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Sample records for chemically vapor deposited

  1. 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…

  2. Chemical Vapor Deposition Of Silicon Carbide

    Science.gov (United States)

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

    1993-01-01

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

  3. 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

  4. Chemical Vapor Deposition of Silicon from Silane Pyrolysis

    Science.gov (United States)

    Praturi, A. K.; Lutwack, R.; Hsu, G.

    1977-01-01

    The four basic elements in the chemical vapor deposition (CVD) of silicon from silane are analytically treated from a kinetic standpoint. These elements are mass transport of silane, pyrolysis of silane, nucleation of silicon, and silicon crystal growth. Rate expressions that describe the various steps involved in the chemical vapor deposition of silicon were derived from elementary principles. Applications of the rate expressions for modeling and simulation of the silicon CVD are discussed.

  5. Chemical vapor deposition of graphene single crystals.

    Science.gov (United States)

    Yan, Zheng; Peng, Zhiwei; Tour, James M

    2014-04-15

    As a two-dimensional (2D) sp(2)-bonded carbon allotrope, graphene has attracted enormous interest over the past decade due to its unique properties, such as ultrahigh electron mobility, uniform broadband optical absorption and high tensile strength. In the initial research, graphene was isolated from natural graphite, and limited to small sizes and low yields. Recently developed chemical vapor deposition (CVD) techniques have emerged as an important method for the scalable production of large-size and high-quality graphene for various applications. However, CVD-derived graphene is polycrystalline and demonstrates degraded properties induced by grain boundaries. Thus, the next critical step of graphene growth relies on the synthesis of large graphene single crystals. In this Account, we first discuss graphene grain boundaries and their influence on graphene's properties. Mechanical and electrical behaviors of CVD-derived polycrystalline graphene are greatly reduced when compared to that of exfoliated graphene. We then review four representative pathways of pretreating Cu substrates to make millimeter-sized monolayer graphene grains: electrochemical polishing and high-pressure annealing of Cu substrate, adding of additional Cu enclosures, melting and resolidfying Cu substrates, and oxygen-rich Cu substrates. Due to these pretreatments, the nucleation site density on Cu substrates is greatly reduced, resulting in hexagonal-shaped graphene grains that show increased grain domain size and comparable electrical properties as to exfoliated graphene. Also, the properties of graphene can be engineered by its shape, thickness and spatial structure. Thus, we further discuss recently developed methods of making graphene grains with special spatial structures, including snowflakes, six-lobed flowers, pyramids and hexagonal graphene onion rings. The fundamental growth mechanism and practical applications of these well-shaped graphene structures should be interesting topics and

  6. Studying chemical vapor deposition processes with theoretical chemistry

    OpenAIRE

    Pedersen, Henrik; Elliott, Simon D.

    2014-01-01

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

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

    Science.gov (United States)

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

    2013-04-01

    The discovery of graphene, a single layer of covalently bonded carbon atoms, has attracted intense interest. Initial studies using mechanically exfoliated graphene unveiled its remarkable electronic, mechanical and thermal properties. There has been a growing need and rapid development in large-area deposition of graphene film and its applications. Chemical vapor deposition on copper has emerged as one of the most promising methods in obtaining large-scale graphene films with quality comparable to exfoliated graphene. In this paper, we review the synthesis and characterizations of graphene grown on copper foil substrates by atmospheric pressure chemical vapor deposition. We also discuss potential applications of such large-scale synthetic graphene.

  8. Chemical-vapor deposition of silicon from silane

    Science.gov (United States)

    Hsu, G. C.; Lutwack, R.; Praturi, A. K.

    1979-01-01

    Report lists tables of standard free-energy change, equilibrium constant, and heat of reaction for chemical vapor deposition (CVD) of silicon from silane over temperature range of 100 to 1000 K. Data indicates silicon CVD may be a commercially economical process for production of silicon for solar arrays and other applications.

  9. Chemical vapor deposition (CVD) growth of graphene films

    Czech Academy of Sciences Publication Activity Database

    Frank, Otakar; Kalbáč, Martin

    Cambridge: Woodhead Publishing, 2014 - (Skákalová, V.; Kaiser, A.), s. 27-49. (Woodhead Publishing Series in Electronic and Optical Materials. 57). ISBN 978-0-85709-508-4 R&D Projects: GA MŠk LL1301 Institutional support: RVO:61388955 Keywords : graphene * chemical vapor deposition (CVD) * isotope labeling Subject RIV: CF - Physical ; Theoretical Chemistry

  10. Chemical Vapor Deposition of Aluminum Oxide Thin Films

    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…

  11. Solvent-assisted dewetting during chemical vapor deposition.

    Science.gov (United States)

    Chen, Xichong; Anthamatten, Mitchell

    2009-10-01

    This study examines the use of a nonreactive solvent vapor, tert-butanol, during initiated chemical vapor deposition (iCVD) to promote polymer film dewetting. iCVD is a solventless technique to grow polymer thin films directly from gas phase feeds. Using a custom-built axisymmetric hot-zone reactor, smooth poly(methyl methacrylate) films are grown from methyl methacrylate (MMA) and tert-butyl peroxide (TBPO). When solvent vapor is used, nonequilibrium dewetted structures comprising of randomly distributed polymer droplets are observed. The length scale of observed topographies, determined using power spectral density (PSD) analysis, ranges from 5 to 100 microm and is influenced by deposition conditions, especially the carrier gas and solvent vapor flow rates. The use of a carrier gas leads to faster deposition rates and suppresses thin film dewetting. The use of solvent vapor promotes dewetting and leads to larger length scales of the dewetted features. Control over lateral length scale is demonstrated by preparation of hierarchal "bump on bump" topographies. Vapor-induced dewetting is demonstrated on silicon wafer substrate with a native oxide layer and also on hydrophobically modified substrate prepared using silane coupling. Autophobic dewetting of PMMA from SiOx/Si during iCVD is attributed to a thin film instability driven by both long-range van der Waals forces and short-range polar interactions. PMID:19670895

  12. 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.

  13. An Overview on Thin Films Prepared by Chemical Vapor Deposition

    International Nuclear Information System (INIS)

    Chemical vapor deposition, (CVD); involves the formation of a solid thin layer on a heated substrate surface by means of chemical reaction in gas or vapor phase. CVD techniques have expanded continuously and developed into the most important method for producing films for solid-state devices. CVD is considered to be the major technique for preparing most films used in the fabrication of semiconductor devices and integrated circuits. It has advantages such as the versatility, compatibility, quality, simplicity, reproducibility, and low cost. CVD has some disadvantages of; the use of comparatively high temperatures in many processes and chemical hazards caused by toxic, explosive, or corrosive gases. Chemical vapor deposition processes can be classified according to the type of their activation energy into thermally-activated CVD, plasma-enhanced CVD, laser-induced CVD, photochemical CVD, and electron-beam assisted CVD. In this paper an attempt is made to present all aspects of CVD equipment design and the variables affecting the deposition rate. Finally the preparation requirements and the application of CVD films are also summarized. 5 figs

  14. Carbon nanostructures and networks produced by chemical vapor deposition

    OpenAIRE

    Kowlgi, N.K.K.; Koper, G.J.M.; Raalten, R.A.D.

    2012-01-01

    The invention pertains to a method for manufacturing crystalline carbon nanostructures and/or a network of crystalline carbon nanostructures, comprising: (i) providing a bicontinuous micro-emulsion containing metal nanoparticles having an average particle size between 1and 100nm; (ii) bringing said bicontinuous micro-emulsion into contact with a substrate; and (iii) subjecting said metal nanoparticles and a gaseous carbon source to chemical vapor deposition, thus forming carbon nanostructures...

  15. Chemical vapor deposition (CVD) of uranium for alpha spectrometry

    International Nuclear Information System (INIS)

    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)

  16. Fundamental studies of chemical vapor deposition diamond growth processes

    International Nuclear Information System (INIS)

    We are developing laser spectroscopic techniques to foster a fundamental understanding of diamond film growth by hot filament chemical vapor deposition (CVD). Several spectroscopic techniques are under investigation to identify intermediate species present in the bulk reactor volume, the thin active volume immediately above the growing film, and the actual growing surface. Such a comprehensive examination of the overall deposition process is necessary because a combination of gas phase and surface chemistry is probably operating. Resonantly enhanced multiphoton ionization (REMPI) techniques have been emphasized. A growth rector that permits through-the-substrate gas sampling for REMPI/time-of-flight mass spectroscopy has been developed. 7 refs., 2 figs

  17. 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...... of CVD processes; however very little information on the process and its characteristics can be found. This work presents the state of the art on the CVD of tantalum in long narrow channels and a reaction mechanism is suggested based on a rudimentary model. The effects of the system pressure...

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

    OpenAIRE

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

    2009-01-01

    The technology of Hot Wire Chemical Vapor Deposition (HWCVD) or Catalytic Chemical Vapor Deposition (Cat-CVD) has made great progress during the last couple of years. This review discusses examples of significant progress. Specifically, silicon nitride deposition by HWCVD (HW-SiNx) is highlighted, as well as thin film silicon single junction and multijunction junction solar cells. The application of HW-SiNx at a deposition rate of 3 nm/s to polycrystalline Si wafer solar cells has led to cell...

  19. Coating of metals with titanium diboride by chemical vapor deposition

    International Nuclear Information System (INIS)

    This study is an experimental investigation of the chemical vapor deposition of titanium diboride on metallic substrates by the hydrogen reduction of TiCl4 and BCl3 at temperatures between 8500C and 11000C. Kovar, tantalum, and several stainless steels were found to be suitable substrates since they could withstand the deposition temperature, had adequate resistance to HCl, a by-product of the deposition reaction, and had thermal expansion coefficients sufficiently close to that of TiB2 (less than or equal to10 x 10-6/0C). The TiB2 coatings produced were 68.2% Ti and thus near stoichiometry and had very low impurity content. They had Knoop hardnesses averaging 3300 kg/mm2 and exhibited extraordinary erosion resistance

  20. Plasma-enhanced chemical vapor deposition of multiwalled carbon nanofibers

    Science.gov (United States)

    Matthews, Kristopher; Cruden, Brett A.; Chen, Bin; Meyyappan, M.; Delzeit, Lance

    2002-01-01

    Plasma-enhanced chemical vapor deposition is used to grow vertically aligned multiwalled carbon nanofibers (MWNFs). The graphite basal planes in these nanofibers are not parallel as in nanotubes; instead they exhibit a small angle resembling a stacked cone arrangement. A parametric study with varying process parameters such as growth temperature, feedstock composition, and substrate power has been conducted, and these parameters are found to influence the growth rate, diameter, and morphology. The well-aligned MWNFs are suitable for fabricating electrode systems in sensor and device development.

  1. Chemical vapor deposition of conformal, functional, and responsive polymer films.

    Science.gov (United States)

    Alf, Mahriah E; Asatekin, Ayse; Barr, Miles C; Baxamusa, Salmaan H; Chelawat, Hitesh; Ozaydin-Ince, Gozde; Petruczok, Christy D; Sreenivasan, Ramaswamy; Tenhaeff, Wyatt E; Trujillo, Nathan J; Vaddiraju, Sreeram; Xu, Jingjing; Gleason, Karen K

    2010-05-11

    Chemical vapor deposition (CVD) polymerization utilizes the delivery of vapor-phase monomers to form chemically well-defined polymeric films directly on the surface of a substrate. CVD polymers are desirable as conformal surface modification layers exhibiting strong retention of organic functional groups, and, in some cases, are responsive to external stimuli. Traditional wet-chemical chain- and step-growth mechanisms guide the development of new heterogeneous CVD polymerization techniques. Commonality with inorganic CVD methods facilitates the fabrication of hybrid devices. CVD polymers bridge microfabrication technology with chemical, biological, and nanoparticle systems and assembly. Robust interfaces can be achieved through covalent grafting enabling high-resolution (60 nm) patterning, even on flexible substrates. Utilizing only low-energy input to drive selective chemistry, modest vacuum, and room-temperature substrates, CVD polymerization is compatible with thermally sensitive substrates, such as paper, textiles, and plastics. CVD methods are particularly valuable for insoluble and infusible films, including fluoropolymers, electrically conductive polymers, and controllably crosslinked networks and for the potential to reduce environmental, health, and safety impacts associated with solvents. Quantitative models aid the development of large-area and roll-to-roll CVD polymer reactors. Relevant background, fundamental principles, and selected applications are reviewed. PMID:20544886

  2. 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.

  3. 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.

  4. Kinetics of chemical vapor deposition of boron on molybdenum

    International Nuclear Information System (INIS)

    Experimental rate data of chemical vapor deposition of boron by reduction of boron trichloride with hydrogen are analyzed to determine the reaction mechanism. The experiments were conducted at atmospheric pressure. The weight change of the sample was noted by means of a thermobalance. Molybdenum was used as the substrate. It has been found that the outer layer of the deposited film is Mo/sub 2/B/sub 5/ and the inner layer is MoB, and in the stational state of the reaction, the diffusion in the solid state is considered not to be rate controlling. When mass transport limitation was absent, the reaction orders with respect to boron trichloride and hydrogen were one third and one half, respectively. By comparing these orders with those obtained from Langmuir-Hinshelwood type equations, the rate controlling mechanism is identified to be the desorption of hydrogen chloride from the substrate

  5. Ion beam induced conductivity in chemically vapor deposited diamond films

    International Nuclear Information System (INIS)

    Polycrystalline diamond films deposited by the microwave plasma chemical vapor deposition (CVD) technique onto quartz substrates have been irradiated with 100 keV C and 320 keV Xe ions at room temperature and at 200 degree C. The dose dependence of the electrical conductivity measured in situ exhibited complicated, nonmonotonic behavior. High doses were found to induce an increase of up to ten orders of magnitude in the electrical conductivity of the film. The dose dependence of the conductivity for the CVD films was found to be very similar to that measured for natural, type IIa, single-crystal diamonds irradiated under identical conditions. This result suggests that the conduction mechanism in ion beam irradiated polycrystalline CVD diamond films is not dominated by grain boundaries and graphitic impurities as one might have expected, but rather is determined by the intrinsic properties of diamond itself

  6. Nitrogen-doped graphene by microwave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Rapid synthesis of nitrogen-doped, few-layer graphene films on Cu foil is achieved by microwave plasma chemical vapor deposition. The films are doped during synthesis by introduction of nitrogen gas in the reactor. Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and scanning tunneling microscopy reveal crystal structure and chemical characteristics. Nitrogen concentrations up to 2 at.% are observed, and the limit is linked to the rigidity of graphene films on copper surfaces that impedes further nitrogen substitutions of carbon atoms. The entire growth process requires only a few minutes without supplemental substrate heating and offers a promising path toward large-scale synthesis of nitrogen-doped graphene films. - Highlights: ► Rapid synthesis of nitrogen doped few layer graphene on Cu foil. ► Defect density increment on 2% nitrogen doping. ► Nitrogen doped graphene is a good protection to the copper metallic surface

  7. The versatility of hot-filament activated chemical vapor deposition

    International Nuclear Information System (INIS)

    In the field of activated chemical vapor deposition (CVD) of polycrystalline diamond films, hot-filament activation (HF-CVD) is widely used for applications where large deposition areas are needed or three-dimensional substrates have to be coated. We have developed processes for the deposition of conductive, boron-doped diamond films as well as for tribological crystalline diamond coatings on deposition areas up to 50 cm x 100 cm. Such multi-filament processes are used to produce diamond electrodes for advanced electrochemical processes or large batches of diamond-coated tools and parts, respectively. These processes demonstrate the high degree of uniformity and reproducibility of hot-filament CVD. The usability of hot-filament CVD for diamond deposition on three-dimensional substrates is well known for CVD diamond shaft tools. We also develop interior diamond coatings for drawing dies, nozzles, and thread guides. Hot-filament CVD also enables the deposition of diamond film modifications with tailored properties. In order to adjust the surface topography to specific applications, we apply processes for smooth, fine-grained or textured diamond films for cutting tools and tribological applications. Rough diamond is employed for grinding applications. Multilayers of fine-grained and coarse-grained diamond have been developed, showing increased shock resistance due to reduced crack propagation. Hot-filament CVD is also used for in situ deposition of carbide coatings and diamond-carbide composites, and the deposition of non-diamond, silicon-based films. These coatings are suitable as diffusion barriers and are also applied for adhesion and stress engineering and for semiconductor applications, respectively

  8. 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.

  9. Effect of vapor-phase oxygen on chemical vapor deposition growth of graphene

    Science.gov (United States)

    Terasawa, Tomo-o.; Saiki, Koichiro

    2015-03-01

    To obtain a large-area single-crystal graphene, chemical vapor deposition (CVD) growth on Cu is considered the most promising. Recently, the surface oxygen on Cu has been found to suppress the nucleation of graphene. However, the effect of oxygen in the vapor phase was not elucidated sufficiently. Here, we investigate the effect of O2 partial pressure (PO2) on the CVD growth of graphene using radiation-mode optical microscopy. The nucleation density of graphene decreases monotonically with PO2, while its growth rate reaches a maximum at a certain pressure. Our results indicate that PO2 is an important parameter to optimize in the CVD growth of graphene.

  10. 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.

  11. 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.

  12. Characterization of Carbon Nanotubes Grown by Chemical Vapor Deposition

    Science.gov (United States)

    Cochrane, J. C.; Zhu, Shen; Su, Ching-Hua; Lehoczky, S. L.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Since the superior properties of multi-wall carbon nanotubes (MWCNT) could improve numerous devices such as electronics and sensors, many efforts have been made in investigating the growth mechanism of MWCNT to synthesize high quality MWCNT. Chemical vapor deposition (CVD) is widely used for MWCNT synthesis, and scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) are useful methods for analyzing the structure, morphology and composition of MWCNT. Temperature and pressure are two important growth parameters for fabricating carbon nanotubes. In MWCNT growth by CVD, the plasma assisted method is normally used for low temperature growth. However a high temperature environment is required for thermal CVD. A systematic study of temperature and pressure-dependence is very helpful to understanding MWCNT growth. Transition metal particles are commonly used as catalysis in carbon nanotube growth. It is also interesting to know how temperature and pressure affect the interface of carbon species and catalyst particles

  13. Neutron detectors made from chemically vapor deposited semiconductors

    International Nuclear Information System (INIS)

    In this paper, the authors present the results of investigations on the use of semiconductors deposited by chemical vapor deposition (CVD) for the fabrication of neutron detectors. For this purpose, 20 microm thick hydrogenated amorphous silicon (a-Si:H) pin diodes and 100 microm thick polycrystalline diamond resistive detectors were fabricated. The detectors were coupled to a neutron-charged particle converter: a layer of either gadolinium or boron (isotope 10 enriched) deposited by evaporation. They have demonstrated the capability of such neutron detectors to operate at neutron fluxes ranging from 101 to 106 neutrons/cm2.s. The fabrication of large area detectors for neutron counting or cartography through the use of multichannel reading circuits is discussed. The advantages of these detectors include the ability to produce large area detectors at low cost, radiation hardness (∼ 4 Mrad for a-Si:H and ∼ 100 Mrad for diamond), and for diamond, operation at temperatures up to 500 C. These properties enable the use of these devices for neutron detection in harsh environments. Thermal neutron detection efficiency up to 22% and 3% are expected by coupling a-Si:H diodes and diamond detectors to 3 microm thick gadolinium (isotope 157) and 2 microm thick boron layers, respectively

  14. Coating particles by chemical vapor deposition in fluidized bed reactors

    International Nuclear Information System (INIS)

    A technique to deposit a thin, adherent, uniformly dispersed coating onto the individual particles in a batch of granular or powdered material is described. We have been able to apply successfully a number of coatings to a variety of particulate materials using a fluidized-bed chemical vapor deposition (CVD) technique. By means of this technique we used tri-isobutylaluminum to apply adherent coatings of aluminum on powdered mica and powdered nickel. The powdered mica was also coated with titanium in a fluidized bed reactor in which titanium precursors were generated in situ by the reaction between HCl and metallic titanium. Post treatment of the titanium coated mica with ammonia produced agglomerates coated with TiN. These systems demonstrate the potential utility of the fluidized bed reactor for depositing a variety of coatings onto metallic and non-metallic dispersed materials. Preparation of such coated powders is likely to be valuable in a variety of industrial applications, such as the manufacture of composite structures. (orig.)

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

  16. 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. PMID:27043922

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

    Science.gov (United States)

    Li, Ming-Yang; Tang, Chiu-Chun; Ling, D. C.; Li, L. J.; Chi, C. C.; Chen, Jeng-Chung

    2013-12-01

    We investigate the effects of defect scatterings on the electric transport properties of chemical vapor deposited (CVD) graphene by measuring the carrier density dependence of the magneto-conductivity. To clarify the dominant scattering mechanism, we perform extensive measurements on large-area samples with different mobility to exclude the edge effect. We analyze our data with the major scattering mechanisms such as short-range static scatters, short-range screened Coulomb disorders, and weak-localization (WL). We establish that the charged impurities are the predominant scatters because there is a strong correlation between the mobility and the charge impurity density. Near the charge neutral point (CNP), the electron-hole puddles that are induced by the charged impurities enhance the inter-valley scattering, which is favorable for WL observations. Away from the CNP, the charged-impurity-induced scattering is weak because of the effective screening by the charge carriers. As a result, the local static structural defects govern the charge transport. Our findings provide compelling evidence for understanding the scattering mechanisms in graphene and pave the way for the improvement of fabrication techniques to achieve high-quality CVD graphene.

  18. Structure of chemical vapor deposition titania/silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Leboda, R.; Gun' ko, V.M.; Marciniak, M.; Malygin, A.A.; Malkin, A.A.; Grzegorczyk, W.; Trznadel, B.J.; Pakhlov, E.M.; Voronin, E.F.

    1999-10-01

    The structure of porous silica gel/titania synthesized using chemical vapor deposition (CVD) of titania via repeated reactions of TiCl{sub 4} with the surface and subsequent hydrolysis of residual Ti-Cl bonds at different temperatures was investigated by means of low-temperature nitrogen adsorption-desorption, X-ray diffraction (XRD), IR spectroscopy, and theoretical methods. A globular model of porous solids with corpuscular structure was applied to estimate the porosity parameters of titania/silica gel adsorbents. The utilization of this model is useful, for example, to predict conditions for synthesis of titania/silica with a specified structure. Analysis of pore parameters and fractal dimension suggests that the porosity and fractality of samples decrease with increasing amount of TiO{sub 2} covering the silica gel surface in a nonuniform layer, which represents small particles embedded in pores and larger particles formed at the outer surface of silica globules. Theoretical simulation shows that the Si-O-Ti linkages between the cover and the substrate can be easily hydrolyzed, which is in agreement with the IR data corresponding to the absence of a band at 950 cm {sup {minus}1} (characteristic of Si-O-Ti bridges) independent of the concentration of CVD-titania.

  19. 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.

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

    Science.gov (United States)

    Zubkov, V. I.; Kucherova, O. V.; Bogdanov, S. A.; Zubkova, A. V.; Butler, J. E.; Ilyin, V. A.; Afanas'ev, A. V.; Vikharev, A. L.

    2015-10-01

    Precision admittance spectroscopy measurements over wide temperature and frequency ranges were carried out for chemical vapor deposition epitaxial diamond samples doped with various concentrations of boron. It was found that the experimentally detected boron activation energy in the samples decreased from 314 meV down to 101 meV with an increase of B/C ratio from 600 to 18000 ppm in the gas reactants. For the heavily doped samples, a transition from thermally activated valence band conduction to hopping within the impurity band (with apparent activation energy 20 meV) was detected at temperatures 120-150 K. Numerical simulation was used to estimate the impurity DOS broadening. Accurate determination of continuously altering activation energy, which takes place during the transformation of conduction mechanisms, was proposed by numerical differentiation of the Arrhenius plot. With increase of boron doping level the gradual decreasing of capture cross section from 3 × 10-13 down to 2 × 10-17 cm2 was noticed. Moreover, for the hopping conduction the capture cross section becomes 4 orders of magnitude less (˜2 × 10-20 cm2). At T > Troom in doped samples the birth of the second conductance peak was observed. We attribute it to a defect, related to the boron doping of the material.

  1. Growth of graphene underlayers by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Fabiane, Mopeli; Khamlich, Saleh; Bello, Abdulhakeem; Dangbegnon, Julien; Momodu, Damilola; Manyala, Ncholu, E-mail: ncholu.manyala@up.ac.za [Department of Physics, Institute of Applied Materials, SARChI Chair in Carbon Technology and Materials, University of Pretoria, Pretoria 0028 (South Africa); Charlie Johnson, A. T. [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

    2013-11-15

    We present a simple and very convincing approach to visualizing that subsequent layers of graphene grow between the existing monolayer graphene and the copper catalyst in chemical vapor deposition (CVD). Graphene samples were grown by CVD and then transferred onto glass substrates by the bubbling method in two ways, either direct-transfer (DT) to yield poly (methyl methacrylate) (PMMA)/graphene/glass or (2) inverted transfer (IT) to yield graphene/PMMA/glass. Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were used to reveal surface features for both the DT and IT samples. The results from FE-SEM and AFM topographic analyses of the surfaces revealed the underlayer growth of subsequent layers. The subsequent layers in the IT samples are visualized as 3D structures, where the smaller graphene layers lie above the larger layers stacked in a concentric manner. The results support the formation of the so-called “inverted wedding cake” stacking in multilayer graphene growth.

  2. 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.

  3. Development of microforming process combined with selective chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Koshimizu Kazushi

    2015-01-01

    Full Text Available Microforming has been received much attention in the recent decades due to the wide use of microparts in electronics and medical purpose. For the further functionalization of these micro devices, high functional surface with noble metals and nanomaterials are strongly required in bio- and medical fields, such as bio-sensors. To realize the efficient manufacturing process, which can deform the submillimeter scale bulk structure and can construct the micro to nanometer scale structures in one process, the present study proposes a combined process of microforming for metal foils with a selective chemical vapor deposition (SCVD on the active surface of work materials. To clarify the availability of this proposed process, the feasibility of SCVD of functional materials to active surface of titanium (Ti was investigated. CVD of iron (Fe and carbon nanotubes (CNTs which construct CNTs on the patterned surface of active Ti and non-active oxidation layer were conducted. Ti thin films on silicon substrate and Fe were used as work materials and functional materials, respectively. CNTs were grown on only Ti surface. Consequently, the selectivity of the active surface of Ti to the synthesis of Fe particles in CVD process was confirmed.

  4. Grain boundaries in graphene grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    The scientific literature on grain boundaries (GBs) in graphene was reviewed. The review focuses mainly on the experimental findings on graphene grown by chemical vapor deposition (CVD) under a very wide range of experimental conditions (temperature, pressure hydrogen/hydrocarbon ratio, gas flow velocity and substrates). Differences were found in the GBs depending on the origin of graphene: in micro-mechanically cleaved graphene (produced using graphite originating from high-temperature, high-pressure synthesis), rows of non-hexagonal rings separating two perfect graphene crystallites are found more frequently, while in graphene produced by CVD—despite the very wide range of growth conditions used in different laboratories—GBs with more pronounced disorder are more frequent. In connection with the observed disorder, the stability of two-dimensional amorphous carbon is discussed and the growth conditions that may impact on the structure of the GBs are reviewed. The most frequently used methods for the atomic scale characterization of the GB structures, their possibilities and limitations and the alterations of the GBs in CVD graphene during the investigation (e.g. under e-beam irradiation) are discussed. The effects of GB disorder on electric and thermal transport are reviewed and the relatively scarce data available on the chemical properties of the GBs are summarized. GBs are complex enough nanoobjects so that it may be unlikely that two experimentally produced GBs of several microns in length could be completely identical in all of their atomic scale details. Despite this, certain generalized conclusions may be formulated, which may be helpful for experimentalists in interpreting the results and in planning new experiments, leading to a more systematic picture of GBs in CVD graphene. (paper)

  5. Molecular designing of precursors for chemical vapor deposition

    International Nuclear Information System (INIS)

    Both tin oxide and antimony oxide, can act as gas sensing material whose activity/selectivity is enhanced by the incorporation of a second metal. We are interested in the formation of bimetallic and trimetallic carboxylates and alkoxides which can be used as single source precursors for such mixed metal oxides. Sb(dmae)/sub 3/ (dmae=OCH/sub 2/CH/sub 2/(CH/sub 3/)sub 2/ has been prepared from Sb(OC/sub 2/H/sub 5/)/sub 3/ and Hdmae and used to generate the bimetallic materials Sb(dmae)/sub 3/Cd(acac)/sub 2/. Sn(acac)/sub 2/ hydrolyses to yield crystalline cage Sn/sub 4/O/sub 6/(dmae)/sub 4/. Sn(dmae)/sub 2/ can also be used to generate bimetallic materials such as [Sn(dmae)/sub 2/ Cd(acac)/sub 2/]/sub 2/]. Bimetallic and trimetallic carboxylates of general formula [R/sub 3/Ge-CHRCH/sub 2/COO]/sub 4-n/SnRn. [Where R=CH/sub 3/, C/sub 2/H/sub 5/, C/sub 6/H/sub 5/, tolyl, cyclohexyl, (CH/sub 3/)/sub 3/ Si CH/sub 2/-etc.] have been prepared and characterized by various analytic techniques. Chemical vapor deposition using Sb(dmae)/sub 3/ Cd(acac)/sub 2/ and various bimetallic carboxylates yield thin films of Cd/sub 2/Sb/sub 2/O/sub 7/ and SnOGeO respectively. (author)

  6. Review of chemical vapor deposition of graphene and related applications.

    Science.gov (United States)

    Zhang, Yi; Zhang, Luyao; Zhou, Chongwu

    2013-10-15

    Since its debut in 2004, graphene has attracted enormous interest because of its unique properties. Chemical vapor deposition (CVD) has emerged as an important method for the preparation and production of graphene for various applications since the method was first reported in 2008/2009. In this Account, we review graphene CVD on various metal substrates with an emphasis on Ni and Cu. In addition, we discuss important and representative applications of graphene formed by CVD, including as flexible transparent conductors for organic photovoltaic cells and in field effect transistors. Growth on polycrystalline Ni films leads to both monolayer and few-layer graphene with multiple layers because of the grain boundaries on Ni films. We can greatly increase the percentage of monolayer graphene by using single-crystalline Ni(111) substrates, which have smooth surface and no grain boundaries. Due to the extremely low solubility of carbon in Cu, Cu has emerged as an even better catalyst for the growth of monolayer graphene with a high percentage of single layers. The growth of graphene on Cu is a surface reaction. As a result, only one layer of graphene can form on a Cu surface, in contrast with Ni, where more than one layer can form through carbon segregation and precipitation. We also describe a method for transferring graphene sheets from the metal using polymethyl methacrylate (PMMA). CVD graphene has electronic properties that are potentially valuable in a number of applications. For example, few-layer graphene grown on Ni can function as flexible transparent conductive electrodes for organic photovoltaic cells. In addition, because we can synthesize large-grain graphene on Cu foil, such large-grain graphene has electronic properties suitable for use in field effect transistors. PMID:23480816

  7. Pattern Dependency and Loading Effect of Pure-Boron-Layer Chemical-Vapor Deposition

    NARCIS (Netherlands)

    Mohammadi, V.; De Boer, W.B.; Scholtes, T.L.M.; Nanver, L.K.

    2012-01-01

    The pattern dependency of pure-boron (PureB) layer chemical-vapor Deposition (CVD) is studied with respect to the correlation between the deposition rate and features like loading effects, deposition parameters and deposition window sizes. It is shown experimentally that the oxide coverage ratio and

  8. The power source effect on SiOx coating deposition by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    SiOx coatings were prepared by capacitively coupled plasma enhanced chemical vapor deposition on polyethyleneterephtalate substrates in 23 kHz middle-frequency and radio frequency power supplies, respectively, where hexamethyldisiloxane was used as gas source. The influences of discharge conditions on gas phase intermediate species and active radicals for SiOx formation was investigated by mass spectrometry as real-time in-situ diagnosis. The deposited SiOx coating chemical structures were also analyzed by Fourier transform infrared spectroscopy. Meanwhile, the film barrier property, oxygen transmission rate, was measured at 23 oC and 50% humidity circumstance. The better barrier property was obtained in the MF power source depositing SiOx coated PET.

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

    OpenAIRE

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

    2013-01-01

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

  10. Deposition and characterization of Ru thin films prepared by metallorganic chemical vapor deposition

    CERN Document Server

    Kang, S Y; Lee, S K; Hwang, C S; Kim, H J

    2000-01-01

    Ru thin films were deposited at 300 approx 400 .deg. C by using Ru(C sub 5 H sub 4 C sub 2 H sub 5) sub 2 (Ru(EtCp) sub 2) as a precursor and low-pressure metalorganic chemical vapor deposition. The addition of O sub 2 gas was essential to form Ru thin films. The deposition rates of the films were about 200 A/min. For low oxygen addition and high substrate temperature, RuO sub 2 phases were formed. Also, thermodynamic calculations showed that all the supplied oxygen was consumed to oxidize carbon and hydrogen, cracked from the precursor ligand, rather than Ru. Thus, metal films could be obtained There was an optimum oxygen to precursor ratio at which the pure Ru phase could be obtained with minimum generation of carbon and RuO sub 2

  11. Vertically aligned peptide nanostructures using plasma-enhanced chemical vapor deposition.

    Science.gov (United States)

    Vasudev, Milana C; Koerner, Hilmar; Singh, Kristi M; Partlow, Benjamin P; Kaplan, David L; Gazit, Ehud; Bunning, Timothy J; Naik, Rajesh R

    2014-02-10

    In this study, we utilize plasma-enhanced chemical vapor deposition (PECVD) for the deposition of nanostructures composed of diphenylalanine. PECVD is a solvent-free approach and allows sublimation of the peptide to form dense, uniform arrays of peptide nanostructures on a variety of substrates. The PECVD deposited d-diphenylalanine nanostructures have a range of chemical and physical properties depending on the specific discharge parameters used during the deposition process. PMID:24400716

  12. 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

  13. Comparative X-ray photoelectron spectroscopy study of plasma enhanced chemical vapor deposition and micro pressure chemical vapor deposition of phosphorus silicate glass layers after rapid thermal annealing

    International Nuclear Information System (INIS)

    In this paper the bonding state of Phosphorus Silicate Glass (PSG) layers obtained by two different technological approaches, i.e. in two types of reactors: Plasma Enhanced Chemical Vapor Deposition (PECVD) and Micro Pressure Chemical Vapor Deposition (MPCVD) are investigated employing XPS and AES. The PSG layers are deposited at 3800C and 4200C in corresponding reactors. XPS and AES analyses show that Si2p peak recorded from PECVD layers are not as expected at their position characteristics of silicon dioxide but instead they are at the characteristic of elemental silicon. Plasma enhancement during deposition leads to less oxidized and more inhomogeneous layer. After rapid thermal annealing the Si2p peak is situated at position characteristic of silicon dioxide. (authors)

  14. Plasma-enhanced chemical vapor deposition for YBCO film fabrication of superconducting fault-current limiter

    Energy Technology Data Exchange (ETDEWEB)

    Jun, Byung Hyuk; Kim, Chan Joong

    2006-05-15

    Since the high-temperature superconductor of oxide type was founded, many researches and efforts have been performed for finding its application field. The YBCO superconducting film fabricated on economic metal substrate with uniform critical current density is considered as superconducting fault-current limiter (SFCL). There are physical and chemical processes to fabricate superconductor film, and it is understood that the chemical methods are more economic to deposit large area. Among them, chemical vapor deposition (CVD) is a promising deposition method in obtaining film uniformity. To solve the problems due to the high deposition temperature of thermal CVD, plasma-enhanced chemical vapor deposition (PECVD) is suggested. This report describes the principle and fabrication trend of SFCL, example of YBCO film deposition by PECVD method, and principle of plasma deposition.

  15. Plasma-enhanced chemical vapor deposition for YBCO film fabrication of superconducting fault-current limiter

    International Nuclear Information System (INIS)

    Since the high-temperature superconductor of oxide type was founded, many researches and efforts have been performed for finding its application field. The YBCO superconducting film fabricated on economic metal substrate with uniform critical current density is considered as superconducting fault-current limiter (SFCL). There are physical and chemical processes to fabricate superconductor film, and it is understood that the chemical methods are more economic to deposit large area. Among them, chemical vapor deposition (CVD) is a promising deposition method in obtaining film uniformity. To solve the problems due to the high deposition temperature of thermal CVD, plasma-enhanced chemical vapor deposition (PECVD) is suggested. This report describes the principle and fabrication trend of SFCL, example of YBCO film deposition by PECVD method, and principle of plasma deposition

  16. Chemical vapor deposition and characterization of titanium dioxide thin films

    Science.gov (United States)

    Gilmer, David Christopher

    1998-12-01

    The continued drive to decrease the size and increase the speed of micro-electronic Metal-Oxide-Semiconductor (MOS) devices is hampered by some of the properties of the SiOsb2 gate dielectric. This research has focused on the CVD of TiOsb2 thin films to replace SiOsb2 as the gate dielectric in MOS capacitors and transistors. The relationship of CVD parameters and post-deposition anneal treatments to the physical and electrical properties of thin films of TiOsb2 has been studied. Structural and electrical characterization of TiOsb2 films grown from the CVD precursors tetraisopropoxotitanium (IV) (TTIP) and TTIP plus Hsb2O is described in Chapter 3. Both types of deposition produced stoichiometric TiOsb2 films comprised of polycrystalline anatase, but the interface properties were dramatically degraded when water vapor was added. Films grown with TTIP in the presence of Hsb2O contained greater than 50% more hydrogen than films grown using only TTIP and the hydrogen content of films deposited in both wet and dry TTIP environments decreased sharply with a post deposition Osb2 anneal. A significant thickness variation of the dielectric constant was observed which could be explained by an interfacial oxide and the finite accumulation thickness. Fabricated TiOsb2 capacitors exhibited electrically equivalent SiOsb2 gate dielectric thicknesses and leakage current densities as low as 38, and 1×10sp{-8} Amp/cmsp2 respectively. Chapter 4 discusses the low temperature CVD of crystalline TiOsb2 thin films deposited using the precursor tetranitratotitanium (IV), TNT, which produces crystalline TiOsb2 films of the anatase phase in UHV-CVD at temperatures as low as 184sp°C. Fabricated TiOsb2 capacitors exhibited electrically equivalent SiOsb2 gate dielectric thicknesses and leakage current densities as low as 17, and 1×10sp{-8} Amp/cmsp2 respectively. Chapter 5 describes the results of a comparison of physical and electrical properties between TiOsb2 films grown via LPCVD using

  17. Thin films of barium fluoride scintillator deposited by chemical vapor deposition

    International Nuclear Information System (INIS)

    We have used metal-organic chemical vapor deposition (MOCVD) technology to coat optical substrates with thin (≅ 1-10 μm thick) films of inorganic BaF2 scintillator. Scanning electron microscope (SEM) photographs indicate that high-quality epitaxial crystalline film growth was achieved, with surface defects typically smaller than optical wavelengths. The scintillation light created by the deposition of ionizing radiation in the scintillating films was measured with a photomultiplier and shown to be similar to bulk melt-grown crystals. The results demonstrate the potential of these composite optical materials for planar and fiber scintillation radiation detectors in high energy and nuclear physics, synchrotron radiation research, and in radiation and X-ray imaging and monitoring. (orig.)

  18. Electron emission from nano-structured carbon films fabricated by hot-filament chemical-vapor deposition and microwave plasma-enhanced chemical vapor deposition

    CERN Document Server

    Park, K H; Lee, K M; Oh, S G; Lee, S I; Koh, K H

    2000-01-01

    The electron-emission characteristics of nano-structured carbon films fabricated by using the HFCVD (hot- filament chemical-vapor deposition) and the MPECVD (microwave plasma-enhanced chemical-vapor deposition) methods with a metal catalyst are presented. According to our observation, neither the formation nor the alignment of nano tubes is absolutely necessary to realize carbon-based electron emitters. However, utilization of chrome as an interlayer between Si substrates and metal catalyst particles results in a great improvement in the emission characteristics and the mechanical stability. Also, fabrication of good electron-emitting carbon films on glass substrates, with sputter-deposited chrome electrodes,at a nominal temperature approx 615 .deg. C was demonstrated.

  19. Early Stages of the Chemical Vapor Deposition of Pyrolytic Carbon Investigated by Atomic Force Microscopy

    OpenAIRE

    Pfrang, Andreas; WAN Yong-Zhong; Schimmel, Thomas

    2009-01-01

    The early stages of chemical vapor deposition of pyrolytic carbon on planar silicon substrates were studied by the atomic force microscopy-based technique of chemical contrast imaging. Short deposition times were chosen to focus on the early stages of the deposition process, and three different types of nucleation were found: random nucleation of single islands, nucleation of carbon islands along lines and secondary nucleation which corresponds to the nucleation of carbon islands at the edges...

  20. Ballistic transport in graphene grown by chemical vapor deposition

    International Nuclear Information System (INIS)

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

  1. Polyimide (PI) films by chemical vapor deposition (CVD): Novel design, experiments and characterization

    OpenAIRE

    Puig-Pey González, Jaime; Lamure, Alain; Senocq, François

    2007-01-01

    International audience Polyimide (PI) has been deposited by chemical vapor deposition (CVD) under vacuum over the past 20 years. In the early nineties, studies, experiences and characterization were mostly studied as depositions from the co-evaporation of the dianhydride and diamine monomers. Later on, several studies about its different applications due to its interesting mechanical and electrical properties enhanced its development. Nowadays, not many researches around PI deposition are ...

  2. 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

  3. High Pressure Chemical Vapor Deposition of Hydrogenated Amorphous Silicon Films and Solar Cells.

    Science.gov (United States)

    He, Rongrui; Day, Todd D; Sparks, Justin R; Sullivan, Nichole F; Badding, John V

    2016-07-01

    Thin films of hydrogenated amorphous silicon can be produced at MPa pressures from silane without the use of plasma at temperatures as low as 345 °C. High pressure chemical vapor deposition may open a new way to low cost deposition of amorphous silicon solar cells and other thin film structures over very large areas in very compact, simple reactors. PMID:27174318

  4. Titanium-based coatings on copper by chemical vapor deposition in fluidized bed reactors

    International Nuclear Information System (INIS)

    Titanium, TiN and TiOx coatings were deposited on copper and Cu-Ni alloys by chemical vapor deposition in fluidized bed reactors. These coatings provide the copper with a tenfold increase in corrosion resistance in chloride aqueous environments, as determined by a.c. impedance studies. (orig.)

  5. 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.

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

    International Nuclear Information System (INIS)

    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

  7. 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…

  8. Low pressure chemical vapor deposition of niobium coating on silicon carbide

    International Nuclear Information System (INIS)

    Nb coatings were prepared on a SiC substrate by low pressure chemical vapor deposition using NbCl5. Thermodynamic calculations were performed to study the effect of temperature and partial pressure of NbCl5 on the final products. The as-deposited coatings were characterized by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. The Nb coatings are oriented and grow in the preferred (2 0 0) plane and (2 1 1) plane, at 1173 K and 1223-1423 K, respectively. At 1123-1273 K, the deposition is controlled by the surface kinetic processes. The activation energy is found to be 133 kJ/mol. At 1273-1373 K, the deposition is controlled by the mass transport processes. The activation energy is found to be 46 kJ/mol. The growth mechanism of the chemical vapor deposited Nb is also discussed based on the morphologies and the deposition rates.

  9. Electro-Optical Properties of Carbon Nanotubes Obtained by High Density Plasma Chemical Vapor Deposition

    OpenAIRE

    Ana Paula Mousinho; Ronaldo D. Mansano

    2011-01-01

    In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a new concept of plasma generation: a planar coil is coupled to an RF system for plasma generation. This was used together with an electrostatic shield, for plasma densification, thereby obtaining high-density plasmas. The carbon nanotubes were deposited using pure methane plasmas. T...

  10. Sealing of micromachined cavities using chemical vapor deposition methods: characterization and optimization

    OpenAIRE

    Liu, Chang; Tai, Yu-Chong

    1999-01-01

    This paper presents results of a systematic investigation to characterize the sealing of micromachined cavities using chemical vapor deposition (CVD) methods. We have designed and fabricated a large number and variety of surface-micromachined test structures with different etch-channel dimensions. Each cavity is then subjected to a number of sequential CVD deposition steps with incremental thickness until the cavity is successfully sealed. At etch deposition interval, the sealing status of ev...

  11. 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.

  12. Properties of Plasma Enhanced Chemical Vapor Deposition Barrier Coatings and Encapsulated Polymer Solar Cells

    International Nuclear Information System (INIS)

    In this paper, we report silicon oxide coatings deposited by plasma enhanced chemical vapor deposition technology (PECVD) on 125 μm polyethyleneterephthalate (PET) surfaces for the purpose of the shelf lifetime extension of sealed polymer solar cells. After optimization of the processing parameters, we achieved a water vapor transmission rate (WVTR) of ca. 10−3 g/m2/day with the oxygen transmission rate (OTR) less than 0.05 cc/m2/day, and succeeded in extending the shelf lifetime to about 400 h in encapsulated solar cells. And then the chemical structure of coatings related to the properties of encapsulated cell was investigated in detail. (plasma technology)

  13. Opening of triangular hole in triangular-shaped chemical vapor deposited hexagonal boron nitride crystal

    OpenAIRE

    Sharma, Subash; Kalita, Golap; Vishwakarma, Riteshkumar; Zulkifli, Zurita; Tanemura, Masaki

    2015-01-01

    In-plane heterostructure of monolayer hexagonal boron nitride (h-BN) and graphene is of great interest for its tunable bandgap and other unique properties. Here, we reveal a H2-induced etching process to introduce triangular hole in triangular-shaped chemical vapor deposited individual h-BN crystal. In this study, we synthesized regular triangular-shaped h-BN crystals with the sizes around 2-10 μm on Cu foil by chemical vapor deposition (CVD). The etching behavior of individual h-BN crystal w...

  14. 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

  15. Fluidized bed as a solid precursor delivery system in a chemical vapor deposition reactor

    OpenAIRE

    Vahlas, Constantin; Caussat, Brigitte; Senocq, François; Gladfelter, Wayne L.; Sarantopoulos, Christos; Toro, David; Moersch, Tyler

    2005-01-01

    Chemical vapor deposition (CVD) using precursors that are solids at operating temperatures and pressures, presents challenges due to their relatively low vapor pressures. In addition, the sublimation rates of solid state precursors in fixed bed reactors vary with particle and bed morphology. In a recent patent application, the use of fluidized bed (FB) technology has been proposed to provide high, reliable, and reproducible flux of such precursors in CVD processes. In the present contribution...

  16. 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.

  17. Development of a Computational Chemical Vapor Deposition Model: Applications to Indium Nitride and Dicyanovinylaniline

    Science.gov (United States)

    Cardelino, Carlos

    1999-01-01

    A computational chemical vapor deposition (CVD) model is presented, that couples chemical reaction mechanisms with fluid dynamic simulations for vapor deposition experiments. The chemical properties of the systems under investigation are evaluated using quantum, molecular and statistical mechanics models. The fluid dynamic computations are performed using the CFD-ACE program, which can simulate multispecies transport, heat and mass transfer, gas phase chemistry, chemistry of adsorbed species, pulsed reactant flow and variable gravity conditions. Two experimental setups are being studied, in order to fabricate films of: (a) indium nitride (InN) from the gas or surface phase reaction of trimethylindium and ammonia; and (b) 4-(1,1)dicyanovinyl-dimethylaminoaniline (DCVA) by vapor deposition. Modeling of these setups requires knowledge of three groups of properties: thermodynamic properties (heat capacity), transport properties (diffusion, viscosity, and thermal conductivity), and kinetic properties (rate constants for all possible elementary chemical reactions). These properties are evaluated using computational methods whenever experimental data is not available for the species or for the elementary reactions. The chemical vapor deposition model is applied to InN and DCVA. Several possible InN mechanisms are proposed and analyzed. The CVD model simulations of InN show that the deposition rate of InN is more efficient when pulsing chemistry is used under conditions of high pressure and microgravity. An analysis of the chemical properties of DCVA show that DCVA dimers may form under certain conditions of physical vapor transport. CVD simulations of the DCVA system suggest that deposition of the DCVA dimer may play a small role in the film and crystal growth processes.

  18. Properties of nitrogen doped silicon films deposited by low-pressure chemical vapor deposition from silane and ammonia

    OpenAIRE

    Temple Boyer, Pierre; Jalabert, L.; Masarotto, L.; Alay, Josep Lluís; Morante i Lleonart, Joan Ramon

    2000-01-01

    Nitrogen doped silicon (NIDOS) films have been deposited by low-pressure chemical vapor deposition from silane SiH4 and ammonia NH3 at high temperature (750°C) and the influences of the NH3/SiH4 gas ratio on the films deposition rate, refractive index, stoichiometry, microstructure, electrical conductivity, and thermomechanical stress are studied. The chemical species derived from silylene SiH2 into the gaseous phase are shown to be responsible for the deposition of NIDOS and/or (silicon rich...

  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. Electronic Transport in Chemical Vapor Deposited Graphene Synthesized on Cu: Quantum Hall Effect and Weak Localization

    OpenAIRE

    Cao, H. L.; Yu, Q. K.; Jauregui, L. A.; Tian, J; Wu, W.; Z. Liu; Jalilian, R.; Benjamin, D. K.; Jiang, Z.; J. Bao; Pei, S S; Chen, Y P

    2009-01-01

    We report on electronic properties of graphene synthesized by chemical vapor deposition (CVD) on copper then transferred to SiO2/Si. Wafer-scale (up to 4 in.) graphene films have been synthesized, consisting dominantly of monolayer graphene as indicated by spectroscopic Raman mapping. Low temperature transport measurements are performed on microdevices fabricated from such CVD graphene, displaying ambipolar field ...

  1. 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.

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

    International Nuclear Information System (INIS)

    A series of cobalt half-sandwich complexes of type [Co(η5-C5H5)(L)(L′)] (1: L, L′ = 1,5-hexadiene; 2: L = P(OEt)3, L′ = H2C=CHSiMe3; 3: L = L′ = P(OEt)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)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/SiO2 (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

  3. 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.

  4. Super-Hydrophobic and Oloephobic Crystalline Coatings by Initiated Chemical Vapor Deposition

    OpenAIRE

    Coclite, Anna Maria; Shi, Yujun; Gleason, Karen K.

    2013-01-01

    Preferred crystallographic orientation (texture) in thin films frequently has a strong effect on the properties of the materials and it is important for stable surface properties. Organized molecular films of poly-perfluorodecylacrylate p(PFDA) were deposited by initiated Chemical Vapor Deposition (iCVD). The high tendency of p(PFDA) to crystallize has been fully retained in the polymers prepared by iCVD. The degree of crystallinity and the preferred orientation of the perfluoro side chains, ...

  5. Plasma enhanced chemical vapor deposition of zirconium nitride thin films

    International Nuclear Information System (INIS)

    Depositions of high quality zirconium nitride, (Zr3N4), films using the metal-organic precursor Zr(NEt2)4 were carried out in a microwave argon/ammonia plasma (2.45 GHz). The films were deposited on crystalline silicon wafers and quartz substrates at temperatures of 200--400 C. The transparent yellow films have resistivity values greater than MΩ cm. The stoichiometry is N/Zr = 1.3, with less than 5 atom % carbon and little or no oxygen. The hydrogen content is less than 9 atom %, and it does not vary with deposition temperature. The growth rates range from 600 to 1,200 angstrom/min, depending on the flow rates and precursor bubbler temperature. X-ray diffraction studies show a Zr3N4 film deposited at 400 C is polycrystalline with some (220) orientation. The crystallite size is approximately 30 angstrom. The band gap, as estimated from transmission spectra, is 3.1 eV

  6. Second harmonic generation in ZnO thin films fabricated by metalorganic chemical vapor deposition

    Science.gov (United States)

    Liu, C. Y.; Zhang, B. P.; Binh, N. T.; Segawa, Y.

    2004-07-01

    Second harmonic generation (SHG) from ZnO thin films fabricated by metalorganic chemical vapor deposition (MOCVD) technique was carried out. By comparing the second harmonic signal generated in a series of ZnO films with different deposition temperatures, we conclude that a significant part of second harmonic signal is generated at the film deposited with appropriate temperature. The second-order susceptibility tensor χ(2)zzz=9.2 pm/V was deduced for a film deposited at 250 °C.

