Filmes finos de TiO2 foram crescidos sobre silício (100) através do processo de deposição química de organometálicos em fase vapor (MOCVD). Os filmes foram crescidos a 400, 500, 600 e 700ºC em um equipamento horizontal tradicional. Tetraisopropóxido de titânio foi utilizado como fonte tanto de titânio como de oxigênio. Nitrogênio foi utilizado como gás de arraste e como gás de purga. Foram realizadas análises de difração de raios-x para a caracterização da estrutura cristalina. Microscopia eletrônica de varredura com canhão de emissão de campo foi utilizada para a avaliação da morfologia e da espessura dos filmes. Os filmes de TiO2 crescidos a 400 e a 500ºC apresentaram fase anatase. O filme crescido a 600ºC apresentou as fases anatase e rutilo, enquanto que o filme crescido a 700ºC apresentou, além de anatase e rutilo, a fase broquita. Para se avaliar o comportamento eletroquímico dos filmes foi utilizada a técnica de voltametria cíclica. Os testes indicaram um forte caráter capacitivo dos filmes de TiO2. O pico de corrente anódica é diretamente proporcional à raiz quadrada da velocidade de varredura para os filmes crescidos a 500ºC, sugerindo que o mecanismo predominante de transporte de cátions seja por difusão linear. Observou-se que o filme crescido por 60 minutos permitiu maior facilidade de intercalação e desintercalação de íons Na+. Os filmes crescidos nas demais condições não apresentaram pico de corrente anódica, embora o acúmulo de cargas se fizesse presente. / Titanium dioxide (TiO2) thin films were grown on silicon substrate (100) by MOCVD process (chemical deposition of organometallic vapor phase). The films were grown at 400, 500, 600 and 700 ° C in a conventional horizontal equipment. Titanium tetraisopropoxide was used as source of both oxygen and titanium. Nitrogen was used as carrier and purge gas. X-ray diffraction technique was used for the characterization of the crystalline structure. Scanning electron microscopy with field emission gun was used to evaluate the morphology and thickness of the films. The films grown at 400 and 500°C presented anatase phase. The film grown at 600ºC presented rutile besides anatase phase, while the film grown at 700°C showed, in addition to anatase and rutile, brookite phase. In order to evaluate the electrochemical behavior of the films cyclic voltammetry technique was used. The tests revealed that the TiO2 films formed exclusively by the anatase phase exhibit strong capacitive character. The anodic current peak is directly proportional to the square root of the scanning rate for films grown at 500ºC, suggesting that linear diffusion is the predominant mechanism of cations transport. It was observed that in the film grown during 60 minutes the Na+ ions intercalate and deintercalate easily. The films grown in the other conditions did not present the anodic current peak, although charge was accumulated in the film.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / Ph.D.

Made available in DSpace on 2014-06-11T19:31:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-06Bitstream added on 2014-06-13T20:41:13Z : No. of bitstreams: 1 queiroz_dp_dr_bauru.pdf: 2041395 bytes, checksum: 33bdbc4d7c9e68649880f4ff3ab88b31 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho eletrodos interdigitados depositados sobre substratos de vidro foram recobertos com filmes de óxido de titânio, óxido de titânio dopado com prata e quitosana/PS-119® e foram usados como sensores tendo como objetivo principal se estudar medidas de capacitância elétrica em função da frequência em misturas de etanol e água. Os resultados mostraram que a formação da dupla camada na interface do líquido com a superfície do sensor contribui de maneira muito significativa para as capacitância dos sensores na região de baixa frequência. Nas altas frequência, a resposta dos sensores é independente da frequência e devida principalmente ao líquido que envolve o sensor, havendo uma variação sistemática da capacitância com a concentração de água nas misturas com etanol. O sensor de óxido de titânio foi usado para estabelecer uma curva de calibração, na frequência de 1 MHz, para identificação de percentuais de água em etanol. O conjunto formado pelos três sensores com filmes e um sensor sem filme foi usado para compor uma língua eletrônica para avaliação de etanol, água e suas misturas. A língua foi capaz de distinguir vários tipos de amostras desde que fossem saturadas com cloreto de sódio. / In this work interdigitated electrodes deposited on the top of a glass slide covered with titanium oxide, titanium oxide doped with silver and chitosan/PS-119 thin films were used as sensors aiming mainly to study measurements of the electric capacitance as function of frequency in mixtures of water in ethanol. Results showed that most important contribution to the sensor response in the low frequency is due to the electric double layer formed on the interface of the liquid and sensor surface. In high frequency, the sensor response is only due to the liquid around the sensor, where there is a systematic variation on the percentage of water in ethanol. The titanium oxide sensor was used to obtain a calibration curve, at 1 MHz, to measure the percentage of water in ethanol. The se of sensors with thin films and one uncovered with thin film were employed to form an electronic tongue for evaluation of ethanol, water and their mixtures. The electronic tongue was able to distinguish the samples only if saturated with sodium chloride.

