No description available.

L’objectif principal de ce travail de thèse a été l’optimisation des conditions de croissance du diamant dans un réacteur MPACVD afin d’une part, obtenir des films de diamant monocristallin à faible densité de dislocations, condition sine qua none pour une utilisation dans le domaine de l’électronique de puissance et, d’autre part, synthétiser des films épais (>100 μm) de diamant monocristallin intrinsèque et fortement dopés au bore sur substrats orientés (111), orientation cristalline connue pour favoriser la formation de macles. Dans une première partie, nous avons développé un procédé d’infléchissement et de confinement desdislocations en utilisant des substrats en forme de pyramide orientés (100) et en déterminant des conditions de croissance bien particulières. Cette étude innovante et originale a permis de lever plusieurs verrous scientifiques et technologiques qui ouvrent la voie à la réalisation de films de diamant monocristallin à faible densité de défauts. Dans une deuxième partie, l’effetdes différents paramètres de croissance a été étudié, afin d’optimiser notre procédé de croissance sur orientation (111). Il a ainsi été mis en évidence l’existence d’une fenêtre de couple pression/puissance micro-onde, température et concentration en méthane qui permettent d’assurer un bon compromis entre qualité cristalline et vitesse de croissance, permettant la synthèse de films épais de diamant fortement dopé au bore sur cette orientation ouvrant ainsi la possibilité de combiner l’efficacité de dopage de type n et la réalisation de composants bipolaires verticaux pour des applications en électronique haute tension-hautetempérature. / The main objective of this PhD thesis is the optimization of diamond growth conditions in a MPACVD reactor in order to one hand, synthesize single crystal diamond films with low dislocation density, prerequisite to their use in the field of power electronics and on the other hand, synthesize thick intrinsic and boron doped monocrystalline diamond films (>100 microns) on (111)-oriented substrates, crystallographic orientation which is well known to promote twinning. In a first part, a process of inflection and confinement of the dislocations has been developed using (100) pyramidal shape substrates coupled with specific growth conditions. This innovative and original study open the way for the fabrication of single crystal diamond films with low defect density. In a second part, the effect of different growth parameters has been studied to optimize our growth process for (111) orientation. It was thus demonstrated the existence of a narrow window of growth parameters pressure, microwavepower, temperature and methane concentration which ensures a good trade-off between crystalline quality and growth rate, allowing the synthesis of heavily boron-doped diamond thick films on this specific orientation, thus opening the possibility of combining the n-type doping efficiency and achieving vertical bipolar components for applications in hightemperaturehigh-voltage electronics.

Yes / The fabrication of osmium nanoclusters from single atoms has been studied in real-time on B-doped and B-free graphitic surfaces. The dynamics of nucleation on both surfaces are identified, captured, and reported. The nucleation is ca. 2× faster on B-doped surface compared to the B-free surface (38 pm min−1versus 18 pm min−1), suggesting osmium–boron interactions within the nanomaterials.

Orientadores: Vitor Baranauskas, Alfredo Carlos Peterlevitz / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-12T10:56:53Z (GMT). No. of bitstreams: 1 Manne_GustavoAndreMograo_M.pdf: 4900447 bytes, checksum: 96ac39c8d4903a68da74c3db411b33b1 (MD5) Previous issue date: 2008 / Resumo: Esta tese apresenta um estudo do crescimento e caracterização do diamante nanocristalino crescido por deposição química a partir da fase vapor (diamante CVD), com a introdução de boro durante o crescimento. Nosso objetivo foi de produzir amostras com boas propriedades para emissão de elétrons para o vácuo por efeito do campo elétrico (FEE). As amostras foram caracterizadas por Microscopia Eletrônica de Varredura de Emissão por Campo (FESEM), micro-espectroscopia Raman e emissão de elétrons por campo elétrico. Os resultados destas caracterizações são apresentados e discutidos. / Abstract: This thesis presents a study of the growth and characterization of nano crystalline diamonds produced by the hot-filament chemical vapor deposition (CVD) with the introduction of boron during the growth process. Our objective was to produce samples with good electrical properties for field induced emission of electrons (FEE) to the vacuum. Characterization of the samples by electron microscopy, Raman micro-spectroscopy, and Field Emission measurements are presented and discussed. / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

No description available.

