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Nandhakumar, Iris. "The early stages of CdTe epitaxial growth on gold single crystal electrode surfaces." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242869.
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Imanieh, Mohsen. "Growth and characterisation of CuInSeâ†2 and CuGAâ†XInâ†1-â†XSeâ†2 single crystals." Thesis, University of Salford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253047.
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Lee, Myoung-Bok. "The growth and spectroscopic characterisation of ultra-thin aluminium oxide films on single crystal metal surfaces." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309877.
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Zhang, Xi. "Vapor Phase Growth of ZnO Single Crystals/Thin Films and Attempts for p-type Doping." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-142870.
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The growth of ZnO single crystals and ZnO thin films on Si substrates by an open-system vapor phase method was studied in this thesis. The as-grown ZnO single crystals were investigated by means of photoluminescence (PL). Two unique emissions were observed in virgin and hydrogenated crystals. The up-to-now attempts for the p-type doping of ZnO were summarized and our doping studies were performed using nitrogen and antimony. The seed-free and open-system vapor phase method is a simple and low cost approach to grow good quality ZnO single crystals. The growth parameters, including flow rates of N2, H2, O2, and growth temperatures, have various influences on the crystal growth, and also on the optical properties of the as grown crystals. The as-grown crystals are c-axis oriented needle crystals, and the crystals typically have a maximum length of 40 mm and a maximum diameter of 1 mm. The needle-shaped crystals are n-type with main donors due to Al, Ga, and In impurities, as determined from the PL spectra. Two unidentified PL emission lines (P1 at 3.3643 eV and P2 at 3.3462 eV) are observed in our vapor phase grown ZnO single crystals. P1 is attributed to the recombination of an exciton bound to a shallow donor，which has a binding energy of 42.2 meV. Hydrogenation of the as-grown ZnO single crystal leads to the appearance of the P2 line and a great reduction of the P1 line. Subsequent isochronal annealing in the ambient atmosphere leads to gradual reduction of P2 and the reappearance of P1. The PL measurements indicate that hydrogen is involved in the defect origins of the P2 line. ZnO thin films were deposited on Si substrates by the vapor phase method. Three different types of configurations with alternative source materials and oxidizers were employed and compared. It is demonstrated that, methods with lower growth temperatures are easier to deposit homogenous ZnO films on Si substrate. Donor-acceptor-pair (DAP) transition at 3.245 eV and its phonon replicas were observed in the PL spectra of the thin films, which are grown by the hydrogen-free vapor phase method. The appearance of DAP transition indicates the presence of acceptor in the films. The long-standing challenge of p-type doping in ZnO is mainly attributed to the low valence band maximum (VBM) at the absolute energy scale, the spontaneous formation of compensating defects and the lack of appropriate acceptors with small ionization energy. Two attempts for the p-type doping of ZnO were performed by nitrogen diffusion into ZnO single crystals from plasma after the growth or by in-situ doping antimony during the growth of ZnO films. No hole conductivity could however be achieved in our doped samplesIn dieser Arbeit wurde das Wachstum von ZnO-Einkristallen und Dünnfilmschichten auf Si durch chemische Gasphasenabscheidung in einem offenen System untersucht. Die hergestellten ZnO-Einkristalle wurden mit Photolumineszenzmessungen (PL) untersucht. Es konnten sowohl in unbehandelten als auch in mit Wasserstoff behandelten Proben zwei charakteristische Linien beobachtet werden. Sowohl die bisherigen Versuche zur p-Typ Dotierung von ZnO als auch die in dieser Arbeit durchgeführten Versuche mit Stickstoff und Antimon werden zusammengefasst und präsentiert. Die Keimkristall-freie Gasphasenabscheidung (CVD) in offenen Systemen ist eine einfache und kostengünstige Methode zur Herstellung von qualitativ hochwertigen ZnO-Einkristallen. Die Wachstumsparameter, einschließlich der Flussraten von N2, H2 und O2 sowie der Wachstumstemperatur beeinflussen das Kristallwachstum sowie die optischen Eigenschaften der hergestellten Kristalle. Die hergestellten Kristalle wachsen typischerweise als entlang der c-Achse orientierte Nadeln mit Längen von bis zu 40 mm und Durchmessern von bis zu 1 mm. Die nadelförmigen Kristalle besitzen eine n-Typ Dotierung, welche hauptsächlich durch Verunreinigung mit Al, Ga und In verursacht wird. Zwei bisher nicht identifizierte PL-Linien (P1 bei 3,3643 eV und P2 bei 3,3462 eV) wurden in den hergestellten Kristallen beobachtet. P1 wird der Rekombination von Exzitonen an flachen Donatoren mit einer Bindungsenergie von 42,2 meV zugeordnet. Eine Wasserstoffbehandlung der hergestellten Kristalle führt zum Erscheinen der P2-Linie und einer starken Unterdrückung der P1-Linie. Anschließende isochronische Temperung in Luft führt zu einer schrittweisen Reduzierung der Intensität der P2-Linie und zu einer Verstärkung der P1-Linie. Photolumineszenzmessungen weisen auf eine Korrelation von P2 mit Wasserstoff hin. Zusätzlich wurden mit der CVD-Methode dünne ZnO-Schichten auf Si-Substraten abgeschieden. Drei unterschiedliche Konfigurationen mit verschiedenen Ausgangsmaterialien (ZnO-Pulver bw. Zn-Pulver) und verschiedenen Oxidationsmitteln (O2 bzw. Wasser) wurden untersucht und verglichen. Es wird gezeigt, dass mit den Konfigurationen mit geringerer Wachstumstemperatur am einfachsten homogene ZnO-Schichten auf Si abgeschieden werden können. Ein Donator-Akzeptor-Paar-Übergang (DAP) bei 3,245 eV und die dazugehörigen Phononenrepliken wurden in den Schichten beobachtet, welche in einer Wasserstoff-freien Konfiguration abgeschieden wurden. Diese DAP-Übergänge sind ein Hinweis auf die Anwesenheit von Akzeptoren. Die seit langem bestehende Herausforderung der p-Typ-Dotierung von ZnO hat ihre Wurzeln hauptsächlich in dem niedrig liegenden Valenzbandmaximum (VBM) auf der absoluten Energieskala, der spontanen Bildung von kompensierenden Defekten sowie dem Mangel an geeigneten Akzeptoren mit geringer Ionisierungsenergie. Zwei Versuche zur p-Typ-Dotierung von ZnO durch Behandlung der Kristalle mit N-Plasma bzw. durch in-situ Dotierung mit Sb während des Kristallwachstums wurden durchgeführt. Allerdings konnte damit keine nachweisbare Löcherleitung in den behandelten Proben erreicht werden
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Al-Dhafiri, Abdullah M. "CdS-CuₓS single crystal and thin film solar cells." Thesis, Durham University, 1988. http://etheses.dur.ac.uk/6617/.
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The work presented in this thesis is concerned with photovoltaic cells formed by plating CdS single crystals and thin films, and Cd(_y) Zn(1 _ y)S single crystals, with copper sulphide. An electroplating technique has been used to control the phase of copper sulphide by changing the electric field during its formation. Different phases of Cu(_x)S have been identified directly using Reflection High Energy Diffraction (RHEED), and indirectly from spectral response measurements. A dramatic change in the spectral response accompanying the reduction in the covellite response associated with an increase in that from chalcocite following argon heat treatment has been achieved. The change from the djurleite phase to that of chalcocite has also been obtained by using argon heat treatment for 5 minutes at 200 C. This effect was found to be reversible in that layers of chalcocite were converted to djurleite when air was used as the ambient for the heat treatment. C-V measurements have demonstrated that with increasing plating bias the donor concentration decreases at first before it assumes a constant value. This led to the effect of decreasing the junction capacitance as the width of the depletion region changed. The problem of the stability of the CdS-Cu(_2)S photovoltaic devices formed by wet plating" is addressed by studying the combined effects of the substrate onto which the CdS is deposited and the ambient used during annealing. Thin film cells have been prepared on both Ag/Cr and SnO substrates, and the device characteristics for each have been investigated as a function of annealing ambient. The results have shown that devices formed on Ag/Cr substrates were more stable following annealing in air than in argon, while the converse was true for cells fabricated on SnO(_x) substrates. The degradation effects of CdS-Cu(_2) S photovoltaic cells have been investigated. While devices stored in the dark showed little or no degradation, those maintained under illumination exhibited a significant deterioration in all operational parameters over a four week period. As far as the combined effect of temperature and ambient on the stability of cells are concerned, it was found that the ageing of devices in argon at room temperature in the dark was negligible, and moreover the fill factor was observed to improve marginally. When the devices were stored in the same ambient conditions at 50 C, they showed a significant improvement in the fill factor, but simultaneously exhibited a considerable reduction in the short circuit current. This process was reversible, since the sensitivity of degraded devices could be restored by annealing them in a hydrogen/nitrogen mixture. By comparing Electron Spectroscopy for Chemical Analysis (ESCA) studies with solar cell device characteristics, it has been shown that the formation of copper oxide on the Cu(_2)S surface plays a significant role in the degradation of CdS-Cu(_2) S devices. The extent of the cross-over between the dark and light J-V characteristics is a function of the period of etching used prior to junction formation. The variation of current and diode factor has been established as a function of the bias value. The dependence of forward current on the temperature at fixed forward voltage has also been investigated. Finally this work has shown that an increase in V(_oc) can be achieved when Cd(_0◦8)Zn(_0◦2)S is used as a base material for solar cells instead of CdS. Different traps were identified through a photocapacitance investigation. An important trap was found at 0.78eV below the conduction band. It has been demonstrated that the effect of this level was found to be diminished much more slowly when the annealing was carried out in argon rather than in air. This level may play an important role in the Cd(0◦8) Zn(0◦2)S-Cu(_2)S solar cell properties.
