Дисертації з теми "Crystal defect analysis"

An experimental technique based on the immobilisation of dislocations by segregation of impurity atoms to the dislocation core (dislocation locking) has been developed and used to investigate the critical conditions for slip occurrence in Czochralski-grown and nitrogen-doped floating-zone-grown silicon crystals. The accumulation of nitrogen and oxygen impurities along a dislocation and the resulting dislocation locking effect has been investigated in silicon samples subjected to different annealing conditions. In particular, the stress needed to unlock the dislocations after their decoration by impurities has been measured as a function of annealing duration and temperature. The approach used in this study has allowed the determination of new diffusivity data for oxygen and nitrogen in silicon in the technologically important range of temperatures 350-850°C. No other data covering such wide temperature range are available in the literature. In addition to transport properties, the binding energy of an impurity atom to a dislocation in silicon has been deduced from the experimental data in the case of oxygen and nitrogen impurities. A discussion in terms of the impurity species responsible for transport (monomers or dimers) and dislocation locking is also presented. The role of oxide precipitates in the generation of glide dislocation loops and the parameters affecting the occurrence of slip have been investigated in silicon samples containing precipitates of different sizes and different morphologies. The fundamental parameters deduced in this work have been used to develop a numerical model to investigate the effect of different heat treatments on the mechanical properties of silicon wafers containing a controlled distribution of impurities. This model has then been used to simulate real wafer processing conditions during device fabrication to show how they may be modified to increase dislocation locking. It is hoped that these results will have relevance to how wafers are processed in order to minimise or eliminate dislocation multiplication and consequent warpage.

Thesis (M.S.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains viii, 70 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 55-57).

Hauptthema der Dissertation ist die Analysis eines nichtlinearen, gekoppelten Systems partieller Differentialgleichungen (PDG), das in der Modellierung der Kristallzüchtung aus der Schmelze mit Magnetfeldern vorkommt. Die zu beschreibenden Phenomäne sind einerseits der im elektromagnetisch geheizten Schmelzofen erfolgende Wärmetransport (Wärmeleitung, -konvektion und -strahlung), und andererseits die Bewegung der Halbleiterschmelze unter dem Einfluss der thermischen Konvektion und der angewendeten elektromagnetischen Kräfte. Das Modell besteht aus den Navier-Stokeschen Gleichungen für eine inkompressible Newtonsche Flüssigkeit, aus der Wärmeleitungsgleichung und aus der elektrotechnischen Näherung des Maxwellschen Systems. Wir erörtern die schwache Formulierung dieses PDG Systems, und wir stellen ein Anfang-Randwertproblem auf, das die Komplexität der Anwendung widerspiegelt. Die Hauptfrage unserer Untersuchung ist die Wohlgestelltheit dieses Problems, sowohl im stationären als auch im zeitabhängigen Fall. Wir zeigen die Existenz schwacher Lösungen in geometrischen Situationen, in welchen unstetige Materialeigenschaften und nichtglatte Trennfläche auftreten dürfen, und für allgemeine Daten. In der Lösung zum zeitabhängigen Problem tritt ein Defektmaß auf, das ausser der Flüssigkeit im Rand der elektrisch leitenden Materialien konzentriert bleibt. Da eine globale Abschätzung der im Strahlungshohlraum ausgestrahlten Wärme auch fehlt, rührt ein Teil dieses Defektmaßes von der nichtlokalen Strahlung her. Die Eindeutigkeit der schwachen Lösung erhalten wir nur unter verstärkten Annahmen: die Kleinheit der gegebenen elektrischen Leistung im stationären Fall, und die Regularität der Lösung im zeitabhängigen Fall. Regularitätseigenschaften wie die Beschränktheit der Temperatur werden, wenn auch nur in vereinfachten Situationen, hergeleitet: glatte Materialtrennfläche und Temperaturunabhängige Koeffiziente im Fall einer stationären Analysis, und entkoppeltes, zeitharmonisches Maxwell für das transiente Problem.
The present PhD thesis is devoted to the analysis of a coupled system of nonlinear partial differential equations (PDE), that arises in the modeling of crystal growth from the melt in magnetic fields. The phenomena described by the model are mainly the heat-transfer processes (by conduction, convection and radiation) taking place in a high-temperatures furnace heated electromagnetically, and the motion of a semiconducting melted material subject to buoyancy and applied electromagnetic forces. The model consists of the Navier-Stokes equations for a newtonian incompressible liquid, coupled to the heat equation and the low-frequency approximation of Maxwell''s equations. We propose a mathematical setting for this PDE system, we derive its weak formulation, and we formulate an (initial) boundary value problem that in the mean reflects the complexity of the real-life application. The well-posedness of this (initial) boundary value problem is the mainmatter of the investigation. We prove the existence of weak solutions allowing for general geometrical situations (discontinuous coefficients, nonsmooth material interfaces) and data, the most important requirement being only that the injected electrical power remains finite. For the time-dependent problem, a defect measure appears in the solution, which apart from the fluid remains concentrated in the boundary of the electrical conductors. In the absence of a global estimate on the radiation emitted in the cavity, a part of the defect measure is due to the nonlocal radiation effects. The uniqueness of the weak solution is obtained only under reinforced assumptions: smallness of the input power in the stationary case, and regularity of the solution in the time-dependent case. Regularity properties, such as the boundedness of temperature are also derived, but only in simplified settings: smooth interfaces and temperature-independent coefficients in the case of a stationary analysis, and, additionally for the transient problem, decoupled time-harmonic Maxwell.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The dissertation focuses on the analysis of the extended defects present in as-grown and proton bombarded β-SiC (annealed and unannealed) grown by chemical vapour deposition (CVD) on (001) Si. The proton irradiation was done to a dose of 2.8 × 1016 protons/cm2 and the annealing took place at 1300°C and 1600°C for 1hr. The main techniques used for the analysis were transmission electron microscopy (TEM) and high resolution TEM (HRTEM). From the diffraction study of the material the phase of the SiC was confirmed to be the cubic beta phase with the zinc-blende structure. The main defects found in the β- SiC were stacking faults (SFs) with their associated partial dislocations and microtwins. The SFs were uniformly distributed throughout the foil. The SFs were identified as having a fault vector of the type 1/3 <111> with bonding partial dislocations of the type 1/6 <121> by using image simulation. The SFs were also found to be predominantly extrinsic in nature by using HRTEM analysis of SFs viewed edge-on. Also both bright and dar-field images of SFs on inclined planes exhibited symmetrical and complementary fringe contrast images. This is a result of the anomalous absorption ratio of SiC lying between that of Si and diamond. The analysis of the annealed and unannealed irradiated β-SiC yielded no evidence of radiation damage or change in the crystal structure of the β-SiC. This confirmed that β-SiC is a radiation resistant material. The critical proton dose for the creation of small dislocation loops seems to be higher than for other compound semiconductors with the zinc-blende structure.

