The purposes of this thesis are to prepare ZnO and tin-doped In2O3 (ITO) films at low temperature and study their microstructure and optoelectronic properties. Low-temperature growth of undoped ZnO films with high transparency and low electrical resistance was prepared by ion beam sputtering. After systematic testing, a sheet resistivity as low as 2.95 x 10-3 £[-cm was obtained at a substrate temperature of 150 oC, ion source voltage of 850 V, and ion beam current of 30 mA. The transmittance of the ZnO films was in the range of 85-90%. Hall measurements showed that a high mobility of 21.41 cm2/Vs was obtained for films less than 200 nm thick. The related microstructures and physical properties were measured and discussed. ZnO nanofilm of (2-1-10) and (01-11) surfaces were prepared on NaCl (001) surface at 200 oC and 400 oC to produce nearly pure (2-1-10) and (01-11) textures respectively and the orientation relationships were determined and the interface discussed. By dissolving the NaCl substrate, the ZnO (2-1-10) and (01-11) surfaces several cm2 in area, which may have some useful applications, can be easily prepared. The photoluminescence spectrum from the (2-1-10) surface showed only a near-band-edge UV emission peak while the (01-11) surface showed a near band-edge UV emission and a broad green emission. Low-temperature preparation of transparent conducting electrode is essential for flexible optoelectronic devices. ITO films of high transparency and low electrical resistance were prepared at room temperature with a radio-frequency ion beam sputtering system. Specimens with a low sheet resistivity of 10-4 £[-cm and a high visible-light transmittance of 85-90% were obtained. Hall measurement was used to measure the mobility and carrier concentrations and the effects on resistivity were discussed. ITO films were deposited on glass substrates at 200 oC at various oxygen flow rates. At low oxygen flow rate the film surface has ITO whiskers with metallic In tips and a crystallographic relationship of (010)In//(110)ITO and (001)In//(001)ITO is present between them. The In tips act as the seeds for the growth of ITO whiskers by a vapor-liquid-solid growth mechanism. As the oxygen flow rate increases, the crystallinity of the ITO film decreases till an amorphous phase is formed. The microstructure, resistivity and transmittance of the films were studied as a function of oxygen flow rate. Thin films of high transmittance (~90%) and low resistivity (6 x 10-4 Ω-cm) were prepared at an intermediate oxygen flow rates.

In this study, the reactive rf magnetron sputtering was used to deposit Ba(Zr0.1,Ti0.9)O3 (BZT) ferroelectric thin films on ITO/Glass substrate, and MFM structure was fabricated. The effects of various sputtering parameters on the characteristics of thin films, such as the oxygen concentrations, substrate temperature, rf power and chamber pressure were discussed, and then the optimal sputtering parameters were determined. The annealing process of rapid thermal annealing (RTA) and conventional thermal annealing (CTA) were used to promote the ferroelectric characteristics. The physical characteristics of BZT thin films were obtained by the analyses of SEM, XRD patterns and AFM morphologies. The surfaces, cross-section, crystallization and surface roughness of thin films were discussed. To investigate the electrical properties, the capacitance-voltage (C-V), current-voltage (I-V) and P-E hysteresis characteristics of BZT thin films were measured by the HP4284A impedance analyzer, HP4156C semiconductor parameter analyzer and computerized radiant technology (RT66), respectively. Furthermore, characteristics of the MFM structure were discussed. From the experimental results, the dielectric constant with optimal sputtering parameters was about 84, and the leakage current of thin film was about 6 ¡Ñ 10-8 A/cm2 when the applied electrical field of thin film was at 0.4 MV/cm. The remanent polarization (Pr) and coercive field (Ec) were 2.87 £gC/cm2 and 259 kV/cm from the P-E hysteresis loops, respectively. In addition, the ferroelectric characteristics of the thin film could be improved after rapid thermal annealing at 550¢J for 3 minutes. The remanent polarization (Pr), coercive field (Ec) and saturated polarization (Ps) were 3.42 £gC/cm2, 266 kV/cm and 6.99 £gC/cm2, respectively.

