Cette thèse porte sur l’étude de l’émissivité et de l’opacité dans les plasmas de fusion inertielle (FCI), et des processus atomiques dans les plasmas de fusion magnétique (FCM).En FCI, nous avons étudié les spectres d’émissivité du hohlraum de l’approche indirecte et d’opacité des dopants de l’ablateur. Leur connaissance permet d’améliorer la compression de la cible de D-T et ainsi favoriser les réactions de fusion. Nous avons caractérisé les spectres lié-lié de l’or, du carbone et du germanium au moyen de méthodes détaillées (code PPP) mais qui s’avèrent coûteuses en temps de calculs et limitées quand le nombre de niveaux/ions augmente. Pour optimiser le temps de calcul sans perdre en précision, une méthode hybride détaillée/statistique (code SCO-RCG) a fait l’objet de comparaison/validation avec le code PPP sur des cas tests. Cette approche a ensuite été appliquée au calcul de l’opacité totale (lié-lié, lié-libre, libre-libre) pour tous les états d’ionisation du germanium et du silicium. Les spectres obtenus sont ensuite comparés dans une large gamme d’énergies en vue d’optimiser la compression de la cible.En FCM, à partir d’expériences effectuées sur les tokamaks Tore Supra (CEA Cadarache) et ASDEX Upgrade (Max Planck Institut, Garching), nous nous proposons de développer une nouvelle base de données de physique atomique (sections efficaces, taux des processus,…) à l’aide du code HULLAC pour analyser des coefficients de transport. Le but de cette étude est la sensibilité aux données atomiques de la reconstruction des coefficients de transport par le code ITC. Pour le cas de l’argon, les sections efficaces de quelques processus sont présentées et les coefficients de taux sont comparés à ceux provenant du consortium ADAS. / The thesis is devoted on the study of emissivity and opacity in inertial confinement fusion plasmas (ICF), and on atomic processes in magnetic fusion plasmas (MCF).In ICF, we have studied the emissivity of the hohlraum and the opacity of ablator’s dopants in the indirect drive scheme. The knowledge of these quantities allows the improvement of the target compression and, as a consequence, the fusion reactions. We have characterized the bound-bound spectrum of gold, carbon and germanium with detailed line calculation (PPP code). Such calculations are time consuming and thus restricted to small numbers of levels/ions. To optimize the time calculation without lack of precision, a hybrid approach statistical/detailed (SCO-RCG code) was compared with the PPP code for test cases. Then the hybrid approach was applied to total opacity calculations (bound-bound, bound-free and free-free transitions) for each ionization state of germanium and silicon. The spectra are compared in a large temperature range in order to optimize the target compression.In MCF, from experiences carried out on Tore Supra (CEA Cadarache) and ASDEX Upgrade (Max Planck Institut, Garching) tokomak, we have provided new atomic data (cross sections, rates of processes) with the HULLAC code in order to analyze the transport coefficients. The aim of this study is the sensitivity of atomic data on the reconstruction of transport coefficients by the ITC code. For the argon case, the cross sections of some processes are presented and the rate coefficients are compared to those of ADAS consortium.

