A CVD Diamond Detector for (n,a) Cross-Section Measurements

CERN Document Server

Weiss, Christina; Griesmayer, Erich; Guerrero, Carlos

A novel detector based on the chemical vapor deposition (CVD) diamond technology has been developed in the framework of this PhD, for the experimental determination of (n,a) cross-sections at the neutron time-of-flight facility n_TOF at CERN. The 59Ni(n,a)56Fe cross-section, which is relevant for astrophysical questions as well as for risk-assessment studies in nuclear technology, has been measured in order to validate the applicability of the detector for such experiments. The thesis is divided in four parts. In the introductory part the motivation for measuring (n,a) cross-sections, the experimental challenges for such measurements and the reasons for choosing the CVD diamond technology for the detector are given. This is followed by the presentation of the n_TOF facility, an introduction to neutron-induced nuclear reactions and a brief summary of the interaction of particles with matter. The CVD diamond technology and the relevant matters related to electronics are given as well in this first part of the t...

CVD carbon powders modified by ball milling

Directory of Open Access Journals (Sweden)

Kazmierczak Tomasz

2015-09-01

Full Text Available Carbon powders produced using a plasma assisted chemical vapor deposition (CVD methods are an interesting subject of research. One of the most interesting methods of synthesizing these powders is using radio frequency plasma. This method, originally used in deposition of carbon films containing different sp2/sp3 ratios, also makes possible to produce carbon structures in the form of powder. Results of research related to the mechanical modification of these powders have been presented. The powders were modified using a planetary ball mill with varying parameters, such as milling speed, time, ball/powder mass ratio and additional liquids. Changes in morphology and particle sizes were measured using scanning electron microscopy and dynamic light scattering. Phase composition was analyzed using Raman spectroscopy. The influence of individual parameters on the modification outcome was estimated using statistical method. The research proved that the size of obtained powders is mostly influenced by the milling speed and the amount of balls. Powders tend to form conglomerates sized up to hundreds of micrometers. Additionally, it is possible to obtain nanopowders with the size around 100 nm. Furthermore, application of additional liquid, i.e. water in the process reduces the graphitization of the powder, which takes place during dry milling.

Large-area selective CVD epitaxial growth of Ge on Si substrates

NARCIS (Netherlands)

Sammak, A.; De Boer, W.; Nanver, L.K.

2011-01-01

Selective epitaxial growth of crystalline Ge on Si in a standard ASM Epsilon 2000 CVD reactor is investigated for the fabrication of Ge p+n diodes. At the deposition temperature of 700?C, most of the lattice mismatch-defects are trapped within first 300nm of Ge growth and good quality single crystal

Investigation of CVD graphene topography and surface electrical properties

International Nuclear Information System (INIS)

Wang, Rui; Pearce, Ruth; Gallop, John; Patel, Trupti; Pollard, Andrew; Hao, Ling; Zhao, Fang; Jackman, Richard; Klein, Norbert; Zurutuza, Amaia

2016-01-01

Combining scanning probe microscopy techniques to characterize samples of graphene, a selfsupporting, single atomic layer hexagonal lattice of carbon atoms, provides far more information than a single technique can. Here we focus on graphene grown by chemical vapour deposition (CVD), grown by passing carbon containing gas over heated copper, which catalyses single atomic layer growth of graphene on its surface. To be useful for applications the graphene must be transferred onto other substrates. Following transfer it is important to characterize the CVD graphene. We combine atomic force microscopy (AFM) and scanning Kelvin probe microscopy (SKPM) to reveal several properties of the transferred film. AFM alone provides topographic information, showing ‘wrinkles’ where the transfer provided incomplete substrate attachment. SKPM measures the surface potential indicating regions with different electronic properties for example graphene layer number. By combining AFM and SKPM local defects and impurities can also be observed. Finally, Raman spectroscopy can confirm the structural properties of the graphene films, such as the number of layers and level of disorder, by observing the peaks present. We report example data on a number of CVD samples from different sources. (paper)

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.

VO{sub x} effectively doping CVD-graphene for transparent conductive films

Energy Technology Data Exchange (ETDEWEB)

Ji, Qinghua; Shi, Liangjing [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Zhang, Qinghong [State Key Laboratory of Modification of Chemical Fibers and Polymer Materials, College of Material Science and Engineering, Donghua University, 2999 North Renmin Road, Shanghai 201620 (China); Wang, Weiqi; Zheng, Huifeng [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Zhang, Yuzhi [The Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences,1295 Dingxi Road, Shanghai 200050 (China); Liu, Yangqiao, E-mail: yqliu@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Sun, Jing, E-mail: jingsun@mail.sic.ac.cn [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

2016-11-30

Highlights: • Doping process operated easily. • Sheet resistance decreased efficiently after doping. • Sheet resistance of doped graphene is stable after exposed in the air. • Mechanism of doping process is studied. - Abstract: Chemical vapor deposition(CVD)-synthesized graphene is potentially an alternative for tin-doped indium oxide (ITO) transparent conductive films (TCFs), however its sheet resistance is still too high to meet many demands. Vanadium oxide has been widely applied as smart window materials, however, no study has been reported to use it as dopant to improve the conductivity of graphene TCFs. In this study, we firstly reported that VO{sub x} doping can effectively lower the sheet resistance of CVD-graphene films while keeping its good optical properties, whose transmittance is as high as 86–90%. The optimized VO{sub x}-doped graphene exhibits a sheet resistance as low as 176 Ω/□, which decreases by 56% compared to the undoped graphene films. The doping process is convenient, stable, economical and easy to operate. What is more, VO{sub x} can effectively increase the work function(WF) of the film, making it more appropriate for use in solar cells. The evolution of the VO{sub x} species annealed at different temperatures below 400 °C has been detailed studied for the first time, based on which the doping mechanism is proposed. The prepared VO{sub x} doped graphene is expected to be a promising candidate for transparent conductive film purposes.

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.

Microstructure fabrication process induced modulations in CVD graphene

Energy Technology Data Exchange (ETDEWEB)

Matsubayashi, Akitomo, E-mail: amatsubayashi@albany.edu; Zhang, Zhenjun; Lee, Ji Ung; LaBella, Vincent P., E-mail: vlabella@albany.edu [College of Nanoscale Science and Engineering, University at Albany, SUNY, Albany, New York 12203 (United States)

2014-12-15

The systematic Raman spectroscopic study of a “mimicked” graphene device fabrication is presented. Upon photoresist baking, compressive stress is induced in the graphene which disappears after it is removed. The indirect irradiation from the electron beam (through the photoresist) does not significantly alter graphene characteristic Raman peaks indicating that graphene quality is preserved upon the exposure. The 2D peak shifts and the intensity ratio of 2D and G band, I(2D)/I(G), decreases upon direct metal deposition (Co and Py) suggesting that the electronic modulation occurs due to sp{sup 2} C-C bond weakening. In contrast, a thin metal oxide film deposited graphene does not show either the significant 2D and G peaks shift or I(2D)/I(G) decrease upon the metal deposition suggesting the oxide protect the graphene quality in the fabrication process.

Microstructure fabrication process induced modulations in CVD graphene

Science.gov (United States)

Matsubayashi, Akitomo; Zhang, Zhenjun; Lee, Ji Ung; LaBella, Vincent P.

2014-12-01

The systematic Raman spectroscopic study of a "mimicked" graphene device fabrication is presented. Upon photoresist baking, compressive stress is induced in the graphene which disappears after it is removed. The indirect irradiation from the electron beam (through the photoresist) does not significantly alter graphene characteristic Raman peaks indicating that graphene quality is preserved upon the exposure. The 2D peak shifts and the intensity ratio of 2D and G band, I(2D)/I(G), decreases upon direct metal deposition (Co and Py) suggesting that the electronic modulation occurs due to sp2 C-C bond weakening. In contrast, a thin metal oxide film deposited graphene does not show either the significant 2D and G peaks shift or I(2D)/I(G) decrease upon the metal deposition suggesting the oxide protect the graphene quality in the fabrication process.

Origin, state of the art and some prospects of the diamond CVD

CERN Document Server

Spitsyn, B V; Alexenko, A E

2000-01-01

A short review on the diamond CVD origin, together with its state of the art and some prospects was given. New hybrid methods of the diamond CVD permit to gain 1.2 to 6 times of growth rate in comparison with ordinary diamond CVD's. Recent results on n-type diamond film synthesis through phosphorus doping in the course of the CVD process are briefly discussed. In comparison with high-pressure diamond synthesis, the CVD processes open new facets of the diamond as ultimate crystal for science and technology evolution. It was stressed that, mainly on the basis of new CVDs of diamond, the properties of natural diamond are not only reproduced, but can be surpassed. As examples, mechanical (fracture resistance), physical (thermal conductivity), and chemical (oxidation stability) properties are mentioned. Some present issues in the field are considered.

Cutting characteristics of dental diamond burs made with CVD technology Características de corte de pontas odontológicas diamantadas obtidas pela tecnologia CVD

Directory of Open Access Journals (Sweden)

Luciana Monti Lima

2006-04-01

Full Text Available The aim of this study was to determine the cutting ability of chemical vapor deposition (CVD diamond burs coupled to an ultrasonic dental unit handpiece for minimally invasive cavity preparation. One standard cavity was prepared on the mesial and distal surfaces of 40 extracted human third molars either with cylindrical or with spherical CVD burs. The cutting ability was compared regarding type of substrate (enamel and dentin and direction of handpiece motion. The morphological characteristics, width and depth of the cavities were analyzed and measured using scanning electron micrographs. Statistical analysis using the Kruskal-Wallis test (p O objetivo deste estudo foi determinar a habilidade de corte das pontas de diamante obtidas pelo processo de deposição química a vapor (CVD associadas ao aparelho de ultra-som no preparo cavitário minimamente invasivo. Uma cavidade padronizada foi preparada nas faces mesial e distal de 40 terceiros molares, utilizando-se pontas de diamante CVD cilíndrica e esférica. A habilidade de corte foi comparada quanto ao tipo de substrato (esmalte e dentina e quanto à direção do movimento realizado com a ponta. As características morfológicas, a largura e profundidade das cavidades foram analisadas e medidas em microscopia eletrônica de varredura. A análise estatística pelo teste de Kruskal-Wallis (p < 0,05 revelou que a largura e profundidade das cavidades foram significativamente maiores em dentina. Cavidades mais largas foram obtidas quando se utilizou a ponta de diamante CVD cilíndrica, e mais profundas quando a ponta esférica foi empregada. A direção do movimento da ponta não influenciou o tamanho das cavidades, sendo os cortes produzidos pelas pontas de diamante CVD precisos e conservadores.

Comparative study of dlc coatings by pvd against cvd technique on textile dents

International Nuclear Information System (INIS)

Malik, M.; Alam, S.; Iftikhar, F.

2007-01-01

Diamond like Carbon (DLC) film is a hard amorphous carbon hydride film formed by Physical or Chemical vapor deposition (PVD or CVD) techniques. Due to its unique properties especially high hardness, lower coefficient of friction and lubricious nature, these coatings are not only used to extend the life of cutting tools but also for non cutting applications such as for forming dies, molds and on many functional parts of textile. In the present work two techniques were employed i.e. PVD and CVD for deposition of diamond like carbon film on textile dents. These dents are used as thread guider in high speed weaving machine. The measurement of coating thickness, adhesion, hardness and roughness values indicates that overall properties of DLC coating developed by PVD LARC technology reduces abrasion and increases the workability and durability of textile dents as well as suppress the need of lubricants. (author)

Crystalline silicon thin film growth by ECR plasma CVD for solar cells

International Nuclear Information System (INIS)

Licai Wang

1999-07-01

This thesis describes the background, motivation and work carried out towards this PhD programme entitled 'Crystalline Silicon Thin Film Growth by ECR Plasma CVD for Solar Cells'. The fundamental principles of silicon solar cells are introduced with a review of silicon thin film and bulk solar cells. The development and prospects for thin film silicon solar cells are described. Some results of a modelling study on thin film single crystalline solar cells are given which has been carried out using a commercially available solar cell simulation package (PC-1D). This is followed by a description of thin film deposition techniques. These include Chemical Vapour Deposition (CVD) and Plasma-Assisted CVD (PACVD). The basic theory and technology of the emerging technique of Electron Cyclotron Resonance (ECR) PACVD, which was used in this research, are introduced and the potential advantages summarised. Some of the basic methods of material and cell characterisation are briefly described, together with the work carried out in this research. The growth by ECR PACVD at temperatures 2 illumination. The best efficiency in the ECR grown structures was 13.76% using an epitaxial emitter. Cell performance was analysed in detail and the factors controlling performance identified by fitting self-consistently the fight and dark current-voltage and spectral response data using PC-1D. Finally, the conclusions for this research and suggestions for further work are outlined. (author)

Graphene growth on Ge(100)/Si(100) substrates by CVD method.

Science.gov (United States)

Pasternak, Iwona; Wesolowski, Marek; Jozwik, Iwona; Lukosius, Mindaugas; Lupina, Grzegorz; Dabrowski, Pawel; Baranowski, Jacek M; Strupinski, Wlodek

2016-02-22

The successful integration of graphene into microelectronic devices is strongly dependent on the availability of direct deposition processes, which can provide uniform, large area and high quality graphene on nonmetallic substrates. As of today the dominant technology is based on Si and obtaining graphene with Si is treated as the most advantageous solution. However, the formation of carbide during the growth process makes manufacturing graphene on Si wafers extremely challenging. To overcome these difficulties and reach the set goals, we proposed growth of high quality graphene layers by the CVD method on Ge(100)/Si(100) wafers. In addition, a stochastic model was applied in order to describe the graphene growth process on the Ge(100)/Si(100) substrate and to determine the direction of further processes. As a result, high quality graphene was grown, which was proved by Raman spectroscopy results, showing uniform monolayer films with FWHM of the 2D band of 32 cm(-1).

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.

Response of CVD diamond detectors to alpha radiation

Energy Technology Data Exchange (ETDEWEB)

Souw, E.-K. [Brookhaven National Lab., Upton, NY (United States); Meilunas, R.J. [Northrop-Grumman Corporation, Bethpage, NY 11714-3582 (United States)

1997-11-21

This article describes some results from an experiment with CVD diamond films used as {alpha} particle detectors. It demonstrates that bulk polarization can be effectively stopped within a reasonable time interval. This will enable detector calibration and quantitative measurement. A possible mechanism for the observed polarization quenching is discussed. It involves two types of carrier traps and a tentative band-gap model derived from the results of photoconductive current measurements. The experiment was set up mainly to investigate {alpha} detection properties of polycrystalline diamond films grown by the technique of microwave plasma enhanced chemical vapor deposition. For comparison, two commercially purchased diamond wafers were also investigated, i.e., one grown by the DC arc jet method, and the other, a type-IIa natural diamond wafer (not preselected). The best response to {alpha} particles was obtained using diamond thin-films grown by the microwave PECVD method, followed by the type-IIa natural diamond, and finally, the CVD diamond grown by the DC arc jet technique. (orig.). 43 refs.

Characterization of thin film deposits on tungsten filaments in catalytic chemical vapor deposition using 1,1-dimethylsilacyclobutane

Energy Technology Data Exchange (ETDEWEB)

Shi, Yujun, E-mail: shiy@ucalgary.ca; Tong, Ling; Mulmi, Suresh [Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4 (Canada)

2016-09-15

Metal filament plays a key role in the technique of catalytic chemical vapor deposition (Cat-CVD) as it serves as a catalyst in dissociating the source gas to form reactive species. These reactive species initiate the gas-phase reaction chemistry and final thin film and nanostructure formation. At the same time, they also react with the metal itself, leading to the formation of metal alloys and other deposits. The deposits on the tungsten filaments when exposed to 1,1-dimethylsilacyclobutane (DMSCB), a single-source precursor for silicon carbide thin films, in the process of Cat-CVD were studied in this work. It has been demonstrated that a rich variety of deposits, including tungsten carbides (W{sub 2}C and WC), tungsten silicide (W{sub 5}Si{sub 3}), silicon carbide, amorphous carbon, and graphite, form on the W filament surfaces. The structural and morphological changes in the tungsten filaments depend strongly on the DMSCB pressure and filament temperature. At 1000 and 2000 °C, the formation of WC and W{sub 2}C dominates. In addition, a thin amorphous carbon layer has been found at 1500 °C with the 0.12 and 0.24 Torr of DMSCB and a lower temperature of 1200 °C with the 0.48 Torr of DMSCB. An increase in the DMSCB sample pressure gives rise to higher Si and C contents. As a result, the formation of SiC and W{sub 5}Si{sub 3} has been observed with the two high-pressure DMSCB samples (i.e., 0.24 and 0.48 Torr). The rich decomposition chemistry of DMSCB on the W surfaces is responsible for the extensive changes in the structure of the W filament, providing support for the close relationship between the gas-phase decomposition chemistry and the nature of alloy formation on the metal surface. The understanding of the structural changes obtained from this work will help guide the development of efficient methods to solve the filament aging problem in Cat-CVD and also to achieve a controllable deposition process.

The effect of percentage carbonon the CVD coating of plain carbon ...

African Journals Online (AJOL)

Two steels En 3 and En 39 were given a TiC-TiN CVD coating in the carburized and uncarburized conditions. The continuity of the coatings and their adherance to the substrate were examined. The thickness of the deposited coatings were also measured, their adherence to the substrate and their thickness was off ected by ...

Computation of flow and thermal fields in a model CVD reactor

Indian Academy of Sciences (India)

Mixing of coaxial jets within a tube in the presence of blockage has been numerically studied. This configuration is encountered during the modelling of flow and heat transfer in CVD (chemical vapour deposition) reactors. For the conditions prevailing in the reactor, the Reynolds numbers are low and flow can be taken to be ...

CVD polycrystalline diamond. A novel neutron detector and applications

International Nuclear Information System (INIS)

Mongkolnavin, R.

1998-01-01

Chemical Vapour Deposition (CVD) Polycrystalline Diamond film has been investigated as a low noise sensor for beta particles, gammas and neutrons using High Energy Physics technologies. Its advantages and disadvantages have been explored in comparison with other particle detectors such as silicon detector and other plastic scintillators. The performance and characteristic of the diamond detector have been fully studied and discussed. These studies will lead to a better understanding of how CVD diamonds perform as a detector and how to improve their performance under various conditions. A CVD diamond detector model has been proposed which is an attempt to explain the behaviour of such an extreme detector material. A novel neutron detector is introduced as a result of these studies. A good thermal and fast neutron detector can be fabricated with CVD diamond with new topologies. This detector will perform well without degradation in a high neutron radiation environment, as diamond is known to be radiation hard. It also offers better neutrons and gammas discrimination for high gamma background applications compared to other semiconductor detectors. A full simulation of the detector has also been done using GEANT, a Monte-Carlo simulation program for particle detectors. Simulation results show that CVD diamond detectors with this novel topology can detect neutrons with great directionality. Experimental work has been done on this detector in a nuclear reactor environment and accelerator source. A novel neutron source which offers a fast pulse high-energy neutrons has also been studied. With this detector, applications in neutron spectrometer for low-Z material have been pursued with various neutron detection techniques. One of these is a low-Z material identification system. The system has been designed and simulated for contraband luggage interrogation using the detector and the novel neutron source. Also other neutron related applications have been suggested. (author)

CVD polycrystalline diamond. A novel neutron detector and applications

International Nuclear Information System (INIS)

Mongkolnavin, R.

1998-07-01

Chemical Vapour Deposition (CVD) Polycrystalline Diamond film has been investigated as a low noise sensor for beta particles, gammas and neutrons using High Energy Physics technologies. Its advantages and disadvantages have been explored in comparison with other particle detectors such as silicon detector and other plastic scintillators. The performance and characteristic of the diamond detector have been fully studied and discussed. These studies will lead to a better understanding of how CVD diamonds perform as a detector and how to improve their performance under various conditions. A CVD diamond detector model has been proposed which is an attempt to explain the behaviour of such an extreme detector material. A novel neutron detector is introduced as a result of these studies. A good thermal and fast neutron detector can be fabricated with CVD diamond with new topologies. This detector will perform well without degradation in a high neutron radiation environment, as diamond is known to be radiation-hard. It also offers better neutrons and gammas discrimination for high gamma background applications compared to other semiconductor detectors. A full simulation of the detector has also been done using GEANT, a Monte Carlo simulation program for particle detectors. Simulation results show that CVD diamond detectors with this novel topology can detect neutrons with great directionality. Experimental work has been done on this detector in a nuclear reactor environment and accelerator source. A novel neutron source which offers a fast pulse high-energy neutrons has also been studied. With this detector, applications in neutron spectrometry for low-Z material have been pursued with various neutron detection techniques. One of these is a low-Z material identification system. The system has been designed and simulated for contraband luggage interrogation using the detector and the novel neutron source. (author)

Laser-Directed CVD 3D Printing System for Refractory Metal Propulsion Hardware, Phase II, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — In this work, Ultramet is developing a three-dimensional (3D) laser-directed chemical vapor deposition (CVD) additive manufacturing system to build free-form...

Wear Mechanism of Chemical Vapor Deposition (CVD) Carbide Insert in Orthogonal Cutting Ti-6Al-4V ELI at High Cutting Speed

International Nuclear Information System (INIS)

Gusri, A. I.; Che Hassan, C. H.; Jaharah, A. G.

2011-01-01

The performance of Chemical Vapor Deposition (CVD) carbide insert with ISO designation of CCMT 12 04 04 LF, when turning titanium alloys was investigated. There were four layers of coating materials for this insert i.e.TiN-Al2O3-TiCN-TiN. The insert performance was evaluated based on the insert's edge resistant towards the machining parameters used at high cutting speed range of machining Ti-6Al-4V ELI. Detailed study on the wear mechanism at the cutting edge of CVD carbide tools was carried out at cutting speed of 55-95 m/min, feed rate of 0.15-0.35 mm/rev and depth of cut of 0.10-0.20 mm. Wear mechanisms such as abrasive and adhesive were observed on the flank face. Crater wear due to diffusion was also observed on the rake race. The abrasive wear occurred more at nose radius and the fracture on tool were found at the feed rate of 0.35 mm/rev and the depth of cut of 0.20 mm. The adhesion wear takes place after the removal of the coating or coating delaminating. Therefore, adhesion or welding of titanium alloy onto the flank and rake faces demonstrates a strong bond at the workpiece-tool interface.

Optimization of CVD parameters for long ZnO NWs grown on ITO

Indian Academy of Sciences (India)

The optimization of chemical vapour deposition (CVD) parameters for long and vertically aligned (VA) ZnO nanowires (NWs) were investigated. Typical ZnO NWs as a single crystal grown on indium tin oxide (ITO)-coated glass substrate were successfully synthesized. First, the conducted side of ITO–glass substrate was ...

Size modulation of nanocrystalline silicon embedded in amorphous silicon oxide by Cat-CVD

International Nuclear Information System (INIS)

Matsumoto, Y.; Godavarthi, S.; Ortega, M.; Sanchez, V.; Velumani, S.; Mallick, P.S.

2011-01-01

Different issues related to controlling size of nanocrystalline silicon (nc-Si) embedded in hydrogenated amorphous silicon oxide (a-SiO x :H) deposited by catalytic chemical vapor deposition (Cat-CVD) have been reported. Films were deposited using tantalum (Ta) and tungsten (W) filaments and it is observed that films deposited using tantalum filament resulted in good control on the properties. The parameters which can affect the size of nc-Si domains have been studied which include hydrogen flow rate, catalyst and substrate temperatures. The deposited samples are characterized by X-ray diffraction, HRTEM and micro-Raman spectroscopy, for determining the size of the deposited nc-Si. The crystallite formation starts for Ta-catalyst around the temperature of 1700 o C.

Hydrogen termination of CVD diamond films by high-temperature annealing at atmospheric pressure

NARCIS (Netherlands)

Seshan, V.; Ullien, D.; Castellanos-Gomez, A.; Sachdeva, S.; Murthy, D.H.K.; Savenije, T.J.; Ahmad, H.A.; Nunney, T.S.; Janssens, S.D.; Haenen, K.; Nesládek, M.; Van der Zant, H.S.J.; Sudhölter, E.J.R.; De Smet, L.C.P.M.

2013-01-01

A high-temperature procedure to hydrogenate diamond films using molecular hydrogen at atmospheric pressure was explored. Undoped and doped chemical vapour deposited (CVD) polycrystalline diamond films were treated according to our annealing method using a H2 gas flow down to ?50 ml/min (STP) at

Natural and CVD type diamond detectors as dosimeters in hadrontherapy applications

International Nuclear Information System (INIS)

Cirrone, G.A.P.; Cuttone, G.; Rafaele, L.; Sabini, M.G.; De Angelis, C.; Onori, S.; Pacilio, M.; Bucciolini, M.; Bruzzi, M.; Sciortino, S.

2003-01-01

Diamond is potentially a suitable material for use as radiation dosimeter; the wide band gap results in low dark currents and low sensitivity to visible light, the high carrier mobility can give rapid response, the very high density of strong bonds in the crystal structure make diamond very resistant to radiation damage; moreover it is tissue equivalent. The more recent advances in the synthesis of polycrystalline diamond by chemical vapour deposition (CVD) techniques have allowed the synthesis of material with electronic properties suitable for dosimetric application. In this paper we will report the results obtained in the study of the response of a natural diamond dosimeter and a CVD one irradiated with 62 AMeV proton beams to demonstrate their possible application in protontherapy

Plasma CVD reactor with two-microwave oscillators for diamond film synthesis

International Nuclear Information System (INIS)

Nagatsu, M.; Miyake, M.; Maeda, J.