ITO is a wide band gap semiconductor material, its band gap is from 4.7 eV to 5.2 eV. Due to the low resistivity, high transmittance to visible light, great absorption to UV light, and high reflection to IR, ITO is wide used to photovoltatic application; such as anodic electrode of Liquid Crystal Display (LCD) and photovoltaic devices. In the thesis, samples are deposited with an ITO layer on color filter (CF) by magnetron sputtering. The conductivity of samples is measured by 4-probe measurement, and the transmittance is characterized by visible spectroscopy. In this work is heat treatment parameters of temperature and annealing time of ITO thin film know been studied, and found an optima condition. From the experiment results, an optima heat treatment condition is temperature of 200¢Jfor 40 minutes, which reveals lower resistivity and improved transmittance of ITO samples. And, it is less process time and lower treatment temperature to used condition for industry presently. The reducing time of heat treatment will increase 9.9 % production, and enhancing the properties of color filter. Depending on the results of this work, there is space to improve performance and reduce power for fabrication of color filter.

This dissertation has focused on the study of the ITO/organic heterojunction and the chemistries therein, it proposes appropriate strategies that enhance the interfacial physical and electronic properties for charge injection with application to organic thin-layer devices. We focused on four major aspects of this work: i) To characterize the ITO surface and chemistries that may be pertinent to interaction with adjacent organic layers in a device configuration. This developed a working model of surface and provided a foundation for modification strategies. Characterization of the electronic properties of the surface indicate less than 5% of the geometrical surface is responsible for the bulk of current flow while the rest is electrically inactive. ii) To determine the extent to which these chemistries are variable and propose circumstances where compositional changes can occur. It is shown that the surface chemistry of ITO is heterogeneous and possible very dynamic with respect to the surrounding environment. iii) To propose a strategy for modification of the interface. Modification of ITO surfaces by small molecules containing carboxylic acid functionalities is investigated. Enhancements in the electron transfer rate coefficient were realized after modification of the ITO electrode. The enhancements are found to stem from a light etching mechanism. Additionally, an elecro-catalytic effect was observed with some of the modifiers. iv) Apply these modifications to organic light emitting diodes (OLEDs) and organic photovoltaic devices (OPVs). Enhancements seen in solution electrochemical experiments are indicative of the enhancements seen for solid state devices. Modifications resulted in substantially lower leakage currents (3 orders of magnitude in some cases) as well as nearly doubling the efficiency.An additional chapter describes the creation and characterization of electrochemically grown polymer nano-structures based on blazed angle diffraction gratings. The discussion details the micro-contact printing process and the electro-catalytic growth of the conductive polymers PANI and PEDOT to form diffraction grating structures in their own right. The resulting diffraction efficiency of these structures is shown to be sensitive to environmental conditions outlining possible uses as chemical sensors. This is demonstrated by utilizing these structures as working pH and potentiometric sensors based on the changing diffraction efficiency.