  7. Photoluminescence properties of poly (p-phenylene vinylene) films deposited by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gedelian, Cynthia A. [Department of Physics, Applied Physics, and Astronomy, Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy 12180-3590, NY (United States); Rajanna, K.C., E-mail: kcrajannaou@yahoo.com [Department of Chemistry, Osmania University, Hyderabad 500007, Andhra Pradesh (India); Premerlani, Brian; Lu, Toh-Ming [Department of Physics, Applied Physics, and Astronomy, Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy 12180-3590, NY (United States)

    2014-01-15

    Photoluminescence spectra of PPV at varying thicknesses and temperatures have been studied. A study of the quenching of the polymer film using a modified version of fluorescence spectroscopy reveals interface effects dominating at thicknesses below about 600 Å, while bulk effects dominate at higher thicknesses. The application of the Stern–Volmer equation to solid film is discussed. Stern–Volmer plots were nonlinear with downward deviations at higher thickness of the film which was explained due to self-quenching in films and larger conformational change and increased restriction from change in electron density due to electron transition during excitation in bulk polymer films over 60 nm thick. PPV deposited into porous (∼4 nm in diameter) nanostructured substrate shows a larger 0–0 than 0–1 transition peak intensity and decreased disorder in the films due to structure imposed by substrate matrix. Temperature dependent effects are measured for a film at 500 Å, right on the border between the two areas. PPV films deposited on porous methyl silsesquioxane (MSQ) were also examined in order to compare the flat film to a substrate that allows for the domination of interface effects. The enthalpies of the first two peaks are very similar, but the third peak demonstrates a lower enthalpy and a larger wavelength shift with temperature. Films deposited inside pores show a smaller amount of disorder than flat films. Calculation of the Huang–Rhys factor at varying temperatures for the flat film and film in porous MSQ shows large temperature dependence for the flat film but a smaller amount of disorder in the nanostructured film. -- Highlights: • Poly (p-phenylene vinylene) films deposited by chemical vapor deposition exhibited photoluminescence properties. • Fluorescence spectra of the polymer films revealed interface effects dominating at thicknesses below about 600 Å, while bulk effects dominate at higher thicknesses. • Stern–Volmer plots were

  8. Photoluminescence properties of poly (p-phenylene vinylene) films deposited by chemical vapor deposition

    International Nuclear Information System (INIS)

    Photoluminescence spectra of PPV at varying thicknesses and temperatures have been studied. A study of the quenching of the polymer film using a modified version of fluorescence spectroscopy reveals interface effects dominating at thicknesses below about 600 Å, while bulk effects dominate at higher thicknesses. The application of the Stern–Volmer equation to solid film is discussed. Stern–Volmer plots were nonlinear with downward deviations at higher thickness of the film which was explained due to self-quenching in films and larger conformational change and increased restriction from change in electron density due to electron transition during excitation in bulk polymer films over 60 nm thick. PPV deposited into porous (∼4 nm in diameter) nanostructured substrate shows a larger 0–0 than 0–1 transition peak intensity and decreased disorder in the films due to structure imposed by substrate matrix. Temperature dependent effects are measured for a film at 500 Å, right on the border between the two areas. PPV films deposited on porous methyl silsesquioxane (MSQ) were also examined in order to compare the flat film to a substrate that allows for the domination of interface effects. The enthalpies of the first two peaks are very similar, but the third peak demonstrates a lower enthalpy and a larger wavelength shift with temperature. Films deposited inside pores show a smaller amount of disorder than flat films. Calculation of the Huang–Rhys factor at varying temperatures for the flat film and film in porous MSQ shows large temperature dependence for the flat film but a smaller amount of disorder in the nanostructured film. -- Highlights: • Poly (p-phenylene vinylene) films deposited by chemical vapor deposition exhibited photoluminescence properties. • Fluorescence spectra of the polymer films revealed interface effects dominating at thicknesses below about 600 Å, while bulk effects dominate at higher thicknesses. • Stern–Volmer plots were

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

    International Nuclear Information System (INIS)

    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 ∼ 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.

  10. Graphene growth with giant domains using chemical vapor deposition

    OpenAIRE

    Yong, Virginia; Hahn, H. Thomas

    2011-01-01

    We report the first demonstration of the growth of giant graphene domains on platinum (Pt), which results in a uniform bilayer graphene film with domain sizes of millimetre scale. These giant graphene domains are attributed to the giant Pt grains attained in post-deposition annealed Pt thin films that exhibit a strong dependency on the Pt film thickness. Giant grains have been claimed to occur in other metallic materials under appropriate film thicknesses and processing conditions. Our findin...

  11. Coating of ceramic powders by chemical vapor deposition techniques (CVD)

    International Nuclear Information System (INIS)

    New ceramic materials with selected advanced properties can be designed by coating of ceramic powders prior to sintering. By variation of the core and coating material a large number of various powders and ceramic materials can be produced. Powders which react with the binder phase during sintering can be coated with stable materials. Thermal expansion of the ceramic materials can be adjusted by varying the coating thickness (ratio core/layer). Electrical and wear resistant properties can be optimized for electrical contacts. A fluidized bed reactor will be designed which allow the deposition of various coatings on ceramic powders. (author)

  12. Growth and properties of few-layer graphene prepared by chemical vapor deposition

    OpenAIRE

    Park, Hye Jin; Meyer, Jannik; Roth, Siegmar; Skakalova, Viera

    2009-01-01

    The structure, and electrical, mechanical and optical properties of few-layer graphene (FLG) synthesized by chemical vapor deposition (CVD) on a Ni coated substrate were studied. Atomic resolution transmission electron microscope (TEM) images show highly crystalline single layer parts of the sample changing to multilayer domains where crystal boundaries are connected by chemical bonds. This suggests two different growth mechanisms. CVD and carbon segregation participate in the growth process ...

  13. 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)

  14. Two dimensional transition metal dichalcogenides grown by chemical vapor deposition

    OpenAIRE

    Tsang, Ka-yi; 曾家懿

    2014-01-01

    An atomically thin film of semiconducting transition metal dichalcogenides (TMDCs) is emerging as a class of key materials in chemistry and physics due to their remarkable chemical and electronic properties. The TMDCs are layered materials with weak out-of-plane van der Waals (vdW) interaction and strong in-plane covalent bonding enabling scalable exfoliation into two-dimensional (2D) layers of atomic thickness. The growth techniques to prepare these 2D TMDC materials in high yield and large ...

  15. 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.

  16. Atmospheric pressure chemical vapor deposition of ZnO: Process modeling and experiments

    Energy Technology Data Exchange (ETDEWEB)

    Deelen, J. van, E-mail: joop.vandeelen@tno.nl [TNO, Department of Thin Film Technology, De Rondom 1, 5612 AP Eindhoven (Netherlands); Illiberi, A.; Kniknie, B.; Beckers, E.H.A. [TNO, Department of Thin Film Technology, De Rondom 1, 5612 AP Eindhoven (Netherlands); Simons, P.J.P.M.; Lankhorst, A. [Celsian, De Rondom 1, 5612 AP Eindhoven (Netherlands)

    2014-03-31

    The deposition of zinc oxide has been performed by atmospheric pressure chemical vapor deposition and trends in growth rates are compared with the literature. Diethylzinc and tertiary butanol were used as the primary reactants and deposition rates above 800 nm/min were obtained. The reaction kinetics were studied and detailed process modeling based on a reaction mechanism that includes the formation of an alkylzinc alkoxide intermediate product is discussed. This mechanism can explain the temperature dependent variety in deposition profiles observed in the static deposition experiments. The capability of modeling to gain insight in the local process conditions inside a reactor is demonstrated. - Highlights: • ZnO deposition at high rates of 800 nm/min • Modeling based on two step mechanism gives good fit. • Modeling gives insight in the inside of the reactor. • Modeling can even predict static deposition profiles.

  17. Atmospheric pressure chemical vapor deposition of ZnO: Process modeling and experiments

    International Nuclear Information System (INIS)

    The deposition of zinc oxide has been performed by atmospheric pressure chemical vapor deposition and trends in growth rates are compared with the literature. Diethylzinc and tertiary butanol were used as the primary reactants and deposition rates above 800 nm/min were obtained. The reaction kinetics were studied and detailed process modeling based on a reaction mechanism that includes the formation of an alkylzinc alkoxide intermediate product is discussed. This mechanism can explain the temperature dependent variety in deposition profiles observed in the static deposition experiments. The capability of modeling to gain insight in the local process conditions inside a reactor is demonstrated. - Highlights: • ZnO deposition at high rates of 800 nm/min • Modeling based on two step mechanism gives good fit. • Modeling gives insight in the inside of the reactor. • Modeling can even predict static deposition profiles

  18. 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.

  19. Chemical vapor deposition of atomically thin materials for membrane dialysis applications

    Science.gov (United States)

    Kidambi, Piran; Mok, Alexander; Jang, Doojoon; Boutilier, Michael; Wang, Luda; Karnik, Rohit; Microfluidics; Nanofluidics Research Lab Team

    2015-11-01

    Atomically thin 2D materials like graphene and h-BN represent a new class of membranes materials. They offer the possibility of minimum theoretical membrane transport resistance along with the opportunity to tune pore sizes at the nanometer scale. Chemical vapor deposition has emerged as the preferable route towards scalable, cost effective synthesis of 2D materials. Here we show selective molecular transport through sub-nanometer diameter pores in graphene grown via chemical vapor deposition processes. A combination of pressure driven and diffusive transport measurements shows evidence for size selective transport behavior which can be used for separation by dialysis for applications such as desalting of biomolecular or chemical solutions. Principal Investigator

  20. LASER-INDUCED DECOMPOSITION OF METAL CARBONYLS FOR CHEMICAL VAPOR DEPOSITION OF MICROSTRUCTURES

    OpenAIRE

    Tonneau, D.; Auvert, G.; Pauleau, Y.

    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...

  1. 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.

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

    International Nuclear Information System (INIS)

    We clarify the difference between the SiH4 consumption efficiency η and the SiH4 depletion fraction D, as measured in the pumping line and the actual reactor of an industrial plasma-enhanced chemical vapor deposition system. In the absence of significant polysilane and powder formation, η is proportional to the film growth rate. Above a certain powder formation threshold, any additional amount of SiH4 consumed translates into increased powder formation rather than into a faster growing Si film. In order to discuss a zero-dimensional analytical model and a two-dimensional numerical model, we measure η as a function of the radio frequency (RF) power density coupled into the plasma, the total gas flow rate, the input SiH4 concentration, and the reactor pressure. The adjunction of a small trimethylboron flow rate increases η and reduces the formation of powder, while the adjunction of a small disilane flow rate decreases η and favors the formation of powder. Unlike η, D is a location-dependent quantity. It is related to the SiH4 concentration in the plasma cp, and to the phase of the growing Si film, whether the substrate is glass or a c-Si wafer. In order to investigate transient effects due to the RF matching, the precoating of reactor walls, or the introduction of a purifier in the gas line, we measure the gas residence time and acquire time-resolved SiH4 density measurements throughout the ignition and the termination of a plasma

  3. The Synthesized of Carbon Nano tubes from Palm Oil by Topas Atomizer Chemical Vapor Deposition Method

    International Nuclear Information System (INIS)

    This paper focused on preparation of Carbon Nano tubes (CNTs) based on palm oil as a natural resource precursor. The Topas Atomizer was utilized to vapor up the carbon gas into the reaction chamber of Chemical Vapor Deposition (CVD) to yield the CNTs in powder form at the inner wall of the Quartz tube. The purpose of this work was to investigate the effects of deposition temperature from 650 - 850 degree Celsius. The samples characteristics were analyzed by Raman spectroscopy. The results revealed that the increasing of the deposition temperature, the ID/IG ratio decreased from 650 - 850 degree Celsius. The results of Field Emission Scanning Electron Microscopy (FESEM) are also presented. (author)

  4. Reactive Chemical Vapor Deposition Method as New Approach for Obtaining Electroluminescent Thin Film Materials

    Directory of Open Access Journals (Sweden)

    Valentina V. Utochnikova

    2012-01-01

    Full Text Available The new reactive chemical vapor deposition (RCVD method has been proposed for thin film deposition of luminescent nonvolatile lanthanide aromatic carboxylates. This method is based on metathesis reaction between the vapors of volatile lanthanide dipivaloylmethanate (Ln(dpm3 and carboxylic acid (HCarb orH2Carb′ and was successfully used in case of HCarb. Advantages of the method were demonstrated on example of terbium benzoate (Tb(bz3 and o-phenoxybenzoate thin films, and Tb(bz3 thin films were successfully examined in the OLED with the following structure glass/ITO/PEDOT:PSS/TPD/Tb(bz3/Ca/Al. Electroluminescence spectra of Tb(bz3 showed only typical luminescent bands, originated from transitions of the terbium ion. Method peculiarities for deposition of compounds of dibasic acids H2Carb′ are established on example of terbium and europium terephtalates and europium 2,6-naphtalenedicarboxylate.

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

    Directory of Open Access Journals (Sweden)

    Mohamed Shuaib Mohamed Saheed

    2014-01-01

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

  6. 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.

  7. Thin Films of Gallium Arsenide and Gallium Aluminum Arsenide by Metalorganic Chemical Vapor Deposition.

    Science.gov (United States)

    Look, Edward Gene Lun

    Low pressure metalorganic chemical vapor deposition (LPMOCVD) of thin films of gallium arsenide (GaAs) and gallium aluminum arsenide (GaAlAs) was performed in a horizontal cold wall chemical vapor deposition (CVD) reactor. The organometallic (group III) sources were triethylgallium (TEGa) and triethylaluminum (TEAl), used in conjunction with arsine (AsH_3) as the group V source. It was found that growth parameters such as growth temperature, pressure, source flow rates and temperatures have a profound effect on the film quality and composition. Depending on the particular combination of conditions, both the surface and overall morphologies may be affected. The films were nondestructively analyzed by Raman and photoreflectance spectroscopies, x-ray diffraction and rocking curve studies, scanning electron microscopy, energy dispersive spectroscopy, Hall measurements and film thicknesses were determined with a step profilometer.

  8. Amorphous and microcrystalline silicon films grown at low temperatures by radio-frequency and hot-wire chemical vapor deposition

    OpenAIRE

    Alpuim, P.; Chu, Virginia; Conde, João Pedro

    1999-01-01

    The effect of hydrogen dilution on the optical, transport, and structural properties of amorphous and microcrystalline silicon thin films deposited by hot-wire (HW) chemical vapor deposition and radio-frequency (rf) plasma-enhanced chemical vapor deposition using substrate temperatures (T-sub) of 100 and 25 degrees C is reported. Microcrystalline silicon (mu c-Si:H) is obtained using HW with a large crystalline fraction and a crystallite size of similar to 30 nm for hydrogen dilutions above 8...

  9. Metastable phase formation during chemical vapor deposition of niobium-germanium films

    International Nuclear Information System (INIS)

    Regularities of different metastable phase formation during chemical vapor deposition of niobium-germanium coatings were investigated. These coatings were deposited on wire and band metal substrates by method of chemical transport reactions with the use of iodine as transporting agent. It was shown that it was possible to deposite the metastable Nb5Ge3 phase with structure of T2 type and X phase with cubic structure and hypothetical Nb2Ge composition during iodide process using Nb3Ge alloy as initial material together with phases existing at state diagram. Metastable T2 and X phases are formed only at high total pressure (more 250-500 Pa) and deposition rate less 1 μm/min. Coatings on the base of Nb3Ge with germanium content from 11 to 23 at.% were obtained

  10. 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.

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

    International Nuclear Information System (INIS)

    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

  12. Corrosion resistant chemical vapor deposited coatings for SiC and Si3N4

    OpenAIRE

    Graham, David W

    1993-01-01

    Silicon carbide and silicon nitride turbine engine components are susceptible to hot corrosion by molten sodium sulfate salts which are formed from impurities in the engine's fuel and air intake. Several oxide materials were identified which may be able to protect these components from corrosion and preserve their structural properties. Ta20, coatings were identified as one of the most promising candidates. Thermochemical calculations showed that the chemical vapor deposition(CVD) of tantalum...

  13. Edge-controlled growth and kinetics of single-crystal graphene domains by chemical vapor deposition

    OpenAIRE

    Ma, Teng; Ren, Wencai; Zhang, Xiuyun; Liu, Zhibo; Gao, Yang; Yin, Li-Chang; Ma, Xiu-Liang; Ding, Feng; Cheng, Hui-Ming

    2013-01-01

    Controlled synthesis of wafer-sized single crystalline high-quality graphene is a great challenge of graphene growth by chemical vapor deposition because of the complicated kinetics at edges that govern the growth process. Here we report the synthesis of single-crystal graphene domains with tunable edges from zigzag to armchair via a growth–etching–regrowth process. Both growth and etching of graphene are strongly dependent on the edge structure. This growth/etching behavior is well explained...

  14. A new polarised hot filament chemical vapor deposition process for homogeneous diamond nucleation on Si(100)

    OpenAIRE

    Cojocaru, Costel Sorin; Larijani, Madjid; Misra, D. S.; Singh, Manoj K.; Veis, Pavel; Le Normand, Francois

    2004-01-01

    A new hot filament chemical vapor deposition with direct current plasma assistance (DC HFCVD) chamber has been designed for an intense nucleation and subsequent growth of diamond films on Si(100).Growth process as well as the If(V) characteristics of the DC discharge are reported. Gas phase constituents activation was obtained by a stable glow discharge between two grid electrodes coupled with two sets of parallel hot filaments settled in-between and polarised at the corresponding plasma pote...

  15. Fabrication of efficient planar perovskite solar cells using a one-step chemical vapor deposition method

    OpenAIRE

    Mohammad Mahdi Tavakoli; Leilei Gu; Yuan Gao; Claas Reckmeier; Jin He; Rogach, Andrey L; Yan Yao; Zhiyong Fan

    2015-01-01

    Organometallic trihalide perovskites are promising materials for photovoltaic applications, which have demonstrated a rapid rise in photovoltaic performance in a short period of time. We report a facile one-step method to fabricate planar heterojunction perovskite solar cells by chemical vapor deposition (CVD), with a solar power conversion efficiency of up to 11.1%. We performed a systematic optimization of CVD parameters such as temperature and growth time to obtain high quality films of CH...

  16. Synthesis of boron-doped graphene monolayers using the sole solid feedstock by chemical vapor deposition.

    Science.gov (United States)

    Wang, Huan; Zhou, Yu; Wu, Di; Liao, Lei; Zhao, Shuli; Peng, Hailin; Liu, Zhongfan

    2013-04-22

    Substitutionally boron-doped monolayer graphene film is grown on a large scale by using a sole phenylboronic acid as the source in a low-pressure chemical vapor deposition system. The B-doped graphene film is a homogeneous monolayer with high crystalline quality, which exhibits a stable p-type doping behavior with a considerably high room-temperature carrier mobility of about 800 cm(2) V(-1) s(-1) . PMID:23463717

  17. Low-temperature synthesis of graphene on nickel foil by microwave plasma chemical vapor deposition

    OpenAIRE

    Kim, Y.; Song, W.; Lee, S. Y.; Jeon, C; Jung, W.; Kim, M.; Park, C. -Y.

    2011-01-01

    Microwave plasma chemical vapor deposition (MPCVD) was employed to synthesize high quality centimeter scale graphene film at low temperatures. Monolayer graphene was obtained by varying the gas mixing ratio of hydrogen and methane to 80:1. Using advantages of MPCVD, the synthesis temperature was decreased from 750 °C down to 450 °C. Optical microscopy and Raman mapping images exhibited that a large area monolayer graphene was synthesized regardless of the temperatures. Since the overall trans...

  18. A new doping method using metalorganics in chemical vapor deposition of 6H-SiC

    Science.gov (United States)

    Yoshida, S.; Sakuma, E.; Misawa, S.; Gonda, S.

    1984-01-01

    Aluminum doping was performed using triethylaluminum as the dopant in chemical vapor deposition of 6H-silicon carbide (SiC). Measurements on the electrical and cathodoluminescent properties of the epilayers indicate that the doping concentration of aluminum can be easily controlled by the flow rate of metalorganics. Electroluminescence was also observed for the pn junctions prepared by the successive growth of a nondoped n layer and a p layer doped with aluminum using metalorganics.

  19. Silicon coatings on copper by chemical vapor deposition in fluidized bed reactors

    International Nuclear Information System (INIS)

    A coating technique based on (a) chemical vapor deposition, (b) fluidized bed technology and (c) subhalide chemistry was used to siliconize copper. Copper samples were siliconized in silicon beds kept at temperatures in the range 350-550degC. Alternating current (a.c.) impedance measurements indicate that the corrosion resistance of the coated samples is significantly better than that of uncoated copper. (orig.)

  20. Microstructure of boron nitride coated on nuclear fuels by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Three nuclear fuels, pure urania, 5% and 10% gadolinia containing fuels were coated with boron nitride to improve nuclear and physical properties. Coating was done by plasma enhanced chemical vapor deposition technique by using boron trichloride and ammonia. The specimens were examined under a scanning electron microscope. Boron nitride formed a grainy structure on all fuels. Gadolinia decreased the grain size of boron nitride. The fractal dimensions of fragmentation and of area-perimeter relation were determined. (orig.)

  1. Microstructure of boron nitride coated on nuclear fuels by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Durmazucar, H.H. [Cumhuriyet Univ., Sivas (Turkey). Kimya Muehendisligi Boeluemue; Guenduez, G. [Kimya Muehendisligi Boeluemue, Orta Dogu Teknik Ueniversitesi, Ankara 06531 (Turkey); Toker, C. [Elektrik-Elektronik Muehendisligi Boeluemue, Orta Dogu Teknik Ueniversitesi, Ankara 06531 (Turkey)

    1998-08-03

    Three nuclear fuels, pure urania, 5% and 10% gadolinia containing fuels were coated with boron nitride to improve nuclear and physical properties. Coating was done by plasma enhanced chemical vapor deposition technique by using boron trichloride and ammonia. The specimens were examined under a scanning electron microscope. Boron nitride formed a grainy structure on all fuels. Gadolinia decreased the grain size of boron nitride. The fractal dimensions of fragmentation and of area-perimeter relation were determined. (orig.) 19 refs.

  2. High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene

    OpenAIRE

    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...

  3. Synthesis of Cobalt Oxides Thin Films Fractal Structures by Laser Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    P. Haniam

    2014-01-01

    Full Text Available Thin films of cobalt oxides (CoO and Co3O4 fractal structures have been synthesized by using laser chemical vapor deposition at room temperature and atmospheric pressure. Various factors which affect the density and crystallization of cobalt oxides fractal shapes have been examined. We show that the fractal structures can be described by diffusion-limited aggregation model and discuss a new possibility to control the fractal structures.

  4. Spectroscopy of Individual Single-Walled Carbon Nanotubes and their Synthesis via Chemical Vapor Deposition

    OpenAIRE

    Kiowski, Oliver

    2008-01-01

    A chemical vapor deposition (CVD) reactor was designed, built and used to grow vertically and horizontally aligned carbon nanotube arrays. The as-grown nanotubes were investigated on a single tube level using nearinfrared photoluminescence (PL) microscopy as well as Raman, atomic force and scanning electron microscopy (SEM). For photoluminescence excitation (PLE) spectroscopy of individual, semiconducting single-walled carbon nanotubes (SWNTs), a specialized PL set-up was constructed.

  5. Gravity Effects in Carbon Nanotube Growth by Thermal Chemical Vapor Deposition

    Science.gov (United States)

    Zhu, S.; Su, C. H.; Cochrane, J. C.; Lehoczky, S. L.; Cui, Y.; Burger, A.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Carbon nanotubes are synthesized using thermal chemical vapor deposition. The sizes of these carbon nanotubes (CNT) are quite uniform and the length of the tube is up to several tens of micrometers. With the substrate surface normal either along or against the gravity vector, different growth orientations of CNT are observed by scanning electron microscopy although the Raman spectra are similar for samples synthesized at different locations. These results suggest the gravitation effects in the growth of long and small diameter CNT.

  6. Hydrogen Storage in High Surface Area Carbon Nanotubes Produced by Catalytic Chemical Vapor Deposition

    OpenAIRE

    Bacsa, Revathi; Laurent, Christophe; Morishima, Ryuta; Suzuki, Hiroshi; Le Lay, Mikako

    2004-01-01

    Carbon nanotubes, mostly single- and double-walled, are prepared by a catalytic chemical vapor deposition method using H2-CH4 atmospheres with different CH4 contents. The maximum hydrogen storage at room temperatures and 10 MPa is 0.5 wt %. Contrary to expectations, purification of the carbon nanotube specimens by oxidative acid treatments or by heating in inert gas decreases the hydrogen storage. Decreasing the residual catalyst content does not necessarily lead to an increase in ASH. Moreov...

  7. Aerosol-Assisted Chemical Vapor Deposited Thin Films for Space Photovoltaics

    Science.gov (United States)

    Hepp, Aloysius F.; McNatt, Jeremiah; Dickman, John E.; Jin, Michael H.-C.; Banger, Kulbinder K.; Kelly, Christopher V.; AquinoGonzalez, Angel R.; Rockett, Angus A.

    2006-01-01

    Copper indium disulfide thin films were deposited via aerosol-assisted chemical vapor deposition using single source precursors. Processing and post-processing parameters were varied in order to modify morphology, stoichiometry, crystallography, electrical properties, and optical properties in order to optimize device-quality material. Growth at atmospheric pressure in a horizontal hot-wall reactor at 395 C yielded best device films. Placing the susceptor closer to the evaporation zone and flowing a more precursor-rich carrier gas through the reactor yielded shinier, smoother, denser-looking films. Growth of (112)-oriented films yielded more Cu-rich films with fewer secondary phases than growth of (204)/(220)-oriented films. Post-deposition sulfur-vapor annealing enhanced stoichiometry and crystallinity of the films. Photoluminescence studies revealed four major emission bands (1.45, 1.43, 1.37, and 1.32 eV) and a broad band associated with deep defects. The highest device efficiency for an aerosol-assisted chemical vapor deposited cell was 1.03 percent.

  8. Rapid and highly efficient growth of graphene on copper by chemical vapor deposition of ethanol

    International Nuclear Information System (INIS)

    The growth of graphene by chemical vapor deposition on metal foils is a promising technique to deliver large-area films with high electron mobility. Nowadays, the chemical vapor deposition of hydrocarbons on copper is the most investigated synthesis method, although many other carbon precursors and metal substrates are used too. Among these, ethanol is a safe and inexpensive precursor that seems to offer favorable synthesis kinetics. We explored the growth of graphene on copper from ethanol, focusing on processes of short duration (up to one min). We investigated the produced films by electron microscopy, Raman and X-ray photoemission spectroscopy. A graphene film with high crystalline quality was found to cover the entire copper catalyst substrate in just 20 s, making ethanol appear as a more efficient carbon feedstock than methane and other commonly used precursors. - Highlights: • Graphene films were grown by fast chemical vapor deposition of ethanol on copper. • High-temperature/short-time growth produced highly crystalline graphene. • The copper substrate was entirely covered by a graphene film in just 20 s. • Addition of H2 had a negligible effect on the crystalline quality

  9. Rapid and highly efficient growth of graphene on copper by chemical vapor deposition of ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Lisi, Nicola, E-mail: nicola.lisi@enea.it [ENEA, Materials Technology Unit, Surface Technology Laboratory, Casaccia Research Centre, Via Anguillarese 301, 00123 Rome (Italy); Buonocore, Francesco; Dikonimos, Theodoros; Leoni, Enrico [ENEA, Materials Technology Unit, Surface Technology Laboratory, Casaccia Research Centre, Via Anguillarese 301, 00123 Rome (Italy); Faggio, Giuliana; Messina, Giacomo [Dipartimento di Ingegneria dell' Informazione, delle Infrastrutture e dell' Energia Sostenibile (DIIES), Università “Mediterranea” di Reggio Calabria, 89122 Reggio Calabria (Italy); Morandi, Vittorio; Ortolani, Luca [CNR-IMM Bologna, Via Gobetti 101, 40129 Bologna (Italy); Capasso, Andrea [ENEA, Materials Technology Unit, Surface Technology Laboratory, Casaccia Research Centre, Via Anguillarese 301, 00123 Rome (Italy)

    2014-11-28

    The growth of graphene by chemical vapor deposition on metal foils is a promising technique to deliver large-area films with high electron mobility. Nowadays, the chemical vapor deposition of hydrocarbons on copper is the most investigated synthesis method, although many other carbon precursors and metal substrates are used too. Among these, ethanol is a safe and inexpensive precursor that seems to offer favorable synthesis kinetics. We explored the growth of graphene on copper from ethanol, focusing on processes of short duration (up to one min). We investigated the produced films by electron microscopy, Raman and X-ray photoemission spectroscopy. A graphene film with high crystalline quality was found to cover the entire copper catalyst substrate in just 20 s, making ethanol appear as a more efficient carbon feedstock than methane and other commonly used precursors. - Highlights: • Graphene films were grown by fast chemical vapor deposition of ethanol on copper. • High-temperature/short-time growth produced highly crystalline graphene. • The copper substrate was entirely covered by a graphene film in just 20 s. • Addition of H{sub 2} had a negligible effect on the crystalline quality.

  10. Direct liquid injection chemical vapor deposition of platinum doped cerium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zanfoni, N.; Avril, L.; Imhoff, L.; Domenichini, B., E-mail: bruno.domenichini@u-bourgogne.fr; Bourgeois, S.

    2015-08-31

    Thin films of Pt-doped CeO{sub 2} were grown by direct liquid injection chemical vapor deposition on silicon wafer covered by native oxide at 400 °C using Ce(IV) alkoxide and organoplatinum(IV) as precursors. X-ray photoelectron spectra evidenced that the platinum oxidation state is linked to the deposition way. For platinum deposited on top of cerium oxide thin films previously grown, metallic platinum particles were obtained. Cerium and platinum codeposition allowed obtaining a Pt{sup 0} and Pt{sup 2+} mixture with the Pt{sup 2+} to Pt ratio strongly dependent on the platinum flow rate during the deposition. Indeed, the lower the platinum precursor flow rate is, the higher the Pt{sup 2+} to Pt ratio is. Moreover, surface and cross-sectional morphologies obtained by scanning electron microscopy evidenced porous layers in any case. - Highlights: • Pt-doped ceria were synthesized. • Films were obtained by direct liquid injection chemical vapor deposition. • Simultaneous deposition of Pt and Ce was used to obtain homogeneous films. • Pt{sup 2+} was revealed through X-ray photoelectron spectroscopy. • Different routes were used to exalt Pt{sup 2+}/Pt ratio.

  11. Direct liquid injection chemical vapor deposition of platinum doped cerium oxide thin films

    International Nuclear Information System (INIS)

    Thin films of Pt-doped CeO2 were grown by direct liquid injection chemical vapor deposition on silicon wafer covered by native oxide at 400 °C using Ce(IV) alkoxide and organoplatinum(IV) as precursors. X-ray photoelectron spectra evidenced that the platinum oxidation state is linked to the deposition way. For platinum deposited on top of cerium oxide thin films previously grown, metallic platinum particles were obtained. Cerium and platinum codeposition allowed obtaining a Pt0 and Pt2+ mixture with the Pt2+ to Pt ratio strongly dependent on the platinum flow rate during the deposition. Indeed, the lower the platinum precursor flow rate is, the higher the Pt2+ to Pt ratio is. Moreover, surface and cross-sectional morphologies obtained by scanning electron microscopy evidenced porous layers in any case. - Highlights: • Pt-doped ceria were synthesized. • Films were obtained by direct liquid injection chemical vapor deposition. • Simultaneous deposition of Pt and Ce was used to obtain homogeneous films. • Pt2+ was revealed through X-ray photoelectron spectroscopy. • Different routes were used to exalt Pt2+/Pt ratio

  12. 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.

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

    International Nuclear Information System (INIS)

    Germanium-carbon coatings were deposited on silicon and glass substrates by plasma enhanced chemical vapor deposition (PECVD) using three different flow ratios of GeH4 and CH4 precursors. Elemental analysis, structural evaluation and microscopic investigation of coatings were performed using laser-induced breakdown spectroscopy (LIBS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. Based on the results, the coatings exhibited a homogeneous and dense structure free of pores with a very good adhesion to substrate. The structural evaluation revealed that the germanium-carbon coatings were a kind of a Ge-rich composite material containing the amorphous and crystalline germanium and amorphous carbon with the mixture of Ge–Ge, Ge–C, C–C, Ge–H and C–H bonds. The result suggested that the amorphisation of the coatings could be increased with raising CH4:GeH4 flow rate ratio and subsequently increasing C amount incorporated into the coating. - Highlights: • Germanium-carbon coatings were prepared by PECVD technique. • The germanium-carbon coatings were a kind of composite material. • The amorphisation of the coatings were increased with raising CH4:GeH4 flow ratio

  14. Integration of polymer electrolytes in dye sensitized solar cells by initiated chemical vapor deposition

    International Nuclear Information System (INIS)

    The mesoporous titanium dioxide electrode of dye sensitized solar cells (DSSC) has been successfully filled with polymer electrolyte to replace the conventional liquid electrolyte. Polymer electrolyte was directly synthesized and deposited using the initiated chemical vapor deposition (iCVD) process, and an iodide-triiodide redox couple in different redox solvents was then incorporated into the polymer. We have investigated different candidate polymer electrolytes, including poly(2-hydroxyethyl methacrylate) (PHEMA). The open circuit voltage of cells fabricated with iCVD PHEMA was found to be higher when compared with a liquid electrolyte that is attributed to a lower rate of electron recombination.

  15. Chemical vapor deposition of tungsten (CVD W) as submicron interconnection and via stud

    International Nuclear Information System (INIS)

    Blanket-deposited chemical vapor deposition of tungsten (CVD W) has been developed and implemented in a 4-Mbit DRAM and equivalent submicron VLSI technologies. CVD W was applied as contact stud, interconnect, and interlevel via stud. The technologies have been proven reliable under several reliability stress conditions. Major technical problems involved in CVD W processing, such as adhesion, contact resistance, etchability, and hole fill are discussed. A novel technique that uses TiN as a contact and adhesion layer is presented. This technique has lead to the resolution of the above technical problem and significantly improved the manufacturability of blanket CVD W processes

  16. Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Durmazucar, Hasan H.; Guenduez, Guengoer E-mail: ggunduz@metu.edu.tr

    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.

  17. Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition

    International Nuclear Information System (INIS)

    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

  18. Growth and Characteristics of Freestanding Hemispherical Diamond Films by Microwave Plasma Chemical Vapor Deposition

    International Nuclear Information System (INIS)

    Freestanding hemispherical diamond films have been fabricated by microwave plasma chemical vapor deposition using graphite and molybdenum (Mo) as substrates. Characterized by Raman spectroscopy and scanning electron microscopy, the crystalline quality of the films deposited on Mo is higher than that on graphite, which is attributed to the difference in intrinsic properties of the two substrates. By decreasing the methane concentration, the diamond films grown on the Mo substrate vary from black to white, and the optical transparency is enhanced. After polishing the growth side, the diamond films show an infrared transmittance of 35–60% in the range 400–4000 cm−1

  19. Growth and Characteristics of Freestanding Hemispherical Diamond Films by Microwave Plasma Chemical Vapor Deposition

    Science.gov (United States)

    Wang, Qi-Liang; Lü, Xian-Yi; Li, Liu-An; Cheng, Shao-Heng; Li, Hong-Dong

    2010-04-01

    Freestanding hemispherical diamond films have been fabricated by microwave plasma chemical vapor deposition using graphite and molybdenum (Mo) as substrates. Characterized by Raman spectroscopy and scanning electron microscopy, the crystalline quality of the films deposited on Mo is higher than that on graphite, which is attributed to the difference in intrinsic properties of the two substrates. By decreasing the methane concentration, the diamond films grown on the Mo substrate vary from black to white, and the optical transparency is enhanced. After polishing the growth side, the diamond films show an infrared transmittance of 35-60% in the range 400-4000 cm-1.

  20. 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.

  1. 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.

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

    Science.gov (United States)

    Xi, X. X.; Pogrebnyakov, A. V.; Xu, S. Y.; Chen, K.; Cui, Y.; Maertz, E. C.; Zhuang, C. G.; Li, Qi; Lamborn, D. R.; Redwing, J. M.; Liu, Z. K.; Soukiassian, A.; Schlom, D. G.; Weng, X. J.; Dickey, E. C.; Chen, Y. B.; Tian, W.; Pan, X. Q.; Cybart, S. A.; Dynes, R. C.

    2007-06-01

    Hybrid physical-chemical vapor deposition (HPCVD) has been the most effective technique for depositing MgB 2 thin films. It generates high magnesium vapor pressures and provides a clean environment for the growth of high purity MgB 2 films. The epitaxial pure MgB 2 films grown by HPCVD show higher-than-bulk Tc due to tensile strain in the films. The HPCVD films are the cleanest MgB 2 materials reported, allowing basic research, such as on magnetoresistance, that reveals the two-band nature of MgB 2. The carbon-alloyed HPCVD films demonstrate record-high Hc2 values promising for high magnetic field applications. The HPCVD films and multilayers have enabled the fabrication of high quality MgB 2 Josephson junctions.

  3. MgB2 thin films by hybrid physical-chemical vapor deposition

    International Nuclear Information System (INIS)

    Hybrid physical-chemical vapor deposition (HPCVD) has been the most effective technique for depositing MgB2 thin films. It generates high magnesium vapor pressures and provides a clean environment for the growth of high purity MgB2 films. The epitaxial pure MgB2 films grown by HPCVD show higher-than-bulk T c due to tensile strain in the films. The HPCVD films are the cleanest MgB2 materials reported, allowing basic research, such as on magnetoresistance, that reveals the two-band nature of MgB2. The carbon-alloyed HPCVD films demonstrate record-high H c2 values promising for high magnetic field applications. The HPCVD films and multilayers have enabled the fabrication of high quality MgB2 Josephson junctions

  4. Chemical vapor deposition of ZrC within a spouted bed by bromide process

    Science.gov (United States)

    Ogawa, T.; Ikawa, K.; Iwamoto, K.

    1981-03-01

    ZrC coatings by chemical vapor deposition were applied to particles of ThO 2, UO 2 and Al 2O 3 at 1623-1873 K. The feed gas mixture consisted of ZrBr 4, CH 4, H 2 and Ar. The results were compared with the calculated chemical equilibria in the Zr-C-H-Br system. It was shown that the weight and composition of the deposit can be calculated by thermochemical analysis after correcting the methane flow rate for a pyrolysis efficiency. Predominant reaction presumably occurring were derived by a mass balance consideration on the calculated equilibrium species. A simplified model of the ZrC deposition was proposed.

  5. LOW PRESSURE CHEMICAL VAPOR DEPOSITION (CVD) ON OXIDE AND NONOXIDE CERAMIC CUTTING TOOLS

    OpenAIRE

    Layyous, A.; Wertheim, R.

    1989-01-01

    Cutting tools made of Al2O3+TiC, silicon nitride, carbide, and stabilized ZrO2 were coated by chemical vapor deposition (CVD) with a multilayer of TiN, TiCN, TiC and Al2O3 in different combinations. The adhesion of the coated layers to the substrate, and the structure of the layers were investigated by optical microscopy, scanning electron microscopy (SEM) and Auger spectroscopy. This made it possible to analyze the chemical interaction between the substrate and the TiN at 1000°C. The cutting...

  6. High-quality, faceted cubic boron nitride films grown by chemical vapor deposition

    Science.gov (United States)

    Zhang, W. J.; Jiang, X.; Matsumoto, S.

    2001-12-01

    Thick cubic boron nitride (cBN) films showing clear crystal facets were achieved by chemical vapor deposition. The films show the highest crystallinity of cBN films ever achieved from gas phase. Clear evidence for the growth via a chemical route is obtained. A growth mechanism is suggested, in which fluorine preferentially etches hBN and stabilizes the cBN surface. Ion bombardment of proper energy activates the cBN surface bonded with fluorine so as to enhance the bonding probability of nitrogen-containing species on the F-stabilized B (111) surface.

  7. Thin film cadmium telluride solar cells by two chemical vapor deposition techniques

    Energy Technology Data Exchange (ETDEWEB)

    Chu, T.L.

    1988-01-15

    Cadmium telluride (CdTe) has long been recognized as a promising thin film photovoltaic material. In this work, polycrystalline p-CdTe films have been deposited by two chemical vapor deposition techniques, namely the combination of vapors of elements (CVE) and close-spaced sublimation (CSS). The CVE technique is more flexible in controlling the composition of deposited films while the CSS technique can provide very high deposition rates. The resistivity of p-CdTe films deposited by the CVE and CSS techniques can be controlled by intrinsic (cadmium vacancies) or extrinsic (arsenic or antimony) doping, and the lowest resistivity obtainable is about 200 ..cap omega.. cm. Both front-wall (CdTe/TCS/glass) and back-wall (TCS/CdTe/substrate) cells have been prepared. The back-wall cells are less efficient because of the high and irreproducible p-CdTe-substrate interface resistance. The CSS technique is superior to the CVE technique because of its simplicity and high deposition rates; however, the cleaning of the substrate in situ is more difficult. The interface cleanliness is an important factor determining the electrical and photovoltaic characteristics of the heterojunction. Heterojunction CdS/CdTe solar cells of area 1 cm/sup 2/ with conversion efficiencies higher than 10% have been prepared and junction properties characterized.

  8. Selective chemical vapor deposition of tungsten films on titanium-ion-irradiated silicon dioxide

    International Nuclear Information System (INIS)

    Selective area deposition of adherent tungsten (W) film on titanium (Ti)-ion-irradiated silicon dioxide (SiO2 is achieved. First, Ti-ion irradiation through a stencil mask is performed at 600 eV for 1.1 x 1016 atoms/cm2 in a reaction chamber. Next, ArF excimer laser (λ = 193 nm) chemical vapor deposition (CVD) with tungsten hexafluoride (WF6) and hydrogen (H2) is carried out for 40 seconds at 400 K. Finally, low-pressure (LP) CVD is carried out at 600 K and then W films are deposited selectively on the ion-irradiated SiO2. Without the laser CVD step, the ion-irradiation pattern disappears during LPCVD and no W film deposition occurs

  9. Laser chemical vapor deposition of W on Si and SiO2/Si

    International Nuclear Information System (INIS)

    Direct write of W on bare Si and native SiO2/Si substrates has been investigated in an laser chemical vapor deposition (LCVD) system. W deposits on bare Si surface via the Si and/or H2 reduction of WF6 were self-limited in thickness to 200 - 600 Angstrom in both cases. Auger electron spectroscopic analysis showed that Si-H bonds could be poisoning the further growth of W. W deposits on native SiO2/Si were only obtainable via the H2 reduction WF6 in our laser direct-write system. The authors' experimental kinetic study indicates that HF desorption from the surface is the rate-controlling step for W deposition via the H2 reduction WF6

  10. Relatively low temperature synthesis of graphene by radio frequency plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    We present a simple, low-cost and high-effective method for synthesizing high-quality, large-area graphene using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) on SiO2/Si substrate covered with Ni thin film at relatively low temperatures (650 deg. C). During deposition, the trace amount of carbon (CH4 gas flow rate of 2 sccm) is introduced into PECVD chamber and the deposition time is only 30 s, in which the carbon atoms diffuse into the Ni film and then segregate on its surface, forming single-layer or few-layer graphene. After deposition, Ni is removed by wet etching, and the obtained single continuous graphene film can easily be transferred to other substrates. This investigation provides a large-area, low temperature and low-cost synthesis method for graphene as a practical electronic material.

  11. Comparison between chemical vapor deposited and physical vapor deposited WSi2 metal gate for InGaAs n-metal-oxide-semiconductor field-effect transistors

    International Nuclear Information System (INIS)

    We compare chemical vapor deposition (CVD) and physical vapor deposition (PVD) WSi2 metal gate process for In0.53Ga0.47As n-metal-oxide-semiconductor field-effect transistors using 10 and 6.5 nm Al2O3 as dielectric layer. The CVD-processed metal gate device with 6.5 nm Al2O3 shows enhanced transistor performance such as drive current, maximum transconductance and maximum effective mobility. These values are relatively better than the PVD-processed counterpart device with improvement of 51.8%, 46.4%, and 47.8%, respectively. The improvement for the performance of the CVD-processed metal gate device is due to the fluorine passivation at the oxide/semiconductor interface and a nondestructive deposition process.

  12. Comparison between chemical vapor deposited and physical vapor deposited WSi2 metal gate for InGaAs n-metal-oxide-semiconductor field-effect transistors

    Science.gov (United States)

    Ong, B. S.; Pey, K. L.; Ong, C. Y.; Tan, C. S.; Antoniadis, D. A.; Fitzgerald, E. A.

    2011-05-01

    We compare chemical vapor deposition (CVD) and physical vapor deposition (PVD) WSi2 metal gate process for In0.53Ga0.47As n-metal-oxide-semiconductor field-effect transistors using 10 and 6.5 nm Al2O3 as dielectric layer. The CVD-processed metal gate device with 6.5 nm Al2O3 shows enhanced transistor performance such as drive current, maximum transconductance and maximum effective mobility. These values are relatively better than the PVD-processed counterpart device with improvement of 51.8%, 46.4%, and 47.8%, respectively. The improvement for the performance of the CVD-processed metal gate device is due to the fluorine passivation at the oxide/semiconductor interface and a nondestructive deposition process.

  13. Stress control of plasma enhanced chemical vapor deposited silicon oxide film from tetraethoxysilane

    International Nuclear Information System (INIS)

    Thin silicon dioxide films have been studied as a function of deposition parameters and annealing temperatures. Films were deposited by tetraethoxysilane (TEOS) dual-frequency plasma enhanced chemical vapor deposition with different time interval fractions of high-frequency and low-frequency plasma depositions. The samples were subsequently annealed up to 930 °C to investigate their stress behavior. Films that were deposited in high-frequency dominated plasma were found to have tensile residual stress after annealing at temperatures higher than 800 °C. The residual stress can be controlled to slightly tensile by changing the annealing temperature. High tensile stress was observed during the annealing of high-frequency plasma-deposited films, leading to film cracks that limit the film thickness, as predicted by the strain energy release rate equation. Thick films without cracks were obtained by iterating deposition and annealing to stack multiple layers. A series of wet cleaning experiments were conducted, and we discovered that water absorption in high-frequency plasma-deposited films causes the residual stress to decrease. A ∼40 nm thick low-frequency deposited oxide cap is sufficient to prevent water from diffusing through the film. Large-area free-standing tensile stressed oxide membranes without risk of buckling were successfully fabricated. (technical note)

  14. Vapor deposition of tantalum and tantalum compounds

    International Nuclear Information System (INIS)

    Tantalum, and many of its compounds, can be deposited as coatings with techniques ranging from pure, thermal chemical vapor deposition to pure physical vapor deposition. This review concentrates on chemical vapor deposition techniques. The paper takes a historical approach. The authors review classical, metal halide-based techniques and current techniques for tantalum chemical vapor deposition. The advantages and limitations of the techniques will be compared. The need for new lower temperature processes and hence new precursor chemicals will be examined and explained. In the last section, they add some speculation as to possible new, low-temperature precursors for tantalum chemical vapor deposition

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

    International Nuclear Information System (INIS)

    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

  16. Plasma-enhanced chemical vapor deposited silicon carbide as an implantable dielectric coating.

    Science.gov (United States)

    Cogan, Stuart F; Edell, David J; Guzelian, Andrew A; Ping Liu, Ying; Edell, Robyn

    2003-12-01

    Amorphous silicon carbide (a-SiC) films, deposited by plasma-enhanced chemical vapor deposition (PECVD), have been evaluated as insulating coatings for implantable microelectrodes. The a-SiC was deposited on platinum or iridium wire for measurement of electrical leakage through the coating in phosphate-buffered saline (PBS, pH 7.4). Low leakage currents of silicon nitride formed by low-pressure chemical vapor deposition (LPCVD). Dissolution rates of LPCVD silicon nitride were 2 nm/h and 0.4 nm/day at 90 and 37 degrees C, respectively, while a-SiC had a dissolution rate of 0.1 nm/h at 90 degrees C and no measurable dissolution at 37 degrees C. Biocompatibility was assessed by implanting a-SiC-coated quartz discs in the subcutaneous space of the New Zealand White rabbit. Histological evaluation showed no chronic inflammatory response and capsule thickness was comparable to silicone or uncoated quartz controls. Amorphous SiC-coated microelectrodes were implanted in the parietal cortex for periods up to 150 days and the cortical response evaluated by histological evaluation of neuronal viability at the implant site. The a-SiC was more stable in physiological saline than LPCVD Si(3)N(4) and well tolerated in the cortex. PMID:14613234

  17. Atmospheric pressure plasma enhanced chemical vapor deposition of zinc oxide and aluminum zinc oxide

    International Nuclear Information System (INIS)

    Zinc oxide (ZnO) and aluminum-doped zinc oxide (AZO) thin films were deposited via atmospheric pressure plasma enhanced chemical vapor deposition. A second-generation precursor, bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N′-diethylethylenediamine) zinc, exhibited significant vapor pressure and good stability at one atmosphere where a vaporization temperature of 110 °C gave flux ∼ 7 μmol/min. Auger electron spectroscopy confirmed that addition of H2O to the carrier gas stream mitigated F contamination giving nearly 1:1 metal:oxide stoichiometries for both ZnO and AZO with little precursor-derived C contamination. ZnO and AZO thin film resistivities ranged from 14 to 28 Ω·cm for the former and 1.1 to 2.7 Ω·cm for the latter. - Highlights: • A second generation precursor was utilized for atmospheric pressure film growth. • Addition of water vapor to the carrier gas stream led to a marked reduction of ZnF2. • Carbonaceous contamination from the precursor was minimal

  18. Atmospheric pressure plasma enhanced chemical vapor deposition of zinc oxide and aluminum zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Kyle W. [Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, ND (United States); Department of Mechanical Engineering, North Dakota State University, Fargo, ND (United States); Guruvenket, Srinivasan; Sailer, Robert A. [Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, ND (United States); Ahrenkiel, S. Phillip [Department of Nanoscience and Nanoengineering, South Dakota School of Mines and Technology, Rapid City, SD (United States); Schulz, Douglas L., E-mail: SBRconsulting@hotmail.com [Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, ND (United States); Department of Mechanical Engineering, North Dakota State University, Fargo, ND (United States)

    2013-12-02

    Zinc oxide (ZnO) and aluminum-doped zinc oxide (AZO) thin films were deposited via atmospheric pressure plasma enhanced chemical vapor deposition. A second-generation precursor, bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N′-diethylethylenediamine) zinc, exhibited significant vapor pressure and good stability at one atmosphere where a vaporization temperature of 110 °C gave flux ∼ 7 μmol/min. Auger electron spectroscopy confirmed that addition of H{sub 2}O to the carrier gas stream mitigated F contamination giving nearly 1:1 metal:oxide stoichiometries for both ZnO and AZO with little precursor-derived C contamination. ZnO and AZO thin film resistivities ranged from 14 to 28 Ω·cm for the former and 1.1 to 2.7 Ω·cm for the latter. - Highlights: • A second generation precursor was utilized for atmospheric pressure film growth. • Addition of water vapor to the carrier gas stream led to a marked reduction of ZnF{sub 2}. • Carbonaceous contamination from the precursor was minimal.

  19. Compositional study of silicon oxynitride thin films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition technique

    International Nuclear Information System (INIS)

    We have used backscattering spectrometry and 15N(1H,α,γ)12C nuclear reaction analysis techniques to study in detail the variation in the composition of silicon oxynitride films with deposition parameters. The films were deposited using 2.45 GHz electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) technique from mixtures of precursors argon, nitrous oxide, and silane at deposition temperature 90 deg. C. The deposition pressure and nitrous oxide-to-silane gas flow rates ratio have been found to have a pronounced influence on the composition of the films. When the deposition pressure was varied for a given nitrous oxide-to-silane gas flow ratio, the amount of silicon and nitrogen increased with the deposition pressure, while the amount of oxygen decreased. For a given deposition pressure, the amount of incorporated nitrogen and hydrogen decreased while that of oxygen increased with increasing nitrous oxide-to-silane gas flow rates ratio. For nitrous oxide-to-silane gas flow ratio of 5, we obtained films which contained neither chemically bonded nor nonbonded nitrogen atoms as revealed by the results of infrared spectroscopy, backscattering spectrometry, and nuclear reaction analysis. Our results demonstrate the nitrogen-free nearly stoichiometric silicon dioxide films can be prepared from a mixture of precursors argon, nitrous oxide, and silane at low substrate temperature using high-density PECVD technique. This avoids the use of a hazardous and an often forbidden pair of silane and oxygen gases in a plasma reactor

  20. The power source effect on SiO{sub x} coating deposition by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Junfeng [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Daxing, Beijing, 102600 (China); Chen Qiang, E-mail: chenqiang@bigc.edu.c [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Daxing, Beijing, 102600 (China); Zhang Yuefei; Liu Fuping; Liu Zhongwei [Laboratory of Plasma Physics and Materials, Beijing Institute of Graphic Communication, Daxing, Beijing, 102600 (China)

    2009-05-29

    SiOx coatings were prepared by capacitively coupled plasma enhanced chemical vapor deposition on polyethyleneterephtalate substrates in 23 kHz middle-frequency and radio frequency power supplies, respectively, where hexamethyldisiloxane was used as gas source. The influences of discharge conditions on gas phase intermediate species and active radicals for SiOx formation was investigated by mass spectrometry as real-time in-situ diagnosis. The deposited SiOx coating chemical structures were also analyzed by Fourier transform infrared spectroscopy. Meanwhile, the film barrier property, oxygen transmission rate, was measured at 23 {sup o}C and 50% humidity circumstance. The better barrier property was obtained in the MF power source depositing SiOx coated PET.

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

    International Nuclear Information System (INIS)

    Polycrystalline diamond has been synthesized on silicon substrates at atmospheric pressure, using a microwave capillary plasma chemical vapor deposition technique. The CH4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C2, Ar, N2, CH, Hβ, and Hα were observed in the emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T2g phonon at 1333 cm−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

  2. Growth of cubic boron nitride on diamond particles by microwave plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Saitoh, H.; Yarbrough, W. A.

    1991-06-01

    The nucleation and growth of cubic boron nitride (c-BN) onto diamond powder using solid NaBH4 in low pressure gas mixtures of NH3 and H2 by microwave plasma enhanced chemical vapor deposition has been studied. Boron nitride was deposited on submicron diamond seed crystals scattered on (100) silicon single crystal wafers and evidence was found for the formation of the cubic phase. Diamond powder surfaces appear to preferentially nucleate c-BN. In addition, it was found that the ratio of c-BN to turbostratic structure boron nitride (t-BN) deposited increases with decreasing NH3 concentration in H2. It is suggested that this may be due to an increased etching rate for t-BN by atomic hydrogen whose partial pressure may vary with NH3 concentration.

  3. 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.

  4. Synthesis and Growth Mechanism of Carbon Filaments by Chemical Vapor Deposition without Catalyst

    Institute of Scientific and Technical Information of China (English)

    Shuhe Liu; Feng Li; Shuo Bai

    2009-01-01

    Carbon filaments with diameter from several to hundreds micrometers were synthesized by chemical vapor deposition of methane without catalyst. The morphology, microstructure and mechanical properties of the carbon filament were investigated by scanning electronic microscopy, optical microscopy, X-ray diffraction and mechanical testing. The results show that the carbon filament is inverted cone shape and grows up along the gas flow direction. The stem of it is formed of annular carbon layers arranged in a tree ring structure while the head is made up of concentrical layers. The tensile strength of the carbon filament is increased after graphitization for the restructuring and growing large of graphene. The growth mechanism of carbon filament was proposed according to the results of two series of experiments with different deposition time and intermittent deposition cycles.