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Barnes, C. J. "Adsorption of metals on single crystal substrates." Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234834.
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Nunes, Benjamin P. (Benjamin Paul) 1976. "Edge-defined film-fed growth of single-crystal piezoelectrics." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/17530.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001.Includes bibliographical references (leaves 97-99).
Many transducer technologies would benefit tremendously from the development of shaped, oriented single-crystals, of a high-strain, piezoelectric material. Recently, unusually high electrostrictive and piezoelectric actuation has been observed in polycrystals and flux-grown <100> single-crystals of ... Using seeded, Edgedefined Film-fed Growth (EFG) and the related Stepanov Technique (ST), low-hysteresis, highstrain, <100> and <111> oriented, single-crystals of BNBZT can be grown in rod and fiber form, with direct applications in active fiber composites and related devices. For this work, <100> and <111> oriented, single-crystal rods and fibers were grown via ST and EFG. Fibers, 260-700[mu]m in diameter and over 1.0 meter long, were grown using a custom built EFG machine and a capillary-shaper; rods, 2-3mm in diameter, up to 110mm long were grown using a floating-shaper. In all cases, strontium titanate (STO) was found to be an effective seed crystal. <111> oriented tetragonal crystals generated low hysteresis actuation consistent with a polarization rotation mechanism [14], but with only modest strains: ... <100> oriented tetragonal BNBZT generated high strains up to ... with hysteresis consistent with 90° domain switching. Electromechanical actuation and crystal structure in this system appear to be strongly affected by deviations from stoichiometry (B-site vacancies). Barium segregation and bismuth vaporization can also compromise electromechanical performance. Hypotheses are posed to explain the low actuation seen from <111> oriented ferroelectrics, and the effects of cation deficiencies on phase-stability. Cracks, pores, and other growth challenges encountered in ST and EFG growth of BNBZT are described.
by Benjamin P. Nunes.
S.M.
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Swift, Michael Joseph Robert. "Aspects of single crystal and thin film high field electroluminescence." Thesis, University of Hull, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304437.
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Hashim, K. I. "A study of crystal growth by field emission microscopy." Thesis, Bangor University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380230.
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Huang, Pao-Cheng. "Analysis of single-crystal semiconductor thin film structure by x-ray diffraction." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/20145.
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To, Chun-kit, and 杜俊傑. "Defect studies of single crystal and thin film zinc oxide by positron annihilation spectroscopy and cathodoluminescence." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B4608955X.
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Munro, Shona. "Adsorption studies of Câ†3 hydrocarbons on single crystal, thin film and supported metal substrates using FTIR spectroscopy." Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387525.
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This study involved the investigation of C3-hydrocarbon adsorption on a range of metal and supported metal surfaces using FTIR spectroscopy. The initial aim was to use 'model' metal surfaces i.e. single crystal and polycrystalline metals, to determine fingerprint spectra for various adsorption complexes of propene and propyne. These fingerprint spectra were then to be used to help determine the nature of surface species formed on 'real' industrial catalysts. The single crystal study involved adsorption of both propene and propyne on Pt(111) at temperatures of 90 K and >300K. Adsorption of propene on Pt(111) at 90 K yielded the first infrared spectrum of the di-σ propene surface complex. Spectra obtained at higher temperatures for this system provided the signature of the propylidyne species. Upon adsorption of propyne on Pt(111) at 90 K the fingerprint spectrum of a 'Type A' propyne surface complex was recorded. Adsorption of propene on thin polycrystalline films of copper and palladium, at low temperature was investigated using transmission infrared spectroscopy. In this study the first infrared spectra of the π-adsorbed propene complex were recorded. The second half of the study involved investigation of the surface species formed on 'real' industrial catalysts, i.e. Al2O3 and Pt/Al2O3. Infrared spectra were recorded for a wide range of surface species such as propene complexes, acrolein, acrylate, carboxylates, hydrogencarbonate, and carbonates. These results showed that the main surface chemistry involved on these catalysts was that of the oxide support and not that of the platinum metal.
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Schulz, Benjamin, Daniela Täuber, Jörg Schuster, Thomas Baumgärtel, and Borczyskowski Christian von. "Influence of mesoscopic structures on single molecule dynamics in thin smectic liquid crystal films." Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-122240.
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Mesoscopic structures in liquids have an impact on the diffusion dynamics of the constituting molecules. Smectic 8CB liquid crystals on silicon wafers show the formation of mesoscopic structures on the μm scale at a film thickness of 200 nm. Depending on the kind of substrate (thermally grown or native SiOx), we observed the formation of focal conic domains (FCDs) and a new type of terraced holes, respectively. Dynamics are described via single perylene diimide tracer molecule tracking of translational diffusion and in the case of FCDs by a combination of translation and rotation detected via fluorescence correlation spectroscopy. Tailoring perylene diimide molecules such that the optical transition dipole moment follows the liquid crystal director allows mapping out FCDs and investigating the dynamics within a single FCD.
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Schulz, Benjamin, Daniela Täuber, Jörg Schuster, Thomas Baumgärtel, and Borczyskowski Christian von. "Influence of mesoscopic structures on single molecule dynamics in thin smectic liquid crystal films." Soft Matter, 2011,7, S. 7431-7440, 2011. https://monarch.qucosa.de/id/qucosa%3A19943.
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Mesoscopic structures in liquids have an impact on the diffusion dynamics of the constituting molecules. Smectic 8CB liquid crystals on silicon wafers show the formation of mesoscopic structures on the μm scale at a film thickness of 200 nm. Depending on the kind of substrate (thermally grown or native SiOx), we observed the formation of focal conic domains (FCDs) and a new type of terraced holes, respectively. Dynamics are described via single perylene diimide tracer molecule tracking of translational diffusion and in the case of FCDs by a combination of translation and rotation detected via fluorescence correlation spectroscopy. Tailoring perylene diimide molecules such that the optical transition dipole moment follows the liquid crystal director allows mapping out FCDs and investigating the dynamics within a single FCD.
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Nakatsuka, Shigeru. "Fabrication of bulk crystal and thin film of Ⅱ-Ⅳ-Ⅴ2 type compound semiconductor ZnSnP2 for photovoltaic application." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225559.
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Zhang, Xi [Verfasser], Jörg [Akademischer Betreuer] Weber, and Peer [Akademischer Betreuer] Schmidt. "Vapor Phase Growth of ZnO Single Crystals/Thin Films and Attempts for p-type Doping / Xi Zhang. Gutachter: Jörg Weber ; Peer Schmidt. Betreuer: Jörg Weber." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://d-nb.info/1068446609/34.
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Adamovic, Dragan. "Molecular Dynamics Studies of Low-Energy Atom Impact Phenomena on Metal Surfaces during Crystal Growth." Doctoral thesis, Linköpings universitet, Teoretisk Fysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7165.
