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Made available in DSpace on 2014-06-11T19:23:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-09-19Bitstream added on 2014-06-13T19:50:19Z : No. of bitstreams: 1 costa_wb_me_bauru.pdf: 1013500 bytes, checksum: af2a82e89ba237d24c1ff8441a9da739 (MD5) / Secretaria de Educação do Estado de São Paulo / Filmes nanocristalinos e amorfos de GaAs tem recentemente chamado a atenção de vários grupos de pesquisa devido as suas possíveis aplicações em novos dispositivos ópticos e eletrônicos. Igualmente atraentes são as novas propriedades físicas relacionadas com a estrutura nanocristalina e os efeitos da desordem na estrutura eletrônicas destes materiais. Entre as aplicações existentes, podemos citar o uso destes filmes como camadas anti-guia em lasers com emissão perpendicular à superfície, as camadas “buffer” em hetero-epitaxias de GaAs sobre Si, e os filtros interferométricos para a região do infravermelho. A preparação e a caracterização de filmes nanocristalinos de GaAs hidrogenados e não hidrogenados usando a técnica de RF magnetron sputtering foram focalizados neste trabalho. Um alvo de GaAs e uma atmosfera controlada contendo quantidades variáveis de argônio (Ar) e hidrogênio (H2) foram usadas na deposição do filme. Foi investigada a influência do fluxo de Ar e H2 na composição, estrutura e propriedades ópticas dos filmes. A influência da temperatura de substrato e potência de deposição também foi analisada. As técnicas de difração de raios-X e análise da energia de dispersão por emissão de raios-X (EDX), foram utilizadas na análise da estrutura e composição do filme, enquanto medidas ópticas de transmitância e refletância permitiram a determinação do coeficiente de absorção óptica e índice de refração dos filmes. A presença de ligações de hidrogênio nos filmes foi confirmada pelas bandas de absorção do Ga-H e As-H usando um espectrofotômetro de transformada de Fourier (FTIR). Os resultados mostram que a microestrutura, a composição e as propriedades ópticas do material são fortemente influenciadas por todos os parâmetros investigados, com destaque para o fluxo de hidrogênio utilizado nas deposições... / The nanocrystalline and amorphous GaAs films are recently attracting the attention of several research groups due to their possible application in new electronic and optical devices. Also attractive are the new physical properties related to the nanocrystalline structure and the effects of disorder in the electronic structure of these materials. Among the existing applications we can mention the use of these films as antiguide layers in surface emitting lasers, as buffer layers in the GaAs hetero-epitaxy onto Si substrates, and as infrared interferometric filters. The preparation and characterization of hydrogenated and non-hydrogenated nanocrystalline GaAs films using the RF magnetron sputtering technique were focused here. An electronic grade GaAs water target and an atmosphere composed of variable amounts of Ar and 'H IND.2' were used in the film depositions. We have investigated the influence of Ar and 'H IND.2' fluxes on composition, structure, and optical properties of the films. The influence of substrate temperature and deposition power were also analyzed. X-ray diffraction and energy dispersive electron analysis (EDX) were used in the analysis of the film structure and composition, while optical transmittance and reflectance measurements allowed the determination of the optical absorption coefficient and refractive index of the films. The presence of bonded hydrogen in the films was confirmed by the Ga-H and As-H absorption bands using Fourier transform infrared spectra (FTIR). The results show that the microstructure, the composition, and the optical properties of the material are strongly influenced by all the investigated parameters, in special the hydrogen flux used in the depositions. The hydrogenated films ('H IND.2' flux of 3.0 sccm / Ar flux of 20.0 sccm) produced at relatively low power (30W) and substrate temperature (60ºC), have presented the widest... (Complete abstract click electronic access below)

