Ces travaux de thèse sont consacrés à l’étude de l’activation des dopants implantés dans le carbure de silicium. L’objectif est de proposer des conditions d’implantation optimisées pour réaliser le dopage de type n dans le 3C-SiC et de type p dans le 4H-SiC.Nous avons tout d’abord étudié les implantations de type n dans le 3C-SiC. Pour cela, des implantations de N, de P et une co-implantation N&P avec les recuits d’activation associés ont été étudiés. L’implantation d’azote suivie d’un recuit à 1400°C-30min a permis une activation proche de 100% tout en conservant une bonne qualité cristalline. Une étude sur les propriétés électriques des défauts étendus dans le 3C-SiC a également été réalisée. A l’aide de mesures SSRM, nous avons mis en évidence l’activité électrique de ces défauts, ce qui rend difficile la réalisation de composants électroniques sur le 3C-SiC.Nous avons ensuite réalisé une étude du dopage de type p par implantation d’Al dans le 4H-SiC, en fonction de la température d’implantation et du recuit d’activation. Nous avons pu montrer qu’une implantation à 200°C suivie d’un recuit à 1850°C-30min donne les meilleures résultats en termes de propriétés physiques et électriques. / This work was dedicated to the activation of implanted dopants in 3C-SiC and 4H-SiC. The goal is to propose optimized process conditions for n-type implantation in 3C-SiC and for p-type in 4H-SiC.We have first studied the n-type implantation in 3C-SiC. To do so, N, P implantations, N&P co-implantation and the associated annealings were performed. The nitrogen implanted sample, annealed at 1400°C-30 min evidences a dopant activation rate close to 100% while maintaining a good crystal quality. Furthermore, the electrical properties of extended defects in 3C-SiC have been studied. Using the SSRM measurements, we have evidenced for the first time that these defects have a very high electrical activity and as a consequence on future devices.Then, we have realized a study on p-type doping by Al implantation in 4H-SiC with different implantation and annealing temperatures. Al implantation at 200°C followed by an annealing at 1850°C-30min lead to the best results in terms of physical and electrical properties.

Le travail présenté ici s'insère dans le cadre des études amont financées par le CNES et SNECMA qui visent à mieux appréhender, et simuler les écoulements cavitants dans les inducteurs à l'amont des turbopompes spatiales. Compte tenu de la complexité des mécanismes mis en jeu dans ce type de géométrie, il a été décidé de réaliser une étude dans une géométrie académique de type marche descendante cavitante comportant les différents mécanismes physiques inhérents aux écoulements de backflow (écoulements instationnaires décollés) présents dans les inducteurs. Cette géométrie simplifiée a permis la mise en place d'une instrumentation de pointe telle que la densitométrie par absorption de rayons X résolue en temps ou encore la PIV-LIF 2D, 3C haute cadence pour la mesure du champ de vitesse liquide. Ces techniques étant couplées à la mesure du champ de pression pariétale, il a donc été possible d'estimer les interactions mutuelles entre la turbulence et la cavitation dans ce type d'écoulement.Les mesures couplées aux champ de pression ont également permis d'utiliser des techniques de traitement POD-LSE pour estimer des termes de corrélations densité-vitesse nécessaires à la validation des modèles de type transport de taux de vide. De manière générale, la cavitation engendre des modifications notables d'origine dilatatoire sur l'agitation turbulente et modifie la dynamique tourbillonnaire. Ces résultats permettent de tirer des conclusions sur les stratégies de modélisation. En effet en régime cavitant l'augmentation de l'énergie cinétique turbulente étant décorrélée du cisaillement moyen, les modèles basés sur une viscosité turbulente semblent inadaptés . D'autre part à fort taux de vide les résultats semblent être en contradiction totale avec les modèles barotropes. / The present study is inserted in the framework of previous research which aim to get a better understanding of turbulent and cavitating phenomena which occur in the spatial turbopump. Actually, the specific topology of the detached flow which takes place upstream the inducer is today miss-predicted by the standard numerical models.Taking into account the huge complexity of such a flow it has been decided to experimentally investigate the backward-facing step flow which is recognized as a benchmark for numerical simulations and cover a large area of similitude with the backflow upstream the inducers.For this purpose, the mean and turbulent quantities of the liquid phase in the presence of the vapor phase as well as spatio-temporal correlations have been investigated using stereoscopic time resolved PIV, the void ratio has been determined using X-Ray attenuation techniques and measurements have been made for different cavitation levels. The main originality of the present work is based on instantaneous measurements of the wall pressure signals correlated with high speed visualizations, PIV and X-Ray measurements. Specific signal processing as Proper Orthogonal Decomposition and Linear