À l'heure actuelle, le développement dans les piles à combustible gagne un regard considérable pour la cogénération de l'énergie propre. Plus particulièrement, les piles à combustible à conduction protonique dont leurs électrolytes sont des oxydes de type pérovskite. Nous nous sommes intéressés aux électrolytes des piles de type PCFC « Proton Ceramic Fuel Cell » dont la température de fonctionnement est intermédiaire. L'intérêt porté pour l'amélioration de la diffusion du proton au sein de ces matériaux implique une compréhension fondamentale de l'interaction du proton avec son environnement. Cette problématique a conduit à une étude systématique en appliquant l'approche de la théorie de la fonctionnelle de la densité sur les matériaux de BaMxZr1-xO3 (M=Y, In et Sc ; x=12,5, 25 et 37,5%). Dans un premier temps, la validation de la méthode appliquée sur le système idéal de BaZrO3 et BaZr0,625Y0,375O3 a été nécessaire afin de reproduire les propriétés électroniques, structurales et de vibration de phonon en bon accord avec les résultats expérimentaux. Dans un deuxième temps, la variation des propriétés électroniques et structurales en fonction de la nature du dopant accepteur (M=Y, In et Sc), sa répartition dans le réseau, et sa concentration ont été étudiées. Une distorsion locale autour de l'atome dopant dans le réseau a été obtenue. Par conséquent, une baisse de symétrie du réseau a été déterminée. Cette distorsion est remarquée quel que soit la nature du dopant. La différence la plus marquée de l'effet de la nature du dopant est trouvée sur les charges atomiques des ions oxygène selon trois environnement possible : Zr-O(1)-Zr, Zr-O(2)-M et M-O(3)-M. Une diminution de la charge (et donc diminution de la basicité) sur le site O3 est bien remarquée dans BaMxZr1-xO3. On attribue cette diminution de charge à la formation d'une liaison covalente à caractère anti-liant Y-O2 (O3). La liaison est ionique pour Sc-O2(O3) et covalente de faible caractère liant pour In-O2 (O3). Nous avons poursuivi nos investigations sur l'insertion d'hydrogène dans les matériaux étudiés. L'analyse des propriétés électroniques, structurales, des vibrations de phonon et l'énergie d'interaction de l'hydrogène des structures BaMxZr1-xO3H, nous ont permis d'établir une corrélation entre le caractère de la liaison chimique M-O, l'insertion du proton et la force de la liaison O-H. L'insertion de H sur le site O3 dans BaYxZr1-xO3 (x=0,25 et 0,375) n'est pas obtenue, probablement à cause de la faible basicité de l'ion oxygène dans la configuration Y-O3-Y. L'insertion du H sur le site O3 pour les deux configurations In-O-In et Sc-O-Sc est obtenue dans BaInxZr1-xO3 (x=0,25 et 0,375) et BaScxZr1-xO3 (x=0,25 et 0,375) respectivement. La variation de l'énergie d'interaction de l'hydrogène avec son environnement dévoile une stabilisation des défauts protoniques significativement plus importante dans le cas de l'atome dopant accepteur yttrium que dans le cas des dopants In et Sc. L'analyse des fréquences de vibration de valence de la liaison O-H a montrée que cette liaison est plus forte dans BaInxZr1-xO3 et BaScxZr1-xO3 que dans BaYxZr1-xO3. En conclusion, nos résultats démontrent que le matériau BaZrO3 dopé en Y favorise plus la formation des défauts protoniques avec une liaison O-H moins forte que dans les matériaux baryum zirconates dopés en In et Sc. / At the present, the development of fuel cells gains a significant interest for their application in clean energy technologies, more specifically, the proton conducting fuel cells. We are interested in the perovskite oxides electrolytes used in PCFC fuel cell “Proton Ceramic Fuel Cell” which operates at intermediate temperature. The interest for the improvement of proton diffusion in these materials necessitates a fundamental systematic understanding of the proton interaction with its environment. Therefore we applied Density Functional Theory based approach on ideal BaZrO3 and doped barium zirconates BaMxZr1-xO3 (M=Y, Sc and In ; x=12.5, 25 and 37.5%), currently known among the best candidates for PCFC electrolytes. First, the validation of the method applied to the ideal system and BaY0.375Zr0.625O3 was necessary in order to reproduce the electronic, structural and phonon vibration in good agreement with the experimental results. Second, the variation of electronic and structural properties and of the phonon vibration was studied as a function of acceptor dopant nature, positions in the lattice and concentration. A local distortion around the dopant atom in the lattice was obtained. Therefore a reduction of the symmetry system has been determined. This distortion is noticeable regardless of the nature of the dopant. The