WorldWideScience

Sample records for forced chemical vapor

  1. Chemical vapor composites (CVC)

    International Nuclear Information System (INIS)

    Reagan, P.

    1993-01-01

    The Chemical Vapor Composite, CVC trademark , process fabricates composite material by simply mixing particles (powders and or fibers) with CVD reactants which are transported and co-deposited on a hot substrate. A key feature of the CVC process is the control provided by varing the density, geometry (aspect ratio) and composition of the entrained particles in the matrix material, during deposition. The process can fabricate composite components to net shape (± 0.013 mm) on a machined substrate in a single step. The microstructure of the deposit is described and several examples of different types of particles in the matrix are illustrated. Mechanical properties of SiC composite material fabricated with SiC powder and fiber will be presented. Several examples of low cost ceramic composite products will be shown. (orig.)

  2. Classification Characteristics of Carbon Nanotube Polymer Composite Chemical Vapor Detectors

    National Research Council Canada - National Science Library

    Hinshaw, Huynh A

    2006-01-01

    .... This is accomplished by the detection and identification of chemical agents. The Air Force has several instruments to detect chemical vapors, but is always looking for lighter, faster, and more accurate technology for a better capability...

  3. Microwave assisted chemical vapor infiltration

    International Nuclear Information System (INIS)

    Devlin, D.J.; Currier, R.P.; Barbero, R.S.; Espinoza, B.F.; Elliott, N.

    1991-01-01

    A microwave assisted process for production of continuous fiber reinforced ceramic matrix composites is described. A simple apparatus combining a chemical vapor infiltration reactor with a conventional 700 W multimode oven is described. Microwave induced inverted thermal gradients are exploited with the ultimate goal of reducing processing times on complex shapes. Thermal gradients in stacks of SiC (Nicalon) cloths have been measured using optical thermometry. Initial results on the ''inside out'' deposition of SiC via decomposition of methyltrichlorosilane in hydrogen are presented. Several key processing issues are identified and discussed. 5 refs

  4. Overview of chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Besmann, T.M.; Stinton, D.P.; Lowden, R.A.

    1993-06-01

    Chemical vapor infiltration (CVI) is developing into a commercially important method for the fabrication of continuous filament ceramic composites. Current efforts are focused on the development of an improved understanding of the various processes in CVI and its modeling. New approaches to CVI are being explored, including pressure pulse infiltration and microwave heating. Material development is also proceeding with emphasis on improving the oxidation resistance of the interfacial layer between the fiber and matrix. This paper briefly reviews these subjects, indicating the current state of the science and technology.

  5. Thermal plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Heberlein, J.; Pfender, E.

    1993-01-01

    Thermal plasmas, with temperatures up to and even exceeding 10 4 K, are capable of producing high density vapor phase precursors for the deposition of relatively thick films. Although this technology is still in its infancy, it will fill the void between the relatively slow deposition processes such as physical vapor deposition and the high rate thermal spray deposition processes. In this chapter, the present state-of-the-art of this field is reviewed with emphasis on the various types of reactors proposed for this emerging technology. Only applications which attracted particular attention, namely diamond and high T c superconducting film deposition, are discussed in greater detail. (orig.)

  6. DuPont Chemical Vapor Technical Report

    International Nuclear Information System (INIS)

    MOORE, T.L.

    2003-01-01

    DuPont Safety Resources was tasked with reviewing the current chemical vapor control practices and providing preventive recommendations on best commercial techniques to control worker exposures. The increased focus of the tank closure project to meet the 2024 Tri-Party Agreement (TPA) milestones has surfaced concerns among some CH2MHill employees and other interested parties. CH2MHill is committed to providing a safe working environment for employees and desires to safely manage the tank farm operations using appropriate control measures. To address worker concerns, CH2MHill has chartered a ''Chemical Vapors Project'' to integrate the activities of multiple CH2MHill project teams, and solicit the expertise of external resources, including an independent Industrial Hygiene expert panel, a communications consultant, and DuPont Safety Resources. Over a three-month time period, DuPont worked with CH2MHill ESH and Q, Industrial Hygiene, Engineering, and the independent expert panel to perform the assessment. The process included overview presentations, formal interviews, informal discussions, documentation review, and literature review. DuPont Safety Resources concluded that it is highly unlikely that workers in the tank farms are exposed to chemicals above established standards. Additionally, the conventional and radiological chemistry is understood, the inherent chemical hazards are known, and the risk associated with chemical vapor exposure is properly managed. The assessment highlighted management's commitment to addressing chemical vapor hazards and controlling the associated risks. Additionally, we found the Industrial Hygiene staff to be technically competent and well motivated. The tank characterization data resides in a comprehensive database containing the tank chemical compositions and relevant airborne concentrations

  7. Ceramic composites by chemical vapor infiltration

    International Nuclear Information System (INIS)

    Stinton, D.P.

    1987-01-01

    Composites consisting of silicon carbide matrices reinforced with continuous ceramic fibers are being developed for high-temperature structural applications. Chemical vapor deposition (CVD) techniques are very effective in fabricating composites with high strengths and exceptional fracture toughness. Mechanical properties of infiltrated composites are controlled by the strength of the interfacial bond between the fibers and matrix. This paper describes two CVD techniques and reviews the models being developed to better understand and control the infiltration process

  8. Advances in modeling of chemical vapor infiltration for tube fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Starr, T.L. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Technology

    1998-04-01

    The forced flow/thermal gradient chemical vapor infiltration process (FCVI) can be used for fabrication of tube-shaped components of ceramic matrix composites. Recent experimental work at Oak Ridge National Laboratory (ORNL) includes process and materials development studies using a small tube reactor. Use of FCVI for this geometry involves significant changes in fixturing as compared to disk-shaped preforms previously fabricated. The authors have used their computer model of the CVI process to simulate tube densification and to identify process modifications that will decrease processing time. This report presents recent model developments and applications.

  9. 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.

  10. Characterization of tin dioxide film for chemical vapors sensor

    International Nuclear Information System (INIS)

    Hafaiedh, I.; Helali, S.; Cherif, K.; Abdelghani, A.; Tournier, G.

    2008-01-01

    Recently, oxide semiconductor material used as transducer has been the central topic of many studies for gas sensor. In this paper we investigated the characteristic of a thick film of tin dioxide (SnO 2 ) film for chemical vapor sensor. It has been prepared by screen-printing technology and deposited on alumina substrate provided with two gold electrodes. The morphology, the molecular composition and the electrical properties of this material have been characterized respectively by Atomic Force Spectroscopy (AFM), Fourier Transformed Infrared Spectroscopy (FTIR) and Impedance Spectroscopy (IS). The electrical properties showed a resistive behaviour of this material less than 300 deg. C which is the operating temperature of the sensor. The developed sensor can identify the nature of the detected gas, oxidizing or reducing

  11. Anisotropic Friction of Wrinkled Graphene Grown by Chemical Vapor Deposition.

    Science.gov (United States)

    Long, Fei; Yasaei, Poya; Yao, Wentao; Salehi-Khojin, Amin; Shahbazian-Yassar, Reza

    2017-06-21

    Wrinkle structures are commonly seen on graphene grown by the chemical vapor deposition (CVD) method due to the different thermal expansion coefficient between graphene and its substrate. Despite the intensive investigations focusing on the electrical properties, the nanotribological properties of wrinkles and the influence of wrinkle structures on the wrinkle-free graphene remain less understood. Here, we report the observation of anisotropic nanoscale frictional characteristics depending on the orientation of wrinkles in CVD-grown graphene. Using friction force microscopy, we found that the coefficient of friction perpendicular to the wrinkle direction was ∼194% compare to that of the parallel direction. Our systematic investigation shows that the ripples and "puckering" mechanism, which dominates the friction of exfoliated graphene, plays even a more significant role in the friction of wrinkled graphene grown by CVD. The anisotropic friction of wrinkled graphene suggests a new way to tune the graphene friction property by nano/microstructure engineering such as introducing wrinkles.

  12. HANFORD CHEMICAL VAPORS WORKER CONCERNS and EXPOSURE EVALUATION

    International Nuclear Information System (INIS)

    ANDERSON, T.J.

    2006-01-01

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

  13. Understanding the chemical vapor deposition of diamond: recent progress

    International Nuclear Information System (INIS)

    Butler, J E; Mankelevich, Y A; Cheesman, A; Ma, Jie; Ashfold, M N R

    2009-01-01

    In this paper we review and provide an overview to the understanding of the chemical vapor deposition (CVD) of diamond materials with a particular focus on the commonly used microwave plasma-activated chemical vapor deposition (MPCVD). The major topics covered are experimental measurements in situ to diamond CVD reactors, and MPCVD in particular, coupled with models of the gas phase chemical and plasma kinetics to provide insight into the distribution of critical chemical species throughout the reactor, followed by a discussion of the surface chemical process involved in diamond growth.

  14. Synthesis of chiral polyaniline films via chemical vapor phase polymerization

    DEFF Research Database (Denmark)

    Chen, J.; Winther-Jensen, B.; Pornputtkul, Y.

    2006-01-01

    Electrically and optically active polyaniline films doped with (1)-(-)-10- camphorsulfonic acid were successfully deposited on nonconductive substrates via chemical vapor phase polymerization. The above polyaniline/ R- camphorsulfonate films were characterized by electrochemical and physical...

  15. 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...

  16. The chemical vapor deposition of zirconium carbide onto ceramic substrates

    International Nuclear Information System (INIS)

    Glass A, John Jr.; Palmisiano, Nick Jr.; Welsh R, Edward

    1999-01-01

    Zirconium carbide is an attractive ceramic material due to its unique properties such as high melting point, good thermal conductivity, and chemical resistance. The controlled preparation of zirconium carbide films of superstoichiometric, stoichiometric, and substoichiometric compositions has been achieved utilizing zirconium tetrachloride and methane precursor gases in an atmospheric pressure high temperature chemical vapor deposition system

  17. 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.

  18. 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.

  19. Growth of graphene underlayers by chemical vapor deposition

    International Nuclear Information System (INIS)

    Fabiane, Mopeli; Khamlich, Saleh; Bello, Abdulhakeem; Dangbegnon, Julien; Momodu, Damilola; Manyala, Ncholu; Charlie Johnson, A. T.

    2013-01-01

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

  20. SAW Sensors for Chemical Vapors and Gases.

    Science.gov (United States)

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

    2017-04-08

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

  1. SAW Sensors for Chemical Vapors and Gases

    Science.gov (United States)

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

    2017-01-01

    Surface acoustic wave (SAW) technology provides a sensitive platform for sensing chemicals in gaseous and fluidic states with the inherent advantages of passive and wireless operation. In this review, we provide a general overview on the fundamental aspects and some major advances of Rayleigh wave-based SAW sensors in sensing chemicals in a gaseous phase. In particular, we review the progress in general understanding of the SAW chemical sensing mechanism, optimization of the sensor characteristics, and the development of the sensors operational at different conditions. Based on previous publications, we suggest some appropriate sensing approaches for particular applications and identify new opportunities and needs for additional research in this area moving into the future. PMID:28397760

  2. Chemical vapor deposition: A technique for applying protective coatings

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, T.C. Sr.; Bowman, M.G.

    1979-01-01

    Chemical vapor deposition is discussed as a technique for applying coatings for materials protection in energy systems. The fundamentals of the process are emphasized in order to establish a basis for understanding the relative advantages and limitations of the technique. Several examples of the successful application of CVD coating are described. 31 refs., and 18 figs.

  3. Laser-induced chemical vapor deposition reactions

    International Nuclear Information System (INIS)

    Teslenko, V.V.

    1990-01-01

    The results of investigation of chemical reactions of deposition of different substances from the gas phase when using the energy of pulse quasicontinuous and continuous radiation of lasers in the wave length interval from 0.193 to 10.6 μm are generalized. Main attetion is paid to deposition of inorganic substances including nonmetals (C, Si, Ge and others), metals (Cu, Au, Zn, Cd, Al, Cr, Mo, W, Ni) and some simple compounds. Experimental data on the effect of laser radiation parameters and reagent nature (hydrides, halogenides, carbonyls, alkyl organometallic compounds and others) on the deposition rate and deposit composition are described in detail. Specific features of laser-chemical reactions of deposition and prospects of their application are considered

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

    Science.gov (United States)

    Terasawa, Tomo-o.; Saiki, Koichiro

    2015-03-01

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

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

    Science.gov (United States)

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

    2017-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-10-01

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

  7. Fabrication and evaluation of chemically vapor deposited tungsten heat pipe.

    Science.gov (United States)

    Bacigalupi, R. J.

    1972-01-01

    A network of lithium-filled tungsten heat pipes is being considered as a method of heat extraction from high temperature nuclear reactors. The need for material purity and shape versatility in these applications dictates the use of chemically vapor deposited (CVD) tungsten. Adaptability of CVD tungsten to complex heat pipe designs is shown. Deposition and welding techniques are described. Operation of two lithium-filled CVD tungsten heat pipes above 1800 K is discussed.

  8. Gas analysis during the chemical vapor deposition of carbon

    International Nuclear Information System (INIS)

    Lieberman, M.L.; Noles, G.T.

    1973-01-01

    Gas chromatographic analyses were performed during the chemical vapor deposition of carbon in both isothermal and thermal gradient systems. Such data offer insight into the gas phase processes which occur during deposition and the interrelations which exist between gas composition, deposition rate, and resultant structure of the deposit. The results support a carbon CVD model presented previously. The application of chromatographic analysis to research, development, and full-scale facilities is shown. (U.S.)

  9. 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.

  10. Low frequency temperature forcing of chemical oscillations.

    Science.gov (United States)

    Novak, Jan; Thompson, Barnaby W; Wilson, Mark C T; Taylor, Annette F; Britton, Melanie M

    2011-07-14

    The low frequency forcing of chemical oscillations by temperature is investigated experimentally in the Belousov-Zhabotinsky (BZ) reaction and in simulations of the Oregonator model with Arrhenius temperature dependence of the rate constants. Forcing with temperature leads to modulation of the chemical frequency. The number of response cycles per forcing cycle is given by the ratio of the natural frequency to the forcing frequency and phase locking is only observed in simulations when this ratio is a whole number and the forcing amplitude is small. The global temperature forcing of flow-distributed oscillations in a tubular reactor is also investigated and synchronisation is observed in the variation of band position with the external signal, reflecting the periodic modulation of chemical oscillations by temperature.

  11. Direct measurements of intermolecular forces by chemical force microscopy

    Science.gov (United States)

    Vezenov, Dmitri Vitalievich

    1999-12-01

    Detailed description of intermolecular forces is key to understanding a wide range of phenomena from molecular recognition to materials failure. The unique features of atomic force microscopy (AFM) to make point contact force measurements with ultra high sensitivity and to generate spatial maps of surface topography and forces have been extended to include measurements between well-defined organic molecular groups. Chemical modification of AFM probes with self-assembled monolayers (SAMs) was used to make them sensitive to specific molecular interactions. This novel chemical force microscopy (CFM) technique was used to probe forces between different molecular groups in a range of environments (vacuum, organic liquids and aqueous solutions); measure surface energetics on a nanometer scale; determine pK values of the surface acid and base groups; measure forces to stretch and unbind a short synthetic DNA duplex and map the spatial distribution of specific functional groups and their ionization state. Studies of adhesion forces demonstrated the important contribution of hydrogen bonding to interactions between simple organic functionalities. The chemical identity of the tip and substrate surfaces as well as the medium had a dramatic effect on adhesion between model monolayers. A direct correlation between surface free energy and adhesion forces was established. The adhesion between epoxy polymer and model mixed SAMs varied with the amount of hydrogen bonding component in the monolayers. A consistent interpretation of CFM measurements in polar solvents was provided by contact mechanics models and intermolecular force components theory. Forces between tips and surfaces functionalized with SAMs terminating in acid or base groups depended on their ionization state. A novel method of force titration was introduced for highly local characterization of the pK's of surface functional groups. The pH-dependent changes in friction forces were exploited to map spatially the

  12. Molecular restrictions for human eye irritation by chemical vapors

    International Nuclear Information System (INIS)

    Cometto-Muniz, J. Enrique; Cain, William S.; Abraham, Michael H.

    2005-01-01

    Previous research showed a cut-off along homologous volatile organic compounds (VOCs) in their ability to produce acute human mucosal irritation. The present study sought to specify the particular cut-off homolog for sensory eye irritation in an acetate and n-alcohol series. A 1900-ml glass vessel system and a three-alternative forced-choice procedure served to test nonyl, decyl, and dodecyl acetate, and 1-nonanol, 1-decanol, and 1-undecanol. Flowrate to the eye ranged from 2 to 8 L/min and time of exposure from 3 to 24 s. Decyl acetate and 1-undecanol were the shortest homologs that failed to produce eye irritation under all conditions, producing a cut-off effect. Increasing the vapor concentration of decyl acetate and 1-undecanol by 3 and 8 times, respectively, via heating them to 37 deg C made either or both VOCs detectable to only half of the 12 subjects tested, even though the higher vapor concentration was well above a predicted eye irritation threshold. When eye irritation thresholds for homologous acetates and n-alcohols were plotted as a function of the longest unfolded length of the molecule, the values for decyl acetate and 1-undecanol fell within a restricted range of 18 to 19 A. The outcome suggests that the basis for the cut-off is biological, that is, the molecule lacks a key size or structure to trigger transduction, rather than physical, that is, the vapor concentration is too low to precipitate detection

  13. Chemical vapor deposition of refractory metals and ceramics III

    International Nuclear Information System (INIS)

    Gallois, B.M.; Lee, W.Y.; Pickering, M.A.

    1995-01-01

    The papers contained in this volume were originally presented at Symposium K on Chemical Vapor Deposition of Refractory Metals and Ceramics III, held at the Fall Meeting of the Materials Research Society in Boston, Massachusetts, on November 28--30, 1994. This symposium was sponsored by Morton International Inc., Advanced Materials, and by The Department of Energy-Oak Ridge National Laboratory. The purpose of this symposium was to exchange scientific information on the chemical vapor deposition (CVD) of metallic and ceramic materials. CVD technology is receiving much interest in the scientific community, in particular, to synthesize new materials with tailored chemical composition and physical properties that offer multiple functionality. Multiphase or multilayered films, functionally graded materials (FGMs), ''smart'' material structures and nanocomposites are some examples of new classes of materials being produced via CVD. As rapid progress is being made in many interdisciplinary research areas, this symposium is intended to provide a forum for reporting new scientific results and addressing technological issues relevant to CVD materials and processes. Thirty four papers have been processed separately for inclusion on the data base

  14. 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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-12-01

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

  16. Kinetics of chemical vapor deposition of boron on molybdenum

    International Nuclear Information System (INIS)

    Tanaka, W.; Nakaanishi, N.; Kato, E.

    1987-01-01

    Experimental rate data of chemical vapor deposition of boron by reduction of boron trichloride with hydrogen are analyzed to determine the reaction mechanism. The reaction orders with respect to the partial pressures of hydrogen and boron trichloride are one half and one third, respectively. It has been found that the outer layer of a deposited film is Mo/sub 2/B/sub 5/ and the inner layer is MoB by the use of X-ray diffraction and EPMA line analysis

  17. Chemical vapor deposition of yttria stabilized zirconia in porous substrates

    International Nuclear Information System (INIS)

    Carolan, M.F.; Michaels, J.N.

    1987-01-01

    Electrochemical vapor deposition (EVD) of yttria stabilized zirconia (YSZ) is the preferred route to the production of thin films of YSZ on porous substrates. This process has been used in the construction of both fuel cells and steam electrolyzers. A critical aspect of the EVD process is an initial chemical vapor deposition phase in which the pores of a porous substrate are plugged by YSZ. In this process, water vapor and a mixture of gaseous zirconium chloride and yttrium chloride diffuse into the porous substrate from opposite sides and react to form YSZ and HCl ga. During the second stage of the process a continuous dense film of electrolyte is formed by a tarnishing-type process. Experimentally it is observed that the pores plug within a few pore diameters of the metal chloride face of the substrate. A kinetic rate expression that is first order in metal chloride but zero order in water is best able to explain this phenomenon. With this rate expression, the pores always plug near the metal chloride face. The model predicts less pore narrowing to occur as the ratio of the reaction rate to the diffusion rate of the metal chloride is increased. A kinetic rate expression that is first order in both water and metal chloride predicts that the pores plug much deeper in the substrate

  18. Chemical driving force for rafting in superalloys

    CSIR Research Space (South Africa)

    Nabarro, FRN

    1997-08-15

    Full Text Available The author provides a brief overview of the chemical driving forces for rafting in superalloys. Until recently, all theories of the driving force for rafting have considered the compositions of the two phases to be fixed, although accepting...

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

    International Nuclear Information System (INIS)

    Kumar, A.; Voevodin, A.A.; Paul, R.; Altfeder, I.; Zemlyanov, D.; Zakharov, D.N.; Fisher, T.S.

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, A., E-mail: kumar50@purdue.edu [Birck Nanotechnolgy Center, Purdue University, West Lafayette, IN 47907 (United States); Voevodin, A.A. [Birck Nanotechnolgy Center, Purdue University, West Lafayette, IN 47907 (United States); Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, OH 45433 (United States); Paul, R. [Birck Nanotechnolgy Center, Purdue University, West Lafayette, IN 47907 (United States); Altfeder, I. [Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, OH 45433 (United States); Zemlyanov, D.; Zakharov, D.N. [Birck Nanotechnolgy Center, Purdue University, West Lafayette, IN 47907 (United States); Fisher, T.S., E-mail: tsfisher@purdue.edu [Birck Nanotechnolgy Center, Purdue University, West Lafayette, IN 47907 (United States); Materials and Manufacturing Directorate, Air Force Research Laboratory, WPAFB, OH 45433 (United States)

    2013-01-01

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

  1. Stress evaluation of chemical vapor deposited silicon dioxide films

    International Nuclear Information System (INIS)

    Maeda, Masahiko; Itsumi, Manabu

    2002-01-01

    Film stress of chemical vapor deposited silicon dioxide films was evaluated. All of the deposited films show tensile intrinsic stresses. Oxygen partial pressure dependence of the intrinsic stress is very close to that of deposition rate. The intrinsic stress increases with increasing the deposition rate under the same deposition temperature, and decreases with increasing substrate temperature. Electron spin resonance (ESR) active defects in the films were observed when the films were deposited at 380 deg. C and 450 deg. C. The ESR signal intensity decreases drastically with increasing deposition temperature. The intrinsic stress correlates very closely to the intensity of the ESR-active defects, that is, the films with larger intrinsic stress have larger ESR-active defects. It is considered that the intrinsic stress was generated because the voids caused by local bond disorder were formed during random network formation among the SiO 4 tetrahedra. This local bond disorder also causes the ESR-active defects

  2. Measurement of gas transport properties for chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-12-01

    In the chemical vapor infiltration (CVI) process for fabricating ceramic matrix composites (CMCs), transport of gas phase reactant into the fiber preform is a critical step. The transport can be driven by pressure or by concentration. This report describes methods for measuring this for CVI preforms and partially infiltrated composites. Results are presented for Nicalon fiber cloth layup preforms and composites, Nextel fiber braid preforms and composites, and a Nicalon fiber 3-D weave composite. The results are consistent with a percolating network model for gas transport in CVI preforms and composites. This model predicts inherent variability in local pore characteristics and transport properties, and therefore, in local densification during processing; this may lead to production of gastight composites.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-05-01

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

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

    International Nuclear Information System (INIS)

    Shin Jinhong; Waheed, Abdul; Winkenwerder, Wyatt A.; Kim, Hyun-Woo; Agapiou, Kyriacos; Jones, Richard A.; Hwang, Gyeong S.; Ekerdt, John G.

    2007-01-01

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

  5. Chemical vapor deposition of TiB2 on graphite

    International Nuclear Information System (INIS)

    Pierson, H.O.; Randich, E.; Mattox, D.M.

    1978-01-01

    This study is an experimental investigation of the coating of graphite with TiB 2 by chemical vapor deposition (CVD) using the hydrogen reduction of BCl 3 and TiCl 4 at 925 0 C and 1 atm. Reasonable matching of the thermal expansion of TiB 2 and graphite was necessary to eliminate cracking. A suitable graphite was POCO DFP-1. Adhesion was improved by having a slightly rough graphite surface. Heat treatment at 2000 0 C and above resulted in a certain degree of diffusion. No melting or solid phases other than TiB 2 and graphite were detected up to 2400 0 C. The coatings showed no failure when repeatedly submitted to an electron beam pulse of 2 KW/cm 2 for 0.8 sec

  6. 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.

  7. Mass transport measurements and modeling for chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-12-01

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

  8. Kinetics of chemical vapor deposition of boron on molybdenum

    International Nuclear Information System (INIS)

    Tanaka, H.; Nakanishi, N.; Kato, E.

    1987-01-01

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

  9. Preparation of hafnium carbide by chemical vapor deposition

    International Nuclear Information System (INIS)

    Hertz, Dominique.

    1974-01-01

    Hard, adhesive coatings of single-phase hafnium carbide were obtained by chemical vapor reaction in an atmosphere containing hafnium tetrachloride, methane and a large excess of hydrogen. By varying the gas phase composition and temperature the zones of formation of the different solid phases were studied and the growth of elementary hafnium and carbon deposits evaluated separately. The results show that the mechanism of hafnium carbide deposition does not hardly involve phenomene of homogeneous-phase methane decomposition or tetrachloride reduction by hydrogen unless the atmosphere is very rich or very poor in methane with respect to tetrachloride. However, hydrogen acting inversely on these two reactions, affects the stoichiometry of the substance deposited. The methane decomposition reaction is fairly slow, the reaction leading to hafnium carbide deposition is faster and that of tetrachloride reduction by hydrogen is quite fast [fr

  10. New luminescence lines in nanodiamonds obtained by chemical vapor deposition

    Science.gov (United States)

    Golubev, V. G.; Grudinkin, S. A.; Davydov, V. Yu.; Smirnov, A. N.; Feoktistov, N. A.

    2017-12-01

    The spectral characteristics of the photoluminescence lines detected for nanodiamonds obtained by the reactive ion etching of diamond particles in oxygen plasma, deposited by chemical vapor deposition on a silicon substrate, are studied. At room temperature, narrow lines are observed in the visible and infrared spectral regions, with a full width at half-maximum in the range of 1-2 nm at an almost complete absence of a broadband photoluminescence background signal. At decreasing temperature, the lines narrowed to 0.2-0.6 nm at T = 79 K, and the minimum line width was 0.055 nm at T = 10 K. With increasing temperature, the narrow lines shifted to the long-wavelength region of the spectrum, and their intensity decreased.

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

    International Nuclear Information System (INIS)

    Ramirez V, M. L.; Rios M, C.; Ramirez O, J.; Davila R, J. I.; Mireles G, F.

    2015-09-01

    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)

  12. Capillary-discharge-based portable detector for chemical vapor monitoring

    International Nuclear Information System (INIS)

    Duan Yixiang; Su Yongxuan; Jin Zhe

    2003-01-01

    Conventional portable instruments for sensing chemical vapors have certain limitations for on-site use. In this article, we develop a genuinely portable detector that is sensitive, powerful, rugged, of simple design, and with very low power needs. Such a detector is based on a dry-cell battery-powered, capillary-discharge-based, microplasma source with optical emission detection. The microscale plasma source has very special features such as low thermal temperature and very low power needs. These features make it possible for the plasma source to be powered with a small dry-cell battery. A specially designed discharge chamber with minielectrodes can be configured to enhance the plasma stability and the system performance. A very small amount of inert gas can be used as sample carrier and plasma supporting gas. Inert gases possess high excitation potentials and produce high-energy metastable particles in the plasma. These particles provide sufficient energy to excite chemical species through Penning ionization and/or energy transfer from metastable species. A molecular emission spectrum can be collected with a palm-sized spectrometer through a collimated optical fiber. The spectrum can be displayed on a notebook computer. With this design and arrangement, the new detector provides high sensitivity for organic chemical species. The advantages and features of the newly developed detector include high sensitivity, simple structure, low cost, universal response, very low power consumption, compact volume with field portable capability, and ease of operation

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

    Science.gov (United States)

    Li, Jing; Lu, Yijiang

    2005-01-01

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

  14. Correlation of chemical evaporation rate with vapor pressure.

    Science.gov (United States)

    Mackay, Donald; van Wesenbeeck, Ian

    2014-09-02

    A new one-parameter correlation is developed for the evaporation rate (ER) of chemicals as a function of molar mass (M) and vapor pressure (P) that is simpler than existing correlations. It applies only to liquid surfaces that are unaffected by the underlying solid substrate as occurs in the standard ASTM evaporation rate test and to quiescent liquid pools. The relationship has a sounder theoretical basis than previous correlations because ER is correctly correlated with PM rather than P alone. The inclusion of M increases the slope of previous log ER versus log P regressions to a value close to 1.0 and yields a simpler one-parameter correlation, namely, ER (μg m(-1) h(-1)) = 1464P (Pa) × M (g mol(-1)). Applications are discussed for the screening level assessment and ranking of chemicals for evaporation rate, such as pesticides, fumigants, and hydrocarbon carrier fluids used in pesticide formulations, liquid consumer products used indoors, and accidental spills of liquids. The mechanistic significance of the single parameter as a mass-transfer coefficient or velocity is discussed.

  15. Advanced deposition model for thermal activated chemical vapor deposition

    Science.gov (United States)

    Cai, Dang

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

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

    Science.gov (United States)

    Nallon, Eric C.

    An electronic nose (e-nose) is a biologically inspired device designed to mimic the operation of the olfactory system. The e-nose utilizes a chemical sensor array consisting of broadly responsive vapor sensors, whose combined response produces a unique pattern for a given compound or mixture. The sensor array is inspired by the biological function of the receptor neurons found in the human olfactory system, which are inherently cross-reactive and respond to many different compounds. The use of an e-nose is an attractive approach to predict unknown odors and is used in many fields for quantitative and qualitative analysis. If properly designed, an e-nose has the potential to adapt to new odors it was not originally designed for through laboratory training and algorithm updates. This would eliminate the lengthy and costly R&D costs associated with materiel and product development. Although e-nose technology has been around for over two decades, much research is still being undertaken in order to find new and more diverse types of sensors. Graphene is a single-layer, 2D material comprised of carbon atoms arranged in a hexagonal lattice, with extraordinary electrical, mechanical, thermal and optical properties due to its 2D, sp2-bonded structure. Graphene has much potential as a chemical sensing material due to its 2D structure, which provides a surface entirely exposed to its surrounding environment. In this configuration, every carbon atom in graphene is a surface atom, providing the greatest possible surface area per unit volume, so that electron transport is highly sensitive to adsorbed molecular species. Graphene has gained much attention since its discovery in 2004, but has not been realized in many commercial electronics. It has the potential to be a revolutionary material for use in chemical sensors due to its excellent conductivity, large surface area, low noise, and versatile surface for functionalization. In this work, graphene is incorporated into a

  17. Chemically vapor deposited coatings for multibarrier containment of nuclear wastes

    International Nuclear Information System (INIS)

    Rusin, J.M.; Shade, J.W.; Kidd, R.W.; Browning, M.F.

    1981-01-01

    Chemical vapor deposition (CVD) was selected as a feasible method to coat ceramic cores, since the technology has previously been demonstrated for high-temperature gas-cooled reactor (HTGR) fuel particles. CVD coatings, including SiC, PyC (pyrolytic carbon), SiO 2 , and Al 2 O 3 were studied. This paper will discuss the development and characterization of PyC and Al 2 O 3 CVD coatings on supercalcine cores. Coatings were applied to 2 mm particles in either fluidized or vibrating beds. The PyC coating was deposited in a fluidized bed with ZrO 2 diluent from C 2 H 2 at temperatures between 1100 and 1200 0 C. The Al 2 O 3 coatings were deposited in a vibrated bed by a two-stage process to minimize loss of PyC during the overcoating operation. This process involved applying 10 μm of Al 2 O 3 using water vapor hydrolysis of AlCl 3 and then switching to the more surface-controlled hydrolysis via the H 2 + CO 2 reaction (3CO 2 + 3H 2 + 2AlCl 3 = Al 2 O 3 + 6HCl + 3CO). Typically, 50 to 80 μm Al 2 O 3 coatings were applied over 30 to 40 μm PyC coatings. The coatings were evaluated by metallographic examination, PyC oxidation tests, and leach resistance. After air oxidation for 100 hours at 750 0 C, the duplex PyC/Al 2 O 3 coated particles exhibited a weight loss of 0.01 percent. Leach resistance is being determined for temperatures from 50 to 150 0 C in various solutions. Typical results are given for selected ions. The leach resistance of supercalcine cores is significantly improved by the application of PyC and/or Al 2 O 3 coatings

  18. Ballistic transport in graphene grown by chemical vapor deposition

    International Nuclear Information System (INIS)

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

    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 ballistically directed by a magnetic field (transverse magnetic focussing) over length scales of ∼1 μm. Comparison with atomic force microscope measurements suggests a correlation between the absence of wrinkles and the presence of ballistic transport in CVD graphene

  19. 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.

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    Katsuyuki Okada

    2007-01-01

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

  2. Intelligent process control of fiber chemical vapor deposition

    Science.gov (United States)

    Jones, John Gregory

    Chemical Vapor Deposition (CVD) is a widely used process for the application of thin films. In this case, CVD is being used to apply a thin film interface coating to single crystal monofilament sapphire (Alsb2Osb3) fibers for use in Ceramic Matrix Composites (CMC's). The hot-wall reactor operates at near atmospheric pressure which is maintained using a venturi pump system. Inert gas seals obviate the need for a sealed system. A liquid precursor delivery system has been implemented to provide precise stoichiometry control. Neural networks have been implemented to create real-time process description models trained using data generated based on a Navier-Stokes finite difference model of the process. Automation of the process to include full computer control and data logging capability is also presented. In situ sensors including a quadrupole mass spectrometer, thermocouples, laser scanner, and Raman spectrometer have been implemented to determine the gas phase reactants and coating quality. A fuzzy logic controller has been developed to regulate either the gas phase or the in situ temperature of the reactor using oxygen flow rate as an actuator. Scanning electron microscope (SEM) images of various samples are shown. A hierarchical control structure upon which the control structure is based is also presented.

  3. 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.

  4. Patterned growth of carbon nanotubes obtained by high density plasma chemical vapor deposition

    Science.gov (United States)

    Mousinho, A. P.; Mansano, R. D.

    2015-03-01

    Patterned growth of carbon nanotubes by chemical vapor deposition represents an assembly approach to place and orient nanotubes at a stage as early as when they are synthesized. In this work, the carbon nanotubes were obtained at room temperature by High Density Plasmas Chemical Vapor Deposition (HDPCVD) system. This CVD system uses a new concept of plasma generation, where a planar coil coupled to an RF system for plasma generation was used with an electrostatic shield for plasma densification. In this mode, high density plasmas are obtained. We also report the patterned growth of carbon nanotubes on full 4-in Si wafers, using pure methane plasmas and iron as precursor material (seed). Photolithography processes were used to pattern the regions on the silicon wafers. The carbon nanotubes were characterized by micro-Raman spectroscopy, the spectra showed very single-walled carbon nanotubes axial vibration modes around 1590 cm-1 and radial breathing modes (RBM) around 120-400 cm-1, confirming that high quality of the carbon nanotubes obtained in this work. The carbon nanotubes were analyzed by atomic force microscopy and scanning electron microscopy too. The results showed that is possible obtain high-aligned carbon nanotubes with patterned growth on a silicon wafer with high reproducibility and control.

  5. An ionic force-field study of monomers, dimers and higher polymers in pentafluoride vapors

    Energy Technology Data Exchange (ETDEWEB)

    Cicek Onem, Z. [Department of Physics, Istanbul University, Istanbul (Turkey); Akdeniz, Z. [Department of Physics, Istanbul University, Istanbul (Turkey); Classe di Scienze, Scuola Normale Superiore, I-56126 Pisa (Italy)], E-mail: zakdeniz@istanbul.edu.tr; Tosi, M.P. [Classe di Scienze, Scuola Normale Superiore, I-56126 Pisa (Italy)], E-mail: tosim@sns.it

    2008-08-01

    Pentafluoride compounds such as NbF{sub 5} and TaF{sub 5} have been reported in the literature to admit various states of polymerization coexisting with monomers in their vapor phase, in relative concentrations that vary with temperature and pressure. We construct a microscopic interionic force-field model for the molecular monomer of these compounds (including VF{sub 5}, SbF{sub 5} and MoF{sub 5} in addition to NbF{sub 5} and TaF{sub 5}), the stable form of the monomer being in the shape of a D{sub 3h} trigonal bipyramid in all cases. The model emulates chemical bonds by allowing for electrical and short-range overlap polarizabilities of the fluorines, and is used to evaluate the structure and the stability of (MF{sub 5}){sub n} molecules with n running from 2 to 6. The dimer is formed by two distorted edge-sharing octahedral, while the trimer and the higher polymers can form rings of distorted corner-sharing octahedra. A chain-like configuration is also found for the trimer of NbF{sub 5}, which consists of a seven-fold coordinated Nb bonded to two distorted octahedra via edge sharing. Comparison of calculated vibrational frequencies and bond lengths with experimental data is made whenever possible. We find that there is a small net gain of energy in the formation of a dimer, while otherwise the static energy of the n-mer is very close to that of n separated monomers. High sensitivity of the state of molecular aggregation to the thermodynamic conditions of the vapor is clearly indicated by our calculations.

  6. Boiling crisis as inhibition of bubble detachment by the vapor recoil force

    International Nuclear Information System (INIS)

    Nikolayev, V.S.; Beysens, D.; Garrabos, Y.

    2004-01-01

    Boiling crisis is a transition between nucleate and film boiling. In this communication we present a physical model of the boiling crisis based on the vapor recoil effect. Our numerical simulations of the thermally controlled bubble growth at high heat fluxes show how the bubble begins to spread over the heater thus forming a germ for the vapor film. The vapor recoil force not only causes the vapor spreading, it also creates a strong adhesion to the heater that prevents the bubble departure, thus favoring the further bubble spreading. Near the liquid-gas critical point, the bubble growth is very slow and allows the kinetics of the bubble spreading to be observed. Since the surface tension is very small in this regime, only microgravity conditions can preserve a convex bubble shape. Under such conditions, we observed an increase of the apparent contact angle and spreading of the dry spot under the bubble, thus confirming our model of the boiling crisis. (authors)

  7. Chemical vapor deposition of Si/SiC nano-multilayer thin films

    International Nuclear Information System (INIS)

    Weber, A.; Remfort, R.; Woehrl, N.; Assenmacher, W.; Schulz, S.

    2015-01-01

    Stoichiometric SiC films were deposited with the commercially available single source precursor Et_3SiH by classical thermal chemical vapor deposition (CVD) as well as plasma-enhanced CVD at low temperatures in the absence of any other reactive gases. Temperature-variable deposition studies revealed that polycrystalline films containing different SiC polytypes with a Si to carbon ratio of close to 1:1 are formed at 1000 °C in thermal CVD process and below 100 °C in the plasma-enhanced CVD process. The plasma enhanced CVD process enables the reduction of residual stress in the deposited films and offers the deposition on temperature sensitive substrates in the future. In both deposition processes the film thickness can be controlled by variation of the process parameters such as the substrate temperature and the deposition time. The resulting material films were characterized with respect to their chemical composition and their crystallinity using scanning electron microscope, energy dispersive X-ray spectroscopy (XRD), atomic force microscopy, X-ray diffraction, grazing incidence X-ray diffraction, secondary ion mass spectrometry and Raman spectroscopy. Finally, Si/SiC multilayers of up to 10 individual layers of equal thickness (about 450 nm) were deposited at 1000 °C using Et_3SiH and SiH_4. The resulting multilayers features amorphous SiC films alternating with Si films, which feature larger crystals up to 300 nm size as measured by transmission electron microscopy as well as by XRD. XRD features three distinct peaks for Si(111), Si(220) and Si(311). - Highlights: • Stoichiometric silicon carbide films were deposited from a single source precursor. • Thermal as well as plasma-enhanced chemical vapor deposition was used. • Films morphology, crystallinity and chemical composition were characterized. • Silicon/silicon carbide multilayers of up to 10 individual nano-layers were deposited.

  8. Chemical Vapor-Deposited (CVD) Diamond Films for Electronic Applications

    Science.gov (United States)

    1995-01-01

    Diamond films have a variety of useful applications as electron emitters in devices such as magnetrons, electron multipliers, displays, and sensors. Secondary electron emission is the effect in which electrons are emitted from the near surface of a material because of energetic incident electrons. The total secondary yield coefficient, which is the ratio of the number of secondary electrons to the number of incident electrons, generally ranges from 2 to 4 for most materials used in such applications. It was discovered recently at the NASA Lewis Research Center that chemical vapor-deposited (CVD) diamond films have very high secondary electron yields, particularly when they are coated with thin layers of CsI. For CsI-coated diamond films, the total secondary yield coefficient can exceed 60. In addition, diamond films exhibit field emission at fields orders of magnitude lower than for existing state-of-the-art emitters. Present state-of-the-art microfabricated field emitters generally require applied fields above 5x10^7 V/cm. Research on field emission from CVD diamond and high-pressure, high-temperature diamond has shown that field emission can be obtained at fields as low as 2x10^4 V/cm. It has also been shown that thin layers of metals, such as gold, and of alkali halides, such as CsI, can significantly increase field emission and stability. Emitters with nanometer-scale lithography will be able to obtain high-current densities with voltages on the order of only 10 to 15 V.

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

    International Nuclear Information System (INIS)

    Schaefer, Lothar; Hoefer, Markus; Kroeger, Roland

    2006-01-01

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

  10. Single crystal diamond detectors grown by chemical vapor deposition

    International Nuclear Information System (INIS)

    Tuve, C.; Angelone, M.; Bellini, V.; Balducci, A.; Donato, M.G.; Faggio, G.; Marinelli, M.; Messina, G.; Milani, E.; Morgada, M.E.; Pillon, M.; Potenza, R.; Pucella, G.; Russo, G.; Santangelo, S.; Scoccia, M.; Sutera, C.; Tucciarone, A.; Verona-Rinati, G.

    2007-01-01

    The detection properties of heteropitaxial (polycrystalline, pCVD) and homoepitaxial (single crystal, scCVD) diamond films grown by microwave chemical vapor deposition (CVD) in the Laboratories of Roma 'Tor Vergata' University are reported. The pCVD diamond detectors were tested with α-particles from different sources and 12 C ions produced by 15MV Tandem accelerator at Southern National Laboratories (LNS) in Catania (Italy). pCVDs were also used to monitor 14MeV neutrons produced by the D-T plasma at Joint European Torus (JET), Culham, U.K. The limit of pCVDs is the poor energy resolution. To overcome this problem, we developed scCVD diamonds using the same reactor parameters that optimized pCVD diamonds. scCVD were grown on a low cost (100) HPHT single crystal substrate. A detector 110μm thick was tested under α-particles and under 14MeV neutron irradiation. The charge collection efficiency spectrum measured under irradiation with a triple α-particle source shows three clearly resolved peaks, with an energy resolution of about 1.1%. The measured spectra under neutron irradiation show a well separated C(n,α 0 ) 9 Be12 reaction peak with an energy spread of 0.5MeV for 14.8MeV neutrons and 0.3MeV for 14.1MeV neutrons, which are fully compatible with the energy spread of the incident neutron beams

  11. 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.

  12. Polycrystalline AlN films with preferential orientation by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Sanchez, G.; Wu, A.; Tristant, P.; Tixier, C.; Soulestin, B.; Desmaison, J.; Bologna Alles, A.

    2008-01-01

    AlN thin films for acoustic wave devices were prepared by Microwave Plasma Enhanced Chemical Vapor Deposition under different process conditions, employing Si (100) and Pt (111)/SiO 2 /Si (100) substrates. The films were characterized by X-ray diffraction, Fourier transform infrared transmission spectroscopy, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy. The values of the distance between the plasma and the tri-methyl-aluminum precursor injector, the radiofrequency bias potential, and the substrate temperature were central in the development of polycrystalline films. The choice of the chamber total pressure during deposition allowed for the development of two different crystallographic orientations, i.e., or . The film microstructures exhibited in general a column-like growth with rounded tops, an average grain size of about 40 nm, and a surface roughness lower than 20 nm under the best conditions

  13. 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...

  14. Chemical vapor deposition based tungsten disulfide (WS2) thin film transistor

    KAUST Repository

    Hussain, Aftab M.; Sevilla, Galo T.; Rader, Kelly; Hussain, Muhammad Mustafa

    2013-01-01

    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

  15. Continuous, Highly Flexible, and Transparent Graphene Films by Chemical Vapor Deposition for Organic Photovoltaics

    KAUST Repository

    Gomez De Arco, Lewis; Zhang, Yi; Schlenker, Cody W.; Ryu, Koungmin; Thompson, Mark E.; Zhou, Chongwu

    2010-01-01

    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

  16. Rapid Thermal Chemical Vapor Deposition for Dual-Gated Sub-100 nm MOSFET's

    National Research Council Canada - National Science Library

    Sturm, James

    2001-01-01

    ... (such as microprocessors and memory chips) is based. This project examines the scaling of MOSFET's to very small channel dimensions using a vertical structure which is defined by Rapid Thermal Chemical Vapor Deposition...

  17. Remote plasma-enhanced metalorganic chemical vapor deposition of aluminum oxide thin films

    NARCIS (Netherlands)

    Volintiru, I.; Creatore, M.; Hemmen, van J.L.; Sanden, van de M.C.M.

    2008-01-01

    Aluminum oxide films were deposited using remote plasma-enhanced metalorganic chemical vapor deposition from oxygen/trimethylaluminum mixtures. Initial studies by in situ spectroscopic ellipsometry demonstrated that the aluminum oxide films deposited at temperatures

  18. Surface chemical reactions probed with scanning force microscopy

    NARCIS (Netherlands)

    Werts, M.P L; van der Vegte, E.W.; Hadziioannou, G

    1997-01-01

    In this letter we report the study of surface chemical reactions with scanning force microscopy (SFM) with chemical specificity. Using chemically modified SFM probes, we can determine the local surface reaction conversion during a chemical surface modification. The adhesion forces between a

  19. Chemically assisted release of transition metals in graphite vaporizers for atomic spectrometry

    International Nuclear Information System (INIS)

    Katskov, Dmitri; Darangwa, Nicholas; Grotti, Marco

    2006-01-01

    decomposition of metal oxide, is the most probable source of chemical energy, which facilitates the vaporization. Intensity of the process depends on chemical properties of the sample and substrate and efficiency of mass and heat transfer by the protective gas. The discussed mechanism of chemically assisted vapor release signifies the energy exchange between all participants of the vaporization process in ET AAS including the matrix, modifier, purge gas and analyte. The finding contributes in the ET AAS theory regarding the mechanisms of vaporization and mass transfer in the presence of matrix and modifiers

  20. 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

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

    International Nuclear Information System (INIS)

    Karamat, S.; Sonuşen, S.; Çelik, Ü.; Uysallı, Y.; Oral, A.