Stochastic Estimation has been performed in order to estimate the velocity-density correlations useful to evaluate the void ratio transport. In this experimental work the physical mechanisms of the vapour phase effects on the large vortex structures, shear layer instability, reattachment wall and reverse flow have been investigated to determine what physical assumptions can be applied in the usual cavitation and turbulence models.It has been found for the cavitating cases that the growth of turbulent kinetic energy is not correlated to mean and turbulent shear stresses. This experimental observation is in contradiction with the Boussinesq hypothesis used for the linear eddy viscosity models.Moreover concerning the phase-change modelization for high void fraction, the barotropic models seem to disagree with our experiments.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-04-19T18:51:20Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TeseCatarina_Final.pdf: 8264334 bytes, checksum: c3137c70a9924ba34f7f1f21851e4495 (MD5) / Made available in DSpace on 2017-04-19T18:51:20Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TeseCatarina_Final.pdf: 8264334 bytes, checksum: c3137c70a9924ba34f7f1f21851e4495 (MD5) Previous issue date: 2015-09-21 / FACEPE / Há muito se estuda o uso de tecnologia da informação em apoio a diversas atividades nas organizações. Um eixo desses estudos convergiu, a partir da década de 1990, para o estudo de sistemas que suportassem o trabalho em grupo, inicialmente colocalizados e, mais recentemente, dispersos. Tais sistemas, nominados sistemas colaborativos, adquiriram maior robustez ao serem beneficiados com as funcionalidades mais sociais da web 2.0, permitindo a interação simultânea e à distância, ampliando as possibilidades de abordagens e arranjos de suas funções. Em outro ângulo, a tarefa de gerar ideias em grupo é algo que acontece no cotidiano desses coletivos e é essencial aumentar o desempenho das organizações perante o cenário dinâmico e competitivo do mercado. Nesta perspectiva, vislumbrou-se acoplar um sistema colaborativo a uma tarefa de geração de ideias expectando que tal dueto poderia facultar um melhor resultado naquela tarefa. Assim, a pesquisa objetivou apurar qual o efeito que a adoção de um sistema colaborativo provocaria na estruturação da tarefa de geração de ideias em grupos virtuais. Para embasar essa discussão, utilizaram-se as lentes de teorias estruturacionais e da atividade, além do modelo 3C de colaboração. Em seguida, para operacionalizar a pesquisa, realizou-se um quase-experimento, no qual funcionários de uma empresa do segmento farmacêutico foram instados a gerar ideias mediados por um sistema colaborativo especificado para a pesquisa, tendo sido aqueles observados sob parâmetros da quantidade e qualidade das ideias geradas e da satisfação com o processo e com o resultado. Os aspectos apurados confirmaram as expectativas iniciais, indicando que há potencial de sucesso, mas, por outro lado, fazem ver que os processos e rotinas bem definidos, a facilitação das atividades pelo sistema e os elementos constantes em encontros presenciais são componentes relevantes em tarefas grupais apoiadas pela TI, especialmente as de geração de ideias. / There has been a lot of studies using information technology as a support for several activities in organizations. In the 90´s decade, an axis of such studies converged for the teamwork’s support systems study, initially co-located and, more recently, dispersed, called collaborative systems. Empowered by the web 2.0 social functionalities, this system strengthens simultaneous and distance interaction, increasing the possibilities of its function as arrangements and approaches. In another perspective, the generating group ideas task is something that happens routinely in a group and it is frequently used to increase the organizational performance in this dynamic and competitive market scenario. From this perspective, there has been an idea of coupling a collaborative system to a task of idea generation expecting that such duet could generate better outcomes. Therefore, the research aims to verify what effects the adoption of a more socially profiled collaborative system would result in the structuring the idea generation tasks in dispersed groups. As a basis for this discussion, the structural and activity theories lenses were used, and also the 3C collaboration model. Then, to operationalize the research, a quasi-experiment was performed, where a pharmaceutical company employees were asked to generate ideas mediated by a collaborative system, developed especially for the research. During the quasi-experiment, it has been observed, using quantitative and qualitative techniques, the number and quality of the generated ideas, the satisfaction with the process and its results. The results confirmed the initial expectation, pointing out that this social and collaborative system type performs an important role in supporting idea generation tasks, moreover, the importance of well-defined processes and routines, the activities facilitation by the system and the elements experienced in face-to-face encounters must be considered as well.