Made available in DSpace on 2014-10-09T12:42:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:19Z (GMT). No. of bitstreams: 1 05229.pdf: 7162265 bytes, checksum: 83c5485a837ef033baed192641f181b2 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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Orientador: Américo Sheitiro Tabata / Banca: Alexandre Levine / Banca: Keizo Yukimitu / Resumo: Uma nova família de semicondutores, a liga quaternária InxGa1-xAs1-yNy, cujo elemento Nitrogênio substitui o elemento Arsênio em pequenas porcentagens, tem recebido grande atenção devido à óptica na região de 1,3 μm, tecnologicamente importante para transmissão de dados em fibra óptica. Estudos sobre caracterização e propriedades ópticas desta liga fornecem maiores informações sobre o comportamento da mesma. Foram estudados poços quânticos, as estruturas básicas de dispositivos optoletrônicos de Inx-Gat-xAso.984N0.0016/GaAs com diferentes valores de concentração x: 26%, 30%, 34%, 38% e 43% crescidas em duas temperaturas diferentes: 400ºC e 430ºC. As amostras foram tratadas termicamente a 700ºC num período de 30 minutos. Com essa liga é tensionada, o foco constou-se em achar um modelo de espessura crítica condinzente para dados experimentais de fotoluminescência. Foram analisadas a dinâmica de portadores, a energia de ativação e a qualidade estrutural das amostras com a técnica de fotoluminescência em diversas condições. Os estudos realizados, aliados ao conhecimento dos parâmetros acima mencionados, têm o objetivo de contribuir para que se possa determinar a aplicabilidade e estimar o rendimento em dispositivos optoeletrônicos, com base neste material / Abstract: A new family of semiconductors has been proposed, the quaternary alloyInxGa1-xAs1-yNy, in which the element Nitrogen replaces the element Arsenic in small percentages. It has received great attention due to the fact of optical emission in the region of 1.3um, technologically important for data transmission at optical fiber. Studies on characterization and optical properties of this alloy provides more information about the conduct of it. It was studied quantum wells, the basic structures of InxGa1-xAs0.016/GaAs optoelectronic devices, with different values of concentration x: 26%, 30%, 34% and 43% grown at two different temperatures: 400ºC and 430ºC. The sample has annealed at 700ºC for 30 min. As this alloy is tensioned, the focus of this research is to find a consistent model of critical thickness for photoluminescence experimental data. It will be done an analysis of the dynamic carriers, activation energy and structural quality of the samples with the analysis of photoluminescence with diverse conditions. With these studies and the knowledge of the parameters mentioned above, it was intended contribute to determine the applicability and estimate the yield of optoeletronic devices based on this material / Mestre

This study shows a detailed report on the morphological, structural and optical properties of CdSe QDs synthesised by the hot injection method. Cadmium acetate dihydrate and Se powder were used as cadmium and selenide precursors, respectively. Various QD sizes were achieved by synthesizing in temperature range of 150ºC, 175ºC, 200ºC, 225ºC, 250ºC, 275ºC and 300ºC, respectively. The as synthesized QDs by the hot injection method were cross-examined for their morphological, structural and optical using HRTEM, FTIR, XRD, RS, and UV-Vis spectroscopy techniques respectively. FTIR analysis has revealed vibrations at 738, 738, 738, 738, 735, 735 and 733 cm-1 for the QDs synthesized at various temperatures of 150, 175, 200, 225, 250, 275, and 300℃, respectively. The presence of the above mentioned peaks confirms the presence of Cd-Se bond in our samples. XRD analysis of CdSe QDs revealed diffraction peaks at 2 angles of 16.66 , 25.20 , 34.77 , 40.9 , 45.39 and 49.1 for 150 17.4 , 25.22 , 34.85 , 41.7 , 44.45 and 47.5 for the QDs synthesized at various temperatures of 175 17.07 , 25.19 , 34.85 , 41.34 , 44.41 and 48.86 for 200 ; 16.34 , 25.20 , 34.76 , 40.6 , 44.74 and 49.48 for 225 ; 17.44 , 25.17 , 34.19 , 41.7 , 44.45 , 49.24 for 250 ; 16.70 , 25.16 , 34.85 , 40.32 , 45.1 and 49.1 7 for 275 ;and 17.35 , 25.18 , 35.13 , 41.63 , 45.7 , 49.48 for 300 . These XRD peaks relate to crystal planes of (100), (002), (102), (220), (103) and (112) which belong to hexagonal Wurtzite CdSe crystal structure. Additionally XRD analysis has revealed a general peak shift to higher 2 values was observed for CdSe QDs. HRTEM analysis showed that the synthesised CdSe QDs have a spherical shape and are monodispersed. Moreover, HRTEM analysis has revealed CdSe QDs modal crystallite size of 1.79 nm, 1.81 nm, 2.06 nm, 2.08 nm, 2.11 nm, 3.10 nm and 3.12 nm for the QDs synthesized at various temperatures of 150ºC, 175ºC, 200ºC, 225ºC, 250ºC, 275ºC and 300ºC, respectively. HRTEM results were in mutual agreement with XRD results. Additionally, the SAED images showed intense electron diffraction rings, which confirmed that the as-synthesised CdSe QDs have a Wurtzite crystal structure. RS analysis showed that CdSe QDs have LO and 2LO vibrational modes which are characteristic peaks for CdSe. The presence of these peaks in Raman spectra further supports our previous observation from XRD analysis and HRTEM analysis that the synthesized CdSe QDs have a Wurtzite crystal structure. The effect of synthesis temperature Raman peak shift, FHWH and peak intensity has been cross examined in this work, Moreover, the effect of increasing temperature on the peak shift, FWHM and peak intensity is discussed in detail below. UV-Vis analysis revealed an absorbance of CdSe QDs in higher wavelengths as temperature was increased. Furthermore, the Yu et al 2003 relation was used to calculate QD size and band gap energy of CdSe QDs. The results showed that QD size increases with increasing synthesis temperature, which is in agreement with HRTEM and XRD results.

