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1
Khanyile, Sfiso Zwelisha. "Deposition of silicon nanostructures by thermal chemical vapour deposition." University of the Western Cape, 2015. http://hdl.handle.net/11394/4445.
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>Magister Scientiae - MScIn this thesis we report on the deposition of silicon nanostructures using a 3-zone thermal chemical vapour deposition process at atmospheric pressure. Nickel and gold thin films, deposited by DC sputtering on crystalline silicon substrates, were used as the catalyst material required for vapour-solid-liquid growth mechanism of the Si nanostructures. The core of this work is centred around the effect of catalyst type, substrate temperature and the source-to-substrate distance on the structural and optical properties of the resultant Si nanostructures, using argon as the carrier gas and Si powder as the source. The morphology and internal structure of the Si nanostructures was probed by using high resolution scanning and transmission electron microscopy, respectively. The crystallinity was measured by x-ray diffraction and the high resolution transmission electron microscopy. For composition and elemental analysis, Fourier transform infrared spectroscopy was used to quantify the bonding configuration, while electron energy-loss spectroscopy in conjunction with electron dispersion spectroscopy reveals the composition. Photoluminescence and UV-visible spectroscopy was used to extract the emission and reflection properties of the synthesized nanostructures.
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Wood, Thomas James. "Vapour-phase deposition of functional nanolayers." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/6929/.
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Vapour-phase deposition techniques have many advantages including being solventless and providing fine control (down to the nanometre level) of coating thickness. This thesis is about the use of both plasmachemical deposition and oxidative vapour-phase deposition to form functional coatings. Chapter 1 provides brief reviews of proton exchange membrane fuel cells and vapour-phase deposition techniques as well as an overall introduction to the thesis. Chapter 2 is a synopsis of the most commonly used experimental techniques used throughout this thesis (especial attention is focused on XPS and FTIR as they are used in every chapter). Chapters 3–4 record the use of plasmachemical deposition to form proton-conducting coatings for potential use in fuel cells. The strategy described is the use of anhydride precursors in order to produce layers with a high density of carboxylic acids. In chapter 4 these layers themselves are used as initiators to graft sulfonic-acid containing polymer brushes for the enhancement of proton conductivity. Chapter 5 describes the fabrication of poly(ionic liquid) layers by depositing an imidazole-containing precursor via pulsed plasmachemical deposition, which is subsequently quaternized via a vapour-phase reaction with 1-bromobutane. The resultant coatings show high values of ionic conductivity above 90 ◦C. In chapter 6 plasma enhanced chemical vapour deposition of metal(II) hexafluoroacetylacetonate precursors is used in order to produce metal-containing nanocomposite layers. The retention of an organic matrix and its chemical rearrangement under plasma conditions leads to high ionic conductivities. Chapters 7–8 utilize an atomized spray delivery system and plasma in conjunction with liquid precursor mixtures in order to form bioactive coatings (chapter 7) and nanocomposite layers (chapter 8) which show good adhesion and lithium-ion conductivity values. Finally chapter 9 utilizes the atomized spray system to deliver high vapour pressures of 3,4-ethylenedioxythiophene in the presence of triflic anhydride which acts as an oxidant. The ensuing vapour-phase reaction yields a conducting polymer coating.
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Cross, David Henry. "Laser induced chemical vapour deposition of aluminium." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/815.
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Sime, Nathan. "Numerical modelling of chemical vapour deposition reactors." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/36227/.
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In this thesis we study the chemical reactions and transport phenomena which occur in a microwave power assisted chemical vapour deposition (MPA-CVD) reactor which facilitates diamond growth. First we introduce a model of an underlying binary gas flow and its chemistry for a hydrogen gas mixture. This system is heated by incorporating a microwave frequency electric field, operating in a resonant mode in the CVD chamber. This heating facilitates the dissociation of hydrogen and the generation of a gas discharge plasma, a key component of carbon deposition in industrial diamond manufacture. We then proceed to summarise the discontinuous Galerkin (DG) finite element discretisation of the standard hyperbolic and elliptic partial differential operators which typically occur in conservation laws of continuum models. Additionally, we summarise the non-stabilised discontinuous Galerkin formulation of the time harmonic Maxwell operator. These schemes are then used as the basis for the discretisation method employed for the numerical approximation of the MPA-CVD model equations. The practical implementation of the resulting DG MPA-CVD model is an extremely challenging task, which is prone to human error. Thereby, we introduce a mathematical approach for the symbolic formulation and computation of the underlying finite element method, based on automatic code generation. We extend this idea further such that the DG finite element formulation is automatically computed following the user's specification of the convective and viscous flux terms of the underlying PDE system in this symbolic framework. We then devise a method for writing a library of automatically generated DG finite element formulations for a hierarchy of partial differential equations with automatic treatment of prescribed boundary conditions. This toolbox for automatically computing DG finite element solutions is then applied to the DG MPA-CVD model. In particular, we consider reactor designs inspired by the AIXTRON and LIMHP reactors which are analysed extensively in the literature.
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Smith, James Anthony. "Laser diagnostics of a diamond depositing chemical vapour deposition gas-phase environment." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247541.
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Cummings, Franscious Riccardo. "Hot-wire chemical vapour deposition of carbon Nanotubes." Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_3108_1205242611.
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In this study we report on the effect of the deposition parameters on the morphology and structural properties of CNTs, synthesized by means of the hot-wire chemical vapour deposition technique. SEM, Raman and XRD results show that the optimum deposition conditions for the HWCVD synthesis of aligned MWCNTs, with diameters between 50 and 150 nm and lengths in the micrometer range are: Furnace temperature of 500 º
C, deposition pressure between 150 and 200 Torr, methane/hydrogen dilution of 0.67 and a substrateto- filament distance of 10 cm.
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Cheng, Timothy Qiang. "Surface science studies of organometallic chemical vapour deposition." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0016/NQ28479.pdf.
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Binions, Russell. "Chemical vapour deposition of metal oxides and phosphides." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1444547/.