L'objectif de ce travail a été de comprendre les mécanismes menant à la formation de Nitrure de Gallium monocristallin ( GaN ) sur substrat de silicium par croissance cristalline en configuration Vapeur-Liquide-Solide (VLS), à partir d'une phase liquide de gallium, dans la perspective d'un amélioration ultérieure de la qualité des couches hétéro-épitaxiales de GaN sur silicium destinées aux composants pour l'électronique de puissance.Notre étude s'est concentrée autour de la croissance sur couche-germe 3C-SiC déposée par CVD sur silicium, l'ajout de cette couche intermédiaire permettant d'obtenir des couches de GaN en compression, tout en évitant les interactions chimiques entre le silicium du substrat et le Ga liquide.Une étude expérimentale paramétrique a mis en lumière la sensibilité de la croissance du GaN vis à vis des principaux paramètres de croissance ( température, flux de précurseur azoté ), et en particulier l'influence de ces paramètres sur les proportions des quantités formées des deux polytypes les plus stables du GaN ( 3C-GaN et 2H-GaN ). Nous avons montré, par exemple, qu'une simple variation de 50°C de la température conduit à une variation importante du mode de nitruration des gouttes de gallium, et à un changement radical du polytype majoritaire du GaN formé. Nous avons aussi montré que la croissance cristalline du GaN est très sensible à l'état de surface de la couche-germe CVD de 3C-SiC hétéro-épitaxial. Celle-ci est composée d'une coalescence d'îlots de SiC. Cette morphologie particulière impose sa géométrie quasi-périodique à la distribution des gouttes de gallium et peut favoriser la nucléation du GaN en périphérie des gouttes dans les premiers stades de la croissance.A partir des résultats de cette exploration préliminaire, nous avons pu identifier des conditions de croissance permettant de réaliser une couche quasi-continue de GaN par coalescence de cristallites résultant de la nitruration de gouttes de gallium liquide submicroniques / The aim of this work was to understand the mechanisms that lead to the formation of monocrystalline gallium nitride ( GaN ) on silicon substrate by crystalline growth with the Vapor-Liquid-Solid (VLS) configuration, from a gallium liquid phase, in the perspective of an ulterior improvement of the GaN hetero-epitaxial layers quality on silicon intended for power electronics components. Our study focused on the growth on 3C-SiC seed-layer deposited by CVD on silicon, this layer adding permits to obtain GaN layers in compression with avoiding any interactions between the silicon substrate and the liquid gallium. A parametric experimental study has enlightened the sensitivity of the GaN growth with the growth conditions (the temperature, the flux of the nitrogen precursor) and particularly the influence of the parameters on the ratio of formed quantities of the two most stable GaN polytypes (3C-GaN ou 2H-GaN). We have shown, for example, that a simple variation of 50°C of the temperature permits an important variation of the gallium droplets nitriding mod, and of the GaN preferential polytype. We also showed that the growth of GaN is very sensitive to surface state of the 3C-SiC CVD hetero-epitaxial seed-layer. This one is composed of some SiC coalescing islands. This peculiar morphology imposes its quasi-periodic geometry at the gallium droplet distribution and can favor the GaN nucleation at the droplet periphery during the first stage of the growth. From the results of this preliminary exploration, we were able to identify some growth conditions allowing to obtain an almost continued layer of GaN resulting of the nitriding of submicronic liquid gallium droplets