    2016-01-01

    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)_2. Ba(OH)_2 is not advisable because of the residues left on the graphene surface which would further trapped in between graphene and SiO_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)_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_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)_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

  2. Metalorganic chemical vapor deposition of gallium nitride on sacrificial substrates

    Science.gov (United States)

    Fenwick, William Edward

    GaN-based light emitting diodes (LEDs) face several challenges if the technology is to continue to make a significant impact in general illumination, and on technology that has become known as solid state lighting (SSL). Two of the most pressing challenges for the continued penetration of SSL into traditional lighting applications are efficacy and total lumens from the device, and their related cost. The development of alternative substrate technologies is a promising avenue toward addressing both of these challenges, as both GaN-based device technology and the associated metalorganic chemical vapor deposition (MOCVD) technology are already relatively mature technologies with a well-understood cost base. Zinc oxide (ZnO) and silicon (Si) are among the most promising alternative substrates for GaN epitaxy. These substrates offer the ability to access both higher efficacy and lumen devices (ZnO) at a much reduced cost. This work focuses on the development of MOCVD growth processes to yield high quality GaN-based materials and devices on both ZnO and Si. ZnO is a promising substrate for growth of low defect-density GaN because of its similar lattice constant and thermal expansion coefficient. The major hurdles for GaN growth on ZnO are the instability of the substrate in a hydrogen atmosphere, which is typical of nitride growth conditions, and the inter-diffusion of zinc and oxygen from the substrate into the GaN-based epitaxial layer. A process was developed for the MOCVD growth of GaN and InxGa 1-xN on ZnO that attempted to address these issues. The structural and optical properties of these films were studied using various techniques. X-ray diffraction (XRD) showed the growth of wurtzite GaN on ZnO, and room-temperature photoluminescence (RT-PL) showed near band-edge luminescence from the GaN and InxGa1-xN layers. However, high zinc and oxygen concentrations due to interdiffusion near the ZnO substrate remained an issue; therefore, the diffusion of zinc and oxygen

  3. Chemical Vapor Detection with a Multispectral Thermal Imager

    National Research Council Canada - National Science Library

    Althouse, Mark L. G; Chang, Chein-I

    1991-01-01

    .... Real-time autonomous detection and alarm is also required. A detection system model by Warren, based on a Gaussian vapor concentration distribution is the basis for detection algorithms. Algorithms recursive in both time and spectral frequency have been derived using Kalman filter theory. Adaptive filtering is used for preprocessing clutter rejection. Various components of the detection system have been tested individually and an integrated system is now being fabricated.

  4. Chemical Vapor Transport Deposition of Molybdenum Disulfide Layers Using H2O Vapor as the Transport Agent

    Directory of Open Access Journals (Sweden)

    Shichao Zhao

    2018-02-01

    Full Text Available Molybdenum disulfide (MoS2 layers show excellent optical and electrical properties and have many potential applications. However, the growth of high-quality MoS2 layers is a major bottleneck in the development of MoS2-based devices. In this paper, we report a chemical vapor transport deposition method to investigate the growth behavior of monolayer/multi-layer MoS2 using water (H2O as the transport agent. It was shown that the introduction of H2O vapor promoted the growth of MoS2 by increasing the nucleation density and continuous monolayer growth. Moreover, the growth mechanism is discussed.

  5. Study on stability of a-SiCOF films deposited by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Ding Shijin; Zhang Qingquan; Wang Pengfei; Zhang Wei; Wang Jitao

    2001-01-01

    Low-dielectric-constant a-SiCOF films have been prepared from TEOS, C 4 F 8 and Ar by using plasma enhanced chemical vapor deposition method. With the aid of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), the chemical bonding configuration, thermal stability and resistance to water of the films are explored

  6. 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…

  7. Industrialization of hot wire chemical vapor deposition for thin film applications

    NARCIS (Netherlands)

    Schropp, Ruud

    2015-01-01

    The consequences of implementing a Hot Wire Chemical Vapor Deposition (HWCVD) chamber into an existing in-line or roll-to-roll reactor are described. The hardware and operation of the HWCVD production reactor is compared to that of existing roll-to-roll reactors based on Plasma Enhanced Chemical

  8. Synthesis of Monolayer MoS2 by Chemical Vapor Deposition

    Science.gov (United States)

    Withanage, Sajeevi; Lopez, Mike; Dumas, Kenneth; Jung, Yeonwoong; Khondaker, Saiful

    Finite and layer-tunable band gap of transition metal dichalcogenides (TMDs) including molybdenum disulfide (MoS2) are highlighted over the zero band gap graphene in various semiconductor applications. Weak interlayer Van der Waal bonding of bulk MoS2 allows to cleave few to single layer MoS2 using top-down methods such as mechanical and chemical exfoliation, however few micron size of these flakes limit MoS2 applications to fundamental research. Bottom-up approaches including the sulfurization of molybdenum (Mo) thin films and co-evaporation of Mo and sulfur precursors received the attention due to their potential to synthesize large area. We synthesized monolayer MoS2 on Si/SiO2 substrates by atmospheric pressure Chemical Vapor Deposition (CVD) methods using sulfur and molybdenum trioxide (MoO3) as precursors. Several growth conditions were tested including precursor amounts, growth temperature, growth time and flow rate. Raman, photoluminescence (PL) and atomic force microscopy (AFM) confirmed monolayer islands merging to create large area were observed with grain sizes up to 70 μm without using any seeds or seeding promoters. These studies provide in-depth knowledge to synthesize high quality large area MoS2 for prospective electronics applications.

  9. Catalyst Design Using Nanoporous Iron for the Chemical Vapor Deposition Synthesis of Single-Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Tarek M. Abdel-Fattah

    2013-01-01

    Full Text Available Single-walled carbon nanotubes (SWNTs have been synthesized via a novel chemical vapor deposition (CVD approach utilizing nanoporous, iron-supported catalysts. Stable aqueous dispersions of the CVD-grown nanotubes using an anionic surfactant were also obtained. The properties of the as-produced SWNTs were characterized through atomic force microscopy and Raman spectroscopy and compared with purified SWNTs produced via the high-pressure CO (HiPCO method as a reference, and the nanotubes were observed with greater lengths than those of similarly processed HiPCO SWNTs.

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

    International Nuclear Information System (INIS)

    Beshkov, G.; Krastev, V.; Gogova, D.; Talik, E.; Adamies, M.

    2008-01-01

    In this paper the bonding state of Phosphorus Silicate Glass (PSG) layers obtained by two different technological approaches, i.e. in two types of reactors: Plasma Enhanced Chemical Vapor Deposition (PECVD) and Micro Pressure Chemical Vapor Deposition (MPCVD) are investigated employing XPS and AES. The PSG layers are deposited at 380 0 C and 420 0 C in corresponding reactors. XPS and AES analyses show that Si2p peak recorded from PECVD layers are not as expected at their position characteristics of silicon dioxide but instead they are at the characteristic of elemental silicon. Plasma enhancement during deposition leads to less oxidized and more inhomogeneous layer. After rapid thermal annealing the Si2p peak is situated at position characteristic of silicon dioxide. (authors)

  11. Turkish Air Force's Experiences in Chemical Material Acquisition

    National Research Council Canada - National Science Library

    Taskiran, Huseyin

    2002-01-01

    .... In addition, it analyzes the chemical material acquisition from business perspective. Due to operating in different environments, the Turkish Air Force and the private sector have different objectives in the acquisition of chemical materials...

  12. Chemical Equilibrium as Balance of the Thermodynamic Forces

    OpenAIRE

    Zilbergleyt, B.

    2004-01-01

    The article sets forth comprehensive basics of thermodynamics of chemical equilibrium as balance of the thermodynamic forces. Based on the linear equations of irreversible thermodynamics, De Donder definition of the thermodynamic force, and Le Chatelier's principle, new thermodynamics of chemical equilibrium offers an explicit account for multiple chemical interactions within the system. Basic relations between energetic characteristics of chemical transformations and reaction extents are bas...

  13. Fabrication of Cf/SiC composite by chemical vapor infiltration

    International Nuclear Information System (INIS)

    Park, Ji Yeon; Kim, Weon Ju

    2003-07-01

    This technical report reviewed the fabrication process of fiber reinforced ceramic composites, characteristics of the chemical vapor infiltration process, and applications for C f /SiC composite to develop a carbon fiber reinforced silicon carbide composite. Infiltration process was performed by the chemical vapor infiltration process using methyltrichlorosilane and hydrogen gas as a source and a diluent, respectively. Infiltration behavior, phase analysis, microstructure observation were carried out. Parameter study results of C f /SiC composite fabricated with some variables such as reaction pressure, reaction temperature, input gas ratio and preform thickness were described

  14. Radiation stable, hybrid, chemical vapor infiltration/preceramic polymer joining of silicon carbide components

    Energy Technology Data Exchange (ETDEWEB)

    Khalifa, Hesham E., E-mail: hesham.khalifa@ga.com [General Atomics, 3550 General Atomics Ct., San Diego 92121, CA (United States); Koyanagi, Takaaki [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge 37831, TN (United States); Jacobsen, George M.; Deck, Christian P.; Back, Christina A. [General Atomics, 3550 General Atomics Ct., San Diego 92121, CA (United States)

    2017-04-15

    This paper reports on a nuclear-grade joining material for bonding of silicon carbide-based components. The joint material is fabricated via a hybrid preceramic polymer, chemical vapor infiltration process. The joint is comprised entirely of β-SiC and results in excellent mechanical and permeability performance. The joint strength, composition, and microstructure have been characterized before and after irradiation to 4.5 dpa at 730 °C in the High Flux Isotope Reactor. The hybrid preceramic polymer-chemical vapor infiltrated joint exhibited complete retention of shear strength and no evidence of microstructural evolution or damage was detected following irradiation.

  15. Thermodynamic properties for applications in chemical industry via classical force fields.

    Science.gov (United States)

    Guevara-Carrion, Gabriela; Hasse, Hans; Vrabec, Jadran

    2012-01-01

    Thermodynamic properties of fluids are of key importance for the chemical industry. Presently, the fluid property models used in process design and optimization are mostly equations of state or G (E) models, which are parameterized using experimental data. Molecular modeling and simulation based on classical force fields is a promising alternative route, which in many cases reasonably complements the well established methods. This chapter gives an introduction to the state-of-the-art in this field regarding molecular models, simulation methods, and tools. Attention is given to the way modeling and simulation on the scale of molecular force fields interact with other scales, which is mainly by parameter inheritance. Parameters for molecular force fields are determined both bottom-up from quantum chemistry and top-down from experimental data. Commonly used functional forms for describing the intra- and intermolecular interactions are presented. Several approaches for ab initio to empirical force field parameterization are discussed. Some transferable force field families, which are frequently used in chemical engineering applications, are described. Furthermore, some examples of force fields that were parameterized for specific molecules are given. Molecular dynamics and Monte Carlo methods for the calculation of transport properties and vapor-liquid equilibria are introduced. Two case studies are presented. First, using liquid ammonia as an example, the capabilities of semi-empirical force fields, parameterized on the basis of quantum chemical information and experimental data, are discussed with respect to thermodynamic properties that are relevant for the chemical industry. Second, the ability of molecular simulation methods to describe accurately vapor-liquid equilibrium properties of binary mixtures containing CO(2) is shown.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-02

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

  17. 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.

  18. Diamond-like carbon films deposited on polycarbonates by plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Guo, C.T. [Department of Computer and Communication, Diwan College of Management, 72141 Taiwan (China)], E-mail: ctguo@dwu.edu.tw

    2008-04-30

    Diamond-like carbon films were coated on optical polycarbonate using plasma-enhanced chemical vapor deposition. A mixture of SiH{sub 4} and CH{sub 4}/H{sub 2} gases was utilized to reduce the internal compressive stress of the deposited films. The structure of the DLC films was characterized as a function of film thickness using Raman spectroscopy. The dependence of G peak positions and the intensity ratio of I{sub D}/I{sub G} on the DLC film thicknesses was analyzed in detail. Other studies involving atomic force microscopy, ultraviolet visible spectrometry, and three adhesion tests were conducted. Good transparency in the visible region, and good adhesion between diamond-like carbon films and polycarbonate were demonstrated. One-time recordings before and after a DLC film was coated on compact rewritable disc substrates were analyzed as a case study. The results reveal that the diamond-like carbon film overcoating the optical polycarbonates effectively protects the storage media.

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

    Energy Technology Data Exchange (ETDEWEB)

    Tiggelaar, R.M. [Mesoscale Chemical Systems, MESA" + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Thakur, D.B.; Nair, H.; Lefferts, L.; Seshan, K. [Catalytic Processes and Materials, MESA" + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Gardeniers, J.G.E., E-mail: j.g.e.gardeniers@utwente.nl [Mesoscale Chemical Systems, MESA" + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2013-05-01

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Santra, T S; Liu, C H [Institute of Nanoengineering and Microsystems (NEMS), National Tsing Hua University, Hsinchu, Taiwan 30043 (China); Bhattacharyya, T K [Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721302, West Bengal (India); Patel, P [Department of Electrical and Computer Engineering, University of Illinois at Urbana Champaign, Urbana, Illinois 61801 (United States); Barik, T K [School of Applied Sciences, Haldia Institute of Technology, Haldia 721657, Purba Medinipur, West Bengal (India)

    2010-06-15

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

  2. Vertically aligned carbon nanotube growth by pulsed laser deposition and thermal chemical vapor deposition methods

    International Nuclear Information System (INIS)

    Sohn, Jung Inn; Nam, Chunghee; Lee, Seonghoon

    2002-01-01

    We have grown vertically aligned carbon nanotubes on the various substrates such as a planar p-type Si(1 0 0) wafer, porous Si wafer, SiO 2 , Si 3 N 4 , Al 2 O 3 , and Cr by thermal chemical vapor deposition (CVD) at 800 deg.C, using C 2 H 2 gas as a carbon source and Fe catalyst films deposited by a pulsed laser on the substrates. The Fe films were deposited for 5 min by pulsed laser deposition (PLD). The advantage of Fe deposition by PLD over other deposition methods lies in the superior adhesion of Fe to a Si substrate due to high kinetic energies of the generated Fe species. Scanning electron microscopy (SEM) images show that vertically well-aligned carbon nanotubes are grown on Fe nanoparticles formed from the thermal annealing of the Fe film deposited by PLD on the various substrates. Atomic force microscopy (AFM) images show that the Fe film annealed at 800 deg.C is broken to Fe nanoparticles of 10-50 nm in size. We show that the appropriate density of Fe nanoparticles formed from the thermal annealing of the film deposited by PLD is crucial in growing vertically aligned carbon nanotubes. Using a PLD and a lift-off method, we developed the selective growth of carbon nanotubes on a patterned Fe-coated Si substrate

  3. Plasma effects in aligned carbon nanoflake growth by plasma-enhanced 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); Zheng, K. [Institute of Microstructure and Properties of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Cheng, Q.J., E-mail: qijin.cheng@xmu.edu.cn [School of Energy Research, Xiamen University, Xiamen 361005 (China); Ostrikov, K. [Plasma Nanoscience Center Australia (PNCA), Manufacturing Flagship, Commonwealth Scientific and Industrial Research Organization, PO Box 218, Lindfield 2070, NSW (Australia); Institute for Future Environments and School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane 4000, QLD (Australia); Plasma Nanoscience, School of Physics, The University of Sydney, Sydney 2006, NSW (Australia)

    2015-01-15

    Highlights: • Plasma-specific effects in the growth of carbon nanoflakes (CNFs) are studied. • Electic field in the plasma sheath promotes separation of CNFs from the substrate. • The orentention of GNFs is related to the combined electic force and growth effects. • The high growth grates of aligned GNFs are plasma-related. - Abstract: Carbon nanofilms are directly grown on silicon substrates by plasma-enhanced hot filament chemical vapor deposition in methane environment. It is shown that the nanofilms are composed of aligned carbon nanoflakes by extensive investigation of experimental results of field emission scanning electron microscopy, micro-Raman spectroscopy and transmission electron microscopy. In comparison with the graphene-like films grown without plasmas, the carbon nanoflakes grow in an alignment mode and the growth rate of the films is increased. The effects of the plasma on the growth of the carbon nanofilms are studied. The plasma plays three main effects of (1) promoting the separation of the carbon nanoflakes from the silicon substrate, (2) accelerating the motion of hydrocarbon radicals, and (3) enhancing the deposition of hydrocarbon ions onto the substrate surface. Due to these plasma-specific effects, the carbon nanofilms can be formed from the aligned carbon nanoflakes with a high rate. These results advance our knowledge on the synthesis, properties and applications of graphene-based materials.

  4. Initiated chemical vapor deposited nanoadhesive for bonding National Ignition Facility's targets

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tom [Univ. of California, Berkeley, CA (United States)

    2016-05-19

    Currently, the target fabrication scientists in National Ignition Facility Directorate at Lawrence Livermore National Laboratory (LLNL) is studying the propagation force resulted from laser impulses impacting a target. To best study this, they would like the adhesive used to glue the target substrates to be as thin as possible. The main objective of this research project is to create adhesive glue bonds for NIF’s targets that are ≤ 1 μm thick. Polyglycidylmethacrylate (PGMA) thin films were coated on various substrates using initiated chemical vapor deposition (iCVD). Film quality studies using white light interferometry reveal that the iCVD PGMA films were smooth. The coated substrates were bonded at 150 °C under vacuum, with low inflow of Nitrogen. Success in bonding most of NIF’s mock targets at thicknesses ≤ 1 μm indicates that our process is feasible in bonding the real targets. Key parameters that are required for successful bonding were concluded from the bonding results. They include inert bonding atmosphere, sufficient contact between the PGMA films, and smooth substrates. Average bond strength of 0.60 MPa was obtained from mechanical shearing tests. The bonding failure mode of the sheared interfaces was observed to be cohesive. Future work on this project will include reattempt to bond silica aerogel to iCVD PGMA coated substrates, stabilize carbon nanotube forests with iCVD PGMA coating, and kinetics study of PGMA thermal crosslinking.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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 12 cm −2 ) together with quite low carrier mobility (∼1350 cm 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.

  6. Reduced chemical warfare agent sorption in polyurethane-painted surfaces via plasma-enhanced chemical vapor deposition of perfluoroalkanes.

    Science.gov (United States)

    Gordon, Wesley O; Peterson, Gregory W; Durke, Erin M

    2015-04-01

    Perfluoralkalation via plasma chemical vapor deposition has been used to improve hydrophobicity of surfaces. We have investigated this technique to improve the resistance of commercial polyurethane coatings to chemicals, such as chemical warfare agents. The reported results indicate the surface treatment minimizes the spread of agent droplets and the sorption of agent into the coating. The improvement in resistance is likely due to reduction of the coating's surface free energy via fluorine incorporation, but may also have contributing effects from surface morphology changes. The data indicates that plasma-based surface modifications may have utility in improving chemical resistance of commercial coatings.

  7. Thermodynamic calculations for chemical vapor deposition of silicon carbide

    International Nuclear Information System (INIS)

    Minato, Kazuo; Fukuda, Kousaku; Ikawa, Katsuichi

    1985-03-01

    The composition of vapor and condensed phases at equilibrium and CVD phase diagrams were calculated for the CH 3 SiCl 3 -H 2 -Ar system using a computer code SOLGASMIX-PV, which is based on the free energy minimization method. These calculations showed that β-SiC, β-SiC+C(s), β-SiC+Si(s), β-SiC+Si(l), Si(s), Si(l), or C(s) would be deposited depending on deposition parameters. In the CH 3 SiCl 3 -Ar system, condensed phase was found to be β-SiC+C(s) or C(s). Comparing the calculated CVD phase diagrams with the experimental results from the literature, β-SiC+C(s) and β-SiC+Si(s) were deposited in the experiments at the high temperature (more than 2000K) and low temperature (less than 1700K) parts of a resion, respectively, where only β-SiC would be deposited in the calculations. These are remakable results to consider the deposition mechanism of silicon carbide. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Watson, A.P.

    2003-07-24

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

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

    Science.gov (United States)

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

    2016-03-01

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

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    InP/InGaP surface quantum dots are interesting materials for optical chemical sensors since they present an intense emission at room temperature, whose intensity changes rapidly and reversibly depending on the composition of the environmental atmosphere. We present here their emission properties by time resolved photoluminescence spectroscopy investigation and we discuss the physico-chemical mechanism behind their sensitivity to the surrounding atmosphere. Photoluminescence transients in inert atmosphere (N 2 ) and in solvent vapours of methanol, chloroform, acetone and water were measured. The presence of vapors of chloroform, acetone and water showed a very weak effect on the transient times, while an increase of up to 15% of the decay time was observed for methanol vapour exposure. On the basis of the vapor molecule nature (polarity, proticity, steric hindrance, etc.) and of the interaction of the vapor molecules with the quantum dots surface a sensing mechanism involving quantum dots non-radiative surface states is proposed. (paper)

  11. 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

  12. Reduced-pressure chemical vapor deposition of boron-doped Si and Ge layers

    International Nuclear Information System (INIS)

    Bogumilowicz, Y.; Hartmann, J.M.

    2014-01-01

    We have studied the in-situ boron (B) doping of germanium (Ge) and silicon (Si) in Reduced Pressure-Chemical Vapor Deposition. Three growth temperatures have been investigated for the B-doping of Ge: 400, 600 and 750 °C at a constant growth pressure of 13300 Pa (i.e. 100 Torr). The B concentration in the Ge:B epilayer increases linearly with the diborane concentration in the gaseous phase. Single-crystalline Ge:B layers with B concentrations in-between 9 ∙ 10 17 and 1 ∙ 10 20 cm −3 were achieved. For the in-situ B doping of Si at 850 °C, two dichlorosilane mass flow ratios (MFR) have been assessed: F[SiH 2 Cl 2 ]/F[H 2 ] = 0.0025 and F[SiH 2 Cl 2 ]/F[H 2 ] = 0.0113 at a growth pressure of 2660 Pa (i.e. 20 Torr). Linear boron incorporation with the diborane concentration in the gas phase has been observed and doping levels in-between 3.5 ∙ 10 17 and 1 ∙ 10 20 cm −3 were achieved. We almost kept the same ratio of B versus Si atoms in the gas phase and in the Si epilayer. By contrast, roughly half of the B atoms present in the gas phase were incorporated in the Ge:B layers irrespective of the growth temperature. X-Ray Diffraction (XRD) allowed us to extract from the angular position of the Ge:B layer diffraction peak the substitutional B concentration. Values close to the B concentrations obtained by 4-probe resistivity measurements were obtained. Ge:B layers were smooth (< 1 m root mean square roughness associated with 20 × 20 μm 2 Atomic Force Microscopy images). Only for high F[B 2 H 6 ]/F[GeH 4 ] MFR (3.2 10 −3 ) did the Ge:B layers became rough; they were however still mono-crystalline (XRD). Above this MFR value, Ge:B layers became polycrystalline. - Highlights: • Boron doping of germanium and silicon in Reduced Pressure-Chemical Vapor Deposition • Linear boron incorporation in Ge:B and Si:B with the diborane flow • Single-crystal Ge:B layers with B concentrations in-between 9 ∙ 10 17 and 1 ∙ 10 20 cm −3 • Single-crystal Si

  13. How deposition parameters control growth dynamics of nc-Si deposited by hot-wire chemical vapor deposition

    International Nuclear Information System (INIS)

    Moutinho, H.R.; To, B.; Jiang, C.-S.; Xu, Y.; Nelson, B.P.; Teplin, C.W.; Jones, K.M.; Perkins, J.; Al-Jassim, M.M.

    2006-01-01

    We studied the growth of silicon films deposited by hot-wire chemical vapor deposition under different values of filament current, substrate temperature, and hydrogen dilution ratio. The physical and electrical properties of the films were studied by Raman spectroscopy, x-ray diffraction, atomic force microscopy, conductive-atomic force microscopy, and transmission electron microscopy. There is an interdependence of the growth parameters, and films grown with different parameters can have similar structures. We discuss why this interdependence occurs and how it influences the properties of the deposited films, as well as the deposition rate. In general, the films have a complex structure, with a mixture of amorphous (220)-oriented crystalline and nanocrystalline phases present in most cases. The amount of each phase can be controlled by the variation of one or more of the growth parameters at a time

  14. Nanoscale leakage current measurements in metal organic chemical vapor deposition crystalline SrTiO3 films

    International Nuclear Information System (INIS)

    Rozier, Y.; Gautier, B.; Hyvert, G.; Descamps, A.; Plossu, C.; Dubourdieu, C.; Ducroquet, F.

    2009-01-01

    The properties of SrTiO 3 thin films, grown by liquid injection metal organic chemical vapor deposition on Si/SiO 2 , using a mixture of precursors, have been investigated at the nanoscale using an Atomic Force Microscope in the so-called Conductive Atomic Force Microscopy mode. Maps of the leakage currents with a nanometric resolution have been obtained on films elaborated at different temperatures and stoichiometries in order to discriminate the role of each parameter on the onset of leakage currents in the resulting layers. It appears that the higher the deposition temperature, the higher the leakage currents of the films. The mapping with a nanometric precision allows to show a heterogeneous behaviour of the surface with leaky grains and insulating boundaries. The study of films elaborated at the same temperature with different compositions supports the assumption that the leakage currents on Ti-rich layers are far higher than on Sr-rich layers

  15. 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.

  16. Low-pressure chemical vapor deposition as a tool for deposition of thin film battery materials

    NARCIS (Netherlands)

    Oudenhoven, J.F.M.; Dongen, van T.; Niessen, R.A.H.; Croon, de M.H.J.M.; Notten, P.H.L.

    2009-01-01

    Low Pressure Chemical Vapor Deposition was utilized for the deposition of LiCoO2 cathode materials for all-solid-state thin-film micro-batteries. To obtain insight in the deposition process, the most important process parameters were optimized for the deposition of crystalline electrode films on

  17. VAPOR SAMPLING DEVICE FOR INTERFACE WITH MICROTOX ASSAY FOR SCREENING TOXIC INDUSTRIAL CHEMICALS

    Science.gov (United States)

    A time-integrated sampling system interfaced with a toxicity-based assay is reported for monitoring volatile toxic industrial chemicals (TICs). Semipermeable membrane devices (SPMDs) using dimethyl sulfoxide (DMSO) as the fill solvent accumulated each of 17 TICs from the vapor...

  18. 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

  19. Metal–organic covalent network chemical vapor deposition for gas separation

    NARCIS (Netherlands)

    Boscher, N.D.; Wang, M.; Perrotta, A.; Heinze, K.; Creatore, A.; Gleason, K.K.

    2016-01-01

    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

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    Metal-catalyst-free chemical vapor deposition (CVD) of large area uniform nanocrystalline graphene on oxidized silicon substrates is demonstrated. The material grows slowly, allowing for thickness control down to monolayer graphene. The as-grown thin films are continuous with no observable pinholes...

  1. Layer-dependent supercapacitance of graphene films grown by chemical vapor deposition on nickel foam

    KAUST Repository

    Chen, Wei; Fan, Zhongli; Zeng, Gaofeng; Lai, Zhiping

    2013-01-01

    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

  2. Plasma-enhanced chemical vapor deposition of aluminum oxide using ultrashort precursor injection pulses

    NARCIS (Netherlands)

    Dingemans, G.; Sanden, van de M.C.M.; Kessels, W.M.M.

    2012-01-01

    An alternative plasma-enhanced chemical vapor deposition (PECVD) method is developed and applied for the deposition of high-quality aluminum oxide (AlOx) films. The PECVD method combines a continuous plasma with ultrashort precursor injection pulses. We demonstrate that the modulation of the

  3. 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

  4. 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

  5. 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

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

    Science.gov (United States)

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

    2011-12-15

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

  7. A kinetic and equilibrium analysis of silicon carbide chemical vapor deposition on monofilaments

    Science.gov (United States)

    Gokoglu, S. A.; Kuczmarski, M. A.

    1993-01-01

    Chemical kinetics of atmospheric pressure silicon carbide (SiC) chemical vapor deposition (CVD) from dilute silane and propane source gases in hydrogen is numerically analyzed in a cylindrical upflow reactor designed for CVD on monofilaments. The chemical composition of the SiC deposit is assessed both from the calculated total fluxes of carbon and silicon and from chemical equilibrium considerations for the prevailing temperatures and species concentrations at and along the filament surface. The effects of gas and surface chemistry on the evolution of major gas phase species are considered in the analysis.

  8. Characterization and electrolytic cleaning of poly(methyl methacrylate) residues on transferred chemical vapor deposited graphene

    Science.gov (United States)

    Sun, Jianbo; Finklea, Harry O.; Liu, Yuxin

    2017-03-01

    Poly(methyl methacrylate) (PMMA) residue has long been a critical challenge for practical applications of the transferred chemical vapor deposited (CVD) graphene. Thermal annealing is empirically used for the removal of the PMMA residue; however experiments imply that there are still small amounts of residues left after thermal annealing which are hard to remove with conventional methods. In this paper, the thermal degradation of the PMMA residue upon annealing was studied by Raman spectroscopy. The study reveals that post-annealing residues are generated by the elimination of methoxycarbonyl side chains in PMMA and are believed to be absorbed on graphene via the π-π interaction between the conjugated unsaturated carbon segments and graphene. The post-annealing residues are difficult to remove by further annealing in a non-oxidative atmosphere due to their thermal and chemical stability. An electrolytic cleaning method was shown to be effective in removing these post-annealing residues while preserving the underlying graphene lattice based on Raman spectroscopy and atomic force microscopy studies. Additionally, a solution-gated field effect transistor was used to study the transport properties of the transferred CVD graphene before thermal annealing, after thermal annealing, and after electrolytic cleaning, respectively. The results show that the carrier mobility was significantly improved, and that the p-doping was reduced by removing PMMA residues and post-annealing residues. These studies provide a more in-depth understanding on the thermal annealing process for the removal of the PMMA residues from transferred CVD graphene and a new approach to remove the post-annealing residues, resulting in a residue-free graphene.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-05

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

  10. 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)

  11. SiC nanofibers grown by high power microwave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Honda, Shin-ichi; Baek, Yang-Gyu; Ikuno, Takashi; Kohara, Hidekazu; Katayama, Mitsuhiro; Oura, Kenjiro; Hirao, Takashi

    2003-01-01

    Silicon carbide (SiC) nanofibers have been synthesized on Si substrates covered by Ni thin films using high power microwave chemical vapor deposition (CVD). Characterization using transmission electron microscopy (TEM) combined with electron energy-dispersive X-ray spectroscopy (EDX) revealed that the resultant fibrous nanostructures were assigned to β-SiC with high crystallinity. The formation of SiC nanofibers can be explained by the vapor liquid solid (VLS) mechanism in which precipitation of SiC occurs from the supersaturated Ni nanoparticle containing Si and C

  12. Relationship between the evaporation rate and vapor pressure of moderately and highly volatile chemicals.

    Science.gov (United States)

    van Wesenbeeck, Ian; Driver, Jeffrey; Ross, John

    2008-04-01

    Volatilization of chemicals can be an important form of dissipation in the environment. Rates of evaporative losses from plant and soil surfaces are useful for estimating the potential for food-related dietary residues and operator and bystander exposure, and can be used as source functions for screening models that predict off-site movement of volatile materials. A regression of evaporation on vapor pressure from three datasets containing 82 pesticidal active ingredients and co-formulants, ranging in vapor pressure from 0.0001 to >30,000 Pa was developed for this purpose with a regression correlation coefficient of 0.98.

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

    International Nuclear Information System (INIS)

    Ndiege, Nicholas; Subramanian, Vaidyanathan; Shannon, Mark A.; Masel, Richard I.

    2008-01-01

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

  14. Alcohol vapor sensing by cadmium-doped zinc oxide thick films based chemical sensor

    Science.gov (United States)

    Zargar, R. A.; Arora, M.; Chackrabarti, S.; Ahmad, S.; Kumar, J.; Hafiz, A. K.

    2016-04-01

    Cadmium-doped zinc oxide nanoparticles were derived by simple chemical co-precipitation route using zinc acetate dihydrate and cadmium acetate dihydrate as precursor materials. The thick films were casted from chemical co-precipitation route prepared nanoparticles by economic facile screen printing method. The structural, morphological, optical and electrical properties of the film were characterized relevant to alcohol vapor sensing application by powder XRD, SEM, UV-VIS and DC conductivity techniques. The response and sensitivity of alcohol (ethanol) vapor sensor are obtained from the recovery curves at optimum working temperature range from 20∘C to 50∘C. The result shows that maximum sensitivity of the sensor is observed at 25∘C operating temperature. On varying alcohol vapor concentration, minor variation in resistance has been observed. The sensing mechanism of sensor has been described in terms of physical adsorption and chemical absorption of alcohol vapors on cadmium-doped zinc oxide film surface and inside film lattice network through weak hydrogen bonding, respectively.

  15. A quantitative infrared spectral library of vapor phase chemicals: applications to environmental monitoring and homeland defense

    Science.gov (United States)

    Sharpe, Steven W.; Johnson, Timothy J.; Sams, Robert L.

    2004-12-01

    The utility of infrared spectroscopy for monitoring and early warning of accidental or deliberate chemical releases to the atmosphere is well documented. Regardless of the monitoring technique (open-path or extractive) or weather the spectrometer is passive or active (Fourier transform or lidar) a high quality, quantitative reference library is essential for meaningful interpretation of the data. Pacific Northwest National Laboratory through the support of the Department of Energy has been building a library of pure, vapor phase chemical species for the last 4 years. This infrared spectral library currently contains over 300 chemicals and is expected to grow to over 400 chemicals before completion. The library spectra are based on a statistical fit to many spectra at different concentrations, allowing for rigorous error analysis. The contents of the library are focused on atmospheric pollutants, naturally occurring chemicals, toxic industrial chemicals and chemicals specifically designed to do damage. Applications, limitations and technical details of the spectral library will be discussed.

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

    Science.gov (United States)

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

    2017-06-01

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

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

    Science.gov (United States)

    Opila, Elizabeth J.

    1994-01-01

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

  18. Stretchable Electronic Sensors of Nanocomposite Network Films for Ultrasensitive Chemical Vapor Sensing.

    Science.gov (United States)

    Yan, Hong; Zhong, Mengjuan; Lv, Ze; Wan, Pengbo

    2017-11-01

    A stretchable, transparent, and body-attachable chemical sensor is assembled from the stretchable nanocomposite network film for ultrasensitive chemical vapor sensing. The stretchable nanocomposite network film is fabricated by in situ preparation of polyaniline/MoS 2 (PANI/MoS 2 ) nanocomposite in MoS 2 suspension and simultaneously nanocomposite deposition onto prestrain elastomeric polydimethylsiloxane substrate. The assembled stretchable electronic sensor demonstrates ultrasensitive sensing performance as low as 50 ppb, robust sensing stability, and reliable stretchability for high-performance chemical vapor sensing. The ultrasensitive sensing performance of the stretchable electronic sensors could be ascribed to the synergistic sensing advantages of MoS 2 and PANI, higher specific surface area, the reliable sensing channels of interconnected network, and the effectively exposed sensing materials. It is expected to hold great promise for assembling various flexible stretchable chemical vapor sensors with ultrasensitive sensing performance, superior sensing stability, reliable stretchability, and robust portability to be potentially integrated into wearable electronics for real-time monitoring of environment safety and human healthcare. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    International Nuclear Information System (INIS)

    Zhao, Yuping; Li, Chengchen; Chen, Mingming; Yu, Xiao; Chang, Yunwei; Chen, Anqi; Zhu, Hai; Tang, Zikang

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-12-09

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

  1. Theoretical Study of Indium Compounds of Interest for Organometallic Chemical Vapor Deposition

    Science.gov (United States)

    Cardelino, B. H.; Moore, C. E.; Cardelino, C. A.; Frazier, D. O.; Backmann, K. J.

    2000-01-01

    The structural. electronic and therinochemical properties of indium compounds which are of interest in halide transport and organometallic chemical vapor deposition processes have been studied by ab initio and statistical mechanics methods. The compounds reported include: indium halides and hydrides (InF, InCl, InCl3, InH, InH2, InH3); indium clusters (In2, In3); methylindium, dimethylindium, and their hydrogen derivatives [In(CH3), In(CH3)H, In(CH3)H2, In(CH3)2, In(CH3)2H]; dimethyl-indium dimer [In2(CH3)4], trimethyl-indium [In(CH3)3]; dehydrogenated methyl, dimethyl and trimethylindium [In(CH3)2CH2, In(CH3)CH2, In(CH2)], trimethylindium adducts with ammonia, trimethylamine and hydrazine [(CH3)3In:NH3, (CH3)3In:N(CH3)3, (CH3)3In:N(H2)N(H2)]; dimethylamino-indium and methylimino-indium [In(CH3)2(NH2), In(CH3)(NH)]; indium nitride and indium nitride dimer (InN, In2N2), indium phosphide, arsenide and antimonide ([InP, InAs, InSb). The predicted electronic properties are based on density functional theory calculations; the calculated thermodynamic properties are reported following the format of the JANAF (Joint Army, Navy, NASA, Air Force) Tables. Equilibrium compositions at two temperatures (298 and 1000 K) have been analyzed for groups of competing simultaneous reactions.

  2. Deposition of controllable preferred orientation silicon films on glass by inductively coupled plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Li Junshuai; Wang Jinxiao; Yin Min; Gao Pingqi; He Deyan; Chen Qiang; Li Yali; Shirai, Hajime

    2008-01-01

    An inductively coupled plasma (ICP) system with the adjustable distance between the inductance coil and substrates was designed to effectively utilize the spatial confinement of ICP discharge, and then control the gas-phase transport process. The effects of the gas phase processes on the crystallinity and preferred orientation of silicon films deposited on glass were systematically investigated. The investigation was conducted in the ICP-chemical vapor deposition process with the precursor gas of a SiH 4 /H 2 mixture at a substrate temperature of 350 deg. Highly crystallized silicon films with different preferred orientations, (111) or (220), could be selectively deposited by adjusting the SiH 4 dilution ratio [R=[SiH 4 ]/([SiH 4 ]+[H 2 ])] or total working pressure. When the total working pressure is 20 Pa, the crystallinity of the silicon films increases with the increase of the SiH 4 dilution ratio, while the preferred orientation was changed from (111) to (220). In the case of the fixed SiH 4 dilution (10%), the silicon film with I (220) /I (111) of about 3.5 and Raman crystalline fraction of about 89.6% has been deposited at 29.7 nm/min when the total working pressure was increased to 40 Pa. At the fixed SiH 4 partial pressure of 2 Pa, the film crystallinity decreases and the preferred orientation is always (111) with increasing the H 2 partial pressure from 18 to 58 Pa. Atomic force microscope reveals that the film deposited at a relatively high H 2 partial pressure has a very rough surface caused by the devastating etching of H atoms to the silicon network

  3. Correlation of the vapor pressure isotope effect with molecular force fields in the liquid state

    International Nuclear Information System (INIS)

    Pollin, J.S.; Ishida, T.

    1976-07-01

    The present work is concerned with the development and application of a new model for condensed phase interactions with which the vapor pressure isotope effect (vpie) may be related to molecular forces and structure. The model considers the condensed phase as being represented by a cluster of regularly arranged molecules consisting of a central molecule and a variable number of molecules in the first coordination shell. The methods of normal coordinate analysis are used to determine the modes of vibration of the condensed phase cluster from which, in turn, the isotopic reduced partition function can be calculated. Using the medium cluster model, the observed vpie for a series of methane isotopes has been successfully reproduced with better agreement with experiment than has been possible using the simple cell model. We conclude, however, that insofar as the medium cluster model provides a reasonable picture of the liquid state, the vpie is not sufficiently sensitive to molecular orientation to permit an experimental determination of intermolecular configuration in the condensed phase through measurement of isotopic pressure ratios. The virtual independence of vapor pressure isotope effects on molecular orientation at large cluster sizes is a demonstration of the general acceptability of the cell model assumptions for vpie calculations

  4. Molecular fouling resistance of zwitterionic and amphiphilic initiated chemically vapor-deposited (iCVD) thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yang, R; Goktekin, E; Wang, MH; Gleason, KK

    2014-08-08

    Biofouling is a universal problem in various applications ranging from water purification to implantable biomedical devices. Recent advances in surface modification have created a rich library of antifouling surface chemistries, many of which can be categorized into one of the two groups: hydrophilic surfaces or amphiphilic surfaces. We report the straightforward preparation of antifouling thin film coatings in both categories via initiated chemical vapor deposition. A molecular force spectroscopy-based method is demonstrated as a rapid and quantitative assessment tool for comparing the differences in antifouling characteristics. The fouling propensity of single molecules, as opposed to bulk protein solution or bacterial culture, is assessed. This method allows for the interrogation of molecular interaction without the complication resulted from protein conformational change or micro-organism group interactions. The molecular interaction follows the same trend as bacterial adhesion results obtained previously, demonstrating that molecular force probe is a valid method for the quantification and mechanistic examination of fouling. In addition, the molecular force spectroscopy-based method is able to distinguish differences in antifouling capability that is not resolvable by traditional static protein adsorption tests. To lend further insight into the intrinsic fouling resistance of zwitterionic and amphiphilic surface chemistries, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, advancing and receding water contact angles, and atomic force microscopy are used to elucidate the film properties that are relevant to their antifouling capabilities.

  5. Process for the preparation of fiber-reinforced ceramic composites by chemical vapor deposition

    Science.gov (United States)

    Lackey, Jr., Walter J.; Caputo, Anthony J.

    1986-01-01

    A chemical vapor deposition (CVD) process for preparing fiber-reinforced ceramic composites. A specially designed apparatus provides a steep thermal gradient across the thickness of a fibrous preform. A flow of gaseous ceramic matrix material is directed into the fibrous preform at the cold surface. The deposition of the matrix occurs progressively from the hot surface of the fibrous preform toward the cold surface. Such deposition prevents the surface of the fibrous preform from becoming plugged. As a result thereof, the flow of reactant matrix gases into the uninfiltrated (undeposited) portion of the fibrous preform occurs throughout the deposition process. The progressive and continuous deposition of ceramic matrix within the fibrous preform provides for a significant reduction in process time over known chemical vapor deposition processes.

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

    DEFF Research Database (Denmark)

    Jiang, Juan; Benter, M.; Taboryski, Rafael Jozef

    2010-01-01

    We report the use of a novel plasma-enhanced chemical vapor deposition chamber with coaxial electrode geometry for the SiOx deposition. This novel plasma setup exploits the diffusion of electrons through the inner most electrode to the interior samples space as the major energy source. This confi......We report the use of a novel plasma-enhanced chemical vapor deposition chamber with coaxial electrode geometry for the SiOx deposition. This novel plasma setup exploits the diffusion of electrons through the inner most electrode to the interior samples space as the major energy source...... 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...

  7. Chemically enhanced mixed region vapor stripping of TCE-contaminated saturated peat and silty clay soils

    International Nuclear Information System (INIS)

    West, O.R.; Cameron, P.A.; Lucero, A.J.; Koran, L.J. Jr.

    1996-01-01

    The objective of this study was to conduct further testing of MRVS, chemically enhanced with calcium oxide conditioning, on field- contaminated soils collected from beneath the NASA Michoud Rinsewater Impoundment. In this study, residual soil VOC levels as a function of vapor stripping time were measured to quantify VOC removal rates. Physical and chemical soil parameters expected to affect MRVS efficiency were measures. The effects of varying the calcium oxide loadings as well as varying the vapor stripping flow rates on VOC removal were also evaluated. The results of this study will be used to determine whether acceptable removals can be achieved within reasonable treatment times, remediation costs being directly proportional to the latter. The purpose of this report is to document the experimental results of this study, as well as to address issues that were raised after completion of the previous Michoud treatability work

  8. Achieving uniform layer deposition by atmospheric-pressure plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae-Ok [Department of Plasma Engineering, Korea Institute of Machinery & Materials (KIMM), Daejeon 305-343 (Korea, Republic of); Kang, Woo Seok, E-mail: kang@kimm.re.kr [Department of Plasma Engineering, Korea Institute of Machinery & Materials (KIMM), Daejeon 305-343 (Korea, Republic of); Department of Environment & Energy Mechanical Engineering, University of Science & Technology (UST), Daejeon 305-350 (Korea, Republic of); Hur, Min; Lee, Jin Young [Department of Plasma Engineering, Korea Institute of Machinery & Materials (KIMM), Daejeon 305-343 (Korea, Republic of); Song, Young-Hoon [Department of Plasma Engineering, Korea Institute of Machinery & Materials (KIMM), Daejeon 305-343 (Korea, Republic of); Department of Environment & Energy Mechanical Engineering, University of Science & Technology (UST), Daejeon 305-350 (Korea, Republic of)

    2015-12-31

    This work investigates the use of plasma-enhanced chemical vapor deposition under atmospheric pressure for achieving uniform layer formation. Electrical and optical measurements demonstrated that the counterbalance between oxygen and precursors maintained the homogeneous discharge mode, while creating intermediate species for layer deposition. Several steps of the deposition process of the layers, which were processed on a stationary stage, were affected by flow stream and precursor depletion. This study showed that by changing the flow streamlines using substrate stage motion uniform layer deposition under atmospheric pressure can be achieved. - Highlights: • Zirconium oxide was deposited by atmospheric-pressure plasma-enhanced chemical vapor deposition. • Homogeneous plasma was maintained by counterbalancing between discharge gas and precursors. • Several deposition steps were observed affected by the gas flow stream and precursor depletion. • Thin film layer was uniformly grown when the substrate underwent a sweeping motion.

  9. 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.

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

    KAUST Repository

    Qaisi, Ramy M.; Smith, Casey; Hussain, Muhammad Mustafa

    2014-01-01

    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.

  11. Complete long-term corrosion protection with chemical vapor deposited graphene

    DEFF Research Database (Denmark)

    Yu, Feng; Camilli, Luca; Wang, Ting

    2018-01-01

    Despite numerous reports regarding the potential of graphene for corrosion protection, examples of chemical vapor deposited (CVD) graphene-based anticorrosive coatings able to provide long-term protection (i.e. several months) of metals have so far been absent. Here, we present a polymer-graphene......Despite numerous reports regarding the potential of graphene for corrosion protection, examples of chemical vapor deposited (CVD) graphene-based anticorrosive coatings able to provide long-term protection (i.e. several months) of metals have so far been absent. Here, we present a polymer......-graphene hybrid coating, comprising two single layers of CVD graphene sandwiched by three layers of polyvinyl butyral, which provides complete corrosion protection of commercial aluminum alloys even after 120 days of exposure to simulated seawater. The essential role played by graphene in the hybrid coating...

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

    International Nuclear Information System (INIS)

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

    2009-01-01

    Diamond was studied as a possible radiation hard technology for use in future high radiation environments. With the commissioning of the LHC expected in 2009, and the LHC upgrades expected in 2013, all LHC experiments are planning for detector upgrades which require radiation hard technologies. Chemical Vapor Deposition (CVD) diamond has now been used extensively in beam conditions monitors as the innermost detectors in the highest radiation areas of BaBar, Belle and CDF and is installed in all LHC experiments. As a result, this material is now being discussed as an alternative sensor material for tracking very close to the interaction region of the super-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.

  13. 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.