2006-01-01

In this study, we present the experimental results of a new type of microwave plasma CVD system, where two of 1.5 kW microwave sources were used for enlarging the plasma discharge and the diamond film growth. One of the microwave oscillators was used to produce the microwave plasma as in the conventional microwave plasma CVD device, while the second one was used to enlarge the plasma by introducing microwave from the launcher mounted at the substrate stage. We demonstrated the enlargement of plasma discharge area from 60 mm to 100 mm in diameter by using the two-microwave oscillators system. Characteristics of diamond films deposited using H 2 /CH 4 plasmas were also investigated using a scanning electron microscope (SEM) and Raman spectroscopy

Surface modification on 304 SS by plasma-immersed ion implantation to improve the adherence of a CVD diamond film

Energy Technology Data Exchange (ETDEWEB)

Nono, M.C.A.; Corat, E.J. (Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, SP (Brazil)); Ueda, M.; Stellati, C.; Barroso, J.J.; Conrad, J.R.; Shamim, M.; Fetherston, P.; Sridharan, K.

1999-02-01

The weak adherence of chemical vapor deposited (CVD) diamond films on steel substrates is an important factor that limits the technological applications of these materials. We are interested in enhancing the film-to-substrate adherence by using substrate surfaces with a previous modification by plasma-immersed ion implantation (PIII). In this work we present and discuss the preliminary results on phase formation, microstructure and adherence evaluations. CVD diamond films were deposited on 304 SS, the surface of which was modified by implanted carbon ions. The samples were first submitted to implantation with 30 keV carbon ions at different doses. Later, these surfaces were examined by Auger spectroscopy (SAM), scanning electron microscopy (SEM) and X-ray diffraction. We observed a metastable carbide phase formed from carbon and iron, which is considered to be a good polycrystalline material for the nucleation of CVD diamond crystals. The CVD diamond nucleation and film growth were observed by SEM and Raman spectroscopy. These results are discussed with the emphasis on the carbon diffusion barrier on the substrate surfaces. The preliminary results of diamond growth were encouraging. (orig.) 7 refs.

Thermoluminescent properties of CVD diamond: applications to ionising radiation dosimetry

International Nuclear Information System (INIS)

Petitfils, A.

2007-09-01

Remarkable properties of synthetic diamond (human soft tissue equivalence, chemical stability, non-toxicity) make this material suitable for medical application as thermoluminescent dosimeter (TLD). This work highlights the interest of this material as radiotherapy TLD. In the first stage of this work, we looked after thermoluminescent (TL) and dosimetric properties of polycrystalline diamond made by Chemically Vapor Deposited (CVD) synthesis. Dosimetric characteristics are satisfactory as TLD for medical application. Luminescence thermal quenching on diamond has been investigated. This phenomenon leads to a decrease of dosimetric TL peak sensitivity when the heating rate increases. The second part of this work analyses the use of synthetic diamond as TLD in radiotherapy. Dose profiles, depth dose distributions and the cartography of an electron beam obtained with our samples are in very good agreement with results from an ionisation chamber. It is clearly shown that CVD) diamond is of interest to check beams of treatment accelerators. The use of these samples in a control of treatment with Intensity Modulated Radiation Therapy underlines good response of synthetic diamond in high dose gradient areas. These results indicate that CVD diamond is a promising material for radiotherapy dosimetry. (author)

Bone repair after osteotomy with diamond burs and CVD ultrasonic tips – histological study in rats

OpenAIRE

Matuda, Fábio S.; Pagani, Clovis; Miranda, Carolina B.; Crema, Aline A. S.; Brentel, Aline S.; Carvalho, Yasmin R.

2010-01-01

This study histologically evaluated the behavior of bone tissue of rats submitted to osteotomy with conventional diamond burs in high speed and a new ultrasonic diamond tips system (CVD – Chemical Vapor Deposition), at different study periods. The study was conducted on 24 Wistar rats. Osteotomy was performed on the posterior paws of each rat, with utilization of diamond burs in high speed under thorough water cooling at the right paw, and CVD tips at the left paw. Animals were killed a...

Electrospray ionization deposition of BSA under vacuum conditions

Science.gov (United States)

Hecker, Dominic; Gloess, Daniel; Frach, Peter; Gerlach, Gerald

2015-05-01

Vacuum deposition techniques like thermal evaporation and CVD with their precise layer control and high layer purity often cannot be applied for the deposition of chemical or biological molecules. The molecules are usually decomposed by heat. To overcome this problem, the Electrospray ionization (ESI) process known from mass spectroscopy is employed to transfer molecules into vacuum and to deposit them on a substrate. In this work, a homemade ESI tool was used to deposit BSA (Bovine serum albumin) layers with high deposition rates. Solutions with different concentrations of BSA were prepared using a methanol:water (MeOH:H2O) mixture (1:1) as solvent. The influence of the substrate distance on the deposition rate and on the transmission current was analyzed. Furthermore, the layer thickness distribution and layer adhesion were investigated.

CVD diamond sensor for UV-photon detection

CERN Document Server

Periale, L; Gervino, G; Lamarina, A M; Palmisano, C; Periale, R; Picchi, P

2012-01-01

A new generation of UV photosensors, based on single crystal Chemical Vapour Deposition (CVD) diamonds to work optically coupled with large volume two-phase liquid-Ar (LAr) or liquid-Xe (LXe) detectors nowadays under design for the next generation of WIMPs experiments, is under development. Preliminary tests and first calibrations show these devices can have better performance than the existing UV sensitive detectors (higher photosensitivity and better signal-to-noise ratio). I-V characteristics, dark current measurements, linearity response to X-ray irradiation, and alpha-particle energy resolution are reported and discussed. (C) 2011 Elsevier B.V. All rights reserved.

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.

The characteristics of photo-CVD SiO{sub 2} and its application on SiC MIS UV photodetectors

Energy Technology Data Exchange (ETDEWEB)

Liu, C.H.; Chang, C.S.; Chang, S.J.; Su, Y.K.; Chiou, Y.Z.; Liu, S.H.; Huang, B.R

2003-07-15

SiO{sub 2} layers were deposited onto SiC by photo-chemical vapor deposition (photo-CVD) using deuterium (D{sub 2}) lamp as the excitation source. For the photo-SiO{sub 2} deposited 500 deg. C, interface state density (D{sub it}) was estimated to be 5.66x10{sup 11} cm{sup -2} eV{sup -1}. With an applied electric field of 4 MV cm{sup -1}, it was found that the leakage current was only 3.15x10{sup -8} A cm{sup -2} for the photo-CVD SiO{sub 2} layer prepared at 500 deg. C. It was also found that photo-SiO{sub 2} could effectively suppress dark current of SiC-based photodetectors (PDs). It was found that we could reduce dark current of SiC-based PDs by about three orders of magnitude by the insertion of a 5 nm-thick photo-CVD SiO{sub 2} film in between Indium-tin-oxide (ITO) contact and the underneath SiC. Photocurrent to dark current ratio of ITO/SiO{sub 2}/SiC MIS PDs was also found to be much larger than that of conventional ITO/SiC Schottky barrier PDs.

The CVD graphene transfer procedure introduces metallic impurities which alter the graphene electrochemical properties.

Science.gov (United States)

Ambrosi, Adriano; Pumera, Martin

2014-01-07

High quality graphene films can be fabricated by chemical vapor deposition (CVD) using Ni and Cu as catalytic substrates. Such a synthesis procedure always requires a subsequent transfer process to be performed in order to eliminate the metallic substrate and transfer the graphene onto the desired surface. We show here that such a transfer process causes significant contamination of the graphene film with residual Fe and Ni metal impurities. Fe contamination derives from the use of Fe-based etching solutions to dissolve Ni (or Cu) substrates, while residual Ni (or Cu) is due to an incomplete metal substrate etching. The presence of these metallic impurities within the transferred graphene film affects tremendously its electrochemical behavior when adopted as an electrode material.

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

Science.gov (United States)

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

2016-03-01

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

CN distribution in flame deposition of diamond and its relation to the growth rate, morphology, and nitrogen incorporation of the diamond layer

NARCIS (Netherlands)

Klein-Douwel, R.J.H.; Schermer, J.J.; Meulen, ter J.J.

1998-01-01

Two-dimensional laser-induced fluorescence (2D-LIF) measurements areapplied to the chemical vapour deposition (CVD) of diamond by anoxyacetylene flame to visualize the distribution of CN in the gas phaseduring the diamond growth process. The obtained diamond deposits arecharacterized by optical as

Electrical characteristics of thermal CVD B-doped Si films on highly strained Si epitaxially grown on Ge(100) by plasma CVD without substrate heating

International Nuclear Information System (INIS)

Sugawara, Katsutoshi; Sakuraba, Masao; Murota, Junichi

2010-01-01

Using an 84% relaxed Ge(100) buffer layer formed on Si(100) by electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (CVD), influence of strain upon electrical characteristics of B-doped Si film epitaxially grown on the Ge buffer have been investigated. For the thinner B-doped Si film, surface strain amount is larger than that of the thicker film, for example, strain amount reaches 2.0% for the thickness of 2.2 nm. It is found that the hole mobility is enhanced by the introduction of strain to Si, and the maximum enhancement of about 3 is obtained. This value is higher than that of the usually reported mobility enhancement by strain using Si 1 -x Ge x buffer. Therefore, introduction of strain using relaxed Ge film formed by ECR plasma enhanced CVD is useful to improve future Si-based device performance.

Preparation of textured high Tc superconducting films by CVD using halides on technical substrates with appropriate buffer layers. Final report

International Nuclear Information System (INIS)

Selbmann, D.; Balarin, M.; Klosowski, J.

1993-01-01

On the basis of a thermodynamical calculation of the system Y-Ba-Cu-O-Hal-C-H, Hal = I, Br, Cl the deposition conditions of the 123-phase and the other phases in this system was investigated. For the practical applications a reaction temperature higher 850 C and an oxidizer excesse higher 5 . 10 3 is necessary in order to deposit halid- and carbon free layers. A new Aerosol-CVD-process has been developed, which allows the reproducible preparation of superconducting YBa 2 Cu 3 O 7 thin films. The process uses a solution source of Y-, Ba-, Cu-bromide dissolved in suitable organic solvents. With the process the films consisting of the 123-phase, however the content of other phases is too high. With this composition it is not possible to deposit textured layers. This behaviour is due to flow technical problems. In order to avoid the formation of oxides in the evaporator it is necessary to mix the oxidizer directly near the substrate. Therefore the development of a new reactor and a process optimization is necessary. (orig.) [de

The effectiveness of Ti implants as barriers to carbon diffusion in Ti implanted steel under CVD diamond deposition conditions

Energy Technology Data Exchange (ETDEWEB)

Weiser, P.S.; Prawer, S. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Hoffman, A. [Technion-Israel Inst. of Tech., Haifa (Israel). Dept. of Chemistry; Evan, P.J. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia); Paterson, P.J.K. [Royal Melbourne Inst. of Tech., VIC (Australia)

1993-12-31

The growth of chemical vapour deposited (CVD) diamond onto iron based substrates complicated by preferential soot formation and carbon diffusion into the substrate [1], leading to poor quality films and poor adhesion. In the initial stages of exposure to a microwave plasma, a layer of graphite is rapidly formed on an untreated Fe based substrate. Once this graphite layer reaches a certain thickness, reasonable quality diamond nucleates and grows upon it. However, the diamond film easily delaminates from the substrate, the weak link being the graphitic layer. Following an initial success in using a TiN barrier layer to inhibit the formation of such a graphitic layer the authors report on attempts to use an implanted Ti layer for the same purpose. This work was prompted by observation that, although the TiN proved to be an extremely effective diffusion barrier, adhesion may be further enhanced by the formation of a TiC interface layer between the diamond film and the Fe substrate. 3 refs., 6 figs.

The effectiveness of Ti implants as barriers to carbon diffusion in Ti implanted steel under CVD diamond deposition conditions

International Nuclear Information System (INIS)

Weiser, P.S.; Prawer, S.; Paterson, P.J.K.

1993-01-01

The growth of chemical vapour deposited (CVD) diamond onto iron based substrates complicated by preferential soot formation and carbon diffusion into the substrate [1], leading to poor quality films and poor adhesion. In the initial stages of exposure to a microwave plasma, a layer of graphite is rapidly formed on an untreated Fe based substrate. Once this graphite layer reaches a certain thickness, reasonable quality diamond nucleates and grows upon it. However, the diamond film easily delaminates from the substrate, the weak link being the graphitic layer. Following an initial success in using a TiN barrier layer to inhibit the formation of such a graphitic layer the authors report on attempts to use an implanted Ti layer for the same purpose. This work was prompted by observation that, although the TiN proved to be an extremely effective diffusion barrier, adhesion may be further enhanced by the formation of a TiC interface layer between the diamond film and the Fe substrate. 3 refs., 6 figs

The effectiveness of Ti implants as barriers to carbon diffusion in Ti implanted steel under CVD diamond deposition conditions

Energy Technology Data Exchange (ETDEWEB)

Weiser, P S; Prawer, S [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Hoffman, A [Technion-Israel Inst. of Tech., Haifa (Israel). Dept. of Chemistry; Evan, P J [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia); Paterson, P J.K. [Royal Melbourne Inst. of Tech., VIC (Australia)

1994-12-31

The growth of chemical vapour deposited (CVD) diamond onto iron based substrates complicated by preferential soot formation and carbon diffusion into the substrate [1], leading to poor quality films and poor adhesion. In the initial stages of exposure to a microwave plasma, a layer of graphite is rapidly formed on an untreated Fe based substrate. Once this graphite layer reaches a certain thickness, reasonable quality diamond nucleates and grows upon it. However, the diamond film easily delaminates from the substrate, the weak link being the graphitic layer. Following an initial success in using a TiN barrier layer to inhibit the formation of such a graphitic layer the authors report on attempts to use an implanted Ti layer for the same purpose. This work was prompted by observation that, although the TiN proved to be an extremely effective diffusion barrier, adhesion may be further enhanced by the formation of a TiC interface layer between the diamond film and the Fe substrate. 3 refs., 6 figs.

Surface modification of pitch-based spherical activated carbon by CVD of NH{sub 3} to improve its adsorption to uric acid

Energy Technology Data Exchange (ETDEWEB)

Liu Chaojun [State Key Laboratory of Chemical Engineering, East China University of Science and Technology (ECUST), Shanghai 200237 (China); Liang Xiaoyi [State Key Laboratory of Chemical Engineering, East China University of Science and Technology (ECUST), Shanghai 200237 (China)], E-mail: xyliang@ecust.edu.cn; Liu Xiaojun; Wang Qin; Zhan Liang; Zhang Rui; Qiao Wenming; Ling Licheng [State Key Laboratory of Chemical Engineering, East China University of Science and Technology (ECUST), Shanghai 200237 (China)

2008-08-30

Surface chemistry of pitch-based spherical activated carbon (PSAC) was modified by chemical vapor deposition of NH{sub 3} (NH{sub 3}-CVD) to improve the adsorption properties of uric acid. The texture and surface chemistry of PSAC were studied by N{sub 2} adsorption, pH{sub PZC} (point of zero charge), acid-base titration and X-ray photoelectron spectroscopy (XPS). NH{sub 3}-CVD has a limited effect on carbon textural characteristics but it significantly changed the surface chemical properties, resulting in positive effects on uric acid adsorption. After modification by NH{sub 3}-CVD, large numbers of nitrogen-containing groups (especially valley-N and center-N) are introduced on the surface of PSAC, which is responsible for the increase of pH{sub PZC}, surface basicity and uric acid adsorption capacity. Pseudo-second-order kinetic model can be used to describe the dynamic adsorption of uric acid on PSAC, and the thermodynamic parameters show that the adsorption of uric acid on PSAC is spontaneous, endothermic and irreversible process in nature.

Thermal Analysis of Cold Vacuum Drying (CVD) of Spent Nuclear Fuel (SNF)

International Nuclear Information System (INIS)

PIEPHO, M.G.

2000-01-01

The thermal analysis examined transient thermal and chemical behavior of the Multi-Canister Overpack (MCO) container for a broad range of cases that represent the Cold Vacuum Drying (CVD) processes. The cases were defined to consider both normal and off-normal operations at the CVD Facility for an MCO with N Reactor spent fuel. This analysis provides the basis for the MCO thermal behavior at the CVD Facility in support of the safety basis documentation

Clean and polymer-free transfer of CVD-grown graphene films on hexagonal boron nitride substrates

Science.gov (United States)

Fujihara, Miho; Ogawa, Shun; Yoshimura, Shintaro; Inoue, Ryosuke; Maniwa, Yutaka; Taniguchi, Takashi; Watanabe, Kenji; Shinohara, Hisanori; Miyata, Yasumitsu

2017-05-01

This report describes the development of a solution-assisted, polymer-free transfer method and the characterization of chemical vapor deposition (CVD)-grown graphene on hexagonal boron nitride. Raman analysis reveals that polymer-free samples have small variations in G- and 2D-mode Raman frequencies and are minimally affected by charge doping as observed for clean exfoliated graphene. Electrical measurements indicate that charge doping, hysteresis, and carrier scattering are suppressed in polymer-free samples. The results demonstrate that this method provides a simple and effective way to prepare clean heterostructures of CVD-grown, large-area graphene and other two-dimensional materials.

A comparative study of the thermoluminescent response to beta irradiation of CVD diamond and LiF dosimeters

Energy Technology Data Exchange (ETDEWEB)

Bogani, F. [Florence Univ. (Italy). Dipt. di Energetica; Borchi, E. [Florence Univ. (Italy). Dipt. di Energetica; Bruzzi, M. [Florence Univ. (Italy). Dipt. di Energetica; Leroy, C. [Florence Univ. (Italy). Dipt. di Energetica; Sciortino, S. [Florence Univ. (Italy). Dipt. di Energetica

1997-04-01

The thermoluminescent (TL) response of chemical vapour deposited (CVD) diamond films to beta irradiation has been investigated. A numerical curve-fitting procedure, calibrated by means of a set of LiF TLD100 experimental spectra, has been developed to deconvolute the complex structured TL glow curves. The values of the activation energy and of the frequency factor related to each of the TL peaks involved have been determined. The TL response of the CVD diamond films to beta irradiation has been compared with the TL response of a set of LiF TLD100 and TLD700 dosimeters. The results have been discussed and compared in view of an assessment of the efficiency of CVD diamond films in future applications as in vivo dosimeters. (orig.).

A comparative study of the thermoluminescent response to beta irradiation of CVD diamond and LiF dosimeters

Science.gov (United States)

Bogani, F.; Borchi, E.; Bruzzi, M.; Leroy, C.; Sciortino, S.

1997-02-01

The thermoluminescent (TL) response of Chemical Vapour Deposited (CVD) diamond films to beta irradiation has been investigated. A numerical curve-fitting procedure, calibrated by means of a set of LiF TLD100 experimental spectra, has been developed to deconvolute the complex structured TL glow curves. The values of the activation energy and of the frequency factor related to each of the TL peaks involved have been determined. The TL response of the CVD diamond films to beta irradiation has been compared with the TL response of a set of LiF TLD100 and TLD700 dosimeters. The results have been discussed and compared in view of an assessment of the efficiency of CVD diamond films in future applications as in vivo dosimeters.

A comparative study of the thermoluminescent response to beta irradiation of CVD diamond and LiF dosimeters

International Nuclear Information System (INIS)

Bogani, F.; Borchi, E.; Bruzzi, M.; Leroy, C.; Sciortino, S.

1997-01-01

The thermoluminescent (TL) response of chemical vapour deposited (CVD) diamond films to beta irradiation has been investigated. A numerical curve-fitting procedure, calibrated by means of a set of LiF TLD100 experimental spectra, has been developed to deconvolute the complex structured TL glow curves. The values of the activation energy and of the frequency factor related to each of the TL peaks involved have been determined. The TL response of the CVD diamond films to beta irradiation has been compared with the TL response of a set of LiF TLD100 and TLD700 dosimeters. The results have been discussed and compared in view of an assessment of the efficiency of CVD diamond films in future applications as in vivo dosimeters. (orig.)

Growth of GaN on SiC/Si substrates using AlN buffer layer by hot-mesh CVD

International Nuclear Information System (INIS)

Tamura, Kazuyuki; Kuroki, Yuichiro; Yasui, Kanji; Suemitsu, Maki; Ito, Takashi; Endou, Tetsuro; Nakazawa, Hideki; Narita, Yuzuru; Takata, Masasuke; Akahane, Tadashi

2008-01-01

GaN films were grown on SiC/Si (111) substrates by hot-mesh chemical vapor deposition (CVD) using ammonia (NH 3 ) and trimetylgallium (TMG) under low V/III source gas ratio (NH 3 /TMG = 80). The SiC layer was grown by a carbonization process on the Si substrates using propane (C 3 H 8 ). The AlN layer was deposited as a buffer layer using NH 3 and trimetylaluminum (TMA). GaN films were formed and grown by the reaction between NH x radicals, generated on a tungsten hot mesh, and the TMG molecules. The GaN films with the AlN buffer layer showed better crystallinity and stronger near-band-edge emission compared to those without the AlN layer

Electrical and optical performance of transparent conducting oxide films deposited by electrostatic spray assisted vapour deposition.

Science.gov (United States)

Hou, Xianghui; Choy, Kwang-Leong; Liu, Jun-Peng

2011-09-01

Transparent conducting oxide (TCO) films have the remarkable combination of high electrical conductivity and optical transparency. There is always a strong motivation to produce TCO films with good performance at low cost. Electrostatic Spray Assisted Vapor Deposition (ESAVD), as a variant of chemical vapour deposition (CVD), is a non-vacuum and low-cost deposition method. Several types of TCO films have been deposited using ESAVD process, including indium tin oxide (ITO), antimony-doped tin oxide (ATO), and fluorine doped tin oxide (FTO). This paper reports the electrical and optical properties of TCO films produced by ESAVD methods, as well as the effects of post treatment by plasma hydrogenation on these TCO films. The possible mechanisms involved during plasma hydrogenation of TCO films are also discussed. Reduction and etching effect during plasma hydrogenation are the most important factors which determine the optical and electrical performance of TCO films.

Ion beam induced surface graphitization of CVD diamond for x-ray beam position monitor applications

International Nuclear Information System (INIS)

Liu, Chian; Shu, D.; Kuzay, T.M.; Wen, L.; Melendres, C.A.; Argonne National Lab., IL

1996-01-01

The Advanced Photon Source at ANL is a third-generation synchrotron facility that generates powerful x-ray beams on its undulator beamlines. It is important to know the position and angle of the x- ray beam during experiments. Due to very high heat flux levels, several patented x-ray beam position monitors (XBPM) exploiting chemical vapor deposition (CVD) diamond have been developed. These XBPMs have a thin layer of low-atomic-mass metallic coating so that photoemission from the x rays generate a minute but measurable current for position determination. Graphitization of the CVD diamond surface creates a very thin, intrinsic and conducting layer that can stand much higher temperatures and minimal x-ray transmission losses compared to the coated metallic layers. In this paper, a laboratory sputter ion source was used to transform selected surfaces of a CVD diamond substrate into graphite. The effect of 1-5 keV argon ion bombardment on CVD diamond surfaces at various target temperatures from 200 to 500 C was studied using Auger electron spectroscopy and in-situ electrical resistivity measurements. Graphitization after the ion bombardment has been confirmed and optimum conditions for graphitization studied. Raman spectroscopy was used to identify the overall diamond structure in the bulk of CVD diamond substrate after the ion bombardments. It was found that target temperature plays an important role in stability and electrical conductivity of the irradiated CVD diamonds

Induction surface hardening of hard coated steels

DEFF Research Database (Denmark)

Pantleon, Karen; Kessler, Olaf; Hoffmann, Franz

1999-01-01

The deposition of hard coatings with CVD-processes is commonly used to improve the wear resistance e.g. of tool steels in forming. The advantages of CVD are undisputed (high deposition rates with simple equipment, excellent coating properties). Nevertheless, the disadvantage of the CVD-process is......The deposition of hard coatings with CVD-processes is commonly used to improve the wear resistance e.g. of tool steels in forming. The advantages of CVD are undisputed (high deposition rates with simple equipment, excellent coating properties). Nevertheless, the disadvantage of the CVD...

Surface photo reaction processes using synchrotron radiation; Hoshako reiki ni yoru hyomenko hanno process

Energy Technology Data Exchange (ETDEWEB)

Imaizumi, Y. [Tohoku University, Sendai (Japan). Institute for Materials Research; Yoshigoe, A. [Toyohashi University of Technology, Aichi (Japan); Urisu, T. [Toyohashi University of Technology, Aichi (Japan). Institute for Molecular Science

1997-08-20

This paper introduces the surface photo reaction processes using synchrotron radiation, and its application. A synchrotron radiation process using soft X-rays contained in electron synchrotron radiated light as an excited light source has a possibility of high-resolution processing because of its short wave length. The radiated light can excite efficiently the electronic state of a substance, and can induce a variety of photochemical reactions. In addition, it can excite inner shell electrons efficiently. In the aspect of its application, it has been found that, if radiated light is irradiated on surfaces of solids under fluorine-based reaction gas or Cl2, the surfaces can be etched. This technology is utilized practically. With regard to radiated light excited CVD process, it may be said that anything that can be deposited by the ordinary plasma CVD process can be deposited. Its application to epitaxial crystal growth may be said a nano processing application in thickness direction, such as forming an ultra-lattice structure, the application being subjected to expectation. In micromachine fabricating technologies, a possibility is searched on application of a photo reaction process of the radiated light. 5 refs., 6 figs.