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This thesis investigates the deposition of thin films of main group metal phosphide and main group metal oxide compounds on glass substrates by the use of dual source atmospheric pressure chemical vapour deposition. Binary phosphide systems with tin, germanium, silicon, antimony, copper or boron have been examined. Binary oxide systems of gallium, antimony, tin or niobium have also been investigated. Additionally these systems were deposited on gas sensor substrates and evaluated as metal oxide semiconductor gas sensors. Halides were used as the metal precursor, RXPH3.X (R = Cychex or Phenyl) were used as phosphorous precursors and either methanol or ethyl acetate were used as oxygen precursors. These coatings showed good uniformity and coverage and the films were adherent passing the Scotch tape test. The tin phosphide films were opaque in appearance with some signs of birefringence due to differential thickness effects. Germanium phosphide and the gallium, antimony, niobium and tin oxide systems were all transparent, once again birefringence was observed. The films produced from the antimony phosphide and silicon phosphide systems were opaque, grey and metallic. Additional work was conducted on the deposition on a variety of alkali metal and alkaline earth metal fluorides on glass substrates using aerosol assisted chemical vapour deposition. In all cases the films were very powdery and were easily wiped off of the substrate. A number of depositions were carried out combining the aerosol and atmospheric pressure methodologies. A tin oxide film was produced from the atmospheric pressure chemical vapour deposition reaction of tin tetrachloride and ethyl acetate. The film contained tungsten, which was introduced into the reaction using a polyoxometalate delivered via aerosol assisted chemical vapour deposition. Films were analysed using Raman microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive analysis of X-rays, electron probe microanalysis, X-ray photoelectron spectroscopy and ultra violet and visible spectroscopy.
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Sein, Htet. "Chemical vapour deposition of diamond onto dental burs." Thesis, Manchester Metropolitan University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555137.
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Chemical vapour deposition (CVD) onto flat substrates has been researched extensively; however, little work has been on done on diamond deposition onto 3-D substrates. Diamond has excellent physical and chemical properties and has considerable potential for use in dental tools and biomedical implants. Since the 1950s sintered diamond burs have been used and are made using diamond particles bonded onto the substrate using a binder matrix material. The binder contains potentially poisonous components such as nickel and CVD technology eliminates the use of such binder materials. Hot Filament Chemical Vapour Deposition (HFCVD) uses a horizontal filament mounted above the substrate. For 3-D substrates the system was modified with the filament mounted vertically and the substrate held concentrically within the coil in a system called vertical filament CVD (VFCVD). Process optimisation was conducted on molybdenum wire and then diamond films were deposited onto metals such as titanium, molybdenum and tungsten carbide (WC-Co) burs. A pre-treatment was required on WC-Co burs using Murakami reagent was used for etching followed by acid etching to remove excess Co from the surface and improve adhesion. The growth rate, adhesion, surface roughness, composition and nucleation densities were all investigated. The substrate temperature influenced the compressive stress of the diamond films due to the thermal gradient, which is related to the position of the substrate within the filament. Machining tests showed that the wear rates of the coated diamond tools were considerably lower than the uncoated burs. These were quantified using a Figure of 5 Merit (F) which was then plotted against the number of holes drilled for uncoated, sintered and VFCVD diamond coated burs to assess the tool performances on human tooth material, acrylic and borosilicate glass. All of the tests showed that the diamond coated dental burs using the new VFCVD process demonstrated a superior performance compared to sintered and uncoated burs.
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Chubarov, Mikhail. "Chemical Vapour Deposition of sp2 Hybridised Boron Nitride." Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-112580.
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The aim of this work was to develop a chemical vapour deposition process and understand the growth of sp2 hybridised Boron Nitride (sp2-BN). Thus, the growth on different substrates together with the variation of growth parameters was investigated in details and is presented in the papers included in this thesis. Deposited films of sp2-BN were characterised with the purpose to determine optimal deposition process parameters for the growth of high crystal quality thin films with further investigations of chemical composition, morphology and other properties important for the implementation of this material towards electronic, optoelectronic devices and devices based on graphene/BN heterostructures. For the growth of sp2-BN triethyl boron and ammonia were employed as B and N precursors, respectively. Pure H2 as carrier gas is found to be necessary for the growth of crystalline sp2-BN. Addition of small amount of silane to the gas mixture improves the crystalline quality of the growing sp2-BN film. It was observed that for the growth of crystalline sp2-BN on c-axis oriented α-Al2O3 a thin and strained AlN buffer layer is needed to support epitaxial growth of sp2-BN, while it was possible to deposit rhombohedral BN (r-BN) on various polytypes of SiC without the need for a buffer layer. The growth temperature suitable for the growth of crystalline sp2-BN is 1500 °C. Nevertheless, the growth of crystalline sp2-BN was also observed on α-Al2O3 with an AlN buffer layer at a lower temperature of 1200 °C. Growth at this low temperature was found to be hardly controllable due to the low amount of Si that is necessary at this temperature and its accumulation in the reaction cell. When SiC was used as a substrate at the growth temperature of 1200 °C, no crystalline sp2-BN was formed, according to X-ray diffraction. Crystalline structure investigations of the deposited films showed formation of twinned r-BN on both substrates used. Additionally, it was found that the growth on α-Al2O3 with an AlN buffer layer starts with the formation of hexagonal BN (h-BN) for a thickness of around 4 nm. The formation of h-BN was observed at growth temperatures of 1200 °C and 1500 °C on α-Al2O3 with AlN buffer layer while there were no traces of h-BN found in the films deposited on SiC substrates in the temperature range between 1200 °C and 1700 °C. As an explanation for such growth behaviour, reproduction of the substrate crystal stacking is suggested. Nucleation and growth mechanism are investigated and presented in the papers included in this thesis.
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Low, Y. H. "Chemical vapour deposition of iron and cobalt layers." Thesis, Queen's University Belfast, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437845.
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Manning, Troy Darrell. "Atmospheric pressure chemical vapour deposition of vanadium oxides." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408676.
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Lane, Stephen John. "Photochemical vapour deposition from gallium and other triiodides." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47530.
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Reale, Francesco. "Chemical vapour deposition of atomically thin tungsten disulphide." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/56620.
