Manufacturing of electronics devices, continuously decreasing in size, commonly requires the vapor phase deposition of materials into small structures on a wafer, often at a nanometer scale. In this thesis the goal is to simulate vapor-phase deposition processes at a scale where fully atomistic simulations using Molecular Dynamics are no longer feasible. This is achieved by combing two methods, one simulating the gas flow and deposition processes and another method simulating the changing surface. A Particle Monte Carlo method, specifically designed for free molecular flow, the typical flow regime at this length scale, is used. The simulation of growing surfaces uses the Level Set Method. Combining these two methods requires some additional coupling steps presented in this work. With the coupled model, different deposition processes are simulated within trenches to observe how well these processes perform for achieving a uniform deposition, as well as evaluating different process conditions.:Table of Contents List of Figures List of Tables List of Abbreviations List of Symbols 1 Introduction 2 Basics 2.1 Surface deposition processes 2.1.1 Chemical Vapor Deposition 2.1.2 Atomic Layer Deposition 2.1.3 Physical Vapor Deposition 2.2 Simulation approaches for surface depositions 2.2.1 Modeling chemical reactions on a surface 2.2.2 Interaction tables for PVD 2.3 Flow regimes 2.4 Molecular Dynamics 2.5 Particle Monte Carlo 2.6 Marker Particle Method 2.7 Level Set Method 2.7.1 Re-initialization of the signed distance function 2.7.2 Extension Velocities 2.7.3 Fast Marching Method 2.7.4 Upwind scheme 2.7.5 Curvature 2.8 Marching-Squares/Cubes Algorithm 3 Methods and Implementation 3.1 Software 3.1.1 External libraries 3.1.2 Geosect 3.2 Initialization of the signed distance field 3.3 Coupling between particle simulations and Level Set 3.3.1 The simulation cycle 3.3.2 Conversion from a grid to a discrete mesh 3.3.3 Extension of growth rates from a mesh to a grid 3.4 Integrating the Level Set Equation 3.4.1 Splitting the number of particles between different steps 3.4.2 Re-initializing the signed distance function 3.4.3 Handling surface coverage 3.4.4 The full update of the surface 3.5 Curvature dependent reflow 3.6 Level Set for radial symmetry 4 Verification 4.1 Testing different integration schemes 4.1.1 Growth of a circle in a linear velocity field 4.1.2 PVD in trenches 4.2 Mass preservation during curvature dependent reflow 4.3 Comparisons between 2D, radial 2D and 3D 4.3.1 Comparing 2D and 3D 4.3.2 Comparing radial 2D and 3D 5 Process Simulations 5.1 Resputter process using a PVD 5.1.1 Simulations and their parameters 5.1.2 Surfaces after the deposition step 5.1.3 Surface growth in the resputter step 5.1.4 Conditions for improved layer thickness 5.2 CVD with an effective sticking coefficient 5.3 Incomplete ALD cycles 5.4 Deposition onto a complex 3D shape 6 Conclusion Bibliography Acknowledgment Statement of authorship

Eine ortsauflösende Spannungs- und Dehnungssensortechnik soll durch die Nutzung magnetostriktiver Materialien auf der Oberfläche von Kohlenstoffeinzelfasern (C-Fasern) und Mikrofeinstrukturierung dieser Schichten erzeugt und zur elektronischen Überwachung des Belastungszustandes von sicherheits- oder servicerelevanten Faserverbundbauteilen eingesetzt werden. Eine auf lokaler Gasphasenabscheidung und Mikrostrukturierung mittels der Focused Ion Beam (FIB)-Technik beruhende Sensorfabrikationsmethode wurde gemeinsam mit dem Institut für Mikrotechnologie Hannover (imt) entwickelt. Mehrschichtig mittels CVD und PVD bedampfte und zusätzlich galvanisch beschichtete C-Fasern weisen neuartige Eigenschaften auf, die im vorgestellten Vorhaben am Lehrstuhl für Verbundwerkstoffe (LVW) charakterisiert wurden. Insbesondere die Untersuchung der verschiedenen Schichten sowie deren Interfaces nehmen eine bedeutende Rolle ein.