most striking difference due to the dopant nature is found for the atomic charges on three possible oxygen environments : Zr-O(1)-Zr, Zr-O(2)-M and M-O(3)-M. A decrease in the atomic charge of O3 site (decrease of basicity) is well observed in BaYxZr1-xO3. This decrease in the charge can be attributed to the formation of a covalent anti-binding Y-O2(O3) bond. The binding is ionic for Sc-O2 and slightly covalent with a maximum of 15% covalency for In-O2. Our next investigations were focused on the insertion of hydrogen in the studied materials. The analysis of the computed electronic and structural properties, phonon vibrations and hydrogen interaction energies allowed us to establish a correlation between the nature of the chemical bonding M-O, the insertion energy of the proton and the O-H bond strength. The insertion of hydrogen in O3 site in BaYxZr1-xO3 (x=0.25 and 0.375) is not obtained, probably due to the low basicity of the oxygen ion in the configuration Y-O-Y. The insertion of H at the oxygen site for both In-O3-In and Sc-O3-Sc configurations found to be energetically favored in BaInxZr1-xO3 (x=0.25 and 0.375) and BaScxZr1-xO3 (x=0.25 and 0.375) respectively. The variation of hydrogen interaction energy with its environment reveals a significantly stronger stabilization of proton defects in the case of yttrium acceptor dopant than in the two other barium zirconates doped with In and Sc. The analysis of O-H stretching vibration frequencies has shown that the O-H bond is stronger in BaInxZr1-xO3 and BaScxZr1-xO3 than in BaYxZr1-xO3. In conclusion, our results show that the Y doped barium zirconate material favors the formation of proton defects, with a weaker O-H bond than in In and Sc doped oxides.

Electrical doping of organic semiconductors with molecular oxidants (p-type) or reductants (n-type) can greatly improve charge injection and conductivity in devices. Simple one electron reductants that are capable of reducing most electron-transport materials will inevitably also be sensitive to reaction with oxygen. Coupling electron transfer step with bond breaking/ making processes in principle can address this problem. The rhodocene dimer and related ruthenium and iridium dimeric sandwich compounds have been discussed as example of such n-dopants, reducing a variety of organic semiconductors to the corresponding radical anions, while forming monomeric cations. This class of n-dopants can be used in both vapor- and solution-processed devices, and the dopant monomer cations are large and, therefore, fairly stable with respect to diffusion. This thesis focused on increasing the utility of these and related electrical dopants. In order to reduce various electron-transport materials with lower electron affinities, which are frequently used in OLEDs, strategies and limitations to develop stronger n-dopants is discussed. Controlling the kinetics of the dopant / semiconductor reactions to allow film processing in ambient conditions, with activation of the dopants being carried out thermally or photochemically in subsequent steps is presented. An approach to covalently tether monomeric cations with themselves, surfaces or electron-transport materials is described. Electrochemical studies that further our understanding of dopant kinetics and thermodynamics is described. The dimer dopant chemistry is also compared to the corresponding hydride-reduced complexes of the cations and manganese tricarbonyl benzene dimer. The directions for future dopant design with improved properties is discussed.

Les matériaux ferroélectriques de type pérovskite PbTiO3 et LiNbO3 présentent un grand intérêt en raison de l'existence de phase ferroélectrique, et la possibilité de modifier leurs propriétés physiques par de nombreuses substitutions ioniques. De plus ces matériaux présentent des propriétés physiques, diélectriques, électro-optiques, optiques non linéaires et électroniques performantes, qui en font des matériaux très utilisés dans de nombreuses applications dans différents domaines. Le travail de cette thèse concerne la synthèse et l'étude des propriétés physicochimiques des pérovskites de type PT:Mg et LN:Mg ou LN:Ho sous forme de poudres, céramiques et le tirage de fibres cristallines à partir de ces poudres. L'intérêt de notre travail, a porté sur l'étude du rôle des dopants, de leur incorporation dans la structure cristalline hôte et l'étude de leurs effets sur les propriétés physiques et fonctionnelles. Les résultats obtenus montrent que le Mg affecte la quadracité du PT, il intègre le site A avant 10% en Mg au-delà, il intègre les deux sites A et B. L'analyse diélectrique montre que le composé conserve le comportement d'un ferroélectrique