No description available.

In this study, we deposit titanium dioxide (TiO2) as gate oxide on thin film transistor (TFT) by liquid phase deposition (LPD) on the amorphous silicon (a-Si) and polycrystalline silicon (poly-Si) substrates. After depositing LPD-TiO2 film, we use to fabricate TFT device. In our experiment, we do some measurement about physical, chemical and electrical properties for LPD-TiO2 film and discussed with them. the TiO2 film morphology and thickness was characterized by scanning electron microscopy ( SEM ), structure was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and chemical properties was characterized by X-ray photoelectron spectroscopy (XPS),and electrical properties was characterized by leakage current: current-voltage (B1500A) and dielectric constant: capacitance-voltage (E4280A). In TFT device study, we complete measurement about physical, chemical and electrical properties for LPD-TiO2 films. The LPD-TiO2 film was used as TFT device, We complete mask manufacture, mesa structure definition, deposit TiO2 thin film, gate definition, photolithography and ICP- etching. Ion implantation is carrying out.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

Semiconductor photocatalysis degrades phenolic pollutants to carbon dioxide and water, but the mechanisms of this potentially attractive method of environmental remediation remain unclear. This study aimed to elucidate the primary molecular events by HPLC analysis of the initial products of degradation in water or aqueous acetonitrile. The position of substituents relative to the hydroxyl group were found to influence the reaction rate and also primary oxidation steps, and hence the intermediate profile. 2,6- Dialkylated phenols reacted fastest and showed high conversion to dehydrodimeric products as a prelude to degradation. In contrast, 3,5-dialkylated phenols and 4-tertbutylphenol reacted more slowly and appeared to degrade directly to small polar compounds with little accumulation of primary carbocyclic intermediates. The rate of photocatalytic degradation of two isomeric dibromohydroxybenzonitriles was also influenced by substitution pattern. 3,5-Dibromo-2-hydroxybenzonitrile, however, is itself photolabile in daylight giving 3-bromo-2,5-dihydroxybenzonitrile in aqueous solution. The analogous reaction does not occur for 3,5-dibromo-4-hydroxybenzonitrile, the difference in behaviour being attributed to differences in the electronic spectra of the two compounds. The mechanism of photocatalysis appears to be influenced by the orientation of the substrate on the catalyst surface. For the alkyl phenols, particularly those with tert-butyl substitution, minimisation of disturbance to the polar network of the solvent directs the more hydrophobic parts of the molecule towards the oxidising surface of the catalyst. In addition, this effect encourages clustering of molecules with the subsequent formation of aggregated products. While part of the behaviour observed may be attributable to the presence of acetonitrile in the solvent, the hydrophobic profile of a substrate undergoing heterogeneous photocatalytic oxidation in water would seem to be a significant determinant of the molecular pathway selected in the first phase of its degradation.

In recent years, titanium oxide thin film has been studied extensively for using in optical devices and electronic devices such as waveguide and future ultra-large scale dynamic random access memory (DRAM). Titanium oxide film is very promising candidates for applications with exhibiting higher dielectric constant, high refractive index and high chemical stability. Liquid phase deposition is a novel method to grow oxide layer. It has the advantage of low-temperature deposition, good step coverage, and selective growth. We use this technology to deposition titanium oxide film instead of the conventional methods of growth titanium oxide film, such as sol-gel, sputtering, LPCVD, APCVD, and PECVD. But low deposition rate is one of the drawbacks drawbacks of LPD process. In previous study, deposition rate of titanium oxide films was very slow (6Å/min). The mixture of H2TiF6(aq) and H3BO3(aq) was used as the principal solution. In this study, we incorporated HNO3(aq) into the principal solution for enhance the deposition rate. In addition, we study the deposition rate and dielectric constant of titanium oxide films as functions of H2O addition, NH4OH(aq), and Ba(OH)2(aq) concentrations in our principal solution. We examine electrical characteristics and thickness of the titanium films by capacitance-voltage measurement and Spectroscopic Reflectance. The deposition rate of titanium oxide film increases from 6 Å/min to 475Å/min and the dielectric constant is about 36.1 with adding HNO3 and opportune NH4OH into the principal solution.

