Um método original para a fabricação de microbocais de diamante com perfil convergente-divergente foi desenvolvido neste trabalho. O método de fabricação desenvolvido utiliza deposição de diamante policristalino sobre moldes que posteriormente são removidos. Os moldes utilizados são fios de tungstênio submetidos a um processo de corrosão eletrolítica para gerar o perfil convergente-divergente de bocal. O microbocal de diamante foi fabricado para ser utilizado como controlador e medidor passivo de vazão de fluidos, quando operando em condições críticas de escoamento. Testes de vazão de gás foram realizados, utilizando os microdispositivos fabricados, para determinar os parâmetros de escoamento necessários para a utilização dos microdispositivos como controladores e medidores de vazão de gás. Os parâmetros críticos de escoamento, a saber, a vazão mássica crítica, a razão crítica de pressão e a vazão volumétrica crítica, bem cmo a faixa do número de Reynolds do escoamento e o coeficiente de descarga, foram determinados para todos os microdispositivos. A faixa de variação do número de Reynolds dos escoamentos obtidos foi de 1x10 POT.3-7x10 POT.4. Por exemplo, o microbocal de diamante com o menor diâmetro de garganta (16+/-1)x10mum apresentou vazão mássica crítica de (0,344+006)g/min, vazão volumétrica crítica de (314+/-5)cm POT.3/min e coeficiente de descarga de (1,27+/-0,19). Assim, foram fabricados com sucesso microbobais de diamante com perfil convergente-divergente e foram determinados os parâmetros críticos de escoamento que possibilitam a estes microbocais atuarem como controladores e medidores passsivos de baixo vazão de gás. / In this work an original method for the fabrication of diamond micronozzles with converget-divergent profile is presented. The method uses the deposition of polycrystalline diamond over a mold, which is subsequently removed. The referred molds are tungsten wires patterned by means of an electrolytic etching procedure in a way that the divergent-convergent profile is generated. The main motivation for producing such micronozzles is its application as passive flow controllers and flow meters elements when operating under critical flow conditions. The micronozzles produced here were tested in order to determine the critical flow parameters that are necessary for its operation, as passive flow controllers and flow meters elements. The critical flow parameters (critical mass flow rate, critical pressure ratio and critical volumetric flow rate), the Reynolds number range and the discharge coefficient were determined for all the microdevices produced. The Reynolds number for the microdevices was found to be in the range of 1x10 POT.3-7x10 POT.4. For instance, the diamond micronozzle with smaller throat diameter, (16+/-1)x10mum, presented critical mass flow rate of (0,344+0,006)g/min, critical volumetric flow rate of (314+/-5)cm POT.3/min and discharge coefficient of (1,27+/-0,19). Therefore, diamond micronozzles were successfully fabricated with convergent-divergent profile and the critical flow parameters necessary for its operation, as passive flow controllers and flow meters elements, were determined.

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

Particle-reinforced MMCs (pMMC) such as aluminum alloys reinforced with ceramic silicon carbide particles (AlSiC) require special cutting tools due to the high hardness and abrasive properties of the ceramic particles. Diamond coated cutting tools are ideal for machining this type of pMMC. Previous research studies focus on the machinability of pMMCs with low ceramic content. The aim of this research is to determine the optimal cutting parameters for machining AlSiC material containing high silicon carbide particle reinforcement (>25%). The optimal cutting parameters are determined by investigating the relationship between cutting forces, tool wear, burr formation, surface roughness, and material removal rate (MRR). Experimental milling tests are conducted using CVD diamond coated end mills and non-diamond tungsten carbide end mills. It was found that low tool rotation speeds, feed rates and depths of cut are necessary to achieve smoother surface finishes of R a < 1 μm. A high MRR to low tool wear and surface roughness ratio was obtainable at a tool rotation speed of 6500 r/min, feed rate of 762 mm/min and depth of cut of 3 mm. Results showed that a smooth surface roughness of the workpiece material was achieved with non-diamond tungsten carbide end mills, however, this was at the expense of extreme tool wear and high burr formation. The use of coolant caused a 50% increase in tool wear compared to the dry-cutting experiments which had lower cutting tool forces.