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It is a well-known fact in the materials science community that the use of low-energy atom impacts during thin film deposition is an effective tool for altering the growth behavior and for increasing the crystallinity of the films. However, the manner in which the incident atoms affect the growth kinetics and surface morphology is quite complicated and still not fully understood. This provides a strong incentive for further investigations of the interaction among incident atoms and surface atoms on the atomic scale. These impact-induced energetic events are non-equilibrium, transient processes which complete in picoseconds. The only accessible technique today which permits direct observation of these events is molecular dynamics (MD) simulations. This thesis deals with MD simulations of low-energy atom impact phenomena on metal surfaces during crystal growth. Platinum is chosen as a model system given that it has seen extended use as a model surface over the past few decades, both in experiments and simulations. In MD, the classical equations of motion are solved numerically for a set of interacting atoms. The atomic interactions are calculated using the embedded atom method (EAM). The EAM is a semi-empirical, pair-functional interatomic potential based on density functional theory. This potential provides a physical picture that includes many-atom effects while retaining computational efficiency needed for larger systems. Single adatoms residing on a surface constitute the smallest possible clusters and are the fundamental components controlling nucleation kinetics. Small two-dimensional clusters on a surface are the result of nucleation and are present during the early stages of growth. These surface structures are chosen as targets in the simulations (papers I and II) to provide further knowledge of the atomistic processes which occur during deposition, to investigate at which impact energies the different kinetic pathways open up, and how they may affect growth behavior. Some of the events observed are adatom scattering, dimer formation, cluster disruption, formation of three-dimensional clusters, and residual vacancy formation. Given the knowledge obtained, papers III and IV deal with growth of several layers with the aim to study the underlying mechanisms responsible for altering growth behavior and how the overall intra- and interlayer atomic migration can be controlled by low-energy atom impacts.On the day of the defence date the status of article II was Accepted.
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Hogan, Royston Hugh. "Scanning tunneling microscopy and photoelectron spectroscopy of thin film dichromium tetraacetate and dimolybdenum tetraacetate on single crystal graphite and molybdenum disulphide." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/184992.
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Scanning tunneling microscopy has been used to investigate the structural characteristics of thin film dimolybdenum tetracetate on single crystal graphite and molybdenum disulphide substrates. The results indicate that the observed surface structures of the films correspond to two-dimensional crystal faces of the three-dimensional X-ray crystal structure of dimolybdenum tetraacetate. The electronic structure of the films was investigated using photoelectron spectroscopy and correlated to the observed surface structures. Furthermore, thin films of dichromium tetraacetate as well as mixed films of the two dimers on graphite and molybdenum disulphide were also investigated by valence photoelectron spectroscopy.
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Liebig, Andreas. "Amorphous, Nanocrystalline, Single Crystalline: Morphology of Magnetic Thin Films and Multilayers." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8355.
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Calamba, Katherine. "Phase stability and defect structures in (Ti1-x,Alx)Ny hard coatings." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0322.
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Cette étude met en évidence le rôle des lacunes d’azote et des défauts structuraux dans l’ingénierie de revêtements durs à stabilité de phase améliorée et dont les propriétés mécaniques sont compatibles avec des applications à haute température. Le nitrure de titane et d’aluminium (Ti,Al)N sous forme de revêtements est un matériau de choix pour la protection des outils de coupe pour métaux en raison de sa résistance supérieure à l’oxydation et à l’usure à haute température. La décomposition spinodale à haute température de la phase métastable cubique (Ti,Al)N en domaines cohérents de taille nanométrique de c-TiN et de c-AlN donne une dureté importante aux températures élevées. Un apport thermique encore plus élevé conduit à la transformation de c-AlN en w-AlN, ce qui nuit aux propriétés mécaniques du revêtement. Un moyen de retarder cette transformation est d'introduire des lacunes d'azote. Dans cette thèse, je montre que la combinaison d’une réduction de la teneur globale en azote du revêtement c-(Ti,Al)Ny(y <1) avec une faible tension de polarisation du substrat lors du dépôt par arc cathodique induit un retard encore plus prononcé de la transformation de la phase c-AlN en w-AlN. Dans de telles conditions, le durcissement par vieillissement est conservé jusqu'à 1100 ° C, ce qui correspond à la température la plus élevée signalée pour les films de (Ti,Al)N. Au cours des opérations de coupe, le mécanisme d'usure des films c-(Ti0.52Al0.48)Ny déposés par arc cathodique avec des teneurs en N de y = 0.92, 0.87 et 0.75 est influencé par l'interaction des lacunes d'azote, de la microstructure et des réactions chimiques avec le matériau de la pièce. Le revêtement y = 0.75 contient le plus grand nombre de macroparticules et présente, après usinage, une microstructure non homogène qui en abaisse la résistance à l'usure sur les flancs et les cratères. Le durcissement par vieillissement de l'échantillon y = 0.92 entraîne une résistance supérieure à l'usure sur le flanc, tandis que la structure dense de l'échantillon y = 0.87 empêche l'usure chimique qui se traduit par une excellente résistance à l'usure sur les cratères. Des films hétéroépitaxiés c-(Ti1-x, Alx)Ny (y = 0.92, 0.79 et 0.67) ont été déposés sur des substrats de MgO(001) et (111) en utilisant une technique de pulvérisation magnétron pour examiner en détail les défauts structuraux pendant la décomposition spinodale. À 900 °C, les films se décomposent pour former des domaines cohérents riches en c-AlN et c-TiN de forme allongée le long de la direction <001>. Les cartographies de déformation montrent que la plupart des contraintes se trouvent près de l'interface des domaines ségrégés et à l'intérieur des domaines c-TiN. Les dislocations s'agrègent favorablement dans c-TiN plutôt que dans c-AlN car ce dernier a une directionnalité plus forte des liaisons chimiques covalentes. À température élevée, la taille de domaine des films de c- (Ti, Al)Ny orientés (001) et (111) augmente avec la teneur en azote. Cela indique qu'il y a un retard dans le grossissement dû à la présence de plus de lacunes d’azote dans le film. [...]This study highlights the role of nitrogen vacancies and defect structures in engineering hard coatings with enhanced phase stability and mechanical properties for high temperature applications. Titanium aluminum nitride (Ti,Al)N based materials in the form of thin coatings has remained as an outstanding choice for protection of metal cutting tools due to its superior oxidation resistance and high-temperature wear resistance. High-temperature spinodal decomposition of metastable (Ti,Al)N into coherent c-TiN and c-AlN nm-sized domains results in high hardness at elevated temperatures. Even higher thermal input leads to transformation of c-AlN to w-AlN, which is detrimental to the mechanical properties of the coating. One mean to delay this transformation is to introduce nitrogen vacancies. In this thesis, I show that by combining a reduction of the overall N-content of the c-(Ti,Al)Ny (y < 1) coating with a low substrate bias voltage during cathodic arc deposition an even more pronounced delay of the c-AlN to w-AlN phase transformation is achieved. Under such condition, age hardening is retained until 1100 °C, which is the highest temperature reported for (Ti,Al)N films. During cutting operations, the wear mechanism of the cathodic-arc-deposited c-(Ti0.52Al0.48)Ny with N-contents of y = 0.92, 0.87, and 0.75 films are influenced by the interplay of nitrogen vacancies, microstructure, and chemical reactions with the workpiece material. The y = 0.75 coating contains the highest number of macroparticles and has an inhomogeneous microstructure after machining, which lower its flank and crater wear resistance. Age hardening of the y = 0.92 sample causes its superior flank wear resistance while the dense structure of the y = 0.87 sample prevents chemical wear that results in excellent crater wear resistance. Heteroepitaxial c-(Ti1-x,Alx)Ny (y = 0.92, 0.79, and0.67) films were grown on MgO(001) and (111) substrates using magnetron putter deposition to examine the details of their defect structures during spinodal decomposition. At 900 °C, the films decompose to form coherent c-AlN- and c-TiN- rich domains with elongated shape along the elastically soft <001> direction. Deformation maps show that most strains occur near the interface of the segregated domains and inside the c-TiN domains. Dislocations favorably aggregate in c-TiN rather than c-AlN because the later has stronger directionality of covalent chemical bonds. At elevated temperature, the domain size of (001) and (111)- oriented c-(Ti,Al)Ny films increases with the nitrogen content. This indicates that there is a delay in coarsening due to the presence of more N vacancies in the film. The structural and functional properties (Ti1-x,Alx)Ny are also influenced by its Al content (x). TiN and (Ti1-x,Alx)Ny (y = 1, x = 0.63 and x = 0.77) thin films were grown on MgO(111) substrates using magnetron sputtering technique. Both TiN and Ti0.27Al0.63N films are single crystals with cubic structure. (Ti0.23,Al0.77)N film has epitaxial cubic structure only in the first few atomic layers then it transitions to an epitaxial wurtzite layer, with an orientation relationship of c-(Ti0.23,Al0.77)N(111)[1-10]ǀǀw-(Ti0.23,Al0.77)N(0001)[11-20]. The w-(Ti0.23,Al0.77)N shows phase separation of coherent nm-sized domains with varying chemical composition during growth. After annealing at high temperature, the domains in w-(Ti0.23,Al0.77)N have coarsened. The domains in w-(Ti0.23,Al0.77)N are smaller compared to the domains in c-(Ti0.27,Al0.63)N film that has undergone spinodal decomposition. The results that emerged from this thesis are of great importance in the cutting tool industry and also in the microelectronics industry, because the layers examined have properties that are well suited for diffusion barriers
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Kim, You Jin. "Preparation and magnetic properties of layered rare-earth ferrites." Kyoto University, 2020. http://hdl.handle.net/2433/259048.
