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QI, YU. "THE APPLICATION OF PULSE MODULATED PLASMA TO THE PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION OF DIELECTRIC MATERIALS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115603610.
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Spooner, Marc. "The application and limitations of PECVD for silicon-based photonics /." View thesis entry in Australian Digital Program, 2005. http://thesis.anu.edu.au/public/adt-ANU20070315.043442/index.html.
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Xiao, Zhigang. "Synthesis of Functional Multilayer Coatings by Plasma Enhanced Chemical Vapor Deposition." Cincinnati, Ohio : University of Cincinnati, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=ucin1081456822.
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Haddad, Farah. "Transmission electron microscopy study of low-temperature silicon epitaxy by plasma enhanced chemical vapor deposition." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX107/document.
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Cette thèse s’intéresse à la croissance épitaxiale à basse température (~200°C) des couches minces de silicium par dépôt chimique en phase vapeur assisté par plasma (PECVD), pour des applications aux cellules solaires. L’objectif de départ était de mieux comprendre cette croissance épitaxiale, en utilisant la microscopie électronique en transmission (MET) comme principal outil expérimental. D’abord, nous avons étudié les premiers stades de cette croissance épitaxiale en chimie SiF4/H2/Ar, en menant une série de dépôts courts – quelques dizaines jusqu’à quelques centaines de secondes – sur différents types de substrats. Nous avons établi une corrélation entre les images MET de coupes et de vues planes et les mesures d’ellipsométrie in-situ. Nous avons discuté les mécanismes de croissance en nous basant sur l’hypothèse de la croissance traditionnelle à base d’atomes, radicaux et ions et l’hypothèse (relativement nouvelle) reposant sur la fonte des nanoparticules générées par le plasma au moment de l’impact avec le substrat. De plus, pour comprendre comment l’épitaxie par PECVD à basse température se maintient, nous avons étudié comment elle se brise ou se perd. Pour cela, des expériences de perte d’épitaxie ont été visées en augmentant soit la puissance de la source RF, soit le flux d’hydrogène, toujours pour une chimie SiF4/H2/Ar. Dans les deux cas, le mécanisme de brisure d’épitaxie fait intervenir des macles et des fautes d’empilement qui interrompent la configuration épitaxiale ; ceci est accompagné par une rugosification de surface. Grâce à cette nouvelle compréhension de la brisure d’épitaxie, nous proposons quelques moyens pour maintenir l’épitaxie pour de plus grandes épaisseurs. En outre, nous avons observé une fascinante quasi-symétrie cinq dans les diagrammes de diffraction pour ces couches et aussi pour d’autres élaborées par un plasma de chimie SiH4/H2/HMDSO/B2H6/Ar. Nous avons attribué une telle symétrie à une brisure d’épitaxie par l’intermédiaire d’un maclage multiple. Nous avons développé une méthode d’analyse quantitative qui permet de discriminer les positions de maclage de celles du microcristal aléatoire dans les diagrammes de diffraction et d’estimer le nombre des opérations de maclage. Nous avons aussi discuté quelques raisons probables pour l’incidence du maclage et du maclage multiple sous forme de symétrie cinq. Finalement, une importante réalisation pour le monde de la MET, durant ce travail doctoral, a été l’optimisation de la préparation traditionnelle d’échantillon (polissage par tripode). Nous l’avons transformée d’une méthode longue et ennuyeuse en une méthode rapide qui devient compétitive par rapport à la technique du FIB relativement chèreThis thesis focuses on low temperature (LT, ~200°C) epitaxial growth of silicon thin films by plasma enhanced chemical vapor deposition (PECVD) for solar cell applications. Our starting goal was to acquire a better understanding of epitaxial growth, by using transmission electron microscopy (TEM) as the main experimental tool. First, we investigated the initial stages of epitaxial growth using SiF4/H2/Ar chemistry by performing a series of short depositions – from few tens to few hundred of seconds – on different types of substrates. We made a correlation between cross-sectional and plan-view TEM images and in-situ ellipsometry measurements. We discussed the growth mechanisms under the hypotheses of the traditional growth mediated by atoms, radicals and ions and the relatively new approach based on the melting of plasma generated nanoparticles upon impact with the substrate. Additionally, in order to understand how epitaxy by LT-PECVD is sustained, we studied how it is lost or how it breaks down. For that, experiments of intentional breakdown of epitaxy were performed by either increasing the RF power or the hydrogen flow rate using the same SiF4/H2/Ar chemistry. In both cases, the breakdown mechanism was based on the development of twins and stacking faults thus disrupting epitaxial configuration; this was accommodated with surface roughening. Thanks to this new understanding of epitaxy breakdown, we can propose some ways to sustain epitaxy for higher thicknesses. Moreover, we fascinatingly observed a quasi-fivefold symmetry in the diffraction patterns for these layers and for layers deposited using SiH4/H2/HMDSO/B2H6/Ar plasma chemistry as well. We attributed such symmetry to the breakdown of epitaxy through multiple twinning. We developed a quantitative analysis method to discriminate twin positions from random microcrystalline ones in the diffraction patterns and to estimate the number of twin operations. We also discussed some probable reasons for the occurrence of twinning and multiple twinning in a fivefold symmetry fashion. Finally, one important achievement to the TEM world is the optimization, during this doctoral work, of the traditional TEM sample preparation (tripod polishing), transforming it from a long and boring method to a fast method that is competitive with the relatively expensive focus ion beam (FIB) technique
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Carbaugh, Daniel J. "Growth and Characterization of Silicon-Based Dielectrics using Plasma Enhanced Chemical Vapor Deposition." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1406644891.
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Jehanathan, Neerushana. "Thermal stability of plasma enhanced chemical vapor deposited silicon nitride thin films." University of Western Australia. School of Mechanical Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0069.
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[Truncated abstract] This study investigates the thermal stability of Plasma Enhanced Chemical Vapor Deposited (PECVD) silicon nitride thin films. Effects of heat-treatment in air on the chemical composition, atomic bonding structure, crystallinity, mechanical properties, morphological and physical integrity are investigated. The chemical composition, bonding structures and crystallinity are studied by means of X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) Spectroscopy and Transmission Electron Microscopy (TEM). The mechanical properties, such as hardness and Young’s modulus, are determined by means of nanoindentation. The morphological and physical integrity are analyzed using Scanning Electron Microscopy (SEM) . . . The Young’s modulus (E) and hardness (H) of the film deposited at 448 K were measured to have E=121±1.8 GPa and H=11.7±0.25 GPa. The film deposited at 573 K has E=150±3.6 GPa and H=14.7±0.6 GPa. For the film deposited at 573 K, the Young’s modulus is not affected by heating up to 1148 K. Heating at 1373 K caused significant increase in Young’s modulus to 180∼199 GPa. This is attributed to the crystallization of the film. For the film deposited at 448 K, the Young’s modulus showed a moderate increase, by ∼10%, after heating to above 673 K. This is consistent with the much lower level of crystallization in this film as compared to the film deposited at 573 K. In summary, low temperature deposited PECVD SiNx films are chemically and structurally unstable when heated in air to above 673 K. The main changes include oxidation to SiO2, crystallization of Si3N4 and physical cracking. The film deposited at 573 K is more stable and damage and oxidation resistant than the film deposited at 448 K.
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Zhou, Ming. "Novel photocatalytic TiO2-based porous membranes prepared by plasma-enhanced chemical vapor deposition (PECVD) for organic pollutant degradation in water." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS090/document.
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Le dépôt chimique en phase vapeur assisté par plasma est appliqué pour préparer des couches minces amorphes de TiO2 à basse température. Un recuit à 300 °C pendant un temps minimum de 4,5 h permet de former la phase cristalline anatase. Les principales caractéristiques de ces couches minces comme leur structure cristalline, leur microstructure, leur largeur de bande interdite et leur hydrophilie de surface, sont déterminées. Leurs performances fonctionnelles comme photocatalyseurs sont d'abord examinées selon le test breveté par Pilkington, consistant à éliminer sous irradiation UV de l'acide stéarique préalablement adsorbé sur les couches de TiO2 ici déposées sur des plaquettes de silicium. Des membranes M100 (couche continue de TiO2) et M800 (couche de TiO2 couvrant les grains de support) sont préparées sur les couches de surface macroporeuses de supports poreux en alumine, de tailles moyennes de pores respectives, 100 nm et 800 nm. Ces membranes sont testées en condition "statique", avec la diffusion d'un soluté organique dilué dans l'eau. Pour le bleu de méthylène, on montre que la quantité de composé détruit par unité de surface de membrane et par unité de temps est égale à 2 × 10-8 mol m-2 s-1 pour la membrane M100 et 1 × 10-8 mol m-2 s- 1 pour la membrane M800. Ces membranes sont également testées dans des conditions "dynamiques", à savoir en procédé baromembranaire, avec deux configurations différentes (couche photocatalytique du côté de l'alimentation ou du côté du perméat) et trois composés organiques différents (bleu de méthylène, acide orange 7 et phénol). La modélisation du procédé (adsorption et réaction photocatalytique) est finalement réalisée à partir des données expérimentales disponiblesPlasma-enhanced chemical vapor deposition is applied to prepare amorphous TiO2 thin films at low temperature. Post-annealing at 300 °C for minimal staying time 4.5 h is required to form crystalline anatase phase. Characteristics of the TiO2 thin films including crystalline structure, microstructure, band gap and surface hydrophilicity, are determined. Functional performance of these anatase thin films as photocatalysts is first examined with patented Pilkington assessment by removing, under UV irradiation, stearic acid initially adsorbed on TiO2 layers here deposited on silicon wafers. Membranes M100 (TiO2 continuous layer) and M800 (TiO2-skin on support grain) are prepared on the macroporous top layer of porous alumina supports with an average pore size of 100 nm and 800 nm, respectively. These membranes are tested in “static” condition under the effect of diffusion of an organic solute in water. For Methylene Blue it is shown that the quantity of destroyed compound per unit of membrane surface area and per unit of time is equal to 2×10−8 mol m-2 s-1 for M100 and 1×10−8 mol m-2 s-1 for M800. These membranes are also tested in “dynamic” conditions, i.e. pressure-driven membrane processes, with two different configurations (photocatalytic layer on the feed side or on the permeate side) and three different organics (Methylene Blue, Acid Orange 7 and phenol). Process modelling (adsorption and photocatalysis reaction) is finally carried out from the available experimental outputs
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Niiranen, Pentti. "Electrically Modified Quartz Crystal Microbalance to Study Surface Chemistry Using Plasma Electrons as Reducing Agents." Thesis, Linköpings universitet, Kemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-176607.
