Boron nitride is found mainly in two crystal structures / in hexagonal structure (h-BN) which is very much like graphite and in cubic structure (c-BN) with properties very close to those of diamond. h-BN is a natural lubricant due to its layered structure. It is generally used in sliding parts of the moving elements such as rotating element beds in turbine shafts. Since c-BN is the hardest known material after diamond it is used in making hard metal covers. In addition to its possible microelectronics applications (can be used to make p-n junction), its resistance to high temperatures and its high forbidden energy gap are its superiorities over diamond. Recent studies have shown that c-BN can be produced by Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD) in plasma. But these studies have failed to determine how all of the production parameters (boron and nitrogen sources, composition of the gas used, substrate, RF power, bias voltage, substrate temperature) affect the c-BN content, mechanical stress and the deposition rate of the product with a systematic approach. The systematic study was realized in the range of available experimental ability of the present PVD and CVD equipment and accessories. The BN films were produced in the plasma equipment for CVD using RF and MW and magnetron sputtering and were studied with the measurement and testing facilities. It is believed that with this approach it will be possible to collect enough experimental data to optimize production conditions of BN with desired mechanical and optoelectronic properties. h-BN films were successfully deposited in both systems. It was possible to deposit c-BN films with the MW power, however they were weak in cubic content. Deposition at low pressures eliminated the hydrogen contamination of the films. High substrate temperatures led to more chemically and mechanically stable films.

abstract: Cubic boron nitride (c-BN) has potential for electronic applications as an electron emitter and serving as a base material for diodes, transistors, etc. However, there has been limited research on c-BN reported, and many of the electronic properties of c-BN and c-BN interfaces have yet to be reported. This dissertation focused on probing thin film c-BN deposited via plasma enhanced chemical vapor deposition (PECVD) with in situ photoelectron spectroscopy (PES). PES measurements were used to characterize the electronic properties of c-BN films and interfaces with vacuum and diamond. First, the interface between c-BN and vacuum were characterized with ultraviolet PES (UPS). UPS measurements indicated that as-deposited c-BN, H2 plasma treated c-BN, and annealed c-BN post H2 plasma treatment exhibited negative electron affinity surfaces. A dipole model suggested dipoles from H-terminated N surface sites were found to be responsible for the NEA surface. Then, Si was introduced into c-BN films to realize n-type doped c-BN. The valence structure and work function of c-BN:Si films were characterized with XPS and UPS measurements. Measurements were unable to confirm n-type character, and it is concluded that silicon nitride formation was the primary effect for the observations. Finally, XPS measurements were employed to measure the band offsets at the c-BN/diamond interface. Measurements indicated the valence band maximum (VBM) of c-BN was positioned ~0.8 eV above the VBM of diamond. / Dissertation/Thesis / Doctoral Dissertation Physics 2016

Cette thèse se place dans le contexte des recherches menées sur l'élaboration de support de haute qualité cristalline pour des applications optoélectronique et piézoélectrique. Les nitrures d'aluminium, AlN, et de bore, BN sont deux matériaux présentant des propriétés physiques intéressantes pour leurs utilisations en tant que substrat et partiellement comme couche active dans de telles applications. Les objectifs de cette thèse étaient de continuer les travaux en cours sur l'hétéroépitaxie d'AlN (avec le mélange H2 – NH3 – AlCl3 en phase gazeuse) sur substrat saphir et silicium, et d'explorer la croissance de BN par dépôt chimique en phase vapeur (CVD) à haute température avec une chimie chlorée (mélange.H2 – NH3 – BCl3 en phase gazeuse). Des études thermodynamiques ont été menées pour évaluer les équilibres ayant lieu entre la phase gazeuse et les matériaux en présence sur une large gamme de température. Ces premiers résultats ont permis d'en déduire des conditions opératoires favorables afin d'éviter toutes réactions parasites qui nuiraient à la croissance des nitrures. Plusieurs études expérimentales ont été effectuées sur les réacteurs du SIMaP. Une étude de l'influence du ratio N/Al dans la phase gazeuse sur la croissance d'AlN a été entreprise. Par la suite les mécanismes de croissance de ces couches sont expliqués afin de comprendre l'effet de ce paramètre. Suite à cela, des dépôts avec plusieurs étapes de croissances à différente température ont permis l'obtention de couches d'AlN peu fissurées, peu contraintes et avec des qualités cristallines satisfaisantes. Concernant le dépôt de BN, des essais ont été menés sur substrats AlN et métalliques (chrome et tungstène). À haute température (1600 °C), le dépôt sur AlN a permis l'obtention de couche turbostratique peu désorientée. La croissance sur substrats métalliques a été effectuée à basse température, ne favorisant pas l'épitaxie de BN sur ces substrats. Enfin, des comparaisons ont été menées entre température de