  14. Finite Element Analysis Modeling of Chemical Vapor Deposition of Silicon Carbide

    Science.gov (United States)

    2014-06-19

    concentrations. This is the method by which species adsorb to the surface of the substrate. The movement resulting from diffusion is governed by...itself. This can be treacherous, however. The mesh is what the entire finite element method is built upon. If the movement of the backbone has... Brownian Motion Algorithm for Tow Scale Modeling of Chemical Vapor Infiltration. Computational Materials Science, 1871-1878. !178 23. Wang, C. & D

  15. Electronic and Mechanical Properties of GrapheneGermanium Interfaces Grown by Chemical Vapor Deposition

    Science.gov (United States)

    2015-10-27

    that graphene acts as a diffusion barrier to ambient contaminants, as similarly prepared bare Ge exposed to ambient conditions possesses a much...in-plane order underneath the graphene (Figure 1b,f). The stabilization of Ge terraces with half-step heights indicates that the graphene modifies the...Electronic and Mechanical Properties of Graphene −Germanium Interfaces Grown by Chemical Vapor Deposition Brian Kiraly,†,‡ Robert M. Jacobberger

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

    International Nuclear Information System (INIS)

    Brusasco, R.M.

    1989-01-01

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

  17. Direct dry transfer of chemical vapor deposition graphene to polymeric substrates

    OpenAIRE

    Fechine, Guilhermino J. M.; Martin-Fernandez, Inigo; Yiapanis, George; de Oliveira, Ricardo V. Bof; Hu, Xiao; Yarovsky, Irene; Neto, Antonio H. Castro; Ozyilmaz, Barbaros

    2014-01-01

    We demonstrate the direct dry transfer of large area Chemical Vapor Deposition graphene to several polymers (low density polyethylene, high density polyethylene, polystyrene, polylactide acid and poly(vinylidenefluoride-co-trifluoroethylene) by means of only moderate heat and pressure, and the later mechanical peeling of the original graphene substrate. Simulations of the graphene-polymer interactions, rheological tests and graphene transfer at various experimental conditions show that contro...

  18. Chemically vapor-deposited tungsten: its high temperature strength and ductility

    International Nuclear Information System (INIS)

    Bryant, W.A.

    1977-01-01

    The high temperature tensile ductility (as measured by total elongation normal to the growth direction) of chemically vapor-deposited tungsten was found to be significantly greater than previously reported. A correlation was found between ductility and void content. However, voids were found to have essentially no effect on the high temperature strength of this material, which is considerably weaker than powder metallurgy tungsten. (Auth.)

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

    International Nuclear Information System (INIS)

    Poet, Torka S.; Timchalk, Chuck

    2006-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Poet, Torka S.; Timchalk, Chuck

    2006-03-24

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

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

    Science.gov (United States)

    Papadimitropoulos, G; Davazoglou, D

    2011-09-01

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

  2. 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.

  3. 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)

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

    International Nuclear Information System (INIS)

    Hart, John; Hazbun, Ramsey; Eldridge, David; Hickey, Ryan; Fernando, Nalin; Adam, Thomas; Zollner, Stefan; Kolodzey, James

    2016-01-01

    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

  5. Evaluating amber force fields using computed NMR chemical shifts.

    Science.gov (United States)

    Koes, David R; Vries, John K

    2017-10-01

    NMR chemical shifts can be computed from molecular dynamics (MD) simulations using a template matching approach and a library of conformers containing chemical shifts generated from ab initio quantum calculations. This approach has potential utility for evaluating the force fields that underlie these simulations. Imperfections in force fields generate flawed atomic coordinates. Chemical shifts obtained from flawed coordinates have errors that can be traced back to these imperfections. We use this approach to evaluate a series of AMBER force fields that have been refined over the course of two decades (ff94, ff96, ff99SB, ff14SB, ff14ipq, and ff15ipq). For each force field a series of MD simulations are carried out for eight model proteins. The calculated chemical shifts for the 1 H, 15 N, and 13 C a atoms are compared with experimental values. Initial evaluations are based on root mean squared (RMS) errors at the protein level. These results are further refined based on secondary structure and the types of atoms involved in nonbonded interactions. The best chemical shift for identifying force field differences is the shift associated with peptide protons. Examination of the model proteins on a residue by residue basis reveals that force field performance is highly dependent on residue position. Examination of the time course of nonbonded interactions at these sites provides explanations for chemical shift differences at the atomic coordinate level. Results show that the newer ff14ipq and ff15ipq force fields developed with the implicitly polarized charge method perform better than the older force fields. © 2017 Wiley Periodicals, Inc.

  6. Conformal coverage of poly(3,4-ethylenedioxythiophene) films with tunable nanoporosity via oxidative chemical vapor deposition

    NARCIS (Netherlands)

    Im, S.G.; Kusters, D.J.N.; Choi, W.; Baxamusa, S.H.; Sanden, van de M.C.M.; Gleason, K.K.

    2008-01-01

    Novel nanoporous poly(3,4-ethylenedioxythiophene) (PEDOT) films with basalt-like surface morphology are successfully obtained via a one-step, vapor phase process of oxidative chemical vapor deposition (oCVD) by introducing a new oxidant, CuCl2, The substrate temperature of the oCVD process is a

  7. Controlled assembly of organic whispering-gallery-mode microlasers as highly sensitive chemical vapor sensors.

    Science.gov (United States)

    Gao, Miaomiao; Wei, Cong; Lin, Xianqing; Liu, Yuan; Hu, Fengqin; Zhao, Yong Sheng

    2017-03-09

    We demonstrate the fabrication of organic high Q active whispering-gallery-mode (WGM) resonators from π-conjugated polymer by a controlled emulsion-solvent-evaporation method, which can simultaneously provide optical gain and act as an effective resonant cavity. By measuring the shift of their lasing modes on exposure to organic vapor, we successfully monitored the slight concentration variation in the chemical gas. These microlaser sensors demonstrated high detection sensitivity and good signal repeatability under continuous chemical gas treatments. The results offer an effective strategy to design miniaturized optical sensors.

  8. Metalorganic chemical vapor deposition and characterization of ZnO materials

    Science.gov (United States)

    Sun, Shangzu; Tompa, Gary S.; Hoerman, Brent; Look, David C.; Claflin, Bruce B.; Rice, Catherine E.; Masaun, Puneet

    2006-04-01

    Zinc oxide is attracting growing interest for potential applications in electronics, optoelectronics, photonics, and chemical and biochemical sensing, among other applications. We report herein our efforts in the growth and characterization of p- and n-type ZnO materials by metalorganic chemical vapor deposition (MOCVD), focusing on recent nitrogen-doped films grown using diethyl zinc as the zinc precursor and nitric oxide (NO) as the dopant. Characterization results, including resistivity, Hall measurements, photoluminescence, and SIMS, are reported and discussed. Electrical behavior was observed to be dependent on illumination, atmosphere, and heat treatment, especially for p-type material.

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

    International Nuclear Information System (INIS)

    Johnson, Kyle W.; Guruvenket, Srinivasan; Sailer, Robert A.; Ahrenkiel, S. Phillip; Schulz, Douglas L.

    2013-01-01

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

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

    Science.gov (United States)

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

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

    Science.gov (United States)

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

    2009-01-01

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

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

    International Nuclear Information System (INIS)

    Zhang, C.; Man, B.Y.; Jiang, S.Z.; Yang, C.; Liu, M.; Chen, C.S.; Xu, S.C.; Feng, D.J.; Bi, D.; Liu, F.Y.; Qiu, H.W.

    2014-01-01

    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 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. Vaporization of chemical species and the production of aerosols during a core debris/concrete interaction

    International Nuclear Information System (INIS)

    Butland, A.T.D.; Mignanelli, M.A.; Potter, P.E.; Smith, P.N.

    1987-01-01

    The equilibrium chemical composition within gas bubbles sparging through isothermal molten corium-concrete mixtures has been evaluated theoretically. A series of sensitivity calculations gives some insight into a number of factors which are of importance in determining the radionuclide and non-radioactive releases during core-concrete interaction. The degree of mixing or layering of the pool has turned out to be of paramount importance in determining the magnitudes of the releases. The presence of unoxidized zirconium in the melt tends to enhance the release of a number of species and the type of concrete used for the base mat can have a significant effect. The predictions can be sensitive to the thermodynamic data used in the calculations. The vaporization of various species into the gas bubbles can require large amounts of heat; the loss of this heat from the melt can have an effect on the extent of the vaporization

  14. 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.

  15. Modeling of an improved chemical vapor infiltration process for ceramic composites fabrication

    International Nuclear Information System (INIS)

    Tai, N.H.; Chou, T.W.

    1990-01-01

    A quasi-steady-state approach is applied to model the pressure-driven, temperature-gradient chemical vapor infiltration (improved CVI process) for ceramic matrix composites fabrication. The deposited matrix in this study is SiC which is converted from the thermal decomposition of methyltrichlorosilane gas under excess hydrogen. A three-dimensional unit cell is adopted to simulate the spatial arrangements of reinforcements in discontinuous fiber mats and three-dimensionally woven fabrics. The objectives of this paper are to predict the temperature and density distributions in a fibrous preform during processing, the advancement of the solidified front, the total fabrication period, and the vapor inlet pressure variation for maintaining a constant flow rate

  16. Controllable growth of nanostructured carbon from coal tar pitch by chemical vapor deposition

    International Nuclear Information System (INIS)

    Liu Xuguang; Yang Yongzhen; Ji Weiyun; Liu Hongyan; Zhang Chunyi; Xu Bingshe

    2007-01-01

    The direct synthesis of vapor grown carbon fibers with different diameters was achieved by the pyrolysis of coal tar pitch by chemical vapor deposition. The products were characterized by field-emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The experimental results demonstrated that ferrocene content, reaction temperature and Ar flow rate strongly influenced the yield and nature of nanostructured carbon materials, pure carbon microbeads, with diameter distribution ranging from 450 to 650 nm, were also obtained in the absence of catalyst, uniform and straight carbon nanofibers with the outer diameter of about 115 nm were obtained and curl and thick carbon fibers with narrow diameter distribution of 300-350 nm were produced

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

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  18. Properties of amorphous silicon thin films synthesized by reactive particle beam assisted chemical vapor deposition

    International Nuclear Information System (INIS)

    Choi, Sun Gyu; Wang, Seok-Joo; Park, Hyeong-Ho; Jang, Jin-Nyoung; Hong, MunPyo; Kwon, Kwang-Ho; Park, Hyung-Ho

    2010-01-01

    Amorphous silicon thin films were formed by chemical vapor deposition of reactive particle beam assisted inductively coupled plasma type with various reflector bias voltages. During the deposition, the substrate was heated at 150 o C. The effects of reflector bias voltage on the physical and chemical properties of the films were systematically studied. X-ray diffraction and Raman spectroscopy results showed that the deposited films were amorphous and the films under higher reflector voltage had higher internal energy to be easily crystallized. The chemical state of amorphous silicon films was revealed as metallic bonding of Si atoms by using X-ray photoelectron spectroscopy. An increase in reflector voltage induced an increase of surface morphology of films and optical bandgap and a decrease of photoconductivity.

  19. Chemical Vapor Deposition of Photocatalyst Nanoparticles on PVDF Membranes for Advanced Oxidation Processes

    Directory of Open Access Journals (Sweden)

    Giovanni De Filpo

    2018-06-01

    Full Text Available The chemical binding of photocatalytic materials, such as TiO2 and ZnO nanoparticles, onto porous polymer membranes requires a series of chemical reactions and long purification processes, which often result in small amounts of trapped nanoparticles with reduced photocatalytic activity. In this work, a chemical vapor deposition technique was investigated in order to allow the nucleation and growth of ZnO and TiO2 nanoparticles onto polyvinylidene difluoride (PVDF porous membranes for application in advanced oxidation processes. The thickness of obtained surface coatings by sputtered nanoparticles was found to depend on process conditions. The photocatalytic efficiency of sputtered membranes was tested against both a model drug and a model organic pollutant in a small continuous flow reactor.

  20. SiO2 coating of silver nanoparticles by photoinduced chemical vapor deposition

    International Nuclear Information System (INIS)

    Boies, Adam M; Girshick, Steven L; Roberts, Jeffrey T; Zhang Bin; Nakamura, Toshitaka; Mochizuki, Amane

    2009-01-01

    Gas-phase silver nanoparticles were coated with silicon dioxide (SiO 2 ) by photoinduced chemical vapor deposition (photo-CVD). Silver nanoparticles, produced by inert gas condensation, and a SiO 2 precursor, tetraethylorthosilicate (TEOS), were exposed to vacuum ultraviolet (VUV) radiation at atmospheric pressure and varying temperatures. The VUV photons dissociate the TEOS precursor, initiating a chemical reaction that forms SiO 2 coatings on the particle surfaces. Coating thicknesses were measured for a variety of operation parameters using tandem differential mobility analysis and transmission electron microscopy. The chemical composition of the particle coatings was analyzed using energy dispersive x-ray spectrometry and Fourier transform infrared spectroscopy. The highest purity films were produced at 300-400 0 C with low flow rates of additional oxygen. The photo-CVD coating technique was shown to effectively coat nanoparticles and limit core particle agglomeration at concentrations up to 10 7 particles cm -3 .

  1. Modeling and control of diffusion and low-pressure chemical vapor deposition furnaces

    Science.gov (United States)

    De Waard, H.; De Koning, W. L.

    1990-03-01

    In this paper a study is made of the heat transfer inside cylindrical resistance diffusion and low-pressure chemical vapor deposition furnaces, aimed at developing an improved temperature controller. A model of the thermal behavior is derived which also covers the important class of furnaces equipped with semitransparent quartz process tubes. The model takes into account the thermal behavior of the thermocouples. It is shown that currently used temperature controllers are highly inefficient for very large scale integration applications. Based on the model an alternative temperature controller of the linear-quadratic-Gaussian type is proposed which features direct wafer temperature control. Some simulation results are given.

  2. Growth of highly oriented carbon nanotubes by plasma-enhanced hot filament chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Z.P.; Xu, J.W.; Ren, Z.F.; Wang, J.H. [Materials Synthesis Laboratory, Departments of Physics and Chemistry, and Center for Advanced Photonic and Electronic Materials (CAPEM), State University of New York at Buffalo, Buffalo, New York 14260 (United States); Siegal, M.P.; Provencio, P.N. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States)

    1998-12-01

    Highly oriented, multiwalled carbon nanotubes were grown on polished polycrystalline and single crystal nickel substrates by plasma enhanced hot filament chemical vapor deposition at temperatures below 666 {degree}C. The carbon nanotubes range from 10 to 500 nm in diameter and 0.1 to 50 {mu}m in length depending on growth conditions. Acetylene is used as the carbon source for the growth of the carbon nanotubes and ammonia is used for dilution gas and catalysis. The plasma intensity, acetylene to ammonia gas ratio, and their flow rates, etc. affect the diameters and uniformity of the carbon nanotubes. {copyright} {ital 1998 American Institute of Physics.}

  3. Precise control of multiwall carbon nanotube diameters using thermal chemical vapor deposition

    Science.gov (United States)

    Siegal, M. P.; Overmyer, D. L.; Provencio, P. P.

    2002-03-01

    We grow multiwall carbon nanotube (CNT) films using thermal chemical vapor deposition at atmospheric pressure using a mixture of acetylene and nitrogen from a 4-nm-thick Ni film catalyst. CNTs are characterized using electron microscopy and Rutherford backscattering spectrometry. CNTs grown with this method are extremely uniform in diameter, both throughout the sample and within the lengths of individual tubes. Nanotube outer diameters, ranging from 5-350 nm, and the total deposition of carbon material, increase exponentially with growth temperature from 630 °C-790 °C.

  4. 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....... According to the model, the predominant tantalum growth species is TaCl3. The temperature is shown to have a pronounced effect onthe morphology and rate of deposition of the tantalum and an apparent change in deposition mechanism occurs between 850–900 °C, resulting in the deposition rate at 900 °C being...

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

    International Nuclear Information System (INIS)

    Wang Zhipeng; Shoji, Mao; Ogata, Hironori

    2011-01-01

    We employ a new gas mixture of CH 4 -Ar to fabricate carbon nanosheets by microwave plasma enhanced chemical vapor deposition at the growth temperature of less than 500 deg. C. The catalyst-free nanosheets possess flower-like structures with a large amount of sharp edges, which consist of a few layers of graphene sheets according to the observation by transmission electron microscopy. These high-quality carbon nanosheets demonstrated a faster electron transfer between the electrolyte and the nanosheet surface, due to their edge defects and graphene structures.

  6. Room-temperature plasma-enhanced chemical vapor deposition of SiOCH films using tetraethoxysilane

    International Nuclear Information System (INIS)

    Yamaoka, K.; Yoshizako, Y.; Kato, H.; Tsukiyama, D.; Terai, Y.; Fujiwara, Y.

    2006-01-01

    Carbon-doped silicon oxide (SiOCH) thin films were deposited by room-temperature plasma-enhanced chemical vapor deposition (PECVD) using tetraethoxysilane (TEOS). The deposition rate and composition of the films strongly depended on radio frequency (RF) power. The films deposited at low RF power contained more CH n groups. The SiOCH films showed high etch rate and low refractive index in proportion to the carbon composition. The deposition with low plasma density and low substrate temperature is effective for SiOCH growth by PECVD using TEOS

  7. Time variant layer control in atmospheric pressure chemical vapor deposition based growth of graphene

    KAUST Repository

    Qaisi, Ramy M.; Smith, Casey; Hussain, Muhammad Mustafa

    2013-01-01

    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.

  8. Test Operations Procedure (TOP) 08-2-188 Chemical Point Detector Vapor Testing

    Science.gov (United States)

    2018-04-27

    Final 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Test Operations Procedure (TOP) 08-2-188 Chemical Point Detector Vapor Testing 5a. CONTRACT...NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING...ORGANIZATION NAME(S) AND ADDRESS(ES) US Army Dugway Proving Ground West Desert Test Center (TEDT-DPW) Dugway, UT 84022-5000 8. PERFORMING ORGANIZATION

  9. A Review of Carbon Nanomaterials’ Synthesis via the Chemical Vapor Deposition (CVD Method

    Directory of Open Access Journals (Sweden)

    Yehia M. Manawi

    2018-05-01

    Full Text Available Carbon nanomaterials have been extensively used in many applications owing to their unique thermal, electrical and mechanical properties. One of the prime challenges is the production of these nanomaterials on a large scale. This review paper summarizes the synthesis of various carbon nanomaterials via the chemical vapor deposition (CVD method. These carbon nanomaterials include fullerenes, carbon nanotubes (CNTs, carbon nanofibers (CNFs, graphene, carbide-derived carbon (CDC, carbon nano-onion (CNO and MXenes. Furthermore, current challenges in the synthesis and application of these nanomaterials are highlighted with suggested areas for future research.

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

    Czech Academy of Sciences Publication Activity Database

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

    2010-01-01

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

  11. A Review of Carbon Nanomaterials’ Synthesis via the Chemical Vapor Deposition (CVD) Method

    Science.gov (United States)

    Manawi, Yehia M.; Samara, Ayman; Al-Ansari, Tareq; Atieh, Muataz A.

    2018-01-01

    Carbon nanomaterials have been extensively used in many applications owing to their unique thermal, electrical and mechanical properties. One of the prime challenges is the production of these nanomaterials on a large scale. This review paper summarizes the synthesis of various carbon nanomaterials via the chemical vapor deposition (CVD) method. These carbon nanomaterials include fullerenes, carbon nanotubes (CNTs), carbon nanofibers (CNFs), graphene, carbide-derived carbon (CDC), carbon nano-onion (CNO) and MXenes. Furthermore, current challenges in the synthesis and application of these nanomaterials are highlighted with suggested areas for future research. PMID:29772760

  12. Time variant layer control in atmospheric pressure chemical vapor deposition based growth of graphene

    KAUST Repository

    Qaisi, Ramy M.

    2013-04-01

    Graphene is a semi-metallic, transparent, atomic crystal structure material which is promising for its high mobility, strength and transparency - potentially applicable for radio frequency (RF) circuitry and energy harvesting and storage applications. Uniform (same number of layers), continuous (not torn or discontinuous), large area (100 mm to 200 mm wafer scale), low-cost, reliable growth are the first hand challenges for its commercialization prospect. We show a time variant uniform (layer control) growth of bi- to multi-layer graphene using atmospheric chemical vapor deposition system. We use Raman spectroscopy for physical characterization supported by electrical property analysis. © 2013 IEEE.

  13. 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.

  14. An Investigation on the Formation of Carbon Nanotubes by Two-Stage Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    M. S. Shamsudin

    2012-01-01

    Full Text Available High density of carbon nanotubes (CNTs has been synthesized from agricultural hydrocarbon: camphor oil using a one-hour synthesis time and a titanium dioxide sol gel catalyst. The pyrolysis temperature is studied in the range of 700–900°C at increments of 50°C. The synthesis process is done using a custom-made two-stage catalytic chemical vapor deposition apparatus. The CNT characteristics are investigated by field emission scanning electron microscopy and micro-Raman spectroscopy. The experimental results showed that structural properties of CNT are highly dependent on pyrolysis temperature changes.

  15. 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.

  16. Growth and characterization of Bi2Se3 crystals by chemical vapor transport

    Directory of Open Access Journals (Sweden)

    W. H. Jiao

    2012-06-01

    Full Text Available Regularly-shaped high-quality Bi2Se3 crystals were grown by a chemical vapor transport using iodine as the transport agent. In addition to exhibiting a characteristic Dirac cone for a topological insulator, the Bi2Se3 crystals show some outstanding properties including additional crystallographic surfaces, large residual resistance ratio (∼10, and high mobility (∼8000 cm2·V−1·s−1. The low-temperature resistivity abnormally increases with applying pressures up to 1.7 GPa, and no superconductivity was observed down to 0.4 K.

  17. Dispersion of carbon nanotubes in hydroxyapatite powder by in situ chemical vapor deposition

    International Nuclear Information System (INIS)

    Li Haipeng; Wang Lihui; Liang, Chunyong; Wang Zhifeng; Zhao Weimin

    2010-01-01

    In the present work, we use chemical vapor deposition of methane to disperse carbon nanotubes (CNTs) within hydroxyapatite (HA) powder. The effect of different catalytic metal particles (Fe, Ni or Co) on the morphological and structural development of the powder and dispersion of CNTs in HA powder was investigated. The results show that the technique is effective in dispersing the nanotubes within HA powder, which simultaneously protects the nanotubes from damage. The results can have important and promising speculations for the processing of CNT-reinforced HA-matrix composites in general.

  18. Aromatic chemicals by iron-catalyzed hydrotreatment of lignin pyrolysis vapor.

    Science.gov (United States)

    Olcese, Roberto Nicolas; Lardier, George; Bettahar, Mohammed; Ghanbaja, Jaafar; Fontana, Sébastien; Carré, Vincent; Aubriet, Frédéric; Petitjean, Dominique; Dufour, Anthony

    2013-08-01

    Lignin is a potential renewable material for the production of bio-sourced aromatic chemicals. We present the first hydrotreatment of lignin pyrolysis vapors, before any condensation, using inexpensive and sustainable iron-silica (Fe/SiO2 ) and iron-activated carbon (Fe/AC) catalysts. Lignin pyrolysis was conducted in a tubular reactor and vapors were injected in a fixed bed of catalysts (673 K, 1 bar) with stacks to investigate the profile of coke deposit. More than 170 GC-analyzable compounds were identified by GCxGC (heart cutting)/flame ionization detector mass spectrometry. Lignin oligomers were analyzed by very high resolution mass spectrometry, called the "petroleomic" method. They are trapped by the catalytic fixed bed and, in particular, by the AC. The catalysts showed a good selectivity for the hydrodeoxygenation of real lignin vapors to benzene, toluene, xylenes, phenol, cresols, and alkyl phenols. The spent catalysts were characterized by temperature-programmed oxidation, transmission electron microscopy (TEM), and N2 sorption. Micropores in the Fe/AC catalyst are completely plugged by coke deposits, whereas the mesoporous structure of Fe/SiO2 is unaffected. TEM images reveal two different types of coke deposit: 1) catalytic coke deposited in the vicinity of iron particles and 2) thermal coke (carbonaceous particles ≈1 μm in diameter) formed from the gas-phase growth of lignin oligomers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Deposition of yttria stabilized zirconia layer for solid oxide fuel cell by chemical vapor infiltration

    International Nuclear Information System (INIS)

    John, John T.; Dubey, Vivekanand; Kain, Vivekanand; Dey, Gautham Kumar; Prakash, Deep

    2011-01-01

    Free energy associated with a chemical reaction can be converted into electricity, if we can split the reaction into an anodic reaction and a cathodic reaction and carry out the reactions in an electrochemical cell using electrodes that will catalyze the reactions. We also have to use a suitable electrolyte, that serves to isolate the chemical species in the two compartments from getting mixed directly but allow an ion produced in one of the reactions to proceed to the other side and complete the reaction. For this reason cracks and porosity are not tolerated in the electrolyte. First generation solid oxide fuel cell (SOFC) uses yttria stabilized zirconia (YSZ) as the electrolyte. In spite of the fact that several solid electrolytes with higher conductivities at lower temperature are being investigated and developed, 8 mol% yttria stabilized zirconia (8YSZ) is considered to be the most favored electrolyte for the SOFC today. The electrolyte should be present as a thin, impervious layer of uniform thickness with good adherence, chemical and mechanical stability, in between the porous cathode and anode. Efforts to produce the 8YSZ coatings on porous lanthanum strontium manganite tubes by electrochemical vapor deposition (ECVD) have met with unexpected difficulties such as impurity pick up and chemical and mechanical instability of the LSM tubes in the ECVD environment. It was also difficult to keep the chemical composition of the YSZ coating at exactly 8 mol% Yttria in zirconia and to control the coating thickness in tight control. These problems were overcome by a two step deposition process where a YSZ layer of required thickness was produced by electrophoretic coating from an acetyl acetone bath at a voltage of 30-300V DC and sintered at 1300 deg C. The resulting porous YSZ layer was made impervious by chemical vapor infiltration (CVI) by the reaction between a mixture of vapors of YCl 3 and ZrCl 4 and steam at 1300 deg C as in the case of ECVD for a short

  20. Analysis of the Si(111) surface prepared in chemical vapor ambient for subsequent III-V heteroepitaxy

    International Nuclear Information System (INIS)

    Zhao, W.; Steidl, M.; Paszuk, A.; Brückner, S.; Dobrich, A.; Supplie, O.; Kleinschmidt, P.; Hannappel, T.

    2017-01-01

    Highlights: • We investigate the Si(111) surface prepared in CVD ambient at 1000 °C in 950 mbar H_2. • UHV-based XPS, LEED, STM and FTIR as well as ambient AFM are applied. • After processing the Si(111) surface is free of contamination and atomically flat. • The surface exhibits a (1 × 1) reconstruction and monohydride termination. • Wet-chemical pretreatment and homoepitaxy are required for a regular step structure. - Abstract: For well-defined heteroepitaxial growth of III-V epilayers on Si(111) substrates the atomic structure of the silicon surface is an essential element. Here, we study the preparation of the Si(111) surface in H_2-based chemical vapor ambient as well as its atomic structure after contamination-free transfer to ultrahigh vacuum (UHV). Applying complementary UHV-based techniques, we derive a complete picture of the atomic surface structure and its chemical composition. X-ray photoelectron spectroscopy measurements after high-temperature annealing confirm a Si surface free of any traces of oxygen or other impurities. The annealing in H_2 ambient leads to a monohydride surface termination, as verified by Fourier-transform infrared spectroscopy. Scanning tunneling microscopy confirms a well ordered, atomically smooth surface, which is (1 × 1) reconstructed, in agreement with low energy electron diffraction patterns. Atomic force microscopy reveals a significant influence of homoepitaxy and wet-chemical pretreatment on the surface morphology. Our findings show that wet-chemical pretreatment followed by high-temperature annealing leads to contamination-free, atomically flat Si(111) surfaces, which are ideally suited for subsequent III-V heteroepitaxy.

  1. Analysis of the Si(111) surface prepared in chemical vapor ambient for subsequent III-V heteroepitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, W.; Steidl, M.; Paszuk, A. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Brückner, S. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Helmholtz-Zentrum Berlin, Institut für Solare Brennstoffe, 14109 Berlin (Germany); Dobrich, A. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Supplie, O. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Helmholtz-Zentrum Berlin, Institut für Solare Brennstoffe, 14109 Berlin (Germany); Kleinschmidt, P. [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Hannappel, T., E-mail: thomas.hannappel@tu-ilmenau.de [Technische Universität Ilmenau, Institut für Physik, 98693 Ilmenau (Germany); Helmholtz-Zentrum Berlin, Institut für Solare Brennstoffe, 14109 Berlin (Germany)

    2017-01-15

    Highlights: • We investigate the Si(111) surface prepared in CVD ambient at 1000 °C in 950 mbar H{sub 2}. • UHV-based XPS, LEED, STM and FTIR as well as ambient AFM are applied. • After processing the Si(111) surface is free of contamination and atomically flat. • The surface exhibits a (1 × 1) reconstruction and monohydride termination. • Wet-chemical pretreatment and homoepitaxy are required for a regular step structure. - Abstract: For well-defined heteroepitaxial growth of III-V epilayers on Si(111) substrates the atomic structure of the silicon surface is an essential element. Here, we study the preparation of the Si(111) surface in H{sub 2}-based chemical vapor ambient as well as its atomic structure after contamination-free transfer to ultrahigh vacuum (UHV). Applying complementary UHV-based techniques, we derive a complete picture of the atomic surface structure and its chemical composition. X-ray photoelectron spectroscopy measurements after high-temperature annealing confirm a Si surface free of any traces of oxygen or other impurities. The annealing in H{sub 2} ambient leads to a monohydride surface termination, as verified by Fourier-transform infrared spectroscopy. Scanning tunneling microscopy confirms a well ordered, atomically smooth surface, which is (1 × 1) reconstructed, in agreement with low energy electron diffraction patterns. Atomic force microscopy reveals a significant influence of homoepitaxy and wet-chemical pretreatment on the surface morphology. Our findings show that wet-chemical pretreatment followed by high-temperature annealing leads to contamination-free, atomically flat Si(111) surfaces, which are ideally suited for subsequent III-V heteroepitaxy.

  2. Natural Attenuation of Hydrocarbon and Trichloroethylene Vapors in the Subsurface Environment at Plattsburgh Air Force Base

    National Research Council Canada - National Science Library

    Ostendorf, David

    1997-01-01

    .... UMASS tested the hypothesis that natural attenuation processes, stimulated by injected air, reduce emissions of hydrocarbons and trichloroethylene vapors to acceptable air quality standards at the site. Drs...

  3. Recovery of rare earths from used polishes by chemical vapor transport process

    International Nuclear Information System (INIS)

    Ozaki, T.; Machida, K.; Adachi, G.

    1998-01-01

    Full text: Rare earth oxide polishes are widely used in the glass industry because of its mechanical and chemical polishing action. The Japanese glass industry use 2000 tons per year of the polishes, and a large portion of them are thrown away after their polishing lifetime. A dry recovery processes for rare earths from the used polishes have been investigated by using a chemical vapor transport method via the formation of vapor complexes RAl n Cl 3+3n (R = rare earths). A flow type reactor with various temperature gradients was employed for the process. The used polishes were mixed with active carbon, and chlorinated with N 2 + Cl 2 mixture at 1273 K. Aluminium oxide were also chlorinated at lower temperature and the resulting AlCl 3 were introduced to the reactor. The rare earth chlorides and AlCl 3 were converted to the vapor complexes. These were driven along the temperature gradient, decomposed according to the reverse reaction, and regenerated RCl 3 . About 90 % of the used polish were chlorinated after 2 hours. Rare earth chlorides, AlCl 3 , and FeCl 3 were fully transported after 82 hours. The rare earth chlorides were mainly condensed over the temperature range 1263-903 K. On the other hand, AlCl 3 and FeCl 3 were deposited at the temperature range below 413 K. CaCl 2 and SrCl 2 were hardly transported and remained in the residue. When the temperature gradient with the smaller slope was used, mutual separation efficiencies among the rare earths was improved. The highest CeCl 3 purity of 80% was obtained in the process

  4. 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.

  5. A systematic study of atmospheric pressure chemical vapor deposition growth of large-area monolayer graphene.

    Science.gov (United States)

    Liu, Lixin; Zhou, Hailong; Cheng, Rui; Chen, Yu; Lin, Yung-Chen; Qu, Yongquan; Bai, Jingwei; Ivanov, Ivan A; Liu, Gang; Huang, Yu; Duan, Xiangfeng

    2012-01-28

    Graphene has attracted considerable interest as a potential material for future electronics. Although mechanical peel is known to produce high quality graphene flakes, practical applications require continuous graphene layers over a large area. The catalyst-assisted chemical vapor deposition (CVD) is a promising synthetic method to deliver wafer-sized graphene. Here we present a systematic study on the nucleation and growth of crystallized graphene domains in an atmospheric pressure chemical vapor deposition (APCVD) process. Parametric studies show that the mean size of the graphene domains increases with increasing growth temperature and CH 4 partial pressure, while the density of domains decreases with increasing growth temperature and is independent of the CH 4 partial pressure. Our studies show that nucleation of graphene domains on copper substrate is highly dependent on the initial annealing temperature. A two-step synthetic process with higher initial annealing temperature but lower growth temperature is developed to reduce domain density and achieve high quality full-surface coverage of monolayer graphene films. Electrical transport measurements demonstrate that the resulting graphene exhibits a high carrier mobility of up to 3000 cm 2 V -1 s -1 at room temperature.

  6. Application of molecular beam mass spectrometry to chemical vapor deposition studies

    International Nuclear Information System (INIS)

    Hsu, W.L.; Tung, D.M.

    1992-01-01

    A molecular beam mass spectrometer system has been designed and constructed for the specific purpose of measuring the gaseous composition of the vapor environment during chemical vapor deposition of diamond. By the intrinsic nature of mass analysis, this type of design is adaptable to a broad range of other applications that rely either on thermal- or plasma-induced chemical kinetics. When gas is sampled at a relatively high process pressure (∼2700 Pa for our case), supersonic gas expansion at the sampling orifice can cause the detected signals to have a complicated dependence on the operating conditions. A comprehensive discussion is given on the effect of gas expansion on mass discrimination and signal scaling with sampling pressure and temperature, and how these obstacles can be overcome. This paper demonstrates that radical species can be detected with a sensitivity better than 10 ppm by the use of threshold ionization. A detailed procedure is described whereby one can achieve quantitative analysis of the detected species with an accuracy of ±20%. This paper ends with an example on the detection of H, H 2 , CH 3 , CH 4 , and C 2 H 2 during diamond growth

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

    International Nuclear Information System (INIS)

    Park, Eunsil; Kim, Jongwon; Lee, Changseop

    2014-01-01

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

  8. Understanding the reaction kinetics to optimize graphene growth on Cu by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, Juergen; Boebel, Lena; Zwaschka, Gregor; Guenther, Sebastian [Technische Universitaet Muenchen, Zentralinstitut fuer Katalyseforschung, Chemie Department, Physikalische Chemie mit Schwerpunkt Katalyse, Garching (Germany)

    2017-11-15

    Understanding and controlling the growth kinetics of graphene is a prerequisite to synthesize this highly wanted material by chemical vapor deposition on Cu, e.g. for the construction of ultra-stable electron transparent membranes. It is reviewed that Cu foils contain a considerable amount of carbon in the bulk which significantly exceeds the expected amount of thermally equilibrated dissolved carbon in Cu and that this carbon must be removed before any high quality graphene may be grown. Starting with such conditioned Cu foils, systematic studies of the graphene growth kinetics in a reactive CH{sub 4}/H{sub 2} atmosphere allow to extract the following meaningful data: prediction of the equilibrium constant of the graphene formation reaction within a precision of a factor of two, the confirmation that the graphene growth proceeds from a C(ad)-phase on Cu which is in thermal equilibrium with the reactive gas phase, its apparent activation barrier and finally the prediction of the achievable growth velocity of the growing graphene flakes during chemical vapor deposition. As a result of the performed study, growth parameters are identified for the synthesis of high quality monolayer graphene with single crystalline domains of 100-1000 μm in diameter within a reasonable growth time. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Carbonized tantalum catalysts for catalytic chemical vapor deposition of silicon films

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Shimin [State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Dalian National Laboratory for Clean Energy, Dalian 116023 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Gao Huiping; Ren Tong; Ying Pinliang [State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Dalian National Laboratory for Clean Energy, Dalian 116023 (China); Li Can, E-mail: canli@dicp.ac.cn [State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Dalian National Laboratory for Clean Energy, Dalian 116023 (China)

    2012-06-01

    Catalytic chemical vapor deposition (Cat-CVD) has been demonstrated as a promising way to prepare device-quality silicon films. However, catalyst ageing due to Si contamination is an urgency to be solved for the practical application of the technique. In this study, the effect of carbonization of tantalum catalyst on its structure and performance was investigated. The carbonized Ta catalyst has a TaC surface layer which is preserved over the temperature range between 1450 and 1750 Degree-Sign C and no Si contamination occurs on the catalyst after long-term use. Si film prepared using the carbonized Ta catalyst has a similar crystal structure to that prepared by uncarbonized Ta catalyst. Formation of the TaC surface layer can alleviate the ageing problem of the catalyst, which shows great potential as a stable catalyst for Cat-CVD of Si films. - Highlights: Black-Right-Pointing-Pointer Si films prepared by catalytic chemical vapor deposition. Black-Right-Pointing-Pointer Carbonized Ta with a TaC surface layer used as catalyst. Black-Right-Pointing-Pointer TaC surface structure preserved after long-term use in a wide temperature range. Black-Right-Pointing-Pointer Help to solve the ageing problem of metal catalysts. Black-Right-Pointing-Pointer Si film obtained has a similar crystal structure to that prepared by Ta catalyst.

  10. Synthesis of electro-active manganese oxide thin films by plasma enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Merritt, Anna R. [Energetics Research Division, Naval Air Warfare Center Weapons Division, China Lake, CA 93555 (United States); Rajagopalan, Ramakrishnan [Department of Engineering, The Pennsylvania State University, Dubois, PA 15801 (United States); Materials Research Institute, The Pennsylvania State University, University Park, PA 16802 (United States); Carter, Joshua D. [Energetics Research Division, Naval Air Warfare Center Weapons Division, China Lake, CA 93555 (United States)

    2014-04-01

    The good stability, cyclability and high specific capacitance of manganese oxide (MnO{sub x}) has recently promoted a growing interest in utilizing MnO{sub x} in asymmetric supercapacitor electrodes. Several literature reports have indicated that thin film geometries of MnO{sub x} provide specific capacitances that are much higher than bulk MnO{sub x} powders. Plasma enhanced chemical vapor deposition (PECVD) is a versatile technique for the production of metal oxide thin films with high purity and controllable thickness. In this work, MnO{sub x} thin films deposited by PECVD from a methylcyclopentadienyl manganese tricarbonyl precursor are presented and the effect of processing conditions on the quality of MnO{sub x} films is described. The film purity and oxidation state of the MnO{sub x} films were studied by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Preliminary electrochemical testing of MnO{sub x} films deposited on carbon fiber electrodes in aqueous electrolytes indicates that the PECVD synthesized films are electrochemically active. - Highlights: • Plasma enhanced chemical vapor deposition of manganese oxide thin films. • Higher plasma power and chamber pressure increase deposition rate. • Manganese oxide thin films are electrochemically active. • Best electrochemical performance observed for pure film with low stress • Lower capacitance observed at higher scan rates despite thin film geometry.

  11. Phase Equilibrium of TiO2 Nanocrystals in Flame-Assisted Chemical Vapor Deposition.

    Science.gov (United States)

    Liu, Changran; Camacho, Joaquin; Wang, Hai

    2018-01-19

    Nano-scale titanium oxide (TiO 2 ) is a material useful for a wide range of applications. In a previous study, we showed that TiO 2 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. Rutile was unexpectedly dominant in oxygen-lean synthesis conditions, whereas 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 TiO 2 nanocrystals with controllable crystal phases. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Chemical vapor deposition. Volume 2. 1975--July, 1978 (a bibliography with abstracts). Report for 1975--July 1978

    International Nuclear Information System (INIS)

    Smith, M.F.

    1978-07-01

    Research on chemical vapor deposition of carbon, carbides, ceramics, metals, and glasses are cited. Applications of this process include optical coatings, semiconducting films, laser materials, solar cells, composite fabrication, and nuclear reactor material fabrication. The physical, mechanical, and chemical properties of these coatings are covered

  13. 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.

  14. Observed Responses of Mesospheric Water Vapor to Solar Cycle and Dynamical Forcings

    Science.gov (United States)

    Remsberg, Ellis; Damadeo, Robert; Natarajan, Murali; Bhatt, Praful

    2018-04-01

    This study focuses on responses of mesospheric water vapor (H2O) to the solar cycle flux at Lyman-α wavelength and to dynamical forcings according to the multivariate El-Nino/Southern Oscillation (ENSO) index. The zonal-averaged responses are for latitudes from 60°S to 60°N and pressure-altitudes from 0.01 to 1.0 hPa, as obtained from multiple linear regression analyses of time series of H2O from the Halogen Occultation Experiment for July 1992 to November 2005. The results compare very well with those from a separate simultaneous temporal and spatial (STS) method that also confirms that there are no significant sampling biases affecting both sets of results. Distributions of the seasonal amplitudes for temperature and H2O are in accord with the seasonal net circulation. In general, the responses of H2O to ENSO are anticorrelated with those of temperature. H2O responses to multivariate ENSO index are negative in the upper mesosphere and largest in the Northern Hemisphere; responses in the lower mesosphere are more symmetric with latitude. H2O responses to the Lyman-α flux (Lya) vary from strong negative values in the uppermost mesosphere to very weak, positive values in the tropical lowermost mesosphere. However, the effects of those H2O responses to the solar activity extend to the rest of the mesosphere via dynamical processes. Profiles of the responses to ENSO and Lya also agree reasonably with published results for H2O at the low latitudes from the Microwave Limb Sounder.

  15. Force Field Benchmark of Organic Liquids: Density, Enthalpy of Vaporization, Heat Capacities, Surface Tension, Isothermal Compressibility, Volumetric Expansion Coefficient, and Dielectric Constant.

    Science.gov (United States)

    Caleman, Carl; van Maaren, Paul J; Hong, Minyan; Hub, Jochen S; Costa, Luciano T; van der Spoel, David

    2012-01-10

    The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys.2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed exposé of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats

  16. 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.

  17. Results of Soil Vapor Sampling at SA 6, McClellan Air Force Base, California

    National Research Council Canada - National Science Library

    1998-01-01

    ...) and total petroleum hydrocarbon (TPH) contamination in site soil. The soil vapor sampling event was performed in accordance with the Final Sampling and Analysis Plan to Support Recommendation for No Further Investigation at SA 6 (Parsons ES, 1998...

  18. 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.

  19. Application of the chemical vapor-etching in polycrystalline silicon solar cells

    International Nuclear Information System (INIS)

    Ben Rabha, M.; Saadoun, M.; Boujmil, M.F.; Bessais, B.; Ezzaouia, H.; Bennaceur, R.

    2005-01-01

    This paper reports a study of the application of chemical vapor-etching (CVE) for the rear surface and in the emitter of polycrystalline silicon (pc-Si) solar cells. The CVE technique consists of exposing pc-Si wafers to a mixture of HF/HNO 3 . This technique is used to groove the rear surface of the pc-Si wafers for acid vapors rich in HNO 3 (HNO 3 /HF > 1/4), in order to realize rear-buried metallic contacts (RBMC) and the formation of a porous silicon (PS) layer on the frontal surface of the cell for volume ratio of HNO 3 /HF = 1/7. A significant increase of the spectral response in the long wavelength range was observed when a RBMC is formed. This increase was attributed to the reduction of the effective thickness of the base of the cells and grain boundary Al gettering. The achievement of a PS layer on the emitter of the pc-Si cells passivates the surface and reduces the reflectivity. The dark I-V characteristics of pc-Si cells with emitter-based PS show an important reduction of the reverse current together with an improvement of the rectifying behaviour. The I-V characteristic under AM1.5 illumination shows an enhancement of both short circuit current density and fill factor. The internal quantum efficiency is improved, particularly in the short wavelengths region

  20. Liquid and vapor phase fluids visualization using an exciplex chemical sensor

    International Nuclear Information System (INIS)

    Kim, Jong Uk; Kim, Guang Hoon; Kim, Chang Bum; Suk, Hyyong

    2001-01-01

    Two dimensional slices of the cross-sectional distributions of fuel images in the combustion chamber were visualized quantitatively using a laser-induced exciplex (excited state complex) fluorescence technique. A new exciplex visualization system consisting of 5%DMA (N, N-dimethylaniline) · 5%1, 4,6-TMN (trimethylnaphthalene) in 90% isooctane (2,2,4-trimethylpentane) fuel was employed. In this method, the vapor phase was tagged by the monomer fluorescence while the liquid phase was tracked by the red-shifted exciplex fluorescence with good spectral and spatial resolution. The direct calibration of the fluorescence intensity as a function of the fluorescing dopant concentrations then permitted the determination of quantitative concentration maps of liquid and vapor phases in the fuel. The 308 nm (XeCl) line of the excimer laser was used to excite the doped molecules in the fuel and the resulting fluorescence images were obtained with an ICCD detector as a function time. In this paper, the spectroscopy of the exciplex chemical sensors as well as the optical diagnostic method of the fluid distribution is discussed in detail.

  1. A predictive model for the chemical vapor deposition of polysilicon in a cold wall, rapid thermal system

    Energy Technology Data Exchange (ETDEWEB)

    Toprac, A.J.; Trachtenberg, I.; Edgar, T.F. (Univ. of Texas, Austin, TX (United States). Dept. of Chemical Engineering)

    1994-06-01

    The chemical vapor deposition of polysilicon from thermally activated silane in a cold wall, single-wafer rapid thermal system was studied by experimentation at a variety of low pressure conditions, including very high temperatures. The effect of diluent gas on polysilicon deposition rates was examined using hydrogen, helium, and krypton. A mass-transfer model for the chemical vapor deposition of polysilicon in a cold wall, rapid thermal system was developed. This model was used to produce an empirical rate expression for silicon deposition from silane by regressing kinetic parameters to fit experimental data. The resulting model provided accurate predictions over widely varying conditions in the experimental data.

  2. Work Plan for the Evaluation of Soil Vapor Extraction Using Internal Combustion Engine Technology at Site SS-42 Luke Air Force Base, Arizona

    National Research Council Canada - National Science Library

    1996-01-01

    ...). Luke AFB is one of several Air Force installations identified as prospective test sites to demonstrate the ICE system with advanced emission controls as part of a low-cost soil vapor extraction (SVE...