This thesis is concerned with the simulation of the contrast in X-ray section topographs due to the strains induced in silicon single crystals by various types of technologically relevant crystal defect. A general introduction to the field of X- ray topography is presented, illustrating that this technique is well suited to the characterisation of defect induced strain in highly perfect crystals. A review of X-ray dynamical theory is given, culminating in Takagi's equations for a crystal containing a defect. Techniques for simulating X-ray section topographs, based on Takagi's equations, are discussed. Computer simulation of section topographs has been used throughout this work to deduce the microscopic strains from the X-ray topographic images. The volume of oxygen precipitates in MCZ silicon was found to increase linearly as lnT, where T is the annealing temperature of the sample. Results suggest that the vast majority of precipitates which survive to maturity are nucleated at approximately the same time, subsequently growing at the same rate. An industrial role for simulation in conjunction with experiment is proposed, in the evaluation of the precipitate depth and the deformation parameter, C, representing the precipitate strain magnitude. The technological relevance of these two quantities is discussed. The effect of surface relaxation on the structure of images due to precipitates has been investigated. The critical depth (_z(_crit)) at which the effect of surface relaxation became negligible was found to increase linearly with lnC. Simulations have been generated for crystals containing oxygen precipitate distributions, with denuded zones. Characteristic image features have been discussed. Studies on precipitate resolvability revealed that the critical separation for two precipitates to be just resolved increases linearly as lnC. An extensive study of intrinsic gettering has been undertaken, in terms of decorated dislocations. The strain distribution due to precipitate decoration was modelled by the cylindrical inclusion model. It was shown that even for very low precipitate strains, precipitate decoration is distinguishable from the associated dislocation by section topography. Hence, an industrial role is proposed for simulation, in conjunction with experiment, in the parameterisation of the strain induced by decorated dislocations. To fully explore the use of the cylindrical inclusion model in this way, the variation in the inclusion strain magnitude was determined as a function of the precipitate strain and density, and the size of the precipitate distribution. It was found that the strain magnitude of the equivalent cylindrical inclusion must increase more rapidly relative to the precipitate deformation parameter for low-order reflections than for high-order reflections. Decorated dislocations have been shown to be resolvable by section topography even in the most dislocation-rich sihcon samples. The industrial usefulness of this characteristic is discussed. A study was made of the critical deformation parameter, C(_crit), for decorated dislocations to be just resolved, as a function of the separation, k, of the dislocations. For k greater than about 45µm, the variation of In(C(_crit) with k was linear. For smaller separations, the linearity breaks down because of the increasingly important strain contribution due to the dislocations. The strains induced by oxide films and devices in the silicon substrates onto which they are formed have been investigated. Experimental section topographs of oxide edge regions and devices on silicon have been simulated, and the visibility of the extra set of fringes found in simulations by another worker has been examined. The variation in image structure with device position on the entrance and exit surfaces has been investigated. An absolute minimum on device width detectable by section topography of lµm has been found. However, this minimum was found to depend on device-induced strain, and for values of strain characteristic of contemporary devices, the minimum detectable device width was found to be at least 3.5µm. This is above the limits set by the geometric and other constraints of the experimental technique. A thorough study has been made of the cancellation of opposing strains due to opposite edges of a device. The total distortion induced by the device was found to be minimised by reducing the device width and increasing the force per unit length, 5, along the device edges. Quantitative information has been obtained on this process. It was found that the fractional increase in lattice parameter at a fixed point, due to device-induced strain, increases linearly with S, with increasing gradient for increasing device width. It was shown that the narrower the device, the faster the relative fall-off in fractional increase in lattice parameter with increasing displacement from one edge of the device.

Thesis (Ph. D.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains xii, 116 p. : ill. Includes abstract. Includes bibliographical references (p. 106-109).