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Shaoguang, Chen. "Experimental Investigation on Mechanical Properties of Nanospring Thin Films Fabricated by Glancing Angle Deposition Technique." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225556.
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French, Kyle J. "Growth of Optical Quality Lead Magnesium Niobate-Lead Titanate Thick Films." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1575993750125728.
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Özer, Ebru [Verfasser], Peter [Akademischer Betreuer] Strasser, Peter [Gutachter] Strasser, and Michael [Gutachter] Bron. "A new inductive-annealing dual electrochemical cell for crystal alloy and thin-film electrode voltammetry : water oxidation on single- and polycrystalline Ir surfaces / Ebru Özer ; Gutachter: Peter Strasser, Michael Bron ; Betreuer: Peter Strasser." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1177881292/34.
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Gagliardi, Luca. "Modèle de film mince pour la croissance et la dissolution de cristaux confinées." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1211/document.
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Cette thèse traite de la modélisation de la croissance et de la dissolution de cristaux confinés. Nous nous concentrons sur la dynamique dans les contacts lubrifiés (ou hydrophiles) et dérivons un modèle de continu de couche mince prenant en compte la diffusion, la cinétique de surface, l’hydrodynamique, la tension de surface et les interactions avec le substrat (pression de disjonction). Premièrement, nous étudions la dissolution induite par une charge extérieure (dissolution sous contrainte). Nous trouvons que la forme fonctionnelle de la pression de disjonction -finie ou divergente au contact- est cruciale dans la détermination des taux de dissolution et des morphologies stationnaires. Ces formes conduisent respectivement à des taux de dissolution dépendant ou indépendants de la charge, et à des profils de surface plats ou pointus. Deuxièmement, nous avons considéré la croissance des cristaux à proximité d’un mur plat. Nous avons constaté qu’une cavité apparaît sur la surface cristalline confinée. Nous obtenons un diagramme de morphologie hors équilibre en accord avec les observations expérimentales. En traversant la ligne de transition, une cavité peut apparaître de manière continue ou discontinue en fonction de la forme de la pression de disjonction (répulsive ou attractive). Pour les épaisseurs de film nanométriques, la viscosité peut entraver la formation de la cavité. Enfin, nous étudions la force de cristallisation exercée par un cristal croissant entre deux parois planes. Nous soulignons l’importance d’une définition précise de l’aire de contact pour définir la pression d’équilibre thermodynamique. Pendant la croissance, la ligne triple subit une transition cinétique dépendant uniquement du rapport entre: la constante de diffusion, et le produit de la constante cinétique de surface et de la distance entre les murs. Après cette transition, la force de cristallisation diminue jusqu’à s’annuler, et un film macroscopique se formeThis thesis discusses the modeling of growth and dissolution of confined crystals. We focus on the dynamics within lubricated (or hydrophilic) contacts and derive a thin film continuum model accounting for diffusion, surface kinetics, hydrodynamics, surface tension and interactions with the substrate (disjoinining pressure). First, we study dissolution induced by an external load (pressure solution). We find the functional form of the disjoining pressure -finite or diverging at contact- to be crucial in determining steady state dissolution rates and morphologies. These forms respectively lead to load-dependent or load-independent dissolution rates, and to flat or pointy surface profiles.Second, we considered crystal growth in the vicinity of a flat wall. We found that a cavity appears on the confined crystal surface. We obtain a non-equilibrium morphology diagram in agreement with experimental observations. When crossing the transition line, a cavity can appear continuously or discontinuously depending on the form of the disjoining pressure (repulsive or attractive). For nanometric film thicknesses, viscosity can hinder the formation of the cavity.Finally, we study the force of crystallization exerted by a crystal growing between two flat walls. We point out the importance of a precise definition of the contact area to define the thermodynamic equilibrium pressure. During growth, the triple-line undergoes a kinetic pinning transition depending solely on the ratio between the diffusion constant and the product of the surface kinetic constant and distance between the walls. After this transition, the crystallization force decreases to zero, and a macroscopic film forms
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Berná, Galiano Antonio. "Estudio espectroelectroquímico de los equilibrios ácido-base de especies adsorbidas sobre electrodos metálicos con superficies monocristalinas bien definidas." Doctoral thesis, Universidad de Alicante, 2014. http://hdl.handle.net/10045/45809.
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PELLOIE, LE DUIGOU BRIGITTE. "Mecanismes de formation de couches minces d'oxydes en plasma d'oxygene." Paris 7, 1987. http://www.theses.fr/1987PA077143.
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Etude des processus de transport ionique sous fort champ electrique, lors de la croissance de couches minces d'oxydes, obtenus a temperature ambiante, par polarisation anodique d'un support metallique ou semiconducteur en plasma d'oxygene. Investigations basees sur la microanalyse nucleaire et ses applications telles que le tracage isotopique, et la mesure de nombres de transport ionique
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Fontaine, Chantal. "Heteroepitaxie par jets moeculaires : systeme (ca,sr)f::(2) - gaas." Toulouse 3, 1987. http://www.theses.fr/1987TOU30135.
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Dans la premiere partie du memoire sont etudies les mecanismes de formation de defauts pendant la croissance cristalline, les contraintes s'exercant sur les couches heteroepitaxiales, la possibilite de relaxation de ces contraintes par creation de defauts ainsi que les solutions pratiques envisagees pour eliminer ces defauts. Dans la seconde partie sont presentes et analyses les resultats experimentaux obtenus sur les structures (ca,sr)f::(2)/gaas et gaas/(ca,sr)f::(2) realisees par epitaxie par jets moleculaires. Sont consideres les proprietes des interfaces, les relations d'epitaxie, les mecanismes de croissance et les contraintes. Finalement, sont discutees les applications potentielles de ce type de structures et leur compatibilite avec les proprietes optiques et electriques des deux materiaux elabores
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Porte, Agnès. "Determination des parametres qui regissent la cinetique et la composition d'un depot de gainas/inp par la methode aux hydrures." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF2D162.
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En s'appuyant sur les resultats experimentaux de la croissance de ga::(x)in::(1-x)as/inp en phase vpeur par la methode aux hydrures et sur une theorie cinetique de croisssance qui permet d'exprimer facilement le rapport des pressions partielles de chlorures en fonction de x, detection et analyse de differents phenomenes en jeu dans la croissance. Calcul des parametres necessaires a la prise en compte de ces phenomenes pour la determination des pressions partielles reelles de chacun des constituants de la phase vapeur dans chaque experience realisee. La maitrise de la cinetique du depot et de la composition de la couche de ga::(x)in::(1-x)as est de ce fait rendue possible dans l'epitaxie par la methode aux hydrures
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Guo, Shu. "Experimental and Numerical Investigations on the Durability and Fracture Mechanics of the Bonded Systems for Microelectronics Application." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28743.