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Metallic films are important in various applications, such as electric devices where it can act as contacts. In electrical devices, the substrate typically consists of silicon dioxide (SiO2) which is a temperature-sensitive substrate. Therefore, plasma enhanced chemical vapor deposition (PECVD) are better suited than thermally activated chemical vapor deposition (CVD). Depositing metallic films with PECVD demands co-reactants that act as reducing agents. However, these are not well-studied and do not always have the power enough to perform the reduction reaction for metals. Recently it has been concluded that electrons can act as reducing agents in the deposition of first row transition metallic films in a PECVD process. By supplying a positive bias to the substrate, the electrons got attracted to the surface of the substrate, which facilitated metal growth. The study concluded that metal growth only occurred at conductive -and semiconductive substrates and that the substrate bias and plasma power affected the metal growth. The process is however not well understood, which causes a knowledge gap, signifying that studies of the surface chemistry are needed. Here a new modified analytical method to study the surface chemistry in the newly developed process mentioned above is presented. The analytical method consists of an electrically modified quartz crystal microbalance (QCM) with gold electrodes as a conductive substrate. This allows the electron current to run through the QCM during the measurement. By supplying a DC-voltage to the front electrode it gets readily biased (negative and positive) and by placing a capacitor in the circuit, it connects the AC-circuit (oscillator circuit) and the DC-circuit (DC-voltage bias circuit). At the same time, it blocks the DC-current from going back to the oscillator but allows the high-frequency signal to pass from the QCM. The results in this thesis concluded that the QCM can be electrically modified to allow an electron flux to the QCM while using it as a substrate when electrons are used as reducing agents. Scanning electron microscopy (SEM) of a QCM crystal revealed that a 2 µm film had been deposited while SEM coupled with energy dispersive X-ray spectroscopy (EDS) showed that the film indeed contained iron. Further analysis was made by high-resolution X-ray photoelectron spectroscopy (HR-XPS) to find the elemental composition of the film, which revealed that the thin film contained 41 at.% iron. In addition, this study investigated if the QCM could be used to study CVD processes where electrons were used as reducing agents. The results indeed revealed that it is possible to study the surface chemistry where electrons are used as reducing agents with the electrically modified QCM to gain knowledge concerning film deposition. Initial results of the QCM showed that film growth could be studied when varying the plasma power between 5 W to 15 W and the QCM bias between -40 V to +40 V. The method generated easily accessible data concerning the process where electrons are used as reducing agents, which gained insight to the method that never has been disclosed before.
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Hellwig, Thomas. "Physical, electrochemical and mechanical characterisation of amorphous boron phosphide coatings prepared by plasma enhanced chemical vapour deposition (PECVD)." Thesis, University of the West of Scotland, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545797.
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Whilst substantial empirical experimental investigation is available in the literature on amorphous Boron phosphide (BP) coatings, there is not much information about the scienti¯c properties exhibited by this material in var- ious applications such as in infra-red imaging systems. Also a great deal of the industrial application of amorphous BP coatings is in the area of infra- red imaging systems. This thesis is based on an attempt to understand the underpinning scienti¯c basis for the properties of amorphous Boron phos- phide coatings, using a range of surface, chemical, physical, electrochemical, computational (quantum mechanics) and mechanical characterisation tools. The results of this investigation has not only helped in unveiling the scien- ti¯c basis of some of the current empirically derived properties of amorphous BP coatings, used in the infra-red imaging industry, but has con¯rmed that amorphous BP is a potential coating for engineering substrates used in var- ious industries if the PECVD deposition process is optimised. This inves- tigation also establishes the link between the properties of amorphous BP coatings and the bonds in the different stoichiometric composition of the coatings.
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Zimmermann, Thomas. "High-rate growth of hydrogenated amorphous and microcrystalline silicon for thin-film silicon solar cells using dynamic very-high frequency plasma-enhanced chemical vapor deposition." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-131765.
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Thin-film silicon tandem solar cells based on a hydrogenated amorphous silicon (a-Si:H) top-cell and a hydrogenated microcrystalline silicon (μc-Si:H) bottom-cell are a promising photovoltaic technology as they use a combination of absorber materials that is ideally suited for the solar spectrum. Additionally, the involved materials are abundant and non-toxic which is important for the manufacturing and application on a large scale.
One of the most important factors for the application of photovoltaic technologies is the cost per watt. There are several ways to reduce this figure: increasing the efficiency of the solar cells, reducing the material consumption and increasing the throughput of the manufacturing equipment.
The use of very-high frequencies has been proven to be beneficial for the material quality at high deposition rates thus enabling a high throughput and high solar cell efficiencies. In the present work a scalable very-high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) technique for state-of-the-art solar cells is developed. Linear plasma sources are applied which facilitate the use of very-high frequencies on large areas without compromising on the homogeneity of the deposition process.
The linear plasma sources require a dynamic deposition process with the substrate passing by the electrodes in order to achieve a homogeneous deposition on large areas. State-of-the-art static radio-frequency (RF) PECVD processes are used as a reference in order to assess the potential of a dynamic VHF-PECVD technique for the growth of high-quality a-Si:H and μc-Si:H absorber layers at high rates.
In chapter 4 the influence of the deposition process of the μc-Si:H i-layer on the solar cell performance is studied for static deposition processes. It is shown that the correlation between the i-layer growth rate, its crystallinity and the solar cell performance is similar for VHF- and RF-PECVD processes despite the different electrode configurations, excitation frequencies and process regimes. It is found that solar cells incorporating i-layers grown statically using VHF-PECVD processes obtain a state-of-the-art efficiency close to 8 % for growth rates up to 1.4 nm/s compared to 0.53 nm/s for RF-PECVD processes.
The influence of dynamic deposition processes on the performance of μc-Si:H solar cells is studied. It is found that μc-Si:H solar cells incorporating dynamically grown i-layers obtain an efficiency of 7.3 % at a deposition rate of 0.95 nm/s. There is a small negative influence of the dynamic deposition process on the solar cell efficiency compared to static deposition processes which is related to the changing growth conditions the substrate encounters during a dynamic i-layer deposition process.
The changes in gas composition during a dynamic i-layer deposition process using the linear plasma sources are studied systematically using a static RF-PECVD regime and applying a time-dependent gas composition. The results show that the changes in the gas composition affect the solar cell performance if they exceed a critical level.
In chapter 5 dynamic VHF-PECVD processes for a-Si:H are developed in order to investigate the influence of the i-layer growth rate, process parameters and deposition technique on the solar performance and light-induced degradation. The results in this work indicate that a-Si:H solar cells incorporating i-layers grown dynamically by VHF-PECVD using linear plasma sources perform as good and better as solar cells with i-layers grown statically by RF-PECVD at the same deposition rate. State-of-the-art stabilized a-Si:H solar cell efficiencies of 7.6 % are obtained at a growth rate of 0.35 nm/s using dynamic VHF-PECVD processes.
It is found that the stabilized efficiency of the a-Si:H solar cells strongly decreases with the i-layer deposition rate. A simplified model is presented that is used to obtain an estimate for the deposition rate dependent efficiency of an a-Si:H/μc-Si:H tandem solar cell based on the photovoltaic parameters of the single-junction solar cells. The aim is to investigate the individual influences of the a-Si:H and μc-Si:H absorber layer deposition rates on the performance of the tandem solar cell.
The results show that a high deposition rate of the μc-Si:H absorber layer has a much higher potential for reducing the total deposition time of the absorber layers compared to high deposition rates for the a-Si:H absorber layer. Additionally, it is found that high deposition rates for a-Si:H have a strong negative impact on the tandem solar cell performance while the tandem solar cell efficiency remains almost constant for higher μc-Si:H deposition rates.
It is concluded that the deposition rate of the μc-Si:H absorber layer is key to reduce the total deposition time without compromising on the tandem solar cell performance. The developed VHF-PECVD technique using linear plasma sources is capable of meeting this criterion while promoting a path to scale the processes to large substrate areas.
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Martins, Gustavo da Silva Pires. "Filtros interferenciais construídos com dielétricos depositados pela técnica de PECVD." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-11082008-215318/.
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Neste trabalho é apresentada a simulação, fabricação e caracterização de filtros interferenciais empregando películas dielétricas amorfas depositadas pela técnica de deposição a vapor assistida por plasma (PECVD) sobre substratos de silício e de Corning Glass (7059). Os dispositivos ópticos foram construídos usando-se processos padrões de microeletrônica e consistiram em camadas periódicas com espessura e índice de refração apropriados para produzir picos da atenuação na transmitância da luz na região visível. Simulações numéricas precedentes foram realizadas baseando-se nas características ópticas das películas dielétricas. Para a caracterização dos filtros interferenciais, uma luz monocromática de um laser de He-Ne, foi injetada nos filtros e a luz obtida na saída foi conduzida então a um detector. O filtro depositado sobre Corning Glass (chamado de filtro vertical) e o filtro depositado sobre silício com cavidades (chamado de filtro suspenso) foram montados sobre dispositivos térmicos e angulares de modo a medir suas respostas à variação angular e térmica. Também, o filtro depositado sobre silício (chamado de filtro horizontal) foi montado sobre um dispositivo térmico, a fim de medir sua resposta à temperatura. Quando os filtros são submetidos a uma mudança na temperatura, uma variação do índice de refração devido ao efeito termo-óptico produz um deslocamento nos picos da atenuação, que podem ser previstos por simulações numéricas. Esta característica permite que estes dispositivos sejam usados como sensores termo-ópticos. Por outro lado, quando o filtro vertical e o filtro suspenso são submetidos a variações angulares entre a normal ao plano do filtro e o feixe de laser, uma variação na potência da luz de saída é produzida. Esta característica permite que estes dispositivos sejam usados como sensores angulares.In this work, we present the simulation, fabrication and characterization of filters employing amorphous dielectric films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique on crystalline silicon and Corning Glass (7059) substrates. The optical devices were fabricated using standard microelectronic processes and consisted of periodic layers with appropriated thickness and refractive indexes to produce transmittance attenuation peaks in the visible region. For this, previous numerical simulations were realized based in the optical parameters of the dielectric films. For the characterization of the optical interferential filters, a monochromatic light, a He-Ne laser, was projected onto the filters and the transmitted output light was then conducted to a detector. The optical filters were produced on Corning Glass (here called vertical filter) and on silicon substrates. The silicon substrate was etch in KOH solution to form cavities and suspend part of the filter (here called suspended filter). The vertical and suspended filters were mounted on thermo and angular devices that allowed the measurement of the optical power as a function of temperature and angle changes. A second type of filter deposited over a silicon substrate (here called horizontal filter) was mounted on thermoelectric device, in order to control the temperature responses. When the filters are submitted to a change in temperature, a variation of the refractive index is originated in the dielectric film due to the thermo-optic effect (TOE), producing a shift in the attenuation peaks, which can be well predicted by numerical simulations. This characteristic allows these devices to be used as thermo-optic sensors. On the other hand, when the vertical filter and the suspended filter were subjected to an angular shift between the filter\'s normal and the laser, a variation of the output optical power is originated. This characteristic allows these devices to be used as angular sensors.
