Le silicium est le matériau de prédilection de l'industrie de la microélectronique. L'augmentation du coût de celui-ci a donc incité les différentes industries à optimiser l'utilisation des plaquettes de silicium. La réutilisation de plaquettes (recyclage) est donc devenue monnaie courante : c'est le cas des plaquettes tests ou des plaquettes de type SOI. Le recyclage présente cependant des limites, en effet, au cours des cycles la qualité des plaquettes diminue plus ou moins rapidement. La compréhension des mécanismes de la dégradation des plaquettes lors de cycles de procédés est donc un enjeu important. Les procédés de recuit haute température sont connus pour être à la fois les plus répandus et les plus dégradants. Pour comprendre quels sont les phénomènes mis en jeu lors de tels cycles, un panel d'échantillons a subi différents nombres de cycles et a été étudié par diverses techniques. Le LST et la microscopie électronique en transmission ont tout particulièrement été utilisés, couplant ainsi des mesures globales de densités et dimensions de défauts à des mesures locales permettant de caractériser la nature des défauts et leur comportement à l'échelle nanométrique. L'évolution de la concentration en oxygène interstitiel dans le matériau, liée à la précipitation d'oxyde de silicium, a été mesurée par IRTF. Il a ainsi été montré que chaque cycle consistait en une étape de nucléation de défauts, principalement des précipités d'oxyde de silicium, et une étape de grossissement. La détermination de la morphologie, ainsi que de la stoechiométrie des précipités a été réalisée. / Silicon is the prefered material of the Microelectronics industry. The increase of its cost incited the industries to optimize the use of wafers. Recycling them thus became current : it is the case for test wafers or SOI wafers. However, recycling presents limits : during the cycles, wafers quality decreases more or less quickly. Impact of process cycles on wafers quality is thus very important. High-temperature annealing is the most detrimental process. To understand what phenomena are involved during annealing cycles, samples which have been cycled were studied by differents techniques. LST and TEM were quite particularly used, coupling global measurements of defects density and size with local measurements to determine defects characteristics. Interstitial oxygen loss during cycles were measured by FTIR. We found that every cycle is composed by a defects nucleation stage, mainly precipitates of silicon oxide, and a growth stage. The determination of morphology and precipitates stoichiometry was realized. The behavior of these precipitates was described by a model taking into account various phenomena : oxygen loss, point defects distribution and cycles effects (ramp up/down and high-temperature stage). The robustness of the model was also tested by comparing the predictions made with the results taken from the bibliography.

Neste trabalho foram fabricados e caracterizados eletricamente capacitores MOS com óxido de silício ultrafino (2,6 nm) com porta de silício policristalino (Si-poli) P+ e N+. Os capacitores MOS com porta de Si-poli dopados com boro tiveram a estrutura Si-poli/SiO2/Si previamente implantada com nitrogênio nas doses de 1.10\'POT.13\', 1.10\'POT.14\', 1.10\'POT.15\' e 5.10\'POT.15\' at.cm-², com o pico da concentração de nitrogênio próximo à interface SiO2/Si. Os capacitores MOS foram fabricados sobre lâminas de silício do tipo p que passaram por uma limpeza química préoxidação tipo RCA mais imersão final em solução diluída em HF. Na seqüência, as lâminas foram oxidadas em um ambiente de O2 (1,5 l/min) + N2/H2 (2l/min; 10 %) que proporcionou óxidos de silício com excelentes características elétricas. Para a fabricação dos capacitores MOS com porta de Si-poli P+, utilizou-se SOG de boro seguido por difusão térmica sobre camada de Si-poli (340 nm). Após testes com receitas de difusão a 950, 1000, 1050 e 1100 °C todas padronizadas por um tempo de 30 min optamos por realizar a difusão a 1050 °C por 30 min, pois essa receita proporcionou concentração de boro superior a 1.10\'POT.20\' at.cm-³ e segregação desprezível do boro em direção ao substrato de Si. A dopagem dos capacitores MOS com porta de Si-poli N+ foi realizada por aplicação do SOG de fósforo seguido por difusão a 1050 °C por 30 min. Os resultados indicaram segregação do boro desprezível para o Si, baixa densidade de estados de interface (< 1.10\'POT.11\' eV-¹ cm-²) e no aumento do campo elétrico de ruptura (de 14 MV/cm para 21 MV/cm) com o aumento da dose de nitrogênio (de 1.10\'POT.13\' a 5.10\'POT.15\' at/cm²). Embora ocorresse uma maior dispersão e um aumento desfavorável da tensão de banda plana com o aumento da dose de nitrogênio, os valores 1.10\'POT.15\' e 5.10\'POT.15\' at.cm-² resultaram em capacitores MOS com tensão de faixa plana próxima ao parâmetro diferença de função trabalho (\'fi\' MS) significando densidade efetiva de cargas no dielétrico de porta inferior à cerca de 1.10\'POT.11\' cm-². / In this work we manufactured and electrically characterized MOS capacitors with ultrathin silicon oxides (2,6 nm) and polysilicon gate (Si-poli), P+ or N+. P+ - doped polysilicon gate MOS capacitors (Si-poli/SiO2/Si structure) were previously implanted with nitrogen using doses of 1.10\'POT.13\', 1.10\'POT.14\', 1.10\'POT.15\' and 5.10\'POT.15\' at.cm-², and implantation peak centered close to the SiO2/Si interface before boron doping. The MOS capacitors were fabricated on p-type silicon wafers, which were submitted to RCA - based cleaning procedure and a final dip in diluted HF solution. Following, the wafers were oxidize in ultrapure O2 (1,5 l/min) + N2/H2 (2l/min; 10 %) having, as a result, silicon gate oxides with excellent electrical characteristics. To obtain P+ polysilicon, it Spin On Glass (SOG) of boron the wafers was annealed at 950, 1000, 1050 or 1100 °C during 30 min. We have chosen a diffusion recipe of 1050 °C during 30 min to obtain volumetric concentration of boron higher than 1.10\'POT.20\' cm-³ and no boron segregation to the silicon. N+ polysilicon was also obtained using phosphorus SOG and diffusion at 1050 °C during 30 min. As a result, besides no boron segregation to Si, the interface states density was low (< 1.10\'POT.11\' eV-¹cm-²) and the breakdown field of the gate oxides increased (from 14 MV/cm to 21 MV/cm) by increasing the nitrogen doses (from 1.10\'POT.13\' to 5.10\'POT.15\' at/cm²). Although a larger dispersion and increasing of the flat-band voltage have occurred as the nitrogen dose was increased, values of 1.10\'POT.15\' and 5.10\'POT.15\' at.cm-² induced flat band voltage close to the parameter workfunction difference (\'fi\'MS) which meant effective charge density in the gate dielectrics lower than about 1.10\'POT.11\' cm-².

