scientific and Technical Information of China (English)

    GAO Jian; LI Jian-ping; ZENG Xiang-cai; MA Wen-cun

    2004-01-01

    In this paper, the dense and columnar crystalline TiCN coating layers with very good bonding strength between a layer and another layer was deposited using Medium Temperature Chemical Vapor Deposition (MT-CVD) where CH3CN organic composite with C/N atomic clusters etc. was utilized at 700 ~ 900 ℃. Effect of coating processing parameters, such as coating temperature, pressure and different gas flow quantity on structures and properties of TiCN coating layers were investigated. The super coating mechanis mand structures were analyzed. The new coating processing parameters and properties of carbide inserts with super coating layers were gained by using the improved high temperature chemical vapor deposition (HTCVD) equipment and HT-CVD, in combination with MT-CVD technology.

  18. Low Temperature Growth of Vertically Aligned Carbon Nanotubes via Floating Catalyst Chemical Vapor Deposition Method

    Institute of Scientific and Technical Information of China (English)

    M.R. Atiyan; D.R. Awang Biak; F. Ahmadun; I.S. Ahamad; F. Mohd Yasin; H. Mohamed Yusoff

    2011-01-01

    Synthesis of carbon nanotubes (CNTs) below 600℃ using supporting catalyst chemical vapor deposition method was reported by many research groups. However, the floating catalyst chemical vapor deposition received less attention due to imperfect nanotubes produced. In this work, the effects of varying the preheating temperature on the synthesis of CNT were investigated. The reaction temperature was set at 570℃. The preheating set temperature was varied from 150 to 400℃ at 50℃ interval. Three O-ring shape heating mantels were used as heating source for the preheater. In situ monitoring device was used to observe the temperature profile in the reactor. Benzene and ferrocene were used as the carbon source and catalyst precursor, respectively. Vertically aligned CNTs were synthesized when the preheating temperature was set at 400℃. When the preheating temperature was increased up to 400℃, both the length and the alignment of CNTs produced were improved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-05-25

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

  20. Atmospheric pressure chemical vapor deposition (APCVD) grown bi-layer graphene transistor characteristics at high temperature

    KAUST Repository

    Qaisi, Ramy M.

    2014-05-15

    We report the characteristics of atmospheric chemical vapor deposition grown bilayer graphene transistors fabricated on ultra-scaled (10 nm) high-κ dielectric aluminum oxide (Al2O3) at elevated temperatures. We observed that the drive current increased by >400% as temperature increased from room temperature to 250 °C. Low gate leakage was maintained for prolonged exposure at 100 °C but increased significantly at temperatures >200 °C. These results provide important insights for considering chemical vapor deposition graphene on aluminum oxide for high temperature applications where low power and high frequency operation are required. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Growth mechanisms of zinc oxide and zinc sulfide films by mist chemical vapor deposition

    Science.gov (United States)

    Uno, Kazuyuki; Yamasaki, Yuichiro; Tanaka, Ichiro

    2017-01-01

    The growth mechanisms of zinc oxide and zinc sulfide films by mist chemical vapor deposition (mist-CVD) were experimentally investigated from the viewpoint of mist behaviors and chemical reactions. The proper growth model, either vaporization or the Leidenfrost model, was studied by supplying two kinds of mists with different kinds of sources, such as H2 16O and H2 18O for ZnO growth and ZnCl2 and thiourea for ZnS growth. Moreover, the origin of the oxygen atoms of ZnO was investigated using a quantitative analysis. The role of chloro complex of zinc in the growth of ZnS from aqueous solutions was also examined by systematic studies.

  2. Strangeness Production in a Chemically Equilibrating Quark-Gluon Plasma

    Institute of Scientific and Technical Information of China (English)

    HE Ze-Jun; LONG Jia-Li; MA Yu-Gang; MA Guo-Liang

    2004-01-01

    @@ We study the strangeness of a chemically equilibrating quark-gluon plasma at finite baryon density based on the and will accelerate with the change of the initial system from a chemically non-equilibrated to an equilibrated system. We also find that the calculated strangeness is very different from the one in the thermodynamic equilibrium system. This study may be helpful to understand the formation of quark-gluon plasma via a chemically non-equilibrated evolution framework.

  3. Proposed Occupational Exposure Limits for Non-Carcinogenic Hanford Waste Tank Vapor Chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Poet, Torka S.; Timchalk, Chuck

    2006-03-24

    A large number of volatile chemicals have been identified in the headspaces of tanks used to store mixed chemical and radioactive waste at the U.S. Department of Energy (DOE) Hanford Site, and there is concern that vapor releases from the tanks may be hazardous to workers. Contractually established occupational exposure limits (OELs) established by the Occupational Safety and Health Administration (OSHA) and American Conference of Governmental Industrial Hygienists (ACGIH) do not exist for all chemicals of interest. To address the need for worker exposure guidelines for those chemicals that lack OSHA or ACGIH OELs, a procedure for assigning Acceptable Occupational Exposure Limits (AOELs) for Hanford Site tank farm workers has been developed and applied to a selected group of 57 headspace chemicals.

  4. TiOxNy coatings grown by atmospheric pressure metal organic chemical vapor deposition

    OpenAIRE

    Maury, Francis; Duminica, Florin-Daniel

    2010-01-01

    International audience; Titanium oxynitride coatings were deposited on various substrates by an original atmospheric pressure metal organic chemical vapor deposition (MOCVD) process using titanium tetra-iso-propoxide as titanium and oxygen precursors and hydrazine as a nitrogen source. The films composition was monitored by controlling the N2H4 mole fraction in the initial reactive gas phase. The variation of the N content in the films results in significant changes in morphological, structur...

  5. Fabrication of Rare Earth-Doped Transparent Glass Ceramic Optical Fibers by Modified Chemical Vapor Deposition

    OpenAIRE

    2011-01-01

    International audience; Rare earth (RE) doped silica-based optical fibers with transparent glass ceramic (TGC) core was fabricated through the well-known modified chemical vapor deposition (MCVD) process without going through the commonly used stage of post-ceramming. The main characteristics of the RE-doped oxyde nanoparticles namely, their density and mean diameter in the fibers are dictated by the concentration of alkaline earth element used as phase separating agent. Magnesium and erbium ...

  6. High index of refraction films for dielectric mirrors prepared by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Brusasco, R.M.

    1989-01-01

    A wide variety of metal oxides with high index of refraction can be prepared by Metal-Organic Chemical Vapor Deposition. We present some recent optical and laser damage results on oxide films prepared by MOCVD which could be used in a multilayer structure for highly reflecting (HR) dielectric mirror applications. The method of preparation affects both optical properties and laser damage threshold. 10 refs., 8 figs., 4 tabs.

  7. Theoretical Descriptions of Carbon Nanotubes Synthesis in a Chemical Vapor Deposition Reactor: A Review

    OpenAIRE

    Lubej, M.; Plazl, I.

    2012-01-01

    The mechanisms by which carbon nanotubes nucleate and grow are still poorly understood. Understanding and mathematically describing the process is crucial for its optimization. This paper reviews different models which have been proposed to explain carbon nanotube growth in the chemical vapor deposition process. The review is divided into two sections, the first section describes some nucleation, growth and termination simulations based on molecular dynamics, and the second section describes ...

  8. Energy recovery from waste glycerol by utilizing thermal water vapor plasma.

    Science.gov (United States)

    Tamošiūnas, Andrius; Valatkevičius, Pranas; Gimžauskaitė, Dovilė; Jeguirim, Mejdi; Mėčius, Vladas; Aikas, Mindaugas

    2017-04-01

    Glycerol, considered as a waste feedstock resulting from biodiesel production, has received much attention in recent years due to its properties, which offer to recover energy. The aim of this study was to investigate the use of a thermal water vapor plasma for waste (crude) glycerol conversion to synthesis gas, or syngas (H2 + CO). In parallel of crude glycerol, a pure glycerol (99.5%) was used as a reference material in order to compare the concentrations of the formed product gas. A direct current (DC) arc plasma torch stabilized by a mixture of argon/water vapor was utilized for the effective glycerol conversion to hydrogen-rich synthesis gas. It was found that after waste glycerol treatment, the main reaction products were gases with corresponding concentrations of H2 50.7%, CO 23.53%, CO2 11.45%, and CH4 3.82%, and traces of C2H2 and C2H6, which concentrations were below 0.5%. The comparable concentrations of the formed gas products were obtained after pure glycerol conversion-H2 46.4%, CO 26.25%, CO2 11.3%, and CH4 4.7%. The use of thermal water vapor plasma producing synthesis gas is an effective method to recover energy from both crude and pure glycerol. The performance of the glycerol conversion system was defined in terms of the produced gas yield, the carbon conversion efficiency, the cold gas efficiency, and the specific energy requirements.

  9. Deposition of thermal and hot-wire chemical vapor deposition copper thin films on patterned substrates.

    Science.gov (United States)

    Papadimitropoulos, G; Davazoglou, D

    2011-09-01

    In this work we study the hot-wire chemical vapor deposition (HWCVD) of copper films on blanket and patterned substrates at high filament temperatures. A vertical chemical vapor deposition reactor was used in which the chemical reactions were assisted by a tungsten filament heated at 650 degrees C. Hexafluoroacetylacetonate Cu(I) trimethylvinylsilane (CupraSelect) vapors were used, directly injected into the reactor with the aid of a liquid injection system using N2 as carrier gas. Copper thin films grown also by thermal and hot-wire CVD. The substrates used were oxidized silicon wafers on which trenches with dimensions of the order of 500 nm were formed and subsequently covered with LPCVD W. HWCVD copper thin films grown at filament temperature of 650 degrees C showed higher growth rates compared to the thermally ones. They also exhibited higher resistivities than thermal and HWCVD films grown at lower filament temperatures. Thermally grown Cu films have very uniform deposition leading to full coverage of the patterned substrates while the HWCVD films exhibited a tendency to vertical growth, thereby creating gaps and incomplete step coverage.

  10. Iodine Determination by Microwave Plasma Torch Atomic Emission Spectrometer Coupled with Online Preconcentration Vapor Generation Technique

    Institute of Scientific and Technical Information of China (English)

    FEI Yan-qun; LUO Gui-min; FENG Guo-dong; CHEN Huan-wen; FEI Qiang; HUAN Yan-fu; JIN Qin-han

    2008-01-01

    This article focuses on iodine determination by microwave plasma torch atomic emission spectrometry (MPT-AES) coupled with online preconcentration vapor generation method.A new desolvation device,multistrand Nation dryer,was used as the substitute for condenser desolvation system.Some experimental conditions,such as preconcentration time,acidity of sample solution,rinsing solution acidity and dynamic linear range were investigated and optimized.The new desolvation system eliminates the problem of decreasing emission intensity of I(I) 206.238 nm line with the increase of working time on a conventional condenser desolvation system,thus greatly improving the reproducibility.

  11. Main species and chemical pathways in cold atmospheric-pressure Ar + H2O plasmas

    Science.gov (United States)

    Liu, Dingxin; Sun, Bowen; Iza, Felipe; Xu, Dehui; Wang, Xiaohua; Rong, Mingzhe; Kong, Michael G.

    2017-04-01

    Cold atmospheric-pressure plasmas in Ar + H2O gas mixtures are a promising alternative to He + H2O plasmas as both can produce reactive oxygen species of relevance for many applications and argon is cheaper than helium. Although He + H2O plasmas have been the subject of multiple experimental and computational studies, Ar + H2O plasmas have received less attention. In this work we investigate the composition and chemical pathways in Ar + H2O plasmas by means of a global model that incorporates 57 species and 1228 chemical reactions. Water vapor concentrations from 1 ppm to saturation (32 000 ppm) are considered in the study and abrupt transitions in power dissipation channels, species densities and chemical pathways are found when the water concentration increases from 100 to 1000 ppm. In this region the plasma transitions from an electropositive discharge in which most power is coupled to electrons into an electronegative one in which most power is coupled to ions. While increasing electronegativity is also observed in He + H2O plasmas, in Ar + H2O plasmas the transition is more abrupt because Penning processes do not contribute to gas ionization and the changes in the electron energy distribution function and mean electron energy caused by the increasing water concentration result in electron-neutral excitation and ionization rates changing by many orders of magnitude in a relatively small range of water concentrations. Insights into the main chemical species and pathways governing the production and loss of electrons, O, OH, OH(A) and H2O2 are provided as part of the study.

  12. Synthesis of magnetic tunnel junctions with full in situ atomic layer and chemical vapor deposition processes

    Energy Technology Data Exchange (ETDEWEB)

    Mantovan, R., E-mail: roberto.mantovan@mdm.imm.cnr.it [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (Italy); Vangelista, S.; Kutrzeba-Kotowska, B.; Cocco, S.; Lamperti, A.; Tallarida, G. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Mameli, D. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (Italy); Dipartimento di Scienze Chimiche, Universita di Cagliari, Cittadella Universitaria, 09042 Monserrato, Cagliari (Italy); Fanciulli, M. [Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (Italy); Dipartimento di Scienza dei Materiali, Universita degli studi Milano-Bicocca, Via R Cozzi 53, 20125 Milano (Italy)

    2012-05-01

    Magnetic tunnel junctions, i.e. the combination of two ferromagnetic electrodes separated by an ultrathin tunnel oxide barrier, are core elements in a large variety of spin-based devices. We report on the use of combined chemical vapor and atomic layer deposition processes for the synthesis of magnetic tunnel junctions with no vacuum break. Structural, chemical and morphological characterizations of selected ferromagnetic and oxide layers are reported, together with the evidence of tunnel magnetoresistance effect in patterned Fe/MgO/Co junctions.

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

    Science.gov (United States)

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

    2016-12-01

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

  14. Fabrication of a multifunctional carbon nanotube "cotton" yarn by the direct chemical vapor deposition spinning process.

    Science.gov (United States)

    Zhong, Xiao-Hua; Li, Ya-Li; Feng, Jian-Min; Kang, Yan-Ru; Han, Shuai-Shuai

    2012-09-21

    A continuous cotton-like carbon nanotube fiber yarn, consisting of multiple threads of high purity double walled carbon nanotubes, was fabricated in a horizontal CVD gas flow reactor with water vapor densification by the direct chemical vapor deposition spinning process. The water vapor interaction leads to homogeneous shrinking of the CNT sock-like assembly in the gas flow. This allows well controlled continuous winding of the dense thread inside the reactor. The CNT yarn is quite thick (1-3 mm), has a highly porous structure (99%) while being mechanically strong and electrically conductive. The water vapor interaction leads to homogeneous oxidation of the CNTs, offering the yarn oxygen-functionalized surfaces. The unique structure and surface of the CNT yarn provide it multiple processing advantages and properties. It can be mechanically engineered into a dense yarn, infiltrated with polymers to form a composite and mixed with other yarns to form a blend, as demonstrated in this research. Therefore, this CNT yarn can be used as a "basic yarn" for various CNT based structural and functional applications.

  15. Nanodispersed Oxides-Plasma-Chemical Synthesis and Properties

    Institute of Scientific and Technical Information of China (English)

    Gheorghi VISSOKOV; Katerina ZAHARIEVA

    2007-01-01

    We discuss the plasma-chemical synthesis and the properties of transition metals oxides, Al2O3, SiO2, rare-earth oxides, oxides for ceramics and metal-ceramics, and oxides used as catalysts. Bearing in mind the indisputable advantages of using plasma-chemically synthesized nanodispersed oxides for the needs of various industrial fields, we set out to review the articles published in the past few years devoted to the problems of plasma-chemical synthesis and characterization of nanodispersed oxides.

  16. Modelling chemical reactions in dc plasma inside oxygen bubbles in water

    Science.gov (United States)

    Takeuchi, N.; Ishii, Y.; Yasuoka, K.

    2012-02-01

    Plasmas generated inside oxygen bubbles in water have been developed for water purification. Zero-dimensional numerical simulations were used to investigate the chemical reactions in plasmas driven by dc voltage. The numerical and experimental results of the concentrations of hydrogen peroxide and ozone in the solution were compared with a discharge current between 1 and 7 mA. Upon increasing the water vapour concentration inside bubbles, we saw from the numerical results that the concentration of hydrogen peroxide increased with discharge current, whereas the concentration of ozone decreased. This finding agreed with the experimental results. With an increase in the discharge current, the heat flux from the plasma to the solution increased, and a large amount of water was probably vaporized into the bubbles.

  17. Conducting Graphite/Cellulose Composite Film as a Candidate for Chemical Vapor-Sensing Material

    Directory of Open Access Journals (Sweden)

    Kaihua Liu

    2014-07-01

    Full Text Available A type of conductive graphite/cellulose composite film used for chemical vapor-sensing material was prepared at room temperature in the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIm]Cl. Graphite was pretreated with both oxidation and reduction processes. Due to the use of N,N-carbonyldiimidazole (CDI, as a covalent cross-linking agent in [BMIm]Cl, there were limited chemical bonds between the graphite and cellulose. The composite film was analyzed using Fourier transform infrared spectroscopy (FT-IR, Raman spectroscopy, and X-ray photoelectron spectroscopy (XRD. When these conducting films were exposed to certain organic vapors, their electrical resistances quickly changed, showing gas sensitivity. The percolation threshold of the conducting film was about 5 wt%. The gas-sensing behavior of these films in solvent were the opposite of those gas-sensing materials based on a non-polar polymer matrix. A typical negative vapor coefficient (NVC was observed when the film was placed in polar organic solvents such as methanol, ethanol, and acetone.

  18. Flexible electrochemical capacitors based on polypyrrole/carbon fibers via chemical polymerization of pyrrole vapor

    Science.gov (United States)

    Yuan, Wei; Han, Gaoyi; Xiao, Yaoming; Chang, Yunzhen; Liu, Cuixian; Li, Miaoyu; Li, Yanping; Zhang, Ying

    2016-07-01

    Polypyrrole (PPy) has been deposited on the carbon fibers (CFs) via chemical oxidation of monomer vapor strategy, during which FeCl3·6H2O in acetonitrile adsorbed on CFs acts as oxidant to polymerize the pyrrole vapor. The morphologies and capacitive properties of the PPy deposited on CFs (PPy/CFs) are strongly influenced by the concentration of oxidant used in the process. The assembled flexible capacitors by using PPy/CFs as electrodes and LiCl/polyvinyl alcohol as gel electrolyte have been evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results show that the composites of PPy/CFs prepared by using 350 mg mL-1 FeCl3·6H2O as oxidant (PPy/CFs-350) exhibit relatively higher specific capacitance and good rate capability. Compared with PPy/CFs prepared by electrochemical deposition (retaining 5% of the initial capacitance), the PPy/CFs prepared by chemically polymerizing monomer vapor shows excellent stability (retaining 85% of initial capacitance after 5000 cycles). Furthermore, cells fabricated by PPy/CFs show a fairly good performance under various bending states, three cells of PPy/CFs-350 connected in series can light up a light emitting diode with a voltage threshold of about 2.5 V for approximate 10 min after being charged for about 3 min, revealing the potential of the cells' practical applications.

  19. MICHIGAN SOIL VAPOR EXTRACTION REMEDIATION (MISER) MODEL: A COMPUTER PROGRAM TO MODEL SOIL VAPOR EXTRACTION AND BIOVENTING OF ORGANIC CHEMICALS IN UNSATURATED GEOLOGICAL MATERIAL

    Science.gov (United States)

    Soil vapor extraction (SVE) and bioventing (BV) are proven strategies for remediation of unsaturated zone soils. Mathematical models are powerful tools that can be used to integrate and quantify the interaction of physical, chemical, and biological processes occurring in field sc...

  20. Uptake rate constants and partition coefficients for vapor phase organic chemicals using semipermeable membrane devices (SPMDs)

    Science.gov (United States)

    Cranor, W.L.; Alvarez, D.A.; Huckins, J.N.; Petty, J.D.

    2009-01-01

    To fully utilize semipermeable membrane devices (SPMDs) as passive samplers in air monitoring, data are required to accurately estimate airborne concentrations of environmental contaminants. Limited uptake rate constants (kua) and no SPMD air partitioning coefficient (Ksa) existed for vapor-phase contaminants. This research was conducted to expand the existing body of kinetic data for SPMD air sampling by determining kua and Ksa for a number of airborne contaminants including the chemical classes: polycyclic aromatic hydrocarbons, organochlorine pesticides, brominated diphenyl ethers, phthalate esters, synthetic pyrethroids, and organophosphate/organosulfur pesticides. The kuas were obtained for 48 of 50 chemicals investigated and ranged from 0.03 to 3.07??m3??g-1??d-1. In cases where uptake was approaching equilibrium, Ksas were approximated. Ksa values (no units) were determined or estimated for 48 of the chemicals investigated and ranging from 3.84E+5 to 7.34E+7. This research utilized a test system (United States Patent 6,877,724 B1) which afforded the capability to generate and maintain constant concentrations of vapor-phase chemical mixtures. The test system and experimental design employed gave reproducible results during experimental runs spanning more than two years. This reproducibility was shown by obtaining mean kua values (n??=??3) of anthracene and p,p???-DDE at 0.96 and 1.57??m3??g-1??d-1 with relative standard deviations of 8.4% and 8.6% respectively.

  1. Low temperature plasma vapor treatment of thermo-sensitive poly(N-isopropylacrylamide) and its application

    Science.gov (United States)

    Chen, Y.; Tang, X. L.; Chen, B. T.; Qiu, G.

    2013-03-01

    In this study, the novel methods of depositing poly(N-isopropylacrylamide) (PNIPAAm) coatings on the surface of glass slides and PS petri dish by plasma polymerization are provided. PNIPAAm can be obtained by plasma polymerization of N-isopropylacrylamide by using the self-made equipment of plasma vapor treatment. The samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle. SEM analysis has revealed that the poly(N-isopropylacrylamide) (PNIPAAm) coatings were formed on the surface of the smooth glass slides. Further evaluation by using XPS, it has shown the presence of PNIPAAm. The wettability can be significantly modified by changing of the temperatures at above and below of the lower critical solution temperature (LCST) from the data of the contact angle test. These results have advantage for further application on the thermo-sensitive textile materials. On the deposition of PNIPAAm onto Polybutylene Terephthalate (PBT) melt-blown nonwovens in atmospheric pressure plasma, water permeability was significantly modified at around LCST. Due to the LCST is close to the temperature of human body, it has advantage on application of PBT melt-blown nonwovens.

  2. MgB{sub 2} thin films by hybrid physical-chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Xi, X.X. [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States)]|[Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)]. E-mail: xxx4@psu.edu; Pogrebnyakov, A.V. [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States)]|[Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Xu, S.Y.; Chen, K.; Cui, Y.; Maertz, E.C. [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States); Zhuang, C.G. [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States)]|[Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)]|[Department of Physics, Peking University, Beijing 100871 (China); Li, Qi [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States); Lamborn, D.R. [Department of Chemical Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Redwing, J.M. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)]|[Department of Chemical Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Liu, Z.K.; Soukiassian, A.; Schlom, D.G.; Weng, X.J.; Dickey, E.C. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Chen, Y.B.; Tian, W.; Pan, X.Q. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Cybart, S.A. [Department of Physics, University of California, Berkeley, CA 94720 (United States); Dynes, R.C. [Department of Physics, University of California, Berkeley, CA 94720 (United States)

    2007-06-01

    Hybrid physical-chemical vapor deposition (HPCVD) has been the most effective technique for depositing MgB{sub 2} thin films. It generates high magnesium vapor pressures and provides a clean environment for the growth of high purity MgB{sub 2} films. The epitaxial pure MgB{sub 2} films grown by HPCVD show higher-than-bulk T {sub c} due to tensile strain in the films. The HPCVD films are the cleanest MgB{sub 2} materials reported, allowing basic research, such as on magnetoresistance, that reveals the two-band nature of MgB{sub 2}. The carbon-alloyed HPCVD films demonstrate record-high H {sub c2} values promising for high magnetic field applications. The HPCVD films and multilayers have enabled the fabrication of high quality MgB{sub 2} Josephson junctions.

  3. Chemical vapor deposition of carbon nanotubes: a review on growth mechanism and mass production.

    Science.gov (United States)

    Kumar, Mukul; Ando, Yoshinori

    2010-06-01

    This review article deals with the growth mechanism and mass production of carbon nanotubes (CNTs) by chemical vapor deposition (CVD). Different aspects of CNT synthesis and growth mechanism are reviewed in the light of latest progresses and understandings in the field. Materials aspects such as the roles of hydrocarbon, catalyst and catalyst support are discussed. Many new catalysts and new carbon sources are described. Growth-control aspects such as the effects of temperature, vapor pressure and catalyst concentration on CNT diameter distribution and single- or multi-wall formation are explained. Latest reports of metal-catalyst-free CNT growth are considered. The mass-production aspect is discussed from the perspective of a sustainable CNT technology. Existing problems and challenges of the process are addressed with future directions.

  4. Copper-vapor-assisted chemical vapor deposition for high-quality and metal-free single-layer graphene on amorphous SiO2 substrate.

    Science.gov (United States)

    Kim, Hyungki; Song, Intek; Park, Chibeom; Son, Minhyeok; Hong, Misun; Kim, Youngwook; Kim, Jun Sung; Shin, Hyun-Joon; Baik, Jaeyoon; Choi, Hee Cheul

    2013-08-27

    We report that high-quality single-layer graphene (SLG) has been successfully synthesized directly on various dielectric substrates including amorphous SiO2/Si by a Cu-vapor-assisted chemical vapor deposition (CVD) process. The Cu vapors produced by the sublimation of Cu foil that is suspended above target substrates without physical contact catalyze the pyrolysis of methane gas and assist nucleation of graphene on the substrates. Raman spectra and mapping images reveal that the graphene formed on a SiO2/Si substrate is almost defect-free and homogeneous single layer. The overall quality of graphene grown by Cu-vapor-assisted CVD is comparable to that of the graphene grown by regular metal-catalyzed CVD on a Cu foil. While Cu vapor induces the nucleation and growth of SLG on an amorphous substrate, the resulting SLG is confirmed to be Cu-free by synchrotron X-ray photoelectron spectroscopy. The SLG grown by Cu-vapor-assisted CVD is fabricated into field effect transistor devices without transfer steps that are generally required when SLG is grown by regular CVD process on metal catalyst substrates. This method has overcome two important hurdles previously present when the catalyst-free CVD process is used for the growth of SLG on fused quartz and hexagonal boron nitride substrates, that is, high degree of structural defects and limited size of resulting graphene, respectively.

  5. On the Plasma-Chemical Synthesis of Nanopowders

    Institute of Scientific and Technical Information of China (English)

    G. Vissokov; Iv. Grancharov; Tsv. Tsvetanov

    2003-01-01

    This paper presents an overview of nanopowders preparation using low-temperature plasma (LTP). LTP with its unique processing capabilities provides an attractive and chemically unspecific route for powder synthesis. Nanopowders such as oxides, nitrides, carbides, catalysts and other nanopowders have been successfully synthesized in LTP reactors based on high intensity arcs, plasma jets and radio-frequency (r. f.) inductively coupled discharges.

  6. The shear viscosity of gauge theory plasma with chemical potentials

    CERN Document Server

    Benincasa, P; Naryshkin, R; Benincasa, Paolo; Buchel, Alex; Naryshkin, Roman

    2007-01-01

    We consider strongly coupled gauge theory plasma with conserved global charges that allow for a dual gravitational description. We study the shear viscosity of the gauge theory plasma in the presence of chemical potentials for these charges. Using gauge theory/string theory correspondence we prove that at large 't Hooft coupling the ratio of the shear viscosity to the entropy density is universal.