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Sel, Kivanc. "The Effects Of Carbon Content On The Properties Of Plasma Deposited Amorphous Silicon Carbide Thin Films." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/2/12608292/index.pdf.
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The structure and the energy band gap of hydrogenated amorphous silicon carbide are theoretically revised. In the light of defect pool model, density of states distribution is investigated for various regions of mobility gap. The films are deposited by plasma enhanced chemical vapor deposition system with various gas concentrations at two different, lower (30 mW/cm2) and higher (90 mW/cm2), radio frequency power densities. The elemental composition of hydrogenated amorphous silicon carbide films and relative composition of existing bond types are analyzed by x-ray photoelectron spectroscopy measurements. The thicknesses, deposition rates, refractive indices and optical band gaps of the films are determined by ultraviolet visible transmittance measurements. Uniformity of the deposited films is analyzed along the radial direction of the bottom electrode of the plasma enhanced chemical vapor deposition reactor. The molecular vibration characteristics of the films are reviewed and analyzed by Fourier transform infrared spectroscopy measurements. Electrical characteristics of the films are analyzed by dc conductivity measurements. Conduction mechanisms, such as extended state, nearest neighbor and variable range hopping in tail states are revised. The hopping conductivities are analyzed by considering the density of states distribution in various regions of mobility gap. The experimentally measured activation energies for the films of high carbon content are too low to be interpreted as the difference between Fermi level and relevant band edge. This anomaly has been successfully removed by introducing hopping conduction across localized tail states of the relevant band. In other words, the second contribution lowers the mobility edge towards the Fermi level.
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Lamberton, Robert William. "A study of the microstructure and growth of ultra-thin film amorphous hydrogenated carbon (a-C:H) prepared by plasma enhanced chemical vapour deposition (PECVD)." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264694.
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Wang, Junkang. "Novel Concepts in the PECVD Deposition of Silicon Thin Films : from Plasma Chemistry to Photovoltaic Device Applications." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX079/document.
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Ce manuscrit présente l'étude de la fabrication de couches minces de silicium basée sur des différents types de dépôt chimique en phase vapeur assisté par plasma (PECVD) pour des applications dans le photovoltaïque. Tout d'abord, nous avons combiné une chimie du plasma halogéné en utilisant un mélange de SiF4/H2 et la technique plasmas distributés matriciellement à résonance cyclotronique électronique (MDECR) PECVD pour le dépôt de μc-Si:H à grande vitesse. Nous trouvons que les conditions d'énergie ionique modérée sont bénéfiques pour obtenir une diminution significative de la densité des nano-vides, et ainis nous pouvons obtenir un matériaux de meilleure qualité avec une meilleure stabilité. Une méthode de dépôt en deux étapes a été introduite comme moyen alternatif d'éliminer la formation d'une couche d'incubation amorphe pendant la croissance du film. Ensuite, nous avons exploré la technique d'excitation Tailored Voltage Waveform (TVW) pour les processus plasma radiofréquence capacitivement couplé (RF-CCP). Grâce à l'utilisation de TVW, il est possible d'étudier indépendamment l'influence de l'énergie ionique sur le dépôt de matériaux à une pression de processus relativement élevée. Basé sur ce point, nous avons étudié le dépôt de μc-Si:H et a-Si:H à partir des plasma de SiF4/H2/Ar et de SiH4/H2, respectivement. A partir d'une analyse des propriétés structurelles et électroniques, nous constatons que la variation de l'énergie ionique peut directement traduite dans la qualité du matériaux. Les résultats se sont appliqués aux dispositifs photovoltaïques et ont établi des liens complets entre les paramètres de plasma contrôlables par TVW et les propriétés de matériaux déposé, et finalement, les performances du dispositif photovoltaïque correspondant. Enfin, nous avons trouvé que dans le cas du dépôt de couches minces de silicium à partir du plasma de SiF4/H2/Ar à l'aide de sawtooth TVW, on peut réaliser un processus de dépôt sur une électrode, sans aucun dépôt ou gravure. contre-électrode. Ceci est dû à deux effets: la nature multi-précurseur du processus de surface résultant et la réponse de plasma spatiale asymétrique par l'effet d'asymétrie de pente de la sawtooth TVW. La découverte de tels procédés “electrode-selective” encourage la perspective que l'on puisse choisir un ensemble de conditions de traitement pour obtenir une grande variété de dépôts désirés sur une électrode, tout en laissant l'autre viergeThis thesis describes the study of silicon thin film materials deposition and the resulting photovoltaic devices fabrication using different types of plasma-enhanced chemical vapour deposition (PECVD) techniques.In the first part, we combine a SiF4/H2 plasma chemistry with the matrix-distributed electron cyclotron resonance (MDECR) PECVD to obtain high growth rate microcrystalline silicon (µc-Si:H). Due to the special design of MDECR system, careful investigation of the impact energy of impinging ions to material deposition can be accessible. We find that moderate ion energy conditions is beneficial to achieve a significant drop in the density of nano-voids, thus a higher quality material with better stability can be obtained. A two-step deposition method is introduced as an alternative way to eliminate the existence of amorphous incubation layer during film growth.The second part of work is dedicate to the exploration of the Tailored Voltage Waveforms (TVWs) excitation technique for capacitively coupled plasmas (CCP) processes. As an advantage over the conventional sinusoidal excitations, TVWs technique provide an elegant solution for the ion flux-energy decoupling in CCP discharges through the electrical asymmetry effect, which makes the independent study of the impact of ion energy for material deposition at relatively high process pressure possible. Based on this insight, we have studied the deposition of µc-Si:H and amorphous silicon (a-Si:H) from the SiF4/H2/Ar and SiH4/H2 plasma chemistry, respectively. From the structural and electronic properties analysis, we find that the variation of ion energy can be directly translated into the material quality. We have further applied these results to photovoltaic applications and established bottom-up links from the controllable plasma parameters via TVWs to the deposited material properties, and eventually to the resulting device quality.In the last part, as a further application of TVWs, an “electrode-selective” effect has been discovered in the CCP processes. In the case of silicon thin film deposition from the SiF4/H2/Ar plasma chemistry, one can achieve a deposition process on one electrode, while at the same time either no deposition or an etching process on the counter electrode. This is due to two effects: the multi-precursor nature of the resulting surface process and the asymmetric plasma response through the utilization of TVWs. Moreover, such deposition/etching balance can be directly controlled through H2 flow rate. From a temporal asymmetry point of view, we have further studied the impact of process pressure and reactor geometry to the asymmetric plasma response for both the single-gas and multi-gas plasmas using the sawtooth waveforms. The product of pressure and inter-electrode distance P·di is deduced to be a crucial parameter in determine the plasma heating mode, so that a more flexible control over the discharge asymmetry as well as the relating “electrode-selective” surface process can be expected
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Poduri, Shripriya Darshini. "THEORETICAL MODELING AND ANALYSIS OF AMMONIA GAS SENSING PROPERTIES OF VERTICALLY ALIGNED MULTIWALLED CARBON NANOTUBE RESISTIVE SENSORS AND ENHANCING THEIR SENSITIVITY." UKnowledge, 2010. http://uknowledge.uky.edu/gradschool_theses/51.
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Vertically aligned Multiwalled Carbon Nanotubes (MWCNTs) were grown in the pores of Anodized Aluminum Oxide (AAO) templates and investigated for resistive sensor applications. High Sensitivity of 23% to low concentration (100 ppm) of ammonia was observed. An equivalent circuit model was developed to understand the current flow path in the resistive sensor. This helped us in achieving high sensitivities through amorphous carbon (a-C) layer thickness tailoring by employing post-growth processing techniques like plasma etching.
A simulation model in MATLAB was developed to calculate the device resistance and the change in the sensitivity as a function of device parameters. The steady state response and transient response of the model to the number of ammonia molecules and its adsorption rate were studied. Effects of oxygen plasma, argon plasma and water plasma etch on thinning of the a-C layer were studied.
In order to enhance the sensitivity, the top and bottom a-C layers were replaced by a more conductive metal layer. This also helped in understanding the current flow in the device and in the estimation of the resistivity of the a-C layer.
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Szili, Endre Jozsef, and endre szili@unisa edu au. "Covalent immobilisation of proteins for biomaterial and biosensing applications." Flinders University. School of Chemistry, Physics and Earth Sciences, 2008. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20080724.214815.
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This thesis focuses on surface science and bioengineering investigations, first for the development of an improved biomaterial for orthopaedic implant applications, and second, for the development of a biosensor device for biomedical diagnostics. A key component considered in this thesis was the covalent linkage of proteins to the materials surface for retaining the proteins immunological and biological activities and for generating a functional interface.