classique en montée en température, par contre en descente, le composé présente un comportement relaxeur. Les caractérisations structurales montrent que l'incorporation du dopant (Mg ou Ho) dans la maille du LN induit une déformation du réseau cristallin. Jusqu'à 5% mol, le Mg substitut le Li (site A), réduit le nombre des défauts intrinsèques (Nb en antisite) et diminue l'intensité de la photoluminescence. Au-delà, il intègre les deux sites A et B. l'holmium incorpore le LN et n'affecte pas l'intensité de la photoluminescence, il intègre la maille en site interstitiel. Nous avons tiré des fibres cristallines de LN et LN:Ho2% par la méthode µ-PD, les fibres obtenues, de longueur de quelques centimètres avec un diamètre inférieur au mm. La caractérisation de ces fibres montre que sont de LN et leurs propriétés peuvent être améliorées par des traitements thermiques / The ferroelectric materials of the perovskite type PbTiO3 and LiNbO3 have of great interest because of the existence of ferroelectric phase, and the possibility of modifying their physical properties by many ionic substitutions. In addition, these materials have physical properties, dielectric, electro-optical, dielectrics, non-linear optical and the performing electronics, who make materials very much used in many applications in various fields. The work of this thesis concerns the synthesis and study of physicochemical properties of perovskites type PT: Mg and LN: Mg or LN: Ho in the form of powders, ceramics and pulling crystalline fibers from these powders. The interest of our work, has focused on studying the role of dopants, the incorporation into the host crystal structure and study of their effects on the physical and functional properties. The results show that Mg affects the quadracité PT, it integrates the Site before 10% Mg, beyond it integrates the two sites A and B. The dielectric analysis shows that the compound retains the behavior of a classical ferroelectric in temperature mounted, for against by descent, the compound exhibits a relaxor behavior. The structural characterizations show that the incorporation of the dopant (Mg or Ho) in the stitch of LN induced a deformation of the crystal stitch. Up to 5% mol the Mg substitute Li (Site A), reduced the number of intrinsic defects (Nb antisite) and decreases the intensity of the photoluminescence. Beyond, it integrates the two sites A and B. holmium incorporates the LN and does not affect the intensity of the photoluminescence, it integrates the stitch in interstitial site. We pulled the crystalline fibers LN and LN: Ho2% by the µ-PD method, the fibers obtained, a few centimeters in length with a diameter less than to mm. The characterization of these fibers shows that are the LN and their properties can be improved by the heat treatments

[pt] Neste trabalho foram obtidos filmes de grafeno usando um precursor sólido, a Trifenilfosfina, num processo de deposição química na fase vapor em alto vácuo (HVCVD). A microscopia eletrônica de Varredura permitiu observar a presença de pequenas regiões inomogêneas na superfície das amostras crescidas. Estas regiões foram observadas na microscopia antes e após o processo de transferência da folha de cobre para o substrato de silício oxidado. Medidas realizadas por XPS permitiram comprovar a incorporação de fósforo no filme crescido. A espectroscopia Raman foi usada para determinar a temperatura de trabalho adequada no sistema de crescimento. A presença de grafeno foi confirmada em todas as amostras, mas observou-se que, em geral, a quantidade de defeitos nas amostras cresceu com o aumento da massa do precursor utilizado no crescimento. Os resultados obtidos são discutidos à luz de recentes trabalhos teóricos que tratam do uso da técnica Raman no estudo de defeitos em grafeno. / [en] In this work graphene films were obtained using a solid precursor, Triphenylphosphine, by chemical vapor deposition in high vacuum (HVCVD). Scanning electron microscopy allowed to observe the presence of small inhomogeneus regions on the surface of the grown samples. These regions were observed in the microscopy before and after the transfer process from the copper foil to silicon oxidized wafer. XPS measurements checked the incorporation of phosphorus in the film grown. Raman spectroscopy was used to determine the suitable working temperature in the growth system. The presence of graphene was confirmed in all samples, but it was observed that in general, the amount of defects in the samples increased with increasing the mass of the precursor used in growth. The results are discussed in light of recent theoretical works that address the use of Raman technique in the study of defects in graphene.