D.C. Arcjet Diamond Deposition

Science.gov (United States)

Russell, Derrek Andrew

1995-01-01

Polycrystalline diamond films synthesized by a D.C. (direct current) arcjet device was reported for the first time in 1988. This device is capable of higher diamond growth rates than any other form of diamond CVD (chemical vapor deposition) process due to its inherent versatility with regard to the enthalpy and fluid properties of the diamond-depositing vapor. Unfortunately, the versatility of this type of device is contrasted by many difficulties such as arc stability and large heat fluxes which make applying it toward diamond deposition a difficult problem. The purpose of this work was to convert the dc arcjet, which is primarily a metallurgical device, into a commercially viable diamond CVD process. The project was divided into two parts: process development and diagnostics. The process development effort concentrated on the certain engineering challenges. Among these was a novel arcjet design that allowed the carbon-source gas to be injected downstream of the tungsten cathode while still facilitating mixture with the main gas feed. Another engineering accomplishment was the incorporation of a water -cooled substrate cooler/spinner that maintained the substrate at the proper temperature, provided the substrate with a large thermal time constant to reduce thermal shock of the diamond film, and enabled the system to achieve a four -inch diameter growth area. The process diagnostics effort concentrated on measurements aimed at developing a fundamental understanding of the properties of the plasma jet such as temperature, plasma density, Mach number, pressure at the substrate, etc. The plasma temperature was determined to be 5195 K by measuring the rotational temperature of C _2 via optical emission spectroscopy. The Mach number of the plasma jet was determined to be ~6.0 as determined by the ratio of the stagnation pressures before and after the shock wave in the plasma jet. The C_2 concentration in the plasma jet was determined to be {~10 }^{12} cm^ {-3} by

Hexagonal Boron Nitride assisted transfer and encapsulation of large area CVD graphene

Science.gov (United States)

Shautsova, Viktoryia; Gilbertson, Adam M.; Black, Nicola C. G.; Maier, Stefan A.; Cohen, Lesley F.

2016-07-01

We report a CVD hexagonal boron nitride (hBN-) assisted transfer method that enables a polymer-impurity free transfer process and subsequent top encapsulation of large-area CVD-grown graphene. We demonstrate that the CVD hBN layer that is utilized in this transfer technique acts as a buffer layer between the graphene film and supporting polymer layer. We show that the resulting graphene layers possess lower doping concentration, and improved carrier mobilities compared to graphene films produced by conventional transfer methods onto untreated SiO2/Si, SAM-modified and hBN covered SiO2/Si substrates. Moreover, we show that the top hBN layer used in the transfer process acts as an effective top encapsulation resulting in improved stability to ambient exposure. The transfer method is applicable to other CVD-grown 2D materials on copper foils, thereby facilitating the preparation of van der Waals heterostructures with controlled doping.

A study of the thermoluminescent properties of CVD diamond detectors

International Nuclear Information System (INIS)

Marczewska, B.; Bilski, P.; Olko, P.; Rebisz, M.; Nesladek, M.; Waligorski, M.P.R.

2002-01-01

A batch of 20 diamond detectors obtained by the chemical vapour deposition (CVD) method at the Institute for Materials Research at the Limburg University, Belgium, was investigated with respect to their thermoluminescent (TL) properties. The investigated detectors demonstrate TL sensitivity similar to that of the standard LiF:Mg, Ti (MTS) thermoluminescent detectors, lack of fading after two weeks from irradiation and apparent linearity of dose response. In spite of the persistent fluctuation of individual detector sensitivity observed in this batch, a new annealing procedure improved the stability of the TL signal. It has been concluded that 1 h annealing at 350 C assures the highest reproducibility for this set of detectors. A 30% discrepancy of the value of the TL signal between individual detectors from the batch may be caused by non-uniform distribution of dopants in the volume of the CVD diamond. A prototype of a planar TL reader equipped with a CCD camera was employed in this investigation. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

Stress analysis of CVD diamond window for ECH system

International Nuclear Information System (INIS)

Takahashi, Koji

2001-03-01

The stress analysis of a chemical vapor deposition (CVD) diamond window for Electron Cyclotron Heating and Current Drive (ECH/ECCD) system of fusion reactors is described. It was found that the real size diamond window (φ aper =70mm, t=2.25mm) withstood 14.5 atm. (1.45 MPa). The calculation results of the diamond window by ABAQUS code agree well with the results of the pressure test. The design parameters of the torus diamond window for a vacuum and a safety barrier were also obtained. (author)

CVD diamond Brewster window: feasibility study by FEM analyses

Directory of Open Access Journals (Sweden)

Vaccaro A.

2012-09-01

Full Text Available Chemical vapor deposition (CVD diamond windows are a crucial component in heating and current drive (H&CD applications. In order to minimize the amount of reflected power from the diamond disc, its thickness must match the desired beam wavelength, thus proper targeting of the plasma requires movable beam reflectors. This is the case, for instance, of the ITER electron cyclotron H&CD system. However, looking at DEMO, the higher heat loads and neutron fluxes could make the use of movable parts close to the plasma difficult. The issue might be solved by using gyrotrons able to tune the beam frequency to the desired resonance, but this concept requires transmission windows that work in a given frequency range, such as the Brewster window. It consists of a CVD diamond disc brazed to two copper cuffs at the Brewster angle. The brazing process is carried out at about 800°C and then the temperature is decreased down to room temperature. Diamond and copper have very different thermal expansion coefficients, therefore high stresses build up during the cool down phase that might lead to failure of the disc. Considering also the complex geometry of the window with the skewed position of the disc, analyses are required in the first place to check its feasibility. The cool down phase was simulated by FEM structural analyses for several geometric and constraint configurations of the window. A study of indirect cooling of the window by water was also performed considering a HE11 mode beam. The results are here reported.

Characteristics of CVD graphene nanoribbon formed by a ZnO nanowire hardmask

Energy Technology Data Exchange (ETDEWEB)

Kang, Chang Goo; Kang, Jang Won; Lee, Seung Yong; Hwang, Hyeon Jun; Lee, Young Gon; Park, Seong-Ju; Lee, Byoung Hun [School of Material Science and Engineering, Gwangju Institute of Science and Technology, Oryong-dong 1, Buk-gu, Gwangju, 500-712 (Korea, Republic of); Lee, Sang Kyung; Cho, Chun Hum [Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Oryong-dong 1, Buk-gu, Gwangju, 500-712 (Korea, Republic of); Heo, Jinseong; Chung, Hyun-Jong; Yang, Heejun [Semiconductor Devices Lab, Samsung Advanced Institute of Technology, Yongin (Korea, Republic of); Seo, Sunae [Department of Physics, Sejong University, Gunja-Dong, Kwanggin-gu, Seoul (Korea, Republic of); Ko, Ki Young; Ahn, Jinho, E-mail: bhl@gist.ac.kr [Division of Materials Science and Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791 (Korea, Republic of)

2011-07-22

A graphene nanoribbon (GNR) is an important basic structure to open a bandgap in graphene. The GNR processes reported in the literature are complex, time-consuming, and expensive; moreover, the device yield is relatively low. In this paper, a simple new process to fabricate a long and straight graphene nanoribbon with a high yield has been proposed. This process utilizes CVD graphene substrate and a ZnO nanowire as the hardmask for patterning. 8 {mu}m long and 50-100 nm wide GNRs were successfully demonstrated in high density without any trimming, and {approx} 10% device yield was realized with a top-down patterning process. After passivating the surfaces of the GNRs using a low temperature atomic layer deposition (ALD) of Al{sub 2}O{sub 3}, high performance GNR MOSFETs with symmetric drain-current-gate-voltage (I{sub d}-V{sub g}) curves were demonstrated and a field effect mobility up to {approx} 1200 cm{sup 2} V{sup -1} s{sup -1} was achieved at V{sub d} = 10 mV.

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.

Investigation of the nucleation process of chemical vapour deposited diamond films

International Nuclear Information System (INIS)

Katai, S.

2001-01-01

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

Growth of Ge films by cluster beam deposition

CERN Document Server

Xu, J L; Feng, J Y

2002-01-01

Ge epitaxial layers with reasonable quality were grown on the Si(1 1 1) substrates by cluster beam deposition (CBD) process. The growth temperature plays a dominant role in the epitaxial growth of Ge films. The substrate temperature for epitaxial growth is about 500 deg. C, which is lower than the reported critical temperature of Ge epitaxial growth by MBE and CVD. A stress induced phase transition of Ge lattice from cubic to tetragonal is also observed in the CBD process, and the mechanism is discussed.

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

Synthesis and characterization of hafnium carbide microcrystal chains with a carbon-rich shell via CVD

International Nuclear Information System (INIS)

Tian, Song; Li, Hejun; Zhang, Yulei; Liu, Sen; Fu, Yangxi; Li, Yixian; Qiang, Xinfa

2013-01-01

Graphical abstract: Novel HfC microcrystal chains have been synthesized via a catalyst-assisted chemical vapor deposition process. SEM results show the chains have a periodically changing diameter and a nanoscale sharpening tip. Analysis of TEM/SAED/EELS/EDX data shows the single-crystal chains grow along a [0 0 1] direction and consist of a HfC core and a thin carbon-rich shell with embedded HfC nanocrystallites surrounding the core. This work achieves the controllable preparation of nanoscale HfC sharpening tips for application as a point electron emission source and facilitates the application of HfC ultrafast laser-triggered tips in attosecond science. Highlights: •HfC microcrystal chains were synthesized by a catalyst-assisted CVD. •The chains grow along a [0 0 1] direction and have a periodically changing diameter. •Single-crystal HfC core is sheathed by a thin carbon-rich shell. •A growth mechanism model is proposed to explain the growth of microcrystal chians. •This work achieves the controllable preparation of nanoscale HfC sharpening tips. -- Abstract: Novel hafnium carbide (HfC) microcrystal chains, with a periodically changing diameter and a nanoscale sharpening tip at the chain end, have been synthesized via a catalyst-assisted chemical vapor deposition (CVD) process. The as-synthesized chains with many octahedral microcrystals have diameters of between several hundreds of nm and 6 μm and lengths of ∼500 μm. TEM diffraction studies show that the chains are single-crystalline HfC and preferentially grow along a [0 0 1] crystal orientation. TEM/EELS/EDX analysis proves the chains are composed of a HfC core and a thin (several tens of nm to 100 nm) carbon-rich shell with the embedded HfC nanocrystallites (typically below 10 nm) surrounding the core. The growth mechanism model for the chains based on the vapor–liquid–solid process, the vapor–solid process, and the HfC crystal growth characteristics is discussed

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

Growth of GaN on SiC/Si substrates using AlN buffer layer by hot-mesh CVD

Energy Technology Data Exchange (ETDEWEB)

Tamura, Kazuyuki [Nagaoka University of Technology, Nagaoka 940-2188 (Japan)], E-mail: kazuyuki@stn.nagaokaut.ac.jp; Kuroki, Yuichiro; Yasui, Kanji [Nagaoka University of Technology, Nagaoka 940-2188 (Japan); Suemitsu, Maki; Ito, Takashi [Center of Interdisciplinary Research, Tohoku University, Sendai 980-8578 (Japan); Endou, Tetsuro [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Nakazawa, Hideki [Faculty of Science and Technology, Hirosaki University, Hirosaki 036-8561 (Japan); Narita, Yuzuru [Center of Interdisciplinary Research, Tohoku University, Sendai 980-8578 (Japan); Takata, Masasuke; Akahane, Tadashi [Nagaoka University of Technology, Nagaoka 940-2188 (Japan)

2008-01-15

GaN films were grown on SiC/Si (111) substrates by hot-mesh chemical vapor deposition (CVD) using ammonia (NH{sub 3}) and trimetylgallium (TMG) under low V/III source gas ratio (NH{sub 3}/TMG = 80). The SiC layer was grown by a carbonization process on the Si substrates using propane (C{sub 3}H{sub 8}). The AlN layer was deposited as a buffer layer using NH{sub 3} and trimetylaluminum (TMA). GaN films were formed and grown by the reaction between NH{sub x} radicals, generated on a tungsten hot mesh, and the TMG molecules. The GaN films with the AlN buffer layer showed better crystallinity and stronger near-band-edge emission compared to those without the AlN layer.

Probing the Gas-Phase Dynamics of Graphene Chemical Vapour Deposition using in-situ UV Absorption Spectroscopy

DEFF Research Database (Denmark)

Shivayogimath, Abhay; Mackenzie, David; Luo, Birong

2017-01-01

The processes governing multilayer nucleation in the chemical vapour deposition (CVD) of graphene are important for obtaining high-quality monolayer sheets, but remain poorly understood. Here we show that higher-order carbon species in the gas-phase play a major role in multilayer nucleation...

Control of Reaction Surface in Low Temperature CVD to Enhance Nucleation and Conformal Coverage

Science.gov (United States)

Kumar, Navneet

2009-01-01

The Holy Grail in CVD community is to find precursors that can afford the following: good nucleation on a desired substrate and conformal deposition in high AR features. Good nucleation is not only necessary for getting ultra-thin films at low thicknesses; it also offers films that are smooth at higher thickness values. On the other hand,…

Prediction of the properties of PVD/CVD coatings with the use of FEM analysis

International Nuclear Information System (INIS)

Śliwa, Agata; Mikuła, Jarosław; Gołombek, Klaudiusz; Tański, Tomasz; Kwaśny, Waldemar; Bonek, Mirosław; Brytan, Zbigniew

2016-01-01

Highlights: • Prediction of the properties of PVD/CVD coatings with the use of (FEM) analysis. • Stress distribution in multilayer Ti/Ti(C,N)/CrN, Ti/Ti(C,N)/(Ti,Al)N coatings. • The experimental values of stresses were determined on X-ray diffraction patterns. • An FEM model was established for the purpose of building a computer simulation. - Abstract: The aim of this paper is to present the results of the prediction of the properties of PVD/CVD coatings with the use of finite element method (FEM) analysis. The possibility of employing the FEM in the evaluation of stress distribution in multilayer Ti/Ti(C,N)/CrN, Ti/Ti(C,N)/(Ti,Al)N, Ti/(Ti,Si)N/(Ti,Si)N, and Ti/DLC/DLC coatings by taking into account their deposition conditions on magnesium alloys has been discussed in the paper. The difference in internal stresses in the zone between the coating and the substrate is caused by, first of all, the difference between the mechanical and thermal properties of the substrate and the coating, and also by the structural changes that occur in these materials during the fabrication process, especially during the cooling process following PVD and CVD treatment. The experimental values of stresses were determined based on X-ray diffraction patterns that correspond to the modelled values, which in turn can be used to confirm the correctness of the accepted mathematical model for testing the problem. An FEM model was established for the purpose of building a computer simulation of the internal stresses in the coatings. The accuracy of the FEM model was verified by comparing the results of the computer simulation of the stresses with experimental results. A computer simulation of the stresses was carried out in the ANSYS environment using the FEM method. Structure observations, chemical composition measurements, and mechanical property characterisations of the investigated materials has been carried out to give a background for the discussion of the results that were

Prediction of the properties of PVD/CVD coatings with the use of FEM analysis

Energy Technology Data Exchange (ETDEWEB)

Śliwa, Agata; Mikuła, Jarosław; Gołombek, Klaudiusz; Tański, Tomasz; Kwaśny, Waldemar; Bonek, Mirosław, E-mail: miroslaw.bonek@polsl.pl; Brytan, Zbigniew

2016-12-01

Highlights: • Prediction of the properties of PVD/CVD coatings with the use of (FEM) analysis. • Stress distribution in multilayer Ti/Ti(C,N)/CrN, Ti/Ti(C,N)/(Ti,Al)N coatings. • The experimental values of stresses were determined on X-ray diffraction patterns. • An FEM model was established for the purpose of building a computer simulation. - Abstract: The aim of this paper is to present the results of the prediction of the properties of PVD/CVD coatings with the use of finite element method (FEM) analysis. The possibility of employing the FEM in the evaluation of stress distribution in multilayer Ti/Ti(C,N)/CrN, Ti/Ti(C,N)/(Ti,Al)N, Ti/(Ti,Si)N/(Ti,Si)N, and Ti/DLC/DLC coatings by taking into account their deposition conditions on magnesium alloys has been discussed in the paper. The difference in internal stresses in the zone between the coating and the substrate is caused by, first of all, the difference between the mechanical and thermal properties of the substrate and the coating, and also by the structural changes that occur in these materials during the fabrication process, especially during the cooling process following PVD and CVD treatment. The experimental values of stresses were determined based on X-ray diffraction patterns that correspond to the modelled values, which in turn can be used to confirm the correctness of the accepted mathematical model for testing the problem. An FEM model was established for the purpose of building a computer simulation of the internal stresses in the coatings. The accuracy of the FEM model was verified by comparing the results of the computer simulation of the stresses with experimental results. A computer simulation of the stresses was carried out in the ANSYS environment using the FEM method. Structure observations, chemical composition measurements, and mechanical property characterisations of the investigated materials has been carried out to give a background for the discussion of the results that were

Hot-wire chemical vapour deposition of carbon nanotubes

CSIR Research Space (South Africa)

Cummings, FR

2006-07-01

Full Text Available ablation of graphite, carbon-arc discharge and chemical vapour deposition (CVD). However, some of these techniques have been shown to be expensive due to high deposition temperatures and are not easily controllable. Recently hot-wire chemical vapour...

Ethylene Gas Sensing Properties of Tin Oxide Nanowires Synthesized via CVD Method

Science.gov (United States)

Akhir, Maisara A. M.; Mohamed, Khairudin; Rezan, Sheikh A.; Arafat, M. M.; Haseeb, A. S. M. A.; Uda, M. N. A.; Nuradibah, M. A.

2018-03-01

This paper studies ethylene gas sensing performance of tin oxide (SnO2) nanowires (NWs) as sensing material synthesized using chemical vapor deposition (CVD) technique. The effect of NWs diameter on ethylene gas sensing characteristics were investigated. SnO2 NWs with diameter of ∼40 and ∼240 nm were deposited onto the alumina substrate with printed gold electrodes and tested for sensing characteristic toward ethylene gas. From the finding, the smallest diameter of NWs (42 nm) exhibit fast response and recovery time and higher sensitivity compared to largest diameter of NWs (∼240 nm). Both sensor show good reversibility features for ethylene gas sensor.

Turbostratic stacked CVD graphene for high-performance devices

Science.gov (United States)

Uemura, Kohei; Ikuta, Takashi; Maehashi, Kenzo

2018-03-01

We have fabricated turbostratic stacked graphene with high-transport properties by the repeated transfer of CVD monolayer graphene. The turbostratic stacked CVD graphene exhibited higher carrier mobility and conductivity than CVD monolayer graphene. The electron mobility for the three-layer turbostratic stacked CVD graphene surpassed 10,000 cm2 V-1 s-1 at room temperature, which is five times greater than that for CVD monolayer graphene. The results indicate that the high performance is derived from maintenance of the linear band dispersion, suppression of the carrier scattering, and parallel conduction. Therefore, turbostratic stacked CVD graphene is a superior material for high-performance devices.

Fabrication of Vertically Aligned CNT Composite for Membrane Applications Using Chemical Vapor Deposition through In Situ Polymerization

Directory of Open Access Journals (Sweden)

Munir Mohammad

2013-01-01

Full Text Available We report the fabrication of vertically aligned carbon nanotubes (CNT composite using thermal chemical vapor deposition (CVD. A forest of vertically aligned CNTs was grown using catalytic CVD. Fluorocarbon polymer, films were deposited in the spaces between vertically aligned MWCNTs using thermal CVD apparatus developed in-house. The excessive polymer top layer was etched by exposing the sample to water plasma. Infrared spectroscopy confirmed the attachment of functional groups to CNTs. Alignment of CNTs, deposition of polymer and postetched specimens were analyzed by field emission scanning electron microscope (FE-SEM. Uniform distribution of monomodel vertically aligned CNTs embedded in the deposited polymer matrix was observed in the micrograph. Observed uniform distribution otherwise is not possible using conventional techniques such as spin coating.

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.

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.

Immobilization of glucoamylase on ceramic membrane surfaces modified with a new method of treatment utilizing SPCP-CVD.

Science.gov (United States)

Ida; Matsuyama; Yamamoto

2000-07-01

Glucoamylase, as a model enzyme, was immobilized on a ceramic membrane modified by surface corona discharge induced plasma chemical process-chemical vapor deposition (SPCP-CVD). Characterizations of the immobilized enzyme were then discussed. Three kinds of ceramic membranes with different amounts of amino groups on the surface were prepared utilizing the SPCP-CVD method. Each with 1-time, 3-times and 5-times surface modification treatments and used for supports in glucoamylase immobilization. The amount of immobilized glucoamylase increased with the increase in the number of surface modification treatments and saturated to a certain maximum value estimated by a two-dimensional random packing. The operational stability of the immobilized glucoamylase also increased with the increase in the number of the surface treatment. It was almost the same as the conventional method, while the activity of immobilized enzyme was higher. The results indicated the possibility of designing the performance of the immobilized enzyme by controlling the amount of amino groups. The above results showed that the completely new surface modification method using SPCP was effective in modifying ceramic membranes for enzyme immobilization.

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

Directory of Open Access Journals (Sweden)

Betty T. Quinton

2013-01-01

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

Deposition and Characterization of Thin Films on Metallic Substrates

Science.gov (United States)

Gatica, Jorge E.

2005-01-01

A CVD method was successfully developed to produce conversion coatings on aluminum alloys surfaces with reproducible results with a variety of precursors. A well defined protocol to prepare the precursor solutions formulated in a previous research was extended to other additives. It was demonstrated that solutions prepared following such a protocol could be used to systematically generate protective coatings onto aluminum surfaces. Experiments with a variety of formulations revealed that a refined deposition protocol yields reproducible conversion coatings of controlled composition. A preliminary correlation between solution formulations and successful precursors was derived. Coatings were tested for adhesion properties enhancement for commercial paints. A standard testing method was followed and clear trends were identified. Only one precursors was tested systematically. Anticipated work on other precursors should allow a better characterization of the effect of intermetallics on the production of conversion/protective coatings on metals and ceramics. The significance of this work was the practical demonstration that chemical vapor deposition (CVD) techniques can be used to systematically generate protective/conversion coating on non-ferrous surfaces. In order to become an effective approach to replace chromate-based pre- treatment processes, namely in the aerospace or automobile industry, the process parameters must be defined more precisely. Moreover, the feasibility of scale-up designs necessitates a more comprehensive characterization of the fluid flow, transport phenomena, and chemical kinetics interacting in the process. Kinetic characterization showed a significantly different effect of magnesium-based precursors when compared to iron-based precursors. Future work will concentrate on refining the process through computer simulations and further experimental studies on the effect of other transition metals to induce deposition of conversion/protective films

GaN-based FETs using Cat-CVD SiN passivation for millimeter-wave applications

International Nuclear Information System (INIS)

Higashiwaki, Masataka; Mimura, Takashi; Matsui, Toshiaki

2008-01-01

We have found that SiN passivation by catalytic chemical vapor deposition (Cat-CVD) can significantly increase an electron density of an AlGaN/GaN heterostructure field-effect transistor (HFET). This effect enables thin-barrier HFET structures to have a high-density two-dimensional electron gas and leads to suppression of short-channel effects. We fabricated 30-nm-gate Al 0.4 Ga 0.6 N(8 nm)/GaN HFETs using Cat-CVD SiN. The maximum drain current density and extrinsic transconductance were 1.49 A/mm and 402 mS/mm, respectively. Current-gain cutoff frequency and maximum oscillation frequency of the HFETs were 181 and 186 GHz, respectively. These high-frequency device characteristics are sufficiently high enough for millimeter-wave applications

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

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...

Enhanced graphitization of c-CVD grown multi-wall carbon nanotube arrays assisted by removal of encapsulated iron-based phases under thermal treatment in argon

International Nuclear Information System (INIS)

Boncel, Slawomir; Koziol, Krzysztof K.K.

2014-01-01

Graphical abstract: - Highlights: • Annealing of the c-CVD MWCNT arrays toward complete removal of iron nanoparticles. • The ICP-AES protocol established for quantitative analysis of Fe-content in MWCNTs. • The vertical alignment from the as-grown MWCNT arrays found intact after annealing. • A route to decrease number of defects/imperfections in the MWCNT graphene walls. • A foundation for commercial purification of c-CVD derived MWCNTs. - Abstract: The effect of annealing on multi-walled carbon nanotube (MWCNT) arrays grown via catalytic Chemical Vapour Deposition (c-CVD) was studied. The treatment enabled to decrease number of defects/imperfections in the graphene walls of MWCNTs’, which was reflected in Raman spectroscopy by reduction of the I D /I G ratio by 27%. Moreover, the vertical alignment from the as-synthesized nanotube arrays was found intact after annealing. Not only graphitization of the nanotube walls occurred under annealing, but the amount of metal iron-based catalyst residues (interfering with numerous physicochemical properties, and hence applications of MWCNTs) was reduced from 9.00 wt.% (for pristine MWCNTs) to 0.02 wt.% as detected by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). This value, established by a new analytical protocol, is the lowest recorded by now for purified c-CVD MWCNTs and, due to operating under atmospheric pressure, medium temperature regime (as for annealing processes), reasonable time-scale and metal residue non-specificity, it could lay the foundation for commercial purification of c-CVD derived MWCNTs

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

Influence of cold rolling and strain rate on plastic response of powder metallurgy and chemical vapor deposition rhenium

International Nuclear Information System (INIS)

Koeppel, B.J.; Subhash, G.