dépôt, vitesse de croissance des couches et sursaturation de la phase gazeuse, permettant la délimitation de domaine de conditions opératoire où l'épitaxie est favorisée. / This work takes place in the context of the development of high crystalline quality supports for optoelectronic and piezoelectric fields. Aluminum and boron nitrides (AlN, and BN) are both materials with interesting physical properties that are used like substrate or active layers in such devices. The aims of this thesis were to continue the work in progress about AlN epitaxy in SIMaP, and to explore the growth of BN by chemical vapor deposition (CVD) with halide chemistry at high temperature. Thermodynamical studies were lead in order to evaluate the equilibrium between the gas phase and the materials in a wide range of temperature. The results were used to choose operating conditions in order to avoid parasitic reactions that could decrease the nitrides growth quality. Several experimental studies were done to evaluate the influence of the N/Al ratios in the gas phase. Growth mechanisms of these layers are explained and consequences of the growth are linked to crystal quality and strain states of the films. Next, multi-steps growth with several temperatures was lead and shows an interesting improvement of the crystal quality and strain state. BN deposits were done on AlN and metallic substrates (chromium and tungsten). High temperature growth was performed on AlN and lead high quality turbostratic films. For lower temperature, BN deposits were done on metallic substrates and lead to the growth of the turbostratic phase. Finally, a comparison between deposition temperature, the growth speed of the films and supersaturation of the gas phase allow to estimate operating conditions domains were the epitaxy of the nitrides are predominant.

Le graphène possède un gaz bidimensionnel de porteurs de charge stable et exposé à l'environnement sans aucune protection. Par conséquent, ses performances électriques sont extrêmement sensibles aux conditions environnementales, notamment aux impuretés chargées et aux corrugations imposées par le substrat sous-jacent. Ces éléments ont une contribution majeure dans la dégradation des propriétés de transport électronique du matériau.L'objectif de cette thèse est d'explorer par diverses techniques des méthodes pour atténuer ces effets par optimisation de son environnement direct.La première méthode consiste à reporter le graphènesur une couche neutre d'un cristal de nitrure de bore hexagonal (BN). Diverses techniques de fabrication d'empilement de Graphène sur BN sont présentées, notamment la croissance directe de graphène sur un cristal de BN exfolié sur un substrat catalytique qui aboutit à la formation d'empilements de structure bien contrôlée. Les échantillons sont mesurés à très basse température. Les effets de localisation faible mesurés par magnéto-transport montrent une amélioration nette des performances notamment de la longueur de cohérence et de la mobilité électronique par rapport à un échantillon de référence constitué du même ruban de graphène déposé sur substrat conventionnel de silicium oxydé.La deuxième technique consiste à isoler le graphène de son support par surgravure de la silice et suspension du graphène sous la forme d'une membrane autosupportée et tenue par ses extrémités. Après avoir introduit des techniques de fabrication spécifiques, les mesures de transport et le couplage à des modes de vibration mécanique sont étudiés température variable. Ces données permettent notamment une mesure du coefficient d'expansion thermique du graphène. / Charge carriers in graphene form stable two-dimensional gases which are fully exposed to the environment. As a consequence, the electrical performance of graphene is strongly affected by surface charged impurities as well as topographic perturbations inherited from the underlying substrate.This thesis addresses several methods to circumvent that issue.The first method consists in embedding graphene in an optimized environment by depositing graphene onto some neutral and crystalline material. Novel 2D insulating materials such as hexagonal boron nitride buffer layer (BN) appears as ideal substrates to get rid of detrimental effect of interfacial charges and corrugation. Several fabrication schemes of Graphene/BN stacks are shown including some direct in-situ growth of graphene on BN crystal using an innovative proximity-driven chemical vapour growth based on BN exfoliation on copper. In order to explore the effects of the improved substrate on the transport properties of graphene, we have performed low temperature magneto-transport studies on these stacks. We present a direct comparison of weak localization signals with those acquired on a graphene/silica reference device. A clear increase of the coherence length is shown on Graphene/BN stacks together with improved electronic mobility and charge neutrality.Removing the substrate and suspending graphene is another approach for optimization of the graphene environment which forms the second topic covered in this thesis. After introducing an improved recipe for preserving the quality of graphene throughout an elaborate fabrication process, we probe the room- and low-temperature performance of the nano-electro-mechanical devices based on doubly clamped suspended graphene ribbons. The obtained data are used for characterizing the thermal expansion of CVD graphene.

Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-11T13:33:18Z No. of bitstreams: 1 arquivototal.pdf: 2568503 bytes, checksum: df847883585ac25cc1e993ba9c1fcd9f (MD5) / Made available in DSpace on 2017-09-11T13:33:18Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2568503 bytes, checksum: df847883585ac25cc1e993ba9c1fcd9f (MD5) Previous issue date: 2017-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The opening a energy gap in graphene is probably one of the most important and urgent topics in its research currently, since most of the proposed applications for graphene in nanoelectronic devices require the ability to adjust its gap. In materials similar to graphene as BN and BC2N, the tuning of some properties is also indispensable so that they can be used as basic components of future nanoelectronic and spintronic. Graphene nanoribbons are strong candidates in this regard. All these systems have widely tunable properties and there are several theoretical and experimental methods which can be used for this purpose, one of them is to incorporate defects, since these defects have been obtained experimentally in these systems. In this context, using first-principles calculations, based on the density functional theory (DFT), we investigate alterations in the structural, electronic, energetic and magnetic properties due to the inclusion of different types of defects in monolayers and nanoribbons of graphene, BN and hybrid graphene-BC2N. As a result of the controlled inclusion of these defects, a series of new results were observed, as well as the tuning of the structural, electronic, energetic and magnetic properties in these systems. / A abertura de um gap de energia no grafeno é provavelmente um dos temas mais importantes e urgentes em sua pesquisa atualmente, uma vez que, a maioria das aplicações propostas para o grafeno em dispositivos nanoeletrônicos requer a capacidade de ajustar seu gap. Em materiais similares ao grafeno como BN e o BC2N o ajuste de algumas propriedades também é indispensável para que eles possam fazer parte como componentes ativos na nanoeletrônica e spintrônica no futuro. As nanofitas são fortes candidatas nesse sentido. Todos esses sistemas possuem propriedades bastante ajustáveis e existem vários métodos teóricos e experimentais que podem ser usados para este fim, um deles, é a inclusão de defeito, defeitos têm sido obtido experimentalmente nesses sistemas. Neste contexto, usando cálculos de primeiros princípios baseados na teoria do funcional da densidade (DFT), investigamos as mudanças provocadas nas propriedades eletrônicas, energéticas, estruturais e magnéticas devido à inclusão de vários tipos de defeitos em monocamadas e nanofitas de grafeno, BN e híbridas de grafeno-BC2N. Como resultado da inclusão controlada desses defeitos, observamos uma série de novos resultados, bem como o ajuste de várias propriedades para esses sistemas através da inclusão controlada de defeitos.