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Transition metal dichalcogenides (TMDs) are van der Waals layered materials that have been known and studied for decades in their bulk form for applications such as solid-state lubricants and catalysts. However, TMDs were largely unexplored in their two-dimensional, atomically thin form. Their unique optical and electrical properties due to their reduced dimensionality started to emerge only in the last decade. In particular, group VI-TMDs (i.e., MoS2, WS2, MoSe2, WSe2) have been recently attracting tremendous attention as emerging post-graphene materials owing to their direct band-gap in the visible range which opens many prospects for diverse optoelectronic devices. Among them, atomically thin tungsten disulphide (WS2) has emerged as unique candidate for future nanotechnologies due to its superior optical, electrical and thermal properties. Any envisioned application of WS2 requires high-quality and large-area material obtainable via a scalable synthesis method. The chemical vapour deposition (CVD) of group VI-TMDs holds promise for the synthesis of high quality monolayered material extended over wafer-size areas. Nevertheless, the CVD growth of high-quality atomically thin WS2 layers requires further development since film continuity and thickness uniformity are normally limited to a few tens of micron-sized areas. The most extensively used CVD method to synthesize WS2 entails co-evaporation of tungsten oxide (WO3) and sulphur (S) powders. This choice of precursors is mainly dictated by their low toxicity compared to halides/organic precursors and effective replacement of O by S. However, due to the high sublimation temperature of WO3, the growth has to be carried out at high temperatures in between 950-1070°C and low pressures. In this work we demonstrate a novel facilitated CVD growth of high-quality atomically thin WS2 by using a novel molecular precursor approach. This strategy involves reagents which are carbon free, volatile and easily decomposable at low temperatures, allowing for the growth of mono- and bi-layered WS2 crystals with lateral sizes of 300µm at temperatures as low as 750°C, and with superior optical and electrical properties than those of naturally occurring materials. The charge carrier mobilities that we report are also higher compared to the ones obtained using innovative synthesis procedures, such as CVD growth on reusable gold substrates or metalorganic CVD on different oxides. Further we demonstrate tunability of the optical and electrical properties of WS2, inducing atomic doping with Indium.
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Biira, Saphina. "Construction of a chemical vapour deposition reactor and the deposition of ZrC layers." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/65947.
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Generation IV high temperature nuclear reactors use TRISO (tristructural isotropic) particles for containment of radioactive fission products. In these particles silicon carbide (SiC) is the main barrier for containing solid fission products. ZrC has been proposed either as an additional layer or replacement of SiC layer of the TRISO fuel particle. This is because ZrC would be a better barrier than SiC against the diffusion of Ag and will be more resistant against palladium attack. This suggestion is based on ZrC‘s excellent physical properties like: low neutron capture cross section, good thermal shock resistance, excellent thermal stability, etc. However these properties depend on a number of factors such as chemical composition, microstructure, morphology, the presence of impurities, etc. Many attempts have been made to grow ZrC layers. However, the growth of high quality polycrystalline ZrC layers with good stoichiometry has remained a challenge. This study focuses on designing a chemical vapour deposition (CVD) reactor for growing ZrC layers and studying the properties of ZrC layers grown under different conditions. CVD was chosen as the most effective process to grow ZrC layers. CVD enables the production of relatively pure uniform layers with good adhesion and reproducibility at fairly good deposition rates. A thermal CVD reactor system operating at atmospheric pressure was designed to grow ZrC layers. Radio frequency (RF) induction heating was used as the energy source, with a vertical-flow design, using thermally stable materials. The ZrC layers were grown while varying the substrate temperature, gas flow ratios, substrate-gas inlet gaps, deposition time and partial pressures. The precursors utilised to grow ZrC were zirconium tetrachloride (ZrCl4) and methane (CH4) in an excess of argon and hydrogen. The deposited ZrC layers were then characterised by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy and field emission scanning electron microscopy (FE-SEM). To optimise the process parameters, response surface methodology was applied. A central composite design was used to investigate the effect of temperature (1200 °C–1600 °C) and molar ratio of CH4/ZrCl4 (6.04–24.44) on the growth rate, atomic ratio of C/Zr and crystallite size of ZrC layers. The temperature of 1353.3 °C and the CH4/ZrCl4 molar ratio of 10.41 were determined as the optimal conditions for growing near-stoichiometric ZrC layers. The optimum values for C/Zr atomic percentage ratio, growth rate and average crystallite size were 1.03, 6.05 ?m/h and 29.8 nm respectively. The influence of the gap between the gas inlet and the substrate (70–170 mm) on the growth rate, surface morphology, phase composition and microstructure of ZrC layers deposited at different temperatures was investigated. The growth rate of ZrC layers prepared at 1400 °C was higher than at 1200 °C, and decreased with increase in the gap at both temperatures. The boundary layer thickness increased with an increase in substrate-inlet gap. The diffusion coefficients of the reactants increased with temperature. A model was used to illustrate the diffusion of source materials through the boundary layer to the reacting surface. An increase in the gap from 70 mm to 170 mm at a temperature of 1400 °C, caused the layers to become more uniform. An increase in particle agglomeration was also observed. By contrast, at 1200 °C the surface crystallites had complex facets that decreased in size as the gap increased from 70 mm to 170 mm.Thesis (PhD)--University of Pretoria, 2017.
Physics
PhD
Unrestricted
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Vinten, Phillip A. "Chemical Vapour Deposition Growth of Carbon Nanotube Forests: Kinetics, Morphology, Composition, and Their Mechanisms." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24165.
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This thesis analyzes the chemical vapour deposition (CVD) growth of vertically aligned carbon nanotube (CNT) forests in order to understand how CNT forests grow, why they stop growing, and how to control the properties of the synthesized CNTs. In situ kinetics data of the growth of CNT forests are gathered by in situ optical microscopy. The overall morphology of the forests and the characteristics of the individual CNTs in the forests are investigated using scanning electron microscopy and Raman spectroscopy. The in situ data show that forest growth and termination are activated processes (with activation energies on the order of 1 eV), suggesting a possible chemical origin. The activation energy changes at a critical temperature for ethanol CVD (approximately 870°C). These activation energies and critical temperature are also seen in the temperature dependence of several important characteristics of the CNTs, including the defect density as determined by Raman spectroscopy. This observation is seen across several CVD processes and suggests a mechanism of defect healing. The CNT diameter also depends on the growth temperature. In this thesis, a thermodynamic model is proposed. This model predicts a temperature and pressure dependence of the CNT diameter from the thermodynamics of the synthesis reaction and the effect of strain on the enthalpy of formation of CNTs. The forest morphology suggests significant interaction between the constituent CNTs. These interactions may play a role in termination. The morphology, in particular a microscale rippling feature that is capable of diffracting light, suggest a non-uniform growth rate across the forest. A gas phase diffusion model predicts a non-uniform distribution of the source gas. This gas phase diffusion is suggested as a possible explanation for the non-uniform growth rate. The gas phase diffusion is important because growth by acetylene CVD is found to be very efficient (approximately 30% of the acetylene is converted to CNTs). It is seen that multiple mechanisms are active during CNT growth. The results of this thesis provide insight into both the basic understanding of the microscopic processes involved in CVD growth and how to control the properties of the synthesized CNTs.