Cardiovascular disease (CVD) is the leading cause of morbidity, mortality, premature death and reduced quality of life for the citizens of the EU. It has been reported that CVD represents a major economic load on health care sys- tems in terms of hospitalizations, rehabilitation services, physician visits and medication. Data Mining techniques with clinical data has become an interesting tool to prevent, diagnose or treat CVD. In this thesis, Knowledge Dis- covery and Data Mining (KDD) was employed to analyse clinical and demographic data, which could be used to diagnose coronary artery disease (CAD). The exploratory data analysis (EDA) showed that female patients at an el- derly age with a higher level of cholesterol, maximum achieved heart rate and ST-depression are more prone to be diagnosed with heart disease. Furthermore, patients with atypical angina are more likely to be at an elderly age with a slightly higher level of cholesterol and maximum achieved heart rate than asymptotic chest pain patients. More- over, patients with exercise induced angina contained lower values of maximum achieved heart rate than those who do not experience it. We could verify that patients who experience exercise induced angina and asymptomatic chest pain are more likely to be diagnosed with heart disease. On the other hand, Logistic Regression, K-Nearest Neighbors, Support Vector Machines, Decision Tree, Bagging and Boosting methods were evaluated by adopting a stratified 10 fold cross-validation approach. The learning models provided an average of 78-83% F-score and a mean AUC of 85-88%. Among all the models, the highest score is given by Radial Basis Function Kernel Support Vector Machines (RBF-SVM), achieving 82.5% ± 4.7% of F-score and an AUC of 87.6% ± 5.8%. Our research con- firmed that data mining techniques can support physicians in their interpretations of heart disease diagnosis in addition to clinical and demographic characteristics of patients.

D. Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / In this study, few layer graphene (Gr) and heteroatom graphene (HGr) were synthesized by chemical vapour deposition (CVD) method. Acetylene gas was used as carbon source for the synthesis of graphene, while a mixture of nitrobenzene and dichloromethane (ratio 1:1) were used as both carbon and dopant sources for the synthesis of the heteroatom graphene (HGr). A mixture of argon and nitrogen gases were carefully combined and used as carrier gasses and purge for both the synthesis of graphene and the synthesis of heteroatom graphene. X-ray diffraction (XRD) characterized showed that the as synthesized materials were crystalline materials, Raman spectroscopy indicated that the synthesized materials consist of sp2 hybridized carbon atoms, while scanning electron microscopy (SEM) and atomic force microscopy (AFM) results showed that the synthesized materials possess regions of 2 to 7 nm of thickness. Transmission electron microscopy (TEM) characterization also showed that the synthesized heteroatom graphene possesses about 5 to 7 layers with about 2 nm thickness, and x-ray photoelectron spectroscopy (XPS) result showed the presence of nitrogen, oxygen and chlorine in the lattice of the synthesized heteroatom graphene while the synthesized material still retained about 80% sp2 hybridization. The synthesized materials were used in the fabrication of modified bioelectrodes for electrobiocatalytic biosensing of glucose and hydroquinone. The fabricated bioelectrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV characterization showed a diffusion-controlled electrode processes in al modified electrodes, while the EIS characterization showed the presence of both diffusion controlled and kinetic controlled impedance at the electrode-electrolyte interface. The fabricated GC/PEDOT-PSS/HGr/Lac modified bioelectrode exhibited a kinetic controlled impedance of 3150 Ω, while the fabricated GC/PEDOT-PSS/Gr/Lac modified bioelectrode exhibited a kinetic controlled impedance of 4138 Ω. Chronoamperometric experiments showed that the fabricated bioelectrodes exhibited swift electrobiocatalytic activity towards glucose and hydroquinone sensing respectively for graphene and heteroatom graphene. The graphene modified bioelectrode exhibited a linear response of 0.2 to 9.8 mM glucose concentration and a sensitivity of 87.0 μA/mM/cm2, while the heteroatom modified bioelectrode also exhibited a swift response to step by step addition of hydroquinone with a limit of detection of 2.07 μM and dynamic range of 2.07μM to 2.97 mM, thus indicating the tremendous potential of the materials in a wide range of electrobiocatalytic and bioelectronics applications.