Part 1 of this thesis investigated surface modification procedures for improving the bioactivity of titanium substrates. Titanium is first coated with a bioactive silica film grown by plasma enhanced chemical vapour deposition (PECVD), referred to as PECVD-Si-Ti. In previous studies, the bone-implant integration process was enhanced 1.6-fold for titanium implants coated with PECVD-Si films compared to uncoated titanium implants in vivo. However, in vitro studies carried out in this thesis showed that the growth of MG63 osteoblast-like cells was 7-fold higher on uncoated titanium compared to PECVD-Si coated titanium. Therefore, to improve cell growth on the surface and, by inference, the integration of PECVD-Si-Ti implants into bone tissue, the implants surface was functionalised with a mitogenic factor, insulin-like growth factor-1 (IGF-1). This was accomplished by modifying the PECVD-Si-Ti surface with an alkoxysilane, 3-isocyanatopropyl triethoxysilane (IPTES), and then by covalent bioconjugation of IGF-1 through isocyanate-amino chemistry. After 72 h of in vitro cell culture in serum-free medium, the growth of MG63 cells was enhanced 1.9-fold on IPTES functionalised PECVD-Si-Ti, which was loaded with covalently immobilised IGF-1 compared to IPTES functionalised PECVD-Si-Ti without IGF-1 (isocyanate reactive groups were quenched with ethanolamine hydrochloride). The attachment and adhesion of MG63 cells were also enhanced on PECVD-Si-Ti by the covalently immobilised IGF-1 in serum-free cell culture conditions. Therefore, the bioactivity of PECVD-Si-Ti was improved by covalently linking IGF-1 to the substrate surface through isocyanate-amino chemistry.
Part 2 of this thesis involved the development of a new optical interferometric biosensor. The biosensor platform was constructed from electrochemically-prepared thin films of porous silicon that acted as a sensing matrix and transducer element. By reflective interferometry using white light, an enzyme-catalysed reaction was discovered (horseradish peroxidase (HRP) mediated oxidation of 3,3,5,5-tetramethylbenzidine (TMB)), which led to an acceleration in the rate of porous silicon corrosion and represented the biosensors readout signal. We discovered that another substrate, which is also oxidised by HRP, OPD, produces an even more pronounced readout signal. The HRP-OPD system was used in an immunoassay for detecting human IgG from an Intragam solution. An important part in the design of the biosensor was the surface functionalisation approach where anti-human IgG, referred to as the capture antibody, is immobilised on the porous silicon surface. The readout signal (produced from the capture of human IgG) was enhanced 4-fold on the porous silicon biosensing platform functionalised with covalently linked anti-human IgG through isocyanate-amino chemistry compared to the porous silicon biosensing platform functionalised with adsorbed anti-human IgG. The optimised biosensor was used to detect IgG from a total human protein concentration of Intragam to a sensitivity of 100 ng/ml.
In summary, isocyanate-amino bioconjugate chemistry was used to covalently link either IGF-1 to PECVD-Si-Ti for improving the biological activity of the orthopaedic implant and to covalently link IgG to porous silicon for developing a sensitive biosensor for the detection of proteins. This surface chemistry approach is very useful for biomaterial and biosensing applications.
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Tariq, Amna. "Design and implementation of a plasma enhanced chemical vapour deposition (PECVD) system for the study of C₆₀-polymer composite thin films and surface fuctionalization effects on C₆₀." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81572.
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This research project aimed at the development of a PECVD process for the deposition of C60-PPPE (plasma polymerized polyethylene) NC thin films. A continuous throughput PECVD system was designed for the co-deposition of a polymer matrix and C60 particles, in effect, yielding composite thin films on 1" quartz and silicon substrates. In this process, the C 60 molecules are sublimated from their solid powder form, transported to the plasma chamber, pre-coated in-flight before being dispersed and co-deposited in the polymeric matrix. The plasma polymerization of ethane in the low pressure, radio frequency (RF) plasma was studied with a mapping of the polymer thin film growth at various deposition times. Percentage coverage of C60 films was studied at several sublimation temperatures ranging from 500-750 °C. Compositional studies of PPPE and C60 films obtained were carried out using FPA-FTIR. The surface morphology and topography of composite films was analyzed using OM and FESEM. Furthermore, samples of C60 deposited in the reactor were analyzed via TEM for possible deagglomeration and nanocoatings.
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Gaufrès, Aurélien. "Élaboration de carbure de silicium amorphe hydrogéné par PECVD : Optimisation des propriétés optiques, structurales et passivantes pour des applications photovoltaïques." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0005.
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Notre étude concerne la mise en place et le développement de dépôts de carbure de silicium amorphe hydrogéné (a-SiCx:H) à basse température (370°C), par voie PECVD, sur un réacteur PECVD semi-industriel à faible fréquence (440 kHz). Les propriétés chimiques, optiques et de passivation de surface des couches déposées sont analysées et l’impact du changement des débits de gaz précurseurs (silane et méthane) est aussi étudié. La possibilité d’utiliser le a-SiCx:H comme couche anti-reflet en face avant d’une cellule solaire est envisagée. Bien que l’indice de réfraction d’une couche riche en carbone soit en accord avec la condition de lame quart-d’onde requise pour une couche anti-reflet, le coefficient d’extinction est trop élevé en raison de la proportion significative de silicium dans la couche. Cette absorption peut être atténuée par l’incorporation d’azote dans la couche (a-SiCxNy:H). En revanche, la passivation de surface s’améliore lorsque la quantité de silane augmente. La plus faible vitesse de recombinaison de surface atteinte sur les échantillons après dépôt est de 10 cm.sOur study deals with the deposition of amorphous hydrogenated silicon carbide (a- SiCx:H) at low temperature (370°C), by PECVD technique, using a semi-industrial lowfrequency PECVD reactor (440 kHz). The deposited films are analyzed for chemical, optical and surface passivation properties, and the impact of the gas flow parameters (silane and methane) is studied. The possible use of a-SiCx:H as an antireflective coating at the front side of solar cells is investigated. Although the refractive index for high carbon concentration could be in agreement with the demand of quarter-wave layer for antireflective coating, the extinction coefficient remains too high due to a significant silicon content in the material. This absorption can be attenuated by incorporating nitrogen in the layer. However, the surface passivation improves with the silane proportion. The lowest surface recombination velocity of an as-deposited samples is about 10 cm.s
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Forhan, Neisy Amparo Escobar. "Fabricação de novas heteroestruturas a partir de estruturas SOI obtidas pela técnica \'smart-cut\'." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-02042008-112321/.
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Esta pesquisa engloba o estudo e desenvolvimento de novas heteroestruturas semicondutoras, tomando como base as estruturas SOI (Silicon-On-Insulator - silício sobre isolante) obtidas pela técnica Smart Cut, estudadas nestes últimos anos no Departamento de Engenharia de Sistemas Eletrônicos da Escola Politécnica da Universidade de São Paulo (EPUSP). Esta técnica combina a solda direta para a união de lâminas e a implantação iônica (I/I) de íons leves para a separação de camadas especificadas. São essenciais na preparação destas estruturas SOI, processos de I/I, limpeza e ativação das superfícies das lâminas e recozimentos em fornos a temperaturas moderadas. Estudamos também, diferentes métodos para a obtenção de novas heteroestruturas, basicamente combinando as técnicas de fabricação da estrutura SOI e os métodos de formação do carbeto de silício (SiC), que chamaremos de heteroestruturas SiCOI (Silicon Carbide-On-Insulator). O método usado para a formação do SiC depende, em cada caso, das características desejadas para o filme que, ao mesmo tempo, estão relacionadas com a aplicação à qual estará destinado. Analisamos três métodos de obtenção do material SiC com características específicas diferentes. A metodologia proposta aborda as seguintes tarefas: Tarefa 1: Obtenção de estruturas SOI pelo método convencional utilizado em trabalhos anteriores e melhoramento das características superficiais da estrutura resultante. Tarefa 2: partindo de uma lâmina de Si previamente coberta por uma camada isolante, fabricar a heteroestrutura SiC/isolante/Si, onde a camada de SiC é crescida pelo método de deposição química de vapor assistida por plasma (PECVD). O filme obtido por deposição PECVD é amorfo e portanto são necessárias etapas de cristalização posteriores ao crescimento. Tarefa 3: partindo de uma estrutura SOI, fabricar a heteroestrutura SiC/SiO2/Si, onde a camada de SiC é obtida por implantação de íons de carbono (C+) na camada ativa de Si da estrutura SOI para sua transformação em SiC. Tarefa 4: partindo de uma estrutura SOI, fabricar a heteroestrutura SiC/SiO2/Si, onde a camada de SiC é obtida por conversão direta da camada ativa de Si da estrutura SOI em SiC como resultado da carbonização do Si usando exposição a ambiente de hidrocarbonetos. Como resultado deste trabalho foram obtidas estruturas SOI Smart Cut com valor médio de rugosidade superficial dentro dos valores esperados segundo a bibliografia consultada. Durante o desenvolvimento de heteroestruturas SiC/isolante/Si obtidas utilizando a técnica de PECVD obtivemos filmes com boas características estruturais. Os recozimentos feitos em ambiente de N2 aparentemente trazem resultados satisfatórios, conduzindo à completa cristalização dos filmes. Nas análises feitas para a fabricação de heteroestruturas SiC/isolante/Si utilizando I/I de carbono confirma-se a formação de c-SiC depois de realizado o recozimento térmico.In this work we study new semiconductors heterostructures, based on SOI (Silicon-On- Insulator) structures obtained by \"Smart-Cut\" process, that were studied in the last years at Departamento de Engenharia de Sistemas Eletrônicos da Escola Politécnica da Universidade de São Paulo (EPUSP). This technique combines high-dose hydrogen ion implantation (I/I) and direct wafer bonding. To produce SOI structures some processes are essential: I/I process, cleaning and activation of the surfaces, and conventional thermal treatments at moderated temperatures. We also investigate different methods to obtain new heterostructures, basically combining SOI technologies and silicon carbide (SiC) growth processes, which will be called as SiCOI (Silicon Carbide-On-Insulator) heterostructures. The utilized methods to obtain the SiC are related, in each case, with the desired film\'s characteristics, which at the same time are associated with the final application. We analyze three methods to obtain SiC material with specific different characteristics. The proposed methodology approaches the following tasks: Task 1: Fabrication of SOI structures by the conventional technology previously used by us, and the improvement of superficial characteristic of the final structure. Task 2: Fabrication of SiC/insulator/Si heterostructures from Si substrate previously covered with an insulator capping layer, where the SiC layer is deposited by plasma enhanced chemical vapor deposition (PECVD). The PECVD film is amorphous and therefore, a thermal annealing step is necessary for crystallization. Task 3: Fabrication of SiC/SiO2/Si heterostructures from SOI structure, where the SiC layer is synthesized through a high dose carbon implantation into the thin silicon overlayer of a SOI wafer. Task 4: Fabrication of SiC/SiO2/Si heterostructures from SOI structure, where the SiC layer is achieved by direct carbonization conversion of the silicon overlayer of a SOI wafer In this work we have obtained Smart Cut SOI structures with surface roughness similar to the previous reported. We also obtained SiC/insulator/Si heterostructures with good structural characteristics using PECVD technique. The investigated N2 thermal annealing appears to be suitable for the crystallization of all the amorphous films deposited by PECVD. We have shown the possibility of using carbon ion implantation and subsequent thermal annealing to form c-SiC for SiC/insulator/Si heterostructures.
