Chemical Vapour Deposition (CVD) diamond detectors were modelled for dosimetry of radiotherapy beams. This was achieved by employing the EGSnrc Monte Carlo (MC) method to investigate certain properties of the detector, such as size, shape and electrode materials. Simulations were carried out for a broad 6 MV photon beam, and water phantoms with both uniform and non-uniform voxel dimensions. A number of critical MC parameters were investigated for the development of a model that can simulate very small voxels. For a given number of histories (100 million), combinations of the following parameters were analyzed: cross section data, boundary crossing algorithm and the HOWFARLESS option, with the rest of the transport parameters being kept at default values. The MC model obtained with the optimized parameters was successfully validated against published data for a 1.25 MeV photon beam and CVD diamond detector with silver/carbon/silver structure with thicknesses of 0.07/0.2/0.07 cm for the electrode/detector/electrode, respectively. The interface phenomena were investigated for a 6 MV beam by simulating different electrode materials: aluminium, silver, copper and gold for perpendicular and parallel detector orientation with regards to the beam. The smallest interface phenomena were observed for parallel detector orientation with electrodes made of the lowest atomic number material, which was aluminium. The simulated percentage depth dose and beam profiles were compared with experimental data. The best agreement between simulation and measurement was achieved for the detector in parallel orientation and aluminium electrodes, with differences of approximately 1%. In summary, investigations related to the CVD diamond detector modelling revealed that the EGSnrc MC code is suitable for simulation of small size detectors. The simulation results are in good agreement with experimental data and the model can now be used to assist with the design and construction of prototype diamond detectors for clinical dosimetry. Future work will include investigating the detector response for different energies, small field sizes, different orientations other than perpendicular and parallel to the beam, and the influence of each electrode on the absorbed dose.

Chemical Vapour Deposition (CVD) diamond detectors were modelled for dosimetry of radiotherapy beams. This was achieved by employing the EGSnrc Monte Carlo (MC) method to investigate certain properties of the detector, such as size, shape and electrode materials. Simulations were carried out for a broad 6 MV photon beam, and water phantoms with both uniform and non-uniform voxel dimensions. A number of critical MC parameters were investigated for the development of a model that can simulate very small voxels. For a given number of histories (100 million), combinations of the following parameters were analyzed: cross section data, boundary crossing algorithm and the HOWFARLESS option, with the rest of the transport parameters being kept at default values. The MC model obtained with the optimized parameters was successfully validated against published data for a 1.25 MeV photon beam and CVD diamond detector with silver/carbon/silver structure with thicknesses of 0.07/0.2/0.07 cm for the electrode/detector/electrode, respectively. The interface phenomena were investigated for a 6 MV beam by simulating different electrode materials: aluminium, silver, copper and gold for perpendicular and parallel detector orientation with regards to the beam. The smallest interface phenomena were observed for parallel detector orientation with electrodes made of the lowest atomic number material, which was aluminium. The simulated percentage depth dose and beam profiles were compared with experimental data. The best agreement between simulation and measurement was achieved for the detector in parallel orientation and aluminium electrodes, with differences of approximately 1%. In summary, investigations related to the CVD diamond detector modelling revealed that the EGSnrc MC code is suitable for simulation of small size detectors. The simulation results are in good agreement with experimental data and the model can now be used to assist with the design and construction of prototype diamond detectors for clinical dosimetry. Future work will include investigating the detector response for different energies, small field sizes, different orientations other than perpendicular and parallel to the beam, and the influence of each electrode on the absorbed dose.