No description available.

The contribution describes the construction of a CVD system, the deposition of thin molybdenum disulphide layers using this system and the analysis of the samples produced. The deposition of thin molybdenum disulphide layers and an intercalation of the silicon carbide substrate used were demonstrated and the measurement results obtained by atomic force microscopy and photoelectron spectroscopy were further discussed.

(ULSI) causes an increase of the resistance of the wiring system by increased scattering of electrons at side walls and grain boundaries in the state of the art Cu technology, which increases the RC delay of the interconnect system and thus degrades the performance of the device. The outstanding properties of carbon nanotubes (CNT) such as a large mean free path, a high thermal conductance and a large resistance against electromigration make them an ideal candidate to replace Cu in future feature nodes. The present thesis contributes to the preparation and properties of CNT based vertical interconnections (vias). In addition, all processes applied during the fabrication are compatible to ULSI and an interface between CNT based vias and a Cu metallization is studied. The methodology for the evaluation of CNT based vias is improved; it is highlighted that by measuring the resistance of one multiwall CNT and taking into account the CNT density, the performance of the CNT based vias can be predicted accurately. This provides the means for a systematic evaluation of different integration procedures and materials. The lowest contact resistance is obtained for carbide forming metals, as long as oxidation during the integration is avoided. Even though metal-nitrides exhibit an enhanced contact resistance, they are recommended to be used at the bottom metallization in order to minimize the oxidation of the metal-CNT contact during subsequent processing steps. Overall a ranking for the materials from the lowest to the highest contact resistance is obtained: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Furthermore the impact of post CNT growth procedures as chemical mechanical planarization, HF treatment and annealing procedures after the CNT based via fabrication are evaluated. The conductance of the incorporated CNTs and the applicable electrical transport regime relative to the CNT quality and the CNT length is discussed. In addition, a strong correlation between the temperature coefficient of resistance and the initial resistance of the CNT based vias at room temperature has been observed. / Die kontinuierliche Miniaturisierung der charakteristischen Abmessungen in hochintegrierten Schaltungen (ULSI) verursacht einen Anstieg des Widerstandes im Zuleitungssystem aufgrund der erhöhten Streuung von Elektronen an Seitenwänden und Korngrenzen in der Cu-Technologie, wodurch die Verzögerungszeit des Zuleitungssystems ansteigt. Die herausragenden Eigenschaften von Kohlenstoffnanoröhren (CNT), wie eine große mittlere freie Weglänge, hohe thermische Leitfähigkeit und eine starke Resistenz gegenüber Elektromigration machen diese zu einem idealen Kandidaten, um Cu in zukünftigen Technologiegenerationen zu ersetzen. Die vorliegende Arbeit beschreibt die Herstellung und daraus resultierenden Eigenschaften von Zwischenebenenkontakten (Vias) basierend auf CNTs. Alle verwendeten Prozessierungsschritte sind kompatibel mit der Herstellung von hochintegrierten Schaltkreisen und eine Schnittstelle zwischen den CNT Vias und einer Cu-Metallisierung ist vorhanden. Insbesondere das Verfahren zur Evaluierung von CNT Vias wurde durch den Einsatz verschiedener Methoden verbessert. Insbesondere soll hervorgehoben werden, dass durch die Messung des Widerstandes eines einzelnen CNTs, bei bekannter CNT Dichte, der Via Widerstand sehr genau vorausgesagt werden kann. Dies ermöglicht eine systematische Untersuchung des Einflusses der verschiedenen Prozessschritte und der darin verwendeten Materialien auf den Via Widerstand. Der niedrigste Kontaktwiderstand wird für Karbidformierende Metalle erreicht, solange Oxidationsprozesse ausgeschlossen werden können. Obwohl Metallnitride einen höheren Kontaktwiderstand aufweisen, sind diese für die Unterseitenmetallisierung zu empfehlen, da dadurch die Oxidation der leitfähigen Schicht minimiert wird. Insgesamt kann eine Reihenfolge beginnend mit dem niedrigsten zum höchsten Kontaktwiderstand aufgestellt werden: Ta < Ti < TaN < TiN « TiO2 « Ta2O5 Desweiteren wurde der Einfluss von Verfahren nach dem CNTWachstum wie die chemischmechanische Planarisierung, eine HF Behandlung und einer Temperaturbehandlung evaluiert, sowie deren Einfluss auf die elektrischen Parameter des Vias untersucht. Die Leitfähigkeit der integrierten CNTs und die daraus resultierenden elektrischen Transporteigenschaften in Abhängigkeit der CNT Qualität und Länge werden besprochen. Ebenso wird die starke Korrelation zwischen dem Temperaturkoeffizienten des elektrischen Widerstandes und des Ausgangswiderstandes der CNT basierten Vias bei Raumtemperatur diskutiert.

