WorldWideScience

Sample records for vapor deposition growth

  1. Epitaxial Growth of Silicon Carbide by Chemical Vapor Deposition

    Science.gov (United States)

    Bhat, Ishwara B.

    The properties of silicon carbide materials are first reviewed, with special emphasis on properties related to power device applications. Epitaxial growth methods for SiC are then discussed with emphasis on recent results for epitaxial growth by the hot-wall chemical vapor deposition method. The growth mechanism for maintaining the polytype, namely step-controlled epitaxy, is discussed. Also described is the selective epitaxial growth carried out on SiC at the author's laboratory, including some unpublished work.

  2. Chemical vapor deposition growth of two-dimensional heterojunctions

    Science.gov (United States)

    Cui, Yu; Li, Bo; Li, JingBo; Wei, ZhongMing

    2018-01-01

    The properties of two-dimensional (2D) layered materials with atom-smooth surface and special interlayer van der Waals coupling are different from those of traditional materials. Due to the absence of dangling bonds from the clean surface of 2D layered materials, the lattice mismatch influences slightly on the growth of 2D heterojunctions, thus providing a flexible design strategy. 2D heterojunctions have attracted extensive attention because of their excellent performance in optoelectronics, spintronics, and valleytronics. The transfer method was utilized for the fabrication of 2D heterojunctions during the early stage of fundamental research on these materials. This method, however, has limited practical applications. Therefore, chemical vapor deposition (CVD) method was recently developed and applied for the preparation of 2D heterojunctions. The CVD method is a naturally down-top growth strategy that yields 2D heterojunctions with sharp interfaces. Moreover, this method effectively reduces the introduction of contaminants to the fabricated heterojunctions. Nevertheless, the CVD-growth method is sensitive to variations in growth conditions. In this review article, we attempt to provide a comprehensive overview of the influence of growth conditions on the fabrication of 2D heterojunctions through the direct CVD method. We believe that elucidating the effects of growth conditions on the CVD method is necessary to help control and improve the efficiency of the large-scale fabrication of 2D heterojunctions for future applications in integrated circuits.

  3. 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.

  4. 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.

  5. High growth rate homoepitaxial diamond film deposition at high temperatures by microwave plasma-assisted chemical vapor deposition

    Science.gov (United States)

    Vohra, Yogesh K. (Inventor); McCauley, Thomas S. (Inventor)

    1997-01-01

    The deposition of high quality diamond films at high linear growth rates and substrate temperatures for microwave-plasma chemical vapor deposition is disclosed. The linear growth rate achieved for this process is generally greater than 50 .mu.m/hr for high quality films, as compared to rates of less than 5 .mu.m/hr generally reported for MPCVD processes.

  6. Chemical vapor deposition growth of bilayer graphene in between molybdenum disulfide sheets

    NARCIS (Netherlands)

    Kwieciñski, Wojciech; Sotthewes, Kai; Poelsema, Bene; Zandvliet, Harold J.W.; Bampoulis, Pantelis

    2017-01-01

    Direct growth of flat micrometer-sized bilayer graphene islands in between molybdenum disulfide sheets is achieved by chemical vapor deposition of ethylene at about 800 °C. The temperature assisted decomposition of ethylene takes place mainly at molybdenum disulfide step edges. The carbon atoms

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

    NARCIS (Netherlands)

    Houweling, Z.S.|info:eu-repo/dai/nl/251874486; Geus, J.W.; de Jong, M.; Harks, P.P.R.M.L.; van der Werf, C.H.M.; Schropp, R.E.I.|info:eu-repo/dai/nl/072502584

    2011-01-01

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

  8. X-ray-reflectivity study of the growth kinetics of vapor-deposited silver films

    NARCIS (Netherlands)

    Thompson, C.; Palasantzas, G.; Feng, Y.P.; Krim, J.

    1994-01-01

    X-ray-reflectivity measurements have been carried out on silver films which were vapor deposited onto silicon substrates, to investigate the thickness evolution of the film’s surface roughness. The growth exponent was found to be β=0.26±0.05, and the roughness exponenet was found to be H=0.70±0.10.

  9. Influence of alcohol on grain growth of tin oxide in chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Matsui, Yuji [New Products Development Center, Technology Development Division, Japan/Asia Pacific General Division Automotive Glass Company, Asahi Glass Co. Ltd., 426-1 Sumida, Aikawa-machi, Aiko-gun, Kanagawa 243-0301 (Japan)]. E-mail: yuuji-matsui@agc.co.jp; Mitsuhashi, Michio [New Products Development Center, Technology Development Division, Japan/Asia Pacific General Division Automotive Glass Company, Asahi Glass Co. Ltd., 426-1 Sumida, Aikawa-machi, Aiko-gun, Kanagawa 243-0301 (Japan); Yamamoto, Yuichi [Research Center, Asahi Glass Co. Ltd., 1150 Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa 221-8755 (Japan); Higashi, Seiji [Research Center, Asahi Glass Co. Ltd., 1150 Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa 221-8755 (Japan)

    2007-01-22

    Morphologies of tin oxide micro-grains in the early stage of film growth were analyzed for films deposited by chemical vapor deposition using tin chloride as a source material. Atomic force microscopy observations revealed increased micro-grain density and decreased size by adding methanol into the reaction system, but X-ray photoelectron spectroscopy analyses suggested that the total deposited volume was unchanged. The relative amount of chlorine contamination at the bottom of alcohol-added films increased in the order of isopropyl alcohol < ethanol < methanol. A model of chlorine desorption through reaction with alcohol, which occurred in the early stage of film growth, can explain the results.

  10. 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.

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

    Science.gov (United States)

    Uno, Kazuyuki; Yamasaki, Yuichiro; Tanaka, Ichiro

    2017-01-01

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

  12. Continuous growth of single-wall carbon nanotubes using chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Grigorian, Leonid; Hornyak, Louis; Dillon, Anne C; Heben, Michael J

    2014-09-23

    The invention relates to a chemical vapor deposition process for the continuous growth of a carbon single-wall nanotube where a carbon-containing gas composition is contacted with a porous membrane and decomposed in the presence of a catalyst to grow single-wall carbon nanotube material. A pressure differential exists across the porous membrane such that the pressure on one side of the membrane is less than that on the other side of the membrane. The single-wall carbon nanotube growth may occur predominately on the low-pressure side of the membrane or, in a different embodiment of the invention, may occur predominately in between the catalyst and the membrane. The invention also relates to an apparatus used with the carbon vapor deposition process.

  13. Continuous growth of single-wall carbon nanotubes using chemical vapor deposition

    Science.gov (United States)

    Grigorian, Leonid [Raymond, OH; Hornyak, Louis [Evergreen, CO; Dillon, Anne C [Boulder, CO; Heben, Michael J [Denver, CO

    2008-10-07

    The invention relates to a chemical vapor deposition process for the continuous growth of a carbon single-wall nanotube where a carbon-containing gas composition is contacted with a porous membrane and decomposed in the presence of a catalyst to grow single-wall carbon nanotube material. A pressure differential exists across the porous membrane such that the pressure on one side of the membrane is less than that on the other side of the membrane. The single-wall carbon nanotube growth may occur predominately on the low-pressure side of the membrane or, in a different embodiment of the invention, may occur predominately in between the catalyst and the membrane. The invention also relates to an apparatus used with the carbon vapor deposition process.

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

    Science.gov (United States)

    Kumar, Mukul; Ando, Yoshinori

    2010-06-01

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

  15. 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.

  16. Low Temperature Metal Free Growth of Graphene on Insulating Substrates by Plasma Assisted Chemical Vapor Deposition.

    Science.gov (United States)

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

    2017-03-01

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

  17. 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.

  18. Chemical etching of copper foils for single-layer graphene growth by chemical vapor deposition

    Science.gov (United States)

    Yoshihara, Naoki; Noda, Masaru

    2017-10-01

    Chemical etching on copper surface is essential as a pre-treatment for single-layer graphene growth by chemical vapor deposition (CVD). Here, we investigated the effect of chemical etching treatment on copper foils for single-layer graphene CVD growth. The chemical etching conditions, such as the type of chemical etchants and the treatment time, were found to strongly influence the graphene domain size. Moreover, a drastic change in the layer structure of graphene sheets, which was attributed to the surface morphology of the etched copper foil, was confirmed by graphene transmittance and Raman mapping measurements.

  19. Phase diagram of interfacial growth modes by vapor deposition and its application for ZnO nanostructures

    Science.gov (United States)

    Shu, Da-Jun; Xiong, Xiang; Liu, Ming; Wang, Mu

    2017-09-01

    Interfacial growth from vapor has been extensively studied. However, a straightforward picture of the growth mode under different growth conditions is still lacking. In this paper, we develop a comprehensive interfacial growth theory based on the stochastic approach. Using a critical interisland separation, we construct a general phase diagram of the growth modes. It has been revealed that if the Ehrlich-Schwoebel barrier EES is smaller than a critical value, the interfacial growth proceeds in a layer-by-layer (LBL) mode at any deposition rate. However, if EES is larger than the critical value, LBL growth occurs only at very small or very large deposition rates relative to the intralayer hopping rate, and multilayer (ML) growth occurs at a moderate deposition rate. Experiments with zinc oxide growth by chemical vapor deposition have been designed to qualitatively demonstrate the theoretical model. By changing the flux of the carrier gas (nitrogen gas) in chemical vapor deposition, we realize LBL, ML, and then reentrance of LBL homoepitaxial growth of ZnO successively. Moreover, we find that surface kinetics of ZnO is suppressed by decreasing oxygen partial pressure by comparing the experimental observations and theoretical models, which is supported by our recent first-principles calculations. Since the influence of the substrate and the growth species on growth can approximately be represented by binding energy and surface kinetics, we suggest that the phase diagram is essential for interfacial growth of different materials by vapor deposition.

  20. Heteroepitaxial growth of 3-5 semiconductor compounds by metal-organic chemical vapor deposition for device applications

    Science.gov (United States)

    Collis, Ward J.; Abul-Fadl, Ali

    1988-01-01

    The purpose of this research is to design, install and operate a metal-organic chemical vapor deposition system which is to be used for the epitaxial growth of 3-5 semiconductor binary compounds, and ternary and quaternary alloys. The long-term goal is to utilize this vapor phase deposition in conjunction with existing current controlled liquid phase epitaxy facilities to perform hybrid growth sequences for fabricating integrated optoelectronic devices.

  1. Growth mechanism of long aligned multiwall carbon nanotube arrays by water-assisted chemical vapor deposition.

    Science.gov (United States)

    Yun, YeoHeung; Shanov, Vesselin; Tu, Yi; Subramaniam, Srinivas; Schulz, Mark J

    2006-11-30

    Highly aligned arrays of multiwalled carbon nanotube (MWCNT) on layered Si substrates have been synthesized by chemical vapor deposition (CVD). The effect of the substrate design and the process parameters on the growth mechanism were studied. Adding water vapor to the reaction gas mixture of hydrogen and ethylene enhanced the growth which led to synthesis of longer CNT arrays with high density. Environmental scanning electron microscopy (ESEM), energy-dispersive spectroscopy (EDS), and atomic force microscopy (AFM) were used to analyze the CNT morphology and composition. Quadrupole mass spectroscopy (QMS) provided in-situ information on the gas spices within the reaction zone. On the basis of results, we verified the top growth mechanism and evaluated the reason of decline and stoppage of the CNT growth after extended period of deposition. Multilayered Si substrates with a top film of Al2O3, having appropriate roughness, provide favorable conditions to form catalyst islands with uniform distribution and size. Using water-assisted CVD process and optimized substrate design, our group succeeded to grow vertically aligned, patterned MWCNT up to 4-mm long. The arrays were of high purity and weak adhesion which allowed to be peeled off easily from the substrate.

  2. Controlled Growth of Organic Semiconductor Films Using Electrospray Vapor-Liquid-Solid Deposition

    Science.gov (United States)

    Shaw, Daniel; Bufkin, Kevin; Johnson, Brad; Patrick, David

    2010-03-01

    Interest in low molecular weight organic semiconductors (OS) for applications such as light-emitting diodes, photovoltaics, and other technologies stems in part from their prospects for enabling significantly reduced manufacturing costs compared to traditional inorganic semiconductors. However many of the best performing prototype devices produced so far have involved expensive or time-consuming fabrication methods, such as the use of single crystals or thin films deposited under high vacuum conditions. New methods are needed capable of rapidly and inexpensively producing high quality polycrystalline films, preferably involving near-ambient conditions. This poster will present studies of one such approach based on an electrospray vapor-liquid-solid growth technique. The method produces polycrystalline OS films deposited via atmospheric-pressure sublimation from a carrier gas (argon) which is partially ionized by a corona discharge. Vapor-phase molecules are then attracted to a charged substrate coated with a thin liquid solvent layer, in which they dissolve and grow as crystals, producing films with large grain sizes. This poster will describe the electrostatic and hydrodynamic features of the deposition mechanism, and the growth kinetics of the resulting polycrystalline films.

  3. Growth study of indium-catalyzed silicon nanowires by plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Zardo, I.; Conesa-Boj, S.; Estradé, S.; Yu, L.; Peiro, F.; Roca I Cabarrocas, P.; Morante, J. R.; Arbiol, J.; Fontcuberta I Morral, A.

    2010-07-01

    Indium was used as a catalyst for the synthesis of silicon nanowires in a plasma enhanced chemical vapor deposition reactor. In order to foster the catalytic activity of indium, the indium droplets had to be exposed to a hydrogen plasma prior to nanowire growth in a silane plasma. The structure of the nanowires was investigated as a function of the growth conditions by electron microscopy and Raman spectroscopy. The nanowires were found to crystallize along the , or growth direction. When growing on the and directions, they revealed a similar crystal quality and the presence of a high density of twins along the {111} planes. The high density and periodicity of these twins lead to the formation of hexagonal domains inside the cubic structure. The corresponding Raman signature was found to be a peak at 495 cm-1, in agreement with previous studies. Finally, electron energy loss spectroscopy indicates an occasional migration of indium during growth.

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

    NARCIS (Netherlands)

    Verlaan, V.

    2008-01-01

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

  5. Anisotropic growth mechanism of tungsten diselenide domains using chemical vapor deposition method

    Science.gov (United States)

    Lee, Yoobeen; Jeong, Heekyung; Park, Yi-Seul; Han, Seulki; Noh, Jaegeun; Lee, Jin Seok

    2018-02-01

    Anisotropic transition metal dichalcogenide (TMDC) domains have stimulated a growing interest mainly due to their electronic properties that depend on the size, shape, and edge structures of the domains. In this work, we investigated the anisotropic morphogenesis and edge terminations of tungsten diselenide (WSe2) domains grown on sapphire substrates by chemical vapor deposition (CVD) using tungsten oxide (WO3) and selenium (Se) powders as precursors. We varied the amount of Se powder and growth temperature during the CVD process, which in turn caused variations in the growth mechanism and kinetic energies of precursors. We succeeded in synthesizing hexagonal, square, circular, and triangular anisotropic WSe2 domains. They were characterized using scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) analyses, and atomic force microscopy (AFM). Furthermore, we proposed the growth mechanism of anisotropic WSe2 domains with different edge terminations based on experimental observations through scanning tunneling microscope (STM).

  6. Nucleation and growth of microdroplets of ionic liquids deposited by physical vapor method onto different surfaces

    Science.gov (United States)

    Costa, José C. S.; Coelho, Ana F. S. M. G.; Mendes, Adélio; Santos, Luís M. N. B. F.

    2018-01-01

    Nanoscience and technology has generated an important area of research in the field of properties and functionality of ionic liquids (ILs) based materials and their thin films. This work explores the deposition process of ILs droplets as precursors for the fabrication of thin films, by means of physical vapor deposition (PVD). It was found that the deposition (by PVD on glass, indium tin oxide, graphene/nickel and gold-coated quartz crystal surfaces) of imidazolium [C4mim][NTf2] and pyrrolidinium [C4C1Pyrr][NTf2] based ILs generates micro/nanodroplets with a shape, size distribution and surface coverage that could be controlled by the evaporation flow rate and deposition time. No indication of the formation of a wetting-layer prior to the island growth was found. Based on the time-dependent morphological analysis of the micro/nanodroplets, a simple model for the description of the nucleation process and growth of ILs droplets is presented. The proposed model is based on three main steps: minimum free area to promote nucleation; first order coalescence; second order coalescence.

  7. Development of a new laser heating system for thin film growth by chemical vapor deposition

    Science.gov (United States)

    Fujimoto, Eiji; Sumiya, Masatomo; Ohnishi, Tsuyoshi; Lippmaa, Mikk; Takeguchi, Masaki; Koinuma, Hideomi; Matsumoto, Yuji

    2012-09-01

    We have developed a new laser heating system for thin film growth by chemical vapor deposition (CVD). A collimated beam from a high-power continuous-wave 808 nm semiconductor laser was directly introduced into a CVD growth chamber without an optical fiber. The light path of the heating laser inside the chamber was isolated mechanically from the growth area by bellows to protect the optics from film coating. Three types of heat absorbers, (10 × 10 × 2 mm3) consisting of SiC, Ni/NiOx, or pyrolytic graphite covered with pyrolytic BN (PG/PBN), located at the backside of the substrate, were tested for heating performance. It was confirmed that the substrate temperature could reach higher than 1500 °C in vacuum when a PG/PBN absorber was used. A wide-range temperature response between 400 °C and 1000 °C was achieved at high heating and cooling rates. Although the thermal energy loss increased in a H2 gas ambient due to the higher thermal conductivity, temperatures up to 1000°C were achieved even in 200 Torr H2. We have demonstrated the capabilities of this laser heating system by growing ZnO films by metalorganic chemical vapor deposition. The growth mode of ZnO films was changed from columnar to lateral growth by repeated temperature modulation in this laser heating system, and consequently atomically smooth epitaxial ZnO films were successfully grown on an a-plane sapphire substrate.

  8. Self-catalytic growth of tin oxide nanowires by chemical vapor deposition process

    CSIR Research Space (South Africa)

    Thabethe, BS

    2013-01-01

    Full Text Available The authors report on the synthesis of tin oxide (SnO(sub2)) nanowires by a chemical vapor deposition (CVD) process. Commercially bought SnO nanopowders were vaporized at 1050°C for 30 minutes with argon gas continuously passing through the system...

  9. Role of hydrogen in graphene chemical vapor deposition growth on a copper surface.

    Science.gov (United States)

    Zhang, Xiuyun; Wang, Lu; Xin, John; Yakobson, Boris I; Ding, Feng

    2014-02-26

    Synthesizing bilayer graphene (BLG), which has a band gap, is an important step in graphene application in microelectronics. Experimentally, it was broadly observed that hydrogen plays a crucial role in graphene chemical vapor deposition (CVD) growth on a copper surface. Here, by using ab initio calculations, we have revealed a crucial role of hydrogen in graphene CVD growth, terminating the graphene edges. Our study demonstrates the following. (i) At a low hydrogen pressure, the graphene edges are not passivated by H and thus tend to tightly attach to the catalyst surface. As a consequence, the diffusion of active C species into the area beneath the graphene top layer (GTL) is prohibited, and therefore, single-layer graphene growth is favored. (ii) At a high hydrogen pressure, the graphene edges tend to be terminated by H, and therefore, its detachment from the catalyst surface favors the diffusion of active C species into the area beneath the GTL to form the adlayer graphene below the GTL; as a result, the growth of BLG or few-layer graphene (FLG) is preferred. This insightful understanding reveals a crucial role of H in graphene CVD growth and paves a way for the controllable synthesis of BLG or FLG. Besides, this study also provides a reasonable explanation for the hydrogen pressure-dependent graphene CVD growth behaviors on a Cu surface.

  10. Controllable poly-crystalline bilayered and multilayered graphene film growth by reciprocal chemical vapor deposition.

    Science.gov (United States)

    Wu, Qinke; Jung, Seong Jun; Jang, Sung Kyu; Lee, Joohyun; Jeon, Insu; Suh, Hwansoo; Kim, Yong Ho; Lee, Young Hee; Lee, Sungjoo; Song, Young Jae

    2015-06-21

    We report the selective growth of large-area bilayered graphene film and multilayered graphene film on copper. This growth was achieved by introducing a reciprocal chemical vapor deposition (CVD) process that took advantage of an intermediate h-BN layer as a sacrificial template for graphene growth. A thin h-BN film, initially grown on the copper substrate using CVD methods, was locally etched away during the subsequent graphene growth under residual H2 and CH4 gas flows. Etching of the h-BN layer formed a channel that permitted the growth of additional graphene adlayers below the existing graphene layer. Bilayered graphene typically covers an entire Cu foil with domain sizes of 10-50 μm, whereas multilayered graphene can be epitaxially grown to form islands a few hundreds of microns in size. This new mechanism, in which graphene growth proceeded simultaneously with h-BN etching, suggests a potential approach to control graphene layers for engineering the band structures of large-area graphene for electronic device applications.

  11. Rapid thermal chemical vapor deposition growth of nanometer-thin SiC on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Steckl, A.J.; Li, J.P. (Univ. of Cincinnati, OH (United States))

    1992-08-28

    Rapid thermal chemical vapor deposition growth of [beta]-SiC ultrathin films on Si (100) was achieved using the carbonization reaction of the silicon substrate with C[sub 3]H[sub 8] gas. Growth rates of 0.5-2 nm s[sup -1] have been achieved at 1100-1300degC using C[sub 3]H[sub 8] flow rates of 7-9 standard cm[sup 3] min[sup -1]. X-ray and electron diffraction indicate single-crystal growth. Therefore nanometer-scale SiC films can be grown by controlling the reaction time to a few seconds. The activation energy at atmospheric pressure is 3.12 eV. The growth rate was found to decrease significantly at higher C[sub 3]H[sub 8] flow rates, leading to films of constant thickness beyond a certain critical reaction time. Using this regime of self-limiting growth, SiC films of 3-5 nm have been grown with relatively little sensitivity to the growth time. (orig.).

  12. 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

  13. Laterally Stitched Heterostructures of Transition Metal Dichalcogenide: Chemical Vapor Deposition Growth on Lithographically Patterned Area

    KAUST Repository

    Li, Henan

    2016-10-31

    Two-dimensional transition metal dichalcogenides (TMDCs) have shown great promise in electronics and optoelectronics due to their unique electrical and optical properties. Heterostructured TMDC layers such as the laterally stitched TMDCs offer the advantages of better electronic contact and easier band offset tuning. Here, we demonstrate a photoresist-free focused ion beam (FIB) method to pattern as-grown TMDC monolayers by chemical vapor deposition, where the exposed edges from FIB etching serve as the seeds for growing a second TMDC material to form desired lateral heterostructures with arbitrary layouts. The proposed lithographic and growth processes offer better controllability for fabrication of the TMDC heterostrucuture, which enables the construction of devices based on heterostructural monolayers. © 2016 American Chemical Society.

  14. Studies in graphene growth and processing using atmospheric pressure chemical vapor deposition

    Science.gov (United States)

    Merrell, Andrew Nephi

    This dissertation focuses on graphene, a promising two-dimensional, carbon material with many favorable electronic properties. The prospect of implementing graphene into a wide variety of potential device applications is enticing, but many factors stand in the way before this goal is realized. Atmospheric pressure chemical vapor deposition (APCVD) is a graphene production method that may be compatible with large-scale growth. Motivated by the need to more fully understand APCVD growth of graphene, a system is constructed, and several studies are carried out. Specifically, a detailed study is presented which involves the effects of hydrogen and contaminant oxygen in APCVD-grown graphene. The research shows that hydrogen is an important factor to control during the cooling stage of APCVD, as it has a direct effect on the formation of oxides on the copper foil (copper is used as the catalyst for graphene growth in APCVD). It is also determined that hydrogen, as well as the reaction chamber, play an important role in the formation of SiO2 nanoparticles, which accumulate on the copper surface during graphene growth. Methods for patterning and processing graphene are also explored in this dissertation, as such methods are crucial in the realization of graphene-based devices. The method of e-beam assisted metal deposition used in conjunction with masked-CVD growth is proposed as an effective alternative to conventional processing methods such as photolithography and electron-beam lithography. The proposed methods have several advantages, which pave the way for lowering graphene/metal contact resistance, and preserving the intrinsic properties of graphene during device fabrication.

  15. H2-dependent attachment kinetics and shape evolution in chemical vapor deposition graphene growth

    Science.gov (United States)

    Meca, Esteban; Shenoy, Vivek B.; Lowengrub, John

    2017-09-01

    Experiments on graphene growth through chemical vapor deposition (CVD) involving methane (CH4) and hydrogen (H2) gases reveal a complex shape evolution and a non-monotonic dependence on the partial pressure of H2 ({{p}{{\\text{H}2}}} ). To explain these intriguing observations, we develop a microkinetic model for the stepwise decomposition of CH4 into mobile radicals and consider two possible mechanisms of attachment to graphene crystals: CH radicals to hydrogen-decorated edges of the crystals and C radicals to bare crystal edges. We derive an effective mass flux and an effective kinetic coefficient, both of which depend on {{p}{{\\text{H}2}}} , and incorporate these into a phase field model. The model reproduces both the non-monotonic dependence on {{p}{{\\text{H}2}}} and the characteristic shapes of graphene crystals observed in experiments. At small {{p}{{\\text{H}2}}} , growth is limited by the kinetics of attachment while at large {{p}{{\\text{H}2}}} growth is limited because the effective mass flux is small. We also derive a simple analytical model that captures the non-monotone behavior, enables the two mechanisms of attachment to be distinguished and provides guidelines for CVD growth of defect-free 2D crystals.

  16. Growth study of indium-catalyzed silicon nanowires by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zardo, I. [Technische Universitaet Muenchen, Walter Schottky Institut and Physik Department, Garching (Germany); Conesa-Boj, S.; Estrade, S.; Peiro, F. [Universitat de Barcelona, Departament d' Electronica, Barcelona, CAT (Spain); Yu, L.; Roca i Cabarrocas, P. [Ecole Polytechnique, CNRS, LPICM, Palaiseau (France); Morante, J.R. [Universitat de Barcelona, Departament d' Electronica, Barcelona, CAT (Spain); Catalonia Institute for Energy Research, Barcelona, CAT (Spain); Arbiol, J. [Universitat de Barcelona, Departament d' Electronica, Barcelona, CAT (Spain); Institucio Catalana de Recerca i Estudis Avancats (ICREA) and Institut de Ciencia de Materials de Barcelona, CSIC, Bellaterra, CAT (Spain); Fontcuberta i.Morral, A. [Technische Universitaet Muenchen, Walter Schottky Institut and Physik Department, Garching (Germany); Ecole Polytechnique Federale de Lausanne, Laboratoire des Materiaux Semiconducteurs, Institut des Materiaux, Lausanne (Switzerland)

    2010-07-15

    Indium was used as a catalyst for the synthesis of silicon nanowires in a plasma enhanced chemical vapor deposition reactor. In order to foster the catalytic activity of indium, the indium droplets had to be exposed to a hydrogen plasma prior to nanowire growth in a silane plasma. The structure of the nanowires was investigated as a function of the growth conditions by electron microscopy and Raman spectroscopy. The nanowires were found to crystallize along the <111>, <112> or <001> growth direction. When growing on the <112> and <111> directions, they revealed a similar crystal quality and the presence of a high density of twins along the {l_brace}111{r_brace} planes. The high density and periodicity of these twins lead to the formation of hexagonal domains inside the cubic structure. The corresponding Raman signature was found to be a peak at 495 cm{sup -1}, in agreement with previous studies. Finally, electron energy loss spectroscopy indicates an occasional migration of indium during growth. (orig.)

  17. Chemical vapor deposition growth of large grapheme single crystal from ethanol

    Science.gov (United States)

    Chen, Xiao; Zhao, Pei; Chiashi, Shohei; Maruyama, Shigeo

    2014-03-01

    Ethanol as a precursor has proven effective in the chemical vapor deposition (CVD) synthesis of graphene on both Ni foils and Cu capsule substrates. For applications of graphene in field effect transistors or as transparent conducting electrodes, larger singe-crystal graphene without any grain boundaries shows superior electrical performance and has attracted enormous interests. Here we report a protocol to synthesize large graphene single crystals (up to 600 μm) using ethanol as precursor on commercially-available polycrystalline Cu foils. We explored the mechanism by studying the influences of different growth parameters such as pressure, flow rate and temperature. Low partial pressure and low flow rate of ethanol is essential in achieving low nucleation density over the metal surface and therefore large graphene grains can be obtained. We found that growth temperature dramatically affects the crystallinity and the growth rate of graphene grains. Moreover, this CVD growth of large graphene single crystals involves no electro-polishing or annealing treatments to the metal surface, presenting a significant simplification to the current graphene synthesis process.

  18. Rapid growth of zinc oxide nanobars in presence of electric field by physical vapor deposition

    Science.gov (United States)

    Jouya, Mehraban; Taromian, Fahime; Siami, Simin

    2018-01-01

    In this contribution, electric field has some effects to increase growth for specific time duration on zinc oxide (ZnO) nanobars. First, the zinc (Zn) thin film has been prepared by 235,000 V/m electric field assisted physical vapor deposition (PVD) at vacuum of 1.33 × 10-5 mbar. Second, strong electric field of 134,000 V/m has been used in ambient for growing ZnO nanobars in term of the time include 2.5 and 10 h. The performances of the ZnO nanostructure in absence and presence of electric field have been determined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results of XRD analysis showed that ZnO has a hexagonal bars structure and a strongly preferred (101) orientation which is strongest than without applying electric field. SEM analysis revealed that physical vapored ZnO thin film in presence of electric field are densely packed with uniform morphological, thinner and denser in distribution. Electric field effect for ZnO growth in 2.5 h is better than it in the 2.5 h without electric field but by passing the time the media influence has good power almost as same as electric field. Through this electric field in PVD, the compact and uniform Zn film has been achieved which is less diameter than ordinary PVD method. Finally, we carry out a series of experiments to grow different-orientation ZnO nanobars with less than 100 nm in diameter, which are the time saving process in base of PVD ever reported. Therefore, the significant conclusion in usage electric field is reducing time of growth.

  19. Nitride film growth morphology using remote plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wintrebert-Fouquet, M.; Butcher, K.S.A.; Chen, P.P.T. [Physics Department, Macquarie University, Sydney, NSW 2109 (Australia); Wuhrer, R. [Microstructural Analysis Unit, Faculty of Science, University of Technology, Sydney, Broadway, NSW 2007 (Australia)

    2007-06-15

    Gallium nitride and indium nitride films have been grown by remote plasma enhanced chemical vapor deposition (RPECVD) at temperatures between 570 and 650 C for GaN and between 350 and 570 C for InN on different substrates. For GaN vast improvements in film morphology and quality have resulted from reductions in background impurities when compared to previous reports. Epitaxial material can now be grown at 650 C under optimized growth conditions. Columnar growth still occurs for growth on some substrates, however film coalescence is observed when using appropriate buffer layers and epitaxial growth can also be observed. High resolution SEM images show examples of this. The root-mean-square surface roughness of epitaxial samples, as measured using atomic force microscopy, shows values of as little as 10 Angstroms. While X-ray diffraction shows that these surfaces are not amorphous but have a strong (0001) preferred axis with FWHM limited by instrumental effects to (2{theta}) 0.085 degrees. The improvement in film quality has allowed heavily doped n-type films to be grown with an electron mobility of 160 cm{sup 2}/V.s for a carrier concentration of {proportional_to}1 x 10{sup 19} cm{sup -3} at 650 C. Moss-Burstein shifted absorption data confirms the high doping level. For InN film growth by RPECVD, columnar growth is commonly observed in the temperature region of interest for films grown directly on sapphire, however film coalescence and epitaxial films are also observed for this material. X-ray diffraction indicates very sharp (0002) peaks with FWHM of (2{theta}) 0.07 degrees. High resolution SEM images show examples of film morphology at different growth temperatures. Electron backscattered diffraction images indicate a wurtzite structure even for InN films with strong deviations from the accepted lattice parameters. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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

    Science.gov (United States)

    Liu, Lixin; Zhou, Hailong; Cheng, Rui; Yu, Woo Jong; Liu, Yuan; Chen, Yu; Shaw, Jonathan; Zhong, Xing; Huang, Yu; Duan, Xiangfeng

    2012-01-01

    Bernal stacked (AB stacked) bilayer graphene is of significant interest for functional electronic and photonic devices due to the feasibility to continuously tune its band gap with a vertical electrical field. Mechanical exfoliation can be used to produce AB stacked bilayer graphene flakes but typically with the sizes limited to a few micrometers. Chemical vapor deposition (CVD) has been recently explored for the synthesis of bilayer graphene but usually with limited coverage and a mixture of AB and randomly stacked structures. Herein we report a rational approach to produce large-area high quality AB stacked bilayer graphene. We show that the self-limiting effect of graphene growth on Cu foil can be broken by using a high H2/CH4 ratio in a low pressure CVD process to enable the continued growth of bilayer graphene. A high temperature and low pressure nucleation step is found to be critical for the formation of bilayer graphene nuclei with high AB stacking ratio. A rational design of a two-step CVD process is developed for the growth of bilayer graphene with high AB stacking ratio (up to 90 %) and high coverage (up to 99 %). The electrical transport studies demonstrated that devices made of the as-grown bilayer graphene exhibit typical characteristics of AB stacked bilayer graphene with the highest carrier mobility exceeding 4,000 cm2/V·s at room temperature, comparable to that of the exfoliated bilayer graphene. PMID:22906199

  1. Structure and Growth of Vapor-Deposited n-Dotriacontane Films Studied by X-ray Reflectivity

    DEFF Research Database (Denmark)

    del Campo, V.; Cisternas, E.; Taub, H.

    2009-01-01

    We have used synchrotron X-ray reflectivity measurements to investigate the structure of n-dotriacontane (n-C32H66 or C32) films deposited from the vapor phase onto a SiO2-coated Si(100) surface. Our primary motivation was to determine whether the structure and growth mode of these films differ...

  2. Chemical vapor deposition growth of boron–carbon–nitrogen layers from methylamine borane thermolysis products

    Science.gov (United States)

    Leardini, Fabrice; Flores, Eduardo; Galvis E, Andrés R.; Ferrer, Isabel J.; Ramón Ares, José; Sánchez, Carlos; Molina, Pablo; van der Meulen, Herko P.; Gómez Navarro, Cristina; López Polin, Guillermo; Urbanos, Fernando J.; Granados, Daniel; García-García, F. Javier; Demirci, Umit B.; Yot, Pascal G.; Mastrangelo, Filippo; Grazia Betti, Maria; Mariani, Carlo

    2018-01-01

    This work investigates the growth of B–C–N layers by chemical vapor deposition using methylamine borane (MeAB) as the single-source precursor. MeAB has been synthesized and characterized, paying particular attention to the analysis of its thermolysis products, which are the gaseous precursors for B–C–N growth. Samples have been grown on Cu foils and transferred onto different substrates for their morphological, structural, chemical, electronic and optical characterizations. The results of these characterizations indicate a segregation of h-BN and graphene-like (Gr) domains. However, there is an important presence of B and N interactions with C at the Gr borders, and of C interacting at the h-BN-edges, respectively, in the obtained nano-layers. In particular, there is a significant presence of C–N bonds, at Gr/h-BN borders and in the form of N doping of Gr domains. The overall B:C:N contents in the layers is close to 1:3:1.5. A careful analysis of the optical bandgap determination of the obtained B–C–N layers is presented, discussed and compared with previous seminal works with samples of similar composition.

  3. Chemical Vapor Deposition Growth. Final Report, December 29, 1975 -- August 31, 1977

    Energy Technology Data Exchange (ETDEWEB)

    Ruth, R. P.; Manasevit, H. M.; Campbell, A. G.; Johnson, R. E.; Kenty, J. L.; Moudy, L. A.; Shaw, G. L.; Simpson, W. I.; Yang, J. J.

    1978-10-01

    The objective of this study was to investigate and develop chemical vapor deposition (CVD) techniques for the growth of large areas of Si sheet on inexpensive substrate materials, with resulting sheet properties suitable for fabricating solar cells that would meet the technical goals of the Low Cost Silicon Solar Array (LSSA) Project. The results of 20 months of experimental work are summarized. The program involved six main technical tasks: (1) modification and test of an existing vertical-chamber CVD reactor system; (2) identification and/or development of suitable inexpensive substrate materials; (3) experimental investigation of CVD process parameters using various candidate substrate materials; (4) preparation of Si sheet samples for various special studies, including solar cell fabrication; (5) evaluation of the properties of the Si sheet material produced by the CVD process; and (6) fabrication and evaluation of experimental solar cell structures by OCLI, using impurity diffusion and other standard and near-standard processing techniques, supplemented late in the program by the in situ CVD growth of n exp + /p/p exp + sheet structures subsquently processed into experimental cells. The principal CVD process used was silane (SiH sub 4 ) pyrolysis, although a few experiments were done with the dichlorosilane (SiH sub 2 Cl sub 2 ) process for Si deposition. The evaluation of various possiblesubstrate materials, the CVD parameter investigations, and the experimental solar cell fabrication and characterization are described in considerable detail. Specific conclusions of the work are discussed, and recommendations for continued investigations in certain areas are given.

  4. Influence of the catalyst type on the growth of carbon nanotubes via methane chemical vapor deposition

    NARCIS (Netherlands)

    Jodin, Lucie; Dupuis, Anne-Claire; Rouvière, Emmanuelle; Reiss, Peter

    2006-01-01

    The preparation of the catalyst is one of the key parameters which governs the quality of carbon nanotubes (CNTs) grown by catalyzed chemical vapor deposition (CVD). We investigated the influence of three different procedures of catalyst preparation on the type and diameter of CNTs formed under

  5. 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.

  6. Reduced-Pressure Chemical Vapor Deposition Growth of Isolated Ge Crystals and Suspended Layers on Micrometric Si Pillars.

    Science.gov (United States)

    Skibitzki, Oliver; Capellini, Giovanni; Yamamoto, Yuji; Zaumseil, Peter; Schubert, Markus Andreas; Schroeder, Thomas; Ballabio, Andrea; Bergamaschini, Roberto; Salvalaglio, Marco; Miglio, Leo; Montalenti, Francesco

    2016-10-05

    In this work, we demonstrate the growth of Ge crystals and suspended continuous layers on Si(001) substrates deeply patterned in high aspect-ratio pillars. The material deposition was carried out in a commercial reduced-pressure chemical vapor deposition reactor, thus extending the "vertical-heteroepitaxy" technique developed by using the peculiar low-energy plasma-enhanced chemical vapor deposition reactor, to widely available epitaxial tools. The growth process was thoroughly analyzed, from the formation of small initial seeds to the final coalescence into a continuous suspended layer, by means of scanning and transmission electron microscopy, X-ray diffraction, and μ-Raman spectroscopy. The preoxidation of the Si pillar sidewalls and the addition of hydrochloric gas in the reactants proved to be key to achieve highly selective Ge growth on the pillars top only, which, in turn, is needed to promote the formation of a continuous Ge layer. Thanks to continuum growth models, we were able to single out the different roles played by thermodynamics and kinetics in the deposition dynamics. We believe that our findings will open the way to the low-cost realization of tens of micrometers thick heteroepitaxial layer (e.g., Ge, SiC, and GaAs) on Si having high crystal quality.

  7. Highly oriented, free-standing, superconducting NbN films growth on chemical vapor deposited graphene

    Directory of Open Access Journals (Sweden)

    Garima Saraswat

    2014-05-01

    Full Text Available NbN films are grown on chemical vapor deposited graphene using dc magnetron sputtering. The orientation and transition temperature of the deposited films is studied as a function of substrate temperature. A superconducting transition temperature of 14 K is obtained for highly oriented (111 films grown at substrate temperature of 150 °C, which is comparable to epitaxial films grown on MgO and sapphire substrates. These films show a considerably high upper critical field of ∼33 T. In addition, we demonstrate a process for obtaining flexible, free-standing NbN films by delaminating graphene from the substrate using a simple wet etching technique. These free-standing NbN layers can be transferred to any substrate, potentially enabling a range of novel superconducting thin-film applications.

  8. Relation between growth rate and structure of graphene grown in a 4″ showerhead chemical vapor deposition reactor

    Science.gov (United States)

    Bekdüz, B.; Beckmann, Y.; Meier, J.; Rest, J.; Mertin, W.; Bacher, G.

    2017-05-01

    The chemical vapor deposition (CVD) growth of graphene on copper is controlled by a complex interplay of substrate preparation, substrate temperature, pressure and flow of reactive gases. A large variety of recipes have been suggested in literature, often quite specific to the reactor, which is being used. Here, we report on a relation between growth rate and quality of graphene grown in a scalable 4″ CVD reactor. The growth rate is varied by substrate pre-treatment, chamber pressure, and methane to hydrogen (CH4:H2) ratio, respectively. We found that at lower growth rates graphene grains become hexagonal rather than randomly shaped, which leads to a reduced defect density and a sheet resistance down to 268 Ω/sq.

  9. Tip-growth mode and base-growth mode of Au-catalyzed zinc oxide nanowires using chemical vapor deposition technique

    Science.gov (United States)

    Pung, Swee-Yong; Choy, Kwang-Leong; Hou, Xianghui

    2010-07-01

    Tip-growth and base-growth modes of Au-catalyzed zinc oxide nanowires (ZnO NWs) were synthesized on Au-film pre-deposited silicon substrates using Chemical Vapor Deposition (CVD) technique. The diameter of tip-growth Au-catalyzed ZnO NWs was proportional to the Au film thickness, whereas the areal density of these NWs was inversely proportional to the Au film thickness. It would be more appropriate to explain the growth of Au-catalyzed ZnO NWs by a combination of Vapor-Liquid-Solid and Vapor-Solid (VLS-VS) mechanisms instead of the conventional VLS mechanism, regardless of tip-growth or base-growth mode of Au-catalyzed ZnO NWs. The competition between the VLS and VS mechanism in the effectiveness of capturing the adsorbed Zn and O atoms would determine the final morphology of ZnO NWs. In addition, Au catalyst promoted the growth rate of NWs as compared to the self-catalyzed ZnO NWs.

  10. Effects of polymethylmethacrylate-transfer residues on the growth of organic semiconductor molecules on chemical vapor deposited graphene

    Energy Technology Data Exchange (ETDEWEB)

    Kratzer, Markus, E-mail: markus.kratzer@unileoben.ac.at; Teichert, Christian [Institute of Physics, Montanuniversitaet Leoben, Franz Josef Straße 18, A 8700 Leoben (Austria); Bayer, Bernhard C. [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Faculty of Physics, University of Vienna, Boltzmanngasse 5, A 1090 Vienna (Austria); Kidambi, Piran R. [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Matković, Aleksandar; Gajić, Radoš [Institute of Physics, Department for Solid State Physics and New Materials, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Cabrero-Vilatela, Andrea; Weatherup, Robert S.; Hofmann, Stephan [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom)

    2015-03-09

    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 H{sub 2} 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.

  11. Water-assisted growth of graphene on carbon nanotubes by the chemical vapor deposition method.

    Science.gov (United States)

    Feng, Jian-Min; Dai, Ye-Jing

    2013-05-21

    Combining carbon nanotubes (CNTs) with graphene has been proved to be a feasible method for improving the performance of graphene for some practical applications. This paper reports a water-assisted route to grow graphene on CNTs from ferrocene and thiophene dissolved in ethanol by the chemical vapor deposition method in an argon flow. A double injection technique was used to separately inject ethanol solution and water for the preparation of graphene/CNTs. First, CNTs were prepared from ethanol solution and water. The injection of ethanol solution was suspended and water alone was injected into the reactor to etch the CNTs. Thereafter, ethanol solution was injected along with water, which is the key factor in obtaining graphene/CNTs. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and Raman scattering analyses confirmed that the products were the hybrid materials of graphene/CNTs. X-ray photo-electron spectroscopy analysis showed the presence of oxygen rich functional groups on the surface of the graphene/CNTs. Given the activity of the graphene/CNT surface, CdS quantum dots adhered onto it uniformly through simple mechanical mixing.

  12. Selective Chemical Vapor Deposition Growth of Cubic FeGe Nanowires That Support Stabilized Magnetic Skyrmions.

    Science.gov (United States)

    Stolt, Matthew J; Li, Zi-An; Phillips, Brandon; Song, Dongsheng; Mathur, Nitish; Dunin-Borkowski, Rafal E; Jin, Song

    2017-01-11

    Magnetic skyrmions are topologically stable vortex-like spin structures that are promising for next generation information storage applications. Materials that host magnetic skyrmions, such as MnSi and FeGe with the noncentrosymmetric cubic B20 crystal structure, have been shown to stabilize skyrmions upon nanostructuring. Here, we report a chemical vapor deposition method to selectively grow nanowires (NWs) of cubic FeGe out of three possible FeGe polymorphs for the first time using finely ground particles of cubic FeGe as seeds. X-ray diffraction and transmission electron microscopy (TEM) confirm that these micron-length NWs with ∼100 nm to 1 μm diameters have the cubic B20 crystal structure. Although Fe 13 Ge 8 NWs are also formed, the two types of NWs can be readily differentiated by their faceting. Lorentz TEM imaging of the cubic FeGe NWs reveals a skyrmion lattice phase under small applied magnetic fields (∼0.1 T) at 233 K, a skyrmion chain state at lower temperatures (95 K) and under high magnetic fields (∼0.4 T), and a larger skyrmion stability window than bulk FeGe. This synthetic approach to cubic FeGe NWs that support stabilized skyrmions opens a route toward the exploration of new skyrmion physics and devices based on similar nanostructures.

  13. Role of boundary layer diffusion in vapor deposition growth of chalcogenide nanosheets: the case of GeS.

    Science.gov (United States)

    Li, Chun; Huang, Liang; Snigdha, Gayatri Pongur; Yu, Yifei; Cao, Linyou

    2012-10-23

    We report a synthesis of single-crystalline two-dimensional GeS nanosheets using vapor deposition processes and show that the growth behavior of the nanosheet is substantially different from those of other nanomaterials and thin films grown by vapor depositions. The nanosheet growth is subject to strong influences of the diffusion of source materials through the boundary layer of gas flows. This boundary layer diffusion is found to be the rate-determining step of the growth under typical experimental conditions, evidenced by a substantial dependence of the nanosheet's size on diffusion fluxes. We also find that high-quality GeS nanosheets can grow only in the diffusion-limited regime, as the crystalline quality substantially deteriorates when the rate-determining step is changed away from the boundary layer diffusion. We establish a simple model to analyze the diffusion dynamics in experiments. Our analysis uncovers an intuitive correlation of diffusion flux with the partial pressure of source materials, the flow rate of carrier gas, and the total pressure in the synthetic setup. The observed significant role of boundary layer diffusions in the growth is unique for nanosheets. It may be correlated with the high growth rate of GeS nanosheets, ~3-5 μm/min, which is 1 order of magnitude higher than other nanomaterials (such as nanowires) and thin films. This fundamental understanding of the effect of boundary layer diffusions may generally apply to other chalcogenide nanosheets that can grow rapidly. It can provide useful guidance for the development of general paradigms to control the synthesis of nanosheets.

  14. The influence of methanol addition during the film growth of SnO 2 by atmospheric pressure chemical vapor deposition

    NARCIS (Netherlands)

    Volintiru, I.; Graaf, A. de; Deelen, J. van; Poodt, P.W.G.

    2011-01-01

    Undoped tin oxide (SnO2) thin films have been deposited in a stagnant point flow chemical vapor deposition reactor from a water/tin tetrachloride mixture. By adding methanol during the deposition process the film electrical properties change significantly: ten times more conductive SnO 2 films are

  15. Epitaxial growth of wide-band-gap ZnGa2O4 films by mist chemical vapor deposition

    Science.gov (United States)

    Oshima, Takayoshi; Niwa, Mifuyu; Mukai, Akira; Nagami, Tomohito; Suyama, Toshihisa; Ohtomo, Akira

    2014-01-01

    ZnGa2O4 films were grown on (100) MgAl2O4 substrates by mist chemical vapor deposition. A growth window for obtaining single spinel phase was revealed by systematic variations of precursor Zn/Ga ratio and growth temperature, where the cation stoichiometry was maintained through sublimation of excess Zn species before crystalized into ZnO. The epitaxial relationship to the substrate was identified to be cube on cube with no rotation domain. The optical properties of the fully relaxed film were characterized by using cathodoluminescence (CL) and absorption spectroscopies. A large Stokes shift was found between the CL peak energy (3.4 eV) and fundamental absorption edge (4.6 eV), reflecting typical property of Ga-based wide-band-gap oxide semiconductors.

  16. In-situ epitaxial growth of heavily phosphorus doped SiGe by low pressure chemical vapor deposition

    CERN Document Server

    Lee, C J

    1998-01-01

    We have studied epitaxial crystal growth of Si sub 1 sub - sub x Ge sub x films on silicon substrates at 550 .deg. C by low pressure chemical vapor deposition. In a low PH sub 3 partial pressure region such as below 1.25x10 sup - sup 3 Pa, both the phosphorus and carrier concentrations increased with increasing PH sub 3 partial pressure, but the deposition rate and the Ge fraction remained constant. In a higher PH sub 3 partial pressure region, the deposition rate, the phosphorus concentration, and the carrier concentration decreased, while the Ge fraction increased. These suggest that high surface coverage of phosphorus suppresses both SiH sub 4 and GeH sub 4 adsorption/reactions on the surfaces, and its suppression effect on SiH sub 4 is actually much stronger than on GeH sub 4. In particular, epitaxial crystal growth is largely controlled by surface coverage effect of phosphorus in a higher PH sub 3 partial pressure region.

  17. Effects of surface oxidation of Cu substrates on the growth kinetics of graphene by chemical vapor deposition.

    Science.gov (United States)

    Chang, Ren-Jie; Lee, Chia-Hao; Lee, Min-Ken; Chen, Chun-Wei; Wen, Cheng-Yen

    2017-02-09

    Although the success of graphene research has opened up a new route for wearable electronic and optoelectronic devices, producing graphene with controllable quality and cost-effective growth on a large scale remains challenging due to the lack of understanding about its growth kinetics. Domain boundaries interrupt lattice continuity of graphene; therefore, lowering the nucleation density at the initial stage of graphene growth in the chemical vapor deposition (CVD) process is beneficial for improving the quality of graphene for applications. Herein, we show that by forming an oxide passivation layer on Cu substrates before CVD graphene growth, graphene nucleation density can be effectively decreased. The nucleation mechanism in the presence of an oxide passivation layer is of interest. The analysis of graphene growth kinetics suggests that the thickness of the boundary layer for mass transfer on the substrate surface plays an important role in controlling the reduction rate of the oxide passivation layer. A thick boundary layer created under slow gas flow causes slow reduction of the oxide passivation layer, making finite sites for graphene nucleation. The domain density in a graphene layer is therefore significantly reduced. Graphene sheets of various domain densities (ranging from 104 to 1 mm-2) can be fabricated by suitably choosing the growth parameters. The graphene sheet with a lower density of domain boundaries exhibits better electrical conductivities.

  18. Impact of microcrystalline silicon carbide growth using hot-wire chemical vapor deposition on crystalline silicon surface passivation

    Energy Technology Data Exchange (ETDEWEB)

    Pomaska, M., E-mail: m.pomaksa@fz-juelich.de [Forschungszentrum Jülich, IEK5-Photovoltaics, Wilhelm-Johnen-Strasse, 52425 Jülich (Germany); Beyer, W. [Helmholtz-Zentrum Berlin für Materialien und Energie, Silicon Photovoltaics, Kekuléstrasse 5, 12489 Berlin (Germany); Neumann, E. [Forschungszentrum Jülich, PGI-8-PT, Wilhelm-Johnen-Strasse, 52425 Jülich (Germany); Finger, F.; Ding, K. [Forschungszentrum Jülich, IEK5-Photovoltaics, Wilhelm-Johnen-Strasse, 52425 Jülich (Germany)

    2015-11-30

    Highly crystalline microcrystalline silicon carbide (μc-SiC:H) with excellent optoelectronic material properties is a promising candidate as highly transparent doped layer in silicon heterojunction (SHJ) solar cells. These high quality materials are usually produced using hot wire chemical vapor deposition under aggressive growth conditions giving rise to the removal of the underlying passivation layer and thus the deterioration of the crystalline silicon (c-Si) surface passivation. In this work, we introduced the n-type μc-SiC:H/n-type μc-SiO{sub x}:H/intrinsic a-SiO{sub x}:H stack as a front layer configuration for p-type SHJ solar cells with the μc-SiO{sub x}:H layer acting as an etch-resistant layer against the reactive deposition conditions during the μc-SiC:H growth. We observed that the unfavorable expansion of micro-voids at the c-Si interface due to the in-diffusion of hydrogen atoms through the layer stack might be responsible for the deterioration of surface passivation. Excellent lifetime values were achieved under deposition conditions which are needed to grow high quality μc-SiC:H layers for SHJ solar cells. - Highlights: • High surface passivation quality was preserved after μc-SiC:H deposition. • μc-SiC:H/μc-SiO{sub x}:H/a-SiO{sub x}:H stack a promising front layer configuration • Void expansion at a-SiO{sub x}:H/c-Si interface for deteriorated surface passivation • μc-SiC:H provides a high transparency and electrical conductivity.

  19. Growth of InAs Quantum Dots on Germanium Substrate Using Metal Organic Chemical Vapor Deposition Technique

    Directory of Open Access Journals (Sweden)

    Tyagi Renu

    2009-01-01

    Full Text Available Abstract Self-assembled InAs quantum dots (QDs were grown on germanium substrates by metal organic chemical vapor deposition technique. Effects of growth temperature and InAs coverage on the size, density, and height of quantum dots were investigated. Growth temperature was varied from 400 to 450 °C and InAs coverage was varied between 1.40 and 2.35 monolayers (MLs. The surface morphology and structural characteristics of the quantum dots analyzed by atomic force microscope revealed that the density of the InAs quantum dots first increased and then decreased with the amount of InAs coverage; whereas density decreased with increase in growth temperature. It was observed that the size and height of InAs quantum dots increased with increase in both temperature and InAs coverage. The density of QDs was effectively controlled by growth temperature and InAs coverage on GaAs buffer layer.

  20. Layer-Controlled Chemical Vapor Deposition Growth of MoS2 Vertical Heterostructures via van der Waals Epitaxy.

    Science.gov (United States)

    Samad, Leith; Bladow, Sage M; Ding, Qi; Zhuo, Junqiao; Jacobberger, Robert M; Arnold, Michael S; Jin, Song

    2016-07-26

    The fascinating semiconducting and optical properties of monolayer and few-layer transition metal dichalcogenides, as exemplified by MoS2, have made them promising candidates for optoelectronic applications. Controllable growth of heterostructures based on these layered materials is critical for their successful device applications. Here, we report a direct low temperature chemical vapor deposition (CVD) synthesis of MoS2 monolayer/multilayer vertical heterostructures with layer-controlled growth on a variety of layered materials (SnS2, TaS2, and graphene) via van der Waals epitaxy. Through precise control of the partial pressures of the MoCl5 and elemental sulfur precursors, reaction temperatures, and careful tracking of the ambient humidity, we have successfully and reproducibly grown MoS2 vertical heterostructures from 1 to 6 layers over a large area. The monolayer MoS2 heterostructure was verified using cross-sectional high resolution transmission electron microscopy (HRTEM) while Raman and photoluminescence spectroscopy confirmed the layer-controlled MoS2 growth and heterostructure electronic interactions. Raman, photoluminescence, and energy dispersive X-ray spectroscopy (EDS) mappings verified the uniform coverage of the MoS2 layers. This reaction provides an ideal method for the scalable layer-controlled growth of transition metal dichalcogenide heterostructures via van der Waals epitaxy for a variety of optoelectronic applications.

  1. Mechanism of high growth rate for diamond-like carbon films synthesized by helicon wave plasma chemical vapor deposition

    Science.gov (United States)

    Peiyu, JI; Jun, YU; Tianyuan, HUANG; Chenggang, JIN; Yan, YANG; Lanjian, ZHUGE; Xuemei, WU

    2018-02-01

    A high growth rate fabrication of diamond-like carbon (DLC) films at room temperature was achieved by helicon wave plasma chemical vapor deposition (HWP-CVD) using Ar/CH4 gas mixtures. The microstructure and morphology of the films were characterized by Raman spectroscopy and scanning electron microscopy. The diagnosis of plasma excited by a helicon wave was measured by optical emission spectroscopy and a Langmuir probe. The mechanism of high growth rate fabrication for DLC films by HWP-CVD has been discussed. The growth rate of the DLC films reaches a maximum value of 54 μm h‑1 at the CH4 flow rate of 85 sccm, which is attributed to the higher plasma density during the helicon wave plasma discharge. The CH and H α radicals play an important role in the growth of DLC films. The results show that the H α radicals are beneficial to the formation and stabilization of C=C bond from sp2 to sp3.

  2. 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…

  3. Synthesis, Characterization and Growth Mechanism of ZnO Nano-flower by Thermal Chemical Vapor Deposition Method at Low Deposition Temperature

    Science.gov (United States)

    Hartini, A. R.; Amizam, S.; Mamat, M. H.; Abdullah, S.; Rusop, M.

    2008-05-01

    Photoluminescence and morphology studies of Zinc Oxide (ZnO) thin films prepared by using Thermal Chemical Vapor Deposition (Thermal-CVD) were investigated. The ZnO compound was synthesized from zinc acetate dehydrate which act as a starting material to form the ZnO thin films. It was deposited on silicon with low deposition temperature ranging from 400-600 °C with Au as a catalyst assisted. Surface morphology of the samples was examined by Scanning Electron Microscope and photoluminescence properties were studied using Photoluminescence Spectrometer. The surface morphologies of the ZnO nano-flower structure was obviously obtained at deposition temperature of 400 °C. The individual nano-rods diameter of nano-flower is about 100-350 nm, but the end of nano-rods are very sharp which is the size is less than 50 nm. Possible growth mechanism of ZnO nano-flower also discussed. Room temperature PL spectra from the ZnO nano-flower revealed a strong UV emission and broad green emission. This result is very useful for sensor, probe tip and light emitter applications.

  4. Undoped and in-situ B doped GeSn epitaxial growth on Ge by atmospheric pressure-chemical vapor deposition

    DEFF Research Database (Denmark)

    Vincent, B.; Gencarelli, F.; Bender, H.