Orientador: Eudes Borges de Araújo / Banca: Rafael Zadorosny / Banca: Jesiel Freitas Carvalho / Resumo: O titanato zirconato de chumbo dopado com lantânio, dado convencionalmente pela fórmula estequiométrica Pb1− x Lax ( Zry ; Ti1− y ) 1− x / 4 O3 , com x = 0,09 e y = 0,65, também conhecido como PLZT 9/65/35, é um importante sistema ferroelétrico relaxor devido as suas propriedades dielétricas, elétricas e eletroóticas. Sendo um ferroelétrico, exibe, também, propriedades tais como piezo e piroeletricidade, dependendo apenas das proporções em que são preparados. Logo, esse sistema é bastante interessante para uma gama de aplicações tecnológicas. Na forma de filmes finos, a composição PLZT 9/65/35 tem sido amplamente estudada e preparada pelos mais diversos métodos. Neste trabalho propõe-se a síntese de filmes finos ferroelétricos da composição PLZT 9/65/35 pelo método dos precursores óxidos, a fim de se compreender a dinâmica dos processos de cristalização e, também, avaliar suas propriedades físicas, como permissividade elétrica e histerese ferroelétrica. A intenção, assim, é colaborar com as informações presentes na literatura sobre as propriedades de filmes finos de PLZT 9/65/35 / Abstract: The lead zirconate titanate doped with lanthanum, conventionally given by stoichiometric formula Pb1− x Lax ( Zry ; Ti1− y ) 1− x / 4 O3 , with x=0,09 and y=0,65, also known as PLZT 9/65/35, is an important relaxor ferroelectric system due to its dielectric, electrical and electrooptical properties. Being a ferroelectric material exhibits also properties such as piezo- and piroelectricity, depending upon the extent to which they are prepared. Therefore, this system is very interesting for a range of technological applications. In the thin films format, the composition PLZT 9/65/35 has been widely studied and prepared by several methods. In this project it is proposed the synthesis of thin films of such material by the oxide precursor method in order to understand the dynamics of crystallization process and also to evaluate their physical properties like electrical permittivity and ferroelectric hysteresis. The intention, thus, is collaborate with the information presented in the literature about the properties of PLZT 9/65/35 thin films / Mestre

No description available.