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Haberer, Elaine D. (Elaine Denise) 1975. "Particle generation in a chemical vapor deposition/plasma-enhanced chemical vapor deposition interlayer dielectric tool." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/8992.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.Includes bibliographical references (p. 77-79).
The interlayer dielectric plays an important role in multilevel integration. Material choice, processing, and contamination greatly impact the performance of the layer. In this study, particle generation, deposition, and adhesion mechanisms are reviewed. In particular, four important sources of interlayer dielectric particle contamination were investigated: the cleanroom environment, improper wafer handling, the backside of the wafer, and microarcing during process.
by Elaine D. Haberer.
S.M.
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Vandenabeele, Cédric. "Étude des mécanismes d'adhésion entre une gomme caoutchouc et un fil métallique revêtu d'une couche mince déposée par plasma." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0047/document.
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L'objectif de cette thèse est de développer un procédé plasma qui puisse se substituer au procédé de dépôt électrolytique de laiton, actuellement appliqué sur les fils d'acier utilisés comme matériaux de renforcement dans un pneu, pour les faire adhérer au caoutchouc. La stratégie employée consiste à déposer une couche mince organochlorée en continu sur un fil d'acier zingué, qui traverse une décharge à barrière diélectrique tubulaire, fonctionnant à la pression atmosphérique, dans une configuration fil-cylindre. Dans un premier temps, les travaux se concentrent sur la caractérisation de la décharge et de la couche mince déposée à la fois en mode statique (substrat immobile dans le réacteur) et dynamique (substrat en défilement). Des relations sont établies entre les paramètres plasma (puissance dissipée dans la décharge, fréquence de la source haute tension, flux de précurseur), les propriétés de la décharge et les caractéristiques du revêtement plasma. Des études morphologique, cinétique et chimique de la couche mince sont réalisées. Dans un second temps, la préparation de la surface du substrat et le dépôt plasma sont optimisés pour permettre d'obtenir les meilleurs niveaux d'adhésion entre l'acier zingué et le caoutchouc. À l'issue de ce travail d'optimisation, des analyses sont réalisées pour identifier la nature de la nouvelle interphase d'adhésion. Cette étude se conclut alors par une discussion sur l'origine possible des liens qui s'opèrent dans ce nouveau systèmeThe primary objective of this thesis project is to develop a plasma process able to replace the electrolytic brass plating process, which is currently performed on steel wires used as reinforcing materials in tires to make them bond with rubber. The chosen strategy consists in depositing organo-chlorinated thin films in a continuous way on zinc-plated steel wires going across a tubular atmospheric pressure dielectric barrier discharge in a wire-cylinder configuration. In a first time, works focus on characterization of both the discharge and the plasma layer, deposited in the static (substrate stationary in the reactor) and dynamic (moving substrate) modes. Relationships are established between the plasma parameters (power dissipated in the discharge, high voltage source frequency, precursor flow rate), the discharge properties and the thin film characteristics. Morphological, kinetic and chemical studies of the plasma layer are carried out. In a second time, the substrate surface preparation and the coating are optimized to enhance the adhesion between zinc-plated steel wires and rubber. Analyses are performed to identify the new adhesion interface nature. At the end of this study, hypotheses concerning the adhesion origin in this system are formulated
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Miller, Larry M. "Plasma enhanced chemical vapor deposition of thin aluminum oxide films." Ohio : Ohio University, 1993. http://www.ohiolink.edu/etd/view.cgi?ohiou1175717717.
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Günther, Marcus. "Harte amorphe wasserstoffhaltige Kohlenstoffschichten mittels mittelfrequenzgepulster Plasmaentladungen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-95197.
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Harte amorphe wasserstoffhaltige Kohlenstoffschichten (a-C:H) haben in den letzten Jahrzehnten stark an Bedeutung gewonnen. Diese Art von Hartstoffschichten wird zunehmend für die Reduzierung von Reibung und Verschleiß in unterschiedlichen Bereichen eingesetzt. In der Forschung, aber auch für Kleinserien, werden a-C:H-Schichten üblicherweise mit Hochfrequenzplasmaentladungen abgeschieden. Eine Alternative ist die Plasmaaktivierung mit einer asymmetrisch bipolar gepulsten Spannung im Mittelfrequenzbereich. Auf diese Weise wird eine homogene Beschichtung großer Substratflächen mit qualitativ hochwertigen Schichten ermöglicht.
Die vorliegende Arbeit beschäftigt sich mit der plasmagestützten Abscheidung von harten a-C:H-Schichten mit mittelfrequenzgepulsten Entladungen. Zur Schichtabscheidung werden Ethin-Argon- und Isobuten-Argon-Gasgemische verwendet. Der Einfluss des Prozessdrucks auf den Abscheideprozess und die Schichteigenschaften wird untersucht. Dazu wurden Argonentladungen und Beschichtungsplasmen mittels optischer Emissionsspektroskopie charakterisiert. Zur Charakterisierung der Schichteigenschaften wurden unter anderem Nanoindentation-Messungen, elastische Rückstreudetektionsanalysen und thermische Desorptionsspektroskopie verwendet. Zur Untersuchung des Einflusses der Ionen auf das Schichtwachstum wird ein Modell zur Identifizierung von Ionenspezies in Beschichtungsplasmen vorgestellt. In Verbindung mit der Messung der Substratströme konnte der Ionenanteil am Schichtwachstum bestimmt werden.
Ein weiterer Teil der vorliegenden Arbeit untersucht ein Hybridverfahren, in dem die mittelfrequenzgepulste Entladung mit einer zusätzlichen ECR-Entladung kombiniert wird. Es wird gezeigt, dass durch dieses Hybridverfahren eine deutliche Steigerung der Abscheiderate harter a-C:H-Schichten erreicht werden kann. Die abgeschiedenen Schichten wurden zusätzlich bezüglich ihrer Oberflächenstruktur und ihrer Verschleißfestigkeit untersucht.
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Spillmann, Adrian. "Flowability modification of fine powders by plasma enhanced chemical vapor deposition /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17927.
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Limb, Scott J. (Scott Jong Ho). "Pulsed plasma enhanced and pyrolytic chemical vapor deposition of fluorocarbon biopassivation coatings." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10412.
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Schmidt, Marek E. "Plasma enhanced chemical vapor deposition of nanocrystalline graphene and device fabrication development." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/347493/.
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Large area growth of high quality graphene remains a challenge, and is currently dominated by chemical vapor deposition (CVD) on metal catalyst films. This method requires a transfer of the graphene onto an insulating substrate for electronic applications, and the graphene film quality and performance can vary with the transfer. A more attractive approach is plasma enhanced chemical vapor deposition (PECVD) of graphene and nanocrystalline graphene (NCG) directly on insulating substrates. The aim of this project was to explore the deposition process and microfabrication processes based on these NCG films. A deposition process for nanocrystalline graphene was developed in this work based on parallel-plate PECVD. NCG with thicknesses between 3 and 35nm were deposited directly on wet thermal oxidized silicon wafers with diameter of 150 mm, quartz glass and sapphire glass. High NCG thickness uniformities of 87% over full wafer were achieved. Surface roughness was measured by atomic force microscopy and shows root mean square (RMS) values of less than 0.23nm for 3nm thin films. NCG films deposited on quartz and sapphire show promising performance as transparent conductor with 13kΩ/X sheet resistance at 85% transparency. Furthermore, the suitability of the developed PECVD NCG films for microfabrication was demonstrated. Microfabrication process development was focused on four device types. NCG membranes were fabricated based on through-wafer inductively coupled plasma etching from the back, and consecutive membrane release by HF vapor etching. The fabrication of suspended NCG strips, based on HF vapor release, shows promising results, but was not entirely successful due to insufficient thickness of the sacrificial oxide. Top gated NCG strips are successfully fabricated, and the increased modulation by the top gate is demonstrated. Finally, NCG nanowire fabrication is performed on 150mm wafers. Experiments yielded an increased back gate modulation effect by a reduced NCG thickness, although no nanowire formation was observed. A highly accurate focused ion beam (FIB) prototyping technique was developed and applied to exfoliated graphene in this work. This technique systematically avoids any exposure of the graphene to Ga+-ions through the use of an alignment marker system, achieving alignment accuracies better than 250 nm. Contacts were deposited by FIB- or e-beam-assisted tungsten deposition, and FIB trench milling was used to confine conduction to a narrow channel. A channel passivation method based on e-beam-assisted insulator deposition has been demonstrated, and showed a reduction of ion damage to the graphene. Three fabricated transistor structures were electrically characterized.
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Peri, Someswara Rao. "Interface Structure of Photonic Films Created by Plasma Enhanced Chemical Vapor Deposition." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271687789.