La technologie lithium-ion est largement utilisée pour le stockage de l’énergie électrique. Le graphite, fréquemment utilisé comme matériau d’anode, peut être avantageusement remplacé par des nanomatériaux hybrides, alliant la forte densité d’énergie du silicium aux nanotubes de carbone qui possèdent des propriétés électriques et mécaniques remarquables. Le procédé de Dépôt Chimique à partir d’une phase Vapeur (CVD) en lit fluidisé est particulièrement performant pour revêtir de façon uniforme des poudres, y compris des micro- et nano-poudres, par des matériaux divers. Des expériences de dépôt de silicium par CVD en lit fluidisé à partir de silane SiH4 ont été menées sur des nanotubes de carbone multiparois enchevêtrés en pelotes de 450 µm de diamètre médian (ARKEMA Graphistrength C100), couvrant la gamme de 10 à 70 % en masse de silicium déposé. Le silicium est déposé uniformément du bord jusqu’au cœur des pelotes, sous forme de nanoparticules réparties régulièrement sur les nanotubes, et dont la taille augmente avec la durée du dépôt. L’étude du comportement hydrodynamique du lit fluidisé révèle que les nanotubes de carbone fluidisent de façon homogène et avec une forte expansion, pour des vitesse de gaz modérées. Ainsi, les transferts de matière entre la phase solide et la phase gaz durant la fluidisation sont très élevés. Enfin, la capacité de cyclage charge-décharge des électrodes nanotubes de carbone - nanoparticules de silicium a été vérifiée en demi-pile au lithium. / Lithium-ion technology is widely used for electrical energy storage. Graphite, frequently used as anode material, could be usefully replaced by hybrid nanomaterials adding the great energy density of silicon to carbon nanotubes, who have remarkable electrical and mechanical properties. The Chemical Vapor Deposition (CVD) in fluidized bed process is specially performant in uniformly coating powders, including micro and nano powders, with various materials. Fluidized bed CVD of silicon experiments, from silane SiH4, have been conducted on multiwalled carbon nanotubes, entangled in pellets, 450 µm in median diameter (ARKEMA Graphistrength C100), covering a range from 10 to 70 % in total mass of deposited silicon. Silicon is uniformly deposited from shell to core of the pellets, forming nanoparticules regularly deposited on nanotubes and size-dependant to the CVD run duration. The study of hydrodynamic behavior of fluidized bed shows that carbon nanotubes fluidize homogeneously and with a wide expansion, for moderated gas velocity. Thus, mass transport between solid and gas phase during the fluidization are very high. Finally, the charge-discharge cycling capacity of carbon nanotubes - silicon nanoparticles electrodes has been checked in lithium half-cell.

L'évolution de la microélectronique est rythmée par l'augmentation constante du nombre de transistors intégrés dans chaque circuit grâce à la miniaturisation des dispositifs. Face à des coûts de fabrication et de développement de plus en plus élevés d'une part et à l'apparition de phénomènes parasites de plus en plus importants dans les dispositifs miniaturisés d'autre part, l'industrie se tourne progressivement vers l'intégration tridimensionnelle où les circuits sont empilés. La phase suivante de cette évolution pourra consister en la fabrication de circuits eux-mêmes tridimensionnels avec des composants répartis sur plusieurs niveaux. Dans ce contexte, la croissance catalysée de nanofils par CVD permet d'obtenir des structures cristallines en silicium sans relation d'épitaxie et de dimensions nanométriques sans photolithographie agressive. Nous avons utilisé ces propriétés pour la réalisation de démonstrateurs de capacités MOS et MIM ultra-denses de respectivement 22 µF/cm² et de 9 µF/cm² grâce à l'importante surface déployée par une assemblée de nanofils. Ces valeurs correspondent à des gains en surface appotée par les nanofils de 27,5 et de 16 pour les capacités MOS et MIM. Nous présentons dans ce travail de thèse, le dimensionnement, la fabrication