This master thesis project was performed in collaboration with Scania CV AB, Engine Materials group. The purpose with the project was to investigate different ceramic TBC (Thermal Barrier Coating) thermal insulation properties inside the combustion chamber. Experimental testing was performed with a Single-Cylinder engine with TBC deposited on selected components. A dummy-valve was developed and manufactured specifically for this test in order to enable a water cooling system and to ease the testing procedure. The dummy-valve consists of a headlock, socket, valve poppet and valve shaft. Additionally, a copper ring is mounted between the cylinder head and the valve poppet to seal the system from combustion gases. Thermocouples attached to the modified valve poppet and valve shaft measured the temperature during engine test to calculate the heat flux. The TBCs consisted of three different materials: 7-8% yttrium-stabilized zirconia (8YSZ), gadolinium zirconia and lanthanum zirconia. The 8YSZ TBC was tested as standard, but also with microstructural modifications. Modifications such as pre-induced segmented cracks, nanostructured zones and sealed porosity were used. The results indicated that the heat flux of 8YSZ-standard, 8YSZ-nano and 8YSZ-segmented cracks was in level with the steel reference. In the case of 8YSZ-sealed porosity the heat flux was measured higher than the steel reference. Since 8YSZ-standard and 8YSZ-sealed porosity are deposited with the same powder it is believed that the high heat flux is caused by radiative heat transfer. The remaining samples have had some microstructural changes during engine testing. 8YSZ-nano had undergone sintering and its nanostructured zones became fewer and almost gone after engine testing leading to less heat barrier in the top coat of the TBC. However, for 8YSZ-segmented cracks and gadolinium zirconia lower heat flux was measured due to the appearance of horizontal cracks. These cracks are believed to act as internal barriers as they are orientated perpendicular to the heat flow. During long-time (5 hour) engine tests the 8YSZ-standard exhibited the same phenomena: a decrease in heat flux due to propagation of horizontal cracks. One-dimensional heat flux was not achieved and the main reason for that was caused by heating and cooling of the shafts outer surface. However, the dummy-valve system has proven to be a quick, easy and stable to perform tests with a Single-Cylinder engine. Both water-cooling and long-time engine tests were conducted with minor issues. The dummy-valve has been further developed for future tests. Changes to the valve shaft are the most remarkable: smaller diameter to reduce heat transfer and smaller pockets to ensure better thermocouple positioning. Another issue was gas leakage from the combustion chamber through the copper ring and valve poppet joint. The copper ring will be designed with a 1 mm thick track to improve sealing, hence better attachment to the valve poppet.

No description available.

