Silicon oxide and silicon oxynitride thin films with in-situ cerium (Ce) doping were deposited using electron-cyclotron-resonance plasma enhanced chemical-vapor deposition (ECR-PECVD) on p-type silicon substrates. Oxygen was gradually substituted by nitrogen to produce SiOxNy thin films with different layer compositions. Refractive indices extracted from variable-angle spectroscopic ellipsometry (VASE) measurements classified the thin films into two main groups, SiOx and SiOxNy. The thin film composition was studied by Rutherford Backscattering Spectrometry (RBS), verifying the gradual increase in nitrogen content. Photoluminescence (PL) spectra of samples were obtained using a 375 nm laser diode as an excitation source. All samples were subjected to post-deposition annealing treatment for 1 hour at different temperatures varying from 800 to 1200 °C in both 95% N2 and 5% H2 and pure N2 gas environment, to investigate the effect of hydrogen passivation on the PL irradiance. Samples subjected to annealing yielded considerably stronger blue/white PL emission than as-deposited ones, due to the formation of Ce-containing clusters at a temperature of 1200 °C. Optimum layer composition and annealing condition to produce SiOxNy thin films with maximized Ce3+ excitation efficiency were determined. Besides, the effect of hydrogen fluoride (HF) etching on PL irradiance was studied, showing that an HF (1%) etching duration of 90 s yields the highest PL irradiance. Electrical measurements were carried out for all Ce doped samples as preliminary work for light-emitting device fabrication. ITO and Al are coated as electrodes on the front side of the thin films and backside of the substrates, respectively, using a radio frequency (RF) magnetron sputtering system. I-V measurements were performed to investigate the carrier injection properties and the dominating mechanism of carrier conduction was determined. / Thesis / Master of Applied Science (MASc)

Le but de ces travaux était de développer des membranes conductrices protoniques de type phosphonique par PECVD radio-fréquence en décharges continue et pulsée à partir du mono-précurseur diméthyl allylphosphonate. De telles membranes sont pressenties comme pouvant avantageusement remplacer la membrane Nafion® ou les membranes conventionnelles de type sulfonique ou phosphonique classiquement utilisées dans les dispositifs piles à combustible ou électrolyseur de type PEM. Ainsi, une étude paramétrique visant à établir des corrélations entre les propriétés des films et les paramètres de dépôt a été menée. Il ressort de cette étude paramétrique que l’utilisation d’une décharge pulsée est favorable à une vitesse de croissance plus élevée et une densité des films plus faible que le mode de décharge continue, favorisant ainsi la conduction protonique. Nous avons également démontré que les dépôts réalisés en mode de décharge pulsée présentent de meilleures capacités de sorption et de rétention d’eau, ce qui est bénéfique pour l’application visée qui est la (photo-)électrolyse de l’eau. Par ailleurs toutes les membranes phosphoniques plasma préparées sont stables d’un point de vue rétention d’eau et réseau covalent jusqu’à au moins 250 °C, ce qui garantit leur utilisation dans des systèmes pouvant fonctionner jusqu’à 120 °C. Par la suite les membranes phosphoniques plasma ont été intégrées en cellule d’électrolyse de l’eau, associées au Nafion® en tant qu’électrolyte. Les caractérisations électrochimiques en cellule ont montré que les membranes phosphoniques plasma sont suffisamment compétitives pour être envisagées dans le futur comme électrolytes solides à part entière dans des AME « tout solide ». / The purpose of this work was to develop phosphonic-type proton conductive membranes by radio-frequency PECVD in a continuous or pulsed discharge from the single precursor dimethyl allylphosphonate. Such membranes could advantageously replace the Nafion® membrane or conventional sulfonic-type or phosphonic acid-type membranes, more classically used in PEM fuel cells and electrolysis devices. A parametric study was carried out in order to establish correlations between the properties of the films and the deposition parameters. It appears that the use of a pulsed discharge promotes better films properties, namely higher growth rate and lower density, than the continuous discharge, thus promoting proton conduction. It was also noticed that the deposits prepared in a pulsed discharge have the highest sorption and water retention capacities, which is particularly beneficial for the intended application i.e. the (photo-) electrolysis of water. Furthermore, all the plasma phosphonic membranes prepared are stable in terms of water retention and covalent network up to at least 250 °C, which ensures their use in systems able to operate up to 120 °C. Subsequently the plasma phosphonic membranes, deposited on the Nafion® as mechanical support, were integrated as electrolyte membrane into a water electrolysis cell. It turns out that plasma phosphonic membranes are competitive enough to be envisaged in the future as integral solid electrolytes in solid membrane-electrodes assemblies.