et la caractérisation de ces dispositifs, depuis la croissance des nanofils jusqu'à l'obtention du démonstrateur complet. Nous nous sommes également intéressés aux principales briques technologiques de la fabrication de transistors verticaux à base de nanofils pour les niveaux d'interconnexion. Nous avons pour cela mis au point une technologie de croissance guidée de nanofils et étudié les qualités d'interface de l'empilement d'une grille déposé à basse température sur les nanofils. Cette étude s'appuie sur la comparaison des propriétés électriques de capacités MOS à base de nanofils obtenus par croissance catalysée avec les mêmes nanostructures obtenues par épitaxie sélective. Les nanofils catalysés présentent une très bonne qualité d'interface avec un empilement à base d'alumine et de nitrure de titane. Les technologies mises au point dans cette thèse ouvrent de nouvelles opportunités pour l'intégration tridimensionnelle au sein d'une même puce. / The main focus of microelectronic industry has been to increase the number of integrated transistors in each circuit thanks to the device miniaturization. However, due to the increasing manufacturing and development costs combined with the increase of parasitic phenomena in transistors when the dimensions decrease, the microelectronic industry is now focusing on the three-dimensional integration in which strategy, the circuits are stacked. The next step of this tendency will be able to consist in a component stacking inside the same three-dimensional circuit. In this context, the catalyzed CVD grown silicon nanowires are a very promising material since they can be grown with a crystalline structure without any epitaxial relationship. They can also have nanoscale dimensions without any aggressive photolithography step. We report in this thesis, the nanowire integration in high density MOS and MIM capacitors using the high developed surface of a nanowire assembly. This way, we have obtained capacitance densities of 22 µF/cm² and of 9 µF/cm² for MOS and MIM capacitors respectively. In this work, we present how the devices have been designed, fabricated and characterized from the nanowire growth to the complete devices. We have also studied the main steps of the nanowire integration MOS transistors for the interconnects. A guided nanowire growth process has been developed and the interface quality of a low temperature deposited gate stack has been investigated. This study is based on a comparison of MOS capacitor electrical performances between catalyzed and unanalyzed silicon nanowires obtained by selective epitaxial growth. The catalyzed nanowires show a very good interface quality with a gate stack composed of alumina and titanium nitride. The technologies developed in this thesis open new opportunities for the 3D integration of devices on the same chip.STAR

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Agradecemos a compreensão. on 2016-11-10T15:50:45Z (GMT) / Submitted by ANDERSON FIGUEIREDO DA COSTA null (and.kairos@hotmail.com) on 2016-11-22T17:09:03Z No. of bitstreams: 1 Dissertação 20161104 - Versão Final Corrigida.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-11-23T17:41:31Z (GMT) No. of bitstreams: 1 costa_af_me_guara.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5) / Made available in DSpace on 2016-11-23T17:41:31Z (GMT). No. of bitstreams: 1 costa_af_me_guara.pdf: 5558976 bytes, checksum: 402eb9e3734833ebc7ccebf113844b8e (MD5) Previous issue date: 16-09-08 / Com o atual avanço de propriedades dos materiais, novas alternativas estão sendo buscadas para manufaturas desses materiais. Entre os processos, a usinagem se caracteriza por ser um processo que emprega milhões de pessoas. Entretanto para alcançar tais objetivos melhorias nas propriedades das ferramentas se faz necessária. Neste seguimento, os revestimentos vêm apresentando avanços significativos, como pode-se destacar o revestimento por CVD (deposição química a vapor) que permite que a ferramenta seja empregada nas temperaturas em torno de 