Une des limitations dans l'exploitation généralisée de l'énergie photonique principalement d'origine solaireest la limitation du rendement des cellules photovoltaiques (pv) qui ne peut être améliorée aujourd’hui au planindustriel, qu’en utilisant des matériaux chers, rares voire dangereux. Le matériau le plus abondant le moinstoxique à la fabrication et au recyclage, qui aujourd’hui est le moins cher et le mieux maîtriséindustriellement est le silicium, mais la part du spectre lumineux convertible en électricité reste incomplètece qui pour conséquence de limiter le rendement.L’introduction de la nanotechnologie photonique permet par un effet de photoconversion multi-étage horsbandgap d'augmenter le rendement de photoconversion en élargissant le spectre photoconvertible du silicumnatif. La nano-unité opérationnelle du silicium cristallin dans ce cas, est nommée "Segton" qui est unevariante de bilacune organisée en couche enterrée et située à l'interface créé artificiellement entre du siliciumamorphe et du silicium cristallin.Ces travaux font le point sur les démonstrateurs réalisés de cellules à photoconversion géante en particuliersur les derniers moyens technologiques pré-industriels exploités pour ces fabrications notamment a ceux misen œuvre avec différents laboratoires.La thèse propose de nouveaux moyens de caractérisation adaptés à la photoconversion en utilisant laphotoluminescence à basse température.Enfin, un bilan est détaillé sur les activités de simulation, de fabrication et de caractérisation se terminant parune présentation prospective de futures productions industrielles
One of the limitations to the widespread use of photonic energy is the limited efficiency of photovoltaic (PV) cells, which can only be improved industrially today by using expensive, rare and toxic materials or fragile devices. Silicon is the most abundant material, the least toxic to manufacture and recycle. It is also the cheapest and the best mastered industrially. However, the proportion of the light spectrum that can be converted into electricity remains incomplete, which limits its efficiency. The introduction of photonic nanotechnology has made it possible to increase photoconversion efficiency by broadening the photoconvertible spectrum of native silicon and by using a multistage photoconversion effect outside the band gap. The operational nano-unit of crystalline silicon in this case is the "Segton", which is avariant of the divacancy organized as a buried layer and located at the artificially created interface between amorphous and crystalline silicon. This work provides an update on the demonstrators of giânt photoconversion cells, and in particular on the latest pre-industrial technological resources used for this type of production. This was implemented incollaboration with various laboratories. This thesis proposes new characterization methods adapted to photoconversion using the low-temperature photoluminescence spectra in order to detect the good generation of divacancies due to the implementation steps during the fabrication. Finally, the simulation, the manufacturing and the characterization activities are reviewed in detail, ending with a prospective to future industrial production

This PhD thesis is devoted to the design, development and implementation of a non-contact hybrid non-destructive testing (NDT) method applied to the analysis of metallic objects that contain embedded defects or fractures. We propose a hybrid opto-acoustic technique that combines laser generated ultrasound as exciter and ultrasound transducers as receivers. This work envisages a detailed study of the detection and one, two or three-dimensional reconstruction of defects, using the proposed hybrid technique and its application as a remotely controlled non-contact NDT. Our device combines several advantages of both photonic and ultrasonic techniques, while reduces some of the drawbacks of both individual methods. Our method relay on the combination of experimental results with high-resolution signal processing procedures based on different mathematical algorithms. Our basic experimental setup uses a nanosecond pulsed laser at 532nm wavelength that impacts onto the surface of the object under study. The laser pulse is rapidly absorbed into a shallow volume of material and creates a localized thermo-elastic expansion inducing a broadband ultrasound pulse that propagate inside the material. The laser beam scans a selected area of the object surface, being remotely controlled by means of a programmable XY scanner. For each excitation point, the ultrasound waves propagate through the object are reflected or scattered by material 3D defects. They are detected by ultrasound transducers and recorded with a PC data-acquisition system for a further process and analysis. As a first step, the time of flight analysis provides enough data for the location and size of the defect in 1D view. The detection capabilities of internal defects in a metallic sample are studied by means of wavelet transform, chosen due to its multi-resolution time-frequency characteristics. A novel algorithm using a density-based spatial clustering is applied to the resulting time frequency maps to estimate the defect’s position. For the 2D visualization and reconstruction of the defects we extended the signal analysis using the synthetic aperture focusing technique (SAFT). We implement a novel 2D apodization window filtering applied along with the SAFT, and we show it removes undesired effects of the side lobes and wide-angle reflections of ultrasound waves, enhancing the reconstructed image of the defect. We move then towards the 3D analysis and reconstruction of defects and in this case we achieve and implement a fully non-contact and automatized experimental configuration allowing the scan areas on different object’s faces. The defect details are recorded from different angles/perspectives and a complete 3D reconstruction is achieved. Finally, we show our results on a complementary topic related to a particular case of the ultrasound propagation in solids. We were concerned on the physical understanding of the propagation and diffraction of ultrasound waves in solid materials from the first moment. The control of the diffraction pattern in solids, using an ultrasonic lens, would help focus/collimate the ultrasound reducing echoes and boundary reflections, resulting in a further improve NDT process. Phononic crystals have been used to regulate the diffraction and frequency response of ultrasonic waves traveling in fluids. However, they were much less studied in solid materials due to the difficulty of building the crystal and to high coupling losses. We perform detailed numerical simulations of the ultrasound propagation in a solid phononic crystal and we show focusing and the self-collimation effects. We further extend our analysis and couple our phononic crystal lens to a solid under study, showing that the diffraction control is preserved inside the target solid object trough the coupling material.
Esta tesis doctoral versa sobre el diseño, estudio e implementación de un método híbrido, sin contacto, de ensayos no destructivos (NDT, non-destructive testing) para el análisis de objetos metálicos que contienen defectos o fracturas internas. Proponemos una técnica híbrida opto-acústica que combina ultrasonidos generados por impacto láser como excitador y transductores de ultrasonidos como receptores. El trabajo plantea un estudio detallado de la detección y reconstrucción en 1D, 2D y 3D de defectos presentes en un objeto metálico, usando la técnica híbrida de NDT sin contacto y controlado remotamente. Nuestro dispositivo presenta varias ventajas de las técnicas fotónicas y de ultrasonidos, reduciendo al mismo tiempo algunos inconvenientes de dichos métodos tomados por separado. Nuestro método combina resultados experimentales con simulaciones numéricas basadas en el procesado de señal de alta resolución. El montaje experimental consiste en un láser pulsado de ns a una longitud de onda de 532 nm, que impacta sobre la superficie del objeto. El pulso láser se absorbe, creando una expansión termoelástica localizada que induce un pulso de ultrasonidos de banda ancha que se propaga en el material. El láser, controlado remotamente, realiza un barrido sobre un área seleccionada de la superficie del objeto. Por cada punto de excitación, el ultrasonido se propaga a través del objeto y se refleja o dispersa en los defectos del material. Dichas ondas se detectan mediante transductores y se registran en un sistema de adquisición de datos para su ulterior procesado. En un primer paso, mediante el análisis del tiempo de vuelo, podemos localizar y determinar el tamaño del defecto en una vista 1D. Las capacidades de detección de defectos internos en una muestra metálica se estudian también mediante transformación wavelet debido a sus características de multi-resolución en tiempo y frecuencia. Se aplica un algoritmo novedoso de agrupamiento (clustering) espacial y se usan los mapas resultantes de tiempo y frecuencia para estimar la posición del defecto. Para la visualización 2D de los defectos ampliamos el análisis de la señal utilizando la técnica de focalización por apertura sintética (SAFT, synthetic aperture focusing technique). Implementamos un novedoso filtro de apodización 2D, juntamente con la técnica SAFT, y demostramos que elimina efectos no deseados, mejorando la resolución de la imagen reconstruida del defecto. El siguiente paso es un análisis y reconstrucción 3D. En este caso conseguimos una configuración experimental totalmente automatizada y sin contacto, permitiendo áreas de barrido sobre diferentes caras de un objeto. Los detalles de los defectos se registran desde diferentes ángulos, consiguiéndose una completa reconstrucción 3D. Finalmente, mostramos nuestros resultados en un tema complementario, relacionado con un caso particular de propagación de ultrasonidos en sólidos. Desde un primer momento, quisimos tener una comprensión física de la propagación y difracción de ondas de ultrasonidos en materiales sólidos. El control de los patrones de difracción en sólidos, mediante el uso de lentes ultrasónicas, ayudaría a la focalización/colimación del ultrasonido, reduciendo ecos y reflexiones en la superficie de contorno, mejorando del proceso de análisis NDT. Los cristales fonónicos se usan para regular la difracción y la respuesta en frecuencia de ondas de ultrasonido que se propagan en fluidos. No obstante, dichas estructuras se han estudiado mucho menos en materiales sólidos. Hemos realizado detalladas simulaciones numéricas de la propagación de ultrasonidos en un cristal fonónico sólido y hemos demostrado efectos de focalización y autocolimación. Finalmente hemos acoplado nuestra lente de cristal fonónico al sólido objeto de estudio, demostrando que el control de la difracción se conserva en el interior de dicho objeto a través del material de acoplamiento. Finalmente, proporcionamos una conclusión general sobre el trabajo declarado en esta tesis y un plan de trabajo futuro donde esta investigación puede extenderse y expandirse aún más a aplicaciones industriales en colaboración con el mercado de producción