Made available in DSpace on 2014-06-12T15:52:19Z (GMT). No. of bitstreams: 2 arquivo2841_1.pdf: 1812233 bytes, checksum: 78abbf363fbd42ac838d1798c601100f (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Entre outras técnicas, os métodos eletroquímicos têm emergido como sendo atrativos devido à sua simplicidade, baixo custo, possibilidade de medição em tempo real e, geralmente, apresentarem alta sensibilidade. Neste estudo, foi desenvolvido um protótipo de um biossensor amperométrico de glicose, parcialmente baseado na tecnologia de impressão jato de tinta (Inkjet). Dois eletrodos foram confecionados pelo método screenprinting em uma fita de PVA (Polivinil Álcool). Em um deles, uma solução de glicose oxidase foi depositada por impresora a jato de tinta, modificada para os experimentos. O eletrodo de referência foi constituído de Ag /AgCl. Antes do processo de impressão, foi realizada uma verificação dos sitema impressor por Microscopia Eletrônica de Varredura, para avaliação dos poros de impressão. A Voltametria cíclica apresentou resposta linear entre concentração de glicose e os picos de corrente anódica em um mesmo intervalo de potencial, indicando a viabilidade do método. Neste trabalho também foi desenvolvido um genosensor para a detecção de sequências específicas de DNA transduzidas por Voltametria de Pulso Diferencial. Os eletrodos foram feitos pela imobilização de sequências de DNA em um eletrodo de ITO (Indium Tin Oxide) modificado com NaOH e APTES. Os resultados demonstraram um aumento do valor de corrente anódica (0,73 μA) quando a sequência de DNA estava presente no eletrodo, diferindo da corrente encontrada nos eletrodos sem a sequência imobilizada. Os resultados também mostraram que após a hibridização do DNA imobilizado com uma sequência complementar de uma região específica do vírus BPV contendo 27 bases, a corrente anódica diminuiu, indicando que o processo de hibridização ocorreu na superfície do eletrodo. A seqüência utilizada para a hibridização foi uma região específica do vírus BPV, contendo 27 bases. Os achados indicam que o eletrodo de ITO poderia ser um instrumento viável e de fácil manipulação para construção de biossensores de DNA

III-V semiconductor nanowires (NWs) are often referred to as one-dimensional (1-D) materials because of their high aspect ratios and excellent quantum confinement properties. Spacing between NWs in a NW array is on the order of ~102 nm, which is close to the wavelength of visible light. These properties make NWs have excellent light trapping effects and suitability for optoelectronic applications, such as solar cells and photodetectors. Gallium arsenide (GaAs) has high electron mobility and a band gap of 1.424 eV, which makes it an ideal material for solar cells. Since GaAs NWs can be grown on either GaAs substrates or foreign substrates such as silicon (Si) substrates without lattice mismatch issues, they are being widely studied for photovoltaic applications. GaAs NWs could be achieved by the vapor-liquid-solid (VLS) method in molecular beam epitaxy (MBE), or etching a GaAs substrate by inductively coupled plasma reactive ion etching (ICP-RIE). Cyclotene was used as the filling material in gaps between NWs to support a low sheet resistance front contact and prevent shunts. An In/ITO contact was developed to achieve a lower contact resistance to n-GaAs NWs than an ITO contact, while it had a similar transmittance as ITO. A crack test also showed that insertion of a thin indium layer between ITO and GaAs NWs solved the ITO crack issue during heating that resulted from a large difference in coefficients of thermal expansion (CTE) between ITO and cyclotene. Energy dispersive x-ray spectrometry (EDS) was used to determine indium diffusion into NWs, and it showed that indium diffusion was not so significant to damage the features in NWs. A novel method to achieve substrate-free NW arrays by combining ICP-RIE and selective chemical etching together was also introduced. This method made it possible to measure the transmittance of NW arrays and contact layers for the first time. Absorption of GaAs NW arrays with various NW diameters and periods were also determined experimentally. / Thesis / Master of Applied Science (MASc)

This thesis presents the fabrication of Sn-doped In2O3 nanostructures on a 50 nm thick SiN membrane and their characterization using monochromated electron energy loss spectroscopy (EELS). Rapidly annealed triangular structures of varying thicknesses (71 nm and 32 nm) and lengths (between 400 nm and 1200 nm) unveil a structural crystallization, as well as a blue-shift and narrowing of surface (first and second order modes) and bulk plasmon peaks as the free carrier concentration increases. Bulk peak positions shift from 515+/-39 meV to 628+/-36 meV for 71 nm thick triangles. The second order surface plasmon modes exhibit a greater blue-shift after annealing (93 meV) than the first order modes (36 meV), consistent with the trend found in boundary element method (BEM) simulations using ellipsometry data. The Richardson-Lucy (RL) deconvolution algorithm is employed to improve the effective energy resolution and reveal these surface plasmons as well as a substrate phonon at 100+/-19 meV. Low-loss EELS spectra for 32 nm thick triangles potentially show a blue-shifting bulk plasmon from 751+/-42 meV to 912+/-42 meV with decreasing triangle size. STEM imaging of the triangle structure cross-sections may show a clustering of oxygen vacancies and indium atoms that could be responsible for this blue-shift. Core-loss EELS spectra between 380-550 eV using the oxygen K-edge signal provide evidence of a change in the bonding across the ITO/SiN interface, although its effect on the electrical properties requires further investigation. / Thesis / Master of Applied Science (MASc) / The push towards smaller, faster electronic devices and sensing equipment has accelerated research into manipulating oscillating groups of electrons, or plasmons. So far, the building blocks of these next-generation systems use metals such as gold and silver; however, new materials must be explored for them to be commercially viable. Thin continuous films of transparent conductive oxides (TCOs) such as Sn-doped Indium Oxide (ITO) are already widely used in conventional silicon-based technologies, and in this work ITO nanostructures are fabricated to visualize their plasmonic response, in the hopes that they could be tailored towards plasmonic devices. The relationships between how these plasmons evolve with varying dimensions and the application of heat are explored using electron microscopy.