Neste trabalho, apresentamos o estudo magnético e magneto-óptico de filmes de R-Co e bicamada Y-Co/R-Co, R=Gd, Tb. Nesses filmes, três tipos de magnetismo são observados: ferromagnetismo (Y-CO), ferrimagnetismo (GdCo), e sperimagnetismo (Tb-Co). As amostras foram depositadas por DC magnetron sputtering sobre substrato de vidro e protegidas da oxidação por camadas de 30nm de espessura de Sl IND.3 N IND.4. A caracterização magnética das amostras foi feita com a utilização dos magnetômetros SQUID, MAVe MEK-bt. Uma grande parede de domínios, localizada na interface da bicamada amorfa YCo IND.2/GdCo IND.2 é formada durante uma transição ferri-ferromagnética macroscópica. O modelo para analisar a parede de domínios é baseado nas energias Zeeman, anisotropia e troca. Como resultado, nós obtivemos três equações interdependentes, relacionando a espessura da parede de domínios , a posição relativa da parede e a constante de troca A, para os pares atômicos Co-Co. Nesta tese, apresentamos a dependência térmica de , e A. O modelo foi aperfeiçoado para levar em conta a forma não usual da parede de domínios presente na interface da bicamada. A parede de domínios ocupa ~64% do volume da bicamada e está localizada, em sua maior parte (~60%),na camada Y-Co. A constante de troca A apresentou um decréscimo monotônico, com os valores variando de ~3.1xl0 POT.-7 erg/cm a 25K para ~2.0xl0 POT.-7 erg/cm à temperatura ambiente. O Gd foi substituído por Tb e o estudo da parede de domínios na bicamada amorfa YCo2/TbCo2 , é apresentado. A principal diferença entre os filmes de Gd-Co e de Th-Co é o tipo de magnetismo que eles apresentam: o primeiro é ferrimagnético e o segundo é sperimagnético. Como consequência, o filme de Tb-Co apresenta um campo de anisotropia multo maior que o filme de Gd-Co, à temperatura ambiente. O efeito da alta anisotropia sobre a bicamada é uma parede de domínios quase que totalmente localizada na camada Y-Co. Este comportamento foi usado para determinar a dependência de com o campo magnético aplicado, e o valor da constante de troca A para as diferentes temperaturas. O valor de A variou de 1.8xl0 POT.-7 erg/cm a 150K para 1.4xl0 POT.-7 erg/cm a 300K e, para todas as temperaturas, decresceu de ~100nm, no campo de transição (Ht), para ~20nm para lkOe. Para aumentar o entendimento sobre as bicamadas à base de Gd e Tb, a dependência térmica da magnetização de saturação de filmes de R-Co (R=Gd, Tb) foi simulada com a teoria de campo médio. Nós fizemos também o estudo introdutório de filmes ternários. As caracterizações magnética e magneto-óptica dos filmes de R-FeCo (R=Gd, Tb) , e da bicamada de Gd-FeCo/Tb-FeCo revelaram anisotropia planar e perpendicular nos filmes à base de Gd e Tb, respetivamente. / In this work we present the magnetic and magneto-optical study of thin films of R-Co and Y-Co/R-Co bilayer, R=Gd, Tb. Three different kínds of magnetism are found in these films: ferromagnetism (Y-Co), ferrimagnetism (Gd-Co) and sperímagnetísm (Tb-Co). The samples were deposíted by DC magnetron sputteríng on glass substrate, and were protected from oxídatíon by 30nm thick Sí3N4, layers. Magnetic characterization of the samples was done using SQUlD, VSM and transverse magneto-optícal Kerr effect (TMOKE) magnetometers. A large doma in wall (DW), localízed at the YCo2/ Gd Co2, amorphous bilayer interface, is formed duríng a macrosropic ferri-ferromagnetíc transitíon. A model to analyze the DW ís based on Zeeman, anísotropy and exchange energies. As a result, we obtained three interdependent equations, relatíng the DW thickness , the relative position of the wall , and the exchange constant A. In this PhD thesis we present the temperature dependence of , and A. The model was ímproved to account for the unusual DW present at the bílayer interface. About 60% of the DW was inside the Y-CO layer, and the DW was found to be quite large, occupying ~64% of the volume of the