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Water-assisted crack growth at an epoxy/glass interface was measured as a function of applied strain energy release rate, G, and temperature using a wedge test geometry. The specimens consist of two glass plates bonded with a thin layer of proprietary epoxy adhesive. The crack fronts along the epoxy/glass interfaces were measured using an optical stereomicroscope. The relationship between G and the debonding rate, v, can be measured using this method, and the threshold value of strain energy release rate, Gth, can be determined from the measured data. Two types of testing procedures were conducted in this study: ex situ, i.e., pre-conditioned wedge tests and in situ ones, in which wedges were applied before the specimens were submerged into water. A preliminary model was developed based on the thermal activation barrier concept, and allows the prediction of Gth for the temperatures beyond the testing region.
Changes in interfacial strain energy release rate caused by thermal residual stresses in a triple-layered specimen were analyzed in Chapter Three. The method is based on linear elastic fracture mechanics and simple beam theory. The curvature of a bimaterial strip was chosen to characterize the residual stress in the specimen, and the strain energy release rate, caused by both tensile and compressive residual stresses in the adhesive, was derived for an asymmetric double cantilever beam (ADCB) geometry. The contribution of the thermal residual and mechanical stress to the global energy release rate was analyzed. The thermally induced energy release rate, GT, is found to be independent of crack length, but is a function of residual stress level and geometric and material parameters of the specimen.
The adhesion of films and coatings to rigid substrates is often measured using blister geometries, which are loaded either by an applied pressure or a central shaft. The measurement will be affected if there are residual stresses that make a contribution to the energy release rate. This effect is investigated using analytical solutions based on the principle of virtual displacements. A geometrically nonlinear finite element analysis is conducted for comparison. Furthermore, the relationships among strain energy release rate, load, deflection, and fracture radius are discussed in detail in Chapter Four. Both analytical solutions and numerical results reveal that uniform tensile residual stresses reduce a specimen's deflection if it experiences plate behavior under small loads. However, this effect diminishes when membrane behavior is dominant.
The mechanics of a single-lap joint with different boundary conditions subjected to tensile loading are investigated. Closed-form solutions are obtained for a specimen configuration considering different clamping methods. Based on the approach pioneered by Goland and Reissner, the solutions reported in this paper provide a simple but useful way to understand the effects of boundary conditions on this test geometry. The solutions in this study suggest that different grip configurations mainly affect the response of the specimens if the grip position is close to the joint edge or the loads are small. Generally, the influence caused by different gripping methods is only limited to the boundary region, and the behavior of the joint part subjected to tensile loading is almost the same as that for a simply-supported case.Ph. D.
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Täuber, Daniela. "Characterization of heterogeneous diffusion in confined soft matter." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-77658.
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A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds.
Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.
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Mc, Grath Oran F. K. "Structural and magnetic properties of epitaxial W/Fe/W and Gd/Fe films grown by pulsed laser deposition." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10209.
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Le but de cette these est d'etudier les proprietes structurales et magnetiques des couches epitaxiees de w/fe/w et gd/fe elaborees par depot laser pulse. La technique de depot laser pulse est presentee dans le premier chapitre. La croissance des couches minces est discutee dans le deuxieme chapitre puis l'analyse des proprietes structurales des couches elaborees est presentee dans le troisieme chapitre. Une revue des proprietes magnetiques des couches ultra-minces, telle que le moment magnetique, l'anisotropie et les excitations thermiques est presentee dans le quatrieme chapitre. La determination experimentale de ces proprietes magnetiques dans les couches de w/fe/w est discutee dans le cinquieme chapitre. Le couplage interfacial dans les couches de gd/fe est analyse dans le dernier chapitre
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Cho, Suyeon. "Synthesis and characterization of refractory oxides doped with transition metal ions." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00856580.
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In this study, the oxygen-deficient TiO2, SrTiO3 systems and transition metal ion (Cr or V) doped TiO2, SrTiO3 and SrZrO3 systems have been investigated. We prepared samples as polycrystals, single crystals and thin films for various desires. Their structural, physical and electronic properties were measured by bulk-sensitive techniques (X-Ray Diffraction, SQUID and Electro Paramagnetic Resonance) or surface-sensitive techniques (Photoemission spectroscopy and X-ray absorption spectroscopy). The measurement of SQUID and EPR showed not only their magnetic properties but also the valence state of Cr dopant. We verified the valence state of Cr ions in oxides and found the key parameters of sample synthesis which control the valence state of Cr ions. Segregated phases such as SrCrO4 were formed when the samples were synthesized under O2 rich environment. The surface properties of Cr doped SrZrO3 films are also discussed. We found the synthesis conditions which influence on not only the behavior of Cr ions but also the resistive-switching behaviors. Various resistive-switching behaviors seem to depend on the surface chemistry of films. We found that the accumulation of Cr3+ on film surface provides a clean interface without any non-stoichiometric oxides and that this sharp interface termination results in a good performance of resistive-switching.
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Stöcker, Christina. "Level set methods for higher order evolution laws." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1205350171405-81971.
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A numerical treatment of non-linear higher-order geometric evolution equations with the level set and the finite element method is presented. The isotropic, weak anisotropic and strong anisotropic situation is discussed. Most of the equations considered in this work arise from the field of thin film growth. A short introduction to the subject is given. Four different models are discussed: mean curvature flow, surface diffusion, a kinetic model, which combines the effects of mean curvature flow and surface diffusion and includes a further kinetic component, and an adatom model, which incorporates in addition free adatoms. As an introduction to the numerical schemes, first the isotropic and weak anisotropic situation is considered. Then strong anisotropies (non-convex anisotropies) are used to simulate the phenomena of faceting and coarsening. The experimentally observed effect of corner and edge roundings is reached in the simulation through the regularization of the strong anisotropy with a higher-order curvature term. The curvature regularization leads to an increase by two in the order of the equations, which results in highly non-linear equations of up to 6th order. For the numerical solution, the equations are transformed into systems of second order equations, which are solved with a Schur complement approach. The adatom model constitutes a diffusion equation on a moving surface. An operator splitting approach is used for the numerical solution. In difference to other works, which restrict to the isotropic situation, also the anisotropic situation is discussed and solved numerically. Furthermore, a treatment of geometric evolution equations on implicitly given curved surfaces with the level set method is given. In particular, the numerical solution of surface diffusion on curved surfaces is presented. The equations are discretized in space by standard linear finite elements. For the time discretization a semi-implicit discretization scheme is employed. The derivation of the numerical schemes is presented in detail, and numerous computational results are given for the 2D and 3D situation. To keep computational costs low, the finite element grid is adaptively refined near the moving curves and surfaces resp. A redistancing algorithm based on a local Hopf-Lax formula is used. The algorithm has been extended by the authors to the 3D case. A detailed description of the algorithm in 3D is presented in this workIn der Arbeit geht es um die numerische Behandlung nicht-linearer geometrischer Evolutionsgleichungen höherer Ordnung mit Levelset- und Finite-Elemente-Verfahren. Der isotrope, schwach anisotrope und stark anisotrope Fall wird diskutiert. Die meisten in dieser Arbeit betrachteten Gleichungen entstammen dem Gebiet des Dünnschicht-Wachstums. Eine kurze Einführung in dieses Gebiet wird gegeben. Es werden vier verschiedene Modelle diskutiert: mittlerer Krümmungsfluss, Oberflächendiffusion, ein kinetisches Modell, welches die Effekte des mittleren Krümmungsflusses und der Oberflächendiffusion kombiniert und zusätzlich eine kinetische Komponente beinhaltet, und ein Adatom-Modell, welches außerdem freie Adatome berücksichtigt. Als Einführung in die numerischen Schemata, wird zuerst der isotrope und schwach anisotrope Fall betrachtet. Anschließend werden starke Anisotropien (nicht-konvexe Anisotropien) benutzt, um Facettierungs- und Vergröberungsphänomene zu simulieren. Der in Experimenten beobachtete Effekt der Ecken- und Kanten-Abrundung wird in der Simulation durch die Regularisierung der starken Anisotropie durch einen Krümmungsterm höherer Ordnung erreicht. Die Krümmungsregularisierung führt zu einer Erhöhung der Ordnung der Gleichung um zwei, was hochgradig nicht-lineare Gleichungen von bis zu sechster Ordnung ergibt. Für die numerische Lösung werden die Gleichungen auf Systeme zweiter Ordnungsgleichungen transformiert, welche mit einem Schurkomplement-Ansatz gelöst werden. Das Adatom-Modell bildet eine Diffusionsgleichung auf einer bewegten Fläche. Zur numerischen Lösung wird ein Operatorsplitting-Ansatz verwendet. Im Unterschied zu anderen Arbeiten, die sich auf den isotropen Fall beschränken, wird auch der anisotrope Fall diskutiert und numerisch gelöst. Außerdem werden geometrische Evolutionsgleichungen auf implizit gegebenen gekrümmten Flächen mit Levelset-Verfahren behandelt. Insbesondere wird die numerische Lösung von Oberflächendiffusion auf gekrümmten Flächen dargestellt. Die Gleichungen werden im Ort mit linearen Standard-Finiten-Elementen diskretisiert. Als Zeitdiskretisierung wird ein semi-implizites Diskretisierungsschema verwendet. Die Herleitung der numerischen Schemata wird detailliert dargestellt, und zahlreiche numerische Ergebnisse für den 2D und 3D Fall sind gegeben. Um den Rechenaufwand gering zu halten, wird das Finite-Elemente-Gitter adaptiv an den bewegten Kurven bzw. den bewegten Flächen verfeinert. Es wird ein Redistancing-Algorithmus basierend auf einer lokalen Hopf-Lax Formel benutzt. Der Algorithmus wurde von den Autoren auf den 3D Fall erweitert. In dieser Arbeit wird der Algorithmus für den 3D Fall detailliert beschrieben
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Stöcker, Christina. "Level set methods for higher order evolution laws." Doctoral thesis, Forschungszentrum caesar, 2007. https://tud.qucosa.de/id/qucosa%3A24054.