Durant ces dernières années, l’apparition de nouvelles architectures (FDSOI, FinFETs ou NW-FETs) et l’utilisation de nouveaux matériaux (notamment SiGe) ont permis de repousser les limites des performances des dispositifs MOS et de contourner l’effet canal court inhérent à la miniaturisation des composants. Cependant, pour toutes ces nouvelles architectures, la résistance de contact se dégrade au fil des nœuds technologiques. Celle-ci dépend fortement de deux paramètres physiques : la concentration de dopants actifs proches de la surface du semi-conducteur et de la hauteur de barrière Schottky du contact siliciuré. De multiples procédés avancés ont été proposé pour améliorer ces deux paramètres physiques (pré-amorphisation, recuit laser, ségrégation de dopants, etc…). Afin d’optimiser les conditions expérimentales de ces nouvelles techniques de fabrication, il est primordial de pouvoir caractériser avec fiabilité leur impact sur les deux grandeurs physiques citées. Dans le cadre de cette thèse, deux thématiques dédiées à l’étude de chacun des paramètres sont abordées, explicitant les méthodes de caractérisation développées ainsi que des exemples concrets d’applications. La première partie concerne l’étude de la concentration de dopants actifs proches de la surface du semi-conducteur. Dans cet axe, nous avons mis en place une méthode d’Effet Hall Différentiel (DHE). Cette technique combine gravures successives et mesures par effet Hall conventionnel afin d’obtenir le profil de concentration de dopants actifs en fonction de la profondeur. Nous avons développé et validé une méthode de gravure chimique et de mesure électrique pour des couches ultra-minces de SiGe et de Si dopées. Les profils de concentration générés ont une résolution en profondeur inférieure à 1 nm et ont permis d’étudier de façon approfondie dans les premiers nanomètres proches de la surface de couches fabriquées grâce à des techniques d’implantation et de recuit avancées comme par exemple, la croissance en phase solide activée par recuit laser. La deuxième partie porte sur la mesure de hauteurs de barrière Schottky pour des contacts siliciurés. Durant cette étude, nous avons transféré une technique se basant sur des diodes en tête bêche pour caractériser l’impact de la ségrégation de différentes espèces à l’interface siliciure/semi-conducteur sur la hauteur de barrière Schottky d’un contact en siliciure de platine. Cette méthode de mesure associée à des simulations physiques a permis d’une part, d’extrairer avec fiabilité des hauteurs de barrières avec une précision de 10meV et d’autre part, d’effectuer une sélection des meilleures conditions de ségrégation de dopants pour la réduction de la hauteur de barrière Schottky. Pour conclure, ce projet a rendu possible le développement de méthodes de caractérisation pour l’étude de matériaux utilisés en nanoélectronique. De plus, nous avons pu apporter des éclaircissements concernant l’impact de techniques d’implantation ionique alternatives sur des couches de Si et SiGe ultrafines, et ce, dans le but de réduire la résistance de contact entre siliciure et semi-conducteur dans le module source-drain de transistors ultimes. / During the past few decades, the emergence of new architectures (FDSOI, FinFETs or NW-FETs) and the use of new materials (like silicon/germanium alloys) allowed to go further in MOS devices scaling by solving short channel effect issues. However, new architectures suffer from contact resistance degradation with size reduction. This resistance strongly depends on two parameters: the active dopant concentration close to the semi-conductor surface and the Schottky barrier height of the silicide contact. Many solutions have been proposed to improve both of these physical parameters: pre-amorphisation, laser annealing, dopant segregation and others. In order to optimize the experimental conditions of these fabrication techniques, it is mandatory to measure precisely and reliably their impact on cited parameters.Within the scope of this thesis, two parts are dedicated to each lever of the contact resistance, each time precising the developed characterization method and concrete application studies. The first part concerns the study of the active dopant concentration close to the semi-conductor surface. In this axis, we developed a Differential Hall Effet method (DHE) which can provide accurate depth profiles of active dopant concentration combining successive etching processes and conventional Hall Effect measurements. To do so, we validated layer chemical etching and precise electrical characterization method for doped Si and SiGe. Obtained generated profiles have a sub-1nm resolution and allowed to scan the first few nanometers of layers fabricated by advanced ion implantation and annealing techniques, like solid-phase epitaxy regrowth activated by laser annealing. In the second part, we focused on the measurement of Schottky barrier height of platinum silicide contact. We transferred a characterization method based on back-to-back diodes structure to measure platinum silicide contacts with different dopant segregation conditions. The electrical measurements were then fitted with physical models to extract Schottky barrier height with a precision of about 10meV. This combination between measurements and simulations allowed to point out the best ion implantation and annealing conditions for Schottky barrier height reduction.To conclude, thanks to this project, we developed highly sensitive characterization methods for nanoelectronics application. Moreover, we brought several clarifications on the impact of alternative ion implantation and annealing processes on Si and SiGe ultra-thin layers in the perspective of contact resistance reduction in FDSOI source-drain module.