    2011-01-01

    In this letter, we propose an atmospheric pressure-chemical vapor deposition technique to grow metastable GeSn epitaxial layers on Ge. We report the growth of defect free fully strained undoped and in-situ B doped GeSn layers on Ge substrates with Sit contents up to 8%. Those metastable layers stay...

  5. In situ Raman characterization of a diamond film during its growth process in a plasma jet chemical vapor deposition reactor

    Science.gov (United States)

    Rosman, N.; Abello, L.; Chabert, J. P.; Verven, G.; Lucazeau, G.

    1995-07-01

    A setup designed for characterization of a diamond film during its growth in a dc plasma jet chemical vapor deposition reactor is described. It is composed of a pulsed laser and the detector is gated in order to synchronize the Raman detection with the laser pulses. The optical components are designed for working in the visible and near UV. The installation is specially designed for remote detection and can be used in industrial reactors as well as in laboratory experiments. The detectivity of the setup is analyzed through some typical diamond spectra and it is shown that it is of the same order as that of a micro-Raman multichannel spectrometer. Some results are reported on how the temperature and the quality of the film can be controlled during the deposition process or during its etching by H2 reactive plasma. These results are discussed and confirmed by ex situ measurements including Raman, infrared, and scanning electron micrographs obtained on the same samples or in the same conditions as for in situ experiments. The secondary nucleation is responsible for the loss of Raman intensity and it could have some cyclic character.

  6. Controlled growth of MoS2 nanopetals on the silicon nanowire array using the chemical vapor deposition method

    Science.gov (United States)

    Chen, Shang-Min; Lin, Yow-Jon

    2018-01-01

    In order to get a physical/chemical insight into the formation of nanoscale semiconductor heterojunctions, MoS2 flakes are deposited on the silicon nanowire (SiNW) array by chemical vapor deposition (CVD). In this study, H2O2 treatment provides a favorable place where the formation of Sisbnd O bonds on the SiNW surfaces that play important roles (i.e., the nucleation centers, catalyst control centers or ;seeds;) can dominate the growth of MoS2 on the SiNWs. Using this configuration, the effect of a change in the S/MoO3 mass ratio (MS/MMoO3) on the surface morphology of MoS2 is studied. It is shown that an increase in the value of MS/MMoO3 leads to the increased nucleation rate, increasing the size of MoS2 nanopetals. This study provides valuable scientific information for directly CVD-grown edge-oriented MoS2/SiNWs heterojunctions for various nanoscale applications, including hydrogen evolution reaction and electronic and optoelectronic devices.

  7. Synthesis of carbon nanomaterials by catalytic chemical vapor deposition: growth mechanisms on metal powders and foils

    OpenAIRE

    Romero Rodríguez, Pablo

    2017-01-01

    Actualmente, las excelentes propiedades proporcionadas a escala nanométrica por los nanomateriales de carbono, como nanotubos y grafeno, motivan la propuesta teórica de un gran número de aplicaciones. Estos nanomateriales se pueden producir por deposición química en fase vapor (CVD), que consiste en la descomposición térmica de hidrocarburos sobre catalizadores metálicos. La técnica de CVD permite, a través del control de las condiciones de síntesis y la composición y morfología del catalizad...

  8. Epitaxial growth of HfS2 on sapphire by chemical vapor deposition and application for photodetectors

    Science.gov (United States)

    Wang, Denggui; Zhang, Xingwang; Liu, Heng; Meng, Junhua; Xia, Jing; Yin, Zhigang; Wang, Ye; You, Jingbi; Meng, Xiang-Min

    2017-09-01

    Group IVB transition metal (Zr and Hf) dichalcogenides (TMDs) have been attracting intensive attention as promising candidates in the modern electronic and/or optoelectronic fields. However, the controllable growth of HfS2 monolayers or few layers still remains a great challenge, thus hindering their further applications so far. Here, for the first time we demonstrate the epitaxial growth of high-quality HfS2 with a controlled number of layers on c-plane sapphire substrates by chemical vapor deposition (CVD). The HfS2 layers exhibit an atomically sharp interface with the sapphire substrate, followed by flat, 2D layers with octahedral coordination. The epitaxial relationship between HfS2 and substrate was determined by x-ray diffraction and transmission electron microscopy measurements to be: HfS2 (0 0 0 1) [10-10]||sapphire (0 0 0 1)[1-100]. Moreover, a high-performance photodetector with a high on/off ratio of more than 103 and an ultrafast response rate of 130 µs for the rise and 155 µs for the decay times were fabricated based on the CVD-grown HfS2 layers on sapphire substrates. This simple and controllable approach opens up a new way to produce highly crystalline HfS2 atomic layers, which are promising materials for nanoelectronics.

  9. Suppression of Graphene Nucleation by Turning Off Hydrogen Supply Just before Atmospheric Pressure Chemical Vapor Deposition Growth

    Directory of Open Access Journals (Sweden)

    Seiya Suzuki

    2017-11-01

    Full Text Available To exploit the extraordinary property of graphene in practical electrical and optical devices, it is necessary to produce large-sized, single-crystal graphene. Atmospheric pressure chemical vapor deposition (APCVD on polycrystalline Cu surface is a promising scalable route of graphene synthesis but the unavoidable multiple nucleation limits their reachable domain size. Here, we report that effective suppression of nucleation was achieved by only turning off hydrogen supply before introduction of the carbon source for graphene growth. The density of graphene decreased from 72.0 to 2.2 domains/cm2 by turning off hydrogen for 15 min. X-ray photoelectron spectroscopy and Raman spectroscopy studies show that the Cu surface was covered with 3–4 nm thick highly crystalline Cu2O, which would be caused by oxidation by residual oxidative gasses in the chamber during the turning off period. It was also revealed that elevating the temperature in Ar followed by annealing in H2/Ar before turning off hydrogen led to the enlargement of the Cu domain, resulting in the further suppression of nucleation. By optimizing such growth parameters in the CVD process, a single-crystal graphene with ~2.6 mm in diameter was successfully obtained.

  10. Recent Progress in the Growth of Mid-Infrared Emitters by Metal-Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Biefeld, R.M.; Allerman, A.A.; Kurtz, S.R.; Baucom, K.C.

    1998-01-01

    We report on recent progress and improvements in the metal-organic chemical vapor deposition (MOCVD) growth of mid-infrared lasers and using a high speed rotating disk reactor (RDR). The devices contain AlAsSb active regions. These lasers have multi-stage, type I InAsSb/InAsP quantum well active regions. A semi-metal GaAsSb/InAs layer acts as an internal electron source for the multi-stage injection lasers and AlAsSb is an electron confinement layer. These structures are the first MOCVD multi-stage devices. Growth in an RDR was necessary to avoid the previously observed Al memory effects found in conventional horizontal reactors. A single stage, optically pumped laser yielded improved power (greater than 650 mW/facet) at 80K and 3.8um. A multi-stage 3.8-3.9um laser structure operated up to T=170K. At 80K, peak power greater than 100mW and a high slope- efficiency were observed in gain guided lasers.

  11. Chemical vapor deposition of sialon

    Science.gov (United States)

    Landingham, R.L.; Casey, A.W.

    A laminated composite and a method for forming the composite by chemical vapor deposition are described. The composite includes a layer of sialon and a material to which the layer is bonded. The method includes the steps of exposing a surface of the material to an ammonia containing atmosphere; heating the surface to at least about 1200/sup 0/C; and impinging a gas containing N/sub 2/, SiCl/sub 4/, and AlCl/sub 3/ on the surface.

  12. Asymmetric growth of bilayer graphene on copper enclosures using low-pressure chemical vapor deposition.

    Science.gov (United States)

    Fang, Wenjing; Hsu, Allen L; Song, Yi; Birdwell, Anthony G; Amani, Matin; Dubey, Madan; Dresselhaus, Mildred S; Palacios, Tomás; Kong, Jing

    2014-06-24

    In this work, we investigated the growth mechanisms of bilayer graphene on the outside surface of Cu enclosures at low pressures. We observed that the asymmetric growth environment of a Cu enclosure can yield a much higher (up to 100%) bilayer coverage on the outside surface as compared to the bilayer growth on a flat Cu foil, where both sides are exposed to the same growth environment. By simultaneously examining the graphene films grown on both the outside and inside surfaces of the Cu enclosure, we find that carbon can diffuse from the inside surface to the outside via exposed copper regions on the inside surface. The kinetics of this process are examined by coupling the asymmetric growth between the two surfaces through a carbon diffusion model. Finally, using these results, we show that the coverage of bilayer graphene can be tuned simply by changing the thickness of the Cu foil, further confirming our model of carbon delivery through the Cu foil.

  13. Controlled Growth of Non-Uniform Arsenic Profiles in Silicon Reduced-Pressure Chemical Vapor Deposition Epitaxial Layers

    NARCIS (Netherlands)

    Popadic, M.; Scholtes, T.L.M.; De Boer, W.; Sarubbi, F.; Nanver, L.K.

    2009-01-01

    An empirical model of As surface segregation during reduced-pressure chemical vapor deposition Si epitaxy is presented. This segregation mechanism determines the resulting doping profile in the grown layer and is here described by a model of simultaneous and independent As adsorption and segregation

  14. Evaporation temperature-tuned physical vapor deposition growth engineering of one-dimensional non-Fermi liquid tetrathiofulvalene tetracyanoquinodimethane thin films

    DEFF Research Database (Denmark)

    Sarkar, I.; Laux, M.; Demokritova, J.

    2010-01-01

    We describe the growth of high quality tetrathiofulvalene tetracyanoquinodimethane (TTF-TCNQ) organic charge-transfer thin films which show a clear non-Fermi liquid behavior. Temperature dependent angle resolved photoemission spectroscopy and electronic structure calculations show that the growth...... of TTF-TCNQ films is accompanied by the unfavorable presence of neutral TTF and TCNQ molecules. The quality of the films can be controlled by tuning the evaporation temperature of the precursor in physical vapor deposition method....

  15. Quenching Phase Separation by Vapor Deposition Polymerization

    Science.gov (United States)

    Tao, Ran; Anthamatten, Mitchell

    2015-03-01

    Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique predominately used to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. We report a template-free method to fabricate continuous-phase porous polymer films by simultaneous phase separation during iCVD. Phase separation during film growth is achieved by condensing an inert porogen, along with initiator, monomer, and crosslinker. When the vapor mixture transports to the cooled substrate, phase separation occurs along with polymerization and crosslinking, which quench the state of phase separation. The kinetics of spontaneously phase separation can be qualitatively understood on the basis of Cahn-Hilliard theory. A series of films were grown by varying monomer and porogen's degree of saturation. Deposited films were studied by electron microscopy and spectroscopic techniques.

  16. Synthetic hierarchical nanostructures: growth of carbon nanofibers on microfibers by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Duan Huanan [Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Rd., Worcester, MA 01609 (United States); Liang Jianyu, E-mail: jianyul@wpi.ed [Department of Mechanical Engineering, Worcester Polytechnic Institute, 100 Institute Rd., Worcester, MA 01609 (United States); Xia Zhenhai [Department of Mechanical Engineering, College of Engineering, University of Akron, Akron, OH 44325 (United States)

    2010-02-15

    In this paper the synthesis of three-dimensional hierarchical nanostructures by pyrolysis of acetylene to grow carbon nanofibers (CNFs) on carbon microfibers (CMFs) and glass microfibers (GMFs) is reported. The morphology and structure of the as-prepared CNFs were studied by scanning electron microscopy and high-resolution transmission electron microscopy. CNFs grown on both substrates typically exhibited two types of morphology: the coil-like CNFs with frequent change in orientation and the relatively straight and long CNFs with parallel graphene sheets. The ethanol pretreatment was effective at improving the yield and distribution of the as-grown CNFs on CMFs, but showed an adverse effect to the CNF growth on GMFs. The influence of different substrates and growth temperatures on CNF morphology and the possible growth mechanism for the observed microstructures was discussed.

  17. Directed growth of graphene nanomesh in purified argon via chemical vapor deposition

    Science.gov (United States)

    Sun, Haibin; Fu, Can; Shen, Xia; Yang, Wenchao; Guo, Pengfei; Lu, Yang; Luo, Yongsong; Yu, Benhai; Wang, Xiaoge; Wang, Chunlei; Xu, Junqi; Liu, Jiangfeng; Song, Fengqi; Wang, Guanghou; Wan, Jianguo

    2017-06-01

    Graphene nanomeshes (GNMs), new graphene nanostructures with tunable bandgaps, are potential building blocks for future electronic or photonic devices, and energy storage and conversion materials. In previous works, GNMs have been successfully prepared on Cu foils by the H2 etching effect. In this paper, we investigated the effect of Ar on the preparation of GNMs, and how the mean density and shape of them vary with growth time. In addition, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM) revealed the typical hexagonal structure of GNM. Atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS) indicated that large copper oxide nanoparticles produced by oxidization in purified Ar can play an essential catalytic role in preparing GNMs. Then, we exhibited the key reaction details for each growth process and proposed a growth mechanism of GNMs in purified Ar.

  18. Epitaxial growth of aligned AlGalnN nanowires by metal-organic chemical vapor deposition

    Science.gov (United States)

    Han, Jung; Su, Jie

    2008-08-05

    Highly ordered and aligned epitaxy of III-Nitride nanowires is demonstrated in this work. M-axis is identified as a preferential nanowire growth direction through a detailed study of GaN/AlN trunk/branch nanostructures by transmission electron microscopy. Crystallographic selectivity can be used to achieve spatial and orientational control of nanowire growth. Vertically aligned (Al)GaN nanowires are prepared on M-plane AlN substrates. Horizontally ordered nanowires, extending from the M-plane sidewalls of GaN hexagonal mesas or islands demonstrate new opportunities for self-aligned nanowire devices, interconnects, and networks.

  19. The generation and detection of high flux atomic oxygen for physical vapor deposition thin film growth

    NARCIS (Netherlands)

    Ingle, N.J.C.; Hammond, R.H.; Beasley, M.R.; Blank, David H.A.

    1999-01-01

    The growth of many epitaxial thin-film oxides is significantly enhanced with the use of an oxidizing agent such as atomic oxygen, ozone, or NO2. We developed a flow-through microwave plasma source to generate large atomic oxygen fluxes while maintaining vacuum pressures of less that 1×10¿4 Torr.

  20. A Comparative Study of Three Different Chemical Vapor Deposition Techniques of Carbon Nanotube Growth on Diamond Films

    Directory of Open Access Journals (Sweden)

    Betty T. Quinton

    2013-01-01

    Full Text Available This paper compares between the methods of growing carbon nanotubes (CNTs on diamond substrates and evaluates the quality of the CNTs and the interfacial strength. One potential application for these materials is a heat sink/spreader for high-power electronic devices. The CNTs and diamond substrates have a significantly higher specific thermal conductivity than traditional heat sink/spreader materials making them good replacement candidates. Only limited research has been performed on these CNT/diamond structures and their suitability of different growth methods. This study investigates three potential chemical vapor deposition (CVD techniques for growing CNTs on diamond: thermal CVD (T-CVD, microwave plasma-enhanced CVD (MPE-CVD, and floating catalyst thermal CVD (FCT-CVD. Scanning electron microscopy (SEM and high-resolution transmission electron microscopy (TEM were used to analyze the morphology and topology of the CNTs. Raman spectroscopy was used to assess the quality of the CNTs by determining the ID/IG peak intensity ratios. Additionally, the CNT/diamond samples were sonicated for qualitative comparisons of the durability of the CNT forests. T-CVD provided the largest diameter tubes, with catalysts residing mainly at the CNT/diamond interface. The MPE-CVD process yielded non uniform defective CNTs, and FCT-CVD resulted in the smallest diameter CNTs with catalyst particles imbedded throughout the length of the nanotubes.

  1. Low-temperature chemical vapor deposition growth of graphene from toluene on electropolished copper foils.

    Science.gov (United States)

    Zhang, Bin; Lee, Wi Hyoung; Piner, Richard; Kholmanov, Iskandar; Wu, Yaping; Li, Huifeng; Ji, Hengxing; Ruoff, Rodney S

    2012-03-27

    A two-step CVD route with toluene as the carbon precursor was used to grow continuous large-area monolayer graphene films on a very flat, electropolished Cu foil surface at 600 °C, lower than any temperature reported to date for growing continuous monolayer graphene. Graphene coverage is higher on the surface of electropolished Cu foil than that on the unelectropolished one under the same growth conditions. The measured hole and electron mobilities of the monolayer graphene grown at 600 °C were 811 and 190 cm(2)/(V·s), respectively, and the shift of the Dirac point was 18 V. The asymmetry in carrier mobilities can be attributed to extrinsic doping during the growth or transfer. The optical transmittance of graphene at 550 nm was 97.33%, confirming it was a monolayer, and the sheet resistance was ~8.02 × 10(3) Ω/□. © 2012 American Chemical Society

  2. Growth of Boron-Rich Nanowires by Chemical Vapor Deposition (CVD

    Directory of Open Access Journals (Sweden)

    H. J. Kleebe

    2006-11-01

    Full Text Available B-rich nanowires are grown on Ni coated oxidized Si(111 substrate using diborane as the gas precursor in a CVD process at 20 torr and 900C∘. These nanowires have diameters around 20–100 nanometers and lengths up to microns. Icosahedron B12 is shown to be the basic building unit forming the amorphous B-rich nanowires as characterized by EDAX, XRD, XPS, and Raman spectroscopies. The gas chemistry at low [B2H6]/ [N2] ratio is monitored by the in situ mass spectroscopy, which identified N2 as an inert carrier gas leading to formation of the B-rich compounds. A nucleation controlled growth mechanism is proposed to explain the rugged nanowire growth of boron. The role of the Ni catalyst in the synthesis of the B-rich nanostructures is also discussed.

  3. Spiral Deposition with Alternating Indium Composition in Growing an InGaN Nanoneedle with the Vapor-Liquid-Solid Growth Mode

    Directory of Open Access Journals (Sweden)

    Wen-Ming Chang

    2012-01-01

    Full Text Available The spiral deposition of InGaN with a quasiperiodical distribution of indium content along the growth direction for forming InGaN nanoneedles (NNs with the vapor-liquid-solid (VLS growth mode is demonstrated. The VLS growth is implemented by using Au nanoparticles (NPs as the catalyst in metalorganic chemical vapor deposition. The Au NPs on a GaN template are generated through pulsed laser irradiation. The observation of spiral deposition is based on the analyses of the scanning results in the high angle annular dark field and energy dispersive X-ray measurements of transmission electron microscopy. In the measurements, the composition variations along and perpendicular to the growth direction (the c-axis are illustrated. The alternating indium content along the growth direction is attributed to a quasiperiodically pulsed behavior of indium supersaturation process in the melted Au NP at the top of an InGaN NN. The spiral deposition of InGaN is due to the formation of an NN at the location of an Au NP with a screw-type dislocation beneath in the GaN template, at which the growth of a quasi-one-dimensional structure can be easily initiated.

  4. Dislocation confinement in the growth of Na flux GaN on metalorganic chemical vapor deposition-GaN

    Science.gov (United States)

    Takeuchi, S.; Asazu, H.; Imanishi, M.; Nakamura, Y.; Imade, M.; Mori, Y.; Sakai, A.

    2015-12-01

    We have demonstrated a GaN growth technique in the Na flux method to confine c-, (a+c)-, and a-type dislocations around the interface between a Na flux GaN crystal and a GaN layer grown by metalorganic chemical vapor deposition (MOCVD) on a (0001) sapphire substrate. Transmission electron microscopy (TEM) clearly revealed detailed interface structures and dislocation behaviors that reduced the density of vertically aligned dislocations threading to the Na flux GaN surface. Submicron-scale voids were formed at the interface above the dislocations with a c component in MOCVD-GaN, while no such voids were formed above the a-type dislocations. The penetration of the dislocations with a c component into Na flux GaN was, in most cases, effectively blocked by the presence of the voids. Although some dislocations with a c component in the MOCVD-GaN penetrated into the Na flux GaN, their propagation direction changed laterally through the voids. On the other hand, the a-type dislocations propagated laterally and collectively near the interface, when these dislocations in the MOCVD-GaN penetrated into the Na flux GaN. These results indicated that the dislocation propagation behavior was highly sensitive to the type of dislocation, but all types of dislocations were confined to within several micrometers region of the Na flux GaN from the interface. The cause of void formation, the role of voids in controlling the dislocation behavior, and the mechanism of lateral and collective dislocation propagation are discussed on the basis of TEM results.

  5. Role of co-vapors in vapor deposition polymerization.

    Science.gov (United States)

    Lee, Ji Eun; Lee, Younghee; Ahn, Ki-Jin; Huh, Jinyoung; Shim, Hyeon Woo; Sampath, Gayathri; Im, Won Bin; Huh, Yang-Il; Yoon, Hyeonseok

    2015-02-12

    Polypyrrole (PPy)/cellulose (PPCL) composite papers were fabricated by vapor phase polymerization. Importantly, the vapor-phase deposition of PPy onto cellulose was assisted by employing different co-vapors namely methanol, ethanol, benzene, water, toluene and hexane, in addition to pyrrole. The resulting PPCL papers possessed high mechanical flexibility, large surface-to-volume ratio, and good redox properties. Their main properties were highly influenced by the nature of the co-vaporized solvent. The morphology and oxidation level of deposited PPy were tuned by employing co-vapors during the polymerization, which in turn led to change in the electrochemical properties of the PPCL papers. When methanol and ethanol were used as co-vapors, the conductivities of PPCL papers were found to have improved five times, which was likely due to the enhanced orientation of PPy chain by the polar co-vapors with high dipole moment. The specific capacitance of PPCL papers obtained using benzene, toluene, water and hexane co-vapors was higher than those of the others, which is attributed to the enlarged effective surface area of the electrode material. The results indicate that the judicious choice and combination of co-vapors in vapor-deposition polymerization (VDP) offers the possibility of tuning the morphological, electrical, and electrochemical properties of deposited conducting polymers.

  6. The growth and characterization of group III-nitride transistor devices grown by metalorganic chemical vapor deposition

    Science.gov (United States)

    Wong, Michael Ming

    The InAlGaN, or III-nitride, material system has received much interest from the research community. A direct wide bandgap semiconductor, GaN offers a high breakdown field (>3 x 106 V/cm) due to its large bandgap energy of 3.4 eV, high electron saturation velocity (1.5 x 10 7 cm/s, predicted peak up to 2.7 x 107 cm/s), good thermal conductivity (≥1.7 W/cm K), and reasonable mobility (800 cm 2/V s). In an AlGaN/GaN heterostructure, the formation of a two-dimensional electron gas (2DEG) leads to a higher electron mobility (2000 cm2/V s) and a high sheet density (1--5 x 1013 cm -2). This makes transistors based on the III-nitride material system ideal for high-temperature, high-power, and high-frequency applications. Two such transistors include the heterojunction field-effect transistor (HFET) and bipolar junction transistor (BJT), which includes the heterojunction bipolar transistor (HBT). Both HFETs and HBTs were studied, and the epitaxial heterostructures were grown by the metalorganic chemical vapor deposition (MOCVD) technique. The MOCVD process and system are described, along with the growth details. As material characterization is important for the optimization of growth, several of the techniques used are discussed. An extensive study to improve the performance of AlGaN/GaN HFETs is detailed. Through the use of a delta-doped, binary barrier novel device structure, the highest reported maximum drain current and transconductance is reported: IDSmax = 1.82 A/mm and gm = 331 mS/mm. The device also exhibits excellent RF characteristics. HBTs based on the III-nitride material system face a more difficult challenge associated with p-type material. Development of HBTs is still in the early stages, although there are reports of working devices. The gain is still below its potential, but many of the issues have been identified. Two novel structures are reported for the first time, a GaN/InGaN/GaN pnp HBT and a AlGaN/GaN npn graded-base and collector-up HBT. The

  7. Two step growth of high quality long n-GaN:Si nanowires using μ-GaN seed on Si(111) by metalorganic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min-Hee; Park, Ji-Hyeon; Yoo, Hee-il [Semiconductor Materials and Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development (RCAMD), Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Kissinger, Suthan [Department of General Studies, Physics Group, Jubail University College, Royal Commission for Jubail, Jubail 10074 (Saudi Arabia); Kim, Jin Soo; Baek, Byung June [Semiconductor Materials and Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development (RCAMD), Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Lee, Cheul-Ro, E-mail: crlee7@jbnu.ac.kr [Semiconductor Materials and Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development (RCAMD), Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2013-12-02

    A two-step growth method for growing high quality long n-GaN:Si nanowires (NWs) on Si(111) substrates using metalorganic chemical vapor deposition (MOCVD) was developed. In the primary step μ-GaN seeds were grown at 710 °C by pulsed growth method using MOCVD and in the secondary stage, we suitably increased the growth temperature to 950 °C in order to grow the high quality long n-GaN:Si NWs by continuous flow mode. We grew n-GaN:Si NWs at various pairs of μ-GaN seed so as to examine its effect on the growth rate. The density and length of n-GaN:Si NWs were improved with the increase of seeds up to 10 pairs. The number of seed pairs determines the density and length of n-GaN:Si NWs, but they did not affect its diameter directly. Field emission scanning electron microscopy, X-ray diffraction, photoluminescence, cathodoluminescence and high-resolution transmission electron microscopy were used to characterize the specimens. - Highlights: • Long n-GaN:Si nanowires were grown on Si(111). • Metalorganic chemical vapor deposition with two-step process was used. • Initially, μ-GaN seeds were grown at low temperature by pulsed growth method. • The temperature was increased to grow the long nanowires by continuous flow mode. • The effect of μ-GaN seed on the growth rate was examined.

  8. Analysis of the surface photoabsorption signal during self-limited submonolayer growth of InP in metalorganic chemical vapor deposition

    CERN Document Server

    Lee, T W; Moon, Y B; Yoon, E J; Kim, Y D

    1999-01-01

    In situ, real-time monitoring of InP atomic layer epitaxy (ALE) was performed in low-pressure metalorganic chemical vapor deposition (LP-MOCVD) by surface photoabsorption (SPA). A self-limiting adsorption condition was obtained from the trimethylindium (TMIn) decomposition experiment at various conditions. It was found that the growth rate was less than 1 monolayer (ML)/cycle. From the in situ, real-time SPA measurement during InP ALE, the incomplete PH sub 3 decomposition on the methyl-terminated In surface was attributed to the self-limiting submonolayer growth per cycle.

  9. Microwave plasma enhanced chemical vapor deposition growth of few-walled carbon nanotubes using catalyst derived from an iron-containing block copolymer precursor.

    Science.gov (United States)

    Wang, Peng; Lu, Jennifer; Zhou, Otto

    2008-05-07

    The microwave plasma enhanced chemical vapor deposition (MPECVD) method is now commonly used for directional and conformal growth of carbon nanotubes (CNTs) on supporting substrates. One of the shortcomings of the current process is the lack of control of the diameter and diameter distribution of the CNTs due to difficulties in synthesizing well-dispersed catalysts. Recently, block copolymer derived catalysts have been developed which offer the potential of fine control of both the size of and the spacing between the metal clusters. In this paper we report the successful growth of CNTs with narrow diameter distribution using polystyrene-block-polyferrocenylethylmethylsilane (PS-b-PFEMS) as the catalyst precursor. The study shows that higher growth pressure leads to better CNT growth. Besides the pressure, the effects on the growth of CNTs of the growth parameters, such as temperature and precursor gas ratio, are also studied.

  10. Bifunctional catalyst of graphite-encapsulated iron compound nanoparticle for magnetic carbon nanotubes growth by chemical vapor deposition

    Science.gov (United States)

    Saraswati, Teguh Endah; Prasiwi, Oktaviana Dewi Indah; Masykur, Abu; Anwar, Miftahul

    2017-01-01

    The carbon nanotube has widely taken great attractive in carbon nanomaterial research and application. One of its preparation methods is catalytic chemical vapor deposition (CCVD) using catalyst i.e. iron, nickel, etc. Generally, except the catalyst, carbon source gasses as the precursor are still required. Here, we report the use of the bifunctional material of Fe3O4/C which has an incorporated core/shell structures of carbon-encapsulated iron compound nanoparticles. The bifunctional catalyst was prepared by submerged arc discharge that simply performed using carbon and carbon/iron oxide electrodes in ethanol 50%. The prepared material was then used as a catalyst in thermal chemical vapor deposition at 800°C flown with ethanol vapor as the primer carbon source in a low-pressure condition. This catalyst might play a dual role as a catalyst and secondary carbon source for growing carbon nanotubes at the time. The synthesized products were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The successful formation of carbon nanotubes was assigned by the shifted X-ray diffracted peak of carbon C(002), the iron oxides of Fe3O4 and γ-Fe2O3, and the other peaks which were highly considered to the other carbon allotropes with sp2 hybridization structures. The other assignment was studied by electron microscopy which successfully observed the presence of single-wall carbon nanotubes. In addition, the as-prepared carbon nanotubes have a magnetic property which was induced by the remaining of metal catalyst inside the CNT.

  11. Parameters study on the growth of GaAs nanowires on indium tin oxide by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Dan; Tang, Xiaohong, E-mail: exhtang@ntu.edu.sg, E-mail: wangk@sustc.edu.cn; Li, Xianqiang [OPTIMUS, Photonics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Wang, Kai, E-mail: exhtang@ntu.edu.sg, E-mail: wangk@sustc.edu.cn [Department of Electrical & Electronic Engineering, South University of Science and Technology of China, 1088 Xueyuan Avenue, Shenzhen 518055 (China); Olivier, Aurelien [CINTRA UMI 3288, School of Electrical and Electronic Engineering, Nanyang Technological University, Research Techno Plaza, 50 Nanyang Drive, Border X Block, Level 6, 637553 Singapore (Singapore)

    2016-03-07

    After successful demonstration of GaAs nanowire (NW) epitaxial growth on indium tin oxide (ITO) by metal organic chemical vapor deposition, we systematically investigate the effect of growth parameters' effect on the GaAs NW, including temperature, precursor molar flow rates, growth time, and Au catalyst size. 40 nm induced GaAs NWs are observed with zinc-blende structure. Based on vapor-liquid-solid mechanism, a kinetic model is used to deepen our understanding of the incorporation of growth species and the role of various growth parameters in tuning the GaAs NW growth rate. Thermally activated behavior has been investigated by variation of growth temperature. Activation energies of 40 nm Au catalyst induced NWs are calculated at different trimethylgallium (TMGa) molar flow rates about 65 kJ/mol. The GaAs NWs growth rates increase with TMGa molar flow rates whereas the growth rates are almost independent of growth time. Due to Gibbs-Thomson effect, the GaAs NW growth rates increase with Au nanoparticle size at different temperatures. Critical radius is calculated as 2.14 nm at the growth condition of 430 °C and 1.36 μmol/s TMGa flow rate. It is also proved experimentally that Au nanoparticle below the critical radius such as 2 nm cannot initiate the growth of NWs on ITO. This theoretical and experimental growth parameters investigation enables great controllability over GaAs NWs grown on transparent conductive substrate where the methodology can be expanded to other III–V material NWs and is critical for potential hybrid solar cell application.

  12. Processing Research on Chemically Vapor Deposited Silicon Nitride.

    Science.gov (United States)

    1979-12-01

    34 sea urchins ") predominated, suggesting that formation was primarily from the vapor phase with little of the nodular growths seen at only slightly...deposition parameters on crystallite size, morphology and deposition rate. Geometries include a cold-wall, flat plate reactor (CW) and 4-inch and 1-inch...typical crossections of banded deposits and deposits which showed transitions from amorphous to crystalline morphologies , respectively. Figure 2-5

  13. Self-Catalyzed Growth of Vertical GaSb Nanowires on InAs Stems by Metal-Organic Chemical Vapor Deposition

    Science.gov (United States)

    Ji, Xianghai; Yang, Xiaoguang; Yang, Tao

    2017-06-01

    We report the first self-catalyzed growth of high-quality GaSb nanowires on InAs stems using metal-organic chemical vapor deposition (MOCVD) on Si (111) substrates. To achieve the growth of vertical InAs/GaSb heterostructure nanowires, the two-step flow rates of the trimethylgallium (TMGa) and trimethylantimony (TMSb) are used. We first use relatively low TMGa and TMSb flow rates to preserve the Ga droplets on the thin InAs stems. Then, the flow rates of TMGa and TMSb are increased to enhance the axial growth rate. Because of the slower radial growth rate of GaSb at higher growth temperature, GaSb nanowires grown at 500 °C exhibit larger diameters than those grown at 520 °C. However, with respect to the axial growth, due to the Gibbs-Thomson effect and the reduction in the droplet supersaturation with increasing growth temperature, GaSb nanowires grown at 500 °C are longer than those grown at 520 °C. Detailed transmission electron microscopy (TEM) analyses reveal that the GaSb nanowires have a perfect zinc-blende (ZB) crystal structure. The growth method presented here may be suitable for other antimonide nanowire growth, and the axial InAs/GaSb heterostructure nanowires may have strong potential for use in the fabrication of novel nanowire-based devices and in the study of fundamental quantum physics.

  14. One step growth of GaN/SiO2 core/shell nanowire in vapor-liquid-solid route by chemical vapor deposition technique

    Science.gov (United States)

    Barick, B. K.; Yadav, Shivesh; Dhar, S.

    2017-11-01

    GaN/SiO2 core/shell nanowires are grown by cobalt phthalocyanine catalyst assisted vapor-liquid-solid route, in which Si wafer coated with a mixture of gallium and indium is used as the source for Ga and Si and ammonia is used as the precursor for nitrogen and hydrogen. Gallium in the presence of indium and hydrogen, which results from the dissociation of ammonia, forms Si-Ga-In alloy at the growth temperature ∼910 °C. This alloy acts as the source of Si, Ga and In. A detailed study using a variety of characterization tools reveals that these wires, which are several tens of micron long, has a diameter distribution of the core ranging from 20 to 50 nm, while the thickness of the amorphous SiO2 shell layer is about 10 nm. These wires grow along [ 1 0 1 bar 0 ] direction. It has also been observed that the average diameter of these wires decreases, while their density increases as the gallium proportion in the Ga-In mixture is increased.

  15. Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza; Lee, Namhoon; Wolak, Matthäus A.; Tan, Teng; Welander, Paul B.; Franzi, Matthew; Tantawi, Sami; Kustom, Robert L.

    2017-02-16

    Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg–Cu alloy layer with occasional intrusion of Mg–Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.

  16. Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical-chemical vapor deposition

    Science.gov (United States)

    Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza; Lee, Namhoon; Wolak, Matthäus A.; Tan, Teng; Welander, Paul B.; Franzi, Matthew; Tantawi, Sami; Kustom, Robert L.

    2017-04-01

    Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20-25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical-chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg-Cu alloy layer with occasional intrusion of Mg-Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.

  17. Chemical Vapor Deposition Growth of Degenerate p-Type Mo-Doped ReS2 Films and Their Homojunction.

    Science.gov (United States)

    Qin, Jing-Kai; Shao, Wen-Zhu; Xu, Cheng-Yan; Li, Yang; Ren, Dan-Dan; Song, Xiao-Guo; Zhen, Liang

    2017-05-10

    Substitutional doping of transition metal dichalcogenide two-dimensional materials has proven to be effective in tuning their intrinsic properties, such as band gap, transport characteristics, and magnetism. In this study, we realized substitutional doping of monolayer rhenium disulfide (ReS2) with Mo via chemical vapor deposition. Scanning transmission electron microscopy demonstrated that Mo atoms are successfully doped into ReS2 by substitutionally replacing Re atoms in the lattice. Electrical measurements revealed the degenerate p-type semiconductor behavior of Mo-doped ReS2 field effect transistors, in agreement with density functional theory calculations. The p-n diode device based on a doped ReS2 and ReS2 homojunction exhibited gate-tunable current rectification behaviors, and the maximum rectification ratio could reach up to 150 at Vd = -2/+2 V. The successful synthesis of p-type ReS2 in this study could largely promote its application in novel electronic and optoelectronic devices.

  18. Ga N nano wires and nano tubes growth by chemical vapor deposition method at different NH{sub 3} flow rate

    Energy Technology Data Exchange (ETDEWEB)

    Li, P.; Liu, Y.; Meng, X. [Wuhan University, School of Physics and Technology, Key Laboratory of Artificial Micro and Nanostructures of Ministry of Education, Wuhan 430072 (China)

    2016-11-01

    Ga N nano wires and nano tubes have been successfully synthesized via the simple chemical vapor deposition method. NH{sub 3} flow rate was found to be a crucial factor in the synthesis of different type of Ga N which affects the shape and the diameter of generated Ga N nano structures. X-ray diffraction confirms that Ga N nano wires grown on Si(111) substrate under 900 degrees Celsius and with NH{sub 3} flow rate of 50 sc cm presents the preferred orientation growth in the (002) direction. It is beneficial to the growth of nano structure through catalyst annealing. Transmission electron microscopy and scanning electron microscopy were used to measure the size and structures of the samples. (Author)

  19. Microstructure of vapor deposited coatings on curved substrates

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, Theron M.; Zhao, Hengbei; Wadley, Haydn N. G., E-mail: haydn@virginia.edu [Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., P.O. Box 400745, Charlottesville, Virginia 22904 (United States)

    2015-09-15

    Thermal barrier coating systems consisting of a metallic bond coat and ceramic over layer are widely used to extend the life of gas turbine engine components. They are applied using either high-vacuum physical vapor deposition techniques in which vapor atoms rarely experience scattering collisions during propagation to a substrate, or by gas jet assisted (low-vacuum) vapor deposition techniques that utilize scattering from streamlines to enable non-line-of-sight deposition. Both approaches require substrate motion to coat a substrate of complex shape. Here, direct simulation Monte Carlo and kinetic Monte Carlo simulation methods are combined to simulate the deposition of a nickel coating over the concave and convex surfaces of a model airfoil, and the simulation results are compared with those from experimental depositions. The simulation method successfully predicted variations in coating thickness, columnar growth angle, and porosity during both stationary and substrate rotated deposition. It was then used to investigate a wide range of vapor deposition conditions spanning high-vacuum physical vapor deposition to low-vacuum gas jet assisted vapor deposition. The average coating thickness was found to increase initially with gas pressure reaching a maximum at a chamber pressure of 8–10 Pa, but the best coating thickness uniformity was achieved under high vacuum deposition conditions. However, high vacuum conditions increased the variation in the coatings pore volume fraction over the surface of the airfoil. The simulation approach was combined with an optimization algorithm and used to investigate novel deposition concepts to tailor the local coating thickness.

  20. Characterization of Metalorganic Chemical Vapor Deposition

    Science.gov (United States)

    Jesser, W. A.

    1998-01-01

    A series of experimental and numerical investigations to develop a more complete understanding of the reactive fluid dynamics of chemical vapor deposition were conducted. In the experimental phases of the effort, a horizontal CVD reactor configuration was used for the growth of InP at UVA and for laser velocimetry measurements of the flow fields in the reactor at LaRC. This horizontal reactor configuration was developed for the growth of III-V semiconductors and has been used by our research group in the past to study the deposition of both GaAs and InP. While the ultimate resolution of many of the heat and mass transport issues will require access to a reduced-gravity environment, the series of groundbased research makes direct contributions to this area while attempting to answer the design questions for future experiments of how low must gravity be reduced and for how long must this gravity level be maintained to make the necessary measurements. It is hoped that the terrestrial experiments will be useful for the design of future microgravity experiments which likely will be designed to employ a core set of measurements for applications in the microgravity environment such as HOLOC, the Fluid Physics/Dynamics Facility, or the Schlieren photography, the Laser Imaging Velocimetry and the Laser Doppler Velocimetry instruments under development for the Advanced Fluids Experiment Module.

  1. The influence of charge effect on the growth of hydrogenated amorphous silicon by the hot-wire chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Q.; Nelson, B.P.; Iwaniczko, E.; Mahan, A.H.; Crandall, R.S.; Benner, J. [National Renewable Energy Lab., Golden, CO (United States)

    1998-09-01

    The authors observe at lower substrate temperatures that the scatter in the dark conductivity on hydrogenated amorphous silicon (a-Si:H) films grown on insulating substrates (e.g., Corning 7059 glass) by the hot-wire chemical vapor deposition technique (HWCVD) can be five orders of magnitude or more. This is especially true at deposition temperatures below 350 C. However, when the authors grow the same materials on substrates with a conductive grid, virtually all of their films have acceptable dark conductivity (< 5 {times} 10{sup {minus}10} S/cm) at all deposition temperatures below 425 C. This is in contrast to only about 20% of the materials grown in this same temperature range on insulating substrates having an acceptable dark conductivity. The authors estimated an average energy of 5 eV electrons reaching the growing surface in vacuum, and did additional experiments to see the influence of both the electron flux and the energy of the electrons on the film growth. Although these effects do not seem to be important for growing a-Si:H by HWCVD on conductive substrates, they help better understand the important parameters for a-Si:H growth, and thus, to optimize these parameters in other applications of HWCVD technology.

  2. Porphyrins as Templates for Site-Selective Atomic Layer Deposition: Vapor Metalation and in Situ Monitoring of Island Growth

    Energy Technology Data Exchange (ETDEWEB)

    Avila, Jason R.; Emery, Jonathan D.; Pellin, Michael J.; Martinson, Alex B. F.; Farha, Omar K.; Hupp, Joseph T.

    2016-08-10

    Examinations of enzymatic catalysts suggest one key to efficient catalytic activity is discrete size metallo clusters. Mimicking enzymatic cluster systems is synthetically challenging because conventional solution methods are prone to aggregation or require capping of the cluster, thereby limiting its catalytic activity. We introduce site-selective atomic layer deposition (ALD) on porphyrins as an alternative approach to grow isolated metal oxide islands that are spatially separated. Surface-bound tetra-acid free base porphyrins (H2TCPP) may be metalated with Mn using conventional ALD precursor exposure to induce homogeneous hydroxide synthetic handles which acts as a nucleation point for subsequent ALD MnO island growth. Analytical fitting of in situ QCM mass uptake reveals island growth to be hemispherical with a convergence radius of 1.74 nm. This growth mode is confirmed with synchrotron grazing-incidence small-angle X-ray scattering (GISAXS) measurements. Finally, we extend this approach to other ALD chemistries to demonstrate the generality of this route to discrete metallo island materials.

  3. Controllable growth of monolayer MoS2 by chemical vapor deposition via close MoO2 precursor for electrical and optical applications.

    Science.gov (United States)

    Xie, Yong; Wang, Zhan; Zhan, Yongjie; Zhang, Peng; Wu, Ruixue; Jiang, Teng; Wu, Shiwei; Wang, Hong; Zhao, Ying; Nan, Tang; Ma, Xiaohua

    2017-02-24

    MoO2 is used as a new source material for the growth of large area and high optical quality monolayer MoS2. However, a systematic study of the growth parameters is still missing and large-area growth of discreet single crystals is still challenging. Hereby, we report the shape evolution of monolayer growth of MoS2 and develop a methodology to achieve centimeter-scaled discrete MoS2 by adopting MoO2 as Mo source material in an atmospheric-pressure chemical vapor deposition process. Our results indicate the growth of monolayer MoS2 could benefit from the precise control of the introduction time of sulfur and the S/MoO2 ratio in experiments. Micro-Raman and photoluminescence spectra confirm the properties of the material. E-beam lithography was utilized to make contact with the as-grown MoS2 located at the selective area. The electrical properties of MoS2 with different morphologies were compared. In the end, the persistent photoconductivity properties of monolayer MoS2 were emphasized and the underlying mechanism was proposed. These studies demonstrate a better understanding of the growth and application of MoS2-based 2D materials.

  4. Effect of Growth Pressure on Epitaxial Graphene Grown on 4H-SiC Substrates by Using Ethene Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Shuxian Cai

    2015-08-01

    Full Text Available The Si(0001 face and C(000-1 face dependences on growth pressure of epitaxial graphene (EG grown on 4H-SiC substrates by ethene chemical vapor deposition (CVD was studied using atomic force microscopy (AFM and micro-Raman spectroscopy (μ-Raman. AFM revealed that EGs on Si-faced substrates had clear stepped morphologies due to surface step bunching. However, This EG formation did not occur on C-faced substrates. It was shown by μ-Raman that the properties of EG on both polar faces were different. EGs on Si-faced substrates were relatively thinner and more uniform than on C-faced substrates at low growth pressure. On the other hand, D band related defects always appeared in EGs on Si-faced substrates, but they did not appear in EG on C-faced substrate at an appropriate growth pressure. This was due to the μ-Raman covering the step edges when measurements were performed on Si-faced substrates. The results of this study are useful for optimized growth of EG on polar surfaces of SiC substrates.

  5. Automated semiconductor vacuum chemical vapor deposition facility

    Science.gov (United States)

    1982-01-01

    A semiconductor vacuum chemical vapor deposition facility (totally automatic) was developed. Wafers arrived on an air track, automatically loaded into a furnace tube, processed, returned to the track, and sent on to the next operation. The entire process was controlled by a computer.

  6. Dynamics of faceted thin films formation during vapor deposition

    Science.gov (United States)

    Li, Kun-Dar; Huang, Po-Yu

    2018-01-01

    In this study, an anisotropic phase-field model was established to simulate the growth of crystalline thin films during vapor deposition. The formation and evolution of characteristic surface with faceted morphologies were demonstrated, in accordance with the regularly obtained microstructure in the actual experiments. In addition, the influences of deposition parameters, such as the deposition rate and the interfacial energy, on the formation mechanism of the characteristic morphology were also illustrated. While a relatively low surface energy of substrate was regarded, the faceted islands were formed, owing to the anisotropic interfacial energy of thin films. In the condition of a high surface energy of substrate, the layered structures of deposited films were produced, which was corresponding to the Frank–van der Merwe growth mode. As various deposition rates were utilized in the numerical simulations, diverse surface morphologies were developed on the basis of the dominant mechanisms, correlating with the adatom diffusion and the deposition kinetics. According to the calculation results, it was observed that a surface character with flattened morphology was generally driven by the adatom diffusion, while the factor of the deposition kinetics was inclined to roughen the surface of thin films. These numerical simulations enhanced the knowledge of thin film growth and facilitated the progress of the vapor deposition technology for advanced applications.

  7. Remote nitrogen microwave plasma chemical vapor deposition from a tetramethyl disilazane precursor. 1. Growth mechanism, structure, and surface morphology of silicon carbonitride films

    Energy Technology Data Exchange (ETDEWEB)

    Blaszczyk-Lezak, I. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland); Wrobel, A.M. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland)]. E-mail: amwrobel@bilbo.cbmm.lodz.pl; Aoki, T. [Research Institute of Electronics, Shizuoka University, Hamamatsu 432 (Japan); Nakanishi, Y. [Research Institute of Electronics, Shizuoka University, Hamamatsu 432 (Japan); Kucinska, I.; Tracz, A

    2006-02-21

    Silicon carbonitride (Si:C:N) films were produced by remote microwave nitrogen plasma chemical vapor deposition (RP-CVD) using a 1,1,3,3-tetramethyldisilazane precursor. The reactivity the precursor with atomic nitrogen was characterized using hexamethyldisilazane as a model compound. The effect of the substrate temperature (T {sub S}) on the kinetics of the RP-CVD process, chemical composition, structure, and surface morphology of resulting film has been investigated. The temperature dependencies of the mass- and thickness-based film growth rate imply that for low substrate temperature range (T {sub S} = 30-200 deg. C) film growth is limited by desorption of film-forming precursors, whereas in high substrate temperature range (T {sub S} = 200-400 deg. C) film growth is independent of the temperature and the rate of RP-CVD is mass-transport limited. The increase of the substrate temperature from 30 to 400 deg. C causes the elimination of organic moieties from the film and the formation of Si-N and Si-C network structure. The hypothetical chemical reactions contributing to film formation are discussed. The films were found to be morphologically homogeneous materials exhibiting very small surface roughness for higher substrate temperatures (T {sub S} 200-400 deg. C)

  8. Optimization of growth conditions for InGaAs/InAlAs/InP quantum cascade lasers by metalorganic chemical vapor deposition

    Science.gov (United States)

    Huang, Yong; Ryou, Jae-Hyun; Dupuis, Russell D.; Pflügl, Christian; Capasso, Federico; Sun, Kewei; Fischer, Alec M.; Ponce, Fernando A.

    2011-02-01

    We investigate the growth conditions for lattice-matched InGaAs/InAlAs/InP quantum cascade lasers (QCLs) by metalorganic chemical vapor deposition (MOCVD). Effect of substrate misorientation, growth temperature, and V/III ratios of InGaAs and InAlAs layers on the surface morphology, optical quality, and impurity incorporation were systematically studied. It was found that epitaxial layers and multi-quantum-well structures grown at 720 °C with V/III ratios of 116 for InGaAs and 21 for InAlAs on InP substrates with an off-cut angle of ˜0.06° exhibit a stable step-flow growth and low oxygen and carbon contamination. Using these conditions, a ˜11.3-μm-thick QCL with an emission wavelength at ˜9.2 μm was grown and fabricated, which demonstrated excellent structural quality and operated at room temperature in pulsed mode with a threshold current density of 2.0 kA/cm 2 and a slope efficiency of 550 mW/A.

  9. Atmospheric-pressure plasma-enhanced chemical vapor deposition of a-SiCN:H films: role of precursors on the film growth and properties.

    Science.gov (United States)

    Guruvenket, Srinivasan; Andrie, Steven; Simon, Mark; Johnson, Kyle W; Sailer, Robert A

    2012-10-24

    Atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) using Surfx Atomflow(TM) 250D APPJ was utilized to synthesize amorphous silicon carbonitride coatings using tetramethyldisilizane (TMDZ) and hexamethyldisilizane (HMDZ) as the single source precursors. The effect of precursor chemistry and substrate temperature (T(s)) on the properties of a-SiCN:H films were evaluated, while nitrogen was used as the reactive gas. Surface morphology of the films was evaluated using atomic force microscopy (AFM); chemical properties were determined using Fourier transform infrared spectroscopy (FTIR); thickness and optical properties were determined using spectroscopic ellipsometry and mechanical properties were determined using nanoindentation. In general, films deposited at substrate temperature (T(s)) films deposited at T(s) > 200 °C depicted strong Si-N and Si-CN absorption. Refractive indices (n) of the thin films showed values between 1.5 and 2.0, depending on the deposition parameters. Mechanical properties of the films determined using nanoindentation revealed that these films have hardness between 0.5 GPa and 15 GPa, depending on the T(s) value. AFM evaluation of the films showed high roughness (R(a)) values of 2-3 nm for the films grown at low T(s) (films grown at T(s) ≥ 300 °C exhibited atomically smooth surface with R(a) of ~0.5 nm. Based on the gas-phase (plasma) chemistry, precursor chemistry and the other experimental observations, a possible growth model that prevails in the AP-PECVD of a-SiCN:H thin films is proposed.

  10. GeSn growth kinetics in reduced pressure chemical vapor deposition from Ge2H6 and SnCl4

    Science.gov (United States)

    Aubin, J.; Hartmann, J. M.

    2018-01-01

    We have investigated the low temperature epitaxy of high Sn content GeSn alloys in a 200 mm industrial Reduced Pressure - Chemical Vapor Deposition tool from Applied Materials. Gaseous digermane (Ge2H6) and liquid tin tetrachloride (SnCl4) were used as the Ge and Sn precursors, respectively. The impact of temperature (in the 300-350 °C range), Ge2H6 and SnCl4 mass-flows on the GeSn growth kinetics at 100 Torr has been thoroughly explored. Be it at 300 °C or 325 °C, a linear GeSn growth rate increase together with a sub-linear Sn concentration increase occurred as the SnCl4 mass-flow increased, irrespective of the Ge2H6 mass flow (fixed or varying). The Sn atoms seemed to catalyze H desorption from the surface, resulting in higher GeSn growth rates for high SnCl4 mass-flows (in the 4-21 nm min-1 range). The evolution of the Sn content x with the F (SnCl4) 2 ·/F (Ge2H6) mass-flow ratio was fitted by x2/(1 - x) = n ·F (SnCl4) 2 ·/F (Ge2H6), with n = 0.25 (325 °C) and 0.60 (300 °C). We have otherwise studied the impact of temperature, in the 300-350 °C range, on the GeSn growth kinetics. The GeSn growth rate exponentially increased with the temperature, from 15 up to 32 nm min-1. The associated activation energy was low, i.e. Ea = 10 kcal mol-1. Meanwhile, the Sn content decreased linearly as the growth temperature increased, from 15% at 300 °C down to 6% at 350 °C.

  11. Vapor-deposited porous films for energy conversion

    Science.gov (United States)

    Jankowski, Alan F.; Hayes, Jeffrey P.; Morse, Jeffrey D.

    2005-07-05

    Metallic films are grown with a "spongelike" morphology in the as-deposited condition using planar magnetron sputtering. The morphology of the deposit is characterized by metallic continuity in three dimensions with continuous and open porosity on the submicron scale. The stabilization of the spongelike morphology is found over a limited range of the sputter deposition parameters, that is, of working gas pressure and substrate temperature. This spongelike morphology is an extension of the features as generally represented in the classic zone models of growth for physical vapor deposits. Nickel coatings were deposited with working gas pressures up 4 Pa and for substrate temperatures up to 1000 K. The morphology of the deposits is examined in plan and in cross section views with scanning electron microscopy (SEM). The parametric range of gas pressure and substrate temperature (relative to absolute melt point) under which the spongelike metal deposits are produced appear universal for other metals including gold, silver, and aluminum.

  12. Chemical vapor deposition coating for micromachines

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-04-21

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

  13. Self-assembled growth and structural analysis of inclined GaN nanorods on nanoimprinted m-sapphire using catalyst-free metal-organic chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Kyuseung Lee

    2016-04-01

    Full Text Available In this study, self-assembled inclined (1-10-3-oriented GaN nanorods (NRs were grown on nanoimprinted (10-10 m-sapphire substrates using catalyst-free metal-organic chemical vapor deposition. According to X-ray phi-scans, the inclined GaN NRs were tilted at an angle of ∼57.5° to the [10-10]sapp direction. Specifically, the GaN NRs grew in a single inclined direction to the [11-20]sapp. Uni-directionally inclined NRs were formed through the one-sided (10-11-faceted growth of the interfacial a-GaN plane layer. It was confirmed that a thin layer of a-GaN was formed on r-facet nanogrooves of the m-sapphire substrate by nitridation. The interfacial a-GaN nucleation affected both the inclined angle and the growth direction of the inclined GaN NRs. Using X-ray diffraction and selective area electron diffraction, the epitaxial relationship between the inclined (1-10-3 GaN NRs and interfacial a-GaN layer on m-sapphire substrates was systematically investigated. Moreover, the inclined GaN NRs were observed to be mostly free of stacking fault-related defects using high-resolution transmission electron microscopy.

  14. Effect of Two-Step Metal Organic Chemical Vapor Deposition Growth on Quality, Diameter and Density of InAs Nanowires on Si (111) Substrate

    Science.gov (United States)

    Yu, Hung Wei; Anandan, Deepak; Hsu, Ching Yi; Hung, Yu Chih; Su, Chun Jung; Wu, Chien Ting; Kakkerla, Ramesh Kumar; Ha, Minh Thien Huu; Huynh, Sa Hoang; Tu, Yung Yi; Chang, Edward Yi

    2017-10-01

    High-density (˜ 80/um2) vertical InAs nanowires (NWs) with small diameters (˜ 28 nm) were grown on bare Si (111) substrates by means of two-step metal organic chemical vapor deposition. There are two critical factors in the growth process: (1) a critical nucleation temperature for a specific In molar fraction (approximately 1.69 × 10-5 atm) is the key factor to reduce the size of the nuclei and hence the diameter of the InAs NWs, and (2) a critical V/III ratio during the 2nd step growth will greatly increase the density of the InAs NWs (from 45 μm-2 to 80 μm-2) and at the same time keep the diameter small. The high-resolution transmission electron microscopy and selected area diffraction patterns of InAs NWs grown on Si exhibit a Wurtzite structure and no stacking faults. The observed longitudinal optic peaks in the Raman spectra were explained in terms of the small surface charge region width due to the small NW diameter and the increase of the free electron concentration, which was consistent with the TCAD program simulation of small diameter (< 40 nm) InAs NWs.

  15. Modeling of chemical vapor deposition. I. General considerations

    Science.gov (United States)

    Korec, J.; Heyen, M.

    1982-12-01

    In this study a general analysis of chemical vapor deposition (CVD) processes carried out in open flow systems is presented. In this treatment the successive process steps, namely mass transport in the gas phase, adsorption, chemical reaction and surface diffusion are included. The proposed approach allows computation of the activity of the material to be deposited; this quantity is determined by a balance between the rates of gas phase diffusion and of surface processes. An expression is presented relating the activity near the interface to the growth rate of the deposited layer. It is shown that the same approach can be used for etching conditions.

  16. Epitaxial growth of SrTiO3/YBa2Cu3O7 - x heterostructures by plasma-enhanced metalorganic chemical vapor deposition

    Science.gov (United States)

    Liang, S.; Chern, C. S.; Shi, Z. Q.; Lu, P.; Safari, A.; Lu, Y.; Kear, B. H.; Hou, S. Y.

    1994-06-01

    We report heteroepitaxial growth of SrTiO3 on YBa2Cu3O7-x/LaAlO3 substrates by plasma-enhanced metalorganic chemical vapor deposition. X-ray diffraction results indicated that SrTiO3 films were epitaxially grown on a (001) YBa2Cu3O7-x surface with [100] orientation perpendicular to the surface. The film composition, with Sr/Ti molar ratio in the range of 0.9 to 1.1, was determined by Rutherford backscattering spectrometry and energy dispersive spectroscopy. The thickness of the SrTiO3 films is 0.1-0.2 μm. The epitaxial growth was further evidenced by high-resolution transmission electron microscopy and selected area diffraction. Atomically abrupt SrTiO3/YBa2Cu3O7-x interface and epitaxial growth with [100]SrTiO3∥[001]YBa2Cu3O7-x were observed in this study. The superconducting transition temperature of the bottom YBa2Cu3O7-x layer, as measured by ac susceptometer, did not significantly degrade after the growth of overlayer SrTiO3. The capacitance-voltage measurements showed that the dielectric constant of the SrTiO3 films was as high as 315 at a signal frequency of 100 KHz. The leakage current density through the SrTiO3 films is about 1×10-6 A/cm2 at 2-V operation. Data analysis on the current-voltage characteristic indicated that the conduction process is related to bulk-limited Poole-Frenkel emission.

  17. Structural evolution during chemical vapor deposition of diamond thin films

    Science.gov (United States)

    Morell, G.; Cancel, L. M.; Figueroa, O. L.; González, J. A.; Weiner, B. R.