Os eletrocatalisadores de PtSn/C-ITO foram preparados pelo método de redução via borohidreto de sódio com uma carga metálica de 20% em massa suportados em carbono Vulcan XC72 e óxidos de estanho e índio (ITO) nas seguintes composições; 50:50, 70:30 e 90:10. Os eletrocatalisadores foram submetidos a análises de caracterização por difração de raios-x (DRX), microscopia de transmissão eletrônica (MET), espectroscopia de energia dispersiva de raios x (EDX) e análises eletroquímicas pelas técnicas de voltametria cíclica e de amperometria para os estudos da oxidação eletroquímica em etanol. Nas técnicas eletroquímicas foi utilizado o eletrodo de camada fina porosa onde os eletrocatalisadores foram testados tanto no meio ácido quanto no meio alcalino. Experimentos em célula unitária alimentadas diretamente por etanol foram testados simulando condições reais de operação. As análises eletroquímicas e de caracterização física em meio ácido permitiram comparar o desempenho e estabilidades dos eletrocatalisadores em estudo e também demonstraram os benefícios da adição do estanho e do ITO, tendo como destaque o eletrocatalisador de PtSn/C-ITO 70:30. Em meio alcalino o eletrocatalisador PtSn/C-ITO 50:50 demonstrou ter o melhor desempenho nas análises de voltametria cíclica e amperometria, entretanto, a mesma eficácia não ocorreu nos experimentos em célula unitária o que leva a crer que em meio alcalino o mecanismo de oxidação do etanol sob temperatura e outros parâmetros reais pertinentes à operação da célula precisam ser mudados e/ou estudados. / PtSn /C-ITO electrocatalysts were prepared by the sodium borohydride reduction method with 20% mass metallic load supported on Vulcan XC72 carbon and tin and indium oxides (ITO) in the following compositions; 50:50, 70:30 and 90:10. The electrocatalysts were subjected to x-ray diffraction characterization (XRD), transmission electron microscope (TEM), energy dispersive x-ray spectroscopy (EDX) and electrochemical analyzes using cyclic voltammetry and amperometric techniques for studies of ethanol electrochemical oxidation. In the electrochemical techniques the thin porous coating was used where the electrocatalysts were tested in both the acidic and alkaline media. Experiments in unit cell fed directly by ethanol were tested simulating real operating conditions. The electrochemical and physical characterization analyzes in acid medium allowed to compare the performance and stabilities of the electrocatalysts under study and also demonstrated the benefits of the addition of tin and ITO, with emphasis at PtSn/C-ITO 70:30 electrocatalyst. In alkaline media the PtSn/C-ITO 50:50 electrocatalyst demonstrated the best performance in the tests of cyclic voltammetry and amperometry, however, the same efficiency did not happen in the unit cell tests which leads to believe that in alkaline medium the oxidation mechanism of ethanol under temperature and other actual pertinent parameters to cell operation need to be changed and/or studied.