Por duas décadas, as nanoestruturas conhecidas como nanotubos de carbono (CNT), tem chamado a atenção de muitos centros de pesquisa, devido a suas propriedades físicas e químicas, que tornam este material uma ferramenta de primeira ordem em diferentes aplicações. Este trabalho pretende pesquisar a fabricação e caracterização destas estruturas, utilizando as técnicas de deposição química a vapor (CVD), e deposição química a vapor assistida por plasma (PECVD), visto que são as que reportam melhores resultados em termos de qualidade e quantidade, além de facilidade. A pesquisa está encaminhada pelo ajuste fino das variáveis que intervém nestes dois tipos de processo, tais como a temperatura, os gases precursores a usar, seus fluxos, e relação entre eles, o tipo de catalizador etc. assim como das variáveis que só fazem parte de cada processo diferenciado, no caso do CVD as altas temperaturas, e no caso do PECVD a pressão, a potência de RF aplicada para a formação do plasma etc. A forma de avaliar os resultados obtidos foi mediante as técnicas mais idôneas relativas aos nanotubos de carbono, as quais são a microscopia Raman, a microscopia eletrônica tanto de varredura como de transmissão, e a dispersão de raios X. Desta forma pretende-se fazer um trabalho exaustivo com a finalidade de conseguir uma síntese idônea das nanoestruturas de carbono para diferentes tipos de aplicações encaminhadas principalmente a dispositivos elétricos. / For the past two decades, the nanostructures known as carbon nanotubes (CNT), have been the center of attention of many research centers, due mainly to its physical and chemical properties, turning them into a first order tool in many kind of applications. This work pretends to study the fabrication and characterization of these nanostructures, using the chemical vapor deposition (CVD), and the plasma enhanced chemical vapor deposition (PECVD) techniques, since they are reported as the best ones in terms of quality, quantity and ease of use. The research is routed by the fine tuning of the variables involved in both processes, such as the temperature, the gas precursors, the gas flows, the flow ratio, the metal catalyst etc. as well as the variables involved in just one of the processes, in the case of CVD, the high temperatures, and in the case of PECVD, the pressure, the RF power for plasma formation etc. The way to evaluate the obtained results was through the most suitable techniques relative to CNT analysis , as Raman microscopy, electron microscopy, both scanning and transmission, and x-ray diffraction. Thus we pretend to perform an exhaustive research with the aim to find a synthesis of carbon nanostructures suitable for different kind of applications, routed principally to electronic devices.