  7. The shear viscosity of gauge theory plasma with chemical potentials

    Science.gov (United States)

    Benincasa, Paolo; Buchel, Alex; Naryshkin, Roman

    2007-02-01

    We consider strongly coupled gauge theory plasma with conserved global charges that allow for a dual gravitational description. We study the shear viscosity of the gauge theory plasma in the presence of chemical potentials for these charges. Using gauge theory/string theory correspondence we prove that at large 't Hooft coupling the ratio of the shear viscosity to the entropy density is universal.

  8. Chemical Species in the Vapor Phase of Hanford Double-Shell Tanks: Potential Impacts on Waste Tank Corrosion Processes

    Energy Technology Data Exchange (ETDEWEB)

    Felmy, Andrew R.; Qafoku, Odeta; Arey, Bruce W.; Boomer, Kayle D.

    2010-09-22

    The presence of corrosive and inhibiting chemicals on the tank walls in the vapor space, arising from the waste supernatant, dictate the type and degree of corrosion that occurs there. An understanding of how waste chemicals are transported to the walls and the affect on vapor species from changing supernatant chemistry (e.g., pH, etc.), are basic to the evaluation of risks and impacts of waste changes on vapor space corrosion (VSC). In order to address these issues the expert panel workshop on double-shell tank (DST) vapor space corrosion testing (RPP-RPT-31129) participants made several recommendations on the future data and modeling needs in the area of DST corrosion. In particular, the drying of vapor phase condensates or supernatants can form salt or other deposits at the carbon steel interface resulting in a chemical composition at the near surface substantially different from that observed directly in the condensates or the supernatants. As a result, over the past three years chemical modeling and experimental studies have been performed on DST supernatants and condensates to predict the changes in chemical composition that might occur as condensates or supernatants equilibrate with the vapor space species and dry at the carbon steel surface. The experimental studies included research on both the chemical changes that occurred as the supernatants dried as well as research on how these chemical changes impact the corrosion of tank steels. The chemical modeling and associated experimental studies were performed at the Pacific Northwest National Laboratory (PNNL) and the research on tank steel corrosion at the Savannah River National Laboratory (SRNL). This report presents a summary of the research conducted at PNNL with special emphasis on the most recent studies conducted in FY10. An overall summary of the project results as well as their broader implications for vapor space corrosion of the DST’s is given at the end of this report.

  9. Chemical vapor deposition of ceramic coatings on metals and ceramic fibers

    Science.gov (United States)

    Nable, Jun Co

    2005-07-01

    The research presented in this study consists of two major parts. The first part is about the development of ceramic coatings on metals by chemical vapor deposition (CVD) and metal-organic chemical vapor deposition (MOCVD). Ceramics such as Al2O3 and Cr2O3, are used as protective coatings for materials used at elevated temperatures (>700°C). These metal oxides either exhibit oxidation resistance or have been used as environmental bond coats. Conventional methods of coating by chemical vapor deposition requires deposition temperatures of >950°C which could damage the substrate material during the coating process. Lower deposition temperatures (400 to 600°C) by MOCVD of these metal oxides were successful on Ni metal substrates. Surface modification such as pre-oxidation and etching were also investigated. In addition, a novel approach for the CVD of TiN on metals was developed. This new approach utilizes ambient pressure conditions which lead to deposition temperatures of 800°C or lower compared to conventional CVD of TiN at 1000°C. Titanium nitride can be used as an abrasive and wear coating on cutting and grinding tools. This nitride can also serve as a diffusion coating in metals. The second major part of this research involves the synthesis of interfacial coatings on ceramic reinforcing fibers for ceramic matrix composites. Aluminum and chromium oxides were deposited onto SiC, and Al2O3-SiO 2 fibers by MOCVD. The effects of the interface coatings on the tensile strength of ceramic fibers are also discussed. New duplex interface coatings consisting of BN or TiN together with Al2O3 or ZrO 2 were also successfully deposited and evaluated on SiC fibers.

  10. Slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry for the direct determination of metal impurities in aluminium oxide ceramic powders.

    Science.gov (United States)

    Peng, T; Chang, G; Wang, L; Jiang, Z; Hu, B

    2001-03-01

    A new analytical procedure for the direct determination of metal impurities (Cr, Cu, Fe and V) in aluminium oxide ceramic powders by slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) is reported. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of impurity elements in aluminium oxide ceramic powders from the graphite tube. A vaporization stage with a long ramp time and a short hold time provided the possibility of temporal analyte-matrix separation. The experimental results indicated that a 10 microL 1% m/v slurry of aluminium oxide could be destroyed and vaporized completely with 600 micrograms PTFE under the selected conditions. Two aluminium oxide ceramic powder samples were used without any additional pretreatment. Analytical results obtained by using standard addition method with aqueous standard solution were checked by comparison of the results with pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition and analyte-matrix separation. The limits of detection (LODs) between 0.30 microgram g-1 (Fe) and 0.08 microgram g-1 (Cu) were achieved, and, the repeatability of measurements was mainly better than 10%.

  11. Significance of vapor phase chemical reactions on CVD rates predicted by chemically frozen and local thermochemical equilibrium boundary layer theories

    Science.gov (United States)

    Gokoglu, Suleyman A.

    1988-01-01

    This paper investigates the role played by vapor-phase chemical reactions on CVD rates by comparing the results of two extreme theories developed to predict CVD mass transport rates in the absence of interfacial kinetic barrier: one based on chemically frozen boundary layer and the other based on local thermochemical equilibrium. Both theories consider laminar convective-diffusion boundary layers at high Reynolds numbers and include thermal (Soret) diffusion and variable property effects. As an example, Na2SO4 deposition was studied. It was found that gas phase reactions have no important role on Na2SO4 deposition rates and on the predictions of the theories. The implications of the predictions of the two theories to other CVD systems are discussed.

  12. LASER-INDUCED DECOMPOSITION OF METAL CARBONYLS FOR CHEMICAL VAPOR DEPOSITION OF MICROSTRUCTURES

    OpenAIRE

    1989-01-01

    Tungsten and nickel carbonyls were used to produce metal microstructures by laser-induced chemical vapor deposition (CVD) on various substrates. The deposition rate of microstructures produced by thermodecomposition of W(CO)6 on Si substrates heated with a cw Ar+ laser beam was relatively low (10 to 30 nm/s) even at high temperatures (above 900°C). Ni microstructures were deposited on quartz substrates irradiated with a CO2 laser beam. Relatively high laser powers were needed to heat the Ni s...

  13. Growth and characterization of Bi2Se3 crystals by chemical vapor transport

    Directory of Open Access Journals (Sweden)

    W. H. Jiao

    2012-06-01

    Full Text Available Regularly-shaped high-quality Bi2Se3 crystals were grown by a chemical vapor transport using iodine as the transport agent. In addition to exhibiting a characteristic Dirac cone for a topological insulator, the Bi2Se3 crystals show some outstanding properties including additional crystallographic surfaces, large residual resistance ratio (∼10, and high mobility (∼8000 cm2·V−1·s−1. The low-temperature resistivity abnormally increases with applying pressures up to 1.7 GPa, and no superconductivity was observed down to 0.4 K.

  14. MgB2 superconducting whiskers synthesized by using the hybrid physical-chemical vapor deposition.

    Science.gov (United States)

    Wang, Yazhou; Zhuang, Chenggang; Gao, Jingyun; Shan, Xudong; Zhang, Jingmin; Liao, Zhimin; Xu, Hongjun; Yu, Dapeng; Feng, Qingrong

    2009-02-25

    In this work, MgB(2) whiskers were fabricated on a copper substrate by using the hybrid physical-chemical vapor deposition, which was one of the most effective ways to make high quality pure MgB(2) films, with the possible growth mechanism discussed. The whiskers are hexagonal and conelike and grow along the [0001] direction with a single-crystal structure. The onset transition temperature is approximately 39 K, which is among the best in the published nanostructure MgB(2) papers. Fabrication of nanoscale MgB(2) whiskers provides the fundamental understanding of the effect of dimensionality and size on superconductivity.

  15. Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition

    Science.gov (United States)

    Durmazuçar, Hasan H.; Gündüz, Güngör

    2000-12-01

    Uranium dioxide-only and uranium dioxide-gadolinium oxide (5% and 10%) ceramic nuclear fuel pellets which were already coated with boron nitride were coated with thin boron layer by chemical vapor deposition to increase the burn-up efficiency of the fuel during reactor operation. Coating was accomplished from the reaction of boron trichloride with hydrogen at 1250 K in a tube furnace, and then sintering at 1400 and 1525 K. The deposited boron was identified by infrared spectrum. The morphology of the coating was studied by using scanning electron microscope. The plate, grainy and string (fiber)-like boron structures were observed.

  16. MgB2 ultrathin films fabricated by hybrid physical chemical vapor deposition and ion milling

    Science.gov (United States)

    Acharya, Narendra; Wolak, Matthäus A.; Tan, Teng; Lee, Namhoon; Lang, Andrew C.; Taheri, Mitra; Cunnane, Dan; Karasik, Boris. S.; Xi, X. X.

    2016-08-01

    In this letter, we report on the structural and transport measurements of ultrathin MgB2 films grown by hybrid physical-chemical vapor deposition followed by low incident angle Ar ion milling. The ultrathin films as thin as 1.8 nm, or 6 unit cells, exhibit excellent superconducting properties such as high critical temperature (Tc) and high critical current density (Jc). The results show the great potential of these ultrathin films for superconducting devices and present a possibility to explore superconductivity in MgB2 at the 2D limit.

  17. Synthesis and oxidation behavior of boron-substituted carbon powders by hot filament chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Boron-substituted carbon powder, BxC1-x with x up to 0.17, has been successfully synthesized by hot filament chemical vapor deposition. The boron concentration in prepared BxC1-x samples can be controlled by varying the relative proportions of methane and diborane. X-ray diffraction, transmission electron microscopy, and electron energy loss spectrum confirm the successful synthesis of an amorphous BC5 compound, which consists of 10―20 nm particles with disk-like morphology. Thermogravimetry measurement shows that BC5 compound starts to oxidize ap-proximately at 620℃ and has a higher oxidation resistance than carbon.

  18. High efficiency AIGaAs/Si monolithic tandem solar cell grown by metalorganic chemical vapor deposition

    OpenAIRE

    Tetsuo, Soga; T.", "Kato; M., Yang; Masayoshi, Umeno; Takashi, Jimbo

    1995-01-01

    The improvements of the AlGaAs solar cell grown on the Si substrate and the AlGaAs/Si tandem solar cell by metalorganic chemical vapor deposition have been investigated. The active‐area conversion efficiency of the Al0.1Ga0.9As solar cell on the Si substrate as high as 12.9% has been obtained by improving the growth sequence and adopting an Al compositionally graded band emitter layer. A high efficiency monolithic AlGaAs/Si tandem solar cell with the active‐area conversion efficiency of 19.9%...

  19. An X-Ray Tomography Based Modeling Solution For Chemical Vapor Infiltration Of Ceramic Matrix Composites

    Science.gov (United States)

    Ros, William; Vignoles, Gérard L.; Germain, Christian

    2010-05-01

    A numerical tool for the simulation of Chemical Vapor Infiltration of carbon/carbon composites is introduced. The structure of the fibrous medium can be studied by high resolution X-Ray Computed Micro Tomography. Gas transport in various regimes is simulated by a random walk technique whilst the morphological evolution of the fluid/solid interface is handled by a Marching Cube technique. The program can be used to evaluate effective diffusivity and first order reaction rate. The numerical tool is validated by comparing computed effective properties of a straight slit pore with reactive walls to their analytical expression. Simulation of CVI processing of a real complex media is then presented.

  20. Growth of straight carbon nanotubes by simple thermal chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    ZOU Xiao-ping; H. ABE; T. SHIMIZU; A. ANDO; H. TOKUMOTO; ZHU Shen-ming; ZHOU Hao-shen

    2006-01-01

    Straight carbon nanotubes (CNTs) were achieved by simple thermal chemical vapor deposition(STCVD) catalyzed by Mo-Fe alloy catalyst on silica supporting substrate at 700 ℃. High-resolution transmission electron microscopy images show that the straight CNTs are well graphitized with no attached amorphous carbon. Mo-Fe alloy catalyst particles play a very crucial role in the growth of straight CNTs. The straight carbon nanotubes contain much less defects than the curved nanotubes and might have potential applications for nanoelectrical devices in the future. The simple synthesis of straight CNTs may have benefit for large-scale productions.

  1. MgB2 ultrathin films fabricated by hybrid physical chemical vapor deposition and ion milling

    Directory of Open Access Journals (Sweden)

    Narendra Acharya

    2016-08-01

    Full Text Available In this letter, we report on the structural and transport measurements of ultrathin MgB2 films grown by hybrid physical-chemical vapor deposition followed by low incident angle Ar ion milling. The ultrathin films as thin as 1.8 nm, or 6 unit cells, exhibit excellent superconducting properties such as high critical temperature (Tc and high critical current density (Jc. The results show the great potential of these ultrathin films for superconducting devices and present a possibility to explore superconductivity in MgB2 at the 2D limit.

  2. Self-catalytic growth of tin oxide nanowires by chemical vapor deposition process

    CSIR Research Space (South Africa)

    Thabethe, BS

    2013-01-01

    Full Text Available Corporation Journal of Nanomaterials Volume 2013, Article ID 712361, 7 pages http://dx.doi.org/10.1155/2013/712361 Research Article Self-Catalytic Growth of Tin Oxide Nanowires by Chemical Vapor Deposition Process Bongani S. Thabethe,1,2 Gerald F. Malgas,1... Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa Correspondence should be addressed to Gerald F. Malgas; gmalgas@csir.co.za and David E. Motaung; dmotaung@csir.co.za Received 20 February 2013; Accepted 10...

  3. Chemical Vapor Deposition of Phosphorous- and Boron-Doped Graphene Using Phenyl-Containing Molecules.

    Science.gov (United States)

    Mekan Ovezmyradov; Magedov, Igor V; Frolova, Liliya V; Chandler, Gary; Garcia, Jill; Bethke, Donald; Shaner, Eric A; Kalugin, Nikolai G

    2015-07-01

    Simultaneous chemical vapor deposition (CVD) of graphene and "in-situ" phosphorous or boron doping of graphene was accomplished using Triphenylphosphine (TPP) and 4-Methoxyphenylboronic acid (4-MPBA). The TPP and 4-MPBA molecules were sublimated and supplied along with CH4 molecules during graphene growth at atmospheric pressure. The grown graphene samples were characterized using Raman spectroscopy. Phosphorous and boron presence in phosphorous and boron doped graphene was confirmed with Auger electron spectroscopy. The possibility of obtaining phosphorous and boron doped graphene using solid-source molecule precursors via CVD can lead to an easy and rapid production of modified large area graphene.

  4. In situ observations during chemical vapor deposition of hexagonal boron nitride on polycrystalline copper

    DEFF Research Database (Denmark)

    Kidambi, Piran R.; Blume, Raoul; Kling, Jens

    2014-01-01

    Using a combination of complementary in situ X-ray photoelectron spectroscopy and X-ray diffraction, we study the fundamental mechanisms underlying the chemical vapor deposition (CVD) of hexagonal boron nitride (h-BN) on polycrystalline Cu. The nucleation and growth of h-BN layers is found to occur...... processing, and that this negatively affects the stability of h-BN on the catalyst. For extended air exposure Cu oxidation is observed, and upon re-heating in vacuum an oxygen-mediated disintegration of the h-BN film via volatile boron oxides occurs. Importantly, this disintegration is catalyst mediated, i...

  5. Fabrication of Isotropic Pyrocarbon at 1400℃ by Thermal Gradient Chemical Vapor Deposition Apparatus

    Institute of Scientific and Technical Information of China (English)

    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.

  6. Hot-Wire Chemical Vapor Deposition of Few-Layer Graphene on Copper Substrates

    Science.gov (United States)

    Soler, Víctor-Manuel Freire; Badia-Canal, Jordi; Roca, Carles Corbella; Miralles, Esther Pascual; Serra, Enric Bertran; Bella, José-Luís Andújar

    2013-01-01

    Chemical vapor deposition (CVD) of graphene on copper is an efficient technology for producing high-quality graphene for large areas. The objective of this work is to deposit graphene/few-layer graphene (FLG) using different types of copper substrate by a new hot-wire CVD process. We carried out the processes at temperatures below 1000 °C with acetylene (C2H2) as a precursor gas. After a general characterization of the samples, the results mostly indicate the formation of FLG on copper samples by this method. Nevertheless, the presence of pure, crystalline, and sufficiently flat surfaces is needed for depositing high-quality graphene layers.

  7. Synthesis and Characterization of Tin(IV) Oxide Obtained by Chemical Vapor Deposition Method

    Science.gov (United States)

    Nagirnyak, Svitlana V.; Lutz, Victoriya A.; Dontsova, Tatiana A.; Astrelin, Igor M.

    2016-07-01

    The effect of precursors on the characteristics of tin oxide obtained by chemical vapor deposition (CVD) method was investigated. The synthesis of nanosized tin(IV) oxide was carried out with the use of two different precursors: tin(II) oxalate obtained using tin chloride(II) and oxalic acid; tin(II) oxalate obtained using tin chloride(II); and ammonium oxalate. The synthesized tin(IV) oxide samples were studied by electron microscopy, X-ray diffraction and optical spectra. The lattice parameters of tin(IV) oxide samples were defined, the bandgap of samples were calculated.

  8. Synthesis and Characterization of Tin(IV) Oxide Obtained by Chemical Vapor Deposition Method

    OpenAIRE

    Nagirnyak, Svitlana V.; Lutz, Victoriya A.; Dontsova, Tatiana A.; Astrelin, Igor M.

    2016-01-01

    The effect of precursors on the characteristics of tin oxide obtained by chemical vapor deposition (CVD) method was investigated. The synthesis of nanosized tin(IV) oxide was carried out with the use of two different precursors: tin(II) oxalate obtained using tin chloride(II) and oxalic acid; tin(II) oxalate obtained using tin chloride(II); and ammonium oxalate. The synthesized tin(IV) oxide samples were studied by electron microscopy, X-ray diffraction and optical spectra. The lattice parame...

  9. High-purity cobalt thin films with perpendicular magnetic anisotropy prepared by chemical vapor deposition

    Science.gov (United States)

    Ootera, Yasuaki; Shimada, Takuya; Kado, Masaki; Quinsat, Michael; Morise, Hirofumi; Nakamura, Shiho; Kondo, Tsuyoshi

    2015-11-01

    A study of the chemical vapor deposition (CVD) of high-purity cobalt thin films is described. The Co layer prepared by a thermal CVD technique with a Pt/Ta underlayer and a Pt cap layer shows a saturation magnetization (Ms) of ∼1.8 T and perpendicular magnetic anisotropy (PMA) with an anisotropy energy (Ku) of ∼105 J/m3. The cobalt thickness dependence of Ku reveals that the interfacial anisotropy at the Pt/Co interface is most likely the origin of the obtained PMA.

  10. Synthesize of N-doped Carbon nanotube according to gas flow rate by Chemical Vapor Deposition

    Science.gov (United States)

    Kim, J. B.; Kim, C. D.; Kong, S. J.; Kim, J. H.; Min, B. K.; Jung, W. S.; Lee, H. R.

    2011-12-01

    Nitrogen-doped (N-doped) Carbon nanotubes (CNTs) have been prepared by Thermal Chemical Vapor Deposition (CVD). As doping accompanies with the recombination of carbon atoms into CNTs in the CVD process, N atoms can be substitutionally doped into the CNTs lattice, which is hard to realize by other synthetic methods. The synthesis technique and the characteristic analysis of N-doped CNT will move up the industrialization and the basic study of CNT. We will elucidate the basic properties of CNT such as the structural characteristics of the N-doped CNT material and study for the industrial application of the N-doped CNTs to the electrode of fuel cell.

  11. Time variant layer control in atmospheric pressure chemical vapor deposition based growth of graphene

    KAUST Repository

    Qaisi, Ramy M.

    2013-04-01

    Graphene is a semi-metallic, transparent, atomic crystal structure material which is promising for its high mobility, strength and transparency - potentially applicable for radio frequency (RF) circuitry and energy harvesting and storage applications. Uniform (same number of layers), continuous (not torn or discontinuous), large area (100 mm to 200 mm wafer scale), low-cost, reliable growth are the first hand challenges for its commercialization prospect. We show a time variant uniform (layer control) growth of bi- to multi-layer graphene using atmospheric chemical vapor deposition system. We use Raman spectroscopy for physical characterization supported by electrical property analysis. © 2013 IEEE.

  12. Observation of growth modes during metal-organic chemical vapor deposition of GaN

    Energy Technology Data Exchange (ETDEWEB)

    Stephenson, G.B.; Eastman, J.A.; Thompson, C.; Auciello, O.; Thompson, L.J. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Munkholm, A. [Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Fini, P.; DenBaars, S.P.; Speck, J.S. [Materials Department, University of California, Santa Barbara, California 93106 (United States)

    1999-05-01

    We present real-time surface x-ray scattering measurements during homoepitaxial growth of GaN by metal-organic chemical vapor deposition. We observed intensity oscillations corresponding to the completion of each monolayer during layer-by-layer growth. The growth rate was found to be temperature independent and Ga-transport limited. Transitions between step-flow, layer-by-layer, and three-dimensional growth modes were determined as a function of temperature and growth rate. {copyright} {ital 1999 American Institute of Physics.}

  13. Low-temperature deposition of crystalline silicon nitride nanoparticles by hot-wire chemical vapor deposition

    Science.gov (United States)

    Kim, Chan-Soo; Youn, Woong-Kyu; Lee, Dong-Kwon; Seol, Kwang-Soo; Hwang, Nong-Moon

    2009-07-01

    The nanocrystalline alpha silicon nitride (α-Si 3N 4) was deposited on a silicon substrate by hot-wire chemical vapor deposition at the substrate temperature of 700 °C under 4 and 40 Torr at the wire temperatures of 1430 and 1730 °C, with a gas mixture of SiH 4 and NH 3. The size and density of crystalline nanoparticles on the substrate increased with increasing wire temperature. With increasing reactor pressure, the crystallinity of α-Si 3N 4 nanoparticles increased, but the deposition rate decreased.

  14. High Quality SiGe Layer Deposited by a New Ultrahigh Vacuum Chemical Vapor Deposition System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    An ultrahigh vacuum chemical vapor deposition (UHV/CVD) system is developed and the details of its construction and operation are reported. Using high purity SiH4 and GeH4 reactant gases,the Si0.82Ge0.18 layer is deposited at 550℃. With the measurements by double crystal X-ray diffraction (DCXRD), transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS) techniques, it is shown that the crystalline quality of the SiGe layer is good,and the underlying SiGe/Si heterointerface is sharply defined.

  15. An Investigation on the Formation of Carbon Nanotubes by Two-Stage Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    M. S. Shamsudin

    2012-01-01

    Full Text Available High density of carbon nanotubes (CNTs has been synthesized from agricultural hydrocarbon: camphor oil using a one-hour synthesis time and a titanium dioxide sol gel catalyst. The pyrolysis temperature is studied in the range of 700–900°C at increments of 50°C. The synthesis process is done using a custom-made two-stage catalytic chemical vapor deposition apparatus. The CNT characteristics are investigated by field emission scanning electron microscopy and micro-Raman spectroscopy. The experimental results showed that structural properties of CNT are highly dependent on pyrolysis temperature changes.

  16. Influences on ionization fraction in an inductively coupled ionized physical vapor deposition device plasma

    Science.gov (United States)

    Juliano, Daniel R.; Ruzic, David N.; Allain, Monica M. C.; Hayden, Douglas B.

    2002-01-01

    A computer simulation was created to model the transport of sputtered atoms through an ionized physical vapor deposition (IPVD) system. The simulation combines Monte Carlo and fluid methods to track the metal atoms that are emitted from the target, interact with the IPVD plasma, and are eventually deposited somewhere in the system. Ground-state neutral, excited, and ionized metal atoms are tracked. The simulation requires plasma conditions to be specified by the user. Langmuir probe measurements were used to determine these parameters in an experimental system in order to compare simulation results with experiment. The primary product of the simulation is a prediction of the ionization fraction of the sputtered atom flux at the substrate under various conditions. This quantity was experimentally measured and the results compared to the simulation. Experiment and simulation differ significantly. It is hypothesized that heating of the background gas due to the intense sputtered atom flux at the target is primarily responsible for this difference. Heating of the background gas is not accounted for in the simulation. Difficulties in accurately measuring plasma parameters, especially electron temperature, are also significant.

  17. Functionalized bioinspired microstructured optical fiber pores for applications in chemical vapor sensing

    Science.gov (United States)

    Calkins, Jacob A.

    Chemical vapor sensing for defense, homeland security, environmental, and agricultural application is a challenge, which due combined requirements of ppt sensitivity, high selectivity, and rapid response, cannot be met using conventional analytical chemistry techniques. New sensing approaches and platforms are necessary in order to make progress in this rapidly evolving field. Inspired by the functionalized nanopores on moth sensilla hairs that contribute to the high selectivity and sensitivity of this biological system, a chemical vapor sensor based on the micro to nanoscale pores in microstructured optical fibers (MOFs) was designed. This MOF based chemical vapor sensor design utilizes MOF pores functionalized with organic self-assembled monolayers (SAMs) for selectivity and separations and a gold plasmonic sensor for detection and discrimination. Thin well-controlled gold films in MOF pores are critical components for the fabrication of structured plasmonic chemical vapor sensors. Thermal decomposition of dimethyl Au(II) trifluoroacetylacetonate dissolved in near-critical CO2 was used to deposit gold island films within the MOF pores. Using a 3mercatopropyltrimethoxysilane adhesion layer, continuous gold thin films as thin as 20--30 nm were deposited within MOF pores as small as 500 nm in diameter. The gold island films proved to be SERS active and were used to detect 900 ppt 2,4 DNT vapor in high pressure nitrogen and 6 ppm benzaldehyde. MOF based waveguide Raman (WGR), which can probe the air/silica interface between a waveguiding core and surrounding pores, was developed to detect and characterize SAMs and other thin films deposited in micro to nanoscale MOF pores. MOF based WGR was used to characterize an octadecyltrichlorosilane (OTS) SAM deposited in 1.6 mum diameter pores iv to demonstrate that the SAM was well-formed, uniform along the pore length, and only a single layer. MOF based WGR was used to detect a human serum albumin monolayer deposited on the

  18. High Temperature Multilayer Environmental Barrier Coatings Deposited Via Plasma Spray-Physical Vapor Deposition

    Science.gov (United States)

    Harder, Bryan James; Zhu, Dongming; Schmitt, Michael P.; Wolfe, Douglas E.

