Dissertations / Theses on the topic 'Diamond'

De nos jours, l'effet du réchauffement planétaire devient une question primordiale pour l'humanité. La plupart des sources d'énergie traditionnelles comme l’énergie thermique, le nucléaire, l'hydroélectricité, etc. sont dangereux et/ou potentiellement dangereux pour la nature et l'être humain. Par conséquent, une «énergie verte» est fortement souhaitée. L'énergie verte a deux caractéristiques : d'une part l’utilisation de sources d'énergie renouvelables comme l'énergie solaire ou géothermique, etc au lieu des sources d'énergie traditionnelles, ainsi qu’un meilleur rendement. Un rapport récent a souligné que la perte d'énergie aux États-Unis est plus importante que la somme de toutes les énergies renouvelables générées. Il est donc essentiel d'utiliser efficacement l'électricité et de limiter les pertes. Malheureusement, les pertes sont l'endémie des composants semi-conducteurs, le dispositif central de tout système de conversion de puissance. Le silicium (Si), le matériau le plus utilisé dans les composants semi-conducteurs a atteint sa limite physique. Des semi-conducteurs à large bande interdite tels que SiC, GaN, Ga2O3 et le diamant sont des matériaux prometteurs pour fabriquer des dispositifs à faibles pertes en état ON et avec une tension de claquage à l’état OFF élevée. Parmi eux, le diamant est un semi-conducteur idéal pour les appareils de haute puissance en raison de ses propriétés physiques supérieures aux autres matériaux. Les progrès récents sur ce sujet permettent de considérer le développement de dispositifs de puissance en diamant, par exemple les MOSFETs. Afin de réaliser un MOSFET en diamant semi-conducteur, le nombre de problèmes à surmonter est important, particulièrement maîtriser l'interface diamant/oxyde. Dans ce contexte, G. Chicot et A. Marechal (anciens doctorants de notre groupe) ont introduit les dispositifs de test MOSCAP O-diamant/Al2O3 et montré que l'alignement des bandes est de type I à l'interface O-diamant/Al2O3, ce qui est favorable pour réaliser à la fois un MOSFET à inversion et un MOSFET à déplétion. Ce doctorat s’inscrit dans la suite de ces deux thèses. Il a eu deux objectifs principaux: 1. Les recherches fondamentales, qui se consacrent à la compréhension de la caractéristique électrique d'un dispositif de test de diamant MOSCAP; 2. Partant de la compréhension du MOSCAP, un MOSFET en diamant est réalisé par le contrôle de la conduction de courant volumique. La thèse comprend ainsi trois chapitres : Le chapitre 1 traite du contexte des dispositifs de puissance ainsi que des propriétés physiques du diamant et de l'état de l'art des dispositifs en diamant. Nous introduisons également le principe de fonctionnement d'un dispositif de test MOSCAP idéal et de l'état de l'art des O-diamant MOSCAP. Le chapitre 2 est consacré à la compréhension fondamentale des O-diamant MOS capacités et comprennent trois parties principales: la partie 1 traite des questions de méthodologie liées à la croissance du diamant, le procédé de fabrication et de caractérisation électrique. Nous allons construire un modèle électrostatique empirique pour les MOSCAP O-diamant. La partie 2 discute de l'origine du courant de fuite et de la dispersion de la caractéristique capacitance-fréquence lorsque la MOSCAP est polarisée en négatif. La partie 3 traite de l'origine du courant de fuite et de la dispersion de la caractéristique capacitance-fréquence lorsque la MOSCAP est polarisée en positif. Le chapitre 3 présente notre approche pour réaliser un MOSFET en diamant dopé au Bore. Les performances du transistor et ses paramètres importants seront quantifiées. Le benchmark du dispositif et la projection vers son amélioration seront mentionnés
Nowadays, global warming effect is one of most challenging issue for human being. Most of “traditional energy” sources like thermal power; nuclear power, hydroelectricity power, etc. are dangerous and/or potentially dangerous for nature and human being. Therefore, the "greener energy" is highly desired. The "greener energy" has two folds meaning: on one hand, using renewable energy sources like solar power, wind power or geothermal energy, etc. instead of the traditional energy sources. One another hand, use the electricity more effectively and more efficiency. A recent report has pointed out that the energy loss in US is in fact more than sum of all renewable energy generate in US. Therefore, effectively utilizing electricity and limiting the waste is critical.Unfortunately, losses are the endemic of semiconductor components, the central device of all power conversion system. Silicon (Si), the main material for semiconductor components has reached its physical limit. Wide band-gap semiconductors such as SiC, GaN, Ga2O3 and diamond are promising materials to fabricate the devices low ON-state loss and high OFF-state breakdown voltage. Among them, diamond is an ideal semiconductor for power devices due to its superior physical properties. Recent progresses on diamond technology permits one consider the diamond power devices, e.g. MOSFET.In order to realize a diamond MOSFET by controlled diamond semiconductor, the numbers of issues needed to be overcome is important, especially mastering the diamond/oxide interface. In this context, G. Chicot and A. Marechal (former PhD students in our group) has introduced the O-diamond/Al2O3 MOSCAP test devices and measured the type I band alignment at O-diamond/Al2O3 interface, which is favorable to realize both inversion MOSFET and depletion MOSFET in his PhD these. This PhD project is a continuation of two-mentioned thesis and including two main objects: 1. Fundamental investigations dedicate to understand the electrical characteristic of an O-diamond MOSCAP test device; 2. Realize a unipolar diamond MOSFET by controlling the diamond semiconductor epilayer. The thesis will include three chapters:Chapter 1 discusses the context of power devices as well as the physical properties of diamond and state-of-the-art of diamond devices. We also introduce the working principle of an ideal MOSCAP test device and States-of-the-art of O-diamond MOSCAP test devices.Chapter 2 dedicates for the fundamental understanding O-diamond MOSCAP and include three main parts: Part 1 addresses the methodology issues related to diamond growth, fabrication processing and electrical characterizations. We will construct an empirical electrostatics model for O-diamond MOSCAP. Part 2 discusses the origin of leakage current and capacitance-frequency dependent when O-diamond MOSCAP is biasing in negative direction. We quantify the interface states density at O-diamond/Al2O3 interface by conductance method and the complete electrostatics model for O-diamond/Al2O3 MOSCAP will be constructed. Part 3 discusses the origin of leakage current and the capacitance-frequency dependent when the O-diamond MOS capacitor is biasing in positive direction.Chapter 3 introduces our approach to realize a depletion mode diamond MOSFET. Transistor performance and the important parameters of the transistor will be quantified. The benchmark of the device and the projection towards its improvement will be mentioned