Por duas décadas, as nanoestruturas conhecidas como nanotubos de carbono (CNT), tem chamado a atenção de muitos centros de pesquisa, devido a suas propriedades físicas e químicas, que tornam este material uma ferramenta de primeira ordem em diferentes aplicações. Este trabalho pretende pesquisar a fabricação e caracterização destas estruturas, utilizando as técnicas de deposição química a vapor (CVD), e deposição química a vapor assistida por plasma (PECVD), visto que são as que reportam melhores resultados em termos de qualidade e quantidade, além de facilidade. A pesquisa está encaminhada pelo ajuste fino das variáveis que intervém nestes dois tipos de processo, tais como a temperatura, os gases precursores a usar, seus fluxos, e relação entre eles, o tipo de catalizador etc. assim como das variáveis que só fazem parte de cada processo diferenciado, no caso do CVD as altas temperaturas, e no caso do PECVD a pressão, a potência de RF aplicada para a formação do plasma etc. A forma de avaliar os resultados obtidos foi mediante as técnicas mais idôneas relativas aos nanotubos de carbono, as quais são a microscopia Raman, a microscopia eletrônica tanto de varredura como de transmissão, e a dispersão de raios X. Desta forma pretende-se fazer um trabalho exaustivo com a finalidade de conseguir uma síntese idônea das nanoestruturas de carbono para diferentes tipos de aplicações encaminhadas principalmente a dispositivos elétricos. / For the past two decades, the nanostructures known as carbon nanotubes (CNT), have been the center of attention of many research centers, due mainly to its physical and chemical properties, turning them into a first order tool in many kind of applications. This work pretends to study the fabrication and characterization of these nanostructures, using the chemical vapor deposition (CVD), and the plasma enhanced chemical vapor deposition (PECVD) techniques, since they are reported as the best ones in terms of quality, quantity and ease of use. The research is routed by the fine tuning of the variables involved in both processes, such as the temperature, the gas precursors, the gas flows, the flow ratio, the metal catalyst etc. as well as the variables involved in just one of the processes, in the case of CVD, the high temperatures, and in the case of PECVD, the pressure, the RF power for plasma formation etc. The way to evaluate the obtained results was through the most suitable techniques relative to CNT analysis , as Raman microscopy, electron microscopy, both scanning and transmission, and x-ray diffraction. Thus we pretend to perform an exhaustive research with the aim to find a synthesis of carbon nanostructures suitable for different kind of applications, routed principally to electronic devices.

Neste trabalho é estudada a viabilidade de produção de dispositivos eletrônicos baseados em filmes semicondutores de carbeto de silício estequiométrico (a-Si0,5C0,5:H) obtidos por deposição química por vapor assistida por plasma, PECVD. A proposta do projeto envolve a realização de uma série de trabalhos que permitam avaliar as potencialidades do a-SiC:H para a fabricação de dispositivos semicondutores simples. Deste modo, desenvolvemos as principais etapas para a construção de dispositivos, as quais envolveram a dopagem elétrica por diferentes técnicas com a utilização de diferentes elementos dopantes, a corrosão seletiva por plasma e a obtenção um dielétrico apropriado e compatível com a tecnologia do SiC, bem como o desenvolvimento de processos de cristalização, que podem se mostrar fundamentais para melhorar as propriedades dos filmes de a-SiC:H. Com tais processos aprimorados, fabricamos estruturas MOSiC (metal-óxidocarbeto de silício) a partir do SiC cristalizado, utilizando como dielétrico de porta o SiO2 crescido por oxidação térmica (seca e úmida) dos próprios filmes de carbeto de silício cristalizados. Essas estruturas apresentaram o comportamento típico de um capacitor MOS, com regiões de acumulação, depleção e inversão bem definidas em todos os casos. Também fabricamos heterojunções de filmes de SiC tipo-p (como depositado e tratado termicamente) sobre substratos de Si tipo-n, os quais mostraram boas caracterísitcas retificadoras para as heteroestruturas formadas pelo a-SiC:H como-depositado e tratado termicamente a 550ºC. Além do mais, também projetamos, fabricamos, modelamos e caracterizamos transistores de filme fino de a-SiC:H. De acordo com as caracterizações elétricas observamos que podemos controlar a condutividade do canal, embora os dispositivos ainda precisem ser aprimorados para se obter melhores níveis de corrente. Vemos, portanto que, embora ainda tenham que ser aperfeiçoados, foram construídos com sucesso dispositivos eletrônicos semicondutores baseados em filmes de a-Si0,5C0,5:H obtidos por PECVD. / In this work we studied the viability to build devices based on stoichiometric amorphous silicon carbide semiconductor films (a-Si0.5C0.5:H), obtained by plasma enhanced chemical vapor deposition technique. The project proposal involves the realization of a series of studies that evaluate the potentialities of the a-SiC:H for the fabrication of simple semiconductor devices. In this way, we developed the main steps for the devices\' fabrication, which involved electric doping, by different doping techniques using different doping sources, selective plasma etching and the obtention of an appropriate and compatible dielectric for SiC technology. Besides, we performed crystallization processes that were essential to improve the properties of the amorphous films. By establishing the processes steps, we manufactured MOSiC (metal-oxidesilicon carbide) structures starting from crystallized SiC and using SiO2 as the gate dielectric, which was obtained by thermal oxidation (wet and dry) of the crystallized silicon carbide films. All the structures presented a typical MOS capacitor behavior, with accumulation, depletion and inversion regions well-defined in all the cases. We also fabricated heterojunctions formed by p-type SiC films (as-deposited and annealed) on n-type silicon substrates that showed good rectifying characteristics for as-deposited and annealed at 550ºC a-SiC:H films. Moreover, we designed, manufactured, modeled and characterized a-SiC:H thin film transistors. The electric characterization demonstrated that it is possible to control the channel conductivity; however, the devices still need to be improved to obtain better current levels. Although some improvement still need to be made, we built successfully electronic semiconductor devices based on a-Si0.5C0.5:H films obtained at low temperatures by PECVD technique.