Diamond is a semiconductor with many superior material properties such as high breakdown field, high saturation velocity, high carrier mobilities and the highest thermal conductivity of all materials. These extreme properties, as compared to other (wide bandgap) semiconductors, make it desirable to develop single-crystalline epitaxial diamond films for electronic device and detector applications. Future diamond devices, such as power diodes, photoconductive switches and high-frequency field effect transistors, could in principle deliver outstanding performance due to diamond's excellent intrinsic properties. However, such electronic applications put severe demands on the crystalline quality of the material. Many fundamental electronic properties of diamond are still poorly understood, which severely holds back diamond-based electronic device and detector development. This problem is largely due to incomplete knowledge of the defects in the material and due to a lack of understanding of how these defects influence transport properties. Since diamond lacks a shallow dopant that is fully thermally activated at room temperature, the conventional silicon semiconductor technology cannot be transferred to diamond devices; instead, new concepts have to be developed. Some of the more promising device concepts contain thin delta-doped layers with a very high dopant concentration, which are fully activated in conjunction with undoped (intrinsic) layers where charges are transported. Thus, it is crucial to better understand transport in high-quality undoped layers with high carrier mobilities. The focus of this doctoral thesis is therefore the study of charge transport and related electronic properties of single-crystalline plasma-deposited (SC-CVD) diamond samples, in order to improve knowledge on charge creation and transport mechanisms. Fundamental characteristics such as drift mobilities, compensation ratios and average pair-creation energy were measured. Comparing them with theoretical predictions from simulations allows for verification of these models and improvement of the diamond deposition process.

In the frame of this thesis, a new experimental setup for the measurement of the energy loss of carbon ions at maximum stopping power in a hot laser-generated plasma has been developed and successfully tested. In this parameter range where the projectile velocity is of the same order of magnitude as the thermal velocity of the plasma free electrons, large uncertainties of up to 50% are present in the stopping-power description. To date, no experimental data are available to perform a theory benchmarking. Testing the different stopping theories is yet essential for inertial confinement fusion and in particular for the understanding of the alpha-particle heating of the thermonuclear fuel. Here, for the first time, precise measurements were carried out in a reproducible and entirely characterized beam-plasma configuration. It involved a nearly fully-stripped ion beam probing a homogeneous fully-ionized plasma. This plasma was generated by irradiating a thin carbon foil with two high-energy laser beams and features a maximum electron temperature of 200 eV. The plasma conditions were simulated with a two-dimensional radiative hydrodynamic code, while the ion-beam charge-state distribution was predicted by means of a Monte-Carlo code describing the charge-exchange processes of projectile ions in plasma. To probe at maximum stopping power, high-frequency pulsed ion bunches were decelerated to an energy of 0.5 MeV per nucleon. The ion energy loss was determined by a time-of-flight measurement using a specifically developed chemical-vapor-deposition diamond detector that was screened against any plasma radiation. A first experimental campaign was carried out using this newly developed platform, in which a precision better than 200 keV on the energy loss was reached. This allowed, via the knowledge of the plasma and of the beam parameters, to reliably test several stopping theories, either based on perturbation theory or on a nonlinear T-Matrix formalism. A preliminary analysis suggests that the energy deposition at maximum stopping power is significantly smaller than predicted, particularly, by perturbation approaches.

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

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.

Machining of Aluminum can be complicated due to large amounts of adhesion and diffusion of the aluminum onto the cutting tool, causing effects such as built-up layers and built-up edges. This leads to poor surface finishes and can significantly affect the tool life. CVD diamond coated tools have shown to be a potential solution to this problem and is tested and analyzed as such in this thesis. CVD diamond coated inserts are tested and compared to uncoated cemented carbide inserts and Polycrystalline diamond tipped inserts, in milling, turning and in refined tribological methods. The workpiece material in both the machine tests and the tribological tests is a high strength aluminum of the name Alumec 89. The machine tests were performed for 5 and 60 seconds at three cutting speeds, 600, 900 and 1200 m/min, keeping other parameters constant. The cutting inserts, the chips and the generated workpiece surface are examined using LOM, SEM and EDS. In the refined tribological testing, a pin-turning tribometer is used, with pins of uncoated and coated (CVD diamond) cemented carbide pins. These are tested at 5 and 30 seconds at 600 and 1200 m/min, applying a constant force of 10 N. In addition, a friction test was performed to measure the friction of the uncoated and the CVD diamond coated cemented carbide. Like the cutting inserts, the used pins were examined in LOM and SEM. The results show that while a large amount of built-up layer and built-up edges gather when using uncoated cemented carbide tools, only minimal amounts can be detected on CVD diamond and PCD. It has also been shown that the reason for the reduced adhesion in the case of diamond tooling materials is most likely due to the lack of chemical interactions between the diamond and the aluminum. The friction of the CVD diamond material was shown to be lower compared to the cemented carbide. The surface finish generated by the different materials, was the best in the case of PCD while the CVD generated multiple small scratches that severely reduced the surface roughness. This thesis provides some initial basic understanding of the interaction of CVD diamond coated inserts with high strength aluminum alloys.