1200ºC. Nesta mesma linha vale destacar o revestimento por PVD (deposição física a vapor) normalmente em uma única camada, o qual permite que a aresta de corte seja positiva, possa trabalhar com menor esforço de corte, e em temperatura aproximadamente em 700ºC. Este trabalho tem como objetivo analisar comparativamente o desempenho de ferramentas de metal duro revestidas pelo processo CVD e PVD no torneamento do aço ABNT 8620 sem uso de fluido de corte. Foram utilizadas duas pastilhas de metal duro revestidas pelo processo de PVD e CVD, com mesma geometria para efeito comparativo. A pastilha revestida por PVD tem espessura do revestimento de 3µm, enquanto que a pastilha revestida por CVD tem espessura do revestimento de 16µm. As pastilhas revestidas foram caracterizadas quanto a composição química dos elementos de revestimentos utilizando um microscópio eletrônico de varredura pela técnica de linescan e mapping. Posteriormente as ferramentas foram aplicadas ao torneamento nas velocidades de corte (Vc) entre 350 a 500m/min, avanço (f) de 0,20mm/rot e profundidade de corte (ap) de 1,00mm, utilizando um torno da marca ROMI, modelo GL240M. As caracterizações foram realizadas com uso de um microscópio óptico, microscópio eletrônico de varredura e um rugosímetro. Os resultados demonstraram que a ferramenta revestida pelo processo CVD apresenta um melhor rendimento, quando comparado ao processo PVD, este fato ocorreu porque a ferramenta revestida pelo processo CVD apresenta um revestimento multicamadas, possuindo um aporte térmico mais elevado, suportando assim, temperaturas de corte mais elevadas durante a usinagem e promovendo um menor desgaste de flanco e de superfície de saída. Portanto, este trabalho demonstra que para uso em uma indústria que torneia o aço ABNT 8620, as ferramentas revestidas com CVD apresentam melhor desempenho, levando a um menor consumo de pastilhas e uma expressiva redução de custos. / With the current advancement of material properties, new alternatives are being sought for manufacturing these materials. Among the processes, machining is characterized as a process that employs millions of people. However to achieve such goals improvements in the tools properties is necessary. In this follow-up, the coatings have shown significant advances, as can highlight the coating by CVD (chemical vapor deposition) that allows the tool to be used at temperatures around 1200°C. In the same line it is worth highlighting the coating by PVD (physical vapor deposition) usually in a single layer, which allows the cutting edge is positive, can work with less shear stress, and temperature approximately 700°C. This study aims at comparing the performance of carbide tools coated by the CVD process and PVD in the steel turning ABNT 8620 without the use of cutting fluid. We used two carbide inserts coated by the PVD and CVD process, with the same geometry for comparison purposes. The tablet is coated by PVD coating thickness of 3μm, while the tablet is coated by CVD coating thickness of 16μm. The coated tablets were characterized as the chemical composition of coatings elements using a scanning electron microscope for linescan technique and mapping. Subsequently the tools were applied to turning the cutting speed (Vc) between 350 to 500 m/min, feed (f) 0.20 mm/rev and depth of cut (ap) of 1.00mm using a lathe ROMI mark, GL240M model. The characterizations were carried out using an optical microscope, scanning electron microscope and roughness. The results demonstrated that the tool coated by the CVD process has a better performance when compared to PVD this occurred because the tool coated by the CVD process has a multilayer coating having a higher heat input, supporting thus cutting temperatures over high during machining and promote a smaller flank wear and output surface. Therefore, this work shows that for use in an industry that sidesteps steel ABNT 8620, tools coated with CVD have better performance, leading to lower consumption of pellets and a significant cost reduction.