bilayer. The exchange constant A presents a monotonically decreasing value, ranging from ~3.1 xl0-7 erg/cm at 25K to ~2.0 Xl0-7 erg/cm at room temperature. Gd was replaced by Tb and a study of the DW in amorphous YCo2/TbCo2, bilayer is presented. The main difference between Gd-Co and Tb-Co films is the kind of magnetism they present, the first is ferrimagnetic and the second is sperimagnetíc. As a consequence, the Tb based film shows a much higher anisotropy field than the Gd-Co film, at room temperature. The high Tb-Co anisotropy effect on the bílayer is a DW almost totally localized in the Y-Co layer. This behavior was used to determine the dependence on the magnetic field and the exchange constant A for different temperatures. A ranged from 1.8xl0-7 erg/cm at 150K to 1.4xl0-7 erg/cm at 300K and, for all temperatures, decreases from ~l00nm, at the transition field (Ht), to ~20nm at lkOe. In order to increase the understanding of the Gd and Tb based bilayers, the temperature dependence of the saturation magnetization of R-Co (R=Gd,Tb) films was simulated by the mean field theory. The values of exchange integrais JR-Co between R and Co atoms are in agreement to the literature. We also studied some ternary tilms, but in less detail. The magnetic and magneto-optical characterization of R-FeCo (R=Gd, Tb) films and GdFeCo/Tb-FeCo bilayer revealed an in-plane and perpendicular anisotropy in Gd and in Tb based fiims, respectively.

Os filmes moleculares constituídos por complexos polipiridínicos de rutênio, clusters trigonais de acetato de rutênio e porfirinas polimetaladas, tem sido investigados de forma sistemática, proporcionando uma ampla variedade de interfaces funcionais, para uso em dispositivos eletrônicos, sensores, células electrocatalíticas e de fotoconversão de energia. Tais filmes tem sido gerados por meio de métodos conhecidos como dip coating, drop casting, e deposição química/eletroquímica, apresentando aspectos morfológicos extremamente ricos, os quais foram investigados nesta tese, por meio de microscopia de varredura de sonda. Estudos de microscopia de força atômica foram dirigidos para os filmes moleculares gerados por dip coating. As imagens foram analisadas com bons resultados através do Programa da Gwyddion, permitindo a avaliação dos parâmetros de rugosidade envolvidos nas formas e distribuição dos grãos superficiais. Os filmes obtidos por drop casting foram investigados por meio da microscopia de força atômica, MACMode, apresentando uma grande variedade morfológica, associada principalmente com o processo de dewetting, sob a influência de interações moleculares específicas. A eletropolimerização dos complexos foi monitorada por meio de AFM condutivo, permitindo sondar as características condutoras dos filmes poliméricos. Filmes de DNA e nanopartículas magnéticas ancoradas sobre superfície de ouro foram investigados através de AFM MACMode, e AFM magnético, respectivamente. Finalmente, uma nova abordagem de sondas ultrassensitivas, foi explorada através da imobilização de nanopartículas magnéticas sobre MACLevers, ampliando os limites de detecção gravimétrica até sub-picograma. / Molecular films constituted by ruthenium polypyridine complexes, triangular ruthenium acetate clusters, and polymetallated porphyrins have been systematically investigated, providing a wide range of functional interfaces for electronic devices, sensors, photoconversion and electrocatalytical cells. Such films have been generated by dip coating, drop casting and electrochemical deposition, displaying very rich morphological aspects, which have been investigated by means of scanning probe microscopy. AFM studies have been carried out for the molecular films generated by dip coating. The images were successfully analysed using the Gwyddion software, allowing the evaluation of the rugosity parameters determining the grain shapes and distribution over the films. The films