Malgré les efforts de la communauté scientifique, les cellules solaires multijonctions à base de matériaux amorphes, sont limitées par la dégradation sous lumière des matériaux actifs qu'elles emploient - notamment, le silicium amorphe hydrogéné (a-Si:H) ou le silicium-germanium amorphe (a-SiGe:H). Compte tenu de la facilité avec laquelle les dispositifs multijonctions peuvent être fabriqués dans cette filière couches minces, pour que cette filière reste compétitive sur le marché photovoltaïque, il est nécessaire de déposer des matériaux présentant les meilleures propriétés de transport possible, avec une énergie de gap variable comprise entre celle du silicium microcristallin hydrogéné (µc-Si:H, 1.1 eV) et celle du a-SiH (1.7 eV), et peu sensibles au vieillissement sous lumière. Le but de ces travaux de thèse était de développer une nouvelle classe de matériaux satisfaisant les critères précédemment cités, alliant carbone et silicium. En effet, les alliages silicium-carbone microcristallins hydrogénés (µc-Si1−xCx:H), sont des candidats prometteurs pour la réalisation de cellules photovoltaïques (PV): d'une part, la structure microcristalline devrait les rend moins sensible au vieillissement sous lumière, et d'autre part, il est possible de faire varier l'énergie de gap en modifiant le taux de carbone de l'alliage. Dans cette thèse, nous avons étudié les propriétés structurales et électriques de ces alliages à l'aide de nombreuses techniques de caractérisation complémentaires, et en faisant varier de nombreux paramètres de dépôt afin de déterminer celles permettant d'obtenir les meilleures propriétés possibles. Nous avons montré en particulier que ces alliages sont composés de cristallites de taille sous-micrométrique, enrobé dans une matrice de silicium-carbone amorphe (a-Si1−xCx:H). En plus, ces matériaux sont caractérisés par une croissance colonnaire, typique du µc-Si:H, avec la taille moyen des grains qui est contrôler en prévalence par la puissance RF utilisé pour le dépôt. L'incorporation de carbone, qui ne peut pas se passer dans la phase cristalline, cause la formation d'un tissue amorphe interstitielle qui enrobe les grain et en empêche la croissance. Ainsi, l'analyse de l'ensemble de nos résultats nous a permis de proposer un modèle cohérent de la croissance de ces alliages. Les propriétés électriques de nos matériaux ont été étudiées à l'aide des mesures de courant d'obscurité et de photocourant en régime stationnaire, de spectroscopie par interférométrie laser et de photocourant modulé. Nous avons pu établir une corrélation directe entre les propriétés électriques et les conditions de dépôt, mettant notamment en évidence que la présence des cristallites assure une conductivité plus élevée par rapport à du a-Si1−xCx:H, et que l'incorporation de carbone amène à des énergies de gap plus grandes que celle du µc-Si:H. Nous avons également montré que les meilleurs matériaux étaient obtenus pour des puissances RF faibles, de l'ordre de 113 mW/cm2. Des résultats de caractérisation de cellules photovoltaïques de type p-i-n ou n-i-p réalisées à partir de nos alliages, ont été aussi présentés. Les rendements obtenus restent encore modestes (de l'ordre de 3,5%) mais nous avons mis en évidence qu'il est possible de faire varier la tension de circuit ouvert (Voc) des cellules en changeant le taux de carbone incorporé dans les alliages. Ainsi, un paramètre autre que la dilution de silane lors du dépôt peut être utilisé pour contrôler Voc. Ces dispositifs sont les tout premiers déposés et nécessitent encore des étapes d'optimisation. Néanmoins, l'étude approfondie