Cette thèse porte sur la fabrication de diodes Schottky sur diamant pour des applications hautes puissances. La croissance du diamant et son dopage sont aujourd'hui bien maîtrisés. La passivation de la surface du diamant (surface à terminaison oxygène) requise pour minimiser les états d'interface et obtenir des contacts redresseurs sur diamant, est également bien maîtrisé. L'apparition des architectures verticales (couche active des diodes épitaxiée sur un substrat de diamant fortement dopée) et pseudo-vertical (épitaxie d'un empilement comprenant la couche active et une couche fortement dopée sur un substrat diamant isolant) ont permis de minimiser la résistance série élevée des diodes sur diamant (énergie d'ionisation élevée des principaux dopants du diamant). Malgré le fait que ces configurations géométriques favorisent courants directs élevés, les performances diodes Schottky verticales ou pseudo verticales sur diamant sont à ce jour limitées par: i) la qualité de la couche active altérée par la propagation de défauts issues de la couche fortement dopée conduisant à de faible champ critiques (environ 3 MV / cm au lieu des 10MV/cm théorique), ii) les contacts Schottky sélectionnés, la stabilité thermique et chimique des interfaces formées avec une surface de diamant à terminaison oxygène. La sélection du métal Schottky et le prétraitement de la surface sont cruciaux pour obtenir de faibles hauteurs barrières (faible chute de tension à l'état passant), une faible densité de défauts au niveau des interfaces (faible courants de fuite), et une interface thermiquement stable (température de fonctionnement élevée). Dans cette thèse, nous avons démontré qu'une diode Schottky diamant pseudo verticale basée sur l'utilisation d'une surface à terminaison oxygène couverte par un métal facilement oxydable comme le zirconium (Zr), et une couche fortement dopée avec une épaisseur optimale, permettent de surmonter ces limitations et de fabriquer des diodes de meilleurs performances que l'état de l'art actuel. Un compromis entre l'épaisseur de la couche fortement dopée et son niveau de dopage à été d'abord établit afin de minimiser la génération de défauts et par conséquent d'améliorer la qualité de la couche active. Le métal (Zr) sélectionné comme contact Schottky donnait lieu à la formation d'une fine couche d'oxyde de zirconium thermiquement stable entre le Zr et le diamant. Les redresseurs fabriqués avaient: une forte densité de courant direct (1000 A par centimètre carré à 6 V), un champ critique supérieur à 7.7 MV /cm (tension de blocage 1000 V avec un courant de fuite inférieur à 1 pA), un facteur de mérite de Baliga supérieur à 244 MW par centimètre carré (la valeur la plus élevée signalée), une bonne reproductibilité indépendamment de la taille des diodes et des échantillons, la possibilité d'obtenir une hauteur de barrière inférieure à 1 eV après recuit, et une stabilité thermique supérieure à 500 ° C
This thesis was focused on high power diamond Schottky diodes fabrication. Diamond growth and its doping are today well mastered. The advent of vertical architectures (diode active layer grown on heavily doped diamond substrate) and pseudo-vertical (stack of diode active layer and heavily doped layer grown on insulating substrate) allowed minimizing the high serial resistance, which was induced by the high ionization energy of acceptor-type dopants (boron doped diamond) preferably used in rectifiers fabrications.Besides these geometrical configurations favoring high forward currents, diamond Schottky diodes (pseudo vertical or vertical structures) were limited by: I) the quality of diode active layer altered by defects propagation from heavily doped layer thus leading to lower blocking voltage (maximum critical field of 3 MV/cm reported) than the theoretical values (theoretical values of critical field of 10 MV/cm), II) Schottky electrodes selected and the thermal and chemical stability of interfaces formed with oxygen-terminated diamond surface (required getting a Schottky contact and reducing as much as possible the interface states). Schottky metal selection and diamond surface pretreatment are crucial to get low barrier heights (low forward voltage drop and so low losses), low defects density at interfaces (low leakage current), and a thermally stable interface (high operating temperature). In this thesis, we demonstrated that a pseudo vertical diamond Schottky diode based on an oxygen-terminated surface covered by an easily oxidizable metal like zirconium (Zr) combined with an optimal heavily doped layer, allows overcoming these limitations. We first found a trade-off between the thickness of heavily doped layer and its doping level in order to minimize defects generations and thus improve the quality of diode active layer grown on the heavily doped layer (Less defects propagations). On a second hand, the Zr metallic electrodes selected gave rise to a thin zirconia interface layer which was thermally stable thus preventing the oxygen layer desorption. Zr/oxidized diamond rectifiers exhibited better features than the current state of art: a high forward current density (1000 A/cm2 at 6 V), a high critical field above 7 MV/cm (1000 V blocking voltage with a leakage current less than 1 pA), a Baliga's power figure of merit above 244 MW/cm2 (the highest value reported), a good reproducibility regardless of diodes and samples, the possibility to get a barrier heights below 1 eV by annealing, and a thermal stability higher than 500°C

Thesis (M.Phil.)--City University of Hong Kong, 2006.
"Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Master of Philosophy" Includes bibliographical references.