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Labelle, Catherine B. 1972. "Pulsed plasma enhanced chemical vapor deposition of fluorocarbon thin films for dielectric applications." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85358.
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Freeman, Mathieu Jon. "Synthesizing diamond films from low pressure chemical vapor deposition /." Online version of thesis, 1990. http://hdl.handle.net/1850/11262.
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Chung, Yong-Sun. "In-situ deposition of YBa₂Cu₃O₇₋x superconducting films by aerosol decomposition in a plasma enhanced chemical vapor deposition reactor." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/20024.
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Chakravarthy, Pramod. "Silicon carbide coatings by plasma-enhanced chemical vapor deposition on silicon and polyimide substrates." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179519920.
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Sharma, Rajan. "Deposition of gate quality dielectrics for Si/Si-Ge heterostructure devices using remote plasma chemical vapor deposition /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Gupta, Atul. "Surface reactions during plasma enhanced chemical vapor deposition of silicon and silicon based dielectrics." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20011031-122441.
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Theoretical ab-initio calculations (including both the Configuration Interaction and Density Functional approaches) are used to describe some of the critical surface reactions during plasma enhanced chemical vapor deposition of amorphous and micro-crystalline silicon films. The energetics as well as the reaction mechanism are calculated for the abstraction of surface hydrogen by incident silyl and hydrogen radicals. Another important reaction involving the insertion of these radicals (silyl and hydrogen) into strained Si-Si bonds on the surface is also evaluated. Experiments involve surface topology evolution studies of plasma deposited a-Si:H films using atomic force microscopy (AFM) as well as structural and electrical characterization of silicon dioxide films using several techniques including infrared spectroscopy, ellipsometry, and current-voltage measurements. A predictive kinetic model to describe the growth of silicon films from a predominantly silyl radical flux is developed to explain experimental observations regarding the properties of plasma deposited amorphous silicon films. The model explains diffusion length enhancements under certain processing conditions as well as lays a foundation for understanding the Si-Si network formation during the deposition of a-Si films.
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Han, Seung Soo. "Modeling and optimization of plasma-enhanced chemical vapor deposition using neural networks and genetic algorithms." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/14904.
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Vaswani, Sudeep. "Surface modification of paper and cellulose using plasma enhanced chemical vapor deposition employing fluorocarbon precursors." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-01142005-123052/.
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Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2005.Bidstrup Allen, Sue Ann, Committee Member ; Ludovice, Peter, Committee Member ; Hess, Dennis, Committee Chair ; Henderson, Clifford, Committee Member ; Patterson, Timothy, Committee Member.
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Chou, Shih-Feng. "Synthesis and characterization of diamond thin films by microwave plasma-enhanced chemical vapor deposition (MPECVD) /." Available to subscribers only, 2005. http://proquest.umi.com/pqdweb?did=1095432871&sid=9&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (M.S.)--Southern Illinois University Carbondale, 2005."Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 65-71). Also available online.
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Yen, Chun-Chieh, and 顏君倢. "Nucleation and growth dynamics of graphene grown through plasma enhanced chemical vapor deposition (PECVD)." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/p5j22g.
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碩士國立中央大學
物理學系
107
As the one of the promising method for graphene growth, chemical vapor deposition (CVD) features the low cost, wafer-scaled graphene layer production. However, the temperature for graphene growth is about 1050℃ which has the problem of energy consumption. The development of plasma enhanced chemical vapor deposition (PECVD) eases the problem. High energy ions and electrons in plasma replace the thermal energy and reduce the needed temperature to about 500-900℃. While, the CVD graphene is limited by its polycrystalline grain which contains many grain boundary and reduce the quality of graphene. Therefore, the pursuit for the large grain size graphene is the important issue. For this purpose, the understanding of growth dynamics of graphene is needed for the controlling of the quality of graphene. In our works, we demonstrate the quick, low power growth process of fully-covered graphene on copper foil by direct capacitive-coupled plasma ratio frequency plasma enhanced chemical vapor deposition (CCP-RF-PECVD) system under low pressure. In addition, the study of nucleation and growth dynamics with different ratio of hydrogen and methane is revealed. By tuning the flow rate of hydrogen, the growth dynamics of graphene is determined by the competition of activation and etching effect of hydrogen. After the characteristic of graphene by SEM and image analysis by Imagej, the growth dynamics is quantified and explained by Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. In low H2 flow rate, nucleation in early stage and high nucleation rate supplies the high growth rate. While in high H2 flow rate, the diffusion of precursor on the substrate surface and epitaxial growth dominated and produced the bigger grain. Furthermore, the simulation of modified JMAK model which considered etching effect of H plasma fits well for experiment data. The dispersive kinetics of growth dynamics has been revealed and further understood.
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Tsai, Tsung-Chan 1982. "Plasma Enhanced Chemical Vapor Deposition on Living Substrates: Development, Characterization, and Biological Applications." Thesis, 2012. http://hdl.handle.net/1969.1/148233.
Full textAbstract:
This dissertation proposed the idea of “plasma-enhanced chemical vapor deposition on living substrates (PECVD on living substrates)” to bridge the gap between the thin film deposition technology and the biological and living substrates. This study focuses on the establishment of the knowledge and techniques necessary to perform “PECVD on living substrates” and contains three main aspects: development, characterization, and biological applications.
First, a PECVD tool which can operate in ambient air and at low temperature was developed using a helium dielectric barrier discharge jet (DBD jet). It was demonstrated that various materials, such as polymeric, metallic, and composite films, can be readily synthesized through this technique. Second, the PMMA and copper films deposited using DBD jets were characterized. High-rate (22 nm/s), low-temperature (39 ºC) PMMA deposition was achieved and the film surface morphology can be tailored by altering the discharge power. Conductive copper films with an electrical resistivity lower than 1×10-7 ohm-m were obtained through hydrogen reduction. Both PMMA and copper films can be grown on temperature-sensitive substrates, such as plastics, pork skin, and even fingernail. The electrical, optical, and imaging characterization of the DBD jets was also conducted and several new findings were reported. Multiple short-duration current pulses instead of only one broad pulse per half voltage cycle were observed when a dielectric substrate was employed. Each short-duration current pulse is induced by a leading ionization wave followed by the formation of a plasma channel. Precursor addition further changed the temporal sequence of the pulses. An increase in the power led to a mode change from a diffuse DBD jet to a concentrated one. This mode change showed significant dependence on the precursor type, tube size, and electrode configuration. These findings regarding the discharge characteristics can thus facilitate the development of DBD-jet operation strategies to improve the deposition efficacy. Finally, this technique was used to grow PMMA films onto agar to demonstrate one of its potential biological applications: sterile bandage deposition. The DBD jet with the film depositing ability enabled the surface to be not only efficiently sanitized but also protected by a coating from being reached by bacteria.
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Cheemalapati, Surya Venkata Sekhar. "The effect of catalyst properties on the synthesis of carbon nanotubes by plasma enhanced chemical vapor deposition." Thesis, 2012. http://hdl.handle.net/1957/35803.
Full textAbstract:
A study of the effect of catalyst properties on the synthesis of carbon nanotubes (CNTs) is done in this thesis. Three different metal alloy catalysts, Fe/Ti, Ni/Ti, Co/Ti, have been studied. Various atomic concentrations and thicknesses were cosputter deposited on clean Si wafers using AJA Orion 4 RF Magnetron sputter deposition tool at 5mtorr and 17��C, and the films were characterized using a scanning electron microscope, Energy-dispersive X-ray spectroscopy. All the alloys have been annealed at 650��C and 3 torr in an argon atmosphere at 100 SCCM, followed by ammonia gas plasma etch at different powers at 3 torr and 50 SCCM NH��� flow in a modified parallel plate RF chemical vapor deposition tool for 1 minute. The influence of plasma power, thickness of catalyst and concentration of Ti the secondary metal in the alloy composition, on the surface morphology of the catalyst are investigated by characterizing them with atomic force microscopy. The study has shown that the surface roughness is affected by Ti concentration, thickness and plasma power. The 35 W power NH��� plasma produced rougher surfaces when compared to the 75 W NH��� plasma. The result is interpreted as follows: ion bombardment leads to greater etching of the catalyst surface. Thus, plasma power must be optimized for catalyst thin film and etch time. The study has provided an in depth analysis and understanding of the various factors that influence catalyst surface morphology which can be applied into further study for optimizing parameters for synthesis of single walled CNTs.
Following this, a study on catalysts for CNT synthesis was performed using Plasma enhanced chemical vapor deposition and characterized by scanning electron microscope. CNTs were synthesized on Ni, Ni-Ti, Co, Co-Ti and Fe catalyst. Ni, Ni-Ti catalyst produced forest like vertically aligned CNTs whereas Co, Co-Ti produced vertically aligned free standing CNTs. The growth was dense and uniform across the substrate. Initial growth runs on Fe, Fe-Ti alloy did not produce any CNTs until catalyst was restructured with a thicker Ti under layer after an investigation using Secondary ion mass spectrometry of suspected Fe catalyst poisoning due to reaction with Si substrate. A room temperature run was carried out on annealed and plasma etched Ni catalyst and no CNTs were produced indicating the importance of substrate temperature of CNTs. A deeper understanding of factors of influence on CNTs such as catalyst types, structure/morphology, and substrate temperature has been achieved with this study.Graduation date: 2013
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"Characterization of Cubic Boron Nitride Interfaces with in situ Photoelectron Spectroscopy." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.38531.