This thesis describes investigations into the role of non-stoichiometry in the surface and bulk properties of SrTiO₃ single crystals. A family of (n×n) reconstructions, where n = 2, 3, 4, 5, 6 are produced by argon ion sputtering of the SrTiO₃ (111) single crystals and subsequent annealing in UHV or in an oxygen rich environment. The sputtering process introduces defects or oxygen vacancies in the surface region of the sample, whilst the annealing gives rise to surface reconstructions. The surface preparation conditions such as sputtering time, annealing temperature and environment are optimized to obtain various reconstructions in a controlled and reproducible manner. High resolution STM images of these reconstructions are also obtained and utilized in the investigation of the surface reactivity. Fullerene molecules are deposited on the reconstructed surfaces to elucidate the surface reactivity through template assisted growth. Fullerene molecules are first deposited with substrate surfaces held at room temperature. Being the most highly reduced among the (n×n) family, the 5×5 reconstruction significantly influenced the growth of fullerenes. Both C₆₀ and C₇₀ adsorb as individual molecules and produce clusters with magic numbers. The 4×4 and 6×6 reconstructed surfaces encourage the formation of close-packed structures upon the deposition at room temperature. When the surface covered with fullerenes is heated to a temperature of around 200 °C, epitaxial islands are observed. The 6×6 reconstructed surface appeared to be less reactive than the 4×4. Electrical transport, cathodoluminescence (CL) and electron spin resonance (ESR) experiments are also carried out to investigate the effect of oxygen vacancies on the bulk properties of UHV annealed SrTiO₃ single crystals. Thermal reduction leads to carrier doping of the material, which not only gives rise to electrical conduction but also induces room temperature luminescence. Both the electrical conductivity and CL intensity increases with annealing time. The work presented in this thesis provides insight into the defect driven properties in both the surface and bulk of SrTiO₃ single crystals, which could play an important role in the development of oxide-based electronic devices.

Trapping centres in as-grown TlInS2 layered single crystals have been studied by using a thermally stimulated current (TSC) technique. TSC measurements have been performed in the temperature range of 10-300 K with various heating rates. Experimental evidence has been found for the presence of five trapping centres with activation energies 12, 14, 400, 570 and 650 meV. Their capture cross-sections and concentrations were also determined. It is concluded that in these centres retrapping is negligible as confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. An exponential distribution of traps was revealed from the analysis of the TSC data obtained at different light excitation temperatures. The transmission and reflection spectra of TlInS2 crystals were measured over the spectral region of 400-1100 nm to determine the absorption coefficient and refractive index. The analysis of the room temperature absorption data revealed the coexistence of the indirect and direct transitions. The absorption edge was observed to shift toward the lower energy values as temperature increases from 10 to 300 K. The oscillator and the dispersion energies, and the zero-frequency refractive index were also reported. Furthermore, the chemical composition of TlInS2 crystals was determined from energy dispersive spectroscopic analysis. The parameters of monoclinic unit cell were found by studying the x-ray powder diffraction.