The work in this thesis examines the effects of the application of oxide coatings on the performance of the single crystalline silicon photovoltaic solar cells. A variety of potential oxide materials for solar cells performance enhancement are investigated. These films are silicon oxide, titanium oxide and rare earth ion-doped gadolinium oxysulfide phosphor. This study compares the electrical characteristics, optical properties and surface chemical composition of mono-crystalline silicon cells before and after coating. The first study investigates the potential for using single and double layers of silicon oxide films produced by low-temperature Plasma Enhanced Chemical Vapour Deposition (PECVD) using tetramethylsilane as a silicon precursor and potassium permanganate oxidising agent for efficiency enhancement of solar cells at low manufacturing cost. Deposition of the films contributes to the increase of the conversion energy of the solar cells on one hand while the variety of colours obtained in this study can be of great importance for building-integrated photovoltaic application on the other hand. The obtained results demonstrated a relative enhancement of 3% in the conversion efficiency of the crystalline silicon solar cell. In the second study, the effects of using a single layer of titanium oxide and a stack of silicon oxide and titanium oxide on the performance of solar cell are demonstrated. Moreover, this study shows the use of different sputtering configurations and oxidation methods. The experimental results showed a relative enhancement of 1.6% for solar cells coated with a stack of silicon oxide/titanium oxide. In the third study, silicon cells were coated with a luminescent layer consisting of down-converting phosphor, gadolinium oxysulfide doped with erbium and terbium, and a polymeric binder of EVA using doctor-blade screen printing technique. A relative enhancement of 4.45% in the energy conversion efficiency of PV solar cell was achieved. Also, the effects of combining silicon oxide layers together with the luminescent composite are also presented in this study.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Robert B. Laughlin. / Ph.D.

Xue Kun. / "July 2005." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract in English and Chinese.