    2014-01-01

    Si-based ceramic matrix composites (CMCs) require environmental barrier coatings (EBCs) in combustion environments to avoid rapid material loss. Candidate EBC materials have use temperatures only marginally above current technology, but the addition of a columnar oxide topcoat can substantially increase the durability. Plasma Spray-Physical Vapor Deposition (PS-PVD) allows application of these multilayer EBCs in a single process. The PS-PVD technique is a unique method that combines conventional thermal spray and vapor phase methods, allowing for tailoring of thin, dense layers or columnar microstructures by varying deposition conditions. Multilayer coatings were deposited on CMC specimens and assessed for durability under high heat flux and load. Coated samples with surface temperatures ranging from 2400-2700F and 10 ksi loads using the high heat flux laser rigs at NASA Glenn. Coating morphology was characterized in the as-sprayed condition and after thermomechanical loading using electron microscopy and the phase structure was tracked using X-ray diffraction.

  19. Determination of mercury in coal by isotope dilution cold-vapor generation inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Long, Stephen E; Kelly, W Robert

    2002-04-01

    A method based on isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICPMS) has been developed for high-accuracy determinations of mercury in bituminous and sub-bituminous coals. A closed-system digestion process employing a Carius tube is used to completely oxidize the coal matrix and chemically equilibrate the mercury in the sample with a 201Hg isotopic spike. The digestates are diluted with high-purity quartz-distilled water, and the mercury is released as a vapor by reduction with tin(II) chloride. Measurements of 201Hg/202Hg isotope ratios are made using a quadrupole ICPMS system in time-resolved analysis mode. The new method has some significant advantages over existing methods. The instrument detection limit is less than 1 pg/mL. The average blank (n = 17) is 30 pg, which is roughly 1 order of magnitude lower than the equivalent microwave digestion procedure. The detection limit in coal is blank limited and is approximately 40 pg/g. Memory effects are very low. The relative reproducibility of the analytical measurements is approximately 0.5% for mercury concentrations in the range 10-150 ng/g. The method has been used to measure mercury concentrations in six coal reference materials, SRM 1632b (77.4 ng/g), SRM 1632c (94.3 ng/g), BCR 40 (433.2 ng/g), BCR 180 (125.0 ng/g), BCR 181 (135.8 ng/g), and SARM 20 (252.6 ng/g), as well as a coal fly ash, SRM 1633b (143.1 ng/g). The method is equally applicable to other types of fossil fuels including both crude and refined oils.

  20. Determination of mercury in coal by isotope dilution cold-vapor generation inductively coupled plasma mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Long, S.E.; Kelly, W.R.

    2002-04-01

    A method based on isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICPMS) has been developed for high-accuracy determinations of mercury in bituminous and sub-bituminous coals. A closed-system digestion process employing a Carius tube is used to completely oxidize the coal matrix and chemically equilibrate the mercury in the sample with a Hg-201 isotopic spike. The digestates are diluted with high-purity quartz-distilled water, and the mercury is released as a vapor by reduction with tin chloride. Measurements of Hg-201/Hg-202 isotope ratios are made using a quadrupole ICPMS system in time-resolved analysis mode. The new method has some significant advantages over existing methods. The instrument detection limit is less than 1 pg/mL. The average blank (n = 17) is 30 pg, which is roughly 1 order of magnitude lower than the equivalent microwave digestion procedure. The detection limit in coal is blank limited and is similar to 40 pg/g. Memory effects are very low. The relative reproducibility of the analytical measurements is similar to 0.5% for mercury concentrations in the range 10-150 ng/g. The method has been used to measure mercury concentrations in six coal reference materials, SRM 1632b (77.4 ng/g), SRM 1632c (94.3 ng/g), BCR 40 (433.2 ng/g), BCR 180 (125.0 ng/g), BCR 181 (135.8 ng/g), and SARM 20 (252.6 ng/g), as well as a coal fly ash, SRM 1633b (143.1 ng/g). The method is equally applicable to other types of fossil fuels including both crude and refined oils.

  1. CMAS Interactions with Advanced Environmental Barrier Coatings Deposited via Plasma Spray- Physical Vapor Deposition

    Science.gov (United States)

    Harder, B. J.; Wiesner, V. L.; Zhu, D.; Johnson, N. S.

    2017-01-01

    Materials for advanced turbine engines are expected to have temperature capabilities in the range of 1370-1500C. At these temperatures the ingestion of sand and dust particulate can result in the formation of corrosive glass deposits referred to as CMAS. The presence of this glass can both thermomechanically and thermochemically significantly degrade protective coatings on metallic and ceramic components. Plasma Spray- Physical Vapor Deposition (PS-PVD) was used to deposit advanced environmental barrier coating (EBC) systems for investigation on their interaction with CMAS compositions. Coatings were exposed to CMAS and furnace tested in air from 1 to 50 hours at temperatures ranging from 1200-1500C. Coating composition and crystal structure were tracked with X-ray diffraction and microstructure with electron microscopy.

  2. Chemical sensing of copper phthalocyanine sol-gel glass through organic vapors

    Energy Technology Data Exchange (ETDEWEB)

    Ridhi, R.; Gawri, Isha; Abbas, Saeed J.; Saini, G. S. S.; Tripathi, S. K. [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh-160 014 (INDIA) Fax: +91-172-2783336; Tel.:+91-172-2544362 (India)

    2015-05-15

    The sensitivities of metallophthalocyanine to vapor phase electron donors has gained significance in many areas and disciplines due to their sensing properties and ease of operation. In the present study the interaction mechanism of organic vapors in Copper Phthalocyanine (CuPc) sol-gel glass has been studied. The interaction mechanism is affected by many factors like morphology, electrical or optical properties of film. CuPc sol-gel glass has been synthesized using chemical route sol-gel method. Its structural characterization was conducted using XRD and the amorphous nature of the silicate glass was observed with characteristic α polymorph phase of CuPc at around 6.64° with 13.30Å interplanar spacing. The size of the particle as determined using Debbye Scherre’s formula comes out around 15.5 nm. The presence of α phase of CuPc was confirmed using FTIR with the appearance of crystal parameter marker band at 787 cm-1. Apart from this A2u and Eu symmetry bands of CuPc have also been observed. The UV absorption spectrum of CuPc exhibits absorption peaks owing to π→ π* and n→ π* transitions. A blue shift in the prepared CuPc glass has been observed as compared to the dopant CuPc salt indicating increase of band gap. A split in B (Soret) band and Q band appears as observed with the help of Lorentzian fitting. CuPc sol gel glass has been exposed with chemical vapors of Methanol, Benzene and Bromine individually and the electrical measurements have been carried out. These measurements show the variation in conductivity and the interaction mechanism has been analyzed.

  3. Nanowatt chemical vapor detection with a self-sensing, piezoelectric microcantilever array

    Science.gov (United States)

    Adams, J. D.; Parrott, G.; Bauer, C.; Sant, T.; Manning, L.; Jones, M.; Rogers, B.; McCorkle, D.; Ferrell, T. L.

    2003-10-01

    The portability, compactness, price, and deployment of sensing systems are determined in large part by the power consumption and simplicity of the sensing platform used. We demonstrate a microcantilever chemical detection platform based on an array of piezoelectric microcantilevers. The sensor-element array power consumption, including actuation, is measured in nanowatts, with impedance of the order of megohms. This is four to five orders of magnitude lower power dissipation than current cantilever chemical detection platforms using optical or piezoresistive detection. The sensor is further characterized in the picowatt regime. The platform comprises three cantilevers wired in series, where variations in the resonant frequency and quality factor of selectively coated cantilevers, during successive impedance measurements, enable detection of ethanol vapor.

  4. Densification mechanism of chemical vapor infiltration technology for carbon/carbon composites

    Institute of Scientific and Technical Information of China (English)

    CHEN Jian-xun; XIONG Xiang; HUANG Qi-zhong; YI Mao-zhong; HUANG Bai-yun

    2007-01-01

    Carbon/carbon composites were fabricated using pressure-gradient chemical vapor infiltration(CVI) technology with propane (C3H6) as the carbon precursor gas and nitrogen (N2) as the carrier gas. The chemical process of deposition of pyrolytic carbon was deduced by analyzing the component of molecules in gas phase and observing the microstructure of deposition carbon. The results show that the process of deposition starts from the breakdown of C-C single bond of propene (C3H6), and forms two kinds of active groups in the heterogeneous gas phase reaction. Afterwards, these active groups form many stable bigger molecules and deposit on carbon fiber surface. At the same time, hydrogen atoms of the bigger molecules absorbed on carbon fiber surface are eliminated and the solid pyrolytic carbon matrix is formed in the heterogeneous reaction process.

  5. Laterally Stitched Heterostructures of Transition Metal Dichalcogenide: Chemical Vapor Deposition Growth on Lithographically Patterned Area

    KAUST Repository

    Li, Henan

    2016-10-31

    Two-dimensional transition metal dichalcogenides (TMDCs) have shown great promise in electronics and optoelectronics due to their unique electrical and optical properties. Heterostructured TMDC layers such as the laterally stitched TMDCs offer the advantages of better electronic contact and easier band offset tuning. Here, we demonstrate a photoresist-free focused ion beam (FIB) method to pattern as-grown TMDC monolayers by chemical vapor deposition, where the exposed edges from FIB etching serve as the seeds for growing a second TMDC material to form desired lateral heterostructures with arbitrary layouts. The proposed lithographic and growth processes offer better controllability for fabrication of the TMDC heterostrucuture, which enables the construction of devices based on heterostructural monolayers. © 2016 American Chemical Society.

  6. Simultaneous Chemical and Optical Patterning of Polyacrylonitrile Film by Vapor-Based Reaction.

    Science.gov (United States)

    Shin, Jae-Won; Lee, Choonghyeon; Cha, Sang-Ho; Jang, Jyongsik; Lee, Kyung Jin

    2015-06-01

    The surface of polyacrylonitrile (PAN) film is treated with ethyleneamines (EDA) in a simple chemical vapor phase reaction. Successful introduction of amine functional groups on the cyano group of PAN backbone is verified by FT-IR and NMR measurements. Further UV-vis and photoluminescence analyses show a red shift of the emission peak after repeated EDA treatment, which might be attributed to the formation of imine conjugation from newly formed carbon-nitrogen bonds on the PAN backbone. Further confocal laser scanning microscopy reveals that selective patterning of EDA on PAN films is possible via local polydimethylsiloxane masking. The results indicate that both chemical and optical patterning on PAN film can be realized via a single reaction and show the potential of this novel methodology in selective patterning.

  7. Suitable alkaline for graphene peeling grown on metallic catalysts using chemical vapor deposition

    Science.gov (United States)

    Karamat, S.; Sonuşen, S.; Çelik, Ü.; Uysallı, Y.; Oral, A.

    2016-04-01

    In chemical vapor deposition, the higher growth temperature roughens the surface of the metal catalyst and a delicate method is necessary for the transfer of graphene from metal catalyst to the desired substrates. In this work, we grow graphene on Pt and Cu foil via ambient pressure chemical vapor deposition (AP-CVD) method and further alkaline water electrolysis was used to peel off graphene from the metallic catalyst. We used different electrolytes i.e., sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) and barium hydroxide Ba(OH)2 for electrolysis, hydrogen bubbles evolved at the Pt cathode (graphene/Pt/PMMA stack) and as a result graphene layer peeled off from the substrate without damage. The peeling time for KOH and LiOH was ∼6 min and for NaOH and Ba(OH)2 it was ∼15 min. KOH and LiOH peeled off graphene very efficiently as compared to NaOH and Ba(OH)2 from the Pt electrode. In case of copper, the peeling time is ∼3-5 min. Different characterizations like optical microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy were done to analyze the as grown and transferred graphene samples.

  8. Evaporation of Droplets in Plasma Spray-Physical Vapor Deposition Based on Energy Compensation Between Self-Cooling and Plasma Heat Transfer

    Science.gov (United States)

    Liu, Mei-Jun; Zhang, Meng; Zhang, Qiang; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2017-08-01

    In the plasma spray-physical vapor deposition process (PS-PVD), there is no obvious heating to the feedstock powders due to the free molecular flow condition of the open plasma jet. However, this is in contrast to recent experiments in which the molten droplets are transformed into vapor atoms in the open plasma jet. In this work, to better understand the heating process of feedstock powders in the open plasma jet of PS-PVD, an evaporation model of molten ZrO2 is established by examining the heat and mass transfer process of molten ZrO2. The results reveal that the heat flux in PS-PVD open plasma jet (about 106 W/m2) is smaller than that in the plasma torch nozzle (about 108 W/m2). However, the flying distance of molten ZrO2 in the open plasma jet is much longer than that in the plasma torch nozzle, so the heating in the open plasma jet cannot be ignored. The results of the evaporation model show that the molten ZrO2 can be partly evaporated by self-cooling, whereas the molten ZrO2 with a diameter heat transfer.

  9. Stability increase of fuel clad with zirconium oxynitride thin film by metalorganic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Jee, Seung Hyun [Department of Materials Science and Engineering, Yonsei University, 134 Sinchon Dong, Seoul 120-749 (Korea, Republic of); Materials Research and Education Center, Dept. of Mechanical Engineering, Auburn University, 275 Wilmore Labs, AL 36849-5341 (United States); Kim, Jun Hwan; Baek, Jong Hyuk [Recycled Fuel Development Division, Korea Atomic Energy Research Institute, P.O. Box 105, Yuseong, Daejeon, 305-600 (Korea, Republic of); Kim, Dong-Joo [Materials Research and Education Center, Dept. of Mechanical Engineering, Auburn University, 275 Wilmore Labs, AL 36849-5341 (United States); Kang, Seong Sik [Regulatory Research Division, Korea Institute of Nuclear Safety, 19, Guseong-Dong, Yuseong-Gu, Daejeon, 305-338 (Korea, Republic of); Yoon, Young Soo, E-mail: yoonys@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, 134 Sinchon Dong, Seoul 120-749 (Korea, Republic of)

    2012-06-01

    A zirconium oxynitride (ZON) thin film was deposited onto HT9 steel as a cladding material by a metalorganic chemical vapor deposition (MOCVD) in order to prevent a fuel-clad chemical interaction (FCCI) between a U-10 wt% Zr metal fuel and a clad material. X-ray diffraction spectrums indicated that the mixture of structures of zirconium nitride, oxide and carbide in the MOCVD grown ZON thin films. Also, typical equiaxial grain structures were found in plane and cross sectional images of the as-deposited ZON thin films with a thickness range of 250-500 nm. A depth profile using auger electron microscopy revealed that carbon and oxygen atoms were decreased in the ZON thin film deposited with hydrogen gas flow. Diffusion couple tests at 800 Degree-Sign C for 25 hours showed that the as-deposited ZON thin films had low carbon and oxygen content, confirmed by the Energy Dispersive X-ray Spectroscopy, which showed a barrier behavior for FCCI between the metal fuel and the clad. This result suggested that ZON thin film cladding by MOCVD, even with the thickness below the micro-meter level, has a high possibility as an effective FCCI barrier. - Highlights: Black-Right-Pointing-Pointer Zirconium oxynitride (ZON) deposited by metal organic chemical vapor deposition. Black-Right-Pointing-Pointer Prevention of fuel cladding chemical interaction (FCCI) investigated. Black-Right-Pointing-Pointer Interfusion reduced by between metal fuel (U-10 wt% Zr) and a HT9 cladding material. Black-Right-Pointing-Pointer Hydrogenation of the ZON during growth improved the FCCI barrier performance.

  10. Heteroepitaxial growth of 3-5 semiconductor compounds by metal-organic chemical vapor deposition for device applications

    Science.gov (United States)

    Collis, Ward J.; Abul-Fadl, Ali

    1988-01-01

    The purpose of this research is to design, install and operate a metal-organic chemical vapor deposition system which is to be used for the epitaxial growth of 3-5 semiconductor binary compounds, and ternary and quaternary alloys. The long-term goal is to utilize this vapor phase deposition in conjunction with existing current controlled liquid phase epitaxy facilities to perform hybrid growth sequences for fabricating integrated optoelectronic devices.

  11. Investigation of the AC Plasma Torch Working Conditions for the Plasma Chemical Applications

    Science.gov (United States)

    Safronov, A. A.; Vasilieva, O. B.; Dudnik, J. D.; E Kuznetsov, V.; Shiryaev, V. N.; Subbotin, D. I.; Pavlov, A. V.

    2017-04-01

    The presented design and parameters of a three-phase AC plasma torch with the power up to 500 kW, flow rate of air 30-50 g/s (temperature up to 5000 K) could be used in different plasma chemical processes. Range of measured plasma temperature is 3500-5000 K. The paper presents investigations of the plasma torch operation modes for its application in plasma chemical technologies. Plasma chemical technologies for various purposes (processing, destruction of various wastes, including technological and hazardous waste, conversion or production of chemicals to obtain nanoscale materials, etc.) are very promising in terms of the process efficiency. Their industrial use is difficult due to the lack of inexpensive and reliable plasma torches providing the desired level of temperature, enthalpy of the working gas and other necessary conditions for the process. This problem can be solved using a considered design of a three-phase alternating current plasma torch with power of 150-500 kW with working gas flow rate of 30-50 g/s with mass average temperature up to 5000K on the basis of which an industrial plasma chemical plant can be created. The basis of the plasma torch operation is a railgun effect that is the principle of arc movement in the field of its own current field. Thanks to single supply of power to the arc, arcs forming in the discharge chamber of the plasma torch move along the electrodes under the action of electrodynamic forces resulting from the interaction of the arc current with its own magnetic field. Under the condition of the three-phase supply voltage, arc transits from the electrode to the electrode with change in the anodic and cathodic phases with frequency of 300 Hz. A special feature of this design is the ability to organize the movement of the arc attachment along the electrode, thus ensuring an even distribution of the thermal load and thus achieve long time of continuous operation of the plasma torch. The parameters of the plasma jet of the

  12. Direct determination of arsenic in fresh and saline waters by electrothermal vaporization inductively coupled plasma mass spectrometry

    Science.gov (United States)

    Conrad Grégoire, D.; de Lourdes Ballinas, Maria

    1997-01-01

    A method is described for the direct determination of arsenic in fresh and saline waters by electrothermal vaporization inductively coupled plasma mass spectrometry. Arsenic could be determined directly in waters containing up to 10 000 μg ml -1 NaCl without interference from the formation of 75ArCl +. For non-saline waters, arsenic was determined directly with the addition to both aqueous calibration standards and samples of 0.1 μg each of Pd and Mg to act as physical carriers. For the analysis of highly saline waters, the use of Pd and Mg chemical modifier served to thermally stabilize arsenic up to a temperature of 1000°C, while the separate addition of 8 mg of ammonium nitrate was used to remove chloride from the sample. This eliminated serious spectral interference on 75As + from 75ArCl +. Although the ArCl + spectral interference was completely eliminated, residual Na co-volatilized with As caused signal suppression, requiring the use of the method of standard additions for calibration. An absolute limit of detection limit for As of 0.069 pg was obtained corresponding to 6.9 pg ml -1 in a 10 μl sample.

  13. Basic analytical investigation of plasma-chemically modified carbon fibers

    Energy Technology Data Exchange (ETDEWEB)

    Bubert, H.; Ai, X.; Haiber, S.; Heintze, M.; Brueser, V.; Pasch, E.; Brandl, W.; Marginean, G

    2002-10-15

    The background of the present investigation is to enhance the overall adherence of vapor grown carbon fibers (VGCF) to the surrounding polymer matrix in different applications by forming polar groups at their surfaces and by modifying the surface morphology. This has been done by plasma treatments using a low-pressure plasma with different gases, flow rates, pressures and powers. Two different types of carbon fibers were investigated: carbon microfibers and carbon nanofibers. The characterization of fiber surfaces was achieved by photoelectron spectroscopy (XPS), contact angle measurements and titration. These investigations were accompanied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The oxygen plasma treatment of the fibers changes the surfaces by forming a layer with a thickness of the order of one nanometer mainly consisting of functional groups like hydroxyl, carbonyl and carboxyl. After functionalization of the complete surface, a further plasma treatment does not enhance the superficial oxygen content but changes slightly the portions of the functional groups. A comparison of the methods applied provides a largely consistent image of the effect of plasma treatment.

  14. The shear viscosity of gauge theory plasma with chemical potentials

    Energy Technology Data Exchange (ETDEWEB)

    Benincasa, Paolo [Department of Applied Mathematics, University of Western Ontario, London, Ontario N6A 5B7 (Canada); Buchel, Alex [Department of Applied Mathematics, University of Western Ontario, London, Ontario N6A 5B7 (Canada) and Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2J 2W9 (Canada)]. E-mail: abuchel@perimeterinstitute.ca; Naryshkin, Roman [Department of Applied Mathematics, University of Western Ontario, London, Ontario N6A 5B7 (Canada); Physics Department, Taras Shevchenko Kiev National University, Prosp. Glushkova 6, Kiev 03022 (Ukraine)

    2007-02-08

    We consider strongly coupled gauge theory plasma with conserved global charges that allow for a dual gravitational description. We study the shear viscosity of the gauge theory plasma in the presence of chemical potentials for these charges. Using gauge theory/string theory correspondence we prove that at large 't Hooft coupling the ratio of the shear viscosity to the entropy density is universal.

  15. Structural, Mechanical and Optical Properties of Plasma-chemical Si-C-N Films

    Directory of Open Access Journals (Sweden)

    A.O. Kozak

    2014-11-01

    Full Text Available An influence of the substrate temperature in the range of 40-400 °C on the properties of the Si-C-N films deposited by plasma enhanced chemical vapor deposition (PECVD technique using hexamethyldisilazane is analyzed. Study of the structure, chemical bonding, surface morphology, mechanical properties and energy gap of the obtained films was carried out using X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, optical measurements and nanoindentation. It was established that all the films were X-ray amorphous and had low surface roughness. Intensive hydrogen effusion from the films takes place, when substrate temperature increases up to 400 °C, which promotes a decrease of roughness and an increase in hardness and Young modules more than twice.

  16. Vapor shielding effects on energy transfer from plasma-gun generated ELM-like transient loads to material surfaces

    Science.gov (United States)

    Kikuchi, Y.; Sakuma, I.; Asai, Y.; Onishi, K.; Isono, W.; Nakazono, T.; Nakane, M.; Fukumoto, N.; Nagata, M.

    2016-02-01

    Energy transfer processes from ELM-like pulsed helium (He) plasmas with a pulse duration of ˜0.1 ms to aluminum (Al) and tungsten (W) surfaces were experimentally investigated by the use of a magnetized coaxial plasma gun device. The surface absorbed energy density of the He pulsed plasma on the W surface measured with a calorimeter was ˜0.44 MJ m-2, whereas it was ˜0.15 MJ m-2 on the Al surface. A vapor layer in front of the Al surface exposed to the He pulsed plasma was clearly identified by Al neutral emission line (Al i) measured with a high time resolution spectrometer, and fast imaging with a high-speed visible camera filtered around the Al i emission line. On the other hand, no clear evaporation in front of the W surface exposed to the He pulsed plasma was observed in the present condition. Discussions on the reduction in the surface absorbed energy density on the Al surface are provided by considering the latent heat of vaporization and radiation cooling due to the Al vapor cloud.

  17. Development of a double plasma gun device for investigation of effects of vapor shielding on erosion of PFC materials under ELM-like pulsed plasma bombardment

    Science.gov (United States)

    Sakuma, I.; Iwamoto, D.; Kitagawa, Y.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2012-10-01

    It is considered that thermal transient events such as type I edge localized modes (ELMs) could limit the lifetime of plasma-facing components (PFCs) in ITER. We have investigated surface damage of tungsten (W) materials under transient heat and particle loads by using a magnetized coaxial plasma gun (MCPG) device at University of Hyogo. The capacitor bank energy for the plasma discharge is 144 kJ (2.88 mF, 10 kVmax). Surface melting of a W material was clearly observed at the energy density of ˜2 MJ/m2. It is known that surface melting and evaporation during a transient heat load could generate a vapor cloud layer in front of the target material [1]. Then, the subsequent erosion could be reduced by the vapor shielding effect. In this study, we introduce a new experiment using two MCPG devices (MCPG-1, 2) to understand vapor shielding effects of a W surface under ELM-like pulsed plasma bombardment. The capacitor bank energy of MCPG-2 is almost same as that of MCPG-1. The second plasmoid is applied with a variable delay time after the plasmoid produced by MCPG-1. Then, a vapor cloud layer could shield the second plasma load. To verify the vapor shielding effects, surface damage of a W material is investigated by changing the delay time. In the conference, the preliminary experimental results will be shown.[4pt] [1] A. Hassanein et al., J. Nucl. Mater. 390-391, pp. 777-780 (2009).

  18. Spectral diagnostics of a vapor-plasma plume produced during welding titanium with a high-power ytterbium fiber laser

    Science.gov (United States)

    Uspenskiy, S. A.; Petrovskiy, V. N.; Bykovskiy, D. P.; Mironov, V. D.; Prokopova, N. M.; Tret'yakov, E. V.

    2015-03-01

    This work is devoted to the research of welding plume during high power ytterbium fiber laser welding of a titanium alloy in the Ar shielding gas environment. High speed video observation of a vapor-plasma plume for visualization of processes occurring at laser welding was carried out. The coefficient of the inverse Bremsstrahlung absorption of laser radiation is calculated for a plasma welding plume by results of spectrometer researches. The conclusion deals with the impact of plasma on a high-power fiber laser radiation.

  19. Spectral diagnostics of a vapor-plasma plume produced during welding with a high-power ytterbium fiber laser

    Science.gov (United States)

    Uspenskiy, S. A.; Shcheglov, P. Yu.; Petrovskiy, V. N.; Gumenyuk, A. V.; Rethmeier, M.

    2013-07-01

    We have conducted spectroscopic studies of the welding plasma formed in the process of welding with an ytterbium fiber laser delivering output power of up to 20 kW. The influence of shielding gases (Ar, He) on different parts of the welding plume is investigated. The absorption coefficient of the laser radiation by the welding-plume plasma is estimated. Scattering of 532-nm probe radiation from particles of the condensed metal vapor within the caustic of a high-power fiber laser beam is measured. Based on the obtained results, conclusions are made on the influence of the plasma formation and metal vapor condensation on the radiation of the high-power fiber laser and the stability of the welding process.

  20. Chemical analysis of plasma-assisted antimicrobial treatment on cotton

    Science.gov (United States)

    Kan, C. W.; Lam, Y. L.; Yuen, C. W. M.; Luximon, A.; Lau, K. W.; Chen, K. S.

    2013-06-01

    This paper explores the use of plasma treatment as a pretreatment process to assist the application of antimicrobial process on cotton fabric with good functional effect. In this paper, antimicrobial finishing agent, Microfresh Liquid Formulation 9200-200 (MF), and a binder (polyurethane dispersion, Microban Liquid Formulation R10800-0, MB) will be used for treating the cotton fabric for improving the antimicrobial property and pre-treatment of cotton fabric by plasma under atmospheric pressure will be employed to improve loading of chemical agents. The chemical analysis of the treated cotton fabric will be conducted by Fourier transform Infrared Spectroscopy.

  1. Generator of chemically active low-temperature plasma

    Science.gov (United States)

    Tyuftyaev, A. S.; Gadzhiev, M. Kh; Sargsyan, M. A.; Demirov, N. A.; Spector, N. O.