No description available.

É crescente o interesse, dentre os diversos tipos de dispositivos fotovoltaicos, nas células solares com corantes (dye-sensitized solar cell, DSCC). Isto é devido não só aos menores custos de produção (química molhada), mas também ao grande número de combinações orgânico/semicondutor que podem ser utilizadas, buscando as propriedades de interesse de cada dispositivo. Em uma DSSC a absorção de luz é realizada pelo material orgânico, que injeta o elétron no semicondutor para sua extração como corrente. A neutralidade da molécula é recuperada através de um eletrólito transportador de carga a partir do outro terminal. Este problema é de difícil investigação experimental, devido ao grande número de variáveis envolvidas, já que qualquer defeito ou mudança na deposição pode alterar o processo de transferência de carga. Da mesma forma, também o estudo teórico apresenta grande dificuldade, sendo necessária a adoção de modelos simplificados para o estudo, buscando um entendimento mais profundo dos processos que ocorrem durante a absorção de luz. Neste trabalho investigamos uma combinação de materiais de alta relevância, ácido retinóico sobre óxido de titânio na fase anatase, a mais importante para nanoestruturas. Realizamos uma investigação detalhada da aplicabilidade de diferentes metodologias ao problema, focalizando as características eletrônicas e óticas, e buscando evidências de transferência de carga. Para tal, analisamos modelos simples (materiais isolados, e outros sistemas diferentes de mesmas características), utilizando métodos vindos de diferentes postulações iniciais, como Hartree-Fock e Funcional da Densidade, e também partindo tanto de implementações ab initio (primeiros princípios) como de formulações semi-empíricas. Por fim, escolhida uma metodologia ideal, estudamos sistemas mais realistas de interfaces orgânico/óxido. Nossos resultados indicam a influência das dimensões nanoscópicas da matriz inorgânica nas propriedades de fotocolheita, assim como a grande importância da ligação covalente, presente na montagem quimissorvida molécula/superfície, que altera as propriedades óticas de ambos os componentes. / There is growing interest, among the many types of photovoltaic devices, in dye-sensitized solar cells (DSSC). The reasons for that are not only the lower costs of production (wet chemistry), but also the large number of organic/semiconductor combinations that can be made, depending on the properties that are interesting for each device. On a DSSC the light absorption occurs in the organic material, from which the electron is transferred to the semiconductor for current generation. The molecule regains its neutrality through an electrolyte that carries charge from the opposing terminal. The experimental investigation of this problem is very difficult, due to the large num- ber of variables involved, as any defect or change on the deposition can affect the charge transfer process. Similarly, the theoretical study is also difficult, making necessary the use of simplified models for the system to gain deeper understanding of the processes of light absorption. In this work we have studied a combination of large relevancy, retinoic acid over titanium oxide, at the anatase phase, the most important for nanostrucutres. We have thoroughly investigated the applicability of several methodologies, focusing at electronic and optical characteristics, and searching for evidences of charge transfer. For this we analyzed sim- ple models (isolated materials, and other systems that share the same characteristics), using methodologies from different starting theories, as Hartree-Fock and Density Functional The- ory, and also applying both ab initio and semi-empirical approaches. Once chosen the best methodology, we studied a more realistic system, true organic/oxide interfaces. Our results show the influence of the nanoscopic dimensions of the inorganic substrate on the properties of the photoharvest, and also the fundamental role played by the covalent bond that exists on the chemisorbed deposition of molecule/surface, that alters the optical properties of both components.

Thesis (M.S.)--University of Nevada, Reno, 2005. / "May, 2005." Includes bibliographical references (leaves100-103). Online version available on the World Wide Web.

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