A síntese, caracterização e propriedades de um novo compósito xerogel formado por óxido de vanádio e óxido de silício, com alta concentração de vanádio foi o objetivo deste trabalho. O compósito xerogel foi obtido mediante a formação de uma rede complexa envolvendo a condensação de polioxovanadato em meio aquoso com concomitante hidrólise e condensação de um alcóxido de silício. Conseqüentemente, este método possibilitou a obtenção de um material multicomponente homogêneo, no qual a rede Si O Si está interpenetrada com as cadeias poliméricas V-O- V e V-OH-V, promovendo uma solubilidade mútua, devido a formação de ligações cruzadas. Além disso, resultados experimentais apontam que, mesmo após a imobilização em matriz de sílica, a estrutura bi-dimensional, bem como as propriedades eletroquímicas do xerogel de pentóxido de vanádio são preservadas. A atividade catalítica do material obtido também foi avaliada na oxidação do cicloocteno e do estireno na fase líquida. O compósito xerogel V2O5/SiO2 obtido com tetraetiltrietóxisilano (TEOS), mediante catálise básica, o qual apresentou área superficial elevada (324 m2/g), e apresentou atividade catalítica em reações de oxidação do estireno e do cicloocteno na presença de PhIO como doador de oxigênio. Contudo, estes materiais apresentaram propriedades eletroquímicas inferiores as do xerogel de pentóxido de vanádio. Por outro lado, o comportamento eletroquímico óxido misto obtido com metiltrietóxisilano (MTES) é muito similar ao xerogel de V2O5; apresentando picos reversíveis ( par redox VV/IV: xe- + xLi+ + V2O5.nH2O ? LixV2O5.nH2O, em solução de LiClO4 0,1 mol.L -1 em acetonitrila). Além disso, a resposta eletroquímica á estável mesmo após sucessivos ciclos de oxidação e redução. Um aspecto interessante é que este compósito é formado por partículas esféricas de sílicas recobertas por xerogel de pentóxido de vanádio Neste contexto, pode-se afirmar que, o método empregado mostrou-se extremamente atrativo devido a sua simplicidade de realização, além de possibilitar um novo método de obtenção de materiais com potencial aplicação como dispositivos eletroquímicos, baterias, catalisadores e sensores químicos. / The synthesis, characterization and properties of new vanadium oxide silicon oxide composite xerogels with high vanadium content through formation of a complex network involving the condensation of polyoxovanadates in aqueous solution with concomitant hydrolysis and condensation of the silica alkoxide precursor have been the goal of this work. As a consequence, this procedure generated a homogeneous multicomponent material, in which Si-O-Si network is interpenetrated with V-V and V-OH-V polymeric chains, where a mutual \"solubility\" due to cross-links and entanglements was observed. In addition, the experimental data evidence that the vanadium pentoxide xerogel embedded in silica retains its bi-dimensional structure as well as its electrochemical properties. Besides, the catalytic activity of this material was evaluated in the oxidation of the cyclooctene and styrene in liquid phase. V2O5-SiO2 composite xerogels obtained from tetraethoxysilane under basic catalysis, present high surface area (324 m2/g) and have catalytic activities in alkene oxidation in the presence of PhIO as oxygen transfer agent and cyclooctene and styrene as substrates. However, these materials do not present a remarkable electrochemical property as evidenced by cyclic voltammetry. In contrast, the voltammetric behavior of the composites xerogel prepared with methyltriethoxysilane is quite similar to that found for V2O5 xerogel; showing reversible peaks (VV/IV redox pair: xe- + xLi+ + V2O5.nH2O LixV2O5.nH2O, in acetonitrile solutions containing 0.1 M LiClO4). Besides, the electrochemical response is stable under several successive redox cycles (over 50). An interesting feature is that is formed by silica spherical particles (4 to 8 micra) covered with V2O5 continuous polymeric network. Therefore, the synthetic approach applied in this study is extremely attractive due to its simplicity and can provide new strategies for tailoring new materials for electrochromic devices, batteries, catalysis and chemical sensing.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Diode lasers have many advantages such as small size, high efficiency and small angular dispersion of the collimated beam. However they also have some problems like lack of frequency stability. They can not be tuned in wavelength. An external cavity can solve these problems and decrease the laser linewidth. To obtain a tunable, narrow linewidth light source, antireflection coatings were applied to commercial diode lasers which were then tested in an external cavity. Laser characteristics, such as threshold current, spectral behavior, I-V-curves, tuning range, and bandwidth were measured for the original diode laser and then compared to the measurements in an external cavity with and without antireflection (AR) coatings. The tuning range approximately doubled after AR coating. The modal stability was found to be better by a factor of 7 in the external cavity. The power amplification through the external cavity was as high as 50. It was also attempted to process laser diodes from material fabricated at OSU, however the resulting diodes showed a high series resistance and were not usable for this project. Additional work needs to be done in this area. The result of this work is a stable external cavity diode laser tunable over an 18 nm bandwidth which can be used as a tunable source in many applications. / Graduation date: 1995

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Silicon oxide (SiO x 1 ∠ x [∠, double =]2) has long been used and considered as a passive and insulating component in the construction of electronic devices. In contrast, here the active role of SiO x in constructing a type of resistive switching memory is studied. From electrode-independent electrical behaviors to the visualization of the conducting filament inside the SiO x matrix, the intrinsic switching picture in SiO x is gradually revealed. The thesis starts with the introduction of some similar phenomenological switching behaviors in different electronic structures (Chapter 1), and then generalizes the electrode-material-independent electrical behaviors on SiO x substrates, providing indirect evidence to the intrinsic SiO x switching (Chapter 2). From planar nanogap systems to vertical sandwiched structures, Chapter 3 further discusses the switching behaviors and properties in SiO x . By localization of the switching site, the conducting filament in SiO x is visualized under transmission electron microscope using both static and in situ imaging methods (Chapter 4). With the intrinsic conduction and switching in SiO x largely revealed, Chapter 5 discusses its impact and implications to the molecular electronics and nanoelectronics where SiO x is constantly used. As comparison, another type of memory effect in semiconductors (carbon nanotubes) based on charge trapping at the semiconductor/SiO x interface is discussed (Chapter 6).