Cette thèse porte sur le développement des méthodes d'analyse structurale de la couche mince de GaP epitaxiées sur le substrat de silicium par l'épitaxie par jets moléculaires (MBE), basées sur la diffraction des rayons X (ORX) et combinées à des techniques complémentaires telles que la microscopie électronique en transmission (TEM), la microscopie à force atomique (AFM) et la microscopie à effet tunnel (STM). Le travail est centré sur la caractérisation quantitative de la densité des défauts cristallins comme les micro-macles et les domaines d'inversion présents dans la couche ainsi que l'évaluation de la qualité de surface et l'interface. L'objectif ultime est d'obtenir une plate-forme GaP/Si parfaitement cristallisée sans défaut, via l'optimisation des paramètres de croissance. Nous avons mis en place et utilisé deux méthodes de quantification des micro-macles par la diffraction des rayons X en condition de laboratoire : les figures de pôles pour la visualisation rapide et l'évaluation de la densité des micro-macles et les « rocking-curves » permettent une extraction précise de la faction volumique de domaine maclé. Les propriétés structurales de la plate-forme de GaP/Si ont été considérablement améliorées, après une procédure d'optimisation impliquant la température de croissance, une procédure de croissance alternée (MEE) et une séquence de croissance en deux étapes. Un échantillon quasiment sans micro-macles a été obtenu par le dépôt de 40 monocouches de GaP par MEE à 350 •c suivi d'une surcroissance de 40 nm de GaP par MBE continue, à 500 •c. La surface de l'échantillon est lisse avec une rugosité de 0.3 nm. L'évaluation des domaines d'inversion par la ORX a été effectuée sur les cartographies de l'espace réciproque centrées sur les réflexions GaP de type (OOL), en laboratoire et sur une ligne synchrotron. Les balayages « transverses » extrait à partir des cartographies de l'espace réciproque sont analysés via une méthode dite "Williamson-Hall like", afin d'obtenir la "mosaïcité" qui est reliée à la micro-désorientation des petits domaines cristallins et la longueur de corrélation latérale correspondant à ces petits domaines. La distance moyenne entre parois de domaines d'inversion et ensuite estimé à partir de cette mesure. En utilisant cette méthode d'analyse et les techniques microscopiques, une optimisation plus poussée a été effectuée sur la dose de Ga au stade initial de croissance, l'utilisation de couches de marqueur AIGaP et l'homoépitaxie d'une couche de silicium avant le GaP. Enfin, nous avons obtenu un échantillon ne présentant pas de signal de micro-macle détectable en conditions standard de laboratoire, et une très faible densité de domaine d'inversion. Nous avons aussi observé une interface de GaP/Si visiblement présentant des bi-marches atomiques très régulières, sur un échantillon avec une couche de silicium déposée avant la croissance du GaP
This thesis deals with the development of structural analysis methods of the GaP thin layers heterogeneously grown on the Si substrate by Molecular Beam Epixay (MBE), based on X-ray diffraction (XRD) analyses, combined with complementary techniques such as transmission electron microscopy (TEM), atomic force microscopy techniques (AFM) and scanning tunneling microscope (STM). The main work is centered on the quantitative characterization of crystalline defect such as micro-twins and the anti-phase domains, and the evaluation of the surface and interface quality. The ultimate goal is to achieve a perfectly crystallized GaP/Si platform without any defect, through the optimization of the growth conditions. We have applied two micro-twin quantification methods using a XRD lab setup. Pole figure method for fast visualization and evaluation of micro-twin density and rocking curves integration for a more precise absolute quantification of the micro-twin volume fraction. The GaP/Si platform structural properties have been significantly improved, after an optimization procedure involving growth temperature, MEE (Migration Enhanced Epitaxy) growth procedure and a twostep growth sequence. GaP layers quasi-free of MTs are obtained, with a r.m.s. roughness of only 0.3 nm. The APD evaluation by XRD has been performed on reciprocal space maps (RSM) centered on the (OOL) GaP reciprocal space lattice point either in lab setup or on synchrotron. Analysis of the transverse scans extracted from such RSM through the "Willamson-Hall like" method permits obtaining the "mosaicity" that is related to the micro-orientation of the small crystalline domains in the GaP layer, and the lateral correlation length which is considered to be related to the mean distance between two APBs, provided that this distance is approximately homogenous and corresponding to the mean APD size, and the density of other defects are very weak so that their influence can be neglected. Using this analytical method and the microscopic techniques, further optimization has been carried out on Ga amount at the initial growth stage, the use of AIGaP marker layers and the homoepitaxie of Si buffer layer. Finally, sample with none MT signal and very low density of APD has been achieved. Moreover, an abrupt GaP/Si interface displaying regular and double atomic steppes is observed on sample with a Si buffer layer prior to the GaP growth

La microscopie à l'angle de Brewster est une nouvelle et tres puissante technique d'étude des films monomoléculaires à la surface de l'eau. Son principe est basé sur les propriétés de réflectivité des interfaces. Elle est sensible à l'épaisseur, la densité et l'anisotropie optique des films. Cette technique a été appliquée à l'étude de couches adsorbées à la surface de solutions aqueuses d'acides gras (acides palmitiques et myristiques). Ces couches traversent pendant leur formation des transitions de phases. Le nombre, la nature et la morphologie de ces phases dépendent de nombreux paramètres dont le pH. Nous avons entre autres observé des phases optiquement anisotropes, contituées de molécules inclinées par rapport à la normale à la solution.Ces phases sont sans doute des mésophases "verrouillées", c'est à dire que la direction des molécules est fixée par rapport aux directions intermoléculaires. Elles présentent différents types de défauts d'orientation, dont des structures en étoile. L'existence de telles structures est expliquée par application d'un modèle d'élasticité continue développé pour l'étude des films minces de cristaux liquides smectiques. Des structures en zig-zag, en spirales et en bandes de largeur déterminée ont également été observées. Nous avons également étudié les couches d'un polymère (le PDMS) à la surface de l'eau. Nous y avons observé la séparation latérale en domaines de densités de surface différentes, à la fois dans le régime monocouche et le régime multicouches.

