Made available in DSpace on 2014-06-11T19:25:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-17Bitstream added on 2014-06-13T19:12:21Z : No. of bitstreams: 1 escanhoelajunior_ca_me_rcla.pdf: 2205069 bytes, checksum: 07cd01b4a104f262986c24bd2a7f874b (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho realizamos a polarização térmica em vidros silicatos com composição (%mol) 22Na2O.8CaO.65SiO2 .5MO2 (M = Si, Ti, Ge, Zr, Sn e Ce). A polarização térmica consiste em aplicar um campo elétrico DC de elevada intensidade (~1 MV/m) em amostras a altas temperaturas. Durante a polarização térmica é gerado um campo elétrico permanente no interior da amostra, na região do anodo, que é responsável por propriedades ópticas nãolineares. Submetemos à polarização térmica amostras dos vidros, com ~1,5 mm de espessura e área de 20 x 20 mm2. Utilizamos eletrodos de Au, com diâmetro de 1 cm. As amostras foram aquecidas no interior de um forno até ~145 oC e aplicamos um campo elétrico de 1 MV/m durante 60 min. Durante a aplicação do campo elétrico, medimos simultaneamente a corrente através do circuito e as temperaturas no forno e na amostra. A corrente elétrica medida no circuito está relacionada com a migração de íons Na+ no interior das amostras do anodo para o catodo. A diminuição da corrente após um determinado tempo de polarização é devido à formação de uma camada com ausência de íons Na+ (camada de depleção) junto ao anodo. Os diferentes cátions tetravalentes, M4+, inseridos no vidro têm funções particulares na estrutura deste e afetam de formas distintas a corrente elétrica. A energia de ativação para a condutividade elétrica em vidros soda-cal-sílica está associada à energia necessária para o íon Na+ transpor a barreira de potencial entre os interstícios adjacentes na rede vítrea. Para determinar a energia de ativação da condutividade elétrica DC, Eσ, destes vidros, submetemos amostras de cada composição a um campo elétrico de 1 MV/m, durante 2 segundos para diferentes temperaturas entre 100 e 220 ºC. Esta energia está relacionada com... / In this work we performed thermal poling in glasses with composition (%mol) 22Na2O.8CaO.65SiO2 .5MO2 (M = Si, Ti, Ge, Zr, Sn and Ce). The thermal poling consist in apply a high intensity DC electric field (~1 MV/m) on samples at high temperatures. During the thermal poling process a permanent electric field is generated in the anode region of the sample, and this field is responsible for nonlinear optical properties of various glasses. We submit to thermal poling samples with ~1.5 mm in thickness and area of 20x20 mm2. We used gold electrodes with a diameter of 1 cm. The samples were heated inside a furnace to ~ 145 oC and an electric field of 1 MV/m was applied for 60 min. During the poling process, we measure simultaneously the current through the circuit and the temperatures in the furnace and of the sample. The electric current of the circuit is related to the migration of sodium ions in the bulk samples from the anode to the cathode. The current decrease with the poling time is due to the formation of a Na+ absent layer (depletion layer) near the anode surface. The different tetravalent cations, M4+, in the glass have different functions in their structures and affect the electrical current in particular manners. The activation energy for electrical conductivity in soda-lime-silica glasses is associated with energy for the Na+ ions to cross the potential barrier, which is submitted to the interstices of the glassy network, and jump into the nearest interstice. The activation energy of DC electrical conductivity, Eσ, of our samples of was determined by applying an electric field of 1 MV/m for 2 seconds, at different temperatures between 100 and 220 ºC. This energy is related to the current, I, through the equation ... The energy calculated is ~0.8 eV. To evaluate the structural and compositional changes of the samples surfaces that were in contact with the ...