The origin of diamonds, their preservation and transport to the surface have been important issues over the last decades after the acknowledgement that diamonds are xenocrysts in the host kimberlites and after the discovery of new transport media such as lamproites. Different types of diamonds -E-type diamonds, P-type diamonds- and different types of hosts - Eclogites, Peridotites- have been distinguished. Each type corresponds to particular formation criteria. Ecogitic Diamonds are mostly related to subduction processes, whereas more uncertainties remain regarding the formation of Peridotitic Diamonds. Komatiite extraction and subduction of graphite-bearing serpentinites have been proposed as the more likely processes involved in their formation. A typical mantle signature for diamonds implies a thick, cool, reduced lithosphere. The keel-shape model is the most popular. Archaean cratons are therefore the most promising exploration target and area selection will expect to follow the Clifford's Rule. However, the evidence of cratonic areas hidden under younger formations · through seismic profiles and the discovery of diamond structurally trapped outside their stability field, have increased the potential of diamondiferous areas. Preservation of diamonds inside the lithosphere requires that the mantleroot remains insulated against excessive reheating and tectonic reworking. Mantle-root friendly and mantle-root destructive structures are distinguished. Small-size cratons are usually the most promising exploration targets. Transport of diamonds to the surface is dependant on' the same criteria of preservation. Only kimberlites and lamproites have been recognized as efficient transport media. Their ascent to the surface is conditioned by a multitude of parameters, amongst them the nature of the magma, the speed of ascent, the presence of pre-existing structures in the crust and the availability of ground water in the near-surface environment. The origin of kimberlite magma probably lies near the transition zone. Mixtures of depleted asthenospheric · sources and metasomatically enriched and possibly subducted materials are likely to be at the origin of the different kimberlite magmas. Kimberlite magmatism correlates generally in time with global tectonic events, triggered by either plume activity or by subduction processes, depending of the tectonic school of thought. Kimberlite alignments have been interpreted as hotspot tracks, and kimberlite magmas as volatile-rich melts issued from the remaining plume tail. The plume head produces flood-basalts in an adjacent "thinspot" of the lithosphere, generally on the edges of the cratons. Kimberlite and lamproite ascent to the surface are unconditionally influenced by regional structures. Rift structures, ring structures, transform faults, suture zones and deep-seated faults have been mentioned as controlling or accompanying features of kimberlite magmatism. Nearsurface emplacement constraints are better understood and the ultimate shape of the intrusion(s) depends on the nature of the country rocks, the availability of ground water and the near-surface faulting pattern. The recent discovery of "fissure" kimberlites is one of the more important breakthroughs of the last decade. With a better understanding of the processes involved in diamond formation, preservation and of kimberlite emplacement, major diamond discoveries have recently increased on all the continents. Successful diamond exploration requires today an integration of all geophysical, petrologic, geochemical and structural information available. The particular study of the northwestern Australian lamproite and kimberlite fields, the Brazilian kimberlites, the easternNorth American kimberlite fields, the Lac de Gras kimberlite field, the South African rich kimberlite provinces, and the Yakutian kimberlite fields provide concrete examples of the geotectonic controls on primary diamond deposits. Area selection criteria based on the previous models and examples, are expected to yield to many more discoveries in the coming years.
KMBT_363
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Includes bibliographical references (leaves 142-160).
The Cullinan kimberlite is a Group I kimberlite and is located in the northeastern region of the Kaapvaal Craton, South Africa. The kimberlite pipe has been dated at 1180 ± 30 Ma and intrudes the Bushveld Igneous Complex (2.05 Ga). This study explores the geochemistry of a suite of one hundred selected diamonds and their associated mineral inclusions. The majority of the diamonds described here are peridotitic (94%) and the remainder are eclogitic. The peridotic inclusions may be further subdivided into harzburgitic and lherzolitic parageneses.

The aim of the thesis is to design, conduct and assess an experiment seeking to look into the utility properties of recent tools manufactured by HAM-FINAL. The tools include polycrystalline diamond (PCD) and CVD diamond cutting edges. In the theoretical part, the attention is devoted to cutting materials with an emphasis on diamond materials, as well as to issues associated with the wearing of the cutting tools, requirements specified for precision of bores and tools used in the manufacture of precision bores. The paper further provides an overview of a selection of world’s leading manufacturers of PCD blanks, CVD diamond coatings, CVD diamond layers and reamers with PCD cutting edges.

Plus de deux décennies de progrès technologiques dans le contrôle de la qualité de la croissance, du dopage et dans la conception de composants ont conduit à l'émergence de nouvelles potentialités pour des applications d'électronique de puissance. Comme le diamant représente le semi-conducteur ultime en raison de ses propriétés physiques supérieures, des efforts ont été réalisés pour développer divers dispositifs électroniques, tels que des diodes Schottky, des transistors à effet de champ (MOSFET), transistor bipolaire, jonctions pin ...Le développement d'outils de simulation capables d'anticiper les propriétés électriques des dispositifs électroniques ainsi que leur architecture pour profiter pleinement des propriétés physiques du diamant est une condition préalable à la mise au point de nouveaux composants de puissance. D'autre part, l'étude expérimentale du contact de grille, la deuxième brique élémentaire du transistor, est fondamentale en vue de développer des dispositifs de haute performance. À cet égard, on peut considérer plusieurs questions ouvertes: (i) Les outils de simulation sont-ils capables de prendre en compte les spécificités du diamant pour modéliser les composants électroniques? (ii) L'oxyde d'aluminium est-il approprié pour développer un contact de grille de transistor? (iii) Si oui, l'interface oxyde/diamant est-elle d'assez bonne qualité? (iv) La fabrication d'un MOSFET en diamant est-elle un obstacle technologique?Ce projet de doctorat, vise à répondre à ces questions et à ouvrir la voie vers la réalisation du MOSFET à canal d'inversion.Les propriétés physiques du diamant seront soulignées et aideront à comprendre pourquoi ce matériau est le semi-conducteur ultime. L'état de l'art des dispositifs en diamant sera présenté en se concentrant sur des transistors à effet de champ. L'anticipation des propriétés électriques et de l'architecture grâce à des logiciels de simulation basés sur la méthode des éléments finis constitue un sujet complémentaire. Ainsi, le besoin d'outils de simulation fiables sera présenté.D'une part, les principaux modèles mis en œuvre dans les outils de simulation seront présentés en insistant sur les propriétés électriques du diamant. Pour la simulation du MOSFET diamant, l'étude de deux briques élémentaires est nécessaire: la jonction pn et le contact de grille. Les propriétés idéales de la grille seront présentées tandis que la jonction pn servira de base pour le calibrage des paramètres physiques mises en œuvre dans le logiciel de simulation. L'influence des modèles de génération-recombinaison sur les propriétés électriques simulée de jonction pn sera discutée. Enfin, la simulation des propriétés électriques d'un MOSFET en diamant sera présentée.D'autre part, l'accent sera mis sur la fabrication et la caractérisation électrique du condensateur diamant métal-oxyde-semi-conducteur (MOSCAP). Plus précisément, le raccordement des bandes à l'interface Al2O3/diamant à terminaison oxygène (O-diamant) a été étudiée en utilisant la méthode de spectroscopie photoélectronique à rayons X. Les résultats ont permis l'établissement du diagramme de bande de l'hétérostructure Al2O3/O-diamant et démontre que l'Al2O3 est utilisable en tant qu'oxyde de grille. Ensuite, l'étude de la densité des états d'interface a révélé l'ancrage du niveau de Fermi à l'interface entre l'Al2O3 et le diamant. En outre, les courants de fuite à travers la couche d'Al2O3 seront discutés en termes d'effet tunnel assisté par pièges de trous de la couche de diamant au contact de grille. Enfin, la caractérisation électrique du premier MOSFET en diamant, effectuée au National Institute for Advanced Industrial Science and Technology (AIST) au Japon, sera présentée. Cette première tentative s'est révélée infructueuse. Néanmoins, les résultats sont très prometteurs pour le développement de diamant MOSFET étant donné que la démonstration de la réalisation du composant est clairement établie
Over two decades of technological progresses in growth quality, doping control and device processing have led to the emergence of new potentialities for power electronic applications. As diamond represents the ultimate semiconductor owing to its superior physical properties, efforts have been conducted to develop various electronic devices, such as Schottky diodes, field effect transistors, bipolar transistor, p-i-n junctions...As a prerequisite to the development of new generation diamond power devices, on one side, is the development of simulation tools able to anticipate the device electrical properties as well as its architecture in order to take full advantage of the material physical properties. On the other hand, experimental study of the gate contact, the second building block of the transistor, is fundamental in order to develop high performance devices. In this regard, one can consider several open questions: (i) Are the simulation tools able to take into account the specificities of diamond to model electrical devices? (ii) Is the aluminum oxide suitable to develop a MOSFET gate contact? (iii) If so, is the oxide/diamond interface of good enough quality? (iv) Is the fabrication of a diamond MOSFET a technological issue?This PhD project, attend to answer these questions and pave the way towards the inversion mode MOSFET.Emphasize on the diamond physical properties will help to understand why this material is the ultimate WBG semiconductor. State of the art diamond devices will be presented focusing on field effect transistors. A complementary topic for the development of new generation diamond power device is the anticipation of device electrical properties and architecture through finite element base simulation software. Thus the need for reliable simulation tools will be presented.On one hand, the main models implemented in the simulation tools will be presented and emphasize on the diamond electrical properties will be given. For the simulation of diamond metal-oxide-semiconductor field effect transistor (MOSFET), the study of two building blocks is required: the p-n junction and the gate contact. The later ideal properties will be presented while the former will serve as a basis for the calibration of the physical parameters implemented in the finite element based software. Generation-recombination models influence on the simulated p-n junction electrical properties will be discussed. Finally, the simulation of the electrical properties of a diamond metal-oxide-semiconductor field effect transistor (MOSFET) will be shown.On the other hand, focus will be made on diamond metal-oxide-semiconductor capacitor (MOSCAP) fabrication and electrical characterization. Specifically, the interfacial band configuration of the Al2O3/oxygen-terminated diamond (O-diamond) has been investigated using X-ray photoelectron spectroscopy. The results allowed establishing the band diagram of the Al2O3/O-diamond heterostructure. Then, the electrical properties of the diamond MOSCAP will be shown. Specifically, investigation of the interface states density revealed the pinning of the Fermi level at the interface between the Al2O3 and the O-diamond. Moreover, the leakage currents through the Al2O3 layer will be discussed in terms of temperature dependent trap assisted tunneling of holes from the diamond layer to the top gate contact. Finally, the electrical characterization of the first diamond MOSFET, performed at the National Institute for Advanced Industrial Science and Technology (AIST) in Japan, will be presented. Even if this first attempt was unsuccessful, it is promising for the development of diamond MOSFET since the demonstration of the actual realization of the device is clearly established