Dans le cadre de cette thèse, un nouveau dispositif expérimental pour la mesure du dépôt d'energie d'ions carbone au maximum du pouvoir d'arrêt dans un plasma généré par laser a été développé et testé avec succès. Dans ce domaine de paramètres où la vitesse du projectile est de l'ordre de grandeur de la vitesse thermique des électrons libres du plasma, l'incertitude théorique sur le pouvoir d'arrêt peut atteindre 50%. Or à l'heure actuelle, aucune donnée expérimentale ne permet de vérifier et de tester les différentes prédictions. Une discrimination des théories existantes du pouvoir d'arrêt est cependant essentielle pour la Fusion par Confinement Inertiel et particulièrement pour comprendre le chauffage du combustible par les particules alpha dans la phase d'allumage. Pour la première fois, des mesures précises du dépôt d'énergie des ions ont été effectuées dans une configuration expérimentale reproductible et entièrement caractérisée. Celle-ci consiste en un faisceau d'ions entièrement ionisé interagissant avec un plasma entièrement ionisé et homogène. Le plasma a été généré par l'irradiation d'une cible mince de carbone avec deux faisceaux laser à haute énergie et présente une température électronique maximale of 200 eV. Les paramètres du plasma ont été simulés à l'aide d'un code hydrodynamique radiatif bi-dimensionel, tandis que la distribution de charge du faisceau d'ions a été estimée avec un code Monte-Carlo qui décrit les processus d'échange de charge des ions dans le plasma. Pour sonder le plasma au maximum du pouvoir d'arrêt, un faisceau d'ions pulsé à haute fréquence a été freiné à une énergie de 0.5 MeV par nucléon. Le dépôt d'énergie des ions a été déterminé via une mesure de temps de vol à l'aide d'un détecteur à base de diamant produit par dépôt chimique en phase vapeur, protégé contre les radiations émises par le plasma. Une première campagne expérimentale a été conduite pour exploiter le nouveau dispositif, dans laquelle le dépôt d'énergie a été mesuré avec une précision inférieure à 200 keV. Cela a permis, grâce à la connaissance des paramètres du plasma et du faisceau d'ions, de tester différentes théories de pouvoir d'arrêt de manière fiable. Une analyse préliminaire des résultats montre que le dépôt d'énergie au maximum du pouvoir d'arrêt est plus faible qu'il n'a été prédit par la plupart des théories, et en particulier par les théories des perturbations. / In the frame of this thesis, a new experimental setup for the measurement of the energy loss of carbon ions at maximum stopping power in a hot laser-generated plasma has been developed and successfully tested. In this parameter range where the projectile velocity is of the same order of magnitude as the thermal velocity of the plasma free electrons, large uncertainties of up to 50% are present in the stopping-power description. To date, no experimental data are available to perform a theory benchmarking. Testing the different stopping theories is yet essential for inertial confinement fusion and in particular for the understanding of the alpha-particle heating of the thermonuclear fuel. Here, for the first time, precise measurements were carried out in a reproducible and entirely characterized beam-plasma configuration. It involved a nearly fully-stripped ion beam probing a homogeneous fully-ionized plasma. This plasma was generated by irradiating a thin carbon foil with two high-energy laser beams and features a maximum electron temperature of 200 eV. The plasma conditions were simulated with a two-dimensional radiative hydrodynamic code, while the ion-beam charge-state distribution was predicted by means of a Monte-Carlo code describing the charge-exchange processes of projectile ions in plasma. To probe at maximum stopping power, high-frequency pulsed ion bunches were decelerated to an energy of 0.5 MeV per nucleon. The ion energy loss was determined by a time-of-flight measurement using a specifically developed chemical-vapor-deposition diamond detector that was screened against any plasma radiation. A first experimental campaign was carried out using this newly developed platform, in which a precision better than 200 keV on the energy loss was reached. This allowed, via the knowledge of the plasma and of the beam parameters, to reliably test several stopping theories, either based on perturbation theory or on a nonlinear T-Matrix formalism. A preliminary analysis suggests that the energy deposition at maximum stopping power is significantly smaller than predicted, particularly, by perturbation approaches. / Im Rahmen dieser Arbeit wurde ein neuer experimentelle Aufbau für die Messung des Energieverlusts von Kohlenstoff-Ionen bei maximalem Bremsvermögen in einem lasererzeugtem Plasma entwickelt und getestet. In diesem Parameterbereich, wo die Projektilgeschwindigkeit nah der thermischen Geschwindigkeit der Plasmaelektronen liegt, weist die theoretische Beschreibung des Bremsvermögens erheblichen Unsicherheiten bis 50% auf. Ausserdem sind bisher keine experimentellen Daten verfügbar, um die theoretischen Vorhersagen zu testen. Eine Bewertung der verschiedenen Theorien des Bremsvermögens ist jedoch von grosser Bedeutung für die Trägheitsfusion und insbesondere für das Verständnis der Heizung des Fusionsbrennstoffs mittels Alpha-Teilchen. Zum ersten Mal wurden präzisen Messungen in einer reproduzierbaren und vollständig bekannten Strahl-Plasma Einstellung durchgeführt. Sie besteht in einem vollionisierten Ionenstrahl, der mit einem homogenen und vollionisierten Plasma wechselwirkt. Das Plasma wurde von der Bestrahlung einer dünnen Kohlenstofffolie mit zwei hochenergetischen Laserstrahlen erzeugt, und weist eine maximale Elektronentemperatur von 200 eV auf. Die Plasmaparameter wurden mithilfe eines zweidimensionalen radiativen hydrodynamischen Codes simuliert, während die Ladungsverteilung des Ionenstrahls wurde mit einem Monte-Carlo Code berechnet, der die Umladungsprozesse von Projektilionen im Plasma beschreibt. Um das Plasma bei maximalem Bremsvermögen zu untersuchen, wurde ein hoch-Frequenz gepulster Ionenstrahl zu einer Energie von 0.5 MeV pro Nukleon heruntergebremst. Der Ionenenergieverlust wurde mit der Flugzeitsmethode mit einem gegen Plasmastrahlung abgeschirmten CVD-Diamant-Detektor gemessen. Eine erste experimentelle Kampagne wurde mit dem neuen Aufbau durchgeführt, in der eine Messungspräzision besser als 200 keV auf dem Energieverlust erreicht wurde. Dies ermöglichte, mit der Kenntnis der Plasma- und Strahlparameter, mehreren Bremsvermögen-Theorien zuverlässig zu testen und zu vergleichen. Eine vorläufige Datenanalyse zeigt, dass die Energiedeposition bei maximalem Bremsvermögen ist kleiner, als insbesondere von den störungstheoretischen Ansätzen vorhergesagt wurde.