    2000-11-01

    In situ phase-modulated ellipsometry was employed to monitor the nucleation and growth processes of diamond thin films fabricated by chemical vapor deposition. The effective extinction coefficient (k) at 1.96 eV was used as a basis for dividing the deposition process into intervals. The film growth was aborted at various k values yielding diamond film samples that represent snapshots of the growth process at different stages. Ex situ characterization of the films was performed using Raman spectroscopy, scanning electron microscopy, and x-ray diffraction. The results indicate that the diamond film deposition process consists of various stages in which the crystalline quality, the net compressive stress, and the relative amount of non-sp3 carbon follow different trends. A correlation between the effective k value measured in situ and the film microstructure characterized ex situ was established which enables the monitoring of the diamond film growth process in real time.

  18. Tellurization Velocity-Dependent Metallic-Semiconducting-Metallic Phase Evolution in Chemical Vapor Deposition Growth of Large-Area, Few-Layer MoTe2.

    Science.gov (United States)

    Yang, Li; Zhang, Wenfeng; Li, Jie; Cheng, Shuai; Xie, Zijian; Chang, Haixin

    2017-02-28

    Phase engineering of two-dimensional (2D) transition metal dichalcogenides (TMDs) such as MoTe2 offers tremendous opportunities in various device applications. However, most of the existing methods so far only address the small-area local phase change or the growth of certain kinds of phases of MoTe2 film by laser irradiation, mechanical strain, or procursor type. Obtaining facile, tunable, reversible, and continuous-phase transition and evolution between different phases in direct growth of large-area, few-layer MoTe2 still remains challenging. Here, we develop a facile method to achieve phase control and transition and report a highly tunable, tellurization velocity-dependent metallic-semiconducting-metallic phase evolution in chemical vapor deposition (CVD) growth of large-area, few-layer MoTe2. We found four different phase stages, including two different types of coexistence phases of both 2H and 1 T' phases, 100% 2H phase, and 100% 1T' phase, would emerge, relying on the adopted tellurization velocity. Importantly, the tellurization velocity should be extremely controlled to obtain 100% 2H phase MoTe2, while 100% 1T' phase requires a fast tellurization velocity. We further found that such metallic-semiconducting-metallic phase evolution took place with a homogeneous spatial distribution and differs from previous reports in which obvious phase separations are usually found during the phase transition. The resulting MoTe2 shows high quality with room-temperature mobility comparable with mechanically exfoliated materials. The results might impact large-scale phase engineering of TMDs and other 2D materials for Weyl semimetal topological physics and potential 2D semiconductor device applications.

  19. The Effect of Alumina and Magnesia Supported Germanium Nanoparticles on the Growth of Carbon Nanotubes in the Chemical Vapor Deposition Method

    Directory of Open Access Journals (Sweden)

    Ghazaleh Allaedini

    2015-01-01

    Full Text Available The effect of alumina and magnesia supported germanium (Ge nanoparticles on the synthesis of carbon nanotubes (CNTs using the chemical vapor deposition (CVD method in atmospheric pressure was investigated. The TEM micrographs confirmed the formation of carbon nanotubes, and the field emission scanning electron microscopy (FESEM analysis suggested a tip-growth mechanism for the grown carbon nanotubes. The X-ray diffraction (XRD pattern indicated a graphitic nature of the carbon nanotubes. The obtained CNTs using Ge nanoparticles supported by MgO resulted in a higher degree of graphitization than the CNTs obtained using Ge nanoparticles supported by Al2O3. Raman spectroscopy analysis of the CNTs confirmed the presence of radial breathing modes (RBM, which verified the formation of CNTs. High frequency Raman analysis demonstrated that the degree of graphitization of the synthesized CNTs using magnesia supported Ge nanoparticles is higher than that of the alumina supported Ge nanoparticles with the values of (ID/IG ratios equal to 0.45 and 0.73, respectively.

  20. Gallium assisted plasma enhanced chemical vapor deposition of silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Zardo, I; Roessler, J; Frimmer, M; Fontcuberta i Morral, A [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall, D-85748 Garching (Germany); Yu, L; Alet, Pierre Jean; Roca i Cabarrocas, P [LPICM, Ecole Polytechnique, CNRS, F-91128 Palaiseau (France); Conesa-Boj, S; Estrade, S; Peiro, F; Arbiol, J; Morante, J R [EME/XaRMAE/IN2UB, Departamento d' Electronica, Universitat de Barcelona, MartIi Franques, E-08028, Barcelona (Spain)

    2009-04-15

    Silicon nanowires have been grown with gallium as catalyst by plasma enhanced chemical vapor deposition. The morphology and crystalline structure has been studied by electron microscopy and Raman spectroscopy as a function of growth temperature and catalyst thickness. We observe that the crystalline quality of the wires increases with the temperature at which they have been synthesized. The crystalline growth direction has been found to vary between <111> and <112>, depending on both the growth temperature and catalyst thickness. Gallium has been found at the end of the nanowires, as expected from the vapor-liquid-solid growth mechanism. These results represent good progress towards finding alternative catalysts to gold for the synthesis of nanowires.

  1. Pendeo-epitaxial growth of GaN on SiC and silicon substrates via metalorganic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Linthicum, K.J.; Gehrke, T.; Thomson, D.; Ronning, C.; Carlson, E.P.; Zorman, C.A.; Mehregany, M.; Davis, R.F.

    1999-07-01

    Pendeo-epitaxial lateral growth (PE) of GaN epilayers on (0001) 6H-silicon carbide and (111) Si substrates has been achieved. Growth on the latter substrate was accomplished through the use of a 3C-SiC transition layer. The coalesced PE GaN epilayers were characterized using scanning electron diffraction, x-ray diffraction and photoluminescence spectroscopy. The regions of lateral growth exhibited {approximately} 0.2{degree} crystallographic tilt relative to the seed layer. The GaN seed and PE epilayers grown on the 3C-SiC/Si substrates exhibited comparable optical characteristics to the GaN seed and PE grown on 6H-SiC substrates. The near band-edge emission of the GaN/3C-SiC/Si seed was 3.450 eV (FWHM {approximately} 19 meV) and the GaN/6H-SiC seed was 3.466 eV (FWHM {approximately} 4 meV).

  2. Chemical vapor deposition of group IIIB metals

    Science.gov (United States)

    Erbil, A.

    1989-11-21

    Coatings of Group IIIB metals and compounds thereof are formed by chemical vapor deposition, in which a heat decomposable organometallic compound of the formula given in the patent where M is a Group IIIB metal, such as lanthanum or yttrium and R is a lower alkyl or alkenyl radical containing from 2 to about 6 carbon atoms, with a heated substrate which is above the decomposition temperature of the organometallic compound. The pure metal is obtained when the compound of the formula 1 is the sole heat decomposable compound present and deposition is carried out under nonoxidizing conditions. Intermetallic compounds such as lanthanum telluride can be deposited from a lanthanum compound of formula 1 and a heat decomposable tellurium compound under nonoxidizing conditions.

  3. Inclined angle-controlled growth of GaN nanorods on m-sapphire by metal organic chemical vapor deposition without a catalyst.

    Science.gov (United States)

    Lee, Kyuseung; Chae, Sooryong; Jang, Jongjin; Min, Daehong; Kim, Jaehwan; Eom, Daeyong; Yoo, Yang-Seok; Cho, Yong-Hoon; Nam, Okhyun

    2015-08-21

    In this study, we have intentionally grown novel types of (11-22)- and (1-10-3)-oriented(3) and self-assembled inclined GaN nanorods (NRs) on (10-10) m-sapphire substrates using metal organic chemical vapor deposition without catalysts and ex situ patterning. Nitridation of the m-sapphire surface was observed to be crucial to the inclined angle as well as the growth direction of the GaN NRs. Polarity-selective KOH etching confirmed that both (11-22) and (1-10-3) GaN NRs are nitrogen-polar. Using pole figure measurements and selective area electron diffraction patterns, the epitaxial relationship between the inclined (11-22) and (1-10-3) GaN NRs and m-sapphire substrates was systematically demonstrated. Furthermore, it was verified that the GaN NRs were single-crystalline wurtzite structures. We observed that stacking fault-related defects were generated during the initial growth stage using high-resolution transmission electron microscopy. The blue-shift of the near band edge (NBE) peak in the inclined angle-controlled GaN NRs can be explained by a band filling effect through carrier saturation of the conduction band, resulting from a high Si-doping concentration; in addition, the decay time of NBE emission in (11-22)- and (1-10-3)-oriented NRs was much shorter than that of stacking fault-related emission. These results suggest that defect-free inclined GaN NRs can be grown on m-sapphire without ex situ treatment.

  4. Mechanical properties of chemical vapor deposited diamond

    Science.gov (United States)

    Kant, Avinash

    The hardness, elastic modulus, subcritical crack growth and fracture toughness of chemical vapor deposited (CVD) polycrystalline diamond films have been investigated on thick (˜100 to 300 mum) free-standing films with regard to the composition, microstructure, failure mechanisms and measurement techniques. The rationale for this study was the uncertainty in measuring these properties in previous research and the variability in the composition and microstructure of the material, which may affect these properties. Two predominant micro-hardness measurement techniques, namely Vickers and Knoop indentation, were employed. Existing Young's modulus measurement techniques such as dynamic resonance and nano-indentation were reviewed for modulus measurement on these films. The validity of indentation fracture toughness measurement for CVD diamond films using micro-hardness indentation has been established based on comparison with the conventional method of tensile testing of pre-notched compact-tension samples. The fracture toughness, Ksbc, of diamond was measured using indentation methods and for the first time by the tensile testing of pre-notched fracture-mechanics type compact-tension samples. Measured Ksbc values were found to be between 5 and 7 MPa-msp{1/2} by either method. Studies on subcritical crack growth (i.e., at stress intensities less than Ksbc) indicated that CVD diamond is essentially immune to stress-corrosion cracking under sustained loads in room air, water and acid environments. Extensive studies of the microstructure and mechanisms of failure were conducted. A commonly known toughening mechanism for ceramics by weakening the grain boundary in order to promote intergranular failure and grain bridging, has been implemented to improve the toughness of CVD diamond films. Several films with nominally the same thickness but small differences in their non-diamond content were studied and a significant variation in the toughness measurements was observed

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

    NARCIS (Netherlands)

    Deelen, J. van; Illiberi, A.; Kniknie, B.; Beckers, E.H.A.; Simons, P.J.P.M.; Lankhorst, A.

    2014-01-01

    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

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

    NARCIS (Netherlands)

    Deelen, J. van; Illiberi, A.; Kniknie, B.; Beckers, E.H.A.; Simons, P.J.P.M.; Lankhorst, A.

    2013-01-01

    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/minwere obtained. The reaction

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

    CERN Document Server

    Pierson, Hugh O

    1999-01-01

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

  8. Continuous Ultra-Thin MOS2 Films Grown by Low-Temperature Physical Vapor Deposition (Postprint)

    Science.gov (United States)

    2014-07-01

    AFRL-RX-WP-JA-2014-0151 CONTINUOUS ULTRA-THIN MOS2 FILMS GROWN BY LOW-TEMPERATURE PHYSICAL VAPOR DEPOSITION (POSTPRINT) Andrey A...DATES COVERED (From – To) 01 July 2010 – 15 June 2014 4. TITLE AND SUBTITLE CONTINUOUS ULTRA-THIN MOS2 FILMS GROWN BY LOW- TEMPERATURE PHYSICAL VAPOR...devices. This Letter describes a vapor phase growth technique for precisely controlled synthesis of continuous, uniform molecular layers of MoS2 on

  9. Heteroepitaxial growth of Ba1 - xSrxTiO3/YBa2Cu3O7 - x by plasma-enhanced metalorganic chemical vapor deposition

    Science.gov (United States)

    Chern, C. S.; Liang, S.; Shi, Z. Q.; Yoon, S.; Safari, A.; Lu, P.; Kear, B. H.; Goodreau, B. H.; Marks, T. J.; Hou, S. Y.

    1994-06-01

    Epitaxial Ba1-xSrxTiO3(BST)/YBa2Cu3O7-x heterostructures with superior electrical and dielectric properties have been fabricated by plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD). Data of x-ray diffraction and high resolution transmission electron microscopy showed that oriented Ba1-xSrxTiO3 layers were epitaxially deposited on epitaxial (001) YBa2Cu3O7-x layers. The leakage current density through the Ba1-xSrxTiO3 films was about 10-7 A/cm2 at 2 V (about 2×105 V/cm) operation. Moreover, the results of capacitance-temperature measurements showed that the PE-MOCVD Ba1-xSrxTiO3 films had Curie temperatures of about 30 °C and a peak dielectric constant of 600 at zero bias voltage. The Rutherford backscattering spectrometry and x-ray diffraction results showed that the BST film composition was controlled between Ba0.75Sr0.25TiO3 and Ba0.8Sr0.2TiO3. The structural and electrical properties of the Ba1-xSrxTiO3/YBa2Cu3O7-x heterostructure indicated that conductive oxide materials with close lattice to Ba1-xSrxTiO3 can be good candidates for the bottom electrode.

  10. Recent Advances in Atmospheric Vapor-Phase Deposition of Transparent and Conductive Zinc Oxide

    NARCIS (Netherlands)

    Illiberi, A.; Poodt, P.; Roozeboom, F.

    2014-01-01

    The industrial need for high-throughput and low-cost ZnO deposition processes has triggered the development of atmospheric vapor-phase deposition techniques which can be easily applied to continuous, in-line manufacturing. While atmospheric CVD is a mature technology, new processes for the growth of

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

    NARCIS (Netherlands)

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

    2009-01-01

    The technology of Hot Wire Chemical Vapor Deposition (HWCVD) or Catalytic Chemical Vapor Deposition (Cat-CVD) has made great progress during the last couple of years. This review discusses examples of significant progress. Specifically, silicon nitride deposition by HWCVD (HW-SiNx) is highlighted,

  12. Facile synthesis of graphene on single mode fiber via chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C. [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Man, B.Y., E-mail: byman@sdnu.edu.cn [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Jiang, S.Z. [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); State Key Lab of Crystal Materials Shandong University, Jinan 250100 (China); Yang, C.; Liu, M.; Chen, C.S.; Xu, S.C. [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China); Feng, D.J. [School of Information Science and Engineering, Shandong University, Jinan 250100 (China); Bi, D.; Liu, F.Y.; Qiu, H.W. [College of Physics and Electronics, Shandong Normal University, Jinan 250014 (China)

    2014-07-01

    Direct deposition of graphene film on the standard single mode fiber is offered using a Cu-vapor-assisted chemical vapor deposition system. The gas flow of H{sub 2} and Ar before the growth process plays a crucial role for the direct deposition of the graphene film and the layers of the graphene can be controlled by the growth time. With a large gas flow, Cu atoms are carried off with the gas flow and hard to deposit on the surface of the single mode fiber before the growth process. Consequently, uniform graphene film is obtained in this case. On the contrary, with a lower one, Cu atoms is facile to deposit on the surface of the single mode fiber and form nanodots acting as active catalytic sites for the growth of carbon nanotubes. This method presents us a promising transfer-free technique for fabrication of the photonic applications.

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

    Science.gov (United States)

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

    1999-01-01

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

  14. 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.

  15. Low-Pressure Chemical Vapor (LPCVD) Graphene Growth Study and Raman Characterization

    Science.gov (United States)

    2013-12-01

    films deposited for a growth study is discussed. Low pressure chemical vapor deposition was utilized to grow graphene layers onto copper foil substrates...exfoliation method (3); however, recent efforts have focused on graphene synthesis by conventional methods, such as chemical vapor deposition ( CVD ) and...ultrahigh vacuum, high temperature annealing (i.e., epitaxial graphene from SiC) (4, 5). CVD , in particular, is a promising growth technique because

  16. Chemical Vapor Deposition of Turbine Thermal Barrier Coatings

    Science.gov (United States)

    Haven, Victor E.

    1999-01-01

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

  17. Low-temperature growth and characterization of single crystalline ZnO nanorod arrays using a catalyst-free inductively coupled plasma-metal organic chemical vapor deposition.

    Science.gov (United States)

    Jeong, Sang-Hun; Lee, Chang-Bae; Moon, Won-Jin; Song, Ho-Jun

    2008-10-01

    Vertically aligned ZnO nanorod arrays have been synthesized on c-plane sapphires at a low temperature of 400 degrees C using catalyst-free inductively coupled plasma (ICP) metal organic chemical vapor deposition (MOCVD) technique by varying the ICP powers. Diameters of the ZnO nanorods changed from 200 nm to 400 nm as the ICP power increased from 200 to 400 Watt. TEM and XRD investigations indicated that the ZnO nanorod arrays grown at ICP powers above 200 Watt had a homogeneous in-plane alignment and single crystalline nature. PL study at room temperature (RT) and 6 K confirmed that the ZnO nanorod arrays in the present study are of high optical quality as well as good crystalline quality, showing only exciton-related emission peaks without any trace of defect-related deep level emissions in visible range. The blueshift of exciton emission peak in RTPL spectra was also found as rod diameter decreased and it is deduced that this shift in emission energy may be due to the surface resonance effect resulted from the increased surface-to-volume ratio, based on the observation and behavior of the surface exciton (SX) emission in the high-resolution 6 K PL spectra.

  18. The Influences of H2Plasma Pretreatment on the Growth of Vertically Aligned Carbon Nanotubes by Microwave Plasma Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Wen Hua-Chiang

    2008-01-01

    Full Text Available AbstractThe effects of H2flow rate during plasma pretreatment on synthesizing the multiwalled carbon nanotubes (MWCNTs by using the microwave plasma chemical vapor deposition are investigated in this study. A H2and CH4gas mixture with a 9:1 ratio was used as a precursor for the synthesis of MWCNT on Ni-coated TaN/Si(100 substrates. The structure and composition of Ni catalyst nanoparticles were investigated using scanning electron microscopy (SEM and transmission electron microscopy (TEM. The present findings showed that denser Ni catalyst nanoparticles and more vertically aligned MWCNTs could be effectively achieved at higher flow rates. From Raman results, we found that the intensity ratio of G and D bands (ID/IG decreases with an increasing flow rate. In addition, TEM results suggest that H2plasma pretreatment can effectively reduce the amorphous carbon and carbonaceous particles. As a result, the pretreatment plays a crucial role in modifying the obtained MWCNTs structures.

  19. A review of theoretical study of graphene chemical vapor deposition synthesis on metals: nucleation, growth, and the role of hydrogen and oxygen

    Science.gov (United States)

    Rezwan Habib, Mohammad; Liang, Tao; Yu, Xuegong; Pi, Xiaodong; Liu, Yingchun; Xu, Mingsheng

    2018-03-01

    Graphene has attracted intense research interest due to its extraordinary properties and great application potential. Various methods have been proposed for the synthesis of graphene, among which chemical vapor deposition has drawn a great deal of attention for synthesizing large-area and high-quality graphene. Theoretical understanding of the synthesis mechanism is crucial for optimizing the experimental design for desired graphene production. In this review, we discuss the three fundamental steps of graphene synthesis in details, i.e. (1) decomposition of carbon feedstocks and formation of various active carbon species, (2) nucleation, and (3) attachment and extension. We provide a complete scenario of graphene synthesis on metal surfaces at atomistic level by means of density functional theory, molecular dynamics (MD), Monte Carlo (MC) and their combination and interface with other simulation methods such as quantum mechanical molecular dynamics, density functional tight binding molecular dynamics, and combination of MD and MC. We also address the latest investigation of the influences of the hydrogen and oxygen on the synthesis and the quality of the synthesized graphene.

  20. Conductimetry and impedance spectroscopy study of low pressure metal organic chemical vapor deposition TiN xO y films as a function of the growth temperature: a percolation approach

    Science.gov (United States)

    Fabreguette, F.; Maglione, M.; Imhoff, L.; Domenichini, B.; Marco de Lucas, M. C.; Sibillot, P.; Bourgeois, S.; Sacilotti, M.

    2001-05-01

    Titanium oxinitride thin films have been grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) using titanium isopropoxide, Ti(OCH(CH 3) 2) 4 (TIP) and NH 3 precursors in a growth temperature range from 450 to 750°C on sapphire substrates. The electrical behaviour of these films was studied between 400 and 173 K, revealing three different behaviours, ranking from a hopping conductivity (450-500°C) to a conducting one (700-750°C), with a dual behaviour for the intermediate growth temperatures. Moreover, at room temperature, both conductimetry and impedance spectroscopy highlighted a percolation behaviour, interpreted in terms of continuum percolation. The effective media theory equations led to the usual percolation parameters ( s, t, Φc) and the difference between the values thus obtained and the expected ones was explained in terms of anisotropic percolation occurring in the columnar film structure.

  1. Graphene by one-step chemical vapor deposition from ferrocene vapors: Properties and electrochemical evaluation

    Science.gov (United States)

    Pilatos, George; Perdikaki, Anna V.; Sapalidis, Andreas; Pappas, George S.; Giannakopoulou, Tatiana; Tsoutsou, Dimitra; Xenogiannopoulou, Evangelia; Boukos, Nikos; Dimoulas, Athanasios; Trapalis, Christos; Kanellopoulos, Nick K.; Karanikolos, Georgios N.

    2016-02-01

    Growth of few-layer graphene using ferrocene as precursor by chemical vapor deposition is reported. The growth did not involve any additional carbon or catalyst source or external hydrocarbon gases. Parametric investigation was performed using different conditions, namely, varying growth temperature from 600 to1000 °C, and growth duration from 5 min to 3 h, as well as using fast quenching or gradual cooling after the thermal treatment, in order to examine the effect on the quality of the produced graphene. The growth took place on silicon wafers and resulted, under optimal conditions, in formation of graphene with 2-3 layers and high graphitic quality, as evidenced by Raman spectroscopy, with characteristic full width at half maximum of the 2D band of 49.46 cm-1, and I2D/IG and ID/IG intensity ratios of 1.15 and 0.26, respectively. Atomic force microscopy and X-ray photoelectron spectroscopy were employed to further evaluate graphene characteristics and enlighten growth mechanism. Electrochemical evaluation of the developed material was performed using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge measurements.

  2. Characteristics of epitaxial garnets grown by CVD using single metal alloy sources. [Chemical Vapor Deposition

    Science.gov (United States)

    Besser, P. J.; Hamilton, T. N.; Mee, J. E.; Stermer, R. L.

    1974-01-01

    Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on (111) gadolinium gallium garnet (GGG) substrates. Data on physical, magnetic and optical properties of representative films is presented and discussed.

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

    Science.gov (United States)

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

    2017-03-01

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

  4. Design and implementation of a novel portable atomic layer deposition/chemical vapor deposition hybrid reactor

    Science.gov (United States)

    Selvaraj, Sathees Kannan; Jursich, Gregory; Takoudis, Christos G.

    2013-09-01

    We report the development of a novel portable atomic layer deposition chemical vapor deposition (ALD/CVD) hybrid reactor setup. Unique feature of this reactor is the use of ALD/CVD mode in a single portable deposition system to fabricate multi-layer thin films over a broad range from "bulk-like" multi-micrometer to nanometer atomic dimensions. The precursor delivery system and control-architecture are designed so that continuous reactant flows for CVD and cyclic pulsating flows for ALD mode are facilitated. A custom-written LabVIEW program controls the valve sequencing to allow synthesis of different kinds of film structures under either ALD or CVD mode or both. The entire reactor setup weighs less than 40 lb and has a relatively small footprint of 8 × 9 in., making it compact and easy for transportation. The reactor is tested in the ALD mode with titanium oxide (TiO2) ALD using tetrakis(diethylamino)titanium and water vapor. The resulting growth rate of 0.04 nm/cycle and purity of the films are in good agreement with literature values. The ALD/CVD hybrid mode is demonstrated with ALD of TiO2 and CVD of tin oxide (SnOx). Transmission electron microscopy images of the resulting films confirm the formation of successive distinct TiO2-ALD and SnOx-CVD layers.

  5. Investigations on the Role of N2:(N2 + CH4) Ratio on the Growth of Hydrophobic Nanostructured Hydrogenated Carbon Nitride Thin Films by Plasma Enhanced Chemical Vapor Deposition at Low Temperature

    Science.gov (United States)

    Khanis, Noor Hamizah; Ritikos, Richard; Ahmad Kamal, Shafarina Azlinda; Abdul Rahman, Saadah

    2017-01-01

    Nanostructured hydrogenated carbon nitride (CNx:H) thin films were synthesized on a crystal silicon substrate at low deposition temperature by radio-frequency plasma-enhanced chemical vapor deposition (PECVD). Methane and nitrogen were the precursor gases used in this deposition process. The effects of N2 to the total gas flow rate ratio on the formation of CNx:H nanostructures were investigated. Field-emission scanning electron microscopy (FESEM), Auger electron spectroscopy (AES), Raman scattering, and Fourier transform of infrared spectroscopies (FTIR) were used to characterize the films. The atomic nitrogen to carbon ratio and sp2 bonds in the film structure showed a strong influence on its growth rate, and its overall structure is strongly influenced by even small changes in the N2:(N2 + CH4) ratio. The formation of fibrous CNx:H nanorod structures occurs at ratios of 0.7 and 0.75, which also shows improved surface hydrophobic characteristic. Analysis showed that significant presence of isonitrile bonds in a more ordered film structure were important criteria contributing to the formation of vertically-aligned nanorods. The hydrophobicity of the CNx:H surface improved with the enhancement in the vertical alignment and uniformity in the distribution of the fibrous nanorod structures. PMID:28772460

  6. Chemical Vapor Deposition and Atomic Layer Deposition of Coatings for Mechanical Applications

    Science.gov (United States)

    Doll, G. L.; Mensah, B. A.; Mohseni, H.; Scharf, T. W.

    2010-01-01

    Chemical vapor deposition (CVD) of films and coatings involves the chemical reaction of gases on or near a substrate surface. This deposition method can produce coatings with tightly controlled dimensions and novel structures. Furthermore, the non-line-of-sight-deposition capability of CVD facilitates the coating of complex-shaped mechanical components. Atomic layer deposition (ALD) is also a chemical gas phase thin film deposition technique, but unlike CVD, it utilizes “self-limiting” surface adsorption reactions (chemisorption) to control the thickness of deposited films. This article provides an overview of CVD and ALD, discusses some of their fundamental and practical aspects, and examines their advantages and limitations versus other vapor processing techniques such as physical vapor deposition in regard to coatings for mechanical applications. Finally, site-specific cross-sectional transmission electron microscopy inside the wear track of an ALD ZnO/ZrO2 8 bilayers nanolaminate coating determined the mechanisms that control the friction and wear.

  7. The development of chemically vapor deposited mullite coatings for the corrosion protection of SiC

    Energy Technology Data Exchange (ETDEWEB)

    Auger, M.; Hou, P.; Sengupta, A.; Basu, S.; Sarin, V. [Boston Univ., MA (United States)

    1998-05-01

    Crystalline mullite coatings have been chemically vapor deposited onto SiC substrates to enhance the corrosion and oxidation resistance of the substrate. Current research has been divided into three distinct areas: (1) Development of the deposition processing conditions for increased control over coating`s growth rate, microstructure, and morphology; (2) Analysis of the coating`s crystal structure and stability; (3) The corrosion resistance of the CVD mullite coating on SiC.

  8. Chemical vapor deposition of carbon nanotube forests

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, J.; Zhong, G.; Esconjauregui, S.; Zhang, C.; Fouquet, M.; Hofmann, S. [Engineering Department, Cambridge University, Cambridge CB2 1PZ (United Kingdom)

    2012-12-15

    We review the growth mechanisms of vertically aligned carbon nanotube forests, in terms of what controls the growth rate and control of the catalyst lifetime. We also review the production of very high-density forests, in terms of increasing the catalyst particle density. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Growth of Carbon Nanostructure Materials Using Laser Vaporization

    Science.gov (United States)

    Zhu, Shen; Su, Ching-Hua; Lehozeky, S.

    2000-01-01

    Since the potential applications of carbon nanotubes (CNT) was discovered in many fields, such as non-structure electronics, lightweight composite structure, and drug delivery, CNT has been grown by many techniques in which high yield single wall CNT has been produced by physical processes including arc vaporization and laser vaporization. In this presentation, the growth mechanism of the carbon nanostructure materials by laser vaporization is to be discussed. Carbon nanoparticles and nanotubes have been synthesized using pulsed laser vaporization on Si substrates in various temperatures and pressures. Two kinds of targets were used to grow the nanostructure materials. One was a pure graphite target and the other one contained Ni and Co catalysts. The growth temperatures were 600-1000 C and the pressures varied from several torr to 500 torr. Carbon nanoparticles were observed when a graphite target was used, although catalysts were deposited on substrates before growing carbon films. When the target contains catalysts, carbon nanotubes (CNT) are obtained. The CNT were characterized by scanning electron microscopy, x-ray diffraction, optical absorption and transmission, and Raman spectroscopy. The temperature-and pressure-dependencies of carbon nanotubes' growth rate and size were investigated.

  10. Chemical vapor deposition of fluorine-doped zinc oxide

    Science.gov (United States)

    Gordon, Roy G.; Kramer, Keith; Liang, Haifan

    2000-06-06

    Fims of fluorine-doped zinc oxide are deposited from vaporized precursor compounds comprising a chelate of a dialkylzinc, such as an amine chelate, an oxygen source, and a fluorine source. The coatings are highly electrically conductive, transparent to visible light, reflective to infrared radiation, absorbing to ultraviolet light, and free of carbon impurity.

  11. 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…

  12. 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...

  13. 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

  14. Micropatterned charge heterogeneities via vapor deposition of aminosilanes.

    Science.gov (United States)

    Pick, Christian; Argento, Christopher; Drazer, German; Frechette, Joelle

    2015-10-06

    Aminosilanes are routinely employed for charge reversal or to create coupling layers on oxide surfaces. We present a chemical vapor deposition method to pattern mica surfaces with regions of high-quality aminosilane (3-aminopropyltriethoxysilane, APTES) monolayers. The approach relies on the vapor deposition of an aminosilane through a patterned array of through-holes in a PDMS (poly(dimethylsiloxane)) membrane that acts as a mask. In aqueous solutions the surfaces have regular patterns of charge heterogeneities with minimal topographical variations over large areas. This versatile dry lift-off deposition method alleviates issues with multilayer formation and can be used to create charge patterns on curved surfaces. We identify the necessary steps to achieve high quality monolayers and charge reversal of the underlying mica surface: (1) hexane extraction to remove unreacted PDMS oligomers from the membrane that would otherwise deposit on and contaminate the substrate, (2) oxygen plasma treatment of the top of the membrane surfaces to generate a barrier layer that blocks APTES transport through the PDMS, and (3) low of the vapor pressure of APTES during deposition to minimize APTES condensation at the mica-membrane-vapor contact lines and to prevent multilayer formation. Under these conditions, AFM imaging shows that the monolayers have a height of 0.9 ± 0.2 nm with an increase in height up to 3 nm at the mica-membrane-vapor contact lines. Fluorescence imaging demonstrates pattern fidelity on both flat and curved surfaces, for feature sizes that vary between 6.5 and 40 μm. We verify charge reversal by measuring the double layer forces between a homogeneous (unpatterned) APTES monolayers and a mica surface in aqueous solution, and we characterize the surface potential of APTES monolayers by measuring the double-layer forces between identical APTES surfaces. We obtain a surface potential of +110 ± 6 mV at pH 4.0.

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

    Science.gov (United States)

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

    1995-01-01

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

  16. Monitoring particle growth in deposition plasmas

    Science.gov (United States)

    Schlebrowski, T.; Bahre, H.; Böke, M.; Winter, J.

    2013-12-01

    Plasma-enhanced chemical vapor deposition methods are frequently used to deposit barrier layers, e.g. on polymers for food packaging. These plasmas may suffer from particle (dust) formation. We report on a flexible monitoring system for dust. It is based on scanning a 3D plasma volume for particles by laser light scattering. The lower size limit of particles detected in the presented system is 20 nm. We report on existence diagrams for obtaining dust free or dust loaded capacitively or inductively coupled rf-plasmas in C2H2 depending on pressure, flow and rf-power. We further present growth rates for dust in these plasmas and show that monodisperse particles are only obtained during the first growth cycle.

  17. Synthesis of polymer nanoparticles via vapor phase deposition onto liquid substrates.

    Science.gov (United States)

    Haller, Patrick D; Gupta, Malancha

    2014-12-01

    In this article, the growth of polymer nanoparticles formed at the liquid-vapor interface via vapor phase polymerization is studied. The particles grow by polymer aggregation, which is driven by the surface tension interaction between the liquid and polymer. It is demonstrated that the mechanism of particle growth is determined by whether polymer particles remain at the liquid-vapor interface or submerge into the liquid. The position of the particles depends on the interaction between the polymer and the liquid. For example, the deposition of poly(n-butyl acrylate) onto poly(dimethyl siloxane) and Krytox liquids leads to the formation of nanoparticles that remain at the liquid-vapor interface. The size of these particles increases as a function of deposition time. The deposition of poly(4-vinylpyridine) onto poly(dimethyl siloxane) and Krytox leads to the formation of nanoparticles that submerge into the liquid. The size of these particles does not significantly change with deposition time. Our study offers a new rapid, one-step synthetic approach for fabricating functional polymer nanoparticles for applications in catalysis, photonics, and drug delivery. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Growth of rough-surface p-GaN layers on InGaN/GaN multiple-quantum-well structures by metalorganic chemical vapor deposition and their application to GaN-based solar cells

    Science.gov (United States)

    Mori, Takuma; Egawa, Takashi; Miyoshi, Makoto

    2017-08-01

    We conducted the study on the growth of rough-surface p-GaN layers on InGaN/GaN multiple-quantum-well (MQW) structures by metalorganic chemical vapor deposition (MOCVD). It was found that the sum of InGaN well thickness t well_total was a predominant factor to form the rough surface, in addition to the growth temperature as low as 800 °C for the p-GaN layers. Microstructure analyses revealed that the rough surfaces consisted of a certain number of hexagonal V-shaped pits starting from dislocations propagated through an under layer and they increased with the increased t well_total. It was confirmed that the light absorption was enlarged for MQW structure samples with rough-surface p-GaN layers on the top, owing to not only the thickness effect in MQWs but also their reduced light reflection on the surfaces. It was also confirmed that these optical properties contributed to the performance improvement in InGaN/GaN MQW solar cells.

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

    NARCIS (Netherlands)

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

    2012-01-01

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

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

    NARCIS (Netherlands)

    Veen, M.K. van

    2003-01-01

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

  1. Dynamical heterogeneity in a vapor-deposited polymer glass

    Science.gov (United States)

    Zhang, Wengang; Douglas, Jack F.; Starr, Francis W.

    2017-05-01

    Recently, there has been great interest in "ultrastable" glasses formed via vapor deposition, both because of emerging engineering applications of these materials (e.g., active layers in light-emitting diodes and photovoltaics) and, theoretically, as materials for probing the equilibrium properties of glassy materials below their glass transition, based on the conjecture that these materials are equivalent to glassy materials aged over astronomical time scales. We use molecular dynamics simulations to examine the properties of ultrastable vapor-deposited and ordinary polymer glasses. Based on the difference in the energy of the deposited and ordinary films, we estimate the effective cooling rate for the vapor deposited films to be 1 to 3 orders of magnitude larger than that of the ordinary film, depending on the deposition temperature. Similarly, we find an increase in the average segmental relaxation time of the vapor-deposited film compared to the ordinary glass. On the other hand, the normal mode spectrum is essentially identical for the vapor-deposited and the ordinary glass film, suggesting that the high-frequency dynamics should be similar. In short, the segmental relaxation dynamics of the polymer vapor-deposited glass are consistent with those of an ordinary polymer glass with a somewhat slower effective cooling rate. Of course, one would expect a larger effect on dynamics approaching the experimental glass transition, where the cooling rates are much slower than accessible in simulation. To more precisely probe the relationship between the dynamics of these glasses, we examine dynamical heterogeneity within the film. Due to the substantial mobility gradient in the glassy films, we find that it is crucial to distinguish the dynamics of the middle part of the film from those of the entire film. Considering the film as a whole, the average dynamical heterogeneity is dominated by the mobility gradient, and as a consequence the heterogeneity is nearly

  2. The Use of Ion Vapor Deposited Aluminum (IVD) for the Space Shuttle Solid Rocket Booster (SRB)

    Science.gov (United States)

    Novak, Howard L.

    2003-01-01

    This viewgraph representation provides an overview of the use of ion vapor deposited aluminum (IVD) for use in the Space Shuttle Solid Rocket Booster (SRB). Topics considered include: schematics of ion vapor deposition system, production of ion vapor deposition system, IVD vs. cadmium coated drogue ratchets, corrosion exposure facilities and tests, seawater immersion facilities and tests and continued research and development issues.

  3. Catalytic transparency of hexagonal boron nitride on copper for chemical vapor deposition growth of large-area and high-quality graphene.

    Science.gov (United States)

    Wang, Min; Kim, Minwoo; Odkhuu, Dorj; Lee, Joohyun; Jang, Won-Jun; Kahng, Se-Jong; Park, Noejung; Ruoff, Rodney S; Song, Young Jae; Lee, Sungjoo

    2014-06-24

    Graphene transferred onto h-BN has recently become a focus of research because of its excellent compatibility with large-area device applications. The requirements of scalability and clean fabrication, however, have not yet been satisfactorily addressed. The successful synthesis of graphene/h-BN on a Cu foil and DFT calculations for this system are reported, which demonstrate that a thin h-BN film on Cu foil is an excellent template for the growth of large-area and high-quality graphene. Such material can be grown on thin h-BN films that are less than 3 nm thick, as confirmed by optical microscopy and Raman spectroscopy. We have evaluated the catalytic growth mechanism and the limits on the CVD growth of high-quality and large-area graphene on h-BN film/Cu by performing Kelvin probe force microscopy and DFT calculations for various thicknesses of h-BN.

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

    Science.gov (United States)

    Rosner, Daniel E.

    1993-01-01

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

  5. 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.

  6. Hydride vapor phase epitaxy growth of GaN, InGaN, ScN, and ScAIN

    NARCIS (Netherlands)

    Bohnen, T.

    2010-01-01

    Chemical vapor deposition (CVD); hydride vapor phase epitaxy (HVPE); gallium nitride (GaN); indium gallium nitride (InGaN); scandium nitride (ScN); scandium aluminum nitride (ScAlN); semiconductors; thin films; nanowires; III nitrides; crystal growth - We studied the HVPE growth of different III

  7. Development and study of chemical vapor deposited tantalum base alloys

    Science.gov (United States)

    Meier, G. H.; Bryant, W. A.

    1976-01-01

    A technique for the chemical vapor deposition of alloys was developed. The process, termed pulsing, involves the periodic injection of reactant gases into a previously-evacuated reaction chamber where they blanket the substrate almost instantaneously. Formation of alternating layers of the alloy components and subsequent homogenization allows the formation of an alloy of uniform composition with the composition being determined by the duration and relative numbers of the various cycles. The technique has been utilized to produce dense alloys of uniform thickness and composition (Ta- 10 wt % W) by depositing alternating layers of Ta and W by the hydrogen reduction of TaCl5 and WCl6. A similar attempt to deposit a Ta - 8 wt % W - 2 wt% Hf alloy was unsuccessful because of the difficulty in reducing HfCl4 at temperatures below those at which gas phase nucleation of Ta and W occurred.

  8. Vapor deposition on doublet airfoil substrates: Control of coating thickness and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, Theron M.; Zhao, Hengbei; Wadley, Haydn N. G., E-mail: haydn@virginia.edu [Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., P.O. Box 400745, Charlottesville, Virginia 22904 (United States)

    2015-11-15

    Gas jet assisted vapor deposition processes for depositing coatings are conducted at higher pressures than conventional physical vapor deposition methods, and have shown promise for coating complex shaped substrates including those with non-line-of-sight (NLS) regions on their surface. These regions typically receive vapor atoms at a lower rate and with a wider incident angular distribution than substrate regions in line-of-sight (LS) of the vapor source. To investigate the coating of such substrates, the thickness and microstructure variation along the inner (curved) surfaces of a model doublet airfoil containing both LS and NLS regions has been investigated. Results from atomistic simulations and experiments confirm that the coating's thickness is thinner in flux-shadowed regions than in other regions for all the coating processes investigated. They also indicated that the coatings columnar microstructure and pore volume fraction vary with surface location through the LS to NLS transition zone. A substrate rotation strategy for optimizing the thickness over the entire doublet airfoil surface was investigated, and led to the identification of a process that resulted in only small variation of coating thickness, columnar growth angle, and pore volume fraction on all doublet airfoil surfaces.

  9. The Corrosion Protection of Metals by Ion Vapor Deposited Aluminum

    Science.gov (United States)

    Danford, M. D.

    1993-01-01

    A study of the corrosion protection of substrate metals by ion vapor deposited aluminum (IVD Al) coats has been carried out. Corrosion protection by both anodized and unanodized IVD Al coats has been investigated. Base metals included in the study were 2219-T87 Al, 7075-T6 Al, Titanium-6 Al-4 Vanadium (Ti-6Al-4V), 4130 steel, D6AC steel, and 4340 steel. Results reveal that the anodized IVD Al coats provide excellent corrosion protection, but good protection is also achieved by IVD Al coats that have not been anodized.

  10. Growth of tapered silica nanowires with a shallow U-shaped vapor chamber: Growth mechanism and structural and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Danqing; Zhang, Xi, E-mail: xizhang@scu.edu.cn; Wei, Jianglin; Gu, Gangxu; Xiang, Gang, E-mail: gxiang@scu.edu.cn [Department of Physics, Sichuan University, Chengdu 610064 (China); Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China)

    2015-04-28

    Traditional chemical vapor deposition method modified with a shallow U-shaped vapor chamber has been used to synthesize tapered bamboo shoot-like (BS-like) amorphous SiO{sub 2} nanowires (NWs) on Si (100) substrates without catalyst. The key innovation of this approach lies in a creation of swirling flow of the reactant vapors during the growth, which leads to a harvest of tapered silica NWs with lengths up to several microns. The unique structures and corresponding luminescence properties of the BS-like NWs were studied and their relationship with the evaporated active reactants was explored. A thermodynamic model that considers the critical role of the vapor flow during the growth is proposed to understand the structural and optical features. The shallow U-shaped vapor chamber-aided approach may provide a viable way to tailor novel structure of NWs for potential applications in nano-devices.

  11. Microspheres for the Growth of Silicon Nanowires via Vapor-Liquid-Solid Mechanism

    Directory of Open Access Journals (Sweden)

    Arancha Gómez-Martínez

    2014-01-01

    Full Text Available Silicon nanowires have been synthesized by a simple process using a suitable support containing silica and carbon microspheres. Nanowires were grown by thermal chemical vapor deposition via a vapor-liquid-solid mechanism with only the substrate as silicon source. The curved surface of the microsized spheres allows arranging the gold catalyst as nanoparticles with appropriate dimensions to catalyze the growth of nanowires. The resulting material is composed of the microspheres with the silicon nanowires attached on their surface.

  12. Transmission electron microscopy studies of YBCO coated conductor deposited using multiple-stage chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, H. [Japan Fine Ceramics Center, Material Research and Development Laboratory, 2-4-1, Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587 (Japan)]. E-mail: hisasaki@jfcc.or.jp; Kato, T. [Japan Fine Ceramics Center, Material Research and Development Laboratory, 2-4-1, Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587 (Japan); Sasaki, Y. [Japan Fine Ceramics Center, Material Research and Development Laboratory, 2-4-1, Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587 (Japan); Hirayama, T. [Japan Fine Ceramics Center, Material Research and Development Laboratory, 2-4-1, Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587 (Japan); Kashima, N. [Electric Power Research and Development Center, Chubu Electric Power Co., Inc., 20-1, Kitasekiyama, Ohdaka-cho, Midori-ku, Nagoya, Aichi 459-8522 (Japan); Nagaya, S. [Electric Power Research and Development Center, Chubu Electric Power Co., Inc., 20-1, Kitasekiyama, Ohdaka-cho, Midori-ku, Nagoya, Aichi 459-8522 (Japan); Izumi, T. [Superconductivity Research Center, 1-10-13, Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Shiohara, Y. [Superconductivity Research Center, 1-10-13, Shinonome, Koto-ku, Tokyo 135-0062 (Japan)

    2005-10-01

    A YBCO film was deposited on Hastelloy tape with highly oriented CeO{sub 2}/Gd{sub 2}Zr{sub 2}O{sub 7} multilayer using multiple-stage chemical vapor deposition. The microstructures of the YBCO coated conductor were examined in detail using transmission electron microscopy. Analysis indicated a YBCO film about 1 {mu}m thick was deposited and consisted mainly of c-axis oriented grains. However, a-axis oriented grains were also observed in the YBCO film, and these a-axis oriented grains grew larger with increasing thickness of the YBCO film.

  13. 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.

  14. 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.

  15. TEXTILE SURFACE MODIFICATION BY PYHSICAL VAPOR DEPOSITION – (REVIEW

    Directory of Open Access Journals (Sweden)

    YUCE Ismail

    2017-05-01

    Full Text Available Textile products are used in various branches of the industry from automotive to space products. Textiles produced for industrial use are generally referred to as technical textiles. Technical textiles are nowadays applied to several areas including transportation, medicine, agriculture, protection, sports, packaging, civil engineering and industry. There are rapid developments in the types of materials used in technical textiles. Therefore, modification and functionalization of textile surfaces is becoming more crucial. The improvements of the properties such as anti-bacterial properties, fire resistivity, UV radiation resistance, electrical conductivity, self cleaning, and super hydrophobic, is getting more concern with respect to developments in textile engineering. The properties of textile surfaces are closely related to the fiber structure, the differences in the polymer composition, the fiber mixture ratio, and the physical and chemical processes applied. Textile surface modifications can be examined in four groups under the name mechanical, chemical, burning and plasma. Surface modifications are made to improve the functionality of textile products. Textile surface modifications affect the properties of the products such as softness, adhesion and wettability. The purpose of this work is to reveal varieties of vapor deposition modifications to improve functionality. For this purpose, the pyhsical vapor deposition methods, their affects on textile products and their end-uses will be reviewed.

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

    Science.gov (United States)

    van Veen, M. K.

    2003-05-01

    In this thesis, the application of the hot-wire chemical vapor deposition (HWCVD) technique for the deposition of silicon thin films is described. The HWCVD technique is based on the dissociation of silicon-containing gasses at the catalytic surface of a hot filament. Advantages of this technique are the high deposition rate, the low equipment costs, and the scalability. The main goal of this thesis is the optimization of the material properties of both hydrogenated amorphous silicon and microcrystalline silicon, so that these materials can be incorporated as the absorbing layers in tandem solar cells. Firstly, the influence of specific deposition parameters on the material quality of hydrogenated amorphous silicon was investigated. With the use of tantalum filaments, the deposition temperature could be decreased to moderate temperatures, while the (electronic) properties of the amorphous silicon were improved. However, at these low filament temperatures the silicide formation at the filaments was enhanced, resulting in a decrease in the deposition rate and a deterioration of the material quality over time. For extensive silicide formation, even epitaxial growth on crystalline wafers was observed. By preheating the filaments at elevated temperature before deposition, the influence of silicide formation could be minimized, which resulted in an improvement in the reproducibility of the material quality. Solar cells, in which the absorbing layer was made at moderate temperature, had high open-circuit voltages and high fill factors. The best n-i-p structured cell on plain stainless steel had an initial efficiency of 7.2 %. The incorporation of amorphous silicon in p-i-n structured cells with a textured front contact resulted in a higher short-circuit current density and a higher efficiency. Occasionally, many n-i-p structured cells showed shunting problems. The number of working cells was directly correlated to the age of the filaments. The presence of silicides on the

  17. Comparison between ZnO nanowires grown by chemical vapor deposition and hydrothermal synthesis

    Science.gov (United States)

    Podrezova, L. V.; Porro, S.; Cauda, V.; Fontana, M.; Cicero, G.

    2013-11-01

    Vertically aligned zinc oxide nanowires (NWs) were synthesized by two different techniques: chemical vapor deposition (CVD) and hydrothermal synthesis. To compare the effects of different growth conditions, both F-doped SnO2 (FTO) coated-glass and silicon wafers were used as substrates. Before NWs growth, all the substrates were covered with a ZnO seed layer film obtained with the same procedure, which acts as nucleation site for the subsequent growth of the nanowires both during CVD and hydrothermal synthesis. We studied the influence of the two synthesis techniques and the growth duration on the final morphology, orientation, and density of the ZnO NWs using electron microscopy and X-ray diffraction, while the NWs optical quality was addressed by UV-Vis spectroscopy. By discussing advantages and disadvantages of both synthesis methods, we finally show that the application purpose often drives the choice of the NWs growth process and the substrate to be used.

  18. Low-level doping of nitrogen to multilayered graphene by chemical vapor deposition of methane including melamine vapor

    Science.gov (United States)

    Bandow, Shunji; Yoshida, Takahiro

    2017-12-01

    Growth of graphene doped with the low level of nitrogen is carried out on the copper foil by conventional chemical vapor deposition. Melamine is used as nitrogen source. Melamine vapor is generated by heating and carried by an argon flow (carrier flow) to a main flow of Ar including methane. Ratio of the number of molecules, melamine/methane, is controlled by changing the mixing rate of the carrier flow and the main flow. Measurements of Raman scattering, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy and sheet resistance clarify the feature of prepared sample. At low melamine/methane ratio in the order of 10-3, quaternary N doped graphene is grown. Then the growth of pyridinic N doped graphene is going to start as increasing the melamine/methane ratio in the order of 10-2. Magnitude of the sheet resistance per one graphene layer decreases by 75% when the nitrogen is in the quaternary site, while it increases twice or more when the pyridine-like configuration increases.

  19. Low temperature deposition of crystalline silicon on glass by hot wire chemical vapor deposition

    Science.gov (United States)

    Chung, Yung-Bin; Park, Hyung-Ki; Lee, Dong-Kwon; Jo, Wook; Song, Jean-Ho; Lee, Sang-Hoon; Hwang, Nong-Moon

    2011-07-01

    Although the deposition of crystalline silicon on a glass substrate has been pursued using hot wire chemical vapor deposition or plasma enhanced chemical vapor deposition for applications in flat panel displays and solar cells, the process has been only partly successful because of the inevitable formation of an amorphous incubation layer on a glass substrate. Currently, the crystalline silicon films are prepared by depositing an amorphous silicon film on a glass substrate and then crystallizing it by excimer laser annealing (ELA), metal induced crystallization or rapid thermal annealing (RTA). Here we report a new process, which can remove the amorphous incubation layer and thereby deposit crystalline silicon directly on glass using HCl. The intrinsic crystalline silicon film has a conductivity of 3.7×10 -5 Scm -1 and the n-type doped crystalline silicon film has the Hall mobility of 15.8 cm 2V -1 s -1, whose values are comparable to those prepared by ELA and RTA, respectively.

  20. Immobilization of whole cells by chemical vapor deposition of silica.

    Science.gov (United States)

    Sizemore, Susan R; Nichols, Robert; Tatum, Randi; Atanassov, Plamen; Johnson, Glenn R; Luckarift, Heather R

    2013-01-01

    Effective entrapment of whole bacterial cells onto solid-phase materials can significantly improve bioprocessing and other biotechnology applications. Cell immobilization allows integration of biocatalysts in a manner that maintains long-term cell viability and typically enhances process output. A wide variety of functionalized materials have been explored for microbial cell immobilization, and specific advantages and limitations were identified. The method described here is a simple, versatile, and scalable one-step process for the chemical vapor deposition of silica to encapsulate and stabilize viable, whole bacterial cells. The immobilized bacterial population is prepared and captured at a predefined physiological state so as to affix bacteria with a selected metabolic or catalytic capability to compatible materials and surfaces. Immobilization of Shewanella oneidensis to carbon electrodes and immobilization of Acinetobacter venetianus to adsorbent mats are described as model systems.

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

    Directory of Open Access Journals (Sweden)

    Fa-Kuei Tung

    2009-01-01

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

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

    Science.gov (United States)

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

    2013-08-27

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

  3. Crack-free yttria stabilized zirconia thin films by aerosol assisted chemical vapor deposition: Influence of water and carrier gas

    Energy Technology Data Exchange (ETDEWEB)

    Schlupp, M.V.F., E-mail: Meike.Schlupp@mat.ethz.ch [Nonmetallic Inorganic Materials, ETH Zuerich, Wolfgang-Pauli-Str. 10, 8093 Zuerich (Switzerland); Binder, S.; Martynczuk, J.; Prestat, M. [Nonmetallic Inorganic Materials, ETH Zuerich, Wolfgang-Pauli-Str. 10, 8093 Zuerich (Switzerland); Gauckler, L.J. [Nonmetallic Inorganic Materials, ETH Zuerich, Wolfgang-Pauli-Str. 10, 8093 Zuerich (Switzerland); International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan)

    2012-11-01

    Yttria stabilized zirconia thin films are deposited on silicon single crystal substrates by aerosol assisted chemical vapor deposition from precursor solutions of zirconium and yttrium 2,4-pentanedionate in ethanol. Continuous films are obtained using pure oxygen, pure nitrogen, or mixtures of both as carrier gas. In the simultaneous presence of water and oxygen, crack formation is observed for films deposited at intermediate substrate temperatures (450 Degree-Sign C), while those deposited at low (300 Degree-Sign C) and high (600 Degree-Sign C) temperatures remain crack-free. Crack-free films can be deposited at 450 Degree-Sign C in a water-free setting, or in the presence of water using pure nitrogen as carrier gas. The addition of water to the precursor solutions also significantly reduces film growth rates. - Highlights: Black-Right-Pointing-Pointer Thin film deposition by aerosol assisted chemical vapor deposition (AA-CVD) Black-Right-Pointing-Pointer Yttria stabilized zirconia (YSZ) thin films deposited between 300 Degree-Sign C and 600 Degree-Sign C Black-Right-Pointing-Pointer Water decreases growth rates and leads to crack formation in AA-CVD of YSZ. Black-Right-Pointing-Pointer Crack-free YSZ thin films deposited using oxygen and/or nitrogen as carrier gas Black-Right-Pointing-Pointer YSZ thin films deposited by AA-CVD show low shrinkage on annealing at 1000 Degree-Sign C.

  4. Formation of SiC thin films by chemical vapor deposition with vinylsilane precursor

    Science.gov (United States)

    Doi, Takuma; Takeuchi, Wakana; Jin, Yong; Kokubun, Hiroshi; Yasuhara, Shigeo; Nakatsuka, Osamu; Zaima, Shigeaki

    2018-01-01

    We have examined the formation of SiC thin films by chemical vapor deposition (CVD) using vinylsilane and investigated the chemical bonding state and crystallinity of the prepared SiC thin films. We achieved the formation of a Si–H–less SiC film at growth temperatures as low as 600 °C. Also, we investigated the in situ doping effect of N by the incorporation of NH3 gas in the SiC growth and demonstrated that the chemical composition of N in SiC thin films was controlled by adjusting the NH3 flow rate. In addition, we examined the growth of SiC thin films on a Cu substrate and achieved the formation of a SiC thin film while avoiding any significant reaction between SiC and Cu at a growth temperature of 700 °C.

  5. 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.

  6. 2017 Report for New LANL Physical Vapor Deposition Capability

    Energy Technology Data Exchange (ETDEWEB)

    Roman, Audrey Rae [Los Alamos National Laboratory; Zhao, Xinxin [Los Alamos National Laboratory; Bond, Evelyn M. [Los Alamos National Laboratory; Gooden, Matthew Edgell [Los Alamos National Laboratory; Rundberg, Robert S. [Los Alamos National Laboratory; Bredeweg, Todd Allen [Los Alamos National Laboratory

    2017-10-03

    There is an urgent need at LANL to achieve uniform, thin film actinide targets that are essential for nuclear physics experiments. The target preparation work is currently performed externally by Professor Walter Loveland at Oregon State University, who has made various evaporated actinide targets such as Th and U for use on several nuclear physics measurements at LANSCE. We are developing a vapor deposition capability, with the goal of evaporating Th and U in the Actinide Research Facility (ARF) at TA-48. In the future we plan to expand this work to evaporating transuranic elements, such as Pu. The ARF is the optimal location for evaporating actinides because this lab is specifically dedicated to actinide research. There are numerous instruments in the ARF that can be used to provide detailed characterization of the evaporated thin films such as: Table top Scanning Electron Microscope, In-situ X-Ray Diffraction, and 3D Raman spectroscopy. These techniques have the ability to determine the uniformity, surface characterization, and composition of the deposits.

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

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre

    2007-02-28

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

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

    Science.gov (United States)

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

    2004-01-01

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

  9. Optical Diagnostics in the Combustion Chemical Vapor Deposition Proces

    Science.gov (United States)

    Luten, Henry; Oljaca, Miodrag; Tomov, Trifon; Metzger, Timothy

    1999-11-01

    Optical emission spectroscopy and IR temperature measurements are used to investigate the structure of a sub-micron droplet spray flame in the Combustion Chemical Vapor Deposition (CCVD) process. The specific system examined in this study is the deposition of barium-strontium-titanate (BaxSr1-xTiO3), a high performance ferroelectric. Spectral measurements were used to determine the decomposition rates of the precursors as well as the lifetimes and relative concentrations of the primary decomposition products. The emissions from atomic and unimolecular species reach a maximum value early in the flame and then decrease sharply, indicating very fast reaction rates. This data, however, is a function of the flame temperature. In order to arrive at proper relative concentration data, the optical emission data must be normalized using measured temperature. Two-dimensional temperature maps were obtained using a non-contact, infrared temperature sensor with peak sensitivity at 4.5 microns. It was found that the sodium emission intensity correlates with the flame temperature, and the sodium emission was used as an internal standard for removing the temperature factor and isolating the relative concentration data. While the flame temperature reaches maximum value at approximately 2 cm, the normalized emission for most species reaches peak intensity closer to the nozzle exit.