Diamond nanophotonics have evolved tremendously from the study of color centers in bulk single crystals and nanocrystals to their characterization in nanostructured environments. This development was facilitated by the ability to generate monolithic, sophisticated nanodevices in high quality single crystal diamond. This thesis presents some recent contributions to the field of diamond nanophotonics: Increase in single photon collection from NV centers embedded in diamond nanowires, broadband spontaneous emission enhancement of single NV centers in plasmonic resonators, and coupling of single NV centers to planar resonators on-chip such as ring resonators and photonic crystal cavities. In addition, the generation of high quality integrated diamond devices allows for the exploration of nonlinear processes in diamond. Here, we show for the first time optical parametric oscillations in diamond resonators.
Engineering and Applied Sciences

Graphene obtained by mechanical exfoliation of graphite displays unique electronic properties with high mobility and saturation velocity. However, this is not a scalable technique, the film being limited to small area. Large area synthesis of good quality graphene has been achieved by CVD. The choice of substrate apparently influences the electronic properties of graphene. Most of reports have used SiO2-Si due to the widespread availability, but it is a poor choice of the material to degrade the graphene performace. In this thesis, more ideal platforms are introduced, including single crystal diamond (SCD), nanodiamond (ND), and diamond-like-carbon (DLC). It was found that different terminations for substrates caused strong effects for graphene properties. For H-terminated diamond, it was found that a p-type layer with good mobility and a small bang gap, whilst when N/F-terminations are introduced it was found that a layer with more metallic-like characters arises. Furthermore, different orientations of H-terminated SCD(100)/(111) were found to induce different band-gap of graphene. Simulation analysis proves the difference. However, the mobility results of graphene-H-terminated ND herostructure are better than graphene supported by SCD, which offers the prospect of low cost sp2 on sp3 technology. Raman and XPS results reveal the influence from the C-H band of ND surface. Impedance measurements show two conductive paths in the graphene-HND heterostructure. Graphene FET was built on this heterostructure, which exhibited n-type and high mobility. The family of amorphous carbon films, DLC, appeal to a preferable choice of graphene supporting substrate since IBM built the high-frequency graphene FET on DLC. For N-termination it was found that the optical band gap of DLC shrinked, whilst for F-terminated DLC it was found that fluorine groups reduce the DLC’s surface energy. Owing to different phonon energies and surface trap densities, graphene-DLC heterostructures give different electronic properties and offer the prospect for 2D lateral control applications.

Recently, great interest has been shown in the fabrication of periodic micro- and nanostructures over large area due to their increasing applications in diverse research fields including optics and electronics, cell biology, bioengineering and medical science. Diamond turning using multi-tip single crystal diamond tools fabricated by focused ion beam (FIB), as a new machining technique, shows powerful capacity in the fabrication of micro- and nanostructures. However, lack of support from systematic theoretical research has seriously hindered the advance and industrialization of this technique. As such, molecular dynamics (MD) simulations and experimental trials have been undertaken in this research work to systematically investigate this new technique from the FIB-induced damage during the tool fabrication process to the nanometric cutting mechanism using nanoscale multi-tip diamond tools. The transmission electron microscope (TEM) measurements were carried out to characterize the FIB-induced damaged layers in single crystal diamond under different ion beam processing voltages. A novel multi-particle collision MD model was developed to simulate the FIB-induced dynamic damage process in diamond. The results indicated that the fabrication of diamond tool by FIB can create an impulse-dependent damaged layer at the tool surface. The nature of FIB-induced damaged layer in the diamond tool is a mixture phase of sp² and sp³ hybridization and accommodates a significant proportion of the implanted gallium. The nanometric cutting process of using nanoscale multi-tip diamond tools was studied by MD simulations. The results provide in-depth understandings of the nanostructure generation process, the cutting force, the thermal effect, and the tool geometry-dependent shape transferability. The investigation shows that the formation mechanism of nanostructures when using multi-tip tools is quite different from that of using single tip tools. Since the nanostructures are synchronously formed by a single cutting pass, the effect of feed rate and the alignment issues associated with the use of single tip tools to achieve the same nanostructure can be completely eliminated when using nanoscale multi-tip tools. The unique tool geometrical parameters of a nanoscale multi-tip tool including the tool tip distance, tip angle, and tip configuration play important roles in the form accuracy of the machined nanostructures. A hypothesis of a minimum ratio of tip distance to tip base width (L/Wf) of the nanoscale multi-tip tool has been proposed and qualitatively validated by nanometric cutting experiments. A series of nanometric cutting experiments and associated MD simulations were further carried out to study the influence of processing parameters on the integrity of the machined nanostructures and tool wear. Under the studied cutting conditions, the burr and structure damage are the two major types of machining defects. With the increase of the depth of cut and the cutting speed, the increasing overlap effect between the tool tips is responsible for the formation of side burrs and structural damage. The tool wear was initially found at the sides of each tool tip after a cutting distance of 2.5 km. The FIB-induced damaged layer, the friction produced at each side of the tool tip, and the high cutting temperature distributed at the tool cutting edges are responsible for the initiation of tool wear. Based on the research objectives achieved, generic suggestions are proposed for the further development of diamond turning using nanoscale multi-tip tools in terms of selective parameters used in tool fabrication, optimal design of tool geometry, and optimization of processing parameters in nanometric cutting practice.