Cette thèse est consacrée principalement à l'analyse mathématique de modèles issus de la physique des cristaux liquides et de la supraconductivité. Ces modèles ont en commun de faire intervenir des systèmes elliptiques dont les solutions présentent des singularités : défauts optiques dans les cristaux liquides, défauts de vorticité en supraconductivité. Les cristaux liquides se composent de molécules allongées qui, tout en étant distribuées « au hasard » comme dans un liquide, tendent à s'aligner dans une direction commune : cet « ordre d'orientation » leur confère des propriétés optiques similaires à celles d'un cristal, à l'origine de leurs nombreuses applications industrielles. On démontre différents résultats liés à la symétrie locale de cet alignement autour des singularités. On présente aussi dans cette thèse différents résultats liés au modèle de Ginzburg-Landau pour les supraconducteurs de type II, et aux « défauts de vorticité » : points isolés autour desquels la supraconductivité est détruite. Une dernière partie de cette thèse traite de la caractérisation de la régularité d'une fonction f à travers la vitesse de convergence de f ∗ ρε pour un certain noyau ρ. Dans un travail commun avec Petru Mironescu, on s'intéresse à la question de la régularité des noyaux ρ qui permettent une telle caractérisation
The present thesis is devoted mainly to the mathematical analysis of models arising in the physics of liquid crystals and superconductivity. A common feature of these models is that one has to deal with elliptic systems whose solutions have singularities: optical defects in liquid crystals, vorticity defects in superconductivity. The rod-like molecules in a liquid crystals, while being (as in a liquid) “randomly” distributed, tend to align in a common direction: this “orientational order” enhances crystal-like optical properties, which are responsible for their many industrial applications. We demonstrate different results related to the local symmetry of this alignement near singularities. We also present some results related to the Ginzburg-Landau model for type II superconductivity, and to “vortices”: isolated points at which superconductivity is destroyed. The last part of this thesis addresses regularity characterization for a function f through the convergence rate of f ∗ ρε, for some kernel ρ. In a joint work with Petru Mironescu we study the minimal regularity of ρ that allows such characterization

碩士
國立交通大學
光電工程系所
93
In this thesis, defect modes of two-dimensional photonic crystal nano-cavity are analyzed. The defect is formed by removing a single air hole from array of air holes of hexagonal lattice arrangement on a dielectric slab. First, the finite difference time domain method with various boundary conditions is introduced. Second, symmetry analysis of defect modes and design rules for high quality factor cavities are presented. Finally, techniques of the simulation and the results of the simulation, like photonic band structures, resonant frequencies, mode profiles, and quality factors are exhibited.

碩士
國立臺灣大學
電子工程學研究所
93
Photonic crystal is an unique structure. It is a kind of periodic variation of dielectric constant by various fabrication processes. Photonic crystal has a special characteristic—photonic bandgap—which the light with certain frequency will not propagate in . We use the “auto-cloning technique” to fabricate three dimensional photonic crystal. On the two dimensional checker-board pattern template, we alternate periodically the depositions of two materials which have different percentage of Al composition. Our material is GaAs system. Then the refractive index difference is changed by using wet oxidation. After wet oxidation the difference is increased to about 2 to fabricate 3D-FCC-photonic crystal. The subject of our research is the influence of the following variations on the photonic bandgap: (i) periods variation; (ii) defect region size variation; (iii) oblique transmission characteristics. Increasing the number of periods will make photonic bandgap more obvious. With increasing defect size, we observed the red shift of defect modes. With oblique incidence, photonic bandgap width will increase.

碩士
中原大學
機械工程研究所
96
Over the last decade, thin-film-transistor liquid-crystal-display (TFT-LCD), as display, has grown rapidly, and has almost replaced the market of cathode ray tube (CRT) monitor. The total value of photoelectric industry has exceeded the one of semiconductor. It has been a glaring industry that the government promotes actively. The manufacturing process of TFT-LCD, including array process, cell process and module assembly process, will be introduced in this technical report. Through the introduction, the importance of inline defect inspection in array process will be pointed out and detailed. In current practice, there are several equipments used for in-line inspection: automatic optical inspection (AOI) machine, micro-review machine, macro/micro machine, and critical-dimension overlap machine. These machines are used for inspecting various kinds of defects in different processes of the manufacturing. The defects are classified and analyzed according to the corresponding engineering. Therefore, the task of in-line inspection is able to enhance the yield rate and increase the business benefit. To achieve the goals of inspection efficiency, yield enhancement, and the production-cost reduction, the future works for inline inspection will be focused on automation and knowledge management. As for the inspection equipment, the key issues will be focused on several points, including how to enlarge the size of equipment, how to improve the accuracy of the measurement, and how to lift the efficiency. These are adapt to the large-size LCD panels, and are the future trends for the design of inspection equipment. In the final we will discuss the future works including the knowledge management and the automatic defect classification. In TFT-LCD manufacturing, there are some unknown defects actually. Due to unknown defects, a high and satisfactory defect classification rate can not be obtained. For solving this problem, it is necessary to develop a knowledge management system to improve the defect classification accuracy. In addition, several techniques, such as image processing, statistical texture extraction, data mining and neural network-based classification, can be used and integrated to achieve the goal of real-time defect recognition. The above-mentioned refers to the automatic defect-classification system.

碩士
國立中山大學
材料科學研究所
94
The main purpose of this study is focused on the defects within the layers of GaN over AlN thin films which were grown on the substrates of silicon (111) and LiAlO2 (100), respectively. The growth of three sapphire crystals is also addressed. During the epitaxial growth period, the Al pre-deposition time is very important for the defect on AlN/Si, and due to the high stacking fault energy, the partial dislocations in the AlN layers can not be observed. Cracks were found in the GaN films because of the great thermal mismatch between GaN itself and AlN which is up to 25%. Although the lattice mismatch between GaN and LiAlO2 is low, the thermal stress effect still could not be avoided. Cracks also occurred in the GaN films which were grown on LiAlO2 substrates. For the sapphire pulled along [100] direction, the crystal has fewer amounts of bubbles at the lower rotation rate. For the sapphire pulled along [001] direction, the crystal with 4.5 mm/hr pulling rate has cracks along [001] direction, but the crystal with 4.0 mm/hr pulling rate has no cracks inside.