  3. Coating of carbon short fibers with thin ceramic layers by chemical vapor deposition

    International Nuclear Information System (INIS)

    Hackl, Gerrit; Gerhard, Helmut; Popovska, Nadejda

    2006-01-01

    Carbon short fiber bundles with a length of 6 mm were uniformly coated using specially designed, continuous chemical vapor deposition (CVD) equipment. Thin layers of titanium nitride, silicon nitride (SiC) and pyrolytic carbon (pyC) were deposited onto several kilograms of short fibers in this large scale CVD reactor. Thermo-gravimetric analyses and scanning electron microscopy investigations revealed layer thicknesses between 20 and 100 nm on the fibers. Raman spectra of pyC coated fibers show a change of structural order depending on the CVD process parameters. For the fibers coated with SiC, Raman investigations showed a deposition of amorphous SiC. The coated carbon short fibers will be applied as reinforcing material in composites with ceramic and metallic matrices

  4. Chemical-vapor-infiltrated silicon nitride, boron nitride, and silicon carbide matrix composites

    International Nuclear Information System (INIS)

    Ventri, R.D.; Galasso, F.S.

    1990-01-01

    This paper reports composites of carbon/chemical-vapor-deposited (CVD) Si 3 N 4 , carbon/CVD BN, mullite/CVD SiC, and SiC yarn/CVD SiC prepared to determine if there were inherent toughness in these systems. The matrices were deposited at high enough temperatures to ensure that they were crystalline, which should make them more stable at high temperatures. The fiber-matrix bonding in the C/Si 3 N 4 composite appeared to be too strong; the layers of BN in the matrix of the C/BN were too weakly bonded; and the mullite/SiC composite was not as tough as the SiC/SiC composites. Only the SiC yarn/CVD SiC composite exhibited both strength and toughness

  5. Spiral growth of few-layer MoS{sub 2} by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dong, X.; Yan, C.; Tomer, D.; Li, L., E-mail: lianli@uwm.edu [Department of Physics, University of Wisconsin, Milwaukee, Wisconsin 53211 (United States); Li, C. H. [Naval Research Laboratory, Washington, DC 20375 (United States)

    2016-08-01

    Growth spirals exhibit appealing properties due to a preferred layer stacking and lack of inversion symmetry. Here, we report spiral growth of MoS{sub 2} during chemical vapor deposition on SiO{sub 2}/Si and epitaxial graphene/SiC substrates, and their physical and electronic properties. We determine the layer-dependence of the MoS{sub 2} bandgap, ranging from 2.4 eV for the monolayer to a constant of 1.3 eV beyond the fifth layer. We further observe that spirals predominantly initiate at the step edges of the SiC substrate, based on which we propose a growth mechanism driven by screw dislocation created by the coalescence of two growth fronts at steps.

  6. Controlled density of vertically aligned carbon nanotubes in a triode plasma chemical vapor deposition system

    International Nuclear Information System (INIS)

    Lim, Sung Hoon; Park, Kyu Chang; Moon, Jong Hyun; Yoon, Hyun Sik; Pribat, Didier; Bonnassieux, Yvan; Jang, Jin

    2006-01-01

    We report on the growth mechanism and density control of vertically aligned carbon nanotubes using a triode plasma enhanced chemical vapor deposition system. The deposition reactor was designed in order to allow the intermediate mesh electrode to be biased independently from the ground and power electrodes. The CNTs grown with a mesh bias of + 300 V show a density of ∼ 1.5 μm -2 and a height of ∼ 5 μm. However, CNTs do not grow when the mesh electrode is biased to - 300 V. The growth of CNTs can be controlled by the mesh electrode bias which in turn controls the plasma density and ion flux on the sample

  7. Conformal coating of amorphous silicon and germanium by high pressure chemical vapor deposition for photovoltaic fabrics

    Science.gov (United States)

    Ji, Xiaoyu; Cheng, Hiu Yan; Grede, Alex J.; Molina, Alex; Talreja, Disha; Mohney, Suzanne E.; Giebink, Noel C.; Badding, John V.; Gopalan, Venkatraman

    2018-04-01

    Conformally coating textured, high surface area substrates with high quality semiconductors is challenging. Here, we show that a high pressure chemical vapor deposition process can be employed to conformally coat the individual fibers of several types of flexible fabrics (cotton, carbon, steel) with electronically or optoelectronically active materials. The high pressure (˜30 MPa) significantly increases the deposition rate at low temperatures. As a result, it becomes possible to deposit technologically important hydrogenated amorphous silicon (a-Si:H) from silane by a simple and very practical pyrolysis process without the use of plasma, photochemical, hot-wire, or other forms of activation. By confining gas phase reactions in microscale reactors, we show that the formation of undesired particles is inhibited within the microscale spaces between the individual wires in the fabric structures. Such a conformal coating approach enables the direct fabrication of hydrogenated amorphous silicon-based Schottky junction devices on a stainless steel fabric functioning as a solar fabric.

  8. 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.

  9. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kaatz, F.H.; Siegal, M.P.; Overmyer, D.L.; Provencio, P.P.; Jackson, J.L

    2003-01-15

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

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

    International Nuclear Information System (INIS)

    Kaatz, F.H.; Siegal, M.P.; Overmyer, D.L.; Provencio, P.P.; Jackson, J.L.

    2003-01-01

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

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

    International Nuclear Information System (INIS)

    Dangbegnon, J.K.; Talla, K.; Roro, K.T.; Botha, J.R.

    2009-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-12-01

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

  14. Surface modification of titanium membrane by chemical vapor deposition and its electrochemical self-cleaning

    International Nuclear Information System (INIS)

    Li, X.W.; Li, J.X.; Gao, C.Y.; Chang, M.

    2011-01-01

    Membrane separation is applied widely in many fields, while concentration polarization and membrane fouling, limiting its promotion and application greatly, are the bottlenecks in membrane application. Among which, membrane fouling is irreversible, membrane must be periodically cleaned or even replaced to restore permeability. Membrane cleaning has become one of Key issues in membrane separation areas. Considering incomparable electrochemical advantages of boron-doped diamond (BDD) film electrode over conventional electrode, a new composite membrane Ti/BDD, made by depositing CVD (chemical vapor deposition) boron-doped diamond film on titanium(Ti) membrane to modify porous titanium surface, that can be cleaned electrochemically is proposed. Feasibility of its preparation and application is discussed in this paper. Results shows that based on the unique electrochemical properties of diamond, cleaning level of this composite Ti/BDD membrane is significantly increased, making membrane life and efficiency improved prominently.

  15. 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.

  16. Characterization of photoluminescent europium doped yttrium oxide thin-films prepared by metallorganic chemical vapor deposition

    International Nuclear Information System (INIS)

    McKittrick, J.; Bacalski, C.F.; Hirata, G.A.; Hubbard, K.M.; Pattillo, S.G.; Salazar, K.V.; Trkula, M.

    1998-01-01

    Europium doped yttrium oxide, (Y 1-x Eu x ) 2 O 3 , thin-films were deposited on silicon and sapphire substrates by metallorganic chemical vapor deposition (MOCVD). The films were grown in a MOCVD chamber reacting yttrium and europium tris(2,2,6,6-tetramethyl-3,5,-heptanedionates) precursors in an oxygen atmosphere at low pressures (5 Torr) and low substrate temperatures (500--700 C). The films deposited at 500 C were flat and composed of nanocrystalline regions of cubic Y 2 O 3 , grown in a textured [100] or [110] orientation to the substrate surface. Films deposited at 600 C developed from the flat, nanocrystalline morphology into a plate-like growth morphology oriented in the [111] with increasing deposition time. Monoclinic Y 2 O 3 :Eu 3+ was observed in x-ray diffraction for deposition temperatures ≥600 C on both (111) Si and (001) sapphire substrates. This was also confirmed by the photoluminescent emission spectra

  17. Comparative study of tantalum deposition by chemical vapor deposition and electron beam vacuum evaporation

    International Nuclear Information System (INIS)

    Spitz, J.; Chevallier, J.

    1975-01-01

    The coating by tantalum of steel parts has been carried out by the two following methods: chemical vapor deposition by hydrogen reduction of TaCl 5 (temperature=1100 deg C, pressure=200 mmHg, H 2 /TaCl 5 =10); electron beam vacuum evaporation. In this case Ta was firstly condensed by ion plating (P(Ar)=5x10 -3 up to 2x10 -2 mmHg; U(c)=3 to -4kV and J(c)=0.2 to 1mAcm -2 ) in order to ensure a good adhesion between deposit and substrate; then by vacuum condensation (substrate temperature: 300 to 650 deg C) to ensure that the coating is impervious to HCl an H 2 SO 4 acids. The advantages and inconveniences of each method are discussed [fr

  18. High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition

    Science.gov (United States)

    Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

    2015-12-01

    Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm2. The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs.

  19. 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.

  20. Monatomic chemical-vapor-deposited graphene membranes bridge a half-millimeter-scale gap.

    Science.gov (United States)

    Lee, Choong-Kwang; Hwangbo, Yun; Kim, Sang-Min; Lee, Seoung-Ki; Lee, Seung-Mo; Kim, Seong-Su; Kim, Kwang-Seop; Lee, Hak-Joo; Choi, Byung-Ik; Song, Chang-Kyu; Ahn, Jong-Hyun; Kim, Jae-Hyun

    2014-03-25

    One of the main concerns in nanotechnology is the utilization of nanomaterials in macroscopic applications without losing their extreme properties. In an effort to bridge the gap between the nano- and macroscales, we propose a clever fabrication method, the inverted floating method (IFM), for preparing freestanding chemical-vapor-deposited (CVD) graphene membranes. These freestanding membranes were then successfully suspended over a gap a half-millimeter in diameter. To understand the working principle of IFM, high-speed photography and white light interferometry were used to characterize and analyze the deformation behaviors of the freestanding graphene membranes in contact with a liquid during fabrication. Some nanoscale configurations in the macroscopic graphene membranes were able to be characterized by simple optical microscopy. The proposed IFM is a powerful approach to investigating the macroscopic structures of CVD graphene and enables the exploitation of freestanding CVD graphene for device applications.

  1. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    Science.gov (United States)

    Wolak, M. A.; Tan, T.; Krick, A.; Johnson, E.; Hambe, M.; Chen, Ke; Xi, X. X.

    2014-01-01

    We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD). To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB2 films on these substrates showed uniformly good superconducting properties including Tc of 37-40 K, residual resistivity ratio of up to 14, and root-mean-square roughness Rq of 20-30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB2 by the HPCVD technique, an important step towards superconducting rf cavities with MgB2 coating.

  2. Stress hysteresis and mechanical properties of plasma-enhanced chemical vapor deposited dielectric films

    Science.gov (United States)

    Thurn, Jeremy; Cook, Robert F.; Kamarajugadda, Mallika; Bozeman, Steven P.; Stearns, Laura C.

    2004-02-01

    A comprehensive survey is described of the responses of three plasma-enhanced chemical vapor deposited dielectric film systems to thermal cycling and indentation contact. All three films—silicon oxide, silicon nitride, and silicon oxy-nitride—exhibited significant nonequilibrium permanent changes in film stress on thermal cycling or annealing. The linear relationship between stress and temperature changed after the films were annealed at 300 °C, representing a structural alteration in the film reflecting a change in coefficient of thermal expansion or biaxial modulus. A double-substrate method was used to deduce both thermoelastic properties before and after the anneal of selected films and the results were compared with the modulus deconvoluted from small-scale depth-sensing indentation experiments (nanoindentation). Rutherford backscattering spectrometry and hydrogen forward scattering were used to deduce the composition of the films and it was found that all the films contained significant amounts of hydrogen.

  3. Growth of carbon nanotubes by Fe-catalyzed chemical vapor processes on silicon-based substrates

    Science.gov (United States)

    Angelucci, Renato; Rizzoli, Rita; Vinciguerra, Vincenzo; Fortuna Bevilacqua, Maria; Guerri, Sergio; Corticelli, Franco; Passini, Mara

    2007-03-01

    In this paper, a site-selective catalytic chemical vapor deposition synthesis of carbon nanotubes on silicon-based substrates has been developed in order to get horizontally oriented nanotubes for field effect transistors and other electronic devices. Properly micro-fabricated silicon oxide and polysilicon structures have been used as substrates. Iron nanoparticles have been obtained both from a thin Fe film evaporated by e-gun and from iron nitrate solutions accurately dispersed on the substrates. Single-walled nanotubes with diameters as small as 1 nm, bridging polysilicon and silicon dioxide “pillars”, have been grown. The morphology and structure of CNTs have been characterized by SEM, AFM and Raman spectroscopy.

  4. One-step microwave plasma enhanced chemical vapor deposition (MW-PECVD) for transparent superhydrophobic surface

    Science.gov (United States)

    Thongrom, Sukrit; Tirawanichakul, Yutthana; Munsit, Nantakan; Deangngam, Chalongrat

    2018-02-01

    We demonstrate a rapid and environmental friendly fabrication technique to produce optically clear superhydrophobic surfaces using poly (dimethylsiloxane) (PDMS) as a sole coating material. The inert PDMS chain is transformed into a 3-D irregular solid network through microwave plasma enhanced chemical vapor deposition (MW-PECVD) process. Thanks to high electron density in the microwave-activated plasma, coating can be done in just a single step with rapid deposition rate, typically much shorter than 10 s. Deposited layers show excellent superhydrophobic properties with water contact angles of ∼170° and roll-off angles as small as ∼3°. The plasma-deposited films can be ultrathin with thicknesses under 400 nm, greatly diminishing the optical loss. Moreover, with appropriate coating conditions, the coating layer can even enhance the transmission over the entire visible spectrum due to a partial anti-reflection effect.

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

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

    Science.gov (United States)

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

    2011-06-01

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

  7. Response of the ionosphere to the injection of chemically reactive vapors

    International Nuclear Information System (INIS)

    Bernhardt, P.A.

    1976-05-01

    As a gas released in the ionosphere expands, it is rapidly cooled. When the vapor becomes sufficiently tenuous, it is reheated by collisions with the ambient atmosphere, and its flow is then governed by diffusive expansion. As the injected gas becomes well mixed with the plasma, a hole is created by chemical processes. In the case of diatomic hydrogen release, depression of the electron concentrations is governed by the charge exchange reaction between oxygen ions and hydrogen, producing positive hydroxyl ions. Hydroxyl ions rapidly react with the electron gas to produce excited oxygen and hydrogen atoms. Enhanced airglow emissions result from the transition of the excited atoms to lower energy states. The electron temperature in the depleted region rises sharply and this rise causes a thermal expansion of the plasma and a further reduction in the local plasma concentration

  8. Stress hysteresis during thermal cycling of plasma-enhanced chemical vapor deposited silicon oxide films

    Science.gov (United States)

    Thurn, Jeremy; Cook, Robert F.

    2002-02-01

    The mechanical response of plasma-enhanced chemical vapor deposited SiO2 to thermal cycling is examined by substrate curvature measurement and depth-sensing indentation. Film properties of deposition stress and stress hysteresis that accompanied thermal cycling are elucidated, as well as modulus, hardness, and coefficient of thermal expansion. Thermal cycling is shown to result in major plastic deformation of the film and a switch from a compressive to a tensile state of stress; both athermal and thermal components of the net stress alter in different ways during cycling. A mechanism of hydrogen incorporation and release from as-deposited silanol groups is proposed that accounts for the change in film properties and state of stress.

  9. Characterization of Cr2O3 thin films obtained by chemical vapor deposition

    International Nuclear Information System (INIS)

    Pillis, M.F.; Galego, E.; Serna, M.M.; Correa, O.V.; Ramanathan, L.V.; Franco, A.C.

    2010-01-01

    The goal of this work was the synthesis and characterization of Cr 2 O 3 thin films, obtained by chemical vapor deposition, using chromium acetylacetonate as chromium precursor. The growth of the films was carried out in a conventional horizontal MOCVD equipment, under pressures varying from 2 to 10 mbar, and temperature of 600 deg C. It was observed that the growth of the films only occurs when oxygen is present in the atmosphere. Under growth pressures of 2 and 5 mbar the growth takes place but under 10 mbar of pressure the precursor is dragged and the growth does not occur. The characterization of the films was performed by using scanning electron microscopy and X-ray diffraction. The films presented a columnar structure, and thickness varying from 40 to 250 nm. The influence of some process parameters is discussed. (author)

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

    International Nuclear Information System (INIS)

    Rius, G; Yoshimura, M

    2013-01-01

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

  11. Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide.

    Science.gov (United States)

    Dankert, André; Pashaei, Parham; Kamalakar, M Venkata; Gaur, Anand P S; Sahoo, Satyaprakash; Rungger, Ivan; Narayan, Awadhesh; Dolui, Kapildeb; Hoque, Md Anamul; Patel, Ram Shanker; de Jong, Michel P; Katiyar, Ram S; Sanvito, Stefano; Dash, Saroj P

    2017-06-27

    The two-dimensional (2D) semiconductor molybdenum disulfide (MoS 2 ) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we report on spin-polarized tunneling through chemical vapor deposited multilayer MoS 2 (∼7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5-2% has been observed, corresponding to spin polarization of 5-10% in the measured temperature range of 300-75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS 2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  13. Chemical vapor deposition of diamond onto iron based substrates. The use of barrier layers

    International Nuclear Information System (INIS)

    Weiser, P.S.; Prawer, S.

    1995-01-01

    When Fe is exposed to the plasma environment suitable for the chemical vapor deposition (CVD) of diamond, the surface is rapidly covered with a thick layer graphitic soot and C swiftly diffuses into the Fe substrate. Once the soot reaches a critical thickness, diamond films nucleate and grow on top of it. However, adhesion of the film to the substrate is poor due to the lack of structural integrity of the soot layer, A thin coating of TiN on the Fe can act to prevent diffusion and soot formation. Diamond readily grows upon the TiN via an a-C interface layer, but the a-C/TiN interface is weak and delamination occurs at this interface. In order to try and improve the adhesion, the use of a high dose Ti implant was investigated to replace the TiN coating. 7 refs., 6 figs

  14. 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.

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

    International Nuclear Information System (INIS)

    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

  16. Environmental effects on the tensile strength of chemically vapor deposited silicon carbide fibers

    Science.gov (United States)

    Bhatt, R. T.; Kraitchman, M. D.

    1985-01-01

    The room temperature and elevated temperature tensile strengths of commercially available chemically vapor-deposited (CVD) silicon carbide fibers were measured after 15 min heat treatment to 1600 C in various environments. These environments included oxygen, air, argon and nitrogen at one atmosphere and vacuum at 10/9 atmosphere. Two types of fibers were examined which differed in the SiC content of their carbon-rich coatings. Threshold temperature for fiber strength degradation was observed to be dependent on the as-received fiber-flaw structure, on the environment and on the coating. Fractographic analyses and flexural strength measurements indicate that tensile strength losses were caused by surface degradation. Oxidation of the surface coating is suggested as one possible degradation mechanism. The SiC fibers containing the higher percentage of SiC near the surface of the carbon-rich coating show better strength retention and higher elevated temperature strength.

  17. Morphology and structure of Ti-doped diamond films prepared by microwave plasma chemical vapor deposition

    Science.gov (United States)

    Liu, Xuejie; Lu, Pengfei; Wang, Hongchao; Ren, Yuan; Tan, Xin; Sun, Shiyang; Jia, Huiling

    2018-06-01

    Ti-doped diamond films were deposited through a microwave plasma chemical vapor deposition (MPCVD) system for the first time. The effects of the addition of Ti on the morphology, microstructure and quality of diamond films were systematically investigated. Secondary ion mass spectrometry results show that Ti can be added to diamond films through the MPCVD system using tetra n-butyl titanate as precursor. The spectra from X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy and the images from scanning electron microscopy of the deposited films indicate that the diamond phase clearly exists and dominates in Ti-doped diamond films. The amount of Ti added obviously influences film morphology and the preferred orientation of the crystals. Ti doping is beneficial to the second nucleation and the growth of the (1 1 0) faceted grains.

  18. Observation of Zn vacancies in ZnO grown by chemical vapor transport

    Energy Technology Data Exchange (ETDEWEB)

    Tuomisto, F.; Saarinen, K. [Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, 02015 TKK (Finland); Grasza, K.; Mycielski, A. [Institute of Physics, Polish Academy of Sciences, Lotnikow 32/46, 02-668 Warsaw (Poland)

    2006-03-15

    We have used positron annihilation spectroscopy to study the vacancy defects in ZnO crystals grown by both the conventional and contactless chemical vapor transport (CVT and CCVT). Our results show that Zn vacancies or Zn vacancy related defects are present in as-grown ZnO, irrespective of the growth method. Zn vacancies are observed in CVT-grown undoped ZnO and (Zn,Mn)O. The Zn vacancies present in undoped CCVT-ZnO are the dominant negatively charged point defect in the material. Doping the material with As introduces also Zn vacancy-related defect complexes with larger open volume. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Surface modification of titanium membrane by chemical vapor deposition and its electrochemical self-cleaning

    Energy Technology Data Exchange (ETDEWEB)

    Li, X.W., E-mail: lynnww@sohu.com [School of Electronic and Information Engieering, Tianjin university, Tianjin, 300072 (China); School of Electronics Information Engieering, Tianjin University of Technology, Tianjin, 300384 (China); Li, J.X. [Tianjin Polytechnic University, Tianjin 300160 (China); Gao, C.Y. [Chinese Peoples Armed Police Forces Academy, Langfang 065000 (China); Chang, M. [School of Electronic and Information Engieering, Tianjin university, Tianjin, 300072 (China); School of Electronics Information Engieering, Tianjin University of Technology, Tianjin, 300384 (China)

    2011-10-15

    Membrane separation is applied widely in many fields, while concentration polarization and membrane fouling, limiting its promotion and application greatly, are the bottlenecks in membrane application. Among which, membrane fouling is irreversible, membrane must be periodically cleaned or even replaced to restore permeability. Membrane cleaning has become one of Key issues in membrane separation areas. Considering incomparable electrochemical advantages of boron-doped diamond (BDD) film electrode over conventional electrode, a new composite membrane Ti/BDD, made by depositing CVD (chemical vapor deposition) boron-doped diamond film on titanium(Ti) membrane to modify porous titanium surface, that can be cleaned electrochemically is proposed. Feasibility of its preparation and application is discussed in this paper. Results shows that based on the unique electrochemical properties of diamond, cleaning level of this composite Ti/BDD membrane is significantly increased, making membrane life and efficiency improved prominently.

  20. Effects of etchants in the transfer of chemical vapor deposited graphene

    Science.gov (United States)

    Wang, M.; Yang, E. H.; Vajtai, R.; Kono, J.; Ajayan, P. M.

    2018-05-01

    The quality of graphene can be strongly modified during the transfer process following chemical vapor deposition (CVD) growth. Here, we transferred CVD-grown graphene from a copper foil to a SiO2/Si substrate using wet etching with four different etchants: HNO3, FeCl3, (NH4)2S2O8, and a commercial copper etchant. We then compared the quality of graphene after the transfer process in terms of surface modifications, pollutions (residues and contaminations), and electrical properties (mobility and density). Our tests and analyses showed that the commercial copper etchant provides the best structural integrity, the least amount of residues, and the smallest doping carrier concentration.

  1. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    M. A. Wolak

    2014-01-01

    Full Text Available We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD. To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB_{2} films on these substrates showed uniformly good superconducting properties including T_{c} of 37–40 K, residual resistivity ratio of up to 14, and root-mean-square roughness R_{q} of 20–30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB_{2} by the HPCVD technique, an important step towards superconducting rf cavities with MgB_{2} coating.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-04-01

    This program is designed to develop a Hall-Heroult aluminum smelting cathode with substantially improved properties. The carbon cathodes in current use require significant anode-to-cathode spacing in order to prevent shorting, causing significant electrical inefficiencies. This is due to the non-wettability of carbon by aluminum which causes instability in the cathodic aluminum pad. It is suggested that a fiber reinforced-TiB{sub 2} matrix composite would have the requisite wettability, strength, strain-to-failure, cost, and lifetime to solve this problem. The approach selected to fabricate such a cathode material is chemical vapor infiltration (CVI). This process produces high purity matrix TiB{sub 2} without damaging the relatively fragile fibers. The program is designed to evaluate potential fiber reinforcements, fabricate test specimens, and scale the process to provide demonstration components.

  3. Mass-Spectrometric Studies of Catalytic Chemical Vapor Deposition Processes of Organic Silicon Compounds Containing Nitrogen

    Science.gov (United States)

    Morimoto, Takashi; Ansari, S. G.; Yoneyama, Koji; Nakajima, Teppei; Masuda, Atsushi; Matsumura, Hideki; Nakamura, Megumi; Umemoto, Hironobu

    2006-02-01

    The mechanism of catalytic chemical vapor deposition (Cat-CVD) processes for hexamethyldisilazane (HMDS) and trisdimethylaminosilane (TDMAS), which are used as source gases to prepare SiNx or SiCxNy films, was studied using three different mass spectrometric techniques: ionization by Li+ ion attachment, vacuum-ultraviolet radiation and electron impact. The results for HMDS show that Si-N bonds dissociate selectively, although Si-C bonds are weaker, and (CH3)3SiNH should be one of the main precursors of deposited films. This decomposition mechanism did not change when NH3 was introduced, but the decomposition efficiency was slightly increased. Similar results were obtained for TDMAS.

  4. Regression Methods for Virtual Metrology of Layer Thickness in Chemical Vapor Deposition

    DEFF Research Database (Denmark)

    Purwins, Hendrik; Barak, Bernd; Nagi, Ahmed

    2014-01-01

    The quality of wafer production in semiconductor manufacturing cannot always be monitored by a costly physical measurement. Instead of measuring a quantity directly, it can be predicted by a regression method (Virtual Metrology). In this paper, a survey on regression methods is given to predict...... average Silicon Nitride cap layer thickness for the Plasma Enhanced Chemical Vapor Deposition (PECVD) dual-layer metal passivation stack process. Process and production equipment Fault Detection and Classification (FDC) data are used as predictor variables. Various variable sets are compared: one most...... algorithm, and Support Vector Regression (SVR). On a test set, SVR outperforms the other methods by a large margin, being more robust towards changes in the production conditions. The method performs better on high-dimensional multivariate input data than on the most predictive variables alone. Process...

  5. Direct Growth of Graphene on Silicon by Metal-Free Chemical Vapor Deposition

    Science.gov (United States)

    Tai, Lixuan; Zhu, Daming; Liu, Xing; Yang, Tieying; Wang, Lei; Wang, Rui; Jiang, Sheng; Chen, Zhenhua; Xu, Zhongmin; Li, Xiaolong

    2018-06-01

    The metal-free synthesis of graphene on single-crystal silicon substrates, the most common commercial semiconductor, is of paramount significance for many technological applications. In this work, we report the growth of graphene directly on an upside-down placed, single-crystal silicon substrate using metal-free, ambient-pressure chemical vapor deposition. By controlling the growth temperature, in-plane propagation, edge-propagation, and core-propagation, the process of graphene growth on silicon can be identified. This process produces atomically flat monolayer or bilayer graphene domains, concave bilayer graphene domains, and bulging few-layer graphene domains. This work would be a significant step toward the synthesis of large-area and layer-controlled, high-quality graphene on single-crystal silicon substrates. [Figure not available: see fulltext.

  6. Diameter Tuning of β-Ga2O3 Nanowires Using Chemical Vapor Deposition Technique.

    Science.gov (United States)

    Kumar, Mukesh; Kumar, Vikram; Singh, R

    2017-12-01

    Diameter tuning of [Formula: see text]-Ga 2 O 3 nanowires using chemical vapor deposition technique have been investigated under various experimental conditions. Diameter of root grown [Formula: see text]-Ga 2 O 3 nanowires having monoclinic crystal structure is tuned by varying separation distance between metal source and substrate. Effect of gas flow rate and mixer ratio on the morphology and diameter of nanowires has been studied. Nanowire diameter depends on growth temperature, and it is independent of catalyst nanoparticle size at higher growth temperature (850-900 °C) as compared to lower growth temperature (800 °C). These nanowires show changes in structural strain value with change in diameter. Band-gap of nanowires increases with decrease in the diameter.

  7. Growth of GaN micro/nanolaser arrays by chemical vapor deposition.

    Science.gov (United States)

    Liu, Haitao; Zhang, Hanlu; Dong, Lin; Zhang, Yingjiu; Pan, Caofeng

    2016-09-02

    Optically pumped ultraviolet lasing at room temperature based on GaN microwire arrays with Fabry-Perot cavities is demonstrated. GaN microwires have been grown perpendicularly on c-GaN/sapphire substrates through simple catalyst-free chemical vapor deposition. The GaN microwires are [0001] oriented single-crystal structures with hexagonal cross sections, each with a diameter of ∼1 μm and a length of ∼15 μm. A possible growth mechanism of the vertical GaN microwire arrays is proposed. Furthermore, we report room-temperature lasing in optically pumped GaN microwire arrays based on the Fabry-Perot cavity. Photoluminescence spectra exhibit lasing typically at 372 nm with an excitation threshold of 410 kW cm(-2). The result indicates that these aligned GaN microwire arrays may offer promising prospects for ultraviolet-emitting micro/nanodevices.

  8. 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%.

  9. Large-scale Fabrication of 2D Materials by Chemical Vapor Deposition

    DEFF Research Database (Denmark)

    Shivayogimath, Abhay

    . This thesis aims to address some of the challenges associated with materials fabrication in order to lay the groundwork for commercial implementation of 2D materials. To improve graphene implementation in electronic applications, copper catalyst foils were engineered to reduce surface roughness, wrinkles...... this vast range of materials - without the lattice mismatch constraints of conventional 3D materials - into atomically engineered, artificial 3D crystals that pave the way for new physics, and subsequently, for new applications. 2D materials are expected to disrupt a number of industries in the future......, such as electronics, displays, energy, and catalysis. The key bottleneck for commercial implementation is in large-scale synthesis and subsequent fabrication of high quality devices. Chemical vapor deposition is considered to be the most economically feasible synthesis method to this end. In the case of graphene...

  10. Catalyst effects of fabrication of carbon nanotubes synthesized by chemical vapor deposition

    International Nuclear Information System (INIS)

    Tian, F.; Li, H.P.; Zhao, N.Q.; He, C.N.

    2009-01-01

    Catalytic effects of the fabrication of carbon nanotubes (CNTs) by chemical vapor deposition of methane were investigated by thermogravimetric analysis. More specifically, the total yield and thermal stability characteristics of the product were examined with respect to physicochemical characteristics of the catalyst. Three kinds of Ni/Al catalysts with 5 wt%, 10 wt% and 15 wt% Ni, respectively were employed to synthesize CNTs. It was determined that an optimal Ni content of the catalyst resulted in maximum yield and most stable product. With increasing the Ni content, the CNT yield increased but they became less stable during heat treatment in air. According to transmission electron microscopy observations, the defect sites along the walls and at the ends of the raw CNTs facilitated the thermal oxidative destruction of the CNTs.

  11. Catalyst-free growth of InN nanorods by metal-organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Kim, Min Hwa; Moon, Dae Young; Park, Jinsub; Nanishi, Yasushi; Yi, Gyu-Chul; Yoon, Euijoon

    2012-01-01

    We demonstrated the growth of catalyst-free InN nanostructures including nanorods on (0001) Al 2 O 3 substrates using metal-organic chemical vapor deposition. As the growth time increased, growth rate along c-direction increased superlinearly with decreasing c-plane area fractions and increasing side wall areas. It was also found that desorption from the sidewalls of InN nanostructures during the InN nanorods formation was one of essential key parameters of the growth mechanism. We propose a growth model to explain the InN nanostructure evolution by considering the side wall desorption and re-deposition of indium at top c-plane surfaces. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Fabrication of thin-wall, freestanding inertial confinement fusion targets by chemical vapor deposition

    International Nuclear Information System (INIS)

    Carroll, D.W.; McCreary, W.J.

    1982-01-01

    To meet the requirements for plasma physics experiments in the inertial confinement fusion (ICF) program, chemical vapor deposition (CVD) in fluid beds was used to fabricate freestanding tungsten spheres and cylinders with wall thicknesses less than 5.0 μm. Molybdenum and molybdenum alloy (TZM) mandrels of the desired geometry were suspended in a carrier bed of dense microspheres contained in an induction-heated fluid-bed reactor. The mandrels were free to float randomly through the bed, and using the reaction WF 6 +3H 2 →/sub /KW +6HF, very fine-grained tungsten was deposited onto the surface at a rate and in a grain size determined by temperature, gas flow rate, system pressure, and duration of the reaction. After coating, a portion of each mandrel was exposed by hole drilling or grinding. The mandrel was then removed by acid leaching, leaving a freestanding tungsten shape. Experimental procedures, mandrel preparation, and results obtained are discussed

  13. Two dimensional radial gas flows in atmospheric pressure plasma-enhanced chemical vapor deposition

    Science.gov (United States)

    Kim, Gwihyun; Park, Seran; Shin, Hyunsu; Song, Seungho; Oh, Hoon-Jung; Ko, Dae Hong; Choi, Jung-Il; Baik, Seung Jae

    2017-12-01

    Atmospheric pressure (AP) operation of plasma-enhanced chemical vapor deposition (PECVD) is one of promising concepts for high quality and low cost processing. Atmospheric plasma discharge requires narrow gap configuration, which causes an inherent feature of AP PECVD. Two dimensional radial gas flows in AP PECVD induces radial variation of mass-transport and that of substrate temperature. The opposite trend of these variations would be the key consideration in the development of uniform deposition process. Another inherent feature of AP PECVD is confined plasma discharge, from which volume power density concept is derived as a key parameter for the control of deposition rate. We investigated deposition rate as a function of volume power density, gas flux, source gas partial pressure, hydrogen partial pressure, plasma source frequency, and substrate temperature; and derived a design guideline of deposition tool and process development in terms of deposition rate and uniformity.

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

    International Nuclear Information System (INIS)

    Shukrullah, S.; Mohamed, N. M.; Shaharun, M. S.; Yasar, M.

    2014-01-01

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-30

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

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

    International Nuclear Information System (INIS)

    Schropp, R.E.I.

    2015-01-01

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

  17. 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.

  18. SiO{sub 2} coating of silver nanoparticles by photoinduced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Boies, Adam M; Girshick, Steven L [Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455 (United States); Roberts, Jeffrey T [Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455 (United States); Zhang Bin; Nakamura, Toshitaka; Mochizuki, Amane, E-mail: jtrob@umn.ed, E-mail: slg@umn.ed [Nitto Denko Technical Corporation, 501 Via Del Monte, Oceanside, CA 92058 (United States)

    2009-07-22

    Gas-phase silver nanoparticles were coated with silicon dioxide (SiO{sub 2}) by photoinduced chemical vapor deposition (photo-CVD). Silver nanoparticles, produced by inert gas condensation, and a SiO{sub 2} precursor, tetraethylorthosilicate (TEOS), were exposed to vacuum ultraviolet (VUV) radiation at atmospheric pressure and varying temperatures. The VUV photons dissociate the TEOS precursor, initiating a chemical reaction that forms SiO{sub 2} coatings on the particle surfaces. Coating thicknesses were measured for a variety of operation parameters using tandem differential mobility analysis and transmission electron microscopy. The chemical composition of the particle coatings was analyzed using energy dispersive x-ray spectrometry and Fourier transform infrared spectroscopy. The highest purity films were produced at 300-400 {sup 0}C with low flow rates of additional oxygen. The photo-CVD coating technique was shown to effectively coat nanoparticles and limit core particle agglomeration at concentrations up to 10{sup 7} particles cm{sup -3}.

  19. Effect of precursor supply on structural and morphological characteristics of fe nanomaterials synthesized via chemical vapor condensation method.

    Science.gov (United States)

    Ha, Jong-Keun; Ahn, Hyo-Jun; Kim, Ki-Won; Nam, Tae-Hyun; Cho, Kwon-Koo

    2012-01-01

    Various physical, chemical and mechanical methods, such as inert gas condensation, chemical vapor condensation, sol-gel, pulsed wire evaporation, evaporation technique, and mechanical alloying, have been used to synthesize nanoparticles. Among them, chemical vapor condensation (CVC) has the benefit of its applicability to almost all materials because a wide range of precursors are available for large-scale production with a non-agglomerated state. In this work, Fe nanoparticles and nanowires were synthesized by chemical vapor condensation method using iron pentacarbonyl (Fe(CO)5) as the precursor. The effect of processing parameters on the microstructure, size and morphology of Fe nanoparticles and nanowires were studied. In particular, we investigated close correlation of size and morphology of Fe nanoparticles and nanowires with atomic quantity of inflow precursor into the electric furnace as the quantitative analysis. The atomic quantity was calculated by Boyle's ideal gas law. The Fe nanoparticles and nanowires with various diameter and morphology have successfully been synthesized by the chemical vapor condensation method.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-31

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

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

    Directory of Open Access Journals (Sweden)

    Tyagi Renu

    2009-01-01

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

  2. Effect of Sn Composition in Ge1- x Sn x Layers Grown by Using Rapid Thermal Chemical Vapor Deposition

    Science.gov (United States)

    Kil, Yeon-Ho; Kang, Sukill; Jeong, Tae Soo; Shim, Kyu-Hwan; Kim, Dae-Jung; Choi, Yong-Dae; Kim, Mi Joung; Kim, Taek Sung

    2018-05-01

    The Ge1- x Sn x layers were grown by using rapid thermal chemical-vapor deposition (RTCVD) on boron-doped p-type Si (100) substrates with Sn compositions up to x = 0.83%. In order to obtain effect of the Sn composition on the structural and the optical characteristics, we utilized highresolution X-ray diffraction (HR-XRD), etch pit density (EPD), atomic force microscopy (AFM), Raman spectroscopy, and photocurrent (PC) spectra. The Sn compositions in the Ge1- x Sn x layers were found to be of x = 0.00%, 0.51%, 0.65%, and 0.83%. The root-mean-square (RMS) of the surface roughness of the Ge1- x Sn x layer increased from 2.02 nm to 3.40 nm as the Sn composition was increased from 0.51% to 0.83%, and EPD was on the order of 108 cm-2. The Raman spectra consist of only one strong peak near 300 cm-1, which is assigned to the Ge-Ge LO peaks and the Raman peaks shift to the wave number with increasing Sn composition. Photocurrent spectra show near energy band gap peaks and their peak energies decrease with increasing Sn composition due to band-gap bowing in the Ge1- x Sn x layer. An increase in the band gap bowing parameter was observed with increasing Sn composition.

  3. Dry transfer of chemical-vapor-deposition-grown graphene onto liquid-sensitive surfaces for tunnel junction applications

    International Nuclear Information System (INIS)

    Feng, Ying; Chen, Ke

    2015-01-01

    We report a dry transfer method that can tranfer chemical vapor deposition (CVD) grown graphene onto liquid-sensitive surfaces. The graphene grown on copper (Cu) foil substrate was first transferred onto a freestanding 4 μm thick sputtered Cu film using the conventional wet transfer process, followed by a dry transfer process onto the target surface using a polydimethylsiloxane stamp. The dry-transferred graphene has similar properties to traditional wet-transferred graphene, characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy, and electrical transport measurements. It has a sheet resistance of 1.6 ∼ 3.4 kΩ/□, hole density of (4.1 ∼ 5.3) × 10 12 cm −2 , and hole mobility of 460 ∼ 760 cm 2 V −1 s −1 without doping at room temperature. The results suggest that large-scale CVD-grown graphene can be transferred with good quality and without contaminating the target surface by any liquid. Mg/MgO/graphene tunnel junctions were fabricated using this transfer method. The junctions show good tunneling characteristics, which demonstrates the transfer technique can also be used to fabricate graphene devices on liquid-sensitive surfaces. (paper)

  4. Surface termination structure of α-Ga{sub 2}O{sub 3} film grown by mist chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Tamba, Daiki; Kubo, Osamu, E-mail: okubo@eei.eng.osaka-u.ac.jp; Osaka, Shun; Takahashi, Kazuki; Tabata, Hiroshi; Katayama, Mitsuhiro [Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, Suita 565-0871 (Japan); Oda, Masaya [Photonics and Electronics Science and Engineering Center, Graduate School of Engineering, Kyoto University, Kyoto 615-8520 (Japan); FLOSFIA Inc., 1-36 Goryoohara, Kyoto 615-8245 (Japan); Kaneko, Kentaro; Fujita, Shizuo [Photonics and Electronics Science and Engineering Center, Graduate School of Engineering, Kyoto University, Kyoto 615-8520 (Japan)

    2016-06-20

    The surface structure of α-Ga{sub 2}O{sub 3}(0001) grown on an α-Al{sub 2}O{sub 3}(0001) substrate by mist chemical vapor deposition was studied by coaxial impact-collision ion scattering spectroscopy (CAICISS) and atomic force microscopy (AFM). The minimum step height observed in the AFM image was 0.21 ± 0.01 nm, coinciding with the height of three atomic layers of α-Ga{sub 2}O{sub 3}(0001). It was revealed by CAICISS analysis that the surface of α-Ga{sub 2}O{sub 3}(0001) is terminated by a Ga layer followed by an O layer, which is consistent with the surface termination of α-Al{sub 2}O{sub 3}(0001). A structural model taking surface relaxation into account was also constructed by fitting the simulated curve for the azimuth angle dependence of the Ga intensity to the experimental dependence. The resultant structural model is similar to the model of an α-Al{sub 2}O{sub 3}(0001) surface, which indicates analogous behavior in corundum crystals.

  5. Numerical analysis of the in-well vapor-stripping system demonstration at Edwards Air Force Base

    International Nuclear Information System (INIS)

    White, M.D.; Gilmore, T.J.

    1996-10-01

    Numerical simulations, with the Subsurface Transport Over Multiple Phases (STOMP) simulator, were applied to the field demonstration of an in-well vapor-stripping system at Edwards Air Force Base (AFB), near Mojave, California. The demonstration field site on the Edwards AFB was previously contaminated from traversing groundwater that was contained a varied composition of volatile organic compounds (VOCs), which primarily includes trichloroethylene (TCE). Contaminant TCE originated from surface basin that had been used to collect runoff during the cleaning of experimental rocket powered planes in the 1960s and 1970s. This report documents those simulations and associated numerical analyses. A companion report documents the in- well vapor-stripping demonstration from a field perspective

  6. Development of Y-BA-CU-O Coated Conductor Using Metal Organic Chemical Vapor Deposition

    National Research Council Canada - National Science Library

    Selvamanickam, V

    2003-01-01

    .... The program includes a study of the a) influence of MOCVD processing conditions such as the flow rate of precursor vapors, precursor vaporization temperatures, oxygen partial pressure, reactor pressure, and the deposition temperature...

  7. Pore-scale modeling of vapor transport in partially saturated capillary tube with variable area using chemical potential

    DEFF Research Database (Denmark)

    Addassi, Mouadh; Schreyer, Lynn; Johannesson, Björn

    2016-01-01

    Here we illustrate the usefulness of using the chemical potential as the primary unknown by modeling isothermal vapor transport through a partially saturated cylindrically symmetric capillary tube of variable cross-sectional area using a single equation. There are no fitting parameters and the nu......Here we illustrate the usefulness of using the chemical potential as the primary unknown by modeling isothermal vapor transport through a partially saturated cylindrically symmetric capillary tube of variable cross-sectional area using a single equation. There are no fitting parameters...... and the numerical solutions to the equation are compared with experimental results with excellent agreement. We demonstrate that isothermal vapor transport can be accurately modeled without modeling the details of the contact angle, microscale temperature fluctuations, or pressure fluctuations using a modification...

  8. Chemical interactions between aerosols and vapors in the primary circuit of an LWR during a severe accident

    International Nuclear Information System (INIS)

    Wheatley, C.J.

    1988-01-01

    Aerosol formation, agglomeration, convection and deposition within the primary circuit of an LWR during a severe accident significantly affect the transport of fission products, even though they may compose only a small fraction of the aerosol material. Intra-particle and vapor chemical interactions are important to this through mass transfer between the aerosol and vapor. The authors will describe a model that attempts to account for these processes and of the two-way coupling that exists with the thermal hydraulics. They will discuss what agglomeration and deposition mechanisms must be included, alternatives for treating intra-particle chemical interactions, mechanisms of aerosol formation, and methods for solving the resulting equations. Results will be presented that illustrate the importance of treating the two-way coupling and the extent to which disequilibrium between the aerosol and vapor affects fission product behavior

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-02-26

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

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

    International Nuclear Information System (INIS)

    Jiang Hao; Hong Lianggou; Venkatasubramanian, N.; Grant, John T.; Eyink, Kurt; Wiacek, Kevin; Fries-Carr, Sandra; Enlow, Jesse; Bunning, Timothy J.

    2007-01-01

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

  11. Controlling the resistivity gradient in aluminum-doped zinc oxide grown by plasma-enhanced chemical vapor deposition

    NARCIS (Netherlands)

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

  12. Electrical Transport and Low-Frequency Noise in Chemical Vapor Deposited Single-Layer MoS2 Devices

    Science.gov (United States)

    2014-03-18

    PERSON 19b. TELEPHONE NUMBER Pullickel Ajayan Deepak Sharma, Matin Amani, Abhishek Motayed, Pankaj B. Shah, A. Glen Birdwell, Sina Najmaei, Pulickel...in chemical vapor deposited single-layer MoS2 devices Deepak Sharma1,2, Matin Amani3, Abhishek Motayed2,4, Pankaj B Shah3, A Glen Birdwell3, Sina

  13. 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

  14. Structural and optical characterization of self-assembled Ge nanocrystal layers grown by plasma-enhanced chemical vapor deposition

    NARCIS (Netherlands)

    Saeed, S.; Buters, F.; Dohnalova, K.; Wosinski, L.; Gregorkiewicz, T.

    2014-01-01

    We present a structural and optical study of solid-state dispersions of Ge nanocrystals prepared by plasma-enhanced chemical vapor deposition. Structural analysis shows the presence of nanocrystalline germanium inclusions embedded in an amorphous matrix of Si-rich SiO2. Optical characterization

  15. A comparison of diamond growth rate using in-liquid and conventional plasma chemical vapor deposition methods

    International Nuclear Information System (INIS)

    Takahashi, Yoshiyuki; Toyota, Hiromichi; Nomura, Shinfuku; Mukasa, Shinobu; Inoue, Toru

    2009-01-01

    In order to make high-speed deposition of diamond effective, diamond growth rates for gas-phase microwave plasma chemical vapor deposition and in-liquid microwave plasma chemical vapor deposition are compared. A mixed gas of methane and hydrogen is used as the source gas for the gas-phase deposition, and a methanol solution of ethanol is used as the source liquid for the in-liquid deposition. The experimental system pressure is in the range of 60-150 kPa. While the growth rate of diamond increases as the pressure increases, the amount of input microwave energy per unit volume of diamond is 1 kW h/mm 3 regardless of the method used. Since the in-liquid deposition method provides a superior cooling effect through the evaporation of the liquid itself, a higher electric input power can be applied to the electrodes under higher pressure environments. The growth rate of in-liquid microwave plasma chemical vapor deposition process is found to be greater than conventional gas-phase microwave plasma chemical vapor deposition process under the same pressure conditions.