que nous avons réalisée sur ces alliages nous laisse penser qu'ils ont un potentiel intéressant pour les applications PV. / Despite continuous effort, thin-film silicon multi-junction solar cells are still limited by the light-induced degradation of amorphous materials that they employ − hydrogenated amorphous silicon layers (a-Si:H) or amorphous silicon-germanium (a-SiGe:H) layers. To survive, this technology must fully benefit from the ease with which it allows multi-band gap photovoltaic (PV) devices to be assembled. To this end, materials that are stable under light soaking and have an electronic band gap between that of hydrogenated microcrystalline silicon (µc-Si:H, 1.1 eV) and that of a-Si:H (1.7 eV) are needed. The goal of this PhD thesis was to develop a new class of materials satisfying all these requirements by alloying carbon and silicon. Indeed, hydrogenated microcrystalline silicon-carbon alloys (µc-Si1−xCx:H) are a promising candidate for expanding the toolbox of useful materials for thin-film photovoltaics. The interest in these alloys lies in the possibility of easily varying their effective band gap by changing the amount of carbon in their composition. In this thesis, the usefulness of such materials in thin-film PV devices was probed using a broad range of deposition and characterization techniques. Using thin-film growth techniques at low temperatures (175−300° C), the range in which such electronically useful materials can be grown has been explored. It was confirmed that even in the condition of small crystallites, no stable sub-stoichiometric Si-C crystalline phase exists (i.e. no parallel for silicon-rich c-SiGe has been observed). Under all deposition techniques utilized, these materials were composed of submicron-size silicon crystallites embedded in an amorphous silicon-carbon (a-Si1−xCx:H) matrix. However, while the presence of the crystallites assures a higher conductivity compared to a-Si1−xCx:H, the carbon incorporation leads to an effective energy gap larger than that of microcrystalline silicon, supporting our investigation of these materials as promising optoelectronic layers. In the first part of this work, different Plasma Enhanced Chemical Vapor Deposition strategies have been investigated to achieve the widest range of processing conditions and to learn the most about the growth conditions required to produce a high quality µc-Si1−xCx:H material. Material properties were extensively characterized both on the structural side and also from an electrical point of view, in order to establish a correlation between the deposition parameters and the microstructural, transport and defect-related properties. The extensive set of results has allowed the proposal of a coherent growth model for such µc-Si1−xCx:H thin films. Exploiting these results, PV devices using these alloys as active layers were made. Although the absolute levels of efficiency (around 3.5 %) are not as high as state-of-the-art microcrystalline silicon, this work showed that it is possible to obtain variations in the open circuit voltage by varying the amount of carbon incorporated in such µc-Si1−xCx:H alloys. This important result shows that a process parameter other than silane dilution can be used to control this aspect of device performance. PV performances are modest so far, which is expected as these are the first ever results concerning the application of such a new class of materials as the active layer in thin-film solar cells. However, with further advancements in such materials, their replacement of the less stable a-SiGe:H is not unforeseeable.