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Djugum, Richard, and n/a. "Novel fabrication processes for thin film vapour deposited strain gauges on mild steel." Swinburne University of Technology, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20070424.115951.
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Pressure measurement using a strain gauge bonded with epoxy adhesive to a metallic
mechanical support has been, and still is, extensively employed, however, for some
applications the use of an epoxy is inadequate, especially when temperatures exceed
120C. There is therefore particular interest in the use of thin film techniques to
vacuum deposit strain gauges directly on metallic substrates. Such devices are highly
cost effective when produced in large quantities due to the manufacturing techniques
involved. This makes them ideally suited for use in large-volume products such as
electronic weighing scales and pressure transducers. In this thesis, new techniques for
fabricating thin film vapour deposited strain gauge transducers on metal substrates for
application as novel pressure sensors in the fastener industry are developed.
Clearly, for a vapour deposited strain gauge to function correctly, it is essential that it be
deposited on a defect free, high quality electrically insulating film. This was a
significant challenge in the present study since all available physical vapour deposition
(PVD) equipment was direct current (DC) and insulators of around 4 um thick were
needed to electrically isolate the strain gauges from metal. As a result, several methods
of depositing insulators using DC were developed. The first involved the use of DC
magnetron sputtering from an aluminium target to reactively deposit up to 4 um thick
AlN. DC magnetron discharges suffer arc instability as the AlN forms on the target and
this limits the maximum thickness that can be deposited. Consequently, the arc
instability was suppressed manually by increasing argon gas flow at the onset of arcing.
Although the deposited AlN showed a high insulating resistance, it was found that the
breakdown voltage could significantly increase by (a) utilising a metallic interlayer
between the thin film insulator and the metallic substrate and (b) annealing in air at
300C. A second deposition method involved the use of DC magnetron sputtering to
deposit modulated thin film insulators in which an aluminium target was used to
reactively deposit alternating layers of aluminium nitride and aluminium oxide. These
films showed significant increases in average breakdown voltage when the number of
layers within the composite film was increased. The third method involved the
deposition of AlN thin film insulators using partially filtered cathodic arc evaporation
with shielding. Initially, AlN was deposited under partially filtered conditions to obtain
a relatively thick (~ 4 um) coating then, while still depositing under partially filtered
conditions, a smooth top coating was deposited by using a shielding technique. The
deposition of metal macroparticles is an inherent problem with cathodic arc deposition
and shielding is one form of macroparticle filtering. Such particles are highly
undesirable in this study as they are electrically conductive. A fourth coating technique
for depositing insulators on steel was based on thermal spray technology. Insulating
films of Al2O3 were plasma sprayed and then polished to thereby fabricate viable
electrical insulators for vapour deposited strain gauges.
With respect to depositing strain gauges two methods were employed. The first
involved the sputter deposition of chromium through a shadow mask to form a strain
gauge with gauge factor sensitivity of around 2. The second used cathodic arc
evaporation to fabricate a multi-layered strain gauge composed of alternating CrN and
TiAlN layers that yielded a gauge factor of around 3.5. The technique achieves better
compatibility between gauge and insulator by allowing a wider selection of materials to
form the gauge composition. Finally, a novel pressure sensor in the form of a load cell
was developed that consisted of a chromium strain gauge on a steel washer electrically
insulated with AlN thin film. The load cell showed good performance when tested under
compressive load.
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Rosenblad, Carsten. "Development of a plasma enhanced chemical vapour deposition system /." [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13601.
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Sanderson, Kevin David. "The atmospheric chemical vapour deposition of coatings on glass." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/11897.
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Wu, Yiquan. "Laser assisted electrostatic spray assisted vapour deposition of ceramics." Thesis, Imperial College London, 2005. http://hdl.handle.net/10044/1/8429.
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Baluti, Florentina. "Monte Carlo Simulations of Chemical Vapour Deposition Diamond Detectors." Thesis, University of Canterbury. Physics and Astronomy, 2009. http://hdl.handle.net/10092/3190.
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Chemical Vapour Deposition (CVD) diamond detectors were modelled for dosimetry of radiotherapy beams. This was achieved by employing the EGSnrc Monte Carlo (MC) method to investigate certain properties of the detector, such as size, shape and electrode materials. Simulations were carried out for a broad 6 MV photon beam, and water phantoms with both uniform and non-uniform voxel dimensions. A number of critical MC parameters were investigated for the development of a model that can simulate very small voxels. For a given number of histories (100 million), combinations of the following parameters were analyzed: cross section data, boundary crossing algorithm and the HOWFARLESS option, with the rest of the transport parameters being kept at default values. The MC model obtained with the optimized parameters was successfully validated against published data for a 1.25 MeV photon beam and CVD diamond detector with silver/carbon/silver structure with thicknesses of 0.07/0.2/0.07 cm for the electrode/detector/electrode, respectively. The interface phenomena were investigated for a 6 MV beam by simulating different electrode materials: aluminium, silver, copper and gold for perpendicular and parallel detector orientation with regards to the beam. The smallest interface phenomena were observed for parallel detector orientation with electrodes made of the lowest atomic number material, which was aluminium. The simulated percentage depth dose and beam profiles were compared with experimental data. The best agreement between simulation and measurement was achieved for the detector in parallel orientation and aluminium electrodes, with differences of approximately 1%. In summary, investigations related to the CVD diamond detector modelling revealed that the EGSnrc MC code is suitable for simulation of small size detectors. The simulation results are in good agreement with experimental data and the model can now be used to assist with the design and construction of prototype diamond detectors for clinical dosimetry. Future work will include investigating the detector response for different energies, small field sizes, different orientations other than perpendicular and parallel to the beam, and the influence of each electrode on the absorbed dose.
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Lenarduzzi, Marlene G. "Characterization and control of a chemical vapour deposition reactor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/MQ28439.pdf.
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Ahmed, Muhammad Shafiq. "Characterization of carbon nanotubes grown by chemical vapour deposition." Thesis, UOIT, 2009. http://hdl.handle.net/10155/26.
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Carbon nanotubes (CNTs), discovered by Ijima in 1991, are one of the allotropes of carbon, and can be described as cylinders of graphene sheet capped by hemifullerenes.