Orientador: Ervino Carlos Ziemath / Banca: Dante Luis Chinaglia / Banca: Victor Ciro Solano Reynoso / Resumo: Neste trabalho realizamos a polarização térmica em vidros silicatos com composição (%mol) 22Na2O.8CaO.65SiO2 .5MO2 (M = Si, Ti, Ge, Zr, Sn e Ce). A polarização térmica consiste em aplicar um campo elétrico DC de elevada intensidade (~1 MV/m) em amostras a altas temperaturas. Durante a polarização térmica é gerado um campo elétrico permanente no interior da amostra, na região do anodo, que é responsável por propriedades ópticas nãolineares. Submetemos à polarização térmica amostras dos vidros, com ~1,5 mm de espessura e área de 20 x 20 mm2. Utilizamos eletrodos de Au, com diâmetro de 1 cm. As amostras foram aquecidas no interior de um forno até ~145 oC e aplicamos um campo elétrico de 1 MV/m durante 60 min. Durante a aplicação do campo elétrico, medimos simultaneamente a corrente através do circuito e as temperaturas no forno e na amostra. A corrente elétrica medida no circuito está relacionada com a migração de íons Na+ no interior das amostras do anodo para o catodo. A diminuição da corrente após um determinado tempo de polarização é devido à formação de uma camada com ausência de íons Na+ (camada de depleção) junto ao anodo. Os diferentes cátions tetravalentes, M4+, inseridos no vidro têm funções particulares na estrutura deste e afetam de formas distintas a corrente elétrica. A energia de ativação para a condutividade elétrica em vidros soda-cal-sílica está associada à energia necessária para o íon Na+ transpor a barreira de potencial entre os interstícios adjacentes na rede vítrea. Para determinar a energia de ativação da condutividade elétrica DC, Eσ, destes vidros, submetemos amostras de cada composição a um campo elétrico de 1 MV/m, durante 2 segundos para diferentes temperaturas entre 100 e 220 ºC. Esta energia está relacionada com... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work we performed thermal poling in glasses with composition (%mol) 22Na2O.8CaO.65SiO2 .5MO2 (M = Si, Ti, Ge, Zr, Sn and Ce). The thermal poling consist in apply a high intensity DC electric field (~1 MV/m) on samples at high temperatures. During the thermal poling process a permanent electric field is generated in the anode region of the sample, and this field is responsible for nonlinear optical properties of various glasses. We submit to thermal poling samples with ~1.5 mm in thickness and area of 20x20 mm2. We used gold electrodes with a diameter of 1 cm. The samples were heated inside a furnace to ~ 145 oC and an electric field of 1 MV/m was applied for 60 min. During the poling process, we measure simultaneously the current through the circuit and the temperatures in the furnace and of the sample. The electric current of the circuit is related to the migration of sodium ions in the bulk samples from the anode to the cathode. The current decrease with the poling time is due to the formation of a Na+ absent layer (depletion layer) near the anode surface. The different tetravalent cations, M4+, in the glass have different functions in their structures and affect the electrical current in particular manners. The activation energy for electrical conductivity in soda-lime-silica glasses is associated with energy for the Na+ ions to cross the potential barrier, which is submitted to the interstices of the glassy network, and jump into the nearest interstice. The activation energy of DC electrical conductivity, Eσ, of our samples of was determined by applying an electric field of 1 MV/m for 2 seconds, at different temperatures between 100 and 220 ºC. This energy is related to the current, I, through the equation ... The energy calculated is ~0.8 eV. To evaluate the structural and compositional changes of the samples surfaces that were in contact with the ... / Mestre

De nombreuses applications modernes nécessitent l’utilisation de matériaux transparents dans le visible et le proche infrarouge. C’est le cas des vitrages pour le bâtiment, des vitres de voitures ou encore d’écrans de téléphone portable. La stratégie mise en place dans ces travaux de thèse est d’obtenir en surface d’un verre sodo-calcique, un matériau barrière aux propriétés similaires à la silice. Deux approches de traitements de surface visent à d’une part, modifier la chimie de surface par un traitement sous champ électrique assisté par voie thermique et d’obtenir une couche riche en SiO2 en surface. D’autre part, un revêtement est déposé sur le verre sodo-calcique, utilisé ici comme substrat. Ce dépôt se fait par pulvérisation cathodique magnétron et permettra de mettre en forme un matériau composite SiO2-TiO2 aux propriétés optiques de transparence et mécaniques de dureté optimisées et d’y associer des propriétés photocatalytiques performantes. / Many applications of the modern wolrd need transparent material especially in the visible range and near-IR. That is the case for windows for building or car, laptop screen. The purpose is to obtain a silica rich layer on the top of a soda-lime glass with similar properties to silica. Two ways have been defined. The first one is thermal poling treatment which consist in a thermal treatment electric field assisted to modify the surface chemistry and monitoring a silica rich layer on the top. The second way is to get a thin film by magnetron sputtering on the top of the soda-lime glass used here as substrate. A SiO2-TiO2 material is got with efficient optical properties of transparencey and mechanical properties (hardness). Photocatalytic activity have been demonstrated and provide self-cleaning properties.