Full textAbstract:
A numerical treatment of non-linear higher-order geometric evolution equations with the level set and the finite element method is presented. The isotropic, weak anisotropic and strong anisotropic situation is discussed. Most of the equations considered in this work arise from the field of thin film growth. A short introduction to the subject is given. Four different models are discussed: mean curvature flow, surface diffusion, a kinetic model, which combines the effects of mean curvature flow and surface diffusion and includes a further kinetic component, and an adatom model, which incorporates in addition free adatoms. As an introduction to the numerical schemes, first the isotropic and weak anisotropic situation is considered. Then strong anisotropies (non-convex anisotropies) are used to simulate the phenomena of faceting and coarsening. The experimentally observed effect of corner and edge roundings is reached in the simulation through the regularization of the strong anisotropy with a higher-order curvature term. The curvature regularization leads to an increase by two in the order of the equations, which results in highly non-linear equations of up to 6th order. For the numerical solution, the equations are transformed into systems of second order equations, which are solved with a Schur complement approach. The adatom model constitutes a diffusion equation on a moving surface. An operator splitting approach is used for the numerical solution. In difference to other works, which restrict to the isotropic situation, also the anisotropic situation is discussed and solved numerically. Furthermore, a treatment of geometric evolution equations on implicitly given curved surfaces with the level set method is given. In particular, the numerical solution of surface diffusion on curved surfaces is presented. The equations are discretized in space by standard linear finite elements. For the time discretization a semi-implicit discretization scheme is employed. The derivation of the numerical schemes is presented in detail, and numerous computational results are given for the 2D and 3D situation. To keep computational costs low, the finite element grid is adaptively refined near the moving curves and surfaces resp. A redistancing algorithm based on a local Hopf-Lax formula is used. The algorithm has been extended by the authors to the 3D case. A detailed description of the algorithm in 3D is presented in this work.In der Arbeit geht es um die numerische Behandlung nicht-linearer geometrischer Evolutionsgleichungen höherer Ordnung mit Levelset- und Finite-Elemente-Verfahren. Der isotrope, schwach anisotrope und stark anisotrope Fall wird diskutiert. Die meisten in dieser Arbeit betrachteten Gleichungen entstammen dem Gebiet des Dünnschicht-Wachstums. Eine kurze Einführung in dieses Gebiet wird gegeben. Es werden vier verschiedene Modelle diskutiert: mittlerer Krümmungsfluss, Oberflächendiffusion, ein kinetisches Modell, welches die Effekte des mittleren Krümmungsflusses und der Oberflächendiffusion kombiniert und zusätzlich eine kinetische Komponente beinhaltet, und ein Adatom-Modell, welches außerdem freie Adatome berücksichtigt. Als Einführung in die numerischen Schemata, wird zuerst der isotrope und schwach anisotrope Fall betrachtet. Anschließend werden starke Anisotropien (nicht-konvexe Anisotropien) benutzt, um Facettierungs- und Vergröberungsphänomene zu simulieren. Der in Experimenten beobachtete Effekt der Ecken- und Kanten-Abrundung wird in der Simulation durch die Regularisierung der starken Anisotropie durch einen Krümmungsterm höherer Ordnung erreicht. Die Krümmungsregularisierung führt zu einer Erhöhung der Ordnung der Gleichung um zwei, was hochgradig nicht-lineare Gleichungen von bis zu sechster Ordnung ergibt. Für die numerische Lösung werden die Gleichungen auf Systeme zweiter Ordnungsgleichungen transformiert, welche mit einem Schurkomplement-Ansatz gelöst werden. Das Adatom-Modell bildet eine Diffusionsgleichung auf einer bewegten Fläche. Zur numerischen Lösung wird ein Operatorsplitting-Ansatz verwendet. Im Unterschied zu anderen Arbeiten, die sich auf den isotropen Fall beschränken, wird auch der anisotrope Fall diskutiert und numerisch gelöst. Außerdem werden geometrische Evolutionsgleichungen auf implizit gegebenen gekrümmten Flächen mit Levelset-Verfahren behandelt. Insbesondere wird die numerische Lösung von Oberflächendiffusion auf gekrümmten Flächen dargestellt. Die Gleichungen werden im Ort mit linearen Standard-Finiten-Elementen diskretisiert. Als Zeitdiskretisierung wird ein semi-implizites Diskretisierungsschema verwendet. Die Herleitung der numerischen Schemata wird detailliert dargestellt, und zahlreiche numerische Ergebnisse für den 2D und 3D Fall sind gegeben. Um den Rechenaufwand gering zu halten, wird das Finite-Elemente-Gitter adaptiv an den bewegten Kurven bzw. den bewegten Flächen verfeinert. Es wird ein Redistancing-Algorithmus basierend auf einer lokalen Hopf-Lax Formel benutzt. Der Algorithmus wurde von den Autoren auf den 3D Fall erweitert. In dieser Arbeit wird der Algorithmus für den 3D Fall detailliert beschrieben.
36
Barbier, Eric. "Epitaxie par la methode des organometalliques d'heterostructures gaas/gaalas a application en hyperfrequence." Orléans, 1987. http://www.theses.fr/1987ORLE2003.
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Croissance reproductible de materiaux de haute purete qui se caracterisent dans le cas de gaas par une concentration en impuretes residuelles voisine de e14 porteurs par cm**(3), une mobilite electronique a 77k superieur a 110. 000 cm**( non2)v. S et dans le cas du gaalas par un niveau de dopage residuel de e15 porteurs par cm**(3) pour une teneur en aluminium de 25%. La caracterisation des interfaces par microscopie demontrent la croissance reproductibles d'heterojonctions aux transitions de l'ordre de la monocouche
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Lassalle, Francis. "Conception et mise en oeuvre d'un reacteur d'epitaxie gainas/inp par la methode aux hydrures, analyse des conditions de croissance." Clermont-Ferrand 2, 1987. http://www.theses.fr/1987CLF2D193.
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Reacteur permettant la croissance de couches epitaxiques dans le systeme (ga,in,as,p) par transport en phase vapeur et par la methode aux hydrures (ph::(3),ash::(3),h::(2),hcl,in,ga). Sa conception autorise la realisation d'heterostructures a interfaces abruptes en conservant une geometrie de reacteur monochambre. Analyse des conditions de croissance du ternaire gainas sur support inp (100). Mise en evidence de l'effet du non equilibre entre les especes as::(2) et as::(4) sur la presence d'un depot parasite en amont de l'echantillon et sur les caracteristiques du depot. Proposition d'un modele rendant compte de l'influence des cinetiques de reactions de surface sur la composition en gallium de gainas
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Lebrun, Marie-Monique. "Instabilites cellulaires en solidification directionnelle : experiences en couches minces." Paris 7, 1987. http://www.theses.fr/1987PA077013.