L’objectif de cette thèse porte sur la synthèse du diamant monocristallin dopé au bore par dépôt chimique en phase vapeur assisté par plasma micro-onde (MPCVD). Ces couches épitaxiées jouent le rôle de couches actives dans des composants pour l’électronique de puissance. Ces travaux s’inscrivent dans le cadre du projet Européen H2020 Greendiamond. Durant cette thèse, un traitement de gravure des défauts surfaciques des substrats de diamant HPHT par plasma Ar/O₂ a été mis au point. L’efficacité de ce traitement a été validée par diffraction des rayons X à haute résolution, spectroscopie Raman et cathodoluminescence. Cette étape s’est révélée essentielle pour l’amélioration des propriétés de transport de couches de diamant dopées au bore pour les applications en électronique.L’optimisation des conditions de croissance de couches de diamant faiblement dopées au bore (<10¹⁶ at.cm⁻¹) a permis la synthèse de films homoépitaxiés allant jusqu’à 5 µm d’épaisseur présentant une haute qualité cristalline. Les propriétés structurales et de transport de ces couches ont été corrélés en combinant différentes méthodes comme la spectroscopie Raman, la cathodoluminescence, la topographie X, l’imagerie MEB des défauts, les mesures par temps de vol et des mesures de Hall.Ces films de diamant dopés au bore ont été intégrés avec succès dans des composants électroniques comme des MESFET ou des diodes Schottky. / This PhD aims to synthetize boron doped single-crystal diamond epilayers by Micro-Wave Plasma Chemical Vapor Deposition (MPCVD) as active layers for power electronic devices. This work was performed in relation with the European H2020 Greendiamond project. A powerful Ar/O₂ plasma etching was optimized which allows the efficient elimination of defects in the subsurface of HPHT diamond substrates as confirmed by High Resolution X-ray Diffraction, Raman spectroscopy and Cathodoluminescence. This step proved to be crucial for the improvement of low boron doped-diamond layers carrier properties for electronic purposes.The optimization of growth conditions performed on low boron-doped diamond layers (<10¹⁶ at.cm⁻³) enabled the synthesis of high quality doped layers, 5 µm thick. The structural and transport properties of these layers were correlated by different techniques: Raman spectroscopy, Cathodoluminescence, X-Ray Topography, SEM imaging of defects, Transient Current Technique, Hall measurements.Finally, low boron doped epilayers were integrated with success in electronic devices such as MESFET or Schottky diodes.

Structurally precision graphene nanoribbons (GNRs) have attracted great interest considering their prospective applications as organic carbon materials for nanoelectronics. The electronic properties of GNRs not only critically depend on the edge structure and width but also on the heteroatom type, doping position, and concentration. Motivated by the recent undisputable progress in the synthesis of stable boron-doped polycyclic aromatic hydrocarbons (B-PAHs), considerable efforts have been devoted to the precision synthesis of the corresponding boron-doped GNRs (B-GNRs) via bottom-up synthesis approach in recent years in view of the extraordinary ability of boron doping on modulating their physiochemical properties. In this review, an overview of the bottom-up organic synthesis of B-GNRs, including the precursor design and synthesis, structure characterization of the resulting B-GNRs, and investigation of their electronic properties is provided. Moreover, the future challenges and perspectives regarding the bottom-up synthesis of B-GNRs are also discussed. The authors hope that this review will further stimulate the synthesis and device integrations of B-GNRs with a combined effort from different disciplines.

This thesis focuses on the effects of dopant compensation on the electrical properties of crystalline silicon relevant to the operation of solar cells. We show that the control of the net dopant density, which is essential to the fabrication of high-efficiency solar cells, is very challenging in ingots crystallized with silicon feedstock containing both boron and phosphorus such as upgraded metallurgical-grade silicon. This is because of the strong segregation of phosphorus which induces large net dopant density variations along directionally solidified silicon crystals. To overcome this issue, we propose to use gallium co-doping during crystallization, and demonstrate its potential to control the net dopant density along p-type and n-type silicon ingots grown with silicon containing boron and phosphorus. The characteristics of the resulting highly-compensated material are identified to be: a strong impact of incomplete ionization of dopants on the majority carrier density, an important reduction of the mobility compared to theoretical models and a recombination lifetime which is determined by the net dopant density and dominated after long-term illumination by the boron-oxygen recombination centre. To allow accurate modelling of upgraded-metallurgical silicon solar cells, we propose a parameterization of these fundamental properties of compensated silicon. We study the light-induced lifetime degradation in p-type and n-type Si with a wide range of dopant concentrations and compensation levels and show that the boron-oxygen defect is a grown-in complex involving substitutional boron and is rendered electrically active upon injection of carriers through a charge-driven reconfiguration of the defect. Finally, we apply gallium co-doping to the crystallization of upgraded-metallurgical silicon and demonstrate that it allows to significantly increase the tolerance to phosphorus without compromising neither the ingot yield nor the solar cells performance before light-induced degradation.