Pour les futures applications en télécommunications 5G, des substrats à base de silicium présentant une faible perte de signal et une excellente linéarité sont nécessaires. Parmi les solutions envisagées, la technologie RF-SOI est la plus avancée. Son empilement contient une couche de Haute Résistivité (HR), riche en pièges pour les porteurs de charges, composée de silicium polycristallin (poly-Si) de haute pureté déposée sur l’oxyde natif d'un substrat HR (HR-Si). Ce système présente certaines limitations provenant essentiellement de l'interface HR-Si/SiO2 et de sa stabilité thermique, mais également de la résistivité insuffisante de la couche riche en pièges. L'objectif principal de cette thèse était d'explorer des approches innovantes pour résoudre ces difficultés tout en restant compatible avec la technologie silicium. Afin d’atteindre ces objectifs, du carbone a été ajouté dans le système au cours des différentes étapes d'élaboration: i) remplacement de la couche interfaciale de SiO2 par une couche mince de 3C-SiC et ii) ajout de carbone pendant le dépôt de poly-Si.En utilisant la technique de dépôt chimique en phase vapeur à pression atmosphérique, des couches HR de poly-Si à l'état de l'art ont été déposée sur oxyde natif avec une épaisseur pouvant aller jusqu'à quelques dizaines de µm. Les résultats ont montré que la résistivité de la couche de poly-Si n'était pas directement dépendante de la taille moyenne des grains. Le remplacement de l'oxyde interfacial par une couche mince de mono- ou de poly-SiC, ainsi que l'adaptation des conditions de croissance ont permis d'atteindre des propriétés équivalentes à l'état de l'art des couches HR de poly-Si. Cet empilement a l'avantage d'être plus stable thermiquement en évitant la dissolution de la couche interfaciale. Cependant, ces améliorations sont accompagnées d’une chute de la résistivité à l’interface attribuée à la conductivité importante du matériau SiC. Par ailleurs, les propriétés de la couche HR et sa stabilité thermique peuvent être améliorées en dopant le poly-Si avec du Carbone, si une concentration adéquate de cette impureté est utilisée. L'insertion périodique de couches minces de SiC dans le poly-Si conduit à la stabilité thermique la plus élevée et à une augmentation de la résistivité moyenne de la couche. Néanmoins, des diminutions périodiques de la résistivité sont observées à chaque insertion de SiC / For future 5G telecommunication applications, Si-based substrates with low signal loss and excellent linearity are required. Among the envisaged solutions, RF-SOI is the most advanced. Its stack contains a High Resistivity (HR) Trap-Rich (TR) layer composed of high purity polycrystalline silicon (poly-Si) deposited on thin SiO2 native oxide of a HR-Si substrate (HR-Si). Some limitations of such system come from the HR-Si/SiO2 interface and its thermal stability, while increasing the resistivity of the TR-layer is also suited. The main objective of this thesis was to explore innovative approaches for solving these difficulties while staying Si-compatible. Towards this end, carbon was added in the system at different elaboration stages by i) replacing the SiO2 interfacial layer by 3C-SiC and by ii) C-engineering of the poly-Si layer during deposition.Using Atmospheric Pressure Chemical Vapor Deposition technique, state-of-the-art poly-Si TR-layers were grown on native oxide with thickness up to few tens of µm. It was found that the resistivity of the poly-Si was not directly dependent on the average grain size. Replacing the interfacial oxide by a thin mono- or poly-SiC layer and adapting the growth process allowed reaching equivalent properties of the poly-Si with the benefit of superior thermal stability by avoiding the interfacial layer dissolution. But it is accompanied by the presence of a resistivity drop at the interface due to the conductivity of the SiC material. By doping the poly-Si with C, both the TR-layer properties and thermal stability can be improved when adequate concentration of this impurity is used. Periodic insertion of thin SiC layers inside the poly-Si led to the highest thermal stability and an increase of the layer mean resistivity while periodic resistivity reductions were observed at each SiC insertion