[pt] Diversos fatores têm atraído esforços para o desenvolvimento de novas estruturas para circuitos planares de microondas. Várias propostas são encontradas na literatura técnica, explorando diferentes formas de miniaturização dos circuitos, melhoria de eficiência de acoplamento, aumento de banda ou redução de perdas. Entre elas, encontra-se a utilização de materiais ferroelétricos, cujas propriedades dielétricas podem ser alteradas com a aplicação de uma tensão elétrica, permitindo a fabricação de uma nova classe de dispositivos ativos compactos; contudo, esses materiais têm desvantagens como altas perdas e dificuldades de fabricação. Em paralelo, a disseminação das telecomunicações ópticas gera uma demanda de novos componentes ópticos para os sistemas: mais eficientes, com maior capacidade e menor custo. A utilização de fibras ópticas de sílica em telecomunicações torna desejável que esses novos componentes sejam realizados em materiais compatíveis com a sílica, como por exemplo alguns tipos de vidro. A polarização eletro térmica surgiu como uma forma de produzir dispositivos eletro-ópticos ativos a partir de vidros utilizados como substratos de guias de onda ópticos passivos. Neste trabalho, os processos de tratamento eletro-térmicos utilizados nos substratos ópticos são aplicados a substratos dielétricos para uso em microondas. São verificados os efeitos resultantes nas alterações das propriedades dielétricas na faixa de microondas e a aplicação potencial em componentes e circuitos. Os tratamentos se constituem fundamentalmente na aplicação de alta tensão ao substrato na presença de temperatura elevada, visando à migração controlada de íons no material. Os substratos estudados são a alumina, substrato tradicional de microondas com elevada constante dielétrica, e os vidros, boro-silicato e sodo-cálcico, que estão atualmente sendo utilizados como substratos para guias ópticos e para construção de dispositivos ópticos ativos. É caracterizada a perda dielétrica dos vidros tratados para utilização como substrato para circuitos planares de microondas. O desenvolvimento de dispositivos ópticos ativos em substratos vítreos também implica na fabricação de circuitos elétricos de microondas sobre o mesmo substrato, para alimentar esses dispositivos com dados em altas taxas. Os vidros possuem altas perdas dielétricas nessa faixa devido à presença de íons alcalinos. A criação, pelo tratamento eletro-térmico, de uma camada de depleção de íons, próxima à superfície abaixo do circuito, permite a redução dessas perdas efetivas em circuitos planares. Outro efeito investigado é a possibilidade de se produzir um comportamento similar ao efeito ferroelétrico em um substrato de microondas. A camada de depleção criada pelo tratamento eletro-térmico provoca alterações na estrutura e permite a gravação de um campo elétrico estático devido ao deslocamento de íons. É estudada a influência desse campo dentro do material na variação de suas propriedades dielétricas, e a resposta à aplicação de uma tensão de controle externa. Estuda-se então a possibilidade de substituição por substratos tratados dos materiais ferroelétricos no desenvolvimento de componentes como chaves, acopladores e atenuadores variáveis e filtros de microondas. / [en] Several factors have been attracting research efforts to the development of new planar structures for microwave planar circuits. Various proposals can be found in the technical literature, exploring different ways of miniaturization of circuits, improvement of coupling efficiency, increase of bandwidth or reduction of losses. Among these is the use of ferroelectric materials, whose dielectric properties can be altered with the application of an electrical voltage, enabling the fabrication of a new class of compact active devices; however, such materials present some disadvantages, like very high losses and difficulties in manufacturing. Parallel to that, the dissemination of optical telecommunications generates a demand for new optical components for the systems, with greater efficiency and capacity but lower cost. Due to the use of silica optical fibers in telecommunications, it is desirable that these new components are fabricated in materials compatible to silica, as for example some types of glass. The electro-thermal polarization emerged as a way of producing active electro-optical devices from glass substrates used for passive optical waveguides. In this work, the processes of electro-thermal treatment used in optical substrates are applied to dielectric substrates for microwave use. The resulting effects on the changes in dielectric properties in the microwave frequency range and potential application in components and circuits are assessed. Such treatments are constituted fundamentally by the application of high voltage to the substrate in the presence of high temperature, aiming at the controlled migration of ions in the material. The substrates considered are alumina, conventional microwave substrate with high dielectric constant, and glasses, borosilicate and soda-lime, which are currently being used as substrates for optical waveguides and for the construction of active optical devices. The dielectric loss of treated glasses as substrates for planar microwave circuits is characterized. The development of active optical devices in vitreous substrates also implies the manufacture of microwave electrical circuits on the same substrate, in order to feed these devices with data at high rates. Glasses have high dielectric losses in this frequency range due to the presence of alkali ions. The creation by the electro-thermal treatment of an ion- depleted layer, near the surface below the planar circuit, enables the reduction of the effective losses in planar circuits. Another investigated effect is the possibility of creating a behavior similar to the ferroelectric effect in the microwave substrate. The depletion layer created by the electro-thermal treatment causes alterations in the structure and allows the recording of a static electric field by the displacement of ions. The influence of this field within the material on the variation of its dielectric properties, and the response to the application of an external control voltage are assessed. Then, the substitution for treated substrates of ferroelectric materials in the development of components such as switches, variable couplers and attenuators and microwave filters is considered.