Nesta dissertação discutem-se os resultados do estudo do efeito da modificação superficial de filmes de diamante dopados com boro (DDB) com partículas de Pt depositadas eletroquimicamente, sobre a reação de oxidação anódica de etanol em meio ácido. Foram investigadas a influência do potencial de deposição, da carga de deposição e do pré-tratamento eletroquímico em potenciais de reação de geração de H2 (RGH) e de O2 (RGO) no grau de dispersão da Pt e na eficiência do eletrodo de BDD-Pt para a reação de oxidação anódica de etanol. Pré-tratamentos catódicos tendem a aumentar a atividade do eletrodo para a RGO, embora este efeito não seja permanente e só seja observado em filmes novos. Polarizações anódicas contribuem para o aumento do sobrepotencial de RGO, assim como causam a diminuição da eficiência de corrente para a deposição de Pt,embora surpreendentemente origine depósitos de Pt com maior área superficial e maior atividade para a oxidação anódica do etanol. Um modelo baseado em interações entre a superfície do diamante e o íon complexo de Pt é proposto para explicar a influência destes parâmetros nas características dos depósitos. / The results from the study of the surfacial modification of boron doped diamond (BDD) films with electrodeposited Pt particles for the anodic oxidation of ethanol in acidic media are discussed. It was investigated the influence of deposition potential, catalyst loading and electrochemical pre-treatment at H2 or O2 evolution reaction (HER and OER, respectively) potentials made prior to catalyst deposition, on the dispersion degree and electrode efficiency for ethanol anodic oxidation. HER polarizations tend to increase the film activity for the OER reaction, though this effect was not found to be permanent and was only observed in recently prepared BDD films. Anodic polarizations on the BDD contribute to the increase of OER overpotential as well as for the decreasing of the current efficiency for the Pt deposition, though it surprisingly resulted in more dispersed (higher surfacial area), more ethanol oxidation active Pt deposits. A tentative model based on interactions between Pt complex ion and O (or H) terminated BDD surfaces is presented.

Recentemente surgiram os instrumentos abrasivos diamantados obtidos pela técnica Chemical Vapor Deposition (CVD) utilizados em ultra -som como uma nova possibilidade na técnica do preparo de cavidade. Tradicionalmente, os preparos cavitários são realizados com instrumentos abrasivos diamantados rotatórios convencionais (IADR) formando uma espessa camada de esfregaço. Com o desenvolvimento dos sistemas adesivos, tornou-se muito importante saber a qualidade e a espessura da camada de esfregaço e a topografia dentinária produzida. Com esse objetivo, foram avaliadas in vitro as características da superfície desgastada e a camada de esfregaço produzida em dentina após serem instrumentadas. Foram preparados 24 corpos de prova (cps) e divididos em 4 grupos (grupo 1 – cps preparados com IADR, grupo 2 – cps preparados com CVD rotatório, grupo 3 - cps preparado com CVD Tangencial por ultra-som e grupo 4 - cps preparados com CVD Impacto por ultra-som). Após os desgastes dentinários descritos, os corpos de prova foram desidratados e devidamente preparados para a observação em MEV. Em análise qualitativa as fotomicrografias realizadas no MEV demonstraram significantes diferenças. Os corpos de prova instrumentados com o sistema rotatório (IADR e CVD rotatório) apresentaram ranhuras com traçado retilíneo e paralelo, maior produção de espessura de esfregaço e maior comprimento de smear plug. Os corpos de prova instrumentados com o sistema ultra-sônico (CVD Tangencial eCVD Impacto) apresentaram padrões de ranhuras e traçados próprios, com menores espessuras de esfregaço e menor comprimento de smear plug. / Abrasive diamond instruments are a recent development, obtained through a technique called Chemical Vapor Deposition (CVD), used in ultrasound as a new possibility in dental cavity preparation. Traditionally, cavity preparations are made with conventional abrasive rotary diamond burs (IADR), forming a thick smear layer. Upon the development of new adhesive systems, it has become very important to know the quality and thickness of the smear layer, as well as the dentin topography produced after preparati on. For this purpose, we conducted an in vitro evaluation of the drilled surface and the smear layer produced in dentin after instrumentation. Twenty-four (24) samples were divided into four (4) groups: (group 1 – samples prepared with IADR, group 2 – samples prepared with rotary CVD, group 3 – samples prepared with Tangential ultrasound -guided CVD, and group 4 – groups prepared with Impact ultrasound-guided CVD). After the dentin drilling described, the samples were dehydrated and adequately prepared for SEM observation. A qualitative analysis conducted by SEM microphotography yielded significant differences. The samples worked with the rotary systems (IADR and rotary CVD) showed straight, parallel grooves, with thicker smear layers and longer smear plugs. The samples submitted to ultrasound-guided drilling (Tangential CVD and Impact CVD) showed distinctive groove and contour patterns, with the lowest smear thicknesses and smear plug lengths.