obtained by drop casting have been investigated by means of MACMode SFM, exhiting a wide variety of morphologies, mainly associated with the dewetting of the samples, under the influence of specific molecular interactions. Electropolymerization of molecular complexes have been monitored by SFM techniques, including the electroconducting mode to probe the conductivity of the polymeric films. Gold anchored films of DNA and magnetic nanoparticles have also been successfully investigated by MACMode SFM and magnetic SFM techniques, respectively. Finally, a new approach for ultra-sensitive probes, based on the immobilization of magnetic nanoparticles onto the MACLevers has been devised, allowing the detection of sub-picogram amounts of analytes

Superconducting thin films are a possible alternative to bulk niobium for superconducting radio frequency cavity applications. Thin film cavities have produced larger Q0 than bulk niobium at low accelerating voltages [1], are less susceptible to external magnetic fields and therefore require less magnetic shielding than bulk niobium cavities [2] and can benefit from substrates which conduct heat more effectively than bulk niobium [3]. The major drawback for current thin film cavity technology is the large Q slope which is observed above accelerating gradients of 6 7 MV/m. The mechanism for the Q slope is not yet fully understood. Theories have been suggested but are not accepted by everyone within the scientific community [2, 4, 5, 6, 7]. It is assumed that a better understanding of the physical properties of superconducting films is required before the origins of the sharp Q slope can be elucidated. This study has been conducted to better understand the physical properties of superconducting thin films deposited by the magnetron sputtering process. In particular, superconducting niobium films have been deposited by high power impulse magnetron sputtering (HiPIMS) and tested by a wide range of analytical techniques as a function of the substrate temperature and applied bias during deposition. Analytical techniques which have been used include x-ray diffraction crystallography, Rutherford backscattering spectroscopy, scanning electron microscopy, residual resistance ratio, DC magnetometry and RF surface resistance measurements. Results showed that the application of an applied bias during deposition resulted in increased energy of bombarding ions and enhanced rates of surface diffusion and defect annihilation within the microstructure of a growing niobium film. However, large numbers of random complex defects formed once the energy of bombarding ions becomes too large. The systematic approach that was described to investigate the changing morphological and DC superconducting properties of deposited films, as a function of the applied bias, allowed the identification of which process conditions produce the fewest random complex defects. The same systematic investigations could be applied to any HiPIMS deposition facility to provide similar results. An important observation during the study is that the initial substrate conditions have a large influence on the properties of a deposited niobium film. Niobium films deposited onto polycrystalline copper substrate that was pre-annealed at 700 ˚C prior to deposition displayed more stable magnetic flux pinning, larger RRR and an enhanced resistance to the onset of flux penetration, than was observed for films deposited with a wide range of process conditions onto as received copper substrate. Superconductors other than niobium have been successfully deposited by HiPIMS and tested. Niobium titanium nitride thin films displayed a superconducting transition temperature up to 16.7 K, with a normal state resistivity as small as 45±7 μΩcm. The findings suggest that similar niobium titanium nitride thin films could produce smaller RF surface resistance than bulk niobium cavities at 4.2 K.