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Etude de l'apparition d'instabilites morphologiques a l'interface liquide-solide dans des echantillons minces d'un corps transparent (tetrabromomethane avec quelques pour mille d'impuretes). Observation en direct a l'aide d'un microscope optique d'une camera video, ce qui donne acces a la dynamique de solidification
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Popel, Aleksej. "The effect of radiation damage by fission fragments on the structural stability and dissolution of the UO2 fuel matrix." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/265103.
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The aim of this work was to study the separate effect of fission fragment damage on the structural integrity and matrix dissolution of uranium dioxide in water. Radiation damage similar to fission damage was created by irradiating bulk undoped and doped ‘SIMFUEL’ disks of UO2, undoped bulk CeO2 and thin films of UO2 and CeO2 with high energy Xe and U ions. The UO2 thin films, with thicknesses in the range of 90 – 150 nm, were deposited onto (001), (110) and (111) orientations of single crystal LSAT (Al10La3O51Sr14Ta7) and YSZ (Yttria-Stabilised Zirconia) substrates. The CeO2 thin films were deposited onto single crystal silicon (001) substrates. Part of the bulk UO2 and CeO2 samples, the thin films of UO2 on the LSAT substrates and the thin films of CeO2 were irradiated with 92 MeV 129Xe23+ ions to a fluence of 4.8 × 1015 ions/cm2 to simulate the damage produced by fission fragments in uranium dioxide nuclear fuel. Part of the bulk UO2 and CeO2 samples and the thin films of UO2 on the YSZ substrates were irradiated with 110 MeV 238U31+ ions to a fluence of 5 × 1010, 5 × 1011 and 5 × 1012 ions/cm2 to study the accumulation of the damage induced. The irradiated and unirradiated samples were studied using scanning electron microscopy (SEM), focused ion beam (FIB), atomic force microscopy (AFM), energy dispersive X-ray (EDX) spectroscopy, electron probe microanalysis (EPMA), X-ray diffraction (XRD), electron backscatter diffraction (EBSD), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS) techniques to characterise the as-produced samples and assess the effects of the ion irradiations. Dissolution experiments were conducted to assess the effect of the Xe ion irradiation on the dissolution of the thin film UO2 samples on the LSAT substrates and the bulk and thin film CeO2 samples. The solutions obtained from the leaching of the irradiated and unirradiated samples were analysed using inductively coupled plasma mass spectrometry (ICP-MS). XRD studies of the bulk UO2 samples showed that the ion irradiations resulted in an increased lattice parameter, microstrain and decreased crystallite size, as expected. The irradiated UO2 thin films on the LSAT substrates underwent significant microstructural and crystallographic rearrangements. It was shown that by irradiating thin films of UO2 with high energy, high fluence ions, it is possible to produce a structure that is similar to a thin slice through the high burn-up structure. It is expected that the ion irradiation induced chemical mixing of the UO2 films with the substrate elements (La, Sr, Al, Ta). As a result, a material similar to a doped SIMFUEL with induced radiation damage was produced.
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Ruterana, Pierre. "Structure des interfaces, etude par microscopie electronique en transmission, application : materiaux semiconduteurs iii-v et multicouches pour optiques dans le domaine des rayons x mous." Caen, 1987. http://www.theses.fr/1987CAEN2032.
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Nous avons surtout utilise le mode "haute resolution" sur un microscope a 200kv. La resolution obtenue etait de 2. 4 a. La technique de peparation d'echantillons que nous avons mise au point pour l'etude du procede de passivation (si::(3)n::(4)/gaas) nous a permis de caracteriser dans de tres bonnes conditions les multicouches pour rayons x mous et les heterostructures de croissance epitaxiale. Ce travail fut un suivi des procedes en conjugaison avec d'autres techniques de caracterisation. La comparaison des resultats de ces diverses techniques nous a permis d'apprehender la chimie et la physique des interfaces dans les materiaux etudies
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Drhourhi, Allal. "Croissance en phase vapeur par flux force : application aux depots de monocristaux de tib::(2) en systeme ouvert et films de ni en systeme ferme." Clermont-Ferrand 2, 1986. http://www.theses.fr/1986CLF21036.
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Elaboration par depot chimique et transport chimique en phase vapeur des monocristaux tib::(2). Comparaison entre les deux methodes. Developpement d'un plan de travail pour obtenir des depots reproductibles. Etude du systeme ni/nio::(4) en tube scelle. Comparaison avec le systeme ouvert. Analyse du transport des flux. Elaboration du modele du transport des flux
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Tonneau, Didier. "Cinétiques et mécanismes de dépôt de matériaux pour la microélectronique obtenus lors de l'interaction d'un faisceau laser avec une surface en présence d'un gaz." Grenoble 1, 1988. http://www.theses.fr/1988GRE10069.
Full textAbstract:
Des molecules de gaz ont ete decomposes sur differentes surfaces irradiees localement par un faisceau laser continu, visible (ar**(+)) ou ir (co::(2)). Par un processus photolytique ou pyrolytique, la dissociation des molecules aboutit a une reaction de depot ou de gravure de la surface. Des etudes cinetiques detaillee ont permis de determiner la nature pyrolytique ou photolytique de la decomposition des gaz et d'identifier les differents mecanismes limitant les vitesses des reactions. C'est dans le domaine de la microelectronique que l'on trouve, a l'heure actuelle, l'application la plus importante des reactions de depot ou de gravure induites par laser. Les reactions presentees dans ce rapport peuvent etre rassemblees dans un procede complet d'interconnexion sur circuits vlsi par microchimie laser
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Roumiantseva, Babakina Marina. "Elaboration et caractérisation des couches minces SnO2(Cu,Ni) pour la détection gazeuse." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0178.
Full textAbstract:
Des couches minces de dioxyde d'etain (sno#2) pures et dopees (cu, ni) ont ete elaborees par le procede pyrosol sur des substrats de silicium oxyde en utilisant la pyrolyse d'un aerosol genere par ultrasons. Une etude systematique a permis de determiner l'influence des conditions d'elaboration sur la composition et la microstructure des couches. L'influence du cu et du ni sur les proprietes electriques de sno#2 a ete etudiee dans la gamme de temperature 77-773 k. Une concentration de cu de 1. 2-1. 5 at% et une concentration de ni de 0. 4-0. 6 at% conduisent a une augmentation de la resistance de h#2s d'un facteur 10#3. Les proprietes electriques des couches obtenues ont ete etudiees en regime stationnaire et en regime dynamique en fonction de la concentration des dopants et de la temperature en presence des melanges gazeux: 100-1200 ppm de h#2s dans l'azote, 300 ppm de co dans l'air et 80 ppm de c#2h#5oh dans l'air. Le dopage par le cu et par le ni augmente la sensibilite de sno#2 a h#2s d'un facteur 10#-#2-10#-#3. Contrairement au cas du cuivre, le nickel augmente la sensibilite de sno#2 en presence de co et de c#2h#5oh. Un modele d'interaction des couches sno#2(cu) et sno#2(ni) avec h#2s et l'oxygene de l'atmosphere est propose. Ce modele est base sur les reactions chimiques qui modifient l'etat des dopants dans sno#2 en fonction de la composition de la phase gazeuse
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Pellissier, Anne. "Etude structurale et microscopique du système Y/Si." Grenoble INPG, 1989. http://www.theses.fr/1989INPG0031.
Full textAbstract:
Le siliciure ysi 1,7 en phase hexagonale s'epitaxie sur un support si(iii) avec un accord de maille quasi parfait. La couche resultante (100-200 a) contient des grains de 50 a 100 a. Une forte anisotropie de structure de bandes est revelee par photoemission. Les lacunes si s'ordonnent en trois dimensions. Mesures electriques: comportement de type semi-metallique et faible hauteur de barriere de schottky pour le contact ysi 1,7/si dope n. Si peut se reepitaxier sur une couche de siliciure d'y elle-meme epitaxiee sur un support si(iii). Un echantillon est obtenu, avec toutefois des defauts d'empilement dans la couche si. La fabrication de couches multiples de cette nature est envisageable
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Lusson, Alain. "Preparation par epitaxie en phase liquide et etude physique des solutions solides cd : :(x)hg::(1-x)te 0,5 <- x <-1." Paris 6, 1987. http://www.theses.fr/1987PA066497.