  5. Development of CaO coatings by thermal and chemical vapor deposition

    International Nuclear Information System (INIS)

    We have developed CaO coatings that are applied by a thermal and chemical vapor deposition process. Several experiments were conducted to study how the deposition of Ca on a V-4Cr-4Ti substrate alloy is affected by variations in process temperature and time, specimen location, and surface preparation and pretreatment. Results showed that thick adherent coatings can be fabricated by thermal/chemical vapor deposition, especially if a double Ca treatment is applied. Extensive microstructural analysis of the coatings showed almost 100% CaO over a coating thickness of 20-30(micro)m; electrical resistance (measured by the two-probe method) of the coatings was at least two orders of magnitude higher than the minimum required for blanket application. The results obtained in this study indicate that CaO is a viable coating for V-Li advanced blankets, but that significant additional effort is needed, especially from the standpoint of structure/composition relationship to its electrical resistance and the coating stability in a flowing Li environment. Furthermore, resistance must be measured in situ in Li to simultaneously evaluate coating integrity, resistance, and Li compatibility

  6. Thermal conductivity of ultra-thin chemical vapor deposited hexagonal boron nitride films

    Science.gov (United States)

    Alam, M. T.; Bresnehan, M. S.; Robinson, J. A.; Haque, M. A.

    2014-01-01

    Thermal conductivity of freestanding 10 nm and 20 nm thick chemical vapor deposited hexagonal boron nitride films was measured using both steady state and transient techniques. The measured value for both thicknesses, about 100 ± 10 W m-1 K-1, is lower than the bulk basal plane value (390 W m-1 K-1) due to the imperfections in the specimen microstructure. Impressively, this value is still 100 times higher than conventional dielectrics. Considering scalability and ease of integration, hexagonal boron nitride grown over large area is an excellent candidate for thermal management in two dimensional materials-based nanoelectronics.

  7. Structural and Electrical Characterization of Bi2Se3 Nanostructures Grown by Metalorganic Chemical Vapor Deposition

    OpenAIRE

    Alegria, L. D.; Schroer, M. D.; Chatterjee, A.; Poirier, G. R.; Pretko, M.; Patel, S. K.; Petta, J.R.

    2011-01-01

    We characterize nanostructures of Bi2Se3 that are grown via metalorganic chemical vapor deposition using the precursors diethyl selenium and trimethyl bismuth. By adjusting growth parameters, we obtain either single-crystalline ribbons up to 10 microns long or thin micron-sized platelets. Four-terminal resistance measurements yield a sample resistivity of 4 mOhm-cm. We observe weak anti-localization and extract a phase coherence length l_phi = 178 nm and spin-orbit length l_so = 93 nm at T = ...

  8. Tunneling characteristics in chemical vapor deposited graphene–hexagonal boron nitride–graphene junctions

    International Nuclear Information System (INIS)

    Large area chemical vapor deposited graphene and hexagonal boron nitride was used to fabricate graphene–hexagonal boron nitride–graphene symmetric field effect transistors. Gate control of the tunneling characteristics is observed similar to previously reported results for exfoliated graphene–hexagonal boron nitride–graphene devices. Density-of-states features are observed in the tunneling characteristics of the devices, although without large resonant peaks that would arise from lateral momentum conservation. The lack of distinct resonant behavior is attributed to disorder in the devices, and a possible source of the disorder is discussed

  9. Carbon nanosheets by microwave plasma enhanced chemical vapor deposition in CH4-Ar system

    International Nuclear Information System (INIS)

    We employ a new gas mixture of CH4-Ar to fabricate carbon nanosheets by microwave plasma enhanced chemical vapor deposition at the growth temperature of less than 500 deg. C. The catalyst-free nanosheets possess flower-like structures with a large amount of sharp edges, which consist of a few layers of graphene sheets according to the observation by transmission electron microscopy. These high-quality carbon nanosheets demonstrated a faster electron transfer between the electrolyte and the nanosheet surface, due to their edge defects and graphene structures.

  10. The structure and growth mechanism of Si nanoneedles prepared by plasma-enhanced chemical vapor deposition

    Czech Academy of Sciences Publication Activity Database

    Červenka, Jiří; Ledinský, Martin; Stuchlík, Jiří; Stuchlíková, The-Ha; Bakardjieva, Snejana; Hruška, Karel; Fejfar, Antonín; Kočka, Jan

    2010-01-01

    Roč. 21, č. 41 (2010), 415604/1-415604/7. ISSN 0957-4484 R&D Projects: GA MŠk(CZ) LC06040; GA AV ČR KAN400100701; GA MŠk LC510 EU Projects: European Commission(XE) 240826 - POLYSIMODE Institutional research plan: CEZ:AV0Z10100521; CEZ:AV0Z40320502 Keywords : nanoneedles * nanowires * silicon * plasma * chemical vapor deposition * crystal structure * growth * phonon * SEM * Raman Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.644, year: 2010

  11. Atmospheric pressure chemical vapor deposition of CdTe—reactor design considerations

    Science.gov (United States)

    Meyers, Peter V.; Kee, Robert J.; Raja, Laxminarayan; Wolden, Colin A.; Aire, Michael

    1999-03-01

    Atmospheric Pressure Chemical Vapor Deposition (APCVD) of polycrystalline thin-film CdTe appears to offer several practical advantages over state-of-the-art manufacturing techniques. APCVD employs the same reaction chemistry utilized to produce 16% efficient CdTe cells (i.e., same reaction chemistry as Close Spaced Sublimation), avoids use of vacuum equipment, allows for physical separation of the source and substrate, and employs forced convection to ensure uniform delivery of source material over large-area substrates. Reactor design considerations and preliminary numerical simulations of mass transport are presented.

  12. 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.

  13. 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.

  14. Quantum Hall effect on centimeter scale chemical vapor deposited graphene films

    Science.gov (United States)

    Shen, Tian; Wu, Wei; Yu, Qingkai; Richter, Curt; Elmquist, Randolph; Newell, David; Chen, Yong

    2012-02-01

    We report observations of well developed half integer quantum Hall effect on mono layer graphene films of 7 mm by 7 mm in size. The graphene films are grown by chemical vapor deposition on copper, then transferred to SiO2/Si substrates, with typical carrier mobilities 4000 cm^2/Vs. The large size graphene with excellent quality and electronic homogeneity demonstrated in this work is promising for graphene-based quantum Hall resistance standards, and can also facilitate a wide range of experiments on quantum Hall physics of graphene and practical applications exploiting the exceptional properties of graphene.

  15. Fabrication of highly ultramicroporous carbon nanofoams by SF6-catalyzed laser-induced chemical vapor deposition

    Science.gov (United States)

    Hattori, Yoshiyuki; Shuhara, Ai; Kondo, Atsushi; Utsumi, Shigenori; Tanaka, Hideki; Ohba, Tomonori; Kanoh, Hirofumi; Takahashi, Kunimitsu; Vallejos-Burgos, Fernando; Kaneko, Katsumi

    2016-05-01

    We have developed a laser-induced chemical vapor deposition (LCVD) method for preparing nanocarbons with the aid of SF6. This method would offer advantages for the production of aggregates of nanoscale foams (nanofoams) at high rates. Pyrolysis of the as-grown nanofoams induced the high surface area (1120 m2 g-1) and significantly enhanced the adsorption of supercritical H2 (16.6 mg g-1 at 77 K and 0.1 MPa). We also showed that the pyrolized nanofoams have highly ultramicroporous structures. The pyrolized nanofoams would be superior to highly microporous nanocarbons for the adsorption of supercritical gases.

  16. Hydrogen dilution effect on microstructure of Si thin film grown by catalyzer enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    The effect of hydrogen dilution on microstructure of in situ polycrystalline Si (poly-Si) films grown by catalyzer-enhanced chemical vapor deposition (CECVD) has been investigated by using transmission electron microscopy (TEM) and transmission electron diffraction (TED) analysis. It was shown that the increase of the hydrogen dilution ratio resulted in transition of microstructure of Si thin film from amorphous to polycrystalline in CECVD at low substrate temperature (∼80 deg. C). These results indicate that the CECVD technique is a promising candidate to grow high-quality in situ polycrystalline Si films on glass or a flexible substrate for low-temperature poly-Si (LTPS) and flexible displays

  17. Hydrogen dilution effect on microstructure of Si thin film grown by catalyzer enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han-Ki [School of Advanced Materials and Systems Engineering, Kumoh National Institute of Technology (KIT), 1 Yangho-dong, Gumi, Gyeongbuk, 730-701 (Korea, Republic of)]. E-mail: hkkim@kumoh.ac.kr

    2006-12-15

    The effect of hydrogen dilution on microstructure of in situ polycrystalline Si (poly-Si) films grown by catalyzer-enhanced chemical vapor deposition (CECVD) has been investigated by using transmission electron microscopy (TEM) and transmission electron diffraction (TED) analysis. It was shown that the increase of the hydrogen dilution ratio resulted in transition of microstructure of Si thin film from amorphous to polycrystalline in CECVD at low substrate temperature ({approx}80 deg. C). These results indicate that the CECVD technique is a promising candidate to grow high-quality in situ polycrystalline Si films on glass or a flexible substrate for low-temperature poly-Si (LTPS) and flexible displays.

  18. 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.

  19. Growth of 2D black phosphorus film from chemical vapor deposition

    Science.gov (United States)

    Smith, Joshua B.; Hagaman, Daniel; Ji, Hai-Feng

    2016-05-01

    Phosphorene, a novel 2D material isolated from bulk black phosphorus (BP), is an intrinsic p-type material with a variable bandgap for a variety of applications. However, these applications are limited by the inability to isolate large films of phosphorene. Here we present an in situ chemical vapor deposition type approach that demonstrates progress towards growth of large area 2D BP with average areas >3 μm2 and thicknesses representing samples around four layers and thicker samples with average areas >100 μm2. Transmission electron microscopy and Raman spectroscopy have confirmed successful growth of 2D BP from red phosphorus.

  20. Growth of 2D black phosphorus film from chemical vapor deposition.

    Science.gov (United States)

    Smith, Joshua B; Hagaman, Daniel; Ji, Hai-Feng

    2016-05-27

    Phosphorene, a novel 2D material isolated from bulk black phosphorus (BP), is an intrinsic p-type material with a variable bandgap for a variety of applications. However, these applications are limited by the inability to isolate large films of phosphorene. Here we present an in situ chemical vapor deposition type approach that demonstrates progress towards growth of large area 2D BP with average areas >3 μm(2) and thicknesses representing samples around four layers and thicker samples with average areas >100 μm(2). Transmission electron microscopy and Raman spectroscopy have confirmed successful growth of 2D BP from red phosphorus. PMID:27087456

  1. 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.

  2. 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.

  3. 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.

  4. High specific surface area carbon nanotubes from catalytic chemical vapor deposition process

    OpenAIRE

    Bacsa, Revathi; Laurent, Christophe; Peigney, Alain; Bacsa, Wolfgang; Vaugien, Thibaud; Rousset, Abel

    2000-01-01

    A carbon nanotube specimen with a carbon content of 83 wt.% (95 vol.%) and a specific surface area equal to 790 m2/g (corresponding to 948 m2/g of carbon) is prepared by a catalytic chemical vapor deposition method. The nanotubes, 90% of which are single- and double-walled, are individual rather than in bundles. High-resolution electron microscopy shows a diameter distribution in the range 0.8-5 nm and Raman spectroscopy shows a high proportion of tubular carbon. Both techniques reveal a maxi...

  5. 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.

  6. Photocatalytic activity of tin-doped TiO{sub 2} film deposited via aerosol assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chua, Chin Sheng, E-mail: cschua@simtech.a-star.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Tan, Ooi Kiang; Tse, Man Siu [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Ding, Xingzhao [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore)

    2013-10-01

    Tin-doped TiO{sub 2} films are deposited via aerosol assisted chemical vapor deposition using a precursor mixture composing of titanium tetraisopropoxide and tetrabutyl tin. The amount of tin doping in the deposited films is controlled by the volume % concentration ratio of tetrabutyl tin over titanium tetraisopropoxide in the mixed precursor solution. X-ray diffraction analysis results reveal that the as-deposited films are composed of pure anatase TiO{sub 2} phase. Red-shift in the absorbance spectra is observed attributed to the introduction of Sn{sup 4+} band states below the conduction band of TiO{sub 2}. The effect of tin doping on the photocatalytic property of TiO{sub 2} films is studied through the degradation of stearic acid under UV light illumination. It is found that there is a 10% enhancement on the degradation rate of stearic acid for the film with 3.8% tin doping in comparison with pure TiO{sub 2} film. This improvement of photocatalytic performance with tin incorporation could be ascribed to the reduction of electron-hole recombination rate through charge separation and an increased amount of OH radicals which are crucial for the degradation of stearic acid. Further increase in tin doping results in the formation of recombination site and large anatase grains, which leads to a decrease in the degradation rate. - Highlights: ► Deposition of tin-doped TiO{sub 2} film via aerosol assisted chemical vapor depositionDeposited anatase films show red-shifted in UV–vis spectrum with tin-dopants. ► Photoactivity improves at low tin concentration but reduces at higher concentration. ► Improvement in photoactivity due to bandgap narrowing from Sn{sup 4+} band states ► Maximum photoactivity achieved occurs for films with 3.8% tin doping.

  7. Chemical Vapor Deposition Synthesis and Raman Spectroscopic Characterization of Large-Area Graphene Sheets

    Science.gov (United States)

    Liao, Chun-Da; Lu, Yi-Ying; Tamalampudi, Srinivasa Reddy; Cheng, Hung-Chieh; Chen, Yit-Tsong

    2013-10-01

    We present a chemical vapor deposition (CVD) method to catalytically synthesize large-area, transferless, single- to few-layer graphene sheets using hexamethyldisilazane (HMDS) on a SiO2/Si substrate as a carbon source and thermally evaporated alternating Ni/Cu/Ni layers as a catalyst. The as-synthesized graphene films were characterized by Raman spectroscopic imaging to identify single- to few-layer sheets. This HMDS-derived graphene layer is continuous over the entire growth substrate, and single- to trilayer mixed sheets can be up to 30 -m in the lateral dimension. With the synthetic CVD method proposed here, graphene can be grown into tailored shapes directly on a SiO2/Si surface through vapor priming of HMDS onto predefined photolithographic patterns. The transparent and conductive HMDS-derived graphene exhibits its potential for widespread electronic and opto-electronic applications.

  8. Latest innovations in large area web coating technology via plasma enhanced chemical vapor deposition source technology

    International Nuclear Information System (INIS)

    In this article, the authors discuss the latest results of our development of large area plasma enhanced chemical vapor deposition (PECVD) source technologies for flexible substrates. A significant challenge is the economical application of thin films for use as vapor barriers, transparent conductive oxides, and optical interference thin films. Here at General Plasma the authors have developed two innovative PECVD source technologies that provide an economical alternative to low temperature sputtering technologies and enable some thin film materials not accessible by sputtering. The Penning Discharge Plasma (PDP trade mark sign ) source is designed for high rate direct PECVD deposition on insulating, temperature sensitive web [J. Modocks, Proceedings of the Society of Vacuum Coaters, 2003 (unpublished), p. 187]. This technology has been utilized to deposit SiO2 and SiC:H for barrier applications [V. Shamamian et al. Proceedings of the Flexible Displays and Manufacturing Conferrence, 2006 (unpublished)]. The Plasma Beam Source (PBS trade mark sign ) is a remote plasma source that is more versatile for deposition on not only insulating flexible substrates but also conductive or rigid substrates for deposition of thin films that are sensitive to the high ion bombardment flux inherent to the PDP trade mark sign technology. The authors have developed PBS thin film processes in our laboratory for deposition of SiO2, SiC:O, SiN:C, SiN:H, ZnO, FeOx, and Al2O3. [M. A. George, Conference Proceedings of the Association of Industrial Metallizers, Coaters, and Laminators (AIMCAL), 2007 (unpublished)]. The authors discuss the design of the patented sources, plasma physics, and chemistry of the deposited thin films.

  9. Process development for the manufacture of an integrated dispenser cathode assembly using laser chemical vapor deposition

    Science.gov (United States)

    Johnson, Ryan William

    2005-07-01

    Laser Chemical Vapor Deposition (LCVD) has been shown to have great potential for the manufacture of small, complex, two or three dimensional metal and ceramic parts. One of the most promising applications of the technology is in the fabrication of an integrated dispenser cathode assembly. This application requires the deposition of a boron nitride-molybdenum composite structure. In order to realize this structure, work was done to improve the control and understanding of the LCVD process and to determine experimental conditions conducive to the growth of the required materials. A series of carbon fiber and line deposition studies were used to characterize process-shape relationships and study the kinetics of carbon LCVD. These studies provided a foundation for the fabrication of the first high aspect ratio multi-layered LCVD wall structures. The kinetics studies enabled the formulation of an advanced computational model in the FLUENT CFD package for studying energy transport, mass and momentum transport, and species transport within a forced flow LCVD environment. The model was applied to two different material systems and used to quantify deposition rates and identify rate-limiting regimes. A computational thermal-structural model was also developed using the ANSYS software package to study the thermal stress state within an LCVD deposit during growth. Georgia Tech's LCVD system was modified and used to characterize both boron nitride and molybdenum deposition independently. The focus was on understanding the relations among process parameters and deposit shape. Boron nitride was deposited using a B3 N3H6-N2 mixture and growth was characterized by sporadic nucleation followed by rapid bulk growth. Molybdenum was deposited from the MoCl5-H2 system and showed slow, but stable growth. Each material was used to grow both fibers and lines. The fabrication of a boron nitride-molybdenum composite was also demonstrated. In sum, this work served to both advance the

  10. 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 ...

  11. Influences of deposition temperature on characteristics of B-doped ZnO films deposited by metal–organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Boron-doped zinc oxide films were fabricated by metal–organic chemical vapor deposition at deposition temperatures (Td) from 150 to 210 °C. The deposition rate increases abruptly and monotonically with increasing Td. The resistivity also varies drastically, and a minimum resistivity of 1.6 × 10−3Ω cm is obtained at Td = 175 °C. The crystal orientation and surface texture show Td dependence. These characteristics correlate with each other. The dependence of these characteristics on Td is caused by the reactivity of the source materials. - Highlights: • Transparent conducting boron-doped zinc oxide films were deposited and characterized. • Comparing various characteristics, these characteristics correlate each other. • These characteristics were influenced by chemical vapor reactions strongly

  12. Modeling chemical vapor deposition of silicon dioxide in microreactors at atmospheric pressure

    International Nuclear Information System (INIS)

    We developed a multiphysics mathematical model for simulation of silicon dioxide Chemical Vapor Deposition (CVD) from tetraethyl orthosilicate (TEOS) and oxygen mixture in a microreactor at atmospheric pressure. Microfluidics is a promising technology with numerous applications in chemical synthesis due to its high heat and mass transfer efficiency and well-controlled flow parameters. Experimental studies of CVD microreactor technology are slow and expensive. Analytical solution of the governing equations is impossible due to the complexity of intertwined non-linear physical and chemical processes. Computer simulation is the most effective tool for design and optimization of microreactors. Our computational fluid dynamics model employs mass, momentum and energy balance equations for a laminar transient flow of a chemically reacting gas mixture at low Reynolds number. Simulation results show the influence of microreactor configuration and process parameters on SiO2 deposition rate and uniformity. We simulated three microreactors with the central channel diameter of 5, 10, 20 micrometers, varying gas flow rate in the range of 5-100 microliters per hour and temperature in the range of 300-800 °C. For each microchannel diameter we found an optimal set of process parameters providing the best quality of deposited material. The model will be used for optimization of the microreactor configuration and technological parameters to facilitate the experimental stage of this research

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-05

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

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

    International Nuclear Information System (INIS)

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

  15. Aerosol assisted chemical vapor deposition using nanoparticle precursors: a route to nanocomposite thin films.

    Science.gov (United States)

    Palgrave, Robert G; Parkin, Ivan P

    2006-02-01

    Gold nanoparticle and gold/semiconductor nanocomposite thin films have been deposited using aerosol assisted chemical vapor deposition (CVD). A preformed gold colloid in toluene was used as a precursor to deposit gold films onto silica glass. These nanoparticle films showed the characteristic plasmon absorption of Au nanoparticles at 537 nm, and scanning electron microscopic (SEM) imaging confirmed the presence of individual gold particles. Nanocomposite films were deposited from the colloid concurrently with conventional CVD precursors. A film of gold particles in a host tungsten oxide matrix resulted from co-deposition with [W(OPh)(6)], while gold particles in a host titania matrix resulted from co-deposition with [Ti(O(i)Pr)(4)]. The density of Au nanoparticles within the film could be varied by changing the Au colloid concentration in the original precursor solution. Titania/gold composite films were intensely colored and showed dichromism: blue in transmitted light and red in reflected light. They showed metal-like reflection spectra and plasmon absorption. X-ray photoelectron spectroscopy and energy-dispersive X-ray analysis confirmed the presence of metallic gold, and SEM imaging showed individual Au nanoparticles embedded in the films. X-ray diffraction detected crystalline gold in the composite films. This CVD technique can be readily extended to produce other nanocomposite films by varying the colloids and precursors used, and it offers a rapid, convenient route to nanoparticle and nanocomposite thin films. PMID:16448130

  16. Thin film passivation of organic light emitting diodes by inductively coupled plasma chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han-Ki [Department of Information and Nano Materials Engineering, Kumoh National Institute of Technology (KIT), 1 Yangho-dong, Gumi, Gyeongbuk, 730-701 (Korea, Republic of)]. E-mail: hkkim@kumoh.ac.kr; Kim, Sang-Woo [Department of Information and Nano Materials Engineering, Kumoh National Institute of Technology (KIT), 1 Yangho-dong, Gumi, Gyeongbuk, 730-701 (Korea, Republic of); Kim, Do-Geun [Surface Technology Research Center, Korea Institute of Machinery and Materials, 66 Sangnam-dong, Changwon-si, Gyeongnam, 641-831 (Korea, Republic of); Kang, Jae-Wook [Organic Light Emitting Diodes (OLED) Center, Seoul National University, Silim-dong, Seoul 151-741 (Korea, Republic of); Kim, Myung Soo [Core Technology Laboratory, Samsung SDI, Co., LTD., 575 Shin-dong, Youngtong-Gu, Suwon, Gyeonggi-Do, 442-391 (Korea, Republic of); Cho, Woon Jo [Nano Device Research Center, Korea Institute of Science and Technology, 39-1, Haweolgok-Dong, Seongbuk-Gu, Seoul, 136-791 (Korea, Republic of)

    2007-04-09

    The characteristics of an SiN {sub x} passivation layer grown by a specially designed inductively coupled plasma chemical vapor deposition (ICP-CVD) system with straight antennas for the top-emitting organic light emitting diodes (TOLEDs) are investigated. Using a high-density plasma on the order of {approx} 10{sup 11} electrons/cm{sup 3} formed by nine straight antennas connected in parallel, a high-density SiN {sub x} passivation layer was deposited on a transparent Mg-Ag cathode at a substrate temperature of 40 deg. C. Even at a low substrate temperature, single SiN {sub x} passivation layer prepared by ICP-CVD showed a low water vapor transmission rate of 5 x 10{sup -2} g/m{sup 2}/day and a transparency of {approx} 85% respectively. In addition, current-voltage-luminescence results of the TOLED passivated by the SiN {sub x} layer indicated that the electrical and optical properties of the TOLED were not affected by the high-density plasma during the SiN {sub x} deposition process.

  17. Noncatalytic thermocouple coatings produced with chemical vapor deposition for flame temperature measurements.

    Science.gov (United States)

    Bahlawane, N; Struckmeier, U; Kasper, T S; Osswald, P

    2007-01-01

    Chemical vapor deposition (CVD) and metal-organic chemical vapor deposition (MOCVD) have been employed to develop alumina thin films in order to protect thermocouples from catalytic overheating in flames and to minimize the intrusion presented to the combustion process. Alumina films obtained with a CVD process using AlCl(3) as the precursor are dense, not contaminated, and crystallize in the corundum structure, while MOCVD using Al(acetyl acetone)(3) allows the growth of corundum alumina with improved growth rates. These films, however, present a porous columnar structure and show some carbon contamination. Therefore, coated thermocouples using AlCl(3)-CVD were judged more suitable for flame temperature measurements and were tested in different fuels over a typical range of stoichiometries. Coated thermocouples exhibit satisfactory measurement reproducibility, no temporal drifts, and do not suffer from catalytic effects. Furthermore, their increased radiative heat loss (observed by infrared spectroscopy) allows temperature measurements over a wider range when compared to uncoated thermocouples. A flame with a well-known temperature profile established with laser-based techniques was used to determine the radiative heat loss correction to account for the difference between the apparent temperature measured by the coated thermocouple and the true flame temperature. The validity of the correction term was confirmed with temperature profile measurements for several flames previously studied in different laboratories with laser-based techniques. PMID:17503931

  18. Graphene-assisted growth of high-quality AlN by metalorganic chemical vapor deposition

    Science.gov (United States)

    Zeng, Qing; Chen, Zhaolong; Zhao, Yun; Wei, Tongbo; Chen, Xiang; Zhang, Yun; Yuan, Guodong; Li, Jinmin

    2016-08-01

    High-quality AlN films were directly grown on graphene/sapphire substrates by metalorganic chemical vapor deposition (MOCVD). The graphene layers were directly grown on sapphire by atmospheric-pressure chemical vapor deposition (APCVD), a low-cost catalyst-free method. We analyzed the influence of the graphene layer on the nucleation of AlN at the initial stage of growth and found that sparse AlN grains on graphene grew and formed a continuous film via lateral coalescence. Graphene-assisted AlN films are smooth and continuous, and the full width at half maximum (FWHM) values for (0002) and (10\\bar{1}2) reflections are 360 and 622.2 arcsec, which are lower than that of the film directly grown on sapphire. The high-resolution TEM images near the AlN/sapphire interface for graphene-assisted AlN films clearly show the presence of graphene, which kept its original morphology after the 1200 °C growth of AlN.

  19. Growth characteristics of graphene synthesized via chemical vapor deposition using carbon tetrabromide precursor

    International Nuclear Information System (INIS)

    Highlights: • Carbon tetrabromide (CBr4) precursor and Cu foil can be used for chemical vapor deposition (CVD) of graphene. • High yield and controllable growth are possible via CVD used with a CBr4 precursor. • CBr4 precursor is a new alternative for use in the mass production of graphene. • Low bond dissociation energy of CBr4 allows lower temperature growth (800 °C) of high-quality graphene film, compared to that (1000 °C) of methane used CVD. - Abstract: A carbon tetrabromide (CBr4) precursor was employed for the chemical vapor deposition (CVD) of graphene, and the graphene growth characteristics as functions of the following key factors were then investigated: growth time, growth temperature, and the partial pressure of the precursor. The graphene was transferred onto a SiO2/Si substrate and characterized using transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, and the electrical properties were measured through the fabrication of field-effect transistors. Our results show that high yield and controllable growth are possible via CVD used with a CBr4 precursor. Thus, CBr4 precursor is a new alternative candidate for use in the mass production of graphene

  20. A Novel Model of the H Radical in Hot-Filament Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    GUO Xiao-Song; BAO Zhong; ZHANG Shan-Shan; XIE Er-Qing

    2011-01-01

    @@ Amorphous hydrogenated and crystalline silicon thin films were prepared by hot-filament chemical vapor deposition.A structural transformation from amorphous phase to crystalline phase by increasing the filament temperature Tfil from 1600°C to 1650°C was observed.This phenomenon may result from the associated abundance of H radicals participating in the growth of the Silms.A probability distribution model of the H radical is proposed to elucidate this phenomenon.According to this model, the phase transition is due to a distinct difference in the probability distribution of the H radicals, which seems to be dependent upon Tfil.%Amorphous hydrogenated and crystalline silicon thin films were prepared by hot-filament chemical vapor deposition. A structural transformation from amorphous phase to crystalline phase by increasing the filament temperature Tfil from 1600℃ to 1650℃ was observed. This phenomenon may result from the associated abundance of H radicals participating in the growth of the films. A probability distribution model of the H radical is proposed to elucidate this phenomenon. According to this model, the phase transition is due to a distinct difference in the probability distribution of the H radicals, which seems to be dependent upon Tfil.

  1. Development of Single Crystal Chemical Vapor Deposition Diamonds for Detector Applications

    Energy Technology Data Exchange (ETDEWEB)

    Kagan, Harris; Kass, Richard; Gan, K. K.

    2014-01-23

    With the LHC upgrades in 2013, and further LHC upgrades scheduled in 2018, most LHC experiments are planning for detector upgrades which require more radiation hard technologies than presently available. At present all LHC experiments now have some form of diamond detector. As a result Chemical Vapor Deposition (CVD) diamond has now been used extensively in beam conditions monitors as the innermost detectors in the highest radiation areas of all LHC experiments. Moreover CVD diamond is now being discussed as an alternative sensor material for tracking very close to the interaction region of the HL-LHC where the most extreme radiation conditions will exist. Our work addressed the further development of the new material, single-crystal Chemical Vapor Deposition diamond, towards reliable industrial production of large pieces and new geometries needed for detector applications. Our accomplishments include: • Developed a two U.S.companies to produce electronic grade diamond, • Worked with companies and acquired large area diamond pieces, • Performed radiation hardness tests using various proton energies: 70 MeV (Cyric, Japan), 800 MeV (Los Alamos), and 24 GeV (CERN).

  2. Hot-wire chemical vapor deposition of silicon nanoparticles on fused silica

    International Nuclear Information System (INIS)

    Silicon nanoparticles on fused silica have potential as recombination centers in infrared detectors due quantum confinement effects that result in a size dependent band gap. Growth on fused silica was realized by etching in HF, annealing under vacuum at 700-750 oC, and cooling to ambient temperature before ramping to the growth temperature of 600 oC. Silicon particles could not be grown in a thermal chemical vapor deposition (CVD) process with adequate size uniformity and density. Seeding fused silica with Si adatoms in a hot-wire chemical vapor deposition (HWCVD) process at a disilane pressure of 1.1 x 10-5 Pa followed by thermal CVD at a disilane pressure of 1.3 x 10-2 Pa, or direct HWCVD at a disilane pressure of 2.1 x 10-5 Pa led to acceptable size uniformity and density. Dangling bonds at the surface of the as-grown nanoparticle were passivated using atomic H formed by cracking H2 over the HWCVD filament.

  3. Synthesis and Characterization of Carbon nanofibers on Co and Cu Catalysts by Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Park, Eunsil; Kim, Jongwon; Lee, Changseop [Keimyung Univ., Daegu (Korea, Republic of)

    2014-06-15

    This study reports on the synthesis of carbon nanofibers via chemical vapor deposition using Co and Cu as catalysts. In order to investigate the suitability of their catalytic activity for the growth of nanofibers, we prepared catalysts for the synthesis of carbon nanofibers with Cobalt nitrate and Copper nitrate, and found the optimum concentration of each respective catalyst. Then we made them react with Aluminum nitrate and Ammonium Molybdate to form precipitates. The precipitates were dried at a temperature of 110 .deg. C in order to be prepared into catalyst powder. The catalyst was sparsely and thinly spread on a quartz tube boat to grow carbon nanofibers via thermal chemical vapor deposition. The characteristics of the synthesized carbon nanofibers were analyzed through SEM, EDS, XRD, Raman, XPS, and TG/DTA, and the specific surface area was measured via BET. Consequently, the characteristics of the synthesized carbon nanofibers were greatly influenced by the concentration ratio of metal catalysts. In particular, uniform carbon nanofibers of 27 nm in diameter grew when the concentration ratio of Co and Cu was 6:4 at 700 .deg. C of calcination temperature; carbon nanofibers synthesized under such conditions showed the best crystallizability, compared to carbon nanofibers synthesized with metal catalysts under different concentration ratios, and revealed 1.26 high amorphicity as well as 292 m{sup 2}g{sup -1} high specific surface area.

  4. Growth characteristics of graphene synthesized via chemical vapor deposition using carbon tetrabromide precursor

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Taejin; Jung, Hanearl; Lee, Chang Wan [Nanodevice Laboratory, School of Electrical and Electronics Engineering, Yonsei University, Seodaemun-Gu, Seoul 120-749 (Korea, Republic of); Mun, Ki-Yeung; Kim, Soo-Hyun [Nano-Devices and Process Laboratory, School of Materials Science and Engineering, Yeungnam University, Dae-Dong, Gyeongsan-Si 712-749 (Korea, Republic of); Park, Jusang [Nanodevice Laboratory, School of Electrical and Electronics Engineering, Yonsei University, Seodaemun-Gu, Seoul 120-749 (Korea, Republic of); Kim, Hyungjun, E-mail: hyungjun@yonsei.ac.kr [Nanodevice Laboratory, School of Electrical and Electronics Engineering, Yonsei University, Seodaemun-Gu, Seoul 120-749 (Korea, Republic of)

    2015-07-15

    Highlights: • Carbon tetrabromide (CBr{sub 4}) precursor and Cu foil can be used for chemical vapor deposition (CVD) of graphene. • High yield and controllable growth are possible via CVD used with a CBr{sub 4} precursor. • CBr{sub 4} precursor is a new alternative for use in the mass production of graphene. • Low bond dissociation energy of CBr{sub 4} allows lower temperature growth (800 °C) of high-quality graphene film, compared to that (1000 °C) of methane used CVD. - Abstract: A carbon tetrabromide (CBr{sub 4}) precursor was employed for the chemical vapor deposition (CVD) of graphene, and the graphene growth characteristics as functions of the following key factors were then investigated: growth time, growth temperature, and the partial pressure of the precursor. The graphene was transferred onto a SiO{sub 2}/Si substrate and characterized using transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, and the electrical properties were measured through the fabrication of field-effect transistors. Our results show that high yield and controllable growth are possible via CVD used with a CBr{sub 4} precursor. Thus, CBr{sub 4} precursor is a new alternative candidate for use in the mass production of graphene.

  5. 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.

  6. Models of Gas-phase and Surface Chemistry for Plasma Enhanced Chemical Vapor Deposition

    Science.gov (United States)

    Meeks, Ellen

    1996-10-01

    Plasma enhanced chemical vapor deposition for inter-metal-layer gap-fill processes are increasingly important in semiconductor device manufacture, as the devices include increasing numbers of metal layers with decreasing linewidth and spacing. Optimization of these processes requires knowledge of the microscopic consequences of variations in reactor operating conditions. Topographical simulation can address the gap-fill performance of a depositing film, but the predictive capabiliities are limited by the ability of the model user to accurately supply ion and radical fluxes at a gas/surface interface. Critical to determining this information are the chemical kinetics between gas-phase species and the deposition surfaces. Recent improvements and extensions to the CHEMKIN and Surface CHEMKIN software allow general inclusion of detailed chemical mechanisms in plasma simulations and in models of plasma-surface interactions. In the results presented here (This work represents a collaboration with R. Larson and P. Ho at Sandia, J. Rey and J. Li at TMA, S. M. Han and E. Aydil of UCSB, and S. Huang at Lam Research Corporation), we have used a CHEMKIN-based well mixed reactor model of a high-density SiH_4/O_2/Ar plasma to predict and characterize species fluxes, oxide-deposition rates, and ion-milling rates on a flat surface. These calculated rates can be used as direct input to a topographical simulator. The gas-phase chemistry in the plasma reactor model is comprised of electron impact reactions with silane, oxygen, hydrogen, and argon, as well as neutral radical recombination, abstraction, and oxidation reactions. The surface reaction mechanism contains four classes of reactions: silicon-containing radical deposition, radical abstraction, ion-induced desorption, and physical ion sputtering. We include relative thermochemistry of the surface and gas species to allow reversible reaction dynamics. The plasma model results show good agreement with measured ion densities, as

  7. Technical Challenges and Progress in Fluidized Bed Chemical Vapor Deposition of Polysilicon

    Institute of Scientific and Technical Information of China (English)

    李建隆; 陈光辉; 张攀; 王伟文; 段继海

    2011-01-01

    Various methods for production of polysilicon have been proposed for lowering the production cost andenergy consumption, and enhancing productivity, which are critical for industrial applications. The fluidized bed chemical vapor deposition (FBCVD) method is a most promising alternative to conventional ones, but the homogeneous reaction of silane in FBCVD results in unwanted formation of fines, which will affect the product qualityand output. There are some other problems, such as heating degeneration due to undesired polysilicon deposition on the walls of the reactor and the heater. This article mainly reviews the technological development on FBCVD of polycrystalline silicon and the research status for solving the above problems. It also identifies a number of challenges to tackle and principles should be followed in the design ofa FBCVD reactor.

  8. 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.

  9. Strategy for silicon based hot-wire chemical vapor deposition without wire silicide formation

    Energy Technology Data Exchange (ETDEWEB)

    Laukart, Artur, E-mail: artur.laukart@ist.fraunhofer.de; Harig, Tino; Höfer, Markus; Schäfer, Lothar

    2015-01-30

    Silicide formation of wires during hot-wire chemical vapor deposition (HWCVD) of silicon based coatings is a key challenge which has to be overcome before HWCVD can be transferred successfully into industry. Silicide formation of tungsten wires is not occurring at temperatures of approximately 1900 °C and above when maintaining a silane partial pressure below approximately 1 Pa. Proceeding silicide formation at the cold ends where the wires are electrically contacted was completely prevented by continuously moving the cold ends of the wires into the hot deposition zone, resulting in a retransformation of the tungsten phase. Thus the maintenance period of a HWCVD manufacturing tool can be freed from wire lifetime.

  10. Formation of high T/sub c/ superconducting films by organometallic chemical vapor deposition

    International Nuclear Information System (INIS)

    The first growth of superconducting YBaCuO films by organometallic chemical vapor deposition is described. Metal β-diketonates were decomposed thermally on MgO substrates in an oxygen-rich atmosphere to produce amorphous brown films. Subsequent annealing in oxygen yielded dull gray films whose thickness corresponded to deposition rates of approximately 8 nm min-1. These films showed semiconductor-like behavior at higher temperatures, followed by a broad resistive transition from 80 to 36 K with the resistance becoming zero at ∼20 K. Analysis of x-ray data indicated the presence of the orthorhombic superconducting phase and various other metal oxides. Profilometer measurements yielded film thicknesses up to 950 nm, and scanning electron microscopy revealed faceted grains from 0.5 to 1.0 μm in size

  11. Tribological properties of diamond films grown by plasma-enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Uniform and continuous diamond films have been deposited on Si, Mo, and many other substrates by plasma-enhanced chemical vapor deposition. We have developed processes to enhance the adhesion of diamond films to metal substrates for tribological applications. The tribological properties of the diamond films are found to be significantly different depending on their morphology, grain size, and roughness. However, under all cases tested using a ring-on-block tribotester, it is found that for diamond films with a small grain size of 1--3 μm, the coefficient of friction of the diamond films sliding against a steel ring under lubrication of a jet of mineral oil is about 0.04

  12. Multi-wall carbon nanotubes supported on carbon fiber paper synthesized by simple chemical vapor deposition

    International Nuclear Information System (INIS)

    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

  13. Selective charge doping of chemical vapor deposition-grown graphene by interface modification

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shengnan, E-mail: wang.shengnan@lab.ntt.co.jp; Suzuki, Satoru; Furukawa, Kazuaki; Orofeo, Carlo M.; Takamura, Makoto; Hibino, Hiroki [NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198 (Japan)

    2013-12-16

    The doping and scattering effect of substrate on the electronic properties of chemical vapor deposition (CVD)-grown graphene are revealed. Wet etching the underlying SiO{sub 2} of graphene and depositing self-assembled monolayers (SAMs) of organosilane between graphene and SiO{sub 2} are used to modify various substrates for CVD graphene transistors. Comparing with the bare SiO{sub 2} substrate, the carrier mobility of CVD graphene on modified substrate is enhanced by almost 5-fold; consistently the residual carrier concentration is reduced down to 10{sup 11} cm{sup −2}. Moreover, scalable and reliable p- and n-type graphene and graphene p-n junction are achieved on various silane SAMs with different functional groups.

  14. Selective charge doping of chemical vapor deposition-grown graphene by interface modification

    International Nuclear Information System (INIS)

    The doping and scattering effect of substrate on the electronic properties of chemical vapor deposition (CVD)-grown graphene are revealed. Wet etching the underlying SiO2 of graphene and depositing self-assembled monolayers (SAMs) of organosilane between graphene and SiO2 are used to modify various substrates for CVD graphene transistors. Comparing with the bare SiO2 substrate, the carrier mobility of CVD graphene on modified substrate is enhanced by almost 5-fold; consistently the residual carrier concentration is reduced down to 1011 cm−2. Moreover, scalable and reliable p- and n-type graphene and graphene p-n junction are achieved on various silane SAMs with different functional groups

  15. Selective charge doping of chemical vapor deposition-grown graphene by interface modification

    Science.gov (United States)

    Wang, Shengnan; Suzuki, Satoru; Furukawa, Kazuaki; Orofeo, Carlo M.; Takamura, Makoto; Hibino, Hiroki

    2013-12-01

    The doping and scattering effect of substrate on the electronic properties of chemical vapor deposition (CVD)-grown graphene are revealed. Wet etching the underlying SiO2 of graphene and depositing self-assembled monolayers (SAMs) of organosilane between graphene and SiO2 are used to modify various substrates for CVD graphene transistors. Comparing with the bare SiO2 substrate, the carrier mobility of CVD graphene on modified substrate is enhanced by almost 5-fold; consistently the residual carrier concentration is reduced down to 1011 cm-2. Moreover, scalable and reliable p- and n-type graphene and graphene p-n junction are achieved on various silane SAMs with different functional groups.

  16. Metalorganic chemical vapor deposition of ZnO:N using NO as dopant

    Energy Technology Data Exchange (ETDEWEB)

    Dangbegnon, J.K., E-mail: JulienKouadio.Dangbegnon@nmmu.ac.z [Department of Physics, PO Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Talla, K.; Roro, K.T.; Botha, J.R. [Department of Physics, PO Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2009-12-01

    Highly c-axis orientated ZnO was grown by metal organic chemical vapor deposition (MOCVD) using NO as both oxidant and nitrogen dopant source. The properties of the deposited material are investigated by X-ray diffraction to study the crystalline quality of the thin films. Photoluminescence measurements are used to determine the optical properties of the material as a function of VI/II ratio and post growth-annealing temperature. Two transitions appear at 3.228 and 3.156 eV and are interpreted as involving active nitrogen acceptors. An increase in the NO flow increases the concentration of nitrogen in the films, which are activated by subsequent annealing at 600 deg. C in an oxygen ambient.

  17. Metalorganic chemical vapor deposition of ZnO:N using NO as dopant

    International Nuclear Information System (INIS)

    Highly c-axis orientated ZnO was grown by metal organic chemical vapor deposition (MOCVD) using NO as both oxidant and nitrogen dopant source. The properties of the deposited material are investigated by X-ray diffraction to study the crystalline quality of the thin films. Photoluminescence measurements are used to determine the optical properties of the material as a function of VI/II ratio and post growth-annealing temperature. Two transitions appear at 3.228 and 3.156 eV and are interpreted as involving active nitrogen acceptors. An increase in the NO flow increases the concentration of nitrogen in the films, which are activated by subsequent annealing at 600 deg. C in an oxygen ambient.

  18. Growth of well-oriented VACNTs using thermal chemical vapor deposition method

    Science.gov (United States)

    Yousefi, Amin Termeh; Mahmood, Mohamad Rusop; Ikeda, Shoichiro

    2016-07-01

    The remarkable properties of carbon nanotubes (CNTs) make them attractive for biosensor applications, especially for medical detecting devices. In this paper, we describe a process to grow high oriented ratio CNT arrays to improve the electrical properties of the devices based on CNTs. Chemical vapor deposition (CVD) was used to grow highly oriented CNT using camphor as the carbon source, and argon and hydrogen as carrier gases to grow perpendicular CNTs on the surface of the silicon substrate in presence of ferrocene as a metallic catalyst. Images were revealed by FESEM indicates that the formation mechanism of oriented CNTs with high morphological purity nanotubes, which is depends significantly on deposition time and applied temperature to the furnaces. This method might be an effective method to produce oriented MWCNT in different length.

  19. Defect Characterization in Ge/(001)Si Epitaxial Films Grown by Reduced-Pressure Chemical Vapor Deposition

    Science.gov (United States)

    Bharathan, Jayesh; Narayan, Jagdish; Rozgonyi, George; Bulman, Gary E.

    2013-10-01

    We studied the microstructural characteristics and electrical properties of epitaxial Ge films grown on Si(001) substrates by x-ray diffraction, atomic force microscopy, and transmission electron microscopy. The films were grown using a two-step technique by reduced-pressure chemical vapor deposition, where the first step promotes two-dimensional growth at a lower substrate temperature. We observed a decrease in defect density with increasing film thickness. Ge films with thickness of 3.5 μm exhibited threading dislocation densities of 5 × 106 cm-2, which yielded devices with dark current density of 5 mA cm-2 (1 V reverse bias). We also noted the presence of stacking faults in the form of lines in the films and establish that this is an important defect for Ge films grown by this deposition technique.

  20. Ion-induced epitaxial growth of chemical vapor deposited Si layers

    Science.gov (United States)

    La Ferla, A.; Rimini, E.; Ferla, G.

    1988-02-01

    Thin layers of Si were chemical vapor deposited onto as-received p-type Si wafers. The samples were subsequently implanted with 1×1015/cm2, 80 keV As. The native oxide film impedes the growth even at 800 °C, 1 h; instead irradiation with 600 keV Kr++ at 450 °C causes the epitaxial growth of the entire deposited and amorphized Si layer. The sheet resistance of these As-doped layers (130 Ω/⧠) coincides with that of samples in which the amorphous layer was obtained by As ion implantation only. The value is at least ten times lower than that of the polycrystalline layer doped with the same amount of As.

  1. Flexible Electronics: High Pressure Chemical Vapor Deposition of Hydrogenated Amorphous Silicon Films and Solar Cells (Adv. Mater. 28/2016).

    Science.gov (United States)

    He, Rongrui; Day, Todd D; Sparks, Justin R; Sullivan, Nichole F; Badding, John V

    2016-07-01

    On page 5939, J. V. Badding and co-workers describe the unrolling of a flexible hydrogenated amorphous silicon solar cell, deposited by high-pressure chemical vapor deposition. The high-pressure deposition process is represented by the molecules of silane infiltrating the small voids between the rolled up substrate, facilitating plasma-free deposition over a very large area. The high-pressure approach is expected to also find application for 3D nanoarchitectures. PMID:27442970

  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. Chemical vapor deposition and analysis of thermally insulating ZrO2 layers on injection molds

    International Nuclear Information System (INIS)

    High quality injection molding requires a precise control of cooling rates. Thermal barrier coating (TBC) of zirconia with a thickness of 20-40 μm on polished stainless steel molds could provide the necessary insulating effect. This paper presents results of zirconia deposition on stainless steel substrates using chemical vapor deposition (CVD) aiming to provide the process parameters for the deposition of uniform zirconia films with such a thickness. The deposition was performed with zirconium (IV) acetylacetonate (Zr(C5H7O2)4) as precursor and synthetic air as co-reactant, which allows deposition at temperatures below 600 C. The experiments were carried out in a hot-wall reactor at pressures between 7.5 mbar and 500 mbar and in a temperature range from 450 C to 600 C. Important growth parameters were characterized and growth rates between 1 and 2.5 μm/h were achieved. Thick and well adhering zirconia layers of 38 μm could be produced on steel within 40 h. The transient heat transfer rate upon contact with a hot surface was also evaluated experimentally with the thickest coatings. These exhibit a good TBC performance. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Preparation and structure of porous dielectrics by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    The preparation of ultralow dielectric constant porous silicon, carbon, oxygen, hydrogen alloy dielectrics, called 'pSiCOH', using a production 200 mm plasma enhanced chemical vapor deposition tool and a thermal treatment is reported here. The effect of deposition temperature on the pSiCOH film is examined using Fourier transform infrared (FTIR) spectroscopy, dielectric constant (k), and film shrinkage measurements. For all deposition temperatures, carbon in the final porous film is shown to be predominantly Si-CH3 species, and lower k is shown to correlate with increased concentration of Si-CH3. NMR and FTIR spectroscopies clearly detect the loss of a removable, unstable, hydrocarbon (CHx) phase during the thermal treatment. Also detected are increased cross-linking of the Si-O skeleton, and concentration changes for three distinct structures of carbon. In the as deposited films, deposition temperature also affects the hydrocarbon (CHx) content and the presence of C=O and C=C functional groups

  5. Incorporation of nitrogen into amorphous carbon films produced by surface-wave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    In order to study the influence of nitrogen incorporated into amorphous carbon films, nitrogenated amorphous carbon films have been deposited by using surface wave plasma chemical vapor deposition under various ratios of N2/CH4 gas flow. Optical emission spectroscopy has been used to monitor plasma features near the deposition zone. After deposition, the samples are checked by Raman spectroscopy and x-ray photo spectroscopy (XPS). Optical emission intensities of CH and N atom in the plasma are found to be enhanced with the increase in the N2/CH4 gas flow ratio, and then reach their maximums when the N2/CH4 gas flow ratio is 5%. A contrary variation is found in Raman spectra of deposited films. The intensity ratio of the D band to the G band (ID/IG) and the peak positions of the G and D bands all reach their minimums when the N2/CH4 gas flow ratio is 5%. These show that the structure of amorphous carbon films has been significantly modified by introduction of nitrogen

  6. Plasma enhanced chemical vapor deposition of thin ZnO layers on glass substrates

    International Nuclear Information System (INIS)

    The plasma enhanced chemical vapor deposition (PECVD) is a powerful and flexible instrument for depositing thin layers, nanocomposites or nanostructures. In this work ZnO layers were grown by metal-organic PECVD (RF – 13.56 MHz) on glass substrates coated with ZnO seed films. Zn acetylacetonate was used as a precursor and oxygen as oxidant. The influence of the oxygen content in gas mixture on the morphology, optical and electrical properties of the deposited layers was studied. ZnO film properties were investigated by scanning electron microscopy (SEM), UV-VIS optical spectrophotometry and current-voltage (I-V) measurements. The results obtained show that the oxygen content in the deposition atmosphere influences the morphology, the optical properties and the electrical resistivity of the obtained ZnO layers. Nanorods with good alignment, vertically orientated to the surface of glass substrate can be observed in the layers deposited at low content of O2 in plasma at substrate temperature of 400°C

  7. Excellent crystalline silicon surface passivation by amorphous silicon irrespective of the technique used for chemical vapor deposition

    NARCIS (Netherlands)

    Schuttauf, J.A.; van der Werf, C.H.M.; Kielen, I.M.; van Sark, W.G.J.H.M.; Rath, J.K.; Schropp, R.E.I.

    2011-01-01

    Crystalline silicon surface passivation by amorphous silicon deposited by three different chemical vapor deposition (CVD) techniques at low (T ∼ 130 °C) temperatures is compared. For all three techniques, surface recombination velocities (SRVs) are reduced by two orders of magnitude after prolonged

  8. Physical properties of nitrogen-doped diamond-like amorphous carbon films deposited by supermagnetron plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Diamond-like amorphous carbon films doped with nitrogen (DAC:N) were deposited on Si and glass wafers intermittently using i-C4H10/N2 repetitive supermagnetron plasma chemical vapor deposition. Deposition duration, which is equal to a plasma heating time of wafer, was selected to be 40 or 60 s, and several layers were deposited repetitively to form one thick film. DAC:N films were deposited at a lower-electrode temperature of 100 deg. C as a function of upper- and lower-electrode rf powers (200 W/200 W-1 kW/1 kW) and N2 concentration (0%-80%). With an increase in N2 concentration and rf power, the resistivity and the optical band gap decreased monotonously. With increase of the deposition duration from 40 to 60 s, resistivity decreased to 0.03Ω cm and optical band gap decreased to 0.02 eV (substantially equal to 0 eV within the range of experimental error), at an N2 concentration of 80% and rf power of 1 kW(/1 kW)

  9. Aerosol assisted atmospheric pressure chemical vapor deposition of silicon thin films using liquid cyclic hydrosilanes

    International Nuclear Information System (INIS)

    Silicon (Si) thin films were produced using an aerosol assisted atmospheric pressure chemical vapor deposition technique with liquid hydrosilane precursors cyclopentasilane (CPS, Si5H10) and cyclohexasilane (CHS, Si6H12). Thin films were deposited at temperatures between 300 and 500 °C, with maximum observed deposition rates of 55 and 47 nm/s for CPS and CHS, respectively, at 500 °C. Atomic force microscopic analyses of the films depict smooth surfaces with roughness of 4–8 nm. Raman spectroscopic analysis indicates that the Si films deposited at 300 °C and 350 °C consist of a hydrogenated amorphous Si (a-Si:H) phase while the films deposited at 400, 450, and 500 °C are comprised predominantly of a hydrogenated nanocrystalline Si (nc-Si:H) phase. The wide optical bandgaps of 2–2.28 eV for films deposited at 350–400 °C and 1.7–1.8 eV for those deposited at 450–500 °C support the Raman data and depict a transition from a-Si:H to nc-Si:H. Films deposited at 450 oC possess the highest photosensitivity of 102–103 under AM 1.5G illumination. Based on the growth model developed for other silanes, we suggest a mechanism that governs the film growth using CPS and CHS. - Highlights: • Si films via AA-APCVD are realized using cyclopentasilane (CPS) and cyclohexasilane (CHS). • Low activation energies of CPS and CHS allow Si thin films at low temperatures (300 °C). • High growth rates of 47–55 nm/s were obtained at 500 °C • Near device quality Si thin films with 2–3 orders of photosensitivity • Si thin films via AA-APCVD are amenable to continuous roll-to-roll manufacturing

  10. Growth and characterization of bismuth selenide thin films by chemical vapor deposition

    Science.gov (United States)

    Brom, Joseph E.