1999-01-01

The plastic response of two kinds of rhenium processed via powder metallurgy (PM) and chemical vapor deposition (CVD) were investigated under uniaxial compression over a range of strain rates. The PM rhenium, further cold rolled to 50 and 80 pct of the original thickness, was also investigated to assess the influence of cold work on the plastic behavior. A strong basal texture was detected in all the preceding materials as a result of processing and cold work. Both CVD and PM rhenium exhibited an increase in yield strength and flow stress with increasing strain rate. In PM rhenium, cold work resulted in an increase in hardness and yield strength and a decrease in the work hardening rate. The deformed microstructures revealed extensive twinning in CVD rhenium. At large strains, inhomogeneous deformation mode in the form of classical cup and cone fracture was noticed

Microcrystalline silicon deposition: Process stability and process control

International Nuclear Information System (INIS)

Donker, M.N. van den; Kilper, T.; Grunsky, D.; Rech, B.; Houben, L.; Kessels, W.M.M.; Sanden, M.C.M. van de

2007-01-01

Applying in situ process diagnostics, we identified several process drifts occurring in the parallel plate plasma deposition of microcrystalline silicon (μc-Si:H). These process drifts are powder formation (visible from diminishing dc-bias and changing spatial emission profile on a time scale of 10 0 s), transient SiH 4 depletion (visible from a decreasing SiH emission intensity on a time scale of 10 2 s), plasma heating (visible from an increasing substrate temperature on a time scale of 10 3 s) and a still puzzling long-term drift (visible from a decreasing SiH emission intensity on a time scale of 10 4 s). The effect of these drifts on the crystalline volume fraction in the deposited films is investigated by selected area electron diffraction and depth-profiled Raman spectroscopy. An example shows how the transient depletion and long-term drift can be prevented by suitable process control. Solar cells deposited using this process control show enhanced performance. Options for process control of plasma heating and powder formation are discussed

Ballistic Transport Exceeding 28 μm in CVD Grown Graphene.

Science.gov (United States)

Banszerus, Luca; Schmitz, Michael; Engels, Stephan; Goldsche, Matthias; Watanabe, Kenji; Taniguchi, Takashi; Beschoten, Bernd; Stampfer, Christoph

2016-02-10

We report on ballistic transport over more than 28 μm in graphene grown by chemical vapor deposition (CVD) that is fully encapsulated in hexagonal boron nitride. The structures are fabricated by an advanced dry van-der-Waals transfer method and exhibit carrier mobilities of up to three million cm(2)/(Vs). The ballistic nature of charge transport is probed by measuring the bend resistance in cross- and square-shaped devices. Temperature-dependent measurements furthermore prove that ballistic transport is maintained exceeding 1 μm up to 200 K.

Topographic and spectroscopic characterization of electronic edge states in CVD grown graphene nanoribbons.

Science.gov (United States)

Pan, Minghu; Girão, E Costa; Jia, Xiaoting; Bhaviripudi, Sreekar; Li, Qing; Kong, Jing; Meunier, V; Dresselhaus, Mildred S

2012-04-11

We used scanning tunneling microscopy and spectroscopy (STM/S) techniques to analyze the relationships between the edge shapes and the electronic structures in as-grown chemical vapor deposition (CVD) graphene nanoribbons (GNRs). A rich variety of single-layered graphene nanoribbons exhibiting a width of several to 100 nm and up to 1 μm long were studied. High-resolution STM images highlight highly crystalline nanoribbon structures with well-defined and clean edges. Theoretical calculations indicate clear spin-split edge states induced by electron-electron Coulomb repulsion. The edge defects can significantly modify these edge states, and different edge structures for both sides of a single ribbon produce asymmetric electronic edge states, which reflect the more realistic features of CVD grown GNRs. Three structural models are proposed and analyzed to explain the observations. By comparing the models with an atomic resolution image at the edge, a pristine (2,1) structure was ruled out in favor of a reconstructed edge structure composed of 5-7 member rings, showing a better match with experimental results, and thereby suggesting the possibility of a defective morphology at the edge of CVD grown nanoribbons. © 2012 American Chemical Society

Fiscal 2000 achievement report. Research and development of semiconductor CVD chamber cleaning systems for electronic device manufacturing using new alternative gas instead of SF6, PFCs, and other gases; 2000 nendo sokkoteki kakushinteki energy kankyo gijutsu kaihatsu seika hokokusho. SF6 tou ni daitaisuru gasu wo riyo shita denshi debaisu seizo cleaning system no kenkyu kaihatsu

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-03-01

The efforts aim to develop a CVD (chemical vapor deposition) mechanism cleaning gas with less environmental impact such as global warming and a CVD process using the same. The candidate gas synthesizing study for the development of such a gas continues from the preceding fiscal year. In addition, various candidate gases and tentatively synthesized gases are evaluated for their cleaning performance using a simplified experimental system. As the result, patent applications were filed for three novel alternative gases low in environmental impact and high in cleaning performance. In the research and development of CVD processes, a verification test process is developed for the evaluation of alternative gases at the real system level using a large CVD evaluation system. Studies are also made in which some existing gases are utilized to improve on CVD cleaning efficiency and to reduce greenhouse gas emissions. In relation to the process, one domestic patent application is made, and three essays are presented at an international conference on electrochemistry in the United States. (NEDO)

Plasma Assisted Chemical Vapour Deposition – Technological Design Of Functional Coatings

Directory of Open Access Journals (Sweden)

Januś M.

2015-06-01

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

Nanocrystalline sp{sup 2} and sp{sup 3} carbons: CVD synthesis and applications

Energy Technology Data Exchange (ETDEWEB)

Terranova, M. L. [Università degli Studi di Roma “Tor Vergata,” via Della Ricerca Scientifica, Dipartimento di Scienze e Tecnologie Chimiche—MinimaLab (Italy); Rossi, M. [Università degli Studi di Roma “Sapienza,” via A. Scarpa, Dipartimento di Scienze di Base e Applicate per l’Ingegneria and Centro di Ricerca per le Nanotecnologie Applicate all’Ingegneria (CNIS) (Italy); Tamburri, E., E-mail: emanuela.tamburri@uniroma2.it [Università degli Studi di Roma “Tor Vergata,” via Della Ricerca Scientifica, Dipartimento di Scienze e Tecnologie Chimiche—MinimaLab (Italy)

2016-11-15

The design and production of innovative materials based on nanocrystalline sp{sup 2}- and sp{sup 3}-coordinated carbons is presently a focus of the scientific community. We present a review of the nanostructures obtained in our labs using a series of synthetic routes, which make use of chemical vapor deposition (CVD) techniques for the selective production of non-planar graphitic nanostructures, nanocrystalline diamonds, and hybrid two-phase nanostructures.

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.

Understanding the electron-stimulated surface reactions of organometallic complexes to enable design of precursors for electron beam-induced deposition

Energy Technology Data Exchange (ETDEWEB)

Spencer, Julie A.; Rosenberg, Samantha G.; Barclay, Michael; Fairbrother, D. Howard [Johns Hopkins University, Department of Chemistry, Baltimore, MD (United States); Wu, Yung-Chien; McElwee-White, Lisa [University of Florida, Department of Chemistry, Gainesville, FL (United States)

2014-12-15

Standard practice in electron beam-induced deposition (EBID) is to use precursors designed for thermal processes, such as chemical vapor deposition (CVD). However, organometallic precursors that yield pure metal deposits in CVD often create EBID deposits with high levels of organic contamination. This contamination negatively impacts the deposit's properties (e.g., by increasing resistivity or decreasing catalytic activity) and severely limits the range of potential applications for metal-containing EBID nanostructures. To provide the information needed for the rational design of precursors specifically for EBID, we have employed an ultra-high vacuum (UHV) surface science approach to identify the elementary reactions of organometallic precursors during EBID. These UHV studies have demonstrated that the initial electron-induced deposition of the surface-bound organometallic precursors proceeds through desorption of one or more of the ligands present in the parent compound. In specific cases, this deposition step has been shown to proceed via dissociative electron attachment, involving low-energy secondary electrons generated by the interaction of the primary beam with the substrate. Electron beam processing of the surface-bound species produced in the initial deposition event usually causes decomposition of the residual ligands, creating nonvolatile fragments. This process is believed to be responsible for a significant fraction of the organic contaminants typically observed in EBID nanostructures. A few ligands (e.g., halogens) can, however, desorb during electron beam processing while other ligands (e.g., PF{sub 3}, CO) can thermally desorb if elevated substrate temperatures are used during deposition. Using these general guidelines for reactivity, we propose some design strategies for EBID precursors. The ultimate goal is to minimize organic contamination and thus overcome the key bottleneck for fabrication of relatively pure EBID nanostructures. (orig.)

Controlled growth of CNT in mesoporous AAO through optimized conditions for membrane preparation and CVD operation

Energy Technology Data Exchange (ETDEWEB)

Ciambelli, P; Sarno, M; Leone, C; Sannino, D [Department of Chemical and Food Engineering, University of Salerno, I-84084 Fisciano (Italy); Arurault, L; Fontorbes, S; Datas, L; Lenormand, P; Le Blond Du Plouy, S, E-mail: msarno@unisa.it, E-mail: arurault@chimie.ups-tlse.fr [Universite de Toulouse, CIRIMAT, UPS/INPT/CNRS, LCMIE, F-31062 Toulouse Cedex 9 (France)

2011-07-01

Anodic aluminium oxide (RAAO) membranes with a mesoporous structure were prepared under strictly controlling experimental process conditions, and physically and chemically characterized by a wide range of experimental techniques. Commercial anodic aluminium oxide (CAAO) membranes were also investigated for comparison. We demonstrated that RAAO membranes have lower content of both water and phosphorus and showed better porosity shape than CAAO. The RAAO membranes were used for template growth of carbon nanotubes (CNT) inside its pores by ethylene chemical vapour deposition (CVD) in the absence of a catalyst. A composite material, containing one nanotube for each channel, having the same length as the membrane thickness and an external diameter close to the diameter of the membrane holes, was obtained. Yield, selectivity and quality of CNTs in terms of diameter, length and arrangement (i.e. number of tubes for each channel) were optimized by investigating the effect of changing the experimental conditions for the CVD process. We showed that upon thermal treatment RAAO membranes were made up of crystallized allotropic alumina phases, which govern the subsequent CNT growth, because of their catalytic activity, likely due to their Lewis acidity. The strict control of experimental conditions for membrane preparation and CNT growth allowed us to enhance the carbon structural order, which is a critical requisite for CNT application as a substitute for copper in novel nano-interconnects.

Anisotropy and dimensional characteristics in CVD route Y1Ba2Cu3O7-δ

International Nuclear Information System (INIS)

Watanabe, K.; Kobayashi, N.; Awaji, S.; Yamane, H.; Hirai, T.; Muto, Y.

1993-01-01

The anisotropic behaviors of the upper critical field B c2 and the critical current density J c were investigated in Y 1 Ba 2 Cu 3 O 7-δ films prepared by a chemical vapor deposition (CVD) route. The angular dependence of J c at fixed temperature, the field dependence of J c at fixed angle, and the temperature dependence of J c at fixed field were measured. The obtained results were explored in terms of the dimensional superconducting characteristics. The important information on the anisotropic behaviors of J c in CVD-Y 1 Ba 2 Cu 3 O 7-δ was discussed from a viewpoint of the flux pinning. (orig.)

Electrical and thermal conductivity of low temperature CVD graphene: the effect of disorder

International Nuclear Information System (INIS)

Vlassiouk, Ivan; Datskos, Panos; Smirnov, Sergei; Ivanov, Ilia; Hensley, Dale; Lavrik, Nickolay V; Fulvio, Pasquale F; Dai Sheng; Meyer, Harry; Chi Miaofang

2011-01-01

In this paper we present a study of graphene produced by chemical vapor deposition (CVD) under different conditions with the main emphasis on correlating the thermal and electrical properties with the degree of disorder. Graphene grown by CVD on Cu and Ni catalysts demonstrates the increasing extent of disorder at low deposition temperatures as revealed by the Raman peak ratio, I G /I D . We relate this ratio to the characteristic domain size, L a , and investigate the electrical and thermal conductivity of graphene as a function of L a . The electrical resistivity, ρ, measured on graphene samples transferred onto SiO 2 /Si substrates shows linear correlation with L a -1 . The thermal conductivity, K, measured on the same graphene samples suspended on silicon pillars, on the other hand, appears to have a much weaker dependence on L a , close to K ∼ L a 1/3 . It results in an apparent ρ ∼ K 3 correlation between them. Despite the progressively increasing structural disorder in graphene grown at lower temperatures, it shows remarkably high thermal conductivity (10 2 -10 3 W K -1 m -1 ) and low electrical (10 3 -3 x 10 5 Ω) resistivities suitable for various applications.

Uranium ore deposits: geology and processing implications

International Nuclear Information System (INIS)

Belyk, C.L.

2010-01-01

There are fifteen accepted types of uranium ore deposits and at least forty subtypes readily identified around the world. Each deposit type has a unique set of geological characteristics which may also result in unique processing implications. Primary uranium production in the past decade has predominantly come from only a few of these deposit types including: unconformity, sandstone, calcrete, intrusive, breccia complex and volcanic ones. Processing implications can vary widely between and within the different geological models. Some key characteristics of uranium deposits that may have processing implications include: ore grade, uranium and gangue mineralogy, ore hardness, porosity, uranium mineral morphology and carbon content. Processing difficulties may occur as a result of one or more of these characteristics. In order to meet future uranium demand, it is imperative that innovative processing approaches and new technological advances be developed in order that many of the marginally economic traditional and uneconomic non-traditional uranium ore deposits can be exploited. (author)

Cold Vacuum Dryer (CVD) Facility Fire Protection System Design Description (SYS 24)

Energy Technology Data Exchange (ETDEWEB)

SINGH, G.

2000-10-17

This system design description (SDD) addresses the Cold Vacuum Drying (CVD) Facility fire protection system (FPS). The primary features of the FPS for the CVD are a fire alarm and detection system, automatic sprinklers, and fire hydrants. The FPS also includes fire extinguishers located throughout the facility and fire hydrants to assist in manual firefighting efforts. In addition, a fire barrier separates the operations support (administrative) area from the process bays and process bay support areas. Administrative controls to limit combustible materials have been established and are a part of the overall fire protection program. The FPS is augmented by assistance from the Hanford Fire Department (HED) and by interface systems including service water, electrical power, drains, instrumentation and controls. This SDD, when used in conjunction with the other elements of the definitive design package, provides a complete picture of the FPS for the CVD Facility.

Preparación de tamices moleculares de carbono por CVD

Directory of Open Access Journals (Sweden)

Manso, R.

2001-02-01

Full Text Available Carbon molecular sieves (CMS have been prepared by chemical vapour deposition (CVD of carbon from the pyrolysis of benzene molecules on activated carbon surfaces. The pyrolysis of benzene at temperatures in the range 650-850 ºC restricts the accessibility of the micropores due to the creation of constrictions on the microporous network. Temperatures higher than 850 ºC (temperature of carbonisation add difficulties due to decomposition and sinterization processes. Low flows of nitrogen (30 mL min-1 and high benzene content (13 % produce a more uniform carbon deposition and wider micropore size distributions. The CVD process on carbons activated to different burn-offs, using temperatures below 850 ºC, flows of 150 mL min-1 and benzene content of 1 %, gives rise to microporous materials which exhibit micropore volumes around 0,25 cm3 g-1 and narrow micropore size distributions: below 0,33 nm, between 0,33-0,41 nm or between 0,41-0,54 nm. The burn-off of the activated carbon has a relative little influence on the textural properties of the CMS that mainly depend on the degree of filling originated by the carbon deposition.

Se han preparado tamices moleculares de carbono (CMS mediante el depósito de átomos de carbono, por pirólisis de benceno, sobre la superficie de carbones activados. La pirólisis de benceno a temperaturas comprendidas entre 650-850 ºC genera el cierre progresivo de los microporos debido a la creación de constricciones en la red microporosa que limitan la accesibilidad de determinadas moléculas. El uso de temperaturas superiores a la temperatura de carbonización del precursor (850 ºC introduce complicaciones debido a la descomposición y sinterización parcial del sólido. Flujos bajos de nitrógeno (30 mL min-1 con alto contenido en benceno (13 % producen un depósito homogéneo a lo largo de las paredes y los materiales presentan distribuciones microporosas mas anchas. El depósito de carbono sobre carbones

Rapid growth of single-layer graphene on the insulating substrates by thermal CVD

Energy Technology Data Exchange (ETDEWEB)

Chen, C.Y. [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Dai, D.; Chen, G.X.; Yu, J.H. [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Nishimura, K. [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Advanced Nano-processing Engineering Lab, Mechanical Systems Engineering, Kogakuin University (Japan); Lin, C.-T. [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Jiang, N., E-mail: jiangnan@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhan, Z.L., E-mail: zl_zhan@sohu.com [Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

2015-08-15

Highlights: • A rapid thermal CVD process has been developed to directly grow graphene on the insulating substrates. • The treating time consumed is ≈25% compared to conventional CVD procedure. • Single-layer and few-layer graphene can be formed on quartz and SiO{sub 2}/Si substrates, respectively. • The formation of thinner graphene at the interface is due to the fast precipitation rate of carbon atoms during cooling. - Abstract: The advance of CVD technique to directly grow graphene on the insulating substrates is particularly significant for further device fabrication. As graphene is catalytically grown on metal foils, the degradation of the sample properties is unavoidable during transfer of graphene on the dielectric layer. Moreover, shortening the treatment time as possible, while achieving single-layer growth of graphene, is worthy to be investigated for promoting the efficiency of mass production. Here we performed a rapid heating/cooling process to grow graphene films directly on the insulating substrates by thermal CVD. The treating time consumed is ≈25% compared to conventional CVD procedure. In addition, we found that high-quality, single-layer graphene can be formed on quartz, but on SiO{sub 2}/Si substrate only few-layer graphene can be obtained. The pronounced substrate effect is attributed to the different dewetting behavior of Ni films on the both substrates at 950 °C.

A novel continuous process for synthesis of carbon nanotubes using iron floating catalyst and MgO particles for CVD of methane in a fluidized bed reactor

Energy Technology Data Exchange (ETDEWEB)

Maghsoodi, Sarah; Khodadadi, Abasali [Catalysis and Nanostructured Materials Research Laboratory, School of Chemical Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Mortazavi, Yadollah, E-mail: mortazav@ut.ac.ir [Nanoelectronics Centre of Excellence, University of Tehran, POB 11365-4563, Tehran (Iran, Islamic Republic of)

2010-02-15

A novel continuous process is used for production of carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CVD) of methane on iron floating catalyst in situ deposited on MgO in a fluidized bed reactor. In the hot zone of the reactor, sublimed ferrocene vapors were contacted with MgO powder fluidized by methane feed to produce Fe/MgO catalyst in situ. An annular tube was used to enhance the ferrocene and MgO contacting efficiency. Multi-wall as well as single-wall CNTs was grown on the Fe/MgO catalyst while falling down the reactor. The CNTs were continuously collected at the bottom of the reactor, only when MgO powder was used. The annular tube enhanced the contacting efficiency and improved both the quality and quantity of CNTs. The SEM and TEM micrographs of the products reveal that the CNTs are mostly entangled bundles with diameters of about 10-20 nm. Raman spectra show that the CNTs have low amount of amorphous/defected carbon with I{sub G}/I{sub D} ratios as high as 10.2 for synthesis at 900 deg. C. The RBM Raman peaks indicate formation of single-walled carbon nanotubes (SWNTs) of 1.0-1.2 nm diameter.

Enhanced graphitization of c-CVD grown multi-wall carbon nanotube arrays assisted by removal of encapsulated iron-based phases under thermal treatment in argon

Energy Technology Data Exchange (ETDEWEB)

Boncel, Slawomir, E-mail: slawomir.boncel@polsl.pl [Department of Organic Chemistry, Biochemistry and Biotechnology, Silesian University of Technology, Krzywoustego 4, 44-100 Gliwice (Poland); Koziol, Krzysztof K.K., E-mail: kk292@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, CB3 0FS Cambridge (United Kingdom)

2014-05-01

Graphical abstract: - Highlights: • Annealing of the c-CVD MWCNT arrays toward complete removal of iron nanoparticles. • The ICP-AES protocol established for quantitative analysis of Fe-content in MWCNTs. • The vertical alignment from the as-grown MWCNT arrays found intact after annealing. • A route to decrease number of defects/imperfections in the MWCNT graphene walls. • A foundation for commercial purification of c-CVD derived MWCNTs. - Abstract: The effect of annealing on multi-walled carbon nanotube (MWCNT) arrays grown via catalytic Chemical Vapour Deposition (c-CVD) was studied. The treatment enabled to decrease number of defects/imperfections in the graphene walls of MWCNTs’, which was reflected in Raman spectroscopy by reduction of the I{sub D}/I{sub G} ratio by 27%. Moreover, the vertical alignment from the as-synthesized nanotube arrays was found intact after annealing. Not only graphitization of the nanotube walls occurred under annealing, but the amount of metal iron-based catalyst residues (interfering with numerous physicochemical properties, and hence applications of MWCNTs) was reduced from 9.00 wt.% (for pristine MWCNTs) to 0.02 wt.% as detected by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). This value, established by a new analytical protocol, is the lowest recorded by now for purified c-CVD MWCNTs and, due to operating under atmospheric pressure, medium temperature regime (as for annealing processes), reasonable time-scale and metal residue non-specificity, it could lay the foundation for commercial purification of c-CVD derived MWCNTs.

[Application of Raman spectroscopy to investigation of CVD-SIC fiber].

Science.gov (United States)

Liu, Bin; Yang, Yan-Qing; Luo, Xian; Huang, Bin

2011-11-01

The CVD-SiC fiber was studied by using laser Raman spectra. It was found that the sharp TO peak exists in the first SiC deposit layer, indicating the larger SiC grains. But the second SiC deposit layer is with small grains. Raman peak of carbon and silicon was detected respectively in the first and second layer. Compared with that of the single SiC fiber, the TO peaks move to the high wave number for the SiC fiber in SiC(f)/Ti-6Al-4V composite. It indicates that the compressive thermal residual stress is present in the SiC fiber during the fabrication of the composite because of the mismatched coefficient of thermal expansion between Ti-6Al-4V matrix and SiC fiber. The average thermal residual stress of the SiC fiber in SiC(f)/Ti-6Al-4V composite was calculated to be 318 MPa and the residual stress in first deposit layer is 436 MPa which is much higher than that in the second layer.

Fermented dairy food and CVD risk.

Science.gov (United States)

Tapsell, Linda C

2015-04-01

Fermented dairy foods such as yoghurt and cheese are commonly found in the Mediterranean diet. Recent landmark research has confirmed the effect of the Mediterranean diet on reducing the CVD risk, but the relative contributions of fermented dairy foods have not been fully articulated. The present study provides a review of the relationship between fermented dairy foods consumption and CVD risk in the context of the whole diet. Studies show that people who eat healthier diets may be more likely to consume yoghurt, so there is a challenge in attributing separate effects to yoghurt. Analyses from large population studies list yoghurt as the food most negatively associated with the risk of weight gain (a problem that may lead to CVD). There is some suggestion that fermented dairy foods consumption (yoghurt or cheese) may be associated with reduced inflammatory biomarkers associated with the development of CVD. Dietary trials suggest that cheese may not have the same effect on raising LDL-cholesterol levels as butter with the same saturated fat content. The same might be stated for yoghurt. The use of different probiotic cultures and other aspects of study design remain a problem for research. Nevertheless, population studies from a range of countries have shown that a reduced risk of CVD occurs with the consumption of fermented dairy foods. A combination of evidence is necessary, and more research is always valuable, but indications remain that fermented dairy foods such as cheese and yoghurt are integral to diets that are protective against CVD.

CVD growth of large-area and high-quality HfS2 nanoforest on diverse substrates

Science.gov (United States)

Zheng, Binjie; Wang, Zegao; Qi, Fei; Wang, Xinqiang; Yu, Bo; Zhang, Wanli; Chen, Yuanfu

2018-03-01

Two-dimensional layered transition metal dichalcogenides (TMDs) have attracted burgeoning attention due to their various properties and wide potential applications. As a new TMD, hafnium disulfide (HfS2) is theoretically predicted to have better electrical performance than widely studied MoS2. The experimental researches also confirmed the extraordinary feature in electronics and optoelectronics. However, the maximal device performance may not be achieved due to its own limitation of planar structure and challenge of transfer without contamination. Here, through the chemical vapor deposition (CVD) technique, inch-size HfS2 nanoforest has been directly grown on diverse objective substrates covering insulating, semiconducting and conducting substrates. This direct CVD growth without conventional transfer process avoids contamination and degradation in quality, suggesting its promising and wide applications in high-quality and multifarious devices. It is noted that all the HfS2 nanoforests grown on diverse substrates are constructed with vertically aligned few-layered HfS2 nanosheets with high crystalline quality and edge orientation. Moreover, due to its unique structure, the HfS2 nanoforest owns abundant exposed edge sites and large active surface area, which is essential to apply in high-performance catalyst, sensor, and energy storage or field emitter.