Este estudo in vitro avaliou a microinfiltração marginal de restaurações de classe V em resina composta, preparadas utilizando-se três técnicas de preparo cavitário: Alta-rotação (AR), ultrassom (US) e a associação das duas técnicas (AR+US); e restauradas após a aplicação de 3 sistemas adesivos, sendo um de condicionamento total (Single-Bond (SB)) e dois autocondicionantes (Clearfil SE Bond (CSE) e Prompt L-Pop (POP)). Foram formados nove grupos (n=14) com terceiros molares que tiveram cavidades preparadas em suas faces vestibular e lingual, e foram classificados como: Grupo1- AR/SB; Grupo 2 AR/CSE; Grupo 3 AR/POP; Grupo 4 US/SB; Grupo 5 US/CSE; Grupo 6 US/POP; Grupo 7 AR+US/SB; Grupo 8 - AR+US/CSE; Grupo 9 - AR+US/POP. Após a aplicação do adesivo as cavidades foram preenchidas com resina composta Z250-3M ESPE e armazenadas em água destilada a 37°C durante 24 horas. Posteriormente, as restaurações foram polidas e os espécimes termociclados (1000 ciclos/ 5 e 55°C), impermeabilizados, imersos em solução de nitrato de prata 50% por 8 horas, seccionados em 3 fatias, imersos em solução fotoreveladora por 16 horas e observados em microscópio óptico acoplado à uma câmera de vídeo. As imagens foram digitalizadas e um software foi utilizado para medir a microinfiltração marginal dos lados oclusal e cervical. Foi realizado ANOVA Split-plot que demonstrou não haver diferenças estatisticamente significantes para os lados oclusal e cervical (p<0.05). A média dos lados oclusal e cervical foi realizada e os dados submetidos à ANOVA 2 Fatores (p=0,05), que mostrou haver diferenças estatisticamente significante entre os grupos, sendo necessário a utilização de um Teste de Tukey (p=0,05). Este teste mostrou não haver diferenças estatisticamente significantes entre os grupos restaurados com o sistema adesivo de condicionamento total (SB), no entanto, os grupos restaurados com os adesivos CSE e POP apresentaram menor microinfiltração para os grupos preparados com US e AR+US. O Grupo US/CSE apresentou o menor índice de microinfiltração e o AR/POP o maior. Nas condições deste estudo, podemos concluir que o método de preparo das cavidades pode alterar a microinfiltração marginal para restaurações que utilizem sistema adesivo autocondicionante. / This in vitro study compared the microleakage of class V resin composite restorations placed in cavities prepared with high-speed dental bur (AR), ultrasonic preparation devices (US) and high-speed dental bur plus ultrasonic preparation devices(AR+US), and restored using three different adhesive systems (One all etch Single Bond (SB) , and two Self-etch Clearfil CSE bond (CSE), Prompt L-Pop (POP)). Nine groups (n= 14) of human third molars each were prepared on the bucal and lingual surfaces were formed: Group 1- AR/SB; Group 2 AR/CSE; Group3 AR/POP; Group4 US/SB; Group 5 US/CSE; Group 6 US/POP; Group 7 AR+US/SB; Group 8 - AR+US/CSE; Group 9 - AR+US/POP. Specimens were built up with Z250/3M ESPE composite and stored in distilled water at 37°C for 24 hours. Then, the restorations were polished and the specimens thermocycling (1000 cycles/ 5°- 55°C), put impermeable, immersed in a 50% silver nitrate solution for 8 hours, sectioned, immersed in a photographic developer solution at darkness for 16 hours, and analyzed for leakage at the oclusal and cervical interface using an optical microscope connected to a video camera. The images were digitalized and software was utilized for microleakage assessment. Upon analyzing the results using a Split-plot ANOVA no statistically significant differences (p<0,05) between the cervical and oclusal interfaces for all groups was observed. The average of the interfaces was held and a Two-Way ANOVA revealed differences in microleakage among the tested groups (p=0,05). Tukey Test for Multiple Comparisons (p=0,05) demonstrated no significant difference between the groups restored with total etch adhesive system (SB), the groups restored with CSE and POP showed the least microleakage for the group prepared with the US and AR/US. The group US/CSE had the lowest microleakage and the group AR/POP had the highest. In the conditions of this study, we can conclude that the method of cavity preparation may affect the microleakage when a selfetch adhesive system is used.