Full textAbstract:
Dans le but d'etudier un materiau utilisable pour la fabrication de detecteurs pour les telecommunications par fibre optique a 1,3 et 1,55mu m, des echantillons de cd::(x) hg::(1-x) te(0,5 x 1) ont ete prepares par epitaxie en phase liquide en tube ouvert. Diverses methodes de caracterisation (microsonde electronique, topographie rx, effet hall, sonde ionique. . . ) ont montre la bonne qualite des couches. Le dopage effectue au cours de la croissance par in et cu a ete aborde. Etude des effets d'alliage dans cdhgte par photoluminescence
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Guille, Claire. "Etude de la formation par epitaxie par jets moleculaires des interfaces entre inas et gaas." Paris 6, 1987. http://www.theses.fr/1987PA066415.
Full textAbstract:
Malgre le fort desaccord parametrique existant entre gaas et inas (7,2%), il est possible de realiser des couches pseudomorphes de l'un des materiaux sur l'autre, en se limitant a des couches d'epaisseurs inferieures a une dizaine d'a. Dans ces conditions,l'interface inas/gaas est plane et chimiquement abrupte, a la demi-couche pres. L'interface inverse est diffuse et rugueuse a l'echelle atomique. Au cours de la formulation de cette heterojonction, il y a segregation d'in en surface et formation d'un compose ternaire. Ce type de phenomene de segregation d'in se produit egalement dans les composes ternaires ingaas et peut etre a l'origine de leur rugosite superficielle. Etude comparative avec d'autres systemes iii-as
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Stragier, Anne-Sophie. "Elaboration et caractérisation de structures Silicium-sur-Isolant réalisées par la technologie Smart Cut™ avec une couche fragile enterrée en silicium poreux." Thesis, Lyon, INSA, 2011. http://www.theses.fr/2011ISAL0108.
Full textAbstract:
Au vu des limitations rencontrées par la miniaturisation des circuits microélectroniques, l’augmentation de performances des systèmes repose largement aujourd’hui sur la fabrication d’empilements de couches minces complexes et innovants pour offrir davantage de compacité et de flexibilité. L’intérêt grandissant pour la réalisation de structures innovantes temporaires, i.e. permettant de réaliser des circuits sur les deux faces d’un même film, nous a mené à évaluer les potentialités d’une technologie combinant le transfert de films minces monocristallins, i.e. la technologie Smart Cut™, et un procédé de de porosification partielle du silicium afin de mettre au point une technologie de double report de film monocristallin. En ce sens, des substrats de silicium monocristallin ont été partiellement porosifiés par anodisation électrochimique. La mise en œuvre de traitements de substrats partiellement poreux a nécessité l’emploi de techniques de caractérisation variées pour dresser une fiche d’identité des couches minces poreuses après anodisation et évaluer l’évolution des propriétés de ces couches en fonction des différents traitements appliqués. Les propriétés chimiques, structurales et mécaniques des couches de Si poreux ont ainsi été étudiées via l’utilisation de différentes techniques de caractérisation (XPS-SIMS, AFM-MEB-XRD, nanoindentation, technique d’insertion de lame, etc.). Ces études ont permis d’appréhender et de décrire les mécanismes physiques mis au jeu au cours des différents traitements et de déterminer les caractéristiques {porosité, épaisseur} optimales des couches poreuses compatibles avec les séquences de la technologie proposée. La technologie Smart Cut™ a ainsi été appliquée à des substrats partiellement porosifiés menant à la fabrication réussie d’une structure temporaire de type Silicium-sur-Isolant avec une couche de silicium poreux enterrée. Ces structures temporaires ont été « démontées » dans un second temps par collage polymère ou collage direct et insertion de lame menant au second report de film mince monocristallin par rupture au sein de la couche porosifiée et donc fragile. Les structures fabriquées ont été caractérisées pour vérifier leur intégrité et leurs stabilités chimique et mécanique. Les propriétés cristallines du film mince de Si monocristallin, reporté en deux temps, ont été vérifiées confirmant ainsi la compatibilité des structures fabriquées avec des applications microélectroniques telles que les applications de type « Back-Side Imager » nécessitant une implémentation de composants sur les deux faces du film. Ainsi une technologie prometteuse et performante a pu être élaborée permettant le double report de films minces monocristallins et à fort potentiel pour des applications variées comme les imageurs visibles ou le photovoltaïqueAs scaling of microelectronic devices is confronted from now to fundamental limits, improving microelectronic systems performances is largely based nowadays on complex and innovative stack realization to offer more compaction and flexibility to structures. Growing interest in the fabrication of innovative temporary structures, allowing for example double sided layer processing, lead us to investigate the capability to combine one technology of thin single crystalline layer transfer, i.e. the Smart Cut™ technology, and partial porosification of silicon substrate in order to develop an original double layer transfer technology of thin single crystalline silicon film. To this purpose, single crystalline silicon substrates were first partially porosified by electrochemical anodization. Application of suitable treatments of porous silicon layer has required the use of several characterization methods to identify intrinsic porous silicon properties after anodization and to verify their evolution as function of different applied treatments. Chemical, structural and mechanical properties of porous silicon layers were studied by using different characterization techniques (XPS-SIMS, AFM-MEB-XRD, nanoindentation, razor blade insertion, etc.). Such studies allowed comprehending and describing physical mechanisms occurring during each applied technological steps and well determining appropriated {porosity, thickness} parameters of porous silicon layer with the developed technological process flow. The Smart Cut™ technology was successfully applied to partially porosified silicon substrates leading to the fabrication of temporary SOI-like structures with a weak embedded porous Si layer. Such structures were then “dismantled” thanks to a second polymer or direct bonding and razor blade insertion to produce a mechanical rupture through the fragile embedded porous silicon layer and to get the second thin silicon film transfer. Each fabricated structure was characterized step by step to check its integrity and its chemical and mechanical stabilities. Crystalline properties of the double transferred silicon layer were verified demonstrating the compatibility of such structures with microelectronic applications such as “Back-Side Imagers” needing double-sided layer processing. Eventually, a promising and efficient technology has been developed to allow the double transfer of thin single crystalline silicon layer which presents a high potential for various applications such as visible imagers or photovoltaic systems
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Dasté, Philippe. "Etude de croissance en phase vapeur aux organometalliques a pression atmospherique d'heterostructures inp/ingaasp et inp/dielectrique a grande uniformite sur substrat de deux pouces." Paris 6, 1986. http://www.theses.fr/1986PA066460.
Full textAbstract:
Presentation de la conception et de la realisation d'un nouveau type de reacteur pour l'epitaxie en phase vapeur a partir des organometalliques a pression atmospherique. Utilisation pour l'etude des heterointerfaces inp/ingaasp avec pour application les doubles heterostructures laser emettant a 1,3mu m, et pour l'etude de l'interface inp/dielectrique avec pour application les transistors m. I. S. Inp. Uniformite d'epaisseur et uniformite de composition pour le quaternaire
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DUPONT-NIVET, ERIC. "Epitaxie en phase vapeur aux organometalliques de gainp et algainp sur gaas : application a la realisation de diodes et de lasers a heterojonctions." Paris 7, 1987. http://www.theses.fr/1987PA077108.
Full textAbstract:
Principes de base de la methode movpe et problemes poses par sa mise en oeuvre. Cas particuliers de gainp et de algainp. Analyse des mecanismes de la methode movpe. Proprietes des interfaces gainp/gaas, algainp/gaas et algainp/gainp et presentation de puits quantiques algainp/gainp. Realisation de dispositifs optoelectroniques: presentations de diodes electroluminescentes a homojonctions en gainp et algainp, examen des travaux des principales equipes epitaxiant algainp, presentation de lasers a heterojonctions algainp/gainp/algainp
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Turco, Françoise. "Applications de techniques d'analyse in situ à l'épitaxie par jets moléculaires du système (Al, Ga, In) As." Grenoble INPG, 1988. http://www.theses.fr/1988INPG0016.
Full textAbstract:
L'etude des oscillations d'intensite de diffraction rheed en incidence rasante dursant la croissance de (al,ga,in)as conduit a un controle en temps reel en fonction des parametres (temperature, composition de la phase solide, pressions incidentes). Le couplage in situ avec la spectroscopie xps a permis de mettre en evidence, au cours de la croissance de algaas, gainas et alinas, la segregation en surface de l'element iii le moins lie a as. Par la technique des oscillations de rheed, determination des variations du coefficient d'incorporation de in dans alinas en fonction de la contrainte de la couche par le support, de la vitesse de croissance et de la pression de as. Le modele thermodynamique permet de rendre compte de ces variations