    2016-11-01

    A new generator of high enthalpy (H 0 > 40 kJ/g), chemically active nitrogen and air plasmas was designed and constructed. Main feature of the generator is an expanding channel of an output electrode; the generator belongs to the class of DC plasma torches with thermionic cathode with an efficiency of 80%. The generator ensures the formation of a slightly divergent plasma jet (2α = 12°) with a diameter of D = 10-12 mm, an electric arc maximum power of 20-50 kW, plasma forming gas flow rate 1.0-2.0 g/s, and the average plasma temperature at an outlet of 8000-11000 K.

  2. a Design of Experiment Study of the Nucleation of Chemical Vapor Deposited Diamond Films.

    Science.gov (United States)

    Tang, Chi

    1995-01-01

    Because of its property, diamond has a unique role in the semiconductor and tool industry. As diamond synthesis technology advances, more and more applications are emerging. However, in order to take advantage of its exceptional property, reliable control of nucleation and growth must be accomplished. In this study, the author systematically studies the nucleation process in chemical vapor deposition (CVD) of diamonds. Among many important intricacies concerning diamond nucleation on foreign surfaces, this study addresses the following issues: the role of ultrasonic pre-treatment in CVD; the correlation between hot filament chemical vapor deposition (HFCVD) and microwave assisted chemical vapor deposition (MACVD) control parameters and the nucleation processes; the role of biasing substrates on the nucleation density in MACVD; the correlation between parameters of biasing substrates and the nucleation density; the reliable control of nucleation in CVD diamond synthesis. To achieve the goal of this research, a multi -purpose deposition system was built enabling the author to eliminate unnecessary variables in the deposition process. To ensure the accuracy of the nucleation effects of parameters investigated, great effort was made to calibrate measurement instruments so that noise or fluctuations in the experiments were minimized. The implementation of design of experiments (DOE), a systematic investigating technique, vastly improved the efficiency of this study over the less sophisticated empirical approach. In addition, DOE allowed the author to quantitatively estimate the effects of control parameters. Finally, diamond deposition was confirmed by Scanning Electron microscope, Micro Raman Scattering and Rutherford Backscattering. This research has successfully implemented DOE in estimating the effects of diamond nucleation quantitatively. The mechanism of ultrasonic pre-treatment is explained, and its effects are ascribed to seeding. The effects of primary CVD

  3. Suitable alkaline for graphene peeling grown on metallic catalysts using chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Karamat, S., E-mail: shumailakaramat@gmail.com [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey); COMSATS Institute of Information Technology, Islamabad 54000 (Pakistan); Sonuşen, S. [Sabancı Üniversitesi (SUNUM), İstanbul 34956 (Turkey); Çelik, Ü. [Nanomagnetics Instruments, Ankara (Turkey); Uysallı, Y. [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey); Oral, A., E-mail: orahmet@metu.edu.tr [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey)

    2016-04-15

    Graphical abstract: - Highlights: • Graphene layers were grown on Pt and Cu foil via ambient pressure chemical vapor deposition method and for the delicate removal of graphene from metal catalysts, electrolysis method was used by using different alkaline (sodium hydroxide, potassium hydroxide, lithium hydroxide and barium hydroxide). • The delamination speed of PMMA/graphene stack was higher during the KOH and LiOH electrolysis as compare to NaOH and Ba(OH){sub 2}. Ba(OH){sub 2} is not advisable because of the residues left on the graphene surface which would further trapped in between graphene and SiO{sub 2}/Si surface after transfer. The average peeling time in case of Pt electrode is ∼6 min for KOH and LiOH and ∼15 min for NaOH and Ba(OH){sub 2}. • Electrolysis method also works for the Cu catalyst. The peeling of graphene was faster in the case of Cu foil due to small size of bubbles which moves faster between the stack and the electrode surface. The average peeling time was ∼3–5 min. • XPS analysis clearly showed that the Pt substrates can be re-used again. Graphene layer was transferred to SiO{sub 2}/Si substrates and to the flexible substrate by using the same peeling method. - Abstract: In chemical vapor deposition, the higher growth temperature roughens the surface of the metal catalyst and a delicate method is necessary for the transfer of graphene from metal catalyst to the desired substrates. In this work, we grow graphene on Pt and Cu foil via ambient pressure chemical vapor deposition (AP-CVD) method and further alkaline water electrolysis was used to peel off graphene from the metallic catalyst. We used different electrolytes i.e., sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) and barium hydroxide Ba(OH){sub 2} for electrolysis, hydrogen bubbles evolved at the Pt cathode (graphene/Pt/PMMA stack) and as a result graphene layer peeled off from the substrate without damage. The peeling time for KOH and Li

  4. Temperature regulated-chemical vapor deposition for incorporating NiO nanoparticles into mesoporous media

    Science.gov (United States)

    Han, Sang Wook; Kim, Il Hee; Kim, Dae Han; Park, Ki Jung; Park, Eun Ji; Jeong, Myung-Geun; Kim, Young Dok

    2016-11-01

    We have developed a novel strategy for incorporating NiO nanoparticles into mesoporous Al2O3 with a mean pore size of ∼12 nm and particle size of ∼1 mm. Ni-precursor vapor and ambient atmosphere were filled in a closed chamber with mesoporous Al2O3, and the chamber was initially heated at ∼100 °C, at which no chemical reaction between the inorganic precursor, oxygen, water vapor in the atmosphere, and the surface of Al2O3 took place. Next, the temperature of the system was increased to 260 °C for deposition of NiO. We found that NiO nanoparticles were not only deposited on the surface, but were also incorporated in a 50 μm-deep region of the mesoporous Al2O3 gel. We also demonstrated high CO oxidation activity and reusability of the deactivated NiO/Al2O3 catalysts prepared by the aforementioned method. These results suggest that our strategy could be widely applicable to the incorporation of various nanoparticles into mesoporous supports.

  5. Design and implementation of a novel portable atomic layer deposition/chemical vapor deposition hybrid reactor.

    Science.gov (United States)

    Selvaraj, Sathees Kannan; Jursich, Gregory; Takoudis, Christos G

    2013-09-01

    We report the development of a novel portable atomic layer deposition chemical vapor deposition (ALD/CVD) hybrid reactor setup. Unique feature of this reactor is the use of ALD/CVD mode in a single portable deposition system to fabricate multi-layer thin films over a broad range from "bulk-like" multi-micrometer to nanometer atomic dimensions. The precursor delivery system and control-architecture are designed so that continuous reactant flows for CVD and cyclic pulsating flows for ALD mode are facilitated. A custom-written LabVIEW program controls the valve sequencing to allow synthesis of different kinds of film structures under either ALD or CVD mode or both. The entire reactor setup weighs less than 40 lb and has a relatively small footprint of 8 × 9 in., making it compact and easy for transportation. The reactor is tested in the ALD mode with titanium oxide (TiO2) ALD using tetrakis(diethylamino)titanium and water vapor. The resulting growth rate of 0.04 nm/cycle and purity of the films are in good agreement with literature values. The ALD/CVD hybrid mode is demonstrated with ALD of TiO2 and CVD of tin oxide (SnOx). Transmission electron microscopy images of the resulting films confirm the formation of successive distinct TiO2-ALD and SnO(x)-CVD layers.

  6. Design and implementation of a novel portable atomic layer deposition/chemical vapor deposition hybrid reactor

    Science.gov (United States)

    Selvaraj, Sathees Kannan; Jursich, Gregory; Takoudis, Christos G.

    2013-09-01

    We report the development of a novel portable atomic layer deposition chemical vapor deposition (ALD/CVD) hybrid reactor setup. Unique feature of this reactor is the use of ALD/CVD mode in a single portable deposition system to fabricate multi-layer thin films over a broad range from "bulk-like" multi-micrometer to nanometer atomic dimensions. The precursor delivery system and control-architecture are designed so that continuous reactant flows for CVD and cyclic pulsating flows for ALD mode are facilitated. A custom-written LabVIEW program controls the valve sequencing to allow synthesis of different kinds of film structures under either ALD or CVD mode or both. The entire reactor setup weighs less than 40 lb and has a relatively small footprint of 8 × 9 in., making it compact and easy for transportation. The reactor is tested in the ALD mode with titanium oxide (TiO2) ALD using tetrakis(diethylamino)titanium and water vapor. The resulting growth rate of 0.04 nm/cycle and purity of the films are in good agreement with literature values. The ALD/CVD hybrid mode is demonstrated with ALD of TiO2 and CVD of tin oxide (SnOx). Transmission electron microscopy images of the resulting films confirm the formation of successive distinct TiO2-ALD and SnOx-CVD layers.

  7. Initiated chemical vapor deposition of thermoresponsive poly(N-vinylcaprolactam) thin films for cell sheet engineering.

    Science.gov (United States)

    Lee, Bora; Jiao, Alex; Yu, Seungjung; You, Jae Bem; Kim, Deok-Ho; Im, Sung Gap

    2013-08-01

    Poly(N-vinylcaprolactam) (PNVCL) is a thermoresponsive polymer known to be nontoxic, water soluble and biocompatible. Here, PNVCL homopolymer was successfully synthesized for the first time by use of a one-step vapor-phase process, termed initiated chemical vapor deposition (iCVD). Fourier transform infrared spectroscopy results showed that radical polymerization took place from N-vinylcaprolactam monomers without damaging the functional caprolactam ring. A sharp lower critical solution temperature transition was observed at 31°C from the iCVD poly(N-vinylcaprolactam) (PNVCL) film. The thermoresponsive PNVCL surface exhibited a hydrophilic/hydrophobic alteration with external temperature change, which enabled the thermally modulated attachment and detachment of cells. The conformal coverage of PNVCL film on various substrates with complex topography, including fabrics and nanopatterns, was successfully demonstrated, which can further be utilized to fabricate cell sheets with aligned cell morphology. The advantage of this system is that cells cultured on such thermoresponsive surfaces could be recovered as an intact cell sheet by simply lowering the temperature, eliminating the need for conventional enzymatic treatments.

  8. A Comparative Study of Three Different Chemical Vapor Deposition Techniques of Carbon Nanotube Growth on Diamond Films

    Directory of Open Access Journals (Sweden)

    Betty T. Quinton

    2013-01-01

    Full Text Available This paper compares between the methods of growing carbon nanotubes (CNTs on diamond substrates and evaluates the quality of the CNTs and the interfacial strength. One potential application for these materials is a heat sink/spreader for high-power electronic devices. The CNTs and diamond substrates have a significantly higher specific thermal conductivity than traditional heat sink/spreader materials making them good replacement candidates. Only limited research has been performed on these CNT/diamond structures and their suitability of different growth methods. This study investigates three potential chemical vapor deposition (CVD techniques for growing CNTs on diamond: thermal CVD (T-CVD, microwave plasma-enhanced CVD (MPE-CVD, and floating catalyst thermal CVD (FCT-CVD. Scanning electron microscopy (SEM and high-resolution transmission electron microscopy (TEM were used to analyze the morphology and topology of the CNTs. Raman spectroscopy was used to assess the quality of the CNTs by determining the ID/IG peak intensity ratios. Additionally, the CNT/diamond samples were sonicated for qualitative comparisons of the durability of the CNT forests. T-CVD provided the largest diameter tubes, with catalysts residing mainly at the CNT/diamond interface. The MPE-CVD process yielded non uniform defective CNTs, and FCT-CVD resulted in the smallest diameter CNTs with catalyst particles imbedded throughout the length of the nanotubes.

  9. Oxidation Protection Systems for Carbon-Carbon Composites Formed by Chemical Vapor Deposition and Plasma Assisted Chemical Vapor Deposition Techniques

    Science.gov (United States)

    1992-04-22

    PURITY SOURCE Si grey < GO0um 99.9 Alpha* SiC alpha yellow lum 99.8 JMAG beta grey lum 99.8 JMAG Zr grey +20 -60mesh 99.9 JMAG ZrC grey 3um- Alpha B brown...325mesh 92.0 Alpha A1203 white -325mesh 99.9 JMAG * Alpha Products, P.O Box 8247, Ward Hill, MA 01835-0747 ** Johnson Matthey Aesat Group. 892

  10. Mechanism of plasma ignition in electrothermal-chemical launcher

    Directory of Open Access Journals (Sweden)

    Yong Jin

    2016-04-01

    Full Text Available Plasma generator is a core component in an electrothermal-chemical (ETC launcher. Its work state directly influences the launch efficiency of a system. The interaction between plasma and propellants is a very important mechanism in ETC technology. Based on the transient radiation model and open air plasma jet experiment, the mechanism of plasma ignition process is analyzed. Results show that the surface temperature of local solid propellant grain can quickly achieve the ignition temperature under the action of early transient plasma radiation. But it needs enough time to maintain the high energy flow to make self-sustained combustion of solid propellant grains. Because of the limited space characteristics of transient radiation, the near-field propellant grains can gain enough energy by the strong transient radiation to be ignited and achieve self-sustained combustion. The far-field propellant grains mainly gain the energy by the activated particles in plasma jet to be ignited and self-sustained combustion. Experiments show that plasma jet always has a high flow velocity in the area of the cartridge. Compared with conventional ignition, the solid propellant grains can obtain more quick and uniform ignition and self-sustained combustion by this kind of ablation controlled arc (ACA plasma via energy skin effect of propellant grains, pre-heat temperature mechanism and high efficient jet diffusion.

  11. Mechanism of plasma ignition in electrothermal-chemical launcher

    Institute of Scientific and Technical Information of China (English)

    Yong JIN; Yan-jie NI; Hai-yuan LI; Bao-ming LI

    2016-01-01

    Plasma generator is a core component in an electrothermal-chemical (ETC) launcher. Its work state directly influences the launch efficiency of a system. The interaction between plasma and propellants is a very important mechanism in ETC technology. Based on the transient radiation model and open air plasma jet experiment, the mechanism of plasma ignition process is analyzed. Results show that the surface temperature of local solid propellant grain can quickly achieve the ignition temperature under the action of early transient plasma radiation. But it needs enough time to maintain the high energy flow to make self-sustained combustion of solid propellant grains. Because of the limited space characteristics of transient radiation, the near-field propellant grains can gain enough energy by the strong transient radiation to be ignited and achieve self-sustained combustion. The far-field propellant grains mainly gain the energy by the activated particles in plasma jet to be ignited and self-sustained combustion. Experiments show that plasma jet always has a high flow velocity in the area of the cartridge. Compared with conventional ignition, the solid propellant grains can obtain more quick and uniform ignition and self-sustained combustion by this kind of ablation controlled arc (ACA) plasma via energy skin effect of propellant grains, pre-heat temperature mechanism and high efficient jet diffusion.

  12. Decomposition of Chemical Chain Molecules with Atmospheric Pressure Plasma

    Science.gov (United States)

    Tansli, Murat; Tasal, Erol

    2016-10-01

    Chemical chain molecules' decomposition is an interesting subject area for the atmospheric pressure plasma applications. The effects of the atmospheric pressure argon plasma on 4-((2-methoxyphenyl)Diazenyl)Benzene-1,3,-Diol molecule at room temperature are investigated. This molecule is one of the industrial dye molecules used widely. When considering the ecological life, this molecule will be very harmful and danger. We suggest a different, easy and useful decomposing method for such molecules. Atmospheric pressure plasma jet was principally treated for this decomposing of the molecule. Fourier transform infrared spectrometry (FT-IR) was used to characterization of the molecule after the plasma application to molecule in liquid phase with ethanol and methanol solvents. The atmospheric-pressure plasma jet of argon (Ar) as non-equilibrium has been formed by ac-power generator with frequency - 24 kHz and voltage - 12 kV. Characterizations for solutions prepared with ethanol and methanol solvents of molecule have been examined after applying (duration: 3 minutes) the atmospheric pressure plasma jet. The molecule was broken at 6C-7N =8N-9C stretching peak after the plasma treatment. The new plasma photo-products for ethanol and methanol solutions were produced as 6C-7N-8N =9C (strong, varying) and 12C =17O (strong, wide) stretching peaks.

  13. Influence of gas phase equilibria on the chemical vapor deposition of graphene.

    Science.gov (United States)

    Lewis, Amanda M; Derby, Brian; Kinloch, Ian A

    2013-04-23

    We have investigated the influence of gas phase chemistry on the chemical vapor deposition of graphene in a hot wall reactor. A new extended parameter space for graphene growth was defined through literature review and experimentation at low pressures (≥0.001 mbar). The deposited films were characterized by scanning electron microscopy, Raman spectroscopy, and dark field optical microscopy, with the latter showing promise as a rapid and nondestructive characterization technique for graphene films. The equilibrium gas compositions have been calculated across this parameter space. Correlations between the graphene films grown and prevalent species in the equilibrium gas phase revealed that deposition conditions associated with a high acetylene equilibrium concentration lead to good quality graphene deposition, and conditions that stabilize large hydrocarbon molecules in the gas phase result in films with multiple defects. The transition between lobed and hexagonal graphene islands was found to be linked to the concentration of the monatomic hydrogen radical, with low concentrations associated with hexagonal islands.

  14. The growth and characterization of ZnSe nanoneedles by a simple chemical vapor deposition method

    Science.gov (United States)

    Fu, Hongzhi; Li, Huanyong; Jie, Wanqi; Yang, Lan

    2006-04-01

    ZnSe nanoneedles were successfully synthesized with the assistance of NiSe through a simple chemical vapor deposition method for the first time. The ZnSe nanoneedles, with the average bottom diameters of 400 nm and the lengths of more than 50 μm, decrease in diameters from bottom to tip. The diameter of the nanoneedle can be controlled by the size of NiSe source. The products were also characterized by XRD, HRTEM, EDS and PL spectrum. The ZnSe nanoneedles are of a single crystal in nature with high crystalline quality, and is the preferential growth direction. A strong emission band around 438.9 nm is observed at room temperature, being attributed to the excitonic emission. A combined mechanism of the redox effect and the VLS mechanism is proposed to understand the growth of ZnSe nanoneedles.

  15. Growth of GaN micro/nanolaser arrays by chemical vapor deposition

    Science.gov (United States)

    Liu, Haitao; Zhang, Hanlu; Dong, Lin; Zhang, Yingjiu; Pan, Caofeng

    2016-09-01

    Optically pumped ultraviolet lasing at room temperature based on GaN microwire arrays with Fabry-Perot cavities is demonstrated. GaN microwires have been grown perpendicularly on c-GaN/sapphire substrates through simple catalyst-free chemical vapor deposition. The GaN microwires are [0001] oriented single-crystal structures with hexagonal cross sections, each with a diameter of ˜1 μm and a length of ˜15 μm. A possible growth mechanism of the vertical GaN microwire arrays is proposed. Furthermore, we report room-temperature lasing in optically pumped GaN microwire arrays based on the Fabry-Perot cavity. Photoluminescence spectra exhibit lasing typically at 372 nm with an excitation threshold of 410 kW cm-2. The result indicates that these aligned GaN microwire arrays may offer promising prospects for ultraviolet-emitting micro/nanodevices.

  16. Simultaneous growth of diamond and nanostructured graphite thin films by hot-filament chemical vapor deposition

    Science.gov (United States)

    Ali, M.; Ürgen, M.

    2012-01-01

    Diamond and graphite films on silicon wafer were simultaneously synthesized at 850 °C without any additional catalyst. The synthesis was achieved in hot-filament chemical vapor deposition reactor by changing distance among filaments in traditional gas mixture. The inter-wire distance for diamond and graphite deposition was kept 5 and 15 mm, whereas kept constant from the substrate. The Raman spectroscopic analyses show that film deposited at 5 mm is good quality diamond and at 15 mm is nanostructured graphite and respective growths confirm by scanning auger electron microscopy. The scanning electron microscope results exhibit that black soot graphite is composed of needle-like nanostructures, whereas diamond with pyramidal featured structure. Transformation of diamond into graphite mainly attributes lacking in atomic hydrogen. The present study develops new trend in the field of carbon based coatings, where single substrate incorporate dual application can be utilized.

  17. Imaging coherent transport in chemical vapor deposition graphene wide constriction by scanning gate microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chuang, Chiashain; Matsunaga, Masahiro; Ochiai, Yuichi; Aoki, Nobuyuki, E-mail: n-aoki@faculty.chiba-u.jp, E-mail: ctliang@phys.ntu.edu.tw [Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522 (Japan); Liu, Fan-Hung [Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan (China); Woo, Tak-Pong [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China); Lin, Li-Hung [Department of Electrophysics, National Chiayi University, Chiayi 600, Taiwan (China); Oto, Kenichi [Graduate School of Science, Chiba University, Chiba 263-8522 (Japan); Liang, Chi-Te, E-mail: n-aoki@faculty.chiba-u.jp, E-mail: ctliang@phys.ntu.edu.tw [Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan (China); Department of Physics, National Taiwan University, Taipei 106, Taiwan (China)

    2016-03-21

    We use a scanning gate microscopy to perturb coherent transport in chemical vapor deposition (CVD) graphene wide constriction. Particularly, we observe conductance oscillations in the wide constriction region (W ∼ 800 nm) characterized by spatial conductance variations, which imply formation of the nanometer-scale ring structure due to the merged domains and intrinsic grain boundaries. Moreover, additional hot charges from high current can suppress the coherent transport, suggesting that the hot carriers with a wide spreading kinetic energy could easily tunnel merged domains and intrinsic grain boundaries in CVD-grown graphene due to the heating effect, a great advantage for applications in graphene-based interference-type nano-electronics.

  18. Nanoscale arrays of antimony telluride single crystals by selective chemical vapor deposition

    Science.gov (United States)

    Huang, Ruomeng; Benjamin, Sophie L.; Gurnani, Chitra; Wang, Yudong; Hector, Andrew L.; Levason, William; Reid, Gillian; De Groot, C. H. (Kees)

    2016-01-01

    Arrays of individual single nanocrystals of Sb2Te3 have been formed using selective chemical vapor deposition (CVD) from a single source precursor. Crystals are self-assembled reproducibly in confined spaces of 100 nm diameter with pitch down to 500 nm. The distribution of crystallite sizes across the arrays is very narrow (standard deviation of 15%) and is affected by both the hole diameter and the array pitch. The preferred growth of the crystals in the orientation along the diagonal of the square holes strongly indicates that the diffusion of adatoms results in a near thermodynamic equilibrium growth mechanism of the nuclei. A clear relationship between electrical resistivity and selectivity is established across a range of metal selenides and tellurides, showing that conductive materials result in more selective growth and suggesting that electron donation is of critical importance for selective deposition. PMID:27283116

  19. Influences of H+ Implantation on the Boron-Doped Synthesized by Chemical Vapor Deposition Diamond Films

    Institute of Scientific and Technical Information of China (English)

    WANG Shuang-Bao

    2000-01-01

    Diamond films (DF) were preliminarily B doped in situ during chemical vapor deposition. Subsequently, the films were implanted with 120keV H+ to dose of 5 × 1014 ~ 5 × 1016cm-2. After the implantation, the B doped DF become insulating and Raman measurements indicate that the implantation has amorphous carbon and graphite etched. It is known that the formation of H-B pairs plays an important pole in property changes. However, for larger dose cases, the electrical resistance of DF is influenced by radiation damage and/or non-diamond phases. In addition to them, annealing makes the specimens conducting again. This phenomenon maybe has potential for application in designing DF device.

  20. Microstructure of carbon fiber preform and distribution of pyrolytic carbon by chemical vapor infiltration

    Institute of Scientific and Technical Information of China (English)

    陈建勋; 黄伯云

    2004-01-01

    The carbon/carbon composites were made by chemical vapor infiltration(CVI) with needled felt preform. The distribution of the pyrolytic carbon in the carbon fiber preform was studied by polarized light microscope(PLM) and scanning electronic microscope(SEM). The experimental results indicate that the amount of pyrolytic carbon deposited on the surface of chopped carbon fiber is more than that on the surface of long carbon fiber. The reason is the different porosity between the layer of chopped carbon fiber and long carbon fiber. The carbon precursor gas which passes through the part of chopped carbon fibers decomposes and deposits on the surface of chopped carbon fiber. The pyrolytic carbon on the surface of long carbon fibers is produced by the carbon precursor gas diffusing from the chopped fiber and the Z-d fiber. Uniform pore distribution and porosity in preform are necessary for producing C/C composites with high properties.

  1. Tungsten-Carbon X-ray Multilayered Mirror Prepared by Photo-Chemical Vapor Deposition

    Science.gov (United States)

    Suzuki, Yoshihiko

    1989-05-01

    A tungsten-carbon(W/C) X-ray multilayered mirror was prepared by photoinduced chemical vapor deposition (photo-CVD) using a low-pressure mercury lamp and an argon-fluoride (ArF) excimer laser. The 40% reflectivity of this mirror was measured using a small-angle X-ray diffractometer with Cu-Kα radiation. This reflectivity is lower than the theoretical reflectivity of 80%. From observations of the transmission electron micrograph from this multilayered mirror, it seems that the reduction of the reflectivity was caused by the indistinct interfaces of the diffused films, and by the roughness of the films introduced by partial crystallization of the tungsten films.

  2. Multi-wall carbon nanotubes supported on carbon fiber paper synthesized by simple chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ya-hao [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Zhengzhou Research Institute of Chalco, Zhengzhou 450041 (China); Gao, Hong-quan [Zhengzhou Research Institute of Chalco, Zhengzhou 450041 (China); Yang, Jian-hong, E-mail: zyy_yjh@rilm.com.cn [Zhengzhou Research Institute of Chalco, Zhengzhou 450041 (China); Gao, Wen-liang; Xiang, Jia [College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044 (China); Li, Qing-yu, E-mail: 13975808173@126.com [School of Chemistry and Chemical Engineering, Guangxi Normal University, Guilin, Guangxi 541004 (China)

    2014-09-15

    Highlights: • We deposited multi-wall carbon nanotubes on carbon fiber paper with a simple CVD. • We investigated the inherent mechanism of Ni particle's self-dispersion. • The MWCNTs/CFP composite possesses wonderful electrical conductivity. - Abstract: Aiming at developing a novel carbon/carbon composite as an electrode in the electrochemical capacitor applications, multi-wall carbon nanotubes (MWCNTs)/carbon fiber paper (CFP) composite has been synthesized using a simple chemical vapor deposition, in which different metal catalysts such as Fe, Ni and Cu are used. However, randomly oriented MWCNTs were only obtained on Ni particles. The mechanism for this unique phenomenon is investigated in this article. The physical and electrochemical properties of as-prepared MWCNTs/CFP composite are characterized and the results show that the as-prepared composite is a promising substrate for electrochemical capacitor applications.

  3. Growth inhibition to enhance conformal coverage in thin film chemical vapor deposition.

    Science.gov (United States)

    Kumar, Navneet; Yanguas-Gil, Angel; Daly, Scott R; Girolami, Gregory S; Abelson, John R

    2008-12-31

    We introduce the use of a growth inhibitor to enhance thin film conformality in low temperature chemical vapor deposition. Films of TiB(2) grown from the single source precursor Ti(BH(4))(3)(dme) are much more highly conformal when grown in the presence of one of the film growth byproducts, 1,2-dimethoxyethane (dme). This effect can be explained in terms of two alternative inhibitory mechanisms: one involving blocking of surface reactive sites, which is equivalent to reducing the rate of the forward reaction leading to film growth, the other analogous to Le Chatelier's principle, in which the addition of a reaction product increases the rate of the back reaction. The reduction in growth rate corresponds to a reduction in the sticking probability of the precursor, which enhances conformality by enabling the precursor to diffuse deeper into a recessed feature before it reacts.