  16. A comparison of diamond growth rate using in-liquid and conventional plasma chemical vapor deposition methods

    Science.gov (United States)

    Takahashi, Yoshiyuki; Toyota, Hiromichi; Nomura, Shinfuku; Mukasa, Shinobu; Inoue, Toru

    2009-06-01

    In order to make high-speed deposition of diamond effective, diamond growth rates for gas-phase microwave plasma chemical vapor deposition and in-liquid microwave plasma chemical vapor deposition are compared. A mixed gas of methane and hydrogen is used as the source gas for the gas-phase deposition, and a methanol solution of ethanol is used as the source liquid for the in-liquid deposition. The experimental system pressure is in the range of 60-150 kPa. While the growth rate of diamond increases as the pressure increases, the amount of input microwave energy per unit volume of diamond is 1 kW h/mm3 regardless of the method used. Since the in-liquid deposition method provides a superior cooling effect through the evaporation of the liquid itself, a higher electric input power can be applied to the electrodes under higher pressure environments. The growth rate of in-liquid microwave plasma chemical vapor deposition process is found to be greater than conventional gas-phase microwave plasma chemical vapor deposition process under the same pressure conditions.

  17. 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...

  18. Nonradioactive Environmental Emissions Chemical Source Term for the Double-Shell Tank (DST) Vapor Space During Waste Retrieval Operations

    International Nuclear Information System (INIS)

    MAY, T.H.

    2000-01-01

    A nonradioactive chemical vapor space source term for tanks on the Phase 1 and the extended Phase 1 delivery, storage, and disposal mission was determined. Operations modeled included mixer pump operation and DST waste transfers. Concentrations of ammonia, specific volatile organic compounds, and quantitative volumes of aerosols were estimated

  19. Dosimetric characterization of chemical-vapor-deposited diamond film irradiated with UV and beta radiation

    Science.gov (United States)

    Meléndrez, R.; Chernov, V.; Pedroza-Montero, M.; Barboza-Flores, M.

    2003-03-01

    Diamond is an excellent prospect for clinical radiation dosimetry due to its tissue-equivalence properties and being chemically inert. The use of diamond in radiation dosimetry has been halted by the high market price; although recently the capability of growing high quality polycrystalline has renewed the interest in using diamond films as detectors and dosimeters. In the present work we have characterized the dosimetric properties of diamond films synthesized by using chemical vapor deposition. The thermoluminescence (TL) of UV and beta exposed samples shows a glow curve composed of at least four peaks; one located around 587 K presents excellent TL properties suitable for dosimetric applications with ionizing and non ionizing radiation. The TL excitation spectrum exhibits maximum TL efficiency at 220 nm. The samples show regions of linear as well as supralinear behavior as a function or irradiation dose. The linear dose dependence was found for up to sixteen minutes of UV irradiation and 300 Gy for beta irradiated samples. The activation energy and the frequency factor were determined and found in the range of 0.32 - 0.89 eV and 1.1x10^2 - 2x10^8s_-1, respectively. The observed TL performance is reasonable appropriate to justify further investigation of diamond films as radiation dosimeters.

  20. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-15

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

  2. 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.

  3. 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.

  4. Core-shell SrTiO3/graphene structure by chemical vapor deposition for enhanced photocatalytic performance

    Science.gov (United States)

    He, Chenye; Bu, Xiuming; Yang, Siwei; He, Peng; Ding, Guqiao; Xie, Xiaoming

    2018-04-01

    Direct growth of high quality graphene on the surface of SrTiO3 (STO) was realized through chemical vapor deposition (CVD), to construct few-layer 'graphene shell' on every STO nanoparticle. The STO/graphene composite shows significantly enhanced UV light photocatalytic activity compared with the STO/rGO reference. Mechanism analysis confirms the role of special core-shell structure and chemical bond (Tisbnd C) for rapid interfacial electron transfer and effective electron-hole separation.

  5. Joining Forces: The Chemical Biology-Medicinal Chemistry Continuum.

    Science.gov (United States)

    Plowright, Alleyn T; Ottmann, Christian; Arkin, Michelle; Auberson, Yves P; Timmerman, Henk; Waldmann, Herbert

    2017-09-21

    The scientific advances being made across all disciplines are creating ever-increasing opportunities to enhance our knowledge of biological systems and how they relate to human disease. One of the central driving forces in discovering new medicines is medicinal chemistry, where the design and synthesis of novel compounds has led to multiple drugs. Chemical biology, sitting at the interface of many disciplines, has now emerged as a major contributor to the understanding of biological systems and is becoming an integral part of drug discovery. Bringing chemistry and biology much closer and blurring the boundaries between disciplines is creating new opportunities to probe and understand biology; both disciplines play key roles and need to join forces and work together effectively to synergize their impact. The power of chemical biology will then reach its full potential and drive innovation, leading to the discovery of transformative medicines to treat patients. Advances in cancer biology and drug discovery highlight this potential. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. 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°.

  7. Limitations of patterning thin films by shadow mask high vacuum chemical vapor deposition

    International Nuclear Information System (INIS)

    Reinke, Michael; Kuzminykh, Yury; Hoffmann, Patrik

    2014-01-01

    A key factor in engineering integrated devices such as electro-optic switches or waveguides is the patterning of high quality crystalline thin films into specific geometries. In this contribution high vacuum chemical vapor deposition (HV-CVD) was employed to grow titanium dioxide (TiO 2 ) patterns onto silicon. The directed nature of precursor transport – which originates from the high vacuum environment during the process – allows shading certain regions on the substrate by shadow masks and thus depositing patterned thin films. While the use of such masks is an emerging field in stencil or shadow mask lithography, their use for structuring thin films within HV-CVD has not been reported so far. The advantage of the employed technique is the precise control of lateral spacing and of the distance between shading mask and substrate surface which is achieved by manufacturing them directly on the substrate. As precursor transport takes place in the molecular flow regime, the precursor impinging rates (and therefore the film growth rates) on the surface can be simulated as function of the reactor and shading mask geometry using a comparatively simple mathematical model. In the current contribution such a mathematical model, which predicts impinging rates on plain or shadow mask structured substrates, is presented. Its validity is confirmed by TiO 2 -deposition on plain silicon substrates (450 °C) using titanium tetra isopropoxide as precursor. Limitations of the patterning process are investigated by the deposition of TiO 2 on structured substrates and subsequent shadow mask lift-off. The geometry of the deposits is according to the mathematical model. Shading effects due to the growing film enables to fabricate deposits with predetermined variations in topography and non-flat top deposits which are complicated to obtain by classical clean room processes. As a result of the enhanced residual pressure of decomposition products and titanium precursors and the

  8. Final Site-Specific Technical Report for the Evaluation of Thermatrix GS Series Flameless Thermal Oxidzer for Off-Gas Treatment of Trichloroethene Vapors at Building 181 Air Force Plant 4, Texas

    National Research Council Canada - National Science Library

    Archabal, Steven

    1998-01-01

    The Air Force Center for Environmental Excellence (AFCEE) has sponsored an ongoing program to promote the use of cost-effective soil vapor treatment technologies in conjunction with soil vapor extraction (SVE...

  9. Site-Specific Technical Report for the Evaluation of Thermatrix GS Series Flameless Thermal Oxidizer for Off-Gas Treatment of Soil Vapors with Volatile Organic Compounds at the Source Area Reduction System, Former Lowry Air Force Base, Colorado

    National Research Council Canada - National Science Library

    Archabal, Steven

    1998-01-01

    The Air Force Center for Environmental Excellence (AFCEE) has sponsored an ongoing program to promote the use of cost-effective soil vapor treatment technologies in conjunction with soil vapor extraction (SVE...

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

    International Nuclear Information System (INIS)

    Breiland, W.G.; Coltrin, M.E.; Ho, P.

    1986-01-01

    Theoretical modeling and experimental measurements have been used to study gas-phase chemistry in the chemical vapor deposition (CVD) of silicon from silane. Pulsed laser Raman spectroscopy was used to obtain temperature profiles and to obtain absolute density profiles of silane during deposition at atmospheric and 6-Torr total pressures for temperatures ranging from 500 to 800 0 C. Laser-excited fluorescence was used to obtain relative density profiles of Si 2 during deposition at 740 0 C in helium with 0-12 Torr added hydrogen. These measurements are compared to predictions from the theoretical model of Coltrin, Kee, and Miller. The predictions agree qualitatively with experiment. These studies indicate that fluid mechanics and gas-phase chemical kinetics are important considerations in understanding the chemical vapor deposition process

  11. 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.

  12. Continuous, highly flexible, and transparent graphene films by chemical vapor deposition for organic photovoltaics.

    Science.gov (United States)

    Gomez De Arco, Lewis; Zhang, Yi; Schlenker, Cody W; Ryu, Koungmin; Thompson, Mark E; Zhou, Chongwu

    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 ( approximately 0.9 nm) and offered sheet resistance down to 230 Omega/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 (eta) of 1.18 and 1.27%, respectively. Furthermore, CVD graphene solar cells demonstrated outstanding capability to operate under bending conditions up to 138 degrees , whereas the ITO-based devices displayed cracks and irreversible failure under bending of 60 degrees . Our work indicates the great potential of CVD graphene films for flexible photovoltaic applications.

  13. Hot-wire chemical vapor synthesis for a variety of nano-materials with novel applications

    International Nuclear Information System (INIS)

    Dillon, A.C.; Mahan, A.H.; Deshpande, R.; Alleman, J.L.; Blackburn, J.L.; Parillia, P.A.; Heben, M.J.; Engtrakul, C.; Gilbert, K.E.H.; Jones, K.M.; To, R.; Lee, S-H.; Lehman, J.H.

    2006-01-01

    Hot-wire chemical vapor deposition (HWCVD) has been demonstrated as a simple economically scalable technique for the synthesis of a variety of nano-materials in an environmentally friendly manner. For example we have employed HWCVD for the continuous production of both carbon single- and multi-wall nanotubes (SWNTs and MWNTs). Unanticipated hydrogen storage on HWCVD-generated MWNTs has led insight into the adsorption mechanism of hydrogen on metal/carbon composites at near ambient temperatures that could be useful for developing a vehicular hydrogen storage system. Recent efforts have been focused on growing MWNT arrays on thin nickel films with a simple HWCVD process. New data suggests that these MWNT arrays could replace the gold black coatings currently used in pyroelectric detectors to accurately measure laser power. Finally, we have very recently employed HWCVD for the production of crystalline molybdenum and tungsten oxide nanotubes and nanorods. These metal oxide nanorods and nanotubes could have applications in catalysis, batteries and electrochromic windows or as gas sensors. A summary of the techniques for growing these novel materials and their various potential applications is provided

  14. Advances in silicon carbide Chemical Vapor Deposition (CVD) for semiconductor device fabrication

    Science.gov (United States)

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

    1991-01-01

    Improved SiC chemical vapor deposition films of both 3C and 6H polytypes were grown on vicinal (0001) 6H-SiC wafers cut from single-crystal boules. These films were produced from silane and propane in hydrogen at one atmosphere at a temperature of 1725 K. Among the more important factors which affected the structure and morphology of the grown films were the tilt angle of the substrate, the polarity of the growth surface, and the pregrowth surface treatment of the substrate. With proper pregrowth surface treatment, 6H films were grown on 6H substrates with tilt angles as small as 0.1 degrees. In addition, 3C could be induced to grow within selected regions on a 6H substrate. The polarity of the substrate was a large factor in the incorporation of dopants during epitaxial growth. A new growth model is discussed which explains the control of SiC polytype in epitaxial growth on vicinal (0001) SiC substrates.

  15. Photoinitiated chemical vapor deposition of cytocompatible poly(2-hydroxyethyl methacrylate) films.

    Science.gov (United States)

    McMahon, Brian J; Pfluger, Courtney A; Sun, Bing; Ziemer, Katherine S; Burkey, Daniel D; Carrier, Rebecca L

    2014-07-01

    Poly(2-hydroxyethyl methacrylate) (pHEMA) is a widely utilized biomaterial due to lack of toxicity and suitable mechanical properties; conformal thin pHEMA films produced via chemical vapor deposition (CVD) would thus have broad biomedical applications. Thin films of pHEMA were deposited using photoinitiated CVD (piCVD). Incorporation of ethylene glycol diacrylate (EGDA) into the pHEMA polymer film as a crosslinker, confirmed via Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, resulted in varied swelling and degradation behavior. 2-Hydroxyethyl methacrylate-only films showed significant thickness loss (up to 40%), possibly due to extraction of low-molecular-weight species or erosion, after 24 h in aqueous solution, whereas films crosslinked with EGDA (9.25-12.4%) were stable for up to 21 days. These results differ significantly from those obtained with plasma-polymerized pHEMA, which degraded steadily over a 21-day period, even with crosslinking. This suggests that the piCVD films differ structurally from those fabricated via plasma polymerization (plasma-enhanced CVD). piCVD pHEMA coatings proved to be good cell culture materials, with Caco-2 cell attachment and viability comparable to results obtained on tissue-culture polystyrene. Thus, thin film CVD pHEMA offers the advantage of enabling conformal coating of a cell culture substrate with tunable properties depending on method of preparation and incorporation of crosslinking agents. © 2013 Wiley Periodicals, Inc.

  16. Chemical vapor deposition diamond based multilayered radiation detector: Physical analysis of detection properties

    International Nuclear Information System (INIS)

    Almaviva, S.; Marinelli, Marco; Milani, E.; Prestopino, G.; Tucciarone, A.; Verona, C.; Verona-Rinati, G.; Angelone, M.; Pillon, M.; Dolbnya, I.; Sawhney, K.; Tartoni, N.

    2010-01-01

    Recently, solid state photovoltaic Schottky diodes, able to detect ionizing radiation, in particular, x-ray and ultraviolet radiation, have been developed at the University of Rome 'Tor Vergata'. We report on a physical and electrical properties analysis of the device and a detailed study of its detection capabilities as determined by its electrical properties. The design of the device is based on a metal/nominally intrinsic/p-type diamond layered structure obtained by microwave plasma chemical vapor deposition of homoepitaxial single crystal diamond followed by thermal evaporation of a metallic contact. The device can operate in an unbiased mode by using the built-in potential arising from the electrode-diamond junction. We compare the expected response of the device to photons of various energies calculated through Monte Carlo simulation with experimental data collected in a well controlled experimental setup i.e., monochromatic high flux x-ray beams from 6 to 20 keV, available at the Diamond Light Source synchrotron in Harwell (U.K.).

  17. Flow-dependent directional growth of carbon nanotube forests by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyeongkeun; Park, Young Chul; Chun, Kyoung-Yong; Kim, Young-Jin; Choi, Jae-Boong [School of Mechanical Engineering, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Kim, Keun Soo; Kang, Junmo; Hong, Byung Hee [SKKU Advanced Institute of Nanotechnology (SAINT) and Center for Human Interface Nano Technology (HINT), Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of); Boo, Jin-Hyo, E-mail: byunghee@skku.edu, E-mail: boong33@skku.edu [Department of Chemistry, RIAN and Institute of Basic Science, Sungkyunkwan University, Suwon, 440-746 (Korea, Republic of)

    2011-03-04

    We demonstrated that the structural formation of vertically aligned carbon nanotube (CNT) forests is primarily affected by the geometry-related gas flow, leading to the change of growth directions during the chemical vapor deposition (CVD) process. By varying the growing time, flow rate, and direction of the carrier gas, the structures and the formation mechanisms of the vertically aligned CNT forests were carefully investigated. The growth directions of CNTs are found to be highly dependent on the nonlinear local gas flows induced by microchannels. The angle of growth significantly changes with increasing gas flows perpendicular to the microchannel, while the parallel gas flow shows almost no effect. A computational fluid dynamics (CFD) model was employed to explain the flow-dependent growth of CNT forests, revealing that the variation of the local pressure induced by microchannels is an important parameter determining the directionality of the CNT growth. We expect that the present method and analyses would provide useful information to control the micro- and macrostructures of vertically aligned CNTs for various structural/electrical applications.

  18. Extent of hydrogen coverage of Si(001) under chemical vapor deposition conditions from ab initio approaches

    International Nuclear Information System (INIS)

    Rosenow, Phil; Tonner, Ralf

    2016-01-01

    The extent of hydrogen coverage of the Si(001) c(4 × 2) surface in the presence of hydrogen gas has been studied with dispersion corrected density functional theory. Electronic energy contributions are well described using a hybrid functional. The temperature dependence of the coverage in thermodynamic equilibrium was studied computing the phonon spectrum in a supercell approach. As an approximation to these demanding computations, an interpolated phonon approach was found to give comparable accuracy. The simpler ab initio thermodynamic approach is not accurate enough for the system studied, even if corrections by the Einstein model for surface vibrations are considered. The on-set of H 2 desorption from the fully hydrogenated surface is predicted to occur at temperatures around 750 K. Strong changes in hydrogen coverage are found between 1000 and 1200 K in good agreement with previous reflectance anisotropy spectroscopy experiments. These findings allow a rational choice for the surface state in the computational treatment of chemical reactions under typical metal organic vapor phase epitaxy conditions on Si(001).

  19. Extent of hydrogen coverage of Si(001) under chemical vapor deposition conditions from ab initio approaches

    Energy Technology Data Exchange (ETDEWEB)

    Rosenow, Phil; Tonner, Ralf, E-mail: tonner@chemie.uni-marburg.de [Fachbereich Chemie and Wissenschaftliches Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Hans-Meerwein-Straße, Marburg 35032 (Germany)

    2016-05-28

    The extent of hydrogen coverage of the Si(001) c(4 × 2) surface in the presence of hydrogen gas has been studied with dispersion corrected density functional theory. Electronic energy contributions are well described using a hybrid functional. The temperature dependence of the coverage in thermodynamic equilibrium was studied computing the phonon spectrum in a supercell approach. As an approximation to these demanding computations, an interpolated phonon approach was found to give comparable accuracy. The simpler ab initio thermodynamic approach is not accurate enough for the system studied, even if corrections by the Einstein model for surface vibrations are considered. The on-set of H{sub 2} desorption from the fully hydrogenated surface is predicted to occur at temperatures around 750 K. Strong changes in hydrogen coverage are found between 1000 and 1200 K in good agreement with previous reflectance anisotropy spectroscopy experiments. These findings allow a rational choice for the surface state in the computational treatment of chemical reactions under typical metal organic vapor phase epitaxy conditions on Si(001).

  20. Extent of hydrogen coverage of Si(001) under chemical vapor deposition conditions from ab initio approaches

    Science.gov (United States)

    Rosenow, Phil; Tonner, Ralf

    2016-05-01

    The extent of hydrogen coverage of the Si(001) c(4 × 2) surface in the presence of hydrogen gas has been studied with dispersion corrected density functional theory. Electronic energy contributions are well described using a hybrid functional. The temperature dependence of the coverage in thermodynamic equilibrium was studied computing the phonon spectrum in a supercell approach. As an approximation to these demanding computations, an interpolated phonon approach was found to give comparable accuracy. The simpler ab initio thermodynamic approach is not accurate enough for the system studied, even if corrections by the Einstein model for surface vibrations are considered. The on-set of H2 desorption from the fully hydrogenated surface is predicted to occur at temperatures around 750 K. Strong changes in hydrogen coverage are found between 1000 and 1200 K in good agreement with previous reflectance anisotropy spectroscopy experiments. These findings allow a rational choice for the surface state in the computational treatment of chemical reactions under typical metal organic vapor phase epitaxy conditions on Si(001).

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

    International Nuclear Information System (INIS)

    Mullendore, A.W.; Whitley, J.B.; Pierson, H.O.; Mattox, D.M.

    1980-01-01

    Chemical vapor deposited coatings of TiB 2 , TiC and boron on graphite substrates are being developed for application as limiter materials in magnetic confinement fusion reactors. In this application severe thermal shock conditions exist and to do effective thermo-mechanical modelling of the material response it is necessary to acquire elastic moduli, fracture strength and strain to fracture data for the coatings. Four point flexure tests have been conducted from room temperature to 2000 0 C on TiB 2 and boron coated graphite with coatings in tension and compression and the mechanical properties extracted from the load-deflection data. In addition, stress relaxation tests from 500 to 1150 0 C were performed on TiB 2 and TiC coated graphite beams to assess the low levels of plastic deformation which occur in these coatings. Significant differences have been observed between the effective mechanical properties of the coatings and literature values of the bulk properties

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

    Science.gov (United States)

    Choo, Sung Joong; Lee, Byung-Chul; Lee, Sang-Myung; Park, Jung Ho; Shin, Hyun-Joon

    2009-09-01

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

  3. 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

  4. Atmospheric Pressure Spray Chemical Vapor Deposited CuInS2 Thin Films for Photovoltaic Applications

    Science.gov (United States)

    Harris, J. D.; Raffaelle, R. P.; Banger, K. K.; Smith, M. A.; Scheiman, D. A.; Hepp, A. F.

    2002-01-01

    Solar cells have been prepared using atmospheric pressure spray chemical vapor deposited CuInS2 absorbers. The CuInS2 films were deposited at 390 C using the single source precursor (PPh3)2CuIn(SEt)4 in an argon atmosphere. The absorber ranges in thickness from 0.75 - 1.0 micrometers, and exhibits a crystallographic gradient, with the leading edge having a (220) preferred orientation and the trailing edge having a (112) orientation. Schottky diodes prepared by thermal evaporation of aluminum contacts on to the CuInS2 yielded diodes for films that were annealed at 600 C. Solar cells were prepared using annealed films and had the (top down) composition of Al/ZnO/CdS/CuInS2/Mo/Glass. The Jsc, Voc, FF and (eta) were 6.46 mA per square centimeter, 307 mV, 24% and 0.35%, respectively for the best small area cells under simulated AM0 illumination.

  5. Rapid Chemical Vapor Infiltration of Silicon Carbide Minicomposites at Atmospheric Pressure.

    Science.gov (United States)

    Petroski, Kenneth; Poges, Shannon; Monteleone, Chris; Grady, Joseph; Bhatt, Ram; Suib, Steven L

    2018-02-07

    The chemical vapor infiltration technique is one of the most popular for the fabrication of the matrix portion of a ceramic matrix composite. This work focuses on tailoring an atmospheric pressure deposition of silicon carbide onto carbon fiber tows using the methyltrichlorosilane (CH 3 SiCl 3 ) and H 2 deposition system at atmospheric pressure to create minicomposites faster than low pressure systems. Adjustment of the flow rate of H 2 bubbled through CH 3 SiCl 3 will improve the uniformity of the deposition as well as infiltrate the substrate more completely as the flow rate is decreased. Low pressure depositions conducted at 50 Torr deposit SiC at a rate of approximately 200 nm*h -1 , while the atmospheric pressure system presented has a deposition rate ranging from 750 nm*h -1 to 3.88 μm*h -1 . The minicomposites fabricated in this study had approximate total porosities of 3 and 6% for 10 and 25 SCCM infiltrations, respectively.

  6. 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.

  7. 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.

  8. Control of nanoparticle agglomeration through variation of the time-temperature profile in chemical vapor synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Djenadic, Ruzica; Winterer, Markus, E-mail: markus.winterer@uni-due.de [Universität Duisburg-Essen, Nanoparticle Process Technology, Faculty of Engineering and CENIDE (Germany)

    2017-02-15

    The influence of the time-temperature history on the characteristics of nanoparticles such as size, degree of agglomeration, or crystallinity is investigated for chemical vapor synthesis (CVS). A simple reaction-coagulation-sintering model is used to describe the CVS process, and the results of the model are compared to experimental data. Nanocrystalline titania is used as model material. Titania nanoparticles are generated from titanium-tetraisopropoxide (TTIP) in a hot-wall reactor. Pure anatase particles and mixtures of anatase, rutile (up to 11 vol.%), and brookite (up to 29 vol.%) with primary particle sizes from 1.7 nm to 10.5 nm and agglomerate particle sizes from 24.3 nm to 55.6 nm are formed depending on the particle time-temperature history. An inductively heated furnace with variable inductor geometry is used as a novel system to control the time-temperature profile in the reactor externally covering a large wall temperature range from 873 K to 2023 K. An appropriate choice of inductor geometry, i.e. time-temperature profile, can significantly reduce the degree of agglomeration. Other particle characteristics such as crystallinity are also substantially influenced by the time-temperature profile.

  9. Controlled surface diffusion in plasma-enhanced chemical vapor deposition of GaN nanowires

    International Nuclear Information System (INIS)

    Hou, W C; Hong, Franklin Chau-Nan

    2009-01-01

    This study investigates the growth of GaN nanowires by controlling the surface diffusion of Ga species on sapphire in a plasma-enhanced chemical vapor deposition (CVD) system. Under nitrogen-rich growth conditions, Ga has a tendency to adsorb on the substrate surface diffusing to nanowires to contribute to their growth. The significance of surface diffusion on the growth of nanowires is dependent on the environment of the nanowire on the substrate surface as well as the gas phase species and compositions. Under nitrogen-rich growth conditions, the growth rate is strongly dependent on the surface diffusion of gallium, but the addition of 5% hydrogen in nitrogen plasma instantly diminishes the surface diffusion effect. Gallium desorbs easily from the surface by reaction with hydrogen. On the other hand, under gallium-rich growth conditions, nanowire growth is shown to be dominated by the gas phase deposition, with negligible contribution from surface diffusion. This is the first study reporting the inhibition of surface diffusion effects by hydrogen addition, which can be useful in tailoring the growth and characteristics of nanowires. Without any evidence of direct deposition on the nanowire surface, gallium and nitrogen are shown to dissolve into the catalyst for growing the nanowires at 900 deg. C.

  10. Planar structured perovskite solar cells by hybrid physical chemical vapor deposition with optimized perovskite film thickness

    Science.gov (United States)

    Wei, Xiangyang; Peng, Yanke; Jing, Gaoshan; Cui, Tianhong

    2018-05-01

    The thickness of perovskite absorber layer is a critical parameter to determine a planar structured perovskite solar cell’s performance. By modifying the spin coating speed and PbI2/N,N-dimethylformamide (DMF) solution concentration, the thickness of perovskite absorber layer was optimized to obtain high-performance solar cells. Using a PbI2/DMF solution of 1.3 mol/L, maximum power conversion efficiency (PCE) of a perovskite solar cell is 15.5% with a perovskite film of 413 nm at 5000 rpm, and PCE of 14.3% was also obtained for a solar cell with a perovskite film of 182 nm thick. It is derived that higher concentration of PbI2/DMF will result in better perovskite solar cells. Additionally, these perovskite solar cells are highly uniform. In 14 sets of solar cells, standard deviations of 11 sets of solar cells were less than 0.50% and the smallest standard deviation was 0.25%, which demonstrates the reliability and effectiveness of hybrid physical chemical vapor deposition (HPCVD) method.

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

    Science.gov (United States)

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

    2017-12-26

    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 (MoS 2 ) by leveraging the natural randomness of their island growth during chemical vapor deposition (CVD). We synthesize a MoS 2 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 MoS 2 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.

  12. 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.

  13. Chemical vapor deposition graphene transfer process to a polymeric substrate assisted by a spin coater

    International Nuclear Information System (INIS)

    Kessler, Felipe; Da Rocha, Caique O C; Medeiros, Gabriela S; Fechine, Guilhermino J M

    2016-01-01

    A new method to transfer chemical vapor deposition graphene to polymeric substrates is demonstrated here, it is called direct dry transfer assisted by a spin coater (DDT-SC). Compared to the conventional method DDT, the improvement of the contact between graphene-polymer due to a very thin polymeric film deposited by spin coater before the transfer process prevented air bubbles and/or moisture and avoided molecular expansion on the graphene-polymer interface. An acrylonitrile-butadiene-styrene copolymer, a high impact polystyrene, polybutadiene adipate-co-terephthalate, polylactide acid, and a styrene-butadiene-styrene copolymer are the polymers used for the transfers since they did not work very well by using the DDT process. Raman spectroscopy and optical microscopy were used to identify, to quantify, and to qualify graphene transferred to the polymer substrates. The quantity of graphene transferred was substantially increased for all polymers by using the DDT-SC method when compared with the DDT standard method. After the transfer, the intensity of the D band remained low, indicating low defect density and good quality of the transfer. The DDT-SC transfer process expands the number of graphene applications since the polymer substrate candidates are increased. (paper)

  14. Flow-dependent directional growth of carbon nanotube forests by chemical vapor deposition

    International Nuclear Information System (INIS)

    Kim, Hyeongkeun; Park, Young Chul; Chun, Kyoung-Yong; Kim, Young-Jin; Choi, Jae-Boong; Kim, Keun Soo; Kang, Junmo; Hong, Byung Hee; Boo, Jin-Hyo

    2011-01-01

    We demonstrated that the structural formation of vertically aligned carbon nanotube (CNT) forests is primarily affected by the geometry-related gas flow, leading to the change of growth directions during the chemical vapor deposition (CVD) process. By varying the growing time, flow rate, and direction of the carrier gas, the structures and the formation mechanisms of the vertically aligned CNT forests were carefully investigated. The growth directions of CNTs are found to be highly dependent on the nonlinear local gas flows induced by microchannels. The angle of growth significantly changes with increasing gas flows perpendicular to the microchannel, while the parallel gas flow shows almost no effect. A computational fluid dynamics (CFD) model was employed to explain the flow-dependent growth of CNT forests, revealing that the variation of the local pressure induced by microchannels is an important parameter determining the directionality of the CNT growth. We expect that the present method and analyses would provide useful information to control the micro- and macrostructures of vertically aligned CNTs for various structural/electrical applications.

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

    International Nuclear Information System (INIS)

    Ramirez, A; Royo, C; Latorre, N; Mallada, R; Monzón, A; Tiggelaar, R M

    2014-01-01

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

  16. On the Growth and Microstructure of Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Handuja Sangeeta

    2010-01-01

    Full Text Available Abstract Carbon nanotubes (CNTs were deposited on various substrates namely untreated silicon and quartz, Fe-deposited silicon and quartz, HF-treated silicon, silicon nitride-deposited silicon, copper foil, and stainless steel mesh using thermal chemical vapor deposition technique. The optimum parameters for the growth and the microstructure of the synthesized CNTs on these substrates are described. The results show that the growth of CNTs is strongly influenced by the substrate used. Vertically aligned multi-walled CNTs were found on quartz, Fe-deposited silicon and quartz, untreated silicon, and on silicon nitride-deposited silicon substrates. On the other hand, spaghetti-type growth was observed on stainless steel mesh, and no CNT growth was observed on HF-treated silicon and copper. Silicon nitride-deposited silicon substrate proved to be a promising substrate for long vertically aligned CNTs of length 110–130 μm. We present a possible growth mechanism for vertically aligned and spaghetti-type growth of CNTs based on these results.

  17. Electrical properties of aluminum-doped zinc oxide (AZO) nanoparticles synthesized by chemical vapor synthesis

    International Nuclear Information System (INIS)

    Hartner, Sonja; Schulz, Christof; Wiggers, Hartmut; Ali, Moazzam; Winterer, Markus

    2009-01-01

    Aluminum-doped zinc oxide nanoparticles have been prepared by chemical vapor synthesis, which facilitates the incorporation of a higher percentage of dopant atoms, far above the thermodynamic solubility limit of aluminum. The electrical properties of aluminum-doped and undoped zinc oxide nanoparticles were investigated by impedance spectroscopy. The impedance is measured under hydrogen and synthetic air between 323 and 673 K. The measurements under hydrogen as well as under synthetic air show transport properties depending on temperature and doping level. Under hydrogen atmosphere, a decreasing conductivity with increasing dopant content is observed, which can be explained by enhanced scattering processes due to an increasing disorder in the nanocrystalline material. The temperature coefficient for the doped samples switches from positive temperature coefficient behavior to negative temperature coefficient behavior with increasing dopant concentration. In the presence of synthetic air, the conductivity firstly increases with increasing dopant content by six orders of magnitude. The origin of the increasing conductivity is the generation of free charge carriers upon dopant incorporation. It reaches its maximum at a concentration of 7.7% of aluminum, and drops for higher doping levels. In all cases, the conductivity under hydrogen is higher than under synthetic air and can be changed reversibly by changing the atmosphere.

  18. Electrical properties of aluminum-doped zinc oxide (AZO) nanoparticles synthesized by chemical vapor synthesis.

    Science.gov (United States)

    Hartner, Sonja; Ali, Moazzam; Schulz, Christof; Winterer, Markus; Wiggers, Hartmut

    2009-11-04

    Aluminum-doped zinc oxide nanoparticles have been prepared by chemical vapor synthesis, which facilitates the incorporation of a higher percentage of dopant atoms, far above the thermodynamic solubility limit of aluminum. The electrical properties of aluminum-doped and undoped zinc oxide nanoparticles were investigated by impedance spectroscopy. The impedance is measured under hydrogen and synthetic air between 323 and 673 K. The measurements under hydrogen as well as under synthetic air show transport properties depending on temperature and doping level. Under hydrogen atmosphere, a decreasing conductivity with increasing dopant content is observed, which can be explained by enhanced scattering processes due to an increasing disorder in the nanocrystalline material. The temperature coefficient for the doped samples switches from positive temperature coefficient behavior to negative temperature coefficient behavior with increasing dopant concentration. In the presence of synthetic air, the conductivity firstly increases with increasing dopant content by six orders of magnitude. The origin of the increasing conductivity is the generation of free charge carriers upon dopant incorporation. It reaches its maximum at a concentration of 7.7% of aluminum, and drops for higher doping levels. In all cases, the conductivity under hydrogen is higher than under synthetic air and can be changed reversibly by changing the atmosphere.

  19. 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.

  20. 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.

  1. Real time monitoring of filament-assisted chemically vapor deposited diamond by spectroscopic ellipsometry

    International Nuclear Information System (INIS)

    Yue Cong; An, I.; Vedam, K.; Collins, R.W.; Nguyen, H.V.; Messier, R.

    1991-01-01

    Spectroscopic ellipsometry over the range 1.5-4.5 eV was applied as a real time probe of the processes occurring in the initial nucleation of thin film diamond by heated-filament assisted chemical vapor deposition. Using both untreated and diamond-polished c-Si substrates, as well as both carburized and uncarburized tungsten filaments, it was possible to separate and characterize competing phenomena, including the increase in surface temperature induced by filament ignition, the formation of carbide layers, contamination of the substrate by tungsten from the filament, annealing of diamond polishing damage, and, finally, diamond nucleation. An accurate measurement of the true temperature of the substrate surface averaged over the top 500 A can be obtained from the energy position of critical points in the c-Si band structure. For diamond deposition, we operated with an initial excess flow of CH 4 to stimulate nucleation. We applied real time feedback and manual control to reduce the CH 4 flow in the first monolayers of deposition. The thickness of diamond and an estimate of its nucleation density can be obtained from real time spectra, and the latter was in good agreement with that obtained from scanning electron microscopy. (orig.)

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

    International Nuclear Information System (INIS)

    Gates, S. M.; Neumayer, D. A.; Sherwood, M. H.; Grill, A.; Wang, X.; Sankarapandian, M.

    2007-01-01

    The preparation of ultralow dielectric constant porous silicon, carbon, oxygen, hydrogen alloy dielectrics, called 'pSiCOH', using a production 200 mm plasma enhanced chemical vapor deposition tool and a thermal treatment is reported here. The effect of deposition temperature on the pSiCOH film is examined using Fourier transform infrared (FTIR) spectroscopy, dielectric constant (k), and film shrinkage measurements. For all deposition temperatures, carbon in the final porous film is shown to be predominantly Si-CH 3 species, and lower k is shown to correlate with increased concentration of Si-CH 3 . NMR and FTIR spectroscopies clearly detect the loss of a removable, unstable, hydrocarbon (CH x ) phase during the thermal treatment. Also detected are increased cross-linking of the Si-O skeleton, and concentration changes for three distinct structures of carbon. In the as deposited films, deposition temperature also affects the hydrocarbon (CH x ) content and the presence of C=O and C=C functional groups

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

    Science.gov (United States)

    Huang, Meng-Wen; Cheng, Yin-Wei; Pan, Ko-Ying; Chang, Chen-Chuan; Shieu, F. S.; Shih, Han C.

    2012-11-01

    Single crystal ZnS nanowires were successfully synthesized in large quantities on Si (1 0 0) substrates by simple thermal chemical vapor deposition without using any catalyst. The morphology, composition, and crystal structure were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and cathodoluminescence (CL) spectroscopy. SEM observations show that the nanowires have diameters about 20-50 nm and lengths up to several tens of micrometers. XRD and TEM results confirmed that the nanowires exhibited both wurtzite and zinc blende structures with growth directions aligned along [0 0 0 2] and [1 1 1], respectively. The CL spectrum revealed emission bands in the UV and blue regions. The blue emissions at 449 and ˜581 nm were attributed to surface states and impurity-related defects of the nanowires, respectively. The perfect crystal structure of the nanowires indicates their potential applications in nanotechnology and in the fabrication of nanodevices.

  4. 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.

  5. Semiconducting Properties of Nanostructured Amorphous Carbon Thin Films Incorporated with Iodine by Thermal Chemical Vapor Deposition

    Science.gov (United States)

    Kamaruzaman, Dayana; Ahmad, Nurfadzilah; Annuar, Ishak; Rusop, Mohamad

    2013-11-01

    Nanostructured iodine-post doped amorphous carbon (a-C:I) thin films were prepared from camphor oil using a thermal chemical vapor deposition (TCVD) technique at different doping temperatures. The structural properties of the films were studied by field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Raman, and Fourier transform infrared (FTIR) studies. FESEM and EDS studies showed successful iodine doping. FTIR and Raman studies showed that the a-C:I thin films consisted of a mixture of sp2- and sp3-bonded carbon atoms. The optical and electrical properties of a-C:I thin films were determined by UV-vis-NIR spectroscopy and current-voltage (I-V) measurement respectively. The optical band gap of a-C thin films decreased upon iodine doping. The highest electrical conductivity was found at 400 °C doping. Heterojunctions are confirmed by rectifying the I-V characteristics of an a-C:I/n-Si junction.

  6. 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.

  7. Preparation of Ti species coating hydrotalcite by chemical vapor deposition for photodegradation of azo dye.

    Science.gov (United States)

    Xiao, Gaofei; Zeng, HongYan; Xu, Sheng; Chen, ChaoRong; Zhao, Quan; Liu, XiaoJun

    2017-10-01

    TiO 2 in anatase crystal phase is a very effective catalyst in the photocatalytic oxidation of organic compounds in water. To improve its photocatalytic activity, the Ti-coating MgAl hydrotalcite (Ti-MgAl-LDH) was prepared by chemical vapor deposition (CVD) method. Response surface method (RSM) was employed to evaluate the effect of Ti species coating parameters on the photocatalytic activity, which was found to be affected by the furnace temperature, N 2 flow rate and influx time of precursor gas. Application of RSM successfully increased the photocatalytic efficiency of the Ti-MgAl-LDH in methylene blue photodegradation under UV irradiation, leading to improved economy of the process. According to the results from X-ray diffraction, scanning electron microscopy, Brunner-Emmet-Teller and Barrett-Joyner-Hallender, thermogravimetric and differential thermal analysis, UV-vis diffuse reflectance spectra analyses, the Ti species (TiO 2 or/and Ti 4+ ) were successfully coated on the MgAl-LDH matrix. The Ti species on the surface of the Ti-MgAl-LDH lead to a higher photocatalytic performance than commercial TiO 2 -P25. The results suggested that CVD method provided a new approach for the industrial preparation of Ti-coating MgAl-LDH material with good photocatalytic performances. Copyright © 2017. Published by Elsevier B.V.

  8. 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.

  9. Effect of thermal history on the structure of chemically and vapor deposited silver films on glass

    International Nuclear Information System (INIS)

    Shelby, J.E.; Nichols, M.C.; Smith, D.K. Jr.; Vitko, J. Jr.

    1981-01-01

    The observation of silver agglomeration in second surface mirrors used for solar applications has emphasized consideration of the effect of thermal history on the optical properties of mirrors. Thermal history effects may arise from the processing of mirrors, the application of protective coatings, or from outdoor exposure. Mirrors may be subject to elevated temperatures (T less than or equal to 400 0 C) for short periods of time, or to low temperatures (T less than or equal to 60 0 C) for long (less than or equal to 30 years) periods of time. Although a significant amount of work has been done on thermally driven agglomeration of silver films, most of these studies have been restricted to vapor deposited films on vitreous silica. Large area reflectors, such as those used in heliostats, will almost certainly be deposited by commercial chemical methods on substrates of soda-lime-silicate or other glasses which differ considerably from vitreous silica in composition and properties. The present study addresses the effect of this change in deposition technique and substrate on silver agglomeration. These problems were studied by optical and scanning electron microscopy, reflectometry, and x-ray diffraction. The results indicate that both the method used to deposit the silver and the type of glass affect the agglomeration process and the character of the reflective film

  10. Growth and electrical properties of AlOx grown by mist chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Toshiyuki Kawaharamura

    2013-03-01

    Full Text Available Aluminum oxide (AlOx thin films were grown using aluminum acetylacetonate (Al(acac3 as a source solute by mist chemical vapor deposition (mist CVD. The AlOx thin films grown at temperatures above 400°C exhibited a breakdown field (EBD over 6 MV/cm and a dielectric constant (κ over 6. It is suggested that residual OH bonding in the AlOx thin films grown at temperatures below 375°C caused degradation of the breakdown field (EBD. With FC type mist CVD, the reaction proceeded efficiently (Ea = 22–24 kJ/mol because the solvent, especially H2O, worked as a stronger oxygen source. The AlOx film could be grown at 450°C with a high deposition rate (23 nm/min and smooth surface (RMS = 1.5 nm. Moreover, the AlOx thin films grown by mist CVD had excellent practicality as insulators because the gate leakage current (IG of the oxide thin film transistor (TFT with an IGZO/AlOx stack was suppressed below 1 pA at a gate voltage (VG of 20 V.

  11. High-pressure catalytic chemical vapor deposition of ferromagnetic ruthenium-containing carbon nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Khavrus, Vyacheslav O., E-mail: V.Khavrus@ifw-dresden.de; Ibrahim, E. M. M.; Bachmatiuk, Alicja; Ruemmeli, Mark H.; Wolter, A. U. B.; Hampel, Silke; Leonhardt, Albrecht [IFW Dresden (Germany)

    2012-06-15

    We report on the high-pressure catalytic chemical vapor deposition (CCVD) of ruthenium nanoparticles (NPs) and single-walled carbon nanotubes (SWCNTs) by means of gas-phase decomposition of acetonitrile and ruthenocene in a tubular quartz flow reactor at 950 Degree-Sign C and at elevated pressures (between 2 and 8 bar). The deposited material consists of Ru metal cores with sizes ranging between 1 and 3 nm surrounded by a carbon matrix. The high-pressure CCVD seems to be an effective route to obtain composite materials containing metallic NPs, Ru in this work, inside a nanostructured carbon matrix protecting them from oxidation in ambient air. We find that in contradiction to the weak paramagnetic properties characterizing bulk ruthenium, the synthesized samples are ferromagnetic as predicted for nanosized particles of nonmagnetic materials. At low pressure, the very small ruthenium catalyst particles are able to catalyze growth of SWCNTs. Their yield decreases with increasing reaction pressure. Transmission electron microscopy, selected area energy-dispersive X-ray analysis, Raman spectroscopy, and magnetic measurements were used to analyze and confirm properties of the synthesized NPs and nanotubes. A discussion on the growth mechanism of the Ru-containing nanostructures is presented.

  12. Defects in silicon carbide grown by fluorinated chemical vapor deposition chemistry

    Science.gov (United States)

    Stenberg, Pontus; Booker, Ian D.; Karhu, Robin; Pedersen, Henrik; Janzén, Erik; Ivanov, Ivan G.

    2018-04-01

    Point defects in n- and p-type 4H-SiC grown by fluorinated chemical vapor deposition (CVD) have been characterized optically by photoluminescence (PL) and electrically by deep-level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS). The results are considered in comparison with defects observed in non-fluorinated CVD growth (e.g., using SiH4 instead of SiF4 as silicon precursor), in order to investigate whether specific fluorine-related defects form during the fluorinated CVD growth, which might prohibit the use of fluorinated chemistry for device-manufacturing purposes. Several new peaks identifying new defects appear in the PL of fluorinated-grown samples, which are not commonly observed neither in other halogenated chemistries, nor in the standard CVD chemistry using silane (SiH4). However, further investigation is needed in order to determine their origin and whether they are related to incorporation of F in the SiC lattice, or not. The electric characterization does not find any new electrically-active defects that can be related to F incorporation. Thus, we find no point defects prohibiting the use of fluorinated chemistry for device-making purposes.

  13. 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.

  14. An efficient laser vaporization source for chemically modified metal clusters characterized by thermodynamics and kinetics

    Science.gov (United States)

    Masubuchi, Tsugunosuke; Eckhard, Jan F.; Lange, Kathrin; Visser, Bradley; Tschurl, Martin; Heiz, Ulrich

    2018-02-01

    A laser vaporization cluster source that has a room for cluster aggregation and a reactor volume, each equipped with a pulsed valve, is presented for the efficient gas-phase production of chemically modified metal clusters. The performance of the cluster source is evaluated through the production of Ta and Ta oxide cluster cations, TaxOy+ (y ≥ 0). It is demonstrated that the cluster source produces TaxOy+ over a wide mass range, the metal-to-oxygen ratio of which can easily be controlled by changing the pulse duration that influences the amount of reactant O2 introduced into the cluster source. Reaction kinetic modeling shows that the generation of the oxides takes place under thermalized conditions at less than 300 K, whereas metal cluster cores are presumably created with excess heat. These characteristics are also advantageous to yield "reaction intermediates" of interest via reactions between clusters and reactive molecules in the cluster source, which may subsequently be mass selected for their reactivity measurements.

  15. 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.

  16. Analysis techniques of lattice fringe images for quantified evaluation of pyrocarbon by chemical vapor infiltration.

    Science.gov (United States)

    Li, Miaoling; Zhao, Hongxia; Qi, Lehua; Li, Hejun

    2014-10-01

    Some image analysis techniques are developed for simplifying lattice fringe images of deposited pyrocarbon in carbon/carbon composites by chemical vapor infiltration. They are mainly the object counting method for detecting the optimum threshold, the self-adaptive morphological filtering, the node-separation technique for breaking the aggregate fringes, and some post processing algorithms for reconstructing the fringes. The simplified fringes are the foundation for defining and extracting quantitative nanostructure parameters of pyrocarbon. The frequency filter window of a Fourier transform is defined as the circular band that retains only those fringes with interlayer distance between 0.3 and 0.45 nm. Some judge criteria are set to define topological relation between fringes. For example, the aspect ratio and area of fringes are employed to detect aggregate fringes. Fringe coaxality and distance between endpoints are used to judge the disconnected fringes. The optimum values are determined by using the iterative correction techniques. The best cut-off value for the short fringes is chosen only when there is a reasonable match between the mean fringe length and the value measured by X-ray diffraction. The adopted techniques have been verified to be feasible and to have the potential to convert the complex lattice fringe image to a set of distinct fringe structures.

  17. 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.