Au cours des dernières années, de nouvelles évidences semblent indiquer que, tout autant que sa séquence, l’organisation d’un génome dans l’espace et le temps est importante pour comprendre la fonction de celui-ci. Une des avancées fonda- mentales sur le sujet a été de présenter à l’échelle du génome la carte des inter- actions ADN-ADN. Ces interactions sont essentiellement de 2 types, soit entre chromosomes ou entre régions du même chromosome. Par la suite, la modélisa- tion a permis de visualiser et appréhender la structure tridimensionnelle (3D) du génome à partir des données 3C, ou d’une modélisation purement théorique. Une question importante et centrale demeure, soit de résoudre les mécanismes res- ponsables de l’organisation spatiale et fonctionnelle du génome. Notamment, une question est de savoir comment des processus nucléaires tels que la transcription affectent la structure du génome. Cependant, l’idée selon laquelle les données de types 3C capturent cette information dans la levure est remise en question par le fait que les modèles théoriques du génome récapitulent les caractéristiques mar- quantes soulignées par 3C. Pour répondre à cette question, nous avons conçu une approche qui, pour évaluer l’importance d’une interaction, se base sur la distri- bution d’interactions entre les 2 régions d’ADN mises en contacts. Nos résultats supportent l’hypothèse selon laquelle les éléments fonctionnels et propres aux données expérimentales de la structure 3D du génome se forment d’une manière spécifique à l’échelle de l’interaction et au type d’interactions. Par ailleurs, nos résultats indiquent qu’un grand nombre de facteurs de transcription induisent la proximité spatiale des gènes dont ils régulent l’expression. / Over the last decade, accumulating empirical evidence suggest that, as much as its sequence, a genome spatiotemporal organization is essential to understand it’s biological function. One of the major breakthroughs has been chromosome conformation capture (3C) experiments presenting DNA-DNA contact for whole genomes at unprecedented resolution (5-10kb). Along with genome-wide maps of DNA contacts came genome 3D modelling from experimental 3C data, and even from purely theoretical and biophysical basis. However, the mechanisms underlying the regulation of the genome spatial functional organization are still not well understood. Among other questions, how the regulation and event of nuclear processes such as transcription modulate genome structure or how genome structure affect these in turn is still not fully resolved. Moreover, computational models of S.cerevisae genome have recapitulated the hallmarks at larger scale of its 3D features. In order to contrast genome structural features arising from the event of biochemical and molecular activity, we have develop a method assessing the significance of structural features. The underlying principle is to consider for a given interaction, the two DNA regions put in contact and the distribution of existing interactions between these before assigning significance to the selected interaction. Using this method, we demonstrate that structural features resulting from potential biochemically active processes occur at precise scale on the genome. Our results also highlight that exact nature of the interaction (between vs across chromosomes) is crucial to such events. Finally, we have also found that a large portion of transcription factors have their targeted genes in spatial proximity.

In recent years, the internet shopping development is quite developed, what every shopping website developed is quite ripe too, and 3C products occupy sizable rates in the internet shopping. So I want to study that 3C shopping website influences factor that influencing consumers¡¦ will to use the internet shopping. This research base on demography and knowledge about 3C products to create the cause-effect model of electronic service convenient, electronic service quality, customer satisfaction, and purchase intention. Through statistics software, probe into the relationship, electronic service convenient, electronic service quality, customer satisfaction, and purchase intention in the internet. In order to have close look to on customer needs is essential. Overall, the entire model fit is acceptable. It is pointed that the whole theory model of this study completes the standard of the fit test. To sum up, the results shows the indeed influential relationship among the four concepts.The customer satisfaction is the most important factor that negative effect purchase intention in the entire model. The second factor is electronic service quality. And electronic service convenient only leads a positive effect on purchase intention via electronic service quality and customer satisfaction. However, the effect is very small.