Le diamant de synthèse présente un intérêt croissant pour des applications diverses dans les domaines de l’optique, la catalyse, la biologie ou encore l’électronique. Par dépôt chimique en phase vapeur (CVD) ou par haute pression et haute température (HPHT), il peut être synthétisé sous forme de films. Les particules de diamant sont généralement produites par détonation ou par broyage de diamant massif. Cependant, il n’existe pas actuellement de particules de diamant combinant à la fois sphéricité, monodispersité et qualité cristalline contrôlée. Dans ce contexte, l’objectif de ce travail de thèse est d’élaborer un matériau diamant répondant à ces critères. Pour cela, des cœur-coquilles de diamant nanocristallin sphériques et monodisperses de taille micrométrique ont été synthétisés à partir de billes de silice ensemencées par des nanodiamants. Le revêtement de diamant nanocristallin a été obtenu dans un réacteur CVD spécifique dédié au traitement de poudres. En faisant varier la composition du mélange gazeux, la nature du revêtement a pu être modifiée, du diamant nanocristallin à un matériau hybride composé de nanodiamants enrobés d’une matrice graphitique. Des méthodes de caractérisations complémentaires comme la spectroscopie Raman et le HR-TEM ont permis de déterminer la structure cristalline de ces différents revêtements. Un traitement d’oxydation des cœur-coquilles a permis de les disperser en suspension colloïdale dans l’eau. En utilisant un traitement basique, des sphères creuses ont pu être obtenues et mises en suspension. Des études préliminaires des performances de ces différents matériaux ont ensuite été menées : les propriétés photo-électrocatalytiques pour la réduction du CO2 et la cytotoxicité in vitro pour des applications en biologie. La méthode d’élaboration des cœur-coquilles de diamant mise au point a été enfin étendue à des cœurs magnétiques de maghémite. / Synthetic diamond is now considered in various fields of applications like optics, catalysis, biology or even electronic. Thin films can be synthesized by Chemical Vapor Deposition (CVD) or by High Pressure/ High Temperature (HPHT), while particles are produced by detonation synthesis or milling of bulk diamond. Nevertheless, among all these diamond materials, there is no material available combining sphericity, monodispersity and crystalline quality. This is the purpose of this thesis work. Core-shell systems made of nanocrystalline diamond shell surrounding a silica core have been synthesized, starting from nanodiamond-seeded silica particles. These particles have been grown in a dedicated home-made CVD reactor, specifically developed to treat powders. Varying the gas composition, the nature of the coating has been tuned, from nanocrystalline diamond to a hybrid material made of nanodiamond particles surrounded by organized graphite. Complementary techniques such as Raman spectroscopy and High Resolution Transmission Electronic Microscopy (HR-TEM) have been used to characterize the crystalline structures. Colloidal suspensions were also obtained with these new diamond core-shells, by oxidation of their surface. Dissolving the silica core, diamond shells were also synthesized, exhibiting stable colloidal properties. Preliminary studies on diamond core-shells performances are also presented in this manuscript: their photocatalytic properties toward CO2 reduction and their in-vitro cytotoxicity considering further biological applications. Finally, the manuscript also reports on the extension of the process to magnetic silica cores for the synthesis of magnetic diamond core-shells.