CNTs have excellent electrical, mechanical, thermal and optical properties and
very small size. Due to their unique properties and small size, CNTs have a great
potential for use in electronics, medical applications, field emission devices (displays,scanning and electronprobes/microscopes) and reinforced composites. CNTs can be grown by different methods from a number of carbon sources such as graphite, CO,C2H4, CH4 and camphor. Under certain conditions, a metallic catalyst is used to initiate the growth. The three main methods used to grow CNTs are: Arc-discharge, laser ablation (LA) and chemical vapour deposition (CVD). In the present work CNTs were grown from a mixture of camphor (C10H16O) and ferrocene (C10H10Fe) using Chemical Vapour Deposition (CVD) and argon was used as a carrier gas. The iron particles from ferrocene acted as catalysts for growth. The substrates used for the growth of CNTs were crystalline Si and SiO2 (Quartz) placed in a quartz tube in a horizontal furnace. Several parameters have been found to affect the CNT growth process. The effects of three parameters: growth temperature, carrier gas (Ar) flow rate and catalyst concentration were investigated in the present work in order to optimize the growth conditions with a simple and economical CVD setup. The samples were characterized using electron microscopy (EM), thermogravimetirc analysis (TGA), Raman and FTIR spectroscopy
techniques. It was found that the quality and yield of the CNTs were best at 800°C
growth temperature, 80sccm flow rate and 4% catalyst concentration.
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Palgrave, Robert. "Chemical vapour deposition of nanoparticulate and nanocomposite thin films." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444997/.
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Gold nanoparticle and gold / semiconductor nanocomposite thin films have been deposited using aerosol assisted chemical vapour deposition. Two gold precursors have been investigated which would be unsuitable for use with conventional atmospheric pressure chemical vapour deposition. HAuCU was used in methanol solution to deposit films at substrate temperatures of 350 - 500 °C. Powder X-ray diffraction and X-ray photoelectron spectroscopy revealed that these films consisted of metallic gold. The optical properties of these films corresponded to nanoscale gold particles, specifically displaying surface plasmon resonance (SPR) absorption. The wavelength of the SPR absorption maximum varied with precursor concentration and substrate temperature from 1000 - 600 nm. Scanning electron microscopy revealed particles a wide variety of sizes and shapes, as well as regions of island growth morphology. Depositions carried out from solutions of HAuCU and a range of quaternary ammonium ion surfactants led to films of particles with narrow size distributions. The use of tetraoctylammonium bromide (TOAB) led to films of spherical particles, the mean diameter of which could be altered by changing HAuCU : TOAB ratio, deposition temperature and solvent volume. Films with mean particle diameters ranging from 65 nm to 120 nm and arithmetic standard deviations of less than 20% of the mean could be deposited in this way. Toluene solutions of pre-formed gold particles were used to deposit films. These films showed similar optical properties to the original precursor solution. Nanocomposite films were deposited by combining HAuCU or pre-formed gold particles with a conventional CVD precursor in a single precursor solution. W(CO)6 , Mo(CO)6 , W(OPh)6 , TiPrU were combined with a gold precursor to deposit metal oxide films with incorporated gold particles. The concentration of gold within the films could be varied by changing the precursor ratios. These films showed SPR peaks that were redshifted compared to gold particles alone.
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Hopkins, John. "The laser induced chemical vapour deposition of gallium arsenide." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/1501.
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McNeill, David William. "Semiconductor layer growth by rapid themal chemical vapour deposition." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238986.
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Buxton, Robert Charles. "Direct simulation Monte Carlo modelling of physical vapour deposition." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426851.
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Redman, Stephen Alan. "Spectroscopic studies of the diamond chemical vapour deposition environment." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297799.
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Wills, Jonathan B. "Laser diagnostics of chemical vapour deposition of diamond films." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251103.
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Wu, Yi-yi. "Dynamic simulation and modelling of chemical vapour deposition process." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41386/.
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This thesis mainly presents the use of CFD modelling to investigate and optimise the MOCVD processes in fabrication of II-VI compounds – cadmium telluride (CdTe) and zinc oxide (ZnO). It gives insight in detailed process modelling and proves the ability of using CFD modelling, which accounts for the interaction between hydrodynamics and chemical reactions in the reactor, to accurately predict the growth rate and thickness uniformity. The growth behaviour of CdTe was investigated in a custom-made inline MOCVD reactor by analysing the influence of the operating process parameters, which involves (a) deposition temperature, (b) operating pressure, (c) total flow rate, and (d) the partial pressure ratio of precursors on the performance of the thin film (i.e. thin film deposition rates, thickness uniformity and material utilisation) in steady flows. The deposition of ZnO was studied in a bespoke horizontal reactor. Flow behaviour, heat transfer and mass transfer involved in the MOCVD reactor were discussed under different process parameters, with the objective to improve MOCVD process control. A thermal field calculation was implemented in the CFD modelling of ZnO deposition. A series of experiments of coating ZnO layers were performed to validate the simulation results. In addition, the analytical model, with reasonable simplifications and approximations for ZnO deposition, were further performed to get an intuitive insight into the mechanism governing the growth rate and uniformity in MOCVD processes. A good agreement was achieved through theory analysis, numeral simulation and experiment. The analysis of the transport phenomena under different process parameters in this study can greatly contribute to optimising the MOCVD equipment and processes, and to achieving the ultimate goal of a better growth rate, uniformity and controllability on thin film with economic use of precursors.
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Piccirillo, Clara. "Chemical vapour deposition of vanadium oxide thermochromic thin films." Doctoral thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/8715.
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Doutoramento em Ciência e Engenharia de MateriaisThermochromic materials change optical properties, such as transmittance or reflectance, with a variation in temperature. An ideal intelligent (smart) material will allow solar radiation in through a window in cold conditions, but reflect that radiation in warmer conditions. The variation in the properties is often associated with a phase change, which takes place at a definite temperature, and is normally reversible. Such materials are usually applied to window glass as thin films. This thesis presents the work on the development of thermochromic vanadium (IV) oxide (VO2) thin films – both undoped and doped with tungsten, niobium and gold nanoparticles – which could be employed as solar control coatings. The films were deposited using Chemical Vapour Deposition (CVD), using improved Atmospheric Pressure (APCVD), novel Aerosol Assisted (AACVD) and novel hybrid AP/AACVD techniques. The effects of dopants on the metalto- semiconductor transition temperature and transmittance/reflectance characteristics were also investigated. This work significantly increased the understanding of the mechanisms behind thermochromic behaviour, and resulted in thermochromic materials based on VO2 with greatly improved properties.