Im Hinblick auf das immense Potential von Diamant als Material für die Mikroelektronik wurden im Rahmen dieser Arbeit undotierte und dotierte Diamantfilme mittels chemischer Gasphasenabscheidung auf Silizium präpariert und anschließend auf ihre elektronischen Eigenschaften hin untersucht. Für Letzteres wurde hauptsächlich die Elektronen-Energieverlustspektroskopie in Transmission verwendet. In situ Gasphasendotierung oder Ionenimplantation wurde zur Dotierung der Filme mit Bor, Lithium oder Phosphor eingesetzt. Bei der Ionenimplantation wurde aufgrund der Erzeugung von Strahlenschäden generell eine Erhöhung des sp2-Anteils beobachtet: Letzterer konnte jedoch im Falle der Bordotierung durch eine, den Implantationsprozeß folgende, Hochtemperaturtemperung wieder deutlich vermindert werden. Für die in situ Dotierung mit Bor wurde eine Verringerung des sp2-Gehaltes mit steigender Dotierkonzentration gefunden. Für den Film mit der höchsten Borkonzentration konnte auch die B1s Absorptionskante untersucht werden. Sie gibt Hinweise auf den überwiegenden Einbau der Boratome in einer tetragonalen Orientierung. Das hiermit verbundene Vorhandensein von Akzeptoren führt zu elektronischen Anregungen im Energiebereich der Bandlücke, welche mittels Infrarotspektroskopie und EELS nachgewiesen werden konnten. Aus den EELS Messungen lassen sich Akzeptorkonzentrationen berechnen, welche wiederum den hohen Anteil an tetraedrisch eingebauten Boratomen bestätigen. Desweiteren untersucht wurden, als interessante Materialklasse mit weitreichendem technologischem Potential, undotierte und stickstoffdotierte, diamantartige amorphe Kohlenstoffilme und hierbei insbesondere die Abhängigkeit der elektronischen und optischen Eigenschaften von der Ionenenergie und dem Stickstoffpartialdruck während der Filmpräparation. Die Plasmonenergien, Massendichten, sp3-Anteile und die optischen Bandlücken der Filme wurden quantitativ bestimmt, wobei das jeweilige Maximum bei einer Ionenenergie von 100 eV gefunden wurde. Alle eben genannten Größen verringern sich kontinuierlich mit zunehmendem Stickstoffanteil. Eine Kramers-Kronig Analyse der Verlustspektren gibt Zugriff auf den Real- und Imaginärteil der dielektrischen Funktion und damit auf das Spektrum der Einteilchenanregungen. Die Hybridisierung der Kohlenstoff- und der Stickstoffatome wurde detailliert aus den jeweiligen 1s Absorptionskanten bestimmt. Weiterhin wurde Diamant als Modellsystem eines Festkörpers mit rein kovalenten Bindungen untersucht, insbesondere die Verlustfunktion von Diamant entlang mehrerer Hochsymmetriekristallrichtungen über einen großen Energie- und Impulsbereich. Aus den EELS Messungen erschließt sich unmittelbar die stark anisotrope Plasmonendispersion von Diamant. Aus dem Vergleich der experimentellen Spektren mit ab initio LDA Rechnungen, die sowohl Kristallokalfeldeffekte als auch Austausch- und Korrelationseffekte beinhalten, lassen sich direkt Rückschlüsse auf den Einfluß der verschiedenen Effekte ziehen. Schon im optischen Limit, aber umso mehr mit steigendem Impulsübertrag q, wird eine Überlagerung der kollektiven Plasmonanregung mit Einteilchenanregungen im Energiebereich des Plasmons beobachtet, woraus eine Kopplung zwischen beiden Arten von Anregungen resultiert. Abgesehen vom deutlichen Einfluß der Bandstruktur auf die Plasmonendispersion läßt die überaus inhomogene Elektronenverteilung von Diamant auf nicht zuvernachlässigende Kristallokalfeldeffekte schließen. Der Vergleich zwischen experimentellen und berechneten Spektren zeigt deutlich, wie die Kristallokalfeldeffekte in der Tat mit steigendem Impulsübertrag an Gewicht zunehmen und die Struktur der Verlustfunktion mitbestimmen. / In the context of the immense potential of diamond as a material for use in the microelectronics industry, in