Les études concernent le développement de dispositifs supraconducteurs de détection de photon unique. Le nitrure niobium (NbN) est un matériau adapté à l’élaboration de fils supraconducteurs de la cible du détecteur. Ces travaux ouvrent des perspectives sur l’élaboration de films de nitrure de niobium épitaxié sur saphir par la méthode de dépôt chimique en phase vapeur (CVD). L’élaboration des films minces (5-100 nm) est effectuée à haute température (1000°C à 1300°C) à partir de chlorure de niobium et d'ammoniaque dilués dans l'hydrogène (H2-NH3-NbCl5). Les substrats sont du saphir monocristallin (Al2O3) orienté (0002), du nitrure d'aluminium (AlN) orienté (0002) et de 'oxyde de magnésium (MgO) orienté (100).L'étude des relations d’épitaxie au cours de la croissance du nitrure de niobium sur le substrat de saphir a tout d'abord été effectuée. L’observation des microstructures et des orientations cristallines des différents films élaborés a permis de mettre en évidence les relations existant entre l'état de surface du substrat et le mode de croissance du NbN. Les perspectives d'utilisation de substrats monocristallins de type MgO et AlN sont présentées en conclusion.L’étude du procédé de croissance et les relations existant entre les conditions d'élaboration et la "qualité" des films minces a permis de dégager les fenêtres expérimentales conduisant à une croissance épitaxiale. L’énergie d’activation des réactions de croissance et les conditions de sursaturation propices à la croissance épitaxiale ont été calculées.L'étude des relations entre les propriétés structurales et les caractéristiques supraconductrices des films a permis de relier la température de transition supraconductrice à la densité de défauts atomiques, aux défauts microstructuraux, à l’épaisseur des films élaborés et à leur état de contrainte. Il existe une relation linéaire entre l’espace interréticulaire des plans parallèles au substrat et la température de transition supraconductrice.Enfin, l'étude de la durabilité des films ultraminces (5 – 8 nm) de nitrure de niobium a été menée. Dans cette étude les propriétés électriques et supraconductrices de films élaborés à 1000°C et 1200°C sur des substrats de saphir et de couches épitaxiales d'AlN ont été analysées sur une durée de six mois. Les propriétés des films évoluent surtout au cours du premier mois. Le dépôt effectué à haute température permet de limiter la dégradation rapide des films et de conserver leurs propriétés supraconductrices. / The studies concern the development of superconducting devices for single photon detection. Niobium nitride (NbN) is a material suitable for the production of superconducting wires for the detector target. This work is opening up perspectives on the development of epitaxial niobium nitride films on sapphire by the chemical vapor deposition (CVD) method. The production of thin films (5-100 nm) is carried out at high temperature (1000°C to 1300°C) from niobium chloride and ammonia diluted in hydrogen (H2-NH3-NbCl5). The substrate is oriented single crystalline sapphire (Al2O3) (0002), aluminum nitride (AlN) (0002) or magnesium oxide (MgO) (100).The study of epitaxial relationships during the growth of niobium nitride on the sapphire substrate was first performed. Observation of the microstructures and crystalline orientations of the various films processed made it possible to highlight the relationships between the surface state of the substrate and the growth mode of NbN. The potential for using single crystal substrates such as MgO and AlN is discussed in the conclusion.The study of the growth process and the relationships between the working conditions and the "quality" of thin films made it possible to identify the experimental windows leading to epitaxial growth. The activation energy of the growth reactions and the supersaturation conditions favorable to epitaxial growth were calculated.The study of the interactions between the structural properties and superconducting properties of films has allowed the superconducting transition temperature to be linked to the density of atomic defects, microstructural defects, the thickness of the films and their stress state. There is a linear relationship between the interplanar space of planes parallel to the substrate and the superconducting transition temperature.Finally, the durability of ultra-thin films (5 - 8 nm) of niobium nitride was studied. The electrical and superconducting properties of films processed at 1000°C and 1200°C on sapphire substrates and epitaxial layers of AlN were analyzed over a period of six months. The properties of films change most notably during the first month. High temperature deposition limits the rapid degradation of the films and preserves their superconducting properties.