Chan, Wing Chit = (La₀.₆₇Ca₀.₃₃MnO₃/La₀.₃₀Ca₀.₇₀MnO₃/La₀.₆₇Sr₀.₃₃MnO₃/La₀.₃₀Ca₀.₇₀MnO₃)多層薄膜的電子輸運特性 / 陳榮捷. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Abstract also in Chinese. / Chan, Wing Chit = (La₀.₆₇Ca₀.₃₃MnO₃/La₀.₃₀Ca₀.₇₀MnO₃/La₀.₆₇Sr₀.₃₃MnO₃/La₀.₃₀Ca₀.₇₀MnO₃) duo ceng bo mo de dian zi shu yun te xing / Chen Rongjie. / Abstract --- p.i / 論文摘要 --- p.iii / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Figures --- p.viii / List of Tables --- p.xiii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Review of Magnetoresistance --- p.1 / Chapter 1.1.1 --- Giant magnetoresistance (GMR) --- p.4 / Chapter 1.1.2 --- Colossal magnetoresistance (CMR) --- p.7 / Chapter 1.2 --- Possible origins of CMR in manganites --- p.10 / Chapter 1.2.1 --- Double exchange mechanism --- p.10 / Chapter 1.2.2 --- Tolerance factor --- p.14 / Chapter 1.2.3 --- Jahn-Teller Distortion --- p.16 / Chapter 1.2.4 --- Magnetic phase diagram and charge ordering (CO) --- p.19 / Chapter 1.2.5 --- Phase separation and percolation theory --- p.23 / Chapter 1.2.6 --- Phase separation at the interfaces in thin films --- p.28 / Chapter 1.3 --- Our motivation --- p.29 / Chapter 1.4 --- Literature review of some manganite multilayer systems --- p.31 / Chapter 1.4.1 --- Ferromagnetic (FM)/antiferromagnetic (AF) multilayers --- p.31 / Chapter 1.4.2 --- Ferromagnetic (FM)/insulating oxides multilayers --- p.32 / Chapter 1.4.3 --- Ferromagnetic (FM)/ferromagnetic (FM) multilayers --- p.33 / Chapter 1.5 --- Scope of this thesis --- p.34 / References --- p.36 / Chapter Chapter 2 --- Instrumentation / Chapter 2.1 --- Thin film deposition --- p.40 / Chapter 2.1.1 --- Facing-target sputtering --- p.41 / Chapter 2.1.2 --- Vacuum system --- p.44 / Chapter 2.2 --- Characterization --- p.46 / Chapter 2.2.1 --- α-step profilometer --- p.46 / Chapter 2.2.2 --- x-ray diffraction (XRD) --- p.46 / Chapter 2.2.3 --- Resistance measurement --- p.49 / References --- p.51 / Chapter Chapter 3 --- Epitaxial growth and characterization of single layer thin films / Chapter 3.1 --- Introduction --- p.52 / Chapter 3.2 --- Fabrication of the sputtering targets --- p.52 / Chapter 3.3 --- Epitaxial growth of single layer thin films --- p.53 / Chapter 3.3.1 --- Substrate materials --- p.54 / Chapter 3.3.2 --- Deposition conditions --- p.55 / Chapter 3.3.3 --- Deposition procedures --- p.57 / Chapter 3.3 --- Characterization of single layer thin films --- p.58 / References --- p.63 / Chapter Chapter 4 --- La0 67Ca0.33MnO3/La030Ca0.70MnO3/La067Sr0.33MnO3/La0.30Ca070MnO3 multilayers / Chapter 4.1 --- Sample preparation --- p.64 / Chapter 4.2 --- Structure characterization of as-deposited samples --- p.68 / Chapter 4.3 --- Transport properties of as-deposited samples --- p.79 / Chapter 4.3.1 --- Series of samples with fixed Lao.3oCao.7oMn03 barrier layer thickness --- p.79 / Chapter 4.3.3.1 --- Samples with thin ferromagnetic layers: C20 and S20 series --- p.82 / Chapter 4.3.1.2 --- Series of samples with thick ferromagnetic layers --- p.87 / Chapter 4.3.1.3 --- Parallel resistors network --- p.96 / Chapter 4.3.2 --- Series of samples with varying Lao.3oCao.7oMn03 barrier layer thickness --- p.101 / Chapter 4.4 --- Discussion --- p.108 / References --- p.114 / Chapter Chapter 5 --- Conclusion / Chapter 5.1 --- Conclusion --- p.116 / Chapter 5.2 --- Future outlook --- p.119 / References --- p.121

Yin, Ling = 銅基化合物薄膜太陽能電池 : 新透明導電電極與缺陷物理 / 尹苓. / Thesis Ph.D. Chinese University of Hong Kong 2015. / Includes bibliographical references. / Abstracts also in Chinese. / Title from PDF title page (viewed on 26, October, 2016). / Yin, Ling = Tong ji hua he wu bo mo tai yang neng dian chi : xin tou ming dao dian dian ji yu que xian wu li / Yin Ling.