Research on wide band gap semiconductors suitable for power electronicdevices has spread rapidly in the last decade. The remarkable results exhibited bysilicon carbide (SiC) Schottky batTier diodes (SBDs), commercially available since2001, showed the potential of wide band gap semiconductors for replacing silicon (Si)in the range of medium to high voltage applications, where high frequency operationis required. With superior physical and electrical properties, diamond became apotential competitor to SiC soon after Element Six reported in 2002 the successfulsynthesis of single crystal plasma deposited diamond with high catTier mobility. This thesis discusses the remarkable properties of diamond and introducesseveral device structures suitable for power electronics. The calculation of severalfigures of merit emphasize the advantages of diamond with respect to silicon andother wide band gap semiconductors and clearly identifies the areas where its impactwould be most significant. Information regarding the first synthesis of diamond,which took place back in 1954, together with data regarding the modern technologicalprocess which leads nowadays to high-quality diamond crystals suitable for electronicdevices, are reviewed. Models regarding the incomplete ionization of atomic dopantsand the variation of catTier mobility with doping level and temperature have beenelaborated and included in numerical simulators. The study introduces the novel diamond M-i-P Schottky diode, a version ofpower Schottky diode which takes advantage of the extremely high intrinsic holemobility. The structure overcomes the drawback induced by the high activationenergies of acceptor dopants in diamond which yield poor hole concentration at roomtemperature. The complex shape of the on-state characteristic exhibited by diamondM-i-P Schottky structures is thoroughly investigated by means of experimentalresults, numerical simulations and theoretical considerations. The fabrication of a ramp oxide termination on a diamond device is for thefirst time reported in this thesis. Both experimental and simulated results show thepotential of this termination structure, previously built on Si and SiC power devices. A comprehensive comparison between the ramp oxide and two other versions of thefield plate termination concept, the single step and the three-step structures, has beenperformed, considering aspects such as electrical performance, occupied area,complexity of technological process and cost. Based on experimental results presented in this study, together withpredictions made via simulations and theoretical models, it is concluded that diamondM-i-P Schottky diodes have the ability to deliver significantly higher performancecompared to that of SiC SBDs if issues such as material defects, Schottky contactformation and measurement of reliable ionization coefficients are carefully addressedin the near future.

Aspects of the crystal structure of diamond, and its associated defects, have been considered with reference to the effect such characteristics might have on its mechanical properties. Also, established resolved shear stress models, which account for anisotropy in conventional Knoop indentation hardness of all single crystals, have been reviewed. Particular attention has been given to the role of microplasticity and the nature of crack formation in the deformed zone formed beneath the indenter. It is then shown that a similar approach can be applied to the case where a cone, made from a softer material, replaces the conventional rigid indenter. By using different materials covering a range of hardness, impressions can be formed beneath which there is a controlled density and depth of dislocations. In this work, the 'soft' indenter technique has been extended to high temperatures and applied to study the plasticity of various types of natural and synthetic diamond. Consequently, the effect of temperature on the critical resolved shear stress of synthetic type Ib, and natural type Ia and type IIa has been established. Above a critical threshold temperature for the onset of plasticity, time dependent growth of the impression volume occurs whilst the mean contact pressure is decreasing. It is shown that geometrical similarity, i.e. the ratio of the impression size to dislocated volume, is maintained whilst the critical mean pressure continues to be exceeded during this process of 'impression creep'. Activation energies of about 2.9 eV and 1.2 eV were determined, from rates of volume change, for natural (both type I and II) and synthetic type Ib respectively. Whilst no significant differences were observed between 98.9% 12C (natural abundance) and 99.9% 12C (isotopically enriched) synthetic diamonds, their behaviour was most like that of a type IIb diamond. Finally, by studying type la diamonds with a nitrogen concentration ranging from 14 - 750 ppm, evidence is obtained which supports the suggestion that this element reduces the intrinsic resistance to dislocation movement and encourages the initiation of cracks in the diamond structure.