La détection de gaz est un enjeu de plus en plus important, aussi bien dans le domaine de la surveillance de la qualité de l’air -intérieur et extérieur- que dans le suivi de procédés. Cet enjeu est d’autant plus critique dans le cas des composés organiques volatiles (COVs) que leur impact sur la santé publique est avéré. Détecter et quantifier leur présence devient une problématique majeure et différentes solutions existent. L’une d’elles, basée sur le couplage d’une nano-poutre résonnante et d’une micro colonne de chromatographie, s’avère être une solution prometteuse. Ces deux dispositifs alliant sélectivité et grande sensibilité nécessitent cependant une fonctionnalisation à l’aide d’une couche sensible. Ces travaux se sont focalisés sur le développement de matériaux sensibles de la famille des SiOCH déposés en couche mince par dépôt chimique en phase vapeur assisté par plasma (PECVD). L’étude de la réponse sous gaz des différents matériaux synthétisés au cours de cette thèse a été réalisée à l’aide de microbalances à cristal de quartz (QCM). Les mesures obtenues ont ensuite été corrélées à un modèle simple permettant de proposer une interprétation de l’interaction entre les SiOCH et le gaz d’intérêt, à l’équilibre mais aussi en régime dépendant du temps. La première partie de l’étude montre l’impact de la composition chimique de ces matériaux sur leur affinité envers un gaz représentatif des COVs aromatiques : le toluène. En s’appuyant sur des caractérisations physico-chimiques, le rôle de différentes liaisons chimiques ainsi que celui de l’hydrophobie des couches minces sur l’interaction avec le gaz d’intérêt a été analysé. Ces travaux montrent qu’un compromis entre composition chimique et hydrophobie doit être trouvé afin de préserver affinité et temps de réponse des SiOCH. L’étude de l’influence de la porosité sur la sensibilité a ensuite été abordée dans un second temps. Pour cela, des procédés originaux de réalisation de couches minces poreuses ont été développés afin de proposer de nouveaux matériaux poreux et d’accroître leur sensibilité vis-à-vis du toluène. Les limites de l’approche soustractive généralement utilisée pour ce type de matériau (i.e. l’approche porogène) ont pu ainsi être dépassées en termes de porosité et de tailles de pores. Concernant la détection de gaz, il s’avère difficile de décorréler l’impact de la chimie de celui de la porosité. Quoi qu’il en soit, l’augmentation de la porosité ouverte n’apparait pas comme le seul paramètre pertinent pour accroître la sensibilité de ces matériaux aux faibles concentrations. / Gas detection is a growing field, both for indoor and outdoor air quality monitoring and for process monitoring. It is indeed particularly critical in the case of volatile organic compounds (VOC) whose impact on public health is proven. Detecting and quantifying their presence becomes a major problem and various solutions are available. One of them, based on the coupling of a resonant beam and a chromatography micro column, appears to be a promising solution. Those two devices combine selectivity and high sensitivity; however, they require functionalization with a sensitive layer. This work focused on SiOCH thin films deposited by PECVD. The gas interaction of the sensitive layers deposited during this work was studied using quartz crystal microbalances (QCM). The obtained measurements were then correlated to a simple model, providing an interpretation of the interaction – for steady-state but also kinetic regime - between the SiOCH and the gas of interest. The first part of the study shows the impact of the chemical composition of those materials on their affinity for toluene, representative for aromatic VOCs. Relying on physico-chemical characterization techniques, the role of various chemical bonds on the solid/gas interaction was investigated. This work shows that a compromise between chemical composition and hydrophobicity has to be reached to preserve SiOCH affinity and temporal response. The influence of porosity was then explored in a second step to further increase the sensitivity of those materials. Original deposition processes were developed in order to propose new porous materials with higher toluene affinity. The limits of the subtractive approach generally used for these PECVD materials (i.e. the porogen approach) were then overcome in terms of porosity and pore size. Concerning gas detection, it is difficult to decorrelate between the impact of chemistry and porosity. Whatever, increasing porosity does not appear to be the only relevant parameter in order to increase these materials affinity at low concentrations.