    Topological insulators are a recently discovered class of materials that have garnered much interest due to their unique surface states. With its relatively high band gap (0.3eV) and nearly ideal band structure, Bi2Se 3 has been a primary material of interest in the study of topological insulating behavior. However, several factors have made this study difficult. Bi2Se3 typically has a high native selenium vacancy concentration, and selenium vacancies act as donors in the material, leading to a high bulk electron concentration. The surface of Bi2Se 3 has also been shown to be susceptible to environmental doping when exposed to ambient air. Combining these two factors means that Bi2Se 3 is usually highly n-type doped, making it difficult to study the surface conducting states by transport measurements. This study investigated the use of two different chemical vapor deposition (CVD) techniques for the growth of Bi2Se3 thin films on sapphire (001): hybrid physicalchemical vapor deposition (HPCVD) and metal-organic chemical vapor deposition (MOCVD). HPCVD is a process which combines the evaporation of elemental selenium with the thermal decomposition of trimethylbismuth (TMBi). The use of elemental selenium immediately around the substrate provides a high overpressure of selenium, allowing for reduction of the selenium vacancy concentration. Bi2Se3 films grown on sapphire were epitaxial and highly oriented parallel to the substrate giving rise to narrow X-ray rocking curves (full-width-at-half-maximum=160 arcsecs for (006) reflection) and 6-fold rotational symmetry as determined by phi scans. The structural properties were consistent with deposition via a van der Waals epitaxy process. The selenium to bismuth ratio (VI/V) ratio proved important for achieving a reduced electron concentration of TMBi) dimethylselenide (DMSe) as precursors. Epitaxial Bi 2Se3 films were also produced by MOCVD on sapphire, however, the electron concentrations were generally higher (1- 3x

  11. Opportunities and challenges in GaN metal organic chemical vapor deposition for electron devices

    Science.gov (United States)

    Matsumoto, Koh; Yamaoka, Yuya; Ubukata, Akinori; Arimura, Tadanobu; Piao, Guanxi; Yano, Yoshiki; Tokunaga, Hiroki; Tabuchi, Toshiya

    2016-05-01

    The current situation and next challenge in GaN metal organic chemical vapor deposition (MOCVD) for electron devices of both GaN on Si and GaN on GaN are presented. We have examined the possibility of increasing the growth rate of GaN on 200-mm-diameter Si by using a multiwafer production MOCVD machine, in which the vapor phase parasitic reaction is well controlled. The impact of a high-growth-rate strained-layer-superlattice (SLS) buffer layer is presented in terms of material properties. An SLS growth rate of as high as 3.46 µm/h, which was 73% higher than the current optimum, was demonstrated. As a result, comparable material properties were obtained. Next, a typical result of GaN doped with Si of 1 × 1016 cm‑3 grown at the growth rate of 3.7 µm/h is shown. For high-voltage application, we need a thick high-purity GaN drift layer with a low carbon concentration, of less than 1016 cm‑3. It is shown that achieving a high growth rate by precise control of the vapor phase reaction is still challenge in GaN MOCVD.

  12. An economic analysis of the deposition of electrochromic WO3 via sputtering or plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    The costs of manufacturing electrochromic WO3 thin films deposited by either radio frequency plasma enhanced chemical vapor deposition (PECVD) or DC reactive magnetron sputtering of metal targets were modeled. Both inline systems for large area glass substrates and roll-to-roll systems for flexible webs were compared. Costs of capital, depreciation, raw materials, labor, power, and other miscellaneous items were accounted for in the model. The results predict that on similar sized systems, PECVD can produce electrochromic WO3 for as little as one-third the cost, and have more than 10 times the annual production capacity of sputtering. While PECVD cost is dominated by raw materials, primarily WF6, sputtering cost is dominated by labor and depreciation

  13. Formation and electron field emission of graphene films grown by hot filament chemical vapor deposition

    International Nuclear Information System (INIS)

    Graphene films with different structures were catalytically grown on the silicon substrate pre-deposited with a gold film by hot filament chemical vapor deposition under different conditions, where methane, hydrogen and nitrogen were used as the reactive gases. The morphological and compositional properties of graphene films were studied using advanced instruments including field emission scanning electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the structure and composition of graphene films are changed with the variation of the growth conditions. According to the theory related to thermodynamics, the formation of graphene films was theoretically analyzed and the results indicate that the formation of graphene films is related to the fast incorporation and precipitation of carbon. The electron field emission (EFE) properties of graphene films were studied in a high vacuum system of ∼10−6 Pa and the EFE results show that the turn-on field is in a range of 5.2–5.64 V μm−1 and the maximum current density is about 63 μ A cm−2 at the field of 7.7 V μm−1. These results are important to control the structure of graphene films and have the potential applications of graphene in various nanodevices. - Highlights: • Graphene films are grown on gold films by hot filament chemical vapor deposition. • Hierarchical nanoflower structures made of graphene flakes are demonstrated. • The size of gold nanodroplets plays an important role in graphene flake formation. • The films show competitive electron field emission properties

  14. Functional metal oxide coatings by molecule-based thermal and plasma chemical vapor deposition techniques.

    Science.gov (United States)

    Mathur, S; Ruegamer, T; Donia, N; Shen, H

    2008-05-01

    Deposition of thin films through vaccum processes plays an important role in industrial processing of decorative and functional coatings. Many metal oxides have been prepared as thin films using different techniques, however obtaining compositionally uniform phases with a control over grain size and distribution remains an enduring challenge. The difficulties are largely related to complex compositions of functional oxide materials, which makes a control over kinetics of nucleation and growth processes rather difficult to control thus resulting in non-uniform material and inhomogeneous grain size distribution. Application of tailor-made molecular precursors in low pressure or plasma-enhanced chemical vapor deposition (CVD) techniques offers a viable solution for overcoming thermodynamic impediments involved in thin film growth. In this paper molecule-based CVD of functional coatings is demonstrated for iron oxide (Fe2O3, Fe3O4), vanadium oxide (V2O5, VO2) and hafnium oxide (HfO2) phases followed by the characterization of their microstructural, compositional and functional properties which support the advantages of chemical design in simplifying deposition processes and optimizing functional behavior. PMID:18572690

  15. Chemical vapor deposition. 1975-1978 (citations from the NTIS Data Base). Report for 1975-78

    Energy Technology Data Exchange (ETDEWEB)

    Cavagnaro, D.M.

    1980-07-01

    This bibliography discusses chemical vapor deposition of carbon, carbides, ceramics, metals, and glasses. Applications of this process include coatings, semiconducting films, laser materials, solar cells, composite fabrication, and nuclear reactor material fabrication. The physical, mechanical, and chemical properties of these coatings are covered. (This updated bibliography contains 246 citations, none of which are new entries to the previous edition.)

  16. Chemical vapor deposition. 1979-June 1980 (citations from the NTIS Data Base). Report for 1979-June 1980

    Energy Technology Data Exchange (ETDEWEB)

    Cavagnaro, D.M.

    1980-07-01

    Research on chemical vapor deposition of carbon, carbides, ceramics, metals, and glasses are cited. Applications of this process include optical coatings, semiconducting films, laser materials, solar cells, composite fabrication, and nuclear reactor material fabrication. The physical, mechanical, and chemical properties of these coatings are covered. (This updated bibliography contains 64 citations, 50 of which are new entries to the previous edition.)

  17. The organometallic chemical vapor deposition of transition metal carbides: The use of homoleptic alkyls

    Energy Technology Data Exchange (ETDEWEB)

    Healy, M.D.; Smith, D.C.; Springer, R.W. [Los Alamos National Lab., NM (United States); Rubiano, R.R. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Nuclear Engineering; Springer, R.W.; Parmeter, J.E. [Sandia National Labs., Albuquerque, NM (United States)

    1993-12-31

    The organometallic chemical vapor deposition of transition metal carbides (M = Ti, Zr, Hf, and Cr) from tetraneopentyl-metal precursors has been carried out. Metal carbides can be deposited on Si, Al{sub 2}O{sub 3}, and stainless steel substrates from M[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} at temperatures in the range of 300 to 750 C and pressures from 10{sup {minus}2} to 10{sup {minus}4} Torr. Thin films have also been grown using a carrier gas (Ar, H{sub 2}). The effects of variation of the metal center, deposition conditions, and reactor design on the resulting material have been examined by SEM, XPS, XRD, ERD and AES. Hydrocarbon fragments generated in the deposition chamber have been studied in by in-situ mass spectrometry. Complementary studies examining the UHV surface decomposition of Zr[CH{sub 2}C(CH{sub 3}){sub 3}]{sub 4} have allowed for a better understanding of the mechanism leading to film growth.

  18. Gas phase chemistry during electron assisted chemical vapor deposition (EACVD) of diamond films

    International Nuclear Information System (INIS)

    Diamond films were deposited in electron assisted chemical vapor deposition (EACVD) reactor using two source mixtures of CH4-H2 and C2H5OH-H2, respectively. The plasma gas composition during diamond growing was investigated in situ using optical emission spectroscopy (OES). In two cases of C2H2OH-H2 and CH4-H2 plasma, it was shown that CH and CH+ were all important precursor species in the diamond deposition reaction while the yields of poor diamond films corresponded to the presence of the C2 emission line. The difference between these two cases was that some oxygen-containing species (CH2O, CHO and O2) were detected in the C2H5OH-H2 plasma. The presence of these products may maintain the quality of the deposited diamond films while increasing carbon source concentration, and the growth rate was thus enhanced. These results imply that the increase in the growth rate of diamond film using C2H5OH-H2 mixture is primarily due to a change in gas phase environment

  19. Characterization of Chemical Vapor Deposited Tetraethyl Orthosilicate based SiO2 Films for Photonic Devices

    Directory of Open Access Journals (Sweden)

    Jhansirani KOTCHARLAKOTA

    2016-05-01

    Full Text Available Silicon has been the choice for photonics technology because of its cost, compatibility with mass production and availability. Silicon based photonic devices are very significant from commercial point of view and are much compatible with established technology. This paper deals with deposition and characterization of SiO2 films prepared by indigenously developed chemical vapor deposition system. Ellipsometry study of prepared films showed an increase in refractive index and film thickness with the increment in deposition temperature. The deposition temperature has a significant role for stoichiometric SiO2 films, FTIR measurement has shown the three characteristics peaks of Si-O-Si through three samples prepared at temperatures 700, 750 and 800 °C while Si-O-Si stretching peak positions were observed to be shifted to lower wavenumber in accordance to the temperature. FESEM analysis has confirmed the smooth surface without any crack or disorder while EDX analysis showed the corresponding peaks of compositional SiO2 films.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7245

  20. Optimization of silicon oxynitrides by plasma-enhanced chemical vapor deposition for an interferometric biosensor

    International Nuclear Information System (INIS)

    In this paper, silicon oxynitride layers deposited with different plasma-enhanced chemical vapor deposition (PECVD) conditions were fabricated and optimized, in order to make an interferometric sensor for detecting biochemical reactions. For the optimization of PECVD silicon oxynitride layers, the influence of the N2O/SiH4 gas flow ratio was investigated. RF power in the PEVCD process was also adjusted under the optimized N2O/SiH4 gas flow ratio. The optimized silicon oxynitride layer was deposited with 15 W in chamber under 25/150 sccm of N2O/SiH4 gas flow rates. The clad layer was deposited with 20 W in chamber under 400/150 sccm of N2O/SiH4 gas flow condition. An integrated Mach–Zehnder interferometric biosensor based on optical waveguide technology was fabricated under the optimized PECVD conditions. The adsorption reaction between bovine serum albumin (BSA) and the silicon oxynitride surface was performed and verified with this device

  1. Controlled synthesis of TiO2 mesoporous microspheres via chemical vapor deposition

    International Nuclear Information System (INIS)

    Graphical abstract: Highlights: → Anatase titanium dioxide (TiO2) mesoporous microspheres with core-shell and hollow structure were successfully prepared on a large scale by a simple template-free chemical vapor deposition method. → The as-synthesized products are high uniformity, and the porosity could be well controlled by optimizing the reaction conditions. → The possible growth mechanism of the multi core-shell and hollow nanostructures has been discussed. - Abstract: Anatase titanium dioxide (TiO2) mesoporous microspheres with core-shell and hollow structure were successfully prepared on a large scale by a one-step template-free chemical vapor deposition method. The effects of various reaction conditions on the morphology, composition and structure of the products were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) technique and photoluminescence (PL) method. The results indicate that the product near the source was composed of core-shell structure TiO2 microspheres with diameters from 3 to 5 μm. With increasing the distance between the source materials and the substrate, the hollow TiO2 spheres with 1-2 μm dominant the products. A localized Ostwald ripening can be use to explain the formation of core-shell and hollow structures, and the size of the initial TiO2 solid nanoparticles plays an important role in determining the evacuation manner of the solid in the ripening-induced hollowing process. The surface area of TiO2 hollow microspheres determined by the adsorption isotherms was measured to be 74.67 m2/g. X-ray photoelectron spectroscopy (XPS) analysis revealed that the O-H peaks of hollow structures have a chemical shift compared with the core-shell structures. The optical property of the products was also discussed.

  2. Self-organized subwavelength ripple by nanosecond laser induced chemical vapor deposition

    International Nuclear Information System (INIS)

    Polymeric hydrogenated amorphous carbon (α-C:H) thin films were prepared by laser induced chemical vapor deposited method using a KrF excimer laser (λ = 248 nm, Ofwhm = 25 ns) with different laser intensities. Field emission scanning electron microscopy and atomic force microscopy were used to investigate the surface morphology of the films. It was found that the surface morphologies were affected by the laser intensity significantly. Self-organized subwavelength fine ripples perpendicular to the laser beam polarization with periodicities of about 200 nm were observed and a reasonable explanation was proposed for the formation of the ripples. Raman spectroscopy and Fourier transform infrared spectroscopy were used to study the structure of the α-C:H films. The results suggested that there was oxygen in the films, which came from the ambient contamination and the incomposited impurities during and after deposition. The relationships between the composition and chemical bond types were discussed in detail. - Highlights: • Polymeric α-C:H thin films prepared by laser induced CVD with the laser wavelength of 248 nm • Fine ripples with periodicities of about 200 nm observed on the surface of the films • Composition and chemical bonds studied by Raman and Fourier transform infrared spectroscopy

  3. 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.

  4. Computational Study of Fluid Flow in a Rotational Chemical Vapor Deposition (CVD) Reactor

    Science.gov (United States)

    Wong, Sun; Jaluria, Yogesh

    2015-11-01

    In a typical Chemical Vapor Deposition (CVD) reactor, the flow of the reacting gases is one of the most important considerations that must be precisely controlled in order to obtain desired film quality. In general, the fluids enter the reactor chamber, travel over to the heated substrate area, where chemical reactions lead to deposition, and then exit the chamber. However, the flow inside the reactor chamber is not that simple. It would often develop recirculation at various locations inside the reactor due to reactor geometry, flow conditions, buoyancy effects from temperature differences and rotational effects cause by the rotating substrate. This recirculation causes hot spots and affects the overall performance of the reactor. A recirculation fluid packet experiences a longer residence time inside the reactor and, thus, it heats up to higher temperatures causing unwanted chemical reactions and decomposition. It decreases the grow rate and uniformity on the substrate. A mathematical and computational model has been developed to help identify these unwanted hot spots occurring inside the CVD reactor. The model can help identify the user parameters needed to reduce the recirculation effects and better control the flow. Flow rates, pressures, rotational speeds and temperatures can all affect the severity of the recirculation within the reactor. The model can also help assist future designs as the geometry plays a big role in controlling fluid flow. The model and the results obtained are discussed in detail.

  5. Polymer Thin Films and Surface Modification by Chemical Vapor Deposition: Recent Progress.

    Science.gov (United States)

    Chen, Nan; Kim, Do Han; Kovacik, Peter; Sojoudi, Hossein; Wang, Minghui; Gleason, Karen K

    2016-06-01

    Chemical vapor deposition (CVD) polymerization uses vapor phase monomeric reactants to synthesize organic thin films directly on substrates. These thin films are desirable as conformal surface engineering materials and functional layers. The facile tunability of the films and their surface properties allow successful integration of CVD thin films into prototypes for applications in surface modification, device fabrication, and protective films. CVD polymers also bridge microfabrication technology with chemical and biological systems. Robust coatings can be achieved via CVD methods as antifouling, anti-icing, and antihydrate surfaces, as well as stimuli-responsive or biocompatible polymers and novel nanostructures. Use of low-energy input, modest vacuum, and room-temperature substrates renders CVD polymerization compatible with thermally sensitive substrates and devices. Compared with solution-based methods, CVD is particularly useful for insoluble materials, such as electrically conductive polymers and controllably crosslinked networks, and has the potential to reduce environmental, health, and safety impacts associated with solvents. This review discusses the relevant background and selected applications of recent advances by two methods that display and use the high retention of the organic functional groups from their respective monomers, initiated CVD (iCVD) and oxidative CVD (oCVD) polymerization. PMID:27276550

  6. Growth process conditions of tungsten oxide thin films using hot-wire chemical vapor deposition

    International Nuclear Information System (INIS)

    Highlights: ► Process parameters to control hot-wire CVD of WO3−x are categorized. ► Growth time, oxygen partial pressure, filament and substrate temperature are varied. ► Chemical and crystal structure, optical bandgap and morphology are determined. ► Oxygen partial pressure determines the deposition rate up to as high as 36 μm min−1. ► Nanostructures, viz. wires, crystallites and closed crystallite films, are controllably deposited. - Abstract: 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 varied from 6.0 × 10−6 to 1.0 mbar and the current through the filaments was varied from 4.0 to 9.0 A, which constitutes a filament temperature of 1390–2340 °C in vacuum. It is observed that the deposition rate of the films is predominantly determined by the oxygen partial pressure; it changes from about 1 to about 36,000 nm min−1 in the investigated range. Regardless of the oxygen partial pressure and filament temperature used, thin films with a nanogranular morphology are obtained, provided that the depositions last for 30 min or shorter. The films consist either of amorphous or partially crystallized WO3−x with high averaged transparencies of over 70% and an indirect optical band gap of 3.3 ± 0.1 eV. A prolonged deposition time entails an extended exposure of the films to thermal radiation from the filaments, which causes crystallization to monoclinic WO3 with diffraction maxima due to the (0 0 2), (2 0 0) and (0 2 0) crystallographic planes, furthermore the nanograins sinter and the films exhibit a cone-shaped growth. By simultaneously influencing the surface mobility, by heating the substrates to Tsurface = 700 ± 100 °C, and the deposition rate, a very good control of the morphology of the

  7. 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.

  8. Growth and characterization of boron doped graphene by Hot Filament Chemical Vapor Deposition Technique (HFCVD)

    Science.gov (United States)

    Jafari, A.; Ghoranneviss, M.; Salar Elahi, A.

    2016-03-01

    Large-area boron doped graphene was synthesized on Cu foil (as a catalyst) by Hot Filament Chemical Vapor Deposition (HFCVD) using boron oxide powder and ethanol vapor. To investigate the effect of different boron percentages, grow time and the growth mechanism of boron-doped graphene, scanning electron microscopy (SEM), Raman scattering and X-ray photoelectron spectroscopy (XPS) were applied. Also in this experiment, the I-V characteristic carried out for study of electrical property of graphene with keithley 2361 system. Nucleation of graphene domains with an average domain size of ~20 μm was observed when the growth time is 9 min that has full covered on the Cu surface. The Raman spectroscopy show that the frequency of the 2D band down-shifts with B doping, consistent with the increase of the in-plane lattice constant, and a weakening of the B-C in-plane bond strength relative to that of C-C bond. Also the shifts of the G-band frequencies can be interpreted in terms of the size of the C-C ring and the changes in the electronic structure of graphene in the presence of boron atoms. The study of electrical property shows that by increasing the grow time the conductance increases which this result in agree with SEM images and graphene grain boundary. Also by increasing the boron percentage in gas mixer the conductance decreases since doping graphene with boron creates a band-gap in graphene band structure. The XPS results of B doped graphene confirm the existence of boron in doped graphene, which indicates the boron atoms doped in the graphene lattice are mainly in the form of BC3. The results showed that boron-doped graphene can be successfully synthesized using boron oxide powder and ethanol vapor via a HFCVD method and also chemical boron doping can be change the electrical conductivity of the graphene.

  9. 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.

  10. 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.

  11. Improved carrier mobility of chemical vapor deposition-graphene by counter-doping with hydrazine hydrate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhiying; Zhang, Yanhui; Zhang, Haoran; Sui, Yanping; Zhang, Yaqian; Ge, Xiaoming; Yu, Guanghui, E-mail: ghyu@mail.sim.ac.cn; Xie, Xiaoming; Li, Xiaoliang [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Jin, Zhi; Liu, Xinyu [Microwave Devices and Integrated Circuits Department, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

    2015-03-02

    We developed a counter-doping method to tune the electronic properties of chemical vapor deposition (CVD)-grown graphene by varying the concentration and time of graphene exposure to hydrazine hydrate (N{sub 2}H{sub 4}·H{sub 2}O). The shift of G and 2D peaks of Raman spectroscopy is analyzed as a function of N{sub 2}H{sub 4}·H{sub 2}O concentration. The result revealed that N{sub 2}H{sub 4}·H{sub 2}O realized n-type doping on CVD grown graphene. X-ray photoelectron spectroscopy measurement proved the existence of nitrogen, which indicated the adsorption of N{sub 2}H{sub 4} on the surface of graphene. After counter-doping, carrier mobility, which was measured by Hall measurements, increased three fold.

  12. Improved carrier mobility of chemical vapor deposition-graphene by counter-doping with hydrazine hydrate

    International Nuclear Information System (INIS)

    We developed a counter-doping method to tune the electronic properties of chemical vapor deposition (CVD)-grown graphene by varying the concentration and time of graphene exposure to hydrazine hydrate (N2H4·H2O). The shift of G and 2D peaks of Raman spectroscopy is analyzed as a function of N2H4·H2O concentration. The result revealed that N2H4·H2O realized n-type doping on CVD grown graphene. X-ray photoelectron spectroscopy measurement proved the existence of nitrogen, which indicated the adsorption of N2H4 on the surface of graphene. After counter-doping, carrier mobility, which was measured by Hall measurements, increased three fold

  13. Tribological behavior of improved chemically vapor-deposited boron on beryllium

    International Nuclear Information System (INIS)

    Earlier chemical vapor deposition (CVD) experiments with diborane as the boron source gave well-bonded boron films up to 10 μm thick on beryllium, with layered intermetallic compounds below a top layer of boron. The films were nonuniform in thickness and cracked badly when given diffusion heat treatments to produce desired intermetallic compounds. By rotating the beryllium samples during the CVD, films of uniform thickness have now been produced. A variety of compounds of beryllium and boron have been produced on the outer surface of the CVD film by varying the concentration of diborane in the CVD gas. Wear and friction tests performed on various CVD surfaces using sapphire and diamond pins showed remarkable differences in that the CVD boron surface appeared to be substantially more compatible with diamond than with sapphire. The results of these tests are discussed. (Auth.)

  14. 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...

  15. Diameter control and emission properties of carbon nanotubes grown using chemical vapor deposition

    International Nuclear Information System (INIS)

    We grow multiwalled carbon nanotubes (CNTs) via thermal chemical vapor deposition from a sputtered 4-nm-thick nickel catalyst film on a tungsten-coated silicon substrate. CNTs grow from a mixture of nitrogen and acetylene gases at temperatures ranging from 630 to 790 deg. C, resulting in CNT outer diameters of 5-350 nm. CNT diameters increase exponentially with temperature. These results define regimes for template growth fabricated in catalytically active anodized aluminum oxide (AAO) with controlled pinhole sizes ranging from 10 to 50 nm. We measure a threshold electron emission field of 3 V/μm and a field enhancement factor β=5230 on randomly oriented 10-nm diameter CNTs

  16. Development of polishing methods for Chemical Vapor Deposited Silicon Carbide mirrors for synchrotron radiation

    International Nuclear Information System (INIS)

    Material properties of Chemical Vapor Deposited Silicon Carbide (CVD SiC) make it ideal for use in mirrors for synchrotron radiation experiments. We developed methods to grind and polish flat samples of CVD SiC down to measured surface roughness values as low as 1.1 Angstroms rms. We describe the processing details, including observations we made during trial runs with alternative processing recipes. We conclude that pitch polishing using progressively finer diamond abrasive, augmented with specific water based lubricants and additives, produces superior results. Using methods based on these results, a cylindrical and a toroidal mirror, each about 100 x 300mm, were respectively finished by Continental Optical and Frank Cooke, Incorporated. WYCO Interferometry shows these mirrors have surface roughness less than 5.7 Angstroms rms. These mirrors have been installed on the LLNL/UC X-ray Calibration and Standards Facility at the Stanford Synthrotron Radiation Laboratory

  17. Thermoelectric Power of Nanocrystalline Silicon Prepared by Hot-Wire Chemical-Vapor Deposition

    Science.gov (United States)

    Kearney, Brian; Liu, Xiao; Jugdersuren, Battogtokh; Queen, Daniel; Metcalf, Thomas; Culbertson, James; Chervin, Christopher; Stroud, Rhonda; Nemeth, William; Wang, Qi

    Although doped bulk silicon possesses a favorable Seebeck coefficient and electrical conductivity, its thermal conductivity is too large for practical thermoelectric applications. Thin film nanocrystalline silicon prepared by hot-wire chemical-vapor deposition (HWCVD) is an established material used in multijunction amorphous silicon solar cells. Its potential in low cost and scalable thermoelectric applications depends on achieving a low thermal conductivity without sacrificing thermoelectric power and electrical conductivity. We examine the thermoelectric power of boron-doped HWCVD nanocrystalline silicon and find that it is comparable to doped nanostructured silicon alloys prepared by other methods. Given the low thermal conductivity and high electrical conductivity of these materials, they can achieve a high thermoelectric figure of merit, ZT. Work supported by the Office of Naval Research.

  18. A model for the growth of cdte by metal organic chemical vapor deposition

    Science.gov (United States)

    Nemirovsky, Y.; Goren, D.; Ruzin, A.

    1991-10-01

    A kinetic model for the metalorganic chemical vapor deposition (MOCVD) growth of CdTe over a wide temperature range is presented. The model yields the growth rate as a function of the gas-phase concentrations of the constituents. The model is corroborated with experimental results obtained by the MOCVD growth of CdTe at 380° C. The major features of the model are the observed two-step surface-controlled pyrolysis and surface saturation, leading initially to a growth rate that increases with the square root of the concentrations of the reacting species and subsequently to a decrease of the growth rate as the concentrations increase. At even higher concentrations, an additional increase of growth rate is observed and modeled.

  19. Improved carrier mobility of chemical vapor deposition-graphene by counter-doping with hydrazine hydrate

    Science.gov (United States)

    Chen, Zhiying; Zhang, Yanhui; Zhang, Haoran; Sui, Yanping; Zhang, Yaqian; Ge, Xiaoming; Yu, Guanghui; Xie, Xiaoming; Li, Xiaoliang; Jin, Zhi; Liu, Xinyu

    2015-03-01

    We developed a counter-doping method to tune the electronic properties of chemical vapor deposition (CVD)-grown graphene by varying the concentration and time of graphene exposure to hydrazine hydrate (N2H4.H2O). The shift of G and 2D peaks of Raman spectroscopy is analyzed as a function of N2H4.H2O concentration. The result revealed that N2H4.H2O realized n-type doping on CVD grown graphene. X-ray photoelectron spectroscopy measurement proved the existence of nitrogen, which indicated the adsorption of N2H4 on the surface of graphene. After counter-doping, carrier mobility, which was measured by Hall measurements, increased three fold.

  20. In situ nitrogen-doped graphene grown from polydimethylsiloxane by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chundong; Zhou, Yungang; He, Lifang; Ng, Tsz-Wai; Hong, Guo; Wu, Qi-Hui; Gao, Fei; Lee, Chun-Sing; Zhang, Wenjun

    2013-01-21

    Due to its unique electronic properties and wide spectrum of promising applications, graphene has attracted much attention from scientists in various fields. Control and engineering of graphene’s semiconducting properties is considered to be the key of its applications in electronic devices. Here, we report a novel method to prepare in situ nitrogen-doped graphene by microwave plasma assisted chemical vapor deposition (CVD) using PDMS (Polydimethylsiloxane) as a solid carbon source. Based on this approach, the concentration of nitrogen-doping can be easily controlled via the flow rate of nitrogen during the CVD process. X-ray photoelectron spectroscopy results indicated that the nitrogen atoms doped into graphene lattice were mainly in the forms of pyridinic and pyrrolic structures. Moreover, first-principles calculations show that the incorporated nitrogen atoms can lead to p-type doping of graphene. This in situ approach provides a promising strategy to prepare graphene with controlled electronic properties.

  1. High-strength chemical-vapor-deposited graphene and grain boundaries.

    Science.gov (United States)

    Lee, Gwan-Hyoung; Cooper, Ryan C; An, Sung Joo; Lee, Sunwoo; van der Zande, Arend; Petrone, Nicholas; Hammerberg, Alexandra G; Lee, Changgu; Crawford, Bryan; Oliver, Warren; Kysar, Jeffrey W; Hone, James

    2013-05-31

    Pristine graphene is the strongest material ever measured. However, large-area graphene films produced by means of chemical vapor deposition (CVD) are polycrystalline and thus contain grain boundaries that can potentially weaken the material. We combined structural characterization by means of transmission electron microscopy with nanoindentation in order to study the mechanical properties of CVD-graphene films with different grain sizes. We show that the elastic stiffness of CVD-graphene is identical to that of pristine graphene if postprocessing steps avoid damage or rippling. Its strength is only slightly reduced despite the existence of grain boundaries. Indentation tests directly on grain boundaries confirm that they are almost as strong as pristine. Graphene films consisting entirely of well-stitched grain boundaries can retain ultrahigh strength, which is critical for a large variety of applications, such as flexible electronics and strengthening components. PMID:23723231

  2. In situ nitrogen-doped graphene grown from polydimethylsiloxane by plasma enhanced chemical vapor deposition.

    Science.gov (United States)

    Wang, Chundong; Zhou, Yungang; He, Lifang; Ng, Tsz-Wai; Hong, Guo; Wu, Qi-Hui; Gao, Fei; Lee, Chun-Sing; Zhang, Wenjun

    2013-01-21

    Due to its unique electronic properties and wide spectrum of promising applications, graphene has attracted much attention from scientists in various fields. Control and engineering of graphene's semiconducting properties is considered to be key to its applications in electronic devices. Here, we report a novel method to prepare in situ nitrogen-doped graphene by microwave plasma assisted chemical vapor deposition (CVD) using PDMS (polydimethylsiloxane) as a solid carbon source. Based on this approach, the concentration of nitrogen-doping can be easily controlled via the flow rate of nitrogen during the CVD process. X-ray photoelectron spectroscopy results indicated that the nitrogen atoms doped into the graphene lattice were mainly in the forms of pyridinic and pyrrolic structures. Moreover, first-principles calculations show that the incorporated nitrogen atoms can lead to p-type doping of graphene. This in situ approach provides a promising strategy to prepare graphene with controlled electronic properties. PMID:23203220

  3. One-step synthesis of chlorinated graphene by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Fan, Liwei; Zhang, Hui; Zhang, Pingping; Sun, Xuhui

    2015-08-01

    We developed an approach to synthesize the chlorinated single layer graphene (Cl-G) by one-step plasma enhanced chemical vapor deposition. Copper foil was simply treated with hydrochloric acid and then CuCl2 formed on the surface was used as Cl source under the assistance of plasma treatment. Compared with other two-step methods by post plasma/photochemical treatment of CVD-grown single layer graphene (SLG), one-step Cl-G synthesis approach is quite straightforward and effective. X-ray photoelectron spectroscopy (XPS) revealed that ∼2.45 atom% Cl remained in SLG. Compared with the pristine SLG, the obvious blue shifts of G band and 2D band along with the appearance of D' band and D + G band in the Raman spectra indicate p-type doping of Cl-G.

  4. Study of surface morphology and alignment of MWCNTs grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    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

  5. Boron nitride nanowires synthesis via a simple chemical vapor deposition at 1200 °C

    International Nuclear Information System (INIS)

    A very simple chemical vapor deposition technique is used to synthesize high quality boron nitride nanowires at 1200 °C within a short growth duration of 30 min. FESEM micrograph shows that the as-synthesized boron nitride nanowires have a clear wire like morphology with diameter in the range of ∼20 to 150 nm. HR-TEM confirmed the wire-like structure of boron nitride nanowires, whereas XPS and Raman spectroscopy are used to find out the elemental composition and phase of the synthesized material. The synthesized boron nitride nanowires have potential applications as a sensing element in solid state neutron detector, neutron capture therapy and microelectronic devices with uniform electronic properties

  6. 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.

  7. Photoluminescence of Ag-doped ZnSe nanowires synthesized by metalorganic chemical vapor deposition

    Science.gov (United States)

    Zhang, X. T.; Ip, K. M.; Li, Quan; Hark, S. K.

    2005-05-01

    Photoluminescence of Ag-doped ZnSe nanowires synthesized by metalorganic chemical vapor deposition is investigated in the temperature range from 10to300K. Ag impurities were introduced into the ZnSe nanowires during the growing process. Some dominating Ag-related centers are found. Especially, the strong zero-phonon bound exciton luminescence with energy near 2.747eV is attributed to a neutral AgZn acceptor complex. This is because the emission peak at the same energy is observed only in the photoluminescence spectrum of the Ag-doped bulk ZnSe. A new luminescence peak at 2.842eV is attributed to the recombination of excitons bound to ionized acceptors (I2h) in the hexagonal phase of ZnSe nanowires. The physical origins of the emissions are briefly discussed.

  8. 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.

  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. Low-temperature synthesis of graphene on nickel foil by microwave plasma chemical vapor deposition

    Science.gov (United States)

    Kim, Y.; Song, W.; Lee, S. Y.; Jeon, C.; Jung, W.; Kim, M.; Park, C.-Y.

    2011-06-01

    Microwave plasma chemical vapor deposition (MPCVD) was employed to synthesize high quality centimeter scale graphene film at low temperatures. Monolayer graphene was obtained by varying the gas mixing ratio of hydrogen and methane to 80:1. Using advantages of MPCVD, the synthesis temperature was decreased from 750 °C down to 450 °C. Optical microscopy and Raman mapping images exhibited that a large area monolayer graphene was synthesized regardless of the temperatures. Since the overall transparency of 89% and low sheet resistances ranging from 590 to 1855 Ω/sq of graphene films were achieved at considerably low synthesis temperatures, MPCVD can be adopted in manufacturing future large-area electronic devices based on graphene film.

  11. Mechanical properties of chemical vapor deposited coatings for fusion reactor application

    International Nuclear Information System (INIS)

    Chemical vapor deposited coatings of TiB2, TiC and boron on graphite substrates are being developed for application as limiter materials in magnetic confinement fusion reactors. In this application severe thermal shock conditions exist and to do effective thermo-mechanical modelling of the material response it is necessary to acquire elastic moduli, fracture strength and strain to fracture data for the coatings. Four point flexure tests have been conducted from room temperature to 20000C on TiB2 and boron coated graphite with coatings in tension and compression and the mechanical properties extracted from the load-deflection data. In addition, stress relaxation tests from 500 to 11500C were performed on TiB2 and TiC coated graphite beams to assess the low levels of plastic deformation which occur in these coatings. Significant differences have been observed between the effective mechanical properties of the coatings and literature values of the bulk properties

  12. Controllable chemical vapor deposition of large area uniform nanocrystalline graphene directly on silicon dioxide

    DEFF Research Database (Denmark)

    Sun, Jie; Lindvall, Niclas; Cole, Matthew T.;

    2012-01-01

    graphene) and up to 13% of electric-field effect. The Hall mobility is similar to 40 cm(2)/ Vs, which is an order of magnitude higher than previously reported values for nanocrystalline graphene. Transmission electron microscopy, Raman spectroscopy, and transport measurements indicate a graphene......Metal-catalyst-free chemical vapor deposition (CVD) of large area uniform nanocrystalline graphene on oxidized silicon substrates is demonstrated. The material grows slowly, allowing for thickness control down to monolayer graphene. The as-grown thin films are continuous with no observable pinholes......, and are smooth and uniform across whole wafers, as inspected by optical-, scanning electron-, and atomic force microscopy. The sp(2) hybridized carbon structure is confirmed by Raman spectroscopy. Room temperature electrical measurements show ohmic behavior (sheet resistance similar to exfoliated...

  13. Uniformity of large-area bilayer graphene grown by chemical vapor deposition

    Science.gov (United States)

    Sheng, Yuewen; Rong, Youmin; He, Zhengyu; Fan, Ye; Warner, Jamie H.

    2015-10-01

    Graphene grown by chemical vapor deposition (CVD) on copper foils is a viable method for large area films for transparent conducting electrode (TCE) applications. We examine the spatial uniformity of large area films on the centimeter scale when transferred onto both Si substrates with 300 nm oxide and flexible transparent polyethylene terephthalate substrates. A difference in the quality of graphene, as measured by the sheet resistance and transparency, is found for the areas at the edges of large sheets that depends on the supporting boat used for the CVD growth. Bilayer graphene is grown with uniform properties on the centimeter scale when a flat support is used for CVD growth. The flat support provides consistent delivery of precursor to the copper catalyst for graphene growth. These results provide important insights into the upscaling of CVD methods for growing high quality graphene and its transfer onto flexible substrates for potential applications as a TCE.

  14. Free-standing thin film Ge single crystals grown by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Outlaw, R. A.; Hopson, P., Jr.

    1984-01-01

    The films, which are approximately 10 microns in thickness, are grown epitaxially on polished (100) NaCl substrates at 450 C by plasma enhanced chemical vapor deposition. Upon cooling, the films are separated from the substrate by differential shear stress, leaving free-standing films of Ge which can be handled. Growths are attained by nucleating at minimum plasma power for very brief intervals and then raising the power to 65 W to increase the growth rate to approximately 10 microns/h. It is found that substrate exposure to the plasma at too high a power for too long a time sputters and erodes the surface, thereby substantially degrading the nucleation process and the ultimate growths. It is noted that the free-standing films are visually specular and exhibit a high degree of crystalline order when examined by X-ray diffraction. Auger electron spectroscopy and energy dispersive analysis of X-rays reveal no detectable bulk contamination.

  15. Thin strain-relaxed SiGe grown by ultrahigh vacuum chemical vapor deposition

    International Nuclear Information System (INIS)

    Large-scale preparation of thin strain-relaxed SiGe is achieved by combining ion implantation and ultrahigh vacuum chemical vapor deposition. The resulting materials were analyzed by double crystal X-ray diffraction, micro-Raman spectroscopy, and tapping mode atomic force microscope. Results revealed that 100-nm-thick Si0.7Ge0.3 layers with the diameter of 125 mm and full strain relaxation are successfully prepared by pre-modifying the Si substrates using 50 keV Ar+ ions. The strain relaxation is also disclosed to change with both ion species and energy. However, post-modification of SiGe by ion implantation will cause serious damage to the crystal structures, and result in the formation of poly-crystal SiGe

  16. Structured nanocarbon on various metal foils by microwave plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    We present a versatile process for the engineering of nanostructures made of crystalline carbon on metal foils. The single step process by microwave plasma-enhance chemical vapor deposition is demonstrated for various substrate materials, such as Ni or Cu. Either carbon nanotubes (CNT) or carbon nanowalls (CNW) are obtained under same growth conditions and without the need of additional catalyst. The use of spacer and insulator implies a certain control over the kind of allotropes that are obtained. High density and large surface area are morphological characteristics of the thus obtained C products. The possibility of application on many metals, and in the alloy composition, on as-delivered commercially available foils indicates that this strategy can be adapted to a bunch of specific applications, while the production of C nanostructures is of remarkable simplicity.

  17. 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.

  18. 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.

  19. Passivation of aluminum nanoparticles by plasma-enhanced chemical vapor deposition for energetic nanomaterials.

    Science.gov (United States)

    Shahravan, Anaram; Desai, Tapan; Matsoukas, Themis

    2014-05-28

    We have produced passivating coatings on 80-nm aluminum particles by plasma-enhanced chemical vapor deposition (PECVD). Three organic precursors--isopropyl alcohol, toluene, and perfluorodecalin--were used to fabricate thin films with thicknesses ranging from 5 nm to 30 nm. The coated samples and one untreated sample were exposed to 85% humidity at 25 °C for two months, and the active Al content was determined by thermogravimetric analysis (TGA) in the presence of oxygen. The results were compared with an uncoated sample stored in a glovebox under argon for the same period. We find that all three coatings provide protection against humidity, compared to the control, and their efficacy ranks in the following order: isopropyl alcohol plasma polymer coatings of this study are suitable passivating thin film for aluminum nanoparticles by providing protection against oxidation while facilitating the complete oxidation of the metallic core at elevated temperature. PMID:24787245

  20. Homogeneous nanocrystalline cubic silicon carbide films prepared by inductively coupled plasma chemical vapor deposition.

    Science.gov (United States)

    Cheng, Qijin; Xu, S; Long, Jidong; Huang, Shiyong; Guo, Jun

    2007-11-21

    Silicon carbide films with different carbon concentrations x(C) have been synthesized by inductively coupled plasma chemical vapor deposition from a SiH(4)/CH(4)/H(2) gas mixture at a low substrate temperature of 500 °C. The characteristics of the films were studied by x-ray photoelectron spectroscopy, x-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared absorption spectroscopy, and Raman spectroscopy. Our experimental results show that, at x(C) = 49 at.%, the film is made up of homogeneous nanocrystalline cubic silicon carbide without any phase of silicon, graphite, or diamond crystallites/clusters. The average size of SiC crystallites is approximately 6 nm. At a lower value of x(C), polycrystalline silicon and amorphous silicon carbide coexist in the films. At a higher value of x(C), amorphous carbon and silicon carbide coexist in the films. PMID:21730481

  1. Structural and electronic characterization of graphene grown by chemical vapor deposition and transferred onto sapphire

    Science.gov (United States)

    Joucken, Frédéric; Colomer, Jean-François; Sporken, Robert; Reckinger, Nicolas

    2016-08-01

    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 × 1012 cm-2) together with quite low carrier mobility (∼1350 cm2/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.

  2. Reducing flicker noise in chemical vapor deposition graphene field-effect transistors

    Science.gov (United States)

    Arnold, Heather N.; Sangwan, Vinod K.; Schmucker, Scott W.; Cress, Cory D.; Luck, Kyle A.; Friedman, Adam L.; Robinson, Jeremy T.; Marks, Tobin J.; Hersam, Mark C.

    2016-02-01

    Single-layer graphene derived from chemical vapor deposition (CVD) holds promise for scalable radio frequency (RF) electronic applications. However, prevalent low-frequency flicker noise (1/f noise) in CVD graphene field-effect transistors is often up-converted to higher frequencies, thus limiting RF device performance. Here, we achieve an order of magnitude reduction in 1/f noise in field-effect transistors based on CVD graphene transferred onto silicon oxide substrates by utilizing a processing protocol that avoids aqueous chemistry after graphene transfer. Correspondingly, the normalized noise spectral density (10-7-10-8 μm2 Hz-1) and noise amplitude (4 × 10-8-10-7) in these devices are comparable to those of exfoliated and suspended graphene. We attribute the reduction in 1/f noise to a decrease in the contribution of fluctuations in the scattering cross-sections of carriers arising from dynamic redistribution of interfacial disorder.

  3. 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.

  4. 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.

  5. Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al2O3 Catalysts via CH4 Chemical Vapor Deposition.

    Science.gov (United States)

    Page, Alister J; Saha, Supriya; Li, Hai-Bei; Irle, Stephan; Morokuma, Keiji

    2015-07-29

    We present quantum chemical simulations demonstrating how single-walled carbon nanotubes (SWCNTs) form, or "nucleate", on the surface of Al2O3 nanoparticles during chemical vapor deposition (CVD) using CH4. SWCNT nucleation proceeds via the formation of extended polyyne chains that only interact with the catalyst surface at one or both ends. Consequently, SWCNT nucleation is not a surface-mediated process. We demonstrate that this unusual nucleation sequence is due to two factors. First, the π interaction between graphitic carbon and Al2O3 is extremely weak, such that graphitic carbon is expected to desorb at typical CVD temperatures. Second, hydrogen present at the catalyst surface actively passivates dangling carbon bonds, preventing a surface-mediated nucleation mechanism. The simulations reveal hydrogen's reactive chemical pathways during SWCNT nucleation and that the manner in which SWCNTs form on Al2O3 is fundamentally different from that observed using "traditional" transition metal catalysts. PMID:26148208

  6. Friction and Wear of Ion-Beam-Deposited Diamondlike Carbon on Chemical-Vapor-Deposited, Fine-Grain Diamond

    Science.gov (United States)

    Miyoshi, Kazuhisa; Wu, Richard L. C.; Lanter, William C.

    1996-01-01

    Friction and wear behavior of ion-beam-deposited diamondlike carbon (DLC) films coated on chemical-vapor-deposited (CVD), fine-grain diamond coatings were examined in ultrahigh vacuum, dry nitrogen, and humid air environments. The DLC films were produced by the direct impact of an ion beam (composed of a 3:17 mixture of Ar and CH4) at ion energies of 1500 and 700 eV and an RF power of 99 W. Sliding friction experiments were conducted with hemispherical CVD diamond pins sliding on four different carbon-base coating systems: DLC films on CVD diamond; DLC films on silicon; as-deposited, fine-grain CVD diamond; and carbon-ion-implanted, fine-grain CVD diamond on silicon. Results indicate that in ultrahigh vacuum the ion-beam-deposited DLC films on fine-grain CVD diamond (similar to the ion-implanted CVD diamond) greatly decrease both the friction and wear of fine-grain CVD diamond films and provide solid lubrication. In dry nitrogen and in humid air, ion-beam-deposited DLC films on fine-grain CVD diamond films also had a low steady-state coefficient of friction and a low wear rate. These tribological performance benefits, coupled with a wider range of coating thicknesses, led to longer endurance life and improved wear resistance for the DLC deposited on fine-grain CVD diamond in comparison to the ion-implanted diamond films. Thus, DLC deposited on fine-grain CVD diamond films can be an effective wear-resistant, lubricating coating regardless of environment.

  7. Low temperature deposition of nanocrystalline silicon carbide films by plasma enhanced chemical vapor deposition and their structural and optical characterization

    International Nuclear Information System (INIS)

    Nanocrystalline silicon carbide (SiC) thin films were deposited by plasma enhanced chemical vapor deposition technique at different deposition temperatures (Td) ranging from 80 to 575 deg. C and different gas flow ratios (GFRs). While diethylsilane was used as the source for the preparation of SiC films, hydrogen, argon and helium were used as dilution gases in different concentrations. The effects of Td, GFR and dilution gases on the structural and optical properties of these films were investigated using high resolution transmission electron microscope (HRTEM), micro-Raman, Fourier transform infrared (FTIR) and ultraviolet-visible optical absorption techniques. Detailed analysis of the FTIR spectra indicates the onset of formation of SiC nanocrystals embedded in the amorphous matrix of the films deposited at a temperature of 300 deg. C. The degree of crystallization increases with increasing Td and the crystalline fraction (fc) is 65%±2.2% at 575 deg. C. The fc is the highest for the films deposited with hydrogen dilution in comparison with the films deposited with argon and helium at the same Td. The Raman spectra also confirm the occurrence of crystallization in these films. The HRTEM measurements confirm the existence of nanocrystallites in the amorphous matrix with a wide variation in the crystallite size from 2 to 10 nm. These results are in reasonable agreement with the FTIR and the micro-Raman analysis. The variation of refractive index (n) with Td is found to be quite consistent with the structural evolution of these films. The films deposited with high dilution of H2 have large band gap (Eg) and these values vary from 2.6 to 4.47 eV as Td is increased from 80 to 575 deg. C. The size dependent shift in the Eg value has also been investigated using effective mass approximation. Thus, the observed large band gap is attributed to the presence of nanocrystallites in the films

  8. 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.

  9. Surface modification of reverse osmosis desalination membranes by thin-film coatings deposited by initiated chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ozaydin-Ince, Gozde, E-mail: gozdeince@sabanciuniv.edu [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Matin, Asif, E-mail: amatin@mit.edu [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Khan, Zafarullah, E-mail: zukhan@mit.edu [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Zaidi, S.M. Javaid, E-mail: zaidismj@kfupm.edu.sa [Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Gleason, Karen K., E-mail: kkgleasn@mit.edu [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2013-07-31

    Thin-film polymeric reverse osmosis membranes, due to their high permeation rates and good salt rejection capabilities, are widely used for seawater desalination. However, these membranes are prone to biofouling, which affects their performance and efficiency. In this work, we report a method to modify the membrane surface without damaging the active layer or significantly affecting the performance of the membrane. Amphiphilic copolymer films of hydrophilic hydroxyethylmethacrylate and hydrophobic perfluorodecylacrylate (PFA) were synthesized and deposited on commercial RO membranes using an initiated chemical vapor deposition technique which is a polymer deposition technique that involves free-radical polymerization initiated by gas-phase radicals. Relevant surface characteristics such as hydrophilicity and roughness could be systematically controlled by varying the polymer chemistry. Increasing the hydrophobic PFA content in the films leads to an increase in the surface roughness and hydrophobicity. Furthermore, the surface morphology studies performed using the atomic force microscopy show that as the thickness of the coating increases average surface roughness increases. Using this knowledge, the coating thickness and chemistry were optimized to achieve high permeate flux and to reduce cell attachment. Results of the static bacterial adhesion tests show that the attachment of bacterial cells is significantly reduced on the coated membranes. - Highlights: • Thin films are deposited on reverse osmosis membranes. • Amphiphilic thin films are resistant to protein attachment. • The permeation performance of the membranes is not affected by the coating. • The thin film coatings delayed the biofouling.

  10. Surface modification of reverse osmosis desalination membranes by thin-film coatings deposited by initiated chemical vapor deposition

    International Nuclear Information System (INIS)

    Thin-film polymeric reverse osmosis membranes, due to their high permeation rates and good salt rejection capabilities, are widely used for seawater desalination. However, these membranes are prone to biofouling, which affects their performance and efficiency. In this work, we report a method to modify the membrane surface without damaging the active layer or significantly affecting the performance of the membrane. Amphiphilic copolymer films of hydrophilic hydroxyethylmethacrylate and hydrophobic perfluorodecylacrylate (PFA) were synthesized and deposited on commercial RO membranes using an initiated chemical vapor deposition technique which is a polymer deposition technique that involves free-radical polymerization initiated by gas-phase radicals. Relevant surface characteristics such as hydrophilicity and roughness could be systematically controlled by varying the polymer chemistry. Increasing the hydrophobic PFA content in the films leads to an increase in the surface roughness and hydrophobicity. Furthermore, the surface morphology studies performed using the atomic force microscopy show that as the thickness of the coating increases average surface roughness increases. Using this knowledge, the coating thickness and chemistry were optimized to achieve high permeate flux and to reduce cell attachment. Results of the static bacterial adhesion tests show that the attachment of bacterial cells is significantly reduced on the coated membranes. - Highlights: • Thin films are deposited on reverse osmosis membranes. • Amphiphilic thin films are resistant to protein attachment. • The permeation performance of the membranes is not affected by the coating. • The thin film coatings delayed the biofouling

  11. 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.

  12. 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.

  13. Atmospheric pressure chemical vapor deposition of titanium dioxide films from TiCl4

    International Nuclear Information System (INIS)

    We report a low temperature atmospheric pressure chemical vapor deposition technique to deposit titanium oxide films on silicon wafers. The growth is achieved by using TiCl·H2O2 and O2 at temperatures ranging from 140 to 280 deg. C. Addition of H2O2 yields a significant reduction in the surface roughness with an enhanced deposition rate at temperatures as low as 170 deg. C. Growth at temperatures below 140 deg. C results in insignificant growth whereas at high temperatures a hazy and three-dimensional growth is observed. Using this technique a growth rate as high as 0.5 μm/h can be obtained with little roughness on the surface of the substrate. XRD, SEM, and FTIR analyses have been exploited to study the physical behavior of the layers. The electrical characterization of the films reveals a relative permittivity (εr) of 19-21 for the samples prepared with H2O2. A breakdown field of 1x107 V/cm is also obtained

  14. The thermal properties of high purity and fully dense tungsten produced by chemical vapor deposition

    International Nuclear Information System (INIS)

    Highlights: • High purity and fully dense CVD-W samples were prepared. • The deposition rate of CVD-W is higher than 0.6 mm/h. • Thermal conductivity of CVD-W is higher than that of forged-W. • CVD-W had a higher threshold energy of crack initiation than that of forged W. • CVD-W has higher energy absorption than that of forged-W. - Abstract: The ultra-high purity (>99.9999 wt.%) and fully dense (19.23 g/cm3) tungsten (W) by chemical vapor deposition (CVD) was prepared with the deposition rate higher than 0.6 mm/h. The thermal diffusivity, specific heat, heat conductivity and coefficient of thermal expansion of CVD-W at the temperature range of 473–1273 K were measured. Thermal shock tests were carried out on a 60 kW electron-beam material testing scenario to investigate the crack-resistant performance of CVD-W, and the crack initiation threshold energies of CVD-W were achieved in 5 ms heating duration. Compared to forged-W, the higher heat conductivity (160.5–111 W/(m K)) and threshold energy of crack initiation (1.1–1.65 MJ/m2) of CVD-W can be attributed to the material characteristics including high purity, fully dense, rough surface composed of pyramid-like grains, and the columnar grain structures

  15. Hybrid Physical-Chemical Vapor Deposition of Bi2Se3 Thin films on Sapphire

    Science.gov (United States)

    Brom, Joseph; Ke, Yue; Du, Renzhong; Gagnon, Jarod; Li, Qi; Redwing, Joan

    2012-02-01

    High quality thin films of topological insulators continue to garner much interest. We report on the growth of highly-oriented thin films of Bi2Se3 on c-plane sapphire using hybrid physical-chemical vapor deposition (HPCVD). The HPCVD process utilizes the thermal decomposition of trimethyl bismuth (TMBi) and evaporation of elemental selenium in a hydrogen ambient to deposit Bi2Se3. Growth parameters including TMBi flow rate and decomposition temperature and selenium evaporation temperature were optimized, effectively changing the Bi:Se ratio, to produce high quality films. Glancing angle x- ray diffraction measurements revealed that the films were c-axis oriented on sapphire. Trigonal crystal planes were observed in atomic force microscopy images with an RMS surface roughness of 1.24 nm over an area of 2μmx2μm. Variable temperature Hall effect measurements were also carried out on films that were nominally 50-70 nm thick. Over the temperature range from 300K down to 4.2K, the carrier concentration remained constant at approximately 6x10^18 cm-3 while the mobility increased from 480 cm^2/Vs to 900 cm^2/Vs. These results demonstrate that the HPCVD technique can be used to deposit Bi2Se3 films with structural and electrical properties comparable to films produced by molecular beam epitaxy.