De nos jours, les produits chimiques toxiques industriels ne sont pas toujours traités proprement, et leurs contaminants peuvent directement affecter la sécurité de l'eau potable. La photocatalyse, «une technologie verte» est une approche efficace et économique qui joue un rôle important dans la conversion de l'énergie solaire et la dégradation des polluants organiques. Ce manuscrit de thèse rapporte sur le développement des matériaux avancés (basés sur TiO2 et ZnO) susceptibles d'exploiter l'énergie solaire renouvelable pour résoudre les problèmes de pollution environnementale. Une partie de ce travail a été consacrée pour l’amélioration de l’activité photocatalytique du TiO2 sous lumière UV et visible. Par conséquent, les nanofibres composites de rGO/TiO2, BN/TiO2 et BN-Ag/TiO2 ont été élaborées en utilisant la technique d'électrofilage (electrospinning). La deuxième partie porte sur le ZnO, ainsi que les nanotubes multi co-centriques de ZnO/ZnAl2O4 et les nanotubes de ZnO dopés Al2O3 qui ont été synthétisés en combinant les deux techniques : dépôt de couche atomique (ALD) et electrospinning. Les propriétés morphologiques, structurelles et optiques de toutes les nanostructures synthétisées ont été étudiées par différentes techniques de caractérisations. Les résultats ont montré que les propriétés chimiques et physiques ont un effet très important sur les propriétés photocatalytiques des matériaux synthétisés. En outre, il a été constaté que l'effet de dopage conduit à une séparation de charge efficace dans le photocatalyseur, ce qui rend l’activité photocatalytique plus efficace. De plus, le méthyle orange et le bleu de méthylène ont été utilisés comme modèle de référence. Une amélioration significative et une stabilité à long terme de l’activité photocatalytique ont été observées avec les matériaux dopés comparés aux matériaux non-dopés sous lumière UV et visible. Des tests antibactériens contre Escherichia coli ont été également effectués; les résultats indiquent que BN-Ag/TiO2 présente à la fois des propriétés photocatalytiques intéressantes pour la dégradation des composés organiques et pour l'élimination des bactéries. / Nowadays, industrial toxic chemicals are still not properly treated and these contaminants may directly impact the safety of drinking water. Photocatalysis “a green technology” is an effective and economical approach and plays an important role in solar energy conversion and degradation of organic pollutants. This thesis manuscript reports on developing advanced materials (based on TiO2 and ZnO) being capable of exploiting renewable solar energy for solving the environmental pollution problems. A part of this work was dedicated to improve the UV and visible light TiO2 photoresponse. Therefore, rGO/TiO2, BN/TiO2 and BN-Ag/TiO2 composties nanofibers were successfully elaborated using the electrospinning technique. The second part focused on ZnO. Novel structures of ZnO/ZnAl2O4 multi co-centric nanotubes and Al2O3 doped ZnO nanotubes were designed by combining the two techniques of atomic layer deposition (ALD) and electrospinning. The morphological, structural and optical properties of all synthesized nanostructures were investigated by several characterization techniques. The results show that the chemical and physical properties have a high impact on the photocatalytic properties of the synthesized materials. Moreover, it was found that the doping effect lead to a more efficient charge separation in the photocatalyst, which is an advantage for photocatalytic activities. In addition, methyl orange and methylene blue were used as model reference. A significant enhancement and a long-term stability in the photocatalytic activity were observed with the doped materials compared to the non-doped ones under both UV and visible light. Antibacterial tests against Escherichia coli have also been performed; the results indicate that BN-Ag/TiO2 present interesting photocatalytic properties for both organic compound degradation and bacterial removal.