碩士
元智大學
光電工程研究所
94
In this study, we designed and analyzed one-dimensional photonic crystals as a narrow-band and a flat filter by using the transfer matrix method. Based on the transfer matrix method, we discussed the thin whole layer structure and the distribution of the thickness of each layer to get a very good narrow-band filter with a nice gain of the electric field of the light wave. Furthermore, we also used the transfer matrix method to calculate their transmissive spectra for three types of Gaussian photonic crystals, such as Gaussian refractive type, and the Gaussian thickness type, and the twin Gaussian type photonic crystal, and we focused and discussed transmissive spectra affected by the material parameters of thickness and refractive index and the defect states appeared in the layer structure. Consequenctly, we analyzed the relation between the Fourier spectra of Gaussian refractive type and Gaussian thickness type photonic crystals and their transmissive spectra.

碩士
國立清華大學
核子工程與科學研究所
101
Silicon carbides (SiC) are considered as one of the promising candidates for structural and core materials used in fusion reactor and high temperature gas-cooled reactor (HTGR) due to its high thermal stability, and good resistance to irradiation and chemical attack. Single crystal 3C-SiC with less intrinsic defects was used to precisely characterize the radiation-induced defects in 3C-SiC. In addition, there are limited discussions related to radiation effect of SA-Tyrannohex fiber-bonded composite at high temperatures. Therefore, in this study, single crystal 3C-SiC thin film and SA-Tyrannohex SiC fiber-bonded composite were irradiated at 1000℃ to 1350℃ with 7MeV Si3+ ion to simulate the neutron irradiation in reactors. The microstructure of the irradiated SiC was examined by using high resolution transmission electron microscope (HRTEM) and spherical aberration corrected scanning TEM (Cs-corrected STEM). In irradiated single crystal 3C-SiC, high resolution images showed that the planar defects were extrinsic stacking faulted loop with changing atomic sequences and intrinsic stacking faulted loop, i.e. vacancy loop. The atomic configurations were confirmed by STEM annular bright field image. However, no void has been found in single crystal 3C-SiC due to formation of vacancy loops, vacancies releasing from surface, or too small to be visible (<1 nm). In addition, dislocation loops, voids, and edge dislocations in SA-Tyrannohex SiC fiber-bonded composite after irradiation were investigated. This SiC composite are able to suppress void growth and lower the void density after high-temperature irradiation due to its small grain size (~300 nm). Besides, larger voids (with diameter 10-40 nm) formed in alumina with preferred orientation after irradiation perhaps resulting in degradation of strength of the SA-Tyrannohex SiC fiber-bonded composite.

博士
國立成功大學
機械工程學系碩博士班
93
The properties of photonic band gaps in chiral photonic crystals are discussed in the thesis. The research is devoted to the photonic defect modes in the chiral photonic structures with gradient pitch length and the introduction of the different kinds of defects. In addition, various optical applications with respect to the defect modes are also demonstrated. Self-organized cholesteric liquid crystals (ChLCs) with spatially varying pitch are the examples. The finite element method and the 4×4 transfer matrix method are carried out for the study of the optical propagation simulations in the ChLC films. First, the optics of the cholesteric medium with constant pitch is talked over, including dispersion relations, the group velocity, the group delays, the electromagnetic density of modes, transmission and reflection spectra, the properties of the defect modes, etc. Then, the optics of the cholesterics with spatially varying pitch is focused on the photonic defect modes created by the following defects: twist defect (phase jump), gradient jump, and pitch jump. The defect mode due to the introduction of a twist defect is considered in the chiral structures with spatially varying pitch. An unusual crossover behavior in reflection at the defect resonance wavelength of a single circularly polarized mode appears when the structure thickness increases over a specific value. Two different resonance wavelengths can be created by a twist defect in the identical ChLC composite film with linearly varying pitch. The behavior constitutes the operational mechanism for a passive optical diode. The introduction of photonic defect modes in a ChLC can be achieved by a global deformation of the helix with a chiral anti-symmetry relative to the middle of the ChLC configuration. The defect modes can be excited only when the circularly polarized incident wave has the same handedness as the ChLC. The transmittance of the defect modes is greatly reduced when the structure thickness is large far away from a critical value, and even some defect modes will be completely suppressed. A wider forbidden band for polarization-selective reflection can be obtained. Such a ChLC film can be useful for the production of the ultra-wide-band reflective polarizer. For normal and near-normal incidence of circularly polarized light with the same handedness as structure, the defect caused by a pitch jump in the cholesteric helix results in discrete peaks within a forbidden band in the transmission. The particular spectrum is similar to the feature of a Fabry-Perot interferometer. By introducing an additional phase jump, linear blue shifts of the defect modes in transmission spectra are correlated with an increase in the twist angle. Polarization-dependent or polarization-independent optical filters based on the special transmission properties of multiple photonic defect modes are described.

碩士
國立虎尾科技大學
光電與材料科技研究所在職專班
102
In this thesis, an optical filter based on photonic crystal structure with liquid crystal is proposed. The software for photonic crystal design, Crystal wave Version 3.2, is used for numerical　simulation in the thesis. Plane Wave Expansion method is adopted to calculate the photonic band gap. Then the propagation behaviors of light under different structures are simulated by FDTD, Finite-difference time-domain method. 　　In this thesis, the photonic crystal waveguide cavity filters with liquid crystal defects are designed and analyze. Because of the birefringence property of the anisotropic liquid crystal, we could analyze the filtering characteristic via changing the externally electric field to control director of liquid crystal under different structure. The electro-optic effect of liquid crystals could be used for the design of tunable photonic crystal filters. The criterions to obtain best performance of filtering could be found via adjusting parameters and they are shown useful for the application on the optical communications.