Os materiais termocrómicos exibem alterações das suas propriedades ópticas, tais como a transmitância ou a reflectância, com a variação da temperatura. Um material inteligente ideal permite a passagem da radiação solar através uma janela quando está frio, mas reflecte a mesma radiação quando está calor. A variação destas propriedades é frequentemente associada a uma transição de fase, a qual ocorre a uma temperatura definida e que, normalmente, é reversível. Estes materiais são geralmente utilizados como filmes finos em vidros de janelas. Nesta tese apresenta-se o desenvolvimento de filmes finos de óxido de vanâdio (IV) (VO2) termocrómicos – não dopados e dopados com tungsténio, nióbio e nanopartículas de ouro – que podem ser utilizados como revestimentos para o controle da passagem da radiação solar. Os filmes foram processados recorrendo à deposição química em fase vapor (CVD), com a técnica “atmospheric pressure” (APCVD) melhorada, e as novas tecnicas “aerosol assisted” (AACVD) e híbrida (AP/AACVD). Foram também estudados os efeitos dos dopantes na temperatura de transição metal – semiconductor, e na transmitância e reflectância dos filmes. O desenvolvimento de materiais termocrómicos baseados em VO2 com propriedades optimizadas aumentou significativamente a compreensão dos mecanismos associados ao comportamento termocrómico.
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Sawtell, David Arthur Gregory. "Plasma enhanced chemical vapour deposition of silica thin films." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/plasma-enhanced-chemical-vapour-deposition-of-silica-thin-films(2c75bbd8-8d89-42f2-b926-b464e619b4aa).html.
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Atmospheric pressure chemical vapour deposition is an industrially significant process for forming functional thin films. There is a great opportunity for increased scientific understanding with the aim of improving current processes and helping to formulate new ones. This work is concerned with developing a methodology to assist this ongoing concern. A combination of spectroscopic and chemometric techniques are used to investigate several chemical vapour deposition processes. The first investigation concerns the spatial concentration mapping of key by-products during the thermal chemical vapour deposition of tin oxide films through the use of near infra red laser diode spectroscopy. This novel two dimensional characterisation of the process has identified reaction hotspots within the process, and has identified the redundancy of part of the exhaust mechanism. Subsequently, there has been improvements to the head design, and the operation of the process.The main thrust of the investigations are focussed towards the use of chemometric methods, such as experimental design and principal components analysis, in conjunction with a suite of spectroscopic measurement techniques, to analyse the plasma enhanced chemical vapour deposition of silica films. This work has shown the importance of active oxygen species on the chemistry. It has also been shown that the film properties are highly dependant on oxygen concentration in the reactor, and hence active oxygen species forming in the plasma. The identification of by-products in the silica deposition process has also been carried out for the first time. Finally, this work also presents the first rigorous studies of a new precursor for silica deposition, dichlorodimethylsilane.
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Ligl, Jana [Verfasser], and Oliver [Akademischer Betreuer] Ambacher. "Aluminium scandium nitride grown by metalorganic chemical vapour deposition." Freiburg : Universität, 2020. http://d-nb.info/1225294118/34.
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Hindley, Sarah. "Atomic layer deposition and metal organic chemical vapour deposition of materials for photovoltaic applications." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/16313/.
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In this thesis, the development of thin films and nanostructures prepared with chemical vapour techniques are investigated for applications in photovoltaics. The deposition of both p-type and n-type oxides are investigated as a means of preparing all oxide p-n junctions. Both CVD and ALD precursors and processes have been developed. Zinc oxide nanowires are of interest as an n-type absorber layer with high surface area. In this thesis, the crystal structures of DEZn and DMZn were revisited and a new understanding of conventional zinc CVD precursors is presented. For DEZn a single structure was isolated and characterised with single crystal XRD. In the case of DMZn two temperature dependant structures were identified: namely α and β at 200K and 150K respectively. The DMZn precursor was subsequently exploited in a series of adduct-based precursors of the notation [DMZn.L] (where L = 1,2-dimethoxyethane, 1,4-dioxane and 1,4-thioxane). The crystal structures of these precursors were determined, and they were subsequently used to grow ZnO and sulphur doped ZnO across a range of CVD growth conditions. The microstructure and electronic properties of the nanowires have been characterised with electron microscopy, x-ray diffraction, Raman spectroscopy and photoluminescence. The II:VI ratio and substrate temperatures were both confirmed as playing a significant role in determining the microstructure of the nanowires. It has been demonstrated that the use of [DMZn.L] can avoid the pre-reaction between DMZn and oxygen. The studies with the thioxane adduct suggests the involvement of the ligand and hence sulphur incorporation in the nanowires. Two copper precursors were selected as the basis of p-type copper oxide film studies. The first Cu(hfac)(COD) has been used previously to deposit copper oxide by conventional CVD. In this thesis it is demonstrated for the first time that a pulsed LI-ALD approach can be exploited to deposit CuO with ozone as the co-reagent. An unexpected outcome of the research was the successful growth of electrically conductive copper metal films with a sheet resistance of 0.83Ω/□ when the precursor was thermally decomposed. The second copper precursor, namely CpCu(tBuNC) was used in atomic layer deposition to successfully deposit CuO or Cu2O with oxygen plasma and water respectively. Having identified that the β-diketonate compound yielded copper, the cyclopentadienyl based precursor was investigated as a route for the deposition of conductive copper metal films. Both thermal decomposition and a hydrogen plasma ALD process have been shown to deposit copper. With the plasma process, deposition of copper was demonstrated as low as 75˚C with a sheet resistance of only 0.55Ω/□. This thesis has demonstrated novel deposition routes for p- and n-type oxide materials which have potential future applications in thin film or nanostructured photovoltaic technology.
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Mohamed, Eman. "Microcrystalline silicon thin films prepared by hot-wire chemical vapour deposition." Thesis, Mohamed, Eman (2004) Microcrystalline silicon thin films prepared by hot-wire chemical vapour deposition. PhD thesis, Murdoch University, 2004. https://researchrepository.murdoch.edu.au/id/eprint/205/.
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Silicon is widely used in optoelectronic devices, including solar cells. In recent years new forms of silicon have become available, including amorphous, microcrystalline and nano-crystalline material. These new forms have great promise for low cost, thin film solar cells and the purpose of this work is to investigate their preparation and properties with a view to their future use in solar cells.