Doutoramento em Física
This work studies diamond growth on copper by microwave plasma chemicalvapour- deposition (MPCVD). Diamond nucleation and growth characteristics are the essential aspects in CVD process. We show that the substrate pre-treatment influences strongly the diamond nucleation. The diamond quality and growth characteristics are mainly controlled by the deposition conditions. In practical applications CVD diamonds fall into two main forms. One is freestanding films and another is adherent coatings on different materials. Copper is a promising substrate material for preparing free-standing diamond films because of its non-carbon affinity. However, the large mismatch in thermal expansion between the diamond and copper usually leads to the film cracking during the post cooling procedure. In order to overcome this problem we develop a two-step growth method which consists of two growth stages. In the first stage a short deposition is performed for obtaining a sufficient but non-continuous nucleation. Then a quick ramp down in plasma power and temperature releases the diamond crystals from their trapped positions. In the second stage a normal deposition is performed for obtaining continuous diamond films of desired quality. No cracking in the film happens during the post cooling procedure after the second deposition. On the other hand, many applications require sufficient adhesion of diamond coating to the substrate. Since direct deposition of diamond on copper yields no adhesion, we propose using an interlayer which can provide adequate adhesion to both the copper substrate and the diamond film. The diffusion behaviour of carbon and copper in different refractory materials as well as their carbide bond strength is considered in order to find a suitable interlayer material. It is shown that titanium is one of the promising candidates. Adherent diamond coatings on copper are obtained using a titanium buffer layer of 0.2-5 pm thick. The electrical conductivity of the diamond films show a strong and controllable dependence on the deposition conditions. Selective deposition of diamond on the Tilcopper are demonstrated. In addition, adherent diamond coating on steel is also obtained by using a titanium interlayer. Quantitative evaluation of the adhesion of diamond coatings is a fundamental subject and has been a long standing concern in various of coatings. We show that conventional methods, like adhesion scratch tests, pull-off tests, indentation tests, and micro-Raman spectroscopy, usually can not give quantitative results when examining the diamond coatings. Therefore, we develop two new methods, trying to solve this problem. The first one is a thermal quench combined with micro-Raman spectroscopy method and the second is a micro-indentation test based model. In the thermal quench method the diamond coatings on TiICu substrate are quenched from room temperature to lower temperatures. The critical temperature at which the film detaches is revealed by the shift of the diamond Raman line to the stress-free value of 1332 cm-'. The coating adhesion is considered to be equivalent to the thermal stress induced by the quench and can be quantitatively calculated from the thermal and mechanical properties of the substrate and the diamond. For the diamond coatings on Tilcopper, this method reveals an adherence of approx. 2.42 GPa. The micro-indentation model is based on the experimental evidence that small indentation load always causes round spallation in the diamond films whatever the shape of the indenter is. An exponential sink-in deformation of the coating under the indentation is proposed (y = -a;bexp(-bx)). The deformation stress at the spallation edge is considered the coating adhesion. The modeled adhesion of the diamond coatings on copper is about 1.921-1.956 GPa, which is in agreement with the thermal quench results. The validity of this model is also verified by its self-consistence. Residual stress is an essential aspect determining the reliability of diamond coatings. We find experimentally that the increase in the film thickness leads to a shift of the diamond Rarnan line from higher wave numbers to 1332 cm-'. A linear relationship between the film thickness and the in-plane stress is observed and a theoretical model is developed to interpret the results. This decrease in stress along the film thickness is usually not taken into account in other stress measurement techniques, like substrate curvature, X-ray diffraction etc. The most important mechanical properties, namely the hardness and wear resistance, of the diamond coatings on copper are investigated. The coating hardness is modeled by considering the coatinglsubstrate a composite material. Tribological tests show a high wear resistance of the diamond coatings. The friction coefficient is found to be proportional to both the wear load and the diamond grain size.
O presente trabalho foi dedicado ao estudo do crescimento de filmes de diamante em substractos de cobre, utilizando, para o efeito, a técnica de Deposição Química na Fase de Vapor Assistido por Micro-Ondas (MPCVD). Foi demonstrado que o processo de nucleação depende sobremaneira do pré-tratamento do substracto enquanto que a qualidade dos filmes e o modo de crescimento são controlados, essencialmente, pelas condições de deposição. De acordo com a aplicação prática a que se destinam, os filmes de diamante podem apresentar-se sob duas formas distintas: filmes livres (free-standing) ou filmes aderentes a outros materiais. No que concerne a preparação de filmes livres, o cobre é geralmente apontado como um substracto promissor, devido à sua não afinidade para com o carbono. Contudo, os valores dos coeficientes de expansão térmica do cobre e do diamante divergem significativamente, conduzindo geralmente à rotura do filme durante o processo de arrefecimento. A fim de ultrapassar este problema foi desenvolvido um processo de crescimento em duas etapas. Na primeira etapa, efectua-se uma deposição de curta duração conducente à obtenção duma nucleação forte e um decréscimo da temperatura e da potência do plasma para libertar os grãos de diamante das suas posições no cobre. Na segunda etapa, procede-se a uma deposição normal para obtenção dum filme continuo e com a qualidade desejada. Nestas condições verificou-se não ocorrer rotura do filme durante o mefecimento. Por outo lado, existem várias aplicações industriais para as quais é requerida uma forte adesão do diamante ao substracto. Sendo conhecido, à priori, que a deposição directa não constituia solução tecnológica viável, foi proposta a introdução de uma camada intermédia com capacidade de aderir tanto ao cobre como ao diamante. Aselecção do material respectivo baseou-se em estudos da difusão do carbono e do cobre em diversos materiais refractários e da energia de formação de carboretos. Neste âmbito constatou-se ser o titânio o material adequado. De facto, os testes efectuados permitiram obter filmes de diamante aderentes usando uma camada intermédia de titânio com 0,2-5 pm de espessura. A condutividade eléctrica dos filmes de diamante é fortemente dependente das condições de deposição que, por seu turno, podem ser devidamente controladas. Deste modo, é possível efectuar uma deposição selectiva de TiICu. Na sequência deste estudo foi também demonstrado ser possível alargar o campo de utilização desta tecnologia a substractos de aço. A análise quantitativa da adesão de filmes é um tema de grande actualidade, fundamentalmente na área dos revestimentos. No caso dos filmes de diamante, tal problema assume ainda maior dimensão uma vez que os métodos convencionais de análise tais como os testes scratch, descolamento, indentação e espectroscopia Raman não permitem a obtenção de resultados fiáveis. Tendo em atenção tais limitações, foram desenvolvidos dois métodos conducentes à avaliação quantitativa da adesão. O primeiro baseou-se na combinação entre um arrefecimento rápido e os espectros de Raman; O segundo baseou-se em testes de micro-indentação. A metodologia do primeiro método pressupõe o arrefecimento de filmes crescidos em TiICu até uma temperatura crítica, abaixo da temperatura ambiente, após a qual ocorre o descolamento do filme. Tal fenómeno é caracterizado por um desvio do pico de Raman relativamente ao obtido em amostras isentas de tensão e cujo valor é de 1332 cm-I. Isto é, considera-se a adesão equivalente à tensão induzida pelo arrefecimento, podendo o cálculo ser efectuado a partir das propriedades térmicas e mecânicas do substracto e do filme. Para os filmes crescidos em TiICu obteve-se uma aderência de 2,42 GPa. O segundo modelo baseia-se em testes de indentação, nomeadamente na evidência experimental que a região do filme que se encontra em redor do indentador descola do substracto. Tal fenómeno resulta do facto da tensão instalada ser superior à adesão. Em resultado do processo de indentação a zona do filme descolada, apresenta uma deformação que é máxima no ponto de indentação. Para caracterizar tal gradiente de deformação proposemos uma lei exponencial do tipo y =-a"exp(-bx). Através do conhecimento do valor de deformação na fronteira da zona descolada foi possível calcular o valor da tensão correspondente tendo como base as características elásticas do diamante. Esta tensão foi considerada equivalente à adesão tendo-se obtido um valor de 1,921-1,956 GPa, isto é um valor semelhante ao obtido pelo método de arrefecimento rápido. A tensão residual é um factor essencial que determina a fiabilidade dos filmes de diamante. Verificou-se experimentalmente que com o aumento da espessura dos filmes a linha de Raman do diamante aproxima-se da linha tipica de filmes isentos de tensões. Foi também detectada a existência duma relação linear entre a espessura do filme e a tensão equivalente, tendo sido desenvolvido um modelo teórico para explicar os resultados. Deve salientar-se que a diminuição da tensão com o aumento da espessura do filme não é tida geralmente em consideração, nomeadamente quando se utilizam outras técnicas de medição da tensão tais como a curvatura do substracto e a difracção de raios X. Finalmente, foi efectuado o estudo de duas propriedades mecânicas fundamentais do filme, a saber a dureza e o desgaste. A dureza foi modelada considerando o filme/subs~,actoc omo um material compósito. Os testes tribológicos mostraram que os filmes apresentam uma elevada resistência ao desgaste sendo o coeficiente de atrito proporcional à carga de desgaste e ao tamanho de grão do diamante.