Este trabalho tem como principais objetivos: desenvolver procedimentos sintéticos e novos materiais poliméricos que apresentem boa condutividade elétrica, estudar o comportamento eletro-óptico dos polímeros obtidos, desenvolver procedimentos para a construção de dispositivos eletroluminescentes, caracterizá-los e correlacionar as características eletro-ópticas observadas com a constituição da camada ativa polimérica. Foram realizadas diversas sínteses objetivando a preparação de polifluorenos com diferentes estruturas químicas a partir de monômeros difuncionais aromáticos boronados e bromados, utilizando uma mesma rota de acoplamento de Suzuki. Assim, foram preparados três polímeros, poli[2,7-(9,9-dioctilfluoreno)] (PF, polifluoreno), poli[1,4-fenileno-alt-2,7- (9,9-dioctilfluoreno)] [PFP, poli(fluoreno-fenileno)] e poli[(1,4-fenileno-2-flúor)-alt-2,7-(9,9- dioctilfluoreno)] [PFPF, poli(fluoreno-fenileno)fluorado]. Para obtenção destes polifluorenos com bom rendimento e com pureza adequada para a preparação de dispositivos poliméricos eletroluminescentes, foi necessário testar diversas condições de reação, até a otimização de um procedimento sintético robusto. Os polifluorenos preparados foram exaustivamente purificados por extração e solubilização-precipitação. Todos os polifluorenos tiveram a sua estrutura e composição químicas caracterizadas e confirmadas pelas técnicas de espectroscopia no infravermelho (FTIR), espectroscopia de ressonância magnética nuclear de hidrogênio (¹HNMR) e espectroscopia de energia dispersiva de raios-X (EDX). As massas molares médias e a polidispersão foram determinadas por cromatografia de permeação em gel (GPC). Soluções em clorofórmio dos polifluorenos foram analisadas por espectroscopias de absorção e emissão no UV-Vis. Estes resultados nos forneceram informações importantes quanto às propriedades de fotoluminescência dos polifluorenos obtidos. Até o momento, sabe-se que todos os três polímeros emitem cor azul e dentre as três estruturas estudadas, o PFPF apresentou maior intensidade de fluorescência. Para a fabricação dos P-OLEDs (Diodos Orgânico-Polimérico Emissor de Luz) foram feitas soluções de clorofórmio em concentrações de 1% dos três tipos de polímeros. Também foi estudada a influência dos compostos ETL (electron transport layer) (Alq3 ou butyl-PBD) com concentrações de 0,5%. Quando aplicada uma tensão no dispositivo, o PFPF apresentou menor tensão de operação entre os polímeros estudados. A partir das curvas de tensão vs. corrente, verificou-se que a adição do butyl-PBD nos três tipos de polímeros diminui a tensão de limiar em comparação com os dispositivos sem composto ETL. Os comprimentos de onda de eletroluminescência dos dispositivos polarizados permaneceram constante mesmo com a adição dos dois compostos ETL (Alq3 ou butyl-PBD). / This work has as main objectives: develop synthetic procedures and new electroluminescent polymeric materials that have good electrical conductivity, study the behavior of polymer systems thus obtained, and develop procedures for the construction of electroluminescent devices, characterize them and correlate the photo- electrical behavior with the features of the constitutive active polymeric layer Several syntheses were performed aiming at preparing polyfluorenes with different structures from boronated and brominated difunctional aromatic monomers using a Suzuki coupling route. So far, three polymers were prepared, poly[2,7-(9,9-dioctylfluorene)] (PF, polyfluorene), poly[1,4-phenylene-alt-2,7-(9,9-dioctylfluorene)] [PFP, poly(fluorenephenylene)] and poly[1,4-phenylene-2-fluoro)-alt-2,7-(9,9-dioctylfluorene)] [PFPF, fluorinated poly(fluorene-phenylene)]. To obtain these polyfluorenos with good yield and purity suitable for preparing polymeric electroluminescent devices, it was necessary to test various reaction conditions and to optimize a robust synthetic procedure. The polyfluorenes prepared were thoroughly purified by extraction and solubilization-precipitation. All polyfluorenes have had their structures and chemical composition characterized and confirmed by infrared spectroscopy (FTIR), and hydrogen and carbon-13 nuclear magnetic resonance spectroscopy (¹HNMR and 13CNMR). The average molar masses and polydispersity were determined by gel permeation chromatography (GPC). Polyfluorenes in chloroform solutions were analyzed by the UV-Vis absorption and emission spectroscopy. These results provided us with important information regarding the photoluminescence properties of polyfluorenes thus obtained. Until now, it is known that all three polymers emit in the blue region and among the three structures, the PFPF has the highest fluorescence intensity. The construction of PLEDs was carried out from the chloroform solutions at concentrations of 1% for each of the all three types of polymers. The influence of an ETL (electron transport layer) compound (Alq3, PBD) was also studied, and its concentration was kept constant at 5% in the polymer solution. Tests of the devices under applied voltage have shown a higher stability for PFPF among all. From the voltage vs. current curves, it was possible to observe that the addition of PBD decreased the threshold voltage for the devices prepared from the three types of polymers. The wavelength of electroluminescence remained constant despite the addition of the ETL compound (Alq3 or butyl-PBD).