碩士
中原大學
電子工程研究所
98
The technical report is to explore “key components of TFT-LCD color filter’s defect analysis and classification in various manufacturing process”. In this report, we will introduce the panel that in recent years has been a lot of use, makes its demand increased, so panel manufacturing plant to increase production and research and development of large size panels. However, the panel defects generated due to manufacturing environment and machine’s stability, resulting in panel yield fell, the cost increased .In order to improve this problem, In-line MQC mechanisms are established that glass substrates are inspected by a randomly sampling ratio in manufacturing process to prevent the occurrence of a large number of unqualified panels. But the current in-line MQC mechanisms are operated under a sampling ratio and are handled manually. To reduce human power, increase processing speed, inspect entire glass substrates and pass relative information to the online engineers immediately. Therefore, it is necessary to introduce automatic inspection machine system. for this technological report will introduce color filter process Then the equipment of the process and the defect cause will be analyzed. In the end, the test result of the “auto defect classification system automation will be the database

碩士
國立成功大學
機械工程學系
102
In this research a series of tunable photonic crystal (PhC) devices are proposed. The magneto-optical (MO) materials are infiltrated into the PhC structure to become point or line defects. With out-of-plane magnetization, the degenerate resonant modes splits into two counter-rotating modes at different frequencies. Furthermore, the quality factor of two splitting modes significantly increases to about 4000, which is suitable for applications of dense wavelength-division-multiplexing (DWDM) systems and refractive index sensors. When the out-of-plane magnetization is applied to the MO line defects in the PhCs, the fundamental waveguide mode vanishes in specific frequency region. This phenomenon causes the fundamental mode waves blocked by the PhC structure. Based on the effect, the power can be switched by applying external magnetic fields. When two MO line defects are put side by side in the PhC structure with opposite direction of magnetization, the time-reversal and space inversion symmetries breaks, which causes the difference of the dispersion curves for opposite propagating directions. Using this effect a PhC diode can be achieved. Computations are performed using plane wave expansion (PWE) and finite difference time domain (FDTD) method.

碩士
臺灣大學
光電工程學研究所
95
Photonic crystals are materials with periodical dielectric constants. The band gap occurs according to the destructive interference, where certain wavelengths are not allowed to pass through. The light at those frequencies can not find a real propagation constant and thus will be scattered. Besides perfect photonic crystals, we are more interested in those photonic crystals with defects because those modes resulted from the defects are spatially confined in comparison with those non-defect modes. In other words, we can control the behavior of the defect modes by adjusting the fine structures in the photonic crystal. This is a very interesting phenomenon. An example of this is the photonic crystal waveguide, where lights will propagate along the direction we design. By developing automatic measurement techniques, we can acquire correct and stable information efficiently. For two-dimensional slab structures, we focus on the resonant cavities formed by the photonic crystals and expect to observe the resonant modes and the field distribution. With the assistance of the motorized stage, we could stably scan the spatial light intensity distribution and then observe the spectrum and the field intensity distribution of the defect modes. With the spectrum and the field distribution of the defect modes, we could understand more about the effects of the resonator. In the structure we designed in this work, we successfully find two resonant modes around 952nm and 960nm on the spectrum by observing the transmitted and the scattered spectrum. On the other hand, owing to the difficulty in constructing the point-defect by the auto-cloning method in three-dimensional checkerboard structures, we designed line-defects instead and then observed the effect from them. We observed the spectra and the spatial distribution of the defect modes. But we can’t find the obvious difference in spatial field distribution between two defect structures which have different sizes. It’s probably limited by the detection resolution and stability.

Granular crystals are compact periodic assemblies of elastic particles in Hertzian contact whose dynamic response can be tuned from strongly nonlinear to linear by the addition of a static precompression force. This unique feature allows for a wide range of studies that include the investigation of new fundamental nonlinear phenomena in discrete systems such as solitary waves, shock waves, discrete breathers and other defect modes. In the absence of precompression, a particularly interesting property of these systems is their ability to support the formation and propagation of spatially localized soliton-like waves with highly tunable properties. The wealth of parameters one can modify (particle size, geometry and material properties, periodicity of the crystal, presence of a static force, type of excitation, etc.) makes them ideal candidates for the design of new materials for practical applications. This thesis describes several ways to optimally control and tailor the propagation of stress waves in granular crystals through the use of heterogeneities (interstitial defect particles and material heterogeneities) in otherwise perfectly ordered systems. We focus on uncompressed two-dimensional granular crystals with interstitial spherical intruders and composite hexagonal packings and study their dynamic response using a combination of experimental, numerical and analytical techniques. We first investigate the interaction of defect particles with a solitary wave and utilize this fundamental knowledge in the optimal design of novel composite wave guides, shock or vibration absorbers obtained using gradient-based optimization methods.

碩士
元智大學
工業工程與管理學系
96
This research proposes a machine vision scheme for mura defect detection in TFT-LCD manufacturing. Mura is a Japanese word for blemish, which typically shows brightness imperfections from its surroundings in the surface. Since mura appears as a low-contrast region without clear edges in the surface, human inspectors need to continuously observe the hardly visible defect from different viewing angles. The traditional automatic visual inspection algorithms detect mura defects from individual still images. They neglect that a mura defect may not be visibly sensed in the image from a still system. In this study, the TFT-LCD panel is assumed to move along a track, where different light sources illuminate from different angles to the inspection panel. While the TFT-LCD panel passes through a fixed camera, the light reflection from different angles can effectively enhance the mura defect in the low-contrast motion images. This research therefore proposes a motion detection scheme based on optical flow techniques to identify mura defects in motion images. Since the TFT-LCD moves along a single direction, both two-dimensional (2D) and one-dimensional (1D) optical flow motion detection methods are developed. Three discriminative features based on the flow magnitude, mean flow magnitude and flow density in the optical flow field are presented to extract the defective regions in each image of the motion sequence. Both real glass substrates and synthetic panels are used to evaluate the efficacy of the proposed inspection schemes. Experimental results have shown that the proposed 1D optical flow method works as well as the 2D optical flow method to detect very low-contrast mura defects of small size, and achieves a high processing rate of 20 frames per seconds for images of size 200 200.