Thesis (M.F.A.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Dept of English. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

This thesis presents initial work in attempting to understand the class of ‘diamond-free’ 3-cs-transitive partial orders. The notion of diamond-freeness, proposed by Gray, says that for any a ≤ b, the set of points between a and b is linearly ordered. A weak transitivity condition called ‘3-cs-transitivity’ is taken from the corresponding notion for cycle-free partial orders, which in that case led to a complete classification [3] of the countable examples. This says that the automorphism group acts transitively on certain isomorphism classes of connected 3-element structures. Classification for diamond-free partial orders seems at present too ambitious, but the strategy is to seek classifications of natural subclasses, and to test conjectures suggested by motivating examples. The body of the thesis is divided into three main inter-related chapters. The first of these, Chapter 3, adopts a topological approach, focussing on an analogue of topological covering maps. It is noted that the class of ‘covering projections’ between diamond-free partial orders can add symmetry or add cycles, and notions such as path connectedness transfer directly. The concept of the ‘nerve’ of a partial order makes this analogy concrete, and leads to useful observations about the fundamental group and the existence of an underlying cycle-free partial order called the universal cover. In Chapter 4, the work of [1] is generalised to show how to decompose ranked diamond- free partial orders. As in the previous chapter, any diamond-free partial order is covered by a specific cycle-free partial order. The paper [1] constructs a diamond-free partial order with cycles of height 1 from a different cycle-free partial order through which the universal covering factors. This is extended to construct a sequence of diamond- free partial orders with cycles of finite height which are not only factors but have the chosen diamond-free partial order as a ‘limit’. This leads to a better understanding of why structures with cycles only of height 1 are special, and the rest divide into structures with cycles of bounded height and a cycle-free backbone, and those for which the cycles have cofinal height. Even these can be expressed as limits of structures with cycles of 6 bounded height, though not directly. A variety of constructions are presented in Chapter 5, based on an underlying cycle- free partial order, and an ‘anomaly’, which in the simplest case given in [5] is a 2-level Dedekind-MacNeille complete 3-cs-transitive partial order, but which here is allowed to be a partial order of greater complexity. A rich class of examples is found, which have very high degrees of homogeneity and help to answer a number of conjectures in the negative.

Ti-rich minerals occur in xenoliths of metasomatized mantle peridotites, MARID and PIC. Xenocrysts produced by disaggregation during the intrusion have equivalent compositions. Early crystallization in the first intrusive stage in kimberlites and related rocks produces olivine phenocrysts that may have trapped inclusions of co-crystallizing rutile, Mg-rich ilmenite to geikielite and chromite. Geikielite may replace Ti-bearing minerals of the xenocrystic suite, producing a suite of magnesian ilmenites of intermediate compositions that follow an Mg enrichment trend depending on the grade of interaction xenocrysts/magma. Phlogopite microphenocrysts can start to crystallize in this stage. A second magmatic stage produces saturation in pyrophanite, that can precipitate or react with all the above Ti-rich minerals, producing crystallization of a suite of intermediate manganoan ilmenites whose compositions depend on that of the replaced Ti-mineral and the grade of interaction of the magma with the above crystals. Lately in this stage, qandilite-ulvöspinel-magnetite start to crystallize, together with perovskite, along with phlogopite microphenocrysts. Finally, the crystallization of ulvöspinel-magnetite crystals may be produced in disequilibria, inducing the development of atoll textures. Groundmass phlogopite crystallize in the late magmagtic stage. Monticellite can be formed in this stage. Interstitial glass can be produced at the end of this stage. Subsolidus hydrothermal processes are widespread in most of the kimberlites, with replacement of the early minerals by hydrous and carbonic fluids of kimberlitic provenance. Olivines and glass are replaced by serpentines and carbonates. A sequence of ilmenites (geikielite followed by pyrophanite) can precipitate directly or replace the above Ti-bearing minerals. Spinels and perovskites may also be replaced by Ti hydrogarnets and late perovskite or kassite accompanied by aeschynite. The composition of the replacing ilmenite depends on that of the replaced mineral. Hence, these ilmenites can retain Nb, Cr, Zr when replacing rutile or perovskite, chromite or crichtonite. Therefore, the trace composition of ilmenite cannot be used to extract petrogenetic information. Mg- or Mn-ilmenites cannot be used as DIM because they are very late minerals formed during the intrusion. When plotting the composition of these minerals in the existing IUGS classification diagrams there is an extensive overlap among kimberlites and related rocks. Thus the existing classification diagrams are not useful and we propose some amendments to the existing classification.

A l’heure des mégadonnées, du traitement et de l’échange d’informations de masse, le développement de nouvelles technologies liées à l’information est un défi important de notre société. Pour répondre à ce besoin grandissant, le monde de l’infiniment petit régi par les lois de la physique quantique offre d’importantes possibilités de développement technologique. Cette thèse s’inscrit dans le contexte de l’émergence des nouvelles technologies quantiques basées sur l’utilisation d’atomes artificiels. Nous nous sommes particulièrement intéressés aux possibilités offertes par les spins nucléaires uniques dans le diamant. Le début de ce mémoire de thèse vise à introduire les propriétés du défaut NV du diamant dont le spin électronique peut être utilisé pour détecter les spins nucléaires présents dans la matrice de diamant. Le caractère anisotrope de l’interaction hyperfine entre le spin électronique du centre NV et les spins nucléaires de 13C sera exploité pour initialiser l’état de ces spins nucléaires en tirant profit d’un anti-croisement de niveau. La structure particulière des niveaux d’énergie de ce système de spins à l’anti-croisement de niveaux nous permettra de revisiter le phénomène de piégeage cohérent de population avec un spin nucléaire unique à température ambiante. Enfin, en vue des applications technologiques de ce système, nous présenterons la mise en place d’une expérience de détection micro-onde du spin électronique associé au défaut NV permettant de s’affranchir de l’illumination optique qui représente la source principale de décohérence de l’état quantique des spins nucléaires. Les résultats obtenus dans cette thèse, relatifs au contrôle des systèmes de spins dans le diamant, s’inscrivent dans la perspective de développement des systèmes quantiques hybrides. Ainsi, l’association des longs temps de cohérence des spins nucléaires aux performances de calcul des bits quantiques supraconducteurs est une voie prometteuse de développement des technologies quantiques de l’information
At a time where processing and exchanging big sets of data is one of the main challenge of our society, the development of technologies related to information based on the principles of quantum physics offer interesting new perspectives. This thesis is within the context of the emergence of new quantum technologies based on artificial atoms. We are particularly interested in the opportunities offered by single nuclear spins in diamond. The beginning of this thesis introduces the properties of the NV coloured center of diamond. In particular, we explain how the NV defect electronic spin can be used to detect nuclear spins dispersed in the diamond matrix. By making use, the anisotropic nature of the hyperfine interaction between the NV electron spin and 13C nuclear spins, we demonstrate nuclear spin initialization close to the nuclear spin levels anti-crossing. The specific structure of the spin system’s energy levels enables us to revisit the phenomenon of coherent population trapping with a single nuclear spin at room temperature. Finally, in the aim of developing new technologies based on this spin system, we describe the beginning of a project going towards the implementation of the micro-wave detection of a single electronic spin in diamond. This project is aiming to get rid of the optical illumination which is the main source of decoherence of the nuclear spin quantum state in diamond. The results obtained in this thesis about the control of spin systems in diamond, can be combined with the development of hybrid quantum systems. Thus, the combination of the long coherence time of nuclear spins with the computing performances of superconducting qu-bits is a promising development of quantum information technology