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abstract: Cubic boron nitride (c-BN) has potential for electronic applications as an electron emitter and serving as a base material for diodes, transistors, etc. However, there has been limited research on c-BN reported, and many of the electronic properties of c-BN and c-BN interfaces have yet to be reported. This dissertation focused on probing thin film c-BN deposited via plasma enhanced chemical vapor deposition (PECVD) with in situ photoelectron spectroscopy (PES). PES measurements were used to characterize the electronic properties of c-BN films and interfaces with vacuum and diamond. First, the interface between c-BN and vacuum were characterized with ultraviolet PES (UPS). UPS measurements indicated that as-deposited c-BN, H2 plasma treated c-BN, and annealed c-BN post H2 plasma treatment exhibited negative electron affinity surfaces. A dipole model suggested dipoles from H-terminated N surface sites were found to be responsible for the NEA surface. Then, Si was introduced into c-BN films to realize n-type doped c-BN. The valence structure and work function of c-BN:Si films were characterized with XPS and UPS measurements. Measurements were unable to confirm n-type character, and it is concluded that silicon nitride formation was the primary effect for the observations. Finally, XPS measurements were employed to measure the band offsets at the c-BN/diamond interface. Measurements indicated the valence band maximum (VBM) of c-BN was positioned ~0.8 eV above the VBM of diamond.Dissertation/Thesis
Doctoral Dissertation Physics 2016
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Bleakie, Alexander Q. "Dynamic feature analysis of an industrial PECVD tool with connection to operation-dependent degradation modeling." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-08-1617.
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An analysis that is based on the monitoring of dynamic features from in-situ sensors of an industrial PECVD tool is presented. Linear Discriminant Analysis is used to determine which features are the most sensitive to various changes in the tool condition. The concept of Confidence Values (CVs) is used to quantify statistical changes of these dynamic features as the condition of the tool changed. Two data sets were collected from a PECVD tool in the facilities of a well-known equipment supplier. Dynamic features coming from the RF plasma power and matching capacitors’ sensors are shown to be sensitive to various changes in the cleaning cycles for Si-N, Si-O₂, and TEOS depositions. Quantifying the statistical distributions of the sensitive sensor features during tool condition changes is important for determining which sensor features are necessary to monitor in order to predict the tool chamber health. Results show that these RF plasma sensors could be used to track changes inside the tool chamber.text
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Ip, Brian Kau. "A study of charges and defects in SiO2 films fabricated by plasma-enhanced chemical vapour deposition (PECVD) techniques." 1989. http://hdl.handle.net/1993/17053.
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RU, Randall, and 呂榮東. "Hazard analysis byproduct analysis of Plasma Enhance chemical vapor deposition (PECVD ) reactor. - for certain solar cell manufactor as example." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/qdy34f.
Full textAbstract:
碩士國立交通大學
工學院產業安全與防災學程
100
Council Of Labor Affairs established Hazardous Work Place Review and Inspection Rules according to Paragraph 2, Article 26 of Labor Inspection Law from May 2,1994, all enterprises must apply for safety review and inspection by labor inspection authorities in accordance with various Hazardous Work Place. The first step of evaluation process is Preliminary Hazard Analysis. In that way, we can identify major potential hazards in the work place through analysis by using one of following safety evaluation methodologies. Checklist What If Hazard and Operability Studies Fault Tree Analysis Failure Modes and Effects Analysis others safety evaluation methodologies which have the same functions approved by Central committee Controll- ing organization Although enterprise pass the safety review and inspection, for example : the using of SiH4 in Category A Hazardous work places, fire and explored accidents still happened. Obviously, it shows the evaluation process exist lot of space to improve in order to prevent fire and explored accidents happened again.
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Xie, Zhen Zhou, and 謝鎮州. "Study of the optical-mechanical properties of amorphous silicon and silicon dioxide fabricated by Plasma Enhance Chemical Vapor Deposition (PECVD)." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/82596798492616505419.
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碩士國立清華大學
光電工程研究所
103
According to Einstein’s general theory of relativity, it will produce gravitational wave when a object was accelerated. In order to meaure gravitaitonal wave directly, LIGO set up large-scale Michelson interferometers to observe whether gravitational wave exist or not. But the signal of gravitational wave is so weak to be detected that it must to reduce the background noise below to the gravitational wave signal. One of them, Coating Brownian noise is the urgent problem that is needed to be reduced. However, it’s very difficult to measure coating Brownian noise directly. Fortunately, it shows that coating Brownian noise is propotional to mechanical loss from fluctuation-dissipation theorem. so our goal is to search and investigate the films which behave low mechanical loss and to reduce mechanical loss as possible as we can then use for LIGO application In this article, CVD process is used for amorphous silicon deposition. There are some advantages that why we choose CVD and this material below. In the aspect of fabrication: CVD process is well-established in semiconductor technologies and it behaves perfect large area (18” wafer) uniformity, this advantage is suitable for LIGO mirrors which size are 35cm diameter. In the aspect of material: Refractive index of amorphous silicon is 3.5 at 1550nm, this high index value makes it desirable for quarter-wave lens coating. On the other hand, mechanical loss of amorphous silicon deposited by ion‐beam sputter is 10-4 order at low temperature in literatures. We expect that mechanical loss of the amorphous silicon films deposited by CVD will be similar low to films deposited by ion‐beam sputter. In the article, optical loss and mechanical loss of the amorphous silicon films which deposit by different temperatures were measured and analyzed. When utilizing PECVD to deposit amorphous silicon film on silicon wafer directly, it existed some hilllocks on the surface. In order to prevent this phenomenon, a buffer silicon dioxide film was deposited between siliocn wafer and amorphous siliocn film. Finally the surface quality improved. The stress of amorphous silicon is compressive stress as deposition temperature from 200 oc to 400 oc. Total mechanical loss after coated amorphous silicon is lower than uncoated substrate. This result is similar to the result of high stress SiNx film coated on siliocn cantilever. We think that silicon cantilever is bent by high stress from film and the bending mechanism reduced some part of the mechanical loss of silicon cantilever first(probably thermo-elastic loss). So even after coated the mechanical loss of coated is still lower than unbending siliocn cantilever substrate.
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Zimmermann, Thomas. "High-rate growth of hydrogenated amorphous and microcrystalline silicon for thin-film silicon solar cells using dynamic very-high frequency plasma-enhanced chemical vapor deposition." Doctoral thesis, 2012. https://tud.qucosa.de/id/qucosa%3A27404.
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Thin-film silicon tandem solar cells based on a hydrogenated amorphous silicon (a-Si:H) top-cell and a hydrogenated microcrystalline silicon (μc-Si:H) bottom-cell are a promising photovoltaic technology as they use a combination of absorber materials that is ideally suited for the solar spectrum. Additionally, the involved materials are abundant and non-toxic which is important for the manufacturing and application on a large scale.
One of the most important factors for the application of photovoltaic technologies is the cost per watt. There are several ways to reduce this figure: increasing the efficiency of the solar cells, reducing the material consumption and increasing the throughput of the manufacturing equipment.
The use of very-high frequencies has been proven to be beneficial for the material quality at high deposition rates thus enabling a high throughput and high solar cell efficiencies. In the present work a scalable very-high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) technique for state-of-the-art solar cells is developed. Linear plasma sources are applied which facilitate the use of very-high frequencies on large areas without compromising on the homogeneity of the deposition process.
The linear plasma sources require a dynamic deposition process with the substrate passing by the electrodes in order to achieve a homogeneous deposition on large areas. State-of-the-art static radio-frequency (RF) PECVD processes are used as a reference in order to assess the potential of a dynamic VHF-PECVD technique for the growth of high-quality a-Si:H and μc-Si:H absorber layers at high rates.
In chapter 4 the influence of the deposition process of the μc-Si:H i-layer on the solar cell performance is studied for static deposition processes. It is shown that the correlation between the i-layer growth rate, its crystallinity and the solar cell performance is similar for VHF- and RF-PECVD processes despite the different electrode configurations, excitation frequencies and process regimes. It is found that solar cells incorporating i-layers grown statically using VHF-PECVD processes obtain a state-of-the-art efficiency close to 8 % for growth rates up to 1.4 nm/s compared to 0.53 nm/s for RF-PECVD processes.
The influence of dynamic deposition processes on the performance of μc-Si:H solar cells is studied. It is found that μc-Si:H solar cells incorporating dynamically grown i-layers obtain an efficiency of 7.3 % at a deposition rate of 0.95 nm/s. There is a small negative influence of the dynamic deposition process on the solar cell efficiency compared to static deposition processes which is related to the changing growth conditions the substrate encounters during a dynamic i-layer deposition process.
The changes in gas composition during a dynamic i-layer deposition process using the linear plasma sources are studied systematically using a static RF-PECVD regime and applying a time-dependent gas composition. The results show that the changes in the gas composition affect the solar cell performance if they exceed a critical level.
In chapter 5 dynamic VHF-PECVD processes for a-Si:H are developed in order to investigate the influence of the i-layer growth rate, process parameters and deposition technique on the solar performance and light-induced degradation. The results in this work indicate that a-Si:H solar cells incorporating i-layers grown dynamically by VHF-PECVD using linear plasma sources perform as good and better as solar cells with i-layers grown statically by RF-PECVD at the same deposition rate. State-of-the-art stabilized a-Si:H solar cell efficiencies of 7.6 % are obtained at a growth rate of 0.35 nm/s using dynamic VHF-PECVD processes.
It is found that the stabilized efficiency of the a-Si:H solar cells strongly decreases with the i-layer deposition rate. A simplified model is presented that is used to obtain an estimate for the deposition rate dependent efficiency of an a-Si:H/μc-Si:H tandem solar cell based on the photovoltaic parameters of the single-junction solar cells. The aim is to investigate the individual influences of the a-Si:H and μc-Si:H absorber layer deposition rates on the performance of the tandem solar cell.
The results show that a high deposition rate of the μc-Si:H absorber layer has a much higher potential for reducing the total deposition time of the absorber layers compared to high deposition rates for the a-Si:H absorber layer. Additionally, it is found that high deposition rates for a-Si:H have a strong negative impact on the tandem solar cell performance while the tandem solar cell efficiency remains almost constant for higher μc-Si:H deposition rates.
It is concluded that the deposition rate of the μc-Si:H absorber layer is key to reduce the total deposition time without compromising on the tandem solar cell performance. The developed VHF-PECVD technique using linear plasma sources is capable of meeting this criterion while promoting a path to scale the processes to large substrate areas.
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Fay, Alexander Gary. "Mitigation of the radioxenon memory effect in beta-gamma detector systems by deposition of thin film diffusion barriers on plastic scintillator." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2305.