A Hot Wire-Deposition Chemical Vapour Deposition CVD (HW-CVD) system was constructed to create a multi-chamber high vacuum system in combination with an existing Plasma Enhanced Chemical Vapour Deposition (PECVD) system; to study the amorphous to crystalline transition in silicon thin films. As the two chambers were linked by a common airlock, it was essential to construct a transfer mechanism to allow the transfer of the sample holder between the two systems. This was accomplished by the incorporation of two gate valves between the two chambers and the common airlock as well as a rail system and a magnetic drive that were designed to support the weight of, and to guide the sample holder through the system.
The effect of different deposition conditions on the properties and structure of the material deposited in the combined HW-CVD:PECVD system were investigated. The conditions needed to obtain a range of materials, including amorphous, nano- and microcrystalline silicon films were determined and then successfully replicated.
The structure of each material was analysed using Transmission Electron Microscopy (TEM). The presence of crystallites in the material was confirmed and the structure of the material detected by TEM was compared to the results obtained by Raman spectroscopy. The Raman spectrum of each sample was decoupled into three components representing the amorphous, intermediate and crystalline phases. The Raman analysis revealed that the amorphous silicon thin film had a dominant amorphous phase with smaller contribution from the intermediate and crystalline phase. This result supported the findings of the TEM studies which showed some medium range order. Analysis of the Raman spectrum for samples deposited at increasing filament temperatures showed that the degree of order within the samples increased, with the evolution of the crystalline phase and decline of the amorphous phase. The Selected Area Diffraction (SAD) patterns obtained from the TEM were analysed to gain qualitative information regarding the change in crystallite size. These findings have been confirmed by the TEM micrograph measurements.
The deposition regime where the transition from amorphous to microcrystalline silicon took place was examined by varying the deposition parameters of filament temperature, total pressure in the chamber, gas flow rate, deposition time and substrate temperature.
The IR absorption spectrum for [mu]c-Si showed the typical peaks at 2100cm-1 and 626cm-1, of the stretching and wagging modes, respectively. The increase in the crystallinity of the thin films was consistent with the evolution of the 2100cm-1 band in IR, and the decreasing hydrogen content, as well as the shift of the wagging mode to lower wavenumber. IR spectroscopy has proven to be a sensitive technique for detecting the crystalline phase in the deposited material.
Several devices were also constructed by depositing the [mu]c-Si thin films as the intrinsic layer in a solar cell, to obtain information on their characteristics. The p- layer (amorphous silicon) was deposited in the PECVD chamber, and the sample was then transferred under vacuum using the transport system to the HW-CVD chamber where the i-layer (microcrystalline silicon) was deposited. The sample holder was transferred back to the PECVD chamber where the n-layer (amorphous silicon) was deposited.
The research presented in this thesis represents a preliminary investigation of the properties of [mu]c-Si thin films. Once the properties and optimum deposition characteristics for thin films are established, this research can form the basis for the optimization of a solar cell consisting of the most efficient combination of amorphous, nano- and microcrystalline materials.
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Mohamed, Eman. "Microcrystalline silicon thin films prepared by hot-wire chemical vapour deposition." Mohamed, Eman (2004) Microcrystalline silicon thin films prepared by hot-wire chemical vapour deposition. PhD thesis, Murdoch University, 2004. http://researchrepository.murdoch.edu.au/205/.
Full textAbstract:
Silicon is widely used in optoelectronic devices, including solar cells. In recent years new forms of silicon have become available, including amorphous, microcrystalline and nano-crystalline material. These new forms have great promise for low cost, thin film solar cells and the purpose of this work is to investigate their preparation and properties with a view to their future use in solar cells.
A Hot Wire-Deposition Chemical Vapour Deposition CVD (HW-CVD) system was constructed to create a multi-chamber high vacuum system in combination with an existing Plasma Enhanced Chemical Vapour Deposition (PECVD) system; to study the amorphous to crystalline transition in silicon thin films. As the two chambers were linked by a common airlock, it was essential to construct a transfer mechanism to allow the transfer of the sample holder between the two systems. This was accomplished by the incorporation of two gate valves between the two chambers and the common airlock as well as a rail system and a magnetic drive that were designed to support the weight of, and to guide the sample holder through the system.
The effect of different deposition conditions on the properties and structure of the material deposited in the combined HW-CVD:PECVD system were investigated. The conditions needed to obtain a range of materials, including amorphous, nano- and microcrystalline silicon films were determined and then successfully replicated.
The structure of each material was analysed using Transmission Electron Microscopy (TEM). The presence of crystallites in the material was confirmed and the structure of the material detected by TEM was compared to the results obtained by Raman spectroscopy. The Raman spectrum of each sample was decoupled into three components representing the amorphous, intermediate and crystalline phases. The Raman analysis revealed that the amorphous silicon thin film had a dominant amorphous phase with smaller contribution from the intermediate and crystalline phase. This result supported the findings of the TEM studies which showed some medium range order. Analysis of the Raman spectrum for samples deposited at increasing filament temperatures showed that the degree of order within the samples increased, with the evolution of the crystalline phase and decline of the amorphous phase. The Selected Area Diffraction (SAD) patterns obtained from the TEM were analysed to gain qualitative information regarding the change in crystallite size. These findings have been confirmed by the TEM micrograph measurements.
The deposition regime where the transition from amorphous to microcrystalline silicon took place was examined by varying the deposition parameters of filament temperature, total pressure in the chamber, gas flow rate, deposition time and substrate temperature.
The IR absorption spectrum for [mu]c-Si showed the typical peaks at 2100cm-1 and 626cm-1, of the stretching and wagging modes, respectively. The increase in the crystallinity of the thin films was consistent with the evolution of the 2100cm-1 band in IR, and the decreasing hydrogen content, as well as the shift of the wagging mode to lower wavenumber. IR spectroscopy has proven to be a sensitive technique for detecting the crystalline phase in the deposited material.
Several devices were also constructed by depositing the [mu]c-Si thin films as the intrinsic layer in a solar cell, to obtain information on their characteristics. The p- layer (amorphous silicon) was deposited in the PECVD chamber, and the sample was then transferred under vacuum using the transport system to the HW-CVD chamber where the i-layer (microcrystalline silicon) was deposited. The sample holder was transferred back to the PECVD chamber where the n-layer (amorphous silicon) was deposited.