Orientador: Vitor Baranauskas / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-05T18:10:58Z (GMT). No. of bitstreams: 1 Correa_WashingtonLuizAlves_D.pdf: 3351242 bytes, checksum: 8f30a26c68d4c1e73a72d065eaedb4f9 (MD5) Previous issue date: 2004 / Resumo: Estudamos processos de dopagem do diamante crescido por deposição química a partir da fase vapor (diamante CVD) com a introdução de impurezas dopantes durante o crescimento do diamante em reatores do tipo filamento-quente. Focalizamos nossa pesquisa na dopagem do diamante com boro, ou nitrogênio, ou enxofre, visando obter diamantes com propriedades semicondutoras com condutividade eletrônica (tipo n) ou condutividade por lacunas (tipo p). Foram utilizadas contaminações intencionais utilizando: trimetil borano (B(CH3)3), ou amônia (NH3), ou dissulfeto de carbono (CS2), misturados com metano e diluídos em hidrogênio. As amostras foram caracterizadas por microscopia eletrônica de varredura (SEM), espectroscopia Raman, espectroscopia de foto-elétrons excitados por raios X (XPS), espectroscopia de emissão de raios X excitado por feixe de prótons (PIXE) e efeito Hall. As dopagens do diamante do tipo p e do tipo n foram obtidas com contaminações de boro e enxofre, respectivamente. O diamante dopado com nitrogênio não apresentou propriedades semicondutoras / Abstract: We studied the diamond doping processes with introduction of doping impurities during the diamond growth in the chemical vapor deposition (CVD) technique, using a hot-filament reactor. Our research focused the use of boron, nitrogen or sulphur atoms in order to obtain diamond films with semiconductor properties of electronic (n-type) or hole (p-type) current transport mechanisms. Trimethyl-borane (B(CH3)3), or ammonia, or carbon disulphide (CS2), mixed with methane and hydrogen were used in the feed gas mixture. The diamond samples were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Proton-induced X-ray emission (PIXE) and Hall effect. p-type and n-type diamonds have been obtained with boron and sulphur doping, respectively. However, the nitrogen doped samples do not presented semiconductor properties / Doutorado / Engenharia de Eletronica e Comunicações / Doutor em Engenharia Elétrica