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-07-12T19:51:09Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Elizane Efigenia de Moraes.pdf: 9079354 bytes, checksum: 7ee5a581c6d0b14cdc6b518cd6aa7276 (MD5) / Made available in DSpace on 2016-07-12T19:51:09Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Elizane Efigenia de Moraes.pdf: 9079354 bytes, checksum: 7ee5a581c6d0b14cdc6b518cd6aa7276 (MD5) Previous issue date: 2015-07-30 / Nesta dissertação estudamos as propriedades de transporte do nitreto de boro cúbico (cBN, para a sigla em inglês) com as superfícies de uma amostra de quatro camadas passivadas com hidrogênio: em uma superfície o H se liga ao B e na outra ao N. As características do transporte são investigadas com a introdução de dois eletrodos de ouro (Au), em equilíbrio eletrostático com a amostra e submetidos a uma diferença de potencial V em intervalos de interesse: 0:2 V 0:2, 1 V 1 e 3 V 3. O teste de tunelamento com voltagem nula também foi realizado. As principais propriedades observadas são brevemente relatadas em seguida: (i) Os eletrodos são idênticos (no cálculo inicial do programa Siesta adicionamos uma camada "tampão"de átomos, a qual é desconsiderada no programa Transiesta-propriedades de transporte. A simetria dos eletrodos (esquerda e direita) se manifesta com PDOS idênticos para voltagem nula nos intervalos de energia investigados; (ii) A característica I-V (corrente versus voltagem) da amostra apresenta um pico acentuado para V 0:25. A origem deste pico é atribuída à ocorrência do nível quase localizado do H, situado abaixo do nível de Fermi e hibridizado com estados sp3 do B, como evidenciado no cálculo de DFT (Siesta) da estrutura eletrônica e densidade de estados do sistema de quatro camadas. De fato, uma análise dos PDOS dos eletrodos e da amostra sugere que esta interpretação é compatível com o cálculo numérico do Transiesta para o tunelamento através da amostra e o cálculo das características IV através da Fórmula de Landauer-Büttiker: na configuração de equilíbrio mencionada, as correntes máximas obtidas foram Imax(V = 0:25 Volts ) = 163 pico Ampéres (pA) e Imax(V = 2:5 ) = 380 pA. (iii) Enfatizamos que, no intervalo 0:2 V 0:2 a característica IV é muito semelhante àquela observada em diodos de junção p-n. Por outro lado, no intervalo 3 V 3 a retificação é bem menos efetiva para jV > 0:2j ; (iV) outra observação de destaque é o aumento da corrente, isto é, jImax(V = 0:8 )j = 9:85 nano Ampéres (nA) quando a distância dos eletrodos e a amostra é diminuída. Os resultados sugerem o prosseguimento e o aprofundamento das investigações, tendo em vista o uso potencial do cBN passivado com hidrogênio em dispositivos eletrônicos. / In this thesis we study the transport properties of cubic boron nitride (cBN) with the surfaces of a sample of four layers hydrogen terminated hydrogen: on a surface, H binds to B and on the other, to N. The characteristics of the transport are investigated after the introduction of two gold electrodes in an electrostatic equilibrium with the sample and subjected to a potential difference V in intervals of interest:0:2 V 0:2, 1 V 1 e 3 V 3. Tunneling test with zero voltage was also made. The main observed properties are reported briefly: (i) the electrodes are identical (within a layer buffer atoms only considered in the initial calculation Siesta program, to simulate a bulk behavior, therefore it is not considered in Transiesta program, that is, for the calculation of transport properties). The symmetry of electrodes (left and right) manifests with identical PDOS to zero voltage in between the energy intervals investigated; (ii) The IV characteristic (current versus voltage) of the sample shows a sharp peak for V 0:25. The origin of this peak is attributed to the occurrence of nearly located H level, situated below the Fermi level and hybridized with sp3 states of B, and evidenced in the DFT calculation (Siesta) of the electronic structure and density of states of the four layer system. The PDOS electrode and the sample analyses suggest that this interpretation is compatible with Transiesta numerical calculation of the tunneling through the sample and to calculate the current versus voltage I (V) by the Landauer-Büttiker formula: the aforementioned balance setting, the maximum currents obtained were Imax(V = 0:25 Volts ) = 163 peak amps (pA) and Imax(V = 2:5 ) = 380 pA; (iii) - Another important observation was the increase in current, i.e. jImax(V = 0:8 )j = 9:85 nano amps (nA) when the distance of the electrodes and the sample is reduced. The results suggest the continuation and deepening of the study, considering the potential use of CBN passivated with hydrogen in electronic devices.