  10. A three-dimensional phase field model for nanowire growth by the vapor-liquid-solid mechanism

    Science.gov (United States)

    Wang, Yanming; Ryu, Seunghwa; McIntyre, Paul C.; Cai, Wei

    2014-07-01

    We present a three-dimensional multi-phase field model for catalyzed nanowire (NW) growth by the vapor-liquid-solid (VLS) mechanism. The equation of motion contains both a Ginzburg-Landau term for deposition and a diffusion (Cahn-Hilliard) term for interface relaxation without deposition. Direct deposition from vapor to solid, which competes with NW crystal growth through the molten catalyst droplet, is suppressed by assigning a very small kinetic coefficient at the solid-vapor interface. The thermodynamic self-consistency of the model is demonstrated by its ability to reproduce the equilibrium contact angles at the VLS junction. The incorporation of orientation dependent gradient energy leads to faceting of the solid-liquid and solid-vapor interfaces. The model successfully captures the curved shape of the NW base and the Gibbs-Thomson effect on growth velocity.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-07-01

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

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

    Science.gov (United States)

    2013-04-11

    potential applications of such large-scale synthetic graphene . Keywords: CVD graphene ; atmospheric pressure CVD growth; copper foil; Raman scat- tering...b) Transparent PMMA/ graphene membrane floating on copper etchant. (c) Three layers of stacked CVD graphene on a cover glass made by consecutively...Deposition on Copper Foils Fig. 3. Raman spectra of tBLG domains on Si/SiO2 substrate. (a) Optical image of transferred CVD graphene film with randomly

  13. CMAS Interactions with Advanced Environmental Barrier Coatings Deposited via Plasma Spray- Physical Vapor Deposition

    Science.gov (United States)

    Harder, B. J.; Wiesner, V. L.; Zhu, D.; Johnson, N. S.

    2017-01-01

    Materials for advanced turbine engines are expected to have temperature capabilities in the range of 1370-1500C. At these temperatures the ingestion of sand and dust particulate can result in the formation of corrosive glass deposits referred to as CMAS. The presence of this glass can both thermomechanically and thermochemically significantly degrade protective coatings on metallic and ceramic components. Plasma Spray- Physical Vapor Deposition (PS-PVD) was used to deposit advanced environmental barrier coating (EBC) systems for investigation on their interaction with CMAS compositions. Coatings were exposed to CMAS and furnace tested in air from 1 to 50 hours at temperatures ranging from 1200-1500C. Coating composition and crystal structure were tracked with X-ray diffraction and microstructure with electron microscopy.

  14. Low-Temperature Deposition of Zinc Oxide Film by Plasma-Assisted Mist Chemical Vapor Deposition

    Science.gov (United States)

    Takenaka, Kosuke; Okumura, Yusuke; Setsuhara, Yuichi

    2012-08-01

    Zinc oxide (ZnO) film deposition using a plasma-assisted mist chemical vapor deposition (CVD) with an inductively-coupled plasma source has been performed and the effects of the plasma exposure on film properties have been investigated with oxygen mixture ratio as a parameter. With increasing oxygen mixture ratio to Ar+O2(10%), the X-ray diffraction (XRD) results showed evident peaks of ZnO(0002), indicating that highly c-axis-oriented films were grown at low substrate temperatures below 200 °C. The deposition rate of ZnO films was as high as 100 nm/min. ZnO films with an optical transmittance of 75% for the visible region and a band gap energy of 3.32 eV have been obtained by using plasma-assisted mist CVD.

  15. 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

  16. 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.

  17. 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.

  18. Effect of cooling condition on chemical vapor deposition synthesis of graphene on copper catalyst.

    Science.gov (United States)

    Choi, Dong Soo; Kim, Keun Soo; Kim, Hyeongkeun; Kim, Yena; Kim, TaeYoung; Rhy, Se-hyun; Yang, Cheol-Min; Yoon, Dae Ho; Yang, Woo Seok

    2014-11-26

    Here, we show that chemical vapor deposition growth of graphene on copper foil is strongly affected by the cooling conditions. Variation of cooling conditions such as cooling rate and hydrocarbon concentration in the cooling step has yielded graphene islands with different sizes, density of nuclei, and growth rates. The nucleation site density on Cu substrate is greatly reduced when the fast cooling condition was applied, while continuing methane flow during the cooling step also influences the nucleation and growth rate. Raman spectra indicate that the graphene synthesized under fast cooling condition and methane flow on cool-down exhibit superior quality of graphene. Further studies suggest that careful control of the cooling rate and CH4 gas flow on the cooling step yield a high quality of graphene.

  19. Numerical study of a three-dimensional chemical vapor deposition reactor with detailed chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Ern, A. [CERMICS-ENPC, Noisy-le-Grand (France); Giovangigli, V. [Encole Polytechnique, Palaiseau (France); Smooke, M.D. [Yale Univ., New Haven, CT (United States)

    1996-06-01

    A numerical model of a three-dimensional, horizontal channel, chemical vapor deposition reactor is presented in order to study gallium arenide growth from trimethylgallium and arsine source reactants. Fluid flow and temperature predictions inside the reactor are obtained using the vorticity-velocity form of the three-dimensional, study-state Navier-Stokes equations coupled with a detailed energy balance equation inside the reactor and on its walls. Detailed gas phase and surface chemistry mechanisms are used to predict the chemical species profiles inside the reactor, the growth rate distribution on the substrate, and the level of carbon incorporation into the grown layer. The species diffusion velocities are written using the recent theory of iterative transport algorithms and account for both thermal diffusion and multicomponent diffusion processes. The influence of susceptor temperature and inlet composition on growth rate and carbon incorporation is found to agree well with previous numerical and experimental work. 46 refs., 15 figs., 3 tabs.

  20. Exploring metalorganic chemical vapor deposition of Si-alloyed Al2O3 dielectrics using disilane

    Science.gov (United States)

    Chan, Silvia H.; Keller, Stacia; Koksaldi, Onur S.; Gupta, Chirag; DenBaars, Steven P.; Mishra, Umesh K.

    2017-04-01

    The alloying of Al2O3 films with Si is a promising route to improve gate dielectric properties in Si- and wide-bandgap- based MOS devices. Here we present a comprehensive investigation of alloyed film growth by metalorganic chemical vapor deposition (MOCVD) using trimethylaluminum, disilane, and oxygen precursors over a variety of temperature and flow conditions. Binary growth rates of Al2O3 and SiO2 were evaluated to explain the aggregate growth kinetics of Si-alloyed Al2O3 films, and refractive indices were used to monitor Si incorporation efficiencies. The temperature dependence of the reaction rate of disilane with oxygen was found to be similar to that of trimethylaluminum and oxygen, leading to well-behaved deposition behavior in the kinetic and mass-transport controlled growth regimes. Compositional predictability and stability was achieved over a wider growth space with disilane-based growths as compared to previous work, which used silane as the Si precursor instead. In situ (Al,Si)O/n-GaN MOS gate stacks were grown and showed increasing reduction of net positive fixed charges with higher Si composition.

  1. Synthesis and characterization of diamond microcrystals and nanorods deposited by hot cathode direct current plasma chemical vapor deposition method

    NARCIS (Netherlands)

    Zeng, L.; Peng, H.; Wang, W.; Chen, Y.; Lei, D.; Qi, W.; Liang, J.; Zhao, J.; Kong, X.; Zhang, H.

    2008-01-01

    (111) diamond microcrystals and (100) diamond microcrystals and nanorods were synthesized on Si substrate by hot cathode direct current plasma chemical vapor deposition method. The morphology, structure, and optical properties of the diamond films were characterized by scanning electron microscopy,

  2. Microstructural Effects and Properties of Non-line-of-Sight Coating Processing via Plasma Spray-Physical Vapor Deposition

    Science.gov (United States)

    Harder, Bryan J.; Zhu, Dongming; Schmitt, Michael P.; Wolfe, Douglas E.

    2017-08-01

    Plasma spray-physical vapor deposition (PS-PVD) is a unique processing method that bridges the gap between conventional thermal spray and vapor phase methods, and enables highly tailorable coatings composed of a variety of materials in thin, dense layers or columnar microstructures with modification of the processing conditions. The strengths of this processing technique are material and microstructural flexibility, deposition speed, and potential for non-line-of-sight (NLOS) capability by vaporization of the feedstock material. The NLOS capability of PS-PVD is investigated here using yttria-stabilized zirconia and gadolinium zirconate, which are materials of interest for turbine engine applications. PS-PVD coatings were applied to static cylindrical substrates approximately 6-19 mm in diameter to study the coating morphology as a function of angle. In addition, coatings were deposited on flat substrates under various impingement configurations. Impingement angle had significant effects on the deposition mode, and microscopy of coatings indicated that there was a shift in the deposition mode at approximately 90° from incidence on the cylindrical samples, which may indicate the onset of more turbulent flow and PVD-like growth. Coatings deposited at non-perpendicular angles exhibited a higher density and nearly a 2× improvement in erosion performance when compared to coatings deposited with the torch normal to the surface.

  3. PROPERTIES AND OPTICAL APPLICATION OF POLYCRYSTALLINE ZINC SELENIDE OBTAINED BY PHYSICAL VAPOR DEPOSITION

    Directory of Open Access Journals (Sweden)

    A. A. Dunaev

    2015-05-01

    Full Text Available Findings on production technology, mechanical and optical properties of polycrystalline zinc selenide are presented. The combination of its physicochemical properties provides wide application of ZnSe in IR optics. Production technology is based on the method of physical vapor deposition on a heated substrate (Physical Vapor Deposition - PVD. The structural features and heterogeneity of elemental composition for the growth surfaces of ZnSe polycrystalline blanks were investigated using CAMEBAX X-ray micro-analyzer. Characteristic pyramid-shaped crystallites were recorded for all growth surfaces. The measurements of the ratio for major elements concentrations show their compliance with the stoichiometry of the ZnSe compounds. Birefringence, optical homogeneity, thermal conductivity, mechanical and optical properties were measured. It is established that regardless of polycrystalline condensate columnar and texturing, the optical material is photomechanically isotropic and homogeneous. The actual performance of parts made of polycrystalline optical zinc selenide in the thermal spectral ranges from 3 to 5 μm and from 8 to 14 μm and in the CO2 laser processing plants with a power density of 500 W/cm2 is shown. The developed technology gives the possibility to produce polycrystalline optical material on an industrial scale.

  4. Anisotropic hydrogen etching of chemical vapor deposited graphene.

    Science.gov (United States)

    Zhang, Yi; Li, Zhen; Kim, Pyojae; Zhang, Luyao; Zhou, Chongwu

    2012-01-24

    We report a simple, clean, and highly anisotropic hydrogen etching method for chemical vapor deposited (CVD) graphene catalyzed by the copper substrate. By exposing CVD graphene on copper foil to hydrogen flow around 800 °C, we observed that the initially continuous graphene can be etched to have many hexagonal openings. In addition, we found that the etching is temperature dependent. Compared to other temperatures (700, 900, and 1000 °C), etching of graphene at 800 °C is most efficient and anisotropic. Of the angles of graphene edges after etching, 80% are 120°, indicating the etching is highly anisotropic. No increase of the D band along the etched edges indicates that the crystallographic orientation of etching is in the zigzag direction. Furthermore, we observed that copper played an important role in catalyzing the etching reaction, as no etching was observed for graphene transferred to Si/SiO(2) under similar conditions. This highly anisotropic hydrogen etching technology may work as a simple and convenient way to determine graphene crystal orientation and grain size and may enable the etching of graphene into nanoribbons for electronic applications. © 2011 American Chemical Society

  5. Backbone-Degradable Polymers Prepared by Chemical Vapor Deposition.

    Science.gov (United States)

    Xie, Fan; Deng, Xiaopei; Kratzer, Domenic; Cheng, Kenneth C K; Friedmann, Christian; Qi, Shuhua; Solorio, Luis; Lahann, Joerg

    2017-01-02

    Polymers prepared by chemical vapor deposition (CVD) polymerization have found broad acceptance in research and industrial applications. However, their intrinsic lack of degradability has limited wider applicability in many areas, such as biomedical devices or regenerative medicine. Herein, we demonstrate, for the first time, a backbone-degradable polymer directly synthesized via CVD. The CVD co-polymerization of [2.2]para-cyclophanes with cyclic ketene acetals, specifically 5,6-benzo-2-methylene-1,3-dioxepane (BMDO), results in well-defined, hydrolytically degradable polymers, as confirmed by FTIR spectroscopy and ellipsometry. The degradation kinetics are dependent on the ratio of ketene acetals to [2.2]para-cyclophanes as well as the hydrophobicity of the films. These coatings address an unmet need in the biomedical polymer field, as they provide access to a wide range of reactive polymer coatings that combine interfacial multifunctionality with degradability. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Chemical vapor deposition of amorphous tungsten nitride for applications in ultra-large scale interconnect technologies

    Science.gov (United States)

    Kelsey, Jean E.

    Increasing demands on computer chip technology require exploration of novel materials and deposition techniques. The driving need to reduce device dimensions without increasing device delay time has forced a move towards copper interconnects. Copper interconnects require an encapsulating barrier layer to prevent diffusion into the dielectric layer, as well as a passivation layer to protect against oxidation. One potential material for the barrier layer is tungsten nitride (WNx). Tungsten nitride is expected to perform well as a barrier because of its refractory nature and excellent thermal, chemical, and mechanical properties. In addition, it can be deposited in amorphous form. Amorphous materials have no grain boundaries, thereby making grain boundary diffusion, a fast path diffusion mechanism, impossible. In this work, a chemical vapor deposition (CVD) process was developed for the deposition of tungsten nitride. CVD was selected because it has the potential to deposit highly conformal film. High conformality is critical in a barrier layer in order to ensure viable coverage at the bottom and sides of device structures without sacrificing critical space that would be better used by the copper metal. In this manner, the total resistivity of the interconnect is minimized. The CVD WNx process was systematically optimized for film conformality, resistivity and growth rate. This was achieved by thoroughly examining film nucleation and growth characteristics, and analyzing resulting film properties. Adhesion of copper to the CVD films was qualified using stud pull tests, while X-ray diffraction was implemented to determine crystallization temperature of the amorphous phase. Additionally, diffusion barrier properties of the CVD tungsten nitride were assessed using sputter deposited copper, and compared to those of sputter deposited tungsten nitride. Thermally activated barrier failure was studied as a function of barrier thickness using Rutherford backscattering

  7. Effects of fabrication method of Al2O3 buffer layer on Rh-catalyzed growth of single-walled carbon nanotubes by alcohol-gas-source chemical vapor deposition

    Science.gov (United States)

    Kiribayashi, Hoshimitsu; Fujii, Takayuki; Kozawa, Akinari; Ogawa, Seigo; Saida, Takahiro; Naritsuka, Shigeya; Maruyama, Takahiro

    2017-06-01

    Amorphous Al2O3 buffer layers have been widely used to enhance the yield in the growth of single-walled carbon nanotubes (SWCNTs). In this study, we carried out SWCNT growth using a Rh catalyst on Al2O3 buffer layers that were prepared by three different methods based on electron beam (EB) evaporation: native oxidation of Al layer deposited by EB; thermal oxidation of Al layer deposited by EB; EB deposition of Al2O3 layer. We investigated the effects of fabrication method of the Al2O3 buffer layer on SWCNT yield and found that the SWCNT yield was the largest for Al2O3 layer prepared by EB deposition of Al2O3, while SWCNTs were not grown on the Al2O3 layer obtained by native oxidation of the Al layer. Based on the results of X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, and atomic force microscopy, we examined the effects of crystalline quality and oxidation degree of Al2O3 layers on the catalytic activity.

  8. Thin CdS films prepared by metalorganic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hiroshi Uda; Yonezawa, Hideo; Ohtsubo, Yoshikazu; Kosaka, Manabu; Sonomura, Hajimu [Kinki Univ., Osaka (Japan). Faculty of Science and Technology

    2003-01-01

    Polycrystalline CdS thin films have been deposited on borosilicate glass substrates coated with ITO film by metalorganic chemical vapor deposition using dimethyl cadmium and diethyl sulfide as source materials. The growth of CdS film occurred at substrate temperatures within the range of 280-360{sup o}C. The deposition rate increased with increasing VI/II molar ratio at any substrate temperature and showed a maximum value at the VI/II molar ratio of 4. The grain size of as-deposited CdS film prepared at substrate temperatures from 300{sup o}C to 360{sup o}C was about 0.1 {mu}m. The CdS films consist of hexagonal form with a preferential orientation of the (0 0 2) plane parallel to the substrate. Thin CdS film with high optical transmittance was prepared at 350{sup o}C with the VI/II molar ratio of 4. The CdS film deposited by MOCVD may be used as a window layer for CdS/CdTe solar cell.(author)

  9. Vapor phase growth of functional pentacene films at atmospheric pressure

    NARCIS (Netherlands)

    Rolin, C.; Vasseur, K.; Niesen, B.; Willegems, M.; Müller, R.; Steudel, S.; Genoe, J.; Heremans, P.

    2012-01-01

    Compared to traditional vacuum evaporation techniques for small organic molecules, organic vapor phase deposition (OVPD) possesses a extra processing parameter: the pressure of process gas Pch. Here, the influence of large Pch variations (from 0.1 mbar to atmospheric pressure) on pentacene thin film

  10. Continuous Fabrication of SiC Fiber Tows by Chemical Vapor Deposition

    Science.gov (United States)

    1993-01-01

    Niobium Carbonitride Films on Carbon Fibers," pp. 300-14 in Proceedings on the Seventh International Conference on Chemical Vapor Deposition, The...34Modeling of the Chemical Vapor Deposition of YI3a 2Cu30z, TiB•, and SiC Thin Films Onto Continuous Ceramic Tows," Ph.D. Dissertation, School of...SUJRJ Ct 7URM’S 15. NUMBER OF PAGES 98 Fibers, Silicon (Carbide. Chemical Vapor Deposition 16. PRICE CODE F SFSCURV C’A1 ’,’-,(AH.T,.)I•sJ $ ,,ui T 7

  11. Aspects of thin film deposition on granulates by physical vapor deposition

    Science.gov (United States)

    Eder, Andreas; Schmid, Gerwin H. S.; Mahr, Harald; Eisenmenger-Sittner, Christoph

    2016-11-01

    Thin film and coating technology has entered fields which may show significant deviations from classical coating applications where films are deposited on plane, sometimes large substrates. Often surfaces of small and irregularly shaped bodies have to be improved in respect to electrical, thermal or mechanical properties. Film deposition and characterization on such small substrates is not a trivial task. This specially holds for methods based on Physical Vapor Deposition (PVD) processes such as sputter deposition and its ion- and plasma assisted varieties. Due to their line of sight nature a key issue for homogenous films is efficient intermixing. If this problem is mastered, another task is the prediction and determination of the film thickness on single particles as well as on large scale ensembles thereof. In this work a mechanism capable of uniformly coating up to 1000 cm3 of granulate with particle sizes ranging from approx. 10 μm to 150 μm by magnetron sputtering is thoroughly described. A method for predicting the average film thickness on the particles is presented and tested for several differently shaped objects like microspheres, irregular grains of sinter powder or micro diamonds. For assessing the film thickness on single particles as well as on particle ensembles several complementary methods based on optics, X-ray analysis and gravimetry are employed. Their respective merits and limitations are discussed. Finally an outlook on adapting the described technology for surface modification by plasma based reactive and non-reactive processes is given.

  12. Large single crystals of graphene on melted copper using chemical vapor deposition.

    Science.gov (United States)

    Wu, Yimin A; Fan, Ye; Speller, Susannah; Creeth, Graham L; Sadowski, Jerzy T; He, Kuang; Robertson, Alex W; Allen, Christopher S; Warner, Jamie H

    2012-06-26

    A simple method is presented for synthesizing large single crystal graphene domains on melted copper using atmospheric pressure chemical vapor deposition (CVD). This is achieved by performing the reaction above the melting point of copper (1090 °C) and using a molybdenum or tungsten support to prevent balling of the copper from dewetting. By controlling the amount of hydrogen during growth, individual single crystal domains of monolayer graphene greater than 200 μm are produced within a continuous film. Stopping growth before a complete film is formed reveals individual hexagonal domains of graphene that are epitaxially aligned in their orientation. Angular resolved photoemission spectroscopy is used to show that the graphene grown on copper exhibits a linear dispersion relationship and no sign of doping. HRTEM and electron diffraction reveal a uniform high quality crystalline atomic structure of monolayer graphene.

  13. Ultrahigh-mobility graphene devices from chemical vapor deposition on reusable copper.

    Science.gov (United States)

    Banszerus, Luca; Schmitz, Michael; Engels, Stephan; Dauber, Jan; Oellers, Martin; Haupt, Federica; Watanabe, Kenji; Taniguchi, Takashi; Beschoten, Bernd; Stampfer, Christoph

    2015-07-01

    Graphene research has prospered impressively in the past few years, and promising applications such as high-frequency transistors, magnetic field sensors, and flexible optoelectronics are just waiting for a scalable and cost-efficient fabrication technology to produce high-mobility graphene. Although significant progress has been made in chemical vapor deposition (CVD) and epitaxial growth of graphene, the carrier mobility obtained with these techniques is still significantly lower than what is achieved using exfoliated graphene. We show that the quality of CVD-grown graphene depends critically on the used transfer process, and we report on an advanced transfer technique that allows both reusing the copper substrate of the CVD growth and making devices with mobilities as high as 350,000 cm(2) V(-1) s(-1), thus rivaling exfoliated graphene.

  14. Microstructural and frictional control of diamond-like carbon films deposited on acrylic rubber by plasma assisted chemical vapor deposition

    NARCIS (Netherlands)

    Martinez-Martinez, D.; Schenkel, M.; Pei, Y.T.; Hosson, J.Th.M. De

    2011-01-01

    In this paper we concentrate on the microstructure of diamond-like carbon films prepared by plasma assisted chemical vapor deposition on acrylic rubber. The temperature variation produced by the ion impingement during plasma cleaning and subsequent film deposition was monitored and controlled as a

  15. 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.

  16. Deposition characteristics of titanium coating deposited on SiC fiber by cold-wall chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Xian, E-mail: luo_shenfan@hotmail.com; Wu, Shuai; Yang, Yan-qing; Jin, Na; Liu, Shuai; Huang, Bin

    2016-12-01

    The deposition characteristics of titanium coating on SiC fiber using TiCl{sub 4}-H{sub 2}-Ar gas mixture in a cold-wall chemical vapor deposition were studied by the combination of thermodynamic analysis and experimental studies. The thermodynamic analysis of the reactions in the TiCl{sub 4}-H{sub 2}-Ar system indicates that TiCl{sub 4} transforms to titanium as the following paths: TiCl{sub 4} → TiCl{sub 3} → Ti, or TiCl{sub 4} → TiCl{sub 3} → TiCl{sub 2} → Ti. The experimental results show that typical deposited coating contains two distinct layers: a TiC reaction layer close to SiC fiber and titanium coating which has an atomic percentage of titanium more than 70% and that of carbon lower than 30%. The results illustrate that a carbon diffusion barrier coating needs to be deposited if pure titanium is to be prepared. The deposition rate increases with the increase of temperature, but higher temperature has a negative effect on the surface uniformity of titanium coating. In addition, appropriate argon gas flow rate has a positive effect on smoothing the surface morphology of the coating. - Highlights: • Both thermodynamic analysis and experimental studies were adopted in this work. • The transformation paths of TiCl{sub 4} to Ti is: TiCl{sub 4} → TiCl{sub 3} → Ti, or TiCl{sub 4} → TiCl{sub 3} → TiCl{sub 2} → Ti. • Typical deposited Ti coating on SiC fiber contained two distinct layers. • Deposition temperature is important on deposition rate and morphologies. • Appropriate argon gas flow rate has a positive effect on smoothing of the coating.

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

    NARCIS (Netherlands)

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

    2015-01-01

    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

  18. A chemical kinetic model for chemical vapor deposition of carbon nanotubes

    Science.gov (United States)

    Raji, K.; Thomas, Shijo; Sobhan, C. B.

    2011-10-01

    Carbon nanotubes (CNTs) are classified among the most promising novel materials due to their exceptional physical properties. Still, optimal fabrication of carbon nanotubes involves a number of challenges. Whatever be the fabrication method, a process optimization can be evolved only on the basis of a good theoretical model to predict the parametric influences on the final product. The work reported here investigates the dependence of the deposition parameters on the controllable parameters for carbon nanotube growth during Chemical vapor deposition (CVD), through a chemical kinetic model. The theoretical model consisted of the design equations and the energy balance equations, based on the reaction kinetics, for the plug flow and the batch reactor, which simulate the CVD system. The numerical simulation code was developed in-house in a g++ environment. The results predicted the growth conditions for CNT: the deposition temperature, pressure and number of atoms, which were found to be influenced substantially by the initial controllable parameters namely the temperature, volumetric flow rate of the carbon precursor, and the reaction time. An experimental study was also conducted on a CVD system developed in the laboratory, to benchmark the computational results. The experimental results were found to agree well with the theoretical predictions obtained from the model.

  19. Effect of AlN growth temperature on trap densities of in-situ metal-organic chemical vapor deposition grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors

    Directory of Open Access Journals (Sweden)

    Joseph J. Freedsman

    2012-06-01

    Full Text Available The trapping properties of in-situ metal-organic chemical vapor deposition (MOCVD grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors (MIS-HFETs with AlN layers grown at 600 and 700 °C has been quantitatively analyzed by frequency dependent parallel conductance technique. Both the devices exhibited two kinds of traps densities, due to AlN (DT-AlN and AlGaN layers (DT-AlGaN respectively. The MIS-HFET grown at 600 °C showed a minimum DT-AlN and DT-AlGaN of 1.1 x 1011 and 1.2 x 1010 cm-2eV-1 at energy levels (ET -0.47 and -0.36 eV. Further, the gate-lag measurements on these devices revealed less degradation ∼ ≤ 5% in drain current density (Ids-max. Meanwhile, MIS-HFET grown at 700 °C had more degradation in Ids-max ∼26 %, due to high DT-AlN and DT-AlGaN of 3.4 x 1012 and 5 x 1011 cm-2eV-1 positioned around similar ET. The results shows MIS-HFET grown at 600 °C had better device characteristics with trap densities one order of magnitude lower than MIS-HFET grown at 700 °C.

  20. Fabrication of nanostructure by physical vapor deposition with glancing angle deposition technique and its applications

    Energy Technology Data Exchange (ETDEWEB)

    Horprathum, M., E-mail: mati.horprathum@nectec.or.th; Eiamchai, P., E-mail: mati.horprathum@nectec.or.th; Patthanasettakul, V.; Limwichean, S.; Nuntawong, N.; Chindaudom, P. [Optical Thin-Film Laboratory National Electronics and Computer Technology Center, Pathumthani, 12120 (Thailand); Kaewkhao, J. [Center of Excellence in Glass Technology and Materials Science (CEGM), Nakhon Pathom Rajabhat University, Nakhon Pathom 73000 (Thailand); Chananonnawathorn, C. [Department of Physics, Faculty of Science and Technology, Thammasat University, Pathumthani, 12121 (Thailand)

    2014-09-25

    A nanostructural thin film is one of the highly exploiting research areas particularly in applications in sensor, photocatalytic, and solar-cell technologies. In the past two decades, the integration of glancing-angle deposition (GLAD) technique to physical vapor deposition (PVD) process has gained significant attention for well-controlled multidimensional nanomorphologies because of fast, simple, cost-effective, and mass-production capability. The performance and functional properties of the coated thin films generally depend upon their nanostructural compositions, i.e., large aspect ratio, controllable porosity, and shape. Such structural platforms make the fabricated thin films very practical for several realistic applications. We therefore present morphological and nanostructural properties of various deposited materials, which included metals, i.e., silver (Ag), and oxide compounds, i.e., tungsten oxide (WO{sub 3}), titanium dioxide (TiO{sub 2}), and indium tin oxide (ITO). Different PVD techniques based on DC magnetron sputtering and electron-beam evaporation, both with the integrated GLAD component, were discussed. We further explore engineered nanostructures which enable controls of optical, electrical, and mechanical properties. These improvements led to several practical applications in surface-enhanced Raman, smart windows, gas sensors, self-cleaning materials and transparent conductive oxides (TCO)

  1. Layer-selective synthesis of bilayer graphene via chemical vapor deposition

    Science.gov (United States)

    Yang, Ning; Choi, Kyoungjun; Robertson, John; Park, Hyung Gyu

    2017-09-01

    A controlled synthesis of high-quality AB-stacked bilayer graphene by chemical vapor deposition demands a detailed understanding of the mechanism and kinetics. By decoupling the growth of the two layers via a growth-and-regrowth scheme, we report the kinetics and termination mechanisms of the bilayer graphene growth on copper. We observe, for the first time, that the secondary layer growth follows Gompertzian kinetics. Our observations affirm the postulate of a time-variant transition from a mass-transport-limited to a reaction-limited regimes and identify the mechanistic disparity between the monolayer growth and the secondary-layer expansion underneath the monolayer cover. It is the continuous carbon supply that drives the expansion of the graphene secondary layer, rather than the initially captured carbon amount, suggesting an essential role of the surface diffusion of reactant adsorbates in the interspace between the top graphene layer and the underneath copper surface. We anticipate that the layer selectivity of the growth relies on the entrance energetics of the adsorbed reactants to the graphene-copper interspace across the primary-layer edge, which could be engineered by tailoring the edge termination state. The temperature-reliant saturation area of the secondary-layer expansion is understood as a result of competitive attachment of carbon and hydrogen adatoms to the secondary-layer graphene edge.

  2. Preparation of membranes using solvent-less vapor deposition followed by in-situ polymerization

    Energy Technology Data Exchange (ETDEWEB)

    O' Brien, Kevin C [San Ramon, CA; Letts, Stephan A [San Ramon, CA; Spadaccini, Christopher M [Oakland, CA; Morse, Jeffrey C [Pleasant Hill, CA; Buckley, Steven R [Modesto, CA; Fischer, Larry E [Los Gatos, CA; Wilson, Keith B [San Ramon, CA

    2012-01-24

    A system of fabricating a composite membrane from a membrane substrate using solvent-less vapor deposition followed by in-situ polymerization. A first monomer and a second monomer are directed into a mixing chamber in a deposition chamber. The first monomer and the second monomer are mixed in the mixing chamber providing a mixed first monomer and second monomer. The mixed first monomer and second monomer are solvent-less vapor deposited onto the membrane substrate in the deposition chamber. The membrane substrate and the mixed first monomer and second monomer are heated to produce in-situ polymerization and provide the composite membrane.

  3. Preparation of membranes using solvent-less vapor deposition followed by in-situ polymerization

    Science.gov (United States)

    O'Brien, Kevin C [San Ramon, CA; Letts, Stephan A [San Ramon, CA; Spadaccini, Christopher M [Oakland, CA; Morse, Jeffrey C [Pleasant Hill, CA; Buckley, Steven R [Modesto, CA; Fischer, Larry E [Los Gatos, CA; Wilson, Keith B [San Ramon, CA

    2010-07-13

    A system of fabricating a composite membrane from a membrane substrate using solvent-less vapor deposition followed by in-situ polymerization. A first monomer and a second monomer are directed into a mixing chamber in a deposition chamber. The first monomer and the second monomer are mixed in the mixing chamber providing a mixed first monomer and second monomer. The mixed first monomer and second monomer are solvent-less vapor deposited onto the membrane substrate in the deposition chamber. The membrane substrate and the mixed first monomer and second monomer are heated to produce in-situ polymerization and provide the composite membrane.

  4. Nonstoichiometric composition shift in physical vapor deposition of CdTe thin films

    Science.gov (United States)

    Chin, Ken K.; Cheng, Zimeng; Delahoy, Alan E.

    2015-05-01

    While it is being debated whether Cd vacancy is an effective p-dopant in CdTe, and whether CdTe thin film in solar energy application should be Cd-deficient or Cd-rich, in the theory of CdTe physical vapor deposition (PVD) it has been assumed that both the source material and the thin film product is stoichiometric. To remediate the lack of effective theory, a new PVD model for CdTe photovoltaic (PV) modules is presented in this work, in which the composition of the CdTe thin film under growth is a parameter determined by the source CdTe composition as well as the growth condition. The solid phase Cd1-δTe1+δ compound under deposition temperature is treated as a solid solution with a mole of excess pure Te or Cd as solute and one mole of congruently grown CdTe as solvent. Assuming that the vapor pressure of Te2 can be calculated by using the law of solid solution PTe=H0+aH1+a2H2 round the congruent composition, where the molar number a and the constants H0, H1 and H2 as functions of temperature T are extracted from the experimental data. Thus, the mole fraction of solute in the grown CdTe thin film as well as the growth rate, as a function of the solute mole fraction in the source CdTe can be determined.

  5. Comparison of a model vapor deposited glass films to equilibrium glass films

    Science.gov (United States)

    Flenner, Elijah; Berthier, Ludovic; Charbonneau, Patrick; Zamponi, Francesco

    Vapor deposition of particles onto a substrate held at around 85% of the glass transition temperature can create glasses with increased density, enthalpy, kinetic stability, and mechanical stability compared to an ordinary glass created by cooling. It is estimated that an ordinary glass would need to age thousands of years to reach the kinetic stability of a vapor deposited glass, and a natural question is how close to the equilibrium is the vapor deposited glass. To understand the process, algorithms akin to vapor deposition are used to create simulated glasses that have a higher kinetic stability than their annealed counterpart, although these glasses may not be well equilibrated either. Here we use novel models optimized for a swap Monte Carlo algorithm in order to create equilibrium glass films and compare their properties with those of glasses obtained from vapor deposition algorithms. This approach allows us to directly assess the non-equilibrium nature of vapor-deposited ultrastable glasses. Simons Collaboration on Cracking the Glass Problem and NSF Grant No. DMR 1608086.

  6. 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.

  7. Tetrasilane and digermane for the ultra-high vacuum chemical vapor deposition of SiGe alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hart, John, E-mail: hartjt@udel.edu [Department of Electrical Engineering, University of Delaware, 140 Evans Hall, Newark, DE 19716 (United States); Hazbun, Ramsey; Eldridge, David; Hickey, Ryan [Department of Electrical Engineering, University of Delaware, 140 Evans Hall, Newark, DE 19716 (United States); Fernando, Nalin [Department of Physics, University of New Mexico, MSC 3D, P.O. Box 30001, Las Cruces, New Mexico 88003-8001 (United States); Adam, Thomas [College of Nanoscale Science and Engineering, SUNY, New York 12203 (United States); Zollner, Stefan [Department of Physics, University of New Mexico, MSC 3D, P.O. Box 30001, Las Cruces, New Mexico 88003-8001 (United States); Kolodzey, James [Department of Electrical Engineering, University of Delaware, 140 Evans Hall, Newark, DE 19716 (United States)

    2016-04-01

    Tetrasilane and digermane were used to grow epitaxial silicon germanium layers on silicon substrates in a commercial ultra-high vacuum chemical vapor deposition tool. Films with concentrations up to 19% germanium were grown at temperatures from 400 °C to 550 °C. For all alloy compositions, the growth rates were much higher compared to using mono-silane and mono-germane. The quality of the material was assessed using X-ray diffraction, atomic force microscopy, and spectroscopic ellipsometry; all indicating high quality epitaxial films with low surface roughness suitable for commercial applications. Studies of the decomposition kinetics with regard to temperature were performed, revealing an unusual growth rate maximum between the high and low temperature deposition regimes. - Highlights: • Higher order precursors tetrasilane and digermane • Low temperature deposition • Thorough film characterization with temperature • Arrhenius growth rate peak.

  8. Growth behavior of Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} thin films on graphene substrate grown by plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chang Wan [Thin Film Materials Research Group, Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); School of Electrical and Electronic Engineering, Yonsei University, Seoul (Korea, Republic of); Kim, Gun Hwan; Kang, Min A.; An, Ki-Seok; Lee, Young Kuk [Thin Film Materials Research Group, Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); Kang, Seong Gu [School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of); Kim, Hyungjun [School of Electrical and Electronic Engineering, Yonsei University, Seoul (Korea, Republic of)

    2017-03-15

    A comparative study of the substrate effect on the growth mechanism of chalcogenide Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} thin films was carried out. Obvious microstructural discrepancy in both the as-deposited Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} thin films was observed when grown on graphene or SiO{sub 2}/Si substrate. Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3} thin films deposited on the graphene substrate were observed to be grown epitaxially along c-axis and show very smooth surface compared to that on SiO{sub 2}/Si substrate. Based on the experimental results of this study, the initial adsorption sites on graphene substrate during deposition process, which had been discussed theoretically, could be demonstrated empirically. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. 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.

  10. Effects of Ni catalyzer on growth velocity and morphology of vapor growth SiC nano-fibers

    Energy Technology Data Exchange (ETDEWEB)

    Xu Xianfeng; Xiao Peng; Xiong Xiang; Huang Boyun [State Key Lab. for Powder Metallurgy, Central South University, Changsha, 410083 (China)], E-mail: xu-xianfeng@163.com

    2009-03-01

    Using Ni granules as a catalyzer, composite felts reinforced by both SiC nano-fibers (SiC-NFs) and carbon fibers were prepared at 1273K. SiC-NFs were deposited on the surface of the carbon fibers in-situ by chemical vapor growth. The microstructure and morphology of the fibers after being electroplated and deposited were characterized by scanning electron microscopy and transmission electron microscopy. The phase of the fibers after being deposited was characterized by X-ray diffractometry. The results show that the SiC-NFs produced by chemical vapor growth are single crystals of {beta}-SiC. It was found that Ni catalyzer had important effects on the growth of SiC-NFs. Smaller nano-granules were more active as catalyzers, resulting SiC-NFs appeared more spindle-like and had a more homogeneous dispersion. The weight change of the samples before and after deposition shows that a longer electroplating times results in SiC-NFs having a faster growth velocity.

  11. Composition and Morphology Control of Metal Dichalcogenides via Chemical Vapor Deposition for Photovoltaic and Nanoelectronic Applications

    Science.gov (United States)

    Samad, Leith L. J.

    The body of work reviewed here encompasses a variety of metal dichalcogenides all synthesized using chemical vapor deposition (CVD) for solar and electronics applications. The first reported phase-pure CVD synthesis of iron pyrite thin films is presented with detailed structural and electrochemical analysis. The phase-pure thin film and improved crystal growth on a metallic backing material represents one of the best options for potential solar applications using iron pyrite. Large tin-sulfur-selenide solid solution plates with tunable bandgaps were also synthesized via CVD as single-crystals with a thin film geometry. Solid solution tin-sulfur-selenide plates were demonstrated to be a new material for solar cells with the first observed solar conversion efficiencies up to 3.1%. Finally, a low temperature molybdenum disulfide vertical heterostructure CVD synthesis with layered controlled growth was achieved with preferential growth enabled by Van der Waals epitaxy. Through recognition of additional reaction parameters, a fully regulated CVD synthesis enabled the controlled growth of 1-6 molybdenum disulfide monolayers for nanoelectronic applications. The improvements in synthesis and materials presented here were all enabled by the control afforded by CVD such that advances in phase purity, growth, and composition control of several metal dichalcogenides were achieved. Further work will be able to take full advantage of these advances for future solar and electronics technologies.

  12. 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)

  13. 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.

  14. 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.

  15. 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...

  16. Microwave Plasma Enhanced Chemical Vapor Deposition of Diamond in Vapor of Methanol-Based Liquid Solutions

    National Research Council Canada - National Science Library

    Tzeng, Yonhua

    2000-01-01

    .... An electrical discharge is generated by microwave power in a metal cavity in order to dissociate the vapor mixture from one of the liquid solutions, from which radicals such as OH, O, and H that etch...

  17. 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.

  18. Plasma enhanced chemical vapor deposition silicon oxynitride optimized for application in integrated optics

    NARCIS (Netherlands)

    Worhoff, Kerstin; Driessen, A.; Lambeck, Paul; Hilderink, L.T.H.; Linders, Petrus W.C.; Popma, T.J.A.

    1999-01-01

    Silicon Oxynitride layers are grown from SiH4/N2, NH3 and N2O by Plasma Enhanced Chemical Vapor Deposition. The process is optimized with respect to deposition of layers with excellent uniformity in the layer thickness, high homogeneity of the refractive index and good reproducibility of the layer

  19. Optimization of plasma-enhanced chemical vapor deposition silicon oxynitride layers for integrated optics applications

    NARCIS (Netherlands)

    Hussein, M.G.; Worhoff, Kerstin; Sengo, G.; Sengo, G.; Driessen, A.

    2007-01-01

    Silicon oxynitride $(SiO_{x}N_{y}:H)$ layers were grown from 2% $SiH_{4}/N_{2}$ and $N_{2}O$ gas mixtures by plasma-enhanced chemical vapor deposition (PECVD). Layer properties such as refractive index, deposition rate, thickness non-uniformity and hydrogen bond content were correlated to the

  20. 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...

  1. Final Report: Vapor Transport Deposition for Thin Film III-V Photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Boettcher, Shannon [Univ. of Oregon, Eugene, OR (United States); Greenaway, Ann [Univ. of Oregon, Eugene, OR (United States); Boucher, Jason [Univ. of Oregon, Eugene, OR (United States); Aloni, Shaul [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2016-02-10

    Silicon, the dominant photovoltaic (PV) technology, is reaching its fundamental performance limits as a single absorber/junction technology. Higher efficiency devices are needed to reduce cost further because the balance of systems account for about two-thirds of the overall cost of the solar electricity. III-V semiconductors such as GaAs are used to make the highest-efficiency photovoltaic devices, but the costs of manufacture are much too high for non-concentrated terrestrial applications. The cost of III-V’s is driven by two factors: (1) metal-organic chemical vapor deposition (MOCVD), the dominant growth technology, employs expensive, toxic and pyrophoric gas-phase precursors, and (2) the growth substrates conventionally required for high-performance devices are monocrystalline III-V wafers. The primary goal of this project was to show that close-spaced vapor transport (CSVT), using water vapor as a transport agent, is a scalable deposition technology for growing low-cost epitaxial III-V photovoltaic devices. The secondary goal was to integrate those devices on Si substrates for high-efficiency tandem applications using interface nanopatterning to address the lattice mismatch. In the first task, we developed a CSVT process that used only safe solid-source powder precursors to grow epitaxial GaAs with controlled n and p doping and mobilities/lifetimes similar to that obtainable via MOCVD. Using photoelectrochemical characterization, we showed that the best material had near unity internal quantum efficiency for carrier collection and minority carrier diffusions lengths in of ~ 8 μm, suitable for PV devices with >25% efficiency. In the second task we developed the first pn junction photovoltaics using CSVT and showed unpassivated structures with open circuit photovoltages > 915 mV and internal quantum efficiencies >0.9. We also characterized morphological and electrical defects and identified routes to reduce those defects. In task three we grew epitaxial

  2. Straining Graphene by Chemical Vapour Deposition Growth on Copper

    OpenAIRE

    Yu, Victor; Whiteway, Eric; Maassen, Jesse; Hilke, Michael

    2011-01-01

    Strain can be used as an alternate way to tune the electronic properties of graphene. Here we demonstrate that it is possible to tune the uniform strain of graphene simply by changing the chemical vapor deposition growth temperature of graphene on copper. Due to the cooling of the graphene on copper system, we can induce a uniform compressive strain on graphene. The strain is analyzed by Raman spectroscopy, where a shift in the 2D peak is observed and compared to our ab initio calculations of...

  3. Physically Unclonable Cryptographic Primitives by Chemical Vapor Deposition of Layered MoS2.

    Science.gov (United States)

    Alharbi, Abdullah; Armstrong, Darren; Alharbi, Somayah; Shahrjerdi, Davood

    2017-11-27

    Physically unclonable cryptographic primitives are promising for securing the rapidly growing number of electronic devices. Here, we introduce physically unclonable primitives from layered molybdenum disulfide (MoS2) by leveraging the natural randomness of their island growth during chemical vapor deposition (CVD). We synthesize a MoS2 monolayer film covered with speckles of multilayer islands, where the growth process is engineered for an optimal speckle density. Using the Clark-Evans test, we confirm that the distribution of islands on the film exhibits complete spatial randomness, hence indicating the growth of multilayer speckles is a spatial Poisson process. Such a property is highly desirable for constructing unpredictable cryptographic primitives. The security primitive is an array of 2048 pixels fabricated from this film. The complex structure of the pixels makes the physical duplication of the array impossible (i.e., physically unclonable). A unique optical response is generated by applying an optical stimulus to the structure. The basis for this unique response is the dependence of the photoemission on the number of MoS2 layers, which by design is random throughout the film. Using a threshold value for the photoemission, we convert the optical response into binary cryptographic keys. We show that the proper selection of this threshold is crucial for maximizing combination randomness and that the optimal value of the threshold is linked directly to the growth process. This study reveals an opportunity for generating robust and versatile security primitives from layered transition metal dichalcogenides.

  4. ZnO Nanowires Synthesized by Vapor Phase Transport Deposition on Transparent Oxide Substrates

    Directory of Open Access Journals (Sweden)

    Taylor Curtis

    2010-01-01

    Full Text Available Abstract Zinc oxide nanowires have been synthesized without using metal catalyst seed layers on fluorine-doped tin oxide (FTO substrates by a modified vapor phase transport deposition process using a double-tube reactor. The unique reactor configuration creates a Zn-rich vapor environment that facilitates formation and growth of zinc oxide nanoparticles and wires (20–80 nm in diameter, up to 6 μm in length, density <40 nm apart at substrate temperatures down to 300°C. Electron microscopy and other characterization techniques show nanowires with distinct morphologies when grown under different conditions. The effect of reaction parameters including reaction time, temperature, and carrier gas flow rate on the size, morphology, crystalline structure, and density of ZnO nanowires has been investigated. The nanowires grown by this method have a diameter, length, and density appropriate for use in fabricating hybrid polymer/metal oxide nanostructure solar cells. For example, it is preferable to have nanowires no more than 40 nm apart to minimize exciton recombination in polymer solar cells.

  5. Suitable alkaline for graphene peeling grown on metallic catalysts using chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Karamat, S., E-mail: shumailakaramat@gmail.com [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey); COMSATS Institute of Information Technology, Islamabad 54000 (Pakistan); Sonuşen, S. [Sabancı Üniversitesi (SUNUM), İstanbul 34956 (Turkey); Çelik, Ü. [Nanomagnetics Instruments, Ankara (Turkey); Uysallı, Y. [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey); Oral, A., E-mail: orahmet@metu.edu.tr [Department of Physics, Middle East Technical University, Ankara 06800 (Turkey)

    2016-04-15

    Graphical abstract: - Highlights: • Graphene layers were grown on Pt and Cu foil via ambient pressure chemical vapor deposition method and for the delicate removal of graphene from metal catalysts, electrolysis method was used by using different alkaline (sodium hydroxide, potassium hydroxide, lithium hydroxide and barium hydroxide). • The delamination speed of PMMA/graphene stack was higher during the KOH and LiOH electrolysis as compare to NaOH and Ba(OH){sub 2}. Ba(OH){sub 2} is not advisable because of the residues left on the graphene surface which would further trapped in between graphene and SiO{sub 2}/Si surface after transfer. The average peeling time in case of Pt electrode is ∼6 min for KOH and LiOH and ∼15 min for NaOH and Ba(OH){sub 2}. • Electrolysis method also works for the Cu catalyst. The peeling of graphene was faster in the case of Cu foil due to small size of bubbles which moves faster between the stack and the electrode surface. The average peeling time was ∼3–5 min. • XPS analysis clearly showed that the Pt substrates can be re-used again. Graphene layer was transferred to SiO{sub 2}/Si substrates and to the flexible substrate by using the same peeling method. - Abstract: In chemical vapor deposition, the higher growth temperature roughens the surface of the metal catalyst and a delicate method is necessary for the transfer of graphene from metal catalyst to the desired substrates. In this work, we grow graphene on Pt and Cu foil via ambient pressure chemical vapor deposition (AP-CVD) method and further alkaline water electrolysis was used to peel off graphene from the metallic catalyst. We used different electrolytes i.e., sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) and barium hydroxide Ba(OH){sub 2} for electrolysis, hydrogen bubbles evolved at the Pt cathode (graphene/Pt/PMMA stack) and as a result graphene layer peeled off from the substrate without damage. The peeling time for KOH and Li

  6. 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

  7. Remote microwave plasma enhanced chemical vapor deposition (RMPECVD) of silica and alumina films

    Energy Technology Data Exchange (ETDEWEB)

    Desmaison, J.; Hidalgo, H.; Tristant, P.; Naudin, F.; Merle, D. [Limoges Univ. (France). Lab. de Sciences des Procedes Ceramiques et Traitements de Surface

    2002-07-01

    Alumina or silica are attractive as insulation and protective layers for sensitive substrates. Oxides are deposited by remote microwave plasma enhanced chemical vapor deposition (RMPECVD) using an oxygen plasma and a mixture of precursor gas silane or trimethylaluminum (TMA) diluted in argon, respectively for silica and alumina, injected in the afterglow. This technique allows to deposit films of SiO{sub 2} and Al{sub 2}O{sub 3} with satisfactory characteristics (density, etch rate, stoichiometry) and high deposition rate. The comparison of the best deposition conditions reveals that in case of alumina higher temperatures and lower pressures are needed. (orig.)

  8. Growth of thin films of organic nonlinear optical materials by vapor growth processes - An overview and examination of shortfalls

    Science.gov (United States)

    Frazier, D. O.; Penn, B. G.; Witherow, W. K.; Paley, M. S.

    1991-01-01

    Research on the growth of second- and third-order nonlinear optical (NLO) organic thin film by vapor deposition is reviewed. Particular attention is given to the experimental methods for growing thin films of p-chlorophenylurea, diacetylenes, and phthalocyanines; characteristics of the resulting films; and approaches for advancing thin film technology. It is concluded that the growth of NLO thin films by vapor processes is a promising method for the fabrication of planar waveguides for nonlinear optical devices. Two innovative approaches are proposed including a method of controlling the input beam frequency to maximize nonlinear effects in thin films and single crystals, and the alternate approach to the molecular design of organic NLO materials by increasing the transition dipole moment between ground and excited states of the molecule.

  9. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-02

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

  11. The reaction of vapor-deposited Al with Cu oxides

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, T.N.; Martin, J.A.

    1990-01-01

    Interfaces formed by controlled deposition of Al on Cu oxides at 300K have been characterized using Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS). When Al is deposited onto a thin oxide grown on Cu(110) by atmospheric exposure, it completely scavenges the oxygen from the substrate material, increasing the O(1s) binding energy by 2.0 eV to give the value found for atmospheric oxidation of a thin Al film. Similar oxygen behavior is seen for Al deposition on sputter-deposited CuO with an enriched oxygen surface region, where multilayers of Al erase the shakeup satellites in the Cu(2p) region of the XPS spectrum to give features like those exhibited by Cu{sub 2}O or metallic Cu. Having calibrated the fluence of the Al source with Rutherford backscattering spectrometry, the attenuation of the Cu 2p{sub 1/2} satellite after approximately one monolayer of Al deposition is associated with the removal of oxygen from the top 20 {angstrom} of the CuO. Approximately 7--8 equivalent monolayers of Al are converted to an oxide in the initial rapid reaction process. Further deposition leads to progressive development of the metallic Al signature in both the XPS and AES spectra. These measurements clearly demonstrate the dominant role played by Al, a strong oxide former, when it is placed in intimate contact with the distinctively weaker Cu oxide. 9 refs., 5 figs.

  12. 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

  13. Luminescence and Structure of ZnO Grown by Physical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    R. García-Gutiérrez

    2012-01-01

    Full Text Available Nanostructured ZnO was deposited on different substrates (Si, SiO2, and Au/SiO2 by an enhanced physical vapor deposition technique that presents excellent luminescent properties. This technique consists in a horizontal quartz tube reactor that uses ultra-high purity Zn and UHP oxygen as precursors. The morphology and structure of ZnO grown in this work were studied by electron microscopy and X-ray diffraction. The XRD patterns revealed the highly crystalline phase of wurtzite polycrystalline structure, with a preferred (1011 growth direction. Room temperature cathodoluminescence studies revealed two features in the luminescence properties of the ZnO obtained by this technique, first a high-intensity narrow peak centered at 390 nm (~3.2 eV corresponding to a near band-to-band emission, and secondly, a broad peak centered around 517 nm (2.4 eV, the typical green-yellow luminescence, related to an unintentionally doped ZnO.

  14. Physical vapor deposited films of a perylene derivative: supramolecular arrangement and thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Jose Diego; Alessio, Priscila; Silva, Matheus Rodrigues Medeiros; Aroca, Ricardo Flavio; Souza, Agda Eunice de; Constantino, Carlos Jose Leopoldo, E-mail: case@fct.unesp.br [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Presidente Prudente, SP (Brazil). Dept. de Fisica

    2017-07-15

    The analysis of supramolecular arrangement is essential to understand the role of this key factor on the optical and electrical properties of organic thin films. In this work, thin solid films of bis(phenethylimido) perylene (PhPTCD) fabricated using physical vapor deposition (PVD) technique (thermal evaporation), deposited simultaneously onto different substrates (Ag mirror, Ge, and quartz plates) contingent on the characterization technique. The main objective is to study the PhPTCD supramolecular arrangement and the thermal stability of this arrangement in PVD films. The ultraviolet-visible absorption reveals a controlled growth of the PVD films, and the micro-Raman scattering data show that the PhPTCD molecule is not thermally degraded in the conditions of these experiments. The microscopy also shows a homogeneous morphological surface of the PVD film at macro and micro scales, with molecular aggregates at nanoscale. Besides, the PVD film roughness does not follow substrate roughness. The X-ray diffraction indicates a crystalline structure for PhPTCD powder and an amorphous form for PhPTCD PVD film. The infrared absorption spectroscopy points to a preferential flat-on organization of the molecules in the PVD films. In addition, the annealing process (200 deg C for 20 minutes) does not affect the supramolecular arrangement of the PhPTCD PVD films. (author)

  15. Fabrication of fin field-effect transistor silicon nanocrystal floating gate memory using photochemical vapor deposition

    Science.gov (United States)

    Kim, Sang Soo; Cho, Won-Ju; Ahn, Chang-Geun; Im, Kiju; Yang, Jong-Heon; Baek, In-Bok; Lee, Seongjae; Lim, Koeng Su

    2006-05-01

    The fin field-effect transistor (FET) silicon nanocrystal floating gate memory using the photochemical vapor deposition and the plasma doping processes was proposed. The silicon nanocrystals with a uniform size were formed on a vertical sidewall surface of the fin channel by the photochemical vapor deposition. The plasma doping was applied to form the junctions at the sidewall of the fin source-drain extension regions with a high aspect ratio. The FinFET silicon nanocrystal floating gate memory with a gate length of 100nm was successfully fabricated and it revealed a memory effect as well as a suppressed short-channel effect.

  16. Modeling free convective gravitational effects in chemical vapor deposition

    Science.gov (United States)

    Stinespring, C. D.; Annen, K. D.

    1987-01-01

    In this paper, a combined fluid-mechanics, mass-transport, and chemistry model describing CVD in an open-tube atmospheric-pressure flow reactor is developed. The model allows gas-phase reactions to proceed to equilibrium and accounts for finite reaction rates at the surface of the deposition substrate. This model is a useful intermediate step toward a model employing fully rate-limited chemistry. The model is used to predict the effects of free convection on flow patterns, temperature and species-concentration profiles, and local deposition rates for silicon deposited by silane pyrolysis. These results are discussed in terms of implications for CVD of silicon and other compounds, microgravity studies, and techniques for testing and validating the model.

  17. Growth of axial SiGe heterostructures in nanowires using pulsed laser deposition

    Science.gov (United States)

    Eisenhawer, Björn; Sivakov, Vladimir; Berger, Andreas; Christiansen, Silke

    2011-07-01

    Axial heterojunctions between pure silicon and pure germanium in nanowires have been realized combining pulsed laser deposition, chemical vapor deposition and electron beam evaporation in a vapor-liquid-solid nanowire growth experiment using gold nanoparticles as catalyst for the 1D wire growth. Energy dispersive x-ray mappings and line scans show a compositional transition from pure silicon to pure germanium and vice versa with exponential and thus comparably sharp transition slopes. Based on these results not only Si-Ge heterojunctions seem to be possible using the vapor-liquid-solid growth process but also heterojunctions in optoelectronic III-V compounds such as InGaAs/GaAs or group III nitride compounds such as InGaN/GaN as well as axial p-n junctions in Si nanowires.

  18. Growth of axial SiGe heterostructures in nanowires using pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Eisenhawer, Bjoern; Sivakov, Vladimir; Berger, Andreas; Christiansen, Silke, E-mail: bjoern.eisenhawer@ipht-jena.de [Institute of Photonic Technology, Albert-Einstein-Strasse 9, D-07745 Jena (Germany)

    2011-07-29

    Axial heterojunctions between pure silicon and pure germanium in nanowires have been realized combining pulsed laser deposition, chemical vapor deposition and electron beam evaporation in a vapor-liquid-solid nanowire growth experiment using gold nanoparticles as catalyst for the 1D wire growth. Energy dispersive x-ray mappings and line scans show a compositional transition from pure silicon to pure germanium and vice versa with exponential and thus comparably sharp transition slopes. Based on these results not only Si-Ge heterojunctions seem to be possible using the vapor-liquid-solid growth process but also heterojunctions in optoelectronic III-V compounds such as InGaAs/GaAs or group III nitride compounds such as InGaN/GaN as well as axial p-n junctions in Si nanowires.

  19. Growth of axial SiGe heterostructures in nanowires using pulsed laser deposition.

    Science.gov (United States)

    Eisenhawer, Björn; Sivakov, Vladimir; Berger, Andreas; Christiansen, Silke

    2011-07-29

    Axial heterojunctions between pure silicon and pure germanium in nanowires have been realized combining pulsed laser deposition, chemical vapor deposition and electron beam evaporation in a vapor-liquid-solid nanowire growth experiment using gold nanoparticles as catalyst for the 1D wire growth. Energy dispersive x-ray mappings and line scans show a compositional transition from pure silicon to pure germanium and vice versa with exponential and thus comparably sharp transition slopes. Based on these results not only Si-Ge heterojunctions seem to be possible using the vapor-liquid-solid growth process but also heterojunctions in optoelectronic III-V compounds such as InGaAs/GaAs or group III nitride compounds such as InGaN/GaN as well as axial p-n junctions in Si nanowires.