Full textAbstract:
The significance of the radioxenon memory effect in the context of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty is introduced as motivation for the project. Existing work regarding xenon memory effect reduction and thin film diffusion barriers is surveyed. Experimental techniques for radioxenon production and exposure, as well as for thin film deposition on plastic by plasma enhanced chemical vapor deposition (PECVD), are detailed. A deposition rate of 76.5 nm min⁻¹ of SiO₂ is measured for specific PECVD parameters. Relative activity calculations show agreement within 5% between identically exposed samples counted on parallel detectors. Memory effect reductions of up to 59±1.8% for 900 nm SiO₂ films produced by plasma enhanced chemical vapor deposition and of up to 77±3.7% for 50 nm Al₂O₃ films produced by atomic layer deposition are shown. Future work is suggested for production of more effective diffusion barriers and expansion to testing in operational monitoring stations.text
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Fu, Qilin. "High dynamic stiffness nano-structured composites for vibration control : A Study of applications in joint interfaces and machining systems." Doctoral thesis, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176869.
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Vibration control requires high dynamic stiffness in mechanical structures for a reliable performance under extreme conditions. Dynamic stiffness composes the parameters of stiffness (K) and damping (η) that are usually in a trade-off relationship. This thesis study aims to break the trade-off relationship. After identifying the underlying mechanism of damping in composite materials and joint interfaces, this thesis studies the deposition technique and physical characteristics of nano-structured HDS (high dynamic stiffness) composite thick-layer coatings. The HDS composite were created by enlarging the internal grain boundary surface area through reduced grain size in nano scale (≤ 40 nm). The deposition process utilizes a PECVD (Plasma Enhanced Chemical Vapour Deposition) method combined with the HiPIMS (High Power Impulse Magnetron Sputtering) technology. The HDS composite exhibited significantly higher surface hardness and higher elastic modulus compared to Poly(methyl methacrylate) (PMMA), yet similar damping property. The HDS composites successfully realized vibration control of cutting tools while applied in their clamping interfaces. Compression preload at essential joint interfaces was found to play a major role in stability of cutting processes and a method was provided for characterizing joint interface properties directly on assembled structures. The detailed analysis of a build-up structure showed that the vibrational mode energy is shifted by varying the joint interface’s compression preload. In a build-up structure, the location shift of vibration mode’s strain energy affects the dynamic responses together with the stiffness and damping properties of joint interfaces. The thesis demonstrates that it is possible to achieve high stiffness and high damping simultaneously in materials and structures. Analysis of the vibrational strain energy distribution was found essential for the success of vibration control.
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Lin, Jui-Ching, and 林瑞青. "Plasma Enhanced Chemical Vapor Deposition of Titanium Nitride Thin Films." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/95513029960525599683.
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碩士國立成功大學
材料科學(工程)學系
86
Titanium nitride (TiN) films were prepared by radio- frequency (RF) capacitively coupled plasma-enhanced chemical vapor deposition (PECVD) using TiCl4 and NH3 as precursors. By varying the flow rate of the precursors, substrate temperature, RF power and chamber pressure, the film characteristics, such as deposition rate, elemental concentration, resistivity and surface morphology are investigated by -step, Auger electron spectroscopy, four-point probe and scanning electron microscopy for the films, respectively. With TiCl4/NH3 flow rate ratio of 40/1.5 and chamber pressure of 0.3Torr, oxygen concentratio of the TiN films decreases from 30at% to 7at% and N/Ti atomic ratio increases from 0.78 to 1.15 as the RF power increases from 50W to 150W. In consistency with the reduction of the oxygen concentration, the film resistivity decreases as the RF power increases. The lowest film resistivity is 131-cm, which is obtained from the film deposited at 450℃ and with RF power of 150W. No carbon and chlorine singnal is detected by Auger electron spectroscopy. The content of the two elements in the TiN films is under the detection limit.
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Hou, Wen-chi, and 侯文棋. "Growth of GaN Nanowires by Plasma-Enhanced Chemical Vapor Deposition." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/84698555689606661883.
Full textAbstract:
博士國立成功大學
化學工程學系碩博士班
97
Gallium nitride (GaN) is a wide band-gap semiconductor with important applications for the development of UV/blue light emitting diode, or laser diode. Recent developments in the fabrication, measurements, and the assembly of semiconductor nanowires have initiated an exciting research field in science and technology. GaN nanowires have been regarded as a potential building block for nanoscale electronics and optoelectronic devices since they possess the unique optical and electronic properties from the one-dimensional geometry. However, there are still many essential scientific issues regarding the control over the growth, interface phenomena, and growth mechanism. Understanding and controlling the growth of nanowires play a crucial role in the further applications. In this thesis, we present the initial work on materials synthesis, characterization and controlling growth to address these important issues. First of all, a novel fabrication method for GaN nanowires by introducing N2 plasma using dielectric barrier discharge (DBD) in a horizontal furnace is successfully developed. This system combines the advantages of plasma-assisted MBE and high temperature furnace for growing GaN nanowires. The growths of single crystal GaN nanowires along the [10-10] direction are observed to follow the vapor-liquid-solid (VLS) growth mechanism using Au as catalyst. The diameters of GaN nanowires range from 70–100 nm and their lengths are up to several micrometers. The PL spectra of the GaN nanowires consisted of mainly a strong band-to-band emission peak at 355 nm without defect-related luminescence at room temperature, indicating the high quality of nanowire crystallites. This is the first successful attempt to introduce stable DBD-type N2 plasma into a horizontal furnace system and demonstrated that the plasma can supply sufficient active nitrogen species to grow high-quality GaN nanowires. The investigations also show the growth and nucleation mechanism of highly vertically-aligned GaN nanowires on a c-plane GaN substrate. A homoepitaxy interface between nanowires and substrate are observed under the appropriate conditions. The results show that the lower growth rate during the nucleation stage is required for the homoepitaxy. After the successful synthesis of high-quality GaN nanowires, we investigate the growth of GaN nanowires by controlling the surface diffusion of Ga species on sapphire in the plasma-enhanced chemical vapor deposition (CVD) system. Under nitrogen-rich growth conditions, Ga has a tendency to adsorb on the substrate surface diffusing to nanowires to contribute to their growth. The nanowires adjacent to the large surface-diffusion spacing obtain up to 70% of their incorporated gallium from surface diffusion under nitrogen-rich conditions. The growth rates of nanowires are strongly dependent on the surface-diffusion spacing under nitrogen-rich conditions. It is found that the addition of 5% hydrogen in nitrogen plasma instantly diminishes the surface diffusion effect under nitrogen-rich conditions. This effect is attributed to the conversion of gallium to gallium hydride at the growth temperature, which has a lower affinity for the sapphire substrate, thereby desorbing easily from the surface and reducing the diffusion length so that the gas phase reaction dominates the growth over the surface diffusion. On the other hand, under gallium-rich growth conditions, nanowire growth is shown to be dominated by the gas phase deposition with negligible contribution from surface diffusion. Compared to the nitrogen supply, the over supply of gallium reactant from gas phase results in the nitrogen species to be the rate determining reactant under the gallium-rich conditions. In the final section of this thesis, the investigations are focused on the Au migration in the Au-assisted growth of GaN nanowires by controlling the gallium partial pressure during growth. The composition of gallium, ranging from 1 to 35 atom%, in the Au-Ga alloy seeds of the nanowires depends on the gallium partial pressures in the plasma-enhanced chemical vapor deposition system. We proposed that a higher excess energy above the melting energy of the Au-Ga seed, which is dependent on the gallium composition, will increase the instability of the top-seed and dramatically increase the detaching rate of catalyst at the growth temperature. Besides, the gallium atoms adsorbed on the sidewalls of nanowires, also dependent on the gallium partial pressures, may act as a surfactant to help the migration of Au atoms. In addition to the vapor-liquid-solid (VLS) growth process observed, the growth of GaN nanowires via the vapor-solid-solid (VSS) process is also observed and reported for the first time, with the detachment of solid Au seeds dramatically inhibited during growth. The migration of Au seed is evidenced by observing, at low gallium partial pressure, the Au-Ga nanoparticles on the sidewalls of nanowires and the catalyzed GaN nanowire branches.
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Huang, Shun-Shing, and 黃相舜. "Characterization pf Plasma-Enhanced Chemical Vapor Deposition pf TiO2 Thin films." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/08927436610035511502.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系
88
Titanium dioxide thin films were fabricated on the silicon substrates using plasma-enhanced chemical vapor deposition (PECVD) and low pressure chemical vapor deposition (LPCVD). The refractive index, crystal structure and surface morphology of the films deposited with various substrate temperatures, rf powers and oxygen flows were investigated. During the deposition, the vapor of Ti-(OC3H7)4 (TTIP) was carried by nitrogen and mixed with oxygen to form TiO2 thin films. The TiO2 films deposited by LPCVD at substrate temperature 400℃ ~ 500℃ show Anatase crystalline structure, but the PECVD TiO2 films are amorphous with substrate temperature of 450℃ ~ 500℃. The PECVD TiO2 film surfaces show fine particles as deposited and the deposition rate was low. Without plasma assistance, the TiO2 surfaces show large crystal grains and the surfaces are rough. By using rf power of 100 W, the refractive indices of PECVD TiO2 films are around 2.45~2.62. The refractive indices are 2.43~2.47 for LPCVD TiO2 films. Therefore, the refractive index of PECVD TiO2 is larger than that of LPCVD TiO2. By varying the oxygen flow rates during deposition, the crystal structures and refractive indices of TiO2 thin films do not change significantly. After annealing at 700℃ and 800℃ in oxygen, the surface roughness of TiO2 films is increased but the refractive index did not change. The dielectric constants of PECVD TiO2 Films deposited with rf power of 100 W and oxygen flows of 100 sccm and 200 sccm were measured using the MIS (Al/TiO2/Si) capacitor structure. We found that the dielectric constant of PECVD TiO2 film deposited at 500℃ is higher than that deposited at 450℃. The highest value is 12.7 and the lowest value is 7.9. Comparing with the literatures, we realize that the values of dielectric constant are quite low. However, the values of refractive index of PECVD TiO2 are suitable for anti-reflection coating applications. Improvement of dielectric properties for PECVD TiO2 shall be further investigated.