Submitted by DIEGO ROSSI null (rossi_diego@ig.com.br) on 2016-02-16T18:58:22Z No. of bitstreams: 1 Dissertação D.Rossi - FINAL.pdf: 4611767 bytes, checksum: 71f830e143f447c9e962c2305462a623 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-02-17T16:11:21Z (GMT) No. of bitstreams: 1 rossi_d_me_bauru.pdf: 4611767 bytes, checksum: 71f830e143f447c9e962c2305462a623 (MD5) / Made available in DSpace on 2016-02-17T16:11:21Z (GMT). No. of bitstreams: 1 rossi_d_me_bauru.pdf: 4611767 bytes, checksum: 71f830e143f447c9e962c2305462a623 (MD5) Previous issue date: 2015-12-21 / Este trabalho tem por finalidade a deposição de filmes finos de carbono amorfo hidrogenado (a-C:H) e de filmes finos de carbono amorfo hidrogenado com silício (a-C:H:Si). Analisar a incorporação gradativa de cloro nos filmes, tornando-os clorados (a-C:H:Cl e a-C:H:Si:Cl). As técnicas utilizadas para a deposição dos filmes foram: (i) a deposição à vapor químico assistido por plasma (PECVD) e (ii) implantação iônica por imersão em plasma (PIIID). Os filmes foram produzidos a partir de misturas de vapores de propanol, CH3(CH2)2OH, vapores de tetrametilsilano, Si(CH3)4, vapores de clorofórmio, CHCl3, e argônio, Ar, respectivamente monômero 1, monômero 2, comonômero e gás plasmogênico. O aumento do clorofórmio na alimentação do reator acarretou em mudanças nas estruturas químicas do material depositado e também alterações nas suas características ópticas. Para averiguar as modificações nas propriedades ópticas dos filmes foram calculados o coeficiente de absorção, o índice de refração e o gap óptico com base em espectros de transmitância óptica na região do Ultravioleta, Visível e Infravermelho Próximo, (Uv/Vis/NIR). As modificações nas estruturas químicas dos filmes foram analisadas por espectroscopia de absorção no infravermelho por transformada de Fourier, FTIR, visando revelar os grupos químicos presentes nos filmes. Espectroscopia de fotoelétrons de raios X, (XPS), foi a técnica utilizada para desvendar a composição química elementar dos filmes e a 6concentração dos elementos presentes. As características de molhabilidade dos filmes foram medidas em um goniômetro, através da análise da interação da gota de um fluído com a superfície dos filmes. Espessuras medidas por perfilômetria foram comparadas a valores teóricos provenientes das constantes ópticas. Os resultados do XPS demonstraram a presença de cloro nos filmes, a concentração máxima obtida foi de ~ 8% at. Houve um aumento na taxa de deposição dos filmes em função do aumento da proporção de clorofórmio na entrada do reator. O ângulo de contato apresentou-se em torno de 75° para os filmes aC:H:Cl e em torno de 80° para os filmes a-C:H:Si:Cl. As análises ópticas Uv/Vis/NIR apresentaram índice de refração de ~1.5, calculadas por modelos computacionais iterativos, o gap de Tauc aumentou de 1,9 eV para 2,5 eV para filmes finos a-C:H clorados. / Thin hydrogenated amorphous carbon (a-C:H) and (a-C:H:Si) films were produced and the gradual incorporation of chlorine turn into a-C:H:Cl films and aC:H:Si:Cl films. The a-C:H:Cl and a-C:H:Si:Cl films were produced by plasma enhanced chemical vapor deposition (PECVD) from mixtures of vapor of propane, CH3(CH2)2OH, tetramethylsilane, Si(CH3)4, chloroform, CHCl3, and argon gas, Ar; respectively monomer 1, monomer 2, comonomer and argon gas. The increase of chloroform in the film composition resulted in changes in the chemical structure of the material and also changes in its optical characteristics. To investigate the changes in the optical properties of the films, the absorption coefficient, refractive index and band gap were calculated from optical transmittance spectra in the Ultraviolet, Visible and Near Infrared (Uv/Vis/NIR) regions. The modifications in chemical structures of the films were analyzed by Fourier transform infrared spectroscopy FTIR. X-ray photoelectron spectroscopy (XPS) was the technique used to measure the chemical composition of the films. The wettability characteristics were measured using a goniometer, through the analysis of the interaction of a fluid drop on the surface of the films. Film thicknesses were measured using perfilometry and compared with theoretical values derived from optical data. The XPS results showed chlorine in the film, and the maximum concentration was about 8% at. There was an increase in the deposition rate as 8chloroform proportion reactor inlet was added. The contact angle showed around 75° to a-C:H:Cl films and around 80° to a-C:H:Si:Cl films. The optical analyses Uv/Vis/NIR showed refractive index of ~1.5, calculated for interactive computer models. The Tauc band gap increased from 1,9 eV to 2,5 eV for a-C:H chlorinated films.