  18. Three dimensional graphene synthesis on nickel foam by chemical vapor deposition from ethylene

    International Nuclear Information System (INIS)

    Trinsoutrot, Pierre; Vergnes, Hugues; Caussat, Brigitte

    2014-01-01

    Highlights: • 3D multi-layers graphene networks were synthesized from ethylene on nickel foam. • The weight of graphene increased with run duration and when decreasing temperature. • Weight percentages of graphene as high as 15% were obtained. • A continuous mechanism of graphene formation probably exists in presence of ethylene. -- Abstract: 3D multi-layers graphene networks were synthesized on nickel foam from ethylene between 700 and 1000 °C by chemical vapor deposition. Large nickel foam substrates were used allowing the accurate measurement of graphene masses. The weight of graphene increased with run duration and when decreasing temperature. Graphene was also present inside the hollow branches of the foam. We demonstrated that the weights of graphene formed largely exceed the masses corresponding to carbon solubility into nickel. Indeed weight percentages of graphene as high as 15% were obtained, corresponding to graphene layers of 500 nm to 1 μm thick. This means that graphene formation could not be due only to carbon dissolution into nickel and then precipitation during the cooling step. Another mechanism probably co-exists, involving continuous graphene formation in presence of ethylene either by segregation from the dissolved carbon into nickel or by surface CVD growth

  19. Low temperature metalorganic chemical vapor deposition of gallium nitride using dimethylhydrazine as nitrogen source

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Y.J.; Hong, L.S.; Huang, K.F.; Tsay, J.E

    2002-11-01

    Gallium nitride (GaN) films have been homoepitaxially grown by low pressure metalorganic chemical vapor deposition technique using dimethylhydrazine (DMHy) and trimethylgallium (TMG) as the reactants at low temperatures ranging from 873 to 923 K and a constant pressure of 10 Torr. The potential of utilizing DMHy as a nitrogen source is evaluated through understanding the kinetics of GaN film growth. A growth rate dependency study with respect to DMHy and TMG concentrations indicates that Langmuir-Hinshelwood typed reaction dominates the film growth. From a model fitting to the experimental film growth rate, the adsorption equilibrium constant of DMHy is found to be approximately 1/20 that of TMG, indicating that V/III feed ratio can be reduced down to 20 to obtain a stoichiometric GaN film. Based on X-ray photoelectron spectroscope measurement, the films formed by DMHy, however, accompany significant carbon contamination due to the strong C-N bonding in DMHy. The contamination can be relieved effectively by introducing H{sub 2} into the reaction.

  20. Low temperature metalorganic chemical vapor deposition of gallium nitride using dimethylhydrazine as nitrogen source

    International Nuclear Information System (INIS)

    Hsu, Y.J.; Hong, L.S.; Huang, K.F.; Tsay, J.E.

    2002-01-01

    Gallium nitride (GaN) films have been homoepitaxially grown by low pressure metalorganic chemical vapor deposition technique using dimethylhydrazine (DMHy) and trimethylgallium (TMG) as the reactants at low temperatures ranging from 873 to 923 K and a constant pressure of 10 Torr. The potential of utilizing DMHy as a nitrogen source is evaluated through understanding the kinetics of GaN film growth. A growth rate dependency study with respect to DMHy and TMG concentrations indicates that Langmuir-Hinshelwood typed reaction dominates the film growth. From a model fitting to the experimental film growth rate, the adsorption equilibrium constant of DMHy is found to be approximately 1/20 that of TMG, indicating that V/III feed ratio can be reduced down to 20 to obtain a stoichiometric GaN film. Based on X-ray photoelectron spectroscope measurement, the films formed by DMHy, however, accompany significant carbon contamination due to the strong C-N bonding in DMHy. The contamination can be relieved effectively by introducing H 2 into the reaction

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

    Energy Technology Data Exchange (ETDEWEB)

    Gencarelli, F., E-mail: federica.gencarelli@imec.be [imec, Kapeldreef 75, 3001 Leuven (Belgium); Dept. of Metallurgy and Materials Engineering, KU Leuven, B-3001 Leuven (Belgium); Shimura, Y. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Kumar, A. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Vincent, B.; Moussa, A.; Vanhaeren, D.; Richard, O.; Bender, H. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, W. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Nuclear and Radiation Physics Section, KU Leuven, B-3001 Leuven (Belgium); Caymax, M.; Loo, R. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Heyns, M. [imec, Kapeldreef 75, 3001 Leuven (Belgium); Dept. of Metallurgy and Materials Engineering, KU Leuven, B-3001 Leuven (Belgium)

    2015-09-01

    In this work, we discuss the characteristics of particular island-type features with an amorphous core that are developed during the low temperature epitaxial growth of Ge and GeSn layers by means of chemical vapor deposition with Ge{sub 2}H{sub 6}. Although further investigations are needed to unambiguously identify the origin of these features, we suggest that they are originated by the formation of clusters of H and/or contaminants atoms during growth. These would initially cause the formation of pits with crystalline rough facets over them, resulting in ring-shaped islands. Then, when an excess surface energy is overcome, an amorphous phase would nucleate inside the pits and fill them. Reducing the pressure and/or increasing the growth temperature can be effective ways to prevent the formation of these features, likely due to a reduction of the surface passivation from H and/or contaminant atoms. - Highlights: • Island features with amorphous cores develop during low T Ge(Sn) CVD with Ge{sub 2}H{sub 6.} • These features are thoroughly characterized in order to understand their origin. • A model is proposed to describe the possible evolution of these features. • Lower pressures and/or higher temperatures avoid the formation of these features.

  2. 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.

  3. Application of Chlorine-Assisted Chemical Vapor Deposition of Diamond at Low Temperatures

    Science.gov (United States)

    Pan, Chenyu; Altemir, David A.; Margrave, John L.; Hauge, Robert H.

    1994-01-01

    Low temperature deposition of diamond has been achieved by a chlorine-assisted diamond chemical vapor deposition (CA-CVD) process. This method begins with the thermal dissociation of molecular chlorine into atomic chlorine in a resistively heated graphite furnace at temperatures between 1300 and 1500 deg. C. The atomic chlorine, upon mixing, subsequently reacts with molecular hydrogen and hydrocarbons. The rapid exchange reactions between the atomic chlorine, molecular hydrogen, and hydrocarbons give rise to the atomic hydrogen and carbon precursors required for diamond deposition. Homoepitaxial diamond growth on diamond substrates has been studied over the substrate temperature range of 100-950 C. It was found that the diamond growth rates are approximately 0.2 microns/hr in the temperature range between 102 and 300 C and that the growth rates do not decrease significantly with a decrease in substrate temperature. This is unique because the traditional diamond deposition using H2/CH4 systems usually disappears at substrate temperatures below approx. 500 deg. C. This opens up a possible route to the deposition of diamond on low-melting point materials such as aluminum and its alloys.

  4. Robust numerical simulation of porosity evolution in chemical vapor infiltration III: three space dimension

    CERN Document Server

    Jin Shi

    2003-01-01

    Chemical vapor infiltration (CVI) process is an important technology to fabricate ceramic matrix composites (CMC's). In this paper, a three-dimension numerical model is presented to describe pore microstructure evolution during the CVI process. We extend the two-dimension model proposed in [S. Jin, X.L. Wang, T.L. Starr, J. Mater. Res. 14 (1999) 3829; S. Jin. X.L. Wang, T.L. Starr, X.F. Chen, J. Comp. Phys. 162 (2000) 467], where the fiber surface is modeled as an evolving interface, to the three space dimension. The 3D method keeps all the virtue of the 2D model: robust numerical capturing of topological changes of the interface such as the merging, and fast detection of the inaccessible pores. For models in the kinetic limit, where the moving speed of the interface is constant, some numerical examples are presented to show that this three-dimension model will effectively track the change of porosity, close-off time, location and shape of all pores.

  5. Morphological Evolution of Vertically Standing Molybdenum Disulfide Nanosheets by Chemical Vapor Deposition.

    Science.gov (United States)

    Zhang, Song; Liu, Jiajia; Ruiz, Karla Hernandez; Tu, Rong; Yang, Meijun; Li, Qizhong; Shi, Ji; Li, Haiwen; Zhang, Lianmeng; Goto, Takashi

    2018-04-20

    In this study, we demonstrated the chemical vapor deposition (CVD) of vertically standing molybdenum disulfide (MoS₂) nanosheets, with an unconventional combination of molybdenum hexacarbonyl (Mo(CO)₆) and 1,2-ethanedithiol (C₂H₆S₂) as the novel kind of Mo and S precursors respectively. The effect of the distance between the precursor’s outlet and substrates (denoted as d ) on the growth characteristics of MoS₂, including surface morphology and nanosheet structure, was investigated. Meanwhile, the relationship between the structure characteristics of MoS₂ nanosheets and their catalytic performance for hydrogen evolution reaction (HER) was elucidated. The formation of vertically standing nanosheets was analyzed and verified by means of an extrusion growth model. The crystallinity, average length, and average depth between peak and valley ( R z) of MoS₂ nanosheets differed depending on the spatial location of the substrate. Good crystalized MoS₂ nanosheets grown at d = 5.5 cm with the largest average length of 440 nm, and the highest R z of 162 nm contributed to a better HER performance, with a respective Tafel slope and exchange current density of 138.9 mV/decade, and 22.6 μA/cm² for raw data (127.8 mV/decade and 19.3 μA/cm² for iR-corrected data).

  6. Properties, synthesis, and growth mechanisms of carbon nanotubes with special focus on thermal chemical vapor deposition.

    Science.gov (United States)

    Nessim, Gilbert D

    2010-08-01

    Carbon nanotubes (CNTs) have been extensively investigated in the last decade because their superior properties could benefit many applications. However, CNTs have not yet made a major leap into industry, especially for electronic devices, because of fabrication challenges. This review provides an overview of state-of-the-art of CNT synthesis techniques and illustrates their major technical difficulties. It also charts possible in situ analyses and new reactor designs that might enable commercialization. After a brief description of the CNT properties and of the various techniques used to synthesize substrate-free CNTs, the bulk of this review analyzes chemical vapor deposition (CVD). This technique receives special attention since it allows CNTs to be grown in predefined locations, provides a certain degree of control of the types of CNTs grown, and may have the highest chance to succeed commercially. Understanding the primary growth mechanisms at play during CVD is critical for controlling the properties of the CNTs grown and remains the major hurdle to overcome. Various factors that influence CNT growth receive a special focus: choice of catalyst and substrate materials, source gases, and process parameters. This review illustrates important considerations for in situ characterization and new reactor designs that may enable researchers to better understand the physical growth mechanisms and to optimize the synthesis of CNTs, thus contributing to make carbon nanotubes a manufacturing reality.

  7. Kinetics of low pressure chemical vapor deposition of tungsten silicide from dichlorocilane reduction of tungsten hexafluoride

    International Nuclear Information System (INIS)

    Srinivas, D.; Raupp, G.B.; Hillman, J.

    1990-01-01

    The authors report on experiments to determine the intrinsic surface reaction rate dependences and film properties' dependence on local reactant partial pressures and wafer temperature in low pressure chemical vapor deposition (LPCVD) of tungsten silicide from dichlorosilane reduction of tungsten hexafluoride. Films were deposited in a commercial-scale Spectrum CVD cold wall single wafer reactor under near differential, gradientless conditions. Over the range of process conditions investigated, deposition rate was found to be first order in dichlorosillane and negative second order in tungsten hexafluoride partial pressure. The apparent activation energy in the surface reaction limited regime was found to be 70-120 kcal/mol. The silicon to tungsten ratio of as deposited silicide films ranged from 1.1 to 2.4, and increased with increasing temperature and dichlorosillane partial pressure, and decreased with increasing tungsten hexafluoride pressure. These results suggest that the apparent silicide deposition rate and composition are controlled by the relative rates of at least two competing reactions which deposit stoichiometric tungsten silicides and/or silicon

  8. Optimization of operating parameters in polysilicon chemical vapor deposition reactor with response surface methodology

    Science.gov (United States)

    An, Li-sha; Liu, Chun-jiao; Liu, Ying-wen

    2018-05-01

    In the polysilicon chemical vapor deposition reactor, the operating parameters are complex to affect the polysilicon's output. Therefore, it is very important to address the coupling problem of multiple parameters and solve the optimization in a computationally efficient manner. Here, we adopted Response Surface Methodology (RSM) to analyze the complex coupling effects of different operating parameters on silicon deposition rate (R) and further achieve effective optimization of the silicon CVD system. Based on finite numerical experiments, an accurate RSM regression model is obtained and applied to predict the R with different operating parameters, including temperature (T), pressure (P), inlet velocity (V), and inlet mole fraction of H2 (M). The analysis of variance is conducted to describe the rationality of regression model and examine the statistical significance of each factor. Consequently, the optimum combination of operating parameters for the silicon CVD reactor is: T = 1400 K, P = 3.82 atm, V = 3.41 m/s, M = 0.91. The validation tests and optimum solution show that the results are in good agreement with those from CFD model and the deviations of the predicted values are less than 4.19%. This work provides a theoretical guidance to operate the polysilicon CVD process.

  9. 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.

  10. Computer Simulation of Temperature Parameter for Diamond Formation by Using Hot-Filament Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Chang Weon Song

    2017-12-01

    Full Text Available To optimize the deposition parameters of diamond films, the temperature, pressure, and distance between the filament and the susceptor need to be considered. However, it is difficult to precisely measure and predict the filament and susceptor temperature in relation to the applied power in a hot filament chemical vapor deposition (HF-CVD system. In this study, the temperature distribution inside the system was numerically calculated for the applied powers of 12, 14, 16, and 18 kW. The applied power needed to achieve the appropriate temperature at a constant pressure and other conditions was deduced, and applied to actual experimental depositions. The numerical simulation was conducted using the commercial computational fluent dynamics software ANSYS-FLUENT. To account for radiative heat-transfer in the HF-CVD reactor, the discrete ordinate (DO model was used. The temperatures of the filament surface and the susceptor at different power levels were predicted to be 2512–2802 K and 1076–1198 K, respectively. Based on the numerical calculations, experiments were performed. The simulated temperatures for the filament surface were in good agreement with the experimental temperatures measured using a two-color pyrometer. The results showed that the highest deposition rate and the lowest deposition of non-diamond was obtained at a power of 16 kW.

  11. Surface functionalization of 3D-printed plastics via initiated chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Christine Cheng

    2017-08-01

    Full Text Available 3D printing is a useful fabrication technique because it offers design flexibility and rapid prototyping. The ability to functionalize the surfaces of 3D-printed objects allows the bulk properties, such as material strength or printability, to be chosen separately from surface properties, which is critical to expanding the breadth of 3D printing applications. In this work, we studied the ability of the initiated chemical vapor deposition (iCVD process to coat 3D-printed shapes composed of poly(lactic acid and acrylonitrile butadiene styrene. The thermally insulating properties of 3D-printed plastics pose a challenge to the iCVD process due to large thermal gradients along the structures during processing. In this study, processing parameters such as the substrate temperature and the filament temperature were systematically varied to understand how these parameters affect the uniformity of the coatings along the 3D-printed objects. The 3D-printed objects were coated with both hydrophobic and hydrophilic polymers. Contact angle goniometry and X-ray photoelectron spectroscopy were used to characterize the functionalized surfaces. Our results can enable the use of iCVD to functionalize 3D-printed materials for a range of applications such as tissue scaffolds and microfluidics.

  12. Top-gated chemical vapor deposition grown graphene transistors with current saturation.

    Science.gov (United States)

    Bai, Jingwei; Liao, Lei; Zhou, Hailong; Cheng, Rui; Liu, Lixin; Huang, Yu; Duan, Xiangfeng

    2011-06-08

    Graphene transistors are of considerable interest for radio frequency (rf) applications. In general, transistors with large transconductance and drain current saturation are desirable for rf performance, which is however nontrivial to achieve in graphene transistors. Here we report high-performance top-gated graphene transistors based on chemical vapor deposition (CVD) grown graphene with large transconductance and drain current saturation. The graphene transistors were fabricated with evaporated high dielectric constant material (HfO(2)) as the top-gate dielectrics. Length scaling studies of the transistors with channel length from 5.6 μm to 100 nm show that complete current saturation can be achieved in 5.6 μm devices and the saturation characteristics degrade as the channel length shrinks down to the 100-300 nm regime. The drain current saturation was primarily attributed to drain bias induced shift of the Dirac points. With the selective deposition of HfO(2) gate dielectrics, we have further demonstrated a simple scheme to realize a 300 nm channel length graphene transistors with self-aligned source-drain electrodes to achieve the highest transconductance of 250 μS/μm reported in CVD graphene to date.

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

    Directory of Open Access Journals (Sweden)

    Jhansirani KOTCHARLAKOTA

    2016-05-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Carol [Northern Illinois Univ., DeKalb, IL (United States); Argonne National Lab., Argonne, IL (United States); Highland, Matthew J.; Perret, Edith; Fuoss, Paul H.; Streiffer, Stephen K.; Stephenson, G. Brian [Argonne National Lab., Argonne, IL (United States); Richard, Marie-Ingrid [Universite Paul Cezanne Aix-Marseille, Marseille (France)

    2012-07-01

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

  15. Chemically vapor-deposited ZrB/sub 2/ as a selective solar absorber

    Energy Technology Data Exchange (ETDEWEB)

    Randich, E.; Allred, D.D.

    1981-09-25

    Coatings of ZrB/sub 2/ and TiB/sub 2/ for photothermal solar absorber applications were prepared using chemical vapor deposition (CVD) techniques. Oxidation tests suggest a maximum temperature limit for air exposure of 600 K for TiB/sub 2/ and 800 K for ZrB/sub 2/. Both materials exhibit innate spectral selectivity with an emittance at 375 K ranging from 0.06 to 0.09, a solar absorptance for ZrB/sub 2/ ranging from 0.67 to 0.77 and a solar absorptance for TiB/sub 2/ ranging from 0.46 to 0.59. ZrB/sub 2/ has better solar selectivity and more desirable oxidation behavior than TiB/sub 2/. A 0.071 ..mu..m antireflection coating of Si/sub 3/N/sub 4/ deposited onto the ZrB/sub 2/ coating leads to an increase in absorptance from 0.77 to 0.93, while the emittance remains unchanged.

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

    International Nuclear Information System (INIS)

    Randich, E.; Allred, D.D.

    1981-01-01

    Coatings of ZrB 2 and TiB 2 for photothermal solar absorber applications were prepared using chemical vapor deposition (CVD) techniques. Oxidation tests suggest a maximum temperature limit for air exposure of 600 K for TiB 2 and 800 K for ZrB 2 . Both materials exhibit innate spectral selectivity with an emittance at 375 K ranging from 0.06 to 0.09, a solar absorptance for ZrB 2 ranging from 0.67 to 0.77 and a solar absorptance for TiB 2 ranging from 0.46 to 0.59. ZrB 2 has better solar selectivity and more desirable oxidation behavior than TiB 2 . A 0.071 μm antireflection coating of Si 3 N 4 deposited onto the ZrB 2 coating leads to an increase in absorptance from 0.77 to 0.93, while the emittance remains unchanged. (Auth.)

  17. Kinetics of the tungsten hexafluoride-silane reaction for the chemical vapor deposition of tungsten

    International Nuclear Information System (INIS)

    Gokce, Huseyin.

    1991-01-01

    In this study, the kinetics of the low-pressure chemical vapor deposition (LPCVD) of tungsten by silane reduction of tungsten hexafluoride on Si(100) surfaces was studied. A single-wafer, cold-wall reactor was sued for the experiments. The SiH 4 /WF 6 ratio was 1.0. The pressure and temperature range were 1-10 torr and 137-385 degree C, respectively. Kinetic data were obtained in the absence of mass-transfer effects. The film thicknesses were measured by gravimetry. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES), x-ray diffraction (XRD), and resistivity measurements were used to analyze the W films. For the horizontal substrate position and 4-minute reaction times, the apparent activation energies were determined to be 0.35 eV/atom for 10 torr, 0.17 eV/atom for 3 torr, and 0.08 eV/atom for 1 torr. Lower temperatures and higher pressures produced porous films, while higher temperatures and lower pressures resulted in continuous films with smoother surfaces. As the Si-W interface, a W(110) preferential orientation was observed. As the W films grew thicker, W orientation switched from (110) to (100). Apparent activation energy seems to change with thickness

  18. Faraday effect of polycrystalline bismuth iron garnet thin film prepared by mist chemical vapor deposition method

    International Nuclear Information System (INIS)

    Yao, Situ; Kamakura, Ryosuke; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa

    2017-01-01

    We have synthesized polycrystalline thin film composed of a single phase of metastable bismuth iron garnet, Bi_3Fe_5O_1_2, on a fused silica substrate, one of the most widely utilized substrates in the solid-state electronics, by using mist chemical vapor deposition (mist CVD) method. The phase purity and stoichiometry are confirmed by X-ray diffraction and Rutherford backscattering spectrometry. The resultant thin film shows a small surface roughness of 3.251 nm. The saturation magnetization at room temperature is 1200 G, and the Faraday rotation angle at 633 nm reaches −5.2 deg/μm. Both the magnetization and the Faraday rotation angles are somewhat higher than those of polycrystalline BIG thin films prepared by other methods. - Highlights: • Thin film of polycrystalline Bi_3Fe_5O_1_2 was prepared by the mist CVD method. • Optimized conditions were found for the synthesis of single phase of Bi_3Fe_5O_1_2. • The Faraday rotation angle at 633 nm is –5.2 deg/μm at room temperature. • The Faraday rotation is interpreted by the electronic transitions of Fe"3"+ ions.

  19. Near room temperature chemical vapor deposition of graphene with diluted methane and molten gallium catalyst.

    Science.gov (United States)

    Fujita, Jun-Ichi; Hiyama, Takaki; Hirukawa, Ayaka; Kondo, Takahiro; Nakamura, Junji; Ito, Shin-Ichi; Araki, Ryosuke; Ito, Yoshikazu; Takeguchi, Masaki; Pai, Woei Wu

    2017-09-28

    Direct growth of graphene integrated into electronic devices is highly desirable but difficult due to the nominal ~1000 °C chemical vapor deposition (CVD) temperature, which can seriously deteriorate the substrates. Here we report a great reduction of graphene CVD temperature, down to 50 °C on sapphire and 100 °C on polycarbonate, by using dilute methane as the source and molten gallium (Ga) as catalysts. The very low temperature graphene synthesis is made possible by carbon attachment to the island edges of pre-existing graphene nuclei islands, and causes no damages to the substrates. A key benefit of using molten Ga catalyst is the enhanced methane absorption in Ga at lower temperatures; this leads to a surprisingly low apparent reaction barrier of ~0.16 eV below 300 °C. The faster growth kinetics due to a low reaction barrier and a demonstrated low-temperature graphene nuclei transfer protocol can facilitate practical direct graphene synthesis on many kinds of substrates down to 50-100 °C. Our results represent a significant progress in reducing graphene synthesis temperature and understanding its mechanism.

  20. Faraday effect of polycrystalline bismuth iron garnet thin film prepared by mist chemical vapor deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Situ; Kamakura, Ryosuke; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa, E-mail: tanaka@dipole7.kuic.kyoto-u.ac.jp

    2017-01-15

    We have synthesized polycrystalline thin film composed of a single phase of metastable bismuth iron garnet, Bi{sub 3}Fe{sub 5}O{sub 12}, on a fused silica substrate, one of the most widely utilized substrates in the solid-state electronics, by using mist chemical vapor deposition (mist CVD) method. The phase purity and stoichiometry are confirmed by X-ray diffraction and Rutherford backscattering spectrometry. The resultant thin film shows a small surface roughness of 3.251 nm. The saturation magnetization at room temperature is 1200 G, and the Faraday rotation angle at 633 nm reaches −5.2 deg/μm. Both the magnetization and the Faraday rotation angles are somewhat higher than those of polycrystalline BIG thin films prepared by other methods. - Highlights: • Thin film of polycrystalline Bi{sub 3}Fe{sub 5}O{sub 12} was prepared by the mist CVD method. • Optimized conditions were found for the synthesis of single phase of Bi{sub 3}Fe{sub 5}O{sub 12}. • The Faraday rotation angle at 633 nm is –5.2 deg/μm at room temperature. • The Faraday rotation is interpreted by the electronic transitions of Fe{sup 3+} ions.

  1. Superhydrophobic multi-scale ZnO nanostructures fabricated by chemical vapor deposition method.

    Science.gov (United States)

    Zhou, Ming; Feng, Chengheng; Wu, Chunxia; Ma, Weiwei; Cai, Lan

    2009-07-01

    The ZnO nanostructures were synthesized on Si(100) substrates by chemical vapor deposition (CVD) method. Different Morphologies of ZnO nanostructures, such as nanoparticle film, micro-pillar and micro-nano multi-structure, were obtained with different conditions. The results of XRD and TEM showed the good quality of ZnO crystal growth. Selected area electron diffraction analysis indicates the individual nano-wire is single crystal. The wettability of ZnO was studied by contact angle admeasuring apparatus. We found that the wettability can be changed from hydrophobic to super-hydrophobic when the structure changed from smooth particle film to single micro-pillar, nano-wire and micro-nano multi-scale structure. Compared with the particle film with contact angle (CA) of 90.7 degrees, the CA of single scale microstructure and sparse micro-nano multi-scale structure is 130-140 degrees, 140-150 degrees respectively. But when the surface is dense micro-nano multi-scale structure such as nano-lawn, the CA can reach to 168.2 degrees . The results indicate that microstructure of surface is very important to the surface wettability. The wettability on the micro-nano multi-structure is better than single-scale structure, and that of dense micro-nano multi-structure is better than sparse multi-structure.

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

    International Nuclear Information System (INIS)

    Iqbal, M. Z.; Kumar Singh, Arun; Iqbal, M. W.; Seo, Sunae; Eom, Jonghwa

    2012-01-01

    We have grown graphene by chemical vapor deposition (CVD) and transferred it onto Si/SiO 2 substrates to make tens of micron scale devices for Raman spectroscopy study. The effect of electron beam (e-beam) irradiation of various doses (600 to 12 000 μC/cm 2 ) on CVD grown graphene has been examined by using Raman spectroscopy. It is found that the radiation exposures result in the appearance of the strong disorder D band attributed the damage to the lattice. The evolution of peak frequencies, intensities, and widths of the main Raman bands of CVD graphene is analyzed as a function of defect created by e-beam irradiation. Especially, the D and G peak evolution with increasing radiation dose follows the amorphization trajectory, which suggests transformation of graphene to the nanocrystalline and then to amorphous form. We have also estimated the strain induced by e-beam irradiation in CVD graphene. These results obtained for CVD graphene are in line with previous findings reported for the mechanically exfoliated graphene [D. Teweldebrhan and A. A. Balandin, Appl. Phys. Lett. 94, 013101 (2009)]. The results have important implications for CVD graphene characterization and device fabrication, which rely on the electron microscopy.

  3. Fabrication and growth mechanism of carbon nanospheres by chemical vapor deposition

    International Nuclear Information System (INIS)

    Tian, F.; He, C.N.

    2010-01-01

    The synthesis of carbon nanospheres (CNSs) by chemical vapor deposition (CVD) of methane on catalyst of Ni-Al composite powders was reported. The influence factors on the growth morphology of CNSs, such as reaction temperature, reaction time and different carrier gases concerning hydrogen, nitrogen as well as no carrier gas were investigated using transmission electron microscope. The results showed that the reaction temperature had great effect on the structure of CNSs, higher temperature led to high-crystallized CNSs with high purity. The reaction time brought no significant influence to the structure of CNSs, but the average diameter of the CNSs was obviously increased with prolonging the reaction time. Relatively pure CNSs could be obtained with hydrogen as the carrier gas but with poor product rate compared with the CNSs with no carrier gas. Proper amount of CNSs with pure characteristic could be obtained with nitrogen as the carrier gas. Finally, a growth mechanism of dissolution-precipitation-diffusion is proposed for elucidating the growth process of general CNSs.

  4. Nitrogen doping of chemical vapor deposition grown graphene on 4H-SiC (0001)

    Energy Technology Data Exchange (ETDEWEB)

    Urban, J. M.; Binder, J.; Wysmołek, A. [Faculty of Physics, University of Warsaw, ul. Hoża 69, 00-681 Warsaw (Poland); Dąbrowski, P.; Strupiński, W. [Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01-919 Warsaw (Poland); Kopciuszyński, M.; Jałochowski, M. [Institute of Physics, Maria Curie-Skłodowska University, pl. M. Curie-Skłodowskiej 1, 20-031 Lublin (Poland); Klusek, Z. [Faculty of Physics and Applied Informatics, University of Łódź, ul. Pomorska 149/153, 90-236 Łódź (Poland); Baranowski, J. M. [Faculty of Physics, University of Warsaw, ul. Hoża 69, 00-681 Warsaw (Poland); Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01-919 Warsaw (Poland)

    2014-06-21

    We present optical, electrical, and structural properties of nitrogen-doped graphene grown on the Si face of 4H-SiC (0001) by chemical vapor deposition method using propane as the carbon precursor and N{sub 2} as the nitrogen source. The incorporation of nitrogen in the carbon lattice was confirmed by X-ray photoelectron spectroscopy. Angle-resolved photoemission spectroscopy shows carrier behavior characteristic for massless Dirac fermions and confirms the presence of a graphene monolayer in the investigated nitrogen-doped samples. The structural and electronic properties of the material were investigated by Raman spectroscopy. A systematical analysis of the graphene Raman spectra, including D, G, and 2D bands, was performed. In the case of nitrogen-doped samples, an electron concentration on the order of 5–10 × 10{sup 12} cm{sup −2} was estimated based upon Raman and Hall effect measurements and no clear dependence of the carrier concentration on nitrogen concentration used during growth was observed. This high electron concentration can be interpreted as both due to the presence of nitrogen in graphitic-like positions of the graphene lattice as well as to the interaction with the substrate. A greater intensity of the Raman D band and increased inhomogeneity, as well as decreased electron mobility, observed for nitrogen-doped samples, indicate the formation of defects and a modification of the growth process induced by nitrogen doping.

  5. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-11-02

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

  7. Surface morphology and preferential orientation growth of TaC crystals formed by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Xiong Xiang, E-mail: Xiong228@sina.co [State Key Lab for Powder Metallurgy, Central South University, Changsha 410083 (China); Chen Zhaoke; Huang Baiyun; Li Guodong [State Key Lab for Powder Metallurgy, Central South University, Changsha 410083 (China); Zheng Feng [School of Material Science and Engineering, Central South University, Changsha 410083 (China); Xiao Peng; Zhang Hongbo [State Key Lab for Powder Metallurgy, Central South University, Changsha 410083 (China)

    2009-04-02

    TaC film was deposited on (002) graphite sheet by isothermal chemical vapor deposition using TaCl{sub 5}-Ar-C{sub 3}H{sub 6} mixtures, with deposition temperature 1200 {sup o}C and pressure about 200 Pa. The influence of deposition position (or deposition rate) on preferential orientation and surface morphology of TaC crystals were investigated by X-ray diffraction and scanning electron microscopy methods. The deposits are TaC plus trace of C. The crystals are large individual columns with pyramidal-shape at deposition rate of 32.4-37.3 {mu}m/h, complex columnar at 37.3-45.6 {mu}m/h, lenticular-like at 45.6-54.6 {mu}m/h and cauliflower-like at 54.6-77.3 {mu}m/h, with <001>, near <001>, <110> and no clear preferential orientation, respectively. These results agree in part with the preditions of the Pangarov's model of the relationship between deposition rate and preferential growth orientation. The growth mechanism of TaC crystals in <001>, near <001>, <111> and no clear preferential orientation can be fairly explained by the growth parameter {alpha} with Van der Drift's model, deterioration model and Meakin model. Furthermore, a nucleation and coalescence model is also proposed to explain the formation mechanism of <110> lenticular-like crystals.

  8. Comparative investigation of smooth polycrystalline diamond films on dental burs by chemical vapor deposition

    Science.gov (United States)

    Sein, Htet; Ahmed, Waqar; Rego, Christopher; Jackson, Mark; Polini, Riccardo

    2006-04-01

    Depositions of hot filament chemical vapor-deposited diamond on cobalt-cemented tungsten carbide (WC-Co) rotary cutting dental burs are presented. Conventional dental tools made of sintered polycrystalline diamond have a number of problems associated with the heterogeneity of the crystallite, decreased cutting efficiency, and short life. A preferential (111) faceted diamond was obtained after 15 h of deposition at a growth rate of 1.1 µm/h. Diamond-coated WC-Co dental burs and conventional sintered burs are mainly used in turning, milling, and drilling operations for machining metal ceramic hard alloys such as CoCr, composite teeth, and aluminum alloy in the dental laboratory. The influence of structure, the mechanical characteristics of both diamond grains and hard alloys on the wear behavior, as well as the regimen of grinding on diamond wear are considered. Erosion wear properties are also investigated under air-sand erosion testing. After machining with excessive cutting performance, calculations can be made on flank and crater wear areas. Diamond-coated WC-Co dental burs offered significantly better erosion and wear resistance compared with uncoated WC-Co tools and sintered burs.

  9. Equilibrium chemical vapor deposition growth of Bernal-stacked bilayer graphene.

    Science.gov (United States)

    Zhao, Pei; Kim, Sungjin; Chen, Xiao; Einarsson, Erik; Wang, Miao; Song, Yenan; Wang, Hongtao; Chiashi, Shohei; Xiang, Rong; Maruyama, Shigeo

    2014-11-25

    Using ethanol as the carbon source, self-limiting growth of AB-stacked bilayer graphene (BLG) has been achieved on Cu via an equilibrium chemical vapor deposition (CVD) process. We found that during this alcohol catalytic CVD (ACCVD) a source-gas pressure range exists to break the self-limitation of monolayer graphene on Cu, and at a certain equilibrium state it prefers to form uniform BLG with a high surface coverage of ∼94% and AB-stacking ratio of nearly 100%. More importantly, once the BLG is completed, this growth shows a self-limiting manner, and an extended ethanol flow time does not result in additional layers. We investigate the mechanism of this equilibrium BLG growth using isotopically labeled (13)C-ethanol and selective surface aryl functionalization, and results reveal that during the equilibrium ACCVD process a continuous substitution of graphene flakes occurs to the as-formed graphene and the BLG growth follows a layer-by-layer epitaxy mechanism. These phenomena are significantly in contrast to those observed for previously reported BLG growth using methane as precursor.

  10. Morphological Evolution of a-GaN on r-Sapphire by Metalorganic Chemical Vapor Deposition

    International Nuclear Information System (INIS)

    Sang Ling; Liu Jian-Ming; Xu Xiao-Qing; Wang Jun; Zhao Gui-Juan; Liu Chang-Bo; Gu Cheng-Yan; Liu Gui-Peng; Wei Hong-Yuan; Liu Xiang-Lin; Yang Shao-Yan; Zhu Qin-Sheng; Wang Zhan-Guo

    2012-01-01

    The morphological evolution of a-GaN deposited by metalorganic chemical vapor deposition (MOCVD) on r-sapphire is studied. The influences of V/III ratio and growth temperature on surface morphology are investigated. V-pits and stripes are observed on the surface of a-GaN grown at 1050°C and 1100°C, respectively. The overall orientation and geometry of V-pits are uniform and independent on the V/III molar ratio in the samples grown at 1050°C, while in the samples grown at 1100°C, the areas of stripes decrease with the adding of V/III ratio. We deduce the origin of V-pits and stripes by annealing the buffer layers at different temperatures. Because of the existence of inclined (101-bar1) facets, V-pits are formed at 1050°C. The (101-bar1) plane is an N terminated surface, which is metastable at higher temperature, so stripes instead of V-pits are observed at 1100°C. Raman spectra suggest that the growth temperature of the first layer in the two-step process greatly affects the strain of the films. Hence, to improve the growth temperature of the first layer in the two-step method may be an effective way to obtain high quality a-GaN film on r-sapphire. (condensed matter: structure, mechanical and thermal properties)

  11. 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.

  12. Epitaxial Oxide Thin Films Grown by Solid Source Metal-Organic Chemical Vapor Deposition.

    Science.gov (United States)

    Lu, Zihong

    1995-01-01

    The conventional liquid source metal-organic chemical vapor deposition (MOCVD) technique is capable of producing large area, high quality, single crystal semiconductor films. However, the growth of complex oxide films by this method has been hampered by a lack of suitable source materials. While chemists have been actively searching for new source materials, the research work reported here has demonstrated the successful application of solid metal-organic sources (based on tetramethylheptanedionate) to the growth of high quality thin films of binary compound cerium dioxide (CeO_2), and two more complex materials, the ternary compound lithium niobate (LiNbO_3), with two cations, and the quaternary compound strontium barium niobate (SBN), with three cations. The growth of CeO_2 thin films on (1012)Al_2O_3 substrates has been used as a model to study the general growth behavior of oxides. Factors affecting deposition rate, surface morphology, out-of-plane mosaic structure, and film orientation have been carefully investigated. A kinetic model based on gas phase prereaction is proposed to account for the substrate temperature dependence of film orientation found in this system. Atomically smooth, single crystal quality cerium dioxide thin films have been obtained. Superconducting YBCO films sputtered on top of solid source MOCVD grown thin cerium dioxide buffer layers on sapphire have been shown to have physical properties as good as those of YBCO films grown on single crystal MgO substrates. The thin film growth of LiNbO_3 and Sr_{1-x}Ba _{x}Nb_2 O_6 (SBN) was more complex and challenging. Phase purity, transparency, in-plane orientation, and the ferroelectric polarity of LiNbO _3 films grown on sapphire substrates was investigated. The first optical quality, MOCVD grown LiNbO _3 films, having waveguiding losses of less than 2 dB/cm, were prepared. An important aspect of the SBN film growth studies involved finding a suitable single crystal substrate material. Mg

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

    International Nuclear Information System (INIS)

    John, John T.; De, P.K.; Dubey, Vivekanand; Srinivasa, Raman

    2009-08-01

    Aluminide coatings are a class of intermetallic coatings applied on nickel and cobalt base superalloys and steels to protect them from different forms of environmental degradation at high temperatures. In this report a CVD system that can produce the aluminide coatings on iron, nickel and nickel base alloys has been described and the result of chemical vapor deposition of aluminide coatings on iron specimens, their characterization, and property evaluation have been presented. The CVD system consists of an AlCl 3 bath, a stainless steel retort as a hot-wall reacto, cold traps and vacuum system. Aluminium chloride vapor was carried in a stream of hydrogen gas at a flow rate of 150 SCCM (standard cubic centimeter per minute) into the CVD reactor maintained in the temperature range of 1173 - 1373 K and at a pressure of 1.33 kPa (10 Torr). Aluminum deposition takes place from aluminium subchlorides produced by reaction between AlCl 3 and pure aluminum kept in the CVD reactor. The aluminum diffuses into the iron samples and iron aluminide phases are formed at the surface. The coatings were shining bright and showed good adherence to the substrate. The coatings consisted of FeAl phase over a wide range of experimental conditions. The growth kinetics of the coating followed a parabolic rate law and the mean activation energy was 212 ±16 kJ/mol. Optical microscopic studies on the transverse section of the coating showed that the aluminide coating on iron consisted of two layers. The top layer had a thickness in the range of 20-50 μm, and the under layer had thickness ranging from 35 to 250 μm depending on coating temperature in two hours. The thickness of the aluminide layer increased with coating duration and temperature. Electron microprobe studies (EPMA) showed that the aluminum concentration decreased steadily as distance from the surface increased. TEM studies showed that the outer most layer had a B2 order (of the FeAl phase), which extended even into the under

  14. Effects of argon and oxygen flow rate on water vapor barrier properties of silicon oxide coatings deposited on polyethylene terephthalate by plasma enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Kim, Sung-Ryong; Choudhury, Moinul Haque; Kim, Won-Ho; Kim, Gon-Ho

    2010-01-01

    Plasma polymer coatings were deposited from hexamethyldisiloxane on polyethylene terephthalate (PET) substrates while varying the operating conditions, such as the Ar and O 2 flow rates, at a fixed radio frequency power of 300 W. The water vapor transmission rate (WVTR) of the untreated PET was 54.56 g/m 2 /day and was decreased after depositing the silicon oxide (SiO x ) coatings. The minimum WVTR, 0.47 g/m 2 /day, was observed at Ar and O 2 flow rates of 4 and 20 sccm, respectively, with a coating thickness of 415.44 nm. The intensity of the peaks for the Si-O-Si bending at 800-820 cm -1 and Si-O-Si stretching at 1000-1150 cm -1 varied depending on the Ar and O 2 flow rates. The contact angle of the SiO x coated PET increased as the Ar flow rate was increased from 2 to 8 sccm at a fixed O 2 flow rate of 20 sccm. It decreased gradually as the oxygen flow rate increased from 12 to 28 sccm at a fixed Ar carrier gas flow rate. The examination by atomic force microscopy revealed a correlation of the SiO x morphology and the water vapor barrier performance with the Ar and O 2 flow rates. The roughness of the deposited coatings increased when either the O 2 or Ar flow rate was increased.

  15. Chemical vapor deposition of three aminosilanes on silicon dioxide: surface characterization, stability, effects of silane concentration, and cyanine dye adsorption.

    Science.gov (United States)

    Zhang, Feng; Sautter, Ken; Larsen, Adam M; Findley, Daniel A; Davis, Robert C; Samha, Hussein; Linford, Matthew R

    2010-09-21

    Covalently bonded monolayers of two monofunctional aminosilanes (3-aminopropyldimethylethoxysilane, APDMES, and 3-aminopropyldiisopropylethoxysilane, APDIPES) and one trifunctional aminosilane (3-aminopropyltriethoxysilane, APTES) have been deposited on dehydrated silicon substrates by chemical vapor deposition (CVD) at 150 °C and low pressure (a few Torr) using reproducible equipment. Standard surface analytical techniques such as x-ray photoelectron spectroscopy (XPS), contact angle goniometry, spectroscopic ellipsometry, atomic force microscopy, and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) have been employed to characterize the resulting films. These methods indicate that essentially constant surface coverages are obtained over a wide range of gas phase concentrations of the aminosilanes. XPS data further indicate that the N1s/Si2p ratio is higher after CVD with the trifunctional silane (APTES) compared to the monofunctional ones, with a higher N1s/Si2p ratio for APDMES compared to that for APDIPES. AFM images show an average surface roughness of 0.12- 0.15 nm among all three aminosilane films. Stability tests indicate that APDIPES films retain most of their integrity at pH 10 for several hours and are more stable than APTES or APDMES layers. The films also showed good stability against storage in the laboratory. ToF-SIMS of these samples showed expected peaks, such as CN(-), as well as CNO(-), which may arise from an interaction between monolayer amine groups and silanols. Optical absorption measurements on adsorbed cyanine dye at the surface of the aminosilane films show the formation of dimer aggregates on the surface. This is further supported by ellipsometry measurements. The concentration of dye on each surface appears to be consistent with the density of the amines.

  16. 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.

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

    KAUST Repository

    Cheng, Yingchun

    2013-01-01

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

  18. Silver chemical vapor generation for atomic absorption spectrometry: Minimization of transport losses, interferences and application to water analysis

    Czech Academy of Sciences Publication Activity Database

    Musil, Stanislav; Kratzer, Jan; Vobecký, Miloslav; Benada, Oldřich; Matoušek, Tomáš

    2010-01-01

    Roč. 25, č. 10 (2010), s. 1618-1626 ISSN 0267-9477 R&D Projects: GA ČR GA203/09/1783 Institutional research plan: CEZ:AV0Z40310501; CEZ:AV0Z50200510 Keywords : chemical vapor generation * 111Ag radioindicator * transport losses Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.372, year: 2010

  19. Tuning of electrical and structural properties of indium oxide films grown by metal organic chemical vapor deposition

    International Nuclear Information System (INIS)

    Wang, Ch.Y.; Cimalla, V.; Romanus, H.; Kups, Th.; Niebelschuetz, M.; Ambacher, O.

    2007-01-01

    Tuning of structural and electrical properties of indium oxide (In 2 O 3 ) films by means of metal organic chemical vapor deposition is demonstrated. Phase selective growth of rhombohedral In 2 O 3 (0001) and body-centered cubic In 2 O 3 (001) polytypes on (0001) sapphire substrates was obtained by adjusting the substrate temperature and trimethylindium flow rate. The specific resistance of the as-grown films can be tuned by about two orders of magnitude by varying the growth conditions

  20. On the Origin of Light Emission in Silicon Rich Oxide Obtained by Low-Pressure Chemical Vapor Deposition

    OpenAIRE

    Aceves-Mijares, M.; González-Fernández, A. A.; López-Estopier, R.; Luna-López, A.; Berman-Mendoza, D.; Morales, A.; Falcony, C.; Domínguez, C.; Murphy-Arteaga, R.

    2012-01-01

    Silicon Rich Oxide (SRO) has been considered as a material to overcome the drawbacks of silicon to achieve optical functions. Various techniques can be used to produce it, including Low-Pressure Chemical Vapor Deposition (LPCVD). In this paper, a brief description of the studies carried out and discussions of the results obtained on electro-, cathode-, and photoluminescence properties of SRO prepared by LPCVD and annealed at 1,100°C are presented. The experimental results lead us to accept th...

  1. Properties of zinc selenide grown by chemical vapor transport and its application to room-temperature radiation detection

    International Nuclear Information System (INIS)

    Brunett, B.A.; Toney, J.E.; Schlesinger, T.E.; Yoon, H.; Goorsky, M.S.; Rudolph, P.

    1998-01-01

    The authors have characterized ZnSe material grown by chemical vapor transport in iodine using triple-axis X-ray diffraction (TAD), photo-induced current transient spectroscopy (PICTS), photoluminescence (PL), current-voltage measurements and gamma-ray spectroscopy. The material was found to have inadequate carrier transport for nuclear spectrometer use, but there was a discernible difference in performance between crystals which could be correlated with crystallinity as determined by the TAD rocking curves

  2. Room temperature synthesis of porous SiO2 thin films by plasma enhanced chemical vapor deposition

    OpenAIRE

    Barranco Quero, Ángel; Cotrino Bautista, José; Yubero Valencia, Francisco; Espinós, J. P.; Rodríguez González-Elipe, Agustín

    2004-01-01

    Synthesis of porous SiO2 thin films in room temperature was carried out using plasma enhanced chemical vapor deposition (CVD) in an electron cyclotron resonance microwave reactor with a downstream configuration.The gas adsorption properties and the type of porosity of the SiO2 thin films were assessed by adsorption isotherms of toluene at room temperature.The method could also permit the tailoring synthesis of thin films when both composition and porosity can be simultaneously and independent...

  3. Near-equilibrium chemical vapor deposition of high-quality single-crystal graphene directly on various dielectric substrates.

    Science.gov (United States)

    Chen, Jianyi; Guo, Yunlong; Jiang, Lili; Xu, Zhiping; Huang, Liping; Xue, Yunzhou; Geng, Dechao; Wu, Bin; Hu, Wenping; Yu, Gui; Liu, Yunqi

    2014-03-05

    By using near-equilibrium chemical vapor deposition, it is demonstrated that high-quality single-crystal graphene can be grown on dielectric substrates. The maximum size is about 11 μm. The carrier mobility can reach about 5650 cm(2) V(-1) s(-1) , which is comparable to those of some metal-catalyzed graphene crystals, reflecting the good quality of the graphene lattice. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    International Nuclear Information System (INIS)

    Huang, Meng-Wen; Cheng, Yin-Wei; Pan, Ko-Ying; Chang, Chen-Chuan; Shieu, F.S.; Shih, Han C.