  16. The thermal properties of high purity and fully dense tungsten produced by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Yanwei, E-mail: lv.yanwei@cxtc.com [Xiamen Honglu Tungsten Molybdenum Industry Co. Ltd., 361021 Xiamen (China); Song, Jiupeng [Xiamen Honglu Tungsten Molybdenum Industry Co. Ltd., 361021 Xiamen (China); Lian, Youyun [Fusion Reactor Design and Material Division, Southwestern Institute of Physics, P.O. Box 432, 610041 Chengdu (China); Yu, Yang [Xiamen Honglu Tungsten Molybdenum Industry Co. Ltd., 361021 Xiamen (China); Liu, Xiang [Fusion Reactor Design and Material Division, Southwestern Institute of Physics, P.O. Box 432, 610041 Chengdu (China); Zhuang, Zhigang [China National R and D Center for Tungsten Technology, Xiamen Tungsten Co. Ltd, 361026 Xiamen (China)

    2015-02-15

    Highlights: • High purity and fully dense CVD-W samples were prepared. • The deposition rate of CVD-W is higher than 0.6 mm/h. • Thermal conductivity of CVD-W is higher than that of forged-W. • CVD-W had a higher threshold energy of crack initiation than that of forged W. • CVD-W has higher energy absorption than that of forged-W. - Abstract: The ultra-high purity (>99.9999 wt.%) and fully dense (19.23 g/cm{sup 3}) tungsten (W) by chemical vapor deposition (CVD) was prepared with the deposition rate higher than 0.6 mm/h. The thermal diffusivity, specific heat, heat conductivity and coefficient of thermal expansion of CVD-W at the temperature range of 473–1273 K were measured. Thermal shock tests were carried out on a 60 kW electron-beam material testing scenario to investigate the crack-resistant performance of CVD-W, and the crack initiation threshold energies of CVD-W were achieved in 5 ms heating duration. Compared to forged-W, the higher heat conductivity (160.5–111 W/(m K)) and threshold energy of crack initiation (1.1–1.65 MJ/m{sup 2}) of CVD-W can be attributed to the material characteristics including high purity, fully dense, rough surface composed of pyramid-like grains, and the columnar grain structures.

  17. Chemical Vapor Deposited Few-Layer Graphene as an Electron Field Emitter.

    Science.gov (United States)

    Behural, Sanjay K; Nayak, Sasmita; Yang, Qiaoqin; Hirose, Akira; Janil, Omkar

    2016-01-01

    Chemical vapor deposition (CVD) growth of graphene on polycrystalline copper (Cu) foil in a low pressure conditions has been presented, aiming to achieve the highest quality with large-scale fabrications, which requires comprehensive understanding and effective controlling of the growth process. Herein, few-layer graphene (FLG) films with large-domain sizes were grown on Cu metal catalyst substrates using a vertical mass-flow hot-filament CVD reactor, with the intention of large scale production, by optimizing the CVD system and three of the process parameters: (i) gas flow compositions, (ii) substrate annealing time and (iii) graphene deposition time. The detailed scanning electron microscope and Raman spectroscopy analysis indicate that all the above mentioned process parameters affect growth of FLG film on Cu substrate. The presence of two intense peaks, G and 2D-band at 1583.6 and 2702.6 cm⁻¹ for synthesized sample at optimized conditions (H₂/CH₄ ratio of 50:1 at graphene deposition time of 10 minutes and substrate annealed time for 20 minutes) revealed the formation of FLG films with large domain size. These graphene films on Cu have shown the room temperature field electron emission characteristics, hence appears to be prospective candidate for vacuum nanoelectronics. PMID:27398456

  18. Growth and morphology of carbon nanostructures on nickel oxide nanoparticles in catalytic chemical vapor deposition

    Science.gov (United States)

    Jana, M.; Sil, A.; Ray, S.

    2014-07-01

    The present study explores the conditions favorable for the growth of cylindrical carbon nanostructures such as multi-walled carbon nanotube (MWCNT) and carbon nanofiber by catalytic chemical vapor deposition (CCVD) method using nickel oxide-based catalyst nanoparticles of different average sizes as well as different levels of doping by copper oxide. The role of doping and the average size have been related to the observed melting behavior of nanoparticles of nickel oxide by thermal and diffraction analysis, and the importance of melting has been highlighted in the context of growth of cylindrical nanostructures. In the reducing environment prevailing in the CCVD chamber due to decomposition of flowing acetylene gas at elevated temperature, there is extensive reduction of oxide nanoparticles. Lack of melting and faster flow of carbon-bearing gases favor the formation of a carbon deposit cover over the catalyst nanoparticles giving rise to the formation of nanobeads. Melting allows rapid diffusion of carbon from the surface to inside catalyst particles, and reduced flow of gas lowers the rate of carbon deposit, both creating conditions favorable for the formation of cylindrical nanostructures, which grows around the catalyst particles. Smaller particle size and lower doping favor growth of MWCNT, while growth of fiber is commonly observed on larger particles having relatively higher level of doping.

  19. Comparisons between a gas-phase model of silane chemical vapor deposition and laser-diagnostic measurements

    International Nuclear Information System (INIS)

    Theoretical modeling and experimental measurements have been used to study gas-phase chemistry in the chemical vapor deposition (CVD) of silicon from silane. Pulsed laser Raman spectroscopy was used to obtain temperature profiles and to obtain absolute density profiles of silane during deposition at atmospheric and 6-Torr total pressures for temperatures ranging from 500 to 8000C. Laser-excited fluorescence was used to obtain relative density profiles of Si2 during deposition at 740 0C in helium with 0-12 Torr added hydrogen. These measurements are compared to predictions from the theoretical model of Coltrin, Kee, and Miller. The predictions agree qualitatively with experiment. These studies indicate that fluid mechanics and gas-phase chemical kinetics are important considerations in understanding the chemical vapor deposition process

  20. Synthesis and characterization of GaN nanowires by a catalyst assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wei Xiaofeng [College of Physics and Electronics, Shandong Normal University, Jinan, 250014 (China); Shi Feng, E-mail: sf751106@163.com [College of Physics and Electronics, Shandong Normal University, Jinan, 250014 (China)

    2011-09-15

    GaN nanowires have been fabricated on Si(1 1 1) substrates by chemical vapor deposition (CVD) method with NiCl{sub 2} as catalyst and their compositions, microstructures, morphologies and light emitting properties were characterized by X-ray diffraction (XRD), FT-IR spectrophotometer (FTIR), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), Raman spectroscopy and photoluminescence (PL). The results demonstrate that the nanowires are single-crystal GaN with hexagonal wurtzite structure and high crystalline quality, having the size of 20-50 nm in diameter and several tens of microns in length with some nano-droplets on their tips, which reveals that the growth mechanism of GaN nanowires agrees with vapor-liquid-solid (VLS) process. Five first-order Raman active phonon bands move to low shift and A{sub 1}(TO), E{sub 1}(TO), and E{sub 2} (high) bands are overlapped and broaden, which is caused by uncertainty in the phonon wave vector. Five non-first-order active Raman phonons also appear, which is caused by the small dimension and high surface disorder degree. A blue-shift of the band-gap emission occurs due to quantum confinement effect.

  1. Growth of titanium silicate thin films by photo-induced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.M.; Fang, Q.; Zhang, J.-Y.; Wu, J.X.; Di, Y.; Chen, W.; Chen, M.L.; Boyd, Ian W

    2004-04-01

    Titanium silicate thin films have been grown on Si substrates by photo-induced chemical vapor deposition using 222-nm ultraviolet excimer lamps. Titanium tetraisopropoxide (TTIP) and tetraethoxysilane (TEOS) were used as precursors. TTIP and TEOS were dissolved together in cyclohexane and introduced into the photochemical reaction chamber through a droplet injector vaporizer. The composition of the film was controlled by changing the ratio of TTIP to TEOS in the precursor solution. High quality titanium silicate films with various Ti/Si ratios and low carbon content have been achieved as revealed by X-ray photoelectron spectroscopy measurements. The atomic percentage of Ti content in the grown silicate films is significantly larger than that in the precursor solution. The films were measured to be 30-80 nm in thickness and 1.91-2.31 in refractive index by ellipsometry. Both the growth rate and refractive index increase with increasing Ti percentage in the silicate films. The evolution of Fourier transform infrared spectra of the silicate films with solution composition shows that the Ti-O-Si absorption at approximately 920 cm{sup -1} becomes stronger, while the Ti-O absorption at approximately 430 cm{sup -1} becomes weaker with decreasing Ti percentage in the solution. A small feature at {approx}1035 cm{sup -1} related to Si-O-Si bonds is also observed in the SiO{sub 2}-rich Ti silicate film.

  2. Aerosol assisted atmospheric pressure chemical vapor deposition of silicon thin films using liquid cyclic hydrosilanes

    Energy Technology Data Exchange (ETDEWEB)

    Guruvenket, Srinivasan, E-mail: guruvenket.srinivasan@ndsu.edu [Center for Nanoscale Energy Related Materials, 1715 NDSU Research Park Drive N, North Dakota State University, Fargo, ND 58102 (United States); Hoey, Justin M.; Anderson, Kenneth J.; Frohlich, Matthew T.; Sailer, Robert A. [Center for Nanoscale Energy Related Materials, 1715 NDSU Research Park Drive N, North Dakota State University, Fargo, ND 58102 (United States); Boudjouk, Philip [Center for Nanoscale Energy Related Materials, 1715 NDSU Research Park Drive N, North Dakota State University, Fargo, ND 58102 (United States); Department of Chemistry and Biochemistry, Ladd-Dunbar Hall, North Dakota State University, Fargo, ND 58102 (United States)

    2015-08-31

    Silicon (Si) thin films were produced using an aerosol assisted atmospheric pressure chemical vapor deposition technique with liquid hydrosilane precursors cyclopentasilane (CPS, Si{sub 5}H{sub 10}) and cyclohexasilane (CHS, Si{sub 6}H{sub 12}). Thin films were deposited at temperatures between 300 and 500 °C, with maximum observed deposition rates of 55 and 47 nm/s for CPS and CHS, respectively, at 500 °C. Atomic force microscopic analyses of the films depict smooth surfaces with roughness of 4–8 nm. Raman spectroscopic analysis indicates that the Si films deposited at 300 °C and 350 °C consist of a hydrogenated amorphous Si (a-Si:H) phase while the films deposited at 400, 450, and 500 °C are comprised predominantly of a hydrogenated nanocrystalline Si (nc-Si:H) phase. The wide optical bandgaps of 2–2.28 eV for films deposited at 350–400 °C and 1.7–1.8 eV for those deposited at 450–500 °C support the Raman data and depict a transition from a-Si:H to nc-Si:H. Films deposited at 450 {sup o}C possess the highest photosensitivity of 10{sup 2}–10{sup 3} under AM 1.5G illumination. Based on the growth model developed for other silanes, we suggest a mechanism that governs the film growth using CPS and CHS. - Highlights: • Si films via AA-APCVD are realized using cyclopentasilane (CPS) and cyclohexasilane (CHS). • Low activation energies of CPS and CHS allow Si thin films at low temperatures (300 °C). • High growth rates of 47–55 nm/s were obtained at 500 °C • Near device quality Si thin films with 2–3 orders of photosensitivity • Si thin films via AA-APCVD are amenable to continuous roll-to-roll manufacturing.

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

    International Nuclear Information System (INIS)

    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 TiO2 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 TiO2. - Highlights: • Iron doped TiO2 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 TiO2 films exhibit a super-hydrophilic effect

  4. Deposition kinetics and characterization of stable ionomers from hexamethyldisiloxane and methacrylic acid by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Urstöger, Georg; Resel, Roland; Koller, Georg; Coclite, Anna Maria

    2016-04-01

    A novel ionomer of hexamethyldisiloxane and methacrylic acid was synthesized by plasma enhanced chemical vapor deposition (PECVD). The PECVD process, being solventless, allows mixing of monomers with very different solubilities, and for polymers formed at high deposition rates and with high structural stability (due to the high number of cross-links and covalent bonding to the substrate) to be obtained. A kinetic study over a large set of parameters was run with the aim of determining the optimal conditions for high stability and proton conductivity of the polymer layer. Copolymers with good stability over 6 months' time in air and water were obtained, as demonstrated by ellipsometry, X-Ray reflectivity, and FT-IR spectroscopy. Stable coatings showed also proton conductivity as high as 1.1 ± 0.1 mS cm-1. Chemical analysis showed that due to the high molecular weight of the chosen precursors, it was possible to keep the plasma energy-input-per-mass low. This allowed limited precursor fragmentation and the functional groups of both monomers to be retained during the plasma polymerization.

  5. Selective epitaxial Si based layers and TiSi 2 deposition by integrated chemical vapor deposition

    Science.gov (United States)

    Regolini, J. L.; Margail, J.; Bodnar, S.; Maury, D.; Morin, C.

    1996-07-01

    High performance IC manufacturing requirements, such as large diameter wafer uniformity, reproducibility, throughput and reliability can be fulfilled by commercial integrated processing, single wafer cluster tools. This paper presents results obtained on an industrial cluster reactor for 200 mm wafers by combining epitaxial silicon related materials and selective deposition of TiSi 2. Low temperature epitaxial Si and SiGe alloys are studied for buried thin layers used in CMOS and HBT devices. The doping profile abruptness for B and P are within SIMS resolution limits. TheTiSi 2/Si selective deposition is also investigated, sequentially and in situ, as a technique for future salicidedS/D with a reduction in technological steps and interface contamination. Statistical electrical results obtained using 0.35 and 0.25 μm CMOS technologies in which the CVD silicide deposition is tested, are presented and compared with the standard salicide technique.

  6. Characterization of titanium oxynitride films deposited by low pressure chemical vapor deposition using amide Ti precursor

    Energy Technology Data Exchange (ETDEWEB)

    Song Xuemei; Gopireddy, Deepthi [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Takoudis, Christos G. [Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States); Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois 60607 (United States)], E-mail: takoudis@uic.edu

    2008-07-31

    In this study, we investigate the use of an amide-based Ti-containing precursor, namely tetrakis(diethylamido)titanium (TDEAT), for TiN{sub x}O{sub y} film deposition at low temperature. Traditionally, alkoxide-based Ti-containing precursor, such as titanium tetra-isopropoxide (TTIP), along with NH{sub 3} is used for titanium oxynitride (TiN{sub x}O{sub y}) film deposition. When TTIP is used, at low temperatures it is difficult to form TiN{sub x}O{sub y} films with high N/O ratios. In this study, by using TDEAT, TiN{sub x}O{sub y} films are deposited on H-passivated Si (100) substrates in a cold wall reactor at 300 {sup o}C and 106 Pa. Rutherford backscattering spectroscopy analysis shows nitrogen incorporation in the TiN{sub x}O{sub y} films to be as high as 28 at.%. X-ray photoelectron spectroscopy analysis of as-deposited films confirms the formation of{sub .} TiN{sub x}O{sub y}, while Fourier transform infrared and Raman spectra indicate that the films have amorphous structure. Moreover, there is no detectable bulk carbon impurity and no SiO{sub 2} formation at the TiN{sub x}O{sub y}/Si interface. Upon annealing the as-deposited films in air at 750 deg. C for 30 min, they oxidize to TiO{sub 2} and crystallize to form a rutile structure with a small amount of anatase phase. Based on these results, TDEAT appears to be a promising precursor for both TiN{sub x}O{sub y} and TiO{sub 2} film deposition.

  7. Pulsed chemical vapor deposition of Cu2S into a porous TiO2 matrix

    International Nuclear Information System (INIS)

    Chalcocite (Cu2S) has been deposited via pulsed chemical vapor deposition (PCVD) into a porous TiO2 matrix using hydrogen sulfide and a metal-organic precursor. The precursor used is similar to the more common Cu(hfac)(tmvs) precursor, but it is fluorine free and exhibits increased thermal stability. The simultaneous exposure of the substrate to the copper precursor and hydrogen sulfide resulted in nonuniform Cu2S films with a temperature independent deposition rate implying gas phase reaction kinetics. The exposure of mesoporous TiO2 and planar ZnO to alternating cycles of the copper precursor and hydrogen sulfide resulted in a PCVD film that penetrated fully into the porous TiO2 layer with a constant deposition rate of 0.08 nm/cycle over a temperature range of 150-400 deg. C The chalcocite (Cu2S) stoichiometry was confirmed with extended x-ray absorption fine structure measurements (EXAFS) and x-ray photoelectron spectroscopy. Calculations of the EXAFS spectrum for different CuxS phases show that EXAFS is sensitive to the different phase stoichiometries. Optical absorption measurements of CVD thin films using photothermal deflection spectroscopy show the presence of a metallic copper-poor phase for gas phase nucleated films less than 100 nm thick and a copper-rich semiconducting phase for thicknesses greater than 100 nm with a direct band gap of 1.8 eV and an indirect bandgap of 1.2 eV.

  8. Fabrication of metal-coated carbon nanowalls synthesized by microwave plasma enhanced chemical vapor deposition.

    Science.gov (United States)

    Lee, Sangjoon; Choi, Won Seok; Yoo, Jinsu; Lim, Dong-Gun; Kim, Hyung Jin; Lee, Hyeoung-Jae; Hong, Byungyou

    2014-12-01

    In this study, the coating of synthesized carbon nanowalls (CNWs) with various metal layers (Ni, Cu, and W) was investigated. CNWs were synthesized by microwave plasma enhanced chemical vapor deposition (PECVD) with a methane (CH4) and hydrogen (H2) gas mixture on a p-type Si wafer, and then coated with metal films (Ni, Cu, and W) using an RF magnetron sputtering system with four-inch targets. Different sputtering times (5, 10, 20, and 30 min) were established to obtain different thicknesses of the metal layers with which the CNWs were coated. Field emission scanning electron microscopy (FE-SEM) was used to examine the cross-sectional and planar conditions of the CNWs, and energy dispersive spectroscopy (EDS) was used to analyze the CNW elements. The FE-SEM analysis of the cross-sectional and planar images confirmed that the metal layers were synthesized to a depth of 0.5 μm from the surfaces of the CNWs, and to a greater depth at the ends of the CNWs, irrespective of the deposition time and the metal species. The resistivity of the as-deposited CNWs appeared as 4.18 x 10(-3) Ω cm; that of the metal-coated CNWs was slightly lower; and that of the Ni-coated CNWs was the lowest (1.74 x 10(-3) Ω cm). The mobility of the metal-coated CNWs was almost unchanged, and that of the as-deposited CNWs was 1.23 x 10(3) cm2 V(-1) s(-1). PMID:25971035

  9. Metal organic chemical vapor deposition of environmental barrier coatings for the inhibition of solid deposit formation from heated jet fuel

    Science.gov (United States)

    Mohan, Arun Ram

    Solid deposit formation from jet fuel compromises the fuel handling system of an aviation turbine engine and increases the maintenance downtime of an aircraft. The deposit formation process depends upon the composition of the fuel, the nature of metal surfaces that come in contact with the heated fuel and the operating conditions of the engine. The objective of the study is to investigate the effect of substrate surfaces on the amount and nature of solid deposits in the intermediate regime where both autoxidation and pyrolysis play an important role in deposit formation. A particular focus has been directed to examining the effectiveness of barrier coatings produced by metal organic chemical vapor deposition (MOCVD) on metal surfaces for inhibiting the solid deposit formation from jet fuel degradation. In the first part of the experimental study, a commercial Jet-A sample was stressed in a flow reactor on seven different metal surfaces: AISI316, AISI 321, AISI 304, AISI 347, Inconel 600, Inconel 718, Inconel 750X and FecrAlloy. Examination of deposits by thermal and microscopic analysis shows that the solid deposit formation is influenced by the interaction of organosulfur compounds and autoxidation products with the metal surfaces. The nature of metal sulfides was predicted by Fe-Ni-S ternary phase diagram. Thermal stressing on uncoated surfaces produced coke deposits with varying degree of structural order. They are hydrogen-rich and structurally disordered deposits, spherulitic deposits, small carbon particles with relatively ordered structures and large platelets of ordered carbon structures formed by metal catalysis. In the second part of the study, environmental barrier coatings were deposited on tube surfaces to inhibit solid deposit formation from the heated fuel. A new CVD system was configured by the proper choice of components for mass flow, pressure and temperature control in the reactor. A bubbler was designed to deliver the precursor into the reactor

  10. Design and chemical vapor deposition of graded TiN/TiC coatings

    International Nuclear Information System (INIS)

    Gradient materials offer the possibility of tailoring properties between a substrate and a functional surface. Continuously graded coatings based on the Ti-C-N system were designed and synthesized in a computer-controlled, hot-wall chemical vapor deposition (CVD) reactor at 1400 K and a total pressure of 10.7 kPa. In order to define processing parameters, Ti(C, N) monolithic coatings with C/C+N ratios in the range 0-1 were first deposited on a graphite substrate under the same conditions. The C/C+N ratio and the growth rate of the coatings increased with increasing CH4/CH4+N2 ratio. The compositions of the monolithic coatings determined by X-ray diffraction were found to be between the thermodynamic and the kinetic predictions. These morphological, kinetic and compositional data were used to synthesize graded coatings with linear or exponential concentration profiles. The compositional profiles deduced from Auger line scans were found to be in good agreement with the designed profiles. (orig.)

  11. Ultrasmooth metallic foils for growth of high quality graphene by chemical vapor deposition

    Science.gov (United States)

    Procházka, Pavel; Mach, Jindřich; Bischoff, Dominik; Lišková, Zuzana; Dvořák, Petr; Vaňatka, Marek; Simonet, Pauline; Varlet, Anastasia; Hemzal, Dušan; Petrenec, Martin; Kalina, Lukáš; Bartošík, Miroslav; Ensslin, Klaus; Varga, Peter; Čechal, Jan; Šikola, Tomáš

    2014-05-01

    Synthesis of graphene by chemical vapor deposition is a promising route for manufacturing large-scale high-quality graphene for electronic applications. The quality of the employed substrates plays a crucial role, since the surface roughness and defects alter the graphene growth and cause difficulties in the subsequent graphene transfer. Here, we report on ultrasmooth high-purity copper foils prepared by sputter deposition of Cu thin film on a SiO2/Si template, and the subsequent peeling off of the metallic layer from the template. The surface displays a low level of oxidation and contamination, and the roughness of the foil surface is generally defined by the template, and was below 0.6 nm even on a large scale. The roughness and grain size increase occurred during both the annealing of the foils, and catalytic growth of graphene from methane (≈1000 °C), but on the large scale still remained far below the roughness typical for commercial foils. The micro-Raman spectroscopy and transport measurements proved the high quality of graphene grown on such foils, and the room temperature mobility of the graphene grown on the template stripped foil was three times higher compared to that of one grown on the commercial copper foil. The presented high-quality copper foils are expected to provide large-area substrates for the production of graphene suitable for electronic applications.

  12. Chemical vapor deposition of high quality graphene films from carbon dioxide atmospheres.

    Science.gov (United States)

    Strudwick, Andrew James; Weber, Nils Eike; Schwab, Matthias Georg; Kettner, Michel; Weitz, R Thomas; Wünsch, Josef R; Müllen, Klaus; Sachdev, Hermann

    2015-01-27

    The realization of graphene-based, next-generation electronic applications essentially depends on a reproducible, large-scale production of graphene films via chemical vapor deposition (CVD). We demonstrate how key challenges such as uniformity and homogeneity of the copper metal substrate as well as the growth chemistry can be improved by the use of carbon dioxide and carbon dioxide enriched gas atmospheres. Our approach enables graphene film production protocols free of elemental hydrogen and provides graphene layers of superior quality compared to samples produced by conventional hydrogen/methane based CVD processes. The substrates and resulting graphene films were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Raman microscopy, sheet resistance and transport measurements. The superior quality of the as-grown graphene films on copper is indicated by Raman maps revealing average G band widths as low as 18 ± 8 cm(-1) at 514.5 nm excitation. In addition, high charge carrier mobilities of up to 1975 cm(2)/(V s) were observed for electrons in transferred films obtained from a carbon dioxide based growth protocol. The enhanced graphene film quality can be explained by the mild oxidation properties of carbon dioxide, which at high temperatures enables an uniform conditioning of the substrates by an efficient removal of pre-existing and emerging carbon impurities and a continuous suppression and in situ etching of carbon of lesser quality being co-deposited during the CVD growth. PMID:25398132

  13. Modeling studies of the chemical vapor deposition of boron films from B 2H 6

    Science.gov (United States)

    Lamborn, Daniel R.; Snyder, David W.; Xi, X. X.; Redwing, Joan M.

    2007-02-01

    The effect of growth conditions on the chemical vapor deposition of boron thin films from diborane (B 2H 6) was investigated using a combination of experimental studies and computational fluid dynamics-based reactor modeling. A multi-physics computational model was developed to simulate the thermal-fluid environment in the reactor. The proposed chemistry model incorporated into the simulations includes gas-phase decomposition and formation of B 2H 6 and surface adsorption and reaction of borane (BH 3). The model accurately predicts the experimentally measured temperature and partial pressure dependence of the boron growth rate using the sticking coefficient of BH 3 on the growth surface as the only adjustable parameter in the calculations. The results indicate that at lower growth temperatures (500 °C) the growth rate is limited by mass transfer of BH 3 to the substrate surface. The studies of boron thin film growth are relevant to the deposition of superconducting MgB 2 thin films, in which B 2H 6 is used as the boron precursor.

  14. Chemically vapor-deposited ZrB2 as a selective solar absorber

    International Nuclear Information System (INIS)

    Coatings of ZrB2 and TiB2 for photothermal solar absorber applications were prepared using chemical vapor deposition (CVD) techniques. Oxidation tests suggest a maximum temperature limit for air exposure of 600 K for TiB2 and 800 K for ZrB2. Both materials exhibit innate spectral selectivity with an emittance at 375 K ranging from 0.06 to 0.09, a solar absorptance for ZrB2 ranging from 0.67 to 0.77 and a solar absorptance for TiB2 ranging from 0.46 to 0.59. ZrB2 has better solar selectivity and more desirable oxidation behavior than TiB2. A 0.071 μm antireflection coating of Si3N4 deposited onto the ZrB2 coating leads to an increase in absorptance from 0.77 to 0.93, while the emittance remains unchanged. (Auth.)

  15. Unraveling the growth of vertically aligned multi-walled carbon nanotubes by chemical vapor deposition

    International Nuclear Information System (INIS)

    The interaction between the main operational variables during the growth of vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) by catalytic chemical vapor deposition is studied. In this contribution, we report the influence of the carbon source (i.e. acetylene, ethylene and propylene), the reaction/activation temperature, the rate of heating, the reaction time, the metal loading, and the metallic nanoparticle size and distribution on the growth and alignment of carbon nanotubes. Fe/Al thin films deposited onto silicon samples by electron-beam evaporation are used as catalyst. A phenomenological growth mechanism is proposed to explain the interaction between these multiple factors. Three different outcomes of the synthesis process are found: i) formation of forests of non-aligned, randomly oriented multi-walled carbon nanotubes, ii) growth of vertically aligned tubes with a thin and homogeneous carbonaceous layer on the top, and iii) formation of vertically aligned carbon nanotubes. This carbonaceous layer (ii) has not been reported before. The main requirements to promote vertically aligned carbon nanotube growth are determined. (paper)

  16. 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.

  17. 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.

  18. Metalorganic chemical vapor deposition of few-layer sp2 bonded boron nitride films

    Science.gov (United States)

    Paduano, Qing; Snure, Michael; Weyburne, David; Kiefer, Arnold; Siegel, Gene; Hu, Jianjun

    2016-09-01

    A systematic study of the growth of atomically smooth few-layer sp2 bonded BN on 50 mm sapphire substrates by metalorganic chemical vapor deposition (MOCVD) using Triethylboron (TEB) and NH3 as precursors is described. Based on the experimental results obtained using Raman spectroscopy, atomic force microscopy (AFM), X-ray reflectance measurements and transmission electron microscopy, we explored the growth parameter space and identified three different growth modes: random three-dimensional (3D) growth, a self-terminating few-layer growth mode, and a very slow layer-by-layer mode. The growth mode depends on the temperature, pressure, V/III ratio, and surface nitridation conditions, as follows: 3D island growth is dominant in the low V/III range and is characterized by a decreasing growth rate with increasing deposition temperature. When the V/III ratio is increased this 3D island growth mode transitions to a self-terminating few-layer growth mode. An additional transition from self-terminating growth to 3D growth occurs when the growth pressure is increased. Very slow layer by layer growth is found at high temperature and low pressure. Finally, substrate surface nitridation promotes self-terminating growth that results in atomically smooth films.

  19. Scanning microwave microscope imaging of micro-patterned monolayer graphene grown by chemical vapor deposition

    Science.gov (United States)

    Myers, J.; Mou, S.; Chen, K.-H.; Zhuang, Y.

    2016-02-01

    Characterization of micro-patterned chemical vapor deposited monolayer graphene using a scanning microwave microscope has been presented. Monolayer graphene sheets deposited on a copper substrate were transferred to a variety of substrates and micro-patterned into a periodic array of parallel lines. The measured complex reflection coefficients exhibit a strong dependency on the operating frequency and on the samples' electrical conductivity and permittivity. The experiments show an extremely high sensitivity by detecting image contrast between single and double layer graphene sheets. Correlating the images recorded at the half- and quarter-wavelength resonant frequencies shows that the relative permittivity of the single layer graphene sheet is above 105. The results are in good agreement with the three dimensional numerical electromagnetic simulations. This method may be instrumental for a comprehensive understanding of the scanning microwave microscope image contrast and provide a unique technique to estimate the local electrical properties with nano-meter scale spatial resolution of two dimensional materials at radio frequency.

  20. Hot-Wire Chemical Vapor Deposition Of Polycrystalline Silicon : From Gas Molecule To Solar Cell

    Science.gov (United States)

    van Veenendaal, P. A. T. T.

    2002-10-01

    Although the effort to investigate the use of renewable energy sources, such as wind and solar energy, has increased, their contribution to the total energy consumption remains insignificant. The conversion of solar energy into electricity through solar cells is one of the most promising techniques, but the use of these cells is limited by the high cost of electricity. The major contributions to these costs are the material and manufacturing costs. Over the past decades, the development of silicon based thin film solar cells has received much attention, because the fabrication costs are low. A promising material for use in thin film solar cells is polycrystalline silicon (poly-Si:H). A relatively new technique to deposit poly-Si:H is Hot-Wire Chemical Vapor Deposition (Hot-Wire CVD), in which the reactant gases are catalytically decomposed at the surface of a hot filament, mainly tungsten and tantalum. The main advantages of Hot-Wire CVD over PE-CVD are absence of ion bombardment, high deposition rate, low equipment cost and high gas utilization. This thesis deals with the full spectrum of deposition, characterization and application of poly-Si:H thin films, i.e. from gas molecule to solar cell. Studies on the decomposition of silane on the filament showed that the process is catalytic of nature and that silane is decomposed into Si and 4H. The dominant gas phase reaction is the reaction of Si and H with silane, resulting in SiH3, Si2H6, Si3H6 and H2SiSiH2. The film growth precursors are Si, SiH3 and Si2H4. Also, XPS results on used tantalum and tungsten filaments are discussed. The position dependent measurements show larger silicon contents at the ends of the tungsten filament, as compared to the middle, due to a lower filament temperature. This effect is insignificant for a tantalum filament. Deposition time dependent measurements show an increase in silicon content of the tungsten filament with time, while the silicon content on the tantalum filament saturates

  1. 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...

  2. Characterization of Boron Carbonitride (BCN Thin Films Deposited by Radiofrequency and Microwave Plasma Enhanced Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    M. A. Mannan

    2008-01-01

    Full Text Available Boron carbonitride (BCN thin films with a thickness of ~4 µ­m were synthesized on Si (100 substrate by radiofrequency and microwave plasma enhanced chemical vapor deposition using trimethylamine borane [(CH33N.BH3] as a molecular precursor. The microstructures of the films were evaluated using field emission scanning electron microscopy (FE-SEM and X-ray diffractometry (XRD. Fourier transform infrared spectroscopy (FT-IR and X-ray photoelectron spectroscopy (XPS were used to analyze the chemical bonding state and composition of the films. It has been observed that the films were adhered well to the silicon substrate even after being broken mechanically. XRD and FE-SEM results showed that the films were x-ray amorphous, rough surface with inhomogeneous microstructure. The micro hardness was measured by nano-indentation tester and was found to be approximately 2~7 GPa. FT-IR suggested the formation of the hexagonal boron carbonitride (h-BCN phase in the films. Broadening of the XPS peaks revealed that B, C and N atoms have different chemical bonds such as B-N, B-C and C-N. The impurity oxygen was detected (13~15 at.% as B-O and/or N-O.

  3. 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.

  4. 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).

  5. Superhydrophobicity of polyvinylidene fluoride membrane fabricated by chemical vapor deposition from solution

    International Nuclear Information System (INIS)

    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.

  6. Flexible Nonvolatile Polymer Memory Array on Plastic Substrate via Initiated Chemical Vapor Deposition.

    Science.gov (United States)

    Jang, Byung Chul; Seong, Hyejeong; Kim, Sung Kyu; Kim, Jong Yun; Koo, Beom Jun; Choi, Junhwan; Yang, Sang Yoon; Im, Sung Gap; Choi, Sung-Yool

    2016-05-25

    Resistive random access memory based on polymer thin films has been developed as a promising flexible nonvolatile memory for flexible electronic systems. Memory plays an important role in all modern electronic systems for data storage, processing, and communication; thus, the development of flexible memory is essential for the realization of flexible electronics. However, the existing solution-processed, polymer-based RRAMs have exhibited serious drawbacks in terms of the uniformity, electrical stability, and long-term stability of the polymer thin films. Here, we present poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3)-based RRAM arrays fabricated via the solvent-free technique called initiated chemical vapor deposition (iCVD) process for flexible memory application. Because of the outstanding chemical stability of pV3D3 films, the pV3D3-RRAM arrays can be fabricated by a conventional photolithography process. The pV3D3-RRAM on flexible substrates showed unipolar resistive switching memory with an on/off ratio of over 10(7), stable retention time for 10(5) s, excellent cycling endurance over 10(5) cycles, and robust immunity to mechanical stress. In addition, pV3D3-RRAMs showed good uniformity in terms of device-to-device distribution. The pV3D3-RRAM will pave the way for development of next-generation flexible nonvolatile memory devices. PMID:27142537

  7. 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.

  8. Superior Mobility in Chemical Vapor Deposition Synthesized Graphene by Grain Size Engineering

    Science.gov (United States)

    Petrone, Nicholas; Dean, Cory; Meric, Inanc; van der Zande, Arend; Huang, Pinshane; Wang, Lei; Muller, David; Shepard, Kenneth; Hone, James

    2012-02-01

    Chemical vapor deposition (CVD) offers a promising method to produce large-area films of graphene, crucial for commercial realization of graphene-based applications. However, electron transport in CVD grown graphene has continued to fall short of the performance demonstrated by graphene derived from mechanical exfoliation. Lattice defects and grain boundaries developed during growth, structural defects and chemical contamination introduced during transfer, and charged scatterers present in sub-optimal dielectric substrates have all been identified as sources of disorder in CVD grown graphene devices. We grow CVD graphene and fabricate field-effect transistors, attempting to minimize potential sources of disorder. We reduce density of grain boundaries in CVD graphene by controlling domain sizes up to 250 microns. By transferring CVD graphene onto h-BN utilizing a dry-transfer method, we minimize trapped charges at the interface between graphene and in the underlying substrate. We report field-effect mobilities up to 110,000 cm2V-1s-1 and oscillations in magnetotransport measurements below 1 T, confirming the high quality and low disorder in our CVD graphene devices.

  9. Chemical vapor deposition-derived graphene with electrical performance of exfoliated graphene.

    Science.gov (United States)

    Petrone, Nicholas; Dean, Cory R; Meric, Inanc; van der Zande, Arend M; Huang, Pinshane Y; Wang, Lei; Muller, David; Shepard, Kenneth L; Hone, James

    2012-06-13

    While chemical vapor deposition (CVD) promises a scalable method to produce large-area graphene, CVD-grown graphene has heretofore exhibited inferior electronic properties in comparison with exfoliated samples. Here we test the electrical transport properties of CVD-grown graphene in which two important sources of disorder, namely grain boundaries and processing-induced contamination, are substantially reduced. We grow CVD graphene with grain sizes up to 250 μm to abate grain boundaries, and we transfer graphene utilizing a novel, dry-transfer method to minimize chemical contamination. We fabricate devices on both silicon dioxide and hexagonal boron nitride (h-BN) dielectrics to probe the effects of substrate-induced disorder. On both substrate types, the large-grain CVD graphene samples are comparable in quality to the best reported exfoliated samples, as determined by low-temperature electrical transport and magnetotransport measurements. Small-grain samples exhibit much greater variation in quality and inferior performance by multiple measures, even in samples exhibiting high field-effect mobility. These results confirm the possibility of achieving high-performance graphene devices based on a scalable synthesis process. PMID:22582828

  10. Growth of thick MgB2 films by impinging-jet hybrid physical-chemical vapor deposition

    International Nuclear Information System (INIS)

    Thick MgB2 films are grown using a novel impinging-jet hybrid physical-chemical vapor deposition process. An increased amount of the boron source gas generates high growth rates. Superconducting properties of the thick films are comparable to previous results from other processes, which indicate that this is a promising new process for MgB2 deposition for coated conductor applications, such as wires and tapes for MRI magnets. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  11. Excellent crystalline silicon surface passivation by amorphous silicon irrespective of the technique used for chemical vapor deposition

    OpenAIRE

    Schuttauf, J.A.; van der Werf, C.H.M.; Kielen, I.M.; Sark, W.G.J.H.M. van; Rath, J.K.; R. E. I. Schropp

    2011-01-01

    Crystalline silicon surface passivation by amorphous silicon deposited by three different chemical vapor deposition (CVD) techniques at low (T ∼ 130 °C) temperatures is compared. For all three techniques, surface recombination velocities (SRVs) are reduced by two orders of magnitude after prolonged thermal annealing at 200 °C. This reduction correlates with a decreased dangling bond density at the amorphous-crystalline interface, indicating that dangling bond saturation is the predominant mec...

  12. Growth of thick MgB{sub 2} films by impinging-jet hybrid physical-chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lamborn, D.R. [Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802 (United States); Wilke, R.H.T.; Li, Q. [Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Xi, X. [Department of Physics, Department of Materials Science and Engineering, Materials Research Institute, The Pennsylvania State University, University Park, PA 16801 (United States); Snyder, D.W. [Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States); Redwing, J.M. [Department of Materials Science and Engineering, Materials Research Institute, The Pennsylvania State University, University Park, PA 16801 (United States)

    2008-01-18

    Thick MgB{sub 2} films are grown using a novel impinging-jet hybrid physical-chemical vapor deposition process. An increased amount of the boron source gas generates high growth rates. Superconducting properties of the thick films are comparable to previous results from other processes, which indicate that this is a promising new process for MgB{sub 2} deposition for coated conductor applications, such as wires and tapes for MRI magnets. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  13. Effect of deposition temperature on boron-doped carbon coatings deposited from a BCl3-C3H6-H2 mixture using low pressure chemical vapor deposition

    International Nuclear Information System (INIS)

    A mixture of propylene, hydrogen and boron trichloride was used to fabricate boron-doped carbon coatings by using low pressure chemical vapor deposition (LPCVD) technique. Effect of deposition temperature on deposition rate, morphologies, compositions and bonding states of boron-doped carbon coatings was investigated. Below 1273 K, the deposition rate is controlled by reaction dynamics. The deposition rate increases with increasing deposition temperature. The activation energy is 208.74 kJ/mol. Above 1273 K, the deposition rate decreases due to smaller critical radius rc and higher nuclei formation rate J with increasing temperature. Scanning electron microscopy shows that the structure changes from glass-like to nano-laminates with increasing deposition temperature. The boron concentration decreases with increasing deposition temperature, corresponding with increasing carbon concentration. The five types of bonding states are B-C, B-sub-C, BC2O, BCO2 and B-O. B-sub-C and BC2O are the main bonding states. The reactions are dominant at all temperatures, in which the B-sub-C and PyC are formed.

  14. 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

  15. [Optical Spectroscopy for High-Pressure Microwave Plasma Chemical Vapor Deposition of Diamond Films].

    Science.gov (United States)

    Cao, Wei; Ma, Zhi-bin

    2015-11-01

    Polycrystalline diamond growth by microwave plasma chemical vapor deposition (MPCVD) at high-pressure (34.5 kPa) was investigated. The CH₄/H₂/O₂plasma was detected online by optical emission spectroscopy (OES), and the spatial distribution of radicals in the CH₄/H₂/O₂plasma was studied. Raman spectroscopy was employed to analyze the properties of the diamond films deposited in different oxygen volume fraction. The uniformity of diamond films quality was researched. The results indicate that the spectrum intensities of C₂, CH and Hα decrease with the oxygen volume fraction increasing. While the intensity ratios of C₂, CH to Hα also reduced as a function of increasing oxygen volume fraction. It is shown that the decrease of the absolute concentration of carbon radicals is attributed to the rise volume fraction of oxygen, while the relative concentration of carbon radicals to hydrogen atom is also reducing, which depressing the growth rate but improving the quality of diamond film. Furthermore, the OH radicals, role of etching, its intensities increase with the increase of oxygen volume fraction. Indicated that the improvement of OH concentration is also beneficial to reduce the content of amorphous carbon in diamond films. The spectrum space diagnosis results show that under high deposition pressure the distribution of the radicals in the CH₄/H₂/O₂plasma is inhomogeneous, especially, that of radical C₂ gathered in the central region. And causing a rapid increase of non-diamond components in the central area, eventually enable the uneven distribution of diamond films quality. PMID:26978897

  16. On-line coating of glass with tin oxide by atmospheric pressure chemical vapor deposition.

    Energy Technology Data Exchange (ETDEWEB)

    Allendorf, Mark D.; Sopko, J.F. (PPF Industries, Pittsburgh, PA); Houf, William G.; Chae, Yong Kee; McDaniel, Anthony H.; Li, M. (PPF Industries, Pittsburgh, PA); McCamy, J.W. (PPF Industries, Pittsburgh, PA)

    2006-11-01

    Atmospheric pressure chemical vapor deposition (APCVD) of tin oxide is a very important manufacturing technique used in the production of low-emissivity glass. It is also the primary method used to provide wear-resistant coatings on glass containers. The complexity of these systems, which involve chemical reactions in both the gas phase and on the deposition surface, as well as complex fluid dynamics, makes process optimization and design of new coating reactors a very difficult task. In 2001 the U.S. Dept. of Energy Industrial Technologies Program Glass Industry of the Future Team funded a project to address the need for more accurate data concerning the tin oxide APCVD process. This report presents a case study of on-line APCVD using organometallic precursors, which are the primary reactants used in industrial coating processes. Research staff at Sandia National Laboratories in Livermore, CA, and the PPG Industries Glass Technology Center in Pittsburgh, PA collaborated to produce this work. In this report, we describe a detailed investigation of the factors controlling the growth of tin oxide films. The report begins with a discussion of the basic elements of the deposition chemistry, including gas-phase thermochemistry of tin species and mechanisms of chemical reactions involved in the decomposition of tin precursors. These results provide the basis for experimental investigations in which tin oxide growth rates were measured as a function of all major process variables. The experiments focused on growth from monobutyltintrichloride (MBTC) since this is one of the two primary precursors used industrially. There are almost no reliable growth-rate data available for this precursor. Robust models describing the growth rate as a function of these variables are derived from modeling of these data. Finally, the results are used to conduct computational fluid dynamic simulations of both pilot- and full-scale coating reactors. As a result, general conclusions are

  17. Van der Waals epitaxial growth of MoS2 on SiO2/Si by chemical vapor deposition

    KAUST Repository

    Cheng, Yingchun

    2013-01-01

    Recently, single layer MoS2 with a direct band gap of 1.9 eV has been proposed as a candidate for two dimensional nanoelectronic devices. However, the synthetic approach to obtain high-quality MoS2 atomic thin layers is still problematic. Spectroscopic and microscopic results reveal that both single layers and tetrahedral clusters of MoS2 are deposited directly on the SiO2/Si substrate by chemical vapor deposition. The tetrahedral clusters are mixtures of 2H- and 3R-MoS2. By ex situ optical analysis, both the single layers and tetrahedral clusters can be attributed to van der Waals epitaxial growth. Due to the similar layered structures we expect the same growth mechanism for other transition-metal disulfides by chemical vapor deposition. © 2013 The Royal Society of Chemistry.

  18. Ultra-precision grinding of chemically vapor deposited silicon carbide mirrors for synchrotron radiation

    International Nuclear Information System (INIS)

    Chemically vapor deposited silicon carbide (CVD-SiC) is the most important material of mirrors for high-brightness synchrotron radiation beamlines, though the material is too difficult to be machined. It takes quite a long time to polish SiC substrate to make mirrors. This paper intends to reduce the machining time to make CVD-SiC mirrors by using ultra-precision grinding technology. The CVD-SiC sample has been ground into 0.4nm rms in surface roughness by a resinoid-bonded diamond wheel and an ultra-precision surface grinder having a glass-ceramic spindle of extremely-low thermal expansion. The surface roughness of ground samples were measured with TOPO-3D and AFM. 88.7% reflectivity has been obtained on the ground CVD-SiC flat surface, measured with X-ray of 0.834 nm in wavelength at the grazing incident angle of 0.7--0.95 degree. The reflectivity depends upon the angle between the direction of incident beam and grinding marks on the sample. The relationship between the surface roughness and grinding conditions was also discussed

  19. Transport Properties of MgB2 Films Grown by Hybrid Physical Chemical Vapor Deposition Method

    International Nuclear Information System (INIS)

    We prepared four different MgB2 films on Al2O3 by hybrid physical chemical vapor deposition method with thicknesses ranging from 0.65 μm to 1.2 μm X-ray diffraction patterns confirm that all the MgB2 films are c-axis oriented perpendicular to Al2O3 substrates. The superconducting onset temperature of MgB2 films were between 39.39K and 40.72K. The residual resistivity ratio of the MgB2 films was in the range between 3.13 and 37.3. We measured the angle dependence of critical current density (Jc) and resistivity, and determined the upper critical field (Hc2 ) from the temperature dependence of the resistivity curves. The anisotropy ratios defined as the ratio of the (Hc2 ) parallel to the ab-plane to that perpendicular to the ab-plane were in the range of 2.13 to 4.5 and were increased as the temperature was decreased. Some samples showed increase of Jc and decrease of resistivity when a magnetic field in applied parallel to the c-axis. We interpret this angle dependence in terms of enhanced flux pinning due to columnar growth of MgB2 along the c-axis.

  20. Support effect on carbon nanotube growth by methane chemical vapor deposition on cobalt catalysts

    International Nuclear Information System (INIS)

    The influence of the support on carbon nanotube production by methane chemical vapor deposition (CVD) on cobalt catalysts was investigated. N2 physisorption, X-ray diffractometry (XRD), temperature programmed reduction (TPR) and H2 and CO chemisorption techniques were used to characterize the structure of cobalt catalysts supported on different metal oxides (Al2O3, SiO2, Nb2O5 and TiO2). Raman spectroscopy, temperature programmed oxidation (TPO) and scanning electron microscopy (SEM) were used for the characterization and quantification of produced carbon species. On carbon nanotube growth, the catalyst produced three main carbon species: amorphous carbon, single walled carbon nanotubes (SWNT) and multi walled carbon nanotubes (MWNT). The characterization techniques showed that the catalyst selectivity to each kind of nanotube depended on the cobalt particle size distribution, which was influenced by the textural properties of the support. Co/TiO2 showed the highest selectivity towards single wall nanotube formation. This high selectivity results from the narrow size distribution of cobalt particles on TiO2. (author)

  1. Thermoluminescence of chemical-vapor-deposited diamond film irradiated with X-rays

    CERN Document Server

    Kim, T K; Park, N G; Son, Y H; Jeong, J I; Woo, J J; Choe, H S; Whang, C N

    2000-01-01

    Diamond film was synthesized by using chemical-vapor deposition (CVD). Three-dimensional thermoluminescence (TL) spectrum of the CVD diamond film irradiated with X-rays showed one TL peak at 430 nm around 560 K. The glow curve of the CVD diamond film produced one dominant 500-K peak that was caused by first-order kinetics. The activation energy and the escape frequency of the 560-K glow curve were calculated to be 0.92 approx 1.05 eV and 1.34x10 sup 7 sec sup - sup 1 , respectively. The emission spectrum at 560 K was split into 1.63-eV, 2.60-eV, and 3.07-eV emission bands. The 1.63-eV emission band is known to be attributable to silicon-vacancy center. Also, the 2.60-eV and the 3.07-eV emission bands were found to be associated with the A center and the H3 center, respectively.

  2. Structure and photoluminescence of molybdenum selenide nanomaterials grown by hot filament chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang, B.B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Plasma Nanoscience Laboratories, Manufacturing Flagship, Commonwealth Scientific and Industrial Research Organization, P. O. Box 218, Lindfield, NSW 2070 (Australia); Zhu, M.K. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Ostrikov, K., E-mail: kostya.ostrikov@qut.edu.au [Plasma Nanoscience Laboratories, Manufacturing Flagship, Commonwealth Scientific and Industrial Research Organization, P. O. Box 218, Lindfield, NSW 2070 (Australia); Institute for Future Environments, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD 4000 (Australia); Plasma Nanoscience, School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia); Shao, R.W.; Zheng, K. [Institute of Microstructure and Properties of Advanced Materials, Beijing University of Technology, Beijing 100124 (China)

    2015-10-25

    Molybdenum selenide nanomaterials with different structures are synthesized on silicon substrates coated with gold films by hot filament chemical vapor deposition (HFCVD) in nitrogen environment, where molybdenum trioxide and selenium powders are used as source materials. The structure and composition of the synthesized molybdenum selenide nanomaterials are studied using field emission scanning electron microscopy, transmission electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the structures of molybdenum selenide change from nanoflakes to nanoparticles with the increase of content of molybdenum trioxide precursor. The photoluminescence (PL) excitation using the 325 nm line of He–Cd laser as the excitation source generates green light with the wavelength of about 512–516 nm. The formation of molybdenum selenide nanomaterials is determined by the decomposition rates of molybdenum trioxide in HFCVD. The possible factors that affect the generation of green PL bands are analyzed. These outcomes of this work enrich our knowledge on the synthesis of transition metal dichalcogenides and contribute to the development of applications of these materials in optoelectronic devices. - Highlights: • Molybdenum selenide nanoflakes, nanoparticles and hybrids produced by HFCVD. • Uncommon MoO{sub 3} and Se precursor co-location and mixing and effective MoO{sub 3} decomposition. • Morphology change from nanoflakes to nanoparticles with higher ratio of MoO{sub 3} precursor. • Strong photoluminescence emission of green light with a wavelength of ∼512–516 nm.

  3. Epitaxial growth of group IV materials by chemical vapor deposition for Germanium Metal Oxide Semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, Benjamin; Loo, Roger; Caymax, Matty [imec, Kapeldreef 75, B-3001 Leuven (Belgium)

    2011-07-01

    Over the past 5-10 years, germanium has attracted a lot of interest to replace Silicon as a high carrier mobility material in future p-Metal Oxide Semiconductors transistors. This paper reviews developments of epitaxial Group IV materials (silicon, germanium, tin and alloys) by means of Reduced Pressure Chemical Vapor Deposition for use as Channel, Gate stack and Source/Drain in high performance Germanium transistors. We first describe Germanium growth on standard Silicon wafers. Selective epitaxial growth within Shallow Trench Isolation structures allows seamless integration of Germanium channels in Si platform with a significant defect reduction down to levels required for state-of-the-art VLSI technology. Next we focus on the most successful passivation approach for Germanium MOS interfaces by means of ultrathin epitaxial Si capping layers. This moves the problem of gate stack formation from a germanium surface to a silicon surface. We discuss novel extremely low temperature CVD processes involving innovative precursors, and impacts of point defects, strain relaxation and Silicon-Germanium intermixing on Germanium device performance. Finally, the implementation of Germanium-Tin alloys in embedded Source/Drain regions in Germanium transistors is proposed as an innovative architecture to implement strain in Germanium channels.

  4. 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.

  5. Thermal stability of multilayer graphene films synthesized by chemical vapor deposition and stained by metallic impurities

    International Nuclear Information System (INIS)

    Thermal stability is an important property of graphene that requires thorough investigation. This study reports the thermal stability of graphene films synthesized by chemical vapor deposition (CVD) on catalytic nickel substrates in a reducing atmosphere. Electron microscopies, atomic force microscopy, and Raman spectroscopy, as well as electronic measurements, were used to determine that CVD-grown graphene films are stable up to 700 °C. At 800 °C, however, graphene films were etched by catalytic metal nanoparticles, and at 1000 °C many tortuous tubular structures were formed in the film and carbon nanotubes were formed at the film edges and at catalytic metal-contaminated sites. Furthermore, we applied our pristine and thermally treated graphene films as active channels in field-effect transistors and characterized their electrical properties. Our research shows that remnant catalytic metal impurities play a critical role in damaging graphene films at high temperatures in a reducing atmosphere: this damage should be considered in the quality control of large-area graphene films for high temperature applications. (paper)

  6. Ultralight boron nitride aerogels via template-assisted chemical vapor deposition

    Science.gov (United States)

    Song, Yangxi; Li, Bin; Yang, Siwei; Ding, Guqiao; Zhang, Changrui; Xie, Xiaoming

    2015-05-01

    Boron nitride (BN) aerogels are porous materials with a continuous three-dimensional network structure. They are attracting increasing attention for a wide range of applications. Here, we report the template-assisted synthesis of BN aerogels by catalyst-free, low-pressure chemical vapor deposition on graphene-carbon nanotube composite aerogels using borazine as the B and N sources with a relatively low temperature of 900 °C. The three-dimensional structure of the BN aerogels was achieved through the structural design of carbon aerogel templates. The BN aerogels have an ultrahigh specific surface area, ultralow density, excellent oil absorbing ability, and high temperature oxidation resistance. The specific surface area of BN aerogels can reach up to 1051 m2 g-1, 2-3 times larger than the reported BN aerogels. The mass density can be as low as 0.6 mg cm-3, much lower than that of air. The BN aerogels exhibit high hydrophobic properties and can absorb up to 160 times their weight in oil. This is much higher than porous BN nanosheets reported previously. The BN aerogels can be restored for reuse after oil absorption simply by burning them in air. This is because of their high temperature oxidation resistance and suggests broad utility as water treatment tools.