  4. III-nitride quantum cascade detector grown by metal organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yu, E-mail: yusong@princeton.edu; Huang, Tzu-Yung; Badami, Pranav; Gmachl, Claire [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08540 (United States); Bhat, Rajaram; Zah, Chung-En [Corning Incorporated, Corning, New York 14831 (United States)

    2014-11-03

    Quantum cascade (QC) detectors in the GaN/Al{sub x}Ga{sub 1−x}N material system grown by metal organic chemical vapor deposition are designed, fabricated, and characterized. Only two material compositions, i.e., GaN as wells and Al{sub 0.5}Ga{sub 0.5}N as barriers are used in the active layers. The QC detectors operates around 4 μm, with a peak responsivity of up to ∼100 μA/W and a detectivity of up to 10{sup 8} Jones at the background limited infrared performance temperature around 140 K.

  5. Chemical vapor infiltration of TiB{sub 2} fibrous composites

    Energy Technology Data Exchange (ETDEWEB)

    Besmann, T.M. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    This program is designed to develop a Hall-Heroult aluminum smelting cathode with substantially improved properties. The carbon cathodes in current use require significant anode-to-cathode spacing in order to prevent shorting, causing significant electrical inefficiencies. This is due to the non-wettability of carbon by aluminum which causes instability in the cathodic aluminum pad. It is suggested that a fiber reinforced-TiB{sub 2} matrix composite would have the requisite wettability, strength, strain-to-failure, cost, and lifetime to solve this problem. The approach selected to fabricate such a cathode material is chemical vapor infiltration (CVI). This process produces high purity matrix TiB{sub 2} without damaging the relatively fragile fibers. The program is designed to evaluate potential fiber reinforcements, fabricate test specimens, and scale the process to provide demonstration components.

  6. Chemical vapor deposition polymerization the growth and properties of parylene thin films

    CERN Document Server

    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.

  7. Nanocrystalline Diamond Films Deposited by Electron Assisted Hot Filament Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nanocrystalline diamond films were deposited on polished Si wafer surface with electron assisted hot filament chemical vapor deposition at 1 kPa gas pressure, the deposited films were characterized and observed by Raman spectrum, X-ray diffraction, atomic force microscopy and semiconductor characterization system. The results show that when 8 A bias current is applied for 5 h, the surface roughness decreases to 28.5 nm. After 6 and 8 A bias current are applied for 1 h, and the nanocrystalline films deposition continue for 4 h with 0 A bias current at 1 kPa gas pressure. The nanocrystalline diamond films with 0.5×109 and 1×1010 Ω·cm resistivity respectively are obtained. It is demonstrated that electron bombardment plays an important role of nucleation to deposit diamond films with smooth surface and high resistivity.

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

    Institute of Scientific and Technical Information of China (English)

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

    2012-01-01

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

  9. Layer-dependent supercapacitance of graphene films grown by chemical vapor deposition on nickel foam

    KAUST Repository

    Chen, Wei

    2013-03-01

    High-quality, large-area graphene films with few layers are synthesized on commercial nickel foams under optimal chemical vapor deposition conditions. The number of graphene layers is adjusted by varying the rate of the cooling process. It is found that the capacitive properties of graphene films are related to the number of graphene layers. Owing to the close attachment of graphene films on the nickel substrate and the low charge-transfer resistance, the specific capacitance of thinner graphene films is almost twice that of the thicker ones and remains stable up to 1000 cycles. These results illustrate the potential for developing high-performance graphene-based electrical energy storage devices. © 2012 Elsevier B.V. All rights reserved.

  10. Study of surface morphology and alignment of MWCNTs grown by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shukrullah, S., E-mail: zshukrullah@gmail.com, E-mail: noranimuti-mohamed@petronas.com.my, E-mail: maizats@petronas.com.my; Mohamed, N. M., E-mail: zshukrullah@gmail.com, E-mail: noranimuti-mohamed@petronas.com.my, E-mail: maizats@petronas.com.my; Shaharun, M. S., E-mail: zshukrullah@gmail.com, E-mail: noranimuti-mohamed@petronas.com.my, E-mail: maizats@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak (Malaysia); Yasar, M., E-mail: Muhammad.yasar@ieee.org [Department of Electrical and Electronic Engineering, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak (Malaysia)

    2014-10-24

    In this research work, Multiwalled Carbon Nanotubes (MWCNTs) have been synthesized successfully by using floating catalytic chemical vapor deposition (FCCVD) method. Different ferrocene amounts (0.1, 0.125 and 0.15 g) were used as catalyst and ethylene was used as a carbon precursor at reaction temperature of 800°C. Characterization of the grown MWCNTs was carried out by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained data showed that the catalyst weight affects the nanotubes diameter, alignment, crystallinity and growth significantly, whereas negligible influence was noticed on CNTs forest length. The dense, uniform and meadow like patterns of grown CNTs were observed for 0.15 g ferrocene. The average diameter of the grown CNTs was found in the range of 32 to 75 nm. Close inspection of the TEM images also confirmed the defects in some of the grown CNTs, where few black spots were evident in CNTs structure.

  11. Characterization of nanocarbon deposited on insulator substrate by alcohol chemical vapor deposition

    Science.gov (United States)

    Tsujimoto, Marina; Murata, Hidenobu; Tachibana, Masaru

    2016-10-01

    Single-layer-graphene-like nanocarbon materials were directly deposited on c-plane sapphire substrates by thermal chemical vapor deposition with ethanol as a carbon source. Scanning electron microscopy (SEM) images show that the deposited materials have sheetlike grains of around 100 nm diameter. Most of them have “hills” with 32 nm diameter on the grains. According to atomic force microscopy (AFM) observation, the height of the sheetlike grains is below 1 nm, which is comparable to that of single-layer graphene, while the hills have a height of several nm. Raman spectra show that the material is similar to graphitic nanocarbon, which has a strong D band. This result implies that there are a number of defects in the nanocarbon materials.

  12. FABRICATION OF DIAMOND TUBES IN BIAS-ENHANCED HOT-FILAMENT CHEMICAL VAPOR DEPOSITION SYSTEM

    Institute of Scientific and Technical Information of China (English)

    CHEN Ming; MA Yuping; XIANG Daohui; SUN Fanghong

    2007-01-01

    Deposition of diamond thin films on tungsten wire Substrate with the gas mixture of acetone and hydrogen by using bias-enhanced hol filament chemical vapor deposition (CVD) with the tantalum wires being optimized arranged is investigated. The self-supported diamond tubes are obtained by etching away the tungsten Substrates. The quality of the diamond film before and after the removal of Substrates is observed by scanning electron microscope (SEM) and Raman spectrum. The results show that the cylindrical diamond tubes with good quality and uniform thickness are obtained on tungsten wires by using bias enhanced hot filament CVD. The compressive stress in diamond film formed during the deposition is released after the Substrate etches away by mixture of H202 and NH4OH. There is no residual stress in diamond tube after Substrate removal.

  13. Catalytic Chemical Vapor Deposition Synthesis of Carbon Aerogels of High-Surface Area and Porosity

    Directory of Open Access Journals (Sweden)

    Armando Peña

    2012-01-01

    Full Text Available In this work carbon aerogels were synthesized by catalytic chemical vapor deposition method (CCVD. Ferrocene were employed as a source both of catalytic material (Fe and of carbon. Gaseous hydrogen and argon were used as reductant and carrier gas, respectively. The products of reaction were collected over alumina. The morphology and textural properties of the soot produced in the reaction chamber were investigated using Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, X-ray photoelectron spectroscopy, and N2 physisorption (BET and BHJ methods. After the evaluation of the porous structure of the synthesized products, 780 ± 20 m2/g of SBET and 0.55 ± 0.02 cm3/g of VBJH were found. The presence of iron carbide and the partial oxidation of carbon nanostructures were revealed by XPS.

  14. Chemical-Vapor-Deposited Graphene as Charge Storage Layer in Flash Memory Device

    Directory of Open Access Journals (Sweden)

    W. J. Liu

    2016-01-01

    Full Text Available We demonstrated a flash memory device with chemical-vapor-deposited graphene as a charge trapping layer. It was found that the average RMS roughness of block oxide on graphene storage layer can be significantly reduced from 5.9 nm to 0.5 nm by inserting a seed metal layer, which was verified by AFM measurements. The memory window is 5.6 V for a dual sweep of ±12 V at room temperature. Moreover, a reduced hysteresis at the low temperature was observed, indicative of water molecules or −OH groups between graphene and dielectric playing an important role in memory windows.

  15. Preparation of diamond/Cu microchannel heat sink by chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    刘学璋; 罗浩; 苏栩; 余志明

    2015-01-01

    A Ti interlayer with thickness about 300 nm was sputtered on Cu microchannels, followed by an ultrasonic seeding with nanodiamond powders. Adherent diamond film with crystalline grains close to thermal equilibrium shape was tightly deposited by hot-filament chemical vapor deposition (HF-CVD). The nucleation and growth of diamond were investigated with micro-Raman spectroscope and field emission scanning electron microscope (FE-SEM) with energy dispersive X-ray detector (EDX). Results show that the nucleation density is found to be up to 1010 cm−2. The enhancement of the nucleation kinetics can be attributed to the nanometer rough Ti interlayer surface. An improved absorption of nanodiamond particles is found, which act as starting points for the diamond nucleation during HF-CVD process. Furthermore, finite element simulation was conducted to understand the thermal management properties of prepared diamond/Cu microchannel heat sink.

  16. Structural and optical properties of tellurium films obtained by chemical vapor deposition(CVD)

    Institute of Scientific and Technical Information of China (English)

    MA Yu-tian; GONG Zhu-Qing; XU Wei-Hong; HUANG Jian

    2006-01-01

    Tellurium thin films were prepared by the chemical vapor deposition method. The structure, surface morphology and optical properties of the Te thin films were analyzed by powder X-ray diffraction, scanning electron microscopy, FTIR transmission,UV/VIS/NIR transmission and reflectance. The results show that the films structural and optical properties are influenced by many factors such as film thickness, crystallite size and substrate temperature. The films as thick as 111-133 nm have high IR transmission across the full 8-13 μm band and highly blocking in the solar spectral region elsewhere, which indicates that Te films thickness in this region can be used as good solar radiation shields in radiative cooling devices.

  17. AB-stacked multilayer graphene synthesized via chemical vapor deposition: a characterization by hot carrier transport.

    Science.gov (United States)

    Diaz-Pinto, Carlos; De, Debtanu; Hadjiev, Viktor G; Peng, Haibing

    2012-02-28

    We report the synthesis of AB-stacked multilayer graphene via ambient pressure chemical vapor deposition on Cu foils and demonstrate a method to construct suspended multilayer graphene devices. In four-terminal geometry, such devices were characterized by hot carrier transport at temperatures down to 240 mK and in magnetic fields up to 14 T. The differential conductance (dI/dV) shows a characteristic dip at longitudinal voltage bias V = 0 at low temperatures, indicating the presence of hot electron effect due to a weak electron-phonon coupling. Under magnetic fields, the magnitude of the dI/dV dip diminishes through the enhanced intra-Landau level cyclotron phonon scattering. Our results provide new perspectives in obtaining and understanding AB-stacked multilayer graphene, important for future graphene-based applications.

  18. Preparation of nanosized sililcon carbide powders by chemical vapor deposition at low temperatures

    Institute of Scientific and Technical Information of China (English)

    LI Bin; ZHANG Changrui; HU Haifeng; QI Gongjin

    2007-01-01

    Liquid carbosilane was synthesized and analyzed by infrared(IR) and H-NMR(nuclear magnetic resonance)spectroscopy.Silicon carbide(SiC)powders were prepared by chemical vapor deposition (CVD)at 850℃ and 900℃ from liquid carbosilanes.The product powders were characterized by IR spectroscopy,X-ray diffractometry(XRD)and scanning electron microscopy (SEM).Results show that liquid carbosilane synthesized was the mixture of several oligomers that had a Si-C backbone.The powders prepared at 850℃ contain some organic segments,and those prepared at 900℃ are pure nanosized SiC powders,which are partly crystallized,the size of which is about 50-70 nm.

  19. Fabrication of Rare Earth-Doped Transparent Glass Ceramic Optical Fibers by Modified Chemical Vapor Deposition

    CERN Document Server

    Blanc, Wilfried; Nguyen, Luan; Bhaktha, S N B; Sebbah, Patrick; Pal, Bishnu P; Dussardier, Bernard

    2011-01-01

    Rare earth (RE) doped silica-based optical fibers with transparent glass ceramic (TGC) core was fabricated through the well-known modified chemical vapor deposition (MCVD) process without going through the commonly used stage of post-ceramming. The main characteristics of the RE-doped oxyde nanoparticles namely, their density and mean diameter in the fibers are dictated by the concentration of alkaline earth element used as phase separating agent. Magnesium and erbium co-doped fibers were fabricated. Optical transmission in term of loss due to scattering as well as some spectroscopic characteristics of the erbium ions was studied. For low Mg content, nano-scale particles could be grown with and relatively low scattering losses were obtained, whereas large Mg-content causes the growth of larger particles resulting in much higher loss. However in the latter case, certain interesting alteration of the spectroscopic properties of the erbium ions were observed. These initial studies should be useful in incorporati...

  20. Modification of tubular ceramic membranes with carbon nanotubes using catalytic chemical vapor deposition.

    Science.gov (United States)

    Tran, Duc Trung; Thieffry, Guillemette; Jacob, Matthieu; Batiot-Dupeyrat, Catherine; Teychene, Benoit

    2015-01-01

    In this study, carbon nanotubes (CNTs) were successfully grown on tubular ceramic membranes using the catalytic chemical vapor deposition (CCVD) method. CNTs were synthesized at 650°C for 3-6 h under a 120 mL min(-1) flow of C2H6 on ceramic membranes impregnated with iron salt. The synthesis procedure was beforehand optimized in terms of catalyst amount, impregnation duration and reaction temperature, using small pieces of tubular ceramic membranes. The yield, size and structure of the CNTs produced were characterized using thermogravimetric analysis and microscopic imaging techniques. Afterwards, preliminary filtration tests with alginate and phenol were performed on two modified tubular membranes. The results indicate that the addition of CNTs on the membrane material increased the permeability of ceramic membrane and its ability to reject alginate and adsorb phenol, yet decreased its fouling resistance.

  1. Modeling of gas phase diffusion transport during chemical vapor infiltration process

    Institute of Scientific and Technical Information of China (English)

    肖鹏; 李娣; 徐永东; 黄伯云

    2002-01-01

    In order to improve the uniformity of both the concentration of gaseous reagent and the deposition of matrix within micro-pores during the chemical vapor infiltration (CVI) process, a calculation modeling of gas phase diffusion transport within micro-pores was established. Taken CH3SiCl3 as precursor for depositing SiC as example, the diffusion coefficient, decomposing reaction rate, concentration within the reactor, and concentration distributing profiling of MTS within micro-pore were accounted, respectively. The results indicate that, increasing the ratio of diffusion coefficient to decomposition rate constant of precursor MTS is propitious to decrease the densification gradient of parts, and decreasing the aspect ratio (L/D) of micro-pore is favorable to make the concentration uniform within pores.

  2. Synthesis of zirconia (ZrO2) nanowires via chemical vapor deposition

    Science.gov (United States)

    Baek, M. K.; Park, S. J.; Choi, D. J.

    2017-02-01

    Monoclinic zirconia nanowires were synthesized by chemical vapor deposition using ZrCl4 powder as a starting material at 1200 °C and 760 Torr. Graphite was employed as a substrate, and an Au thin film was pre-deposited on the graphite as a catalyst. The zirconia nanostructure morphology was observed through scanning electron microscopy and transmission electron microscopy. Based on X-ray diffraction, selected area electron diffraction, and Raman spectroscopy data, the resulting crystal structure was found to be single crystalline monoclinic zirconia. The homogeneous distributions of Zr, O and Au were studied by scanning transmission electron microscopy with energy dispersive X-ray spectroscopy mapping, and there was no metal droplet at the nanowire tips despite the use of an Au metal catalyst. This result is apart from that of conventional metal catalyzed nanowires.

  3. Surface Structure of GaN(0001) in the Chemical Vapor Deposition Environment

    Energy Technology Data Exchange (ETDEWEB)

    Munkholm, A. [Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Stephenson, G.B.; Eastman, J.A.; Thompson, C.; Auciello, O. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Thompson, C. [Department of Physics, Northern Illinois University, DeKalb, Illinois 60115 (United States); Fini, P.; Speck, J.S.; DenBaars, S.P. [Materials Department, University of California, Santa Barbara, California 93106 (United States); Fuoss, P.H. [ATT Laboratories---Research, Florham Park, New Jersey 07932 (United States)

    1999-07-01

    We report the first observation of the atomic-scale structure of the GaN(0001) surface in the metal-organic chemical vapor deposition environment. Measurements were performed using {ital in situ} grazing-incidence x-ray scattering. We determined the surface equilibrium phase diagram as a function of temperature and ammonia partial pressure, which contains two phases with 1{times}1 and ({radical} (3) {times}2{radical} (3) )R30{degree} symmetries. The ({radical} (3) {times}2{radical} (3) )R30{degree} phase is found to have a novel {open_quotes}missing row{close_quotes} structure with 1/3 of the surface Ga atoms absent. {copyright} {ital 1999} {ital The American Physical Society }

  4. Growth of carbon nanotubes by Fe-catalyzed chemical vapor processes on silicon-based substrates

    Science.gov (United States)

    Angelucci, Renato; Rizzoli, Rita; Vinciguerra, Vincenzo; Fortuna Bevilacqua, Maria; Guerri, Sergio; Corticelli, Franco; Passini, Mara

    2007-03-01

    In this paper, a site-selective catalytic chemical vapor deposition synthesis of carbon nanotubes on silicon-based substrates has been developed in order to get horizontally oriented nanotubes for field effect transistors and other electronic devices. Properly micro-fabricated silicon oxide and polysilicon structures have been used as substrates. Iron nanoparticles have been obtained both from a thin Fe film evaporated by e-gun and from iron nitrate solutions accurately dispersed on the substrates. Single-walled nanotubes with diameters as small as 1 nm, bridging polysilicon and silicon dioxide “pillars”, have been grown. The morphology and structure of CNTs have been characterized by SEM, AFM and Raman spectroscopy.

  5. Ultrahigh-mobility graphene devices from chemical vapor deposition on reusable copper

    Science.gov (United States)

    Banszerus, Luca; Schmitz, Michael; Engels, Stephan; Dauber, Jan; Oellers, Martin; Haupt, Federica; Watanabe, Kenji; Taniguchi, Takashi; Beschoten, Bernd; Stampfer, Christoph

    2015-01-01

    Graphene research has prospered impressively in the past few years, and promising applications such as high-frequency transistors, magnetic field sensors, and flexible optoelectronics are just waiting for a scalable and cost-efficient fabrication technology to produce high-mobility graphene. Although significant progress has been made in chemical vapor deposition (CVD) and epitaxial growth of graphene, the carrier mobility obtained with these techniques is still significantly lower than what is achieved using exfoliated graphene. We show that the quality of CVD-grown graphene depends critically on the used transfer process, and we report on an advanced transfer technique that allows both reusing the copper substrate of the CVD growth and making devices with mobilities as high as 350,000 cm2 V–1 s–1, thus rivaling exfoliated graphene. PMID:26601221

  6. Edge oxidation effect of chemical-vapor-deposition-grown graphene nanoconstriction.

    Science.gov (United States)

    Iqbal, Muhammad Waqas; Iqbal, Muhammad Zahir; Jin, Xiaozhan; Hwang, Chanyong; Eom, Jonghwa

    2014-03-26

    The edge oxidation effects of chemical-vapor-deposition-grown graphene devices with nanoconstrictions of different sizes are presented. The effects of edge oxidation on the doping level of a nanoconstriction graphene device were identified by Raman spectroscopy and using the back-gate-voltage-dependent resistance. Strong p-type doping was observed as the size of nanoconstriction decreased. The Dirac point of the graphene device shifted toward positive voltage, and the positions of the G and 2D peaks in Raman spectroscopy shifted toward a higher wave number, indicating the p-type doping effect of the graphene device. p-type doping was lifted by deep-ultraviolet light illumination under a nitrogen atmosphere at room temperature. p-type doping was restored by deep-ultraviolet light illumination under an oxygen atmosphere at room temperature. Edge oxidation in the narrow structures explains the origin of the p-type doping effect widely observed in graphene nanodevices.

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

    Science.gov (United States)

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

    2016-06-01

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

  8. Non-classical crystallization of silicon thin films during hot wire chemical vapor deposition

    Science.gov (United States)

    Jung, Jae-Soo; Lee, Sang-Hoon; Kim, Da-Seul; Kim, Kun-Su; Park, Soon-Won; Hwang, Nong-Moon

    2017-01-01

    The deposition behavior of silicon films by hot wire chemical vapor deposition (HWCVD) was approached by non-classical crystallization, where the building block of deposition is a nanoparticle generated in the gas phase of the reactor. The puzzling phenomenon of the formation of an amorphous incubation layer on glass could be explained by the liquid-like property of small charged nanoparticles (CNPs), which are generated in the initial stage of the HWCVD process. Using the liquid-like property of small CNPs, homo-epitaxial growth as thick as 150 nm could be successfully grown on a silicon wafer at 600 °C under the processing condition where CNPs as small as possible could be supplied steadily by a cyclic process which periodically resets the process. The size of CNPs turned out to be an important parameter in the microstructure evolution of thin films.

  9. Structure and magnetic properties of iron nanoparticles synthesized by chemical vapor condensation

    Science.gov (United States)

    Lee, D. H.; Jang, T. S.; Lee, D. W.; Kim, B. K.

    2004-06-01

    Iron nanoparticles were synthesized by chemical vapor condensation (CVC) without the aid of LN2 chiller. The powder synthesized at 400 °C was a mixture of amorphous and crystalline -Fe. Fully crystallized iron particles were then obtained at and above 600 °C. When the reactor temperature was 1000 °C, however, nonmagnetic -Fe was stabilized together with -Fe. The synthesized particles, mostly possessing the core-shell type structure, were all nearly spherical, but the average particle size rapidly increased as the temperature increased. The surface layer that enclosed the iron core and became thicker in smaller particles was Fe3O4 or Fe3O4-related amorphous. Except for the one synthesized at 1000 °C, the iron nanoparticles were not fully saturated. The iron nanoparticles (20 nm) synthesized at 600 °C exhibited iHc 1.0 kOe and Ms 170 emu/g.

  10. Elastic and anelastic properties of chemical vapor deposited epitaxial 3C-SiC

    Science.gov (United States)

    Su, C. M.; Wuttig, Manfred; Fekade, A.; Spencer, M.

    1995-06-01

    Chemical vapor deposited 3C-SiC films were micromachined into free standing cantilevers and their anelastic and elastic properties were determined by a vibrating reed technique. Despite a high density of defects, epitaxial 3C-SiC exhibits extremely high mechanical Q which is essential for resonator sensors and actuators. An anelastic relaxation peak was found with an associated activation energy of 0.94 eV. Doping caused splitting of this peak. The mechanism of the mechanical relaxation peak is discussed in relation to defect movement under stress. Young's modulus of epitaxial undoped 3C-SiC was found to be 694 GPa, p-doping reduced it to 474 Gpa.

  11. Spiral growth of few-layer MoS2 by chemical vapor deposition

    Science.gov (United States)

    Dong, X.; Yan, C.; Tomer, D.; Li, C. H.; Li, L.

    2016-08-01

    Growth spirals exhibit appealing properties due to a preferred layer stacking and lack of inversion symmetry. Here, we report spiral growth of MoS2 during chemical vapor deposition on SiO2/Si and epitaxial graphene/SiC substrates, and their physical and electronic properties. We determine the layer-dependence of the MoS2 bandgap, ranging from 2.4 eV for the monolayer to a constant of 1.3 eV beyond the fifth layer. We further observe that spirals predominantly initiate at the step edges of the SiC substrate, based on which we propose a growth mechanism driven by screw dislocation created by the coalescence of two growth fronts at steps.

  12. Carbon impurities on graphene synthesized by chemical vapor deposition on platinum

    Energy Technology Data Exchange (ETDEWEB)

    Ping, Jinglei; Fuhrer, Michael S., E-mail: michael.fuhrer@monash.edu [Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742-4111, USA and School of Physics, Monash University, 3800 Victoria (Australia)

    2014-07-28

    We report nanocrystalline carbon impurities coexisting with graphene synthesized via chemical vapor deposition on platinum. For certain growth conditions, we observe micron-size island-like impurity layers which can be mistaken for second graphene layers in optical microscopy or scanning electron microscopy. The island orientation depends on the crystalline orientation of the Pt, as shown by electron backscatter diffraction, indicating growth of carbon at the platinum surface below graphene. Dark-field transmission electron microscopy indicates that in addition to uniform single-crystal graphene, our sample is decorated with nanocrystalline carbon impurities with a spatially inhomogeneous distribution. The impurity concentration can be reduced significantly by lowering the growth temperature. Raman spectra show a large D peak, however, electrical characterization shows high mobility (∼8000 cm{sup 2}/Vs), indicating a limitation for Raman spectroscopy in characterizing the electronic quality of graphene.

  13. Wet Etching of Heat Treated Atomic Layer Chemical Vapor Deposited Zirconium Oxide in HF Based Solutions

    Science.gov (United States)

    Balasubramanian, Sriram; Raghavan, Srini

    2008-06-01

    Alternative materials are being considered to replace silicon dioxide as gate dielectric material. Of these, the oxides of hafnium and zirconium show the most promise. However, integrating these new high-k materials into the existing complementary metal-oxide-semiconductor (CMOS) process remains a challenge. One particular area of concern is the wet etching of heat treated high-k dielectrics. In this paper, work done on the wet etching of heat treated atomic layer chemical vapor deposited (ALCVD) zirconium oxide in HF based solutions is presented. It was found that heat treated material, while refractory to wet etching at room temperature, is more amenable to etching at higher temperatures when methane sulfonic acid is added to dilute HF solutions. Selectivity over SiO2 is still a concern.

  14. Controlled Synthesis of Atomically Layered Hexagonal Boron Nitride via Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Juanjuan Liu

    2016-11-01

    Full Text Available Hexagonal boron nitrite (h-BN is an attractive material for many applications including electronics as a complement to graphene, anti-oxidation coatings, light emitters, etc. However, the synthesis of high-quality h-BN is still a great challenge. In this work, via controlled chemical vapor deposition, we demonstrate the synthesis of h-BN films with a controlled thickness down to atomic layers. The quality of as-grown h-BN is confirmed by complementary characterizations including high-resolution transition electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray photo-electron spectroscopy. This work will pave the way for production of large-scale and high-quality h-BN and its applications as well.

  15. Fabrication of copper (Ⅰ) nitride nanorods within SBA-15 by metal organic chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Copper (Ⅰ) nitride nanorods grown in channels of mesoporous silica SBA-15 by chemical vapor deposition method has been synthesized. The morphology and microstructure of the resulting product were characterized by XRD patters, TEM images, EDS analysis and Raman spectra. The XRD and TEM revealed that the Cu3N phase was confined in channels of SBA-15 forming continuous nanowires with 6 nm around and hundreds of nanometers in length. Raman spectra of the final product and pure Cu3N showed peaks shift due to the quantum confinement effect of the nanowires. This preparation methodology only requires a mild working condition and is capable of template synthesis of other binary nitride nanostructures with controlled morphology inside the channels of mesoporous materials.