  20. Zno Micro/Nanostructures Grown on Sapphire Substrates Using Low-Temperature Vapor-Trapped Thermal Chemical Vapor Deposition: Structural and Optical Properties

    Directory of Open Access Journals (Sweden)

    Po-Sheng Hu

    2017-12-01

    Full Text Available In this research, the Zn(C5H7O22·xH2O-based growth of ZnO micro/nanostructures in a low temperature, vapor-trapped chemical vapor deposition system was attempted to optimize structural and optical properties for potential biomedical applications. By trapping in-flow gas molecules and Zinc vapor inside a chamber tube by partially obstructing a chamber outlet, a high pressure condition can be achieved, and this experimental setup has the advantages of ease of synthesis, being a low temperature process, and cost effectiveness. Empirically, the growth process proceeded under a chamber condition of an atmospheric pressure of 730 torr, a controlled volume flow rate of input gas, N2/O2, of 500/500 Standard Cubic Centimeters per Minute (SCCM, and a designated oven temperature of 500 °C. Specifically, the dependence of structural and optical properties of the structures on growth duration and spatially dependent temperature were investigated utilizing scanning electron microscopy, X-ray diffraction (XRD, photoluminescence (PL, and ultraviolet-visible transmission spectroscopy. The experimental results indicate that the grown thin film observed with hexagonal structures and higher structural uniformity enables more prominent structural and optical signatures. XRD spectra present the dominant peaks along crystal planes of (002 and (101 as the main direction of crystallization. In addition, while the structures excited with laser wavelength of 325 nm emit a signature radiation around 380 nm, an ultraviolet lamp with a wavelength of 254 nm revealed distinctive photoluminescence peaks at 363.96 nm and 403.52 nm, elucidating different degrees of structural correlation as functions of growth duration and the spatial gradient of temperature. Transmittance spectra of the structures illustrate typical variation in the wavelength range of 200 nm to 400 nm, and its structural correlation is less significant when compared with PL.

  1. Experimental verification of corrosive vapor deposition rate theory in high velocity burner rigs

    Science.gov (United States)

    Gokoglu, S. A.; Santoro, G. J.

    1986-01-01

    The ability to predict deposition rates is required to facilitate modelling of high temperature corrosion by fused salt condensates in turbine engines. A corrosive salt vapor deposition theory based on multicomponent chemically frozen boundary layers (CFBL) has been successfully verified by high velocity burner rig experiments. The experiments involved internally air-impingement cooled, both rotating full and stationary segmented cylindrical collectors located in the crossflow of sodium-seeded combustion gases. Excellent agreement is found between the CFBL theory an the experimental measurements for both the absolute amounts of Na2SO4 deposition rates and the behavior of deposition rate with respect to collector temperature, mass flowrate (velocity) and Na concentration.

  2. Vapor deposition of copper on stainless steel 304L

    Energy Technology Data Exchange (ETDEWEB)

    Vasofsky, R.W.

    1993-08-17

    Y-12 Plant is seeking to minimize the generation of hazardous wastes in its operations. The standard procedure for electroplating a thin layer of copper on type 304L stainless steel requires several aqueous pretreatment steps which generate Resource Conservation and Recovery Act (RCRA) hazardous wastes. We have evaluated a more environmentally acceptable procedure. Copper was vacuum deposited onto 304L coupons under differing deposition conditions and properties of coatings produced, including microstructure and adhesive strength, were examined. Results indicated that a noncolumnar, fine grain copper coating with high adhesion can be produced using this environmentally more acceptable approach.

  3. Transparent conductive zinc-oxide-based films grown at low temperature by mist chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shirahata, Takahiro [New Energy and Environmental Business Division, Toshiba Mitsubishi-Electric Industrial Systems Corporation, Kobe International Business Center (KIBC) 509, 5-5-2 Minatojima-Minami, Chuo-Ku, Kobe 650-0047 (Japan); Kawaharamura, Toshiyuki [Research Institute, Kochi University of Technology, Kami, Kochi 780-8502 (Japan); School of Systems Engineering, Kochi University of Technology, Kami, Kochi 780-8502 (Japan); Fujita, Shizuo, E-mail: fujitasz@kuee.kyoto-u.ac.jp [Photonics and Electronics Science and Engineering Center, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8520 (Japan); Orita, Hiroyuki [New Energy and Environmental Business Division, Toshiba Mitsubishi-Electric Industrial Systems Corporation, Kobe International Business Center (KIBC) 509, 5-5-2 Minatojima-Minami, Chuo-Ku, Kobe 650-0047 (Japan)

    2015-12-31

    Atmospheric pressure mist chemical vapor deposition (Mist–CVD) systems have been developed to grow zinc-oxide-based (ZnO-based) transparent conductive oxide (TCO) films. Low-resistive aluminum-doped ZnO (AZO) TCOs, showing resistivity of the order on 10{sup −4} Ωcm, previously were grown using a safe source material zinc acetate [Zn(ac){sub 2}], at a growth temperature as high as 500 °C. To grow superior TCOs at lower temperatures, we proposed the addition of NH{sub 3} to accelerate the reaction of acetylacetonate compounds. As the result, we could grow gallium-doped ZnO (GZO) TCOs with a resistivity of 2.7 × 10{sup −3} Ω cm and transmittance higher than 90% at 300 °C by using zinc acetylacetonate [Zn(acac){sub 2}] as the Zn source. To grow boron-doped ZnO (BZO) TCOs at a lower growth temperature of 200 °C, we used boron doping along with a toluene solution of diethylzinc (DEZ), that maintained high reactivity without being flammable. These BZO TCOs showed a resistivity of 1.5 × 10{sup −3} Ω cm and transmittance higher than 90%, despite the use of a non-vacuum-based open-air technology. - Highlights: • Introduction of Mist–CVD as a non-vacuum-based, safe, and cost-effective growth technology • Process evolution of the growth technology to lower the growth temperature. • Achievement of low resistive ZnO films at 200oC.

  4. Ballistic transport in graphene grown by chemical vapor deposition

    NARCIS (Netherlands)

    Calado, V.E.; Zhu, S.E.; Goswami, S.; Xu, Q.; Watanabe, K.; Taniguchi, T.; Janssen, G.C.A.M.; Vandersypen, L.M.K.

    2014-01-01

    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

  5. On diffusion-controlled interface microstructure of vapor deposited ...

    Indian Academy of Sciences (India)

    after deposition could be explained by the existing laws, the profiles for others are found to be distinctly different and are ... Thickness of the layers removed is obtained by calibrating the time of etching at a given Ar+ ion gun set- ... of the Fourier series solution of the Fick's law for isothermal diffusion with a con- stant diffusion ...

  6. Large-Area WS2 Film with Big Single Domains Grown by Chemical Vapor Deposition

    Science.gov (United States)

    Liu, Pengyu; Luo, Tao; Xing, Jie; Xu, Hong; Hao, Huiying; Liu, Hao; Dong, Jingjing

    2017-10-01

    High-quality WS2 film with the single domain size up to 400 μm was grown on Si/SiO2 wafer by atmospheric pressure chemical vapor deposition. The effects of some important fabrication parameters on the controlled growth of WS2 film have been investigated in detail, including the choice of precursors, tube pressure, growing temperature, holding time, the amount of sulfur powder, and gas flow rate. By optimizing the growth conditions at one atmospheric pressure, we obtained tungsten disulfide single domains with an average size over 100 μm. Raman spectra, atomic force microscopy, and transmission electron microscopy provided direct evidence that the WS2 film had an atomic layer thickness and a single-domain hexagonal structure with a high crystal quality. And the photoluminescence spectra indicated that the tungsten disulfide films showed an evident layer-number-dependent fluorescence efficiency, depending on their energy band structure. Our study provides an important experimental basis for large-area, controllable preparation of atom-thick tungsten disulfide thin film and can also expedite the development of scalable high-performance optoelectronic devices based on WS2 film.

  7. Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, Satoshi; Ranjan, Mukesh; Heinig, Karl-Heinz; Facsko, Stefan; Smith, Roger, E-mail: s.numazawa@hzdr.de [Helmholtz-Zentrum Dresden Rossendorf (HZDR), Institut fuer Ionenstrahlphysik und Materialforschung, PO Box 510119, 01314 Dresden (Germany)

    2011-06-08

    Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO{sub 2} surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and {approx}1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns. (fast track communication)

  8. Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO2.

    Science.gov (United States)

    Numazawa, Satoshi; Ranjan, Mukesh; Heinig, Karl-Heinz; Facsko, Stefan; Smith, Roger

    2011-06-08

    Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO(2) surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and ≈1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns.

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

    Science.gov (United States)

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

    2017-05-01

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

  10. Synthesis of Graphene Nanoribbons by Ambient-Pressure Chemical Vapor Deposition and Device Integration.

    Science.gov (United States)

    Chen, Zongping; Zhang, Wen; Palma, Carlos-Andres; Lodi Rizzini, Alberto; Liu, Bilu; Abbas, Ahmad; Richter, Nils; Martini, Leonardo; Wang, Xiao-Ye; Cavani, Nicola; Lu, Hao; Mishra, Neeraj; Coletti, Camilla; Berger, Reinhard; Klappenberger, Florian; Kläui, Mathias; Candini, Andrea; Affronte, Marco; Zhou, Chongwu; De Renzi, Valentina; Del Pennino, Umberto; Barth, Johannes V; Räder, Hans Joachim; Narita, Akimitsu; Feng, Xinliang; Müllen, Klaus

    2016-11-30

    Graphene nanoribbons (GNRs), quasi-one-dimensional graphene strips, have shown great potential for nanoscale electronics, optoelectronics, and photonics. Atomically precise GNRs can be "bottom-up" synthesized by surface-assisted assembly of molecular building blocks under ultra-high-vacuum conditions. However, large-scale and efficient synthesis of such GNRs at low cost remains a significant challenge. Here we report an efficient "bottom-up" chemical vapor deposition (CVD) process for inexpensive and high-throughput growth of structurally defined GNRs with varying structures under ambient-pressure conditions. The high quality of our CVD-grown GNRs is validated by a combination of different spectroscopic and microscopic characterizations. Facile, large-area transfer of GNRs onto insulating substrates and subsequent device fabrication demonstrate their promising potential as semiconducting materials, exhibiting high current on/off ratios up to 6000 in field-effect transistor devices. This value is 3 orders of magnitude higher than values reported so far for other thin-film transistors of structurally defined GNRs. Notably, on-surface mass spectrometry analyses of polymer precursors provide unprecedented evidence for the chemical structures of the resulting GNRs, especially the heteroatom doping and heterojunctions. These results pave the way toward the scalable and controllable growth of GNRs for future applications.

  11. Increased stability of CuZrAl metallic glasses prepared by physical vapor deposition

    OpenAIRE

    Bokas, G. B.; L. Zhao; Morgan, D.; Szlufarska, I.

    2017-01-01

    We carried out molecular dynamics simulations (MD) using realistic empirical potentials for the vapor deposition (VD) of CuZrAl glasses. VD glasses have higher densities and lower potential and inherent structure energies than the melt-quenched glasses for the same alloys. The optimal substrate temperature for the deposition process is 0.625$\\times T_\\mathrm{g}$. In VD metallic glasses (MGs), the total number of icosahedral like clusters is higher than in the melt-quenched MGs. Surprisingly, ...

  12. Metal-Organic Covalent Network Chemical Vapor Deposition for Gas Separation.

    Science.gov (United States)

    Boscher, Nicolas D; Wang, Minghui; Perrotta, Alberto; Heinze, Katja; Creatore, Mariadriana; Gleason, Karen K

    2016-09-01

    The chemical vapor deposition (CVD) polymerization of metalloporphyrin building units is demonstrated to provide an easily up-scalable one-step method toward the deposition of a new class of dense and defect-free metal-organic covalent network (MOCN) layers. The resulting hyper-thin and flexible MOCN layers exhibit outstanding gas-separation performances for multiple gas pairs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Chemical vapor deposition of diamond films on patterned substrates

    OpenAIRE

    O.R. Monteiro

    2002-01-01

    The interest in using CVD diamond in the fabrication of microelectro-mechanical components has steadly increased over the last few years. Typical technology for manufacturing such components involve the molds patterned in silicon or silicon dioxide, which are filled by diamond deposition. The degree of conformality of the CVD film and the characteristics of the diamond-substrate interface becomes critical for the successful fabrication and performance of such devices. We have investigated the...

  14. Complementary Metal Oxide Semiconductor-Compatible, High-Mobility, ⟨111⟩-Oriented GaSb Nanowires Enabled by Vapor-Solid-Solid Chemical Vapor Deposition.

    Science.gov (United States)

    Yang, Zai-Xing; Liu, Lizhe; Yip, SenPo; Li, Dapan; Shen, Lifan; Zhou, Ziyao; Han, Ning; Hung, Tak Fu; Pun, Edwin Yue-Bun; Wu, Xinglong; Song, Aimin; Ho, Johnny C

    2017-04-25

    Using CMOS-compatible Pd catalysts, we demonstrated the formation of high-mobility ⟨111⟩-oriented GaSb nanowires (NWs) via vapor-solid-solid (VSS) growth by surfactant-assisted chemical vapor deposition through a complementary experimental and theoretical approach. In contrast to NWs formed by the conventional vapor-liquid-solid (VLS) mechanism, cylindrical-shaped Pd5Ga4 catalytic seeds were present in our Pd-catalyzed VSS-NWs. As solid catalysts, stoichiometric Pd5Ga4 was found to have the lowest crystal surface energy and thus giving rise to a minimal surface diffusion as well as an optimal in-plane interface orientation at the seed/NW interface for efficient epitaxial NW nucleation. These VSS characteristics led to the growth of slender NWs with diameters down to 26.9 ± 3.5 nm. Over 95% high crystalline quality NWs were grown in ⟨111⟩ orientation for a wide diameter range of between 10 and 70 nm. Back-gated field-effect transistors (FETs) fabricated using the Pd-catalyzed GaSb NWs exhibit a superior peak hole mobility of ∼330 cm2 V-1 s-1, close to the mobility limit for a NW channel diameter of ∼30 nm with a free carrier concentration of ∼1018 cm-3. This suggests that the NWs have excellent homogeneity in phase purity, growth orientation, surface morphology and electrical characteristics. Contact printing process was also used to fabricate large-scale assembly of Pd-catalyzed GaSb NW parallel arrays, confirming the potential constructions and applications of these high-performance electronic devices.

  15. Nanostructure Fabrication by Electron-Beam-Induced Deposition with Metal Carbonyl Precursor and Water Vapor

    Science.gov (United States)

    Takeguchi, Masaki; Shimojo, Masayuki; Furuya, Kazuo

    2007-09-01

    Nanorod fabrication is performed by electron beam induced deposition (EBID) with iron carbonyl [Fe(CO)5] and tungsten carbonyl [W(CO)6] precursors. The effects of water vapor addition to each metal carbonyl on the microstructure and composition of the obtained nanorods are studied. Normally, EBID-fabricated metal nanorods consist of an amorphous phase containing a considerable amount of carbon. However, it is found that water vapor addition to iron carbonyl can effectively reduce the carbon content of the nanorods and induce the formation of carbon-free crystalline Fe3O4 nanorods with increasing partial pressure ratio of water vapor to iron carbonyl. In contrast, for tungsten carbonyl, water vapor addition has no obvious effect on carbon content reduction. The obtained nanorods consist of a carbon-rich amorphous matrix containing tungsten oxide nanocrystals inside.

  16. Hybrid vapor phase-solution phase growth techniques for improved CZT(S,Se) photovoltaic device performance

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Liang-Yi; Gershon, Talia S.; Haight, Richard A.; Lee, Yun Seog

    2016-12-27

    A hybrid vapor phase-solution phase CZT(S,Se) growth technique is provided. In one aspect, a method of forming a kesterite absorber material on a substrate includes the steps of: depositing a layer of a first kesterite material on the substrate using a vapor phase deposition process, wherein the first kesterite material includes Cu, Zn, Sn, and at least one of S and Se; annealing the first kesterite material to crystallize the first kesterite material; and depositing a layer of a second kesterite material on a side of the first kesterite material opposite the substrate using a solution phase deposition process, wherein the second kesterite material includes Cu, Zn, Sn, and at least one of S and Se, wherein the first kesterite material and the second kesterite material form a multi-layer stack of the absorber material on the substrate. A photovoltaic device and method of formation thereof are also provided.

  17. Materials characterization of rapid thermal chemical vapor deposition of titanium disilicide

    Science.gov (United States)

    Gladden-Green, Dannellia Banay

    Technological advancements of novel processes and materials involving refractory metal silicides for ultra large scale integration is of paramount importance to the semiconductor industry. Scaling of devices to meet the demands for increased packing density and speed requires such novel processes and materials. Rapid thermal chemical vapor deposition (RTCVD) of titanium disilicide (TiSisb2) was investigated in an effort to meet some of the challenges of ultra large scale integration (ULSI) technology. Selective RTCVD of TiSisb2 offers an optimal technological vehicle for achieving contacts to ultra-shallow junctions. Of all of the metal silicides, TiSisb2 has the lowest resistivity and meets the microelectronics demands for a thermally stable contact. The research results presented in this dissertation explores the mechanisms of selective RTCVD of TiSisb2 in terms of thermodynamic trends and kinetic driving forces for nucleation and growth. The present research addresses the qualitative and quantitative parameters that affect the controlling mechanisms for nucleation and therefore the results provide significant data and theoretical insights into a state-of-the-art process. Just as the fundamental building block in understanding the kinetic constraints of a process lie in the realm of thermodynamic exploration, understanding the complex processes involved in RTCVD TiSisb2 begin with characterization of the mechanisms governing thin film nucleation. In this work, the early stages of growth are investigated as they offer insight into how process parameters are optimized to render desired silicide film properties. Equilibrium simulations have been used to model the CVD reaction with very good trend indicating accuracy. Empirical investigations of CVD TiSisb2 took place in a low-pressure rapid-thermal environment using the SiHsb4 + TiClsb4 gas system on silicon (100) substrates. Secondary ion mass spectroscopy (SIMS) has been used to qualify the benefits of vacuum and

  18. Femtosecond fluorescence upconversion spectroscopy of vapor-deposited tris(8-hydroxyquinoline) aluminum films.

    NARCIS (Netherlands)

    Humbs, W.; Zhang, H.; Glasbeek, M.

    2000-01-01

    Abstract Vapor-deposited Alq3 is used as the green emitting layer in a class of organic light-emitting diodes. In this paper, the time dependence of the fluorescence from thin Alq3 films has been studied by means of the femtosecond fluorescence upconversion technique. From the temporally resolved

  19. A Kinetic Study of the Electrochemical Vapor Deposition of Solid Oxide Electrolyte Films on Porous Substrates

    NARCIS (Netherlands)

    Lin, Y.S.; de Haart, L.G.J.; de Vries, K.J.; Burggraaf, A.J.

    1990-01-01

    The electrochemical vapor deposition (EVD) method is a very promising technique for making gas-tight dense solidelectrolyte films on porous substrates. In this paper, theoretical and experimental studies on the kinetics of the depositionof dense yttria-stabilized zirconia films on porous ceramic

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

    Science.gov (United States)

    2015-03-01

    DISULFIDE ( MoS2 ) Daniel Kaplan Kendall Mills Venkataraman Swaminathan March 2015 Approved for public release...4. TITLE AND SUBTITLE CHEMICAL VAPOR DEPOSITION OF ATOMICALLY-THIN MOLYBDENUM DISULFIDE ( MoS2 ) 5a. CONTRACT NUMBER 5b. GRANT NUMBER...distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT A method of synthesizing monolayers of molybdenum disulfide ( MoS2 ) via

  1. Single Molecule Source Reagents for Chemical Vapor Deposition of B- Silicon Carbide

    Science.gov (United States)

    1992-12-10

    Phase I conclusively showed the feasibility of rational design of single molecule -source reagents that could lead to improvements in the chemical...vapor deposition of stoichiometric Beta silicon carbide. Four single molecule sources were synthesized, their decomposition pathways studied, and their

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

    NARCIS (Netherlands)

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

    2015-01-01

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

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

    NARCIS (Netherlands)

    Gaitas, A.

    2013-01-01

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

  4. 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…

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

    DEFF Research Database (Denmark)

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

    2016-01-01

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

  6. Ceramic membranes by electrochemical vapor deposition of zirconia-yttria-terbia layers on porous substrates

    NARCIS (Netherlands)

    Brinkman, H.W.; Brinkman, Hendrik W.; Burggraaf, Anthonie; Burggraaf, Anthonie J.

    1995-01-01

    By means of electrochemical vapor deposition (EVD), it is possible to grow thin, dense layers of zirconia/yttria/terbiasolid solution (ZYT) on porous ceramic substrates. These layers can be used as ceramic membranes for oxygen separation.The kinetics of the EVD process, the morphology of the grown

  7. Modeling of chemical vapor deposition. II. Gas phase epitaxy of (100) GaAs

    Science.gov (United States)

    Korec, J.; Heyen, M.

    1982-12-01

    The approach described in part I of this paper is applied here to model the CVD of GaAs in a halide transport system. A quantitative description of the effect of growth temperature on the growth rate is obtained. Also the effect of GaCl and arsenic vapor pressure on the growth rate is described. The theoretical estimate of the transition point between etching and growth is close to the experimental value.

  8. Single crystal monolayer MoS2 triangles with wafer-scale spatial uniformity by MoO3 pre-deposited chemical vapor deposition

    Science.gov (United States)

    Cheng, Zhaofang; Xia, Minggang; Hu, Ruixue; Liang, Chunping; Liang, Gongying; Zhang, Shengli

    2017-12-01

    Two-dimensional transition metal dichalcogenides (TMDs) show a potential application in photoelectric device due to their excellent electrical and optical properties. Here, we report that the MoO3 pre-deposited chemical vapor deposition (CVD) is used to synthesize single crystal monolayer MoS2 triangles on 4 in. wafer. We found that the wafer-scale uniformity of MoS2 can be greatly improved by regularly depositing MoO3 particles on substrate before CVD growth. Therefore, a piece of cleanroom wiper was used as a template for implementing precise control of MoO3 pre-deposition. We found that the optimal deposition size of MoO3 particles and the distance between MoO3 particles are about 15 μm and 0.9 mm, respectively. Both microscopic and spectroscopic characterization results demonstrate that the as-grown MoS2 is highly uniform in space distribution and crystal structure. The electronic performance of MoS2 synthesized by our method is comparable to or even slightly better than those in common CVD samples. The role of MoO3 pre-deposition is not only to effectively control the MoS2 nucleation density but also to overcome poor diffusion of MoO3 source. Our method is expected to accelerate the industrial synthesis of the atomically thin TMD materials.

  9. Ballistic transport in graphene grown by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Calado, V. E.; Goswami, S.; Xu, Q.; Vandersypen, L. M. K., E-mail: l.m.k.vandersypen@tudelft.nl [Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft (Netherlands); Zhu, Shou-En; Janssen, G. C. A. M. [Micro and Nano Engineering Laboratory, Precision and Microsystems Engineering, Delft University of Technology, 2628 CD Delft (Netherlands); Watanabe, K.; Taniguchi, T. [Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)

    2014-01-13

    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.

  10. Vertically aligned Si nanocrystals embedded in amorphous Si matrix prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD)

    Energy Technology Data Exchange (ETDEWEB)

    Nogay, G. [Department of Physics, Middle East Technical University (METU), Ankara 06800 (Turkey); Center of Solar Energy Research and Application (GÜNAM), Middle East Technical University (METU), Ankara 06800 (Turkey); Saleh, Z.M., E-mail: zaki.saleh@aauj.edu [Center of Solar Energy Research and Application (GÜNAM), Middle East Technical University (METU), Ankara 06800 (Turkey); Department of Physics, Arab American University–Jenin (AAUJ), Jenin, Palestine (Country Unknown); Özkol, E. [Center of Solar Energy Research and Application (GÜNAM), Middle East Technical University (METU), Ankara 06800 (Turkey); Department of Chemical Engineering, Middle East Technical University (METU), Ankara 06800 (Turkey); Turan, R. [Department of Physics, Middle East Technical University (METU), Ankara 06800 (Turkey); Center of Solar Energy Research and Application (GÜNAM), Middle East Technical University (METU), Ankara 06800 (Turkey)

    2015-06-15

    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 (X{sub c}) 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 X{sub c}.

  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. Copper Oxidation through Nucleation Sites of Chemical Vapor Deposited Graphene

    DEFF Research Database (Denmark)

    Luo, Birong; Whelan, Patrick Rebsdorf; Shivayogimath, Abhay

    2016-01-01

    and amorphous carbon. These defects would serve as a pathway for the diffusion of 02 during thermal annealing, allowing oxidation of Cu to progress gradually from the nucleation center toward the growth edge. The oxidation process follows the graphene morphology closely; the shape of the oxidized area of Cu has...

  13. Sequential microcontroller-based control for a chemical vapor deposition process

    Directory of Open Access Journals (Sweden)

    Edgar Serrano Pérez

    2017-12-01

    Full Text Available A cost-effective direct liquid injection system is developed for a chemical vapor deposition process using a microcontroller. The precursor gas phase is controlled by the precise sequential injection of a liquid precursor solution to a vaporizing chamber prior deposition. The electronic control system allows the human–machine interface through a LCD display and a keypad matrix. The core of the electronic system is based on an electro mechanical injector operated in time and frequency as a sequential control system by a popular PIC16F877A chip. The software has been developed in the BASIC language and it can be easily modified through an ICSP programmer for different sequential automatized routines. The injection calibration test has proven the linearity of the injection control system for different operation parameters. The results reported the sequential injection MOCVD deposition of alumina thin film.

  14. Quasi-Isentropic Compression of Vapor Deposited Hexanitroazobenzene (HNAB): Experiments and Analysis

    Science.gov (United States)

    Yarrington, Cole; Tappan, Alexander; Specht, Paul; Knepper, Robert

    2017-06-01

    Vapor-deposited hexanitroazobenzene (HNAB) is an explosive with unique physical characteristics resulting from the deposition process that make it desirable for the study of microstructure effects. A relatively understudied high explosive (HE), few data are available on the equation of state (EOS) of HNAB reactants or products. HNAB samples exhibiting high density and sub-micron porosity and grain size were prepared using physical vapor deposition onto polymethyl methacrylate (PMMA) and lithium fluoride (LiF) substrates. The samples were quasi-isentropically ramp compressed using VELOCE, a compact pulsed power generator. Evidence of a low pressure phase transition was observed in HNAB. Interferometric measurements of reference and sample interface velocities enabled inference of the unreacted EOS for HNAB using DAKOTA, an optimization toolkit. Initial simulations of the HNAB critical thickness experiment have been carried out using the parameterized EOS, and a products EOS from thermal equilibrium calculations.

  15. 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.

  16. Modeling of chemical vapor deposition. III. Silicon epitaxy from chlorosilanes

    Science.gov (United States)

    Korec, J.

    1983-02-01

    The approach presented in part I is applied here to model epitaxial growth of silicon from SiH 2Cl 2, SiHCl 3 and SiCl 4. We adopt the system of chemical reactions proposed by Nishizawa and Nihira and we assume the rate determining step to be the chemical reaction between adsorbed SiCl 2 and gaseous H 2. The basis of this approach is the computation of the activity of silicon in the gas phase near the substrate surface from the balance between the rate of mass transport in the gas phase and surface processes. The considered surface processes are: adsorption and surface diffusion of SiCl 2 and heterogenous chemical reaction. The calculated growth rate of the film agrees with experimental data for a wide range of technological conditions.

  17. Synthesis of boron nitride nanostructures from catalyst of iron compounds via thermal chemical vapor deposition technique

    Science.gov (United States)

    da Silva, Wellington M.; Ribeiro, Hélio; Ferreira, Tiago H.; Ladeira, Luiz O.; Sousa, Edésia M. B.

    2017-05-01

    For the first time, patterned growth of boron nitride nanostructures (BNNs) is achieved by thermal chemical vapor deposition (TCVD) technique at 1150 °C using a mixture of FeS/Fe2O3 catalyst supported in alumina nanostructured, boron amorphous and ammonia (NH3) as reagent gas. This innovative catalyst was synthesized in our laboratory and systematically characterized. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The X-ray diffraction profile of the synthesized catalyst indicates the coexistence of three different crystal structures showing the presence of a cubic structure of iron oxide and iron sulfide besides the gamma alumina (γ) phase. The results show that boron nitride bamboo-like nanotubes (BNNTs) and hexagonal boron nitride (h-BN) nanosheets were successfully synthesized. Furthermore, the important contribution of this work is the manufacture of BNNs from FeS/Fe2O3 mixture.

  18. 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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  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. Band gap engineering of chemical vapor deposited graphene by in situ BN doping.

    Science.gov (United States)

    Chang, Cheng-Kai; Kataria, Satender; Kuo, Chun-Chiang; Ganguly, Abhijit; Wang, Bo-Yao; Hwang, Jeong-Yuan; Huang, Kay-Jay; Yang, Wei-Hsun; Wang, Sheng-Bo; Chuang, Cheng-Hao; Chen, Mi; Huang, Ching-I; Pong, Way-Faung; Song, Ker-Jar; Chang, Shoou-Jinn; Guo, Jing-Hua; Tai, Yian; Tsujimoto, Masahiko; Isoda, Seiji; Chen, Chun-Wei; Chen, Li-Chyong; Chen, Kuei-Hsien

    2013-02-26

    Band gap opening and engineering is one of the high priority goals in the development of graphene electronics. Here, we report on the opening and scaling of band gap in BN doped graphene (BNG) films grown by low-pressure chemical vapor deposition method. High resolution transmission electron microscopy is employed to resolve the graphene and h-BN domain formation in great detail. X-ray photoelectron, micro-Raman, and UV-vis spectroscopy studies revealed a distinct structural and phase evolution in BNG films at low BN concentration. Synchrotron radiation based XAS-XES measurements concluded a gap opening in BNG films, which is also confirmed by field effect transistor measurements. For the first time, a significant band gap as high as 600 meV is observed for low BN concentrations and is attributed to the opening of the π-π* band gap of graphene due to isoelectronic BN doping. As-grown films exhibit structural evolution from homogeneously dispersed small BN clusters to large sized BN domains with embedded diminutive graphene domains. The evolution is described in terms of competitive growth among h-BN and graphene domains with increasing BN concentration. The present results pave way for the development of band gap engineered BN doped graphene-based devices.

  1. Grain boundary-mediated nanopores in molybdenum disulfide grown by chemical vapor deposition.

    Science.gov (United States)

    Elibol, Kenan; Susi, Toma; O Brien, Maria; Bayer, Bernhard C; Pennycook, Timothy J; McEvoy, Niall; Duesberg, Georg S; Meyer, Jannik C; Kotakoski, Jani

    2017-01-26

    Molybdenum disulfide (MoS 2 ) is a particularly interesting member of the family of two-dimensional (2D) materials due to its semiconducting and tunable electronic properties. Currently, the most reliable method for obtaining high-quality industrial scale amounts of 2D materials is chemical vapor deposition (CVD), which results in polycrystalline samples. As grain boundaries (GBs) are intrinsic defect lines within CVD-grown 2D materials, their atomic structure is of paramount importance. Here, through atomic-scale analysis of micrometer-long GBs, we show that covalently bound boundaries in 2D MoS 2 tend to be decorated by nanopores. Such boundaries occur when differently oriented MoS 2 grains merge during growth, whereas the overlap of grains leads to boundaries with bilayer areas. Our results suggest that the nanopore formation is related to stress release in areas with a high concentration of dislocation cores at the grain boundaries, and that the interlayer interaction leads to intrinsic rippling at the overlap regions. This provides insights for the controlled fabrication of large-scale MoS 2 samples with desired structural properties for applications.

  2. Morphology and photoresponse of crystalline antimony film grown on mica by physical vapor deposition

    Directory of Open Access Journals (Sweden)

    Shafa Muhammad

    2016-09-01

    Full Text Available Antimony is a promising material for the fabrication of photodetectors. This study deals with the growth of a photosensitive thin film by the physical vapor deposition (PVD of antimony onto mica surface in a furnace tube. The geometry of the grown structures was studied via scanning electron microscopy (SEM, X-ray diffraction (XRD, energy-dispersive X-ray spectroscopy (EDX and elemental diffraction analysis. XRD peaks of the antimony film grown on mica mostly matched with JCPDF Card. The formation of rhombohedral crystal structures in the film was further confirmed by SEM micrographs and chemical composition analysis. The Hall measurements revealed good electrical conductivity of the film with bulk carrier concentration of the order of 1022 Ω·cm-3 and mobility of 9.034 cm2/Vs. The grown film was successfully tested for radiation detection. The photoresponse of the film was evaluated using its current-voltage characteristics. These investigations revealed that the photosensitivity of the antimony film was 20 times higher than that of crystalline germanium.

  3. Thermal barrier coatings on gas turbine blades: Chemical vapor deposition (Review)

    Science.gov (United States)

    Igumenov, I. K.; Aksenov, A. N.

    2017-12-01

    Schemes are presented for experimental setups (reactors) developed at leading scientific centers connected with the development of technologies for the deposition of coatings using the CVD method: at the Technical University of Braunschweig (Germany), the French Aerospace Research Center, the Materials Research Institute (Tohoku University, Japan) and the National Laboratory Oak Ridge (USA). Conditions and modes for obtaining the coatings with high operational parameters are considered. It is established that the formed thermal barrier coatings do not fundamentally differ in their properties (columnar microstructure, thermocyclic resistance, thermal conductivity coefficient) from standard electron-beam condensates, but the highest growth rates and the perfection of the crystal structure are achieved in the case of plasma-chemical processes and in reactors with additional laser or induction heating of a workpiece. It is shown that CVD reactors can serve as a basis for the development of rational and more advanced technologies for coating gas turbine blades that are not inferior to standard electron-beam plants in terms of the quality of produced coatings and have a much simpler and cheaper structure. The possibility of developing a new technology based on CVD processes for the formation of thermal barrier coatings with high operational parameters is discussed, including a set of requirements for industrial reactors, high-performance sources of vapor precursors, and promising new materials.

  4. 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.

  5. Microstructure and field emission characteristics of ZnO nanoneedles grown by physical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    George, A.; Kumari, P.; Soin, N. [Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), University of Ulster at Jordanstown, Shore Road, Northern Ireland, BT37 0QB (United Kingdom); Roy, S.S., E-mail: s.sinha-roy@ulster.ac.uk [Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), University of Ulster at Jordanstown, Shore Road, Northern Ireland, BT37 0QB (United Kingdom); McLaughlin, J.A., E-mail: jad.mclaughlin@ulster.ac.uk [Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), University of Ulster at Jordanstown, Shore Road, Northern Ireland, BT37 0QB (United Kingdom)

    2010-10-01

    Single crystalline zinc oxide (ZnO) nanoneedles have been grown on Au coated Si (1 0 0) substrates in an inert gas atmosphere by physical vapor deposition (PVD) process. A mixture of ZnO and graphite powder was used as precursor for the production of nanoneedles. Their structure has been assessed by a range of techniques including scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The synthesized ZnO nanoneedles have tip diameter around 30 nm and average length of {approx}5 {mu}m. The XRD patterns and HRTEM measurements revealed the highly crystalline phase of wurtzite single crystalline structure, with a preferred <0 0 0 1> growth direction. Field emission from these nanoneedles was investigated and a low turn on voltage of 5.07 V {mu}m{sup -1} at a current density of 10 {mu}A cm{sup -2} was observed.

  6. Laser-assisted chemical vapor deposition setup for fast synthesis of graphene patterns

    Science.gov (United States)

    Zhang, Chentao; Zhang, Jianhuan; Lin, Kun; Huang, Yuanqing

    2017-05-01

    An automatic setup based on the laser-assisted chemical vapor deposition method has been developed for the rapid synthesis of graphene patterns. The key components of this setup include a laser beam control and focusing unit, a laser spot monitoring unit, and a vacuum and flow control unit. A laser beam with precision control of laser power is focused on the surface of a nickel foil substrate by the laser beam control and focusing unit for localized heating. A rapid heating and cooling process at the localized region is induced by the relative movement between the focalized laser spot and the nickel foil substrate, which causes the decomposing of gaseous hydrocarbon and the out-diffusing of excess carbon atoms to form graphene patterns on the laser scanning path. All the fabrication parameters that affect the quality and number of graphene layers, such as laser power, laser spot size, laser scanning speed, pressure of vacuum chamber, and flow rates of gases, can be precisely controlled and monitored during the preparation of graphene patterns. A simulation of temperature distribution was carried out via the finite element method, providing a scientific guidance for the regulation of temperature distribution during experiments. A multi-layer graphene ribbon with few defects was synthesized to verify its performance of the rapid growth of high-quality graphene patterns. Furthermore, this setup has potential applications in other laser-based graphene synthesis and processing.

  7. Gaseous material capacity of open plasma jet in plasma spray-physical vapor deposition process

    Science.gov (United States)

    Liu, Mei-Jun; Zhang, Meng; Zhang, Qiang; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2018-01-01

    Plasma spray-physical vapor deposition (PS-PVD) process, emerging as a highly efficient hybrid approach, is based on two powerful technologies of both plasma spray and physical vapor deposition. The maximum production rate is affected by the material feed rate apparently, but it is determined by the material vapor capacity of transporting plasma actually and essentially. In order to realize high production rate, the gaseous material capacity of plasma jet must be fundamentally understood. In this study, the thermal characteristics of plasma were measured by optical emission spectrometry. The results show that the open plasma jet is in the local thermal equilibrium due to a typical electron number density from 2.1 × 1015 to 3.1 × 1015 cm-3. In this condition, the temperature of gaseous zirconia can be equal to the plasma temperature. A model was developed to obtain the vapor pressure of gaseous ZrO2 molecules as a two dimensional map of jet axis and radial position corresponding to different average plasma temperatures. The overall gaseous material capacity of open plasma jet, take zirconia for example, was further established. This approach on evaluating material capacity in plasma jet would shed light on the process optimization towards both depositing columnar coating and a high production rate of PS-PVD.

  8. 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

  9. Lapping of chemical vapor deposited diamond films using copper vapor laser

    Energy Technology Data Exchange (ETDEWEB)

    Park, Y.J.; Baik, Y.J. [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    1999-04-01

    Laser lapping of diamond films is performed with focused beam of copper vapor laser. Both spherical and rod-shape laser beam are used. Diamond surface is scanned at various scan speeds(0.125, 0.5, 0.75 mm/sec) and beam shifts(5, 10, 20, 40, 100 {mu}m). At 0.125 mm/sec, 10 {mu}m scan condition, the level difference of diamond surface of about 700 {mu}m over 20 mm is reduced to 200 {mu}m. In addition, surface roughness is also improved from 3.53 {mu}m to 2.47 {mu}m at 5 {mu}m beam shift. But, at higher beam shift than 10{mu}m, laser scan makes the surface rougher, which is considered to be due to the non uniform spatial distribution of laser energy. It is concluded that homogenized laser beam with high average power is needed for large area laser lapping of diamond films at appreciable rates. 12 refs., 9 figs.

  10. In Situ Infrared Spectroscopy of the Gaseous Species Present in a Diamond Chemical Vapor Deposition System

    Science.gov (United States)

    Morell, G.; Weiner, B. R.

    1998-01-01

    We interfaced a Hot-Filament Chemical Vapor Deposition (HFCVD) system to the emission port of an FT-IR spectrometer, in order to study the gas phase species present during the deposition of diamond thin films. The implementation of the infrared (IR) emission technique in situ allowed the study of various carbon-containing species believed to be crucial in diamond film growth. The two IR-active vibrational fundamentals of methane, v(3)(f2) and v(4)(f2), were observed at three different filament temperatures: 1000, 1500 and 2000 C. However, the net signal of v(3) was emission, while that of v(4) was absorption. These results indicate that the v(4) fundamental is excited beyond equilibrium, while the v(3) fundamental remains mostly in the ground state. This is due to the small concentration of methane, the low energy of v(4) compared to v(3) or to the Hz vibrational mode, and symmetry considerations that forbid interaction among the four fundamentals of methane. Thus, the excitation of v(3) is more likely than its decay under HFCVD conditions, producing a non-equilibrium population. At a filament temperature of 2000 C, the v(3) (sigma(+)(3)) fundamental of acetylene and a band at 1328 cm-l also ascribed to acetylene (v5 (pi(U)) + v4) appear in net absorption. This correlates well with the onset of molecular hydrogen breaking by the filament, which occurs at temperatures around 2000 C and above. The hydrogen atoms produced in this heterogeneous reaction give rise to a chain of reactions that lead to acetylene, among other carbonaceous species.

  11. Single crystal growth in spin-coated films of polymorphic phthalocyanine derivative under solvent vapor

    Energy Technology Data Exchange (ETDEWEB)

    Higashi, T.; Ohmori, M.; Ramananarivo, M. F.; Fujii, A., E-mail: afujii@opal.eei.eng.osaka-u.ac.jp; Ozaki, M. [Division of Electrical, Electronic, and Information Engineering, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan)

    2015-12-01

    The effects of solvent vapor on spin-coated films of a polymorphic phthalocyanine derivative were investigated. Growth of single crystal films via redissolving organic films under solvent vapor was revealed by in situ microscopic observations of the films. X-ray diffraction measurement of the films after exposing to solvent vapor revealed the phase transition of polymorphs under solvent vapor. The direction of crystal growth was clarified by measuring the crystal orientation in a grown monodomain film. The mechanism of crystal growth based on redissolving organic films under solvent vapor was discussed in terms of the different solubilities of the polymorphs.

  12. Nanocalorimetry of vapor-deposited organic glasses: tris-naphthylbenzene, decalin and ortho-terphenyl

    Science.gov (United States)

    Whitaker, Katherine R.

    Physical vapor deposition can be used to prepare glasses with extraordinary properties. By optimizing the substrate temperature and deposition rate, glasses with low enthalpy, high density and high kinetic stability, as compared to the ordinary liquid-cooled glass, can be produced. The heat capacity of 'stable glasses' has been measured with conventional calorimetry, but such techniques are limited to bulk samples; the properties of more technologically relevant thin films cannot be measured. In this thesis, nanocalorimetry was utilized to measure the heat capacity of thin films of four organic glassformers: alpha,alpha,beta-tris-naphthylbenzene (alphaalphabeta-TNB),cis- and trans-decahydronaphthalene (cis- and trans -decalin) and o-terphenyl. A number of new and important results came out of the AC nanocalorimetry experiments on these molecules. alphaalphabeta-TNB thin films showed thickness dependent transformation times for films up to one micron in thickness, consistent with the work on indomethacin. This result suggested that highly suppressed bulk transformation rates are a general feature associated with the kinetics of stable glass transformation. One way glassformers can be characterized is by their fragility, or their temperature dependent behavior as Tg is approached. Decalin, the molecular glassformer with the highest reported fragility, was shown to be capable of forming stable glasses when vapor-deposited. This result implies that surface mobility, which is deemed the controlling mechanism for stable glass formation, is also present in high fragility systems. Experiments on a variety of cis/trans-decalin mixture compositions showed that vapor deposition can also be used to make stable glasses of mixtures. The ability of an array of compositions to form stable glasses is a strong argument against nanocrystals being responsible for the extraordinary properties of stable glasses. Finally, in situ experiments on o-terphenyl were able to span the range of

  13. High Luminescence Efficiency in MoS2 Grown by Chemical Vapor Deposition.

    Science.gov (United States)

    Amani, Matin; Burke, Robert A; Ji, Xiang; Zhao, Peida; Lien, Der-Hsien; Taheri, Peyman; Ahn, Geun Ho; Kirya, Daisuke; Ager, Joel W; Yablonovitch, Eli; Kong, Jing; Dubey, Madan; Javey, Ali

    2016-07-26

    One of the major challenges facing the rapidly growing field of two-dimensional (2D) transition metal dichalcogenides (TMDCs) is the development of growth techniques to enable large-area synthesis of high-quality materials. Chemical vapor deposition (CVD) is one of the leading techniques for the synthesis of TMDCs; however, the quality of the material produced is limited by defects formed during the growth process. A very useful nondestructive technique that can be utilized to probe defects in semiconductors is the room-temperature photoluminescence (PL) quantum yield (QY). It was recently demonstrated that a PL QY near 100% can be obtained in MoS2 and WS2 monolayers prepared by micromechanical exfoliation by treating samples with an organic superacid: bis(trifluoromethane)sulfonimide (TFSI). Here we have performed a thorough exploration of this chemical treatment on CVD-grown MoS2 samples. We find that the as-grown monolayers must be transferred to a secondary substrate, which releases strain, to obtain high QY by TFSI treatment. Furthermore, we find that the sulfur precursor temperature during synthesis of the MoS2 plays a critical role in the effectiveness of the treatment. By satisfying the aforementioned conditions we show that the PL QY of CVD-grown monolayers can be improved from ∼0.1% in the as-grown case to ∼30% after treatment, with enhancement factors ranging from 100 to 1500× depending on the initial monolayer quality. We also found that after TFSI treatment the PL emission from MoS2 films was visible by eye despite the low absorption (5-10%). The discovery of an effective passivation strategy will speed the development of scalable high-performance optoelectronic and electronic devices based on MoS2.

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

    Directory of Open Access Journals (Sweden)

    A. Salar Elahi

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

  15. On the possibility to grow zinc oxide-based transparent conducting oxide films by hot-wire chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Abrutis, Adulfas, E-mail: adulfas.abrutis@chf.vu.lt; Silimavicus, Laimis; Kubilius, Virgaudas; Murauskas, Tomas; Saltyte, Zita; Kuprenaite, Sabina; Plausinaitiene, Valentina [Faculty of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius (Lithuania)

    2014-03-15

    Hot-wire chemical vapor deposition (HW-CVD) was applied to grow zinc oxide (ZnO)-based transparent conducting oxide (TCO) films. Indium (In)-doped ZnO films were deposited using a cold wall pulsed liquid injection CVD system with three nichrome wires installed at a distance of 2 cm from the substrate holder. The wires were heated by an AC current in the range of 0–10 A. Zn and In 2,2,6,6-tetramethyl-3,5-heptanedionates dissolved in 1,2-dimethoxyethane were used as precursors. The hot wires had a marked effect on the growth rates of ZnO, In-doped ZnO, and In{sub 2}O{sub 3} films; at a current of 6–10 A, growth rates were increased by a factor of ≈10–20 compared with those of traditional CVD at the same substrate temperature (400 °C). In-doped ZnO films with thickness of ≈150 nm deposited on sapphire-R grown at a wire current of 9 A exhibited a resistivity of ≈2 × 10{sup −3} Ωcm and transparency of >90% in the visible spectral range. These initial results reveal the potential of HW-CVD for the growth of TCOs.

  16. Influence of Molecular Shape on the Thermal Stability and Molecular Orientation of Vapor-Deposited Organic Semiconductors.

    Science.gov (United States)

    Walters, Diane M; Antony, Lucas; de Pablo, Juan J; Ediger, M D

    2017-07-20

    High thermal stability and anisotropic molecular orientation enhance the performance of vapor-deposited organic semiconductors, but controlling these properties is a challenge in amorphous materials. To understand the influence of molecular shape on these properties, vapor-deposited glasses of three disk-shaped molecules were prepared. For all three systems, enhanced thermal stability is observed for glasses prepared over a wide range of substrate temperatures and anisotropic molecular orientation is observed at lower substrate temperatures. For two of the disk-shaped molecules, atomistic simulations of thin films were also performed and anisotropic molecular orientation was observed at the equilibrium liquid surface. We find that the structure and thermal stability of these vapor-deposited glasses results from high surface mobility and partial equilibration toward the structure of the equilibrium liquid surface during the deposition process. For the three molecules studied, molecular shape is a dominant factor in determining the anisotropy of vapor-deposited glasses.

  17. 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.

  18. Development of Nb{sub 3}Sn Cavity Vapor Diffusion Deposition System

    Energy Technology Data Exchange (ETDEWEB)

    Eremeev, Grigory V.; Macha, Kurt M.; Clemens, William A.; Park, HyeKyoung; Williams, R. Scott

    2014-02-01

    Nb{sub 3}Sn is a BCS superconductors with the superconducting critical temperature higher than that of niobium, so theoretically it surpasses the limitations of niobium in RF fields. The feasibility of technology has been demonstrated at 1.5 GHz with Nb{sub 3}Sn vapor deposition technique at Wuppertal University. The benefit at these frequencies is more pronounced at 4.2 K, where Nb{sub 3}Sn coated cavities show RF resistances an order of magnitude lower than that of niobium. At Jefferson Lab we started the development of Nb{sub 3}Sn vapor diffusion deposition system within an R\\&D development program towards compact light sources. Here we present the current progress of the system development.

  19. Communication: Surface-facilitated softening of ordinary and vapor-deposited glasses

    Science.gov (United States)

    Cubeta, Ulyana; Bhattacharya, Deepanjan; Sadtchenko, Vlad

    2017-08-01

    A common distinction between the ordinary glasses formed by melt cooling and the stable amorphous films formed by vapor deposition is the apparent mechanism of their devitrification. Using quasi-adiabatic, fast scanning calorimetry that is capable of heating rates in excess of 105 K s-1, we have investigated the softening kinetics of micrometer-scale, ordinary glass films of methylbenzene and 2-propanol. At the limit of high heating rates, the transformation mechanism of ordinary glasses is identical to that of their stable vapor-deposited counterparts. In both cases, softening is likely to begin at the sample surface and progress into its bulk via a transformation front. Furthermore, such a surface-facilitated mechanism complies with zero-order, Arrhenius rate law. The activation energy barriers for the softening transformation imply that the kinetics must be defined, at least in part, by the initial thermodynamic and structural state of the samples.

  20. 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

  1. 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.

  2. Thickness measurement methods for physical vapor deposited aluminum coatings in packaging applications: A review

    OpenAIRE

    Lindner, Martina; Schmid, Markus

    2017-01-01

    The production of barrier packaging materials, e.g., for food, by physical vapor deposition (PVD) of inorganic coatings such as aluminum on polymer substrates is an established and well understood functionalization technique today. In order to achieve a sufficient barrier against gases, a coating thickness of approximately 40 nm aluminum is necessary. This review provides a holistic overview of relevant methods commonly used in the packaging industry as well as in packaging research for deter...

  3. Thickness Measurement Methods for Physical Vapor Deposited Aluminum Coatings in Packaging Applications: A Review

    OpenAIRE

    Martina Lindner; Markus Schmid

    2017-01-01

    The production of barrier packaging materials, e.g., for food, by physical vapor deposition (PVD) of inorganic coatings such as aluminum on polymer substrates is an established and well understood functionalization technique today. In order to achieve a sufficient barrier against gases, a coating thickness of approximately 40 nm aluminum is necessary. This review provides a holistic overview of relevant methods commonly used in the packaging industry as well as in packaging research for deter...

  4. Upcycling Waste Lard Oil into Vertical Graphene Sheets by Inductively Coupled Plasma Assisted Chemical Vapor Deposition

    OpenAIRE

    Wu, Angjian; Li, Xiaodong; Yang, Jian; Du, Changming; Shen, Wangjun; Yan, Jianhua

    2017-01-01

    Vertical graphene (VG) sheets were single-step synthesized via inductively coupled plasma (ICP)-enhanced chemical vapor deposition (PECVD) using waste lard oil as a sustainable and economical carbon source. Interweaved few-layer VG sheets, H2, and other hydrocarbon gases were obtained after the decomposition of waste lard oil. The influence of parameters such as temperature, gas proportion, ICP power was investigated to tune the nanostructures of obtained VG, which indicated that a proper tem...

  5. Fabrication of GaAs-Mo-Si structures by metalorganic chemical vapor deposition and laser annealing

    Science.gov (United States)

    Okakmoto, K.; Imai, T.

    1983-06-01

    After depositing undoped polycrystalline GaAs layers on Mo layers by means of metal-organic chemical vapor deposition, the samples were immersed in SnCl2-dissolved methanol in order to undergo annealing through irradiation by a Q-switched ruby laser. Recrystallization and doping of the GaAs layers was carried out succesfully, and Schottky characteristics were observed between the top GaAs layer and the Mo layer underneath. The barrier height was measured to be 0.53 eV.

  6. InAs/GaSb core-shell nanowires grown on Si substrates by metal-organic chemical vapor deposition

    Science.gov (United States)

    Ji, Xianghai; Yang, Xiaoguang; Du, Wenna; Pan, Huayong; Luo, Shuai; Ji, Haiming; Xu, Hongqi; Yang, Tao

    2017-06-01

    We report the growth of InAs/GaSb core-shell heterostructure nanowires with smooth sidewalls on Si substrates using metal-organic chemical vapor deposition (MOCVD) with no assistance from foreign catalysts. Sb adatoms were observed to strongly influence the morphology of the GaSb shell. In particular, Ga droplets form on the nanowire tips when a relatively low TMSb flow rate is used, whereas the droplets are missing and the radial growth of the GaSb is enhanced due to a reduction in the diffusion length of the Ga adatoms when the TMSb flow rate is increased. Moreover, transmission electron microscopy measurements revealed that the GaSb shell coherently grew on the InAs core without any misfit dislocations.

  7. Role of defects in tuning the electronic properties of monolayer WS{sub 2} grown by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jie; Zheliuk, Oleksandr; Lu, Jianming; Ye, Jianting [Zernike Institute for Advanced Materials, University of Groningen, Groningen (Netherlands); Gordiichuk, Pavlo [Zernike Institute for Advanced Materials, University of Groningen, Groningen (Netherlands); Department of Chemistry, Northwestern University, Evanston, IL (United States); Herrmann, Andreas [Zernike Institute for Advanced Materials, University of Groningen, Groningen (Netherlands); Molecular Biophysics, Department of Biology, Humboldt-Universitaet Berlin (Germany)

    2017-10-15

    Two-dimensional transition metal dichalcogenides have already attracted enormous research interest. To understand the dependence of electronic properties on the quality and defect morphology is vital for synthesizing high quality materials and the realization of functional devices. Here, we demonstrate the mapping of the conductive variations by conducting atomic force microscopy (C-AFM) in the monolayer tungsten disulfide (WS{sub 2}) grown by chemical vapor deposition. The electronic properties are strongly affected by the formation of vacancies in monolayer WS{sub 2} during growth, which is also verified by the photoluminescence. This spatial study of defects provides opportunities for optimization of the growth process for enhancing devices performance of TMDs monolayers. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Aerosol - assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

    Czech Academy of Sciences Publication Activity Database

    Vallejos, S.; Pizúrová, Naděžda; Čechal, J.; Grácia, I.; Cané, C.

    2017-01-01

    Roč. 2017, Č. 127 (2017), č. článku e56127. ISSN 1940-087X Institutional support: RVO:68081723 Keywords : Zinc oxide * columnar structures * rods * AACVD * non-catalyzed growth * vapor-solid mechanism Subject RIV: CA - Inorganic Chemistry OBOR OECD: Polymer science Impact factor: 1.232, year: 2016 https://www.jove.com/video/56127

  9. Comparative Study of Solution Phase and Vapor Phase Deposition of Aminosilanes on Silicon Dioxide Surfaces

    Science.gov (United States)

    Yadav, Amrita R.; Sriram, Rashmi; Carter, Jared A.; Miller, Benjamin L.

    2014-01-01

    The uniformity of aminosilane layers typically used for the modification of hydroxyl bearing surfaces such as silicon dioxide is critical for a wide variety of applications, including biosensors. However, in spite of many studies that have been undertaken on surface silanization, there remains a paucity of easy-to-implement deposition methods reproducibly yielding smooth aminosilane monolayers. In this study, solution- and vapor-phase deposition methods for three aminoalkoxysilanes differing in the number of reactive groups (3-aminopropyl triethoxysilane (APTES), 3-aminopropyl methyl diethoxysilane (APMDES) and 3-aminopropyl dimethyl ethoxysilane (APDMES)) were assessed with the aim of identifying methods that yield highly uniform and reproducible silane layers that are resistant to minor procedural variations. Silane film quality was characterized based on measured thickness, hydrophilicity and surface roughness. Additionally, hydrolytic stability of the films was assessed via these thickness and contact angle values following desorption in water. We found that two simple solution-phase methods, an aqueous deposition of APTES and a toluene based deposition of APDMES, yielded high quality silane layers that exhibit comparable characteristics to those deposited via vapor-phase methods. PMID:24411379

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

    OpenAIRE

    M. A. Mannan; Nagano, M.; K. Shigezumi; Kida, T.; Hirao, N.; Baba, Y.

    2008-01-01

    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 [(CH3)3N.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 t...

  11. Remote nitrogen microwave plasma chemical vapor deposition from a tetramethyldisilazane precursor. 2. Properties of deposited silicon carbonitride films

    Energy Technology Data Exchange (ETDEWEB)

    Blaszczyk-Lezak, I. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland); Wrobel, A.M. [Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, PL-90-363 Lodz (Poland)]. E-mail: amwrobel@bilbo.cbmm.lodz.pl; Bielinski, D.M. [Institute of Polymers, Faculty of Chemistry, Technical University of Lodz, 90-924 Lodz (Poland)

    2006-02-21

    The physical, optical, and mechanical properties of silicon carbonitride (Si:C:N) films produced by the remote nitrogen plasma chemical vapor deposition (RP-CVD) from tetramethyldisilazane have been investigated in relation to their chemical composition and structure. The films deposited at different substrate temperature (30-400 deg. C) were characterized in terms of their density, refractive index, hardness, elastic modulus, and friction coefficient. The correlations between the film compositional parameters, expressed by the atomic concentration ratios N / Si, C / Si, and N / C, as well as structural parameters described by the relative integrated intensities of the infrared absorption bands from the Si-N, Si-C, and SiMe units (controlled by substrate temperature) were investigated. On the basis of the results of these studies, reasonable structure-property relationships have been determined.

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

    Science.gov (United States)

    Tzeng, Yonhua (Inventor)

    2009-01-01

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

  13. III-Vs at Scale: A PV Manufacturing Cost Analysis of the Thin Film Vapor-Liquid-Solid Growth Mode

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Maxwell; Horowitz, Kelsey; Woodhouse, Michael; Battaglia, Corsin; Kapadia, Rehan; Javey, Ali

    2016-06-01

    The authors present a manufacturing cost analysis for producing thin-film indium phosphide modules by combining a novel thin-film vapor-liquid-solid (TF-VLS) growth process with a standard monolithic module platform. The example cell structure is ITO/n-TiO2/p-InP/Mo. For a benchmark scenario of 12% efficient modules, the module cost is estimated to be $0.66/W(DC) and the module cost is calculated to be around $0.36/W(DC) at a long-term potential efficiency of 24%. The manufacturing cost for the TF-VLS growth portion is estimated to be ~$23/m2, a significant reduction compared with traditional metalorganic chemical vapor deposition. The analysis here suggests the TF-VLS growth mode could enable lower-cost, high-efficiency III-V photovoltaics compared with manufacturing methods used today and open up possibilities for other optoelectronic applications as well.