  7. One-step synthesis of chlorinated graphene by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Highlights: • We developed a simple approach to synthesize the single layer chlorinated graphene. • CuCl2 on Cu surface is used as Cl source under the plasma treatment. • The formation of covalent C−Cl bond has been investigated by Raman and XPS. • Raman results indicate the p-type doping effect of chlorination. - Abstract: We developed an approach to synthesize the chlorinated single layer graphene (Cl-G) by one-step plasma enhanced chemical vapor deposition. Copper foil was simply treated with hydrochloric acid and then CuCl2 formed on the surface was used as Cl source under the assistance of plasma treatment. Compared with other two-step methods by post plasma/photochemical treatment of CVD-grown single layer graphene (SLG), one-step Cl-G synthesis approach is quite straightforward and effective. X-ray photoelectron spectroscopy (XPS) revealed that ∼2.45 atom% Cl remained in SLG. Compared with the pristine SLG, the obvious blue shifts of G band and 2D band along with the appearance of D’ band and D + G band in the Raman spectra indicate p-type doping of Cl-G

  8. Early evaluation of potential environmental impacts of carbon nanotube synthesis by chemical vapor deposition.

    Science.gov (United States)

    Plata, Desirée L; Hart, A John; Reddy, Christopher M; Gschwend, Philip M

    2009-11-01

    The carbon nanotube (CNT) industry is expanding rapidly, yet little is known about the potential environmental impacts of CNT manufacture. Here, we evaluate the effluent composition of a representative multiwalled CNT synthesis by catalytic chemical vapor deposition (CVD) in order to provide data needed to design strategies for mitigating any unacceptable emissions. During thermal pretreatment of the reactant gases (ethene and H(2)), we found over 45 side-products were formed, including methane, volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs). This finding suggests several environmental concerns with the existing process, including potential discharges of the potent greenhouse gas, methane (up to 1.7%), and toxic compounds such as benzene and 1,3-butadiene (up to 36000 ppmv). Extrapolating these laboratory-scale data to future industrial CNT production, we estimate that (1) contributions of atmospheric methane will be negligible compared to other existing sources and (2) VOC and PAH emissions may become important on local scales but will be small when compared to national industrial sources. As a first step toward reducing such unwanted emissions, we used continuous in situ measures of CNT length during growth and sought to identify which thermally generated compounds correlated with CNT growth rate. The results suggested that, in future CNT production approaches, key reaction intermediates could be delivered to the catalyst without thermal treatment. This would eliminate the most energetically expensive component of CVD synthesis (heating reactant gases), while reducing the formation of unintended byproducts. PMID:19924971

  9. The production of oxygenated polycrystalline graphene by one-step ethanol-chemical vapor deposition.

    Science.gov (United States)

    Paul, Rajat K; Badhulika, Sushmee; Niyogi, Sandip; Haddon, Robert C; Boddu, Veera M; Costales-Nieves, Carmen; Bozhilov, Krassimir N; Mulchandani, Ashok

    2011-10-01

    Large-area mono- and bilayer graphene films were synthesized on Cu foil (~ 1 inch(2)) in about 1 min by a simple ethanol-chemical vapor deposition (CVD) technique. Raman spectroscopy and high resolution transmission electron microscopy revealed the synthesized graphene films to have polycrystalline structures with 2-5 nm individual crystallite size which is a function of temperature up to 1000°C. X-ray photoelectron spectroscopy investigations showed about 3 atomic% carboxylic (COOH) functional groups were formed during growth. The field-effect transistor devices fabricated using polycrystalline graphene as conducting channel (L(c)=10 μm; W(c)=50 μm) demonstrated a p-type semiconducting behavior with high drive current and Dirac point at ~35 V. This simple one-step method of growing large area polycrystalline graphene films with semiconductor properties and easily functionalizable groups should assist in the realization of potential of polycrystalline graphene for nanoelectronics, sensors and energy storage devices. PMID:22408276

  10. Doping Graphene Transistors Using Vertical Stacked Monolayer WS2 Heterostructures Grown by Chemical Vapor Deposition.

    Science.gov (United States)

    Tan, Haijie; Fan, Ye; Rong, Youmin; Porter, Ben; Lau, Chit Siong; Zhou, Yingqiu; He, Zhengyu; Wang, Shanshan; Bhaskaran, Harish; Warner, Jamie H

    2016-01-27

    We study the interactions in graphene/WS2 two-dimensional (2D) layered vertical heterostructures with variations in the areal coverage of graphene by the WS2. All 2D materials were grown by chemical vapor deposition and transferred layer by layer. Photoluminescence (PL) spectroscopy of WS2 on graphene showed PL quenching along with an increase in the ratio of exciton/trion emission, relative to WS2 on SiO2 surface, indicating a reduction in the n-type doping levels of WS2 as well as reduced radiative recombination quantum yield. Electrical measurements of a total of 220 graphene field effect transistors with different WS2 coverage showed double-Dirac points in the field effect measurements, where one is shifted closer toward the 0 V gate neutrality position due to the WS2 coverage. Photoirradiation of the WS2 on graphene region caused further Dirac point shifts, indicative of a reduction in the p-type doping levels of graphene, revealing that the photogenerated excitons in WS2 are split across the heterostructure by electron transfer from WS2 to graphene. Kelvin probe microscopy showed that regions of graphene covered with WS2 had a smaller work function and supports the model of electron transfer from WS2 to graphene. Our results demonstrate the formation of junctions within a graphene transistor through the spatial tuning of the work function of graphene using these 2D vertical heterostructures. PMID:26756350

  11. Heteroepitaxial growth of wafer scale highly oriented graphene using inductively coupled plasma chemical vapor deposition

    Science.gov (United States)

    Gao, Libo; Xu, Hai; Li, Linjun; Yang, Yang; Fu, Qiang; Bao, Xinhe; Loh, Kian Ping

    2016-06-01

    The chemical vapor deposition (CVD) of graphene on Cu has attracted much attention because of its industrial scalability. Herein, we report inductively coupled plasma-assisted CVD of epitaxially grown graphene on (111)-textured Cu film alloyed with a small amount of Ni, where large area high quality graphene film can be grown in less than 5 min at 800 °C, thus affording industrial scalability. The epitaxially grown graphene films on (111)-textured Cu contain grains which are predominantly aligned with the Cu lattice and about 10% of 30°-rotated grains (anti-grains). Such graphene films are exclusively monolayer and possess good electrical conductivity, high carrier mobility, and room temperature quantum Hall effect. Magnetoresistance measurements reveal that the reduction of the grain sizes from 150 nm to 50 nm produce increasing Anderson localization and the appearance of a transport gap. Owing to the presence of grain boundaries in these anti-grains, epitaxially grown graphene films possess n-type characteristics and exhibit ultra-high sensitivity to adsorbates.

  12. Optical emission diagnostics of plasmas in chemical vapor deposition of single-crystal diamond

    International Nuclear Information System (INIS)

    A key aspect of single crystal diamond growth via microwave plasma chemical vapor deposition is in-process control of the local plasma–substrate environment, that is, plasma gas phase concentrations of activated species at the plasma boundary layer near the substrate surface. Emission spectra of the plasma relative to the diamond substrate inside the microwave plasma reactor chamber have been analyzed via optical emission spectroscopy. The spectra of radical species such as CH, C2, and H (Balmer series) important for diamond growth were identified and analyzed. The emission intensities of these electronically excited species were found to be more dependent on operating pressure than on microwave power. Plasma gas temperatures were calculated from measurements of the C2 Swan band (d3Π → a3Π transition) system. The plasma gas temperature ranges from 2800 to 3400 K depending on the spatial location of the plasma ball, microwave power and operating pressure. Addition of Ar into CH4+H2 plasma input gas mixture has little influence on the Hα, Hβ, and Hγ intensities and single-crystal diamond growth rates

  13. Investigation of metalorganic chemical vapor deposition grown CdTe/CdS solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Sudharsanan, R.; Rohatgi, A. (Georgia Inst. of Tech., Atlanta (USA). School of Electrical Engineering)

    1991-03-01

    Polycrystalline CdTe films were grown on CdS/SnO{sub 2}/glass substrates by metalorganic chemical vapor deposition (MOCVD) for solar cell applications. Cells fabricated on these films showed efficiency of 9.7% which is the highest efficiency reported so far for MOCVD grown CdTe solar cells. The bias-dependent spectral response of the 9.7% efficient cell showed an external quantum efficiency greater than 0.85 at zero bias but a significant wavelength-independent reduction in spectral response at higher voltages. The interface recombination model was used to calculate the interface collection function term to quantify the open-circuit voltage (V{sub oc}) and fill factor losses in the high efficiency cell. It was found that the interface recombination reduces the V{sub oc} and fill factor by 60 mV and 0.1 respectively. It was estimated that efficiency as high as 13.5% can be achieved by improving CdTe/CdS interface quality. (orig.).

  14. Improvement of the dosimetric properties of chemical-vapor-deposited diamond films by neutron irradiation

    International Nuclear Information System (INIS)

    The performance of chemical-vapor-deposited (CVD) diamond films as on-line dosimeters has been substantially improved after irradiation with fast neutrons up to a fluence of 5x1014 n/cm2. This is correlated to a decrease of more than one order of magnitude in the concentration of deep levels with activation energy in the range 0.9-1.4 eV, as observed by thermally stimulated current and photoinduced current transient spectroscopy. As a consequence, a fast and reproducible dynamic response is observed during irradiation with a 6 MV photon beam from linear accelerator and with a Co60 source. A quasilinear dependence of the current on the dose rate is obtained in the range of interest for clinical applications (0.1-10 Gy/min). The resulting sensitivity is definitely higher than that of standard ionization chambers, and compares favorably with those of standard silicon dosimeters and of best-quality natural and CVD diamond devices

  15. Amorphous inclusions during Ge and GeSn epitaxial growth via chemical vapor deposition

    International Nuclear Information System (INIS)

    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 Ge2H6. 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 Ge2H6. • 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

  16. In situ synchrotron X-ray studies during metal-organic chemical vapor deposition of semiconductors

    International Nuclear Information System (INIS)

    In-situ, time-resolved techniques provide valuable insight into the complex interplay of surface structural and chemical evolution occurring during materials synthesis and processing of semiconductors. Our approach is to observe the evolution of surface structure and morphology at the atomic scale in real-time during metal organic vapor phase deposition (MOCVD) by using grazing incidence x-ray scattering and X-ray fluorescence, coupled with visible light scattering. Our vertical-flow MOCVD chamber is mounted on a 'z-axis' surface diffractometer designed specifically for these studies of the film growth, surface evolution and the interactions within a controlled growth environment. These techniques combine the ability of X-rays to penetrate a complex environment for measurements during growth and processing, with the sensitivity of surface scattering techniques to atomic and nanoscale structure. In this talk, we outline our program and discuss examples from our in-situ and real-time X-ray diffraction and fluorescence studies of InN, GaN, and InGaN growth on GaN(0001).

  17. Desalination by Membrane Distillation using Electrospun Polyamide Fiber Membranes with Surface Fluorination by Chemical Vapor Deposition.

    Science.gov (United States)

    Guo, Fei; Servi, Amelia; Liu, Andong; Gleason, Karen K; Rutledge, Gregory C

    2015-04-22

    Fibrous membranes of poly(trimethyl hexamethylene terephthalamide) (PA6(3)T) were fabricated by electrospinning and rendered hydrophobic by applying a conformal coating of poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) using initiated chemical vapor deposition (iCVD). A set of iCVD-treated electrospun PA6(3)T fiber membranes with fiber diameters ranging from 0.25 to 1.8 μm were tested for desalination using the air gap membrane distillation configuration. Permeate fluxes of 2-11 kg/m2/h were observed for temperature differentials of 20-45 °C between the feed stream and condenser plate, with rejections in excess of 99.98%. The liquid entry pressure was observed to increase dramatically, from 15 to 373 kPa with reduction in fiber diameter. Contrary to expectation, for a given feed temperature the permeate flux was observed to increase for membranes of decreasing fiber diameter. The results for permeate flux and salt rejection show that it is possible to construct membranes for membrane distillation even from intrinsically hydrophilic materials after surface modification by iCVD and that the fiber diameter is shown to play an important role on the membrane distillation performance in terms of permeate flux, salt rejection, and liquid entry pressure. PMID:25835769

  18. Triggering the Growth of Large Single Crystal Graphene by Chemical Vapor Deposition

    Science.gov (United States)

    Wu, Tianru; Wang, Haomin; Ding, Guqiao; Jiang, Da; Xie, Xiaoming; Jiang, Mianheng

    2013-03-01

    Graphene, a monolayer of sp2 carbon atoms, has been attracting great interests as an ideal two dimensional crystalline material. Fabrication technique for wafer scale graphene via chemical vapor deposition (CVD) was developed several years ago. However, large scale graphene films from CVD method so far are found to be polycrystalline, consisting of numerous grain boundaries, which greatly degrade the electrical and mechanical properties of graphene. Recently, we obtained hexagonal-shaped single-crystal monolayer graphene domains (~1.2 mm). We adapted a strategy to synthesize larger size single crystal grains by regulating the supply of reactants and hytrogen. Nucleation density can be decreased to less than 1000 nuclei /m2. Gradually increase in the supply of reactants could break the equilibrium of growth and etching at the edge of hexagonal-shaped graphene grains. It drives the reaction toward quick growth of graphene domains during the whole CVD process. The graphene grains we obtained show high crystalline quality with high mobility of ~13000 cm2V-1s-1, which is comparable to that of exfoliated graphene. The results achieved will definitely benefit for further practical application of graphene electronics.

  19. Effect of e-beam irradiation on graphene layer grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    We have grown graphene by chemical vapor deposition (CVD) and transferred it onto Si/SiO2 substrates to make tens of micron scale devices for Raman spectroscopy study. The effect of electron beam (e-beam) irradiation of various doses (600 to 12 000 μC/cm2) on CVD grown graphene has been examined by using Raman spectroscopy. It is found that the radiation exposures result in the appearance of the strong disorder D band attributed the damage to the lattice. The evolution of peak frequencies, intensities, and widths of the main Raman bands of CVD graphene is analyzed as a function of defect created by e-beam irradiation. Especially, the D and G peak evolution with increasing radiation dose follows the amorphization trajectory, which suggests transformation of graphene to the nanocrystalline and then to amorphous form. We have also estimated the strain induced by e-beam irradiation in CVD graphene. These results obtained for CVD graphene are in line with previous findings reported for the mechanically exfoliated graphene [D. Teweldebrhan and A. A. Balandin, Appl. Phys. Lett. 94, 013101 (2009)]. The results have important implications for CVD graphene characterization and device fabrication, which rely on the electron microscopy.

  20. Delta-doping of boron atoms by photoexcited chemical vapor deposition

    International Nuclear Information System (INIS)

    Boron delta-doped structures in Si crystals were fabricated by means of photoexcited chemical vapor deposition (CVD). Core electronic excitation with high-energy photons ranging from vacuum ultraviolet to soft x rays decomposes B2H6 molecules into fragments. Combined with in situ monitoring by spectroscopic ellipsometry, limited number of boron hydrides can be delivered onto a Si(100) surface by using the incubation period before the formation of a solid boron film. The boron-covered surface is subsequently embedded in a Si cap layer by Si2H6 photo-excited CVD. The crystallinity of the Si cap layer depended on its thickness and the substrate temperature. The evaluation of the boron depth profile by secondary ion mass spectroscopy revealed that boron atoms were confined within the delta-doped layer at a concentration of 2.5 x 1020 cm-3 with a full width at half maximum of less than 9 nm, while the epitaxial growth of a 130-nm-thick Si cap layer was sustained at 420 deg. C.

  1. TiOx thin films grown on Pd(100) and Pd(111) by chemical vapor deposition

    Science.gov (United States)

    Farstad, M. H.; Ragazzon, D.; Grönbeck, H.; Strømsheim, M. D.; Stavrakas, C.; Gustafson, J.; Sandell, A.; Borg, A.

    2016-07-01

    The growth of ultrathin TiOx (0≤x≤2) films on Pd(100) and Pd(111) surfaces by chemical vapor deposition (CVD), using Titanium(IV)isopropoxide (TTIP) as precursor, has been investigated by high resolution photoelectron spectroscopy, low energy electron diffraction and scanning tunneling microscopy. Three different TiOx phases and one Pd-Ti alloy phase have been identified for both surfaces. The Pd-Ti alloy phase is observed at the initial stages of film growth. Density functional theory (DFT) calculations for Pd(100) and Pd(111) suggest that Ti is alloyed into the second layer of the substrate. Increasing the TTIP dose yields a wetting layer comprising Ti2 + species (TiOx, x ∼0.75). On Pd(100), this phase exhibits a mixture of structures with (3 × 5) and (4 × 5) periodicity with respect to the Pd(100) substrate, while an incommensurate structure is formed on Pd(111). Most importantly, on both surfaces this phase consists of a zigzag pattern similar to observations on other reactive metal surfaces. Further increase in coverage results in growth of a fully oxidized (TiO2) phase on top of the partially oxidized layer. Preliminary investigations indicate that the fully oxidized phase on both Pd(100) and Pd(111) may be the TiO2(B) phase.

  2. Growth of epitaxial sodium-bismuth-titanate films by metal-organic chemical vapor phase deposition

    Energy Technology Data Exchange (ETDEWEB)

    Schwarzkopf, J., E-mail: schwarzkopf@ikz-berlin.de [Leibniz Institute for Crystal Growth, Max-Born-Strasse 2, 12489 Berlin (Germany); Schmidbauer, M.; Duk, A.; Kwasniewski, A. [Leibniz Institute for Crystal Growth, Max-Born-Strasse 2, 12489 Berlin (Germany); Anooz, S. Bin [Leibniz Institute for Crystal Growth, Max-Born-Strasse 2, 12489 Berlin (Germany); Physics Department, Faculty of Science, Hadhramout University of Science and Technology, Mukalla 50511, Republic of Yemen (Yemen); Wagner, G. [Leibniz Institute for Crystal Growth, Max-Born-Strasse 2, 12489 Berlin (Germany); Devi, A. [Inorganic Materials Chemistry, Ruhr-University Bochum, Universitaetsstr. 150, 44801 Bochum (Germany); Fornari, R. [Leibniz Institute for Crystal Growth, Max-Born-Strasse 2, 12489 Berlin (Germany)

    2011-10-31

    The liquid-delivery spin metal-organic chemical vapor phase deposition method was used to grow epitaxial sodium-bismuth-titanate films of the system Bi{sub 4}Ti{sub 3}O{sub 12} + xNa{sub 0.5}Bi{sub 0.5}TiO{sub 3} on SrTiO{sub 3}(001) substrates. Na(thd), Ti(O{sup i}Pr){sub 2}(thd){sub 2} and Bi(thd){sub 3}, solved in toluene, were applied as source materials. Depending on the substrate temperature and the Na/Bi ratio in the gas phase several structural phases of sodium-bismuth-titanate were detected. With increasing temperature and/or Na/Bi ratio, phase transitions from an Aurivillius phase with m = 3 to m = 4 via an interleaved state with m = 3.5, and, finally, to Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} with perovskite structure (m = {infinity}) were established. These phase transitions proceed at remarkably lower temperatures than in ceramics or bulk crystals for which they had been exclusively observed so far.

  3. 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.

  4. 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

    2016-02-01

    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. PMID:26662621

  5. Ion-beam-induced epitaxial crystallization of implanted and chemical vapor deposited amorphous silicon

    Science.gov (United States)

    La Ferla, A.; Priolo, F.; Spinella, C.; Rimini, E.; Baroetto, F.; Ferla, G.

    1989-03-01

    The dependence of ion-beam enhanced epitaxial growth of amorphous Si layers on impurities either dissolved in the film or present at the film-substrate interface is considered. In the case of ion implanted layers, electrically active dopants, like B, P, As at concentrations above 1 × 10 20/cm 3, enhance the rate by a factor of 2 with respect to the undoped layer. The enhancement shows also a weak dependence on the dopant concentration. Inert impurities, like Ar, which prevent pure thermal regrowth, do not show any appreciable influence on the ion-beam-induced growth rate. Chemical vapor deposited Si layers with a thin native interfacial oxide layer can also be epitaxially regrown under ion irradiation. A critical fluence is needed before the interfacial oxide breaks down and broadens, allowing the epitaxial crystallization to take place. This process is characterized by an activation energy of 0.44 eV. The complex phenomenon of ion-beam-induced crystallization involves a dynamical interaction between production and annealing of point defects. The presence of electrically active dopants probably influences the lifetime of point defects. Impurities which prevent thermal regrowth are instead dissolved by ballistic effects and/or radiation-enhanced mixing.

  6. Low-temperature-grown continuous graphene films from benzene by chemical vapor deposition at ambient pressure

    Science.gov (United States)

    Jang, Jisu; Son, Myungwoo; Chung, Sunki; Kim, Kihyeun; Cho, Chunhum; Lee, Byoung Hun; Ham, Moon-Ho

    2015-12-01

    There is significant interest in synthesizing large-area graphene films at low temperatures by chemical vapor deposition (CVD) for nanoelectronic and flexible device applications. However, to date, low-temperature CVD methods have suffered from lower surface coverage because micro-sized graphene flakes are produced. Here, we demonstrate a modified CVD technique for the production of large-area, continuous monolayer graphene films from benzene on Cu at 100-300 °C at ambient pressure. In this method, we extended the graphene growth step in the absence of residual oxidizing species by introducing pumping and purging cycles prior to growth. This led to continuous monolayer graphene films with full surface coverage and excellent quality, which were comparable to those achieved with high-temperature CVD; for example, the surface coverage, transmittance, and carrier mobilities of the graphene grown at 300 °C were 100%, 97.6%, and 1,900-2,500 cm2 V-1 s-1, respectively. In addition, the growth temperature was substantially reduced to as low as 100 °C, which is the lowest temperature reported to date for pristine graphene produced by CVD. Our modified CVD method is expected to allow the direct growth of graphene in device manufacturing processes for practical applications while keeping underlying devices intact.

  7. Structure and photoluminescence of molybdenum selenide nanomaterials grown by hot filament chemical vapor deposition

    International Nuclear Information System (INIS)

    Molybdenum selenide nanomaterials with different structures are synthesized on silicon substrates coated with gold films by hot filament chemical vapor deposition (HFCVD) in nitrogen environment, where molybdenum trioxide and selenium powders are used as source materials. The structure and composition of the synthesized molybdenum selenide nanomaterials are studied using field emission scanning electron microscopy, transmission electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The results indicate that the structures of molybdenum selenide change from nanoflakes to nanoparticles with the increase of content of molybdenum trioxide precursor. The photoluminescence (PL) excitation using the 325 nm line of He–Cd laser as the excitation source generates green light with the wavelength of about 512–516 nm. The formation of molybdenum selenide nanomaterials is determined by the decomposition rates of molybdenum trioxide in HFCVD. The possible factors that affect the generation of green PL bands are analyzed. These outcomes of this work enrich our knowledge on the synthesis of transition metal dichalcogenides and contribute to the development of applications of these materials in optoelectronic devices. - Highlights: • Molybdenum selenide nanoflakes, nanoparticles and hybrids produced by HFCVD. • Uncommon MoO3 and Se precursor co-location and mixing and effective MoO3 decomposition. • Morphology change from nanoflakes to nanoparticles with higher ratio of MoO3 precursor. • Strong photoluminescence emission of green light with a wavelength of ∼512–516 nm

  8. Probing weak localization in chemical vapor deposition graphene wide constriction using scanning gate microscopy

    Science.gov (United States)

    Chuang, C.; Matsunaga, M.; Liu, F.-H.; Woo, T.-P.; Aoki, N.; Lin, L.-H.; Wu, B.-Y.; Ochiai, Y.; Liang, C.-T.

    2016-02-01

    Low-temperature scanning gate microscopy (LT-SGM) studies of graphene allow one to obtain important spatial information regarding coherent transport such as weak localization (WL) and universal conductance fluctuations. Although fascinating LT-SGM results on pristine graphene prepared by mechanical exfoliation have been reported in the literature, there appears to be a dearth of LT-SGM results on chemical vapor deposition (CVD)-grown graphene whose large scale and flexible substrate transferability make it an ideal candidate for coherent electronic applications. To this end, we have performed LT-SGM studies on CVD-grown graphene wide constriction (0.8 μm), which can be readily prepared by cost-effective optical lithography fully compatible with those in wafer foundry, in the WL regime. We find that the movable local gate can sensitively modulate the total conductance of the CVD graphene constriction possibly due to the intrinsic grain boundaries and merged domains, a great advantage for applications in coherent electronics. Moreover, such a conductance modulation by LT-SGM provides an additional, approximately magnetic-field-independent probe for studying coherent transport such as WL in graphene and spatial conductance variation.

  9. Formation and Transport of Atomic Hydrogen in Hot-Filament Chemical Vapor Deposition Reactors

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In this paper we focus on diamond film hot-filament chemical vapor deposition reactors where the only reactant ishydrogen so as to study the formation and transport of hydrogen atoms. Analysis of dimensionless numbers forheat and mass transfer reveals that thermal conduction and diffusion are the dominant mechanisms for gas-phaseheat and mass transfer, respectively. A simplified model has been established to simulate gas-phase temperature andH concentration distributions between the filament and the substrate. Examination of the relative importance ofhomogeneous and heterogeneous production of H atoms indicates that filament-surface decomposition of molecularhydrogen is the dominant source of H and gas-phase reaction plays a negligible role. The filament-surface dissociationrates of H2 for various filament temperatures were calculated to match H-atom concentrations observed in the liter-ature or derived from power consumption by filaments. Arrhenius plots of the filament-surface hydrogen dissociationrates suggest that dissociation of H2 at refractory filament surface is a catalytic process, which has a rather lowereffective activation energy than homogeneous thermal dissociation. Atomic hydrogen, acting as an important heattransfer medium to heat the substrate, can freely diffuse from the filament to the substrate without recombination.

  10. Analysis of hydrogen plasma in a microwave plasma chemical vapor deposition reactor

    Science.gov (United States)

    Shivkumar, G.; Tholeti, S. S.; Alrefae, M. A.; Fisher, T. S.; Alexeenko, A. A.

    2016-03-01

    The aim of this work is to build a numerical model of hydrogen plasma inside a microwave plasma chemical vapor deposition system. This model will help in understanding and optimizing the conditions for the growth of carbon nanostructures. A 2D axisymmetric model of the system is implemented using the finite element high frequency Maxwell solver and the heat transfer solver in COMSOL Multiphysics. The system is modeled to study variation in parameters with reactor geometry, microwave power, and gas pressure. The results are compared with experimental measurements from the Q-branch of the H2 Fulcher band of hydrogen using an optical emission spectroscopy technique. The parameter γ in Füner's model is calibrated to match experimental observations at a power of 500 W and 30 Torr. Good agreement is found between the modeling and experimental results for a wide range of powers and pressures. The gas temperature exhibits a weak dependence on power and a strong dependence on gas pressure. The inclusion of a vertical dielectric pillar that concentrates the plasma increases the maximum electron temperature by 70%, the maximum gas temperature by 50%, and the maximum electron number density by 70% when compared to conditions without the pillar at 500 W and 30 Torr. Experimental observations also indicate intensified plasma with the inclusion of a pillar.

  11. Growth temperature dependence of partially Fe filled MWCNT using chemical vapor deposition

    Science.gov (United States)

    Sengupta, Joydip; Jacob, Chacko

    2009-12-01

    This investigation deals with the effect of growth temperature on the growth behavior of Fe filled multi-walled carbon nanotubes (MWCNTs). Carbon nanotube (CNT) synthesis was carried out in a thermal chemical vapor deposition (CVD) reactor in the temperature range 650-950 °C using propane as the carbon source, Fe as the catalyst material, and Si as the catalyst support. Atomic force microscopy (AFM) analysis of the catalyst exhibits that at elevated temperature clusters of catalyst coalesce and form macroscopic islands. Field emission scanning electron microscopy (FESEM) results show that with increased growth temperature the average diameter of the nanotubes increases but their density decreases. High-resolution transmission electron microscopy (HRTEM) studies suggest that the nanotubes have multi-walled structure with partial Fe filling for all growth temperatures. The X-ray diffraction (XRD) pattern of the grown materials indicates that they are graphitic in nature. The characterization of nanotubes by Raman spectroscopy reveals that the optimized growth temperature for Fe filled CNTs is 850 °C, in terms of quality. A simple model for the growth of Fe filled carbon nanotubes is proposed.

  12. One-step synthesis of chlorinated graphene by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Liwei; Zhang, Hui; Zhang, Pingping; Sun, Xuhui, E-mail: xhsun@suda.edu.cn

    2015-08-30

    Highlights: • We developed a simple approach to synthesize the single layer chlorinated graphene. • CuCl{sub 2} on Cu surface is used as Cl source under the plasma treatment. • The formation of covalent C−Cl bond has been investigated by Raman and XPS. • Raman results indicate the p-type doping effect of chlorination. - Abstract: We developed an approach to synthesize the chlorinated single layer graphene (Cl-G) by one-step plasma enhanced chemical vapor deposition. Copper foil was simply treated with hydrochloric acid and then CuCl{sub 2} formed on the surface was used as Cl source under the assistance of plasma treatment. Compared with other two-step methods by post plasma/photochemical treatment of CVD-grown single layer graphene (SLG), one-step Cl-G synthesis approach is quite straightforward and effective. X-ray photoelectron spectroscopy (XPS) revealed that ∼2.45 atom% Cl remained in SLG. Compared with the pristine SLG, the obvious blue shifts of G band and 2D band along with the appearance of D’ band and D + G band in the Raman spectra indicate p-type doping of Cl-G.

  13. Ultrathin 2D Photodetectors Utilizing Chemical Vapor Deposition Grown WS2 With Graphene Electrodes.

    Science.gov (United States)

    Tan, Haijie; Fan, Ye; Zhou, Yingqiu; Chen, Qu; Xu, Wenshuo; Warner, Jamie H

    2016-08-23

    In this report, graphene (Gr) is used as a 2D electrode and monolayer WS2 as the active semiconductor in ultrathin photodetector devices. All of the 2D materials are grown by chemical vapor deposition (CVD) and thus pose as a viable route to scalability. The monolayer thickness of both electrode and semiconductor gives these photodetectors ∼2 nm thickness. We show that graphene is different to conventional metal (Au) electrodes due to the finite density of states from the Dirac cones of the valence and conduction bands, which enables the photoresponsivity to be modulated by electrostatic gating and light input control. We demonstrate lateral Gr-WS2-Gr photodetectors with photoresponsivities reaching 3.5 A/W under illumination power densities of 2.5 × 10(7) mW/cm(2). The performance of monolayer WS2 is compared to bilayer WS2 in photodetectors and we show that increased photoresponsivity is achieved in the thicker bilayer WS2 crystals due to increased optical absorption. This approach of incorporating graphene electrodes in lateral TMD based devices provides insights on the contact engineering in 2D optoelectronics, which is crucial for the development of high performing ultrathin photodetector arrays for versatile applications. PMID:27440384

  14. Improving source efficiency for aluminum nitride grown by metal organic chemical vapor deposition

    Science.gov (United States)

    Foronda, Humberto M.; Laurent, Matthew A.; Yonkee, Benjanim; Keller, Stacia; DenBaars, Steven P.; Speck, James S.

    2016-08-01

    Parasitic pre-reactions are known to play a role in the growth of aluminum nitride (AlN) via metal organic chemical vapor deposition, where they can deplete precursor molecules before reaching the substrate, leading to poor growth efficiency. Studies have shown that reducing the growth pressure and growth temperature results in improved growth efficiency of AlN; however, superior crystal quality and reduced impurity incorporation are generally best obtained when growing at high temperatures. This study shows that, with proper alkyl source dilution, parasitic pre-reactions can be suppressed while maintaining high growth temperatures. The results show an 18× increase in growth rate and efficiency of AlN films: from 0.04 μm h‑1 to 0.73 μm h‑1, and 26 μm mol‑1 to 502 μm mol‑1, respectively; under constant TMAl flow and a small change in total gas flow. This results in 6.8% of Al atoms from the injected TMAl being utilized for AlN layer growth for this reactor configuration. This is better than the standard GaN growth, where 6.0% of the Ga atoms injected from TMGa are utilized for GaN growth.

  15. Synthesis of Graphene Films on Copper Foils by Chemical Vapor Deposition.

    Science.gov (United States)

    Li, Xuesong; Colombo, Luigi; Ruoff, Rodney S

    2016-08-01

    Over the past decade, graphene has advanced rapidly as one of the most promising materials changing human life. Development of production-worthy synthetic methodologies for the preparation of various types of graphene forms the basis for its investigation and applications. Graphene can be used in the forms of either microflake powders or large-area thin films. Graphene powders are prepared by the exfoliation of graphite or the reduction of graphene oxide, while graphene films are prepared predominantly by chemical vapor deposition (CVD) on a variety of substrates. Both metal and dielectric substrates have been explored; while dielectric substrates are preferred over any other substrate, much higher quality graphene large-area films have been grown on metal substrates such as Cu. The focus here is on the progress of graphene synthesis on Cu foils by CVD, including various CVD techniques, graphene growth mechanisms and kinetics, strategies for synthesizing large-area graphene single crystals, graphene transfer techniques, and, finally, challenges and prospects are discussed. PMID:26991960

  16. 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.

  17. 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.

  18. Further development of chemical vapor deposition process for production of large diameter carbon-base monofilaments

    Science.gov (United States)

    Hough, R. L.; Richmond, R. D.

    1974-01-01

    The development of large diameter carbon-base monofilament in the 50 micron to 250 micron diameter range using the chemical vapor deposition process is described. The object of this program was to determine the critical process variables which control monofilament strength, monofilament modulus, and monofilament diameter. It was confirmed that wide scatter in the carbon substrate strength is primarily responsible for the scatter in the monofilament strength. It was also shown through etching experiments that defective substrate surface conditions which can induce low strength modular growth in the monofilament layers are best controlled by processing improvements during the synthesis of the substrate. Modulus was found to be linearily proportional to monofilament boron content. Filament modulus was increased to above 27.8MN/sq cm but only by a considerable increase in monofilament boron content to 60 wt. % or more. Monofilament diameter depended upon dwell time in the synthesis apparatus. A monofilament was prepared using these findings which had the combined properties of a mean U.T.S. of 398,000 N/sq cm, a modulus of 18.9 MN/sq cm (24,000,000 psi), and a diameter of 145 microns. Highest measured strength for this fiber was 451,000 N/sq cm (645,000 psi).

  19. Modeling of Sheath Ion-Molecule Reactions in Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes

    Science.gov (United States)

    Hash, David B.; Govindan, T. R.; Meyyappan, M.

    2004-01-01

    In many plasma simulations, ion-molecule reactions are modeled using ion energy independent reaction rate coefficients that are taken from low temperature selected-ion flow tube experiments. Only exothermic or nearly thermoneutral reactions are considered. This is appropriate for plasma applications such as high-density plasma sources in which sheaths are collisionless and ion temperatures 111 the bulk p!asma do not deviate significantly from the gas temperature. However, for applications at high pressure and large sheath voltages, this assumption does not hold as the sheaths are collisional and ions gain significant energy in the sheaths from Joule heating. Ion temperatures and thus reaction rates vary significantly across the discharge, and endothermic reactions become important in the sheaths. One such application is plasma enhanced chemical vapor deposition of carbon nanotubes in which dc discharges are struck at pressures between 1-20 Torr with applied voltages in the range of 500-700 V. The present work investigates The importance of the inclusion of ion energy dependent ion-molecule reaction rates and the role of collision induced dissociation in generating radicals from the feedstock used in carbon nanotube growth.

  20. Chemical vapor deposition synthesis of carbon nanospheres over Fe-based glassy alloy particles

    International Nuclear Information System (INIS)

    Highlights: • A mass of carbon nanospheres have been synthesized. • The Fe76Si9B10P5 particles were employed as both the catalyst and support. • Carbon nanospheres with amorphous walls have uniform size distribution (50–150 nm). - Abstract: A mass of carbon nanospheres (CNSs) have been synthesized by chemical vapor deposition of C2H2 directly over Fe-based glassy alloy particles (Fe76Si9B10P5) without the addition of an external catalyst. The morphology and microstructure as well as the growth mechanism of the CNSs have been investigated by using scanning and transmission electron microscopy. The results showed that the obtained products consist of hollow CNSs and CNSs with Fe nanoparticles encapsulated. The CNSs with amorphous walls have high purity (>95%) and uniform size distribution (50–150 nm). The possible formation and growth mechanism of the CNSs were discussed on the basis of the investigation on their initial growth stages

  1. Influence of thin film nickel pretreatment on catalytic thermal chemical vapor deposition of carbon nanofibers

    International Nuclear Information System (INIS)

    Nickel and other metal nanoparticles are known to be active as catalysts in the synthesis of carbon nanofibers. In this paper we investigate how dewetting and break-up of nickel thin films depends on film thickness, film–substrate interaction and pretreatment conditions. This is evaluated for films evaporated on oxidized silicon and fused silica substrates with or without tantalum coating, which were subsequently exposed to different pretreatment atmospheres (vacuum, nitrogen, air and hydrogen; 1 h, 650 °C). Atomic force microscopy, scanning electron microscopy and energy dispersive X-ray analysis were used to characterize the films. Pretreated Ni films were subjected to a thermal catalytic chemical vapor deposition procedure with brief ethylene exposures (0.5–3 min, 635 °C). It was found that only on the spherical nanoparticles originating from a hydrogen pretreatment of a Ni film with Ta adhesion layer, homogeneously distributed, randomly-oriented, well-attached, and semi-crystalline carbon nanofibers be synthesized. - Highlights: • On the formation of nanoparticles required for carbon nanofiber (CNF) synthesis • Various evaporated thin films on oxidized silicon and fused silica: Ni and Ni/Ta • Pretreatment of nickel-based thin films in vacuum, nitrogen, air and hydrogen • Only on reduced Ni/Ta fast – within 3 min – initiation of CNF nucleation and growth

  2. Hydrogen-free spray pyrolysis chemical vapor deposition method for the carbon nanotube growth: Parametric studies

    International Nuclear Information System (INIS)

    Spray pyrolysis chemical vapor deposition (CVD) in the absence of hydrogen at low carrier gas flow rates has been used for the growth of carbon nanotubes (CNTs). A parametric study of the carbon nanotube growth has been conducted by optimizing various parameters such as temperature, injection speed, precursor volume, and catalyst concentration. Experimental observations and characterizations reveal that the growth rate, size and quality of the carbon nanotubes are significantly dependent on the reaction parameters. Scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy techniques were employed to characterize the morphology, structure and crystallinity of the carbon nanotubes. The synthesis process can be applied to both semiconducting silicon wafer and conducting substrates such as carbon microfibers and stainless steel plates. This approach promises great potential in building various nanodevices with different electron conducting requirements. In addition, the absence of hydrogen as a carrier gas and the relatively low synthesis temperature (typically 750 deg. C) qualify the spray pyrolysis CVD method as a safe and easy way to scale up the CNT growth, which is applicable in industrial production.

  3. Selective growth of graphene in layer-by-layer via chemical vapor deposition

    Science.gov (United States)

    Park, Jaehyun; An, Hyosub; Choi, Dong-Chul; Hussain, Sajjad; Song, Wooseok; An, Ki-Seok; Lee, Won-Jun; Lee, Naesung; Lee, Wan-Gyu; Jung, Jongwan

    2016-07-01

    Selective and precise control of the layer number of graphene remains a critical issue for the practical applications of graphene. First, it is highly challenging to grow a continuous and uniform few-layer graphene since once the monolayer graphene fully covers a copper (Cu) surface, the growth of the second layer stops, resulting in mostly nonhomogeneous films. Second, from the selective adlayer growth point of view, there is no clear pathway for achieving this. We have developed the selective growth of a graphene adlayer in layer-by-layer via chemical vapor deposition (CVD) which makes it possible to stack graphene on a specific position. The key idea is to deposit a thin Cu layer (~40 nm thick) on pre-grown monolayer graphene and to apply additional growth. The thin Cu atop the graphene/Cu substrate acts as a catalyst to decompose methane (CH4) gas during the additional growth. The adlayer is grown selectively on the pre-grown graphene, and the thin Cu is removed through evaporation during CVD, eventually forming large-area and uniform double layer graphene. With this technology, highly uniform graphene films with precise thicknesses of 1 to 5 layers and graphene check patterns with 1 to 3 layers were successfully demonstrated. This method provides precise LBL growth for a uniform graphene film and a technique for the design of new graphene devices.Selective and precise control of the layer number of graphene remains a critical issue for the practical applications of graphene. First, it is highly challenging to grow a continuous and uniform few-layer graphene since once the monolayer graphene fully covers a copper (Cu) surface, the growth of the second layer stops, resulting in mostly nonhomogeneous films. Second, from the selective adlayer growth point of view, there is no clear pathway for achieving this. We have developed the selective growth of a graphene adlayer in layer-by-layer via chemical vapor deposition (CVD) which makes it possible to stack graphene

  4. 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.

  5. Chemical vapor deposition of aluminide coatings on iron, nickel and superalloys

    International Nuclear Information System (INIS)

    Aluminide coatings are a class of intermetallic coatings applied on nickel and cobalt base superalloys and steels to protect them from different forms of environmental degradation at high temperatures. In this report a CVD system that can produce the aluminide coatings on iron, nickel and nickel base alloys has been described and the result of chemical vapor deposition of aluminide coatings on iron specimens, their characterization, and property evaluation have been presented. The CVD system consists of an AlCl3 bath, a stainless steel retort as a hot-wall reacto, cold traps and vacuum system. Aluminium chloride vapor was carried in a stream of hydrogen gas at a flow rate of 150 SCCM (standard cubic centimeter per minute) into the CVD reactor maintained in the temperature range of 1173 - 1373 K and at a pressure of 1.33 kPa (10 Torr). Aluminum deposition takes place from aluminium subchlorides produced by reaction between AlCl3 and pure aluminum kept in the CVD reactor. The aluminum diffuses into the iron samples and iron aluminide phases are formed at the surface. The coatings were shining bright and showed good adherence to the substrate. The coatings consisted of FeAl phase over a wide range of experimental conditions. The growth kinetics of the coating followed a parabolic rate law and the mean activation energy was 212 ±16 kJ/mol. Optical microscopic studies on the transverse section of the coating showed that the aluminide coating on iron consisted of two layers. The top layer had a thickness in the range of 20-50 μm, and the under layer had thickness ranging from 35 to 250 μm depending on coating temperature in two hours. The thickness of the aluminide layer increased with coating duration and temperature. Electron microprobe studies (EPMA) showed that the aluminum concentration decreased steadily as distance from the surface increased. TEM studies showed that the outer most layer had a B2 order (of the FeAl phase), which extended even into the under

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

    OpenAIRE

    Mohamed Shuaib Mohamed Saheed; Norani Muti Mohamed; Zainal Arif Burhanudin

    2014-01-01

    The paper reported the investigation of the substrate preparation technique involving deposition of iron catalyst by electron beam evaporation and ferrocene vaporization in order to produce vertically aligned multiwalled carbon nanotubes array needed for fabrication of tailored devices. Prior to the growth at 700°C in ethylene, silicon dioxide coated silicon substrate was prepared by depositing alumina followed by iron using two different methods as described earlier. Characterization analysi...

  7. Organometallic chemical vapor deposition of silicon nitride films enhanced by atomic nitrogen generated from surface-wave plasma

    International Nuclear Information System (INIS)

    Organometallic chemical vapor deposition of silicon nitride films enhanced by atomic nitrogen generated from surface-wave plasma is investigated. Feasibility of precursors of triethylsilane (TES) and bis(dimethylamino)dimethylsilane (BDMADMS) is discussed based on a calculation of bond energies by computer simulation. Refractive indices of 1.81 and 1.71 are obtained for deposited films with TES and BDMADMS, respectively. X-ray photoelectron spectroscopy (XPS) analysis of the deposited film revealed that TES-based film coincides with the stoichiometric thermal silicon nitride

  8. 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°.

  9. Spray Chemical Vapor Deposition of Single-Source Precursors for Chalcopyrite I-III-VI2 Thin-Film Materials

    Science.gov (United States)

    Hepp, Aloysius F.; Banger, Kulbinder K.; Jin, Michael H.-C.; Harris, Jerry D.; McNatt, Jeremiah S.; Dickman, John E.

    2008-01-01

    Thin-film solar cells on flexible, lightweight, space-qualified substrates provide an attractive approach to fabricating solar arrays with high mass-specific power. A polycrystalline chalcopyrite absorber layer is among the new generation of photovoltaic device technologies for thin film solar cells. At NASA Glenn Research Center we have focused on the development of new single-source precursors (SSPs) for deposition of semiconducting chalcopyrite materials onto lightweight, flexible substrates. We describe the syntheses and thermal modulation of SSPs via molecular engineering. Copper indium disulfide and related thin-film materials were deposited via aerosol-assisted chemical vapor deposition using SSPs. Processing and post-processing parameters were varied in order to modify morphology, stoichiometry, crystallography, electrical properties, and optical properties to optimize device quality. Growth at atmospheric pressure in a horizontal hotwall reactor at 395 C yielded the best device films. Placing the susceptor closer to the evaporation zone and flowing a more precursor-rich carrier gas through the reactor yielded shinier-, smoother-, and denser-looking films. Growth of (112)-oriented films yielded more Cu-rich films with fewer secondary phases than growth of (204)/(220)-oriented films. Post-deposition sulfur-vapor annealing enhanced stoichiometry and crystallinity of the films. Photoluminescence studies revealed four major emission bands and a broad band associated with deep defects. The highest device efficiency for an aerosol-assisted chemical vapor deposited cell was one percent.

  10. Photocatalytic Functional Coating of TiO2 Thin Film Deposited by Cyclic Plasma Chemical Vapor Deposition at Atmospheric Pressure

    Science.gov (United States)

    Kwon, Jung-Dae; Rha, Jong-Joo; Nam, Kee-Seok; Park, Jin-Seong

    2011-08-01

    Photocatalytic TiO2 thin films were prepared with titanium tetraisopropoxide (TTIP) using cyclic plasma chemical vapor deposition (CPCVD) at atmospheric pressure. The CPCVD TiO2 films contain carbon-free impurities up to 100 °C and polycrystalline anatase phases up to 200 °C, due to the radicals and ion-bombardments. The CPCVD TiO2 films have high transparency in the visible wavelength region and absorb wavelengths below 400 nm (>3.2 eV). The photocatalytic effects of the CPCVD TiO2 and commercial sprayed TiO2 films were measured by decomposing methylene blue (MB) solution under UV irradiation. The smooth CPCVD TiO2 films showed a relatively lower photocatalytic efficiency, but superior catalyst-recycling efficiency, due to their high adhesion strength on the substrates. This CPCVD technique may provide the means to produce photocatalytic thin films with low cost and high efficiency, which would be a reasonable candidate for practical photocatalytic applications, because of the reliability and stability of their photocatalytic efficiency in a practical environment.

  11. Microstructured Films Formed on Liquid Substrates via Initiated Chemical Vapor Deposition of Cross-Linked Polymers.

    Science.gov (United States)

    Bradley, Laura C; Gupta, Malancha

    2015-07-28

    We studied the formation of microstructured films at liquid surfaces via vapor phase polymerization of cross-linked polymers. The films were composed of micron-sized coral-like structures that originate at the liquid-vapor interface and extend vertically. The growth mechanism of the microstructures was determined to be simultaneous aggregation of the polymer on the liquid surface and wetting of the liquid on the growing aggregates. We demonstrated that we can increase the height of the microstructures and increase the surface roughness of the films by either decreasing the liquid viscosity or decreasing the polymer deposition rate. Our vapor phase method can be extended to synthesize functional, free-standing copolymer microstructured thin films for potential applications in tissue engineering, electrolyte membranes, and separations. PMID:26176742

  12. Global and local planarization of surface roughness by chemical vapor deposition of organosilicon polymer for barrier applications

    Energy Technology Data Exchange (ETDEWEB)

    Coclite, Anna Maria; Gleason, Karen K. [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2012-04-01

    Particulates and asperities on the surface of plastic substrates limit the performance of the current protective barrier coatings for flexible electronics. By applying a smoothing layer to the substrate, prior to barrier deposition, permeation is reduced. While application of smoothing layers from the liquid-phase application and curing of acrylate monomers is well known, reports of planarization achieved by vapor deposition are quite limited. In the current work, the chemical vapor deposition (CVD) of a flexible smoothing layer, requiring no curing, is implemented in the same reactor chamber and from the same organosilicon monomer used for depositing the multilayer barrier stack. The process similarity between the smoothing and barrier layer deposition steps has the potential to lower the overall cost of the process and to improve interfacial properties, such as adhesion between the smoothing layer and the barrier stack. The current methods adapts and combines features of two well established methods for CVD of organic layers, plasma enhancement (PECVD) and the specific use of an initiator species (iCVD). The novel, initiated plasma enhanced chemical vapor deposition (iPECVD) method achieves a far greater degree of planarization of flexible organic layer than either of its predecessors. Polystyrene microspheres serve as model defects and allow the degree of planarization to be quantitatively measured. Both cross-sectional scanning electron micrographs and atomic force micrographs demonstrate that when the iPECVD organic layer is 1.8 {mu}m thick, the degree of global planarization is 99%. A model demonstrates that the planarization is achieved as a result of the coating viscosity and the surface tension. Finally, the water vapor barrier performance of a 20-nm-thick SiO{sub x} layer is two orders of magnitude improved when it is deposited on a planarized substrate.

  13. Residual stresses in chemically vapor deposited coatings in the Ti-C-N system

    International Nuclear Information System (INIS)

    Residual stresses in chemically vapor deposited monolithic and graded coatings in the Ti-C-N system were investigated as a function of substrate material and coating composition by X-ray diffraction Sin2 Ψ method. The thermal expansion coefficients (CTEs) of the graphite substrates ranged from 2.5x10-6 K-1 to 8.6x10-6 K-1. Titanium nitride (CTE 9.35x10-6 K-1) and titanium carbide (CTE 7.5x10-6 K-1) coatings deposited on the low-expansion substrates (CTEs 2.5-3.5x10-6 K-1) exhibited crack networks which accounted for low stress levels measured in the coatings. A phenomenalogical explanation of the crack patterns was given. The coatings grown on the substrates with high coefficients of thermal expansion (CTEs 7.8-8.6x10-6 K-1) had no cracks. Residual stresses in the TiN coatings on these substrates were measured to be tensile. Whereas TiC coatings always exhibited compressive stresses ranging from -54±10 MPa to -288±18 MPa. The TiCxNy coatings deposited on the substrate with a thermal expansion coefficient of 8.6x10-6 K-1 also had compressive stresses increased with increasing TiC mole fraction in the TiCxNy up to about 0.9 above which stresses decreased. The residual stresses in the top TiC layers of the graded TiN/TiC coatings with linear, parabolic and exponentional composition profiles grown on the the same substrate (CTE 8.6x10-6 K-1) were measured to be compressive and about 475 MPa. Stresses in the coatings were calculated and attributed to the thermal expansion mismatch between the coating and the substrate. It was shown that the measured stresses were, in general, found to be in good agreement with the calculated ones. (orig.)

  14. Chemical Vapor Deposition of MoS2: Insight Into the Growth Mechanism by Separated Gas Flow Experiments.

    Science.gov (United States)

    Yanase, Takashi; Watanabe, Sho; Weng, Mengting; Nagahama, Taro; Shimada, Toshihiro

    2016-04-01

    We report detailed experiments on chemical vapor deposition of an atomic' layer semiconductor MoS2. We developed a new type of CVD system in which MoO3 and S sources are separately supplied to the substrates. It has become possible to precisely control the supply of the materials separately in the order of seconds. Raman and XPS analysis of the films grown under various conditions revealed that the initially obtained films are S-deficient and complete stoichiometry is reached after several minutes under S vapor flow. PMID:27451608

  15. Germanium-on-Silicon Strain Engineered Materials for Improved Device Performance Grown by Chemical Vapor Deposition

    Science.gov (United States)

    Bharathan, Jayesh Moorkoth

    The primary goal of this research is to develop a chemical vapor deposition process for growing epitaxial films of germanium on silicon (001) substrates with two-dimensional (2-D) morphology, and a low density of threading dislocations. Growth was carried out in a reduced-pressure chemical vapor deposition (RPCVD) system by a two-step growth technique. An accurate knowledge of elastic constants of thin films is important in understanding the effect of strain on material properties. Residual thermal strain was used to measure the Poisson ratio of Ge films grown on Si(001) substrates, by the sin2Psi method and highresolution x-ray diffraction. The Poisson ratio of the Ge films was measured to be 0.25, compared to the bulk value of 0.27. The result was found to be independent of film thickness and defect density, which confirmed that the strain is associated with the elastic response of the film. The study showed that the use of Poisson ratio instead of bulk compliance values yields a more accurate description of the state of in-plane strain present in the film. The experimentally measured in-plane strain in Ge films was found to be lower than the theoretical calculations based on the differential thermal expansion coefficients of Si and Ge. The mechanism of thermal misfit strain relaxation in epitaxial Ge films grown on Si(001) substrates was investigated by x-ray diffraction, and transmission electron microscopy. Lattice misfit strain associated with Ge/(001)Si mismatched epitaxy is relieved by a network of Lomer edge misfit dislocations during the first step of the growth technique. However, thermal misfit strain energy during growth is relieved by interdiffusion mechanism at the heterointerface. Two SiGe compositions containing 0.5 and 6.0 atomic percent Si were detected that relieve the thermal mismatch strain associated with the two steps of the growth process. This study discusses the importance of interdiffusion mechanism in relieving small misfit strains

  16. Chemical vapor deposition on chabazite (CHA) zeolite membranes for effective post-combustion CO2 capture.

    Science.gov (United States)

    Kim, Eunjoo; Lee, Taehee; Kim, Hyungmin; Jung, Won-Jin; Han, Doug-Young; Baik, Hionsuck; Choi, Nakwon; Choi, Jungkyu

    2014-12-16

    Chabazite (CHA) zeolites with a pore size of 0.37 × 0.42 nm(2) are expected to separate CO2 (0.33 nm) from larger N2 (0.364 nm) in postcombustion flue gases by recognizing their minute size differences. Furthermore, the hydrophobic siliceous constituent in CHA membranes can allow for maintaining the CO2/N2 separation performance in the presence of H2O in contrast with the CO2 affinity-based membranes. In an attempt to increase the molecular sieving ability, the pore mouth size of all silica CHA (Si-CHA) particles was reduced via the chemical vapor deposition (CVD) of a silica precursor (tetraethyl orthosilicate). Accordingly, an increase of the CVD treatment duration decreased the penetration rate of CO2 into the CVD-treated Si-CHA particles. Furthermore, the CVD process was applied to siliceous CHA membranes in order to improve their CO2/N2 separation performance. Compared to the intact CHA membranes, the CO2/N2 maximum separation factor (max SF) for CVD-treated CHA membranes was increased by ∼ 2 fold under dry conditions. More desirably, the CO2/N2 max SF was increased by ∼ 3 fold under wet conditions at ∼ 50 °C, a representative temperature of the flue gas stream. In fact, the presence of H2O in the feed disfavored the permeation of N2 more than that of CO2 through CVD-modified CHA membranes and thus, contributed to the increased CO2/N2 separation factor. PMID:25479409

  17. Growth of Mg-doped InN by Metal Organic Chemical Vapor Deposition

    Science.gov (United States)

    Khan, N.; Nepal, N.; Lin, J. Y.; Jiang, H. X.