Em processos de crescimento de cristais pelo método de Czochralski, é observado que um campo elétrico aplicado ao cristal durante o processo de crescimento modifica a quantidade de dopante incorporada ao cristal. É desenvolvido um modelo, baseado na teoria de Burton, Prim e Slichter, levando-se em consideração as duas classes de material envolvidas, os óxidos e os semicondutores, e os efeitos produzidos pelo campo elétrico, eletromigração, subresfriamento constitucional, Efeito Peltier e efeito Seebeck. Resultados experimentais obtidos em crescimentos de LiNbO3:Cr2O3 e Si:Al são usados para aplicações do modelo / In crystal growth processes through the Czochralski method, it is observed that an electrical field applied to the crystal during the growth process modifies the quatity of the dopant incorporated to the crystal. A model is developed based on Burton, Prim and Slichter´s theory, taking into consideration two classes of materials, the oxides and the semiconductors, and the effects produced by the electrical field, electromigration, constitutional supercooling, Peltier Effect, Seebeck Effect. Experimental results obtained from the growth of the LiNbO3:Cr2O3 e Si:Al singlecrystals are used to the model application

A busca pelo aprimoramento de materiais nanocristalinos baseia-se na variação do processo de síntese e na alteração de sua estrutura através da inserção de defeitos na estrutura cristalina. O processo de dopagem tem sido considerado de fundamental importância para estabilizar determinadas fases ou faces cristalinas. Por outro lado, o uso de uma metodologia de síntese versátil como a síntese hidrotérmica e solvotérmica mostra-se como uma proposta interessante para obter materiais já produzidos por técnicas convencionais, mas que apresentam propriedades diferenciadas. Nesse trabalho, verificou-se o efeito do método de síntese utilizado e da adição de íons dopantes como Mg+2 e Ni+2 nas propriedades morfológicas e estruturais do composto titanato de cálcio (CaTiO3) que foi preparado através dos métodos hidrotérmico e solvotérmico. Através das técnicas de difração de raios X e microscopia eletrônica de varredura, foi verificado o efeito dos parâmetros de síntese (tempo e temperatura) e dos materiais precursores nas propriedades estruturais e microestruturais das amostras. Na avaliação de fotoatividade realizada (fotodegradação do corante rodamina B) foi observado que os compostos sintetizados pelo método hidrotérmico com os precursores oxisulfato de titânio e cloreto de cálcio apresentaram melhor atividade fotocatalítica que os compostos sintetizados pelo método solvotérmico (solvente PEG-200). / The search for the improvement of nanocrystalline materials is based on the variation of the synthesis process and the modification of its structure through the insertion of defects in its crystalline structure. The doping process has been considered of fundamental importance to stabilize certain crystalline phases or faces of nanomaterials. On the other hand, the use of a versatile synthesis methodology such as hydrothermal and solvothermal methods is an interesting proposal to obtain materials already produced by conventional techniques, but with different properties. In this work, the effect of the synthesis method and the addition of dopant ions such as Mg+2 and Ni+2 on the morphological and structural properties of the calcium titanate (CaTiO3) compound was verified, which was prepared by hydrothermal and solvothermal methods. The effect of the synthesis parameters (time and temperature) and the precursor materials on the structural and microstructural properties of the samples were verified by means of the X-ray diffraction and scanning electron microscopy techniques. It was observed that the compounds synthesized by the hydrothermal method with the titanium oxysulfate and calcium chloride precursors presented better photocatalytic activity than the compounds synthesized by the solvothermal method (solvent PEG-200).