Made available in DSpace on 2016-08-18T18:19:29Z (GMT). No. of bitstreams: 1 Karl Marx Silva.pdf: 2976285 bytes, checksum: 02b42e292682101cc350470d85dea0d7 (MD5) Previous issue date: 2007-08-21 / The Nanotechnology quickly advances to the development of new nanodevices. One of most important in the electronics is clocks that they synchronize the functioning of diverse devices in a determined circuit. In this work we study the development of nanooscillators based upon Carbon nanotubes and Boron-Nitride nanotubes. The atom that oscillates in the interior of each tube is the Neon atom under various temperature conditions and for different nanotubes lengths. The results indicate oscillation stability in a large range of temperatures, what it could mean its potential construction and application as a new device for nanoelectronics. / A Nanotecnologia avança rapidamente para o desenvolvimento de novos nanodispositivos. Uns dos mais importantes na eletrônica são os clocks que sincronizam o funcionamento de diversos dispositivos num determinado circuito. Neste trabalho estudamos o desenvolvimento de nanoosciladores a base de nanotubos de Carbono e nitreto de Boro. O átomo que oscila no interior de cada tubo é o átomo de Neônio sob diversas condições de temperatura e para diferentes comprimentos de nanotubos. Os resultados indicam estabilidade de oscilação numa ampla faixa de temperatura, o que pode significar o seu potencial construção e aplicação como um novo dispositivo para nanoeletrônica.

Orientadores: Abner de Siervo, Richard Landers / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-25T18:41:09Z (GMT). No. of bitstreams: 1 DeLima_LuisHenrique_D.pdf: 24142455 bytes, checksum: b13ea70fe8434614a9b9ec40d25b3770 (MD5) Previous issue date: 2014 / Resumo: Monocamadas sp2 de grafeno e nitreto de boro hexagonal (h-BN) têm atraído muita atenção devido ao descobrimento de importantes propriedades, por exemplo, alta resistência mecânica, boa condutividade térmica e excelente estabilidade química e térmica. Porém, enquanto o grafeno é um semicondutor de gap nulo com alta mobilidade dos portadores de carga; o h-BN é um isolante com um largo band gap. Além disso, quando estas monocamadas sp2 são obtidas na superfície de uma variedade de substratos, elas podem exibir superestruturas corrugadas com parâmetro de rede no plano da ordem de nanômetros. Estas superestruturas são importantes para o autoordenamento de moléculas, átomos ou aglomerados de átomos e também para a intercalação de partículas e átomos em posições específicas na interface entre a monocamada sp2 e o substrato. Nesta tese, realizou-se um estudo, básico e aplicado, de monocamadas sp2 de grafeno e h-BN obtidas sobre a superfície do SiC(0001) e do Rh(111), respectivamente. Do ponto de vista básico, foi aplicada a técnica de Difração de Fotoelétrons (XPD) para um estudo da estrutura atômica do grafeno obtido por aquecimento na superfície do SiC(0001) e para a camada de interface entre o grafeno e o SiC, denominada buffer layer (BL). Os resultados de XPD mostraram particularidades distintas na estrutura atômica dessas monocamadas, o que explicaria a diferen_ca na estrutura eletrônica entre a BL e o grafeno. Do ponto de vista aplicado, foi mostrada a viabilidade do nanotemplate de grafeno/BL/SiC(0001) para a obtenção de aglomerados de Co e subsequente estudo das suas propriedades magnéticas por Dicroísmo Circular Magnético de Raios X (XMCD). Os aglomerados de Co foram obtidos sobre a camada de grafeno e os resultados evidenciam uma possível interação cluster-cluster de longo alcance, com influência nas propriedades magnéticas das partículas. Foi investigada também a intercalação dos átomos de Co entre o grafeno e a BL, formando uma rede quase periódica de clusters 2D. O grafeno forma uma barreira de proteção contra oxidação, preservando o caráter metálico das partículas. A monocamada de h-BN sobre a superfície do Rh(111) foi utilizada para a implantação de átomos de Rb. Para a implantação, foi construída uma evaporadora de íons de Rb que permite acelera-los numa faixa de energia possível para penetrar a monocamada de h-BN. Imagens de STM mostraram que os átomos de Rb termalizam entre a monocamada de h-BN e a superfície do Rh(111) em posições especificas da superestrutura, formando o que se denominou de nanotent. A formação dos nanotents e dos defeitos de vacância gerados pelo choque dos íons é uma forma de funcionalização do h-BN, sendo estas estruturas possíveis pontos