    2007-03-01

    InN with an energy gap of ˜ 0.7 eV, has recently attracted extensive attention due to its potential applications in semiconductor devices such as light emitting diodes, lasers, and high efficiency solar cells. However the ability to grow both p-type and n-type InN is essential to realize these devices. All as grown unintentionally doped InN are n-type. The tendency of native defects in InN to form donors manifests itself severely at surfaces where high levels of electron accumulation are observed. The highly n-type conductive layer at the surface of InN films creates difficulties in the demonstration of p-type InN. Nevertheless it is important to investigate the optical and structural properties of Mg-doped InN. We report here on the growth of Mg-doped InN epilayers by metal organic chemical vapor deposition. Photoluminescence (PL) was employed to study the effects of different growth conditions of Mg-doped InN. PL studies revealed that in addition to emission peak at ˜ 0.82 eV in undoped InN layers, Mg-doped InN layers exhibit an emission peak at ˜ 0.75 eV. The peak at ˜ 0.75eV for Mg-doped InN could be related to defects generated by Mg doping in InN. Various other measurements such as Hall effect measurement, X-ray diffraction and atomic force microscopy were carried out to provide further understanding.

  18. Nanoscale coatings of tungsten by radio frequency plasma assisted chemical vapor deposition on graphite

    International Nuclear Information System (INIS)

    Future thermonuclear fusion reactors including ITER are heading towards full scale operations with tungsten being the material for the divertor, limiter and probably the first wall too. Tungsten has several superior properties over its low Z competitors in terms of higher melting point, lower sputtering yield, low fuel retention (D - T) etc. So far, fusion experimentalists have gained enough experience and have rich databases with carbon as its first wall as well as target materials in tokamaks. However, database for tungsten line radiation in variety of plasmas i.e. basic laboratory scale to high density and high temperature plasmas is rare and this requires immediate attention to construct a database with experimental evidences. Such studies are not limited to only large scale fusion reactors but small and medium scale toroidally confined devices can be suitably utilized. Present day tokamaks are now switching to plasma facing components made up of tungsten. As the complete replacement of the wall and target materials from carbon to tungsten in existing tokamaks is challenging and time consuming exercise, tungsten coatings on selected target materials remains a very feasible option for the purpose. This paper will present the development of indigenous tungsten coating reactor which has successfully produced tungsten coated graphite tiles of sample dimensions. The tungsten coated graphite tiles are produced by RF plasma assisted chemical vapor deposition of tungsten on graphite substrates. The RF plasma is produced with 60 - 100 W power and tungsten nano ions are produced by dissociating the precursor gas tungsten hexa-fluoride (WF6) in sufficient hydrogen background. Further, challenges in handling WF6 plasma at high pressures and in-situ spectroscopy results during the coating process will be presented. (author)

  19. Carrier transport in undoped CdO films grown by atmospheric-pressure chemical vapor deposition

    International Nuclear Information System (INIS)

    Temperature dependent Hall effect measurements were performed for the undoped CdO films with carrier concentrations (n) ranging from 2.4 × 1019 to 2.0 × 1020 cm−3 grown on c- and r-plane sapphire substrates by the atmospheric-pressure chemical vapor deposition using Cd powder and H2O as source materials. The n dependence of the optical gap energy (Eopt) could be explained by the combination of the band gap widening due to Burstein–Moss shift and the band gap shrinkages due to the electron–electron and electron–impurity interactions. For all the films, the carrier concentrations (n) were independent of measurement temperature (T), indicating that these films were n-type degenerate semiconductors. The barrier heights at grain boundaries determined from the 1000/T-ln(μT) curves were smaller than the thermal energy at 300 K, suggesting that the grain boundary scattering plays a minor role on the carrier transport in comparison with the intra-grain scattering. The n dependence of the gradient of the μ–T curve revealed the continuous transformation of the dominant intra-grain scattering mechanism from the phonon scattering to the ionized impurity scattering with increasing n. - Highlights: • Undoped CdO films were grown on c- and r-plane sapphire substrates by CVD. • Hall effect measurements were performed for the CdO films at 83–343 K. • For many CdO films, the carrier concentration n was independent of temperature. • The grain boundary scattering plays a minor role in the CdO films. • The dominant intra-grain scattering exhibited the continuous change with n

  20. The preparation and cathodoluminescence of ZnS nanowires grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    Highlights: ► ZnS nanowires have been achieved by thermal evaporation. ► The nanowires were 20–50 nm in diameter and up to tens of nanometers in length. ► Single-crystalline wurtzite and sphalerite ZnS phase are coexist in the nanowires. ► The ZnS nanowires showed almost identical blue luminescence at room temperature. ► ZnS nanowires may be appropriate for use in UV/blue LED phosphor materials. - Abstract: Single crystal ZnS nanowires were successfully synthesized in large quantities on Si (1 0 0) substrates by simple thermal chemical vapor deposition without using any catalyst. The morphology, composition, and crystal structure were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and cathodoluminescence (CL) spectroscopy. SEM observations show that the nanowires have diameters about 20–50 nm and lengths up to several tens of micrometers. XRD and TEM results confirmed that the nanowires exhibited both wurtzite and zinc blende structures with growth directions aligned along [0 0 0 2] and [1 1 1], respectively. The CL spectrum revealed emission bands in the UV and blue regions. The blue emissions at 449 and ∼581 nm were attributed to surface states and impurity-related defects of the nanowires, respectively. The perfect crystal structure of the nanowires indicates their potential applications in nanotechnology and in the fabrication of nanodevices.

  1. Synthesis of chemical vapor deposition graphene on tantalum wire for supercapacitor applications

    Energy Technology Data Exchange (ETDEWEB)

    Li, Mingji, E-mail: limingji@163.com [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China); Guo, Wenlong [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China); Li, Hongji, E-mail: hongjili@yeah.net [Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384 (China); Xu, Sheng [School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072 (China); Qu, Changqing; Yang, Baohe [Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384 (China)

    2014-10-30

    Highlights: • The capacitance of graphene/tantalum (Ta) wire electrodes is firstly reported. • Graphene was grown on the Ta surface by hot-filament chemical vapor deposition. • Graphene/Ta wire structure is favorable for fast ion and electron transfer. • The graphene/Ta wire electrode shows high capacitive properties. - Abstract: This paper studies the synthesis and electrochemical characterization of graphene/tantalum (Ta) wires as high-performance electrode material for supercapacitors. Graphene on Ta wires is prepared by the thermal decomposition of methane under various conditions. The graphene nanosheets on the Ta wire surface have an average thickness of 1.3–3.4 nm and consist typically of a few graphene monolayers, and TaC buffer layers form between the graphene and Ta wire. A capacitor structure is fabricated using graphene/Ta wire with a length of 10 mm and a diameter of 0.6 mm as the anode and Pt wire of the same size as the cathode. The electrochemical behavior of the graphene/Ta wires as supercapacitor electrodes is characterized by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy in 1 M Na{sub 2}SO{sub 4} aqueous electrolyte. The as-prepared graphene/Ta electrode has highest capacitance of 345.5 F g{sup −1} at current density of 0.5 A g{sup −1}. The capacitance remains at about 84% after 1000 cycles at 10 A g{sup −1}. The good electrochemical performance of the graphene/Ta wire electrode is attributed to the unique nanostructural configuration, high electrical conductivity, and large specific surface area of the graphene layer. This suggests that graphene/Ta wire electrode materials have potential applications in high-performance energy storage devices.

  2. Spatial/temporal photocurrent and electronic transport in monolayer molybdenum disulfide grown by chemical vapor deposition

    Science.gov (United States)

    Yang, Zhengfeng; Grassi, Roberto; Freitag, Marcus; Lee, Yi-Hsien; Low, Tony; Zhu, Wenjuan

    2016-02-01

    We systematically investigate the spatial/temporal photocurrent in photodetectors and electronic transport in transistors/Hall-bar devices based on monolayer MoS2 grown by chemical vapor deposition (CVD). We found that the maximum photocurrent occurs when the laser spot is close to the metal/MoS2 contact and is tunable by the applied drain voltage, which can be explained by the modulation of the local electric field at the Schottky barrier, consistent with predictions from our quantum transport simulation. We observed that the maximum photocurrent at drain contact is much larger than the one at the source contact, and the DC currents show rectifying behavior. These phenomena can be explained by the different Schottky barrier heights at the two contacts. By measuring Hall-bar structure at various temperatures from 100 K to 400 K, we extracted the barrier heights at the source and drain contacts, separately. We found that the barrier height at drain contact is about 50 mV larger than the one at the source contact, consistent with the photocurrent and DC current observations. We measured the photocurrent at various powers, and a photoresponsivity of 3.07 mA/W was extracted at low powers. When the power increases above 20 μW, the photocurrent starts to saturate. Temporal response of the photocurrent is also dependent on the laser power. At high laser powers, photocurrent overshoot was observed. The photocurrent saturation at high powers and the overshoot in temporal photocurrent are likely due to the same mechanism: an accumulation of electrons in the channel, flattening out the band structure, since the laser spot is located near the drain contact in these measurements. These studies of photocurrents and electronic transport in CVD MoS2 highlight the importance of the contacts in the electronic/optoelectronic devices and reveal the physical mechanism of the photocurrent/electronic transport in these devices.

  3. A new apparatus for multilayer growth by chemical vapor deposition: The sliding-boat close-spaced technique

    Science.gov (United States)

    Yoshikawa, Akihiko; Yoshihara, Seiji; Kasai, Haruo; Nishimaki, Masao

    1980-10-01

    A new apparatus for multilayer growth by chemical vapor deposition, the sliding-boat close-spaced tecnique (SBCST), is presented. The structure of the SBCST growth apparatus is quite similar to that of the conventional liquid phase epitaxy sliding-boat. The possibility of obtaining thin multilayer films by SBCST is shown. Preliminary experimental results for its application to the growth of n-CdS/p-InP heterojunction solar cells are also shown.

  4. Formation of Graphene Grain Boundaries on Cu(100) Surface and a Route Towards Their Elimination in Chemical Vapor Deposition Growth

    OpenAIRE

    Qinghong Yuan; Guangyao Song; Deyan Sun; Feng Ding

    2014-01-01

    Grain boundaries (GBs) in graphene prepared by chemical vapor deposition (CVD) greatly degrade the electrical and mechanical properties of graphene and thus hinder the applications of graphene in electronic devices. The seamless stitching of graphene flakes can avoid GBs, wherein the identical orientation of graphene domain is required. In this letter, the graphene orientation on one of the most used catalyst surface — Cu(100) surface, is explored by density functional theory (DFT) calculatio...

  5. Effects of Feed Gas Composition and Catalyst Thickness on Carbon Nanotube and Nanofiber Synthesis by Plasma Enhanced Chemical Vapor Deposition

    OpenAIRE

    R K Garg; Kim, S. S.; Hash, D. B; Gore, Jay P.; Fisher, Timothy

    2008-01-01

    Many engineering applications require carbon nanotubes with specific characteristics such as wall structure, chirality and alignment. However, precise control of nanotube properties grown to application specifications remains a significant challenge. Plasma-enhanced chemical vapor deposition (PECVD) offers a variety of advantages in the synthesis of carbon nanotubes in that several important synthesis parameters can be controlled independently. This paper reports an experimental study of the ...

  6. Catalytic Chemical Vapor Deposition of Methane to Carbon Nanotubes: Copper Promoted Effect of Ni/MgO Catalysts

    OpenAIRE

    Wen Yang; Yanyan Feng; Wei Chu

    2014-01-01

    The Ni/MgO and Ni-Cu/MgO catalysts were prepared by sol-gel method and used as the catalysts for synthesis of carbon nanotubes by thermal chemical vapor deposition. The effect of Cu on the carbon yield and structure was investigated, and the effects of calcination temperature and reaction temperature were also investigated. The catalysts and synthesized carbon materials were characterized by temperature programmed reduction (TPR), thermogravimetric analysis (TGA), and scanning electron micros...

  7. Influence of reaction parameters on synthesis of high-quality single-layer graphene on Cu using chemical vapor deposition

    International Nuclear Information System (INIS)

    Large-area monolayer graphene samples grown on polycrystalline copper foil by thermal chemical vapor deposition with differing CH4 flux and growth time are investigated by Raman spectra, scanning electron microscopy, atomic force microscopy, and scanning tunneling microscopy. The defects, number of layers, and quality of graphene are shown to be controllable through tuning the reaction conditions: ideally to 2–3 sccm CH4 for 30 minutes. (rapid communication)

  8. Investigation of deposition characteristics and properties of high-rate deposited silicon nitride films prepared by atmospheric pressure plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Silicon nitride (SiN x) films have been prepared at extremely high deposition rates by the atmospheric pressure plasma chemical vapor deposition (AP-PCVD) technique on Si(001) wafers from gas mixtures containing He, H2, SiH4 and N2 or NH3. A 150 MHz very high frequency (VHF) power supply was used to generate high-density radicals in the atmospheric pressure plasma. Deposition rate, composition and morphology of the SiN x films prepared with various deposition parameters were studied by scanning electron microscopy and Auger electron spectroscopy. Fourier transformation infrared (FTIR) absorption spectroscopy was also used to characterize the structure and the chemical bonding configurations of the films. Furthermore, etching rate with buffered hydrofluoric acid (BHF) solution, refractive index and capacitance-voltage (C-V) characteristics were measured to evaluate the dielectric properties of the films. It was found that effective passivation of dangling bonds and elimination of excessive hydrogen atoms at the film-growing surface seemed to be the most important factor to form SiN x film with a dense Si-N network. The C-V curve of the optimized film showed good interface properties, although further improvement was necessary for use in the industrial metal-insulator-semiconductor (MIS) applications

  9. Aligned synthesis of multi-walled carbon nanotubes with high purity by aerosol assisted chemical vapor deposition: Effect of water vapor

    International Nuclear Information System (INIS)

    Aligned multi-walled carbon nanotubes (MWCNTs) with high purity and bulk yield were achieved on a silicon substrate by an aerosol-assisted chemical vapor deposition. The introduction of specific amounts of water vapor played a key role in in situ controlling the purity and surface defects of the nanotubes. The morphology, surface quality and structure of MWCNTs were characterized by secondary and backscattered electron imaging in a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Crystallinity and defects of the MWCNTs' were investigated by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. In this work, water vapor was found to provide a weak oxidative environment, which enhanced and purified the MWCNTs' growth. However, excessive water vapor would inhibit the MWCNTs growth with a poor surface quality. In addition, it has been found that the surface morphology of the CNTs can be modified intentionally through producing some surface defects by tuning the amount of the water vapor, which may offer more nucleation sites on the chemically inert CNT surface for various applications such as catalyst support.

  10. 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.

  11. Using hot wire and initiated chemical vapor deposition for gas barrier thin film encapsulation

    International Nuclear Information System (INIS)

    Hot wire CVD (HWCVD) and initiated CVD (iCVD) are very well suited deposition techniques for the fabrication of transparent thin film gas barriers. Single inorganic or organic layers, however, face challenges, which are hard to overcome: unavoidable defects and low intrinsic barrier function. We demonstrate that by combining inorganic HWCVD films and organic iCVD films, a water vapor transmission rate a low as 5 ∗ 10−6 g/m2/day at 60 °C and 90% RH for a simple pinhole free three layer structure is obtained even with non-optimized individual layers. Given the 100 °C deposition temperature, the layer stacks can be deposited on any sensitive electronic device

  12. Controllable chemical vapor deposition growth of few layer graphene for electronic devices.

    Science.gov (United States)

    Wei, Dacheng; Wu, Bin; Guo, Yunlong; Yu, Gui; Liu, Yunqi

    2013-01-15

    Because of its atomic thickness, excellent properties, and widespread applications, graphene is regarded as one of the most promising candidate materials for nanoelectronics. The wider use of graphene will require processes that produce this material in a controllable manner. In this Account, we focus on our recent studies of the controllable chemical vapor deposition (CVD) growth of graphene, especially few-layer graphene (FLG), and the applications of this material in electronic devices. CVD provides various means of control over the morphologies of the produced graph ene. We studied several variables that can affect the CVD growth of graphene, including the catalyst, gas flow rate, growth time, and growth temperature and successfully achieved the controlled growth of hexagonal graphene crystals. Moreover, we developed several modified CVD methods for the controlled growth of FLGs. Patterned CVD produced FLGs with desired shapes in required areas. By introducing dopant precursor in the CVD process, we produced substitutionally doped FLGs, avoiding the typically complicated post-treatment processes for graphene doping. We developed a template CVD method to produce FLG ribbons with controllable morphologies on a large scale. An oxidation-activated surface facilitated the CVD growth of polycrystalline graphene without the use of a metal catalyst or a complicated postgrowth transfer process. In devices, CVD offers a controllable means to modulate the electronic properties of the graphene samples and to improve device performance. Using CVD-grown hexagonal graphene crystals as the channel materials in field-effect transistors (FETs), we improved carrier mobility. Substitutional doping of graphene in CVD opened a band gap for efficient FET operation and modulated the Fermi energy level for n-type or p-type features. The similarity between the chemical structure of graphene and organic semiconductors suggests potential applications of graphene in organic devices. We

  13. Green light emission from terbium doped silicon rich silicon oxide films obtained by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Podhorodecki, A.; Zatryb, G.; Misiewicz, J.; Wojcik, J.; Wilson, P. R. J.; Mascher, P.

    2012-11-01

    The effect of silicon concentration and annealing temperature on terbium luminescence was investigated for thin silicon rich silicon oxide films. The structures were deposited by means of plasma enhanced chemical vapor deposition. The structural properties of these films were investigated by Rutherford backscattering spectrometry, transmission electron microscopy and Raman scattering. The optical properties were investigated by means of photoluminescence and photoluminescence decay spectroscopy. It was found that both the silicon concentration in the film and the annealing temperature have a strong impact on the terbium emission intensity. In this paper, we present a detailed discussion of these issues and determine the optimal silicon concentration and annealing temperature.

  14. Carbon diffusion in uncoated and titanium nitride coated iron substrates during microwave plasma assisted chemical vapor deposition of diamond

    International Nuclear Information System (INIS)

    Auger Electron Spectroscopy has been employed to investigate the effectiveness of thin films of TiN as barriers to carbon diffusion during Chemical Vapor Deposition (CVD) of diamond onto Fe substrates. Auger Depth Profiling was used to monitor the C concentration in the TiN layer, through the interface and into the substrate both before and after CVD diamond deposition. The results show that a layer of TiN only 250 Angstroems thick is sufficient to inhibit soot formation on the Fe surface and C diffusion into the Fe bulk. 14 refs., 4 figs

  15. Molecular Dynamics Simulation of Chemical Vapor Deposition of Amorphous Carbon: Dependence on H/C Ratio of Source Gas

    OpenAIRE

    Ito, Atsushi M.; Takayama, Arimichi; Saito, Seiki; Ohno, Noriyasu; Kajita, Shin; Nakamura, Hiroaki

    2010-01-01

    By molecular dynamics simulation, the chemical vapor deposition of amorphous carbon onto graphite and diamond surfaces was studied. In particular, we investigated the effect of source H/C ratio, which is the ratio of the number of hydrogen atoms to the number of carbon atoms in a source gas, on the deposition process. In the present simulation, the following two source gas conditions were tested: one was that the source gas was injected as isolated carbon and hydrogen atoms, and the other was...

  16. Design of a compact ultrahigh vacuum-compatible setup for the analysis of chemical vapor deposition processes

    International Nuclear Information System (INIS)

    Optimizing thin film deposition techniques requires contamination-free transfer from the reactor into an ultrahigh vacuum (UHV) chamber for surface science analysis. A very compact, multifunctional Chemical Vapor Deposition (CVD) reactor for direct attachment to any typical UHV system for thin film analysis was designed and built. Besides compactness, fast, easy, and at the same time ultimately clean sample transfer between reactor and UHV was a major goal. It was achieved by a combination of sample manipulation parts, sample heater, and a shutter mechanism designed to fit all into a NW38 Conflat six-ways cross. The present reactor design is versatile to be employed for all commonly employed variants of CVD, including Atomic Layer Deposition. A demonstration of the functionality of the system is provided. First results of the setup (attached to an Omicron Multiprobe x-ray photoelectron spectroscopy system) on the temperature dependence of Pulsed Spray Evaporation-CVD of Ni films from Ni acetylacetonate as the precursor demonstrate the reactor performance and illustrate the importance of clean sample transfer without breaking vacuum in order to obtain unambiguous results on the quality of CVD-grown thin Ni films. The widely applicable design holds promise for future systematic studies of the fundamental processes during chemical vapor deposition or atomic layer deposition

  17. Design of a compact ultrahigh vacuum-compatible setup for the analysis of chemical vapor deposition processes

    Science.gov (United States)

    Weiss, Theodor; Nowak, Martin; Mundloch, Udo; Zielasek, Volkmar; Kohse-Höinghaus, Katharina; Bäumer, Marcus

    2014-10-01

    Optimizing thin film deposition techniques requires contamination-free transfer from the reactor into an ultrahigh vacuum (UHV) chamber for surface science analysis. A very compact, multifunctional Chemical Vapor Deposition (CVD) reactor for direct attachment to any typical UHV system for thin film analysis was designed and built. Besides compactness, fast, easy, and at the same time ultimately clean sample transfer between reactor and UHV was a major goal. It was achieved by a combination of sample manipulation parts, sample heater, and a shutter mechanism designed to fit all into a NW38 Conflat six-ways cross. The present reactor design is versatile to be employed for all commonly employed variants of CVD, including Atomic Layer Deposition. A demonstration of the functionality of the system is provided. First results of the setup (attached to an Omicron Multiprobe x-ray photoelectron spectroscopy system) on the temperature dependence of Pulsed Spray Evaporation-CVD of Ni films from Ni acetylacetonate as the precursor demonstrate the reactor performance and illustrate the importance of clean sample transfer without breaking vacuum in order to obtain unambiguous results on the quality of CVD-grown thin Ni films. The widely applicable design holds promise for future systematic studies of the fundamental processes during chemical vapor deposition or atomic layer deposition.

  18. Ultrasharp Si nanowires produced by plasma-enhanced chemical vapor deposition

    Czech Academy of Sciences Publication Activity Database

    Červenka, Jiří; Ledinský, Martin; Stuchlíková, The-Ha; Stuchlík, Jiří; Výborný, Zdeněk; Holovský, Jakub; Hruška, Karel; Fejfar, Antonín; Kočka, Jan

    2010-01-01

    Roč. 4, 1-2 (2010), s. 37-39. ISSN 1862-6254 R&D Projects: GA MŠk(CZ) LC06040; GA AV ČR KAN400100701; GA MŠk LC510 Institutional research plan: CEZ:AV0Z10100521 Keywords : nanowires * silicon * scanning electron microscopy * hemical vapor deposition * Raman spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.660, year: 2010 http://www3.interscience.wiley.com/cgi-bin/fulltext/123213957/HTMLSTART

  19. Preparation of glasses in the Ge-S-I system by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Mochalov, L. A.; Churbanov, M. F.; Velmuzhov, A. P.; Lobanov, A. S.; Kornev, R. A.; Sennikov, G. P.

    2015-08-01

    The glass samples of the Ge-S-I system were synthesized by plasma-enhanced chemical vapor deposition (PECVD) in a low-temperature non-equilibrium RF-plasma discharge. The vapors of S and GeI4 were the initial substances. The process was carried out in a flowing quartz reactor at the walls temperature of 300-500 °C and the total pressure range of 1.9-22.8 Torr. The phase and the elemental compositions of the deposited glassy batches were investigated. The glasses obtained by melting of the solid reaction products were homogenized in the evacuated quartz glass ampoule and they were studied by DSC, X-ray microanalysis, and atomic emission spectroscopy. The proposed method allows to prepare the glasses of the system Ge-S-I with Si content less than 3 ṡ 10-5 wt.%.

  20. Heat and Mass Transfer during Chemical Vapor Deposition on the Particle Surface Subjected to Nanosecond Laser Heating

    CERN Document Server

    Peng, Quan; He, Yaling; Mao, Yijin

    2016-01-01

    A thermal model of chemical vapor deposition of titanium nitride (TiN) on the spherical particle surface under irradiation by a nanosecond laser pulse is presented in this paper. Heat and mass transfer on a single spherical metal powder particle surface subjected to temporal Gaussian heat flux is investigated analytically. The chemical reaction on the particle surface and the mass transfer in the gas phase are also considered. The surface temperature, thermal penetration depth, and deposited film thickness under different laser fluence, pulse width, initial particle temperature, and particle radius are investigated. The effect of total pressure in the reaction chamber on deposition rate is studied as well. The particle-level model presented in this paper is an important step toward development of multiscale model of LCVI.

  1. Formation of SiC Nanostruture Using Hexamethyldisiloxane During Plasma-Assisted Hot-Filament Chemical Vapor Deposition

    International Nuclear Information System (INIS)

    Growth of SiC nanowires in plasma-assisted hot filament chemical-vapor-deposition by using hexamethyldisiloxane (HMDSO) as the gas source is reported. The SiC nanowires (SiC-NWs) grew on Au-coated silicon substrate with core-shell structure, where the core consisted of polycrystalline SiC grains and the shell exhibited amorphous structure. The featured structures such as cones, polyhedrons, ball-liked particles were observed in the case without plasma assistance. The underlying mechanism for the growth of nanostructures was also discussed. The high chemical activity induced by the plasma process plays an important role in using monomer to generate nanostructure.

  2. The reason why thin-film silicon grows layer by layer in plasma-enhanced chemical vapor deposition

    OpenAIRE

    Takuya Kuwahara; Hiroshi Ito; Kentaro Kawaguchi; Yuji Higuchi; Nobuki Ozawa; Momoji Kubo

    2015-01-01

    Thin-film Si grows layer by layer on Si(001)-(2 × 1):H in plasma-enhanced chemical vapor deposition. Here we investigate the reason why this occurs by using quantum chemical molecular dynamics and density functional theory calculations. We propose a dangling bond (DB) diffusion model as an alternative to the SiH3 diffusion model, which is in conflict with first-principles calculation results and does not match the experimental evidence. In our model, DBs diffuse rapidly along an upper layer c...

  3. Simple, green, and clean removal of a poly(methyl methacrylate) film on chemical vapor deposited graphene

    Science.gov (United States)

    Park, J.-H.; Jung, W.; Cho, D.; Seo, J.-T.; Moon, Y.; Woo, S. H.; Lee, C.; Park, C.-Y.; Ahn, J. R.

    2013-10-01

    The clean removal of a poly(methyl methacrylate) (PMMA) film on graphene has been an essential part of the process of transferring chemical vapor deposited graphene to a specific substrate, influencing the quality of the transferred graphene. Here we demonstrate that the clean removal of PMMA can be achieved by a single heat-treatment process without the chemical treatment that was adopted in other methods of PMMA removal. The cleanness of the transferred graphene was confirmed by four-point probe measurements, synchrotron radiation x-ray photoemission spectroscopy, optical images, and Raman spectroscopy.

  4. Chemical vapor deposition of ruthenium–phosphorus alloy thin films: Using phosphine as the phosphorus source

    Energy Technology Data Exchange (ETDEWEB)

    Bost, Daniel E.; Ekerdt, John G., E-mail: ekerdt@che.utexas.edu

    2014-05-02

    The use of PH{sub 3} as the P source in the growth of amorphous ruthenium–phosphorus (Ru(P)) alloy films by dual-source chemical vapor deposition (CVD) with Ru{sub 3}(CO){sub 12} to produce thin (∼ 3 nm) Cu diffusion barriers is examined. Comparisons are made to films grown using P(CH{sub 3}){sub 3}. Carbon contamination of 10 at.% carbon or less was observed in PH{sub 3}-produced Ru(P) films, compared to greater than 30 atomic % carbon in films using P(CH{sub 3}){sub 3}, and lower resistivity was also observed. PH{sub 3} was found to be much more reactive than previously-used P precursors, requiring the use of very low PH{sub 3} partial pressures (∼ 0.13 mPa) and a sequenced addition process that allowed accumulated P to diffuse into the Ru(P) film during growth. X-ray reflectivity and atomic force microscopy indicate that films of good continuity and smoothness can be grown by CVD in the 3 nm thickness range. X-ray diffraction shows the amorphous phase to be stable for annealing at 400 °C for 3 h. Electric field stress tests to failure for Cu/Ru(P)/SiO{sub 2}/Si stacks indicate that low-carbon Ru(P) barrier films function at least as well as their higher-carbon counterparts as Cu barriers and better than Ta/TaN stacks of similar thickness grown for comparison purposes. - Highlights: • Reports the CVD growth of 3 to 5 nm amorphous Ru(P) thin films PH{sub 3} as the P source • PH{sub 3}-grown Ru(P) films have ∼ 10% C content the same as films with zero % P. • Fast PH{sub 3} decomposition at 250 °C can lead to P accumulation on the growth surface. • Amorphous, continuous 3 nm Ru(P) films realized for P content > 20 atom % • Electrical field stress tests indicate 3 nm Ru(P) function as a Cu diffusion barrier.

  5. The Tribological Behaviors of Three Films Coated on Biomedical Titanium Alloy by Chemical Vapor Deposition

    Science.gov (United States)

    Wang, Song; Liao, Zhenhua; Liu, Yuhong; Liu, Weiqiang

    2015-11-01

    Three thin films (DLC, a-C, and TiN) were performed on Ti6Al4V by chemical vapor deposition. Carbon ion implantation was pretreated for DLC and a-C films while Ti transition layer was pretreated for TiN film to strengthen the bonding strength. X-ray diffraction, Raman measurement, nano-hardness and nano-scratch tester, and cross-section etching by FIB method were used to analyze film characteristics. Tribological behaviors of these coatings were studied by articulation with both ZrO2 and UHMWPE balls using ball-on-disk sliding. The thickness values reached ~0.46, ~0.33, and ~1.67 μm for DLC, a-C, and TiN film, respectively. Nano-hardness of the coatings compared with that of untreated and bonding strength (critical load in nano-scratch test) values of composite coatings compared with that of monolayer film all increased significantly, respectively. Under destructive test (ZrO2 ball conterface) in bovine serum lubrication, TiN coating revealed the best wear resistance while DLC showed the worst. Film failure was mainly attributed to the plowing by hard ZrO2 ball characterized by abrasive and adhesive wear. Under normal test (UHMWPE ball conterface), all coatings showed significant improvement in wear resistance both in dry sliding and bovine serum lubrication. Both DLC and a-C films showed less surface damage than TiN film due to the self-lubricating phenomenon in dry sliding. TiN film showed the largest friction coefficient both in destructive and normal tests, devoting to the big TiN grains thus leading to much rougher surface and then a higher value. The self-lubricating film formed on DLC and a-C coating could also decrease their friction coefficients. The results indicated that three coatings revealed different wear mechanisms, and thick DLC or a-C film was more promising in application in lower stress conditions such as artificial cervical disk.

  6. Chemical vapor deposition of ruthenium–phosphorus alloy thin films: Using phosphine as the phosphorus source

    International Nuclear Information System (INIS)

    The use of PH3 as the P source in the growth of amorphous ruthenium–phosphorus (Ru(P)) alloy films by dual-source chemical vapor deposition (CVD) with Ru3(CO)12 to produce thin (∼ 3 nm) Cu diffusion barriers is examined. Comparisons are made to films grown using P(CH3)3. Carbon contamination of 10 at.% carbon or less was observed in PH3-produced Ru(P) films, compared to greater than 30 atomic % carbon in films using P(CH3)3, and lower resistivity was also observed. PH3 was found to be much more reactive than previously-used P precursors, requiring the use of very low PH3 partial pressures (∼ 0.13 mPa) and a sequenced addition process that allowed accumulated P to diffuse into the Ru(P) film during growth. X-ray reflectivity and atomic force microscopy indicate that films of good continuity and smoothness can be grown by CVD in the 3 nm thickness range. X-ray diffraction shows the amorphous phase to be stable for annealing at 400 °C for 3 h. Electric field stress tests to failure for Cu/Ru(P)/SiO2/Si stacks indicate that low-carbon Ru(P) barrier films function at least as well as their higher-carbon counterparts as Cu barriers and better than Ta/TaN stacks of similar thickness grown for comparison purposes. - Highlights: • Reports the CVD growth of 3 to 5 nm amorphous Ru(P) thin films PH3 as the P source • PH3-grown Ru(P) films have ∼ 10% C content the same as films with zero % P. • Fast PH3 decomposition at 250 °C can lead to P accumulation on the growth surface. • Amorphous, continuous 3 nm Ru(P) films realized for P content > 20 atom % • Electrical field stress tests indicate 3 nm Ru(P) function as a Cu diffusion barrier

  7. A hot-wire chemical vapor deposition (HWCVD) method for metal oxide and their alloy nanowire arrays

    International Nuclear Information System (INIS)

    A concept for synthesizing nanowire arrays of transition metal oxides and their alloys using hot wire chemical vapor deposition (HWCVD) is discussed. Here, unlike conventional HWCVD, the hot filaments act as the source of the metal for the synthesis of one dimensional nanostructures. In the present concept, the chemical vapor transport of metal oxides generated by heating the filaments in low amounts of oxygen, onto substrates maintained at lower temperatures leads to the formation of metal oxide nanowires. Experiments performed using tungsten and molybdenum filaments showed that the nucleation density of the resulting metal oxide nanowires could be varied by varying the substrate temperature. Experiments performed using a magnesium source inside the reactor, in addition to tungsten filaments, resulted in the formation of MgWO4 nanowires. This clearly indicates the possibility of either doping the metal oxide nanowires or alloying during synthesis.

  8. 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.

  9. Superconducting MgB2 film prepared by chemical vapor deposition at atmospheric pressure of N2

    International Nuclear Information System (INIS)

    A simple and effective chemical vapor deposition equipment was developed for deposition of superconducting MgB2 thin films. The pure precursor Boron films were prepared in base pressure of low vacuum and deposited in atmospheric pressure. After the precursor film annealed in Mg vapor, the superconducting MgB2 film was fabricated. During the precursor Boron films preparation, N2 and Ar were used as carrier gas. Compared to Ar gas, the films show better crystallization, surface morphology and superconducting performance when N2 is adopted as carrier gas. With flow rate of 200 sccm of N2 gas, the fabricated MgB2 films exhibit the highest superconducting transition temperature of 39.5 K, which is among the best results of MgB2 thin films. This method provides a suitable method to realize high quality MgB2 Josephson junctions and industrial manufacture of MgB2 superconducting thin films on a large scale. - Highlights: • Boron films were deposited in atmospheric pressure. • Boron films deposited in N2 atmosphere have better morphology than that of in Ar. • MgB2 films show better crystallization and superconductivity in N2 atmosphere

  10. Formation of TiO2 Thin Films using NH3 as Catalyst by Metalorganic Chemical Vapor Deposition

    Science.gov (United States)

    Jung, Sung-Hoon; Kang, Sang-Won

    2001-05-01

    We have studied metalorganic chemical vapor deposition of TiO2 thin films using titanium tetra-isopropoxide [TTIP, Ti(O--C3H7)4] and NH3 as a catalyst at deposition temperatures ranging from 250 to 365°C. At deposition temperatures above 330°C, pyrolytic self-decomposition of TTIP is dominant regardless of the use of NH3, and the activation energy for TiO2 film formation is 152 kJ/mol. At deposition temperatures below 330°C, the films can be formed with the help of the catalytic activity of NH3, and the activation energy is reduced to 55 kJ/mol. TiO2 films deposited through the pyrolytic self-decomposition of TTIP have an anatase structure before and after performing post-deposition annealing in oxygen ambient for 30 min at 750°C. On the other hand, the as-deposited films formed through the catalytic reaction of TTIP with NH3 incorporate nitrogen impurities and have microcrystallites of the rutile structure within the amorphous matrix. However, the post-deposition annealing, the nitrogen impurities are completely removed from the films, and the films are converted into polycrystalline TiO2 films with the rutile structure, which have a high dielectric constant of 82 and a low leakage current.

  11. Properties and electric characterizations of tetraethyl orthosilicate-based plasma enhanced chemical vapor deposition oxide film deposited at 400 °C for through silicon via application

    International Nuclear Information System (INIS)

    The dielectric via liner of through silicon vias was deposited at 400 °C using a tetraethyl orthosilicate (TEOS)-based plasma enhanced chemical vapor deposition process in a via-middle integration scheme. The morphology, conformality and chemical compositions of the liner film were characterized using field emission scanning electron microscopy and Fourier Transform Infrared spectroscopy. The thermal properties and electrical performance of blanket TEOS films were investigated by high temperature film stress and mercury probe Capacitance–Voltage measurements. The TEOS SiO2 films show good conformality, excellent densification, low thermal stress, high breakdown voltage and low current leakage. - Highlights: • Tetraethyl orthosilicate-based oxide films were deposited for packaging application. • The oxide films deposited plasma-enhanced chemical vapor deposition (PECVD) at 400 °C. • The PECVD oxide films exhibit good step coverage. • The 400 °C PECVD oxide films exhibit low thermal stress and current leakage. • The 400 °C PECVD oxide films show high breakdown voltage and acceptable permittivity

  12. Properties and electric characterizations of tetraethyl orthosilicate-based plasma enhanced chemical vapor deposition oxide film deposited at 400 °C for through silicon via application

    Energy Technology Data Exchange (ETDEWEB)

    Su, Meiying, E-mail: sumeiying@ime.ac.cn [Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029 (China); National Center for Advanced Packaging, Wuxi 214135 (China); Yu, Daquan, E-mail: yudaquan@ime.ac.cn [Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029 (China); National Center for Advanced Packaging, Wuxi 214135 (China); Jiangsu R and D Center for Internet of Things, Wuxi 214135 (China); Liu, Yijun [Piotech Co. Ltd, Shenyang 110179 (China); Wan, Lixi [Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029 (China); Song, Chongshen; Dai, Fengwei [Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029 (China); National Center for Advanced Packaging, Wuxi 214135 (China); Xue, Kai [National Center for Advanced Packaging, Wuxi 214135 (China); Jing, Xiangmeng [Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029 (China); National Center for Advanced Packaging, Wuxi 214135 (China); Guidotti, Daniel [Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029 (China)

    2014-01-01

    The dielectric via liner of through silicon vias was deposited at 400 °C using a tetraethyl orthosilicate (TEOS)-based plasma enhanced chemical vapor deposition process in a via-middle integration scheme. The morphology, conformality and chemical compositions of the liner film were characterized using field emission scanning electron microscopy and Fourier Transform Infrared spectroscopy. The thermal properties and electrical performance of blanket TEOS films were investigated by high temperature film stress and mercury probe Capacitance–Voltage measurements. The TEOS SiO{sub 2} films show good conformality, excellent densification, low thermal stress, high breakdown voltage and low current leakage. - Highlights: • Tetraethyl orthosilicate-based oxide films were deposited for packaging application. • The oxide films deposited plasma-enhanced chemical vapor deposition (PECVD) at 400 °C. • The PECVD oxide films exhibit good step coverage. • The 400 °C PECVD oxide films exhibit low thermal stress and current leakage. • The 400 °C PECVD oxide films show high breakdown voltage and acceptable permittivity.

  13. Sheet Resistance and Gas-Sensing Properties of Tin Oxide Thin Films by Plasma Enhanced Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    刘彭义; 陈俊芳; 孙汪典

    2004-01-01

    Tin oxide (SnO2) thin films are prepared at different temperatures by plasmaenhanced chemical vapor deposition (PECVD). The structural characterizations of the films are investigated by various analysis techniques. X-ray diffraction patterns (XRD) show that the phase of SnO2 films are different at different deposition temperatures. The sheet resistance of the films decreases with increase of deposition temperature. X-ray photoelectron spectroscopy (XPS) shows that the SnO2 thin film is non-stoichiometric. The sheet resistance increases with increase in oxygen flow. Sb-doped SnO2 thin films are more sensitive to alcohol than carbon monoxide, and its maximum sensitivity is about 220%.

  14. 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.

  15. Biased electron cyclotron resonance chemical-vapor deposition of silicon dioxide inter-metal dielectric thin films

    International Nuclear Information System (INIS)

    A low-temperature, single-step, gap-fill process has been developed for use in inter-metal dielectric (IMD) applications on wafers up to 200 mm in diameter. Sub-0.5 μm, high aspect ratio gaps were filled with high quality SiO2 dielectric on 200 mm wafers with a process suitable for use in semiconductor manufacturing. The SiO2 IMD was deposited from an O2-Ar-SiH4 gas mixture using a biased electron cyclotron resonance plasma-enhanced chemical-vapor deposition (ECR-CVD) system. This article examines the basic physical and chemical phenomena underlying this process. Film growth is shown to occur through a heterogeneous, ion-activated reaction between oxygen species streaming onto the wafer from the ECR source and silane species adsorbed on the wafer. (orig.)

  16. Effects of argon and oxygen flow rate on water vapor barrier properties of silicon oxide coatings deposited on polyethylene terephthalate by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Plasma polymer coatings were deposited from hexamethyldisiloxane on polyethylene terephthalate (PET) substrates while varying the operating conditions, such as the Ar and O2 flow rates, at a fixed radio frequency power of 300 W. The water vapor transmission rate (WVTR) of the untreated PET was 54.56 g/m2/day and was decreased after depositing the silicon oxide (SiOx) coatings. The minimum WVTR, 0.47 g/m2/day, was observed at Ar and O2 flow rates of 4 and 20 sccm, respectively, with a coating thickness of 415.44 nm. The intensity of the peaks for the Si-O-Si bending at 800-820 cm-1 and Si-O-Si stretching at 1000-1150 cm-1 varied depending on the Ar and O2 flow rates. The contact angle of the SiOx coated PET increased as the Ar flow rate was increased from 2 to 8 sccm at a fixed O2 flow rate of 20 sccm. It decreased gradually as the oxygen flow rate increased from 12 to 28 sccm at a fixed Ar carrier gas flow rate. The examination by atomic force microscopy revealed a correlation of the SiOx morphology and the water vapor barrier performance with the Ar and O2 flow rates. The roughness of the deposited coatings increased when either the O2 or Ar flow rate was increased.

  17. Smart Windows, Switchable between Transparent, Mirror, and Black States, Fabricated Using Rough and Smooth Indium Tin Oxide Films Deposited by Spray Chemical Vapor Deposition

    Science.gov (United States)

    Onodera, Ryou; Seki, Yoshiyuki; Seki, Shigeyuki; Yamada, Katsumi; Sawada, Yutaka; Uchida, Takayuki

    2013-02-01

    Two types of indium-tin oxide films, rough and smooth, with an average grain size of 434 and 71 nm, respectively, were deposited by spray pyrolysis chemical vapor deposition. Using both these films, we fabricated glare tunable transparent electrochemical devices exhibiting reversible optical changes between transparent, mirror, and black states, without any treatments. Under zero bias conditions, the transmittance of the transparent state reached 81.1% at 700 nm. With a bias of -2.5 V, the reflectance of the mirror state reached 82.0% at 700 nm. The total transmittances in the mirror and black state amounted to 0.6% in the visible range.

  18. Improving chemical vapor deposition graphene conductivity using molybdenum trioxide: An in-situ field effect transistor study

    International Nuclear Information System (INIS)

    By using in situ field effect transistor characterization integrated with molecular beam epitaxy technique, we demonstrate the strong surface transfer p-type doping effect of single layer chemical vapor deposition (CVD) graphene, through the surface functionalization of molybdenum trioxide (MoO3) layer. After doping, both the hole and electron mobility of CVD graphene are nearly retained, resulting in significant enhancement of graphene conductivity. With coating of 10 nm MoO3, the conductivity of CVD graphene can be increased by about 7 times, showing promising application for graphene based electronics and transparent, conducting, and flexible electrodes

  19. High-efficiency CdTe thin-film solar cells using metalorganic chemical vapor deposition techniques

    Science.gov (United States)

    Nouhi, A.; Stirn, R. J.; Meyers, P. V.; Liu, C. H.

    1989-06-01

    Energy conversion efficiency of metalorganic chemical vapor deposited CdTe as an intrinsic active layer in n-i-p solar cell structures is reported. Small-area devices with efficiencies over 9 percent have been demonstrated. I-V characteristics, photospectral response, and the results of Auger profiling of structural composition for typical devices will be presented. Also presented are preliminary results on similar photovoltaic devices having Cd(0.85)Mn(0.15)Te in place of CdTe as an i layer.

  20. High-efficiency CdTe thin-film solar cells using metalorganic chemical vapor deposition techniques

    Energy Technology Data Exchange (ETDEWEB)

    Nouhi, A.; Stirn, R.J.; Meyers, P.V.; Liu, C.H.

    1989-05-01

    Energy conversion efficiency of metalorganic chemical vapor deposited CdTe as an intrinsic active layer in n-i-p solar cell structures is reported. Small-area devices with efficiencies over 9% have been demonstrated. I--V characteristics, photospectral response, and the results of Auger profiling of structural composition for typical devices will be presented. Also presented are preliminary results on similar photovoltaic devices having Cd/sub 0.85/Mn/sub 0.15/Te in place of CdTe as an i layer.

  1. Synthesis of multi-layer graphene films on copper tape by atmospheric pressure chemical vapor deposition method

    International Nuclear Information System (INIS)

    Graphene films were successfully synthesized by atmospheric pressure chemical vapor deposition (APCVD) method. Methane (CH4) gas and copper (Cu) tapes were used as a carbon source and a catalyst, respectively. The CVD temperature and time were in the range of 800–1000 °C and 10 s to 45 min, respectively. The role of the CVD temperature and time on the growth of graphene films was investigated in detail via scanning electron microscopy (SEM) and Raman spectroscopy techniques. The results of SEM images and Raman spectra show that the quality of the graphene films was improved with increasing of CVD temperature due to the increase of catalytic activity. (paper)

  2. In-situ characterization of trapped charges in amorphous semiconductor films during plasma-enhanced chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    S. Nunomura

    2014-09-01

    Full Text Available The subband-gap absorption current in a hydrogenated amorphous silicon film has been measured during plasma-enhanced chemical vapor deposition. The current is probed by a near-infrared laser while photoexcited carriers are generated under visible laser illumination. The trapped charge density is determined from the magnitude of current under the assumption of carrier generation and recombination kinetics. The result indicates that trapped charges are distributed uniformly in the film during growth, and they are reduced after the growth. The trapped charge density is minimized at a growth temperature of ≈ 473 K.

  3. Corn-shape carbon nanofibers with dense graphite synthesized by microwave plasma-enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Corn-shape carbon nanofibers (CCNFs) with metal-free tips have been synthesized by a microwave plasma-enhanced chemical-vapor deposition method using CH4 and H2 gasses. The CCNFs were grown on Ni/SiO2/Si and Ni/Mo mesh substrates using a bias-enhanced growth method, and they were analyzed by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The cones are composed of cylindrical pure graphite sheets, and have nanometer-sized tips and roots. The tips' apex angles of CCNFs have cone angles of 20 deg., 39 deg., and 60 deg. depending on the growth conditions such as substrate temperature

  4. Effect of MoO3 constituents on the growth of MoS2 nanosheets by chemical vapor deposition

    Science.gov (United States)

    Wang, Xuan; Zhang, Yong Ping; Qian Chen, Zhi

    2016-06-01

    The highly crystalline and uniform MoS2 film was grown on Si substrate by a low-pressure chemical vapor deposition method using S and MoO3 as precursors at an elevated temperature. The structures and properties of MoS2 nanosheets vary greatly with the content of MoO3 constituents in the films. The nanostructured MoS2 film exhibits strong photoluminescence in the visible range. This work may provide a pathway to synthesizing MoS2 nanosheets and facilitate the development of applicable devices.

  5. Hydrodynamic study of fine metallic powders in an original spouted bed contactor in view of chemical vapor deposition treatments

    OpenAIRE

    Caussat, Brigitte; Juarez, Fernando L.; Vahlas, Constantin

    2006-01-01

    An original gas–solid contactor was developed so as to treat by chemical vapor deposition, fine (mean diameter 23 μm) and dense (bulk density 7700 kg/m3) NiCoCrAlYTa powders with large size distribution. In order to avoid the presence of a distributor in the reactive zone, a spouted bed configuration was selected, consisting in a glass cylindrical column associated through a 60° cone to an inlet tube, connected at its bottom to a grid so as to support the powders at rest. A hydrodynamic study...

  6. High-efficiency CdTe thin-film solar cells using metalorganic chemical vapor deposition techniques

    Science.gov (United States)

    Nouhi, A.; Stirn, R. J.; Meyers, P. V.; Liu, C. H.

    1989-01-01

    Energy conversion efficiency of metalorganic chemical vapor deposited CdTe as an intrinsic active layer in n-i-p solar cell structures is reported. Small-area devices with efficiencies over 9 percent have been demonstrated. I-V characteristics, photospectral response, and the results of Auger profiling of structural composition for typical devices will be presented. Also presented are preliminary results on similar photovoltaic devices having Cd(0.85)Mn(0.15)Te in place of CdTe as an i layer.

  7. INTERACTION-MEDIATED GROWTH OF CARBON NANOTUBES ON ACICULAR SILICA-COATED α-Fe CATALYST BY CHEMICAL VAPOR DEPOSITION

    Institute of Scientific and Technical Information of China (English)

    Qixiang Wang; Guoqing Ning; Fei Wei; Guohua Luo

    2003-01-01

    Multi-walled carbon nanotubes (MWNTs) with 20 nm outer diameter were prepared by chemical vapor deposition of ethylene using ultrafine surface-modified acicular α-Fe catalyst particles. The growth mechanism of MWNTs on the larger catalyst particles are attributed to the interaction between the Fe nanoparticles with the surface-modified silica layer. This interaction-mediated growth mechanism is illustrated by studying the electronic, atomic and crystal properties of surface-modified catalysts and MWNTs products by characterization with X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), thermal gravimetric analysis (TGA) and Raman spectra.

  8. Graphene Films: Synthesis of Graphene Films on Copper Foils by Chemical Vapor Deposition (Adv. Mater. 29/2016).

    Science.gov (United States)

    Li, Xuesong; Colombo, Luigi; Ruoff, Rodney S

    2016-08-01

    Synthesis of graphene films on copper foils is discussed by X. Li, L. Colombo, and R. S. Ruoff on page 6247. Graphene can grow on metal substrates by chemical vapor deposition of hydrocarbons. Hydrocarbons crack on a metal surface, nucleate, grow, and finally merge to form a continuous graphene film. Copper is one of the best candidates for graphene growth due to the advantages of good control over the graphene thickness, the growth of high-quality graphene, and the ease for graphene transfer, and has been widely used for production of large-area graphene films in both academia and industry. PMID:27478085

  9. Water vapor-controlled thermal plasma chemical vapor deposition of double-layered TiN/PSZ coatings on Si and WC-Co substrates

    International Nuclear Information System (INIS)

    Double-layer TiN/PSZ film coatings were deposited on Si wafers and WC-Co cutting tools from Ti-, Zr-, and Y-alkoxide solutions by thermal plasma chemical vapor deposition (CVD) containing water vapor. The partially stabilized zirconia (PSZ) layer was coated on a TiN film by oxidation of Zr- and Y-alkoxides with H2O supplied by both constant and step-wise methods. Double-layer TiN/PSZ coatings deposited on Si wafers and WC-Co by the two H2O supply methods were approximately 2 μm thick. TEM observation showed that the interface between the TiN and PSZ in the double-layer TiN/PSZ formed by the step-wise H2O supply is more adhesive than under constant H2O supply. Double-layer TiN/PSZ films coated on WC-Co substrates by the step-wise supply exhibited good crater wear resistance, comparable to a commercial double-layer TiN/Al2O3 coating by thermal CVD.