Os compostos semicondutores ternários, dentre eles o Ga1-xInxSb, têm sido objeto de interesse de pesquisadores e da indústria microeletrônica devido à possibilidade de ajuste da constante de rede, assim como a correspondente modificação da banda proibida de energia e do intervalo de emissão e absorção óptica, com a variação da fração molar de x. A flexibilidade destas propriedades estruturais torna este composto apropriado como substratos para epitaxias de outros compostos ternários e quaternários, na formação de mono e heterojunções. A maneira mais econômica para obtenção de substratos de materiais semicondutores é através do crescimento de cristais a partir da fase líquida. Porém, os parâmetros que regem a obtenção de lingotes de Ga1-xInxSb com qualidade comercial, a partir da fase líquida, ainda não estão bem definidos. O índio tende a segregar para o líquido, pois seu coeficiente de segregação é menor que a unidade (k < 1), resultando num perfil composicional variado ao longo do lingote. Como os binários GaSb e InSb apresentam configurações de defeitos intrínsecos que originam condutividades de tipos opostos, tipo p e tipo n, respectivamente, a mudança na composição da liga, durante o crescimento, provavelmente resulta na modificação da concentração de cada um destes defeitos. A dopagem com telúrio consiste numa alternativa para minimizar a segregação do índio e diminuir a densidade dos defeitos pontuais, melhorando a qualidade estrutural de cristais de Ga1-xInxSb obtidos através do método Bridgman convencional. Desta forma foram crescidos cristais ternários Ga1-xInxSb, com e sem agitação do líquido durante a síntese, com fração molar inicial de índio de 10% e 20%, alguns deles dopados com 1020 átomos/cm3 de telúrio, pelo método Bridgman vertical. A caracterização estrutural em termos de formação de defeitos lineares, interfaciais e volumétricos foi realizada através de imagens obtidas por microscopia óptica, eletrônica de varredura e de transmissão. A homogeneidade composicional e distribuição de fases foi avaliada através de medidas de espectroscopia por dispersão de energia. Medidas de resistividade e efeito Hall foram utilizadas para a caracterização elétrica, enquanto que a transmitância óptica e a banda proibida de energia foram avaliadas por espectrometria FTIR. Os padrões de difração obtidos através da microscopia eletrônica de transmissão foram utilizados para avaliar a cristalinidade das amostras e determinar o parâmetro de rede. Os resultados obtidos indicam que o telúrio atua de forma compensatória, minimizando a segregação de índio e contribuindo para a homogeneidade composicional e redução de defeitos, principalmente de discordâncias. Além disso, altera a condutividade do Ga1-xInxSb para tipo n, mesmo em frações molares de In inferiores a x = 0,5, diminuindo o número de cargas positivas na rede atribuídas aos defeitos tipo GaSb e VGaGaSb e, desta forma, aumenta a concentração de portadores de carga e reduz a resistividade. Na condição de alta dopagem, reduz a transmitância óptica no infravermelho e aumenta a banda proibida de energia através do efeito Burstein-Moss. A avaliação de cristais de Ga1-xInxSb, dopados e não dopados, crescidos pelo método Bridgman convencional contribuiu para o entendimento do comportamento de dopantes em compostos semicondutores ternários. / Ternary compound semiconductors, including Ga1-xInxSb, have been subject of interest of researchers and microelectronics industry because of the possibility of adjusting the lattice constant, as well as the corresponding modification in the band gap energy, and in the optical absorption and emission range, by varying the mole fraction x. The flexibility of their structural properties makes this compound suitable as substrates for epitaxy of other ternary and quaternary compounds, in the formation of mono- and heterojunctions. The most economical way to obtain semiconductor substrates is by crystal growth from the liquid phase. However, the parameters governing the outcoming of Ga1-xInxSb ingots with commercial quality, from liquid phase, are not well defined. Indium tends to segregate to the liquid, since its segregation coefficient is less than the unity (k < 1), resulting in a varied compositional profile along the ingot. As the binary GaSb and InSb have intrinsic defects configurations that originate opposite conductivities, type p and type n, respectively, the change in the alloy composition, while growing, probably results in a modification of the concentration on each of these defects. Doping with tellurium is an alternative to minimize the indium segregation