The research presented in this thesis represents a preliminary investigation of the properties of [mu]c-Si thin films. Once the properties and optimum deposition characteristics for thin films are established, this research can form the basis for the optimization of a solar cell consisting of the most efficient combination of amorphous, nano- and microcrystalline materials.
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Bain, Michael. "The deposition and characterisation of CVD tungsten." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326383.
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Bengasi, Giuseppe [Verfasser]. "Synthesis and Deposition of Directly Fused Porphyrin Tapes by Chemical Vapour Deposition Approach / Giuseppe Bengasi." Mainz : Universitätsbibliothek Mainz, 2020. http://d-nb.info/1212543610/34.
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Ferguson, Andrew John. "Photophysical properties of organic thin films grown by vapour deposition." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420394.
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Basharat, Siama. "Precursor Synthesis and Chemical Vapour Deposition of Group 13 Oxides." Thesis, University College London (University of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487670.
Full textAbstract:
This thesis is primarily concerned with the precursor synthesis and chemical vapour deposition of group 13 oxides. The gas sensing properties of some of the films prepared have also been investigated. Chapter 1 gives an introduction to techniques used for deposition, in particular chemical vapour deposition (CYD). Chapter 2 describes the synthesis of gallium and indium alkoxides incorporating donor functionalised ligands. The donor-functionalised alkoxides [R2M(OR,)h (M =Ga, R = Et; M = In, R = Me; R' = CH2CH2NMe2, CH(CH2NMe2h CH2CH20Me, CH(CH3)CH2NMe2, C(CH3hCH20Me) were synthesised by the 1 : I reaction of R3M with R'OH in toluene at room temperature. Gallium and indium bis-alkoxides [RM(OR')2] (M =Ga, R =Et; M =In, R =Me; R' = CH2CH2NMe2, CH(CH2NMe2)2, CH2CH20Me, CH(CH3)CH2NMe2, C(CH3hCH20Me) have also been synthesised by the I : 6 reaction of R3M with R'OH i.n toluene under reflux conditions. Homoleptic gallium trisalkoxides [Ga(ORhh have been prepared by the I : 6, reaction of [Ga(NMe2hh with R'OH. Decomposition of all the compounds have been studied by thermal gravimetric analysis in Chapter 3. The formation of thin-films of gallium oxide 'via single-source low pressure chemical vapour deposition (LPCYD) methodology was investigated including detailed film growth studies and characterisation. The compounds described above were used as precursors and deposition was achieved at 550°C. Chapter 3 also investigates the formation of thin-films of gallium and indium oxide using aerosol assisted chemical vapour deposition (AACYD). This involved the ill situ reaction of [Ga(NMe2hh or R3M with a donor functionalised alcohol (R'OH). Gas sensing experiments on selected Ga203 films deposited by AACVD are described in Chapter 4.
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Ohashi, Fumitaka. "Fabrication of carbon nanotube devices using thermal chemical vapour deposition." Thesis, University of Surrey, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505963.
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Baluti, Silviu Ioan. "Experimental characterization of flow dynamics of pulsed-chemical vapour deposition." Thesis, University of Canterbury. Mechanical Engineering, 2005. http://hdl.handle.net/10092/6593.
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This research is a study of the precursor mass transport, the first variable that affects the film
deposition rate, uniformity, coverage, and microstructure of resulted films on substrates
inside Chemical Vapour Deposition (CVD) reactors. The Pulsed-CVD reactant flow field
uniformities in pulse flow were compared to equivalent steady flow regimes. For mass
limited transport CVD processes this represents an important matter, as precursor flux
increase leads directly to increased deposition rates.
The objective of the research was to develop design relations and define operational
parameter ranges to achieve flow field uniformity through experimental investigations.
Metered gaseous N2 reactant quantities were injected at equal time intervals into the
continuously evacuated reactor. The resulting reactor pressure cycle crosses all the three
pressure flow regimes, from viscous, to transition and finally to molecular flow. Nondimensional
flow parameters for this unique pulse pressure flow regime were developed
from first principles and were studied for relation to design and operation of Pulsed-CVD
equipment and processes.
Because of the reactor low pressures and non-steady conditions, temperature induced
buoyancy driven flows have low effect on the flow field dynamics of the gaseous N2 flow
(low Grashof number). Thus this research into pulsed pressure flow field uniformity was
conducted for isothermal reactor conditions, without the heater powered.
For the reactor flow field uniformity determination, the naphthalene sublimation technique
has been employed. This method is usually employed in viscous flow for the determination
of the convective heat transfer coefficient through the heat and mass transfer analogy. In this
research a method was developed to use the sublimation rate of several samples placed at
different locations in the reactor volume to measure the relative convective and pressure
conditions, and thus the uniformity of the reactor flow field.
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Experiments have been run by subsequently varying the pulsing cycle length, the reactor
pressure (implicitly the injected reactant mass), and the deposition substrate geometry. The
rest of the deposition variables have been kept constant.
The experimental results show that cycle time greater than or equal to four times the reactor
molecular time constant lead to best pulse flow uniformities, and that for these cycle times
the 3D flow field uniformities in pulse flow regimes are always better than in equivalent
steady flow ones. Comparable uniformities in both flows between stacked wafer substrates
have been determined, with slightly better uniformities in pulse flow than in equivalent
steady flow experiments.
In order to determine the steady flow field uniformities inside the experimental reactor, as
well as when varying its geometrical characteristics, the gas flow was simulated using the
finite volume Computational Fluid Dynamics (CFD) method and the commercial software
Fluent 6.1.
Design and process parameters are proposed, and the reactor pressure is analytically
modelled for the pulse flow regime.
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Milne, David Kerr. "Laser chemical vapour deposition of Si and Si-C alloys." Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/937.
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Ahmed, W. "Studies in low pressure chemical vapour deposition of polycrystalline silicon." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376853.
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Peters, Emily Sarah. "Precursor synthesis and chemical vapour deposition of transition metal sulfides." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408505.
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Tobin, Neil Lawrence. "Improved precursors for the chemical vapour deposition of metal oxides." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417972.
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Hiscock, Jonathan Nicholas. "An optoelectronic study of diamond grown by chemical vapour deposition." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313713.
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Allers, Lars. "A spectroscopic study of diamond grown by chemical vapour deposition." Thesis, King's College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309667.
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Cook, Gary. "Replication of organic materials by chemical vapour deposition of oxides." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268780.
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White, Andrew James. "Photon-enhanced chemical vapour deposition of amorphous carbon thin films." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320045.
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