de ancoragem de moléculas, átomos ou clusters de átomos / Abstract: Graphene and hexagonal boron nitride (h-BN) sp2 monolayers have attracted much attention due the discoveries of their important properties, such as high mechanical strength, good thermal conductivity and excellent chemical and thermal stability. However, while graphene is a zero band gap semiconductor with high carrier mobility; h-BN is a wide band gap insulator. Furthermore, when these sp2 monolayers are obtained on the surface of a variety of substrates, they can exhibit corrugated superstructures with a few nanometers in-plane lattice constants. Such superstructures are important for the self-assembly of molecules, atoms or clusters of atoms and also for the intercalation of these structures at specific positions between the sp2 monolayer and the substrate. In this thesis, we performed a study, fundamental and applied, of sp2 monolayers of graphene and h-BN obtained on the surface of SiC(0001) and Rh(111), respectively. From a fundamental point of view, the Photoelectron Di_raction (XPD) technique was applied for the study of the atomic structure of graphene obtained by heating the surface of the SiC(0001) and for the interface layer between the SiC and graphene, named buffer layer (BL). The XPD results showed distinct peculiarities in the atomic structure of these monolayers, which would explain the difference in electronic structure between BL and graphene. From the applied point of view, it has shown the feasibility of graphene/BL/SiC(0001) nanotemplate to obtain Co clusters and subsequent study of their magnetic properties by X-ray Magnetic Circular Dichroism (XMCD). The Co clusters were obtained on the graphene layer and the results suggest a possible clustercluster long-range interaction, that has influence on the magnetic properties of the particles. It was also investigated the intercalation of Co atoms between graphene, forming a quasi-periodic lattice of 2D-clusters. Moreover, graphene acts as a barrier to oxidation, preserving the metallic character of the clusters. The h-BN monolayer on the surface of Rh(111) was used for the implantation of Rb atoms. For the implantation, it was constructed an evaporator that allows the acceleration of Rb ions to an energy that enables the penetration through the h-BN monolayer. STM images show that the Rb atoms thermalize between the h-BN monolayer and the surface of the Rh(111) at specific positions of the superstructure, forming what is called a \\nanotent\". The formation of the nanotents and the vacancy defects generated by the collision of the ions is a form to functionalize the h-BN, with these structures being possible points for the anchoring of molecules, atoms or clusters of atoms / Doutorado / Física / Doutor em Ciências

L’objectif de cette thèse est de réaliser des revêtements de nitrure de bore sur différents types de substrats comme le graphite, le quartz, le pyrex, en allant jusqu’aux métaux et en particulier le titane. Le choix de la voie PDCs s’avère intéressant grâce à la maîtrise du précurseur de départ au niveau atomique d’une part et à la facilité du procédé de dépôt, d’autre part. Nos objectifs étaient d’étudier la faisabilité de réaliser des revêtements BN sur différents types de substrat en utilisant un traitement thermique résistif et de mettre en place un dispositif qui nous permette de pyrolyser les films polymériques sur métaux sans dommage pour le substrat, en vue de leur protection contre l’oxydation ou d’autres applications mécaniques. Dans ce sens, nous avons démontré la possibilité d’utiliser un traitement thermique alternatif par lampe halogène émettant dans l’infra-rouge pour densifier les revêtement BN déposer sur substrats métalliques. / The aim of this work was to prepare boron nitride coatings onto different substrates using the Polymers Derived Ceramics (PDCs) approach. In that way, BN coatings were obtained onto graphite, pure silica and metal especially titanium. The first part of this thesis was to study parameters (of the solution used and of the dip-coating process), to obtain the best coatings in terms of morphology, cristallinity and chemical composition. The second part was dedicated to BN coatings obtained onto metal substrates using an alternative thermal treatment allowing the polymer-to-ceramic conversion without any damage for the metal. Actually, annealing by infrared irradiation allows heating only the coating, energy being reflected by the metal.