In the past few years, “green technologies and touch screen technologies for portable devices has came to hot topic in consumer market. The demand for transparent conducting oxides (TCO) is increasing continuously. Therefore, the potential replacement of indium tin oxide (ITO), which is the most widely used TCO in industry, by aluminum zinc oxide (AZO) draws much attention in order to solve the problem of shortage of ITO one day due to the consisting of rare-earth element. In this work, electrical and optical properties of AZO had been characterized according to different sputtering parameters such as oxygen contents, working pressures and gas flow ratios. Physics of electrical conduction and optical transparency of AZO films were revealed and analyzed in order to set up a more complete relationship between mechanism and performance. Meanwhile, a comparison of sensitivity between AZO and zinc oxide (ZnO) to sputtering environment had been made and behaviors of AZO at low temperature had been presented. Optimum sputtering conditions for AZO had been established as a function of sputtering time and the film resistivity reached down to 7 x 10-4 Ω·cm while film transmittance was above 85% when t = 140 mins having film thickness about 610 nm. Degradation of AZO had been investigated. Application of AZO in OLED fabrication had been carried out after film refinement and device performance had been given. Finally, simulation of OLED structure was done for better device performance

Made available in DSpace on 2014-10-09T12:26:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:18Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:26:37Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:21Z (GMT). No. of bitstreams: 0 / Dissertacao (Mestrado Profissionalizante em Lasers em Odontologia) / IPEN/D-MPLO / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP; Faculdade de Odontologia, Universidade de Sao Paulo, Sao Paulo

Submitted by Luiz Antonio Saska Júnior (mat09083@feg.unesp.br) on 2017-04-06T13:55:56Z No. of bitstreams: 1 Defesa Mestrado Luiz Antonio Saska Junior.pdf: 2401538 bytes, checksum: 4a12ff9f083a1dc7ffb358112e9d48a6 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-04-12T19:12:08Z (GMT) No. of bitstreams: 1 saskajunior_la_me_bauru.pdf: 2401538 bytes, checksum: 4a12ff9f083a1dc7ffb358112e9d48a6 (MD5) / Made available in DSpace on 2017-04-12T19:12:08Z (GMT). No. of bitstreams: 1 saskajunior_la_me_bauru.pdf: 2401538 bytes, checksum: 4a12ff9f083a1dc7ffb358112e9d48a6 (MD5) Previous issue date: 2017-02-06 / Cerâmicas à base de CaCu3Ti4O12 (CCTO) com estrutura perovskita ABO3 geraram grande interesse científico devido à descoberta da constante dielétrica (κ) gigante, propriedade não ôhmica elevada e propriedade fotoluminescente. Neste trabalho foram preparadas cerâmicas policristalinas na forma de pó com a seguinte composição: Ca1-xSrxCu3Ti4O12 (0,0 ≤ x ≤ 1,0) na qual o Ca2+ (sitio A) foi gradativamente substituído pelo cátion Sr2+. Foram analisados os efeitos desta substituição gradativa nas propriedades estruturais e microestruturais dos pós policristalinos. Mediante técnicas de análise termogravimétrica dos pós, produzidos por reação do estado sólido, determinou a temperatura de calcinação a 950ºC. Analisando as fases presentes no material por meio da técnica de difratometria raios X observa-se que a estrutura cristalina formada é do tipo perovskita. Ao realizar os estudos semi-quantitativos, mediante microscopia eletrônica de varredura com detector de energia dispersiva, se obteve a morfologia e composição química dos pós cerâmicos. Por meio das técnicas de espectroscopia (de infravermelho, de absorção ultravioleta-visível e de fotoluminescência) foram obtidos os valores 548 cm-1, 500 cm-1 e 415 cm-1, para os módulos vibracionais das ligações O-Ti-O, o band gap de 2,85 eV para as amostras estudadas e determinou-se as propriedades ópticas da cerâmica policristalina na forma de pó. / Ceramics made of CaCu3Ti4O12 (CCTO) create great scientific interest after the discovery of its giant dielectric constant (κ), the high non-ohmic property and photolumenescence. In this study were prepared polycrystalline ceramics in the form of powder with the following composition: Ca1-xSrxCu3Ti4O12 (0.0 ≤ x ≤ 1.0), in which Ca2+ (site A) was gradually replaced by a cation Sr2+. The effects of this graduated replacement were analyzed in the structural and microstructure properties of polycrystalline powders. By the thermogravimetric analysis of the powders, produced by solid state reaction, determined the calcination temperature at 1223K. Analyzing the phases present in the material by the diffraction technique of X-rays its observed that the crystal structure formed is perovskite. When conducting semi-quantitative studies, by the scanning electron microscope with energy dispersive spectroscopy, it was obtained the morphology and chemical composition of the ceramics powders. By the techniques of spectroscopy (infrared, ultraviolet-visible absorption and photoluminescence) were obtained the values 548 cm-1, 500 cm-1 and 415 cm-1, for the vibrational modules of the bonding O-Ti-O, the band gap of 2,85 eV for the studied samples and the optical properties of the powder polycrystalline ceramics were determined.