  14. Polycrystalline indium phosphide on silicon by indium assisted growth in hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Metaferia, Wondwosen; Sun, Yan-Ting, E-mail: yasun@kth.se; Lourdudoss, Sebastian [Laboratory of Semiconductor Materials, Department of Materials and Nano Physics, KTH—Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Pietralunga, Silvia M. [CNR-Institute for Photonics and Nanotechnologies, P. Leonardo da Vinci, 32 20133 Milano (Italy); Zani, Maurizio; Tagliaferri, Alberto [Department of Physics Politecnico di Milano, P. Leonardo da Vinci, 32 20133 Milano (Italy)

    2014-07-21

    Polycrystalline InP was grown on Si(001) and Si(111) substrates by using indium (In) metal as a starting material in hydride vapor phase epitaxy (HVPE) reactor. In metal was deposited on silicon substrates by thermal evaporation technique. The deposited In resulted in islands of different size and was found to be polycrystalline in nature. Different growth experiments of growing InP were performed, and the growth mechanism was investigated. Atomic force microscopy and scanning electron microscopy for morphological investigation, Scanning Auger microscopy for surface and compositional analyses, powder X-ray diffraction for crystallinity, and micro photoluminescence for optical quality assessment were conducted. It is shown that the growth starts first by phosphidisation of the In islands to InP followed by subsequent selective deposition of InP in HVPE regardless of the Si substrate orientation. Polycrystalline InP of large grain size is achieved and the growth rate as high as 21 μm/h is obtained on both substrates. Sulfur doping of the polycrystalline InP was investigated by growing alternating layers of sulfur doped and unintentionally doped InP for equal interval of time. These layers could be delineated by stain etching showing that enough amount of sulfur can be incorporated. Grains of large lateral dimension up to 3 μm polycrystalline InP on Si with good morphological and optical quality is obtained. The process is generic and it can also be applied for the growth of other polycrystalline III–V semiconductor layers on low cost and flexible substrates for solar cell applications.

  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

    . This configuration enables a gentle treatment of sensitive materials like low-density polyethylene foils and biodegradable materials. SiOx coatings deposited in the novel setup were compared with other state of the art plasma coatings and were found to possess equally good or better barrier properties. The barrier...... effect of single-layer coatings deposited under different reaction conditions was studied. The coating thickness and the carbon content in the coatings were found to be the critical parameters for the barrier property. The novel barrier coating was applied on different polymeric materials...

  16. Characterization of catalytic chemical vapor-deposited SiCN thin film coatings

    Science.gov (United States)

    Neethirajan, Suresh; Ono, Takahita; Masayoshi, Esashi

    2012-06-01

    Silicon carbonitride thin films of 480 to 730-nm thicknesses were grown on silicon substrate using ammonia and hexamethyldisilazane gas sources using catalytic chemical vapor deposition process. Compositions of silicon, carbon and nitrogen in the SiCN films were varied by changing the flow rate of ammonia gas. The effect of deposition conditions on the structural, optical and mechanical properties of SiCN thin films was examined. X-ray photoelectron spectroscopy analysis indicated that the higher flow rate of ammonia gas results in higher nitrogen and lower carbon content in the deposited thin films. The measurement of stress as a function of substrate temperature in the SiCN film showed that the stress changes from compressive to tensile in the range of 275°C to 325°C. With these preliminary characterization tests, it is expected that SiCN nano-thin films can be used for developing sensors for harsh environment.

  17. Metal-free plasma-enhanced chemical vapor deposition of large area nanocrystalline graphene

    Science.gov (United States)

    Schmidt, Marek E.; Xu, Cigang; Cooke, Mike; Mizuta, Hiroshi; Chong, Harold M. H.

    2014-04-01

    This paper reports on large area, metal-free deposition of nanocrystalline graphene (NCG) directly onto wet thermally oxidized 150 mm silicon substrates using parallel-plate plasma-enhanced chemical vapor deposition. Thickness non-uniformities as low as 13% are achieved over the whole substrate. The cluster size {{L}_{\\text{a}}} of the as-obtained films is determined from Raman spectra and lies between 1.74 and 2.67 nm. The film uniformity was further confirmed by Raman mapping. The sheet resistance {{R}_{\\text{sq}}} of 3.73 \\text{k}\\Omega and charge carrier mobility μ of 2.49\\;\\text{c}{{\\text{m}}^{2}}\\;{{\\text{V}}^{-1}}\\;{{\\text{s}}^{-1}} are measured. We show that the NCG films can be readily patterned by reactive ion etching. NCG is also successfully deposited onto quartz and sapphire substrates and showed >85% optical transparency in the visible light spectrum.

  18. 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.

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

    Science.gov (United States)

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

    2017-12-01

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

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

    Science.gov (United States)

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

    2017-09-01

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

  1. Deposition of titanium coating on SiC fiber by chemical vapor deposition with Ti-I2 system

    Science.gov (United States)

    Luo, Xian; Wu, Shuai; Yang, Yan-qing; Jin, Na; Liu, Shuai; Huang, Bin

    2017-06-01

    Titanium coating was prepared on SiC fiber using titanium-iodine (Ti-I2) mixture by hot-wall chemical vapor deposition. Thermodynamic analysis and experimental observation were carried out in this work. The thermodynamic analysis of the reactions in the Ti-I2 system indicates that Ti and I2 raw powder materials transform to titanium coating as follows: Ti + I2 → (TiI2, TiI3), and (TiI2, TiI3) → Ti. In theory, the conversions of TiI3 and TiI2 reach the maximum when Ti:I2 is 1:1.5, while in actual experiment that reached the maximum when Ti:I2 was 1:2, as there existed the waste of I2 due to sublimation. Typical deposited coating is relatively flat and uniform. However, as SiC is prone to react with Ti at high temperatures, the obtained coating contained some Si and C elements except for Ti. So the coating was not a pure Ti coating but contained some carbides and silicides. Deposition rate of the coating increased with the increase of temperature. The deposited thickness increased with the increase of heat preservation time, and achieved the maximum thickness at 90 min.

  2. Tris(phosphino)borato silver(I) complexes as precursors for metallic silver aerosol-assisted chemical vapor deposition.

    Science.gov (United States)

    McCain, Matthew N; Schneider, Sven; Salata, Michael R; Marks, Tobin J

    2008-04-07

    A series of light- and air-stable tris(phosphino)borato silver(I) complexes has been synthesized, structurally and spectroscopically characterized, and implemented in the growth of low resistivity metallic silver thin films by aerosol-assisted chemical vapor deposition (AACVD). Of the four complexes in the series, [RB(CH2PR'2) 3]AgPEt3 (R = Ph (1, 3), (n)Bu (2, 4); R' = Ph (1, 2), (i)Pr (3, 4), complexes 1 and 2 have been characterized by single-crystal X-ray diffraction. Complex 2 represents a significant improvement over previously available nonfluorinated Ag precursors, owing to ease of handling and efficient film deposition characteristics. Thermogravimetric analysis (TGA) shows that the thermolytic properties of these complexes can be significantly modified by altering the ligand structure. Polycrystalline cubic-phase Ag thin films were grown on glass, MgO(100), and 52100 steel substrates. Ag films of thicknesses 3 microm, grown at rates of 14-18 nm/min, exhibit low levels of extraneous element contamination by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) indicate that film growth proceeds primarily via an island growth (Volmer-Weber) mechanism.

  3. Fabrication of polyimide shells by vapor phase deposition for use as ICF targets

    Energy Technology Data Exchange (ETDEWEB)

    Alfonso, E.L.; Tsai, F.Y.; Chen, S.H.; Gram, R.Q.; Harding, D.R. [Univ. of Rochester, NY (United States). Lab. for Laser Energetics

    1999-03-01

    Hollow polyimide shells, for use as ICF targets, were fabricated by co-depositing monomer precursors from the vapor phase onto bounced spherical mandrels. The process involved two stages: first, the deposited monomers (pyromellitic dianhydride and 4,4{prime}-oxydianiline) reacted on the mandrel surface to form polyamic acid; second, the mandrel was heated to 300 C to imidize the polyamic acid and to decompose the mandrel. During this latter process the decomposed mandrel diffused through the thermally stable coating, leaving a polyimide shell. Depositions were performed under low ({approximately}10{sup {minus}3} Torr) and high ({approximately}10{sup {minus}6} Torr) vacuum. Also, flat witness films of polyimide deposited on Si wafers and NaCl allowed the mechanical properties and chemical composition of the film during the heating cycle to be measured. Polyimide shells with diameters ranging from 700 to 950 {micro}m and wall thicknesses ranging from 2 to 13 {micro}m were produced. The shell`s sphericity was greater than 99%. Burst and buckle pressure tests on these shells yielded the estimated mechanical strength properties. The elastic modulus and tensile strength were {approximately}15 GPa and {approximately}300 MPa, respectively. The permeability of D{sub 2} through polyamic acid at 25 C was 7.4 {times} 10{sup {minus}17} mol{center_dot}m/m{sup 2}{center_dot}Pa{center_dot}s and increased to 6.4 {times} 10{sup {minus}16} mol{center_dot}m/m{sup 2}{center_dot}Pa{center_dot}s at 25 C upon curing the shell to 150 C. The permeability of D{sub 2} at 25 C through vapor-deposited polyimide flat films was measured to be 240 times greater than through the as-deposited polyamic acid, and about 7 times greater than through commercially available solution-cast Kapton.

  4. The impact of hydrogen and oxidizing impurities in chemical vapor deposition of graphene on copper

    Science.gov (United States)

    Choubak, Saman

    Graphene, the single-atom layer of carbon, has attracted scientists and technologists due to its outstanding physical and opto/electronic properties. The use of graphene in practical applications requires a reliable and cost-effective method to produce large area graphene films with low defects and controlled thicknesses. Direct growth of graphene using chemical vapor deposition (CVD) on copper, in which carbonaceous gaseous species react with the metal substrate in the presence of hydrogen at high temperatures (850-1100° C), led to high coverage of high quality graphene, opening up a promising future for methods of this type and a large step towards commercial realization of graphene products. The present thesis deals with the synthesis of graphene via low pressure CVD (LP-CVD) on copper catalyst using methane as the carbon precursor. The focus is mainly on the determination of the role of hydrogen and oxidizing impurities during graphene formation with an ultimate purpose: to elucidate a viable and reproducible method for the production of high quality graphene films compatible with industrial manufacturing processes. The role of molecular hydrogen in graphene CVD is explored in the first part of the thesis. Few studies claimed that molecular hydrogen etches graphene films on copper by conducting annealing experiments. On the other hand, we speculated that this graphene etching reaction is due to the presence of trace amount of oxygen in the furnace atmosphere. Thus, we took another approach and designed systematic annealing experiments to investigate the role of hydrogen in the etching reaction of graphene on copper foils. No evidence of graphene etching on copper was observed when purified ultra high purity (UHP) hydrogen was used at 825 °C and 500 mTorr. Nevertheless, graphene films exposed to the unpurified UHP hydrogen were etched due to the presence of oxidizing impurities. Our results show that hydrogen is not responsible for graphene etching reaction

  5. Deposition of titanium coating on SiC fiber by chemical vapor deposition with Ti-I{sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Xian, E-mail: luo_shenfan@hotmail.com; Wu, Shuai; Yang, Yan-qing; Jin, Na; Liu, Shuai; Huang, Bin

    2017-06-01

    Highlights: • The transformation paths of (Ti + I{sub 2}) powder to Ti coating is: Ti + I{sub 2} → (TiI{sub 2}, TiI{sub 3}) → Ti. • Uniform coating was obtained on SiC fiber, but it contained Si and C elements. • Deposition rate of the coating increased with the increase of temperature. • Deposition thickness increased with time and achieved the maximum at 90 min. - Abstract: Titanium coating was prepared on SiC fiber using titanium-iodine (Ti-I{sub 2}) mixture by hot-wall chemical vapor deposition. Thermodynamic analysis and experimental observation were carried out in this work. The thermodynamic analysis of the reactions in the Ti-I{sub 2} system indicates that Ti and I{sub 2} raw powder materials transform to titanium coating as follows: Ti + I{sub 2} → (TiI{sub 2}, TiI{sub 3}), and (TiI{sub 2}, TiI{sub 3}) → Ti. In theory, the conversions of TiI{sub 3} and TiI{sub 2} reach the maximum when Ti:I{sub 2} is 1:1.5, while in actual experiment that reached the maximum when Ti:I{sub 2} was 1:2, as there existed the waste of I{sub 2} due to sublimation. Typical deposited coating is relatively flat and uniform. However, as SiC is prone to react with Ti at high temperatures, the obtained coating contained some Si and C elements except for Ti. So the coating was not a pure Ti coating but contained some carbides and silicides. Deposition rate of the coating increased with the increase of temperature. The deposited thickness increased with the increase of heat preservation time, and achieved the maximum thickness at 90 min.

  6. Substrate Effect on Plasma Clean Efficiency in Plasma Enhanced Chemical Vapor Deposition System

    Directory of Open Access Journals (Sweden)

    Shiu-Ko JangJian

    2007-01-01

    Full Text Available The plasma clean in a plasma-enhanced chemical vapor deposition (PECVD system plays an important role to ensure the same chamber condition after numerous film depositions. The periodic and applicable plasma clean in deposition chamber also increases wafer yield due to less defect produced during the deposition process. In this study, the plasma clean rate (PCR of silicon oxide is investigated after the silicon nitride deposited on Cu and silicon oxide substrates by remote plasma system (RPS, respectively. The experimental results show that the PCR drastically decreases with Cu substrate compared to that with silicon oxide substrate after numerous silicon nitride depositions. To understand the substrate effect on PCR, the surface element analysis and bonding configuration are executed by X-ray photoelectron spectroscopy (XPS. The high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS is used to analyze microelement of metal ions on the surface of shower head in the PECVD chamber. According to Cu substrate, the results show that micro Cu ion and the CuOx bonding can be detected on the surface of shower head. The Cu ion contamination might grab the fluorine radicals produced by NF3 ddissociation in the RPS and that induces the drastic decrease on PCR.

  7. Parametric study on vapor-solid-solid growth mechanism of multiwalled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Shukrullah, S., E-mail: zshukrullah@gmail.com [Center of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, 32610, Bandar Seri Iskandar, Perak (Malaysia); Mohamed, N.M. [Center of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, 32610, Bandar Seri Iskandar, Perak (Malaysia); Shaharun, M.S. [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, 32610, Bandar Seri Iskandar, Perak (Malaysia); Naz, M.Y. [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 32610, Bandar Seri Iskandar, Perak (Malaysia)

    2016-06-15

    This study aimed at investigating the effect of the fluidized bed chemical vapor deposition (FBCVD) process parameters on growth mechanism, morphology and purity of the multiwalled carbon nanotubes (MWCNTs). Nanotubes were produced in a vertical FBCVD reactor by catalytic decomposition of ethylene over Al{sub 2}O{sub 3} supported nano-iron catalyst buds at different flow rates. FESEM, TEM, Raman spectroscopy and TGA thermograms were used to elaborate the growth parameters of the as grown MWCNTs. As the growth process was driven by the process temperatures well below the iron-carbon eutectic temperature (1147 °C), the appearance of graphite platelets from the crystallographic faces of the catalyst particles suggested a solid form of the catalyst during CNT nucleation. A vapor-solid-solid (VSS) growth mechanism was predicted for nucleation of MWCNTs with very low activation energy. The nanotubes grown at optimized temperature and ethylene flow rate posed high graphitic symmetry, purity, narrow diameter distribution and shorter inter-layer spacing. In Raman and TGA analyses, small I{sub D}/I{sub G} ratio and residual mass revealed negligible ratios of structural defects and amorphous carbon in the product. However, several structural defects and impurity elements were spotted in the nanotubes grown under unoptimized process parameters. - Graphical abstract: Arrhenius plot of relatively pure MWCNTs grown over Al2O3 supported nano-iron buds. - Highlights: • Vapor–solid–solid growth mechanism of MWCNTs was studied in a vertical FBCVD reactor. • MWCNTs were grown over Al2O3 supported nano-iron buds at very low activation energy. • FBCVD reactor was operated at temperatures well below the iron-carbon eutectic point. • Ideally graphitized structures were obtained at a process temperature of 800 °C. • Tube diameter revealed a narrow distribution of 20–25 nm at the optimum temperature.

  8. Vapor-liquid-solid growth of silicon and silicon germanium nanowires

    Science.gov (United States)

    Nimmatoori, Pramod

    2009-12-01

    Si and Si1-xGex nanowires are promising materials with potential applications in various disciplines of science and technology. Small diameter nanowires can act as model systems to study interesting phenomena such as tunneling that occur in the nanometer regime. Furthermore, technical challenges in fabricating nanoscale size devices from thin films have resulted in interest and research on nanowires. In this perspective, vertical integrated nanowire field effect transistors (VINFETs) fabricated from Si nanowires are promising devices that offer better control on device properties and push the transistor architecture into the third dimension potentially enabling ultra-high transistor density circuits. Transistors fabricated from Si/Si 1-xGex nanowires have also been proposed that can have high carrier mobility. In addition, the Si and Si1-xGe x nanowires have potential to be used in various applications such as sensing, thermoelectrics and solar cells. Despite having considerable potential, the understanding of the vapor-liquid-solid (VLS) mechanism utilized to fabricate these wires is still rudimentary. Hence, the objective of this thesis is to understand the effects of nanoscale size and the role of catalyst that mediates the wire growth on the growth rate of Si and Si1-xGe x nanowires and interfacial abruptness in Si/Si1-xGe x axial heterostructure nanowires. Initially, the growth and structural properties of Si nanowires with tight diameter distribution grown from 10, 20 and 50 nm Au particles dispersed on a polymer-modified substrate was studied. A nanoparticle application process was developed to disperse Au particles on the substrate surface with negligible agglomeration and sufficient density. The growth temperature and SiH4 partial pressure were varied to optimize the growth conditions amenable to VLS growth with smooth wire morphology and negligible Si thin film deposition on wire sidewalls. The Si nanowire growth rate was studied as a function of growth

  9. 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°.

  10. Structural properties of Al-rich AlInN grown on c-plane GaN substrate by metal-organic chemical vapor deposition.

    Science.gov (United States)

    Lin, Pei-Yin; Chen, Jr-Yu; Shih, Yi-Sen; Chang, Li

    2014-01-01

    The attractive prospect for AlInN/GaN-based devices for high electron mobility transistors with advanced structure relies on high-quality AlInN epilayer. In this work, we demonstrate the growth of high-quality Al-rich AlInN films deposited on c-plane GaN substrate by metal-organic chemical vapor deposition. X-ray diffraction, scanning electron microscopy, and scanning transmission electron microscopy show that the films lattice-matched with GaN can have a very smooth surface with good crystallinity and uniform distribution of Al and In in AlInN.

  11. Vapor deposition of polystyrene thin films by intense laser vibrational excitation

    DEFF Research Database (Denmark)

    Bubb, D.M.; Papantonakis, M.R.; Horwitz, J.S.

    2002-01-01

    -induced damage to the target can be seen. RIR-PLD is a fundamentally new approach to polymer thin film growth as the absorption of radiation resonant with vibrational modes allow the energy to be deposited into the polymer and transfers between macromolecules in such a way as to promote efficient, non......Polystyrene films were deposited using resonant infrared pulsed laser depositions (RIR-PLD). Thin films were grown on Si(1 1 1) wafers and NaCl substrates and analyzed by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The depositions were carried out...... in vacuum (10(-4)-10(-5) Torr) at wavelengths 3.28, 3.30, 3.42 and 3.48 mum which are resonant with CH2 stretching modes in the polymer. We also attempted to deposit a films using non-resonant infrared (RIR) excitation (2.90 mum). At this wavelength no films were deposited, and evidence for laser...

  12. Low-Cost Growth of III-V Layers on Si Using Close-Spaced Vapor Transport

    Energy Technology Data Exchange (ETDEWEB)

    Boucher, Jason W.; Greenaway, Ann L.; Ritenour, Andrew J.; Davis, Allison L.; Bachman, Benjamin F.; Aloni, Shaul; Boettcher, Shannon W.

    2015-06-14

    Close-spaced vapor transport (CSVT) uses solid precursors to deposit material at high rates and with high precursor utilization. The use of solid precursors could significantly reduce the costs associated with III-V photovoltaics, particularly if growth on Si substrates can be demonstrated. We present preliminary results of the growth of GaAs1-xPx with x ≈ 0.3 and 0.6, showing that CSVT can be used to produce III-V-V’ alloys with band gaps suitable for tandem devices. Additionally, we have grown GaAs on Si by first thermally depositing films of Ge and subsequently depositing GaAs by CSVT. Patterning the Ge into islands prevents cracking due to thermal mismatch and is useful for potential tandem structures.

  13. An Investigation of Solid-State Amidization and Imidization Reactions in Vapor Deposited Poly (amic acid)

    Energy Technology Data Exchange (ETDEWEB)

    Anthamatten, M; Letts, S A; Day, K; Cook, R C; Gies, A P; Hamilton, T P; Nonidez, W K

    2004-06-28

    The condensation polymerization reaction of 4,4'-oxydianiline (ODA) with pyromellitic dianhydride (PMDA) to form poly(amic acid) and the subsequent imidization reaction to form polyimide were investigated for films prepared using vapor deposition polymerization techniques. Fourier-transform infrared spectroscopy (FT-IR), thermal analysis, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) of films at different temperatures indicate that additional solid-state polymerization occurs prior to imidization reactions. Experiments reveal that, upon vapor deposition, poly(amic acid) oligomers form that have a number-average molecular weight of about 1500 Daltons. Between 100 - 130 C these chains undergo additional condensation reaction to form slightly higher molecular weight oligomers. Calorimetry measurements show that this reaction is exothermic ({Delta}H {approx} -30 J/g) with an activation energy of about 120 kJ/mol. Experimental reaction enthalpies are compared to results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150 - 300 C) imidization of amide linkages occurs as an endothermic reaction ({Delta}H {approx} +120 J/g) with an activation energy of about 130 kJ/mol. Solid-state kinetics were found to depend on reaction conversion as well as the processing conditions used to deposit films.

  14. Fabrication and characterization of a cell electrostimulator device combining physical vapor deposition and laser ablation

    Science.gov (United States)

    Aragón, Angel L.; Pérez, Eliseo; Pazos, Antonio; Bao-Varela, Carmen; Nieto, Daniel

    2017-08-01

    In this work we present the process of fabrication and optimization of a prototype of a cell electrostimulator device for medical application combining physical vapor deposition and laser ablation. The fabrication of the first prototype begins with a deposition of a thin layer of 200 nm of aluminium on a borosilicate glass substrate using physical vapor deposition (PVD). In the second stage the geometry design of the electrostimulator is made in a CAD-like software available in a Nd:YVO4 Rofin Power line 20E, operating at the fundamental wavelength of 1064 nm and 20 ns pulse width. Choosing the proper laser parameters the negative of the electrostimulator desing is ablated. After that the glass is assembled between two polycarbonate sheets and a thick sheet of polydimethylsiloxane (PDMS). The PDMS sheet has a round hole in where cells are placed. There is also included a thin soda-lime silicate glass (100 μm) between the electrostimulator and the PMDS to prevent the cells for being in contact with the electric circuit. In order to control the electrical signal applied to the electrostimulator is used a digital I/O device from National Instruments (USB-6501) which provides 5 V at the output monitored by a software programmed in LabVIEW. Finally, the optical and electrical characterization of the cell electrostimulator device is presented.

  15. Optical and structural properties of ZnO hexagonal rods prepared by thermal chemical vapor deposition technique

    Directory of Open Access Journals (Sweden)

    A Reyhani

    2014-11-01

    Full Text Available In this research, ZnO nanostructure hexagonal pyramid rods with high optical and structural quality were synthesized by the simple thermal chemical vapor deposition of Zn powder without a metal catalyst. Surface morphologies were characterized by scanning electron microscopy (SEM. XRD analyses demonstrated that ZnO hexagonal pyramid rods had a wurtzite structure with the orientation of (002. Investigation of optical properties of samples by photoluminescence spectrum exhibited a sharp UV emission peak at 380nm. The quality and composition of the ZnO pyramid rods were characterized using the Fourier transform infrared spectrum (FTIR at room temperature. In addition, the growth mechanism of ZnO hexagonal rods is also briefly discussed.

  16. Chemical Vapor Deposited Graphene-Based Derivative As High-Performance Hole Transport Material for Organic Photovoltaics.

    Science.gov (United States)

    Capasso, Andrea; Salamandra, Luigi; Faggio, Giuliana; Dikonimos, Theodoros; Buonocore, Francesco; Morandi, Vittorio; Ortolani, Luca; Lisi, Nicola

    2016-09-14

    The development of efficient charge transport layers is a key requirement for the fabrication of efficient and stable organic solar cells. A graphene-based derivative with planar resistivity exceeding 10(5) Ω/□ and work function of 4.9 eV is here produced by finely tuning the parameters of the chemical vapor deposition process on copper. After the growth, the film is transferred to glass/indium tin oxide and used as hole transport layer in organic solar cells based on a PBDTTT-C-T:[70]PCBM blend. The cells attained a maximum power conversion efficiency of 5%, matching reference cells made with state-of-the-art PSS as the hole transport layer. Our results indicate that functionalized graphene could represent an effective alternative to PSS as hole transport/electron blocking layer in solution-processed organic photovoltaics.

  17. Structural and electronic properties of InN epitaxial layer grown on c-plane sapphire by chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Barick, Barun Kumar, E-mail: bkbarick@gmail.com; Prasad, Nivedita; Saroj, Rajendra Kumar; Dhar, Subhabrata [Department of Physics, Indian Institute of Technology, Bombay, Mumbai 400076 (India)

    2016-09-15

    Growth of InN epilayers on c-plane sapphire substrate by chemical vapor deposition technique using pure indium metal and ammonia as precursors has been systematically explored. It has been found that [0001] oriented indium nitride epitaxial layers with smooth surface morphology can be grown on c-plane sapphire substrates by optimizing the growth conditions. Bandgap of the film is observed to be Burstein–Moss shifted likely to be due to high background electron concentration. It has been found that the concentration of this unintentional doping decreases with the increase in the growth temperature and the ammonia flux. Epitaxial quality on the other hand deteriorates as the growth temperature increases. Moreover, the morphology of the deposited layer has been found to change from flat top islands to faceted mounds as the flow rate of ammonia increases. This phenomenon is expected to be related to the difference in surface termination character at low and high ammonia flow rates.

  18. Chemical vapor deposition techniques and related methods for manufacturing microminiature thermionic converters

    Energy Technology Data Exchange (ETDEWEB)

    King, Donald B. (Albuquerque, NM); Sadwick, Laurence P. (Salt Lake City, UT); Wernsman, Bernard R. (Clairton, PA)

    2002-06-25

    Methods of manufacturing microminiature thermionic converters (MTCs) having high energy-conversion efficiencies and variable operating temperatures using MEMS manufacturing techniques including chemical vapor deposition. The MTCs made using the methods of the invention incorporate cathode to anode spacing of about 1 micron or less and use cathode and anode materials having work functions ranging from about 1 eV to about 3 eV. The MTCs also exhibit maximum efficiencies of just under 30%, and thousands of the devices can be fabricated at modest costs.

  19. Synthesis of single-crystalline anisotropic gold nano-crystals via chemical vapor deposition

    Science.gov (United States)

    Manna, Sohini; Kim, Jong Woo; Takahashi, Yukiko; Shpyrko, Oleg G.; Fullerton, Eric E.

    2016-05-01

    We report on a novel one-step catalyst-free, thermal chemical vapor deposition procedure to synthesize gold nanocrystals on silicon substrates. This approach yields single-crystal nanocrystals with various morphologies, such as prisms, icosahedrons, and five-fold twinned decahedrons. Our approach demonstrates that high-quality anisotropic crystals composed of fcc metals can be produced without the need for surfactants or templates. Compared with the traditional wet chemical synthesis processes, our method enables direct formation of highly pure and single crystalline nanocrystals on solid substrates which have applications in catalysis. We investigated the evolution of gold nanocrystals and established their formation mechanism.

  20. Raman and optical characterization of multilayer turbostratic graphene grown via chemical vapor deposition

    OpenAIRE

    Lenski, Daniel R.; Fuhrer, Michael S.

    2010-01-01

    We synthesize large-area graphene via atmospheric-pressure (AP) chemical vapor deposition (CVD) on copper, and transfer to SiO2 wafers. In contrast to low-pressure (LP) CVD on copper, optical contrast and atomic force microscopy measurements show AP-CVD graphene contains significant multi-layer areas. Raman spectroscopy always shows a single Lorentzian 2D peak, however systematic differences are observed in the 2D peak energy, width, and intensity for single- and multi-layer regions. We concl...

  1. Vapor Phase Sensing Using Metal Nanorod Thin Films Grown by Cryogenic Oblique Angle Deposition

    Directory of Open Access Journals (Sweden)

    Piyush Shah

    2013-01-01

    Full Text Available We demonstrate the chemical sensing capability of silver nanostructured films grown by cryogenic oblique angle deposition (OAD. For comparison, the films are grown side by side at cryogenic (~100 K and at room temperature (~300 K by e-beam evaporation. Based on the observed structural differences, it was hypothesized that the cryogenic OAD silver films should show an increased surface enhanced Raman scattering (SERS sensitivity. COMSOL simulation results are presented to validate this hypothesis. Experimental SERS results of 4-aminobenzenethiol (4-ABT Raman test probe molecules in vapor phase show good agreement with the simulation and indicate promising SERS applications for these nanostructured thin films.

  2. Porous tungsten prepared by atmospheric-pressure chemical vapor deposition with WF6 and its characterization

    Science.gov (United States)

    Li, Ying; Yu, Xiaodong; Tan, Chengwen; Wang, Fuchi; Ma, Honglei; Yue, Jintao

    2017-05-01

    Porous tungsten (W) is used in aeronautic and aerospace engineering, power electronics field and metallurgical industry. In this study, porous W with 98wt% W was prepared on a carbon foam substrate by atmospheric-pressure chemical vapor deposition (CVD) with tungsten fluoride (WF6) as the precursor. The porous W with 78.1346% porosity displayed a pure α-W phase and the uniform surface. The mode pore diameter of porous W is 208.0 µm. In a compression test, the fracture strength of porous W is 20.3 MPa.

  3. ZnO nanowall network grown by chemical vapor deposition technique

    Science.gov (United States)

    Mukherjee, Amrita; Dhar, Subhabrata

    2015-06-01

    Network of wedge shaped ZnO nanowalls are grown on c-sapphire by Chemical Vapor Deposition (CVD) technique. Structural studies using x-ray diffraction show much better crystallinity in the nanowall sample as compared to the continuous film. Moreover, the defect related broad green luminescence is found to be suppressed in the nanowall sample. The low temperature photoluminescence study also suggests the quantum confinement of carriers in nanowall sample. Electrical studies performed on the nanowalls show higher conductivity, which has been explained in terms of the reduction of scattering cross-section as a result of 1D quantum confinement of carriers on the tip of the nanowalls.

  4. ZnO nanowall network grown by chemical vapor deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Amrita, E-mail: but.then.perhaps@gmail.com; Dhar, Subhabrata [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai-400076 (India)

    2015-06-24

    Network of wedge shaped ZnO nanowalls are grown on c-sapphire by Chemical Vapor Deposition (CVD) technique. Structural studies using x-ray diffraction show much better crystallinity in the nanowall sample as compared to the continuous film. Moreover, the defect related broad green luminescence is found to be suppressed in the nanowall sample. The low temperature photoluminescence study also suggests the quantum confinement of carriers in nanowall sample. Electrical studies performed on the nanowalls show higher conductivity, which has been explained in terms of the reduction of scattering cross-section as a result of 1D quantum confinement of carriers on the tip of the nanowalls.

  5. Fabrication and characterization of a planar gradient-index, plasma-enhanced chemical vapor deposition lens.

    Science.gov (United States)

    Beltrami, D R; Love, J D; Durandet, A; Samo, A; Cogswell, C J

    1997-10-01

    A thin, one-dimensional, gradient-index slab lens with a parabolic profile was designed and fabricated in fluorine-doped silica by use of plasma-enhanced chemical vapor deposition in a Helicon plasma reactor. The refractive-index profile of the fabricated lens was determined by the application of an inversion technique to the values of modal effective index measured with a prism coupler. The periodic refocusing property of the lens and the independence of the wavelength were measured with the fluorescence of a specially doped, thin polymer layer spin-coated onto the surface of the lens.

  6. Preparation of Bismuth Titanate Films by Electron Cyclotron Resonance Plasma Sputtering-Chemical Vapor Deposition

    OpenAIRE

    Masumoto, H.; Hirai, T.

    1995-01-01

    Bismuth titanate (Bi4Ti3O12 : BIT) thin films were prepared on the Pt courted MgO(100) substrate by electron cyclotron resonance plasma sputtering-chemical vapor deposition (ECR plasma sputtering-CVD). Bi2O3 was used as a sputtering target and tetra-isopropoxy-titanium [Ti(i-C3H7O)4] as a CVD source. The composition of films was controlled by changing RF power (PRF) of Bi2O3 target and Ti source temperature (TTi). The stoichiometric BIT film was prepared under the condition of PRF=500W, TTi=6...

  7. 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.

  8. A sub-atmospheric chemical vapor deposition process for deposition of oxide liner in high aspect ratio through silicon vias.

    Science.gov (United States)

    Lisker, Marco; Marschmeyer, Steffen; Kaynak, Mehmet; Tekin, Ibrahim

    2011-09-01

    The formation of a Through Silicon Via (TSV) includes a deep Si trench etching and the formation of an insulating layer along the high-aspect-ratio trench and the filling of a conductive material into the via hole. The isolation of the filling conductor from the silicon substrate becomes more important for higher frequencies due to the high coupling of the signal to the silicon. The importance of the oxide thickness on the via wall isolation can be verified using electromagnetic field simulators. To satisfy the needs on the Silicon dioxide deposition, a sub-atmospheric chemical vapor deposition (SA-CVD) process has been developed to deposit an isolation oxide to the walls of deep silicon trenches. The technique provides excellent step coverage of the 100 microm depth silicon trenches with the high aspect ratio of 20 and more. The developed technique allows covering the deep silicon trenches by oxide and makes the high isolation of TSVs from silicon substrate feasible which is the key factor for the performance of TSVs for mm-wave 3D packaging.

  9. Controlling the resistivity gradient in aluminum-doped zinc oxide grown by plasma-enhanced chemical vapor deposition

    Science.gov (United States)

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

    2012-08-01

    Aluminum-doped ZnO (ZnO:Al) grown by chemical vapor deposition (CVD) generally exhibit a major drawback, i.e., a gradient in resistivity extending over a large range of film thickness. The present contribution addresses the plasma-enhanced CVD deposition of ZnO:Al layers by focusing on the control of the resistivity gradient and providing the solution towards thin (≤300 nm) ZnO:Al layers, exhibiting a resistivity value as low as 4 × 10-4 Ω cm. The approach chosen in this work is to enable the development of several ZnO:Al crystal orientations at the initial stages of the CVD-growth, which allow the formation of a densely packed structure exhibiting a grain size of 60-80 nm for a film thickness of 95 nm. By providing an insight into the growth of ZnO:Al layers, the present study allows exploring their application into several solar cell technologies.

  10. Will it form a stable glass? How the stability of vapor deposited glasses depends on molecular structure

    Science.gov (United States)

    Tylinski, Michael; Beasley, Madeleine; Chua, Yeong Zen; Schick, Christoph; Ediger, Mark

    Over the past nine years physical vapor deposition has been used to prepare molecular glasses with exceptional properties. When heated, transformation of these highly stable glasses takes orders of magnitude longer than the transformation of liquid-cooled glasses. Until recently, it appeared that most organic molecules could form stable glasses when vapor deposited. We test the generality of stable glass formation by vapor-depositing a wide range of small organic molecules, including hydroxyl, carbonyl, phosphate, aromatic, and aliphatic functional groups. When prepared under conditions expected to yield highly stable glasses, we observe glasses with a wide range of kinetic stabilities, depending on the functional groups in the molecule. In general, alcohols and molecules with long aliphatic chains do not form highly stable glasses while aromatic molecules do. We also test the hypothesis that the surface mobility during deposition determines if a molecule is able to create highly stable glasses.

  11. Crystal Engineering for Low Defect Density and High Efficiency Hybrid Chemical Vapor Deposition Grown Perovskite Solar Cells.

    Science.gov (United States)

    Ng, Annie; Ren, Zhiwei; Shen, Qian; Cheung, Sin Hang; Gokkaya, Huseyin Cem; So, Shu Kong; Djurišić, Aleksandra B; Wan, Yangyang; Wu, Xiaojun; Surya, Charles

    2016-12-07

    Synthesis of high quality perovskite absorber is a key factor in determining the performance of the solar cells. We demonstrate that hybrid chemical vapor deposition (HCVD) growth technique can provide high level of versatility and repeatability to ensure the optimal conditions for the growth of the perovskite films as well as potential for batch processing. It is found that the growth ambient and degree of crystallization of CH3NH3PbI3 (MAPI) have strong impact on the defect density of MAPI. We demonstrate that HCVD process with slow postdeposition cooling rate can significantly reduce the density of shallow and deep traps in the MAPI due to enhanced material crystallization, while a mixed O2/N2 carrier gas is effective in passivating both shallow and deep traps. By careful control of the perovskite growth process, a champion device with power conversion efficiency of 17.6% is achieved. Our work complements the existing theoretical studies on different types of trap states in MAPI and fills the gap on the theoretical analysis of the interaction between deep levels and oxygen. The experimental results are consistent with the theoretical predictions.

  12. SiC/Si heterojunction diodes fabricated by self-selective and by blanket rapid thermal chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yih, P.H.; Li, J.P.; Steckl, A.J. (Univ. of Cincinnati, OH (United States). Dept. of Electrical and Computer Engineering)

    1994-03-01

    SiC/Si heterojunction diodes have been fabricated by two different rapid thermal chemical vapor deposition (RTCVD) processes: a localized self-selective growth and blanket growth. The self-selective growth of crystalline cubic ([beta]) SiC was obtained by propane carbonization of the Si substrate in regions unprotected by an SiO[sub 2] layer, producing planar diodes. Mesa diodes were fabricated using the blanket growth of polycrystalline [beta]-SiC produced by the decomposition of methylsilane (CH[sub 3]SiH[sub 3]). The SiC/Si heterojunction diodes show good rectifying properties for both device structures. Reverse breakdown voltage of 50 V was obtained with the self-selective SiC/Si diode. The mesa diodes exhibited even higher breakdown voltages (V[sub br]) of 150 V and excellent ideality factors of 1.06 at 25 C. The high V[sub br] and good forward rectifying characteristics indicate that the SiC/Si heterojunction diode represents a promising approach for the fabrication of wide-gap emitter SiC/Si heterojunction bipolar transistors.

  13. Fabrication of ZnO Thin-Film Transistors by Chemical Vapor Deposition Method using Zinc Acetate Solution

    Science.gov (United States)

    Alias, Afishah; Hazawa, Kouta; Kawashima, Nobuaki; Fukuda, Hisashi; Uesugi, Katsuhiro

    2011-01-01

    Zinc oxide (ZnO) thin-film transistors (TFTs) were fabricated by thermal chemical vapor deposition (CVD) using aqueous solutions of zinc acetate (ZnAc2) dihydrate as a source. The precursor was supplied to the substrate by the nitrogen bubbling method through a plate with numerous orifices in the ZnAc2 solution. The ZnO thin films were grown on silicon substrates in the growth temperature (TG) range from 280 to 700 °C. The growth rate of ZnO thin films were linearly proportional to the growth temperature, which suggested that the growth rate is limited by the decomposition of ZnAc2. Depletion-mode TFTs with the ZnO film grown at TG = 350 °C was found to exhibit a relatively low saturation mobility (µsat). However, µsat increased from 1 to 14 cm2·V-1·s-1 and the operational mode was changed from the depletion mode to the enhancement mode by annealing treatment at 200 °C for 2 h under N2 ambient.

  14. Thermal recrystallization of physical vapor deposition based germanium thin films on bulk silicon (100)

    KAUST Repository

    Hussain, Aftab M.

    2013-08-16

    We demonstrate a simple, low-cost, and scalable process for obtaining uniform, smooth surfaced, high quality mono-crystalline germanium (100) thin films on silicon (100). The germanium thin films were deposited on a silicon substrate using plasma-assisted sputtering based physical vapor deposition. They were crystallized by annealing at various temperatures ranging from 700 °C to 1100 °C. We report that the best quality germanium thin films are obtained above the melting point of germanium (937 °C), thus offering a method for in-situ Czochralski process. We show well-behaved high-κ /metal gate metal-oxide-semiconductor capacitors (MOSCAPs) using this film. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. RF-plasma vapor deposition of siloxane on paper. Part 1: Physical evolution of paper surface

    Science.gov (United States)

    Sahin, Halil Turgut

    2013-01-01

    An alternative, new approach to improve the hydrophobicity and barrier properties of paper was evaluated by radio-frequency (RF) plasma octamethylcyclotetrasiloxane (OMCTSO) vapor treatment. The interaction between OMCTSO and paper, causing the increased hydophobicity, is likely through covalent bonding. The deposited thin silicone-like polymeric layer from OMCTSO plasma treatment possessed desirable hydrophobic properties. The SEM micrographs showed uniformly distributed grainy particles with various shapes on the paper surface. Deposition of the silicone polymer-like layer with the plasma treatment affects the distribution of voids in the network structure and increases the barrier against water intake and air. The water absorptivity was reduced by 44% for the OMCTSO plasma treated sheet. The highest resistance to air flow was an approximately 41% lower air permeability than virgin paper.

  16. Preparation of γ-Al2O3 films by laser chemical vapor deposition

    Science.gov (United States)

    Gao, Ming; Ito, Akihiko; Goto, Takashi

    2015-06-01

    γ- and α-Al2O3 films were prepared by chemical vapor deposition using CO2, Nd:YAG, and InGaAs lasers to investigate the effects of varying the laser wavelength and deposition conditions on the phase composition and microstructure. The CO2 laser was found to mostly produce α-Al2O3 films, whereas the Nd:YAG and InGaAs lasers produced γ-Al2O3 films when used at a high total pressure. γ-Al2O3 films had a cauliflower-like structure, while the α-Al2O3 films had a dense and columnar structure. Of the three lasers, it was the Nd:YAG laser that interacted most with intermediate gas species. This promoted γ-Al2O3 nucleation in the gas phase at high total pressure, which explains the cauliflower-like structure of nanoparticles observed.

  17. Plasma-Assisted Mist Chemical Vapor Deposition of Zinc Oxide Films Using Solution of Zinc Acetate

    Science.gov (United States)

    Takenaka, Kosuke; Okumura, Yusuke; Setsuhara, Yuichi

    2013-01-01

    Zinc oxide (ZnO) film deposition has been carried out by plasma-assisted mist chemical vapor deposition (CVD) using a solution of zinc acetate [Zn(CH3COO)2], and the effects of plasma exposure on film properties have been investigated in terms of RF power. With increasing RF power, the results of the X-ray diffraction (XRD) patterns of ZnO films with plasma exposure showed the existence of crystallized ZnO films with plasma exposure. Under this condition, the substrate temperature was as low as 200 °C for a plasma exposure time of 20 min. The surface morphology shown by scanning electron microscopy (SEM) images shows that the ZnO films were textured with round grains, which is attributed to the effect of the use of mist with the precursor.

  18. Phase Equilibrium of TiO2 Nanocrystals in Flame-Assisted Chemical Vapor Deposition.

    Science.gov (United States)

    Liu, Changran; Camacho, Joaquin; Wang, Hai

    2017-10-23

    Nano-scale titanium oxide (TiO2) is a material useful for a wide range of applications. In a previous study, we showed that TiO2 nanoparticles of both rutile and anatase crystal phases could be synthesized over the size range of 5 to 20 nm in flame-assisted chemical vapor deposition. While rutile was unexpectedly dominant in oxygen-lean synthesis conditions, anatase is the preferred phase in oxygen-rich gases. The observation is in contrast to the 14 nm rutile-anatase crossover size derived from the existing crystal-phase equilibrium model. In the present work, we made additional measurements over a wider range of synthesis conditions; the results confirm the earlier observations. We propose an improved model for the surface energy that considers the role of oxygen desorption at high temperatures. The model successfully explains the observations made in the current and previous work. The current results provide a useful path to designing flame-assisted chemical vapor deposition of TiO2 nanocrystals with controllable crystal phases. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Multifaceted and route-controlled "click" reactions based on vapor-deposited coatings.

    Science.gov (United States)

    Sun, Ting-Pi; Tai, Ching-Heng; Wu, Jyun-Ting; Wu, Chih-Yu; Liang, Wei-Chieh; Chen, Hsien-Yeh

    2016-02-01

    "Click" reactions provide precise and reliable chemical transformations for the preparation of functional architectures for biomaterials and biointerfaces. The emergence of a multiple-click reaction strategy has paved the way for a multifunctional microenvironment with orthogonality and precise multitasking that mimics nature. We demonstrate a multifaceted and route-controlled click interface using vapor-deposited functionalized poly-para-xylylenes. Distinctly clickable moieties of ethynyl and maleimide were introduced into poly-para-xylylenes in one step via a chemical vapor deposition (CVD) copolymerization process. The advanced interface coating allows for a double-click route with concurrent copper(i)-catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC) and the thiol-maleimide click reaction. Additionally, double-click reactions can also be performed in a cascade manner by controlling the initiation route to enable the CuAAC and/or thiol-yne reaction using a mono-functional alkyne-functionalized poly-para-xylylene. The use of multifaceted coatings to create straightforward and orthogonal interface properties with respect to protein adsorption and cell attachment is demonstrated and characterized.

  20. Vapor phase deposition of functional polymers onto paper-based microfluidic devices for advanced unit operations.

    Science.gov (United States)

    Kwong, Philip; Gupta, Malancha

    2012-11-20

    Paper-based microfluidic devices have recently received significant attention as a potential platform for low-cost diagnostic assays. However, the number of advanced unit operations, such as separation of analytes and fluid manipulation, that can be applied to these devices has been limited. Here, we use a vapor phase polymerization process to sequentially deposit functional polymer coatings onto paper-based microfluidic devices to integrate multiple advanced unit operations while retaining the fibrous morphology necessary to generate capillary-driven flow. A hybrid grafting process was used to apply hydrophilic polymer coatings with a high surface concentration of ionizable groups onto the surface of the paper fibers in order to passively separate analytes, which allowed a multicomponent mixture to be separated into its anionic and cationic components. Additionally, a UV-responsive polymer was sequentially deposited to act as a responsive switch to control the path of fluid within the devices. This work extends the advanced unit operations available for paper-based microfluidics and allows for more complex diagnostics. In addition, the vapor phase polymerization process is substrate independent, and therefore, these functional coatings can be applied to other textured materials such as membranes, filters, and fabrics.

  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. Synthesis of coaxial nanotubes of polyaniline and poly(hydroxyethyl methacrylate by oxidative/initiated chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Alper Balkan

    2017-04-01

    Full Text Available Vapor-phase synthesis techniques of polymeric nanostructures offer unique advantages over conventional, solution-based techniques because of their solventless nature. In this work, we report the fabrication of coaxial polymer nanotubes using two different chemical vapor deposition methods. The fabrication process involves the deposition of an outer layer of the conductive polyaniline (PANI by oxidative chemical vapor deposition, followed by the deposition of the inner layer of poly(2-hydroxyethyl methacrylate (pHEMA hydrogel by initiated chemical vapor deposition. The vapor-phase techniques allowed for fine-tuning of the thickness of the individual layers, keeping the functionalities of the polymers intact. The response of the single components and the coaxial nanotubes to changes in humidity was investigated for potential humidity sensor applications. For single-component conductive PANI nanotubes, the resistance changed parabolically with relative humidity because of competing effects of doping and swelling of the PANI polymer under humid conditions. Introducing a hydrogel inner layer increased the overall resistance, and enhanced swelling, which caused the resistance to continuously increase with relative humidity.

  3. Synthesis of coaxial nanotubes of polyaniline and poly(hydroxyethyl methacrylate) by oxidative/initiated chemical vapor deposition.

    Science.gov (United States)

    Balkan, Alper; Armagan, Efe; Ozaydin Ince, Gozde

    2017-01-01

    Vapor-phase synthesis techniques of polymeric nanostructures offer unique advantages over conventional, solution-based techniques because of their solventless nature. In this work, we report the fabrication of coaxial polymer nanotubes using two different chemical vapor deposition methods. The fabrication process involves the deposition of an outer layer of the conductive polyaniline (PANI) by oxidative chemical vapor deposition, followed by the deposition of the inner layer of poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel by initiated chemical vapor deposition. The vapor-phase techniques allowed for fine-tuning of the thickness of the individual layers, keeping the functionalities of the polymers intact. The response of the single components and the coaxial nanotubes to changes in humidity was investigated for potential humidity sensor applications. For single-component conductive PANI nanotubes, the resistance changed parabolically with relative humidity because of competing effects of doping and swelling of the PANI polymer under humid conditions. Introducing a hydrogel inner layer increased the overall resistance, and enhanced swelling, which caused the resistance to continuously increase with relative humidity.

  4. Control of the nucleation and quality of graphene grown by low-pressure chemical vapor deposition with acetylene

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Meng, E-mail: youmou@rift.mech.tohoku.ac.jp [Department of Nanomechanics, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Sasaki, Shinichirou [Department of Nanomechanics, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Suzuki, Ken; Miura, Hideo [Fracture and Reliability Research Institute, Tohoku University, Sendai 980-8579 (Japan)

    2016-03-15

    Graphical abstract: - Highlights: • For the first time, we succeeded in the LPCVD growth of monolayer graphene using acetylene as the precursor gas. • The growth rate is very high when acetylene is used as the source gas. Our process has exhibited the potential to shorten the growth time of CVD graphene. • We found that the domain size, defects density, layer number and the sheet resistance of graphene can be changed by changing the acetylene flow rates. • We found that it is also possible to form bilayer graphene using acetylene. However, further study are necessary to reduce the defects density. - Abstract: Although many studies have reported the chemical vapor deposition (CVD) growth of large-area monolayer graphene from methane, synthesis of graphene using acetylene as the source gas has not been fully explored. In this study, the low-pressure CVD (LPCVD) growth of graphene from acetylene was systematically investigated. We succeeded in regulating the domain size, defects density, layer number and the sheet resistance of graphene by changing the acetylene flow rates. Scanning electron microscopy and Raman spectroscopy were employed to confirm the layer number, uniformity and quality of the graphene films. It is found that a low flow rate of acetylene (0.28 sccm) is required to form high-quality monolayer graphene in our system. On the other hand, the high acetylene flow rate (7 sccm) will induce the growth of the bilayer graphene domains with high defects density. On the basis of selected area electron diffraction (SAED) pattern, the as-grown monolayer graphene domains were analyzed to be polycrystal. We also discussed the relation between the sheet resistacne and defects density in graphene. Our results provide great insights into the understanding of the CVD growth of monolayer and bilayer graphene from acetylene.

  5. Electrical characteristics and hydrogen concentration of chemical vapor deposited silicon dioxide films: Effect of water treatment

    Science.gov (United States)

    Li, S. C.; Murarka, S. P.

    1992-11-01

    The effect of exposing chemical vapor deposited silicon dioxide directly to water has been investigated. Unlike the effect of the water-related traps in thermally grown silicon dioxide, the capacitance-voltage (C-V) shift due to diffused-in water molecules is directly observed without using the method of avalanche injection. The resonate nuclear reaction technique with 15N ion beam has been used to measure the hydrogen concentration of water-boiled, as-deposited, and rapid thermal-annealed silicon dioxide films. These depth profiles show that the hydrogen-containing species, that are most likely water molecules, diffuse in and out and redistribute in the as-deposited and rapid thermal-annealed films. These hydrogen depth profiles also indicate that the amount of diffused-in water molecules in the oxide is limited by the solubility of the water in the oxide. The solubility of water in the oxide annealed at high temperatures is found to be significantly lower than that in the as-deposited oxide. It is found that diffused-in water molecules, in order to satisfy the water solubility of the oxide, play a compensating role in controlling the oxide charges. Water molecules would continue to diffuse in, and interact with oxide charges and produce charges with reverse polarity that compensate the existing oxide charges until water solubility is satisfied.

  6. Axial heterostructure of Au-catalyzed InGaAs/GaAs nanowires grown by metal-organic chemical vapor deposition

    Science.gov (United States)

    Yuan, Huibo; Li, Lin; Li, Zaijin; Wang, Yong; Qu, Yi; Ma, Xiaohui; Liu, Guojun

    2018-01-01

    Nanowires (NWs) of GaAs and InGaAs/GaAs axial heterostructure are fabricated by metal-organic chemical vapor deposition (MOCVD) following the vapor-liquid-solid (VLS) mechanism. Thin film of Au is coated to generate catalytic droplets and the impact of film thickness on distribution of catalytic droplets is studied. With growth temperature varying, different geometries of GaAs NWs are observed and an assumption has been proposed to explain the phenomenon. InGaAs/GaAs NWs with axial heterostructures are synthesized. Most of InGaAs/GaAs NWs are perpendicular to substrates with cylindrical morphology and distinct heterostructure interface. Energy Dispersive X-ray Spectroscopy (EDX) line-scan's been applied to investigate the concentration changes of nanowires, indicating pure axial heterostructures without radial growth.

  7. InP by Planar Reactive Deposition and GaAs by Low Pressure Metal Organic Chemical Vapor Deposition.

    Science.gov (United States)

    1981-02-01

    used. This is not As 3 I ;. . :-- . .... ......... " -~~- -- -- . . . . .. 10071-3 5Om 4’ * ~POSITION 4’ F i gure 17. SEI itigi’ view of GaiAs ~ f ilm...Deposition," presented at the Third Conference on Crystal Growth, 12-13 January 1978, U.S. Naval Postgraduate School , Monterey, CA. K. Zatnio, L. Fraas, F

  8. Flux growth in a horizontal configuration: An analog to vapor transport growth

    Science.gov (United States)

    Yan, J.-Q.; Sales, B. C.; Susner, M. A.; McGuire, M. A.

    2017-07-01

    Flux growth of single crystals is normally performed in a vertical configuration with an upright refractory container holding the flux melt. At high temperatures, flux dissolves the charge, forming a homogeneous solution before nucleation and growth of crystals takes place under proper supersaturation generated by cooling or evaporating the flux. In this work, we report flux growth in a horizontal configuration with a temperature gradient along the horizontal axis: a liquid transport growth analogous to the vapor transport technique. In a typical liquid transport growth, the charge is kept at the hot end of the refractory container and the flux melt dissolves the charge and transfers it to the cold end. Once the concentration of charge is above the solubility limit at the cold end, the thermodynamically stable phase nucleates and grows. Compared to the vertical flux growth, the liquid transport growth can provide a large quantity of crystals in a single growth since the charge/flux ratio is not limited by the solubility limit at the growth temperature. This technique is complementary to the vertical flux growth and can be considered when a large amount of crystals is needed but the yield from the conventional vertical flux growth is limited. We applied this technique to the growth of IrSb3, Mo3Sb7 , and MnBi from self-flux, and the growth of FeSe, CrTe3, NiPSe3, FePSe3, CuInP2S6 , RuCl3, and OsCl4 from a halide flux.

  9. Magmatic-vapor expansion and the formation of high-sulfidation gold deposits: Chemical controls on alteration and mineralization

    Science.gov (United States)

    Henley, R.W.; Berger, B.R.

    2011-01-01

    Large bulk-tonnage high-sulfidation gold deposits, such as Yanacocha, Peru, are the surface expression of structurally-controlled lode gold deposits, such as El Indio, Chile. Both formed in active andesite-dacite volcanic terranes. Fluid inclusion, stable isotope and geologic data show that lode deposits formed within 1500. m of the paleo-surface as a consequence of the expansion of low-salinity, low-density magmatic vapor with very limited, if any, groundwater mixing. They are characterized by an initial 'Sulfate' Stage of advanced argillic wallrock alteration ?? alunite commonly with intense silicification followed by a 'Sulfide' Stage - a succession of discrete sulfide-sulfosalt veins that may be ore grade in gold and silver. Fluid inclusions in quartz formed during wallrock alteration have homogenization temperatures between 100 and over 500 ??C and preserve a record of a vapor-rich environment. Recent data for El Indio and similar deposits show that at the commencement of the Sulfide Stage, 'condensation' of Cu-As-S sulfosalt melts with trace concentrations of Sb, Te, Bi, Ag and Au occurred at > 600 ??C following pyrite deposition. Euhedral quartz crystals were simultaneously deposited from the vapor phase during crystallization of the vapor-saturated melt occurs to Fe-tennantite with progressive non-equilibrium fractionation of heavy metals between melt-vapor and solid. Vugs containing a range of sulfides, sulfosalts and gold record the changing composition of the vapor. Published fluid inclusion and mineralogical data are reviewed in the context of geological relationships to establish boundary conditions through which to trace the expansion of magmatic vapor from source to surface and consequent alteration and mineralization. Initially heat loss from the vapor is high resulting in the formation of acid condensate permeating through the wallrock. This Sulfate Stage alteration effectively isolates the expansion of magmatic vapor in subsurface fracture arrays

  10. Imposed layer by layer growth by pulsed laser interval deposition

    NARCIS (Netherlands)

    Koster, Gertjan; Rijnders, Augustinus J.H.M.; Blank, David H.A.; Rogalla, Horst

    1999-01-01

    Pulsed laser deposition has become an important technique to fabricate novel materials. Although there is the general impression that, due to the pulsed deposition, the growth mechanism differs partially from continuous physical and chemical deposition techniques, it has hardly been used. Here, we

  11. Role of kinetic factors in chemical vapor deposition synthesis of uniform large area graphene using copper catalyst.

    Science.gov (United States)

    Bhaviripudi, Sreekar; Jia, Xiaoting; Dresselhaus, Mildred S; Kong, Jing

    2010-10-13

    In this article, the role of kinetics, in particular, the pressure of the reaction chamber in the chemical vapor deposition (CVD) synthesis of graphene using low carbon solid solubility catalysts (Cu), on both the large area thickness uniformity and the defect density are presented. Although the thermodynamics of the synthesis system remains the same, based on whether the process is performed at atmospheric pressure (AP), low pressure (LP) (0.1-1 Torr) or under ultrahigh vacuum (UHV) conditions, the kinetics of the growth phenomenon are different, leading to a variation in the uniformity of the resulting graphene growth over large areas (wafer scale). The kinetic models for APCVD and LPCVD are discussed, thereby providing insight for understanding the differences between APCVD vs LPCVD/UHVCVD graphene syntheses. Interestingly, graphene syntheses using a Cu catalyst in APCVD processes at higher methane concentrations revealed that the growth is not self-limiting, which is in contrast to previous observations for the LPCVD case. Additionally, nanoribbons and nanostrips with widths ranging from 20 to 100 nm were also observed on the APCVD grown graphene. Interactions between graphene nanofeatures (edges, folds) and the contaminant metal nanoparticles from the Cu etchant were observed, suggesting that these samples could potentially be employed to investigate the chemical reactivity of single molecules, DNA, and nanoparticles with monolayer graphene.