  16. Fabrication of copper (Ⅰ) nitride nanorods within SBA-15 by metal organic chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ying; Frank Leung-Yuk Lam; YAN ZiFeng; HU XiJun

    2009-01-01

    Copper (Ⅰ) nitride nanorods grown in channels of mesoporous silica SBA-15 by chemical vapor depo- sition method has been synthesized. The morphology and microstructure of the resulting product were characterized by XRD patters, TEM images, EDS analysis and Raman spectra. The XRD and TEM re-vealed that the Cu3N phase was confined in channels of SBA-15 forming continuous nanowires with 6 nm around and hundreds of nanometers in length. Raman spectra of the final product and pure Cu3N showed peaks shift due to the quantum confinement effect of the nanowires. This preparation meth-odology only requires a mild working condition and is capable of template synthesis of other binary nitride nanostructures with controlled morphology inside the channels of mesoporous materials.

  17. Surface modification of titanium membrane by chemical vapor deposition and its electrochemical self-cleaning

    Science.gov (United States)

    Li, X. W.; Li, J. X.; Gao, C. Y.; Chang, M.

    2011-10-01

    Membrane separation is applied widely in many fields, while concentration polarization and membrane fouling, limiting its promotion and application greatly, are the bottlenecks in membrane application. Among which, membrane fouling is irreversible, membrane must be periodically cleaned or even replaced to restore permeability. Membrane cleaning has become one of the key issues in membrane separation areas. Considering incomparable electrochemical advantages of boron-doped diamond (BDD) film electrode over conventional electrode, a new composite membrane Ti/BDD, made by depositing CVD (chemical vapor deposition) boron-doped diamond film on titanium(Ti) membrane to modify porous titanium surface, that can be cleaned electrochemically is proposed. Feasibility of its preparation and application is discussed in this paper. Results shows that based on the unique electrochemical properties of diamond, cleaning level of this composite Ti/BDD membrane is significantly increased, making membrane life and efficiency improved prominently.

  18. Faraday effect of polycrystalline bismuth iron garnet thin film prepared by mist chemical vapor deposition method

    Science.gov (United States)

    Yao, Situ; Kamakura, Ryosuke; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa

    2017-01-01

    We have synthesized polycrystalline thin film composed of a single phase of metastable bismuth iron garnet, Bi3Fe5O12, on a fused silica substrate, one of the most widely utilized substrates in the solid-state electronics, by using mist chemical vapor deposition (mist CVD) method. The phase purity and stoichiometry are confirmed by X-ray diffraction and Rutherford backscattering spectrometry. The resultant thin film shows a small surface roughness of 3.251 nm. The saturation magnetization at room temperature is 1200 G, and the Faraday rotation angle at 633 nm reaches -5.2 deg/μm. Both the magnetization and the Faraday rotation angles are somewhat higher than those of polycrystalline BIG thin films prepared by other methods.

  19. Preparation of γ-Al2O3 films by laser chemical vapor deposition

    Science.gov (United States)

    Gao, Ming; Ito, Akihiko; Goto, Takashi

    2015-06-01

    γ- and α-Al2O3 films were prepared by chemical vapor deposition using CO2, Nd:YAG, and InGaAs lasers to investigate the effects of varying the laser wavelength and deposition conditions on the phase composition and microstructure. The CO2 laser was found to mostly produce α-Al2O3 films, whereas the Nd:YAG and InGaAs lasers produced γ-Al2O3 films when used at a high total pressure. γ-Al2O3 films had a cauliflower-like structure, while the α-Al2O3 films had a dense and columnar structure. Of the three lasers, it was the Nd:YAG laser that interacted most with intermediate gas species. This promoted γ-Al2O3 nucleation in the gas phase at high total pressure, which explains the cauliflower-like structure of nanoparticles observed.

  20. Synthesis of multiferroic Er-Fe-O thin films by atomic layer and chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Mantovan, R., E-mail: roberto.mantovan@mdm.imm.cnr.it; Vangelista, S.; Wiemer, C.; Lamperti, A.; Tallarida, G. [Laboratorio MDM IMM-CNR, I-20864 Agrate Brianza (MB) (Italy); Chikoidze, E.; Dumont, Y. [GEMaC, Université de Versailles St. Quentin en Yvelines-CNRS, Versailles (France); Fanciulli, M. [Laboratorio MDM IMM-CNR, I-20864 Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Milano (Italy)

    2014-05-07

    R-Fe-O (R = rare earth) compounds have recently attracted high interest as potential new multiferroic materials. Here, we report a method based on the solid-state reaction between Er{sub 2}O{sub 3} and Fe layers, respectively grown by atomic layer deposition and chemical vapor deposition, to synthesize Er-Fe-O thin films. The reaction is induced by thermal annealing and evolution of the formed phases is followed by in situ grazing incidence X-ray diffraction. Dominant ErFeO{sub 3} and ErFe{sub 2}O{sub 4} phases develop following subsequent thermal annealing processes at 850 °C in air and N{sub 2}. Structural, chemical, and morphological characterization of the layers are conducted through X-ray diffraction and reflectivity, time-of-flight secondary ion-mass spectrometry, and atomic force microscopy. Magnetic properties are evaluated by magnetic force microscopy, conversion electron Mössbauer spectroscopy, and vibrating sample magnetometer, being consistent with the presence of the phases identified by X-ray diffraction. Our results constitute a first step toward the use of cost-effective chemical methods for the synthesis of this class of multiferroic thin films.

  1. Synthesis of multiferroic Er-Fe-O thin films by atomic layer and chemical vapor deposition

    Science.gov (United States)

    Mantovan, R.; Vangelista, S.; Wiemer, C.; Lamperti, A.; Tallarida, G.; Chikoidze, E.; Dumont, Y.; Fanciulli, M.

    2014-05-01

    R-Fe-O (R = rare earth) compounds have recently attracted high interest as potential new multiferroic materials. Here, we report a method based on the solid-state reaction between Er2O3 and Fe layers, respectively grown by atomic layer deposition and chemical vapor deposition, to synthesize Er-Fe-O thin films. The reaction is induced by thermal annealing and evolution of the formed phases is followed by in situ grazing incidence X-ray diffraction. Dominant ErFeO3 and ErFe2O4 phases develop following subsequent thermal annealing processes at 850 °C in air and N2. Structural, chemical, and morphological characterization of the layers are conducted through X-ray diffraction and reflectivity, time-of-flight secondary ion-mass spectrometry, and atomic force microscopy. Magnetic properties are evaluated by magnetic force microscopy, conversion electron Mössbauer spectroscopy, and vibrating sample magnetometer, being consistent with the presence of the phases identified by X-ray diffraction. Our results constitute a first step toward the use of cost-effective chemical methods for the synthesis of this class of multiferroic thin films.

  2. Fabrication of copper nanorods by low-temperature metal organic chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ying; Frank Leung-Yuk Lam; HU Xijun; YAN Zifeng

    2006-01-01

    Copper nanorods have been synthesized in mesoporous SBA-15 by a low-temperature metal organic chemical vapor deposition (MOCVD)employing copper (Ⅱ) acetylacetonate, Cu(acac)2,and hydrogen as a precursor and reactant gas, respectively. The hydrogen plays an important role in chemical reduction of oganometallic precursor which enhances mass transfer in the interior of the SBA-15 porous substrate. Such copper nanostructures are of great potentials in the semiconductor due to their unusual optical, magnetic and electronic properties.In addition, it has been found that chemically modifying the substrate surface by carbon deposition is crucial to such synthesis of copper nanostructures in the interior of the SBA-15, which is able to change the surface properties of SBA-15 from hydrophilic to hydrophobic to promote the adsorption of organic cupric precursor. It has also been found that the copper nanoparticles deposited on the external surface are almost eliminated and the copper nanorods are more distinct while the product was treated with ammonia. This approach could be achieved under a mild condition: a low temperature (400℃) and vacuum (2 kPa) which is extremely milder than the conventional method. It actually sounds as a foundation which is the first time to synthesize a copper nanorod at a mild condition of a low reaction temperature and pressure.

  3. Prediction of aqueous solubility, vapor pressure and critical micelle concentration for aquatic partitioning of perfluorinated chemicals.

    Science.gov (United States)

    Bhhatarai, Barun; Gramatica, Paola

    2011-10-01

    The majority of perfluorinated chemicals (PFCs) are of increasing risk to biota and environment due to their physicochemical stability, wide transport in the environment and difficulty in biodegradation. It is necessary to identify and prioritize these harmful PFCs and to characterize their physicochemical properties that govern the solubility, distribution and fate of these chemicals in an aquatic ecosystem. Therefore, available experimental data (10-35 compounds) of three important properties: aqueous solubility (AqS), vapor pressure (VP) and critical micelle concentration (CMC) on per- and polyfluorinated compounds were collected for quantitative structure-property relationship (QSPR) modeling. Simple and robust models based on theoretical molecular descriptors were developed and externally validated for predictivity. Model predictions on selected PFCs were compared with available experimental data and other published in silico predictions. The structural applicability domains (AD) of the models were verified on a bigger data set of 221 compounds. The predicted properties of the chemicals that are within the AD, are reliable, and they help to reduce the wide data gap that exists. Moreover, the predictions of AqS, VP, and CMC of most common PFCs were evaluated to understand the aquatic partitioning and to derive a relation with the available experimental data of bioconcentration factor (BCF).

  4. SiO{sub 2} coating of silver nanoparticles by photoinduced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Boies, Adam M; Girshick, Steven L [Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455 (United States); Roberts, Jeffrey T [Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455 (United States); Zhang Bin; Nakamura, Toshitaka; Mochizuki, Amane, E-mail: jtrob@umn.ed, E-mail: slg@umn.ed [Nitto Denko Technical Corporation, 501 Via Del Monte, Oceanside, CA 92058 (United States)

    2009-07-22

    Gas-phase silver nanoparticles were coated with silicon dioxide (SiO{sub 2}) by photoinduced chemical vapor deposition (photo-CVD). Silver nanoparticles, produced by inert gas condensation, and a SiO{sub 2} precursor, tetraethylorthosilicate (TEOS), were exposed to vacuum ultraviolet (VUV) radiation at atmospheric pressure and varying temperatures. The VUV photons dissociate the TEOS precursor, initiating a chemical reaction that forms SiO{sub 2} coatings on the particle surfaces. Coating thicknesses were measured for a variety of operation parameters using tandem differential mobility analysis and transmission electron microscopy. The chemical composition of the particle coatings was analyzed using energy dispersive x-ray spectrometry and Fourier transform infrared spectroscopy. The highest purity films were produced at 300-400 {sup 0}C with low flow rates of additional oxygen. The photo-CVD coating technique was shown to effectively coat nanoparticles and limit core particle agglomeration at concentrations up to 10{sup 7} particles cm{sup -3}.

  5. Development of a new laser heating system for thin film growth by chemical vapor deposition.

    Science.gov (United States)

    Fujimoto, Eiji; Sumiya, Masatomo; Ohnishi, Tsuyoshi; Lippmaa, Mikk; Takeguchi, Masaki; Koinuma, Hideomi; Matsumoto, Yuji

    2012-09-01

    We have developed a new laser heating system for thin film growth by chemical vapor deposition (CVD). A collimated beam from a high-power continuous-wave 808 nm semiconductor laser was directly introduced into a CVD growth chamber without an optical fiber. The light path of the heating laser inside the chamber was isolated mechanically from the growth area by bellows to protect the optics from film coating. Three types of heat absorbers, (10 × 10 × 2 mm(3)) consisting of SiC, Ni/NiO(x), or pyrolytic graphite covered with pyrolytic BN (PG/PBN), located at the backside of the substrate, were tested for heating performance. It was confirmed that the substrate temperature could reach higher than 1500 °C in vacuum when a PG/PBN absorber was used. A wide-range temperature response between 400 °C and 1000 °C was achieved at high heating and cooling rates. Although the thermal energy loss increased in a H(2) gas ambient due to the higher thermal conductivity, temperatures up to 1000 °C were achieved even in 200 Torr H(2). We have demonstrated the capabilities of this laser heating system by growing ZnO films by metalorganic chemical vapor deposition. The growth mode of ZnO films was changed from columnar to lateral growth by repeated temperature modulation in this laser heating system, and consequently atomically smooth epitaxial ZnO films were successfully grown on an a-plane sapphire substrate.

  6. Development of aerosol assisted chemical vapor deposition for thin film fabrication

    Science.gov (United States)

    Maulana, Dwindra Wilham; Marthatika, Dian; Panatarani, Camellia; Mindara, Jajat Yuda; Joni, I. Made

    2016-02-01

    Chemical vapor deposition (CVD) is widely used to grow a thin film applied in many industrial applications. This paper report the development of an aerosol assisted chemical vapor deposition (AACVD) which is one of the CVD methods. Newly developed AACVD system consists of a chamber of pyrex glass, two wire-heating elements placed to cover pyrex glass, a substrate holder, and an aerosol generator using an air brush sprayer. The temperature control system was developed to prevent condensation on the chamber walls. The control performances such as the overshoot and settling time were obtained from of the developed temperature controller. Wire-heating elements were controlled at certain setting value to heat the injected aerosol to form a thin film in the substrate. The performance of as-developed AACVD system tested to form a thin film where aerosol was sprayed into the chamber with a flow rate of 7 liters/minutes, and vary in temperatures and concentrations of precursor. The temperature control system have an overshoot around 25 °C from the desired set point temperature, very small temperature ripple 2 °C and a settling time of 20 minutes. As-developed AACVD successfully fabricated a ZnO thin film with thickness of below 1 µm. The performances of system on formation of thin films influenced by the generally controlled process such as values of setting temperature and concentration where the aerosol flow rate was fixed. Higher temperature was applied, the more uniform ZnO thin films were produced. In addition, temperature of the substrate also affected on surface roughness of the obtained films, while concentration of ZnO precursor determined the thickness of produce films. It is concluded that newly simple AACVD can be applied to produce a thin film.

  7. Dynamics of chemical vapor sensing with MoS2 using 1T/2H phase contacts/channel

    Science.gov (United States)

    Friedman, Adam L.; Perkins, F. Keith; Hanbicki, Aubrey T.; Culbertson, James C.; Campbell, Paul M.

    2016-06-01

    Ultra-thin transition metal dichalcogenides (TMDs) films show remarkable potential for use in chemical vapor sensing devices. Electronic devices fabricated from TMD films are inexpensive, inherently flexible, low-power, amenable to industrial-scale processing because of emergent growth techniques, and have shown high sensitivity and selectivity to electron donor analyte molecules important for explosives and nerve gas detection. However, for devices reported to date, the conductance response to chemical vapors is dominated by Schottky contacts, to the detriment of the sensitivity, selectivity, recovery, and obscuring their intrinsic behavior. Here, we use contact engineering to transition the contacts in a MoS2 FET-based chemical vapor sensor to the 1T conducting phase, while leaving the channel in the 2H semiconducting state, and thus providing Ohmic contacts to the film. We demonstrate that the resultant sensors have much improved electrical characteristics, are more selective, and recover fully after chemical vapor exposure--all major enhancements to previously MoS2 sensor devices. We identify labile nitrogen-containing electron donors as the primary species that generate a response in MoS2, and we study the dynamics of the sensing reactions, identifying two possible qualitative models for the chemical sensing reaction.

  8. Synthesis of coaxial nanotubes of polyaniline and poly(hydroxyethyl methacrylate by oxidative/initiated chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Alper Balkan

    2017-04-01

    Full Text Available Vapor-phase synthesis techniques of polymeric nanostructures offer unique advantages over conventional, solution-based techniques because of their solventless nature. In this work, we report the fabrication of coaxial polymer nanotubes using two different chemical vapor deposition methods. The fabrication process involves the deposition of an outer layer of the conductive polyaniline (PANI by oxidative chemical vapor deposition, followed by the deposition of the inner layer of poly(2-hydroxyethyl methacrylate (pHEMA hydrogel by initiated chemical vapor deposition. The vapor-phase techniques allowed for fine-tuning of the thickness of the individual layers, keeping the functionalities of the polymers intact. The response of the single components and the coaxial nanotubes to changes in humidity was investigated for potential humidity sensor applications. For single-component conductive PANI nanotubes, the resistance changed parabolically with relative humidity because of competing effects of doping and swelling of the PANI polymer under humid conditions. Introducing a hydrogel inner layer increased the overall resistance, and enhanced swelling, which caused the resistance to continuously increase with relative humidity.

  9. Synthesis of nanoscale materials via a novel chemical vapor deposition based apparatus

    Science.gov (United States)

    Klug, Kevin L.

    Nanoscale materials are of interest due to the unusual properties afforded by their size. Two such morphologies, nanoparticles and the recently discovered "nanobelt" materials, are explored in this thesis. A novel nanoscale material synthesis apparatus was constructed. It consists of four primary components: an evaporation chamber, a chemical vapor deposition furnace, a collection chamber, and a powder reservoir. A two-stage subsonic jet separates the first two components, permitting nanoparticle production to occur independently of subsequent chemical and thermal treatment. An experimental design was conducted to examine the roles of several variables during the formation of graphite-encapsulated nickel nanoparticles. Coating morphology was strongly dependent on furnace temperature, which exhibited a more subtle influence on mean particle size. The percentage of nickel surviving acid treatment depended primarily on hydrocarbon identity, as well as furnace temperature and carbon atom flux. Acetylene at high temperature yielded crystalline carbon coatings and the greatest percentage of protected nickel achieved, but with an excess of carbon in the product. Additional encapsulated nickel experiments were conducted with reduced acetylene flowrates and a staggered furnace temperature. Thermogravimetric analysis of the as-collected powder revealed that the coating was a crystalline and amorphous carbon hybrid. While this coating effectively protected large clumps of embedded nickel, removal of the amorphous carbon by oxidation rendered individual particles susceptible to hydrochloric acid attack. Amorphous silica was introduced as an alternative coating material via tetraethoxysilane decomposition. Transmission electron microscopy confirmed the production of well-dispersed, acid-resistant particles with a nickel core and silica shell. The synthesis of nanoscale alumina heterogeneous catalyst substrates was investigated. Exposure of aluminum nanoparticles to large

  10. Influence of Chemical Precleaning on the Plasma Treatment Efficiency of Aluminum by RF Plasma Pencil

    Science.gov (United States)

    Vadym, Prysiazhnyi; Pavel, Slavicek; Eliska, Mikmekova; Milos, Klima

    2016-04-01

    This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces. The results of our study showed that the state of the topmost surface layer (i.e. the surface morphology and chemical groups) of plasma modified aluminum significantly depends on the chemical precleaning. Commonly used chemicals (isopropanol, trichlorethane, solution of NaOH in deionized water) were used as precleaning agents. The plasma treatments were done using a radio frequency driven atmospheric pressure plasma pencil developed at Masaryk University, which operates in Ar, Ar/O2 gas mixtures. The effectiveness of the plasma treatment was estimated by the wettability measurements, showing high wettability improvement already after 0.3 s treatment. The effects of surface cleaning (hydrocarbon removal), surface oxidation and activation (generation of OH groups) were estimated using infrared spectroscopy. The changes in the surface morphology were measured using scanning electron microscopy. Optical emission spectroscopy measurements in the near-to-surface region with temperature calculations showed that plasma itself depends on the sample precleaning procedure.

  11. Thin-layer chromatography combined with diode laser thermal vaporization inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Bednařík, Antonín; Tomalová, Iva; Kanický, Viktor; Preisler, Jan

    2014-10-17

    Here we present a novel coupling of thin-layer chromatography (TLC) to diode laser thermal vaporization inductively coupled plasma mass spectrometry (DLTV ICP MS). DLTV is a new technique of aerosol generation which uses a diode laser to induce pyrolysis of a substrate. In this case the cellulose stationary phase on aluminum-backed TLC sheets overprinted with black ink to absorb laser light. The experimental arrangement relies on economic instrumentation: an 808-nm 1.2-W continuous-wave infrared diode laser attached to a syringe pump serving as the movable stage. Using a glass tubular cell, the entire length of a TLC separation channel is scanned. The 8-cm long lanes were scanned in ∼35 s. The TLC - DLTV ICP MS coupling is demonstrated on the separation of four cobalamins (hydroxo-; adenosyl-; cyano-; and methylcobalamin) with limits of detection ∼2 pg and repeatability ∼15% for each individual species. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Consequences of plasma oxidation and vacuum annealing on the chemical properties and electron accumulation of In2O3 surfaces

    Science.gov (United States)

    Berthold, Theresa; Rombach, Julius; Stauden, Thomas; Polyakov, Vladimir; Cimalla, Volker; Krischok, Stefan; Bierwagen, Oliver; Himmerlich, Marcel

    2016-12-01

    The influence of oxygen plasma treatments on the surface chemistry and electronic properties of unintentionally doped and Mg-doped In2O3(111) films grown by plasma-assisted molecular beam epitaxy or metal-organic chemical vapor deposition is studied by photoelectron spectroscopy. We evaluate the impact of semiconductor processing technology relevant treatments by an inductively coupled oxygen plasma on the electronic surface properties. In order to determine the underlying reaction processes and chemical changes during film surface-oxygen plasma interaction and to identify reasons for the induced electron depletion, in situ characterization was performed implementing a dielectric barrier discharge oxygen plasma as well as vacuum annealing. The strong depletion of the initial surface electron accumulation layer is identified to be caused by adsorption of reactive oxygen species, which induce an electron transfer from the semiconductor to localized adsorbate states. The chemical modification is found to be restricted to the topmost surface and adsorbate layers. The change in band bending mainly depends on the amount of attached oxygen adatoms and the film bulk electron concentration as confirmed by calculations of the influence of surface state density on the electron concentration and band edge profile using coupled Schrödinger-Poisson calculations. During plasma oxidation, hydrocarbon surface impurities are effectively removed and surface defect states, attributed to oxygen vacancies, vanish. The recurring surface electron accumulation after subsequent vacuum annealing can be consequently explained by surface oxygen vacancies.

  13. Nonradioactive Environmental Emissions Chemical Source Term for the Double Shell Tank (DST) Vapor Space During Waste Retrieval Operations

    Energy Technology Data Exchange (ETDEWEB)

    MAY, T.H.

    2000-04-21

    A nonradioactive chemical vapor space source term for tanks on the Phase 1 and the extended Phase 1 delivery, storage, and disposal mission was determined. Operations modeled included mixer pump operation and DST waste transfers. Concentrations of ammonia, specific volatile organic compounds, and quantitative volumes of aerosols were estimated.

  14. Extension of the lifetime of tantalum filaments in the hot-wire (Cat) 3 Chemical Vapor Deposition process

    CSIR Research Space (South Africa)

    Knoesen, D

    2008-01-01

    Full Text Available One of the prime components of a hot-wire (Cat) Chemical Vapor Deposition system is the filament used to pyro-catalytically crack the gases like silane. Burnt out tantalum filaments were studied to determine the possible improvement of lifetime...

  15. The influence of methanol addition during the film growth of SnO 2 by atmospheric pressure chemical vapor deposition

    NARCIS (Netherlands)

    Volintiru, I.; Graaf, A. de; Deelen, J. van; Poodt, P.W.G.

    2011-01-01

    Undoped tin oxide (SnO2) thin films have been deposited in a stagnant point flow chemical vapor deposition reactor from a water/tin tetrachloride mixture. By adding methanol during the deposition process the film electrical properties change significantly: ten times more conductive SnO 2 films are o

  16. Vertically aligned carbon nanotube field emitter arrays with Ohmic base contact to silicon by Fe-catalyzed chemical vapor deposition

    NARCIS (Netherlands)

    Morassutto, M.; Tiggelaar, Roald M.; Smithers, M.A.; Smithers, M.A.; Gardeniers, Johannes G.E.

    2016-01-01

    Abstract In this study, dense arrays of aligned carbon nanotubes are obtained by thermal catalytic chemical vapor deposition, using Fe catalyst dispersed on a thin Ta layer. Alignment of the carbon nanotubes depends on the original Fe layer thickness from which the catalyst dispersion is obtained by

  17. Chemical reaction and dust formation studies in laboratory hydrocarbon plasmas.

    Science.gov (United States)

    Hippler, Rainer; Majumdar, Abhijit; Thejaswini, H. C.

    Plasma chemical reaction studies with relevance to, e.g., Titan's atmosphere have been per-formed in various laboratory plasmas [1,2]. Chemical reactions in a dielectric barrier discharge at medium pressure of 250-300 mbar have been studied in CH4 /N2 and CH4 /Ar gas mixtures by means of mass spectrometry. The main reaction scheme is production of H2 by fragmenta-tion of CH4 , but also production of larger hydrocarbons like Cn Hm with n up to 10 including formation of different functional CN groups is observed. [1] A. Majumdar and R. Hippler, Development of dielectric barrier discharge plasma processing apparatus for mass spectrometry and thin film deposition, Rev. Sci. Instrum. 78, 075103 (2007) [2] H.T. Do, G. Thieme, M. Frühlich, H. Kersten, and R. Hippler, Ion Molecule and Dust Particle Formation in Ar/CH4 , Ar/C2 H2 and Ar/C3 H6 Radio-frequency Plasmas, Contrib. Plasma Phys. 45, No. 5-6, 378-384 (2005)

  18. Vapor Phase Alkyne Coating of Pharmaceutical Excipients: Discrimination Enhancement of Raman Chemical Imaging for Tablets.

    Science.gov (United States)

    Yamashita, Mayumi; Sasaki, Hiroaki; Moriyama, Kei

    2015-12-01

    Raman chemical imaging has become a powerful analytical tool to investigate the crystallographic characteristics of pharmaceutical ingredients in tablet. However, it is often difficult to discriminate some pharmaceutical excipients from each other by Raman spectrum because of broad and overlapping signals, limiting their detailed assessments. To overcome this difficulty, we developed a vapor phase coating method of excipients by an alkyne, which exhibits a distinctive Raman signal in the range of 2100-2300 cm(-1) . We found that the combination of two volatile reagents, propargyl bromide and triethylamine, formed a thin and nonvolatile coating on the excipient and observed the Raman signal of the alkyne at the surface. We prepared alkyne-coated cellulose by this method and formed a tablet. The Raman chemical imaging of the tablet cross-section using the alkyne peak area intensity of 2120 cm(-1) as the index showed a much clearer particle image of cellulose than using the peak area intensity of 1370 cm(-1) , which originated from the cellulose itself. Our method provides an innovative technique to analyze the solid-state characteristics of pharmaceutical excipients in tablets.