Cyclic voltammetry response of an undoped CVD diamond electrodes

Energy Technology Data Exchange (ETDEWEB)

Fabisiak, K., E-mail: kfab@ukw.edu.pl [Institute of Physics, Kazimierz Wielki University, Powstancow Wielkopolskich 2, 85-090 Bydgoszcz (Poland); Torz-Piotrowska, R. [Faculty of Chemical Technology and Engineering, UTLS Seminaryjna 3, 85-326 Bydgoszcz (Poland); Staryga, E. [Institute of Physics, Technical University of Lodz, Wolczanska 219, 90-924 Lodz (Poland); Szybowicz, M. [Faculty of Technical Physics, Poznan University of Technology, Nieszawska 13A, 60-965 Poznan (Poland); Paprocki, K.; Popielarski, P.; Bylicki, F. [Institute of Physics, Kazimierz Wielki University, Powstancow Wielkopolskich 2, 85-090 Bydgoszcz (Poland); Wrzyszczynski, A. [Institute of Physics, Technical University of Lodz, Wolczanska 219, 90-924 Lodz (Poland)

2012-09-01

Highlights: Black-Right-Pointing-Pointer Correlation was found between diamond quality and its electrochemical performance. Black-Right-Pointing-Pointer The electrode sensitivity depends on the content of sp{sup 2} carbon phase in diamond layer. Black-Right-Pointing-Pointer The sp{sup 2} carbon phase content has little influence on the CV peak separation ({Delta}E{sub p}). - Abstract: The polycrystalline undoped diamond layers were deposited on tungsten wire substrates by using hot filament chemical vapor deposition (HFCVD) technique. As a working gas the mixture of methanol in excess of hydrogen was used. The morphologies and quality of as-deposited films were monitored by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy respectively. The electrochemical activity of the obtained diamond layers was monitored by using cyclic voltammetry measurements. Analysis of the ferrocyanide-ferricyanide couple at undoped diamond electrode suggests that electrochemical reaction at diamond electrode has a quasireversibile character. The ratio of the anodic and cathodic peak currents was always close to unity. In this work we showed that the amorphous carbon admixture in the CVD diamond layer has a crucial influence on its electrochemical performance.

Síntesis de materiales cerámicos mediante técnicas químicas en fase vapor (CVD

Directory of Open Access Journals (Sweden)

Gómez-Aleixandre, C.

2003-02-01

Full Text Available Chemical vapour deposition (CVD has been successfully used for the synthesis of a large variety of compounds. Initially the technique was developed for microelectronic applications and then was widespread used for the preparation of hard coatings, optoelectronic and superconductor materials. Among the characteristics inherent to the CVD technique it is worth mentioning the preparation of homogeneous deposits at relatively low temperatures mostly when the reaction is electrically or laser plasma or photon activated. New materials with given characteristics can be produced by properly choosing the reactant gas mixture as well as its relative composition. The presentation will be also focussed onto the deposition of different materials, such as carbon films (both crystalline, and amorphous with diamond-like properties, deposited by plasma assisted CVD techniques using methane and hydrogen gas mixtures. Also, the deposition of binary compounds, as boron nitride will be reviewed. Finally, the experimental requirements for obtaining new ternary compounds from the system Si-B-N-C (i.e.: CBN, SiBN will be discussed. The properties of these materials strongly depend on their composition and structure. Therefore, by adequate selection of the experimental parameters, it is possible to obtain ternary compounds with tailored characteristics.

Actualmente, la técnica de CVD está siendo utilizada en la síntesis de una gran variedad de compuestos cerámicos, generalmente en forma de capa delgada. La técnica, desarrollada inicialmente para su aplicación en microelectrónica, ha sido después utilizada con éxito en otras áreas de gran actividad científica y tecnológica (recubrimientos duros, dispositivos optoelectrónicos, materiales superconductores, etc.. Entre las características más positivas de las técnicas de CVD, cabe destacar la obtención de depósitos homogéneos a temperaturas relativamente bajas, sobre todo cuando la activación de

Prediction of the properties of PVD/CVD coatings with the use of FEM analysis

Science.gov (United States)

Śliwa, Agata; Mikuła, Jarosław; Gołombek, Klaudiusz; Tański, Tomasz; Kwaśny, Waldemar; Bonek, Mirosław; Brytan, Zbigniew

2016-12-01

The aim of this paper is to present the results of the prediction of the properties of PVD/CVD coatings with the use of finite element method (FEM) analysis. The possibility of employing the FEM in the evaluation of stress distribution in multilayer Ti/Ti(C,N)/CrN, Ti/Ti(C,N)/(Ti,Al)N, Ti/(Ti,Si)N/(Ti,Si)N, and Ti/DLC/DLC coatings by taking into account their deposition conditions on magnesium alloys has been discussed in the paper. The difference in internal stresses in the zone between the coating and the substrate is caused by, first of all, the difference between the mechanical and thermal properties of the substrate and the coating, and also by the structural changes that occur in these materials during the fabrication process, especially during the cooling process following PVD and CVD treatment. The experimental values of stresses were determined based on X-ray diffraction patterns that correspond to the modelled values, which in turn can be used to confirm the correctness of the accepted mathematical model for testing the problem. An FEM model was established for the purpose of building a computer simulation of the internal stresses in the coatings. The accuracy of the FEM model was verified by comparing the results of the computer simulation of the stresses with experimental results. A computer simulation of the stresses was carried out in the ANSYS environment using the FEM method. Structure observations, chemical composition measurements, and mechanical property characterisations of the investigated materials has been carried out to give a background for the discussion of the results that were recorded during the modelling process.

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.

Earth Surface Processes, Landforms and Sediment Deposits

Science.gov (United States)

Bridge, John; Demicco, Robert

Earth surface processes, landforms and sediment deposits are intimately related - involving erosion of rocks, generation of sediment, and transport and deposition of sediment through various Earth surface environments. These processes, and the landforms and deposits that they generate, have a fundamental bearing on engineering, environmental and public safety issues; on recovery of economic resources; and on our understanding of Earth history. This unique textbook brings together the traditional disciplines of sedimentology and geomorphology to explain Earth surface processes, landforms and sediment deposits in a comprehensive and integrated way. It is the ideal resource for a two-semester course in sedimentology, stratigraphy, geomorphology, and Earth surface processes from the intermediate undergraduate to beginning graduate level. The book is also accompanied by a website hosting illustrations and material on field and laboratory methods for measuring, describing and analyzing Earth surface processes, landforms and sediments.

Diamond like carbon coatings deposited by microwave plasma CVD ...

Indian Academy of Sciences (India)

WINTEC

photoelectron spectroscopy (XPS) and spectroscopic ellipsometry techniques for estimating sp. 3. /sp. 2 ratio. ... ion beam deposition (Savvidas 1986), pulsed laser deposi- ... carrier gas (10 sccm) by passing 150 watts of microwave power.

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.

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)

Flash-lamp-crystallized polycrystalline silicon films with high hydrogen concentration formed from Cat-CVD a-Si films

International Nuclear Information System (INIS)

Ohdaira, Keisuke; Tomura, Naohito; Ishii, Shohei; Matsumura, Hideki

2011-01-01

We investigate residual forms of hydrogen (H) atoms such as bonding configuration in poly-crystalline silicon (poly-Si) films formed by the flash-lamp-induced crystallization of catalytic chemical vapor deposited (Cat-CVD) a-Si films. Raman spectroscopy reveals that at least part of H atoms in flash-lamp-crystallized (FLC) poly-Si films form Si-H 2 bonds as well as Si-H bonds with Si atoms even using Si-H-rich Cat-CVD a-Si films, which indicates the rearrangement of H atoms during crystallization. The peak desorption temperature during thermal desorption spectroscopy (TDS) is as high as 900 o C, similar to the reported value for bulk poly-Si.

The CVD ZrB2 as a selective solar absorber

Science.gov (United States)

Randich, E.; Allred, D. D.

Coatings of ZrB2 and TiB2 for photothermal solar absorber applications were prepared using chemical vapor deposition (CVD) techniques. Oxidation tests suggest a maximum temperature limit for air exposure of 600 K for TiB2 and 800 K for Z4B2. Both materials exhibit innate spectral selectivity with emittance at 375 K ranging from 0.06 to 0.09 and solar absorptance for ZrB2 ranging from 0.67 to 0.77 and solar absorptance for TiB2 ranging from 0.46 to 0.58. ZrB2 has better solar selectivity and more desirable oxidation behavior than TiB2. A 0.071 micrometer antireflection coating of Si3N4 deposited on the ZrB2 coating leads to an increase in absorptance from 0.77 to 0.93, while the emittance remains unchanged.

FABRICATION OF CNTS BY TOLUENE DECOMPOSITION IN A NEW REACTOR BASED ON AN ATMOSPHERIC PRESSURE PLASMA JET COUPLED TO A CVD SYSTEM

Directory of Open Access Journals (Sweden)

FELIPE RAMÍREZ-HERNÁNDEZ

2017-03-01

Full Text Available Here, we present a method to produce carbon nanotubes (CNTs based on the coupling between two conventional techniques used for the preparation of nanostructures: an arc-jet as a source of plasma and a chemical vapour deposition (CVD system. We call this system as an “atmospheric pressure plasma (APP-enhanced CVD” (APPE-CVD. This reactor was used to grow CNTs on non-flat aluminosilicate substrates by the decomposition of toluene (carbon source in the presence of ferrocene (as a catalyst. Both, CNTs and by-products of carbon were collected at three different temperatures (780, 820 and 860 °C in different regions of the APPE-CVD system. These samples were analysed by thermogravimetric analysis (TGA and DTG, scanning electron microscopy (SEM and Raman spectroscopy in order to determine the effect of APP on the thermal stability of the as-grown CNTs. It was found that the amount of metal catalyst in the synthesised CNTs is reduced by applying APP, being 820 °C the optimal temperature to produce CNTs with a high yield and carbon purity (95 wt. %. In contrast, when the synthesis temperature was fixed at 780 °C or 860 °C, amorphous carbon or CNTs with different structural defects, respectively, was formed through APEE-CVD reactor. We recommended the use of non-flat aluminosilicate particles as supports to increase CNT yield and facilitate the removal of deposits from the substrate surface. The approach that we implemented (to synthesise CNTs by using the APPE-CVD reactor may be useful to produce these nanostructures on a gram-scale for use in basic studies. The approach may also be scaled up for mass production.

Effect of mixture ratios and nitrogen carrier gas flow rates on the morphology of carbon nanotube structures grown by CVD

CSIR Research Space (South Africa)

Malgas, GF

2008-02-01

Full Text Available This paper reports on the growth of carbon nanotubes (CNTs) by thermal Chemical Vapour Deposition (CVD) and investigates the effects of nitrogen carrier gas flow rates and mixture ratios on the morphology of CNTs on a silicon substrate by vaporizing...

Thermoluminescence in CVD diamond films: application to actinometric dosimetry

International Nuclear Information System (INIS)

Barboza-Flores, M.; Melendrez, R.; Chernov, V.; Castaneda, B.; Pedroza-Montero, M.; Gan, B.; Ahn, J.; Zhang, Q.; Yoon, S.F.

2002-01-01

Diamond is considered a tissue-equivalent material since its atomic number (Z=6) is close to the effective atomic number of biological tissue (Z=7.42). Such a situation makes it suitable for radiation detection purposes in medical applications. In the present work the analysis is reported of the thermoluminescence (TL) and dosimetric features of chemically vapour deposited (CVD) diamond film samples subjected to ultraviolet (UV) irradiation in the actinometric region. The TL glow curve shows peaks at 120, 220, 320 and 370 deg. C. The 120 and 370 deg. C peaks are too weak and the first one fades away in a few seconds after exposure. The overall room temperature fading shows a 50% TL decay 30 min after exposure. The 320 deg. C glow peak is considered to be the most adequate for dosimetric applications due to its low fading and linear TL behaviour as a function of UV dose in the 180-260 nm range. The TL excitation spectrum presents a broad band with at least two overlapped components around 205 and 220 nm. The results indicate that the TL behaviour of CVD diamond film can be a good alternative to the currently available dosemeter and detector in the actinometric region as well as in clinical and medical applications. (author)

Erosion behaviour of physically vapour-deposited and chemically vapour-deposited SiC films coated on molybdenum during oxygenated argon beam thinning

International Nuclear Information System (INIS)

Shikama, T.; Kitajima, M.; Fukutomi, M.; Okada, M.

1984-01-01

The erosion behaviour during bombardment with a 5 keV argon beam at room temperature was studied for silicon carbide (SiC) films of thickness of about 10 μm coated on molybdenum by physical vapour deposition (PVD) and chemical vapour deposition (CVD). The PVD SiC (plasma-assisted ion plating) exhibited a greater thinning rate than the CVD SiC film. Electron probe X-ray microanalysis revealed that the chemical composition of PVD SiC was changed to a composition enriched in silicon by the bombardment, and there was a notable change in its surface morphology. The CVD SiC retained its initial chemical composition with only a small change in its surface morphology. Auger electron spectroscopy indicated that silicon oxide was formed on the surface of PVD SiC by the bombardment. The greater thinning rate and easier change in chemical composition in PVD SiC could be attributed to its readier chemical reaction with oxygen due to its more non-uniform structure and weaker chemical bonding. Oxygen was present as one of the impurities in the argon beam. (Auth.)

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

Application of CVD diamond film for radiation detection

International Nuclear Information System (INIS)

Zhou Haiyang; Zhu Xiaodong; Zhan Rujuan

2005-01-01

With the development of diamond synthesis at low pressure, the CVD diamond properties including electronic characteristics have improved continuously. Now the fabrication of electronic devices based on the CVD diamond has been one of hot research subjects in this field. Due to many unique advantages, such as high signal-noise ratio, fast time response, and normal output in extremely harsh surrounding, the CVD diamond radiation detector has attracted more and more interest. In this paper, we have reviewed the development and status of the CVD diamond radiation detector. The prospect of this detector is described. (authors)

Direct fabrication of a W-C SNS Josephson junction using focused-ion-beam chemical vapour deposition

International Nuclear Information System (INIS)

Dai, Jun; Kometani, Reo; Ishihara, Sunao; Warisawa, Shin’ichi; Onomitsu, Koji; Krockenberger, Yoshiharu; Yamaguchi, Hiroshi

2014-01-01

A tungsten-carbide (W-C) superconductor/normal metal/superconductor (SNS) Josephson junction has been fabricated using focused-ion-beam chemical vapour deposition (FIB-CVD). Under certain process conditions, the component ratio has been tuned from W: C: Ga = 26%: 66%: 8% in the superconducting wires to W: C: Ga = 14%: 79%: 7% in the metallic junction. The critical current density at 2.5 K in the SNS Josephson junction is 1/3 of that in W-C superconducting nanowire. Also, a Fraunhofer-like oscillation of critical current in the junction with four periods is observed. FIB-CVD opens avenues for novel functional superconducting nanodevices. (paper)

Optical characterization of single-crystal diamond grown by DC arc plasma jet CVD

Science.gov (United States)

Hei, Li-fu; Zhao, Yun; Wei, Jun-jun; Liu, Jin-long; Li, Cheng-ming; Lü, Fan-xiu

2017-12-01

Optical centers of single-crystal diamond grown by DC arc plasma jet chemical vapor deposition (CVD) were examined using a low-temperature photoluminescence (PL) technique. The results show that most of the nitrogen-vacancy (NV) complexes are present as NV- centers, although some H2 and H3 centers and B-aggregates are also present in the single-crystal diamond because of nitrogen aggregation resulting from high N2 incorporation and the high mobility of vacancies under growth temperatures of 950-1000°C. Furthermore, emissions of radiation-induced defects were also detected at 389, 467.5, 550, and 588.6 nm in the PL spectra. The reason for the formation of these radiation-induced defects is not clear. Although a Ni-based alloy was used during the diamond growth, Ni-related emissions were not detected in the PL spectra. In addition, the silicon-vacancy (Si-V)-related emission line at 737 nm, which has been observed in the spectra of many previously reported microwave plasma chemical vapor deposition (MPCVD) synthetic diamonds, was absent in the PL spectra of the single-crystal diamond prepared in this work. The high density of NV- centers, along with the absence of Ni-related defects and Si-V centers, makes the single-crystal diamond grown by DC arc plasma jet CVD a promising material for applications in quantum computing.

Hard coatings by plasma CVD on polycarbonate for automotive and optical applications

International Nuclear Information System (INIS)

Schmauder, T.; Nauenburg, K.-D.; Kruse, K.; Ickes, G.

2006-01-01

In many applications, plastic surfaces need coatings as a protection against abrasion or weathering. Leybold Optics is developing Plasma CVD processes and machinery for transparent hard coatings (THC) for polycarbonate parts. In this paper we present the current features and remaining challenges of this technique. The coatings generally show excellent adhesion. Abrasion resistance is superior to commonly used lacquers. Climate durability of the coating has been improved to pass the tests demanded by automotive specifications. Current activities are focused on improving the durability under exposure to UV radiation. Estimations show that our high-rate plasma CVD hard coating process is also economically competitive to lacquering

Efecto del argon en películas CNxHy depositadas mediante ECR-CVD

Directory of Open Access Journals (Sweden)

Albella, J. M.

2004-04-01

Full Text Available Carbon nitride films have been deposited by ECR-CVD, from Ar/CH4/N2 gas mixtures with different methane concentrations. Infrared Spectroscopy (IRS and Elastic Recoil Detection Analysis (ERDA have been used for films characterisation and Optical Emission Spectroscopy (OES for plasma analysis. Argon concentration in the gas mixture controls the growth rate as well as the composition of the film. In the proposed model, argon plays a key role in the activation of methane molecules. Also, during the growth of the film, two processes may be considered: i Film formation and ii Etching of the growing surface. Changing the gas mixture composition affects both processes, which results in films with different composition and structure as well as different deposition rates.Se ha estudiado el efecto del argon durante el proceso de CVD asistido por un plasma ECR para la síntesis de películas de nitruro de carbono (CNxHy a partir de mezclas gaseosas Ar/CH4/N2 con diferente contenido de metano. Las películas depositadas han sido analizadas mediante espectroscopía infrarroja (IRS y ERDA (Elastic Recoil Detection Analysis, y el análisis del plasma ha sido realizado utilizando la técnica de espectroscopía de emisión óptica (OES. La velocidad de deposición y la composición de las películas depositadas se encuentran determinadas por la concentración de argon en la mezcla gaseosa. Se propone un modelo, según el cual el argon juega un papel fundamental como activador de las moléculas de metano. El modelo propuesto incluye dos procesos simultáneos durante el crecimiento de las capas : i formación de la capa y ii ataque de la superficie de crecimiento. Según la composición de la mezcla gaseosa se favorece uno u otro proceso, lo que conduce a velocidades de deposición diferentes así como a depósitos con diferente composición y estructura atómica.

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.

Ultrashort pulse laser deposition of thin films

Science.gov (United States)

Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.

2002-01-01

Short pulse PLD is a viable technique of producing high quality films with properties very close to that of crystalline diamond. The plasma generated using femtosecond lasers is composed of single atom ions with no clusters producing films with high Sp.sup.3 /Sp.sup.2 ratios. Using a high average power femtosecond laser system, the present invention dramatically increases deposition rates to up to 25 .mu.m/hr (which exceeds many CVD processes) while growing particulate-free films. In the present invention, deposition rates is a function of laser wavelength, laser fluence, laser spot size, and target/substrate separation. The relevant laser parameters are shown to ensure particulate-free growth, and characterizations of the films grown are made using several diagnostic techniques including electron energy loss spectroscopy (EELS) and Raman spectroscopy.

Fabrication of Ultrasensitive Field-Effect Transistor DNA Biosensors by a Directional Transfer Technique Based on CVD-Grown Graphene.

Science.gov (United States)

Zheng, Chao; Huang, Le; Zhang, Hong; Sun, Zhongyue; Zhang, Zhiyong; Zhang, Guo-Jun

2015-08-12

Most graphene field-effect transistor (G-FET) biosensors are fabricated through a routine process, in which graphene is transferred onto a Si/SiO2 substrate and then devices are subsequently produced by micromanufacture processes. However, such a fabrication approach can introduce contamination onto the graphene surface during the lithographic process, resulting in interference for the subsequent biosensing. In this work, we have developed a novel directional transfer technique to fabricate G-FET biosensors based on chemical-vapor-deposition- (CVD-) grown single-layer graphene (SLG) and applied this biosensor for the sensitive detection of DNA. A FET device with six individual array sensors was first fabricated, and SLG obtained by the CVD-growth method was transferred onto the sensor surface in a directional manner. Afterward, peptide nucleic acid (PNA) was covalently immobilized on the graphene surface, and DNA detection was realized by applying specific target DNA to the PNA-functionalized G-FET biosensor. The developed G-FET biosensor was able to detect target DNA at concentrations as low as 10 fM, which is 1 order of magnitude lower than those reported in a previous work. In addition, the biosensor was capable of distinguishing the complementary DNA from one-base-mismatched DNA and noncomplementary DNA. The directional transfer technique for the fabrication of G-FET biosensors is simple, and the as-constructed G-FET DNA biosensor shows ultrasensitivity and high specificity, indicating its potential application in disease diagnostics as a point-of-care tool.

Processing of SiO2 protective layer using HMDS precursor by combustion CVD.

Science.gov (United States)

Park, Kyoung-Soo; Kim, Youngman

2011-08-01

Hexamethyldisilazane (HMDS, [(CH3)3Si]2NH) was used as a precursor to form SiO2 protective coatings on IN738LC alloys by combustion chemical vapor deposition (CCVD). SEM and XPS showed that the processed coatings were composed mainly of SiO2. The amount of HMDS had the largest effect on the size of the SiO2 agglomerates and the thickness of the deposited coatings. The specimens coated with SiO2 using the 0.05 mol/l HMDS solution showed a significantly higher temperature oxidation resistance than those deposited under other conditions.

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...

Crystal growth of CVD diamond and some of its peculiarities

CERN Document Server

Piekarczyk, W

1999-01-01

Experiments demonstrate that CVD diamond can form in gas environments that are carbon undersaturated with respect to diamond. This fact is, among others, the most serious violation of principles of chemical thermodynamics. In this $9 paper it is shown that none of the principles is broken when CVD diamond formation is considered not a physical process consisting in growth of crystals but a chemical process consisting in accretion of macro-molecules of polycyclic $9 saturated hydrocarbons belonging to the family of organic compounds the smallest representatives of which are adamantane, diamantane, triamantane and so forth. Since the polymantane macro-molecules are in every respect identical with $9 diamond single crystals with hydrogen-terminated surfaces, the accretion of polymantane macro- molecules is a process completely equivalent to the growth of diamond crystals. However, the accretion of macro-molecules must be $9 described in a way different from that used to describe the growth of crystals because so...

Near-room temperature deposition of W and WO3 thin films by hydrogen atom assisted chemical vapor deposition

International Nuclear Information System (INIS)

Lee, W.W.; Reeves, R.R.

1992-01-01

A novel near-room temperatures CVD process has been developed using H-atoms reaction with WF 6 to produced tungsten and tungsten oxide films. The chemical, physical and electrical properties of these films were studied. Good adhesion and low resistivity of W films were measured. Conformal WO 3 films were obtained on columnar tungsten using a small amount of molecular oxygen in the gas stream. A reaction mechanism was evaluated on the basis of experimental results. The advantages of the method include deposition of adherent films in a plasma-free environment, near-room temperature, with a low level of impurity

Simulation and experimental approach to CVD-FBR aluminide coatings on ferritic steels under steam oxidation

International Nuclear Information System (INIS)

Leal, J.; Alcala, G.; Bolivar, F.J.; Sanchez, L.; Hierro, M.P.; Perez, F.J.

2008-01-01

The ferritic steels used to produce structural components for steam turbines are susceptible to strong corrosion and creep damage due to the extreme working conditions pushed to increase the process efficiency and to reduce pollutants release. The response of aluminide coatings on the P-92 ferritic steel, deposited by CVD-FBR, during oxidation in a simulated steam environment was studied. The analyses were performed at 650 deg. C in order to simulate the working conditions of a steam turbine, and 800 deg. C in order to produce a critical accelerated oxidation test. The Thermo-Calc software was used to predict the different solid phases that could be generated during the oxidation process, in both, coated and uncoated samples. In order to validate the thermodynamic results, the oxides scales produced during steam tests were characterized by different techniques such as XRD, SEM and EDS. The preliminary results obtained are discussed in the present work

The study on diamond-coated insert by DC plasma jet CVD

International Nuclear Information System (INIS)

Zhou Kesong; Dai Mingjiang; Song Jinbing; Kuang Tongchun; Liu Zhengyi

2001-01-01

Diamond coating were deposited on cemented carbide inserts by DC plasma jet CVD. The cemented carbide inserts were pretreated by methods including chemical etching of Co, Ar/H 2 plasma etching. The characteristics of diamond film, interface structure, adhesion strength and film stress were analysized by different methods such as SEM, XRD, Raman spectrum etc. A comparing experiment of cutting Al - 22 % Si alloy was carried out with diamond-coated cemented carbide inserts and uncoated cemented carbide inserts. The results show that the diamond-coated cemented carbide insert has a great advantage for cutting abrasive high content Al - Si alloy. (author)

Chemical vapour deposition synthetic diamond: materials, technology and applications

International Nuclear Information System (INIS)

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

2009-01-01

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

CVD apparatus and process for the preparation of fiber-reinforced ceramic composites

Science.gov (United States)

Caputo, A.J.; Devore, C.E.; Lowden, R.A.; Moeller, H.H.