  12. Defect structure of metal-organic chemical vapor deposition-grown epitaxial (0001) GaN/Al2O3

    Science.gov (United States)

    Wu, X. H.; Brown, L. M.; Kapolnek, D.; Keller, S.; Keller, B.; DenBaars, S. P.; Speck, J. S.

    1996-09-01

    Defect structures were investigated by transmission electron microscopy for GaN/Al2O3 (0001) epilayers grown by metal-organic chemical vapor deposition using a two-step process. The defect structures, including threading dislocations, partial dislocation bounding stacking faults, and inversion domains, were analyzed by diffraction contrast, high-resolution imaging, and convergent beam diffraction. GaN film growth was initiated at 600 °C with a nominal 20 nm nucleation layer. This was followed by high-temperature growth at 1080 °C. The near-interfacial region of the films consists of a mixture of cubic and hexagonal GaN, which is characterized by a high density of stacking faults bounded by Shockley and Frank partial dislocations. The near-interfacial region shows a high density of inversion domains. Above ˜0.5 μm thickness, the film consists of isolated threading dislocations of either pure edge, mixed, or pure screw character with a total density of ˜7×108 cm-2. The threading dislocation reduction in these films is associated with cubic to hexagonal transformation of the nucleation layer region during high temperature growth.

  13. Chemical vapor deposition of refractory ternary nitrides for advanced diffusion barriers

    Energy Technology Data Exchange (ETDEWEB)

    Custer, Jonathan S.; Fleming, James G.; Roherty-Osmun, Elizabeth; Smith, Paul Martin

    1998-09-22

    Refractory ternary nitride films for diffusion barriers in microelectronics have been grown using chemical vapor deposition. Thin films of titanium-silicon-nitride, tungsten-boron-nitride, and tungsten-silicon-nitride of various compositions have been deposited on 150 mm Si wafers. The microstructure of the films are either fully amorphous for the tungsten based films, or nauocrystalline TiN in an amorphous matrix for titanium-silicon-nitride. All films exhibit step coverages suitable for use in future microelectronics generations. Selected films have been tested as diffusion barriers between copper and silicon, and generally perform extremely weH. These fiIms are promising candidates for advanced diffusion barriers for microelectronics applications. The manufacturing of silicon wafers into integrated circuits uses many different process and materials. The manufacturing process is usually divided into two parts: the front end of line (FEOL) and the back end of line (BEOL). In the FEOL the individual transistors that are the heart of an integrated circuit are made on the silicon wafer. The responsibility of the BEOL is to wire all the transistors together to make a complete circuit. The transistors are fabricated in the silicon itself. The wiring is made out of metal, currently aluminum and tungsten, insulated by silicon dioxide, see Figure 1. Unfortunately, silicon will diffuse into aluminum, causing aluminum spiking of junctions, killing transistors. Similarly, during chemical vapor deposition (CVD) of tungsten from ~fj, the reactivity of the fluorine can cause "worn-holes" in the silicon, also destroying transistors. The solution to these problems is a so-called diffusion barrier, which will allow current to pass from the transistors to the wiring, but will prevent reactions between silicon and the metal.

  14. Physical vapor deposition of CdTe thin films at low temperature for solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Heisler, Christoph; Brueckner, Michael; Lind, Felix; Kraft, Christian; Reisloehner, Udo; Ronning, Carsten; Wesch, Werner [Institute of Solid State Physics, University of Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

    2012-07-01

    Cadmium telluride is successfully utilized as an absorber material for thin film solar cells. Industrial production makes use of high substrate temperatures for the deposition of CdTe absorber layers. However, in order to exploit flexible substrates and to simplify the manufacturing process, lower deposition temperatures are beneficial. Based on the phase diagram of CdTe, predictions on the stoichiometry of CdTe thin films grown at low substrate temperatures are made in this work. These predictions were verified experimentally using additional sources of Cd and Te during the deposition of the CdTe thin films at different substrate temperatures. The deposited layers were analyzed with energy-dispersive X-ray spectroscopy. In case of CdTe layers which were deposited at substrate temperatures lower than 200 C without usage of additional sources we found a non-stoichiometric growth of the CdTe layers. The application of the additional sources leads to a stoichiometric growth for substrate temperatures down to 100 C which is a significant reduction of the substrate temperature during deposition.

  15. Growth of Wide Band Gap II-VI Compound Semiconductors by Physical Vapor Transport

    Science.gov (United States)

    Su, Ching-Hua; Sha, Yi-Gao

    1995-01-01

    The studies on the crystal growth and characterization of II-VI wide band gap compound semiconductors, such as ZnTe, CdS, ZnSe and ZnS, have been conducted over the past three decades. The research was not quite as extensive as that on Si, III-V, or even narrow band gap II-VI semiconductors because of the high melting temperatures as well as the specialized applications associated with these wide band gap semiconductors. In the past several years, major advances in the thin film technology such as Molecular Beam Epitaxy (MBE) and Metal Organic Chemical Vapor Deposition (MOCVD) have demonstrated the applications of these materials for the important devices such as light-emitting diode, laser and ultraviolet detectors and the tunability of energy band gap by employing ternary or even quaternary systems of these compounds. At the same time, the development in the crystal growth of bulk materials has not advanced far enough to provide low price, high quality substrates needed for the thin film growth technology.

  16. Hot wire chemical vapor deposition chemistry in the gas phase and on the catalyst surface with organosilicon compounds.

    Science.gov (United States)

    Shi, Yujun

    2015-02-17

    CONSPECTUS: Hot wire chemical vapor deposition (HWCVD), also referred to as catalytic CVD (Cat-CVD), has been used to produce Si-containing thin films, nanomaterials, and functional polymer coatings that have found wide applications in microelectronic and photovoltaic devices, in automobiles, and in biotechnology. The success of HWCVD is largely due to its various advantages, including high deposition rate, low substrate temperatures, lack of plasma-induced damage, and large-area uniformity. Film growth in HWCVD is induced by reactive species generated from primary decomposition on the metal wire or from secondary reactions in the gas phase. In order to achieve a rational and efficient optimization of the process, it is essential to identify the reactive species and to understand the chemical kinetics that govern the production of these precursor species for film growth. In this Account, we report recent progress in unraveling the complex gas-phase reaction chemistry in the HWCVD growth of silicon carbide thin films using organosilicon compounds as single-source precursors. We have demonstrated that laser ionization mass spectrometry is a powerful diagnostic tool for studying the gas-phase reaction chemistry when combined with the methods of isotope labeling and chemical trapping. The four methyl-substituted silane molecules, belonging to open-chain alkylsilanes, dissociatively adsorb on W and Ta filaments to produce methyl radical and H2 molecule. Under the typical deposition pressures, with increasing number of methyl substitution, the dominant chemistry occurring in the gas phase switches from silylene/silene reactions to free-radical short chain reactions. This change in dominant reaction intermediates from silylene/silene to methyl radicals explains the observation from thin film deposition that silicon carbide films become more C-rich with a decreasing number of Si-H bonds in the four precursor molecules. In the case of cyclic monosilacyclobutanes, we have

  17. Deposition Velocity of Iodine Vapor (I{sub 2}) for Radish Plants and Its Root-Translocation Factor: Results of Experimental Exposures

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Yong Ho; Lim, Kwang Muk; Park, Doo Won; Keum, Dong Kwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-06-15

    In order to measure the deposition velocity of I{sub 2} vapor for radish plants and its translocation factor for their roots, radish plants were exposed to I{sub 2} vapor for 80 min. at different growth stages between 29 and 53 d after sowing. The exposure was performed in a transparent chamber during the morning time. Deposition velocities () were on the whole in the range of 1.0 X 10{sup 4} - 2.0 X 10{sup 4} showing an increasing tendency with an increase in the biomass density. The results showed some agreement with existing reports that a higher relative humidity would lead to a higher deposition velocity. The acquired deposition velocities were lower than by factors of several tens than some field measurements probably due to a very low wind speed (about 0.2 ms{sup -1} ) in the chamber. Translocation factors (ratio of the total iodine in the roots at harvest to the total plant deposition), estimated in a more or less conservative way, were 1.3 X 10{sup -3} for an exposure at 29 d after sowing and 5.0 X 10{sup -3} for an exposure at 53 d after sowing. In using the present experimental data, meteorological conditions and chemical and physical forms of iodine need to be carefully considered.

  18. Criteria for significance of simultaneous presence of both condensible vapors and aerosol particles on mass transfer (deposition) rates

    Science.gov (United States)

    Gokoglu, S. A.

    1987-01-01

    The simultaneous presence of aerosol particles and condensible vapors in a saturated boundary layer which may affect deposition rates to subcooled surfaces because of vapor-particle interactions is discussed. Scavenging of condensible vapors by aerosol particles may lead to increased particle size and decreased vapor mass fraction, which alters both vapor and particle deposition rates. Particles, if sufficiently concentrated, may also coagulate. Criteria are provided to assess the significance of such phenomena when particles are already present in the mainstream and are not created inside the boundary layer via homogeneous nucleation. It is determined that there is direct proportionality with: (1) the mass concentration of both condensible vapors and aerosol particles; and (2) the square of the boundary layer thickness to particle diameter ratio (delta d sub p) square. Inverse proportionality was found for mainstream to surface temperature difference if thermophoresis dominates particle transport. It is concluded that the square of the boundary layer thickness to particle diameter ratio is the most critical factor to consider in deciding when to neglect vapor-particle interactions.

  19. Thermal conductivity of amorphous and nanocrystalline silicon films prepared by hot-wire chemical-vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Jugdersuren, B.; Kearney, B. T.; Queen, D. R.; Metcalf, T. H.; Culbertson, J. C.; Chervin, C. N.; Stroud, R. M.; Nemeth, W.; Wang, Q.; Liu, Xiao

    2017-07-01

    We report 3..omega.. thermal conductivity measurements of amorphous and nanocrystalline silicon thin films from 85 to 300 K prepared by hot-wire chemical-vapor deposition, where the crystallinity of the films is controlled by the hydrogen dilution during growth. The thermal conductivity of the amorphous silicon film is in agreement with several previous reports of amorphous silicon prepared by a variety of deposition techniques. The thermal conductivity of the as-grown nanocrystalline silicon film is 70% higher and increases 35% more after an anneal at 600 degrees C. They all have similarly weak temperature dependence. Structural analysis shows that the as-grown nanocrystalline silicon is approximately 60% crystalline, nanograins and grain boundaries included. The nanograins, averaging 9.1 nm in diameter in the as-grown film, are embedded in an amorphous matrix. The grain size increases to 9.7 nm upon annealing, accompanied by the disappearance of the amorphous phase. We extend the models of grain boundary scattering of phonons with two different non-Debye dispersion relations to explain our result of nanocrystalline silicon, confirming the strong grain size dependence of heat transport for nanocrystalline materials. However, the similarity in thermal conductivity between amorphous and nanocrystalline silicon suggests the heat transport mechanisms in both structures may not be as dissimilar as we currently understand.

  20. Cobalt(I) Olefin Complexes: Precursors for Metal-Organic Chemical Vapor Deposition of High Purity Cobalt Metal Thin Films.

    Science.gov (United States)

    Hamilton, Jeff A; Pugh, Thomas; Johnson, Andrew L; Kingsley, Andrew J; Richards, Stephen P

    2016-07-18

    We report the synthesis and characterization of a family of organometallic cobalt(I) metal precursors based around cyclopentadienyl and diene ligands. The molecular structures of the complexes cyclopentadienyl-cobalt(I) diolefin complexes are described, as determined by single-crystal X-ray diffraction analysis. Thermogravimetric analysis and thermal stability studies of the complexes highlighted the isoprene, dimethyl butadiene, and cyclohexadiene derivatives [(C5H5)Co(η(4)-CH2CHC(Me)CH2)] (1), [(C5H5)Co(η(4)-CH2C(Me)C(Me)CH2)] (2), and [(C5H5)Co(η(4)-C6H8)] (4) as possible cobalt metal organic chemical vapor deposition (MOCVD) precursors. Atmospheric pressure MOCVD was employed using precursor 1, to synthesize thin films of metallic cobalt on silicon substrates under an atmosphere (760 torr) of hydrogen (H2). Analysis of the thin films deposited at substrate temperatures of 325, 350, 375, and 400 °C, respectively, by scanning electron microscopy and atomic force microscopy reveal temperature-dependent growth features. Films grown at these temperatures are continuous, pinhole-free, and can be seen to be composed of hexagonal particles clearly visible in the electron micrograph. Powder X-ray diffraction and X-ray photoelectron spectroscopy all show the films to be highly crystalline, high-purity metallic cobalt. Raman spectroscopy was unable to detect the presence of cobalt silicides at the substrate/thin film interface.

  1. Rapid assessment of mid-infrared refractive index anisotropy using a prism coupler: chemical vapor deposited ZnS.

    Science.gov (United States)

    Qiao, H A; Lipschultz, Kristen A; Anheier, N C; McCloy, J S

    2012-05-01

    A state-of-the-art mid-infrared prism coupler was used to study suspected anisotropy in the refractive index of forward-looking-infrared grade chemical vapor deposited (CVD) zinc sulfide. Samples were prepared with columnar grain structure in and perpendicular to the sample plane, as well as from different depths in the CVD growth body. This study was motivated by the growing industry concern among optical design engineers, as well as developers of mid-infrared systems, over the reliability of historically accepted index data. Prior photoluminescence and x-ray diffraction measurements have suggested that refractive index may vary according to sample orientation with respect to the grain structure. Measurements were conducted to provide optical dispersion and thermal index (dn/dT) data at discrete laser wavelengths between 0.633 and 10.591 μm at two temperature set points (30 °C and 90 °C). Refractive index measurements between samples exhibited an average standard deviation comparable to the uncertainty of the prism coupler measurement (0.0004 refractive index units), suggesting that the variation in refractive index as a function of sample orientation and CVD deposition time is negligible and should have no impact on subsequent optical designs. Measured dispersion data at mid-infrared wavelengths were also found to agree well with prior published measurements.

  2. Structural, optical and electrical study of undoped GaN layers obtained by metalorganic chemical vapor deposition on sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Rangel-Kuoppa, Victor-Tapio, E-mail: tapio.rangel@gmail.co [Institute of Semiconductor and Solid State Physics, Johannes Kepler Universitaet, A-4040 Linz (Austria); Aguilar, Cesia Guarneros [Seccion de Electronica del Estado Solido, Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, A.P. 14740, C.P. 07360, Mexico, Distrito Federal (Mexico); Sanchez-Resendiz, Victor, E-mail: victors@sees.cinvestav.m [Seccion de Electronica del Estado Solido, Departamento de Ingenieria Electrica, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional, A.P. 14740, C.P. 07360, Mexico, Distrito Federal (Mexico)

    2011-01-31

    We investigate optical, structural and electrical properties of undoped GaN grown on sapphire. The layers were prepared in a horizontal reactor by low pressure metal organic chemical vapor deposition at temperatures of 900 {sup o}C and 950 {sup o}C on a low temperature grown (520 {sup o}C) GaN buffer layer on (0001) sapphire substrate. The growth pressure was kept at 10,132 Pa. The photoluminescence study of such layers revealed a band-to-band emission around 366 nm and a yellow band around 550 nm. The yellow band intensity decreases with increasing deposition temperature. X-ray diffraction, atomic force microscopy and scanning electron microscopy studies show the formation of hexagonal GaN layers with a thickness of around 1 {mu}m. The electrical study was performed using temperature dependent Hall measurements between 35 and 373 K. Two activation energies are obtained from the temperature dependent conductivity, one smaller than 1 meV and the other one around 20 meV. For the samples grown at 900 {sup o}C the mobilities are constant around 10 and 20 cm{sup 2} V{sup -1} s{sup -1}, while for the sample grown at 950 {sup o}C the mobility shows a thermally activated behavior with an activation energy of 2.15 meV.

  3. Deposition of vaporized species onto glassy fallout from a near-surface nuclear test

    Science.gov (United States)

    Weisz, David G.; Jacobsen, Benjamin; Marks, Naomi E.; Knight, Kim B.; Isselhardt, Brett H.; Matzel, Jennifer E.; Weber, Peter K.; Prussin, Stan G.; Hutcheon, Ian D.

    2017-03-01

    In a near-surface nuclear explosion where the resultant fireball can interact with the surface, vaporized materials from the nuclear device can be incorporated into molten soil and other carrier materials from that surface. This mixed material becomes a source of glassy fallout upon quenching and is locally deposited. Fallout formation models have been proposed; however, the specific mechanisms and physical conditions by which soil and other carrier materials interact in the fireball, as well as the subsequent incorporation of device materials with carrier materials, are not well constrained. We observe a surface deposition layer preserved at interfaces where two aerodynamic fallout glasses agglomerated and fused, and characterized 11 such boundaries using spatial analyses to better understand the vaporization and condensation behavior of species in the fireball. Using nanoscale secondary ion mass spectrometry (NanoSIMS), we identify higher enrichments of uranium from the device (235U/238U ratio >7.5) in 8 of the interface layers. Major element analysis of the interfaces reveals the deposition layer to be enriched in Fe, Ca, Mg, Mn, and Na-bearing species and depleted in Ti and Al-bearing species. Most notably, the Fe and Ca-bearing species are enriched approximately 50% at the interface layer relative to the average concentrations measured within the fallout glasses, while Ti and Al-bearing species are depleted by approximately 20%. SiO2 is found to be relatively invariable across the samples and interfaces (∼3% standard deviation). The notable depletion of Al, a refractory oxide abundant in the soil, together with the enrichment of 235U and Fe, suggests an anthropogenic source of the enriched species or an unexpected vaporization/condensation behavior. The presence of both refractory (e.g., Ca and U) and volatile (e.g., Na) species approximately co-located in most of the observed layers (within 1.5 μm) suggests a continuous condensation process may also be

  4. Laser-induced chemical vapor deposition of nanostructured silicon carbonitride thin films

    Science.gov (United States)

    Besling, W. F. A.; Goossens, A.; Meester, B.; Schoonman, J.

    1998-01-01

    Laser-induced chemical vapor deposition of silicon carbonitride thin films has been investigated using a continuous wave CO2 laser in parallel configuration with the substrate. The reactant gases in this process, hexamethyl disilazane and ammonia, are rapidly heated by CO2 laser radiation due to their absorption of the laser energy. Polymerlike silicon carbonitride films or agglomerated nanosized particles are formed depending on process conditions. Dense, smooth films or nanostructured deposits have been synthesized at low substrate temperatures (Tssilicon and can be obtained with controlled microstructures. Surface morphology, composition, and type of chemical bonding have been studied with electron microscopy and spectroscopic analysis and are correlated to the most important laser process parameters. X-ray photoelectron spectroscopy and reflectance Fourier transform infrared spectroscopy show that the deposits consist of Si-N, Si-C, and Si-O bonds, linked together in a x-ray amorphous, polymerlike structure. The nitrogen content is about 40% and can be varied by adding ammonia to the reactant gas flow. The layers are readily contaminated with oxygen after exposure to air, caused by hydrolysis and/or oxidation.

  5. Plasma-Assisted Mist Chemical Vapor Deposition of Zinc Oxide Films for Flexible Electronics

    Science.gov (United States)

    Takenaka, Kosuke; Uchida, Giichiro; Setsuhara, Yuichi

    2015-09-01

    Plasma-assisted mist chemical vapor deposition of ZnO films was performed for transparent conductive oxide formation of flexible electronics. In this study, ZnO films deposition using atmospheric-pressure He plasma generated by a micro-hollow cathode-type plasma source has been demonstrated. To obtain detail information according to generation of species in the plasma, the optical emission spectra of the atmospheric pressure He plasma with and without mist were measured. The result without mist shows considerable emissions of He lines, emissions attributed to the excitation and dissociation of air including N2 and O2 (N, O, and NO radials, and N2 molecule; N2 second positive band and first positive band), while the results with mist showed strong emissions attributed to the dissociation of H2O (OH and H radicals). The deposition of ZnO films was performed using atmospheric-pressure He plasma. The XRD patterns showed no crystallization of the ZnO films irradiated with pure He. On the other hand, the ZnO film crystallized with the irradiation with He/O2 mixture plasma. These results indicate that the atmospheric-pressure He/O2 mixture plasma has sufficient reactivity necessary for the crystallization of ZnO films at room temperature. This work was supported partly by The Grant-in-Aid for Scientific Research (KAKENHI) (Grant-in-Aid for Scientific Research(C)) from the Japan Society for the Promotion of Science (JSPS).

  6. Self-Catalyzed Growth of Vertically Aligned InN Nanorods by Metal-Organic Vapor Phase Epitaxy.

    Science.gov (United States)

    Tessarek, C; Fladischer, S; Dieker, C; Sarau, G; Hoffmann, B; Bashouti, M; Göbelt, M; Heilmann, M; Latzel, M; Butzen, E; Figge, S; Gust, A; Höflich, K; Feichtner, T; Büchele, M; Schwarzburg, K; Spiecker, E; Christiansen, S

    2016-06-08

    Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal-organic vapor phase epitaxy without any foreign catalyst. The In droplets on top of the nanorods indicate a self-catalytic vapor-liquid-solid growth mode. A systematic study on important growth parameters has been carried out for the optimization of nanorod morphology. The nanorod N-polarity, induced by high temperature nitridation of the sapphire substrate, is necessary to achieve vertical growth. Hydrogen, usually inapplicable during InN growth due to formation of metallic indium, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the sapphire surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temperature is similar. Transmission electron microscopy, spatially resolved energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been performed to analyze the structural properties. Spatially resolved cathodoluminescence investigations are carried out to verify the optical activity of the InN nanorods. The InN nanorods are expected to be the material of choice for high-efficiency hot carrier solar cells.

  7. CATALYTIC EFFECTS OF FERROCENE ON BONDING, OPTICAL AND STRUCTURAL PROPERTIES OF DIAMOND-LIKE CARBON FILMS DEPOSITED BY MICROWAVE SURFACE-WAVE PLASMA CHEMICAL VAPOR DEPOSITION

    OpenAIRE

    SUDIP ADHIKARI; SUNIL ADHIKARY; HIDEO UCHIDA; MASAYOSHI UMENO

    2006-01-01

    This paper reports catalytic effects of ferrocene on bonding, optical and structural properties of diamond-like carbon (DLC) thin films grown on silicon and quartz substrates by microwave surface-wave plasma chemical vapor deposition. For film deposition, helium and methane gases were used as plasma source. Bonding, optical and structural properties of the DLC films were measured both with and without using ferrocene as a catalyst. The ferrocene content in the DLC was confirmed by X-ray spect...

  8. Dzyaloshinskii-Moriya interaction in Pt/Co/Pt films prepared by chemical vapor deposition with various substrate temperatures

    Directory of Open Access Journals (Sweden)

    M. Quinsat

    2017-05-01

    Full Text Available We deposited perpendicularly magnetized Co(∼1nm/Pt(6nm bilayers by thermal chemical vapor deposition (CVD on top of 3nm thick Pt layer using various deposition temperature. Observed Ms increased with the increase of deposition temperature Ts, and reached the value of pure-Co at Ts = 500°C. We measured a (left-handed negative Dzyaloshinskii-Moriya interaction in CVD films indicating a dominant role of the bottom Pt/Co interface.

  9. 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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. 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

    2016-06-07

    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.

  11. Initiated chemical vapor deposition of thermoresponsive poly(N-vinylcaprolactam) thin films for cell sheet engineering.

    Science.gov (United States)

    Lee, Bora; Jiao, Alex; Yu, Seungjung; You, Jae Bem; Kim, Deok-Ho; Im, Sung Gap

    2013-08-01

    Poly(N-vinylcaprolactam) (PNVCL) is a thermoresponsive polymer known to be nontoxic, water soluble and biocompatible. Here, PNVCL homopolymer was successfully synthesized for the first time by use of a one-step vapor-phase process, termed initiated chemical vapor deposition (iCVD). Fourier transform infrared spectroscopy results showed that radical polymerization took place from N-vinylcaprolactam monomers without damaging the functional caprolactam ring. A sharp lower critical solution temperature transition was observed at 31°C from the iCVD poly(N-vinylcaprolactam) (PNVCL) film. The thermoresponsive PNVCL surface exhibited a hydrophilic/hydrophobic alteration with external temperature change, which enabled the thermally modulated attachment and detachment of cells. The conformal coverage of PNVCL film on various substrates with complex topography, including fabrics and nanopatterns, was successfully demonstrated, which can further be utilized to fabricate cell sheets with aligned cell morphology. The advantage of this system is that cells cultured on such thermoresponsive surfaces could be recovered as an intact cell sheet by simply lowering the temperature, eliminating the need for conventional enzymatic treatments. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

    Fuchs, B.A.; Brown, N.J.

    1987-01-01

    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.

  13. Current Issues and Problems in the Chemical Vapor Deposition of Diamond

    Science.gov (United States)

    Yarbrough, Walter A.; Messier, Russell

    1990-02-01

    Current issues and problems in the chemical vapor deposition (CVD) of diamond are those which relate to its characterization, its nucleation on foreign surfaces, the question of its formation in preference to the other phases of solid carbon (for example, graphite, chaoite, or lonsdaleite), why different morphologies and crystallographic orientations (textures) are seen in different experiments or with different parameters in the same experiment, and finally whether well-crystallized metastable phases can be obtained by CVD in other material systems or are only a peculiarity of carbon chemistry. Whether a given carbon coating is justly described as diamond has been such an issue, and coatings should clearly show evidence for diamond by x-ray diffraction and Raman spectroscopy before the claim of diamond is made. Experimental results have not been consistent in many cases, and much work remains to be done before an accurate assessment can be made of the technological impact of the development.

  14. Graphene-laminated architectures obtained by chemical vapor deposition: From graphene to graphite

    Science.gov (United States)

    Kitayama, Hiroki; Shimizu, Kengo; Ohba, Tomonori

    2017-11-01

    Graphene and graphite are of great interest in materials science. Using chemical vapor deposition at various CH4:H2 ratios, we synthesized materials with graphene-laminated architectures, ranging from graphene to graphite. A lower proportion of CH4 and lower synthesis temperature produced fewer graphene layers. The transparent properties changed from transparent to semi-transparent, black, and silver as the number of graphene layers was increased. The sheet electrical resistivity ranged from 106 to 0.2 Ω □-1, and the smaller resistivity was nearly equaled as the values of highly orientated pyrolytic graphite and glassy carbon. The graphene-laminated materials featured a wide range of transmittance, reflectance, and electrical conductance properties.

  15. Photoluminescence characterization of the grain boundary thermal stability in chemical vapor deposition grown WS2

    Science.gov (United States)

    Cai, Shuang; Zhao, Weiwei; Zafar, Amina; Wu, Zhangting; Tao, Yi; Bi, Kedong; Wei, Zhiyong; Ni, Zhenhua; Chen, Yunfei

    2017-10-01

    Monolayer transition metal dichalcogenides (TMDs) such as MoS2 and WS2 have been considered as promising candidate materials in nanophotonic applications. However, the structure stability of TMDs based optoelectronic devices is highly sensitive to the working environment. Here we present a successive photoluminescence study of the thermal stability characterization of grain boundary in chemical vapor deposition grown monolayer WS2. Results show that PL intensity enhancement in grain boundaries can be significantly weakened during the annealing process. Transformation temperature starts around 210 °C, substantially lower than the surrounding non-grain-boundary area. First-principle calculations results show that the PL quenching of grain boundaries is caused by the increased structural defects induced by annealing process, which makes the transition of electrons more difficult. Our results provide a route for characterizing the structure stability of two dimensional (2D) semiconductors, calling for extra attention to nanophotonic device working condition.

  16. Macrokinetics of carbon nanotubes synthesis by the chemical vapor deposition method

    Science.gov (United States)

    Rukhov, Artem; Dyachkova, Tatyana; Tugolukov, Evgeny; Besperstova, Galina

    2017-11-01

    A new approach to studying and developing basic processes which take place on the surface of a metal catalyst during the thermal decomposition of carbonaceous substances in the carbon nanotubes synthesis by the chemical vapor deposition method was proposed. In addition, an analysis was made of the interrelationships between these thermal, diffusion, hydrodynamic and other synthesis processes. A strong effect of the catalyst regeneration stage on the stage of nanotube formation has been shown. Based on the developed approach, a mathematical model was elaborated. Comparison of the calculation and the experiment carried out with the NiO-MgO catalyst at propane flow rate of 50 mL/min (standard conditions) and ethanol flow rate 0.3 mL/min (liq.) has revealed a discrepancy of less than 10%.

  17. Carrier dynamics in InS nanowires grown via chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Othonos, Andreas [Department of Physics, Research Centre of Ultrafast Science, University of Cyprus, P.O. Box 20537, 1678 Nicosia (Cyprus); Zervos, Matthew [Department of Mechanical and Manufacturing Engineering, Nanostructured Materials and Devices Laboratory, Materials Science Group, University of Cyprus, P.O. Box 20537, 1678 Nicosia (Cyprus)

    2010-10-15

    Transient femtosecond absorption spectroscopy and time-correlating single photon counting (TCSPC) photoluminescence (PL) were employed to study InS nanowires (NWs) grown by chemical vapor deposition (CVD) and determine the relaxation mechanisms in these nanostructures. Intensity dependent measurements revealed that Auger recombination plays an important role in the relaxation of photogenerated carriers at fluences larger than 0.4 x 10{sup 15} photons/cm{sup 2}. Calculations provided an estimated of the Auger recombination coefficient to be 1.1 {+-} 0.5 x 10{sup -31} cm{sup 6}/s. At the low fluence regime TCSPC PL revealed three relaxation mechanisms with time constants ranging from ps to nanosecond providing evidence of the importance of non-radiative decay channels associated with defect/trap states within the NWs. Auger recombination appears to dominate the carrier dynamics in InS NWs with increasing incident photon flux. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  18. Synthesis of boron nitride nanotubes by Argon supported Thermal Chemical Vapor Deposition

    Science.gov (United States)

    Ahmad, Pervaiz; Khandaker, Mayeen Uddin; Amin, Yusoff Mohd

    2015-03-01

    Thermal Chemical Vapor Deposition technique is modified with the use of Argon gas flow inside the chamber as an alternative for vacuum and orientation of one end closed quartz test tube. The use of Argon gas not only simplified the experimental set up, but also made it ~ 18 % cost effective compared to the conventional set up. Field Emission Scanning Electron Microscopy micrographs show straight and long BNNTs along with some cotton like morphologies. Transmission electron microscopy revealed bamboo like structure inside the tube and ~0.34 nm interlayer spacing for highly crystalline nature of boron nitride nanotubes. X-ray photon spectroscopy shows B 1s peak at 191.08 eV and N 1s peak at 398.78 eV that represents h-BN. Whereas, Raman spectrum indicates a major peak at ~1379.60 (cm-1) that correspond to E2g mode of h-BN.

  19. The Use af Ion Vapor Deposited Aluminum (IVD) for the Space Shuttle Solid Rocket Booster (SRB)

    Science.gov (United States)

    Novak, Howard L.

    2002-01-01

    The USA LLC Materials & Processes (M&P) Engineering Department had recommended the application and evaluation of Ion Vapor Deposition (IVD) aluminum to SRB Hardware for corrosion protection and elimination of hazardous materials and processes such as cadmium plating. IVD is an environmentally friendly process that has no volatile organic compounds (VOCs), or hazardous waste residues. It lends itself to use with hardware exposed to corrosive seacoast environments as found at Kennedy Space Center (KSC), and Cape Canaveral Air Force Station (CCAFS), Florida. Lifting apparatus initially coated with cadmium plating for corrosion protection; was stripped and successfully re-coated with IVD aluminum after the cadmium plating no longer protected the GSE from corrosion, Since then, and after completion of a significant test program, the first flight application of the IVD Aluminum process on the Drogue Parachute Ratchet Assembly is scheduled for 2002.

  20. Characterization of ultra-short pulsed discharge plasma for CVD processing. [Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Mizuno, Akira (Toyohashi Univ. of Technology (Japan). Dept. of Ecological Engineering); Okazaki, Ken (Tokyo Inst. of Technology (Japan). Research Center for Carbon Recycling and Utilization); Takekoshi, Takashi (Mitsubishi Kasei Co., Okayama (Japan). Mizushima Works); Tobe, Ryoki (Anelva Corp., Tokyo (Japan). Research Development Center)

    Characteristics of pulsed discharge plasma of methane-hydrogen gas mixture and Ar gas have been studied for active control of plasma chemical vapor deposition (CVD) processing. Voltage-current characteristics, time-lag of the current pulse, and the photon emission intensity profile have been investigated using high-voltage pulses of 50-1000 ns duration. In such a pulse discharge, voltages much higher than those in a dc glow discharge can be applied without any plasma nonuniformity or arcing because voltage amplitude falls to zero before glow to arc transition. A current value of more than 10[sup 3] times those in a glow discharge can be established. Very high photon emission intensity from CH radicals and H ions have been observed near the anode in a pulsed plasma. This is different in dc plasma, where the negative glow region near the cathode is the brightest.

  1. Controlled Synthesis of Atomically Layered Hexagonal Boron Nitride via Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Juanjuan Liu

    2016-11-01

    Full Text Available Hexagonal boron nitrite (h-BN is an attractive material for many applications including electronics as a complement to graphene, anti-oxidation coatings, light emitters, etc. However, the synthesis of high-quality h-BN is still a great challenge. In this work, via controlled chemical vapor deposition, we demonstrate the synthesis of h-BN films with a controlled thickness down to atomic layers. The quality of as-grown h-BN is confirmed by complementary characterizations including high-resolution transition electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray photo-electron spectroscopy. This work will pave the way for production of large-scale and high-quality h-BN and its applications as well.

  2. Synthesis of Y-Tip Graphitic Nanoribbons from Alcohol Catalytic Chemical Vapor Deposition on Piezoelectric Substrate

    Directory of Open Access Journals (Sweden)

    Zainab Yunusa

    2015-01-01

    Full Text Available We report the synthesis of Graphitic Nanoribbons (GNRs using Alcohol Catalytic Chemical Vapor Deposition (ACCVD. Bulk GNR was synthesized directly on a piezoelectric substrate using one-step ACCVD. The synthesized GNRs were characterized by X-Ray Diffraction (XRD, Scanning Electron Microscope (SEM, Transmission Electron Microscope (TEM, Energy Dispersive X-Ray (EDX, Atomic Force Microscopy (AFM, and Raman spectroscopy. The characterization results showed Y-tip morphology of bulk and filamentous as-grown GNR having varying width that lies between tens and hundreds of nm and length of several microns. Based on the thickness obtained from the AFM and the analysis from the Raman spectroscopy, it was concluded that the synthesized GNRs are multiple-layered and graphitic in nature. With the direct synthesis of GNR on a piezoelectric substrate, it could have applications in the sensor industries, while the Y-tip GNR could have potentialities in semiconductor applications.

  3. 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.

  4. Minimizing artifact formation in magnetorheological finishing of chemical vapor deposition ZnS flats

    Science.gov (United States)

    Kozhinova, Irina A.; Romanofsky, Henry J.; Maltsev, Alexander; Jacobs, Stephen D.; Kordonski, William I.; Gorodkin, Sergei R.

    2005-08-01

    The polishing performance of magnetorheological (MR) fluids prepared with a variety of magnetic and nonmagnetic ingredients was studied on four types of initial surface for chemical vapor deposition (CVD) ZnS flats from domestic and foreign sources. The results showed that it was possible to greatly improve smoothing performance of magnetorheological finishing (MRF) by altering the fluid composition, with the best results obtained for nanoalumina abrasive used with soft carbonyl iron and altered MR fluid chemistry. Surface roughness did not exceed 20 nm peak to valley and 2 nm rms after removal of 2 μm of material. The formation of orange peel and the exposure of a pebblelike structure inherent in ZnS from the CVD process were suppressed.

  5. Investigation on the corrosion behavior of physical vapor deposition coated high speed steel

    Directory of Open Access Journals (Sweden)

    R Ravi Raja Malarvannan

    2015-08-01

    Full Text Available This work emphasizes on the influence of the TiN and AlCrN coatings fabricated on high speed steel form tool using physical vapor deposition technique. The surface microstructure of the coatings was studied using scanning electron microscope. Hardness and corrosion studies were also performed using Vickers hardness test and salt spray testing, respectively. The salt spray test results suggested that the bilayer coated (TiN- bottom layer and AlCrN- top layer substrate has undergone less amount of corrosion, and this is attributed to the dense microstructure. In addition to the above, the influence of the above coatings on the machining performance of the high speed steel was also evaluated and compared with that of the uncoated material and the results suggested that the bilayered coating has undergone very low weight loss when compared with that of the uncoated substrate depicting enhanced wear resistance.

  6. Carbon nanowalls grown by microwave plasma enhanced chemical vapor deposition during the carbonization of polyacrylonitrile fibers

    Energy Technology Data Exchange (ETDEWEB)

    Li Jiangling; Su Shi; Kundrat, Vojtech; Abbot, Andrew M.; Ye, Haitao [School of Engineering and Applied Science, Aston University, Birmingham B4 7ET (United Kingdom); Zhou Lei [Department of Metallurgy and Materials, University of Birmingham, Birmingham B15 2TT (United Kingdom); Mushtaq, Fajer [Department of Mechanical Engineering, ETH Zurich, Zurich 8092 (Switzerland); Ouyang Defang [School of Life and Health Science, Aston University, Birmingham B4 7ET (United Kingdom); James, David; Roberts, Darren [Thermo Fisher Scientific, Stafford House, Hemel Hempstead HP2 7GE (United Kingdom)

    2013-01-14

    We used microwave plasma enhanced chemical vapor deposition (MPECVD) to carbonize an electrospun polyacrylonitrile (PAN) precursor to form carbon fibers. Scanning electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the fibers at different evolution stages. It was found that MPECVD-carbonized PAN fibers do not exhibit any significant change in the fiber diameter, whilst conventionally carbonized PAN fibers show a 33% reduction in the fiber diameter. An additional coating of carbon nanowalls (CNWs) was formed on the surface of the carbonized PAN fibers during the MPECVD process without the assistance of any metallic catalysts. The result presented here may have a potential to develop a novel, economical, and straightforward approach towards the mass production of carbon fibrous materials containing CNWs.

  7. Macroscopic Synthesis of Vertically Aligned Carbon Nanotubes Using Floating Catalyst Chemical Vapor Deposition Method

    Science.gov (United States)

    Mirbagheri, S. Ahmad; Kazemzadeh, Asghar; Abedin Maghanaki, Amir

    2012-01-01

    In this paper, we report an efficient process to grow well-aligned carbon nanotube (CNT) arrays with a good area distribution density (about 5.6 ×107 CNT/mm2). Vertically aligned carbon nanotubes (VA-CNTs) have been produced by controlling flow rate, temperature and catalyst nanoparticles using a floating catalyst chemical vapor deposition (FC-CVD) technique. They were synthesized on quartz substrates at 800 °C from toluene as a carbon source. VA-CNT samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and their surface area and pore size were determined by nitrogen adsorption analysis. The synthesized CNTs have a length of 500 µm and diameters ranging from 120±40 nm. The CNT filaments form a strength structure and exhibit a good vertical alignment. The remarkable properties of CNTs make them attractive for separation applications, especially for water and wastewater treatment.

  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. Uniformity of quantum well heterostructure GaAlAs lasers grown by metalorganic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Scifres, D.R.; Burnham, R.D.; Bernstein, M.; Chung, H.; Endicott, F.; Mosby, W.; Tramontana, J.; Walker, J.; Yingling, R.D. Jr.

    1982-09-15

    The threshold current density, laser wavelength, grown layer thickness, reverse breakdown voltage, and far-field radiation pattern as a function of position on the grown wafer are reported for broad area multiple quantum well GaAlAs heterostructure lasers grown by metalorganic chemical vapor deposition. It is found that the layer thickness varies across a 1.5-in. sample by as much as 20% at the outer edges of the water, leading to a lasing wavelength shift of as much as 150 A owing to the quantum size effect. It is shown that this thickness variation has only a small effect on the threshold current density across the water such that the uniformity of threshold current density is comparable to that reported previously for molecular beam epitaxy-grown conventional double heterostructure lasers.

  10. 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.

  11. Silicon Chemical Vapor Deposition Process Using a Half-Inch Silicon Wafer for Minimal Manufacturing System

    Science.gov (United States)

    Li, Ning; Habuka, Hitoshi; Ikeda, Shin-ichi; Hara, Shiro

    A chemical vapor deposition reactor for producing thin silicon films was designed and developed for achieving a new electronic device production system, the Minimal Manufacturing, using a half-inch wafer. This system requires a rapid process by a small footprint reactor. This was designed and verified by employing the technical issues, such as (i) vertical gas flow, (ii) thermal operation using a highly concentrated infrared flux, and (iii) reactor cleaning by chlorine trifluoride gas. The combination of (i) and (ii) could achieve a low heating power and a fast cooling designed by the heat balance of the small wafer placed at a position outside of the reflector. The cleaning process could be rapid by (iii). The heating step could be skipped because chlorine trifluoride gas was reactive at any temperature higher than room temperature.

  12. 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.

  13. 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.

  14. Integrating atomic layer deposition and ultra-high vacuum physical vapor deposition for in situ fabrication of tunnel junctions.

    Science.gov (United States)

    Elliot, Alan J; Malek, Gary A; Lu, Rongtao; Han, Siyuan; Yu, Haifeng; Zhao, Shiping; Wu, Judy Z

    2014-07-01

    Atomic Layer Deposition (ALD) is a promising technique for growing ultrathin, pristine dielectrics on metal substrates, which is essential to many electronic devices. Tunnel junctions are an excellent example which require a leak-free, ultrathin dielectric tunnel barrier of typical thickness around 1 nm between two metal electrodes. A challenge in the development of ultrathin dielectric tunnel barriers using ALD is controlling the nucleation of dielectrics on metals with minimal formation of native oxides at the metal surface for high-quality interfaces between the tunnel barrier and metal electrodes. This poses a critical need for integrating ALD with ultra-high vacuum (UHV) physical vapor deposition. In order to address these challenges, a viscous-flow ALD chamber was designed and interfaced to an UHV magnetron sputtering chamber via a load lock. A sample transportation system was implemented for in situ sample transfer between the ALD, load lock, and sputtering chambers. Using this integrated ALD-UHV sputtering system, superconductor-insulator-superconductor (SIS) Nb-Al/Al2O2/Nb Josephson tunnel junctions were fabricated with tunnel barriers of thickness varied from sub-nm to ~1 nm. The suitability of using an Al wetting layer for initiation of the ALD Al2O3 tunnel barrier was investigated with ellipsometry, atomic force microscopy, and electrical transport measurements. With optimized processing conditions, leak-free SIS tunnel junctions were obtained, demonstrating the viability of this integrated ALD-UHV sputtering system for the fabrication of tunnel junctions and devices comprised of metal-dielectric-metal multilayers.

  15. Integrating atomic layer deposition and ultra-high vacuum physical vapor deposition for in situ fabrication of tunnel junctions

    Science.gov (United States)

    Elliot, Alan J.; Malek, Gary A.; Lu, Rongtao; Han, Siyuan; Yu, Haifeng; Zhao, Shiping; Wu, Judy Z.

    2014-07-01

    Atomic Layer Deposition (ALD) is a promising technique for growing ultrathin, pristine dielectrics on metal substrates, which is essential to many electronic devices. Tunnel junctions are an excellent example which require a leak-free, ultrathin dielectric tunnel barrier of typical thickness around 1 nm between two metal electrodes. A challenge in the development of ultrathin dielectric tunnel barriers using ALD is controlling the nucleation of dielectrics on metals with minimal formation of native oxides at the metal surface for high-quality interfaces between the tunnel barrier and metal electrodes. This poses a critical need for integrating ALD with ultra-high vacuum (UHV) physical vapor deposition. In order to address these challenges, a viscous-flow ALD chamber was designed and interfaced to an UHV magnetron sputtering chamber via a load lock. A sample transportation system was implemented for in situ sample transfer between the ALD, load lock, and sputtering chambers. Using this integrated ALD-UHV sputtering system, superconductor-insulator-superconductor (SIS) Nb-Al/Al2O2/Nb Josephson tunnel junctions were fabricated with tunnel barriers of thickness varied from sub-nm to ˜1 nm. The suitability of using an Al wetting layer for initiation of the ALD Al2O3 tunnel barrier was investigated with ellipsometry, atomic force microscopy, and electrical transport measurements. With optimized processing conditions, leak-free SIS tunnel junctions were obtained, demonstrating the viability of this integrated ALD-UHV sputtering system for the fabrication of tunnel junctions and devices comprised of metal-dielectric-metal multilayers.

  16. Effects of feed gas composition and catalyst thickness on carbon nanotube and nanofiber synthesis by plasma enhanced chemical vapor deposition.

    Science.gov (United States)

    Garg, R K; Kim, S S; Hash, D B; Gore, J P; Fisher, T S

    2008-06-01

    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 effects of reacting gas composition (percentage methane in hydrogen) and catalyst film thickness on carbon nanotube (CNT) growth and a computational study of gas-phase composition for the inlet conditions of experimentally observed carbon nanotube growth using different chemical reaction mechanisms. The simulations seek to explain the observed effects of reacting gas composition and to identify the precursors for CNT formation. The experimental results indicate that gas-phase composition significantly affects the synthesized material, which is shown to be randomly aligned nanotube and nanofiber mats for relatively methane-rich inlet gas mixtures and non-tubular carbon for methane-lean incoming mixtures. The simulation results suggest that inlet methane-hydrogen mixture coverts to an acetylene-methane-hydrogen mixture with minor amounts of ethylene, hydrogen atom, and methyl radical. Acetylene appears to be the indicator species for solid carbon formation. The simulations also show that inlet methane-hydrogen mixture does not produce enough gas-phase precursors needed to form quality CNTs below 5% CH4 concentrations in the inlet stream.

  17. Quasi-periodic nanoripples in graphene grown by chemical vapor deposition and its impact on charge transport.

    Science.gov (United States)

    Ni, Guang-Xin; Zheng, Yi; Bae, Sukang; Kim, Hye Ri; Pachoud, Alexandre; Kim, Young Soo; Tan, Chang-Ling; Im, Danho; Ahn, Jong-Hyun; Hong, Byung Hee; Ozyilmaz, Barbaros

    2012-02-28

    The technical breakthrough in synthesizing graphene by chemical vapor deposition methods (CVD) has opened up enormous opportunities for large-scale device applications. To improve the electrical properties of CVD graphene grown on copper (Cu-CVD graphene), recent efforts have focused on increasing the grain size of such polycrystalline graphene films to 100 μm and larger. While an increase in grain size and, hence, a decrease of grain boundary density is expected to greatly enhance the device performance, here we show that the charge mobility and sheet resistance of Cu-CVD graphene is already limited within a single grain. We find that the current high-temperature growth and wet transfer methods of CVD graphene result in quasi-periodic nanoripple arrays (NRAs). Electron-flexural phonon scattering in such partially suspended graphene devices introduces anisotropic charge transport and sets limits to both the highest possible charge mobility and lowest possible sheet resistance values. Our findings provide guidance for further improving the CVD graphene growth and transfer process.

  18. Inverted polymer solar cells based on thin ZnO films grown by Mist chemical vapor deposition system

    Science.gov (United States)

    Biswas, Chandan; Ma, Zhu; Zhu, Xiaodan; Kawaharamura, Toshiyuki; Wang, Kang L.

    2014-10-01

    Extensive investigations have been conducted in order to synthesize high quality Zinc oxide (ZnO) thin films for numerous applications. These methods are either expensive to make or result polycrystalline thin films with low optoelectronic properties. Here we demonstrated a simple and inexpensive method to grow high quality ZnO thin films by a mist chemical vapor assisted depositing (Mist-CVD) system for inverted polymer solar cell (IPSC) application. The IPSC performance fabricated by Mist-CVD grown ZnO thin films were compared with two different Zn precursors (Zinc acetylacetonate hydrate and Zinc acetate dehydrate). Variations in IPSC performance on the growth temperature and growth time of the ZnO thin films were prominently demonstrated. The surface morphology of the ZnO films was investigated using scanning electron microscopy, atomic force microscopy and correlated with IPSC performance. The IPSC performance using two different precursors has been compared thoroughly. A 24% increase in solar cell efficiency (contributed from 21% increase in fill factor and 151% increase in shunt resistance) was achieved using Zinc acetate dehydrate compare to Zinc acetylacetonate hydrate precursor. The transmittance of ZnO thin films was evaluated by transmission spectroscopy. High performance IPSC can be fabricated using this simple and inexpensive method by synthesizing high quality thin ZnO films.

  19. Red emission from Eu-doped GaN luminescent films grown by metalorganic chemical vapor deposition

    Science.gov (United States)

    Pan, M.; Steckl, A. J.

    2003-07-01

    Bright red emission has been obtained at room temperature from Eu-doped GaN films pumped by 325 nm HeCd laser. The luminescent films were grown by metalorganic chemical vapor deposition on GaN/Al2O3 substrates. Trimethylgallium (TMGa), ammonia (NH3), and europium 2,2,4,4-tetramethyl-3,5-heptanedionate were used as sources for Ga, N, and Eu dopant, respectively. The influence of the V/III ratio during growth on the photoluminescence (PL) intensity has been studied using a fixed TMGa flow rate of 92 μmol/min and varying the NH3 flow rate. The film growth rate (˜2 μm/h) is nearly constant with V/III ratio over the range from ˜30 to ˜1000. The Eu incorporation in GaN films was found to decrease with increasing V/III ratio. The Eu PL intensity (normalized to the Eu concentration) exhibited a maximum at a V/III ratio of ˜100.

  20. Properties of a-C:H:O plasma polymer films deposited from acetone vapors

    Energy Technology Data Exchange (ETDEWEB)

    Drabik, M., E-mail: martin.drabik@gmail.com [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland); Celma, C. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland); Kousal, J.; Biederman, H. [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, V Holešovičkách 2, 180 00 Prague 8 (Czech Republic); Hegemann, D. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen (Switzerland)

    2014-12-31

    To gain insight into the deposition and stability of oxygen-containing plasma polymer films, the properties of amorphous oxygenated hydrocarbon (a-C:H:O) plasma polymer coatings deposited from acetone vapors under various experimental conditions are investigated. Apart from the discharge power, the influence of the reactive carbon dioxide (CO{sub 2}) gas on the structure of the resulting films is studied. It is found by characterization using X-ray Photoelectron Spectroscopy and Fourier-Transform Infrared Spectroscopy that the experimental conditions particularly influence the amount of oxygen in the deposited a-C:H:O plasma polymer films. The O/C elemental ratio increases with increasing amount of CO{sub 2} in the working gas mixture (up to 0.2 for 24 sccm of CO{sub 2} at 30 W) and decreases with increasing RF discharge power (down to 0.17 for 50 W). Furthermore, the nature of bonds between the oxygen and carbon atoms has been examined. Only low amounts of double and triple bonded carbon are observed. This has a particular influence on the aging of the plasma polymer films which is studied both in ambient air and in distilled water for up to 4 months. Overall, stable a-C:H:O plasma polymer films are deposited comprising low amounts (up to about 5%) of ester/carboxyl groups. - Highlights: • Hydrocarbon plasma polymer films with variable oxygen content can be prepared. • Stable oxygenated hydrocarbon plasma polymers contain max 5% of ester/carboxyl groups. • Acetone-derived plasma polymer films can be used as permanent hydrophilic surfaces.

  1. Synthesis and modeling of uniform complex metal oxides by close-proximity atmospheric pressure chemical vapor deposition.

    Science.gov (United States)

    Hoye, Robert L Z; Muñoz-Rojas, David; Musselman, Kevin P; Vaynzof, Yana; MacManus-Driscoll, Judith L

    2015-05-27

    A close-proximity atmospheric pressure chemical vapor deposition (AP-CVD) reactor is developed for synthesizing high quality multicomponent metal oxides for electronics. This combines the advantages of a mechanically controllable substrate-manifold spacing and vertical gas flows. As a result, our AP-CVD reactor can rapidly grow uniform crystalline films on a variety of substrate types at low temperatures without requiring plasma enhancements or low pressures. To demonstrate this, we take the zinc magnesium oxide (Zn(1-x)Mg(x)O) system as an example. By introducing the precursor gases vertically and uniformly to the substrate across the gas manifold, we show that films can be produced with only 3% variation in thickness over a 375 mm(2) deposition area. These thicknesses are significantly more uniform than for films from previous AP-CVD reactors. Our films are also compact, pinhole-free, and have a thickness that is linearly controllable by the number of oscillations of the substrate beneath the gas manifold. Using photoluminescence and X-ray diffraction measurements, we show that for Mg contents below 46 at. %, single phase Zn(1-x)Mg(x)O was produced. To further optimize the growth conditions, we developed a model relating the composition of a ternary oxide with the bubbling rates through the metal precursors. We fitted this model to the X-ray photoelectron spectroscopy measured compositions with an error of Δx = 0.0005. This model showed that the incorporation of Mg into ZnO can be maximized by using the maximum bubbling rate through the Mg precursor for each bubbling rate ratio. When applied to poly(3-hexylthiophene-2,5-diyl) hybrid solar cells, our films yielded an open-circuit voltage increase of over 100% by controlling the Mg content. Such films were deposited in short times (under 2 min over 4 cm(2)).

  2. Influence of vicinal sapphire substrate on the properties of N-polar GaN films grown by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Zhiyu; Zhang, Jincheng, E-mail: jchzhang@xidian.edu.cn; Xu, Shengrui; Chen, Zhibin; Yang, Shuangyong; Tian, Kun; Hao, Yue [Key Lab of Wide Band-Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi' an, Shaanxi 710071 (China); Su, Xujun [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215123 (China); Shi, Xuefang [School of Advanced Materials and Nanotechnology, Xidian University, Xi' an, Shaanxi 710071 (China)

    2014-08-25

    The influence of vicinal sapphire substrates on the growth of N-polar GaN films by metal-organic chemical vapor deposition is investigated. Smooth GaN films without hexagonal surface feature are obtained on vicinal substrate. Transmission electron microscope results reveal that basal-plane stacking faults are formed in GaN on vicinal substrate, leading to a reduction in threading dislocation density. Furthermore, it has been found that there is a weaker yellow luminescence in GaN on vicinal substrate than that on (0001) substrate, which might be explained by the different trends of the carbon impurity incorporation.

  3. Transport properties of the top and bottom surfaces in monolayer MoS2 grown by chemical vapor deposition.

    Science.gov (United States)

    Kurabayashi, S; Nagashio, K

    2017-09-14

    The advantage of MoS2, compared with graphene, is the direct growth on various oxide substrates by chemical vapor deposition (CVD) without utilizing catalytic metal substrates, which facilitates practical applications for electronics. The carrier mobility is, however, degraded from the intrinsic limit mainly due to short-range scattering caused by S vacancies formed during CVD growth. If the upper limit for the crystallinity of CVD-MoS2 on oxide substrates is determined by the MoS2/substrate interaction during growth, it will hinder the advantage. In this study, we investigated the interaction between monolayer MoS2 and a SiO2/Si substrate and the difference in crystallinity between the top and bottom S surfaces due to the MoS2/substrate interaction. Raman and photoluminescence spectroscopy indicated that doping and strain were induced in MoS2 from the substrate, but they could be removed by transferring MoS2 to a new substrate using polymers. The newly developed polymer-transfer technique enabled selective transfer of the bottom or top surface of CVD-MoS2 onto a new SiO2/Si substrate. The metal-insulator transition was clearly observed for both the normal and inverse transfers, suggesting that the crystallinity of CVD-MoS2 is high and that the crystallinity of the bottom surface interacting with the substrate was similar to that of the top free surface. These results provide positive prospects for the further improvement of the crystallinity of MoS2 on oxide substrates by reconsidering the growth conditions.

  4. Biocompatibility of Titania Nanotube Coatings Enriched with Silver Nanograins by Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Piotr Piszczek

    2017-09-01

    Full Text Available Bioactivity investigations of titania nanotube (TNT coatings enriched with silver nanograins (TNT/Ag have been carried out. TNT/Ag nanocomposite materials were produced by combining the electrochemical anodization and chemical vapor deposition methods. Fabricated coatings were characterized by scanning electron microscopy (SEM, X-ray photoelectron spectroscopy (XPS, and Raman spectroscopy. The release effect of silver ions from TNT/Ag composites immersed in bodily fluids, has been studied using inductively coupled plasma mass spectrometry (ICP-MS. The metabolic activity assay (MTT was applied to determine the L929 murine fibroblasts adhesion and proliferation on the surface of TNT/Ag coatings. Moreover, the results of immunoassays (using peripheral blood mononuclear cells—PBMCs isolated from rats allowed the estimation of the immunological activity of TNT/Ag surface materials. Antibacterial activity of TNT/Ag coatings with different morphological and structural features was estimated against two Staphylococcus aureus strains (ATCC 29213 and H9. The TNT/Ag nanocomposite layers produced revealed a good biocompatibility promoting the fibroblast adhesion and proliferation. A desirable anti-biofilm activity against the S. aureus reference strain was mainly noticed for these TiO2 nanotube coatings, which contain dispersed Ag nanograins deposited on their surface.