  19. Superhydrophobicity of polyvinylidene fluoride membrane fabricated by chemical vapor deposition from solution

    Energy Technology Data Exchange (ETDEWEB)

    Zheng Zhenrong [College of Textiles, Tianjin Polytechnic University, Tianjin 300160 (China); Gu Zhenya, E-mail: zhenyagu@hotmail.com [College of Textiles, Tianjin Polytechnic University, Tianjin 300160 (China); Huo Ruiting; Ye Yonghong [College of Textiles, Tianjin Polytechnic University, Tianjin 300160 (China)

    2009-05-30

    Due to the chemical stability and flexibility, polyvinylidene fluoride (PVDF) membranes are widely used as the topcoat of architectural membrane structures, roof materials of vehicle, tent fabrics, and so on. Further modified PVDF membrane with superhydrophobic property may be even superior as the coating layer surface. The lotus flower is always considered to be a sacred plant, which can protect itself against water, dirt, and dust. The superhydrophobic surface of lotus leaf is rough, showing the micro- and nanometer scale morphology. In this work, the microreliefs of lotus leaf were mimicked using PVDF membrane and the nanometer scale peaks on the top of the microreliefs were obtained by the method of chemical vapor deposition from solution. The surface morphology of PVDF membrane was investigated by scanning electronic microscopy (SEM) and atomic force microscope (AFM). Elemental composition analysis by X-ray photoelectron spectroscopy (XPS) revealed that the material of the nanostructure of PVDF membrane was polymethylsiloxane. On the lotus-leaf-like PVDF membrane, the water contact angle and sliding angle were 155 deg. and 4 deg., respectively, exhibiting superhydrophobic property.

  20. Superhydrophobicity of polyvinylidene fluoride membrane fabricated by chemical vapor deposition from solution

    Science.gov (United States)

    Zheng, Zhenrong; Gu, Zhenya; Huo, Ruiting; Ye, Yonghong

    2009-05-01

    Due to the chemical stability and flexibility, polyvinylidene fluoride (PVDF) membranes are widely used as the topcoat of architectural membrane structures, roof materials of vehicle, tent fabrics, and so on. Further modified PVDF membrane with superhydrophobic property may be even superior as the coating layer surface. The lotus flower is always considered to be a sacred plant, which can protect itself against water, dirt, and dust. The superhydrophobic surface of lotus leaf is rough, showing the micro- and nanometer scale morphology. In this work, the microreliefs of lotus leaf were mimicked using PVDF membrane and the nanometer scale peaks on the top of the microreliefs were obtained by the method of chemical vapor deposition from solution. The surface morphology of PVDF membrane was investigated by scanning electronic microscopy (SEM) and atomic force microscope (AFM). Elemental composition analysis by X-ray photoelectron spectroscopy (XPS) revealed that the material of the nanostructure of PVDF membrane was polymethylsiloxane. On the lotus-leaf-like PVDF membrane, the water contact angle and sliding angle were 155° and 4°, respectively, exhibiting superhydrophobic property.

  1. Gas temperature measurements inside a hot wall chemical vapor synthesis reactor.

    Science.gov (United States)

    Notthoff, Christian; Schilling, Carolin; Winterer, Markus

    2012-11-01

    One key but complex parameter in the chemical vapor synthesis (CVS) of nanoparticles is the time temperature profile of the gas phase, which determines particle characteristics such as size (distribution), morphology, microstructure, crystal, and local structure. Relevant for the CVS process and for the corresponding particle characteristics is, however, not the T(t)-profile generated by an external energy source such as a hot wall or microwave reactor but the temperature of the gas carrying reactants and products (particles). Due to a complex feedback of the thermodynamic and chemical processes in the reaction volume with the external energy source, it is very difficult to predict the real gas phase temperature field from the externally applied T(t)-profile. Therefore, a measurement technique capable to determine the temperature distribution of the gas phase under process conditions is needed. In this contribution, we demonstrate with three proof of principle experiments the use of laser induced fluorescence thermometry to investigate the CVS process under realistic conditions.

  2. Monolayer MoSe 2 Grown by Chemical Vapor Deposition for Fast Photodetection

    KAUST Repository

    Chang, Yung-Huang

    2014-08-26

    Monolayer molybdenum disulfide (MoS2) has become a promising building block in optoelectronics for its high photosensitivity. However, sulfur vacancies and other defects significantly affect the electrical and optoelectronic properties of monolayer MoS2 devices. Here, highly crystalline molybdenum diselenide (MoSe2) monolayers have been successfully synthesized by the chemical vapor deposition (CVD) method. Low-temperature photoluminescence comparison for MoS2 and MoSe 2 monolayers reveals that the MoSe2 monolayer shows a much weaker bound exciton peak; hence, the phototransistor based on MoSe2 presents a much faster response time (<25 ms) than the corresponding 30 s for the CVD MoS2 monolayer at room temperature in ambient conditions. The images obtained from transmission electron microscopy indicate that the MoSe exhibits fewer defects than MoS2. This work provides the fundamental understanding for the differences in optoelectronic behaviors between MoSe2 and MoS2 and is useful for guiding future designs in 2D material-based optoelectronic devices. © 2014 American Chemical Society.

  3. Chemical vapor deposition of poly-p-xylylene in narrow tubes

    Science.gov (United States)

    Bröskamp, Sara Felicitas; Redka, David; Möhlmann, Alexander; Franz, Gerhard; Jocham, Dieter

    2017-07-01

    Depositing a film via chemical vapor deposition results in superior conformity compared with other deposition techniques, primarily due to the unique chemical interactions between the surface and the reactive compounds. This technique requires a readily accessible surface and so, if the transport of the reactive species is impeded, irrespective of whether this depletion is caused by diffusion or convective flow, a homogeneous layer thickness cannot be achieved. This is often the case when applying films to the interiors of tubes, especially tubes with a dead-end, such that the inevitable loss of film-building components leads to a drop in thickness along the deposition length. The present work examined the deposition of the organic polymer poly-p-xylylene, using a reactor with dimensions that were large compared with the mean free path and tubes in which this factor (the Knudsen number) becomes unity, such that the deposition can be approximately described with the continuum model. A so-called temperature seesaw was employed to mitigate variations in layer thickness by generating an opposing temperature gradient. It was found that, under a vacuum of several tens of mTorr, the polymer could be deposited on the interior wall of a tube with an aspect ratio of at least 100 with an accuracy of ±7.5 %. The true ceiling temperature for the N derivate of this polymer was also determined to be 70 ±2 °C.

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

    Science.gov (United States)

    Miyoshi, Kazuhisa

    2000-01-01

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

  5. Unraveling the complex chemistry using dimethylsilane as a precursor gas in hot wire chemical vapor deposition.

    Science.gov (United States)

    Toukabri, Rim; Shi, Yujun

    2014-05-07

    The gas-phase reaction chemistry when using dimethylsilane (DMS) as a source gas in a hot-wire chemical vapor deposition (CVD) process has been studied in this work. The complex chemistry is unraveled by using a soft 10.5 eV single photon ionization technique coupled with time-of-flight mass spectrometry in combination with the isotope labelling and chemical trapping methods. It has been demonstrated that both free-radical reactions and those involving silylene/silene intermediates are important. The reaction chemistry is characterized by the formation of 1,1,2,2-tetramethyldisilane (TMDS) from dimethylsilylene insertion into the Si-H bond of DMS, trimethylsilane (TriMS) from free-radical recombination, and 1,3-dimethyl-1,3-disilacyclobutane (DMDSCB) from the self dimerization of either dimethylsilylene or 1-methylsilene. At low filament temperatures and short reaction time, silylene chemistry dominates. The free-radical reactions become more important with increasing temperature and time. The same three products have been detected when using tantalum and tungsten filaments, indicating that changing the filament material from Ta to W does not affect much the gas-phase reaction chemistry when using DMS as a source gas in a hot-wire CVD reactor.

  6. Chemical vapor transport and solid-state exchange synthesis of new copper selenite bromides

    Science.gov (United States)

    Charkin, Dmitri O.; Kayukov, Roman A.; Zagidullin, Karim A.; Siidra, Oleg I.

    2017-02-01

    A new dimorphic copper selenite bromide, Cu5(SeO3)4Br2 was obtained via chemical transport reactions. α-Cu5(SeO3)4Br2, monoclinic (1m) and β-Cu5(SeO3)4Br2, triclinic (1a) polymorphs were produced simultaneously upon reaction of amorphous, partially dehydrated copper selenite and copper bromide. 1m is similar to Cu5(SeO3)4Cl2, whereas 1a is distantly related to Ni5(SeO3)4Br2 and Co5(SeO3)4Br2. Attempts to reproduce synthesis of 1a via exchange reaction between Na2SeO3 and CuBr2 resulted in a new Na2[Cu7O2](SeO3)4Br4 (2). Current study demonstrates for the first time, that both chemical vapor and exchange reactions can be employed in preparation of new selenite halides.

  7. Continuous, Highly Flexible, and Transparent Graphene Films by Chemical Vapor Deposition for Organic Photovoltaics

    KAUST Repository

    Gomez De Arco, Lewis

    2010-05-25

    We report the implementation of continuous, highly flexible, and transparent graphene films obtained by chemical vapor deposition (CVD) as transparent conductive electrodes (TCE) in organic photovoltaic cells. Graphene films were synthesized by CVD, transferred to transparent substrates, and evaluated in organic solar cell heterojunctions (TCE/poly-3,4- ethylenedioxythiophene:poly styrenesulfonate (PEDOT:PSS)/copper phthalocyanine/fullerene/bathocuproine/aluminum). Key to our success is the continuous nature of the CVD graphene films, which led to minimal surface roughness (∼ 0.9 nm) and offered sheet resistance down to 230 Ω/sq (at 72% transparency), much lower than stacked graphene flakes at similar transparency. In addition, solar cells with CVD graphene and indium tin oxide (ITO) electrodes were fabricated side-by-side on flexible polyethylene terephthalate (PET) substrates and were confirmed to offer comparable performance, with power conversion efficiencies (η) of 1.18 and 1.27%, respectively. Furthermore, CVD graphene solar cells demonstrated outstanding capability to operate under bending conditions up to 138°, whereas the ITO-based devices displayed cracks and irreversible failure under bending of 60°. Our work indicates the great potential of CVD graphene films for flexible photovoltaic applications. © 2010 American Chemical Society.

  8. Gas temperature measurements inside a hot wall chemical vapor synthesis reactor

    Science.gov (United States)

    Notthoff, Christian; Schilling, Carolin; Winterer, Markus

    2012-11-01

    One key but complex parameter in the chemical vapor synthesis (CVS) of nanoparticles is the time temperature profile of the gas phase, which determines particle characteristics such as size (distribution), morphology, microstructure, crystal, and local structure. Relevant for the CVS process and for the corresponding particle characteristics is, however, not the T(t)-profile generated by an external energy source such as a hot wall or microwave reactor but the temperature of the gas carrying reactants and products (particles). Due to a complex feedback of the thermodynamic and chemical processes in the reaction volume with the external energy source, it is very difficult to predict the real gas phase temperature field from the externally applied T(t)-profile. Therefore, a measurement technique capable to determine the temperature distribution of the gas phase under process conditions is needed. In this contribution, we demonstrate with three proof of principle experiments the use of laser induced fluorescence thermometry to investigate the CVS process under realistic conditions.

  9. Photoinitiated chemical vapor deposition of polymeric thin films using a volatile photoinitiator.

    Science.gov (United States)

    Chan, Kelvin; Gleason, Karen K

    2005-12-06

    Photoinitiated chemical vapor deposition (piCVD) is an evolutionary CVD technique for depositing polymeric thin films in one step without using any solvents. The technique requires no pre- or post-treatment and uses a volatile photoinitiator to initiate free-radical polymerization of gaseous monomers under UV irradiation. Glycidyl methacrylate (GMA) was used as a test monomer for its ability to undergo free-radical polymerization, and 2,2'-azobis(2-methylpropane) (ABMP) was used as the photoinitiator, as it is known to produce radicals when excited by photons. GMA and ABMP vapors were fed into a vacuum chamber in which film growth was observed on a substrate exposed to UV irradiation. The resulting poly(glycidyl methacrylate) (PGMA) thin films were comprised of linear chains and had high structural resemblance to conventionally polymerized PGMA, as shown by the high solubility in tetrahydrofuran and the infrared and X-ray photoelectron spectroscopy measurements. The introduction of ABMP into the vacuum chamber significantly increased growth rates. The maximum growth rate achieved was approximately 140 nm/min and represents a 7-fold enhancement over the case without ABMP. The molecular weight was found to increase with increasing monomer-to-initiator (M/I) feed ratio, and the polydispersity indexes (PDIs) of the samples were between 1.8 and 2.2, lower than the values obtained in conventional batch polymerization but in agreement with the theoretical expressions developed for low-conversion solution-phase polymerization, which are applicable to continuous processes such as piCVD. Molecular-weight distributions can be narrowed by filtering out wavelengths shorter than 300 nm, which induce branching and/or cross-linking. The strong dependence of the molecular weight on the M/I ratio, the rate enhancement due to the use of a radical photoinitiator, the good agreement between the experimental, and the theoretical PDIs provide evidence of a free-radical mechanism in pi

  10. Transport and chemical loss rates in Saturn's inner plasma disk

    Science.gov (United States)

    Holmberg, M. K. G.; Wahlund, J.-E.; Vigren, E.; Cassidy, T. A.; Andrews, D. J.

    2016-03-01

    The Kronian moon Enceladus is constantly feeding its surrounding with new gas and dust, from cryovolcanoes located in its south polar region. Through photoionization and impact ionization of these neutrals, a plasma disk is created, which mainly contains hydrogen ions and water group ions. This paper investigates the importance of ion loss by outward radial transport and ion loss by dissociative recombination, which is the dominant chemical loss process in the inner plasma disk. We use plasma densities derived from several years of measurements by the Cassini Radio and Plasma Wave Science electric field power spectral density and Langmuir probe to calculate the total flux tube content NL2. Our calculation shows that NL2 agrees well with earlier estimates within dipole L shell 8. We also show that loss by transport dominates chemical loss between L shells 4 and 10. Using extrapolation of available measurements, we extend the study to include L shells 2.5 to 4. The results indicate that loss by transport dominates chemical loss also between L shells 2.5 and 4. The loss rate by transport is around five times larger at L shell 5, and the difference increases as L7.7 beyond L = 5, for the net ion population. Chemical loss may still be important for the structure of the plasma disk in the region closest to Enceladus (around ±0.5 RS) at 3.95 RS (1 RS = Saturn's equatorial radius = 60,268 km), since the transport and chemical loss rates only differ by a factor of ˜2 in this region. We also derive the total plasma content of the plasma disk between L shells 4 and 10 to be 1.9 × 1033 ions and the total ion source rate for the same region to be 5.8 × 1027 s-1. The estimated equatorial ion production rate P ranges from 2.6 × 10-5 cm-3 s-1 (at L = 10) to 1.1 × 10-4 cm-3 s-1 (at L = 4.8). The net mass loading rate is derived to be 123 kg/s for L shells 4 to 10.

  11. Numerical simulation of chemical processes in atmospheric plasmas

    Institute of Scientific and Technical Information of China (English)

    Ouyang Jian-Ming; Guo Wei; Wang Long; Shao Fu-Qiu

    2004-01-01

    A model is built to study chemical processes in atmospheric plasmas at low altitude (high pressure) and at high altitude (low pressure). The plasma lifetime and the temporal evolution of the main charged species are presented.The electron number density does not strictly obey the exponential damping law in a long period. The heavy charged species are dominant at low altitude in comparison with the light species at high altitude. Some species of small amount in natural air play an important role in the processes.

  12. Microstructural, chemical and textural characterization of ZnO nanorods synthesized by aerosol assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sáenz-Trevizo, A.; Amézaga-Madrid, P.; Fuentes-Cobas, L.; Pizá-Ruiz, P.; Antúnez-Flores, W.; Ornelas-Gutiérrez, C. [Centro de Investigación en Materiales Avanzados, S.C., Chihuahua, Chihuahua 31109 (Mexico); Pérez-García, S.A. [Centro de Investigación en Materiales Avanzados, S.C., Unidad Monterrey, Apodaca, Nuevo León 66600 (Mexico); Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx [Centro de Investigación en Materiales Avanzados, S.C., Chihuahua, Chihuahua 31109 (Mexico)

    2014-12-15

    ZnO nanorods were synthesized by aerosol assisted chemical vapor deposition onto TiO{sub 2} covered borosilicate glass substrates. Deposition parameters were optimized and kept constant. Solely the effect of different nozzle velocities on the growth of ZnO nanorods was evaluated in order to develop a dense and uniform structure. The crystalline structure was characterized by conventional X-ray diffraction in grazing incidence and Bragg–Brentano configurations. In addition, two-dimensional grazing incidence synchrotron radiation diffraction was employed to determine the preferred growth direction of the nanorods. Morphology and growth characteristics analyzed by electron microscopy were correlated with diffraction outcomes. Chemical composition was established by X-ray photoelectron spectroscopy. X-ray diffraction results and X-ray photoelectron spectroscopy showed the presence of wurtzite ZnO and anatase TiO{sub 2} phases. Morphological changes noticed when the deposition velocity was lowered to the minimum, indicated the formation of relatively vertically oriented nanorods evenly distributed onto the TiO{sub 2} buffer film. By coupling two-dimensional X-ray diffraction and computational modeling with ANAELU it was proved that a successful texture determination was achieved and confirmed by scanning electron microscopy analysis. Texture analysis led to the conclusion of a preferred growth direction in [001] having a distribution width Ω = 20° ± 2°. - Highlights: • Uniform and pure single-crystal ZnO nanorods were obtained by AACVD technique. • Longitudinal and transversal axis parallel to the [001] and [110] directions, respectively. • Texture was determined by 2D synchrotron diffraction and electron microscopy analysis. • Nanorods have its [001] direction distributed close to the normal of the substrate. • Angular spread about the preferred orientation is 20° ± 2°.

  13. Nanostructure and nanochemistry of gate dielectrics and processing of tunable dielectrics by chemical vapor deposition

    Science.gov (United States)

    Wang, Chang-Gong

    2002-01-01

    PbTiO3-SrTiO3 (PST) thin films that are voltage tunable were developed for high-frequency application by a metal-organic chemical vapor deposition technique at rates of 10--15 nm/min. PST films (90--150nm) were deposited on Pt/TiO2/SiO2/Si and Sapphire (0001) substrates and characterized by various techniques to control the composition and structure. The tunability and dielectric loss (tandelta) of a 90nm PST film were 37% and 0.02, respectively, at 1MHz and 3V in a parallel plates capacitor (Pt/PST/Pt) configuration. PST films on (0001) Sapphire were epitaxial with an orientation relationship of PST [1 1 1]// Sapphire [0 0 0 1], and in-plane alignment of PST [1 i 0]// Sapphire [2 i i 0] and PST [i i 2]// Sapphire [0 1 i 0]. A coplanar waveguide structure was used to determine the tunability (31.3%) and figure of merit (13 degrees/dB) of an epitaxial 100nm PST film on Sapphire at 12 GHz. The tandelta, derived from transmission-type resonator, is explained in terms of composition inhomogeneities and in-plane biaxial stress due to lattice mismatch between PST and Sapphire. A 4nm-ZrOx/1.2nm-SiOx layer structure was formed on 200mm Si wafers by a manufacturable atomic layer chemical vapor deposition (ALCVD) technique for advanced metal oxide semiconductor gate dielectrics. The nanostructure and nanochemistry of this gate stack were investigated by various techniques, before and after oxygen annealing (700°C). The results showed that a multiphase and heterogeneous structure evolved, defined as Zr-O/interlayer(IL)/Si stack. The critical parameters that control the nanostructural and nanochemical evolution are discussed using some simple mechanistic explanations and literature data. The stacks were characterized for their dielectric and electrical properties using a Pt/Zr-O/IL/Si capacitor configuration. The flat band shift (DeltaV FB), capacitance voltage hysteresis, and leakage current density were correlated with defects and roughness of the interface, thickness of IL

  14. Determination of trace elements in medicinal activated charcoal using slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry with low vaporization temperature.

    Science.gov (United States)

    Chen, Chien-Chou; Jiang, Shiuh-Jen; Sahayam, A C

    2015-01-01

    The determination of Cd, Sb, Te, Hg, Tl and Pb in medicinal activated charcoal by ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) was described. EDTA was used as the modifier to enhance the volatility of elements studied. The influences of instrument operating conditions and slurry preparation on the ion signals were studied. A relatively low vaporization temperature of 1000°C was used, which separated the analyte from the major matrix components that improved ion signals. The method has been applied to determine Cd, Sb, Te, Hg, Tl and Pb in an NIST SRM 1633b Coal Fly Ash reference material and three brands of medicinal activated charcoal capsules using isotope dilution and standard addition calibration methods. The concentrations that are in ng g(-1) levels were in good agreement between different calibration methods. The precision between sample replicates was better than 7% with USS-ETV-ICP-MS technique. The method detection limit estimated from standard addition curves was 0.4, 0.3, 0.3, 0.3, 0.04 and 0.9 ng g(-1) for Cd, Sb, Te, Hg, Tl and Pb, respectively, in original medicinal activated charcoal.

  15. Photochemical vapor generation of lead for inductively coupled plasma mass spectrometric detection

    Science.gov (United States)

    Duan, Hualing; Zhang, Ningning; Gong, Zhenbin; Li, Weifeng; Hang, Wei

    2016-06-01

    Photochemical vapor generation (PCVG) of lead was successfully achieved with a simplified and convenient system, in which only low molecular weight organic acid and a high-efficiency photochemical reactor were needed. The reactor was used to generate lead volatile species when a solution of lead containing a small amount of low molecular weight organic acid was pumped through. Several factors, including the concentration of acetic acid, the concentration of hydrochloride acid, and the irradiation time of UV light were optimized. Under the optimal conditions, including the addition of 0.90% (v/v) acetic acid and 0.03% (v/v) hydrochloride acid, and irradiation time of 28 s, intense and repeatable signal of lead volatile species was successfully obtained and identified with inductively coupled plasma mass spectrometry (ICPMS). In addition, the effects from inorganic anions and transition metal ions, including Cl-, NO3-, SO42 -, Cu2 +, Fe3 +, Co2 + and Ni2 +, were investigated, which suggests that their suppression to the PCVG of lead was in the order of Cl- anions and Ni2 +, Co2 + < Fe3 + < Cu2 + for transition metal ions. Under optimized conditions, relative standard derivation (RSD) of 4.4% was achieved from replicate measurements (n = 5) of a standard solution of 0.1 μg L- 1 lead. And, the limit of quantitation (LOQ, 10σ) of 0.012 μg L- 1 lead was obtained using this method and the method blank could be easily controlled down to 0.023 μg L- 1. To validate applicability of this method, it was also employed for the determination of lead in tap water, rain water and lake water.

  16. Study of filament performance in heat transfer and hydrogen dissociation in diamond chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Hot-filament chemical vapor deposition (HFCVD) is a promising method for commercial production of diamond films.Filament performance in heat transfer and hydrogen decomposition in reactive environment was investigated. Power consumption by the filament in vacuum, helium and 2% CH4/H2 was experimentally determined in temperature range 1300℃-2200℃. Filament heat transfer mechanism in C-H reactive environment was calculated and analyzed. The result shows that due to surface carburization and slight carbon deposition, radiation in stead of hydrogen dissociation, becomes the largest contributor to power consumption. Filament-surface dissociation of H2 was observed at temperatures below 1873K, demonstrating the feasibility of diamond growth at low filament temperatures. The effective activation energies of hydrogen dissociation on several clean refractory filaments were derived from power consumption data in literatures. They are all lower than that of thermal dissociation of hydrogen, revealing the nature of catalytic dissociation of hydrogen on filament surface. Observation of substrate temperature suggested a weakerrole of atomic hydrogen recombination in heating substrates in C-H environment than in pure hydrogen.

  17. Equilibrium chemical vapor deposition growth of Bernal-stacked bilayer graphene.

    Science.gov (United States)

    Zhao, Pei; Kim, Sungjin; Chen, Xiao; Einarsson, Erik; Wang, Miao; Song, Yenan; Wang, Hongtao; Chiashi, Shohei; Xiang, Rong; Maruyama, Shigeo

    2014-11-25

    Using ethanol as the carbon source, self-limiting growth of AB-stacked bilayer graphene (BLG) has been achieved on Cu via an equilibrium chemical vapor deposition (CVD) process. We found that during this alcohol catalytic CVD (ACCVD) a source-gas pressure range exists to break the self-limitation of monolayer graphene on Cu, and at a certain equilibrium state it prefers to form uniform BLG with a high surface coverage of ∼94% and AB-stacking ratio of nearly 100%. More importantly, once the BLG is completed, this growth shows a self-limiting manner, and an extended ethanol flow time does not result in additional layers. We investigate the mechanism of this equilibrium BLG growth using isotopically labeled (13)C-ethanol and selective surface aryl functionalization, and results reveal that during the equilibrium ACCVD process a continuous substitution of graphene flakes occurs to the as-formed graphene and the BLG growth follows a layer-by-layer epitaxy mechanism. These phenomena are significantly in contrast to those observed for previously reported BLG growth using methane as precursor.

  18. High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene

    Science.gov (United States)

    Liu, Lixin; Zhou, Hailong; Cheng, Rui; Yu, Woo Jong; Liu, Yuan; Chen, Yu; Shaw, Jonathan; Zhong, Xing; Huang, Yu; Duan, Xiangfeng

    2012-01-01

    Bernal stacked (AB stacked) bilayer graphene is of significant interest for functional electronic and photonic devices due to the feasibility to continuously tune its band gap with a vertical electrical field. Mechanical exfoliation can be used to produce AB stacked bilayer graphene flakes but typically with the sizes limited to a few micrometers. Chemical vapor deposition (CVD) has been recently explored for the synthesis of bilayer graphene but usually with limited coverage and a mixture of AB and randomly stacked structures. Herein we report a rational approach to produce large-area high quality AB stacked bilayer graphene. We show that the self-limiting effect of graphene growth on Cu foil can be broken by using a high H2/CH4 ratio in a low pressure CVD process to enable the continued growth of bilayer graphene. A high temperature and low pressure nucleation step is found to be critical for the formation of bilayer graphene nuclei with high AB stacking ratio. A rational design of a two-step CVD process is developed for the growth of bilayer graphene with high AB stacking ratio (up to 90 %) and high coverage (up to 99 %). The electrical transport studies demonstrated that devices made of the as-grown bilayer graphene exhibit typical characteristics of AB stacked bilayer graphene with the highest carrier mobility exceeding 4,000 cm2/V·s at room temperature, comparable to that of the exfoliated bilayer graphene. PMID:22906199

  19. Chemical vapor deposition based tungsten disulfide (WS2) thin film transistor

    KAUST Repository

    Hussain, Aftab M.

    2013-04-01

    Tungsten disulfide (WS2) is a layered transition metal dichalcogenide with a reported band gap of 1.8 eV in bulk and 1.32-1.4 eV in its thin film form. 2D atomic layers of metal dichalcogenides have shown changes in conductivity with applied electric field. This makes them an interesting option for channel material in field effect transistors (FETs). Therefore, we show a highly manufacturable chemical vapor deposition (CVD) based simple process to grow WS2 directly on silicon oxide in a furnace and then its transistor action with back gated device with room temperature field effect mobility of 0.1003 cm2/V-s using the Schottky barrier contact model. We also show the semiconducting behavior of this WS2 thin film which is more promising than thermally unstable organic materials for thin film transistor application. Our direct growth method on silicon oxide also holds interesting opportunities for macro-electronics applications. © 2013 IEEE.