    2012-01-01

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

  5. Structure and properties of braided sleeve preforms for chemical vapor infiltration

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-04-01

    In all composites the properties and structure of the reinforcement strongly influence the performance of the material. For some composites, however, the reinforcement also affects the fabrication process itself exerting an additional, second order influence on performance. This is the case for the chemical vapor infiltration (CVI) process for fabrication of ceramic matrix composites. In this process the matrix forms progressively as a solid deposit, first onto the fiber surfaces, then onto the previous layer of deposit, ultimately growing to fill the inter-fiber porosity. The transport of reactants to the surfaces and the evolved morphology of the matrix depend on the initial reinforcement structure. This structure can vary greatly and is controlled by such factors as fiber size and cross-section, the number of filaments and amount of twist per tow or yarn, and the weave or braid architecture. Often the choice of reinforcement is based on mechanical performance analysis or on the cost and availability of the material or on the temperature stability of the fiber. Given this choice, the composite densification process--CVI--must be optimized to attain a successful material. Ceramic fiber in the form of cylindrical braided sleeve is an attractive choice for fabrication of tube-form ceramic matrix composites. Multiple, concentric layers of sleeve can be placed over a tubular mandrel, compressed and fixed with a binder to form a freestanding tube preform. This fiber architecture is different than that created by layup of plain weave cloth--the material used in most previous CVI development. This report presents the results of the investigation of CVI densification of braided sleeve preforms and the evolution of their structure and transport properties during processing.

  6. Phosphorus atomic layer doping in SiGe using reduced pressure chemical vapor deposition

    International Nuclear Information System (INIS)

    Yamamoto, Yuji; Heinemann, Bernd; Murota, Junichi; Tillack, Bernd

    2014-01-01

    Phosphorus (P) atomic layer doping in SiGe is investigated at temperatures between 100 °C to 600 °C using a single wafer reduced pressure chemical vapor deposition system. SiGe(100) surface is exposed to PH 3 at different PH 3 partial pressures by interrupting SiGe growth. The impact of the SiGe buffer/cap growth condition (total pressure/SiGe deposition precursors) on P adsorption, incorporation, and segregation are investigated. In the case of SiH 4 -GeH 4 -H 2 gas system, steeper P spikes due to lower segregation are observed by SiGe cap deposition at atmospheric (ATM) pressure compared with reduced pressure (RP). The steepness of P spike of ∼ 5.7 nm/dec is obtained for ATM pressure without reducing deposition temperature. This result may be due to the shift of equilibrium of P adsorption/desorption to desorption direction by higher H 2 pressure. Using Si 2 H 6 -GeH 4 -H 2 gas system for SiGe cap deposition in RP, lowering the SiGe growth temperature is possible, resulting in higher P incorporation and steeper P profile due to reduced desorption and segregation. In the case of Si 2 H 6 -GeH 4 -H 2 gas system, the P dose could be simulated assuming a Langmuir-type kinetics model. Incorporated P shows high electrical activity, indicating P is adsorbed mostly in lattice position. - Highlights: • Phosphorus (P) atomic layer doping in SiGe (100) is investigated using CVD. • P adsorption is suppressed by the hydrogen termination of Ge surface. • By SiGe cap deposition at atmospheric pressure, P segregation was suppressed. • By using Si 2 H 6 -based SiGe cap, P segregation was also suppressed. • The P adsorption process is self-limited and follows Langmuir-type kinetics model

  7. Role of hydrogen in the chemical vapor deposition growth of MoS2 atomic layers

    Science.gov (United States)

    Li, Xiao; Li, Xinming; Zang, Xiaobei; Zhu, Miao; He, Yijia; Wang, Kunlin; Xie, Dan; Zhu, Hongwei

    2015-04-01

    Hydrogen plays a crucial role in the chemical vapor deposition (CVD) growth of graphene. Here, we have revealed the roles of hydrogen in the two-step CVD growth of MoS2. Our study demonstrates that hydrogen acts as the following: (i) an inhibitor of the thermal-induced etching effect in the continuous film growth process; and (ii) a promoter of the desulfurization reaction by decreasing the S/Mo atomic ratio and the oxidation reaction of the obtained MoSx (0 desulfurization reaction by decreasing the S/Mo atomic ratio and the oxidation reaction of the obtained MoSx (0 < x < 2) films. A high hydrogen content of more than 100% in argon forms nano-sized circle-like defects and damages the continuity and uniformity of the film. Continuous MoS2 films with a high crystallinity and a nearly perfect S/Mo atomic ratio were finally obtained after sulfurization annealing with a hydrogen content in the range of 20%-80%. This insightful understanding reveals the crucial roles of hydrogen in the CVD growth of MoS2 and paves the way for the controllable synthesis of two-dimensional materials. Electronic supplementary information (ESI) available: Low-magnification optical images; Raman spectra of 0% and 5% H2 samples; AFM characterization; Schematic of the film before and after sulfurization annealing; Schematic illustrations of two typical Raman-active phonon modes (E12g, A1g); Raman (mapping) spectra for 40% and 80% H2 samples before and after sulfurization annealing; PL spectra. See DOI: 10.1039/c5nr00904a

  8. 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.

  9. On the tungsten single crystal coatings achieved by chemical vapor transportation deposition

    Energy Technology Data Exchange (ETDEWEB)

    Shi, J.Q.; Shen, Y.B.; Yao, S.Y.; Zhang, P.J.; Zhou, Q.; Guo, Y.Z. [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Tan, C.W., E-mail: tanchengwen@bit.edu.cn [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); China Astronaut Research and Training Center, Beijing 100094 (China); Yu, X.D. [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); China Astronaut Research and Training Center, Beijing 100094 (China); Nie, Z.H. [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Ma, H.L. [China Astronaut Research and Training Center, Beijing 100094 (China); Cai, H.N. [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)

    2016-12-15

    The tungsten single crystal has many excellent properties, namely a high melting point, high anti-creeping strength. Chemical vapor transportation deposition (CVTD) is a possible approach to achieve large-sized W single crystals for high-temperature application such as the cathode of a thermionic energy converter. In this work, CVTD W coatings were deposited on the monocrystalline molybdenum substrate (a tube with < 111 > axial crystalline orientation) using WCl{sub 6} as a transport medium. The microstructures of the coatings were investigated by a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The as-deposited coatings are hexagonal prisms—rough surfaces perpendicular to < 110 > with alternating hill-like bulges and pits at the side edges of the prisms, and flat surfaces perpendicular to < 112 > with arc-shaped terraces at the side faces. This can be explained by two-dimensional nucleation -mediated lateral growth model. Some parts of the coatings contain hillocks of an exotic morphology (noted as “abnormal growth”). The authors hypothesize that the abnormal growth is likely caused by the defects of the Mo substrate, which facilitate W nucleation sites, cause orientation difference, and may even form boundaries in the coatings. A dislocation density of 10{sup 6} to 10{sup 7} (counts/cm{sup 2}) was revealed by an etch-pit method and synchrotron X-ray diffraction. As the depositing temperature rises, the dislocation density decreases, and no sub-boundaries are found on samples deposited over 1300 °C, as a result of atom diffusion and dislocation climbing. - Highlights: •The varied growth rate causes the different morphologies of different planes. •The W coating is a single crystal when only single hillocks appear. •The (110) plane tends to have the lowest dislocation density. •The dislocation density tends to decrease as the temperature increases.

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

    International Nuclear Information System (INIS)

    Shirahata, Takahiro; Kawaharamura, Toshiyuki; Fujita, Shizuo; Orita, Hiroyuki

    2015-01-01

    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"−"4 Ωcm, previously were grown using a safe source material zinc acetate [Zn(ac)_2], at a growth temperature as high as 500 °C. To grow superior TCOs at lower temperatures, we proposed the addition of NH_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"−"3 Ω cm and transmittance higher than 90% at 300 °C by using zinc acetylacetonate [Zn(acac)_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"−"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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-30

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

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

    International Nuclear Information System (INIS)

    Li, Mingji; Guo, Wenlong; Li, Hongji; Xu, Sheng; Qu, Changqing; Yang, Baohe

    2014-01-01

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

  13. On the tungsten single crystal coatings achieved by chemical vapor transportation deposition

    International Nuclear Information System (INIS)

    Shi, J.Q.; Shen, Y.B.; Yao, S.Y.; Zhang, P.J.; Zhou, Q.; Guo, Y.Z.; Tan, C.W.; Yu, X.D.; Nie, Z.H.; Ma, H.L.; Cai, H.N.

    2016-01-01

    The tungsten single crystal has many excellent properties, namely a high melting point, high anti-creeping strength. Chemical vapor transportation deposition (CVTD) is a possible approach to achieve large-sized W single crystals for high-temperature application such as the cathode of a thermionic energy converter. In this work, CVTD W coatings were deposited on the monocrystalline molybdenum substrate (a tube with < 111 > axial crystalline orientation) using WCl 6 as a transport medium. The microstructures of the coatings were investigated by a scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). The as-deposited coatings are hexagonal prisms—rough surfaces perpendicular to < 110 > with alternating hill-like bulges and pits at the side edges of the prisms, and flat surfaces perpendicular to < 112 > with arc-shaped terraces at the side faces. This can be explained by two-dimensional nucleation -mediated lateral growth model. Some parts of the coatings contain hillocks of an exotic morphology (noted as “abnormal growth”). The authors hypothesize that the abnormal growth is likely caused by the defects of the Mo substrate, which facilitate W nucleation sites, cause orientation difference, and may even form boundaries in the coatings. A dislocation density of 10 6 to 10 7 (counts/cm 2 ) was revealed by an etch-pit method and synchrotron X-ray diffraction. As the depositing temperature rises, the dislocation density decreases, and no sub-boundaries are found on samples deposited over 1300 °C, as a result of atom diffusion and dislocation climbing. - Highlights: •The varied growth rate causes the different morphologies of different planes. •The W coating is a single crystal when only single hillocks appear. •The (110) plane tends to have the lowest dislocation density. •The dislocation density tends to decrease as the temperature increases.

  14. Tribological properties of nitrogen-containing amorphous carbon film produced by dc plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Zhang Wei; Wazumi, Koichiro; Tanaka, Akihiro; Koga, Yoshinori

    2003-01-01

    The nitrogen-contained amorphous carbon (a-C:N) films were deposited in a dc plasma chemical vapor deposition system with different substrate bias voltages. The structural, mechanical, and tribological properties of the a-C:N films were investigated. The influence of the bias voltage on the tribological behaviors of the a-C:N films was evaluated under various environments (dry air, O 2 , N 2 , and vacuum) using a ball-on-disk friction tester. It showed that the sp 3 C and hydrogen concentration of the a-C:N films decreases with increasing the bias voltage. However, the nitrogen concentration increases with increasing the bias voltage. As a result, the hardness and internal stress decrease and the critical load for fracturing increases as the substrate bias increases. For the tribological properties of the a-C:N films, the friction coefficient of the films slightly decreases in the environments of N 2 , O 2 , or dry air, but increases slightly in the vacuum environment by increasing the bias voltage. It indicates that the incorporated nitrogen in the a-C:N films would decrease the friction coefficient of the films in N 2 or O 2 environments, but slightly increases the friction coefficient of the films in a vacuum. The excellent wear resistance of the a-C:N films, in the level of 10 -9 -10 -8 mm 3 /Nm, can be observed in N 2 , vacuum, and dry air environments. In addition, the effect of the bias voltage on the wear rate of the a-C:N films becomes less obvious by nitrogen incorporation. So, we suggest the incorporated nitrogen, which bonded to carbon and restrained the increase of the fraction of sp 2 C-C, would restrain the wear of the a-C:N films in different environments, especially in dry air

  15. Tungsten chemical vapor deposition characteristics using SiH4 in a single wafer system

    International Nuclear Information System (INIS)

    Rosler, R.S.; Mendonca, J.; Rice, M.J. Jr.

    1988-01-01

    Several workers have recently begun using silane as a high-rate, low-temperature alternative to hydrogen for the reduction of WF 6 in the chemical vapor deposition of W. The deposition and film characteristics of both selective and blanket W using this new chemistry are explored in a radiantly heated single wafer system using closed-loop temperature control with a thermocouple in direct contact with the backside of the wafer. Selective W deposition rates of up to 1.5 μm/min were measured over the temperature range 250--550 0 C with blanket W rates typically 2--5 x lower. Resistivity is in the 10--15 μΩcm range at 300 0 C for SiH 4 /WF 6 ratios of 0.2 to 1.0, while above 400 0 C the range is 7.5--8.5 μΩcm. Si content in the W films is quite low at 10 16 to 10 17 atoms/cm 3 . Adhesion to silicon is excellent at temperatures of 350 0 C and above. Selective W using SiH 4 reduction for doped silicon contact fill shows none of the consumption or encroachment problems common to H 2 reduction, although selectivity is more sensitive. Contact resistance for p + and n + silicon contacts are comparable to aluminum controls and to previously published data. Blanket deposition into narrow geometries gives ≥0% step coverage and without keyholes in the 250--450 0 C deposition temperature range. For low-SiH 4 flows, deposition at 500 0 C causes small keyholes, while at 550 0 C even larger keyholes result. At higher SiH 4 flows, keyholes are typically not seen from 250 to 550 0 C

  16. Analysis of mechanical properties of N2in situ doped polycrystalline 3C-SiC thin films by chemical vapor deposition using single-precursor hexamethyildisilane

    International Nuclear Information System (INIS)

    Kim, Kang-San; Han, Ki-Bong; Chung, Gwiy-Sang

    2010-01-01

    This paper describes the mechanical properties of poly (polycrystalline) 3C-SiC thin films with N 2 in situ doping. In this work, in situ doped poly 3C-SiC film was deposited by using the atmospheric pressure chemical vapor deposition (APCVD) method at 1200 deg. C using single-precursor hexamethyildisilane: Si 2 (CH 3 ) 6 (HMDS) as Si and C precursors, and 0∼100 sccm N 2 as the dopant source gas. The mechanical properties of doped poly 3C-SiC thin films were measured by nano-indentation. Young's modulus and hardness were measured to be 285 and 35 GPa at 0 sccm N 2 , respectively. Young's modulus and hardness decreased with increasing N 2 flow rate. Surface morphology was evaluated by atomic force microscopy (AFM) according to N 2 flow rate.

  17. Laser chemical vapor deposition of millimeter scale three-dimensional shapes

    Science.gov (United States)

    Shaarawi, Mohammed Saad

    2001-07-01

    Laser chemical vapor deposition (LCVD) has been successfully developed as a technique to synthesize millimeter-scale components directly from the gas phase. Material deposition occurs when heat generated by the interaction of a laser beam with a substrate thermally decomposes the gas precursor. Selective illumination or scanning the laser beam over portions of a substrate forms the single thin layer of material that is the building block of this process. Sequential scanning of the laser in a pre-defined pattern on the substrate and subsequent deposit causes the layers to accumulate forming the three-dimensional shape. The primary challenge encountered in LCVD shape forming is the synthesis of uniform layers. Three deposition techniques are studied to address this problem. The most successful technique, Active Surface Deposition, is based on the premise that the most uniform deposits are created by measuring the deposition surface topology and actively varying the deposition rate in response to features at the deposition surface. Defects observed in the other techniques were significantly reduced or completely eliminated using Active Surface Deposition. The second technique, Constant Temperature Deposition, maintains deposit uniformity through the use of closed-loop modulation of the laser power to sustain a constant surface temperature during deposition. The technique was successful in depositing high quality graphite tubes >2 mm tall from an acetylene precursor and partially successful in depositing SiC + C composite tubes from tetramethylsilane (TMS). The final technique, Constant Power Deposition, is based on the premise that maintaining a uniform power output throughout deposition would result in the formation of uniform layers. Constant Power Deposition failed to form coherent shapes. Additionally, LCVD is studied using a combination of analytic and numerical models to gain insight into the deposition process. Thermodynamic modeling is used to predict the

  18. High performance emitter for thermionic diode obtained by chemical vapor deposition

    International Nuclear Information System (INIS)

    Faron, R.; Bargues, M.; Durand, J.P.; Gillardeau, J.

    1973-01-01

    Vapor deposition process conditions presently known for tungsten and molybdenum (specifically the range of high temperatures and low pressures) permit the achievement of high performance thermionic emitters when used with an appropriate technology. One example of this uses the following series of successive vapor deposits, the five last vapor deposits constituting the fabrication of the emitting layer: Mo deposit for the formation of the nuclear fuel mechanical support; Mo deposit, which constitutes the sheath of the nuclear fuel; epitaxed Mo--W alloy deposit; epitaxed tungsten deposit; fine-grained tungsten deposit; and tungsten deposit with surface orientation according to plane (110)W. In accordance with vapor deposition techniques previously developed, such a sequence of deposits can easily be achieved with the same equipment, even without having to take out the part during the course of the process. (U.S.)

  19. Evaluation of Personal Chemical Vapor Protection for Patrol and Tactical Law Enforcement

    National Research Council Canada - National Science Library

    Fedele, Paul D; Lake, William L; Arca, Victor J; Marshall, Stephen M; Mitchell, David B

    2002-01-01

    ... functions in law enforcement. Various Level C, impermeable and charcoal impregnated, vapor-absorptive, air-permeable protective clothing ensembles, worn with the MSA Millenium respiratory protective mask/butyl hood, and seven-mil...

  20. Determination of forces induced by steam flow in turbines; Determinacion de fuerzas inducidas por flujo de vapor en turbinas

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Castrejon, Juan Carlos

    2008-09-15

    blades, has a harmonic pattern. The pressure field variation as time function is uniform: the peaks and valleys across the axial clearance are always in phase. However the instant picture of the pressure field it's different: the peaks and valleys are not in phase and the number of peaks and valley changed across the clearance. In the case of the forces acting on blades, a Fourier on the forces calculated was used to determine the coefficients and frequency of a Fourier equation which can be used to calculate the alternating stresses on the blade in order to predict the useful life blades. [Spanish] Las vibraciones inducidas por flujo de vapor en turbinas representan uno de los problemas que enfrenta la operacion de turbinas de vapor cuya capacidad rebasa los 300 MW. Ademas estas constituyen uno de los limites tecnologicos para el desarrollo de turbinas de vapor de mas de 1 GW. Este tipo de fenomeno tiene su origen en la interaccion del rotor con el fluido que se encuentra en sus proximidades. El flujo de vapor dentro de la turbina es complejo, ya que es turbulento e inestable. A medida que el flujo pasa una etapa de estator o de rotor, se generan secundarios, vortices en los filos de salida, estelas con caracteristicas de flujo diferentes al flujo principal en los pasajes. Estas variaciones en el flujo son las que inducen vibraciones forzadas en los alabes. Ademas existen varios factores que contribuyen a la aplicacion de vibraciones en alabes inducidas por flujo como son: inestabilidad del flujo de vapor en los claros de los sellos, secuencia de apertura de las valvulas, estelas de las toberas, obstrucciones en algunas de las toberas y diferente espaciamiento en las toberas. Las vibraciones por flujo pueden ser peligrosas si su frecuencia coincide con la frecuencia natural del sistema, provocando efectos mas nocivos que las vibraciones por desbalance o por desalineamiento, pues tienen amplitudes mas grandes y provocan esfuerzos alternantes en los componentes del

  1. 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.

  2. Transport of Chemical Vapors from Subsurface Sources to Atmosphere as Affected by Shallow Subsurface and Atmospheric Conditions

    Science.gov (United States)

    Rice, A. K.; Smits, K. M.; Hosken, K.; Schulte, P.; Illangasekare, T. H.

    2012-12-01

    Understanding the movement and modeling of chemical vapor through unsaturated soil in the shallow subsurface when subjected to natural atmospheric thermal and mass flux boundary conditions at the land surface is of importance to applications such as landmine detection and vapor intrusion into subsurface structures. New, advanced technologies exist to sense chemical signatures at the land/atmosphere interface, but interpretation of these sensor signals to make assessment of source conditions remains a challenge. Chemical signatures are subject to numerous interactions while migrating through the unsaturated soil environment, attenuating signal strength and masking contaminant source conditions. The dominant process governing movement of gases through porous media is often assumed to be Fickian diffusion through the air phase with minimal or no quantification of other processes contributing to vapor migration, such as thermal diffusion, convective gas flow due to the displacement of air, expansion/contraction of air due to temperature changes, temporal and spatial variations of soil moisture and fluctuations in atmospheric pressure. Soil water evaporation and interfacial mass transfer add to the complexity of the system. The goal of this work is to perform controlled experiments under transient conditions of soil moisture, temperature and wind at the land/atmosphere interface and use the resulting dataset to test existing theories on subsurface gas flow and iterate between numerical modeling efforts and experimental data. Ultimately, we aim to update conceptual models of shallow subsurface vapor transport to include conditionally significant transport processes and inform placement of mobile sensors and/or networks. We have developed a two-dimensional tank apparatus equipped with a network of sensors and a flow-through head space for simulation of the atmospheric interface. A detailed matrix of realistic atmospheric boundary conditions was applied in a series of

  3. Synthesis of Three-dimensional Polymer Nanostructures via Chemical Vapor Deposition

    Science.gov (United States)

    Cheng, Kenneth

    Chemical vapor deposition (CVD) is a widely practiced methodology for preparing thin film polymer coatings, and the coatings can be applied to a broad range of materials, including three-dimensional solid structures and low-vapor pressure liquids. Reactive poly(p-xylylene) (PPX) coatings prepared by CVD can be used as a powerful tool for surface functionalization and bio-conjugation. The first portion of this dissertation serves to extend the use of CVD-based reactive PPX coatings as a surface functionalization strategy for the conjugation of biomolecules. Micro-structured PPX coatings having multiple surface reactive groups were fabricated. Multiple orthogonal click reactions were then employed to selectively immobilize galactose and mannobiose to the micro-structured polymer coatings. The presence of different types of carbohydrate enables lectins binding for examining ligands/cell receptor interactions. This dissertation also demonstrates the use of CVD-based reactive PPX coatings as intermediate layers to immobilize adenoviral vectors onto tissue scaffolds. The ability to tether adenoviral vectors on tissue scaffolds localizes the transduction near the scaffold surface and reduces acute toxicity and hepatic pathology cause by direct administration of the viral vector, providing a safe and efficient gene therapy delivery strategy. In the second portion of this dissertation, we explore the CVD of PPX onto surfaces coated with a thin layer of liquid crystal (LC). Instead of forming a conformal PPX coating encapsulating the LC layer, PPX assembled into an array of high-aspect ratio nanofibers inside the LC layer. The LC layer was demonstrated to act as a template where the anisotropic internal ordering of the LC facilitated the formation of nanofibers. The diameter of the nanofibers was in the range of 100 nm and could be tuned by type of LC template used, and the length of the nanofibers could be precisely controlled by varying the thickness of the LC film. The

  4. Numerical modeling of condensation from vapor-gas mixtures for forced down flow inside a tube

    International Nuclear Information System (INIS)

    Yuann, R.Y.; Schrock, V.E.; Chen, Xiang, M.

    1995-01-01

    Laminar film condensation is the dominant heat transfer mode inside tubes. In the present paper direct numerical simulation of the detailed transport process within the steam-gas core flow and in the condensate film is carried out. The problem was posed as an axisymmetric two dimensional (r, z) gas phase inside an annular condensate film flow with an assumed smooth interface. The fundamental conservation equations were written for mass, momentum, species concentration and energy in the gaseous phase with effective diffusion parameters characterizing the turbulent region. The low Reynolds number two equation κ-ε model was employed to determine the eddy diffusion coefficients. The liquid film was described by similar formulation without the gas species equation. An empirical correlation was employed to correct for the effect of film waviness on the interfacial shear. A computer code named COAPIT (Condensation Analysis Program Inside Tube) was developed to implement numerical solution of the fundamental equations. The equations were solved by a marching technique working downstream from the entrance of the condensing section. COAPIT was benchmarked against experimental data and overall reasonable agreement was found for the key parameters such as heat transfer coefficient and tube inner wall temperature. The predicted axial development of radial profiles of velocity, composition and temperature and occurrence of metastable vapor add insight to the physical phenomena

  5. Numerical modeling of condensation from vapor-gas mixtures for forced down flow inside a tube

    Energy Technology Data Exchange (ETDEWEB)

    Yuann, R Y [Taiwan Power Company, Taipei (Taiwan, Province of China); Schrock, V E [Univ. of California, Berkeley, CA (United States); Chen, Xiang

    1995-09-01

    Laminar film condensation is the dominant heat transfer mode inside tubes. In the present paper direct numerical simulation of the detailed transport process within the steam-gas core flow and in the condensate film is carried out. The problem was posed as an axisymmetric two dimensional (r, z) gas phase inside an annular condensate film flow with an assumed smooth interface. The fundamental conservation equations were written for mass, momentum, species concentration and energy in the gaseous phase with effective diffusion parameters characterizing the turbulent region. The low Reynolds number two equation {kappa}-{epsilon} model was employed to determine the eddy diffusion coefficients. The liquid film was described by similar formulation without the gas species equation. An empirical correlation was employed to correct for the effect of film waviness on the interfacial shear. A computer code named COAPIT (Condensation Analysis Program Inside Tube) was developed to implement numerical solution of the fundamental equations. The equations were solved by a marching technique working downstream from the entrance of the condensing section. COAPIT was benchmarked against experimental data and overall reasonable agreement was found for the key parameters such as heat transfer coefficient and tube inner wall temperature. The predicted axial development of radial profiles of velocity, composition and temperature and occurrence of metastable vapor add insight to the physical phenomena.

  6. 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.

  7. Study of the fluidized bed chemical vapor deposition process on very dense powder for nuclear applications

    International Nuclear Information System (INIS)

    Vanni, Florence

    2015-01-01

    This thesis is part of the development of low-enriched nuclear fuel, for the Materials Test Reactors (MTRs), constituted of uranium-molybdenum particles mixed with an aluminum matrix. Under certain conditions under irradiations, the U(Mo) particles interact with the aluminum matrix, causing unacceptable swelling of the fuel plate. To inhibit this phenomenon, one solution consists in depositing on the surface of the U(Mo) particles, a thin silicon layer to create a barrier effect. This thesis has concerned the study of the fluidized bed chemical vapor deposition (CVD) process to deposit silicon from silane, on the U(Mo) powder, which has an exceptional density of 17,500 kg/m 3 . To achieve this goal, two axes were treated during the thesis: the study and the optimization of the fluidization of a so dense powder, and then those of the silicon deposition process. For the first axis, a series of tests was performed on a surrogate tungsten powder in different columns made of glass and made of steel with internal diameters ranging from 2 to 5 cm, at room temperature and at high temperature (650 C) close to that of the deposits. These experiments helped to identify wall effects phenomena within the fluidized bed, which can lead to heterogeneous deposits or particles agglomeration. Some dimensions of the fluidization columns and operating conditions allowing a satisfactory fluidization of the powder were identified, paving the way for the study of silicon deposition. Several campaigns of deposition experiments on the surrogate powder and then on the U(Mo) powder were carried out in the second axis of the study. The influence of the bed temperature, the inlet molar fraction of silane diluted in argon, and the total gas flow of fluidization, was examined for different diameters of reactor and for various masses of powder. Morphological and structural characterization analyses (SEM, XRD..) revealed a uniform silicon deposition on all the powder and around each particle

  8. Chemical vapor deposition growth of single-walled carbon nanotubes with controlled structures for nanodevice applications.

    Science.gov (United States)

    Chen, Yabin; Zhang, Jin

    2014-08-19

    Single-walled carbon nanotubes (SWNTs), a promising substitute to engineer prospective nanoelectronics, have attracted much attention because of their superb structures and physical properties. The unique properties of SWNTs rely sensitively on their specific chiral structures, including the diameters, chiral angles, and handedness. Furthermore, high-performance and integrated circuits essentially require SWNT samples with well-aligned arrays, of single conductive type and of pure chirality. Although much effort has been devoted to chemical vapor deposition (CVD) growth of SWNTs, their structure control, growth mechanism, and structural characterizations are still the primary obstacles for the fabrication and application of SWNT-based nanodevices. In this Account, we focus on our established CVD growth methodology to fulfill the requirements of nanodevice applications. A rational strategy was successfully exploited to construct complex architectures, selectively enrich semiconducting (s) or metallic (m) SWNTs, and control chirality. First, well-aligned and highly dense SWNT arrays are beneficial for nanodevice integration. For the directed growth mode, anisotropic interactions between the SWNTs and the crystallographic structure of substrate are crucial for their growth orientation. Just as crystals possess various symmetries, SWNTs with controlled geometries have the corresponding turning angles. Their complex architectures come from the synergetic effect of lattice and gas flow directed modes. Especially, the aligned orientations of SWNTs on graphite are chirality-selective, and their chiral angles, handedness, and (n,m) index have been conveniently and accurately determined. Second, UV irradiation and sodium dodecyl sulfate (SDS) washing-off methods have been explored to selectively remove m-SWNTs, leaving only s-SWNT arrays on the surface. Moreover, the UV-assisted technique takes the advantages of low cost and high efficiency and it directly produces a high

  9. Filling high aspect ratio trenches by superconformal chemical vapor deposition: Predictive modeling and experiment

    Science.gov (United States)

    Wang, Wenjiao B.; Abelson, John R.

    2014-11-01

    Complete filling of a deep recessed structure with a second material is a challenge in many areas of nanotechnology fabrication. A newly discovered superconformal coating method, applicable in chemical vapor deposition systems that utilize a precursor in combination with a co-reactant, can solve this problem. However, filling is a dynamic process in which the trench progressively narrows and the aspect ratio (AR) increases. This reduces species diffusion within the trench and may drive the component partial pressures out of the regime for superconformal coating. We therefore derive two theoretical models that can predict the possibility for filling. First, we recast the diffusion-reaction equation for the case of a sidewall with variable taper angle. This affords a definition of effective AR, which is larger than the nominal AR due to the reduced species transport. We then derive the coating profile, both for superconformal and for conformal coating. The critical (most difficult) step in the filling process occurs when the sidewalls merge at the bottom of the trench to form the V shape. Experimentally, for the Mg(DMADB)2/H2O system and a starting AR = 9, this model predicts that complete filling will not be possible, whereas experimentally we do obtain complete filling. We then hypothesize that glancing-angle, long-range transport of species may be responsible for the better than predicted filling. To account for the variable range of species transport, we construct a ballistic transport model. This incorporates the incident flux from outside the structure, cosine law re-emission from surfaces, and line-of-sight transport between internal surfaces. We cast the transport probability between all positions within the trench into a matrix that represents the redistribution of flux after one cycle of collisions. Matrix manipulation then affords a computationally efficient means to determine the steady-state flux distribution and growth rate for a given taper angle. The

  10. The Tribological Behaviors of Three Films Coated on Biomedical Titanium Alloy by Chemical Vapor Deposition

    Science.gov (United States)

    Wang, Song; Liao, Zhenhua; Liu, Yuhong; Liu, Weiqiang

    2015-11-01

    Three thin films (DLC, a-C, and TiN) were performed on Ti6Al4V by chemical vapor deposition. Carbon ion implantation was pretreated for DLC and a-C films while Ti transition layer was pretreated for TiN film to strengthen the bonding strength. X-ray diffraction, Raman measurement, nano-hardness and nano-scratch tester, and cross-section etching by FIB method were used to analyze film characteristics. Tribological behaviors of these coatings were studied by articulation with both ZrO2 and UHMWPE balls using ball-on-disk sliding. The thickness values reached ~0.46, ~0.33, and ~1.67 μm for DLC, a-C, and TiN film, respectively. Nano-hardness of the coatings compared with that of untreated and bonding strength (critical load in nano-scratch test) values of composite coatings compared with that of monolayer film all increased significantly, respectively. Under destructive test (ZrO2 ball conterface) in bovine serum lubrication, TiN coating revealed the best wear resistance while DLC showed the worst. Film failure was mainly attributed to the plowing by hard ZrO2 ball characterized by abrasive and adhesive wear. Under normal test (UHMWPE ball conterface), all coatings showed significant improvement in wear resistance both in dry sliding and bovine serum lubrication. Both DLC and a-C films showed less surface damage than TiN film due to the self-lubricating phenomenon in dry sliding. TiN film showed the largest friction coefficient both in destructive and normal tests, devoting to the big TiN grains thus leading to much rougher surface and then a higher value. The self-lubricating film formed on DLC and a-C coating could also decrease their friction coefficients. The results indicated that three coatings revealed different wear mechanisms, and thick DLC or a-C film was more promising in application in lower stress conditions such as artificial cervical disk.

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

    International Nuclear Information System (INIS)

    Gedelian, Cynthia A.; Rajanna, K.C.; Premerlani, Brian; Lu, Toh-Ming

    2014-01-01

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

  12. An efficient fabrication of vertically aligned carbon nanotubes on flexible aluminum foils by catalyst-supported chemical vapor deposition

    International Nuclear Information System (INIS)

    Yoshikawa, Naoki; Kishi, Naoki; Sugai, Toshiki; Shinohara, Hisanori; Asari, Takuma; Hayashi, Shigeo

    2008-01-01

    An efficient and versatile growth of thin-layer carbon nanotubes on a flexible aluminum foil (for kitchen use) by catalyst-supported chemical vapor deposition is reported. The aluminum foil used in the present experiment is commercially available for kitchen use. The electron-beam vapor deposition and dip-coating have been used for preparing catalysts on the aluminum foil. Vertically aligned thin-layer CNTs with typical diameters of 2.5-6.0 nm and lengths up to 90 μm are obtained when ethanol is used in combination with Fe and Co catalyst particles at a growth temperature of around 650 deg. C under an Ar/H 2 gas flow. Thermo-gravimetric analyses together with HR-TEM observations indicate that the purity of the CNTs synthesized by the current technique is very high

  13. 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.

  14. Epoxy Resin Modified Quartz Crystal Microbalance Sensor for Chemical Warfare Agent Sulfur Mustard Vapor Detection

    Directory of Open Access Journals (Sweden)

    Rajendra BUNKAR

    2010-02-01

    Full Text Available An epoxy resin polymer coated quartz crystal microbalance (PC-QCM is used for detection of sulfur mustard vapor (SM. When SM vapor is exposed to PC-QCM sensor frequency shift is observed. The response of the sensor in ambient condition is 554 Hz with ±10 % variation upon exposure of 155 ppm of the SM concentration. The observed response loss is nearly 40 % over the period of 15 months. The response of the sensor is higher for SM than compare to structurally similar chloroethyl ether (CEE and other interferences.

  15. Chemical vapor deposition growth of single-crystalline cesium lead halide microplatelets and heterostructures for optoelectronic applications

    Institute of Scientific and Technical Information of China (English)

    Yiliu Wang; Xun Guan; Dehui Li; Hung-Chieh Cheng; Xidong Duan; Zhaoyang Lin; Xiangfeng Duan

    2017-01-01

    Orgaruc-inorganic hybrid halide perovskites,such as CH3NH3PbI3,have emerged as an exciting class of materials for solar photovoltaic applications;however,they are currently plagued by insufficient environmental stability.To solve this issue,all-inorganic halide perovskites have been developed and shown to exhibit significantly improved stability.Here,we report a single-step chemical vapor deposition growth of cesium lead halide (CsPbX3) microcrystals.Optical microscopy studies show that the resulting perovskite crystals predominantly adopt a square-platelet morphology.Powder X-ray diffraction (PXRD) studies of the resulting crystals demonstrate a highly crystalline nature,with CsPbC13,CsPbBr3,and CsPbI3 showing tetragonal,monoclinic,and orthorhombic phases,respectively.Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies show that the resulting platelets exhibit well-faceted structures with lateral dimensions of the order of 10-50 μm,thickness around 1 μm,and ultra-smooth surface,suggesting the absence of obvious grain boundaries and the single-crystalline nature of the individual microplatelets.Photoluminescence (PL) images and spectroscopic studies show a uniform and intense emission consistent with the expected band edge transition.Additionally,PL images show brighter emission around the edge of the platelets,demonstrating a wave-guiding effect in high-quality crystals.With a well-defined geometry and ultra-smooth surface,the square platelet structure can function as a whispering gallery mode cavity with a quality factor up to 2,863 to support laser emission at room temperature.Finally,we demonstrate that such microplatelets can be readily grown on a variety of substrates,including silicon,graphene,and other two-dimensional materials such as molybdenum disulfide,which can readily allow the construction of heterostructure optoelectronic devices,including a graphene/perovskite/ graphene vertically-stacked photodetector with

  16. 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

  17. Semi-continuous high speed gas analysis of generated vapors of chemical warfare agents

    NARCIS (Netherlands)

    Trap, H.C.; Langenberg, J.P.

    1999-01-01

    A method is presented for the continuous analysis of generated vapors of the nerve agents soman and satin and the blistering agent sulfur mustard. By using a gas sampling valve and a very short (15 cm) column connected to an on-column injector with a 'standard length' column, the system can either

  18. Review on mechanism of directly fabricating wafer-scale graphene on dielectric substrates by chemical vapor deposition

    Science.gov (United States)

    Ning, Jing; Wang, Dong; Chai, Yang; Feng, Xin; Mu, Meishan; Guo, Lixin; Zhang, Jincheng; Hao, Yue

    2017-07-01

    To date, chemical vapor deposition on transition metal catalysts is a potential way to achieve low cost, high quality and uniform wafer-scale graphene. However, the removal and transfer process of the annoying catalytic metals underneath can bring large amounts of uncertain factors causing the performance deterioration of graphene, such as the pollution of surface polymeric residues, unmentioned doping and structural damages. Thus, to develop a technique of directly fabricating graphene on dielectric substrates is quite meaningful. In this review, we will present specific methods of catalyst- or transfer-free techniques for graphene growth and discuss the diversity of growth mechanisms.

  19. Oxygen source-oriented control of atmospheric pressure chemical vapor deposition of VO2 for capacitive applications

    Directory of Open Access Journals (Sweden)

    Dimitra Vernardou

    2016-06-01

    Full Text Available Vanadium dioxides of different crystalline orientation planes have successfully been fabricated by chemical vapor deposition at atmospheric pressure using propanol, ethanol and O2 gas as oxygen sources. The thick a-axis textured monoclinic vanadium dioxide obtained through propanol presented the best electrochemical response in terms of the highest specific discharge capacity of 459 mAh g-1 with a capacitance retention of 97 % after 1000 scans under constant specific current of 2 A g-1. Finally, the electrochemical impedance spectroscopy indicated that the charge transfer of Li+ through the vanadium dioxide / electrolyte interface was easier for this sample enhancing significantly its capacitance performance.

  20. Anatase thin film with diverse epitaxial relationship grown on yttrium stabilized zirconia substrate by chemical vapor deposition

    International Nuclear Information System (INIS)

    Miyagi, Takahira; Ogawa, Tomoyuki; Kamei, Masayuki; Wada, Yoshiki; Mitsuhashi, Takefumi; Yamazaki, Atsushi

    2003-01-01

    An anatase epitaxial thin film with diverse epitaxial relationship, YSZ (001) // anatase (001), YSZ (010) // anatase (110), was grown on a single crystalline yttrium stabilized zirconia (YSZ) (001) substrate by metal organic chemical vapor deposition (MOCVD). The full width at half maximum (FWHM) of the (004) reflection of this anatase epitaxial film was 0.4deg, and the photoluminescence of this anatase epitaxial film showed visible emission with broad spectral width and large Stokes shift at room temperature. These results indicate that this anatase epitaxial film possessed almost equal crystalline quality compared with that grown under identical growth conditions on single crystalline SrTiO 3 substrate. (author)

  1. Limiting Size of Monolayer Graphene Flakes Grown on Silicon Carbide or via Chemical Vapor Deposition on Different Substrates

    Science.gov (United States)

    Alekseev, N. I.

    2018-05-01

    The maximum size of homogeneous monolayer graphene flakes that form during the high-temperature evaporation of silicon from a surface of SiC or during graphene synthesis via chemical vapor deposition is estimated, based on the theoretical calculations developed in this work. Conditions conducive to the fragmentation of a monolayer graphene sheet to form discrete fragments or terrace-type structures in which excess energy due to dangling bonds at the edges is compensated for by the lack of internal stress are indentified and described. The results from calculations for the sizes of graphene structures are compared with experimental findings for the most successful graphene syntheses reported in the literature.

  2. 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.

  3. Carbon diffusion in uncoated and titanium nitride coated iron substrates during microwave plasma assisted chemical vapor deposition of diamond

    International Nuclear Information System (INIS)

    Weiser, P.S.; Prawer, S.; Manory, R.R.; Paterson, P.J.K.; Stuart, Sue-Anne

    1992-01-01

    Auger Electron Spectroscopy has been employed to investigate the effectiveness of thin films of TiN as barriers to carbon diffusion during Chemical Vapor Deposition (CVD) of diamond onto Fe substrates. Auger Depth Profiling was used to monitor the C concentration in the TiN layer, through the interface and into the substrate both before and after CVD diamond deposition. The results show that a layer of TiN only 250 Angstroems thick is sufficient to inhibit soot formation on the Fe surface and C diffusion into the Fe bulk. 14 refs., 4 figs

  4. ZnO/SnO{sub 2} nanoflower based ZnO template synthesized by thermal chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Sin, N. D. Md., E-mail: diyana0366@johor.uitm.edu.my; Amalina, M. N., E-mail: amalina0942@johor.uitm.edu.my [NANO-ElecTronic Centre, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Fakulti Kejuruteraan Elektrik, Universiti Teknologi MARA Cawangan Johor, Kampus Pasir Gudang, 81750 Masai, Johor (Malaysia); Ismail, Ahmad Syakirin, E-mail: kyrin-samaxi@yahoo.com; Shafura, A. K., E-mail: shafura@ymail.com; Ahmad, Samsiah, E-mail: samsiah.ahmad@johor.uitm.edu.my; Mamat, M. H., E-mail: mhmamat@salam.uitm.edu.my [NANO-ElecTronic Centre, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); Rusop, M., E-mail: rusop@salam.uitm.edu.my [NANO-ElecTronic Centre, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia); NANO-SciTech Centre (NST), Institute of Science (IOS), Universiti Teknologi MARA - UiTM, 40450 Shah Alam, Selangor (Malaysia)

    2016-07-06

    The ZnO/SnO{sub 2} nanoflower like structures was grown on a glass substrate deposited with seed layer using thermal chemical vapor deposition (CVD) with combining two source materials. The ZnO/SnO{sub 2} nanoflower like structures had diameter in the range 70 to 100 nm. The atomic percentage of ZnO nanoparticle , SnO{sub 2} nanorods and ZnO/SnO{sub 2} nanoflower was taken using EDS. Based on the FESEM observations, the growth mechanism is applied to describe the growth for the synthesized nanostructures.

  5. Identification of vapor-phase chemical warfare agent simulants and rocket fuels using laser-induced breakdown spectroscopy

    International Nuclear Information System (INIS)

    Stearns, Jaime A.; McElman, Sarah E.; Dodd, James A.

    2010-01-01

    Application of laser-induced breakdown spectroscopy (LIBS) to the identification of security threats is a growing area of research. This work presents LIBS spectra of vapor-phase chemical warfare agent simulants and typical rocket fuels. A large dataset of spectra was acquired using a variety of gas mixtures and background pressures and processed using partial least squares analysis. The five compounds studied were identified with a 99% success rate by the best method. The temporal behavior of the emission lines as a function of chamber pressure and gas mixture was also investigated, revealing some interesting trends that merit further study.

  6. Identification of vapor-phase chemical warfare agent simulants and rocket fuels using laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stearns, Jaime A.; McElman, Sarah E.; Dodd, James A.

    2010-05-01

    Application of laser-induced breakdown spectroscopy (LIBS) to the identification of security threats is a growing area of research. This work presents LIBS spectra of vapor-phase chemical warfare agent simulants and typical rocket fuels. A large dataset of spectra was acquired using a variety of gas mixtures and background pressures and processed using partial least squares analysis. The five compounds studied were identified with a 99% success rate by the best method. The temporal behavior of the emission lines as a function of chamber pressure and gas mixture was also investigated, revealing some interesting trends that merit further study.

  7. Long-term stable water vapor permeation barrier properties of SiN/SiCN/SiN nanolaminated multilayers grown by plasma-enhanced chemical vapor deposition at extremely low pressures

    International Nuclear Information System (INIS)

    Choi, Bum Ho; Lee, Jong Ho

    2014-01-01

    We investigated the water vapor permeation barrier properties of 30-nm-thick SiN/SiCN/SiN nanolaminated multilayer structures grown by plasma enhanced chemical vapor deposition at 7 mTorr. The derived water vapor transmission rate was 1.12 × 10 −6 g/(m 2 day) at 85 °C and 85% relative humidity, and this value was maintained up to 15 000 h of aging time. The X-ray diffraction patterns revealed that the nanolaminated film was composed of an amorphous phase. A mixed phase was observed upon performing high resolution transmission electron microscope analysis, which indicated that a thermodynamically stable structure was formed. It was revealed amorphous SiN/SiCN/SiN multilayer structures that are free from intermixed interface defects effectively block water vapor permeation into active layer

  8. Incorporation of Titanium into H-ZSM-5 Zeolite via Chemical Vapor Deposition: Effect of Steam Treatment

    International Nuclear Information System (INIS)

    Xu, Cheng Hua; Jin, Tai Huan; Jhung, Sung Hwa; Hwang, Jin Soo; Chang, Jong San; Qiu, Fa Li; Park, Sang Eon

    2004-01-01

    Ti-ZSM-5 prepared by secondary synthesis, from the reaction of H-ZSM-5 with vapor phase TiCl 4 , was characterized with several physicochemical techniques including FT-IR and UV/VIS-DRS. It was found that zeolite structure, surface area and pore volume did not change, and the framework aluminum could not be replaced by titanium atom during the secondary synthesis of Ti-ZSM-5. The incorporation of titanium into the framework might be due to reaction of TiCl 4 with the silanol groups associated with defects or surface sites. The formation of extra-framework titanium could not be avoided, unless the samples were further treated by water vapor at 550 .deg. C or higher temperature. High temperature steam treatment of Ti-ZSM-5 prepared by chemical vapor deposition with TiCl 4 was efficient to prevent the formation of non-framework titanium species. Ti-ZSM-5 zeolites prepared in this work contained only framework titanium species and exhibited improved catalytic property close to TS-1 prepared by hydrothermal synthesis

  9. Incorporation of Titanium into H-ZSM-5 Zeolite via Chemical Vapor Deposition: Effect of Steam Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Cheng Hua; Jin, Tai Huan; Jhung, Sung Hwa; Hwang, Jin Soo [Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); Chang, Jong San; Qiu, Fa Li [Chinese Academy of Sciences(CAS), Chengdu (China); Park, Sang Eon [Inha University, Incheon (Korea, Republic of)

    2004-05-15

    Ti-ZSM-5 prepared by secondary synthesis, from the reaction of H-ZSM-5 with vapor phase TiCl{sub 4}, was characterized with several physicochemical techniques including FT-IR and UV/VIS-DRS. It was found that zeolite structure, surface area and pore volume did not change, and the framework aluminum could not be replaced by titanium atom during the secondary synthesis of Ti-ZSM-5. The incorporation of titanium into the framework might be due to reaction of TiCl{sub 4} with the silanol groups associated with defects or surface sites. The formation of extra-framework titanium could not be avoided, unless the samples were further treated by water vapor at 550 .deg. C or higher temperature. High temperature steam treatment of Ti-ZSM-5 prepared by chemical vapor deposition with TiCl{sub 4} was efficient to prevent the formation of non-framework titanium species. Ti-ZSM-5 zeolites prepared in this work contained only framework titanium species and exhibited improved catalytic property close to TS-1 prepared by hydrothermal synthesis.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-08-15

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

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

    International Nuclear Information System (INIS)

    Ghrib, M.; Gaidi, M.; Ghrib, T.; Khedher, N.; Ben Salam, M.; Ezzaouia, H.