this thesis pristine and doped diamond films have been deposited on silicon using chemical vapour deposition. Subsequently their electronic properties have been investigated using mainly electron energy-loss spectroscopy. Doping of the films with boron, lithium or phosphorous was carried out either via in-situ gas phase doping during film growth or using ion implantation. Upon ion implantation an increase of the carbon content with sp2 hybridisation has generally been found due to ion beam induced damage. In the case of boron doping it was possible to significantly reduce this sp2-contribution using a high temperature anneal. For the in-situ doping with boron, upon increasing doping concentration a decrease of the sp2-contribution was found. For the sample with the highest boron content the boron 1s absorption edge could also be investigated, providing evidence for the preferential incorporation of the boron atoms into tetrahedrally co-ordinated sites. This boron incorporation leads to the existence of electronic excitations in the energy range of the band gap, which could be observed using both infrared and electron energy-loss spectroscopy. From the electron energy-loss measurements it was possible to calculate acceptor concentrations which were consistent with the large amount of tetrahedrally co-ordinated boron atoms. A second theme in this thesis involved the study of pristine and nitrogen doped diamond-like amorphous carbon films, which are an interesting material class with far-reaching technological potential. Here the focus of the research concerned the dependency of the electronic and optical properties of the films upon the ion energy and the nitrogen partial pressure applied during the film preparation. The plasmon energies, mass densities, sp3 contribution and the optical band gaps of the samples were determined quantitatively, whereby the maximum in all these quantities was found to occur for ion energies of 100 eV. Furthermore, all of these characteristics were found to decrease continually with increasing nitrogen content. A Kramers-Kronig analysis of the loss spectra enabled the derivation of the real and imaginary parts of the dielectric function and with this of the complete spectrum of single particle excitations. The hybridization between the carbon and nitrogen atoms was also studied in detail from the analysis of the respective 1s absorption edges. Furthermore this thesis deals with the investigation of diamond as a model system for solids with pure covalent bonds. In particular, the loss function of diamond was measured along different high symmetry directions over a wide range of energy and momentum. Firstly, the EELS measurements showed directly the strongly anisotropic nature of the plasmon dispersion in diamond. Secondly, by the comparison of the experimental spectra with ab initio LDA-based calculations that include crystal local field effects as well as exchange and correlation contributions, conclusions can be drawn as to the influence of these quantities. In the optical limit, but even more so with increasing momentum transfer q, a superposition of the collective plasmon excitation and the single particle excitations in the energy range of the plasmon is observed. This energetic proximity results in a coupling between both types of excitations. Apart from the distinct influence of the bandstructure on the plasmon dispersion, the considerably inhomogeneous electron distribution of diamond would lead one to expect significant crystal local field effects in this system. The comparison between the experimental and the calculated spectra shows explicitly that the crystal local field effects increase with increasing momentum transfer and play an important role in defining the structure of the loss function.