  20. Graphene Coating of Silicon Nanoparticles with CO2 -Enhanced Chemical Vapor Deposition.

    Science.gov (United States)

    Son, In Hyuk; Park, Jong Hwan; Kwon, Soonchul; Choi, Jang Wook; Rümmeli, Mark H

    2016-02-03

    Understanding the growth of graphene over Si species is becoming ever more important as the huge potential for the combination of these two materials becomes more apparent, not only for device fabrication but also in energy applications, particularly in Li-ion batteries. Thus, the drive for the direct fabrication of graphene over Si is crucial because indirect approaches, by their very nature, require processing steps that, in general, contaminate, damage, and are costly. In this work, the direct chemical vapor deposition growth of few-layer graphene over Si nanoparticles is systematically explored through experiment and theory with the use of a reducer, H2 or the use of a mild oxidant, CO2 combined with CH4 . Unlike the case of CH4 , with the use of CO2 as a mild oxidant in the reaction, the graphene layers form neatly over the surface and encapsulate the Si particles. SiC formation is also prevented. These structures show exceptionally good electrochemical performance as high capacity anodes for lithium-ion batteries. Density functional theory studies show the presence of CO2 not only prevents SiC formation but helps enhance the catalytic activity of the particles by maintaining an SiOx surface. In addition, CO2 can enhance graphitization.

  1. Chemical vapor deposition graphene transfer process to a polymeric substrate assisted by a spin coater

    Science.gov (United States)

    Kessler, Felipe; da Rocha, Caique O. C.; Medeiros, Gabriela S.; Fechine, Guilhermino J. M.

    2016-03-01

    A new method to transfer chemical vapor deposition graphene to polymeric substrates is demonstrated here, it is called direct dry transfer assisted by a spin coater (DDT-SC). Compared to the conventional method DDT, the improvement of the contact between graphene-polymer due to a very thin polymeric film deposited by spin coater before the transfer process prevented air bubbles and/or moisture and avoided molecular expansion on the graphene-polymer interface. An acrylonitrile-butadiene-styrene copolymer, a high impact polystyrene, polybutadiene adipate-co-terephthalate, polylactide acid, and a styrene-butadiene-styrene copolymer are the polymers used for the transfers since they did not work very well by using the DDT process. Raman spectroscopy and optical microscopy were used to identify, to quantify, and to qualify graphene transferred to the polymer substrates. The quantity of graphene transferred was substantially increased for all polymers by using the DDT-SC method when compared with the DDT standard method. After the transfer, the intensity of the D band remained low, indicating low defect density and good quality of the transfer. The DDT-SC transfer process expands the number of graphene applications since the polymer substrate candidates are increased.

  2. Laser-assisted chemical vapor deposition setup for fast synthesis of graphene patterns

    Science.gov (United States)

    Zhang, Chentao; Zhang, Jianhuan; Lin, Kun; Huang, Yuanqing

    2017-05-01

    An automatic setup based on the laser-assisted chemical vapor deposition method has been developed for the rapid synthesis of graphene patterns. The key components of this setup include a laser beam control and focusing unit, a laser spot monitoring unit, and a vacuum and flow control unit. A laser beam with precision control of laser power is focused on the surface of a nickel foil substrate by the laser beam control and focusing unit for localized heating. A rapid heating and cooling process at the localized region is induced by the relative movement between the focalized laser spot and the nickel foil substrate, which causes the decomposing of gaseous hydrocarbon and the out-diffusing of excess carbon atoms to form graphene patterns on the laser scanning path. All the fabrication parameters that affect the quality and number of graphene layers, such as laser power, laser spot size, laser scanning speed, pressure of vacuum chamber, and flow rates of gases, can be precisely controlled and monitored during the preparation of graphene patterns. A simulation of temperature distribution was carried out via the finite element method, providing a scientific guidance for the regulation of temperature distribution during experiments. A multi-layer graphene ribbon with few defects was synthesized to verify its performance of the rapid growth of high-quality graphene patterns. Furthermore, this setup has potential applications in other laser-based graphene synthesis and processing.

  3. Impedance spectroscopy of manganite films prepared by metalorganic chemical vapor deposition.

    Science.gov (United States)

    Nakamura, Toshihiro; Homma, Kohei; Tachibana, Kunihide

    2011-09-01

    Polycrystalline Pr(1-x)CaxMnO3 (PCMO) films were prepared by liquid source metalorganic chemical vapor deposition using in situ infrared spectroscopic monitoring. The electric properties of the PCMO-based devices with Ni and Al electrodes (Ni-PCMO-Ni and Al-PCMO-Al devices) were studied by dc current-voltage (I-V) measurements and ac impedance spectroscopy. The current varied linearly with the applied voltage in Ni-PCMO-Ni devices, while nonlinear behavior was observed in I-V curves for Al-PCMO-Al devices. Impedance spectra were also different between Ni-PCMO-Ni and Al-PCMO-Al devices. The Cole-Cole plots for the Ni-PCMO-Ni devices showed only a single semicircular arc, which was assigned to the PCMO bulk impedance. Impedance spectra for the Al-PCMO-Al devices had two distinct components, which could be attributed to the PCMO bulk and to the interface between the PCMO film and the Al electrode, respectively. The bias dependence of the impedance spectra suggested that the resistance switching in the Al-PCMO-Al devices was mainly due to the resistance change in the interface between the film and the electrode. The metal electrode plays an important role in the resistance switching in the PCMO-based devices. The choice of the optimum metal electrodes is essential to the ReRAM application of the manganite-based devices.

  4. Growth of High TcYBaCuO Thin Films by Metalorganic Chemical Vapor Deposition

    Science.gov (United States)

    Kirlin, Peter S.; Binder, R.; Gardiner, R.; Brown, Duncan W.

    1990-03-01

    Thin films of YBa2Cu3O7-x were grown on MgO(100) by metalorganic chemical vapor deposition (MOCVD). Low pressure growth studies were carried out between 400 and 600°C using metal β-diketonate complexes as source reagents for Y, Ba, and Cu. As-deposited films were amorphous and a two stage annealing protocol was used in which fluorine was first removed in a Ar/H20 stream between 700 and 850°C, followed by calcination in flowing oxygen between 500 and 950°C. Scanning electron microscopy, X-ray diffraction and energy dispersive analysis indicate that good compositional and dimensional uniformity could be achieved. The temperature of the oxygen annealing step was shown to have a dramatic impact on the physical and electrical properties of the YBa2Cu307-x thin films. Annealing temperatures exceeding 910°C gave large crystallites and semiconducting resistivity above Tc; annealing temperatures below 910°C yielded films with metallic conductivity whose density and superconducting transition varied inversely with maximum annealing temperature. Optimized deposition/annealing protocols yielded films with a preferred c-axis orientation, R273/R100 ratios of 2, onsets as high as 94K and zero resistance exceeding 90K.

  5. Surface Analysis of Hexagonal Boron Nitride Grown by Chemical Vapor Deposition

    Science.gov (United States)

    Robinson, Zachary; Hite, J. K.; Eddy, C. R., Jr.; Bermudez, V. M.; Feigelson, B. N.

    Hexagonal boron nitride (hBN) is an important material for development of 2-dimensional heterostructures. Chemical vapor deposition of hBN on Cu-foil substrates is one possible route towards large-scale production of hBN films with low defect density. Therefore, studying the growth kinetics of hBN on different orientations of Cu is an important first step towards understanding and controlling the growth process. In this work, hBN was simultaneously grown on Cu(111), Cu(100), Cu(110), and Cu-foil in order to investigate how the different substrate orientations affect the hBN overlayer. The post-growth crystallographic orientations were measured with electron backscatter diffraction (EBSD), and film coverages we measured with XPS. In addition, a grazing-incidence infrared reflection absorption spectroscopy (IRRAS) technique was developed to quickly characterize each hBN film. It was found that the growth rate was inversely proportional to the surface free energy of the Cu surface, with Cu(111) having the most h-BN surface coverage. The Cu foil predominately crystallized with a (100) surface orientation, and had a film coverage very close to the Cu(100).

  6. Structural and electronic characterization of graphene grown by chemical vapor deposition and transferred onto sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Joucken, Frédéric, E-mail: frederic.joucken@unamur.be; Colomer, Jean-François; Sporken, Robert; Reckinger, Nicolas

    2016-08-15

    Highlights: • CVD graphene is transferred onto sapphire. • Transport measurements reveal relatively low charge carriers mobility. • Scanning probe microscopy experiments reveal the presence of robust contaminant layers between the graphene and the sapphire, responsible for the low carriers mobility. - Abstract: We present a combination of magnetotransport and local probe measurements on graphene grown by chemical vapor deposition on copper foil and subsequently transferred onto a sapphire substrate. A rather strong p-doping is observed (∼9 × 10{sup 12} cm{sup −2}) together with quite low carrier mobility (∼1350 cm{sup 2}/V s). Atomic force and tunneling imaging performed on the transport devices reveals the presence of contaminants between sapphire and graphene, explaining the limited performance of our devices. The transferred graphene displays ridges similar to those observed whilst graphene is still on the copper foil. We show that, on sapphire, these ridges are made of different thicknesses of the contamination layer and that, contrary to what was reported for hBN or certain transition metal dichalcogenides, no self-cleansing process of the sapphire substrate is observed.

  7. Exploring metalorganic chemical vapor deposition of Si-alloyed Al2O3 dielectrics using disilane

    Science.gov (United States)

    Chan, Silvia H.; Keller, Stacia; Koksaldi, Onur S.; Gupta, Chirag; DenBaars, Steven P.; Mishra, Umesh K.

    2017-04-01

    The alloying of Al2O3 films with Si is a promising route to improve gate dielectric properties in Si- and wide-bandgap- based MOS devices. Here we present a comprehensive investigation of alloyed film growth by metalorganic chemical vapor deposition (MOCVD) using trimethylaluminum, disilane, and oxygen precursors over a variety of temperature and flow conditions. Binary growth rates of Al2O3 and SiO2 were evaluated to explain the aggregate growth kinetics of Si-alloyed Al2O3 films, and refractive indices were used to monitor Si incorporation efficiencies. The temperature dependence of the reaction rate of disilane with oxygen was found to be similar to that of trimethylaluminum and oxygen, leading to well-behaved deposition behavior in the kinetic and mass-transport controlled growth regimes. Compositional predictability and stability was achieved over a wider growth space with disilane-based growths as compared to previous work, which used silane as the Si precursor instead. In situ (Al,Si)O/n-GaN MOS gate stacks were grown and showed increasing reduction of net positive fixed charges with higher Si composition.

  8. Initiated chemical vapor deposited nanoadhesive for bonding National Ignition Facility's targets

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tom [Univ. of California, Berkeley, CA (United States)

    2016-05-19

    Currently, the target fabrication scientists in National Ignition Facility Directorate at Lawrence Livermore National Laboratory (LLNL) is studying the propagation force resulted from laser impulses impacting a target. To best study this, they would like the adhesive used to glue the target substrates to be as thin as possible. The main objective of this research project is to create adhesive glue bonds for NIF’s targets that are ≤ 1 μm thick. Polyglycidylmethacrylate (PGMA) thin films were coated on various substrates using initiated chemical vapor deposition (iCVD). Film quality studies using white light interferometry reveal that the iCVD PGMA films were smooth. The coated substrates were bonded at 150 °C under vacuum, with low inflow of Nitrogen. Success in bonding most of NIF’s mock targets at thicknesses ≤ 1 μm indicates that our process is feasible in bonding the real targets. Key parameters that are required for successful bonding were concluded from the bonding results. They include inert bonding atmosphere, sufficient contact between the PGMA films, and smooth substrates. Average bond strength of 0.60 MPa was obtained from mechanical shearing tests. The bonding failure mode of the sheared interfaces was observed to be cohesive. Future work on this project will include reattempt to bond silica aerogel to iCVD PGMA coated substrates, stabilize carbon nanotube forests with iCVD PGMA coating, and kinetics study of PGMA thermal crosslinking.

  9. Direct-Liquid-Evaporation Chemical Vapor Deposition of Nanocrystalline Cobalt Metal for Nanoscale Copper Interconnect Encapsulation.

    Science.gov (United States)

    Feng, Jun; Gong, Xian; Lou, Xiabing; Gordon, Roy G

    2017-03-29

    In advanced microelectronics, precise design of liner and capping layers become critical, especially when it comes to the fabrication of Cu interconnects with dimensions lower than its mean free path. Herein, we demonstrate that direct-liquid-evaporation chemical vapor deposition (DLE-CVD) of Co is a promising method to make liner and capping layers for nanoscale Cu interconnects. DLE-CVD makes pure, smooth, nanocrystalline, and highly conformal Co films with highly controllable growth characteristics. This process allows full Co encapsulation of nanoscale Cu interconnects, thus stabilizing Cu against diffusion and electromigration. Electrical measurements and high-resolution elemental imaging studies show that the DLE-CVD Co encapsulation layer can improve the reliability and thermal stability of Cu interconnects. Also, with the high conductivity of Co, the DLE-CVD Co encapsulation layer have the potential to further decrease the power consumption of nanoscale Cu interconnects, paving the way for Cu interconnects with higher efficiency in future high-end microelectronics.

  10. Effect of Chemical Composition on Enthalpy of Evaporation and Equilibrium Vapor Pressure

    CERN Document Server

    Dobruskin, Vladimir Kh

    2010-01-01

    Proceeding from the Clausius-Clapeyron equation, the relation is derived that establishes a correlation between the partial enthalpy of evaporation from binary solutions, concentrations of components, and equilibrium vapor pressures. The difference between enthalpies of evaporation of components from solutions and those from the pure liquids, D(DH), depends on the chemical nature and concentrations, X, of solutions. The effect of concentrations on D(DH) makes different appearances in ideal and non-ideal solutions, although, as a whole, D(DH) increases with the growth of concentration of the second component. A model is introduced, which considers D(DH) as the sum of energetic changes of three sequential stages: passage of molecules from the bulk liquid into the surface layer, exit of the molecules on the outer side of the interface, and the following desorption into the gas phase. In the framework of the model, the main contribution to enthalpy of evaporation comes from the processes in the surface layer. It ...

  11. Robust numerical simulation of porosity evolution in chemical vapor infiltration III: three space dimension

    CERN Document Server

    Jin Shi

    2003-01-01

    Chemical vapor infiltration (CVI) process is an important technology to fabricate ceramic matrix composites (CMC's). In this paper, a three-dimension numerical model is presented to describe pore microstructure evolution during the CVI process. We extend the two-dimension model proposed in [S. Jin, X.L. Wang, T.L. Starr, J. Mater. Res. 14 (1999) 3829; S. Jin. X.L. Wang, T.L. Starr, X.F. Chen, J. Comp. Phys. 162 (2000) 467], where the fiber surface is modeled as an evolving interface, to the three space dimension. The 3D method keeps all the virtue of the 2D model: robust numerical capturing of topological changes of the interface such as the merging, and fast detection of the inaccessible pores. For models in the kinetic limit, where the moving speed of the interface is constant, some numerical examples are presented to show that this three-dimension model will effectively track the change of porosity, close-off time, location and shape of all pores.

  12. Chemical vapor deposition fabrication and characterization of silica-coated carbon fiber ultramicroelectrodes.

    Science.gov (United States)

    Zhao, G; Giolando, D M; Kirchhoff, J R

    1995-08-01

    Carbon fiber disk ultramicroelectrodes (UMEs) with well-defined geometries were prepared by chemical vapor deposition techniques. Transparent silica films with thicknesses from 1 to 600 microns were deposited on the cylindrical length of 5 and 10 microns carbon fibers from a SiCl4, H2, and O2 ternary precursor system at 850-1150 degrees C or sequential deposition from Si(OEt)4 as a single source precursor at 700 degrees C followed by the SiCl4, H2, and O2 precursor system. Film thickness, film adhesion to the fiber substrate, and the overall dimensions of the silica-coated carbon fiber were studied and found to be a function of the precursor system, precursor concentrations, fiber diameter, deposition time, and fiber temperature. The silica films were found to be free of microcracks and characterized by a quality seal between the carbon fiber and the coating. As a result, the silica-coated disk UME exhibits an excellent electrochemical response without the need to use an epoxy sealant at the electrode tip. Furthermore, the deposition of hard and inert ceramic materials imparts durability to fragile carbon fibers and facilitates the handling of UMEs in microenvironments. Finally, the advantage of concentric deposition about the fibers to produce a disk UME in the center of an insulating plane was used to examine the effect of the thickness of the insulating coating on the limiting current response.

  13. Amorphous inclusions during Ge and GeSn epitaxial growth via chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gencarelli, F., E-mail: federica.gencarelli@imec.be [imec, Kapeldreef 75, 3001 Leuven (Belgium); Dept. of Metallurgy and Materials Engineering, KU Leuven, B-3001 Leuven (Belgium); Shimura, Y. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Kumar, A. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Vincent, B.; Moussa, A.; Vanhaeren, D.; Richard, O.; Bender, H. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, W. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Caymax, M.; Loo, R. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Heyns, M. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Dept. of Metallurgy and Materials Engineering, KU Leuven, B-3001 Leuven (Belgium)

    2015-09-01

    In this work, we discuss the characteristics of particular island-type features with an amorphous core that are developed during the low temperature epitaxial growth of Ge and GeSn layers by means of chemical vapor deposition with Ge{sub 2}H{sub 6}. Although further investigations are needed to unambiguously identify the origin of these features, we suggest that they are originated by the formation of clusters of H and/or contaminants atoms during growth. These would initially cause the formation of pits with crystalline rough facets over them, resulting in ring-shaped islands. Then, when an excess surface energy is overcome, an amorphous phase would nucleate inside the pits and fill them. Reducing the pressure and/or increasing the growth temperature can be effective ways to prevent the formation of these features, likely due to a reduction of the surface passivation from H and/or contaminant atoms. - Highlights: • Island features with amorphous cores develop during low T Ge(Sn) CVD with Ge{sub 2}H{sub 6.} • These features are thoroughly characterized in order to understand their origin. • A model is proposed to describe the possible evolution of these features. • Lower pressures and/or higher temperatures avoid the formation of these features.

  14. Propeller-Shaped ZnO Nanostructures Obtained by Chemical Vapor Deposition: Photoluminescence and Photocatalytic Properties

    Directory of Open Access Journals (Sweden)

    S. L. Wang

    2012-01-01

    Full Text Available Propeller-shaped and flower-shaped ZnO nanostructures on Si substrates were prepared by a one-step chemical vapor deposition technique. The propeller-shaped ZnO nanostructure consists of a set of axial nanorod (50 nm in tip, 80 nm in root and 1 μm in length, surrounded by radial-oriented nanoribbons (20–30 nm in thickness and 1.5 μm in length. The morphology of flower-shaped ZnO nanostructure is similar to that of propeller-shaped ZnO, except the shape of leaves. These nanorods leaves (30 nm in diameter and 1–1.5 μm in length are aligned in a radial way and pointed toward a common center. The flower-shaped ZnO nanostructures show sharper and stronger UV emission at 378 nm than the propeller-shaped ZnO, indicating a better crystal quality and fewer structural defects in flower-shaped ZnO. In comparison with flower-shaped ZnO nanostructures, the propeller-shaped ZnO nanostructures exhibited a higher photocatalytic property for the photocatalytic degradation of Rhodamine B under UV-light illumination.

  15. Experimental study of flow and heat transfer in a rotating chemical vapor deposition reactor

    Science.gov (United States)

    Wong, Sun

    An experimental model was set up to study the rotating vertical impinging chemical vapor deposition reactor. Deposition occurs only when the system has enough thermal energy. Therefore, understanding the fluid characteristic and heat transfer of the system will provide a good basis to understand the full model. Growth rate and the uniformity of the film are the two most important factors in CVD process and it is depended on the flow and thermal characteristic within the system. Optimizing the operating parameters will result in better growth rate and uniformity. Operating parameters such as inflow velocity, inflow diameter and rotational speed are used to create different design simulations. Fluid velocities and various temperatures are recorded to see the effects of the different operating parameters. Velocities are recorded by using flow meter and hot wire anemometer. Temperatures are recorded by using various thermocouples and infrared thermometer. The result should provide a quantitative basis for the prediction, design and optimization of the system and process for design and fabrication of future CVD reactors. Further assessment of the system results will be discuss in detail such as effects of buoyancy and effects of rotation. The experimental study also coupled with a numerical study for further validation of both model. Comparisons between the two models are also presented.

  16. Layer-selective synthesis of bilayer graphene via chemical vapor deposition

    Science.gov (United States)

    Yang, Ning; Choi, Kyoungjun; Robertson, John; Park, Hyung Gyu

    2017-09-01

    A controlled synthesis of high-quality AB-stacked bilayer graphene by chemical vapor deposition demands a detailed understanding of the mechanism and kinetics. By decoupling the growth of the two layers via a growth-and-regrowth scheme, we report the kinetics and termination mechanisms of the bilayer graphene growth on copper. We observe, for the first time, that the secondary layer growth follows Gompertzian kinetics. Our observations affirm the postulate of a time-variant transition from a mass-transport-limited to a reaction-limited regimes and identify the mechanistic disparity between the monolayer growth and the secondary-layer expansion underneath the monolayer cover. It is the continuous carbon supply that drives the expansion of the graphene secondary layer, rather than the initially captured carbon amount, suggesting an essential role of the surface diffusion of reactant adsorbates in the interspace between the top graphene layer and the underneath copper surface. We anticipate that the layer selectivity of the growth relies on the entrance energetics of the adsorbed reactants to the graphene-copper interspace across the primary-layer edge, which could be engineered by tailoring the edge termination state. The temperature-reliant saturation area of the secondary-layer expansion is understood as a result of competitive attachment of carbon and hydrogen adatoms to the secondary-layer graphene edge.

  17. Current-Perpendicular-to-Plane Magnetoresistance in Chemical Vapor Deposition-Grown Multilayer Graphene

    Directory of Open Access Journals (Sweden)

    Sandipan Pramanik

    2013-09-01

    Full Text Available Current-perpendicular-to-plane (CPP magnetoresistance (MR effects are often exploited in various state-of-the-art magnetic field sensing and data storage technologies. Most of the CPP-MR devices are artificial layered structures of ferromagnets and non-magnets, and in these devices, MR manifests, due to spin-dependent carrier transmission through the constituent layers. In this work, we explore another class of artificial layered structure in which multilayer graphene (MLG is grown on a metallic substrate by chemical vapor deposition (CVD. We show that depending on the nature of the graphene-metal interaction, these devices can also exhibit large CPP-MR. Magnetoresistance ratios (>100% are at least two orders of magnitude higher than “transferred” graphene and graphitic samples reported in the literature, for a comparable temperature and magnetic field range. This effect is unrelated to spin injection and transport and is not adequately described by any of the MR mechanisms known to date. The simple fabrication process, large magnitude of the MR and its persistence at room temperature make this system an attractive candidate for magnetic field sensing and data storage applications and, also, underscore the need for further fundamental investigations on graphene-metal interactions.

  18. Uniformly Distributed Graphene Domain Grows on Standing Copper via Low-Pressure Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Shih-Hao Chan

    2013-01-01

    Full Text Available Uniformly distributed graphene domains were synthesized on standing copper foil by a low-pressure chemical vapor deposition system. This method improved the distribution of the graphene domains at different positions on the same piece of copper foil along the forward direction of the gas flow. Scanning electron microscopy (SEM showed the average size of the graphene domains to be about ~20 m. This results show that the sheet resistance of monolayer graphene on a polyethylene terephthalate (PET substrate is about ~359 /□ whereas that of the four-layer graphene films is about ~178 /□, with a transmittance value of 88.86% at the 550 nm wavelength. Furthermore, the sheet resistance can be reduced with the addition of HNO3 resulting in a value of 84 /□. These values meet the absolute standard for touch sensor applications, so we believe that this method can be a candidate for some transparent conductive electrode applications.

  19. SiGeSn growth studies using reduced pressure chemical vapor deposition towards optoelectronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Wirths, S., E-mail: s.wirths@fz-juelich.de [Peter Grünberg Institute (PGI 9-IT) and JARA-FIT, Forschungszentrum Juelich, 52425 (Germany); Buca, D. [Peter Grünberg Institute (PGI 9-IT) and JARA-FIT, Forschungszentrum Juelich, 52425 (Germany); Ikonic, Z.; Harrison, P. [Institute of Microwaves and Photonics, School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom); Tiedemann, A.T.; Holländer, B.; Stoica, T.; Mussler, G. [Peter Grünberg Institute (PGI 9-IT) and JARA-FIT, Forschungszentrum Juelich, 52425 (Germany); Breuer, U. [Central Institute for Engineering, Electronics and Analytics (ZEA-3), Forschungszentrum Juelich, 52425 (Germany); Hartmann, J.M. [CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble (France); Grützmacher, D.; Mantl, S. [Peter Grünberg Institute (PGI 9-IT) and JARA-FIT, Forschungszentrum Juelich, 52425 (Germany)

    2014-04-30

    In this contribution, we propose a laser concept based on a double heterostructure consisting of tensile strained Ge as the active medium and SiGeSn ternaries as cladding layers. Electronic band-structure calculations were used to determine the Si and Sn concentrations yielding a type I heterostructure with appropriate band-offsets (50 meV) between strained Ge and SiGeSn. Reduced pressure chemical vapor deposition system was employed to study the laser structure growth. Detailed analyses regarding layer composition, crystal quality, surface morphology and elastic strain are presented. A strong temperature dependence of the Si and Sn incorporation has been obtained, ranging from 4 to 19 at.% Si and from 4 to 12 at.% Sn (growth temperatures between 350 °C and 475 °C). The high single crystalline quality and low surface roughness of 0.5–0.75 nm demonstrate that our layers are suitable for heterostructure laser fabrication. - Highlights: • Sn based group IV materials for photonics • Bandstructure calculations of SiGeSn/strained Ge double heterostructures. • Si and Sn concentrations in SiGeSn layers between 4 and 19 at.% and 4 and 11 at.%, respectively. • Growth of SiGeSn layers with high crystalline quality for optoelectronic applications.

  20. Synthesis of monolayer hexagonal boron nitride on Cu foil using chemical vapor deposition.

    Science.gov (United States)

    Kim, Ki Kang; Hsu, Allen; Jia, Xiaoting; Kim, Soo Min; Shi, Yumeng; Hofmann, Mario; Nezich, Daniel; Rodriguez-Nieva, Joaquin F; Dresselhaus, Mildred; Palacios, Tomas; Kong, Jing

    2012-01-11

    Hexagonal boron nitride (h-BN) is very attractive for many applications, particularly, as protective coating, dielectric layer/substrate, transparent membrane, or deep ultraviolet emitter. In this work, we carried out a detailed investigation of h-BN synthesis on Cu substrate using chemical vapor deposition (CVD) with two heating zones under low pressure (LP). Previous atmospheric pressure (AP) CVD syntheses were only able to obtain few layer h-BN without a good control on the number of layers. In contrast, under LPCVD growth, monolayer h-BN was synthesized and time-dependent growth was investigated. It was also observed that the morphology of the Cu surface affects the location and density of the h-BN nucleation. Ammonia borane is used as a BN precursor, which is easily accessible and more stable under ambient conditions than borazine. The h-BN films are characterized by atomic force microscopy, transmission electron microscopy, and electron energy loss spectroscopy analyses. Our results suggest that the growth here occurs via surface-mediated growth, which is similar to graphene growth on Cu under low pressure. These atomically thin layers are particularly attractive for use as atomic membranes or dielectric layers/substrates for graphene devices.