La microscopie à force atomique (AFM) permet d’étudier à l’échelle nanométrique la surface d’échantillons. Elle offre de nombreux avantages par rapport aux microscopes optiques et aux microscopes électroniques, tout en évitant des étapes de préparation particulières : pas de nécessité de congeler, de métalliser ou de teinter l’échantillon ni de travailler sous vide. La résolution de l'imagerie AFM est principalement déterminée par la morphologie de la sonde utilisée et peut atteindre la résolution moléculaire. Toutefois, les sondes en silicium sont très fragiles. De plus, leur forme pyramidale ou conique génère des artefacts sur l’image résultante. Parmi les sondes actuellement en développement, les sondes à nanotubes de carbone mono-paroi offrent de bonnes caractéristiques en termes de qualité d'imagerie et de longévité. Ces sondes sont plus résistantes et de plus petite taille que les sondes traditionnelles.Cette thèse s’intéresse à la fabrication directe de sondes à nanotubes mono-paroi sur des extrémités de pointes AFM commerciales par la méthode de dépôt chimique en phase vapeur assistée par filament chaud dans un réacteur développé au CBMN. En jouant sur les paramètres de synthèse, tels que la quantité de catalyseur ou la température, nous optimisons le protocole de synthèse originel en collaboration avec son auteur Anne-Marie Bonnot afin de l’adapter à notre réacteur. Les nanotubes obtenus sont caractérisés par les microscopies Raman, électronique à balayage et transmission et à force atomique. La caractérisation montre que les nanotubes obtenus ont une structure mono-paroi. Le rendement d’obtention de sondes nanotubes utilisables est de 30%.Les courbes d’approche-retrait d'AFM nous donnent des informations sur la sonde à nanotube utilisée, telles que sa raideur, le nombre de nanotubes en contact avec la surface. Ces courbes nous permettent de sélectionner les paramètres d’imagerie. Deux échantillons sont testés avec les sondes produites : du graphite pyrolytique haute orientation et des origamis d’ADN rectangulaires. Nous réalisons des expériences d’imagerie avec des sondes à nanotube dans l’air en mode dynamique FM et en milieu liquide en mode Peak Force. Les résultats montrent des images à haute résolution de l’origami d’ADN où la période de 5,8 nm est observable. Les sondes à nanotube présentent également une plus longue durée de vie que les pointes AFM en silicium. / Atomic force microscopy (AFM) is used to study at nanometer scale samples on surfaces. It offers many advantages over conventional optical microscopes and electron microscopes: no freezing, metal coating, vacuum or dye is needed to prepare the sample. The AFM imaging resolution is mostly determined by the sharpness of the used probe and can reach molecular resolution. However, silicon probes are brittle. Additionally, their pyramidal or conical shape generates artifacts on the resulting image. Among the probes currently under development, single-walled carbon nanotube probes offer good characteristics in terms of imaging quality and longevity. These probes are more resistant and smaller in size than traditional probes.This thesis focuses on the direct fabrication of single-wall nanotube probes at the apex of commercial AFM tips by the hot-filament chemical vapor deposition method in a reactor developed at CBMN. By playing on the synthesis parameters, such as the amount of catalyst or the temperature of synthesis, we optimize the original synthesis protocol in collaboration with its author Anne-Marie Bonnot in order to adapt it to our reactor. The nanotubes obtained are characterized by Raman, scanning electron microscopy and transmission electron microscopy and AFM. The characterization shows that the nanotubes obtained have a single-wall structure. The yield of nanotube probes for AFM is 30%.AFM approach-retract curves give us information about the nanotube probe used, such as its stiffness or the number of nanotubes in contact with the surface. These curves allow us to select the imaging parameters. Two samples are tested with the produced probes: highly oriented pyrolytic graphite and rectangular DNA origamis. We image the samples with nanotube probes in both air with dynamical FM mode and in liquid medium with Peak Force mode. The results show high resolution images of DNA origami where the 5.8 nm period is observable. Nanotube probes also have longer life than silicon AFM tips.