Neste trabalho é estudada a viabilidade de produção de dispositivos eletrônicos baseados em filmes semicondutores de carbeto de silício estequiométrico (a-Si0,5C0,5:H) obtidos por deposição química por vapor assistida por plasma, PECVD. A proposta do projeto envolve a realização de uma série de trabalhos que permitam avaliar as potencialidades do a-SiC:H para a fabricação de dispositivos semicondutores simples. Deste modo, desenvolvemos as principais etapas para a construção de dispositivos, as quais envolveram a dopagem elétrica por diferentes técnicas com a utilização de diferentes elementos dopantes, a corrosão seletiva por plasma e a obtenção um dielétrico apropriado e compatível com a tecnologia do SiC, bem como o desenvolvimento de processos de cristalização, que podem se mostrar fundamentais para melhorar as propriedades dos filmes de a-SiC:H. Com tais processos aprimorados, fabricamos estruturas MOSiC (metal-óxidocarbeto de silício) a partir do SiC cristalizado, utilizando como dielétrico de porta o SiO2 crescido por oxidação térmica (seca e úmida) dos próprios filmes de carbeto de silício cristalizados. Essas estruturas apresentaram o comportamento típico de um capacitor MOS, com regiões de acumulação, depleção e inversão bem definidas em todos os casos. Também fabricamos heterojunções de filmes de SiC tipo-p (como depositado e tratado termicamente) sobre substratos de Si tipo-n, os quais mostraram boas caracterísitcas retificadoras para as heteroestruturas formadas pelo a-SiC:H como-depositado e tratado termicamente a 550ºC. Além do mais, também projetamos, fabricamos, modelamos e caracterizamos transistores de filme fino de a-SiC:H. De acordo com as caracterizações elétricas observamos que podemos controlar a condutividade do canal, embora os dispositivos ainda precisem ser aprimorados para se obter melhores níveis de corrente. Vemos, portanto que, embora ainda tenham que ser aperfeiçoados, foram construídos com sucesso dispositivos eletrônicos semicondutores baseados em filmes de a-Si0,5C0,5:H obtidos por PECVD. / In this work we studied the viability to build devices based on stoichiometric amorphous silicon carbide semiconductor films (a-Si0.5C0.5:H), obtained by plasma enhanced chemical vapor deposition technique. The project proposal involves the realization of a series of studies that evaluate the potentialities of the a-SiC:H for the fabrication of simple semiconductor devices. In this way, we developed the main steps for the devices\' fabrication, which involved electric doping, by different doping techniques using different doping sources, selective plasma etching and the obtention of an appropriate and compatible dielectric for SiC technology. Besides, we performed crystallization processes that were essential to improve the properties of the amorphous films. By establishing the processes steps, we manufactured MOSiC (metal-oxidesilicon carbide) structures starting from crystallized SiC and using SiO2 as the gate dielectric, which was obtained by thermal oxidation (wet and dry) of the crystallized silicon carbide films. All the structures presented a typical MOS capacitor behavior, with accumulation, depletion and inversion regions well-defined in all the cases. We also fabricated heterojunctions formed by p-type SiC films (as-deposited and annealed) on n-type silicon substrates that showed good rectifying characteristics for as-deposited and annealed at 550ºC a-SiC:H films. Moreover, we designed, manufactured, modeled and characterized a-SiC:H thin film transistors. The electric characterization demonstrated that it is possible to control the channel conductivity; however, the devices still need to be improved to obtain better current levels. Although some improvement still need to be made, we built successfully electronic semiconductor devices based on a-Si0.5C0.5:H films obtained at low temperatures by PECVD technique.

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 disponibles. / Plasma-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.