PML et les corps nucléaires (CN) sont impliqués dans la défense antivirale. En effet, notre équipe a montré que la surexpression de PMLIII confère la résistance au virus de la stomatite vésiculaire, au virus de l'influenza, au virus foamy mais pas au virus de l'encéphalomyocardite (EMCV). J'ai montré dans mon travail de thèse que l'EMCV contrecarre le pouvoir antiviral de PMLIII en induisant sa dégradation par un processus dépendant du protéasome et de SUMO. Cependant, les cellules de souris invalidées pour PML sont plus sensibles à l'infection par l'EMCV que les cellules issues de souris parentales. Pour déterminer l'isoforme de PML responsable de cet effet antiviral, j'ai analysé l'effet des sept isoformes de PML (PMLI-VII) et j'ai montré que seule l'expression en stable de PMLIV confère la résistance à l'EMCV en séquestrant la polymérase virale 3Dpol au sein des CN PML. De plus la déplétion de PMLIV augmente la production de l'EMCV dans les cellules traitées par l'interféron. Ces données indiquent le mécanisme par lequel PML confère la résistance à l'EMCV et révèlent que PML est l'une des protéines médiatrices des effets anti-EMCV de l'interféron.

Title from PDF of title page. / Document formatted into pages; contains 100 pages. / Thesis (M.S.Ch.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Silicon Carbide has been a semiconductor material of interest as a high power and temperature replacement for Silicon (Si) in harsh environments due to the higher thermal conductivity and chemical stability of SiC. The cost, however, to produce this material is quite high. There are also defects in the substrate material (SiC) that penetrate into the active devices layers which are known device killers. Silicon is a material that provides a low cost substrate material for epitaxial growth and does not contain the defects that SiC substrates have. However, the large ( 22%) lattice mismatch between Si and SiC creates dislocations at the SiC/Si interface and defects in the SiC epitaxial layer. These defects result in high leakage currents in 3C-SiC/Si devices. The main focus of the this research was to reduce or eliminate these defects using novel Si substrates. / ABSTRACT: First a 3C-SiC on Si baseline process was developed under atmospheric pressure conditions consisting of 3 steps - an in-situ hydrogen etch to remove the native oxide, a carbonization step to convert the Si surface to SiC, and finally a growth step to thicken the SiC layer to the desired value. This process was then modified to establish a high-quality, low-pressure 3C-SiC CVD growth process. This LPCVD process was then used to grow 3C-SiC on numerous novel Si substrates, including porous Si, porous 3C-SiC "free-standing" substrates and SOI substrates which consisted on thin Si films bonded to poly-crystalline SiC plates. The results of these experiments are presented along with suggestions for future work so that device-grade films of 3C-SiC can be developed for various applications. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

The growth of bulk cubic silicon carbide has for a long time seemed to be something for the future. However, in this thesis the initial steps towards bulk cubic silicon carbide have been taken. The achievement of producing bulk cubic silicon carbide will have a great impact in various fields of science and industry such as for example the fields of semiconductor technology within electronic- and optoelectronic devices and bio-medical applications. The process that has been used to grow the bulk cubic silicon carbide is a modification of the seeded sublimation growth, and the seeds have been grown by sublimation epitaxy. Selected samples have been characterized with a variety of different methods. The surface morphology of the samples has been examined using optical microscope, atomic force microscope and scanning electron microscope. The crystal structure has been investigated by the methods X-ray diffraction and transmission electron microscopy. The electrical resistance of the grown seeds was evaluated by four probe measurements. High crystal quality seeds have been grown with semiconductor properties and bulk silicon carbide was demonstrated using the seeds.