  5. Ultras-stable Physical Vapor Deposited Amorphous Teflon Films with Extreme Fictive Temperature Reduction

    Science.gov (United States)

    McKenna, Gregory; Yoon, Heedong; Koh, Yung; Simon, Sindee

    In the present work, we have produced highly stable amorphous fluoropolymer (Teflon AF® 1600) films to study the calorimetric and relaxation behavior in the deep in the glassy regime. Physical vapor deposition (PVD) was used to produce 110 to 700 nm PVD films with substrate temperature ranging from 0.70 Tg to 0.90 Tg. Fictive temperature (Tf) was measured using Flash DSC with 600 K/s heating and cooling rates. Consistent with prior observations for small molecular weight glasses, large enthalpy overshoots were observed in the stable amorphous Teflon films. The Tf reduction for the stable Teflon films deposited in the vicinity of 0.85 Tg was approximately 70 K compared to the Tgof the rejuvenated system. The relaxation behavior of stable Teflon films was measured using the TTU bubble inflation technique and following Struik's protocol in the temperature range from Tf to Tg. The results show that the relaxation time decreases with increasing aging time implying that devitrification is occurring in this regime.

  6. Low-Temperature Cu-Cu Bonding Using Silver Nanoparticles Fabricated by Physical Vapor Deposition

    Science.gov (United States)

    Wu, Zijian; Cai, Jian; Wang, Junqiang; Geng, Zhiting; Wang, Qian

    2018-02-01

    Silver nanoparticles (Ag NPs) fabricated by physical vapor deposition (PVD) were introduced in Cu-Cu bonding as surface modification layer. The bonding structure consisted of a Ti adhesive/barrier layer and a Cu substrate layer was fabricated on the silicon wafer. Ag NPs were deposited on the Cu surface by magnetron sputtering in a high-pressure environment and a loose structure with NPs was obtained. Shear tests were performed after bonding, and the influences of PVD pressure, bonding pressure, bonding temperature and annealing time on shear strength were assessed. Cu-Cu bonding with Ag NPs was accomplished at 200°C for 3 min under the pressure of 30 MPa without a post-annealing process, and the average bonding strength of 13.99 MPa was reached. According to cross-sectional observations, a void-free bonding interface with an Ag film thickness of around 20 nm was achieved. These results demonstrated that a reliable low-temperature short-time Cu-Cu bonding was realized by the sintering process of Ag NPs between the bonding pairs, which indicated that this bonding method could be a potential candidate for future ultra-fine pitch 3D integration.

  7. Synthesis of Hybrid Silica-Carbon Tubular Structures by Chemical Vapor Deposition with Methane or Ethene

    Directory of Open Access Journals (Sweden)

    Victor R. Sepulveda

    2017-12-01

    Full Text Available Silica microtube and carbon nanotube hybrid structures have been synthesized by catalytic chemical vapor deposition using either methane or ethene as the carbon source, and cobalt-grafted or impregnated silica tubes (200–800 nm as catalyst. The cobalt-grafted catalyst shows a high resistance to reduction (>1000 °C and selectivity to single-wall carbon nanotubes (SWCNT. While ethene deposition produces more carbonaceous material, methane experiments show higher selectivity for SWCNT. After removing the silica with an excess of HF, the carbon nanostructure endured, resulting in a coaxial carbon nanostructure. The novel hybrid nanostructures obtained consist of a submicron-sized tube, with walls that are formed by a succession of carbon/silica/carbon layers to which multiwall (20–25 nm and/or single-wall (0.6–2.0 nm carbon nanotubes are attached. This synthesis approach combines the mechanical properties of carbon nanotubes and the thermal properties of silica tubes into a synergetic nanostructured material, opening further possibilities for polymer reinforcement and potential applications in catalysis.

  8. Electrical properties of low pressure chemical vapor deposited silicon nitride thin films for temperatures up to 650 °C

    NARCIS (Netherlands)

    Tiggelaar, Roald M.; Groenland, A.W.; Sanders, Remco G.P.; Gardeniers, Johannes G.E.

    2009-01-01

    The results of a study on electrical conduction in low pressure chemical vapor deposited silicon nitride thin films for temperatures up to 650 °C are described. Current density versus electrical field characteristics are measured as a function of temperature for 100 and 200 nm thick stoichiometric

  9. Extension of the lifetime of tantalum filaments in the hot-wire (Cat) 3 Chemical Vapor Deposition process

    CSIR Research Space (South Africa)

    Knoesen, D

    2008-01-01

    Full Text Available One of the prime components of a hot-wire (Cat) Chemical Vapor Deposition system is the filament used to pyro-catalytically crack the gases like silane. Burnt out tantalum filaments were studied to determine the possible improvement of lifetime...

  10. 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...

  11. Vertically aligned carbon nanotube field emitter arrays with Ohmic base contact to silicon by Fe-catalyzed chemical vapor deposition

    NARCIS (Netherlands)

    Morassutto, M.; Tiggelaar, Roald M.; Smithers, M.A.; Smithers, M.A.; Gardeniers, Johannes G.E.

    2016-01-01

    Abstract In this study, dense arrays of aligned carbon nanotubes are obtained by thermal catalytic chemical vapor deposition, using Fe catalyst dispersed on a thin Ta layer. Alignment of the carbon nanotubes depends on the original Fe layer thickness from which the catalyst dispersion is obtained by

  12. High-quality AlN films grown on chemical vapor-deposited graphene films

    Directory of Open Access Journals (Sweden)

    Chen Bin-Hao

    2016-01-01

    Full Text Available We report the growth of high-quality AlN films on graphene. The graphene films were synthesized by CVD and then transferred onto silicon substrates. Epitaxial aluminum nitride films were deposited by DC magnetron sputtering on both graphene as an intermediate layer and silicon as a substrate. The structural characteristics of the AlN films and graphene were investigated. Highly c-axis-oriented AlN crystal structures are investigated based on the XRDpatterns observations.

  13. Effects of intermittent atomization on the properties of Al-doped ZnO thin films deposited by aerosol-assisted chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Linjie; Wang, Lixin [Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China); Qin, Xiujuan, E-mail: qinxj@ysu.edu.cn [Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China); Cui, Li [Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China); Shao, Guangjie [Hebei Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China); State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2016-04-30

    Al-doped ZnO (AZO) thin films were prepared on glass substrates with different atomization interval times by aerosol-assisted chemical vapor deposition method. The structure, morphology, and optical and electrical properties were investigated by X-ray diffractometer, atomic force microscope, UV-vis double beam spectrophotometer and 4 point probe method. ZnO thin films exhibited strong growth orientation along the (002) plane and the crystalline was affected by the atomization interval time. All the films had high transmittance and the films with interval times of 2 min and 4 min had good haze values for the transparent conducting oxide silicon solar cell applications. The AZO thin film had the best optical and electrical properties when the atomization interval time was 4 min. This is very important for the optoelectronic device applications. The surface morphology of AZO films depended on the atomization interval time. - Highlights: • Intermittent atomization is proved to be an effective measure. • Atomization interval time has an important influence on the crystallinity of films. • The surface morphology of ZnO films depends on atomization interval time. • Different hazes can be obtained by changing the atomization interval time.

  14. Using deposition rate to increase the thermal and kinetic stability of vapor-deposited hole transport layer glasses via a simple sublimation apparatus

    Science.gov (United States)

    Kearns, Kenneth L.; Krzyskowski, Paige; Devereaux, Zachary

    2017-05-01

    Deposition rate is known to affect the relative stability of vapor-deposited glasses; slower rates give more stable materials due to enhanced mobility at the free surface of the film. Here we show that the deposition rate can affect both the thermodynamic and kinetic stabilities of N ,N' -bis(3-methylphenyl)-N ,N' -diphenylbenzidine (TPD) and N ,N' -di-[(1-naphthyl)-N ,N' -diphenyl]-1,1'-biphenyl)-4,4'-diamine (NPD) glasses used as hole transport layers for organic light emitting diodes (OLEDs). A simple, low-vacuum glass sublimation apparatus and a high vacuum deposition chamber were used to deposit the glass. 50 μm thick films were deposited in the sublimation apparatus and characterized by differential scanning calorimetry while 75 nm thick films were prepared in the high vacuum chamber and studied by hot-stage spectroscopic ellipsometry (SE). The thermodynamic stability from both preparation chambers was consistent and showed that the fictive temperature (Tfictive) was more than 30 K lower than the conventional glass transition temperature (Tg) at the slowest deposition rates. The kinetic stability, measured as the onset temperature (Tonset) where the glass begins to transform into the supercooled liquid, was 16-17 K greater than Tg at the slowest rates. Tonset was systematically lower for the thin films characterized by SE and was attributed to the thickness dependent transformation of the glass into the supercooled liquid. These results show the first calorimetric characterization of the stability of glasses for OLED applications made by vapor deposition and the first direct comparison of deposition apparatuses as a function of the deposition rate. The ease of fabrication will create an opportunity for others to study the effect of deposition conditions on glass stability.

  15. Step-flow growth of a nanowire in the vapor-liquid-solid and vapor-solid-solid processes

    Science.gov (United States)

    Golovin, A. A.; Davis, S. H.; Voorhees, P. W.

    2008-10-01

    Consider the growth of a nanowire by a step-flow mechanism in the course of vapor-liquid-solid and vapor-solid-solid processes. The growth is initiated by the nucleation of a circular step at the nanowire-catalyst interface near the edge of the nanowire (the triple junction) and proceeds by the propagation toward the center by the Burton-Cabrera-Frank mechanism. Two cases are considered: (i) bulk transport, where the interfacial diffusion of adatoms and the step motion are coupled to the diffusion flux of atoms from the bulk of the catalyst particle, and (ii) surface transport, where atoms from the vapor phase are adsorbed at the surface of the catalyst particle and diffuse along the surface toward the triple line, whence they diffuse to the nanowire-catalyst interface. The attachment kinetics of adatoms at the step, the adsorption kinetics of atoms from the bulk phase, the exchange kinetics at the triple contact line, and the capillarity of the step are taken into account. In case (i) the problem is reduced to an integral equation for the diffusion flux of atoms from the bulk phase to the nanowire-catalyst interface. This equation is solved numerically, and the flux, interfacial concentration of adatoms, and the bulk concentration near the interface are determined. The step velocity is calculated as a function of the step radius and the kinetic parameters. As a result, the growth rate of a nanowire is computed as a function of its radius. In case (ii) analytical solutions for the surface and interfacial concentrations are obtained. In the absence of step capillarity, an analytical formula for the dependence of the nanowire growth rate on the nanowire radius is derived. It is shown in both cases (i) and (ii) that the nanowire growth rate decreases with increasing nanowire radius due to the decrease in the magnitude of the concentration gradients. However, in case (ii), in the limit of negligible desorption of adatoms into the gas phase, the nanowire growth rate is

  16. Influence of the growth parameters on TiO2 thin films deposited using the MOCVD method

    Directory of Open Access Journals (Sweden)

    Bernardi M. I. B.

    2002-01-01

    Full Text Available In this work we report the synthesis of TiO2 thin films by the Organometallic Chemical Vapor Deposition (MOCVD method. The influence of deposition parameters used during the growth in the obtained structural characteristics was studied. Different temperatures of the organometallic bath, deposition time, temperature and type of the substrate were combined. Using Scanning Electron Microscopy associated to Electron Dispersive X-Ray Spectroscopy, Atomic Force Microscopy and X-ray Diffraction, the strong influence of these parameters in the thin films final microstructure was verified.

  17. Chemical Vapor Deposition of Bi-Te-Ni-Fe on Magnesium Oxide Substrate and Its Seebeck Effect

    Directory of Open Access Journals (Sweden)

    Yong X. Gan

    2017-10-01

    Full Text Available In this work, a Bi-Te-Ni-Fe complex coating material was obtained on magnesium oxide substrate by a single step ambient pressure chemical vapor deposition (CVD. Nickel acetate, bismuth acetate, iron (III nitrate, and tellurium (IV chloride dissolved in N,N-dimethylformamide (DMF served as the metal sources for Ni, Bi, Fe, and Te, respectively. Hydrogen was used as the carrier gas. The substrate was kept at 500 °C in a quartz tube reaction chamber. The chemical vapor deposition time was two hours. Scanning electron microscopic observation revealed porous morphology of the deposited material with a needle-like submicron fine structure. These needle-like entities form networks with fairly uniform distribution on the substrate. Thermoelectric property test showed that the coating is p-type with a Seebeck coefficient of 179 µV/K. Time-dependent potential data were obtained to show the sensitivity of the Seebeck effect to temperature changes.

  18. Synthesis of MoS{sub 2} ribbons and their branched structures by chemical vapor deposition in sulfur-enriched environment

    Energy Technology Data Exchange (ETDEWEB)

    Mahyavanshi, Rakesh D., E-mail: rmahyavanshi@gmail.com [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Sharma, Kamal P. [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kondo, Masuharu; Dewa, Takeshita [Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kawahara, Toshio [Department of Electronics and Information Engineering, Chubu University, 1200 Matsumoto-cho, Kasugai 487-8501 (Japan); Tanemura, Masaki [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2017-07-01

    Highlights: • We demonstrate synthesis of monolayer MoS{sub 2} ribbons and their branched structures. • Unidirectional, bi and tri-directional growth of ribbons from the nucleation point are obtained. • Unidirectional and other branched structures can be synthesized controlling the composition of MoO{sub 3} and sulfur vapor. • The ribbons possess uneven edge structures with angles of 60° and 120°, indicating molybdenum and sulfur terminations. - Abstract: Here, we demonstrate the synthesis of monolayer molybdenum disulfide (MoS{sub 2}) ribbons and their branched structures by chemical vapor deposition (CVD) in sulfur-enriched environment. The growth of the MoS{sub 2} ribbons, triangular and other crystals significantly depends on the exposure of sulfur and concentration of molybdenum oxide (MoO{sub 3}) vapor on the substrate surface. The width and length of the synthesized ribbons is around 5–10 and 50–100 μm, respectively, where the width reduces from the nucleation point toward the end of the ribbon. Unidirectional, bi and tri-directional growth of ribbons from the nucleation point with an angle of 60° and 120° were obtained attributing to crystallographic growth orientation of MoS{sub 2} crystals. The directional growth of dichalcogenides ribbons is a significant challenge, our process shows that such unidirectional and other branched structures can be achieved by controlling the stoichiometric composition of MoO{sub 3} and sulfur exposure on the substrate surface. Interestingly, all the individual and branched ribbons possess uneven abundant edge structures, where the edges are formed with angles of 60° and 120°, indicating variation in molybdenum and sulfur edge terminations. The directional growth of MoS{sub 2} ribbons with defined edge structures in particular CVD condition can open up new possibilities for electronic and electrochemical applications.

  19. Catalytic chemical vapor deposition of large-area uniform two-dimensional molybdenum disulfide using sodium chloride

    Science.gov (United States)

    Song, Jeong-Gyu; Ryu, Gyeong Hee; Kim, Youngjun; Woo, Whang Je; Ko, Kyung Yong; Kim, Yongsung; Lee, Changseung; Oh, Il-Kwon; Park, Jusang; Lee, Zonghoon; Kim, Hyungjun

    2017-11-01

    The effective synthesis of atomically thin molybdenum disulfides (MoS2) of high quality and uniformity over a large area is essential for their use in electronic and optical devices. In this work, we synthesize MoS2 that exhibit a high quality and large area uniformity using chemical vapor deposition (CVD) with volatile S organic compound and NaCl catalysts. In the latter process, the NaCl enhances the growth rate (5 min for synthesis of monolayer MoS2) and purity of the synthesized MoS2. The optical microscopy, Raman spectroscopy, x-ray photoemission spectroscopy, photoluminescence, and transmission electron microscopy measurements indicate that the NaCl-CVD MoS2 has a large grain size, clear Raman shift, strong photoluminescence, good stoichiometry, and 6-fold coordination symmetry. Moreover, we demonstrate that the electron mobility (10.4 cm2 V‑1 s‑1) and on/off current ratio (3 × 107) of monolayer MoS2 measured using a field-effect transistor are comparable to those of previously reported MoS2 synthesized using CVD.

  20. Iron selenide films by aerosol assisted chemical vapor deposition from single source organometallic precursor in the presence of surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, Raja Azadar [Department of Chemistry, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Badshah, Amin, E-mail: aminbadshah@yahoo.com [Department of Chemistry, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Younis, Adnan [School of Materials Science and Engineering, University of New South Wales, Sydney 2052, NSW (Australia); Khan, Malik Dilshad [Department of Chemistry, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Akhtar, Javeed [Department of Physics, COMSATS Institute of Information Technology, Park Road, Chak Shahzad, Islamabad (Pakistan)

    2014-09-30

    This article presents the synthesis and characterization (multinuclear nuclear magnetic resonance, Fourier transform infrared spectroscopy, carbon–hydrogen–nitrogen–sulfur analyzer, atomic absorption spectrometry and thermogravimetric analysis) of a single source organometallic precursor namely 1-acetyl-3-(4-ferrocenylphenyl)selenourea for the fabrication of iron selenide (FeSe) films on glass substrates using aerosol assisted chemical vapor deposition (AACVD). The changes in the morphologies of the films have been monitored by the use of two different surfactants i.e. triton X-100 and tetraoctylphosphonium bromide during AACVD. The role of surfactant has been evaluated by examining the interaction of the surfactants with the precursor by using UV–vis spectroscopy and cyclic voltammetry. The fabricated FeSe films have been characterized with powder X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. - Highlights: • Ferrocene incorporated selenourea (FIS) has been synthesized and characterized. • FeSe thin films have been fabricated from FIS. • Mechanism of film growth was studied with cyclic voltammetry and UV–vis spectroscopy.

  1. Monolayer Single-Crystal 1T'-MoTe2 Grown by Chemical Vapor Deposition Exhibits Weak Antilocalization Effect.

    Science.gov (United States)

    Naylor, Carl H; Parkin, William M; Ping, Jinglei; Gao, Zhaoli; Zhou, Yu Ren; Kim, Youngkuk; Streller, Frank; Carpick, Robert W; Rappe, Andrew M; Drndić, Marija; Kikkawa, James M; Johnson, A T Charlie

    2016-07-13

    Growth of transition metal dichalcogenide (TMD) monolayers is of interest due to their unique electrical and optical properties. Films in the 2H and 1T phases have been widely studied but monolayers of some 1T'-TMDs are predicted to be large-gap quantum spin Hall insulators, suitable for innovative transistor structures that can be switched via a topological phase transition rather than conventional carrier depletion [ Qian et al. Science 2014 , 346 , 1344 - 1347 ]. Here we detail a reproducible method for chemical vapor deposition of monolayer, single-crystal flakes of 1T'-MoTe2. Atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy confirm the composition and structure of MoTe2 flakes. Variable temperature magnetotransport shows weak antilocalization at low temperatures, an effect seen in topological insulators and evidence of strong spin-orbit coupling. Our approach provides a pathway to systematic investigation of monolayer, single-crystal 1T'-MoTe2 and implementation in next-generation nanoelectronic devices.

  2. One-step chemical vapor deposition synthesis and supercapacitor performance of nitrogen-doped porous carbon–carbon nanotube hybrids

    Directory of Open Access Journals (Sweden)

    Egor V. Lobiak

    2017-12-01

    Full Text Available Novel nitrogen-doped carbon hybrid materials consisting of multiwalled nanotubes and porous graphitic layers have been produced by chemical vapor deposition over magnesium-oxide-supported metal catalysts. CNx nanotubes were grown on Co/Mo, Ni/Mo, or Fe/Mo alloy nanoparticles, and MgO grains served as a template for the porous carbon. The simultaneous formation of morphologically different carbon structures was due to the slow activation of catalysts for the nanotube growth in a carbon-containing gas environment. An analysis of the obtained products by means of transmission electron microscopy, thermogravimetry and X-ray photoelectron spectroscopy methods revealed that the catalyst's composition influences the nanotube/porous carbon ratio and concentration of incorporated nitrogen. The hybrid materials were tested as electrodes in a 1M H2SO4 electrolyte and the best performance was found for a nitrogen-enriched material produced using the Fe/Mo catalyst. From the electrochemical impedance spectroscopy data, it was concluded that the nitrogen doping reduces the resistance at the carbon surface/electrolyte interface and the nanotubes permeating the porous carbon provide fast charge transport in the cell.

  3. Synthesis of large scale graphene oxide using plasma enhanced chemical vapor deposition method and its application in humidity sensing

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang; Chen, Yuming, E-mail: yumingchen@fudan.edu.cn [Institute for Electric Light Sources, Fudan University, 220 Handan Road, Shanghai 200433 (China); Engineering Research Center of Advanced Lighting Technology, Ministry of Education, 220 Handan Road, Shanghai 00433 (China)

    2016-03-14

    Large scale graphene oxide (GO) is directly synthesized on copper (Cu) foil by plasma enhanced chemical vapor deposition method under 500 °C and even lower temperature. Compared to the modified Hummer's method, the obtained GO sheet in this article is large, and it is scalable according to the Cu foil size. The oxygen-contained groups in the GO are introduced through the residual gas of methane (99.9% purity). To prevent the Cu surface from the bombardment of the ions in the plasma, we use low intensity discharge. Our experiment reveals that growth temperature has important influence on the carbon to oxygen ratio (C/O ratio) in the GO; and it also affects the amount of π-π* bonds between carbon atoms. Preliminary experiments on a 6 mm × 12 mm GO based humidity sensor prove that the synthesized GO reacts well to the humidity change. Our GO synthesis method may provide another channel for obtaining large scale GO in gas sensing or other applications.

  4. Unpredicted surface termination of α-Fe2O3(0001) film grown by mist chemical vapor deposition

    Science.gov (United States)

    Osaka, Shun; Kubo, Osamu; Takahashi, Kazuki; Oda, Masaya; Kaneko, Kentaro; Tabata, Hiroshi; Fujita, Shizuo; Katayama, Mitsuhiro

    2017-06-01

    We analyze the surface structure of an α-Fe2O3(0001) film grown on a c-plane sapphire substrate by mist chemical vapor deposition (CVD), which has been recently developed as a simple, safe, and cost-effective film growth method. Using coaxial impact-collision ion scattering spectroscopy, we found that the atomic-layer sequence of the surface termination of an α-Fe2O3(0001) film grown by mist CVD was Fe-O3-Fe- from the top layer. This surface termination is predicted to form in an oxygen-poor environment by density functional theory combined with a thermodynamical approach despite that the mist CVD process is performed with atmospheric-pressure air. The surface structure markedly changes after annealing above 600 °C in ultrahigh vacuum. We found that only a couple of layers from the top layer transform into Fe3O4(111) after 650 °C annealing, which would be so-called biphase reconstruction. Complete transformation into a Fe3O4(111) film occurs at 700 °C, whose atomic-layer sequence is determined to be Fe-O4-Fe3- from the top layer.

  5. Effect of Mo concentration on shape and size of monolayer MoS2 crystals by chemical vapor deposition

    Science.gov (United States)

    Wang, Wenzhao; Zeng, Xiangbin; Wu, Shaoxiong; Zeng, Yang; Hu, Yishuo; Ding, Jia; Xu, Sue

    2017-10-01

    Monolayer molybdenum disulfide (MoS2), a new two-dimensional direct-bandgap semiconductor, has attracted research interests into applications in atomically thin electronics and optoelectronics. Growing monolayer MoS2 film by chemical vapor deposition is the most commonly used approach. Little is known, however, about the cause of the shape and size evolution. Here, we explore how the precursor’s concentration affects the MoS2 crystals’ shape and size. When S concentration is stable, the shape of the MoS2 domain evolves from triangle to hexagon and then truncated triangle, finally back to a triangle as the concentration of Mo elevates. Regulating the concentration of Mo leads to the controllable growth of MoS2 crystal. By controlling the concentration of Mo, we eventually synthesized over 100 µm monolayer MoS2 crystals. Our results are a significant step forward in realizing the ultimate promise of large atomic MoS2 monolayer crystals for flexible, electronic, optoelectronic devices.

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

    Directory of Open Access Journals (Sweden)

    Wen Yang

    2014-01-01

    Full Text Available 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 microscopy (SEM. Results showed that the addition of Cu promoted the reduction of nickel species, subsequently improving the growth and yield of CNTs. Meanwhile, CNTs were synthesized by the Ni/MgO and Ni-Cu/MgO catalysts with various calcination temperatures and reaction temperatures, and results suggested that the obtained CNTs on Ni-Cu/MgO catalyst with the calcination temperature of 500°C and the reaction temperature of 650°C were of the greatest yield and quantity of 927%.

  7. Facile Route to the Controlled Synthesis of Tetragonal and Orthorhombic SnO2 Films by Mist Chemical Vapor Deposition.

    Science.gov (United States)

    Bae, Jae-Yoon; Park, Jozeph; Kim, Hyun You; Kim, Hyun-Suk; Park, Jin-Seong

    2015-06-10

    Two types of tin dioxide (SnO2) films were grown by mist chemical vapor deposition (Mist-CVD), and their electrical properties were studied. A tetragonal phase is obtained when methanol is used as the solvent, while an orthorhombic structure is formed with acetone. The two phases of SnO2 exhibit different electrical properties. Tetragonal SnO2 behaves as a semiconductor, and thin-film transistors (TFTs) incorporating this material as the active layer exhibit n-type characteristics with typical field-effect mobility (μ(FE)) values of approximately 3-4 cm(2)/(V s). On the other hand, orthorhombic SnO2 is found to behave as a metal-like transparent conductive oxide. Density functional theory calculations reveal that orthorhombic SnO2 is more stable under oxygen-rich conditions, which correlates well with the experimentally observed solvent effects. The present study paves the way for the controlled synthesis of functional materials by atmospheric pressure growth techniques.

  8. Vapor transport growth of organic solids in microgravity and unit gravity: some comparisons and results to date

    Science.gov (United States)

    Zugrav, Maria Ittu; Carswell, William E.; Haulenbeek, Glen B.; Sanghadasa, Mohan; O'Brien, Sue K.; Ghita, Bogdan C.; Gathings, William E.

    2002-01-01

    Thin films of an organic nonlinear optical (NLO) material, N, N-dimethyl-p-(2,2-dicyanovinyl) aniline (DCVA), have been grown in space and on the ground by physical vapor transport in an effusive ampoule arrangement. The thin film growth technique developed on the ground is a direct result of information gleaned from experiments in microgravity. This paper covers the results of our experimental investigations for establishing "ideal" terrestrial conditions for deposition of a DCVA film. The active control during the deposition process was exercised by three deposition variables: the material source temperature, the background pressure external to the growth ampoule and the substrate temperature. Successful growth occurred when the difference in temperature between the source material and the copper substrate was 14 degrees C and the background nitrogen pressure was such that the transport was either diffusive or convective. A qualitative diffusion limited boundary was estimated to occur at a pressure of approximately 20 torr. We have probed the DCVA thin films with visible-near infrared reflection absorption spectroscopy, polarized Fourier transform infrared spectrometry, differential interference contrast optical microscopy, and stylus profilometry.

  9. RF sputtering enhanced the morphology and photoluminescence of multi-oriented ZnO nanostructure produced by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Al-Salman, Husam S., E-mail: husam.shakir@yahoo.com [School of Physics, University Sains Malaysia, Penang 11800 (Malaysia); Dept. of Physics, College of Science, University of Basrah, Basrah (Iraq); Abdullah, M.J. [School of Physics, University Sains Malaysia, Penang 11800 (Malaysia)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer A ZnO nanostructure was synthesized using the CVD and RF techniques. Black-Right-Pointing-Pointer High-quality ZnO nanorods were obtained. Black-Right-Pointing-Pointer The nanorods grow at a random angle on the substrate surface. Black-Right-Pointing-Pointer The RF sputter-coating step enhanced the structural quality of the ZnO film. - Abstract: Pure hexagonal wurtzite ZnO nanostructure was successfully synthesized by chemical vapor deposition (CVD) and RF-magnetron sputtering without using any catalysts. In the two-step process, high-quality multi-oriented ZnO nanorods were obtained. Multi-oriented spear-like ZnO rods were pre-deposited on the SiO{sub 2}/Si(1 0 0) substrate by CVD at 700 Degree-Sign C followed by RF sputtering of the ZnO nanostructure. The synthesized ZnO nanostructures were characterized by X-ray diffraction, field emission scanning electron microscopy, and photoluminescence (PL). The results show that the RF sputtering of the ZnO nanostructure, which was coated with a ZnO film produced by CVD, might have promoted the uniformity and crystalline quality of the multi-oriented spear-like ZnO film. The PL spectra revealed a sharp and dominant peak located at approximately 382 nm with a UV-to-visible PL intensity ratio (I{sub UV}/I{sub VS}) of 42 for the sample that was produced by the two-step process. The growth mechanism of the multi-oriented spear-like ZnO nanorods was investigated.

  10. Catalyst-free selective-area epitaxy of GaAs nanowires by metal-organic chemical vapor deposition using triethylgallium

    Science.gov (United States)

    Kim, Hyunseok; Ren, Dingkun; Farrell, Alan C.; Huffaker, Diana L.

    2018-02-01

    We demonstrate catalyst-free growth of GaAs nanowires by selective-area metal-organic chemical vapor deposition (MOCVD) on GaAs and silicon substrates using a triethylgallium (TEGa) precursor. Two-temperature growth of GaAs nanowires—nucleation at low temperature followed by nanowire elongation at high temperature—almost completely suppresses the radial overgrowth of nanowires on GaAs substrates while exhibiting a vertical growth yield of almost 100%. A 100% growth yield is also achieved on silicon substrates by terminating Si(111) surfaces by arsenic prior to the nanowire growth and optimizing the growth temperature. Compared with trimethylgallium (TMGa) which has been exclusively employed in the vapor–solid phase growth of GaAs nanowires by MOCVD, the proposed growth technique using TEGa is advantageous because of lower growth temperature and fully suppressed radial overgrowth. It is also known that GaAs grown by TEGa induce less impurity incorporation compared with TMGa, and therefore the proposed method could be a building block for GaAs nanowire-based high-performance optoelectronic and nanoelectronic devices on both III–V and silicon platforms.

  11. X-ray absorption study of diamond films grown by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, X.; Ruckman, M.W.; Skotheim, T.A. (Brookhaven National Laboratory, Upton, New York 11973 (USA)); den Boer, M.; Zheng, Y. (The City University of New York, New York, New York 10021 (USA)); Badzian, A.R.; Badzian, T.; Messier, R. (The Pennsylvania State University, University Park, Pennsylvania 16802 (USA)); Srivatsa, A.R. (Moltech Corporation, Stony Brook, New York 11974 (USA))

    1991-05-01

    Carbon {ital k}-edge x-ray absorption fine structure (XAFS) is used to study the structure and bonding of chemical vapor deposition (CVD) grown diamond and diamond-like carbon films. Diamond films grown at 875 {degree}C on silicon using a 1% CH{sub 4} /H{sub 2} mixture have near-edge spectra resembling type 1(a) natural diamond. The {ital k}-edges of the diamond-like films grown by electron cyclotron resonance CVD at 200 {degree}C using 10{sup {minus}4} Torr of CH{sub 4} show a broad main peak lacking the sharp structure of graphite or diamond. Comparing the near edges of the CVD diamond film with other carbon compounds (i.e., graphite) and the CVD diamond film, the diamond-like film shows a strong {pi}* feature at 285 eV indicative of sp{sup 2} bonded carbon and a feature at 289 eV, the {sigma}*(C--H) resonance indicating C--H bonds. The relatively weak extended x-ray absorption fine structure (EXAFS) shows that the diamond-like carbon film is highly disordered on an atomic level.

  12. Microwave plasma-assisted chemical vapor deposition of porous carbon film as supercapacitive electrodes

    Science.gov (United States)

    Wu, Ai-Min; Feng, Chen-Chen; Huang, Hao; Paredes Camacho, Ramon Alberto; Gao, Song; Lei, Ming-Kai; Cao, Guo-Zhong

    2017-07-01

    Highly porous carbon film (PCF) coated on nickel foam was prepared successfully by microwave plasma-assisted chemical vapor deposition (MPCVD) with C2H2 as carbon source and Ar as discharge gas. The PCF is uniform and dense with 3D-crosslinked nanoscale network structure possessing high degree of graphitization. When used as the electrode material in an electrochemical supercapacitor, the PCF samples verify their advantageous electrical conductivity, ion contact and electrochemical stability. The test results show that the sample prepared under 1000 W microwave power has good electrochemical performance. It displays the specific capacitance of 62.75 F/g at the current density of 2.0 A/g and retains 95% of its capacitance after 10,000 cycles at the current density of 2.0 A/g. Besides, its near-rectangular shape of the cyclic voltammograms (CV) curves exhibits typical character of an electric double-layer capacitor, which owns an enhanced ionic diffusion that can fit the requirements for energy storage applications.

  13. Enabling organosilicon chemistries on inert polymer surfaces with a vapor-deposited silica layer.

    Science.gov (United States)

    Anderson, A; Ashurst, W R

    2009-10-06

    Given the large surface area-to-volume ratios commonly encountered in microfluidics applications, the ability to engineer the chemical properties of surfaces encountered in these applications is critically important. However, as various polymers are rapidly replacing glass and silicon as the chosen materials for microfluidics devices, the ability to easily modify the surface chemistry has been diminished by the relatively inert nature of some commonly employed polymer surfaces, such as poly(methyl methacrylate) (PMMA), polystyrene, and polydimethylsiloxane (PDMS). This paper describes the low-temperature, vapor-phase deposition of robust silica layers to PMMA, polystyrene, and PDMS surfaces, which enables the functionalization of these surfaces by standard organosilane chemistries. Attenuated total reflection infrared spectroscopy, contact angle goniometry, ellipsometry, and atomic force microscopy are used to characterize the silica layers that form on these surfaces. Aqueous immersion experiments indicate that the silica layer has excellent stability in aqueous environments, which is a prerequisite for microfluidics applications, but for PMMA surfaces, low adhesion of the silica layer to the underlying substrate is problematic. For PDMS substrates, the presence of the silica layer helps to slow the process of hydrophobic recovery, which is an additional advantage.

  14. Radiative recombination mechanisms in CdTe thin films deposited by elemental vapor transport

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Shamara [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Vatavu, Sergiu, E-mail: svatavu@usm.md [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., Chisinau, MD-2009, Republic of Moldova (Moldova, Republic of); Evani, Vamsi; Khan, Md; Bakhshi, Sara; Palekis, Vasilios [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States); Rotaru, Corneliu [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., Chisinau, MD-2009, Republic of Moldova (Moldova, Republic of); Ferekides, Chris [Department of Electrical Engineering, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 (United States)

    2015-05-01

    A photoluminesence (PL) study of the radiative recombination mechanisms for CdTe films deposited under different Cd and Te overpressure by elemental vapor transport is presented. The experiment and analysis have been carried out in the temperature range of 12-130 K. The intensity of the PL laser excitation beam was varied by two orders of magnitude. It has been established that the bands in the 1.47-1.50 eV are determined by transitions involving shallow D and A states and the 1.36x-1.37x eV band is due to band to level transitions. Deep transitions at 1.042 eV and 1.129 eV are due to radiative transitions to levels determined by CdTe native defects. - Highlights: • Photoluminescense (PL) of CdTe thin films is present in the 0.8-1.6 eV spectral region. • High intensity excitonic peaks are among the main radiative paths. • Radiative transitions at 1.36x eV are assisted by dislocations caused levels. • Extremal Cd/Te overpressure ratios enhance PL for 1.497 eV, 1.486 eV, 1.474 eV bands. • PL intensity reaches its max value for the 0.45 and 1.25 Cd/Te overpressure ratios.

  15. Effect of transition metal salts on the initiated chemical vapor deposition of polymer thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kwong, Philip; Seidel, Scott; Gupta, Malancha, E-mail: malanchg@usc.edu [Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, 925 Bloom Walk, Los Angeles, California 90089 (United States)

    2015-05-15

    In this work, the effect of transition metal salts on the initiated chemical vapor deposition of polymer thin films was studied using x-ray photoelectron spectroscopy. The polymerizations of 4-vinyl pyridine and 1H,1H,2H,2H-perfluorodecyl acrylate were studied using copper(II) chloride (CuCl{sub 2}) and iron(III) chloride (FeCl{sub 3}) as the transition metal salts. It was found that the surface coverages of both poly(4-vinyl pyridine) (P4VP) and poly(1H,1H,2H,2H-perfluorodecyl acrylate) were decreased on CuCl{sub 2}, while the surface coverage of only P4VP was decreased on FeCl{sub 3}. The decreased polymer surface coverage was found to be due to quenching of the propagating radicals by the salt, which led to a reduction of the oxidation state of the metal. The identification of this reaction mechanism allowed for tuning of the effectiveness of the salts to decrease the polymer surface coverage through the adjustment of processing parameters such as the filament temperature. Additionally, it was demonstrated that the ability of transition metal salts to decrease the polymer surface coverage could be extended to the fabrication of patterned cross-linked coatings, which is important for many practical applications such as sensors and microelectronics.

  16. 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.

  17. Thickness Measurement Methods for Physical Vapor Deposited Aluminum Coatings in Packaging Applications: A Review

    Directory of Open Access Journals (Sweden)

    Martina Lindner

    2017-01-01

    Full Text Available The production of barrier packaging materials, e.g., for food, by physical vapor deposition (PVD of inorganic coatings such as aluminum on polymer substrates is an established and well understood functionalization technique today. In order to achieve a sufficient barrier against gases, a coating thickness of approximately 40 nm aluminum is necessary. This review provides a holistic overview of relevant methods commonly used in the packaging industry as well as in packaging research for determining the aluminum coating thickness. The theoretical background, explanation of methods, analysis and effects on measured values, limitations, and resolutions are provided. In industrial applications, quartz micro balances (QCM and optical density (OD are commonly used for monitoring thickness homogeneity. Additionally, AFM (atomic force microscopy, electrical conductivity, eddy current measurement, interference, and mass spectrometry (ICP-MS are presented as more packaging research related methods. This work aims to be used as a guiding handbook regarding the thickness measurement of aluminum coatings for packaging technologists working in the field of metallization.

  18. Hierarchical chrysanthemum-flower-like carbon nanomaterials grown by chemical vapor deposition

    Science.gov (United States)

    Ding, Er-Xiong; Geng, Hong-Zhang; Wang, Jing; Luo, Zhi-Jia; Li, Guangfen; Wang, Wen-Yi; Li, Lin-Ge; Yang, Hai-Jie; Da, Shi-Xun; Wang, Jie; Jiang, Hua; Kauppinen, Esko I.

    2016-02-01

    Novel hierarchical chrysanthemum-flower-like carbon nanomaterials (CFL-CNMs) were synthesized by thermal chemical vapor deposition based on acetylene decomposition. A scanning electron microscope and a transmission electron microscope were employed to observe the morphology and structure of the unconventional nanostructures. It is found that the CFL-CNMs look like a blooming chrysanthemum with a stem rather than a spherical flower. The carbon flower has an average diameter of 5 μm, an average stem diameter of 150 nm, branch diameters ranging from 20 to 70 nm, and branch lengths ranging from 0.5 to 3 μm. The morphologies of the CFL-CNMs are unlike any of those previously reported. Fishbone-like carbon nanofibers with a spindle-shaped catalyst locating at the tip can also be found. Furthermore, the catalyst split was proposed to elucidate the formation mechanism of CFL-CNMs. A large and glomerate catalyst particle at the tip of the carbon nanofiber splits into smaller catalyst particles which are catalytic-active points for branch formation, resulting in the formation of CFL-CNMs.

  19. 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.

  20. A study of color modulation of porous alumina processed by physical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xulongqi; Zhang Haijun; Zhang Dongxian, E-mail: zhangdx@zju.edu.cn [State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, 310027 (China)

    2011-02-01

    With the development of the porous alumina (PA) fabrication technology, more and more scholars plough into the research of its properties, especially optical properties. Recently, we observed an interesting phenomenon that the PA templates processed by Physical Vapor Deposition (PVD) show color differences related to light path difference. Our work attempts to make the principle clear and to find an effective method to modulate the color of PA samples. This article describes the details of our experimental and theoretical results. We successfully prepared some PA templates with different pore-depth by controlling the time of anodization in oxalic acid solution. In order to enhance the reflectivity of air-PA interface, a layer of TiO{sub 2} film of 18 nm is coated with PVD technique, which makes PA templates display quite distinct colors with different hole-depth. By modelling and analyzing PA samples, we make the interpretation of this optical property by taking the PA sample with 150 nm pore-depth as an example, and then put forward a way to simulate sample's color within its hole-depth and material refraction-index. The results are in good agreement with our theoretical analysis, which proves the feasibility of our simulation mode.

  1. Uniformly Distributed Graphene Domain Grows on Standing Copper via Low-Pressure Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Shih-Hao Chan

    2013-01-01

    Full Text Available Uniformly distributed graphene domains were synthesized on standing copper foil by a low-pressure chemical vapor deposition system. This method improved the distribution of the graphene domains at different positions on the same piece of copper foil along the forward direction of the gas flow. Scanning electron microscopy (SEM showed the average size of the graphene domains to be about ~20 m. This results show that the sheet resistance of monolayer graphene on a polyethylene terephthalate (PET substrate is about ~359 /□ whereas that of the four-layer graphene films is about ~178 /□, with a transmittance value of 88.86% at the 550 nm wavelength. Furthermore, the sheet resistance can be reduced with the addition of HNO3 resulting in a value of 84 /□. These values meet the absolute standard for touch sensor applications, so we believe that this method can be a candidate for some transparent conductive electrode applications.

  2. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Joucken, Frédéric, E-mail: frederic.joucken@unamur.be; Colomer, Jean-François; Sporken, Robert; Reckinger, Nicolas

    2016-08-15

    Highlights: • CVD graphene is transferred onto sapphire. • Transport measurements reveal relatively low charge carriers mobility. • Scanning probe microscopy experiments reveal the presence of robust contaminant layers between the graphene and the sapphire, responsible for the low carriers mobility. - Abstract: We present a combination of magnetotransport and local probe measurements on graphene grown by chemical vapor deposition on copper foil and subsequently transferred onto a sapphire substrate. A rather strong p-doping is observed (∼9 × 10{sup 12} cm{sup −2}) together with quite low carrier mobility (∼1350 cm{sup 2}/V s). Atomic force and tunneling imaging performed on the transport devices reveals the presence of contaminants between sapphire and graphene, explaining the limited performance of our devices. The transferred graphene displays ridges similar to those observed whilst graphene is still on the copper foil. We show that, on sapphire, these ridges are made of different thicknesses of the contamination layer and that, contrary to what was reported for hBN or certain transition metal dichalcogenides, no self-cleansing process of the sapphire substrate is observed.

  4. Photoluminescence Segmentation within Individual Hexagonal Monolayer Tungsten Disulfide Domains Grown by Chemical Vapor Deposition.

    Science.gov (United States)

    Sheng, Yuewen; Wang, Xiaochen; Fujisawa, Kazunori; Ying, Siqi; Elias, Ana Laura; Lin, Zhong; Xu, Wenshuo; Zhou, Yingqiu; Korsunsky, Alexander M; Bhaskaran, Harish; Terrones, Mauricio; Warner, Jamie H

    2017-05-03

    We show that hexagonal domains of monolayer tungsten disulfide (WS2) grown by chemical vapor deposition (CVD) with powder precursors can have discrete segmentation in their photoluminescence (PL) emission intensity, forming symmetric patterns with alternating bright and dark regions. Two-dimensional maps of the PL reveal significant reduction within the segments associated with the longest sides of the hexagonal domains. Analysis of the PL spectra shows differences in the exciton to trion ratio, indicating variations in the exciton recombination dynamics. Monolayers of WS2 hexagonal islands transferred to new substrates still exhibit this PL segmentation, ruling out local strain in the regions as the dominant cause. High-power laser irradiation causes preferential degradation of the bright segments by sulfur removal, indicating the presence of a more defective region that is higher in oxidative reactivity. Atomic force microscopy (AFM) images of topography and amplitude modes show uniform thickness of the WS2 domains and no signs of segmentation. However, AFM phase maps do show the same segmentation of the domain as the PL maps and indicate that it is caused by some kind of structural difference that we could not clearly identify. These results provide important insights into the spatially varying properties of these CVD-grown transition metal dichalcogenide materials, which may be important for their effective implementation in fast photo sensors and optical switches.

  5. A directly patternable click-active polymer film via initiated chemical vapor deposition (iCVD)

    Energy Technology Data Exchange (ETDEWEB)

    Im, Sung Gap; Kim, Byeong-Su; Tenhaeff, Wyatt E.; Hammond, Paula T. [Department of Chemical Engineering and Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Gleason, Karen K., E-mail: kkg@mit.ed [Department of Chemical Engineering and Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2009-04-30

    A new 'click chemistry' active functional polymer film was directly obtained from a commercially available monomer of propargyl acrylate (PA) via easy, one-step process of initiated chemical vapor deposition (iCVD). Fourier transform infrared (FTIR) spectra confirmed that significant amount of the click-active acetylene functional group was retained after the iCVD process. The degree of crosslinking could be controlled by intentionally adding crosslinker, such as ethylene glycol diacrylate (EGDA) that was polymerized with PA to form click-active, completely insoluble copolymer. The formed iCVD polymers could also be grafted on various inorganic substrates with silane coupling agents. These crosslinking and grafting techniques give iCVD polymers chemical and mechanical stability, which allows iCVD polymers applicable to various click chemistry without any modification of reaction conditions. Pre-patterned iCVD polymer could be obtained via photolithography and an azido-functionalized dye molecule was also successfully attached on iCVD polymer via click chemistry. Moreover, pPA film demonstrated sensitivity to e-beam irradiation, which enabled clickable substrates having nanometer scale patterns without requiring the use of an additional e-beam resist. Direct e-beam exposure of this multifunctional iCVD layer, a 200 nm pattern, and QD particles were selectively conjugated on the substrates via click chemistry. Thus, iCVD pPA has shown dual functionality as of 'clickable' e-beam sensitive material.

  6. Upcycling Waste Lard Oil into Vertical Graphene Sheets by Inductively Coupled Plasma Assisted Chemical Vapor Deposition.

    Science.gov (United States)

    Wu, Angjian; Li, Xiaodong; Yang, Jian; Du, Changming; Shen, Wangjun; Yan, Jianhua

    2017-10-12

    Vertical graphene (VG) sheets were single-step synthesized via inductively coupled plasma (ICP)-enhanced chemical vapor deposition (PECVD) using waste lard oil as a sustainable and economical carbon source. Interweaved few-layer VG sheets, H₂, and other hydrocarbon gases were obtained after the decomposition of waste lard oil. The influence of parameters such as temperature, gas proportion, ICP power was investigated to tune the nanostructures of obtained VG, which indicated that a proper temperature and H₂ concentration was indispensable for the synthesis of VG sheets. Rich defects of VG were formed with a high I D / I G ratio (1.29), consistent with the dense edges structure observed in electron microscopy. Additionally, the morphologies, crystalline degree, and wettability of nanostructure carbon induced by PECVD and ICP separately were comparatively analyzed. The present work demonstrated the potential of our PECVD recipe to synthesize VG from abundant natural waste oil, which paved the way to upgrade the low-value hydrocarbons into advanced carbon material.

  7. Upcycling Waste Lard Oil into Vertical Graphene Sheets by Inductively Coupled Plasma Assisted Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Angjian Wu

    2017-10-01

    Full Text Available Vertical graphene (VG sheets were single-step synthesized via inductively coupled plasma (ICP-enhanced chemical vapor deposition (PECVD using waste lard oil as a sustainable and economical carbon source. Interweaved few-layer VG sheets, H2, and other hydrocarbon gases were obtained after the decomposition of waste lard oil. The influence of parameters such as temperature, gas proportion, ICP power was investigated to tune the nanostructures of obtained VG, which indicated that a proper temperature and H2 concentration was indispensable for the synthesis of VG sheets. Rich defects of VG were formed with a high I D / I G ratio (1.29, consistent with the dense edges structure observed in electron microscopy. Additionally, the morphologies, crystalline degree, and wettability of nanostructure carbon induced by PECVD and ICP separately were comparatively analyzed. The present work demonstrated the potential of our PECVD recipe to synthesize VG from abundant natural waste oil, which paved the way to upgrade the low-value hydrocarbons into advanced carbon material.

  8. Monolayer MoSe2 grown by chemical vapor deposition for fast photodetection.

    Science.gov (United States)

    Chang, Yung-Huang; Zhang, Wenjing; Zhu, Yihan; Han, Yu; Pu, Jiang; Chang, Jan-Kai; Hsu, Wei-Ting; Huang, Jing-Kai; Hsu, Chang-Lung; Chiu, Ming-Hui; Takenobu, Taishi; Li, Henan; Wu, Chih-I; Chang, Wen-Hao; Wee, Andrew Thye Shen; Li, Lain-Jong

    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 MoSe2 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.

  9. Ultraviolet-light-driven doping modulation in chemical vapor deposition grown graphene.

    Science.gov (United States)

    Iqbal, M Z; Iqbal, M W; Khan, M F; Eom, Jonghwa

    2015-08-28

    The tuning of charge carrier density of graphene is an essential factor to achieve the integration of high-efficiency electronic and optoelectronic devices. We demonstrate the reversible doping in graphene using deep ultraviolet (UV) irradiation and treatment with O2 and N2 gases. The Dirac point shift towards a positive gate voltage of chemical vapor deposition grown graphene field-effect transistors confirms the p-type doping, which is observed under UV irradiation and treatment with O2 gas, while it restores its pristine state after treatment with N2 gas under UV irradiation. The emergence of an additional peak in the X-ray photoelectron spectra during UV irradiation and treatment with O2 gas represents the oxidation of graphene, and the elimination of this peak during UV irradiation and treatment with N2 gas reveals the restoration of graphene in its pristine state. The shift in the G and 2D bands in Raman spectra towards higher and then lower wavenumber also suggests p-type doping and then reversible doping in graphene. The controlled doping and its reversibility in large area grown graphene offer a new vision for electronic applications.

  10. Synthesis of scalable and tunable slightly oxidized graphene via chemical vapor deposition.

    Science.gov (United States)

    Sagar, Rizwan Ur Rehman; Namvari, Mina; Navale, Sachin T; Stadler, Florian J

    2017-03-15

    Semiconducting, large sheets of carbon as an active material in optoelectronic research are missing and reduced graphene oxide (rGO) can be a good candidate. However, chemical synthesis cannot produce large sheets of rGO (i.e. maximum: 20-30μm) as well as high quality rGO due to the restraints of fabrication method. Thus, a novel strategy for the synthesis of large sheets of semiconducting rGO is urgently required. Large area slightly oxidized graphene (SOG) is fabricated at the interface of silicon dioxide (SiO2) and silicon via Chemical Vapor Deposition (CVD) method, herein for the first time. Carbon atoms bond with oxygen functionalities (i.e. CO, COH) at the time of diffusion in SiO2 allowing for C/O ratios from 7 to 10 adjustable by the variation of SiO2 thickness, indicating the tunable oxidation. Moreover, electronic structure and morphology of SOG are similar to the chemically grown rGO. The fabrication mechanism of SOG is also investigated. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. 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.

  12. Fabrication of Nanocarbon Composites Using In Situ Chemical Vapor Deposition and Their Applications.

    Science.gov (United States)

    He, Chunnian; Zhao, Naiqin; Shi, Chunsheng; Liu, Enzuo; Li, Jiajun

    2015-09-23

    Nanocarbon (carbon nanotubes (CNTs) and graphene (GN)) composites attract considerable research interest due to their fascinating applications in many fields. Here, recent developments in the field of in situ chemical vapor deposition (CVD) for the design and controlled preparation of advanced nanocarbon composites are highlighted, specifically, CNT-reinforced bulk structural composites, as well as CNT, GN, and CNT/GN functional composites, together with their practical and potential applications. In situ CVD is a very attractive approach for the fabrication of composites because of its engaging features, such as its simplicity, low-cost, versatility, and tunability. The morphologies, structures, dispersion, and interface of the resulting nanocarbon composites can be easily modulated by varying the experimental parameters (such as temperature, catalysts, carbon sources, templates or template catalysts, etc.), which enables a great potential for the in situ synthesis of high-quality nanocarbons with tailored size and dimension for constructing high-performance composites, which has not yet been achieved by conventional methods. In addition, new trends of the in situ CVD toward nanocarbon composites are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. 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.

  14. Aspects of nitrogen surface chemistry relevant to TiN chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Schulberg, M.T.; Allendorf, M.D.; Outka, D.A.

    1996-08-01

    NH{sub 3} is an important component of many chemical vapor deposition (CVD) processes for TiN films, which are used for diffusion barriers and other applications in microelectronic circuits. In this study, the interaction of NH{sub 3} with TiN surfaces is examined with temperature programmed desorption (TPD) and Auger electron spectroscopy. NH{sub 3} has two adsorption states on TiN: a chemisorbed state and a multilayer state. A new method for analyzing TPD spectra in systems with slow pumping speeds yields activation energies for desorption for the two states of 24 kcal/mol and 7.3 kcal/mol, respectively. The sticking probability into the chemisorption state is {approximately}0.06. These results are discussed in the context of TiN CVD. In addition, the high temperature stability of TiN is investigated. TiN decomposes to its elements only after heating to 1300 K, showing that decomposition is unlikely to occur under CVD conditions.

  15. Optical spectroscopic characterization of amorphous germanium carbide materials obtained by X-Ray Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Paola Antoniotti

    2015-05-01

    Full Text Available Amorphous germanium carbides have been prepared by X-ray activated Chemical Vapor Deposition from germane/allene systems. The allene percentage and irradiation time (total dose were correlated to the composition, the structural features, and the optical coefficients of the films, as studied by IR and UV-VIS spectroscopic techniques. The materials composition is found to change depending on both the allene percentage in the mixture and the irradiation time. IR spectroscopy results indicate that the solids consist of randomly bound networks of carbon and germanium atoms with hydrogen atoms terminating all the dangling bonds. Moreover, the elemental analysis results, the absence of both unsaturated bonds and CH3 groups into the solids and the absence of allene autocondensation reactions products, indicate that polymerization reactions leading to mixed species, containing Ge-C bonds, are favored. Eopt values around 3.5 eV have been found in most of the cases, and are correlated with C sp3-bonding configuration. The B1/2 value, related to the order degree, has been found to be dependent on solid composition, atoms distribution in the material and hydrogenation degree of carbon atoms.

  16. 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.

  17. Feasibility study of the microforming 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 applications. For the further functionalization of these micro devices, high functional surfaces with noble metals and nanomaterials are strongly required in bio- and medical fields, such as bio-sensors. To realize an 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 surfaces of the working material. To demonstrate feasibility of this proposed process, feasibility of SCVD of functional materials onto active surfaces of titanium (Ti was investigated. CVD of iron (Fe and carbon nanotubes (CNTs which construct CNTs on the patterned surfaces of the active Ti and non-active Ti oxidation layers were conducted. Ti thin films on silicon substrate and Fe were used as working materials and functional materials respectively. CNTs were grown only on the Ti surface. Consequently, selectivity of the active surface of Ti to the synthesis of Fe particles in CVD was confirmed.

  18. Growth of a dry spot under a vapor bubble at high heat flux and high pressure

    CERN Document Server

    Nikolayev, Vadim; Lagier, G -L; Hegseth, J

    2016-01-01

    We report a 2D modeling of the thermal diffusion-controlled growth of a vapor bubble attached to a heating surface during saturated boiling. The heat conduction problem is solved in a liquid that surrounds a bubble with a free boundary and in a semi-infinite solid heater by the boundary element method. At high system pressure the bubble is assumed to grow slowly, its shape being defined by the surface tension and the vapor recoil force, a force coming from the liquid evaporating into the bubble. It is shown that at some typical time the dry spot under the bubble begins to grow rapidly under the action of the vapor recoil. Such a bubble can eventually spread into a vapor film that can separate the liquid from the heater thus triggering the boiling crisis (critical heat flux).

  19. Preparation of high-pressure phase boron nitride films by physical vapor deposition

    CERN Document Server

    Zhu, P W; Zhao, Y N; Li, D M; Liu, H W; Zou Guang Tian

    2002-01-01

    The high-pressure phases boron nitride films together with cubic, wurtzic, and explosive high-pressure phases, were successfully deposited on the metal alloy substrates by tuned substrate radio frequency magnetron sputtering. The percentage of cubic boron nitride phase in the film was about 50% as calculated by Fourier transform infrared measurements. Infrared peak position of cubic boron nitride at 1006.3 cm sup - sup 1 , which is close to the stressless state, indicates that the film has very low internal stress. Transition electron microscope micrograph shows that pure cubic boron nitride phase exits on the surface of the film. The growth mechanism of the BN films was also discussed.

  20. Ni–Mo and Co–Mo alloy nanoparticles for catalytic chemical vapor deposition synthesis of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Lobiak, E.V., E-mail: lobiakev@niic.sbras.ru [Nikolaev Institute of Inorganic Chemistry, SB RAS, 3 Acad. Lavrentiev Ave., 630090 Novosibirsk (Russian Federation); Shlyakhova, E.V.; Bulusheva, L.G.; Plyusnin, P.E.; Shubin, Yu.V.; Okotrub, A.V. [Nikolaev Institute of Inorganic Chemistry, SB RAS, 3 Acad. Lavrentiev Ave., 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090 (Russian Federation)

    2015-02-05

    Highlights: • Thermal decomposition of the ε-Keggin-type polyoxomolybdate clusters Mo{sub 12}O{sub 28}(μ{sub 2}-OH){sub 12}{Ni(H_2O)_3}{sub 4} and Mo{sub 12}O{sub 28}(μ{sub 2}-OH){sub 12}{Co(H_2O)_3}{sub 4} produces NiMoO{sub 4} and CoMoO{sub 4} phases. • The NiMoO{sub 4} and CoMoO{sub 4} phases are converted in alloys with a metal ratio of 1:1. • The Ni–Mo and Co–Mo alloy nanoparticles catalyze a CCVD growth of carbon nanotubes. - Abstract: Here, we show for the first time a catalytic chemical vapor deposition (CCVD) synthesis of carbon nanotubes (CNTs) using polyoxomolybdate clusters Mo{sub 12}O{sub 28}(μ{sub 2}-OH){sub 12}{Ni(H_2O)_3}{sub 4} and Mo{sub 12}O{sub 28}(μ{sub 2}-OH){sub 12}{Co(H_2O)_3}{sub 4} as a source of catalyst nanoparticles. X-ray diffraction analyses indicated that the products of thermal decomposition of the clusters contain NiMoO{sub 4} and CoMoO{sub 4} phases, which are converted into Ni–Mo and Co–Mo alloys at 900 °C in hydrogen environment. High-resolution transmission electron microscopy in combination with energy-dispersive X-ray spectroscopy confirmed the CNT growth from bimetallic nanoparticles. Synergism between two metals in an alloy resulted in large-scale production of non-bundled few-walled CNTs with narrow diameter distribution and high quality.