Alors que la demande en électronique haute puissance et haute fréquence ne fait qu’augmenter, les semi-conducteurs classiques montrent leurs limites. Des approches basées soit sur des nouvelles architectures ou sur des matériaux à large bande interdite devraient permettre de les dépasser. Le diamant, avec ses propriétés exceptionnelles, semble être le semi-conducteur ultime pour répondre à ces attentes. Néanmoins, il souffre aussi de certaines limitations, en particulier d’une forte énergie d’ionisation du dopant de type p (bore) qui se traduit par une faible concentration de porteurs libres à la température ambiante. Des solutions innovantes s'appuyant sur un gaz 2D et /ou l’effet de champ ont été imaginées pour résoudre ce problème. Ce travail est axé sur deux de ces solutions : i) le diamant delta dopé au bore qui consiste en une couche fortement dopée entre deux couches intrinsèques, afin d’obtenir une conduction combinant une grande mobilité avec une grande concentration de porteurs et ii) le transistor à effet de champ métal oxide semiconducteur( MOSFET ), où l’état « on » et l’état « off » du canal sont obtenus grâce au contrôle électrostatique de la courbure de bandes à l' interface de diamant/oxyde. Pour ces deux structures, beaucoup de défis technologiques doivent être surmontés avant de pouvoir fabriquer un transistor. La dépendance en température de la densité surfacique de trous et de la mobilité de plusieurs couche de diamant delta dopées au bore a été étudiée expérimentalement et théoriquement sur une large gamme de température (6 K <T < 500 K). Deux types de conduction ont été détectés: métallique et non métallique. Une mobilité constante comprise entre 2 et 4 cm2/Vs a été mesurée pour toutes les couches delta métalliques quelle que soient leurs épaisseurs ou le substrat utilisé pour la croissance. Cette valeur particulière est discutée en comparaison à d'autres valeurs expérimentales reportées dans la littérature et aussi de calculs théoriques. Une conduction parallèle à travers les régions faiblement dopées qui encapsule la couche delta, a également été mise en évidence dans certains échantillons. Une très faible mobilité a été mesurée pour les couches delta non métalliques et a été attribuée à un mécanisme de conduction par saut. Des structures métal oxyde semi-conducteur utilisant de l'oxyde d'aluminium comme isolant et du diamant monocristallin (100) de type p en tant que semi-conducteur ont été fabriquées et étudiées par des mesures capacité tension C(V) et courant tension I(V). L'oxyde d'aluminium a été déposé en utilisant un dépôt par couche atomique (Atomic Layer Deposition : ALD) à basse température sur une surface oxygénée de diamant. Les mesures C(V) démontrent que les régimes d'accumulation , de déplétion et de déplétion profonde peuvent être contrôlés grâce à la tension de polarisation appliquée sur la grille. Un diagramme de bande est proposée et discutée pour expliquer le courant de fuite étonnamment élevé circulant en régime d’accumulation. Aucune amélioration significative de la mobilité n’a été observée dans les structures delta, même pour les plus fines d’entre elles (2 nm). Cependant, la démonstration du contrôle de l’état du canal de la structure MOS ouvre la voie pour la fabrication d’un MOSFET en diamant, même si un certain nombre de verrous technologiques subsistent. / As the demand in high power and high frequency electronics is still growing, standard semiconductors show their limits. Approaches based either on new archi- tectures or wide band gap materials should allow to overcome these limits. Diamond, with its outstanding properties, seems to be the ultimate semiconductor. Neverthe- less, it also suffers from limitations, especially the high ionization energy of the boron p-type dopant that results in a low carrier concentration at room temperature. In- novative solutions relying on 2D gas or/and field effect ionization has been imagined to overcome this problem. This work is focused on two of these solutions: i) boron delta-doping consisting in highly doped layer between two intrinsic layers, resulting in a conduction combining a high mobility with a large carrier concentration and ii) metal-oxide-semiconductor field effect transistor (MOSFET) where the conducting or insulating behavior of the channel is based on the electrostatic control of the band curvature at the oxide/semiconducting diamond interface. For both structures, a lot of technological challenges need to be surmounted before fabricating the related transistor. On one hand, the temperature dependence of the hole sheet density and mobility of several nano-metric scaled delta boron doped has been investigated experimentally and theoretically over a large temperature range (6 K <T< 500 K). Two types of conduction behaviors were detected : metallic and non metallic. A constant mobility between 2 and 4 cm2/V.s was found for all the metallic degenerated delta layers whatever its thickness or the substrate used for the growth. This particular value is discussed in comparison of other experimental values reported in literature and theoretical calculations. A parallel conduction through the low doped regions, in which the delta is embedded, has also been brought to light in certain cases. A very low mobility was measured for non metallic conduction delta layers and has been attributed to an hopping conduction mechanism which is discussed. On the other hand, metal-oxide-semiconductor structures with aluminum oxide as insulator and p−type (100) mono-crystalline diamond as semiconductor have been fabricated and investigated by capacitance versus voltage C(V) and current versus voltage I(V) measurements. The aluminum oxide dielectric was deposited using low temperature atomic layer deposition on an oxygenated diamond surface. The C(V) measurements demonstrate that accumulation, depletion and deep depletion regimes can be controlled by the bias voltage. A band diagram is proposed and discussed to explain the surprisingly high leakage current flowing in accumulation regimes. To sum up, no significant improvement of mobility has been observed in delta structures even for the thinnest one (2 nm). However, the MOS channel control demonstration opens the route for diamond MOSFET even if technological chal- lenges remain.