1990-01-23

An apparatus and process for the chemical vapor deposition of a matrix into a preform having circumferentially wound ceramic fibers, comprises heating one surface of the preform while cooling the other surface thereof. The resulting product may have fibers that are wound on radial planes or at an angle from the radial planes. The fibers can also be precoated with pyrolytic carbon before application of the matrix. The matrix is applied by passing reactant gas through the preform thereof to the other side thereof for the initial deposition of matrix near such other surface of the preform. The matrix fills in the preform from the other side surface thereof to the surface of the side of application thereof until a desired amount of matrix has been deposited. 6 figs.

Performance of CVD diamond as an optically and thermally stimulated luminescence dosemeter

International Nuclear Information System (INIS)

Preciado-Flores, S.; Schreck, M.; Melendrez, R.; Chernov, V.; Bernal, R.; Cruz-Vazquez, C.; Cruz-Zaragoza, E.; Barboza-Flores, M.

2006-01-01

Diamond is a material with extreme physical properties. Its radiation hardness, chemical inertness and tissue equivalence qualify it as an ideal material for radiation dosimetry. In the present work, the optically stimulated luminescence (OSL) and thermoluminescence (TL) characteristics of a 10 μm thick CVD diamond (polycrystalline diamond films prepared by chemical vapor deposition) film were studied in order to test its performance as a beta radiation dosemeter. The TL response is composed of four main TL glow peaks; two of these are in the range of 150-200 deg. C and two additional peaks in the 250-400 deg. C temperature range. The integrated TL as a function of radiation dose is linear up to 100 Gy and increases with increasing dose exposure. The dose dependence of the integrated OSL exhibits a similar behavior. The observed OSL/TL behavior for the CVD diamond film clearly demonstrate its capability for applications in radiation dosimetry with special relevance in medical dosimetry owing to the diamond's intrinsic material properties. (authors)

Heparin free coating on PLA membranes for enhanced hemocompatibility via iCVD

Science.gov (United States)

Wang, Hui; Shi, Xiao; Gao, Ailin; Lin, Haibo; Chen, Yongliang; Ye, Yumin; He, Jidong; Liu, Fu; Deng, Gang

2018-03-01

In the present work, we report one-step immobilization of nano-heparin coating on PLA membranes via initiated chemical vapor deposition (iCVD) for enhanced hemocompatibility. The nano-coating introduced onto the membrane surface via the crosslinking of P(MAA-EGDA) was confirmed by the FTIR, SEM and weight measurement respectively. The negative carboxyl groups could form the hydration interaction with the protein and platelets and electrostatic interaction with amide groups of thrombin by the mediation of antithrombin, which is similar but different with heparin. The P(MAA-EGDA) coated membranes showed suppressed platelet adhesion and prolonged clotting time (APTTs increased to 59 s, PTs increased to 20.4 s, TTs increased to 17.5 s, and the FIBs declined by 30 mg/dL). Moreover, the complement activation tests demonstrated the formation of C3a and C5a was inhibited. All results demonstrated that the nano-coating of P(MAA-EGDA) via iCVD significantly enhanced the hemocompatibility of PLA membranes, which is also applicable for various membranes.

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.

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.

Organic solar cells using CVD-grown graphene electrodes

International Nuclear Information System (INIS)

Kim, Hobeom; Han, Tae-Hee; Lim, Kyung-Geun; Lee, Tae-Woo; Bae, Sang-Hoon; Ahn, Jong-Hyun

2014-01-01

We report on the development of flexible organic solar cells (OSCs) incorporating graphene sheets synthesized by chemical vapor deposition (CVD) as transparent conducting electrodes on polyethylene terephthalate (PET) substrates. A key barrier that must be overcome for the successful fabrication of OSCs with graphene electrodes is the poor-film properties of water-based poly(3,4-ethylenedioxythiphene):poly(styrenesulfonate) (PEDOT:PSS) when coated onto hydrophobic graphene surfaces. To form a uniform PEDOT:PSS film on a graphene surface, we added perfluorinated ionomers (PFI) to pristine PEDOT:PSS to create ‘GraHEL’, which we then successfully spin coated onto the graphene surface. We systematically investigated the effect of number of layers in layer-by-layer stacked graphene anode of an OSC on the performance parameters including the open-circuit voltage (V oc ), short-circuit current (J sc ), and fill factor (FF). As the number of graphene layers increased, the FF tended to increase owing to lower sheet resistance, while J sc tended to decrease owing to the lower light absorption. In light of this trade-off between sheet resistance and transmittance, we determined that three-layer graphene (3LG) represents the best configuration for obtaining the optimal power conversion efficiency (PCE) in OSC anodes, even at suboptimal sheet resistances. We finally developed efficient, flexible OSCs with a PCE of 4.33%, which is the highest efficiency attained so far by an OSC with CVD-grown graphene electrodes to the best of our knowledge. (paper)

Transport mechanisms through PE-CVD coatings: influence of temperature, coating properties and defects on permeation of water vapour

International Nuclear Information System (INIS)

Kirchheim, Dennis; Jaritz, Montgomery; Hopmann, Christian; Dahlmann, Rainer; Mitschker, Felix; Awakowicz, Peter; Gebhard, Maximilian; Devi, Anjana; Brochhagen, Markus; Böke, Marc

2017-01-01

Gas transport mechanisms through plastics are usually described by the temperature-dependent Arrhenius-model and compositions of several plastic layers are represented by the CLT. When it comes to thin films such as plasma-enhanced chemical vapour deposition (PE-CVD) or plasma-enhanced atomic layer deposition (PE-ALD) coatings on substrates of polymeric material, a universal model is lacking. While existing models describe diffusion through defects, these models presume that permeation does not occur by other means of transport mechanisms. This paper correlates the existing transport models with data from water vapour transmission experiments. (paper)

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

Development of a fluorine-free chemical solution deposition route for rare-earth cuprate superconducting tapes and its application to reel-to-reel processing

DEFF Research Database (Denmark)

Tang, Xiao

temperature, REBCO (RE= rare earth) has some evident advantages compared to other high-temperature superconductors in retaining high current densities under strong magnetic fields, thus REBCO high temperature superconducto rs have significant potential for high field engineering applications. Compared...... to Pulsed Laser Deposition (PLD) and Chemical Vapor Deposition (CVD), the trifluoroacetate metal-organic deposition (TFA-MOD) route is more promising for producing REBCO superconducting films, owing to the high-Jc, high reproducibility, and low cost of this technique, which doesn't require any high vacuum...... on the microstructure and performance of FF-MOD derived YBCO films was investigated. Chapter 9 is the summary of the thesis....

Novel composite cBN-TiN coating deposition method: structure and performance in metal cutting

International Nuclear Information System (INIS)

Russell, W.C.; Malshe, A.P.; Yedave, S.N.; Brown, W.D.

2001-01-01

Cubic boron nitride coatings are under development for a variety of applications but stabilization of the pure cBN form and adhesion of films deposited by PVD and ion-based methods has been difficult. An alternative method for depositing a composite cBN-TiN film has been developed for wear related applications. The coating is deposited in a two-stage process utilizing ESC (electrostatic spray coating) and CVI (chemical vapor infiltration). Fully dense films of cBN particles evenly dispersed in a continuous TiN matrix have been developed. Testing in metal cutting has shown an increase in tool life (turning - 4340 steel) of three to seven times, depending of machining parameters, in comparison with CVD deposited TiN films. (author)

Chemical vapour deposition of carbon nanotubes

CSIR Research Space (South Africa)

Arendse, CJ

2006-02-01

Full Text Available , effective, more versatile and easily scalable to large substrate sizes. In this paper, we present a design of the hot-wire CVD system constructed at the CSIR for the deposition of CNTs. Additionally, we will report on the structure of CNTs deposited... exhibit exceptional chemical and physical properties related to toughness, chemical inertness, magnetism, and electrical and thermal conductivity. A variety of preparation methods to synthesise CNTs are known, e.g. carbon-arc discharge, laser ablation...

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.

Preparation of LiMn2O4 cathode thin films for thin film lithium secondary batteries by a mist CVD process

International Nuclear Information System (INIS)

Tadanaga, Kiyoharu; Yamaguchi, Akihiro; Sakuda, Atsushi; Hayashi, Akitoshi; Tatsumisago, Masahiro; Duran, Alicia; Aparacio, Mario

2014-01-01

Highlights: • LiMn 2 O 4 thin films were prepared by using the mist CVD process. • An aqueous solution of lithium and manganese acetates is used for the precursor solution. • The cell with the LiMn 2 O 4 thin films exhibited a capacity of about 80 mAh/g. • The cell showed good cycling performance during 10 cycles. - Abstract: LiMn 2 O 4 cathode thin films for thin film lithium secondary batteries were prepared by using so-called the “mist CVD process”, employing an aqueous solution of lithium acetate and manganese acetate, as the source of Li and Mn, respectively. The aqueous solution of starting materials was ultrasonically atomized to form mist particles, and mists were transferred by nitrogen gas to silica glass substrate to form thin films. FE-SEM observation revealed that thin films obtained by this process were dense and smooth, and thin films with a thickness of about 750 nm were obtained. The electrochemical cell with the thin films obtained by sintering at 700 °C exhibited a capacity of about 80 mAh/g, and the cell showed good cycling performance during 10 cycles

Investigation of PA-CVD of TiN: relations between process parameters, spectroscopic measurements and layer properties

International Nuclear Information System (INIS)

Rie, K.T.; Gebauer, A.; Woehle, J.

1993-01-01

The plasma-assisted chemical vapour deposition of TiN layers on steel substrates was investigated for various process parameters in this work. Optical emission spectroscopy (OES) was used to identify the species in the electrical discharge during the deposition process. The layer properties of the deposited TiN layers were determined by various methods (scanning electron microscopy, energy- and wavelength-dispersive X-ray analysis). The deposited layers have a constant amount of titanium, while the contents of nitrogen and chlorine show a contrary behaviour for different deposition parameters. The hardness of the layers is related among other things to the chlorine content. The OES investigations show that the Ti + and N 2 + emission is related to the layer growth rate. The formation of TiN in a gas phase reaction degrades the quality of the layers, such as their hardness. (orig.)

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

CVD-grown horizontally aligned single-walled carbon nanotubes: synthesis routes and growth mechanisms.

Science.gov (United States)

Ibrahim, Imad; Bachmatiuk, Alicja; Warner, Jamie H; Büchner, Bernd; Cuniberti, Gianaurelio; Rümmeli, Mark H

2012-07-09

Single-walled carbon nanotubes (SWCNTs) have attractive electrical and physical properties, which make them very promising for use in various applications. For some applications however, in particular those involving electronics, SWCNTs need to be synthesized with a high degree of control with respect to yield, length, alignment, diameter, and chirality. With this in mind, a great deal of effort is being directed to the precision control of vertically and horizontally aligned nanotubes. In this review the focus is on the latter, horizontally aligned tubes grown by chemical vapor deposition (CVD). The reader is provided with an in-depth review of the established vapor deposition orientation techniques. Detailed discussions on the characterization routes, growth parameters, and growth mechanisms are also provided. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Use of Kelvin probe force microscopy for identification of CVD grown graphene flakes on copper foil

Science.gov (United States)

Kumar, Rakesh; Mehta, B. R.; Kanjilal, D.

2017-05-01

Graphene flakes have been grown by chemical vapour deposition (CVD) method on Cu foils. The obtained graphene flakes have been characterized by optical microscopy, field emission scanning electron microscopy, Kelvin probe force microscopy (KPFM) and Raman spectroscopy. The graphene flakes grown on Cu foil comprise mainly single layer graphene and confirm that the nucleation for graphene growth starts very quickly. Moreover, KPFM has been found to be a valuable technique to differentiate between covered and uncovered portion of Cu foil by graphene flakes deposited for shorter duration. The results show that KPFM can be a very useful technique in understanding the mechanism of graphene growth.

Liquid-phase exfoliation of chemical vapor deposition-grown single layer graphene and its application in solution-processed transparent electrodes for flexible organic light-emitting devices

International Nuclear Information System (INIS)

Wu, Chaoxing; Li, Fushan; Wu, Wei; Chen, Wei; Guo, Tailiang

2014-01-01

Efficient and low-cost methods for obtaining high performance flexible transparent electrodes based on chemical vapor deposition (CVD)-grown graphene are highly desirable. In this work, the graphene grown on copper foil was exfoliated into micron-size sheets through controllable ultrasonication. We developed a clean technique by blending the exfoliated single layer graphene sheets with conducting polymer to form graphene-based composite solution, which can be spin-coated on flexible substrate, forming flexible transparent conducting film with high conductivity (∼8 Ω/□), high transmittance (∼81% at 550 nm), and excellent mechanical robustness. In addition, CVD-grown-graphene-based polymer light emitting diodes with excellent bendable performances were demonstrated

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.

Sub-10-nm patterning via directed self-assembly of block copolymer films with a vapour-phase deposited topcoat

Science.gov (United States)

Suh, Hyo Seon; Kim, Do Han; Moni, Priya; Xiong, Shisheng; Ocola, Leonidas E.; Zaluzec, Nestor J.; Gleason, Karen K.; Nealey, Paul F.

2017-07-01

Directed self-assembly (DSA) of the domain structure in block copolymer (BCP) thin films is a promising approach for sub-10-nm surface patterning. DSA requires the control of interfacial properties on both interfaces of a BCP film to induce the formation of domains that traverse the entire film with a perpendicular orientation. Here we show a methodology to control the interfacial properties of BCP films that uses a polymer topcoat deposited by initiated chemical vapour deposition (iCVD). The iCVD topcoat forms a crosslinked network that grafts to and immobilizes BCP chains to create an interface that is equally attractive to both blocks of the underlying copolymer. The topcoat, in conjunction with a chemically patterned substrate, directs the assembly of the grating structures in BCP films with a half-pitch dimension of 9.3 nm. As the iCVD topcoat can be as thin as 7 nm, it is amenable to pattern transfer without removal. The ease of vapour-phase deposition, applicability to high-resolution BCP systems and integration with pattern-transfer schemes are attractive properties of iCVD topcoats for industrial applications.

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

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.

Physically vapor deposited coatings on tools: performance and wear phenomena

International Nuclear Information System (INIS)

Koenig, W.; Fritsch, R.; Kammermeier, D.

1991-01-01

Coatings produced by physical vapor deposition (PVD) enhance the performance of tools for a broad variety of production processes. In addition to TiN, nowadays (Ti,Al)N and Ti(C,N) coated tools are available. This gives the opportunity to compare the performance of different coatings under identical machining conditions and to evaluate causes and phenomena of wear. TiN, (Ti,Al)N and Ti(C,N) coatings on high speed steel (HSS) show different performances in milling and turning of heat treated steel. The thermal and frictional properties of the coating materials affect the structure, the thickness and the flow of the chips, the contact area on the rake face and the tool life. Model tests show the influence of internal cooling and the thermal conductivity of coated HSS inserts. TiN and (Ti,Zr)N PVD coatings on cemented carbides were examined in interrupted turning and in milling of heat treated steel. Experimental results show a significant influence of typical time-temperature cycles of PVD and chemical vapor deposition (CVD) coating processes on the physical data and on the performance of the substrates. PVD coatings increase tool life, especially towards lower cutting speeds into ranges which cannot be applied with CVD coatings. The reason for this is the superior toughness of the PVD coated carbide. The combination of tough, micrograin carbide and PVD coating even enables broaching of case hardened sliding gears at a cutting speed of 66 m min -1 . (orig.)

Chemical vapor deposition of NiSi using Ni(PF3)4 and Si3H8

International Nuclear Information System (INIS)

Ishikawa, M.; Muramoto, I.; Machida, H.; Imai, S.; Ogura, A.; Ohshita, Y.

2007-01-01

NiSi x films were deposited using chemical vapor deposition (CVD) with a Ni(PF 3 ) 4 and Si 3 H 8 /H 2 gas system. The step coverage quality of deposited NiSi x was investigated using a horizontal type of hot-wall low pressure CVD reactor, which maintained a constant temperature throughout the deposition area. The step coverage quality improved as a function of the position of the gas flow direction, where PF 3 gas from decomposition of Ni(PF 3 ) 4 increased. By injecting PF 3 gas into the Ni(PF 3 ) 4 and Si 3 H 8 /H 2 gas system, the step coverage quality markedly improved. This improvement in step coverage quality naturally occurred when PF 3 gas was present, indicating a strong relationship. The Si/Ni deposit ratio at 250 deg. C is larger than at 180 deg. C. It caused a decreasing relative deposition rate of Ni to Si. PF 3 molecules appear to be adsorbed on the surface of the deposited film and interfere with faster deposition of active Ni deposition species

Urchin-like artificial gallium oxide nanowires grown by a novel MOCVD/CVD-based route for random laser application

Energy Technology Data Exchange (ETDEWEB)

Melo, Ronaldo P. de [Programa de Pós-Graduação em Ciências de Materiais, Universidade Federal de Pernambuco, Recife (Brazil); Colégio Militar do Recife, Exército Brasileiro, Recife PE 50730-120 (Brazil); Oliveira, Nathalia Talita C. [Programa de Pós-Graduação em Ciências de Materiais, Universidade Federal de Pernambuco, Recife (Brazil); Dominguez, Christian Tolentino; Gomes, Anderson S. L.; Araújo, Cid B. de [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Falcão, Eduardo H. L.; Alves, Severino; Luz, Leonis L. da [Departamento de Química Fundamental, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Chassagnon, Remi [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47870, 21078 Dijon Cedex (France); Sacilotti, Marco [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife (Brazil); Nanoform Group, Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne, Dijon (France)

2016-04-28

A novel procedure based on a two-step method was developed to obtain β-Ga{sub 2}O{sub 3} nanowires by the chemical vapor deposition (CVD) method. The first step consists in the gallium micro-spheres growth inside a metal-organic chemical vapor deposition environment, using an organometallic precursor. Nanoscale spheres covering the microspheres were obtained. The second step involves the CVD oxidization of the gallium micro-spheres, which allow the formation of β-Ga{sub 2}O{sub 3} nanowires on the micro-sphere surface, with the final result being a nanostructure mimicking nature's sea urchin morphology. The grown nanomaterial is characterized by several techniques, including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, and photoluminescence. A discussion about the growth mechanism and the optical properties of the β-Ga{sub 2}O{sub 3} material is presented considering its unknown true bandgap value (extending from 4.4 to 5.68 eV). As an application, the scattering properties of the nanomaterial are exploited to demonstrate random laser emission (around 570 nm) when it is permeated with a laser dye liquid solution.

A systematic study of the controlled generation of crystalline iron oxide nanoparticles on graphene using a chemical etching process

Directory of Open Access Journals (Sweden)

Peter Krauß

2017-09-01

Full Text Available Chemical vapor deposition (CVD of carbon precursors employing a metal catalyst is a well-established method for synthesizing high-quality single-layer graphene. Yet the main challenge of the CVD process is the required transfer of a graphene layer from the substrate surface onto a chosen target substrate. This process is delicate and can severely degrade the quality of the transferred graphene. The protective polymer coatings typically used generate residues and contamination on the ultrathin graphene layer. In this work, we have developed a graphene transfer process which works without a coating and allows the transfer of graphene onto arbitrary substrates without the need for any additional post-processing. During the course of our transfer studies, we found that the etching process that is usually employed can lead to contamination of the graphene layer with the Faradaic etchant component FeCl3, resulting in the deposition of iron oxide FexOy nanoparticles on the graphene surface. We systematically analyzed the removal of the copper substrate layer and verified that crystalline iron oxide nanoparticles could be generated in controllable density on the graphene surface when this process is optimized. It was further confirmed that the FexOy particles on graphene are active in the catalytic growth of carbon nanotubes when employing a water-assisted CVD process.

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

Study on the low leakage current of an MIS structure fabricated by ICP-CVD

Energy Technology Data Exchange (ETDEWEB)

Tsai, S-Y; Hon, M-H [Department of Materials Science and Engineering, National Cheng Kung University, 1, Ta-Hsueh Road, Tainan, 701 Taiwan (China); Lu, Y-M, E-mail: ymlumit@yahoo.com.tw

2008-03-15

As the dimensions of electric devices continue to shrink, it is becoming increasingly important to understand how to obtain good quality gate oxide film materials wilth higher carrier mobility, lower leakage current and greater reliability. All of them have become major concerns in the fabrication of thin film oxide transistors. A novel film deposition method called Inductively Coupled Plasma-Chemical Vapor Deposition (ICP-CVD) has received attraction in the semiconductor industry, because it can be capable of generating high density plasmas at extremely low temperature, resulting in less ion bombardment of the material surface. In this work, we present the results of crystallized silicon dioxide films deposited by inductively coupled plasma chemical vapor deposition technique at an extremely low temperature of 90 deg. C. The value of the refractive index of the crystallized ICP-CVD SiO{sub 2} film depends on the r.f. power of the ICP system, and approximates to be 1.46. This value is comparable to that of SiO{sub 2} films prepared by thermal oxidation. As the r.f. power of ICP applied more than 1250 Watts, still only the (111) diffraction peak is observed by XRD, which implies a very strong preferred orientation or single crystal structure. Too low or too high r.f. power both produces amorphous SiO{sub 2} films. From the I-V curve, the MIS device with a SiO{sub 2} dielectric film has a lower leakage current density of 6.8x10{sup -8}A/cm{sup 2} at 1V as the film prepared at 1750 watts. The highest breakdown field in this study is 15.8 MV/cm. From the FTIR analysis, it was found that more hydrogen atoms incorporate into films and form Si-OH bonds as the r.f. power increases. The existence of Si-OH bonds leads to a poor reliability of the MIS device.

CVD diamond - fundamental phenomena

Energy Technology Data Exchange (ETDEWEB)

Yarbrough, W.A. [Pennsylvania State Univ., University Park (United States)

1993-01-01

This compilation of figures and diagrams addresses the basic physical processes involved in the chemical vapor deposition of diamond. Different methods of deposition are illustrated. For each method, observations are made of the prominent advantages and disadvantages of the technique. Chemical mechanisms of nucleation are introduced.

Test of radiation hardness of pcCVD detectors

Energy Technology Data Exchange (ETDEWEB)

Schlemme, Steffen [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Technische Universitaet Darmstadt (Germany); Enders, Joachim [Technische Universitaet Darmstadt (Germany); Figuera, P.; Salamone, S. [LNS-INFN Catania (Italy); Fruehauf, J.; Kis, Mladen; Kratz, A.; Kurz, N.; Loechner, S.; Nociforo, Chiara; Schirru, Fabio; Szczepanczyk, B.; Traeger, M.; Visinka, R. [GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Musumarra, A. [LNS-INFN Catania (Italy); University of Catania (Italy)

2016-07-01

The new in-flight separator Super-FRS is under construction at the Facility for Antiproton and Ion Research (FAIR, Darmstadt). Ion rates up to 3 x 10{sup 11} {sup 238}U/spill demand an adaption of detectors to a high radiation environment. A test experiment to investigate the radiation hardness of polycrystalline diamond detectors (pcCVD) was performed at the LNS-INFN in Catania using a {sup 12}C beam at 62 MeV/u and intensities of up to 1.5 pnA. The setup consisted of pcCVD strip detectors to measure the beam profile, a single crystal diamond detector to calibrate the ionisation chamber working in current mode as a beam intensity monitor and a pcCVD sample to be irradiated. The IC used was designed for FAIR and showed a stable counting rate allowing us to calibrate and perform beam intensity measurements with it. The total measured counts on the sample were 8.25 x 10{sup 11} counts/mm{sup 2} over a period of 60 hours. Digital waveforms of the pcCVD signals were taken with an oscilloscope and analysed. The results showed no change of the pcCVD signal properties during the entire irradiation.

CVD boron nitride infiltration of fibrous structures: properties of low temprature deposits

International Nuclear Information System (INIS)

Gebhardt, J.J.

1973-01-01

The pyrolytic infiltration of boron nitride and silica fibrous structures with boron nitride was investigated using the thermal decomposition of B-trichloroborazole (TCB) to provide the matrix surrounding felted and 4-directional braided constructions. The deposition precursor was generated on a continuous basis by the reaction between boron trichloride and ammonium chloride in a fixed bed reactor under conditions of total conversion of the trichloride: 3BCl 3 + 3NH 4 Cl = B 3 N 3 H 3 Cl 3 + 9HCl. Deposition rates in boron nitride felt specimens varied between 8 and 28 μm/h, depending on the distance from the exterior surface at the minimum deposition temperature used (1100 0 C ). Infiltration of 4-directional silica braids was poorer because of clogging of the fiber bundle surfaces and access paths to voids in the weave. Deposits prepared at 1100 0 C and above were stable to moisture and consisted of glassy transparent materials which had no discernible x-ray diffraction pattern. Heat treatment of low temperature deposits in nitrogen at 1800 0 C caused significant growth of the crystallites and the emergence of x-ray patterns characteristic of hexagonal boron nitride. Heat treatment in vacuum caused changes in the infrared spectrum which could be correlated with mass analyses of the gases evolved. Loss of hydrogen with amines predominated to about 1500 0 C above which point the loss of nitrogen became significant. (14 figures) (U.S.)