    2011-01-01

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

  12. Force Field Benchmark of the TraPPE_UA for Polar Liquids: Density, Heat of Vaporization, Dielectric Constant, Surface Tension, Volumetric Expansion Coefficient, and Isothermal Compressibility.

    Science.gov (United States)

    Núñez-Rojas, Edgar; Aguilar-Pineda, Jorge Alberto; Pérez de la Luz, Alexander; de Jesús González, Edith Nadir; Alejandre, José

    2018-02-08

    The transferable potential for a phase equilibria force field in its united-atom version, TraPPE_UA, is evaluated for 41 polar liquids that include alcohols, thiols, ethers, sulfides, aldehydes, ketones, and esters to determine its ability to reproduce experimental properties that were not included in the parametrization procedure. The intermolecular force field parameters for pure components were fit to reproduce experimental boiling temperature, vapor-liquid coexisting densities, and critical point (temperature, density, and pressure) using Monte Carlo simulations in different ensembles. The properties calculated in this work are liquid density, heat of vaporization, dielectric constant, surface tension, volumetric expansion coefficient, and isothermal compressibility. Molecular dynamics simulations were performed in the gas and liquid phases, and also at the liquid-vapor interface. We found that relative error between calculated and experimental data is 1.2% for density, 6% for heat of vaporization, and 6.2% for surface tension, in good agreement with the experimental data. The dielectric constant is systematically underestimated, and the relative error is 37%. Evaluating the performance of the force field to reproduce the volumetric expansion coefficient and isothermal compressibility requires more experimental data.

  13. Nanostructured Thin Film Synthesis by Aerosol Chemical Vapor Deposition for Energy Storage Applications

    Science.gov (United States)

    Chadha, Tandeep S.

    Renewable energy sources offer a viable solution to the growing energy demand while mitigating concerns for greenhouse gas emissions and climate change. This has led to a tremendous momentum towards solar and wind-based energy harvesting technologies driving efficiencies higher and costs lower. However, the intermittent nature of these energy sources necessitates energy storage technologies, which remain the Achilles heel in meeting the renewable energy goals. This dissertation focusses on two approaches for addressing the needs of energy storage: first, targeting direct solar to fuel conversion via photoelectrochemical water-splitting and second, improving the performance of current rechargeable batteries by developing new electrode architectures and synthesis processes. The aerosol chemical vapor deposition (ACVD) process has emerged as a promising single-step approach for nanostructured thin film synthesis directly on substrates. The relationship between the morphology and the operating parameters in the process is complex. In this work, a simulation based approach has been developed to understand the relationship and acquire the ability of predicting the morphology. These controlled nanostructured morphologies of TiO2 , compounded with gold nanoparticles of various shapes, are used for solar water-splitting applications. Tuning of light absorption in the visible-light range along with reduced electron-hole recombination in the composite structures has been demonstrated. The ACVD process is further extended to a novel single-step synthesis of nanostructured TiO2 electrodes directly on the current collector for applications as anodes in lithium-ion batteries, mainly for electric vehicles and hybrid electric vehicles. The effect of morphology of the nanostructures has been investigated via experimental studies and electrochemical transport modelling. Results demonstrate the exceptional performance of the single crystal one-dimensional nanostructures over granular

  14. TL and OSL studies on undoped diamond films grown by hot filament chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Soni, Anuj, E-mail: anujsoni.phy@gmail.com [Radiological Physics and Advisory Division, Bhabha Atomic Research Center, Mumbai 400 085 (India); Choudhary, R.K. [Materials Processing Division, Bhabha Atomic Research Center, Mumbai 400 085 (India); Polymeris, G.S. [Ankara University, Institute of Nuclear Sciences (Turkey); Mishra, D.R. [Radiological Physics and Advisory Division, Bhabha Atomic Research Center, Mumbai 400 085 (India); Mishra, P. [Materials Processing Division, Bhabha Atomic Research Center, Mumbai 400 085 (India); Kulkarni, M.S. [Radiation Safety Systems Division, Bhabha Atomic Research Center, Mumbai 400 085 (India)

    2016-09-15

    In this work, approximately 0.5 µm thick diamond films were grown on a silicon substrate by hot filament chemical vapour deposition (HFCVD) method in a gas mixture of hydrogen and methane. The batch to batch reproducibility of the sample using this technique was found to be very good. The obtained film was characterized by micro laser Raman spectroscopy (MLRS), grazing incidence X-ray diffractometry (GIXRD), scanning electron microscopy (SEM) and atomic force miscroscopy (AFM) techniques. MLRS and GIXRD results confirmed the formation of diamond whereas SEM and AFM analyses indicated uniform morphology of the film with an average grain size of 200 nm. The deposited film was studied for ionizing radiation dosimetry applications using the thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques after irradiating the film by a calibrated 5 mCi, {sup 90}Sr/{sup 90}Y beta source. In the TL measurement, for a heating rate of 4 K/s, broad glow curve was obtained which was deconvoluted into seven TL peaks. The integrated TL counts were found to vary linearly with increasing the radiation dose up to 10 kGy. The characteristic TL output seen in the temperature range 200–300 °C, may be considered good for thermal stability of the film and it could also avoid TL fading during storage and non-interference of any black body radiation during the measurement. However, in comparison to TL output, the OSL response for 470 nm LED stimulation was found to be lesser. The CW–OSL decay curve has shown two components contributing to the OSL signal, having photoionization cross-section 1.5×10{sup −18} and 5.2×10{sup −19} cm{sup 2} respectively. The studies have revealed the possibility of using diamond film for high dose radiation dosimetry with TL/OSL method.

  15. Functionalized multi-walled carbon nanotube paper for monitoring chemical vapors

    Czech Academy of Sciences Publication Activity Database

    Slobodian, P.; Říha, Pavel; Olejník, R.; Saha, P.

    2015-01-01

    Roč. 15, č. 5 (2015), s. 4003-4008 ISSN 1533-4880 Grant - others:GA MŠk(CZ) ED2.1.00/03.0111; GA MŠk(CZ) EE.2.3.20.0104 Institutional research plan: CEZ:AV0Z20600510 Institutional support: RVO:67985874 Keywords : carbon nanotube network * electrical resistance * organic vapor sensor Subject RIV: BK - Fluid Dynamics Impact factor: 1.338, year: 2015

  16. Vaporous Decontamination Methods: Potential Uses and Research Priorities for Chemical and Biological Contamination Control

    Science.gov (United States)

    2006-06-01

    over time. Ammonia gas is typically used to neutralise formaldehyde forming a white precipitate, hexamethylene- tetramine, which is then washed down...sulphite scrubbers DSTO-GD-0465 4 and a carbon bed to prevent any leakage of the ClO2 gas into the environment. The decontamination period (12...of ammonia gas) produces a broad-spectrum decontaminant against C agents [7]. However, initial studies have shown that the modified vaporous

  17. Process-property relationships of SiC chemical vapor deposition in the Si/H/C/O system

    International Nuclear Information System (INIS)

    Richardson, C.; Takoudis, C.G.

    1999-01-01

    The thermal, chemical, and physical properties of SiC make it an attractive material for a wide range of applications from wear resistant coatings on tools to high temperature microelectronics operations. A comprehensive thermodynamic analysis has been performed for the Si/H/C/O system from which a priori process-property relationships of the chemical vapor deposition (CVD) of silicon carbide (SiC) are obtained. The parameter space for pure silicon carbide growth is reported for five orders of magnitude of the system water vapor level (1 ppb--100 ppm), four orders of magnitude of system pressure (0.1--760 Torr), and two orders of magnitude of C/Si feed ratio (0.25--20) and H 2 /Si feed ratio (50--10,000). Lower growth temperatures for pure SiC are predicted in clean systems with low system water vapor levels, at stoichiometric to near carbon excess conditions (C/Si ≅ 1 to C/Si > 1), at high carrier gas flow rates (large H 2 /Si feed ratios), and at low operating pressures. Because relative C/Si and H 2 /Si feed ratios have been considered, the predictions in this study are applicable to both multiple and single precursor systems. Further, these results are valid for the CVD of α-SiC as well as β-SiC. Experimental data reported on the growth of α-SiC and β-SiC are found to be in satisfactory agreement with the theoretical predictions, for numerous systems that include multiple and single source, silicon and carbon, species

  18. Evaluation of Personal Chemical Vapor Protection for Patrol and Tactical Law Enforcement

    National Research Council Canada - National Science Library

    Fedele, Paul D; Lake, William L; Arca, Victor J; Marshall, Stephen M; Mitchell, David B

    2002-01-01

    In Domestic Preparedness efforts, the US Army Soldier and Biological Chemical Command and the Maryland State Police, have evaluated personal chemical protective systems for use in patrol and tactical...

  19. Role of chlorine in the nanocrystalline silicon film formation by rf plasma-enhanced chemical vapor deposition of chlorinated materials

    International Nuclear Information System (INIS)

    Shirai, Hajime

    2004-01-01

    We demonstrate the disorder-induced low-temperature crystallization in the nanocrystalline silicon film growth by rf plasma-enhanced chemical vapor deposition of H 2 -diluted SiH 2 Cl 2 and SiCl 4 . The combination of the chemical reactivity of SiCld (d: dangling bond) and SiHCl complexes and the release of the disorder-induced stress near the growing surface tightly correlate with the phase transitionity of SiCld and SiHCl complexes near the growing surface with the aid of atomic hydrogen, which induce higher degree of disorder in the a-Si network. These features are most prominent in the SiCl 4 compared with those of SiH 2 Cl 2 and SiH 4 , which preferentially enhance the nanocrystalline Si formation

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

    Science.gov (United States)

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

    2016-06-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-02

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

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

    International Nuclear Information System (INIS)

    Sulyaeva, Veronica S.; Kosinova, Marina L.; Rumyantsev, Yurii M.; Kuznetsov, Fedor A.; Kesler, Valerii G.; Kirienko, Viktor V.

    2014-01-01

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

  3. 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.

  4. The role of surface chemical analysis in a study to select replacement processes for TCA vapor degreasing

    Science.gov (United States)

    Lesley, Michael W.; Davis, Lawrence E.; Moulder, John F.; Carlson, Brad A.

    1995-01-01

    The role of surface-sensitive chemical analysis (ESCA, AES, and SIMS) in a study to select a process to replace 1, 1, 1-trichloroethane (TCA) vapor degreasing as a steel and aluminum bonding surface preparation method is described. The effort was primarily concerned with spray-in-air cleaning processes involving aqueous alkaline and semi-aqueous cleaners and a contamination sensitive epoxy-to-metal bondline. While all five cleaners tested produced bonding strength results equal to or better than those produced by vapor degreasing, the aqueous alkaline cleaners yielded results which were superior to those produced by the semi-aqueous cleaners. The main reason for the enhanced performance appears to be a silicate layer left behind by the aqueous alkaline cleaners. The silicate layer increases the polarity of the surface and enhances epoxy-to-metal bonding. On the other hand, one of the semi-aqueous cleaners left a nonpolar carbonaceous residue which appeared to have a negative effect on epoxy-to-metal bonding. Differences in cleaning efficiency between cleaners/processes were also identified. These differences in surface chemistry, which were sufficient to affect bonding, were not detected by conventional chemical analysis techniques.

  5. Concise and Efficient Fluorescent Probe via an Intromolecular Charge Transfer for the Chemical Warfare Agent Mimic Diethylchlorophosphate Vapor Detection.

    Science.gov (United States)

    Yao, Junjun; Fu, Yanyan; Xu, Wei; Fan, Tianchi; Gao, Yixun; He, Qingguo; Zhu, Defeng; Cao, Huimin; Cheng, Jiangong

    2016-02-16

    Sarin, used as chemical warfare agents (CWAs) for terrorist attacks, can induce a number of virulent effects. Therefore, countermeasures which could realize robust and convenient detection of sarin are in exigent need. A concise charge-transfer colorimetric and fluorescent probe (4-(6-(tert-butyl)pyridine-2-yl)-N,N-diphenylaniline, TBPY-TPA) that could be capable of real-time and on-site monitoring of DCP vapor was reported in this contribution. Upon contact with DCP, the emission band red-shifted from 410 to 522 nm upon exposure to DCP vapor. And the quenching rate of TBPY-TPA reached up to 98% within 25 s. Chemical substances such as acetic acid (HAc), dimethyl methylphosphonate (DMMP), pinacolyl methylphosphonate (PAMP), and triethyl phosphate (TEP) do not interfere with the detection. A detection limit for DCP down to 2.6 ppb level is remarkably achieved which is below the Immediately Dangerous to Life or Health concentration. NMR data suggested that a transformation of the pyridine group into pyridinium salt via a cascade reaction is responsible for the sensing process which induced the dramatic fluorescent red shift. All of these data suggest TBPY-TPA is a promising fluorescent sensor for a rapid, simple, and low-cost method for DCP detection, which could be easy to prepare as a portable chemosensor kit for its practical application in real-time and on-site monitoring.

  6. Initiated chemical vapor deposition of pH responsive poly(2-diisopropylamino)ethyl methacrylate thin films

    Energy Technology Data Exchange (ETDEWEB)

    Karaman, Mustafa, E-mail: karamanm@selcuk.edu.tr [Department of Chemical Engineering, Selcuk University (Turkey); Advanced Technology Research and Application Center, Selcuk University (Turkey); Cabuk, Nihat [Department of Chemical Engineering, Selcuk University (Turkey)

    2012-08-31

    Poly(2-(diisopropylamino)ethyl methacrylate) (PDPAEMA) thin films were deposited on low temperature substrates by initiated chemical vapor deposition (iCVD) method using tertbutyl peroxide as an initiator. Very high deposition rates up to 38 nm/min were observed at low filament temperatures due to the use of the initiator. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy show the formation of PDPAEMA films with high retention of tertiary amine functionality which is responsible for pH induced changes in the wetting behavior of the surfaces. As-deposited PDPAEMA thin films on flat Si surface showed a reversible switching of water contact angle values between 87 Degree-Sign and 28 Degree-Sign ; after successive treatments of high and low pH water solutions, respectively. Conformal and non-damaging nature of iCVD allowed to functionalize fragile and rough electrospun poly(methyl methacrylate) fiber mat surfaces by PDPAEMA, which creates a surface with a switching behavior between superhydrophobic and approaching superhydrophilic with contact angle values of 155 {+-} 3 Degree-Sign and 22 {+-} 5 Degree-Sign , respectively. - Highlights: Black-Right-Pointing-Pointer Poly(2-diisopropylaminoethyl methacrylate) thin films were deposited by a dry process. Black-Right-Pointing-Pointer Initiated chemical vapor deposition can produce thin films on fragile substrates. Black-Right-Pointing-Pointer We report a reversible pH-induced transition from hydrophilic to super-hydrophobic.

  7. An evaluation of absorption spectroscopy to monitor YBa2Cu3O7-x precursors for metal organics chemical vapor deposition processing

    International Nuclear Information System (INIS)

    Matthew Edward Thomas

    1999-01-01

    Absorption spectroscopy was evaluated as a technique to monitor the metal organics chemical vapor deposition (MOCVD) process for forming YBa 2 Cu 3 O 7-x superconducting coated conductors. Specifically, this study analyzed the feasibility of using absorption spectroscopy to monitor the MOCVD supply vapor concentrations of the organic ligand 2,2,6,6-tetramethyl-3,5-heptanedionate (TMHD) metal chelates of barium, copper, and yttrium. Ba(TMHD) 2 , Cu(TMHD) 2 , and Y(TMHD) 3 compounds have successfully been vaporized in the MOCVD processing technique to form high temperature superconducting ''coated conductors,'' a promising technology for wire fabrication. The absorption study of the barium, copper, and yttrium (TMHD) precursors was conducted in the ultraviolet wavelength region from 200nm to 400nm. To simulate the MOCVD precursor flows the Ba(TMHD) 2 , Cu(TMHD) 2 , and Y(TMHD) 3 complexes were vaporized at vacuum pressures of (0.03--10)Torr. Spectral absorption scans of each precursor were conducted to examine potential measurement wavelengths for determining vapor concentrations of each precursor via Beer's law. The experimental results show that under vacuum conditions the barium, copper, and yttrium (TMHD) precursors begin to vaporize between 90 C and 135 C, which are considerably lower vaporization temperatures than atmospheric thermal gravimetric analyses indicate. Additionally, complete vaporization of the copper and yttrium (TMHD) precursors occurred during rapid heating at temperatures between 145 C and 195 C and after heating at constant temperatures between 90 C and 125 C for approximately one hour, whereas the Ba(TMHD) 2 precursor did not completely vaporize. At constant temperatures, near constant vaporization levels for each precursor were observed for extended periods of time. Detailed spectroscopic scans at stable vaporization conditions were conducted

  8. Trace detection of hydrogen peroxide vapor using a carbon-nanotube-based chemical sensor.

    Science.gov (United States)

    Lu, Yijiang; Meyyappan, M; Li, Jing

    2011-06-20

    The sensitive detection of hydrogen peroxide in the vapor phase is achieved using a nanochemical sensor consisting of single-walled carbon nanotubes as the sensing material. The interdigitated electrode-based sensor is constructed using a simple and standard microfabrication approach. The test results indicate a sensing capability of 25 ppm and response and recovery times in seconds. The sensor array consisting of 32 sensor elements with variations in sensing materials is capable of discriminating hydrogen peroxide from water and methanol. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Ultrasharp Si nanowires produced by plasma-enhanced chemical vapor deposition

    Czech Academy of Sciences Publication Activity Database

    Červenka, Jiří; Ledinský, Martin; Stuchlíková, The-Ha; Stuchlík, Jiří; Výborný, Zdeněk; Holovský, Jakub; Hruška, Karel; Fejfar, Antonín; Kočka, Jan

    2010-01-01

    Roč. 4, 1-2 (2010), s. 37-39 ISSN 1862-6254 R&D Projects: GA MŠk(CZ) LC06040; GA AV ČR KAN400100701; GA MŠk LC510 Institutional research plan: CEZ:AV0Z10100521 Keywords : nanowires * silicon * scanning electron microscopy * hemical vapor deposition * Raman spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.660, year: 2010 http://www3.interscience.wiley.com/ cgi -bin/fulltext/123213957/HTMLSTART

  10. 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

  11. Building A Better Force: Regular Army / Reserve Components Integration In The Army Chemical Corps

    Science.gov (United States)

    2016-05-26

    a significant effect on the shape of the Chemical Corps, emphasizing contamination avoidance and decontamination . Russia, the United States...future will center on how to shape the force to balance these capabilities. 13 Mauroni, Albert J., America’s Struggle with Chemical -Biological Warfare ...War of Nerves: Chemical Warfare from World War I to Al-Qaeda (New York: Anchor, 2007), 365-366. 19 Damien McElroy, “ISIS Storms Saddam-Era Chemical

  12. Chemical and morphological modifications of single layer graphene submitted to annealing in water vapor

    Science.gov (United States)

    Rolim, Guilherme Koszeniewski; Corrêa, Silma Alberton; Galves, Lauren Aranha; Lopes, João Marcelo J.; Soares, Gabriel Vieira; Radtke, Cláudio

    2018-01-01

    Modifications of single layer graphene transferred to SiO2/Si substrates resulting from annealing in water vapor were investigated. Near edge X-ray absorption fine structure spectroscopy evidenced graphene puckering between 400 and 500 °C. Synchrotron radiation based X-ray photoelectron spectroscopy showed variation of sp2 and sp3C bonding configurations specially in this same temperature range. Moreover, oxygen related functionalities are formed as a result of water vapor annealing. Based on these results and complementary Raman and nuclear reaction analysis, one distinguishes three different regimes of water interaction with graphene concerning modifications of the graphene layer. In the low temperature range (200-400 °C), no prominent modification of graphene itself is observed. At higher temperatures (400-500 °C), to accommodate newly formed oxygen functionalities, the flat and continuous sp2 bonding network of graphene is disrupted, giving rise to a puckered layer. For 600 °C and above, shrinking of graphene domains and a higher doping level take place.

  13. Functional Fit Evaluation to Determine Optimal Ease Requirements in Canadian Forces Chemical Protective Gloves

    National Research Council Canada - National Science Library

    Tremblay-Lutter, Julie

    1995-01-01

    A functional fit evaluation of the Canadian Forces (CF) chemical protective lightweight glove was undertaken in order to quantify the amount of ease required within the glove for optimal functional fit...

  14. Parametric Investigation of the Isothermal Kinetics of Growth of Graphene on a Nickel Catalyst in the Process of Chemical Vapor Deposition of Hydrocarbons

    Science.gov (United States)

    Futko, S. I.; Shulitskii, B. G.; Labunov, V. A.; Ermolaeva, E. M.

    2016-11-01

    A kinetic model of isothermal synthesis of multilayer graphene on the surface of a nickel foil in the process of chemical vapor deposition, on it, of hydrocarbons supplied in the pulsed regime is considered. The dependences of the number of graphene layers formed and the time of their growth on the temperature of the process, the concentration of acetylene, and the thickness of the nickel foil were calculated. The regime parameters of the process of chemical vapor deposition, at which single-layer graphene and bi-layer graphene are formed, were determined. The dynamics of growth of graphene domains at chemical-vapor-deposition parameters changing in wide ranges was investigated. It is shown that the time dependences of the rates of growth of single-layer graphene and bi-layer graphene are nonlinear in character and that they are determined by the kinetics of nucleation and growth of graphene and the diffusion flow of carbon atoms in the nickel foil.

  15. The influence of chemical composition of LNG on the supercritical heat transfer in an intermediate fluid vaporizer

    Science.gov (United States)

    Xu, Shuangqing; Chen, Xuedong; Fan, Zhichao; Chen, Yongdong; Nie, Defu; Wu, Qiaoguo

    2018-04-01

    A three-dimensional transient computational fluid dynamics (CFD) model has been established for the simulations of supercritical heat transfer of real liquefied natural gas (LNG) mixture in a single tube and a tube bundle of an intermediate fluid vaporizer (IFV). The influence of chemical composition of LNG on the thermal performance has been analyzed. The results have also been compared with those obtained from the one-dimensional steady-state calculations using the distributed parameter model (DPM). It is found that the current DPM approach can give reasonable prediction accuracy for the thermal performance in the tube bundle but unsatisfactory prediction accuracy for that in a single tube as compared with the corresponding CFD data. As benchmarked against pure methane, the vaporization of an LNG containing about 90% (mole fraction) of methane would lead to an absolute deviation of 5.5 K in the outlet NG temperature and a maximum relative deviation of 11.4% in the tube side HTC in a bundle of about 816 U tubes at the inlet pressure of 12 MPa and mass flux of 200 kg·m-2·s-1. It is concluded that the influence of LNG composition on the thermal performance should be taken into consideration in order to obtain an economic and reliable design of an IFV.

  16. Synthesis of diamond films by pulsed liquid injection chemical vapor deposition using a mixture of acetone and water as precursor

    International Nuclear Information System (INIS)

    Apatiga, L.M.; Morales, J.

    2009-01-01

    A chemical vapor deposition reactor based on the flash evaporation of an organic liquid precursor was used to grow diamond films on Si substrates. An effective pulsed liquid injection mechanism consisting of an injector, normally used for fuel injection in internal combustion engines, injects micro-doses of the precursor to the evaporation zone at 280 o C and is instantly evaporated. The resulting vapor mixture is transported by a carrier gas to the high-temperature reaction chamber where the diamond nucleates and grows on the substrate surface at temperatures ranging from 750 to 850 o C. The injection frequency, opening time, number of pulses and other injector parameters are controlled by a computer-driven system. The diamond film morphology and structure were characterized by scanning electron microscopy and Raman spectroscopy. The as-deposited diamond films show a ball-shaped morphology with a grain size that varies from 100 to 400 nm, as well as the characteristic diamond Raman band at 1332 cm -1 . The effects of the experimental parameters and operation principle on the diamond films quality are analyzed and discussed in terms of crystallinity, composition, structure, and morphology.

  17. High-aspect-ratio and high-flatness Cu3(SiGe) nanoplatelets prepared by chemical vapor deposition.

    Science.gov (United States)

    Klementová, Mariana; Palatinus, Lukás; Novotný, Filip; Fajgar, Radek; Subrt, Jan; Drínek, Vladislav

    2013-06-01

    Cu3(SiGe) nanoplatelets were synthesized by low-pressure chemical vapor deposition of a SiH3C2H5/Ge2(CH3)6 mixture on a Cu-substrate at 500 degrees C, total pressure of 110-115 Pa, and Ge/Si molar ratio of 22. The nanoplatelets with composition Cu76Si15Ge12 are formed by the 4'-phase, and they are flattened perpendicular to the [001] direction. Their lateral dimensions reach several tens of micrometers in size, but they are only about 50 nm thick. Their surface is extremely flat, with measured root mean square roughness R(q) below 0.2 nm. The nanoplatelets grow via the non-catalytic vapor-solid mechanism and surface growth. In addition, nanowires and nanorods of various Cu-Si-Ge alloys were also obtained depending on the experimental conditions. Morphology of the resulting Cu-Si-Ge nanoobjects is very sensitive to the experimental parameters. The formation of nanoplatelets is associated with increased amount of Ge in the alloy.

  18. One-dimensional surface-imprinted polymeric nanotubes for specific biorecognition by initiated chemical vapor deposition (iCVD).

    Science.gov (United States)

    Ince, Gozde Ozaydin; Armagan, Efe; Erdogan, Hakan; Buyukserin, Fatih; Uzun, Lokman; Demirel, Gokhan

    2013-07-24

    Molecular imprinting is a powerful, generic, and cost-effective technique; however, challenges still remain related to the fabrication and development of these systems involving nonhomogeneous binding sites, insufficient template removing, incompatibility with aqueous media, low rebinding capacity, and slow mass transfer. The vapor-phase deposition of polymers is a unique technique because of the conformal nature of coating and offers new possibilities in a number of applications including sensors, microfluidics, coating, and bioaffinity platforms. Herein, we demonstrated a simple but versatile concept to generate one-dimensional surface-imprinted polymeric nanotubes within anodic aluminum oxide (AAO) membranes based on initiated chemical vapor deposition (iCVD) technique for biorecognition of immunoglobulin G (IgG). It is reported that the fabricated surface-imprinted nanotubes showed high binding capacity and significant specific recognition ability toward target molecules compared with the nonimprinted forms. Given its simplicity and universality, the iCVD method can offer new possibilities in the field of molecular imprinting.

  19. Synthesis and characterization of beta-Ga2O3 nanorod array clumps by chemical vapor deposition.

    Science.gov (United States)

    Shi, Feng; Wei, Xiaofeng

    2012-11-01

    beta-Ga2O3 nanorod array clumps were successfully synthesized on Si (111) substrates by chemical vapor deposition. The composition, microstructure, morphology, and light-emitting property of these clumps were characterized by X-ray diffraction, Fourier transform infrared spectrophotometry, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence. The results demonstrate that the sample synthesized at 1050 degrees C for 15 min was composed of monoclinic beta-Ga2O3 nanorod array clumps, where each single nanorod was about 300 nm in diameter with some nano-droplets on its tip. These results reveal that the growth mechanism agrees with the vapor-liquid-solid (VLS) process. The photoluminescence spectrum shows that the Ga2O3 nanorods have a blue emission at 438 nm, which may be attributed to defects, such as oxygen vacancies and gallium-oxygen vacancy pairs. Defect-energy aggregation confinement growth theory was proposed to explain the growth mechanism of Ga2O3 nanorod array clumps collaborated with the VLS mechanism.

  20. the deployment of soviet chemical forces in afghanistan and south

    African Journals Online (AJOL)

    toms observed in people suffering from tricho- thecene poisoning and those suffered by victims of many chemical attacks. However, this correla- tion is still not close enough to explain reports such as the following, especially the last sen- tence: 'Two L-19 airplanes made an attack on Pha Na. Khun, a Laotian village of some ...

  1. Understanding and improving the chemical vapor deposition process for solar grade silicon production

    OpenAIRE

    Ramos Cabal, Alba

    2015-01-01

    Esta Tesis Doctoral se centra en la investigación del proceso de producción de polisilicio para aplicaciones fotovoltaicas (FV) por la vía química; mediante procesos de depósito en fase vapor (CVD). El polisilicio para la industria FV recibe el nombre de silicio de grado solar (SoG Si). Por un lado, el proceso que domina hoy en día la producción de SoG Si está basado en la síntesis, destilación y descomposición de triclorosilano (TCS) en un reactor CVD -denominado reactor Siemens-. El materia...

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

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  3. Physico-chemical characterization antituberculosis thioacetazone: Vapor pressure, solubility and lipophilicity

    International Nuclear Information System (INIS)

    Sharapova, Angelica; Ol'khovich, Marina; Blokhina, Svetlana; Perlovich, German

    2017-01-01

    Highlights: • Vapor pressures of antituberculosis thioacetazone were determined by transpiration method. • Solubilities of the TAZ in four modeling solvents were measured at different temperatures. • Temperature dependence of octanol/buffer pH 7.4 partition coefficients was obtained. • Thermodynamics parameters of solubility, sublimation, solvation and transfer were calculated. - Abstract: Vapor pressure of thioacetazone (TAZ) has been determined in the temperature range of 404.15–429.15 K by the transpiration method. The obtained data were used to calculate the standard molar enthalpy of sublimation that was found to be 164.1 kJ/mol at T = 298.15 K. The drug solubility was measured at seven temperatures from 288.15 to 318.15 K in modeling solvents: octanol, hexane and aqueous buffers pH 2.0 and 7.4 by the saturation shake-flask method by using spectrophotometric analysis. It has been found that TAZ has poor solubility in hexane and buffer solutions and limited solubility in octanol. The experimental data were well correlated by van’t Hoff and modified Apelblat equations. A temperature dependence of TAZ partition coefficient in the octanol/buffer pH 7.4 system has been derived. The partition coefficient value in this system (logP = 1.82) refers to the optimal interval for oral absorption drugs. The thermodynamic parameters of sublimation, solubility, solvation and transfer have been determined based on experimental data. The dominant effect of enthalpy and entropy contributions to the Gibbs energy of the investigated processes has been revealed.

  4. The electrical properties of low pressure chemical vapor deposition Ga doped ZnO thin films depending on chemical bonding configuration

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hanearl [School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Kim, Doyoung [School of Electrical and Electronic Engineering, Ulsan College, 57 Daehak-ro, Nam-gu, Ulsan 680-749 (Korea, Republic of); Kim, Hyungjun, E-mail: hyungjun@yonsei.ac.kr [School of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749 (Korea, Republic of)

    2014-04-01

    Highlights: • Undoped and Ga doped ZnO thin films were deposited using DEZ and TMGa. • Effects of Ga doping using TMGa in Ga doped ZnO were investigated. • Degraded properties from excessive doping were analyzed using chemical bondings. - Abstract: The electrical and chemical properties of low pressure chemical vapor deposition (LP-CVD) Ga doped ZnO (ZnO:Ga) films were systematically investigated using Hall measurement and X-ray photoemission spectroscopy (XPS). Diethylzinc (DEZ) and O{sub 2} gas were used as precursor and reactant gas, respectively, and trimethyl gallium (TMGa) was used as a Ga doping source. Initially, the electrical properties of undoped LP-CVD ZnO films depending on the partial pressure of DEZ and O{sub 2} ratio were investigated using X-ray diffraction (XRD) by changing partial pressure of DEZ from 40 to 140 mTorr and that of O{sub 2} from 40 to 80 mTorr. The resistivity was reduced by Ga doping from 7.24 × 10{sup −3} Ω cm for undoped ZnO to 2.05 × 10{sup −3} Ω cm for Ga doped ZnO at the TMG pressure of 8 mTorr. The change of electric properties of Ga doped ZnO with varying the amount of Ga dopants was systematically discussed based on the structural crystallinity and chemical bonding configuration, analyzed by XRD and XPS, respectively.

  5. Causal knowledge extraction by natural language processing in material science: a case study in chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Yuya Kajikawa

    2006-11-01

    Full Text Available Scientific publications written in natural language still play a central role as our knowledge source. However, due to the flood of publications, the literature survey process has become a highly time-consuming and tangled process, especially for novices of the discipline. Therefore, tools supporting the literature-survey process may help the individual scientist to explore new useful domains. Natural language processing (NLP is expected as one of the promising techniques to retrieve, abstract, and extract knowledge. In this contribution, NLP is firstly applied to the literature of chemical vapor deposition (CVD, which is a sub-discipline of materials science and is a complex and interdisciplinary field of research involving chemists, physicists, engineers, and materials scientists. Causal knowledge extraction from the literature is demonstrated using NLP.

  6. Controlling single and few-layer graphene crystals growth in a solid carbon source based chemical vapor deposition

    International Nuclear Information System (INIS)

    Papon, Remi; Sharma, Subash; Shinde, Sachin M.; Vishwakarma, Riteshkumar; Tanemura, Masaki; Kalita, Golap

    2014-01-01

    Here, we reveal the growth process of single and few-layer graphene crystals in the solid carbon source based chemical vapor deposition (CVD) technique. Nucleation and growth of graphene crystals on a polycrystalline Cu foil are significantly affected by the injection of carbon atoms with pyrolysis rate of the carbon source. We observe micron length ribbons like growth front as well as saturated growth edges of graphene crystals depending on growth conditions. Controlling the pyrolysis rate of carbon source, monolayer and few-layer crystals and corresponding continuous films are obtained. In a controlled process, we observed growth of large monolayer graphene crystals, which interconnect and merge together to form a continuous film. On the other hand, adlayer growth is observed with an increased pyrolysis rate, resulting few-layer graphene crystal structure and merged continuous film. The understanding of monolayer and few-layer crystals growth in the developed CVD process can be significant to grow graphene with controlled layer numbers.

  7. Residual stress in thick low-pressure chemical-vapor deposited polycrystalline SiC coatings on Si substrates

    Science.gov (United States)

    Choi, D.; Shinavski, R. J.; Steffier, W. S.; Spearing, S. M.

    2005-04-01

    Residual stress in thick coatings of polycrystalline chemical-vapor deposited SiC on Si substrates is a key variable that must be controlled if SiC is to be used in microelectromechanical systems. Studies have been conducted to characterize the residual stress level as a function of deposition temperature, Si wafer and SiC coating thickness, and the ratios of methyltrichlorosilane to hydrogen and hydrogen chloride. Wafer curvature was used to monitor residual stress in combination with a laminated plate analysis. Compressive intrinsic (growth) stresses were measured with magnitudes in the range of 200-300MPa; however, these can be balanced with the tensile stress due to the thermal-expansion mismatch to leave near-zero stress at room temperature. The magnitude of the compressive intrinsic stress is consistent with previously reported values of surface stress in combination with the competition between grain-boundary energy and elastic strain energy.

  8. Anisotropic electrical conduction and reduction in dangling-bond density for polycrystalline Si films prepared by catalytic chemical vapor deposition

    Science.gov (United States)

    Niikura, Chisato; Masuda, Atsushi; Matsumura, Hideki

    1999-07-01

    Polycrystalline Si (poly-Si) films with high crystalline fraction and low dangling-bond density were prepared by catalytic chemical vapor deposition (Cat-CVD), often called hot-wire CVD. Directional anisotropy in electrical conduction, probably due to structural anisotropy, was observed for Cat-CVD poly-Si films. A novel method to separately characterize both crystalline and amorphous phases in poly-Si films using anisotropic electrical conduction was proposed. On the basis of results obtained by the proposed method and electron spin resonance measurements, reduction in dangling-bond density for Cat-CVD poly-Si films was achieved using the condition to make the quality of the included amorphous phase high. The properties of Cat-CVD poly-Si films are found to be promising in solar-cell applications.

  9. Synthesis and growth mechanism of Fe-catalyzed carbon nanotubes by plasma-enhanced chemical vapor deposition

    International Nuclear Information System (INIS)

    Jiang Jun; Feng Tao; Cheng Xinhong; Dai Lijuan; Cao Gongbai; Jiang Bingyao; Wang Xi; Liu Xianghuai; Zou Shichang

    2006-01-01

    Plasma-enhanced chemical vapor deposition (PECVD) was used to grow Fe-catalyzed carbon nanotubes (CNTs). The nanotubes had a uniform diameter in the range of about 10-20 nm. A base growth mode was responsible for the CNTs growth using a mixture of H 2 (60 sccm) and C 2 H 2 (15 sccm). For a mixture of H 2 (100 sccm) and C 2 H 2 (25 sccm), a complicated growth mechanism took place involving both the base growth and the tip growth. X-ray photoelectron spectroscopy measurements revealed that the grown CNTs contained C-H covalent bonds and Fe-C bonds located at the interface between them and the substrates. The factors determining the growth mechanism of CNTs are discussed and their growth mechanisms with the different gas ratios are suggested

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

    Directory of Open Access Journals (Sweden)

    V. Prajzler

    2008-01-01

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

  11. Immobilization of carbon nanotubes on functionalized graphene film grown by chemical vapor deposition and characterization of the hybrid material

    Directory of Open Access Journals (Sweden)

    Prashanta Dhoj Adhikari

    2014-01-01

    Full Text Available We report the surface functionalization of graphene films grown by chemical vapor deposition and fabrication of a hybrid material combining multi-walled carbon nanotubes and graphene (CNT–G. Amine-terminated self-assembled monolayers were prepared on graphene by the UV-modification of oxidized groups introduced onto the film surface. Amine-termination led to effective interaction with functionalized CNTs to assemble a CNT–G hybrid through covalent bonding. Characterization clearly showed no defects of the graphene film after the immobilization reaction with CNT. In addition, the hybrid graphene material revealed a distinctive CNT–G structure and p–n type electrical properties. The introduction of functional groups on the graphene film surface and fabrication of CNT–G hybrids with the present technique could provide an efficient, novel route to device fabrication.

  12. Modeling of gas-phase chemistry in the chemical vapor deposition of polysilicon in a cold wall system

    Energy Technology Data Exchange (ETDEWEB)

    Toprac, A.J.; Edgar, T.F.; Trachtenberg, I. (Univ. of Texas, Austin, TX (United States). Dept. of Chemical Engineering)

    1993-06-01

    The relative contribution of gas-phase chemistry to deposition processes is an important issue both from the standpoint of operation and modeling of these processes. In polysilicon deposition from thermally activated silane in a cold wall rapid thermal chemical vapor deposition (RTCVD) system, the relative contribution of gas-phase chemistry to the overall deposition rate was examined by a mass-balance model. Evaluating the process at conditions examined experimentally, the model indicated that gas-phase reactions may be neglected to good accuracy in predicting polysilicon deposition rate. The model also provided estimates of the level of gas-phase generated SiH[sub 2] associated with deposition on the cold-process chamber walls.

  13. Sensitivity of chemical vapor deposition diamonds to DD and DT neutrons at OMEGA and the National Ignition Facility

    Science.gov (United States)

    Kabadi, N. V.; Sio, H.; Glebov, V.; Gatu Johnson, M.; MacPhee, A.; Frenje, J. A.; Li, C. K.; Seguin, F.; Petrasso, R.; Forrest, C.; Knauer, J.; Rinderknecht, H. G.

    2016-11-01

    The particle-time-of-flight (pTOF) detector at the National Ignition Facility (NIF) is used routinely to measure nuclear bang-times in inertial confinement fusion implosions. The active detector medium in pTOF is a chemical vapor deposition diamond. Calibration of the detectors sensitivity to neutrons and protons would allow measurement of nuclear bang times and hot spot areal density (ρR) on a single diagnostic. This study utilizes data collected at both NIF and Omega in an attempt to determine pTOF's absolute sensitivity to neutrons. At Omega pTOF's sensitivity to DT-n is found to be stable to within 8% at different bias voltages. At the NIF pTOF's sensitivity to DD-n varies by up to 59%. This variability must be decreased substantially for pTOF to function as a neutron yield detector at the NIF. Some possible causes of this variability are ruled out.

  14. Defect-Free Graphene Synthesized Directly at 150 °C via Chemical Vapor Deposition with No Transfer.

    Science.gov (United States)

    Park, Byeong-Ju; Choi, Jin-Seok; Eom, Ji-Ho; Ha, Hyunwoo; Kim, Hyun You; Lee, Seonhee; Shin, Hyunjung; Yoon, Soon-Gil

    2018-02-27

    Direct graphene synthesis on substrates via chemical vapor deposition (CVD) is an attractive approach for manufacturing flexible electronic devices. The temperature for graphene synthesis must be below ∼200 °C to prevent substrate deformation while fabricating flexible devices on plastic substrates. Herein, we report a process whereby defect-free graphene is directly synthesized on a variety of substrates via the introduction of an ultrathin Ti catalytic layer, due to the strong affinity of Ti to carbon. Ti with a thickness of 10 nm was naturally oxidized by exposure to air before and after the graphene synthesis, and the various functions of neither the substrates nor the graphene were influenced. This report offers experimental evidence of high-quality graphene synthesis on Ti-coated substrates at 150 °C via CVD. The proposed methodology was applied to the fabrication of flexible and transparent thin-film capacitors with top electrodes of high-quality graphene.

  15. Non-catalytic direct synthesis of graphene on Si (111) wafers by using inductively-coupled plasma chemical vapor deposition

    Science.gov (United States)

    Hwang, Sung Won; Shin, Hyunho; Lee, Bongsoo; Choi, Suk-Ho

    2016-08-01

    We employ inductively-coupled plasma chemical vapor deposition for non-catalytic growth of graphene on a Si (111) wafer or glass substrate, which is useful for practical device applications of graphene without transfer processes. At a RF power (P) of 500 W under C2H2 flow, defect-free 3 ˜ 5-layer graphene is grown on Si (111) wafers, but on glass substrate, the layer is thicker and defective, as characterized by Raman spectroscopy and electron microscopy. The graphene is produced on Si (111) for P down to 190 W whereas it is almost not formed on glass for P < 250 W, possibly resulting from the weak catalytic-reaction-like effect on glass. These results are discussed based on possible growth mechanisms.

  16. Characteristics of Ge-Sb-Te films prepared by cyclic pulsed plasma-enhanced chemical vapor deposition.

    Science.gov (United States)

    Suk, Kyung-Suk; Jung, Ha-Na; Woo, Hee-Gweon; Park, Don-Hee; Kim, Do-Heyoung

    2010-05-01

    Ge-Sb-Te (GST) thin films were deposited on TiN, SiO2, and Si substrates by cyclic-pulsed plasma-enhanced chemical vapor deposition (PECVD) using Ge{N(CH3)(C2H5)}, Sb(C3H7)3, Te(C3H7)3 as precursors in a vertical flow reactor. Plasma activated H2 was used as the reducing agent. The growth behavior was strongly dependent on the type of substrate. GST grew as a continuous film on TiN regardless of the substrate temperature. However, GST formed only small crystalline aggregates on Si and SiO2 substrates, not a continuous film, at substrate temperatures > or = 200 degrees C. The effects of the deposition temperature on the surface morphology, roughness, resistivity, crystallinity, and composition of the GST films were examined.

  17. Structural and optical characterization of self-assembled Ge nanocrystal layers grown by plasma-enhanced chemical vapor deposition.

    Science.gov (United States)

    Saeed, Saba; Buters, Frank; Dohnalova, Katerina; Wosinski, Lech; Gregorkiewicz, Tom

    2014-10-10

    We present a structural and optical study of solid-state dispersions of Ge nanocrystals prepared by plasma-enhanced chemical vapor deposition. Structural analysis shows the presence of nanocrystalline germanium inclusions embedded in an amorphous matrix of Si-rich SiO(2).Optical characterization reveals two prominent emission bands centered around 2.6 eV and 3.4 eV, and tunable by excitation energy. In addition, the lower energy band shows an excitation power-dependent blue shift of up to 0.3 eV. Decay dynamics of the observed emission contains fast (nanosecond) and slow (microseconds) components, indicating contributions of several relaxation channels. Based on these material characteristics, a possible microscopic origin of the individual emission bands is discussed.

  18. Interwell coupling effect in Si/SiGe quantum wells grown by ultra high vacuum chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Loh Ter-Hoe

    2007-01-01

    Full Text Available AbstractSi/Si0.66Ge0.34coupled quantum well (CQW structures with different barrier thickness of 40, 4 and 2 nm were grown on Si substrates using an ultra high vacuum chemical vapor deposition (UHV-CVD system. The samples were characterized using high resolution x-ray diffraction (HRXRD, cross-sectional transmission electron microscopy (XTEM and photoluminescence (PL spectroscopy. Blue shift in PL peak energy due to interwell coupling was observed in the CQWs following increase in the Si barrier thickness. The Si/SiGe heterostructure growth process and theoretical band structure model was validated by comparing the energy of the no-phonon peak calculated by the 6 + 2-bandk·pmethod with experimental PL data. Close agreement between theoretical calculations and experimental data was obtained.

  19. On the Origin of Light Emission in Silicon Rich Oxide Obtained by Low-Pressure Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    M. Aceves-Mijares

    2012-01-01

    Full Text Available Silicon Rich Oxide (SRO has been considered as a material to overcome the drawbacks of silicon to achieve optical functions. Various techniques can be used to produce it, including Low-Pressure Chemical Vapor Deposition (LPCVD. In this paper, a brief description of the studies carried out and discussions of the results obtained on electro-, cathode-, and photoluminescence properties of SRO prepared by LPCVD and annealed at 1,100°C are presented. The experimental results lead us to accept that SRO emission properties are due to oxidation state nanoagglomerates rather than to nanocrystals. The emission mechanism is similar to Donor-Acceptor decay in semiconductors, and a wide emission spectrum, from 450 to 850 nm, has been observed. The results show that emission is a function of both silicon excess in the film and excitation energy. As a result different color emissions can be obtained by selecting the suitable excitation energy.

  20. Effects of potassium hydroxide post-treatments on the field-emission properties of thermal chemical vapor deposited carbon nanotubes.

    Science.gov (United States)

    Lee, Li-Ying; Lee, Shih-Fong; Chang, Yung-Ping; Hsiao, Wei-Shao

    2011-12-01

    In this study, a simple potassium hydroxide treatment was applied to functionalize the surface and to modify the structure of multi-walled carbon nanotubes grown on silicon substrates by thermal chemical vapor deposition. Scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive spectrometry were employed to investigate the mechanism causing the modified field-emission properties of carbon nanotubes. From our experimental data, the emitted currents of carbon nanotubes after potassium hydroxide treatment are enhanced by more than one order of magnitude compared with those of untreated carbon nanotubes. The emitted current density of carbon nanotubes increases from 0.44 mA/cm2 to 7.92 mA/cm2 after 30 minutes KOH treatment. This technique provides a simple, economical, and effective way to enhance the field-emission properties of carbon nanotubes.