Not available / text

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Western Australia, 2005.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 170-178).

No description available.

The push to advance the capabilities of semiconductor devices relies on the continual advancement of emerging materials and novel device structures. Due to the expensive costs of semiconductor fabrication in terms of both resources and time, device modeling has always been necessary to estimate device performance and provide design optimizations prior to their fabrication. However, commonly used device simulation methodologies, such as drift-diffusion, require the input of phenomenological parameters, which can be difficult to obtain especially for technologically immature materials. Using the Monte Carlo method, many of these parameters can be extracted with first-principles calculations. Furthermore, the physical models included in Monte Carlo simulations make it better suited for simulating sub-micrometer scale and high-field devices compared to drift-diffusion. This thesis focuses on the Monte Carlo method for simulating semiconductor materials and devices using the simulation software developed at Boston University. In depth descriptions and visualizations of the Monte Carlo simulation process are provided, including visualizations of the 3D bandstructure and carrier-phonon interactions. We demonstrate three levels of physical accuracy of Monte Carlo simulations, with bandstructures obtained analytically, semi-empirically, or entirely from first-principles. Since higher levels of physical accuracy incur higher computational costs, we also demonstrate appropriate scenarios for the implementation of each type of bandstructure. Results of device simulations and simulations of carrier transport phenomena are presented for a wide variety of materials with bandgaps ranging from 0.3 eV to 6.4 eV. Finally, we also demonstrate how values extracted from Monte Carlo simulations can be used in other simulation methodologies, including drift-diffusion. In addition to the standard Monte Carlo methodology, we also introduce a 3D quantum correction model for carrier transport at band crossing and anti-crossing points. Quantum corrections are necessary to accurately simulate carrier transport in most wurtzite materials, which includes technologically significant materials such as 4H silicon carbide and aluminum nitride. The methodology behind its implementation and integration within the Monte Carlo infrastructure is discussed, and comparisons of calculations with and without the quantum corrections are presented. Finally, we also present preliminary device simulations incorporating this fully quantum model and speculate about its future within the Monte Carlo paradigm.

Le mémoire explore l'intégration d'une matrice de photodiode et d'un spectromètre dans un microscope *STED* [1], il se concentre sur deux objectifs principaux : **l'intégration d'une matrice de photodiodes et d'un spectromètre dans un microscope *STED*** et **le développement et mise en œuvre d'algorithmes pour le traitement des données temporelles**. Le premier objectif présente des travaux sur l'intégration d'une matrice de photodiodes, un spectromètre capable de mesurer les longueurs d'onde des photons dans une plage spécifique. Ce développement permet l'acquisition d'images de bactéries contenant divers fluorophores, résolus à la fois temporellement et spectralement. Le second objectif se concentre sur le déploiement, la caractérisation, et la mise en œuvre d'algorithmes pour le traitement des données temporelles générées par le système de détection. Les algorithmes *MLE*, *phaseurs* [2] et *FLI-NET* [3] ont été testés sur des données simulées et expérimentales pour mesurer le temps de vie des fluorophores et la proportion entre deux populations caractérisées par deux temps de vie distincts. Une étude approfondie de ces algorithmes a été réalisée sur des images *FLIM* simulées et réelles pour évaluer leur efficacité. Le mémoire aborde également l'application de la technique *SPLIT-STED* [4], qui améliore la résolution spatiale du microscope *STED* en exploitant les informations temporelles. Cette méthode a montré des améliorations notables de la résolution, particulièrement utiles pour l'analyse d'échantillons vivants. Le mémoire met en lumière les limitations existantes dans le traitement des données *FLIM*, notamment en termes de mesure des temps de vie et des proportions associées, surtout lorsque le nombre de photons est limité. Il présente des solutions potentielles, telles que l'utilisation d'un réseau *U-NET* [5] pour une analyse plus approfondie des données, combinant les informations spatiales, temporelles et spectrales. Ces développements ouvrent la voie à des analyses plus précises et détaillées dans la recherche biologique, en utilisant la microscopie de super-résolution et la microscopie *S-FLIM*. / This master thesis explores the integration of a photodiode array and a spectrometer into a *STED* microscope [1], focusing on two main objectives: **the integration of a photodiode array and a spectrometer into a STED microscope** and **the development and implementation of algorithms for processing temporal data**. The first objective presents work on the integration of a photodiode array with a spectrometer capable of measuring the wavelengths of photons within a specific range. This development allows for the acquisition of images of bacteria containing various fluorophores, resolved both temporally and spectrally. The second objective focuses on the deployment, characterization, and implementation of algorithms for processing the temporal data generated by the detection system. The *MLE*, *phasor* [2], and *FLI-NET* [3] algorithms were tested on simulated and experimental data to measure the fluorophore lifetimes and the proportion between two populations characterized by two distinct lifetimes. An in-depth study of these algorithms was conducted on simulated and real *FLIM* images to evaluate their effectiveness. This master thesis also discusses the application of the *SPLIT-STED* technique [4], which improves the spatial resolution of the *STED* microscope by exploiting temporal information. This method has shown notable improvements in resolution, particularly useful for the analysis of living samples. The master thesis highlights the existing limitations in *FLIM* data processing, particularly in terms of measuring lifetimes and associated proportions, especially when the number of photons is limited. It presents potential solutions, such as the use of a *U-NET* network [5] for a more in-depth analysis of the data, combining spatial, temporal, and spectral information. These developments pave the way for more accurate and detailed analyses in biological research, using super-resolution microscopy and *S-FLIM* microscopy.