Summary in English.
Bibliography: pages 102-118.
Synthetic diamonds are successfully substituting for natural diamonds in the area of industrial application. Synthetic diamonds increased their market share from 10% in 1960 to 50% in 1968 and to 90% in 1994. The success of synthetic diamonds may be ascribed largely to technological advance in the area of diamond manufacture. Two technologies in particular contributed to this advance: (i) High pressure and high temperature (HPHT) processes for crystallising carbon material and (ii) chemical vapour deposition (CVD) of these materials. The substitution of synthetic for natural diamond occurred in a systematic and predictable manner. Further technological advance could threaten the concept of diamond as a unique and desirable substance in the minds of the consumers and may require the repositioning of its image.

The first diamond mine in North America was discovered in 1906 when John W. Huddleston found two diamonds on his farm just south of Murfreesboro in Pike County, Arkansas. Experts soon confirmed that the diamond-bearing formation on which Huddleston made his discovery was the second largest of its kind and represented 25 percent of all known diamond-bearing areas in the world. Discovery of the field generated nearly a half century of speculative activity by men trying to demonstrate and exploit its commercial viability. The field, however, lacked the necessary richness for successful commercial ventures, and mining was eventually replaced in the early 1950s by tourist attractions that operated successfully until 1972. At that time the State of Arkansas purchased the field and converted it to a state park. Thus this work tell the rich and complicated story of America'a once and only diamond field, analyzes the reasons for the repeated failures of efforts to make it commercially viable, and explains how it eventually succeeded as a tourist venture.

Diamond is a promising material for high-power, high-frequency and hightemperatureelectronics applications, where its outstanding physical propertiescan be fully exploited. It exhibits an extremely high energy gap, veryhigh carrier mobilities, high breakdown field strength, and the highest thermalconductivity of any wide bandgap material. It could therefore producethe fastest switching, the highest power density, and the most efficient electronicdevices obtainable, with applications in the RF power, automotive andaerospace industries. Lightweight diamond devices, capable of high temperatureoperation in harsh environments, could also be used in radiationdetectors and particle physics applications where no other semiconductordevices would survive.The high defect and impurity concentration in natural diamond or polycrystallinehigh-pressure-high-temperature (HPHT) diamond substrates hasmade it difficult to establish reliable results when studying the electronicproperties of diamond. However, recent progress in the growth of high puritySingle-Crystal Chemical Vapor Deposited Diamond (SC-CVD) has openedthe perspective of applications under such extreme conditions based on thistype of artificial diamond.Despite the improvements, there are still many questions which must beanswered. This work will focus on electrical characterization of (SC-CVD)diamond by different measurements techniques such as internal photoemission,I-V, C-V, Hall and in particular, time-of-flight (TOF) carrier driftvelocity measurements. With the mentioned techniques, some importantproperties of diamond such as drift mobilities, lateral carrier transit velocities,compensation ratio and Schottky barrier heights have been investigated.Low compensation ratios (ND/NA) < 10-4 have been achieved in boron-dopeddiamond and a drift mobility of about 860 cm2 / V for the hole transit nearthe surface in a lateral TOF configuration could be measured.

Thesis (M.S.)--Southern Illinois University Carbondale, 2006.
"Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 99-102). Also available online.

Two-dimensional images of synthetic industrial diamond particles were obtained using a camera, framegrabber and PC-based image analysis software. Various methods for shape quantification were applied, including two-dimensional shape factors, Fourier series expansion of radius as a function of angle, boundary fractal analysis, polygonal harmonics, and corner counting methods. The shape parameter found to be the most relevant was axis ratio, defined as the ratio of the minor axis to the major axis of the ellipse with the same second moments of area as the particle. Axis ratio was used in an analysis of the sorting of synthetic diamonds on a vibrating table. A model was derived based on the probability that a particle of a given axis ratio would travel to a certain bin. The model described the sorting of bulk material accurately but it was found not to be applicable if the shape mix of the feed material changed dramatically. This was attributed to the fact that the particle-particle interference was not taken into account. An expert system and a neural network were designed in an attempt to classify particles by a combination of four shape parameters. These systems gave good results when discriminating between particles from bin I and bin 9 but not for neighbouring bins or for more than two classes. The table sorting process was discussed in light of the findings and it was demonstrated that the shape distributions of sorted diamond fractions can be quantified in a useful and meaningful way.

This thesis describes the application of total energy pseudopotential calculations to the study of the mechanical deformation of diamond. It begins with a description of the theoretical basis for these calculations. Following this is an outline of the elements required for an implementation of the theory for periodic systems and using a basis set of plane waves. The simulations performed on the deformation of diamond approximate the system of interest to one in which the system is periodically repeated. The importance of this approximation is studied in detail and the errors introduced are found to be small enough to neglect. Next, a study of one of the most unusual aspects of the mechanical deformation of diamond is presented. Diamond polishing and in particular the very strong anisotropy between different polishing directions on the (110) surface is simulated. The experimental evidence regarding diamond polishing is presented and the approximations made in representing the polishing process by the simulations are discussed. Differences in the mechanism of material removal between polishing directions are related to processes of nanogroove formation and are shown to be consistent with the experimental findings. A preliminary study which investigates the resolution limit of Atomic Force Microscopy (AFM) in the contract mode is presented. A central problem in contact mode AFM has been whether or not tips which have a single atom at the apex can support the long range attractive van de Waals force. Two vertical scans of a single atom diamond tip into a diamond (111) surface are presented. These simulations indicate that, in this system, the single atom tip is resistant to force in the vertical direction but that lateral movement results in removal of the apex atom from the tip. The thesis concludes with a brief survey of the central results and a discussion of the likely future developments in the field.