  10. Water vapor-controlled thermal plasma chemical vapor deposition of double-layered TiN/PSZ coatings on Si and WC-Co substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, Takanori [Graduate School of Engineering, Hokkaido University, West-8, North-13, Kita-ku, Sapporo 060-8628 (Japan); Shimada, Shiro, E-mail: shimashi@eng.hokudai.ac.jp [Graduate School of Engineering, Hokkaido University, West-8, North-13, Kita-ku, Sapporo 060-8628 (Japan); Kiyono, Hajime [Graduate School of Engineering, Hokkaido University, West-8, North-13, Kita-ku, Sapporo 060-8628 (Japan); Tsujino, Jiro [Research and Development Department, Hokkaido Electric Power Co. Ltd., 2-1, Tsuishikari, Ebetsu City 067-0033 (Japan); Yamazaki, Isao [Hokkaido Sumiden Precision Industries Ltd., 776 Naie, Sorachi-gun, Hokkaido 079-0304 (Japan)

    2010-08-25

    Double-layer TiN/PSZ film coatings were deposited on Si wafers and WC-Co cutting tools from Ti-, Zr-, and Y-alkoxide solutions by thermal plasma chemical vapor deposition (CVD) containing water vapor. The partially stabilized zirconia (PSZ) layer was coated on a TiN film by oxidation of Zr- and Y-alkoxides with H{sub 2}O supplied by both constant and step-wise methods. Double-layer TiN/PSZ coatings deposited on Si wafers and WC-Co by the two H{sub 2}O supply methods were approximately 2 {mu}m thick. TEM observation showed that the interface between the TiN and PSZ in the double-layer TiN/PSZ formed by the step-wise H{sub 2}O supply is more adhesive than under constant H{sub 2}O supply. Double-layer TiN/PSZ films coated on WC-Co substrates by the step-wise supply exhibited good crater wear resistance, comparable to a commercial double-layer TiN/Al{sub 2}O{sub 3} coating by thermal CVD.

  11. Reduced thermal budget processing of Y-Ba-Cu-O films by rapid isothermal processing assisted metalorganic chemical vapor deposition

    International Nuclear Information System (INIS)

    Metalorganic chemical vapor deposition (MOCVD) has the potential of emerging as a viable technique to fabricate ribbons, tapes, coated wires, and the deposition of films of high-temperature superconductors, and related materials. As a reduced thermal budget processing technique, rapid isothermal processing (RIP) based on incoherent radiation as the source of energy can be usefully coupled to conventional MOCVD. In this paper we report on the deposition and characterization of high quality superconducting thin films of Y-Ba-Cu-O (YBCO) on yttrium stabilized zirconia substrates by RIP assisted MOCVD. Using O2 gas as the source of oxygen, YBCO films deposited initially at 600 degree C for 1 min and at 745 degree C for 25 min followed by deposition at 780 degree C for 45 s are primarily c-axis oriented and zero resistance is observed at 89--90 K. The zero magnetic field current density at 53 and 77 K are 1.2x106 and 3x105 A/cm2, respectively. By using a mixture of N2O and O2 as the oxygen source substrate temperature was further reduced in the deposition of YBCO films. The films deposited initially at 600 degree C for 1 min and than at 720 degree C for 30 min are c-axis oriented and with zero resistance being observed at 91 K. The zero magnetic field current densities at 53 and 77 K are 3.4x106 and 1.2x106 A/cm2, respectively. To the best of our knowledge this is the highest value of critical current density, Jc for films deposited by MOCVD at a substrate temperature as low as 720 degree C. It is envisioned that high energy photons from the incoherent light source and the use of a mixture of N2O and O2 as the oxygen source, assist chemical reactions and lower overall thermal budget for processing of these films

  12. Low temperature deposition and effect of plasma power on tin oxide thin films prepared by modified plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    This work presents low temperature (200 and 300 deg. C) thin film deposition of tin oxide (SnO2) using modified plasma enhanced chemical vapor deposition as a function of radio frequency power (100 - 500 W). Stannic chloride (SnCl4) was used as precursor and oxygen (O2, 300 SCCM) as reactant gas. Fine granular morphology was observed with tetragonal rutile structure grown along the [110] direction, at all the deposition conditions. Higher plasma power resulted in smoother morphology, improved crystallinity, and enhanced conductivity. Electrical resistivity value of as low as ∼0.01 Ω cm was obtained at the deposition temperature of 300 deg. C and 250 W of plasma power

  13. Atomic-layer chemical-vapor-deposition of TiN thin films on Si(100) and Si(111)

    CERN Document Server

    Kim, Y S; Kim, Y D; Kim, W M

    2000-01-01

    An atomic-layer chemical vapor deposition (AL-CVD) system was used to deposit TiN thin films on Si(100) and Si(111) substrates by cyclic exposures of TiCl sub 4 and NH sub 3. The growth rate was measured by using the number of deposition cycles, and the physical properties were compared with those of TiN films grown by using conventional deposition methods. To investigate the growth mechanism, we suggest a growth model for TiN n order to calculate the growth rate per cycle with a Cerius program. The results of the calculation with the model were compared with the experimental values for the TiN film deposited using the AL-CVD method. The stoichiometry of the TiN film was examined by using Auger electron spectroscopy, and the chlorine and the oxygen impurities were examined. The x-ray diffraction and the transmission electron microscopy results for the TiN film exhibited a strong (200) peak and a randomly oriented columnar microstructure. The electrical resistivity was found to decrease with increasing deposit...

  14. Optical Properties of One-Dimensional Structured GaN:Mn Fabricated by a Chemical Vapor Deposition Method

    Directory of Open Access Journals (Sweden)

    Sang-Wook Ui

    2013-01-01

    Full Text Available Group III nitride semiconductors with direct band gaps have recently become increasingly important in optoelectronics and microelectronics applications due to their direct band gaps, which cover the whole visible spectrum and a large part of the UV range. Major developments in wide band gap III–V nitride semiconductors have recently led to the commercial production of high-temperature, high-power electronic devices, light-emitting diodes (LEDs, and laser diodes (LDs. In this study, GaN nanowires were grown on horizontal reactors by chemical vapor deposition (CVD employing a vapor-solid mechanism. Many studies have described how to control the diameters of wires in the liquid phase catalytic process, but one-dimensional nanostructures, which are grown using a noncatalytic process, are relatively unexplored due to the challenge of producing high-quality synthetic materials of controlled size. However, vapor-solid mechanisms to make synthesized nanowires are simple to implement. We obtained results from GaN nanostructures that were a preferential c-axis orientation from the substrate. The morphology and crystallinity of the GaN nanowires were characterized by field-emission scanning electron microscopy and X-ray diffraction. The chemical compositions of GaN with Mn were analyzed by energy dispersive X-ray spectroscopy. Optical properties were investigated using photo luminescence and cathode-luminescence measurements.

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

    OpenAIRE

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

    2014-01-01

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

  16. Multiwalled Carbon Nanotube Forest Grown via Chemical Vapor Deposition from Iron Catalyst Nanoparticles, by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, David S.; Kanyal, Supriya S.; Madaan, Nitesh; Vail, Michael A.; Dadson, Andrew; Engelhard, Mark H.; Linford, Matthew R.

    2013-09-25

    Carbon nanotubes (CNTs) have unique chemical and physical properties. Herein, we report an XPS analysis of a forest of multiwalled CNTs using monochromatic Al Kα radiation. Survey scans show only one element: carbon. The carbon 1s peak is centered 284.5 eV. The C 1s envelope also shows the expected π → π* shake-up peak at ca. 291 eV. The valence band and carbon KVV Auger signals are presented. When patterned, the CNT forests can be used as a template for subsequent deposition of metal oxides to make thin layer chromatography plates.1-3

  17. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

    Science.gov (United States)

    Johnston, Jamin M.; Catledge, Shane A.

    2016-02-01

    Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W2CoB2 with average hardness from 23 to 27 GPa and average elastic modulus of 600-730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

  18. Atomic MoS2 monolayers synthesized from a metal-organic complex by chemical vapor deposition

    Science.gov (United States)

    Liu, Lina; Qiu, Hailong; Wang, Jingyi; Xu, Guanchen; Jiao, Liying

    2016-02-01

    The controllable synthesis of MoS2 monolayers is the key challenge for their practical applications. Here we report the chemical vapor deposition (CVD) growth of single layered MoS2 by utilizing a bifunctional precursor. This precursor is a metal-organic complex which supplies both Mo sources and organic seeding promoters for the efficient CVD growth of MoS2 monolayers. The successful growth of high quality MoS2 flakes indicates that the rational design of bifunctional precursors will open up a new way for the controllable CVD growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs).The controllable synthesis of MoS2 monolayers is the key challenge for their practical applications. Here we report the chemical vapor deposition (CVD) growth of single layered MoS2 by utilizing a bifunctional precursor. This precursor is a metal-organic complex which supplies both Mo sources and organic seeding promoters for the efficient CVD growth of MoS2 monolayers. The successful growth of high quality MoS2 flakes indicates that the rational design of bifunctional precursors will open up a new way for the controllable CVD growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs). Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09089j

  19. Experimentation and simulation of tin oxide deposition on glass based on the SnCl4 hydrolysis in an in-line atmospheric pressure chemical vapor deposition reactor

    International Nuclear Information System (INIS)

    Tin oxide thin films were deposited on glass substrates in an in-line atmospheric pressure chemical vapor deposition reactor under various conditions, which were numerically simulated using a commercial package. A soda-lime glass sheet was used as a deposition substrate, and SnCl4 and H2O in gas phase were separately supplied as the precursor and the oxidizer, respectively. By assuming that the main chemical reactions followed the Rideal–Eley mechanism, the experimentally determined deposition rates were fitted to obtain the reaction factors needed to describe the deposition process. The role of barrier gas injection for minimizing unwanted surface reaction or particle generation inside of the reactor, and not on the target (glass backplane itself) has been elucidated. Furthermore, the optimal operating conditions for the deposition on glass with the additives such as CH3OH and HF have been investigated. - Highlights: • Tin oxide deposition on glass based on the SnCl4 hydrolysis in an in-line reactor • Simulations using Rideal–Eley mechanism were compared to experimental observations. • Results: activation energy—79.3 kJ/mol and frequency factor—1.93 × 1010 m4/kmol·s • Influences of additives on transmittances, hazes, and electrical resistivities

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

    International Nuclear Information System (INIS)

    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.

  1. Effects of polymethylmethacrylate-transfer residues on the growth of organic semiconductor molecules on chemical vapor deposited graphene

    International Nuclear Information System (INIS)

    Scalably grown and transferred graphene is a highly promising material for organic electronic applications, but controlled interfacing of graphene thereby remains a key challenge. Here, we study the growth characteristics of the important organic semiconductor molecule para-hexaphenyl (6P) on chemical vapor deposited graphene that has been transferred with polymethylmethacrylate (PMMA) onto oxidized Si wafer supports. A particular focus is on the influence of PMMA residual contamination, which we systematically reduce by H2 annealing prior to 6P deposition. We find that 6P grows in a flat-lying needle-type morphology, surprisingly independent of the level of PMMA residue and of graphene defects. Wrinkles in the graphene typically act as preferential nucleation centers. Residual PMMA does however limit the length of the resulting 6P needles by restricting molecular diffusion/attachment. We discuss the implications for organic device fabrication, with particular regard to contamination and defect tolerance

  2. Transmission electron microscopy on early-stage tin oxide film morphology grown by atmospheric pressure chemical vapor deposition

    International Nuclear Information System (INIS)

    Nucleation and morphology development during the early stages of chemical vapor deposition (CVD) processes are believed to be of major importance for the overall film properties. Here, the authors have investigated the nucleation of tin oxide films, comparing different tin precursors (tin tetrachloride (TTC) and monobutyl tin trichloride (MBTC)) and focusing on the effect of methanol addition on the film morphology. Employing electron transparent silicon oxide membranes as substrates and combining transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis on the same set of samples, we describe a detailed picture of nucleation behavior and film growth during early stages of film formation. Our main conclusion is that methanol addition during deposition acts as surfactant, lowering the surface energy of the substrate and resulting in a higher nucleation grain density. Based on these results, we propose a film growth model based on surface energy to explain morphology differences in tin oxide films resulting from methanol addition.

  3. Surface roughening during plasma-enhanced chemical-vapor deposition of hydrogenated amorphous silicon on crystal silicon substrates

    International Nuclear Information System (INIS)

    The morphology of a series of thin films of hydrogenated amorphous silicon (a-Si:H) grown by plasma-enhanced chemical-vapor deposition (PECVD) is studied using scanning tunneling microscopy. The substrates were atomically flat, oxide-free, single-crystal silicon. Films were grown in a PECVD chamber directly connected to a surface analysis chamber with no air exposure between growth and measurement. The homogeneous roughness of the films increases with film thickness. The quantification of this roughening is achieved by calculation of both rms roughness and lateral correlation lengths of the a-Si:H film surface from the height difference correlation functions of the measured topographs. Homogeneous roughening occurs over the film surface due to the collective behavior of the flux of depositing radical species and their interactions with the growth surface. copyright 1997 The American Physical Society

  4. Metalorganic chemical vapor deposition of anatase titanium dioxide on Si: Modifying the interface by pre-oxidation

    Science.gov (United States)

    Sandell, A.; Andersson, M. P.; Johansson, M. K.-J.; Karlsson, P. G.; Alfredsson, Y.; Schnadt, J.; Siegbahn, H.; Uvdal, P.

    2003-04-01

    The formation of TiO 2 films on clean and pre-oxidized Si(1 1 1) through chemical vapor deposition of titanium(IV) isopropoxide (TTIP) in ultra-high vacuum has been examined by synchrotron radiation photoelectron spectroscopy, X-ray absorption spectroscopy (XAS) and scanning tunneling microscopy. In both cases, TTIP deposition at 500 °C eventually results in an anatase TiO 2 film with a carbon-free surface and the surface morphology of the anatase films is very similar. By using a novel way of combining photoemission and XAS data, it is demonstrated that the two situations have substantially different interfacial properties. Pre-oxidation of the surface at 500 °C passivates the surface so that the thickness of the amorphous TiSi xO y interface layer decreases from 30-35 to 15-25 Å and eliminates the formation of interfacial carbon completely.

  5. Determination of photocatalytic activity in amorphous and crystalline titanium oxide films prepared using plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Wu, Cheng-Yang; Chiang, Bo-Sheng; Chang, Springfield; Liu, Day-Shan

    2011-01-01

    Hydro-oxygenated amorphous titanium oxide (a-TiO x:OH) films were prepared by plasma-enhanced chemical vapor deposition (PECVD) using precursors of titanium tetraisopropoxide (TTIP) and oxygen. The influences of chemical states and crystal quality on the photocatalytic activity were systematically investigated in the as-deposited and post-annealed films. The degree of the photocatalytic activity was deeply correlated with the porosity related to the hydroxyl (OH) groups in the as-deposited amorphous film. The crystallized anatase structures was observed from the 200 °C-deposited a-TiO x:OH film after a post-annealing treatment at 400 °C. The photocatalytic activity related to the film with anatase structure was markedly superior to that of an amorphous film with porous structures. The larger the crystal size of the anatase structure, the higher the photocatalytic activity obtained. At elevated annealed temperatures, the inferior anatase structure due to the crystalline transformation led to a low photocatalytic activity. It was concluded that the photocatalytic activity of an amorphous TiO x film prepared using PECVD was determined by the porosity originating from the functional OH groups in the film, whereas the crystalline quality of anatase phase in the annealed poly-TiO x film was crucial to the photocatalytic activity.

  6. Reduced thermal budget processing of Y--Ba--Cu--O high temperature superconducting thin films by metalorganic chemical vapor deposition

    International Nuclear Information System (INIS)

    Metalorganic chemical vapor deposition (MOCVD) has the potential of emerging as a viable technique to fabricate ribbons, tapes, coated wires, and the deposition of films of high temperature superconductors, and related materials. As a reduced thermal budget processing technique, rapid isothermal processing (RIP) based on incoherent radiation as the source of energy can be usefully coupled to conventional MOCVD. In this paper we report on the deposition and characterization of high quality superconducting thin films of Y--Ba--Cu--O (YBCO) on MgO and SrTiO3 substrates by RIP assisted MOCVD. By using a mixture of N2O and O2 as the oxygen source films deposited initially at 600 degree C for 1 min and then at 740 degree C for 30 min are primarily c-axis oriented and with zero resistance being observed at 84 and 89 K for MgO and SrTiO3 substrates, respectively. The zero magnetic field current densities at 77 K for MgO and SrTiO3 substrates are 1.2x106 and 1.5x106 A/cm2, respectively. It is envisaged that high energy photons from the incoherent light source and the use of a mixture of N2O and O2 as the oxygen source, assist chemical reactions and lower overall thermal budget for processing of these films

  7. Hybrid Physical Chemical Vapor Deposition of Superconducting Magnesium Diboride Coatings for Large Scale Radio Frequency Cavities

    Science.gov (United States)

    Lee, Namhoon; Withanage, Wenura; Tan, Teng; Wolak, Matthaeus; Xi, Xiaoxing

    2016-03-01

    Magnesium diboride (MgB2) is considered to be a great candidate for next generation superconducting radio frequency (SRF) cavities due to its higher critical temperature Tc (40 K) and increased thermodynamic critical field Hc compared to other conventional superconductors. These properties significantly reduce the BCS surface resistance (RsBCS)and residual resistance (Rres) according to theoretical studies and suggest the possibility of an enhanced accelerating field (Eacc) . We have investigated the possibility of coating the inner surface of a 3 GHz SRF cavity with MgB2 by using a hybrid physical-vapor deposition (HPCVD) system which was modified for this purpose. To simulate a real 3 GHz SRF cavity, a stainless steel mock cavity has been employed for the study. The film quality was characterized on small substrates that were placed at selected locations within the cavity. MgB2 films on stainless steel foils, niobium pieces and SiC substrates showed transition temperatures of above 36 K. Dielectric resonance measurements resulted in promising Q values as obtained for the MgB2 films grown on the various substrates. By employing the HPCVD technique, a uniform film was achieved across the cavity interior, demonstrating the feasibility of HPCVD for MgB2 coatings for SRF cavities.

  8. Fabrication and characterization of silicon based thermal neutron detector with hot wire chemical vapor deposited boron carbide converter

    International Nuclear Information System (INIS)

    In order to utilize the well established silicon detector technology for neutron detection application, a silicon based thermal neutron detector was fabricated by integrating a thin boron carbide layer as a neutron converter with a silicon PIN detector. Hot wire chemical vapor deposition (HWCVD), which is a low cost, low temperature process for deposition of thin films with precise thickness was explored as a technique for direct deposition of a boron carbide layer over the metalized front surface of the detector chip. The presence of B-C bonding and 10B isotope in the boron carbide film were confirmed by Fourier transform infrared spectroscopy and secondary ion mass spectrometry respectively. The deposition of HWCVD boron carbide layer being a low temperature process was observed not to cause degradation of the PIN detector. The response of the detector with 0.2 µm and 0.5 µm thick boron carbide layer was examined in a nuclear reactor. The pulse height spectrum shows evidence of thermal neutron response with signature of (n, α) reaction. The results presented in this article indicate that HWCVD boron carbide deposition technique would be suitable for low cost industrial fabrication of PIN based single element or 1D/2D position sensitive thermal neutron detectors

  9. Characterization of Ru and RuO2 thin films prepared by pulsed metal organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Ultra-thin ruthenium (Ru) layers were fabricated by pulsed metal organic chemical vapor deposition in an Aixtron Tricent reactor using a metal-organic Ru precursor. Layer deposition was performed on different metal barrier combinations and on Al2O3 dielectric layers used in the fabrication of advanced Metal-Insulator-Metal (MIM) capacitor structures and on thermal SiO2 as reference structure. Ru layers with a thickness of 10 nm were characterized by Spectroscopic Ellipsometry (SE) and additional reference methods such as Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and X-Ray Reflectometry (XRR). As deposited and in situ annealed Ru layers were characterized by SE applying Drude-Lorentz- and Effective Medium Approximation (EMA) models. It was shown that the deposited layers consist of a Ru-RuO2 bilayer structure. By in situ annealing, the RuO2 layer thickness is reduced and highly pure Ru films are obtained. On the metal barriers the formation of a metal oxide interface, which is related to the deposition process, was determined. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Characterization of Ru and RuO{sub 2} thin films prepared by pulsed metal organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Roeder, G.; Petersen, S.; Yanev, V.; Schellenberger, M.; Pfitzner, L.; Ryssel, H. [Fraunhofer Institute of Integrated Systems and Device Technology (IISB), Schottkystrasse 10, Erlangen (Germany); Manke, C.; Baumann, P.K. [AIXTRON AG, Kackertstrasse 15-17, Aachen (Germany); Gschwandtner, A.; Ruhl, G. [Infineon Technologies AG, Wernerwerkstrasse 2, Regensburg (Germany); Petrik, P. [Research Institute for Technical Physics and Materials Science, Konkoly Thege Miklos ut 29-33, Budapest (Hungary)

    2008-05-15

    Ultra-thin ruthenium (Ru) layers were fabricated by pulsed metal organic chemical vapor deposition in an Aixtron Tricent reactor using a metal-organic Ru precursor. Layer deposition was performed on different metal barrier combinations and on Al{sub 2}O{sub 3} dielectric layers used in the fabrication of advanced Metal-Insulator-Metal (MIM) capacitor structures and on thermal SiO{sub 2} as reference structure. Ru layers with a thickness of 10 nm were characterized by Spectroscopic Ellipsometry (SE) and additional reference methods such as Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and X-Ray Reflectometry (XRR). As deposited and in situ annealed Ru layers were characterized by SE applying Drude-Lorentz- and Effective Medium Approximation (EMA) models. It was shown that the deposited layers consist of a Ru-RuO{sub 2} bilayer structure. By in situ annealing, the RuO{sub 2} layer thickness is reduced and highly pure Ru films are obtained. On the metal barriers the formation of a metal oxide interface, which is related to the deposition process, was determined. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Chemical vapor deposition and analysis of thermally insulating ZrO{sub 2} layers on injection molds

    Energy Technology Data Exchange (ETDEWEB)

    Atakan, Burak; Khlopyanova, Victoria; Mausberg, Simon; Kandzia, Adrian; Pflitsch, Christian [Thermodynamik (IVG) and Cenide, Universitaet Duisburg-Essen, Lotharstr. 1, 47057 Duisburg (Germany); Mumme, Frank [Kunststoff-Institut Luedenscheid, Karolinenstrasse 8, 58507 Luedenscheid (Germany)

    2015-07-15

    High quality injection molding requires a precise control of cooling rates. Thermal barrier coating (TBC) of zirconia with a thickness of 20-40 μm on polished stainless steel molds could provide the necessary insulating effect. This paper presents results of zirconia deposition on stainless steel substrates using chemical vapor deposition (CVD) aiming to provide the process parameters for the deposition of uniform zirconia films with such a thickness. The deposition was performed with zirconium (IV) acetylacetonate (Zr(C{sub 5}H{sub 7}O{sub 2}){sub 4}) as precursor and synthetic air as co-reactant, which allows deposition at temperatures below 600 C. The experiments were carried out in a hot-wall reactor at pressures between 7.5 mbar and 500 mbar and in a temperature range from 450 C to 600 C. Important growth parameters were characterized and growth rates between 1 and 2.5 μm/h were achieved. Thick and well adhering zirconia layers of 38 μm could be produced on steel within 40 h. The transient heat transfer rate upon contact with a hot surface was also evaluated experimentally with the thickest coatings. These exhibit a good TBC performance. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Vertically aligned Si nanocrystals embedded in amorphous Si matrix prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD)

    International Nuclear Information System (INIS)

    Highlights: • Inductively-coupled plasma is used for nanostructured silicon at room temperature. • Low temperature deposition allows device processing on various substrates. • Deposition pressure is the most effective parameter in controlling nanostructure. • Films consist of quantum dots in a-Si matrix and exhibit columnar vertical growth. • Films are porous to oxygen infusion along columnar grain boundaries. - Abstract: Vertically-aligned nanostructured silicon films are deposited at room temperature on p-type silicon wafers and glass substrates by inductively-coupled, plasma-enhanced chemical vapor deposition (ICPCVD). The nanocrystalline phase is achieved by reducing pressure and increasing RF power. The crystalline volume fraction (Xc) and the size of the nanocrystals increase with decreasing pressure at constant power. Columnar growth of nc-Si:H films is observed by high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The films exhibit cauliflower-like structures with high porosity that leads to slow but uniform oxidation after exposure to air at room temperature. Films deposited at low pressures exhibit photoluminescence (PL) signals that may be deconvoluted into three distinct Gaussian components: 760–810, 920–935, and 990–1000 nm attributable to the quantum confinement and interface defect states. Hydrogen dilution is manifested in significant enhancement of the PL, but it has little effect on the nanocrystal size and Xc

  13. Fabrication and characterization of silicon based thermal neutron detector with hot wire chemical vapor deposited boron carbide converter

    Science.gov (United States)

    Chaudhari, Pradip; Singh, Arvind; Topkar, Anita; Dusane, Rajiv

    2015-04-01

    In order to utilize the well established silicon detector technology for neutron detection application, a silicon based thermal neutron detector was fabricated by integrating a thin boron carbide layer as a neutron converter with a silicon PIN detector. Hot wire chemical vapor deposition (HWCVD), which is a low cost, low temperature process for deposition of thin films with precise thickness was explored as a technique for direct deposition of a boron carbide layer over the metalized front surface of the detector chip. The presence of B-C bonding and 10B isotope in the boron carbide film were confirmed by Fourier transform infrared spectroscopy and secondary ion mass spectrometry respectively. The deposition of HWCVD boron carbide layer being a low temperature process was observed not to cause degradation of the PIN detector. The response of the detector with 0.2 μm and 0.5 μm thick boron carbide layer was examined in a nuclear reactor. The pulse height spectrum shows evidence of thermal neutron response with signature of (n, α) reaction. The results presented in this article indicate that HWCVD boron carbide deposition technique would be suitable for low cost industrial fabrication of PIN based single element or 1D/2D position sensitive thermal neutron detectors.

  14. Fabrication and characterization of silicon based thermal neutron detector with hot wire chemical vapor deposited boron carbide converter

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhari, Pradip, E-mail: pradipcha@gmail.com [Semiconductor Thin Films and Plasma Processing Laboratory, Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai – 400076 (India); Singh, Arvind, E-mail: arvindsingh1884@gmail.com [Electronics Division, Bhabha Atomic Research Centre, Trombay, Mumbai – 400085 (India); Topkar, Anita, E-mail: anita.topkar@gmail.com [Electronics Division, Bhabha Atomic Research Centre, Trombay, Mumbai – 400085 (India); Dusane, Rajiv, E-mail: rodusane@iitb.ac.in [Semiconductor Thin Films and Plasma Processing Laboratory, Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai – 400076 (India)

    2015-04-11

    In order to utilize the well established silicon detector technology for neutron detection application, a silicon based thermal neutron detector was fabricated by integrating a thin boron carbide layer as a neutron converter with a silicon PIN detector. Hot wire chemical vapor deposition (HWCVD), which is a low cost, low temperature process for deposition of thin films with precise thickness was explored as a technique for direct deposition of a boron carbide layer over the metalized front surface of the detector chip. The presence of B-C bonding and {sup 10}B isotope in the boron carbide film were confirmed by Fourier transform infrared spectroscopy and secondary ion mass spectrometry respectively. The deposition of HWCVD boron carbide layer being a low temperature process was observed not to cause degradation of the PIN detector. The response of the detector with 0.2 µm and 0.5 µm thick boron carbide layer was examined in a nuclear reactor. The pulse height spectrum shows evidence of thermal neutron response with signature of (n, α) reaction. The results presented in this article indicate that HWCVD boron carbide deposition technique would be suitable for low cost industrial fabrication of PIN based single element or 1D/2D position sensitive thermal neutron detectors.

  15. 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

  16. Effects of precursor evaporation temperature on the properties of the yttrium oxide thin films deposited by microwave electron cyclotron resonance plasma assisted metal organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Yttrium oxide thin films are deposited using indigenously developed metal organic precursor (2,2,6,6-tetra methyl-3,5-hepitane dionate) yttrium, commonly known as Y(thd)3 (synthesized by ultrasound method). Microwave electron cyclotron resonance plasma assisted metal organic chemical vapor deposition process was used for these depositions. Depositions were carried out at a substrate temperature of 350 oC with argon to oxygen gas flow rates fixed to 1 sccm and 10 sccm respectively throughout the experiments. The precursor evaporation temperature (precursor temperature) was varied over a range of 170-275 oC keeping all other parameters constant. The deposited coatings are characterized by X-ray photoelectron spectroscopy, glancing angle X-ray diffraction and infrared spectroscopy. Thickness and refractive index of the coatings are measured by the spectroscopic ellipsometry. Hardness and elastic modulus of the films are measured by load depth sensing nanoindentation technique. C-Y2O3 phase is deposited at lower precursor temperature (170 oC). At higher temperature (220 oC) cubic yttrium oxide is deposited with yttrium hydroxide carbonate as a minor phase. When the temperature of the precursor increased (275 oC) further, hexagonal Y2O3 with some multiphase structure including body centered cubic yttria and yttrium silicate is observed in the deposited film. The properties of the films drastically change with these structural transitions. These changes in the film properties are correlated here with the precursor evaporation characteristics obtained at low pressures.

  17. Role of fluorine atoms in the oxidation-hydrolysis process of plasma assisted chemical vapor deposition fluorinated silicon nitride film

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, O.; Gomez-Aleixandre, C.; Palacio, C. (Universidad Autonoma de Madrid (Spain))

    The oxidation and/or hydrolysis of a plasma assisted chemical vapor deposition fluorinated silicon nitride film in a moisture atmosphere has been studied. The film presents fluorine atoms incorporated as -SiF, -SiF[sub 2], -SiF[sub 3], and [-SiF[sub 2]-][sub n] groups. The open structure of the film, due to the high fluorine content as [-SiF[sub 2]-][sub n], favors the penetration of oxygen and water molecules in the network. The evolution of the film has been explained by the different reactivity of the silicon atoms depending on their chemical environment. The role of fluorine atoms incorporated into the film has been established. 12 refs., 3 figs., 1 tab.

  18. Extent of hydrogen coverage of Si(001) under chemical vapor deposition conditions from ab initio approaches

    Science.gov (United States)

    Rosenow, Phil; Tonner, Ralf

    2016-05-01

    The extent of hydrogen coverage of the Si(001) c(4 × 2) surface in the presence of hydrogen gas has been studied with dispersion corrected density functional theory. Electronic energy contributions are well described using a hybrid functional. The temperature dependence of the coverage in thermodynamic equilibrium was studied computing the phonon spectrum in a supercell approach. As an approximation to these demanding computations, an interpolated phonon approach was found to give comparable accuracy. The simpler ab initio thermodynamic approach is not accurate enough for the system studied, even if corrections by the Einstein model for surface vibrations are considered. The on-set of H2 desorption from the fully hydrogenated surface is predicted to occur at temperatures around 750 K. Strong changes in hydrogen coverage are found between 1000 and 1200 K in good agreement with previous reflectance anisotropy spectroscopy experiments. These findings allow a rational choice for the surface state in the computational treatment of chemical reactions under typical metal organic vapor phase epitaxy conditions on Si(001).

  19. Effect of wall conditions on the self-limiting deposition of metal oxides by pulsed plasma-enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Pulsed plasma-enhanced chemical vapor deposition has been engineered to deliver self-limiting growth (i.e., ∼A /pulse) of metal oxides such as Ta2O5 and Al2O3. In this process the reactor walls are alternately exposed to atomic oxygen and metal precursors. The degree of adsorption in the latter step can dramatically influence both deposition rates and film quality. The impact of precursor adsorption on the plasma and gas-phase composition in these systems was quantified using optical emission spectroscopy and quadrupole mass spectrometry, respectively. It is shown that the time scale for a complete adsorption on the chamber walls is much greater than gas-phase residence times. Adsorbed compounds significantly alter the reactor composition, particularly at the initiation of each plasma pulse. As a consequence, careful attention must be paid to reactor design and operation to control deposition rates and maintain film quality

  20. Control of carbon content in amorphous GeTe films deposited by plasma enhanced chemical vapor deposition (PE-MOCVD) for phase-change random access memory applications

    International Nuclear Information System (INIS)

    Amorphous and smooth GeTe thin films are deposited on 200 mm silicon substrates by plasma enhanced—metal organic chemical vapor deposition (PE–MOCVD) using the commercial organometallic precursors TDMAGe and DIPTe as Ge and Te precursors, respectively. X-ray photoelectron spectroscopy (XPS) measurements show a stoichiometric composition of the deposited GeTe films but with high carbon contamination. Using information collected by Optical Emission Spectroscopy (OES) and XPS, the origin of carbon contamination is determined and the dissociation mechanisms of Ge and Te precursors in H2 + Ar plasma are proposed. As a result, carbon level is properly controlled by varying operating parameters such as plasma radio frequency power, pressure and H2 rate. Finally, GeTe films with carbon level as low as 5 at. % are obtained. (paper)

  1. Control of carbon content in amorphous GeTe films deposited by plasma enhanced chemical vapor deposition (PE-MOCVD) for phase-change random access memory applications

    Science.gov (United States)

    Aoukar, M.; Szkutnik, P. D.; Jourde, D.; Pelissier, B.; Michallon, P.; Noé, P.; Vallée, C.

    2015-07-01

    Amorphous and smooth GeTe thin films are deposited on 200 mm silicon substrates by plasma enhanced—metal organic chemical vapor deposition (PE-MOCVD) using the commercial organometallic precursors TDMAGe and DIPTe as Ge and Te precursors, respectively. X-ray photoelectron spectroscopy (XPS) measurements show a stoichiometric composition of the deposited GeTe films but with high carbon contamination. Using information collected by Optical Emission Spectroscopy (OES) and XPS, the origin of carbon contamination is determined and the dissociation mechanisms of Ge and Te precursors in H2 + Ar plasma are proposed. As a result, carbon level is properly controlled by varying operating parameters such as plasma radio frequency power, pressure and H2 rate. Finally, GeTe films with carbon level as low as 5 at. % are obtained.

  2. Structural and optical properties of silicon thin-films deposited by hot-wire chemical vapor deposition: The effects of silane concentrations

    International Nuclear Information System (INIS)

    In this paper, the structural and optical properties of a series of silicon (Si) thin-films deposited using hot-wire chemical vapor deposition with different silane concentrations (SCs) are presented. All the films are characterized by Raman spectroscopy, scanning electron microscopy (SEM) and photoluminescence (PL). In the Raman analysis, the first order and specifically the second order Raman spectra indicate increase in crystalline grain size as well as crystalline volume fraction in the films with a reduction in SC, which is also confirmed by the SEM analysis. At the higher SC, the Si microcrystalline grains get embedded in the nanocrystalline Si network. The Gaussian fitted peaks in the PL analysis reveal the emission due to either band to band tail-state transitions or tail-state to mid-gap defect-state transitions due to Si-dangling bonds present in the films. - Highlights: • Growth of silicon (Si) thin-films using Hot-Wire Chemical Vapor Deposition. • Scanning Electron Microscopy, Raman and Photoluminescence Spectropscopy characterization. • Increment in Si crystalline volume fraction with decrease in Silane concentration. • Microcrystalline Si grains embedded in nanocrystalline Si tissues

  3. Tantalum coating on porous Ti6Al4V scaffold using chemical vapor deposition and preliminary biological evaluation

    International Nuclear Information System (INIS)

    Porous tantalum (Ta), produced via chemical vapor deposition (CVD) of commercially pure Ta onto a vitreous carbon, is currently available for use in orthopedic applications. However, the relatively high manufacturing cost and the incapability to produce customized implant using medical image data have limited its application to gain widespread acceptance. In this study, Ta film was deposited on porous Ti6Al4V scaffolds using CVD technique. Digital microscopy and scanning electron microscopy indicated that the Ta coating evenly covered the entire scaffold structure. X-ray diffraction analysis showed that the coating consisted of α and β phases of Ta. Goat mesenchymal stem cells were seeded and cultured on the Ti6Al4V scaffolds with and without coating. The tetrazolium-based colorimetric assay exhibited better cell adhesion and proliferation on Ta-coated scaffolds compared with uncoated scaffolds. The porous scaffolds were subsequently implanted in goats for 12 weeks. Histological analysis revealed similar bone formation around the periphery of the coated and uncoated implants, but bone ingrowth is better within the Ta-coated scaffolds. To demonstrate the ability of producing custom implant for clinical applications via this technology, we designed and fabricated a porous Ti6Al4V scaffold with segmental mandibular shape derived from patient computerized tomography data. - Highlights: • Ta film was coated on porous Ti6Al4V scaffold using chemical vapor deposition. Tantalum coating allowed for higher levels of cell adhesion and proliferation. • Better new bone formation occurred inside the tantalum-coated scaffolds. • Clinical image data was integrated with EBM to fabricate customized scaffold

  4. Fabrication of single-phase ε-GaSe films on Si(100) substrate by metal organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Single-phase ε-gallium selenide (GaSe) films were fabricated on Si(100) substrate by metal organic chemical vapor deposition using dual-source precursors: triethylgallium (TEG) and hydrogen selenide (H2Se) with the flow ratio of [H2Se]/[TEG] being maintained at 1.2. In particular, an arsine (AsH3) flow was introduced to the Si substrate before the film deposition to induce an arsenic (As)-passivation effect on the substrate. The crystalline structure of GaSe films prepared was analyzed using X-ray diffraction and the surface morphology of them was characterized by scanning electron microscopy. It was found that the film quality could be improved by the As-passivation effect. The optical properties of the films were studied by temperature dependent photoluminescence (PL) measurements. PL spectra obtained with different distributions and intensities favored for resolving the superior material quality of the films produced on the substrate with As-passivation compared to those produced on the substrate without As-passivation. The former was dominated by the excitonic emissions for the whole temperature range of 20–300 K examined, while the latter was initially dominated by the defect-related emission at 1.907 eV for a low-temperature range ≦ 80 K and then became dominated by the weak excitonic emission band instead. The ε modification of GaSe films prepared was further recognized by the Raman scattering measurements conducted at room temperature. - Highlights: • Gallium selenide (GaSe) layered structures are fabricated on Si(100) substrate. • Metal–organic chemical vapor deposition is used for film fabrication. • Arsenic-passivation effects of Si substrate on the GaSe film quality are analyzed. • Photoluminescence measurements of GaSe polycrystals are reported

  5. Very high temperature chemical vapor deposition of new carbon thin films using organic semiconductor molecular beam sources

    Energy Technology Data Exchange (ETDEWEB)

    Noguchi, Takuya [Department of Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan); Shimada, Toshihiro, E-mail: shimada@chem.s.u-tokyo.ac.j [Department of Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan); Hanzawa, Akinori; Hasegawa, Tetsuya [Department of Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan)

    2009-11-30

    We carried out the preparation and characterization of new carbon films deposited using an organic molecular beam deposition apparatus with very high substrate temperature (from room temperature to 2670 K), which we newly developed. When we irradiated molecular beam of organic semiconductor perylene tetracarboxylic acid dianhydride (PTCDA) on Y{sub 0.07}Zr{sub 0.93}O{sub 2} (111) at 2170 K, a new carbon material was formed via decomposition and fusing of the molecules. The films were characterized with an atomic force microscope (AFM), Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Zirconium carbide (ZrC) films were identified beneath the topmost carbon layer by XRD and XPS analyses, which results from chemical reactions of the substrate and the molecules. Partially graphitized aromatic rings of PTCDA were observed from Raman spectroscopy. The present technique - very high temperature chemical vapor deposition using organic semiconductor sources - will be useful to study a vast unexplored field of covalent carbon solids.

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

    International Nuclear Information System (INIS)

    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. (paper)

  7. Effects of H{sub 2} and Ar flow rates on the deposition of hydrogenated silicon thin films by an inductive coupled plasma-chemical vapor deposition system

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuan, E-mail: cli10@yahoo.com [Department of Biomedical Engineering, National Yang Ming University, Taipei, 11221, Taiwan (China); Department of Mechanical Engineering, National Central University, Jhongli, Taoyuan, 32001, Taiwan (China); Hsieh, J.H. [Department of Materials Engineering, Ming Chi University of Technology, Taishan, Taipei, 24301, Taiwan (China); Huang, K.L.; Shao, Yu Ting; Chen, Yi Wen [Department of Biomedical Engineering, National Yang Ming University, Taipei, 11221, Taiwan (China)

    2013-10-01

    Amorphous hydrogenated silicon films were deposited on quartz substrates in an inductive coupled plasma-chemical vapor deposition system with four internal low inductance antennas units. Different Ar and hydrogen flow rates were tested for their influences on the structures of deposited films. For monitoring purposes, Langmuir probe and optical emission spectrometer were installed to detect the variation of electrical field in plasma during deposition. Data from Langmuir probe and optical emission spectrometer were analyzed subsequently. After deposition, the films were examined by X-ray diffraction and Raman spectrometer for their microstructures. Results indicate that under the supply of pure Ar flow, the deposition rate can be expedited to 3.5 nm/s and amorphous films were formed on quartz substrates. With the supply of mixed hydrogen and argon (Ar 15 sccm + H{sub 2} 50 sccm + SiH{sub 4} 50 sccm), the deposition rate can reach 4.5 nm/s. Although it is well known that a high supply of H{sub 2} helps the formation of micro-crystalline silicon, these deposited hydrogenated Si films, confirmed by X-ray diffraction patterns and Raman spectroscopy, all maintained their amorphousness under various range of Ar and H{sub 2} flow rates. - Highlights: • Amorphous hydrogenated silicon films were deposited by inductive coupled plasma. • Different Ar and H{sub 2} flow rates were tested for their effects on the structures of films. • Under pure Ar flow, the deposition rate of can be expedited to 3.5 nm/sec. • The deposition rate reached 4.5 nm/sec under Ar 15 sccm, H{sub 2} 50 sccm, SiH{sub 4} 50 sccm. • All films are amorphous confirmed by X-ray diffraction and Raman spectroscopy.

  8. Large-area SiC membrane produced by plasma enhanced chemical vapor deposition at relatively high temperature

    International Nuclear Information System (INIS)

    Advances in the growth of silicon carbide (SiC) thin films with outstanding thermal and mechanical properties have received considerable attention. However, the fabrication of large-area free-standing SiC membrane still remains a challenge. Here, the authors report a plasma enhanced chemical vapor deposition process at a relatively high temperature to improve the free-standing SiC membrane area. A systematic study on the microstructural, mechanical, and optical properties of hydrogenated polycrystalline silicon carbide (poly-SiCx:H) thin films deposited at 600 °C with different annealing temperatures has been performed. In the as-deposited state, SiCx:H thin films show a polycrystalline structure. The crystallinity degree can be further improved with the increase of the postdeposition annealing temperature. The resulting process produced free-standing 2-μm-thick SiC membranes up to 70 mm in diameter with root mean square roughness of 3.384 nm and optical transparency of about 70% at 632.8 nm wavelength. The large-area SiC membranes made out of poly-SiCx:H thin films deposited at a relatively high temperature can be beneficial for a wide variety of applications, such as x-ray diffractive optical elements, optical and mechanical filtering, lithography mask, lightweight space telescopes, etc

  9. Parameters influencing interfacial morphology in GaAs/Ge superlattices grown by metal organic chemical vapor deposition

    Science.gov (United States)

    Jia, Roger; Fitzgerald, Eugene A.

    2016-02-01

    We investigated the epitaxy and morphology of GaAs/Ge superlattices grown by metal organic chemical vapor deposition (MOCVD) under a range of conditions. The surfaces of Ge layers deposited on GaAs at 650 °C and 100 Torr are observed to be rough in cross-sectional transmission electron microscopy. When either the temperature is lowered to 500 °C or the pressure is increased to 250 Torr, the surface of the first deposited Ge layer is observed to be smooth. This behavior suggests that Ge roughening is a thermodynamically favorable process that can be kinetically limited with appropriate growth conditions. At 500 °C, GaAs islands on Ge do not completely coalesce into one film. This may result from poor surface coverage; the short depositions would not be sufficient to coarsen and completely coalesce the islands. At 650 °C, growth on offcut substrates did not suppress antiphase boundaries, likely due to the unique conditions for GaAs/Ge superlattice growth. A wide-range of two- and three- dimensional nanostructures are formed and should allow insight in structure-property correlations in semiconducting thermoelectric materials.

  10. Large-area SiC membrane produced by plasma enhanced chemical vapor deposition at relatively high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yu; Xie, Changqing, E-mail: xiechangqing@ime.ac.cn [Key Laboratory of Microelectronics Devices and Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)

    2015-09-15

    Advances in the growth of silicon carbide (SiC) thin films with outstanding thermal and mechanical properties have received considerable attention. However, the fabrication of large-area free-standing SiC membrane still remains a challenge. Here, the authors report a plasma enhanced chemical vapor deposition process at a relatively high temperature to improve the free-standing SiC membrane area. A systematic study on the microstructural, mechanical, and optical properties of hydrogenated polycrystalline silicon carbide (poly-SiC{sub x}:H) thin films deposited at 600 °C with different annealing temperatures has been performed. In the as-deposited state, SiC{sub x}:H thin films show a polycrystalline structure. The crystallinity degree can be further improved with the increase of the postdeposition annealing temperature. The resulting process produced free-standing 2-μm-thick SiC membranes up to 70 mm in diameter with root mean square roughness of 3.384 nm and optical transparency of about 70% at 632.8 nm wavelength. The large-area SiC membranes made out of poly-SiC{sub x}:H thin films deposited at a relatively high temperature can be beneficial for a wide variety of applications, such as x-ray diffractive optical elements, optical and mechanical filtering, lithography mask, lightweight space telescopes, etc.

  11. Hot-wire chemical vapor deposition and characterization of p-type nanocrystalline Si films for thin film photovoltaic applications

    International Nuclear Information System (INIS)

    P-type nanocrystalline Si (p-nc-Si) films were deposited by hot-wire chemical vapor deposition (HWCVD) system using SiH4, B2H6, and H2 as reactants. The effect of H2 flow rate on the material properties of p-nc-Si films were investigated using Raman spectroscopy, X-ray diffractormeter, ultraviolet–visible-near infrared spectrophotometer, Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Moreover, the electrical properties, such as carrier concentration, activation energy, dark conductivity, and Hall mobility, of p-nc-Si films were also measured. It was found that H2 flow rate played an important role in forming of p-nc-Si, decreasing the deposition rate, and increasing the crystallinity of p-nc-Si films. FESEM and TEM micrographs also showed the enhancement of crystallinity with adding H2 flow rate. Furthermore, the change of microstructure at various H2 flow rates was found to affect the electrical properties of p-nc-Si films. Details of the growth mechanism in p-nc-Si films will be discussed also. Moreover, the optimum p-nc-Si film was used as window layer in n-type crystalline Si heterojunction (HJ) solar cell. After the deposition parameters were optimized, the Si HJ solar cell with the open-circuit voltage of 0.58 V, short-circuit current density of 33.46 mA/cm2, fill factor of 64.44%, and the conversion efficiency of 12.5% could be obtained. - Highlights: ► p-nc-Si films prepared by hot-wire chemical vapor deposition. ► H2 flow rate had an important role in decreasing the deposition rate of p-nc-Si films. ► H2 flow rate had an important role in increasing the crystallinity of p-nc-Si films. ► Change of microstructure found to affect the electrical properties of p-nc-Si films. ► A simple Si heterojunction solar cell with a conversion efficiency of 12.5 % was achieved.

  12. Pattern Dependency of Pure-Boron-Layer Chemical-Vapor Depositions

    NARCIS (Netherlands)

    Mohammadi, V.; De Boer, W.B.; Scholtes, T.L.M.; Nanver, L.K.

    2012-01-01

    The pattern dependency of pure-boron (PureB) layer chemicalvapor depositions (CVD) is studied with respect to the correlation between the deposition rate and features like loading effects, deposition parameters and deposition window sizes. It is shown experimentally that the oxide coverage ratio and

  13. 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.

  14. Organometallic chemical vapor-phase deposition (MOCVD) of oxidic high-ε layers

    International Nuclear Information System (INIS)

    The considered materials in this work are (Ba,Sr)TiO3, SrTiO3 and SrTa2O6 and the oxides from the group IVb metals: Ti, Zr and Hf. The films were deposited on Platinum and Silicon substrates in order to evaluate the dielectric properties for applications in metal-insulator-metal (MIM) structures as well as in metal-insulator-semiconductor (MIS) structures. The high-k films were grown by metal organic chemical vapour deposition (MOCVD) and the evaluation and optimisation of the production processes is a major part of this work. Different approaches were investigated: mixing of conventional precursors for the example of (Ba,Sr)TiO3, test of a single source precursor for SrTa2O6 and tests of newly designed precursors for the group IVb-metal oxides, M-(O-I-Pr)2(tbaoac)2. In addition, compatibility tests of the new Titanium precursors with the conventional Strontium precursor are presented for the example of SrTiO3. Most detailed investigations were performed on the nucleation and growth processes of (Ba,Sr)TiO3 on platinum . Details of the nucleation were obtained from the new method of conductivity scans with the AFM. These investigations were combined with XRD, SEM, HRTEM, SPM and XPS and give a consistent picture of development of the structural properties and their dependencies on growth temperature and chemical composition. The electrical properties, especially capacity and leakage current indicate a strong dependency from film thickness, which can be explained by separating the bulk- from the interface capacity. Based on these results the interface layer was optimised by changing the interfacial stoichiometry. Additionally, SrTa2O6 was tested as an alternative material with low tunability and shows promising electrical results. For the example of SrTiO3 on silicon details of the growth kinetics of the interfacial layer were investigated by HRTEM. The first results from group IVb oxides, which are the most promising candidates for gate oxides, are presented. (orig.)

  15. Metallic impurity-activated crystal growth of boron phosphide by chemical vapor deposition and its physical properties

    International Nuclear Information System (INIS)

    Needle single crystals of boron monophosphide as large as 5 - 100 μm in diameter and 4 mm in length were obtained by chemical vapor deposition on an impurity painted zone of quartz substrate at 1060 - 1120 0C. The impurities such as Mn, Ni, Pt, Ag or Au were painted on the substrate in a form of aqueous solution of their salts and decomposed or reduced to the respective metal in hydrogen atmosphere at 10000C. Needle crystals with the homo p-n junction were also prepared using Ni impurity. The colors of grown crystals varied with the change of gas composition. Differences of electrical resistivity and thermoelectric power were found between the crystals of different colors. (auth.)

  16. Suppression of indium droplet formation by adding CCl4 during metalorganic chemical vapor deposition growth of InN films

    International Nuclear Information System (INIS)

    In this work, the influences of CCl4 on the metalorganic chemical vapor deposition (MOCVD) growth of InN were studied for the first time. It was found that the addition of CCl4 can effectively suppress the formation of metal indium (In) droplets during InN growth, which was ascribed to the etching effect of Cl to In. However, with increasing of CCl4 flow, the InN growth rate decreased but the lateral growth of InN islands was enhanced. This provides a possibility of promoting islands coalescence toward a smooth surface of the InN film by MOCVD. The influence of addition of CCl4 on the electrical properties was also investigated

  17. Immobilization of carbon nanotubes on functionalized graphene film grown by chemical vapor deposition and characterization of the hybrid material

    Directory of Open Access Journals (Sweden)

    Prashanta Dhoj Adhikari

    2014-01-01

    Full Text Available We report the surface functionalization of graphene films grown by chemical vapor deposition and fabrication of a hybrid material combining multi-walled carbon nanotubes and graphene (CNT–G. Amine-terminated self-assembled monolayers were prepared on graphene by the UV-modification of oxidized groups introduced onto the film surface. Amine-termination led to effective interaction with functionalized CNTs to assemble a CNT–G hybrid through covalent bonding. Characterization clearly showed no defects of the graphene film after the immobilization reaction with CNT. In addition, the hybrid graphene material revealed a distinctive CNT–G structure and p–n type electrical properties. The introduction of functional groups on the graphene film surface and fabrication of CNT–G hybrids with the present technique could provide an efficient, novel route to device fabrication.

  18. The photosensitivity and ultraviolet absorption change of Sn-doped silica film fabricated by modified chemical vapor deposition

    International Nuclear Information System (INIS)

    10.5 μm thick Sn-doped silica films were prepared by the modified chemical vapor deposition followed by the solution-doping method. The films were exposed to 248 and 266 nm laser light, respectively. Positive refractive index change up to 2x10-4 at 1550 nm was observed by measuring the reflectivity based on Fresnel formulas. The data of UV absorption spectra suggest that the photosensitivity of the Sn-doped silica film under high energy density laser irradiation should be mainly due to the bond breaking of oxygen deficient defects, while under relatively low energy density laser irradiation, the refractive index change probably originates from photoconversion of optically active defects

  19. Three Dimensional P-doped Graphene Synthesized by Eco-Friendly Chemical Vapor Deposition for Oxygen Reduction Reactions.

    Science.gov (United States)

    Li, Xiaoguang; Qiu, Yunfeng; Hu, Ping An

    2016-06-01

    Heteroatom doping provides possibilities for changing the electronic properties of graphene. Three Dimensional P-doped graphene (3DPG) was fabricated via chemical vapor deposition (CVD) using nickel foam as template and triphenylphosphine (TPP) as C and P sources simultaneously without using toxic organic solvent as carrier liquid. The invasion of P atoms into graphene networks make them non-electroneutral and consequently favor the adsorption of oxygen and O-O bond cleavage due to the charge polarization increase of the P-C bond. Thus, the as-prepared 3DPG served as an efficient electrocatalyst for oxygen reduction reaction (ORR). Additionally, the 3D porous structure is favorable for the mass transfer of electrolytes ions, hence 3DPG exhibit better electrocatalytic activity, long-term stability, and tolerance to crossover effect of methanol than pristine 3D graphene and Pt/C for ORR. PMID:27427693

  20. Formation of Graphene Grain Boundaries on Cu(100) Surface and a Route Towards Their Elimination in Chemical Vapor Deposition Growth

    Science.gov (United States)

    Yuan, Qinghong; Song, Guangyao; Sun, Deyan; Ding, Feng

    2014-10-01

    Grain boundaries (GBs) in graphene prepared by chemical vapor deposition (CVD) greatly degrade the electrical and mechanical properties of graphene and thus hinder the applications of graphene in electronic devices. The seamless stitching of graphene flakes can avoid GBs, wherein the identical orientation of graphene domain is required. In this letter, the graphene orientation on one of the most used catalyst surface -- Cu(100) surface, is explored by density functional theory (DFT) calculations. Our calculation demonstrates that a zigzag edged hexagonal graphene domain on a Cu(100) surface has two equivalent energetically preferred orientations, which are 30 degree away from each other. Therefore, the fusion of graphene domains on Cu(100) surface during CVD growth will inevitably lead to densely distributed GBs in the synthesized graphene. Aiming to solve this problem, a simple route, that applies external strain to break the symmetry of the Cu(100) surface, was proposed and proved efficient.