O conhecimento da distribuição espectral da radiação X emitida por unidades de radiodiagnóstico fornece importantes informações, que podem ser aplicadas aos programas de Garantia de Qualidade e de Proteção Radiológica. Detectores que utilizam fotodiodos PIN de Si como ponta de prova vêm sendo utilizados nos últimos anos devido, principalmente, ao seu baixo custo e por trabalharem a temperatura ambiente, não precisando dos tanques de nitrogênio líquido necessários em detectores de Ge e Si(Li). Embora, a princípio, os fotodiodos PIN tenham uma pior resolução, quando comparada com os detectores de Ge, ela é suficientemente boa para a maior parte das aplicações em radiodiagnóstico. Além disso, o desenvolvimento de sistemas refrigerados termoelétricamente e de pré-amplificadores de baixo ruído têm feito com que os fotodiodos PIN cheguem a resoluções comparáveis às do Ge. Este trabalho visa estabelecer as propriedades de detectores constituídos por fotodiodos PIN de Si e desenvolver o processo de correção dos espectros brutos para a eficiência do detector e outros fatores pertinentes, a fim de se obter o espectro real emitido por equipamentos de radiodiagnóstico. Espectros de radiação de equipamentos de radiodiagnóstico obtidos experimentalmente foram comparados com espectros teóricos calculados a partir de um modelo semi-empírico. Além disso, foram obtidos espectros de radiação emitidos por unidades de mamografia, espalhados por um objeto simulador de mama. Como aplicação direta dos espectros medidos experimentalmente, foram desenvolvidas metodologias para a determinação da tensão aceleradora de tubos de Raios X (kVp), para fins de calibração de medidores de kVp, e da camada semi-redutora (CSR) dos feixes de interesse. / Knowledge of the spectral distribution of radiation emitted by radiodiagnostic units provides important information, which can be applied to the Quality Assurance and Radiological Protection programs. Detectors which utilize Silicon PIN Photodiodes have been increasingly used in recent years, due to their low cost and being worked with at room temperature, the liquid nitrogen containers used with Ge and Si(Li) detectors not being necessary. Although, initially, the PIN photodiodes have a poorer energy resolution, as compared with Ge detectors, it\'s good enough for most purposes. Moreover, the development of thermoelectrically cooled systems and low noise level pre-amplifiers have resulted in PIN photodiodes achieving comparable resolutions to Ge ones. This work seeks to establish the properties of detectors made with Silicon PIN photodiodes and to develop the correctional process of the raw specffa both for the efficiency of the detector and other relevant factors, with the aim of obtaining the true spectrum emitted by radiodiagnostic equipment. The radiation spectra of radiodiagnostic equipment experimentally obtained were compared with theoretical spectra calculated from a semi-empirical model. Furthermore, mammography x-ray spectra scattered by a breast simulator were obtained. As a direct application of these experimentally measured spectra, methodologies were developed to determine the peak kilovoltage (kvp) of X-Ray tubes, to be able to calibrate kVp meters, and the half-value layer (HW) of the beams of interest.