Os eletrocatalisadores de PtSn/C-ITO foram preparados pelo método de redução via borohidreto de sódio com uma carga metálica de 20% em massa suportados em carbono Vulcan XC72 e óxidos de estanho e índio (ITO) nas seguintes composições; 50:50, 70:30 e 90:10. Os eletrocatalisadores foram submetidos a análises de caracterização por difração de raios-x (DRX), microscopia de transmissão eletrônica (MET), espectroscopia de energia dispersiva de raios x (EDX) e análises eletroquímicas pelas técnicas de voltametria cíclica e de amperometria para os estudos da oxidação eletroquímica em etanol. Nas técnicas eletroquímicas foi utilizado o eletrodo de camada fina porosa onde os eletrocatalisadores foram testados tanto no meio ácido quanto no meio alcalino. Experimentos em célula unitária alimentadas diretamente por etanol foram testados simulando condições reais de operação. As análises eletroquímicas e de caracterização física em meio ácido permitiram comparar o desempenho e estabilidades dos eletrocatalisadores em estudo e também demonstraram os benefícios da adição do estanho e do ITO, tendo como destaque o eletrocatalisador de PtSn/C-ITO 70:30. Em meio alcalino o eletrocatalisador PtSn/C-ITO 50:50 demonstrou ter o melhor desempenho nas análises de voltametria cíclica e amperometria, entretanto, a mesma eficácia não ocorreu nos experimentos em célula unitária o que leva a crer que em meio alcalino o mecanismo de oxidação do etanol sob temperatura e outros parâmetros reais pertinentes à operação da célula precisam ser mudados e/ou estudados. / PtSn /C-ITO electrocatalysts were prepared by the sodium borohydride reduction method with 20% mass metallic load supported on Vulcan XC72 carbon and tin and indium oxides (ITO) in the following compositions; 50:50, 70:30 and 90:10. The electrocatalysts were subjected to x-ray diffraction characterization (XRD), transmission electron microscope (TEM), energy dispersive x-ray spectroscopy (EDX) and electrochemical analyzes using cyclic voltammetry and amperometric techniques for studies of ethanol electrochemical oxidation. In the electrochemical techniques the thin porous coating was used where the electrocatalysts were tested in both the acidic and alkaline media. Experiments in unit cell fed directly by ethanol were tested simulating real operating conditions. The electrochemical and physical characterization analyzes in acid medium allowed to compare the performance and stabilities of the electrocatalysts under study and also demonstrated the benefits of the addition of tin and ITO, with emphasis at PtSn/C-ITO 70:30 electrocatalyst. In alkaline media the PtSn/C-ITO 50:50 electrocatalyst demonstrated the best performance in the tests of cyclic voltammetry and amperometry, however, the same efficiency did not happen in the unit cell tests which leads to believe that in alkaline medium the oxidation mechanism of ethanol under temperature and other actual pertinent parameters to cell operation need to be changed and/or studied.