Chemical vapor deposition of nanocrystalline diamond films

International Nuclear Information System (INIS)

Vyrovets, I.I.; Gritsyna, V.I.; Dudnik, S.F.; Opalev, O.A.; Reshetnyak, O.M.; Strel'nitskij, V.E.

2008-01-01

The brief review of the literature is devoted to synthesis of nanocrystalline diamond films. It is shown that the CVD method is an effective way for deposition of such nanostructures. The basic technological methods that allow limit the size of growing diamond crystallites in the film are studied.

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.

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

A nitrogen doped low-dislocation density free-standing single crystal diamond plate fabricated by a lift-off process

Energy Technology Data Exchange (ETDEWEB)

Mokuno, Yoshiaki, E-mail: mokuno-y@aist.go.jp; Kato, Yukako; Tsubouchi, Nobuteru; Chayahara, Akiyoshi; Yamada, Hideaki; Shikata, Shinichi [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan)

2014-06-23

A nitrogen-doped single crystal diamond plate with a low dislocation density is fabricated by chemical vapor deposition (CVD) from a high pressure high temperature synthetic type IIa seed substrate by ion implantation and lift-off processes. To avoid sub-surface damage, the seed surface was subjected to deep ion beam etching. In addition, we introduced a nitrogen flow during the CVD step to grow low-strain diamond at a relatively high growth rate. This resulted in a plate with low birefringence and a dislocation density as low as 400 cm{sup −2}, which is the lowest reported value for a lift-off plate. Reproducing this lift-off process may allow mass-production of single crystal CVD diamond plates with low dislocation density and consistent quality.

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.

Expanding thermal plasma chemical vapour deposition of ZnO:Al layers for CIGS solar cells

NARCIS (Netherlands)

Sharma, K.; Williams, B.L.; Mittal, A.; Knoops, H.C.M.; Kniknie, B.J.; Bakker, N.J.; Kessels, W.M.M.; Schropp, R.E.I.; Creatore, M.

2014-01-01

Aluminium-doped zinc oxide (ZnO:Al) grown by expanding thermal plasma chemical vapour deposition (ETP-CVD) has demonstrated excellent electrical and optical properties, which make it an attractive candidate as a transparent conductive oxide for photovoltaic applications. However, when depositing

Effect of process conditions and chemical composition on the microstructure and properties of chemically vapor deposited SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x)

Science.gov (United States)

Pickering, Michael A.; Taylor, Raymond L.; Goela, Jitendra S.; Desai, Hemant D.

1992-01-01

Subatmospheric pressure CVD processes have been developed to produce theoretically dense, highly pure, void-free and large area bulk materials, SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x). These materials are used for optical elements, such as mirrors, lenses and windows, over a wide spectral range from the VUV to the IR. We discuss the effect of CVD process conditions on the microstructure and properties of these materials, with emphasis on optical performance. In addition, we discuss the effect of chemical composition on the properties of the composite material ZnS(x)Se(1-x). We first present a general overview of the bulk CVD process and the relationship between process conditions, such as temperature, pressure, reactant gas concentration and growth rate, and the microstructure, morphology and properties of CVD-grown materials. Then we discuss specific results for CVD-grown SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x).

Role of hydrogen in Sb film deposition and characterization of Sb and GexSby films deposited by cyclic plasma enhanced chemical vapor deposition using metal-organic precursors

International Nuclear Information System (INIS)

Kim, Hyung Keun; Jung, Jin Hwan; Choi, Doo Jin

2012-01-01

th increase were explained via the bonding characteristics of each element. - Highlights: ► We used non-toxic precursors not containing Si, Cl nor N elements. ► We investigated the role of H 2 gas during GeSb film deposition. ► GeSb films were deposited by chemical vapor deposition (CVD). ► Atomic ratio of Ge and Sb was well controlled by our custom made CVD system. ► Electrical switching behaviors were clearly observed in CVD-deposited GeSb film.

Fabrication and Characterization of FeNiCr Matrix-TiC Composite for Polishing CVD Diamond Film

Institute of Scientific and Technical Information of China (English)

Zhuji Jin; Zewei Yuan; Renke Kang; Boxian Dong

2009-01-01

Dynamic friction polishing (DFP) is one of the most promising methods appropriate for polishing CVD diamond film with high efficiency and low cost.By this method CVD diamond film is polished through being simply pressed against a metal disc rotating at a high speed utilizing the thermochemical reaction occurring as a result of dynamic friction between them in the atmosphere.However, the relatively soft materials such as stainless steel, cast iron and nickel alloy widely used for polishing CVD diamond film are easy to wear and adhere to diamond film surface, which may further lead to low efficiency and poor polishing quality.In this paper, FeNiCr matrix-TiC composite used as grinding wheel for polishing CVD diamond film was obtained by combination of mechanical alloying (MA) and spark plasma sintering (SPS).The process of ball milling,composition, density, hardness, high-temperature oxidation resistance and wear resistance of the sintered piece were analyzed.The results show that TiC was introduced in MA-SPS process and had good combination with FeNiCr matrix and even distribution in the matrix.The density of composite can be improved by mechanical alloying.The FeNiCr matrix-TiC composite obtained at 1273 K was found to be superior to at 1173 K sintering in hardness, high-temperature oxidation resistance and wearability.These properties are more favorable than SUS304 for the preparation of high-performance grinding wheel for polishing CVD diamond film.

Unravelling merging behaviors and electrostatic properties of CVD-grown monolayer MoS2 domains

International Nuclear Information System (INIS)

Hao, Song; Yang, Bingchu; Gao, Yongli

2016-01-01

The presence of grain boundaries is inevitable for chemical vapor deposition (CVD)-grown MoS 2 domains owing to various merging behaviors, which greatly limits its potential applications in novel electronic and optoelectronic devices. It is therefore of great significance to unravel the merging behaviors of the synthesized polygon shape MoS 2 domains. Here we provide systematic investigations of merging behaviors and electrostatic properties of CVD-grown polycrystalline MoS 2 crystals by multiple means. Morphological results exhibit various polygon shape features, ascribed to polycrystalline crystals merged with triangle shape MoS 2 single crystals. The thickness of triangle and polygon shape MoS 2 crystals is identical manifested by Raman intensity and peak position mappings. Three merging behaviors are proposed to illustrate the formation mechanisms of observed various polygon shaped MoS 2 crystals. The combined photoemission electron microscopy and kelvin probe force microscopy results reveal that the surface potential of perfect merged crystals is identical, which has an important implication for fabricating MoS 2 -based devices.

A CVD diamond beam telescope for charged particle tracking

CERN Document Server

Adam, W; Bergonzo, P; de Boer, Wim; Bogani, F; Borchi, E; Brambilla, A; Bruzzi, Mara; Colledani, C; Conway, J; D'Angelo, P; Dabrowski, W; Delpierre, P A; Dulinski, W; Doroshenko, J; Doucet, M; van Eijk, B; Fallou, A; Fischer, P; Fizzotti, F; Kania, D R; Gan, K K; Grigoriev, E; Hallewell, G D; Han, S; Hartjes, F G; Hrubec, Josef; Husson, D; Kagan, H; Kaplon, J; Kass, R; Keil, M; Knöpfle, K T; Koeth, T W; Krammer, Manfred; Meuser, S; Lo Giudice, A; MacLynne, L; Manfredotti, C; Meier, D; Menichelli, D; Mishina, M; Moroni, L; Noomen, J; Oh, A; Pan, L S; Pernicka, Manfred; Perera, L P; Riester, J L; Roe, S; Rudge, A; Russ, J; Sala, S; Sampietro, M; Schnetzer, S; Sciortino, S; Stelzer, H; Stone, R; Suter, B; Trischuk, W; Tromson, D; Vittone, E; Weilhammer, Peter; Wermes, N; Wetstein, M; Zeuner, W; Zöller, M

2002-01-01

CVD diamond is a radiation hard sensor material which may be used for charged particle tracking near the interaction region in experiments at high luminosity colliders. The goal of the work described here is to investigate the use of several detector planes made of CVD diamond strip sensors for charged particle tracking. Towards this end a tracking telescope composed entirely of CVD diamond planes has been constructed. The telescope was tested in muon beams and its tracking capability has been investigated.

Effect of heat treatment on the characteristics of tool steel deposited by the directed energy deposition process

Science.gov (United States)

Park, Jun Seok; Lee, Min-Gyu; Cho, Yong-Jae; Sung, Ji Hyun; Jeong, Myeong-Sik; Lee, Sang-Kon; Choi, Yong-Jin; Kim, Da Hye

2016-01-01

The directed energy deposition process has been mainly applied to re-work and the restoration of damaged steel. Differences in material properties between the base and the newly deposited materials are unavoidable, which may affect the mechanical properties and durability of the part. We investigated the effect of heat treatment on the characteristics of tool steel deposited by the DED process. We prepared general tool steel materials of H13 and D2 that were deposited onto heat-treated substrates of H13 and D2, respectively, using a direct metal tooling process. The hardness and microstructure of the deposited steel before and after heat treatment were investigated. The hardness of the deposited H13 steel was higher than that of wrought H13 steel substrate, while that of the deposited D2 was lower than that of wrought D2. The evolution of the microstructures by deposition and heat treatment varied depending on the materials. In particular, the microstructure of the deposited D2 steel after heat treatment consisted of fine carbides in tempered martensite and it is expected that the deposited D2 steel will have isotropic properties and high hardness after heat treatment.

A comparison of different spray chemical vapour deposition methods for the production of undoped ZnO thin films

International Nuclear Information System (INIS)

Garnier, Jerome; Bouteville, Anne; Hamilton, Jeff; Pemble, Martyn E.; Povey, Ian M.

2009-01-01

Two different methods of spray chemical vapour deposition have been used to grow ZnO thin films on glass substrates from zinc acetate solution over the temperature range 400 o C to 550 o C. The first of these is named InfraRed Assisted Spray Chemical Vapour Deposition (IRAS-CVD). This method uses intense IR radiation to heat not only the substrate but also the gaseous species entering the reactor. The second method is a more conventional approach known simply as ultrasonic spray CVD, which utilises IR lamps to heat the substrate only. By way of comparing these two approaches we present data obtained from contact angle measurements, crystallinity and mean crystallite size, photoluminescence, electrical and optical properties. Additionally we have examined the role of annealing within the IRAS-CVD reactor environment.

Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage.

Science.gov (United States)

Guan, Cao; Wang, John

2016-10-01

Electrode materials play a decisive role in almost all electrochemical energy storage devices, determining their overall performance. Proper selection, design and fabrication of electrode materials have thus been regarded as one of the most critical steps in achieving high electrochemical energy storage performance. As an advanced nanotechnology for thin films and surfaces with conformal interfacial features and well controllable deposition thickness, atomic layer deposition (ALD) has been successfully developed for deposition and surface modification of electrode materials, where there are considerable issues of interfacial and surface chemistry at atomic and nanometer scale. In addition, ALD has shown great potential in construction of novel nanostructured active materials that otherwise can be hardly obtained by other processing techniques, such as those solution-based processing and chemical vapor deposition (CVD) techniques. This review focuses on the recent development of ALD for the design and delivery of advanced electrode materials in electrochemical energy storage devices, where typical examples will be highlighted and analyzed, and the merits and challenges of ALD for applications in energy storage will also be discussed.

Enhanced B doping in CVD-grown GeSn:B using B δ-doping layers

Science.gov (United States)

Kohen, David; Vohra, Anurag; Loo, Roger; Vandervorst, Wilfried; Bhargava, Nupur; Margetis, Joe; Tolle, John

2018-02-01

Highly doped GeSn material is interesting for both electronic and optical applications. GeSn:B is a candidate for source-drain material in future Ge pMOS device because Sn adds compressive strain with respect to pure Ge, and therefore can boost the Ge channel performances. A high B concentration is required to obtain low contact resistivity between the source-drain material and the metal contact. To achieve high performance, it is therefore highly desirable to maximize both the Sn content and the B concentration. However, it has been shown than CVD-grown GeSn:B shows a trade-off between the Sn incorporation and the B concentration (increasing B doping reduces Sn incorporation). Furthermore, the highest B concentration of CVD-grown GeSn:B process reported in the literature has been limited to below 1 × 1020 cm-3. Here, we demonstrate a CVD process where B δ-doping layers are inserted in the GeSn layer. We studied the influence of the thickness between each δ-doping layers and the δ-doping layers process conditions on the crystalline quality and the doping density of the GeSn:B layers. For the same Sn content, the δ-doping process results in a 4-times higher B doping than the co-flow process. In addition, a B doping concentration of 2 × 1021 cm-3 with an active concentration of 5 × 1020 cm-3 is achieved.

Cardiovascular disease (CVD and chronic kidney disease (CKD event rates in HIV-positive persons at high predicted CVD and CKD risk: A prospective analysis of the D:A:D observational study.

Directory of Open Access Journals (Sweden)

Mark A Boyd

2017-11-01

Full Text Available The Data Collection on Adverse Events of Anti-HIV Drugs (D:A:D study has developed predictive risk scores for cardiovascular disease (CVD and chronic kidney disease (CKD, defined as confirmed estimated glomerular filtration rate [eGFR] ≤ 60 ml/min/1.73 m2 events in HIV-positive people. We hypothesized that participants in D:A:D at high (>5% predicted risk for both CVD and CKD would be at even greater risk for CVD and CKD events.We included all participants with complete risk factor (covariate data, baseline eGFR > 60 ml/min/1.73 m2, and a confirmed (>3 months apart eGFR 1%-5%, >5% and fitted Poisson models to assess whether CVD and CKD risk group effects were multiplicative. A total of 27,215 participants contributed 202,034 person-years of follow-up: 74% male, median (IQR age 42 (36, 49 years, median (IQR baseline year of follow-up 2005 (2004, 2008. D:A:D risk equations predicted 3,560 (13.1% participants at high CVD risk, 4,996 (18.4% participants at high CKD risk, and 1,585 (5.8% participants at both high CKD and high CVD risk. CVD and CKD event rates by predicted risk group were multiplicative. Participants at high CVD risk had a 5.63-fold (95% CI 4.47, 7.09, p < 0.001 increase in CKD events compared to those at low risk; participants at high CKD risk had a 1.31-fold (95% CI 1.09, 1.56, p = 0.005 increase in CVD events compared to those at low risk. Participants' CVD and CKD risk groups had multiplicative predictive effects, with no evidence of an interaction (p = 0.329 and p = 0.291 for CKD and CVD, respectively. The main study limitation is the difference in the ascertainment of the clinically defined CVD endpoints and the laboratory-defined CKD endpoints.We found that people at high predicted risk for both CVD and CKD have substantially greater risks for both CVD and CKD events compared with those at low predicted risk for both outcomes, and compared to those at high predicted risk for only CVD or CKD events. This suggests that CVD and

TiO2 anatase thin films deposited by spray pyrolysis of an aerosol of titanium diisopropoxide

International Nuclear Information System (INIS)

Conde-Gallardo, A.; Guerrero, M.; Castillo, N.; Soto, A.B.; Fragoso, R.; Cabanas-Moreno, J.G.

2005-01-01

Titanium dioxide thin films were deposited on crystalline silicon (100) and fused quartz substrates by spray pyrolysis (SP) of an aerosol, generated ultrasonically, of titanium diisopropoxide. The evolution of the crystallization, studied by X-ray diffraction (XRD), atomic force (AFM) and scanning electron microscopy (SEM), reflection and transmission spectroscopies, shows that the deposition process is nearly close to the classical chemical vapor deposition (CVD) technique, producing films with smooth surface and good crystalline properties. At deposition temperatures below 400 deg. C, the films grow in amorphous phase with a flat surface (roughness∼0.5 nm); while for equal or higher values to this temperature, the films develop a crystalline phase corresponding to the TiO 2 anatase phase and the surface roughness is increased. After annealing at 750 deg. C, the samples deposited on Si show a transition to the rutile phase oriented in (111) direction, while for those films deposited on fused quartz no phase transition is observed

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

Atomic-layer chemical-vapor-deposition of TiN thin films on Si(100) and Si(111)

CERN Document Server

Kim, Y S; Kim, Y D; Kim, W M

2000-01-01

An atomic-layer chemical vapor deposition (AL-CVD) system was used to deposit TiN thin films on Si(100) and Si(111) substrates by cyclic exposures of TiCl sub 4 and NH sub 3. The growth rate was measured by using the number of deposition cycles, and the physical properties were compared with those of TiN films grown by using conventional deposition methods. To investigate the growth mechanism, we suggest a growth model for TiN n order to calculate the growth rate per cycle with a Cerius program. The results of the calculation with the model were compared with the experimental values for the TiN film deposited using the AL-CVD method. The stoichiometry of the TiN film was examined by using Auger electron spectroscopy, and the chlorine and the oxygen impurities were examined. The x-ray diffraction and the transmission electron microscopy results for the TiN film exhibited a strong (200) peak and a randomly oriented columnar microstructure. The electrical resistivity was found to decrease with increasing deposit...

A new CVD diamond mosaic-detector for (n, α) cross-section measurements at the n{sub T}OF experiment at CERN

Energy Technology Data Exchange (ETDEWEB)

Weiß, C., E-mail: christina.weiss@cern.ch [Atominstitut, Technische Universität Wien (Austria); European Organization for Nuclear Research (CERN), Geneva (Switzerland); Griesmayer, E. [Atominstitut, Technische Universität Wien (Austria); Guerrero, C. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Altstadt, S. [Johann-Wolfgang-Goethe Universität, Frankfurt (Germany); Andrzejewski, J. [Uniwersytet Łódzki, Lodz (Poland); Audouin, L. [Centre National de la Recherche Scientifique/IN2P3 - IPN, Orsay (France); Badurek, G. [Atominstitut, Technische Universität Wien (Austria); Barbagallo, M. [Istituto Nazionale di Fisica Nucleare, Bari (Italy); Bécares, V. [Centro de Investigaciones Energeticas Medioambientales y Tecnológicas (CIEMAT), Madrid (Spain); Bečvář, F. [Charles University, Prague (Czech Republic); Belloni, F. [Commissariat à l’Énergie Atomique (CEA) Saclay - Irfu, Gif-sur-Yvette (France); Berthoumieux, E. [Commissariat à l’Énergie Atomique (CEA) Saclay - Irfu, Gif-sur-Yvette (France); European Organization for Nuclear Research (CERN), Geneva (Switzerland); Billowes, J. [University of Manchester, Oxford Road, Manchester (United Kingdom); Boccone, V. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Bosnar, D. [Department of Physics, Faculty of Science, University of Zagreb (Croatia); Brugger, M.; Calviani, M. [European Organization for Nuclear Research (CERN), Geneva (Switzerland); Calviño, F. [Universitat Politecnica de Catalunya, Barcelona (Spain); and others

2013-12-21

At the n{sub T}OF experiment at CERN a dedicated single-crystal chemical vapor deposition (sCVD) Diamond Mosaic-Detector has been developed for (n,α) cross-section measurements. The detector, characterized by an excellent time and energy resolution, consists of an array of 9 sCVD diamond diodes. The detector has been characterized and a cross-section measurement has been performed for the {sup 59}Ni(n,α){sup 56}Fe reaction in 2012. The characteristics of the detector, its performance and the promising preliminary results of the experiment are presented. -- Highlights: •A large-area detector of 3 ×3 sCVD diamonds was built for (n, α) measurements. •The {sup 59}Ni(n, α){sup 56}Fe cross-section was measured successfully at n{sub T}OF/CERN. •The energy resolution of the detector meets the expectations from simulations. •The reaction products during the measurement at n{sub T}OF could clearly be separated. •The detector is suitable for (n, α) measurements in a heterogeneous beam.

Microscopic characterisation of suspended graphene grown by chemical vapour deposition

NARCIS (Netherlands)

Bignardi, L.; Dorp, W.F. van; Gottardi, S.; Ivashenko, O.; Dudin, P.; Barinov, A.; de Hosson, J.T.M.; Stöhr, M.; Rudolf, P.

2013-01-01

We present a multi-technique characterisation of graphene grown by chemical vapour deposition (CVD) and thereafter transferred to and suspended on a grid for transmission electron microscopy (TEM). The properties of the electronic band structure are investigated by angle-resolved photoelectron

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

Unravelling merging behaviors and electrostatic properties of CVD-grown monolayer MoS{sub 2} domains

Energy Technology Data Exchange (ETDEWEB)

Hao, Song; Yang, Bingchu, E-mail: bingchuyang@csu.edu.cn [College of Physics and Electronics, Institute of Super Microstructure and Ultrafast Process in Advanced Materials, Central South University, 605 South Lushan Road, Changsha 410012 (China); Hunan Key Laboratory for Super-Microstructure and Ultrafast Process, Central South University, 932 South Lushan Road, Changsha 410012 (China); Gao, Yongli [College of Physics and Electronics, Institute of Super Microstructure and Ultrafast Process in Advanced Materials, Central South University, 605 South Lushan Road, Changsha 410012 (China); Hunan Key Laboratory for Super-Microstructure and Ultrafast Process, Central South University, 932 South Lushan Road, Changsha 410012 (China); Department of Physics and Astronomy, University of Rochester, Rochester, New York 14534 (United States)

2016-08-28

The presence of grain boundaries is inevitable for chemical vapor deposition (CVD)-grown MoS{sub 2} domains owing to various merging behaviors, which greatly limits its potential applications in novel electronic and optoelectronic devices. It is therefore of great significance to unravel the merging behaviors of the synthesized polygon shape MoS{sub 2} domains. Here we provide systematic investigations of merging behaviors and electrostatic properties of CVD-grown polycrystalline MoS{sub 2} crystals by multiple means. Morphological results exhibit various polygon shape features, ascribed to polycrystalline crystals merged with triangle shape MoS{sub 2} single crystals. The thickness of triangle and polygon shape MoS{sub 2} crystals is identical manifested by Raman intensity and peak position mappings. Three merging behaviors are proposed to illustrate the formation mechanisms of observed various polygon shaped MoS{sub 2} crystals. The combined photoemission electron microscopy and kelvin probe force microscopy results reveal that the surface potential of perfect merged crystals is identical, which has an important implication for fabricating MoS{sub 2}-based devices.

Application of Cat-CVD for ULSI technology

International Nuclear Information System (INIS)

Akasaka, Yoichi

2008-01-01

The ULSI technology has been following Moore's law into the sub-100 nm era, although several challenging technical issues must be resolved. This paper describes possible application of Cat-CVD for ULSI technology beyond the 45 nm node. Especially, Cat-CVD SiN film for a transistor gate sidewall and/or a pre-metallic liner layer, and removal of photo resist (ash) by Cat-induced hydrogen atoms in the interconnect structure with an extreme low-k material are mainly discussed

Influence of Gas Flow Rate on the Deposition Rate on Stainless Steel 202 Substrates

OpenAIRE

M.A. Chowdhury; D.M. Nuruzzaman

2012-01-01

Solid thin films have been deposited on stainless steel 202 (SS 202) substrates at different flow rates of natural gas using a hot filament thermal chemical vapor deposition (CVD) reactor. In the experiments, the variations of thin film deposition rate with the variation of gas flow rate have been investigated. The effects of gap between activation heater and substrate on the deposition rate have also been observed. Results show that deposition rate on SS 202 increases with the increase in g...

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.

Large-scale synthesis of NbS2 nanosheets with controlled orientation on graphene by ambient pressure CVD.

Science.gov (United States)

Ge, Wanyin; Kawahara, Kenji; Tsuji, Masaharu; Ago, Hiroki

2013-07-07

We report ambient pressure chemical vapor deposition (CVD) growth of single-crystalline NbS2 nanosheets with controlled orientation. On Si and SiO2 substrates, NbS2 nanosheets grow almost perpendicular to the substrate surface. However, when we apply transferred CVD graphene on SiO2 as a substrate, NbS2 sheets grow laterally lying on the graphene. The NbS2 sheets show the triangular and hexagonal shapes with a thickness of about 20-200 nm and several micrometres in the lateral dimension. Analyses based on X-ray diffraction and Raman spectroscopy indicate that the NbS2 nanosheets are single crystalline 3R-type with a rhombohedral structure of R3m space group. Our findings on the formation of highly aligned NbS2 nanosheets on graphene give new insight into the formation mechanism of NbS2 and would contribute to the templated growth of various layered materials.

CVD and obesity in transitional Syria: a perspective from the Middle East.

Science.gov (United States)

Barakat, Hani; Barakat, Hanniya; Baaj, Mohamad K

2012-01-01

Syria is caught in the middle of a disruptive nutritional transition. Its healthcare system is distracted by challenges and successes in other areas while neglecting to address the onslaught of Syria's cardiovascular disease (CVD) epidemic. Despite the official viewpoint touting improvement in health indicators, current trends jeopardize population health, and several surveys in the Syrian population signal the epidemic spreading far and wide. The goal is to counteract the indifference towards obesity as a threat to Syrian's health, as the country is slowly becoming a leader in CVD mortality globally. PubMed, World Health Organization, and official government websites were searched for primary surveys in Syria related to CVD morbidity, mortality, and risk factors. Inclusion criteria ensured that results maximized relevance while producing comparable studies. Statistical analysis was applied to detect the most common risk factor and significant differences in risk factor prevalence and CVD rates. Obesity remained the prevailing CVD risk factor except in older Syrian men, where smoking and hypertension were more common. CVD mortality was more common in males due to coronary disease, while stroke dominated female mortality. The young workforce is especially impacted, with 50% of CVD mortality occurring before age 65 years and an 81% prevalence of obesity in women over 45 years. Syria can overcome its slow response to the CVD epidemic and curb further deterioration by reducing obesity and, thus, inheritance and clustering of risk factors. This can be achieved via multilayered awareness and intensive parental and familial involvement. Extinguishing the CVD epidemic is readily achievable as demonstrated in other countries.