and decrease the density of point defects, therefore improving the structural quality of Ga1-xInxSb crystals obtained through the conventional Bridgman method. Thus, ternary Ga1-xInxSb crystals were grown by vertical Bridgman method with and without stirring the melt during the synthesis, with 10% and 20% initial molar fraction of indium and some of them were tellurium-doped at 1020 atoms/cm3. The structural characterization regarding linear, interfacial, and volumetric defects formation was performed by using images obtained through optical, scanning and transmission electron microscopy. The compositional homogeneity and phase distribution was assessed by energy-dispersive spectroscopy measurements. Resistivity and Hall Effect measurements were used for the electrical characterization, while the optical transmittance and the band gap energy were examined by FTIR spectroscopy. Diffraction patterns obtained by transmission electron microscopy were used to evaluate the crystallinity of the samples and determine the lattice parameter. The results indicate that tellurium acts in a compensatory way, minimizing indium segregation and contributing to the compositional homogeneity and defect reduction, especially in dislocations. In addition, it changes the conductivity of Ga1-xInxSb to n-type, even in mole fraction of In lower than x = 0.5, reducing the number of positive charges on the network assigned to GaSb and VGaGaSb defects, thus increasing the concentration of charge carriers and reducing the resistivity. In high doping condition, it reduces the optical transmittance in the infrared region and increases the energy of the band gap by the Burstein-Moss Effect. The evaluation of Ga1-xInxSb crystals, doped and undoped, grown by the conventional Bridgman method contributed to the understanding of dopants behavior in ternary compound semiconductors.

A busca pelo aprimoramento de materiais nanocristalinos baseia-se na variação do processo de síntese e na alteração de sua estrutura através da inserção de defeitos na estrutura cristalina. O processo de dopagem tem sido considerado de fundamental importância para estabilizar determinadas fases ou faces cristalinas. Por outro lado, o uso de uma metodologia de síntese versátil como a síntese hidrotérmica e solvotérmica mostra-se como uma proposta interessante para obter materiais já produzidos por técnicas convencionais, mas que apresentam propriedades diferenciadas. Nesse trabalho, verificou-se o efeito do método de síntese utilizado e da adição de íons dopantes como Mg+2 e Ni+2 nas propriedades morfológicas e estruturais do composto titanato de cálcio (CaTiO3) que foi preparado através dos métodos hidrotérmico e solvotérmico. Através das técnicas de difração de raios X e microscopia eletrônica de varredura, foi verificado o efeito dos parâmetros de síntese (tempo e temperatura) e dos materiais precursores nas propriedades estruturais e microestruturais das amostras. Na avaliação de fotoatividade realizada (fotodegradação do corante rodamina B) foi observado que os compostos sintetizados pelo método hidrotérmico com os precursores oxisulfato de titânio e cloreto de cálcio apresentaram melhor atividade fotocatalítica que os compostos sintetizados pelo método solvotérmico (solvente PEG-200). / The search for the improvement of nanocrystalline materials is based on the variation of the synthesis process and the modification of its structure through the insertion of defects in its crystalline structure. The doping process has been considered of fundamental importance to stabilize certain crystalline phases or faces of nanomaterials. On the other hand, the use of a versatile synthesis methodology such as hydrothermal and solvothermal methods is an interesting proposal to obtain materials already produced by conventional techniques, but with different properties. In this work, the effect of the synthesis method and the addition of dopant ions such as Mg+2 and Ni+2 on the morphological and structural properties of the calcium titanate (CaTiO3) compound was verified, which was prepared by hydrothermal and solvothermal methods. The effect of the synthesis parameters (time and temperature) and the precursor materials on the structural and microstructural properties of the samples were verified by means of the X-ray diffraction and scanning electron microscopy techniques. It was observed that the compounds synthesized by the hydrothermal method with the titanium oxysulfate and calcium chloride precursors presented better photocatalytic activity than the compounds synthesized by the solvothermal method (solvent PEG-200).