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.

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.

CVD refractory metals and alloys for space nuclear power application

International Nuclear Information System (INIS)

Yang, L.; Gulden, T.D.; Watson, J.F.

1984-01-01

CVD technology has made significant contributions to the development of space nuclear power systems during the period 1962 to 1972. For the in-core thermionic concept, CVD technology is essential to the fabrication of the tungsten electron emitter. For the liquid metal cooled fuel pin using uranium nitride as fuel and T-111 and Nb-1 Zr as cladding, a tungsten barrier possibly produced by CVD methods is essential to the fuel-cladding compatibility at the designed operating temperature. Space power reactors may use heat pipes to transfer heat from the reactor core to the conversion system. CVD technology has been used for fabricating the heat pipe used as cross-flow heat exchanger, including the built-in channels on the condenser wall for liquid lithium return. 28 references, 17 figures

Investigation of defects in CVD diamond: Influence for radiotherapy applications

International Nuclear Information System (INIS)

Guerrero, M.J.; Tromson, D.; Bergonzo, P.; Barrett, R.

2005-01-01

In this study we present the potentialities of CVD diamond as an ionisation chamber for radiotherapy applications. Trapping levels present in CVD diamond are characterised using Thermally Stimulated Current (TSC) method with X-ray sources. The influence of the corresponding defects on the detector response is investigated and compared to those observed in natural diamond. Also, their spatial distribution across a large area polycrystalline diamond ionisation chamber is discussed. Results show the relative influence of two different populations of trapping levels in CVD diamond whose effect is crucial for radiotherapy applications. To partially overcome the defect detrimental effects, we propose to use CVD diamond ionisation chambers at moderate temperatures from 70 to 100 deg. C that could be provided by self heating of the device, for a dramatically improved stability and reproducibility

The formation of tritium permeation barriers by CVD

International Nuclear Information System (INIS)

Forcey, K.S.; Perujo, A.; Reiter, F.; Lolli-Ceroni, P.L.

1993-01-01

The effectiveness as permeation barriers of the following CVD coatings have been investigated: TiC (1 to 2 μm in thickness); a bi-layer of TiN on TiC (3 μm total thickness) and CVD Al 2 O 3 on a TiN/TiC bi-layer. The substrate materials were TZM (a Mo alloy) and 316L stainless steel in the form of discs of diameter 48 mm and thickness 0.1 or 1 mm. Permeation measurements were performed in the temperature range 515-742 K using deuterium at pressures in the range 1-50 kPa. CVD layers were shown to form reasonably effective permeation barriers. At a temperature of 673 K TiC is around 6000 times less permeable to deuterium than 316L stainless steel. (orig.)

P-type sp3-bonded BN/n-type Si heterodiode solar cell fabricated by laser-plasma synchronous CVD method

International Nuclear Information System (INIS)

Komatsu, Shojiro; Nagata, Takahiro; Chikyo, Toyohiro; Sato, Yuhei; Watanabe, Takayuki; Hirano, Daisuke; Takizawa, Takeo; Nakamura, Katsumitsu; Hashimoto, Takuya; Nakamura, Takuya; Koga, Kazunori; Shiratani, Masaharu; Yamamoto, Atsushi

2009-01-01

A heterojunction of p-type sp 3 -bonded boron nitride (BN) and n-type Si fabricated by laser-plasma synchronous chemical vapour deposition (CVD) showed excellent rectifying properties and proved to work as a solar cell with photovoltaic conversion efficiency of 1.76%. The BN film was deposited on an n-type Si (1 0 0) substrate by plasma CVD from B 2 H 6 + NH 3 + Ar while doping of Si into the BN film was induced by the simultaneous irradiation of an intense excimer laser with a pulse power of 490 mJ cm -2 , at a wavelength of 193 nm and at a repetition rate of 20 Hz. The source of dopant Si was supposed to be the Si substrate ablated at the initial stage of the film growth. The laser enhanced the doping (and/or diffusion) of Si into BN as well as the growth of sp 3 -bonded BN simultaneously in this method. P-type conduction of BN films was determined by the hot (thermoelectric) probe method. The BN/Si heterodiode with an essentially transparent p-type BN as a front layer is supposed to efficiently absorb light reaching the active region so as to potentially result in high efficiency.

Diamond coating deposition by synergy of thermal and laser methods-A problem revisited

International Nuclear Information System (INIS)

Ristic, Gordana S.; Trtica, Milan S.; Bogdanov, Zarko D.; Romcevic, Nebojsa Z.; Miljanic, Scepan S.

2007-01-01

Diamond coatings were deposited by synergy of the hot filament CVD method and the pulse TEA CO 2 laser, in spectroactive and spectroinactive diamond precursor atmospheres. Resulting diamond coatings are interpreted relying on evidence of scanning electron microscopy as well as microRaman spectroscopy. Thermal synergy component (hot filament) possesses an activating agent for diamond deposition, and contributes significantly to quality and extent of diamond deposition. Laser synergy component comprises a solid surface modification as well as the spectroactive gaseous atmosphere modification. Surface modification consists in changes of the diamond coating being deposited and, at the same time, in changes of the substrate surface structure. Laser modification of the spectroactive diamond precursor atmosphere means specific consumption of the precursor, which enables to skip the deposition on a defined substrate location. The resulting process of diamond coating elimination from certain, desired locations using the CO 2 laser might contribute to tailoring diamond coatings for particular applications. Additionally, the substrate laser modification could be optimized by choice of a proper spectroactive precursor concentration, or by a laser radiation multiple pass through an absorbing medium

Conformal deposition of an insulator layer and Ag nano paste filling of a through silicon via for a 3D interconnection

Energy Technology Data Exchange (ETDEWEB)

Baek, Kyu-Ha; Kim, Dong-Pyo; Park, Kun-Sik; Ham, Yong-Hyun; Do, Lee-Mi [Electronics and Telecommunications Research Institute, Daejeon (Korea, Republic of); Lee, Ki-Jun [Chungnam National University, Daejeon (Korea, Republic of); Kim, Kyung-Seob [Yeoju Institute of Technology, Yeoju (Korea, Republic of)

2011-09-15

In this study, we reported the feasibility of filling a high-aspect-ratio through silicon via (HARTSV) with Ag nano paste for a 3D interconnection. TSVs with aspect ratios of 8:1 {approx} 10:1 were fabricated in a deep reactive etching system by using the Bosch process. Then, SiO{sub 2} insulators were deposited by using various chemical vapor deposition (CVD) processes, including plasma enhanced CVD oxides, of which precursors were silane (PECVD Oxide) and tetraethoxysilane (PECVDTEOS), and sub-atmospheric CVD oxide (SACVD oxide). We succeeded in obtaining a SiO{sub 2} layer with good step coverage over 80% for all via CD sizes by using SACVD oxidation process. The thickness of SiO{sub 2} for the via top and the via bottom were in the range 158.8 {approx} 161.5 nm and 162.6 {approx} 170.7 nm, respectively. The HAR-TSVs were filled with Ag nano paste by using vacuum assisted paste printing. Then, the samples were cured on a hotplate at 80 .deg. C for 2 min. The temperature was increased to 180 .deg. C at a rate of 25 .deg. C/min and the samples were re-annealed for 2 min. We investigated the effects for the time of evacuation/purge process and of the vacuum drying on the filling properties. A field emission scanning electron microscope (FE-SEM), X-ray microscope and focused ion beam (FIB) microscope were used to investigate the filling profile of the TSV with Ag nano pastes. By increasing the evacuation/purge time and the vacuum drying time, we could fully fill the TSV was full filled with Ag nano paste and then form a metal plug.

A CVD diamond detector for (n,α) cross-section measurements

International Nuclear Information System (INIS)

Weiss, C.

2014-01-01

A novel detector based on the chemical vapor deposition (CVD) diamond technology has been developed in the framework of this PhD, for the experimental determination of (n,α) cross-sections at the neutron time-of-flight facility n⎽TOF at CERN. The 59 Ni(n,α) 56 Fe cross-section, which is relevant for astrophysical questions as well as for risk-assessment studies in nuclear technology, has been measured in order to validate the applicability of the detector for such experiments. The thesis is divided in four parts. In the introductory part the motivation for measuring (n,α) cross-sections, the experimental challenges for such measurements and the reasons for choosing the CVD diamond technology for the detector are given. This is followed by the presentation of the n⎽TOF facility, an introduction to neutron-induced nuclear reactions and a brief summary of the interaction of particles with matter. The CVD diamond technology and the relevant matters related to electronics are given as well in this first part of the thesis. The second part is dedicated to the design and production of the Diamond Mosaic-Detector (DM-D) and its characterization. The 59 Ni(n,α) 56 Fe cross-section measurement at n⎽TOF and the data analysis are discussed in detail in the third part of the thesis, before the summary of the thesis and an outlook to possible future developments and applications conclude the thesis in the forth part. In this work, the Diamond Mosaic-Detector, which consist of eight single-crystal (sCVD) diamond sensors and one 'Diamond on Iridium' (DOI) sensor has proven to be well suited for (n,α) cross-section measurements for 1 MeV < E α < 22 MeV. The upper limit is given by the thickness of the sensors, d = 150 μm, while the lower limit is dictated by background induced by neutron capture reactions in in-beam materials. The cross-section measurement was focussed on the resonance integral of 59 Ni(n,α) 56 Fe at E n = 203 eV, with the aim of clarifying

Building of nested components by a double-nozzle droplet deposition process

Science.gov (United States)

Li, SuLi; Wei, ZhengYing; Du, Jun; Zhao, Guangxi; Wang, Xin; Lu, BingHeng

2016-07-01

According to the nested components jointed with multiple parts,a double-nozzle droplet deposition process was put forward in this paper, and the experimental system was developed. Through the research on the properties of support materials and the process of double-nozzle droplet deposition, the linkage control of the metal droplet deposition and the support material extrusion was realized, and a nested component with complex construction was fabricated directly. Compared with the traditional forming processes, this double-nozzle deposition process has the advantages of short cycle, low cost and so on. It can provide an approach way to build the nested parts.

Parametric optimization during machining of AISI 304 Austenitic Stainless Steel using CVD coated DURATOMIC cutting insert

Directory of Open Access Journals (Sweden)

M. Kaladhar

2012-08-01

Full Text Available In this work, Taguchi method is applied to determine the optimum process parameters for turning of AISI 304 austenitic stainless steel on CNC lathe. A Chemical vapour deposition (CVD coated cemented carbide cutting insert is used which is produced by DuratomicTM technology of 0.4 and 0.8 mm nose radii. The tests are conducted at four levels of Cutting speed, feed and depth of cut. The influence of these parameters are investigated on the surface roughness and material removal rate (MRR. The Analysis Of Variance (ANOVA is also used to analyze the influence of cutting parameters during machining. The results revealed that cutting speed significantly (46.05% affected the machined surface roughness values followed by nose radius (23.7%. The influence of the depth of cut (61.31% in affecting material removal rate (MRR is significantly large. The cutting speed (20.40% is the next significant factor. Optimal range and optimal level of parameters are also predicted for responses.

Preparation of LiMn{sub 2}O{sub 4} cathode thin films for thin film lithium secondary batteries by a mist CVD process

Energy Technology Data Exchange (ETDEWEB)

Tadanaga, Kiyoharu, E-mail: tadanaga@chem.osakafu-u.ac.jp [Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka, 599-8531 (Japan); Yamaguchi, Akihiro; Sakuda, Atsushi; Hayashi, Akitoshi; Tatsumisago, Masahiro [Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka, 599-8531 (Japan); Duran, Alicia; Aparacio, Mario [Instituto de Cerámica y Vidrio, Consejo Superior de Investigaciones Científicas, Kelsen 5 (Campus de Cantoblanco), Madrid, 28049 (Spain)

2014-05-01

Highlights: • LiMn{sub 2}O{sub 4} thin films were prepared by using the mist CVD process. • An aqueous solution of lithium and manganese acetates is used for the precursor solution. • The cell with the LiMn{sub 2}O{sub 4} thin films exhibited a capacity of about 80 mAh/g. • The cell showed good cycling performance during 10 cycles. - Abstract: LiMn{sub 2}O{sub 4} cathode thin films for thin film lithium secondary batteries were prepared by using so-called the “mist CVD process”, employing an aqueous solution of lithium acetate and manganese acetate, as the source of Li and Mn, respectively. The aqueous solution of starting materials was ultrasonically atomized to form mist particles, and mists were transferred by nitrogen gas to silica glass substrate to form thin films. FE-SEM observation revealed that thin films obtained by this process were dense and smooth, and thin films with a thickness of about 750 nm were obtained. The electrochemical cell with the thin films obtained by sintering at 700 °C exhibited a capacity of about 80 mAh/g, and the cell showed good cycling performance during 10 cycles.

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

International Nuclear Information System (INIS)

Park, Joong-Hyun; Han, Sang-Myeon; Park, Sang-Geun; Han, Min-Koo; Shin, Moon-Young

2006-01-01

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

Synthesis of carbon nanostructures from high density polyethylene (HDPE) and polyethylene terephthalate (PET) waste by chemical vapour deposition

Science.gov (United States)

Hatta, M. N. M.; Hashim, M. S.; Hussin, R.; Aida, S.; Kamdi, Z.; Ainuddin, AR; Yunos, MZ

2017-10-01

In this study, carbon nanostructures were synthesized from High Density Polyethylene (HDPE) and Polyethylene terephthalate (PET) waste by single-stage chemical vapour deposition (CVD) method. In CVD, iron was used as catalyst and pyrolitic of carbon source was conducted at temperature 700, 800 and 900°C for 30 minutes. Argon gas was used as carrier gas with flow at 90 sccm. The synthesized carbon nanostructures were characterized by FESEM, EDS and calculation of carbon yield (%). FESEM micrograph shows that the carbon nanostructures were only grown as nanofilament when synthesized from PET waste. The synthesization of carbon nanostructure at 700°C was produced smooth and the smallest diameter nanofilament compared to others. The carbon yield of synthesized carbon nanostructures from PET was lower from HDPE. Furthermore, the carbon yield is recorded to increase with increasing of reaction temperature for all samples. Elemental study by EDS analysis were carried out and the formation of carbon nanostructures was confirmed after CVD process. Utilization of polymer waste to produce carbon nanostructures is beneficial to ensure that the carbon nanotechnology will be sustained in future.

Validation of a model to investigate the effects of modifying cardiovascular disease (CVD) risk factors on the burden of CVD: the rotterdam ischemic heart disease and stroke computer simulation (RISC) model.

Science.gov (United States)

van Kempen, Bob J H; Ferket, Bart S; Hofman, Albert; Steyerberg, Ewout W; Colkesen, Ersen B; Boekholdt, S Matthijs; Wareham, Nicholas J; Khaw, Kay-Tee; Hunink, M G Myriam

2012-12-06

We developed a Monte Carlo Markov model designed to investigate the effects of modifying cardiovascular disease (CVD) risk factors on the burden of CVD. Internal, predictive, and external validity of the model have not yet been established. The Rotterdam Ischemic Heart Disease and Stroke Computer Simulation (RISC) model was developed using data covering 5 years of follow-up from the Rotterdam Study. To prove 1) internal and 2) predictive validity, the incidences of coronary heart disease (CHD), stroke, CVD death, and non-CVD death simulated by the model over a 13-year period were compared with those recorded for 3,478 participants in the Rotterdam Study with at least 13 years of follow-up. 3) External validity was verified using 10 years of follow-up data from the European Prospective Investigation of Cancer (EPIC)-Norfolk study of 25,492 participants, for whom CVD and non-CVD mortality was compared. At year 5, the observed incidences (with simulated incidences in brackets) of CHD, stroke, and CVD and non-CVD mortality for the 3,478 Rotterdam Study participants were 5.30% (4.68%), 3.60% (3.23%), 4.70% (4.80%), and 7.50% (7.96%), respectively. At year 13, these percentages were 10.60% (10.91%), 9.90% (9.13%), 14.20% (15.12%), and 24.30% (23.42%). After recalibrating the model for the EPIC-Norfolk population, the 10-year observed (simulated) incidences of CVD and non-CVD mortality were 3.70% (4.95%) and 6.50% (6.29%). All observed incidences fell well within the 95% credibility intervals of the simulated incidences. We have confirmed the internal, predictive, and external validity of the RISC model. These findings provide a basis for analyzing the effects of modifying cardiovascular disease risk factors on the burden of CVD with the RISC model.

Validation of a model to investigate the effects of modifying cardiovascular disease (CVD risk factors on the burden of CVD: the rotterdam ischemic heart disease and stroke computer simulation (RISC model

Directory of Open Access Journals (Sweden)

van Kempen Bob JH

2012-12-01

Full Text Available Abstract Background We developed a Monte Carlo Markov model designed to investigate the effects of modifying cardiovascular disease (CVD risk factors on the burden of CVD. Internal, predictive, and external validity of the model have not yet been established. Methods The Rotterdam Ischemic Heart Disease and Stroke Computer Simulation (RISC model was developed using data covering 5 years of follow-up from the Rotterdam Study. To prove 1 internal and 2 predictive validity, the incidences of coronary heart disease (CHD, stroke, CVD death, and non-CVD death simulated by the model over a 13-year period were compared with those recorded for 3,478 participants in the Rotterdam Study with at least 13 years of follow-up. 3 External validity was verified using 10 years of follow-up data from the European Prospective Investigation of Cancer (EPIC-Norfolk study of 25,492 participants, for whom CVD and non-CVD mortality was compared. Results At year 5, the observed incidences (with simulated incidences in brackets of CHD, stroke, and CVD and non-CVD mortality for the 3,478 Rotterdam Study participants were 5.30% (4.68%, 3.60% (3.23%, 4.70% (4.80%, and 7.50% (7.96%, respectively. At year 13, these percentages were 10.60% (10.91%, 9.90% (9.13%, 14.20% (15.12%, and 24.30% (23.42%. After recalibrating the model for the EPIC-Norfolk population, the 10-year observed (simulated incidences of CVD and non-CVD mortality were 3.70% (4.95% and 6.50% (6.29%. All observed incidences fell well within the 95% credibility intervals of the simulated incidences. Conclusions We have confirmed the internal, predictive, and external validity of the RISC model. These findings provide a basis for analyzing the effects of modifying cardiovascular disease risk factors on the burden of CVD with the RISC model.

Advances in the electro-spark deposition coating process

International Nuclear Information System (INIS)

Johnson, R.N.; Sheldon, G.L.

1986-04-01

Electro-spark deposition (ESD) is a pulsed-arc micro-welding process using short-duration, high-current electrical pulses to deposit an electrode material on a metallic substrate. It is one of the few methods available by which a fused, metallurgically bonded coating can be applied with such a low total heat input that the bulk substrate material remains at or near ambient temperatures. The short duration of the electrical pulse allows an extremely rapid solidification of the deposited material and results in an exceptionally fine-grained, homogenous coating that approaches (and with some materials, actually is) an amorphous structure. This structure is believed to contribute to the good tribological and corrosion performance observed for hardsurfacing materials used in the demanding environments of high temperatures, liquid metals, and neutron irradiation. A brief historical review of the process is provided, followed by descriptions of the present state-of-the-art and of the performance and applications of electro-spark deposition coatings in liquid-metal-cooled nuclear reactors

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.

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.

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.

New materials for advanced lithium battery. Especially on plasma-assisted CVD of TiS sub 2

Energy Technology Data Exchange (ETDEWEB)

Kikkawa, Shin' ichi [Osaka Univ. (Japan)

1989-03-15

Intercalation can be applied to cathode reaction of rechargeable battery. Three kinds of candidate materials, TiS{sub 2}, NbS{sub 3} and alkali transition metal dioxides such as LiCoO{sub 2} were studied as the battery cathode. TiS{sub 2} is closest to a practical usage. Lithium ion has to diffuse in the TiS{sub 2} crystal lattice during the intercalation. Large surface area is necessary to obtain high current density. Preferred orientation of the crystallite is also required in its film formation to further enhance its current density. CVD reactor was used to obtain TiS{sub 2} fine powder and its thin film. Black fine power was obtained on a thin film deposited on a glass substrate. The powder was obtained in high yield under a pressure of 120 Pa at the electrode center where the plasma density was high. In conclusion, TiS{sub 2} fine power with submicron diameter and also highly preferred oriented TiS{sub 2} thin film were obtained using plasma-CVD. 21 refs., 8 figs.

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.

Effects of temperature and Mo2C layer on stress and structural properties in CVD diamond film grown on Mo foil

International Nuclear Information System (INIS)

Long, Fen; Wei, Qiuping; Yu, Z.M.; Luo, Jiaqi; Zhang, Xiongwei; Long, Hangyu; Wu, Xianzhe

2013-01-01

Highlights: •Polycrystalline diamond films were grown on Mo foil substrates by HF-CVD. •We investigated the temperature dependence of the film stress for each sample. •We show that how the thermal stress and intrinsic stress affects the total stress. •The stress of Mo foil substrate obtained by XRD was investigated in this study. •The effect of Mo 2 C interface layer for stress of multilayer system was considered. -- Abstract: Polycrystalline diamond films have been prepared by hot-filament-assisted chemical vapor deposition (HFCVD) on Mo foils. The morphology, growth rate, phase composition, element distribution and residual stress of the films at different temperature were investigated by field-emission scanning electron microscopy, Raman spectrum, field emission electron probe microanalysis and X-ray diffraction. Results show that the residual stress of the diamond films is compressive. The thermal stress plays a decisive role in the total stress, while the intrinsic stress can change the trend of the total stress. The residual stress of substrate gradually changes from tensile stress to compressive stress with the increase of the deposited temperature. A Mo 2 C interlayer is formed during deposition process, and this layer has an important influence on the stresses of films and substrates

Modeling of gas flow and deposition profile in HWCVD processes

Energy Technology Data Exchange (ETDEWEB)

Pflug, Andreas; Höfer, Markus; Harig, Tino; Armgardt, Markus; Britze, Chris; Siemers, Michael; Melzig, Thomas; Schäfer, Lothar

2015-11-30

Hot wire chemical vapor deposition (HWCVD) is a powerful technology for deposition of high quality films on large area, where drawbacks of plasma based technology such as defect generation by ion bombardment and high equipment costs are omitted. While processes for diamond coatings using H{sub 2} and CH{sub 4} as precursor have been investigated in detail since 1990 and have been transferred to industry, research also focuses on silicon based coatings with H{sub 2}, SiH{sub 4} and NH{sub 3} as process gases. HWCVD of silicon based coatings is a promising alternative for state-of-the-art radiofrequency-plasma enhanced chemical vapor deposition reactors. The film formation in HWCVD results from an interaction of several concurrent chemical reactions such as gas phase chemistry, film deposition, abstraction of surplus hydrogen bonds and etching by atomic hydrogen. Since there is no easy relation between process parameters and resulting deposition profiles, substantial experimental effort is required to optimize the process for a given film specification and the desired film uniformity. In order to obtain a deeper understanding of the underlying mechanisms and to enable an efficient way of process optimization, simulation methods come into play. While diamond deposition occurs at pressures in the range of several kPa HWCVD deposition of Si based coatings operates at pressures in the 0.1–30 Pa range. In this pressure regime, particle based simulation methods focused on solving the Boltzmann equation are computationally feasible. In comparison to computational fluid dynamics this yields improved accuracy even near small gaps or orifices, where characteristic geometric dimensions approach the order of the mean free path of gas molecules. At Fraunhofer IST, a parallel implementation of the Direct Simulation Monte Carlo (DSMC) method extended by a reactive wall chemistry model is developed. To demonstrate the feasibility of three-dimensional simulation of HWCVD processes

Aerosol processing for nanomanufacturing

International Nuclear Information System (INIS)

Girshick, Steven L.

2008-01-01

Advances in nanoparticle synthesis are opening new opportunities for a broad variety of technologies that exploit the special properties of matter at the nanoscale. To realize this potential will require the development of new technologies for processing nanoparticles, so as to utilize them in a manufacturing context. Two important classes of such processing technologies include the controlled deposition of nanoparticles onto surfaces, and the application of chemically specific coatings onto individual nanoparticles, so as to either passivate or functionalize their surfaces. This paper provides an overview of three technologies related to these objectives, with an emphasis on aerosol-based methods: first, the deposition of nanoparticles by hypersonic impaction, so as so spray-coat large areas with nanoparticles; second, the use of aerodynamic lenses to produce focused beams of nanoparticles, with beam widths of a few tens of microns, so as to integrate nanoparticle-based structures into microelectromechanical systems; and third, the coating of individual nanoparticles by means of photoinduced chemical vapor deposition (photo-CVD), driven by excimer lamps. We also discuss the combination of these technologies, so that nanoparticle synthesis, together with multiple processing steps, can be accomplished in a single flow stream.