Le poling thermique est une technique consistant à appliquer un fort champ électrique (DC) à un substrat de verre chauffé. Après traitement, un champ électrique est figé au sein de la matrice vitreuse, brisant sa centrosymmétrie. La présence de ce champ permet d’accéder à des propriétés d’optique nonlinéaire du second ordre, habituellement interdite dans un milieu centrosymmétrique tel que le verre. En plus des propriétés d’optique nonlinéaire, la présence du champ électrique a été associée à des modifications structurelles et compositionnelles mais également à des changements de propriétés de surface. Notre objectif a été d’utiliser cette technique pour modifier les propriétés de réactivité de surface et optique de verres d’oxyde (borosilicate et borophosphate de niobium (BPN)) et de verres de chalcogénures. Après poling, les modifications structurelles ont été caractérisée par spectroscopie vibrationnelle Raman et infrarouge. L’intensité et la localisation du champ électrique ont été caractérisées par des techniques de génération de seconde harmonique (SHG) : une analyse quantitative avec les franges de Maker et une d’imagerie μSHG. Le traitement a permis d’augmenter localement la réactivité de surface du verre borosilicate. Dans les verres BPN et chalcogénures, le traitement a permis de contrôler les propriétés optiques à la fois linéaire et nonlinéaire à l’échelle micrométrique. Ces résultats permettent d’envisager l’utilisation du poling thermique pour des applications en photonique intégrée. / Thermal poling is a technique which consists in the application of a strong DC electric field to a heated glass substrate. Following the treatment, a static electric field is frozen inside the glass matrix, effectively breaking its centrosymmetry. Presence of the electric field allows for second order non-linear optical properties usually forbidden in centrosymmetric medium such as glasses. In addition to nonlinear optical properties, the presence of the electric field has been associated with structural/compositional modifications as well as surface property changes. Our objective was to use this technique to tailor surface reactivity and optical properties in oxide (borosilicate and niobium borophosphate) and chalcogenide glasses. After poling, structural modifications were investigated using Raman and infrared spectroscopy. Strength and localization of the electric field were characterized by Second Harmonic Generation (SHG) techniques: quantitative Maker fringes analysis and μSHG imaging. The treatment has successfully allowed to locally enhanced the surface reactivity of a borosilicate glass. In niobium borophosphate and chalcogenide glasses, the treatment has permitted to control optical properties both linearly and non-linearly at the micrometric scale. These results show that thermal poling could be used to create functional devices for applications in integrated photonics.

Le développement des technologies optiques dans le domaine de la communication engendre un intérêt pour les matériaux présentant des propriétés non linéaires. Le matériau idéal doit combiner un coefficient non linéaire élevé, de bonnes propriétés optiques et un faible coût de fabrication. Les matériaux vitreux restent de bons candidats pour ce type d’application. La polarisation thermique permet de générer ce genre de propriétés dans les verres. En effet, à des températures de l’ordre de 300°C, l’application d’un champ électrique provoque la migration d’ions mobiles dans le matériau depuis l’anode vers la cathode. Une zone de déplétion en surface est ainsi créée donnant naissance à un champ électrique enterré. En combinant une technique de dépôt métallique, une irradiation laser et l’application d’un champ électrique (poling), il devient possible de réaliser des architectures complexes de migration et d’obtenir ainsi des propriétés optiques non linéaires structurées. / Optical technologies development for communication has triggered a real interest about materials with nonlinear properties. The ideal material should combine a high nonlinear coefficient, good optical properties and a low production cost. Glasses remain very good materials for this kind of applications.Thermal poling is now well known for breaking glasses natural centro-symmetry and inducing second order nonlinearities. Indeed, at temperatures close to 300°C, the application of an electric field induces mobile ions migration from the anode to the cathode.In that case, the space charge created during the poling process generates an efficient macroscopic electrostatic field trapped under the anodic surface of the glass.The combination of silver deposition, femtosecond laser irradiation and thermal poling has been successfully used to realize a complex architecture of ionic migration leading to structuring of second order nonlinear properties at the microscopic scale.

Le but de ce travail de thèse est de contrôler via un traitement de polarisation les propriétés physico-chimiques de surface des verres. Pour cela, l'implémentation d'une charge d'espace au sein de différents verres silicates et borosilicates a été caractérisée. Ces études comparatives ont montré que la déplétion des cations de l’anode vers la cathode induit l’apparition d’un champ électrique et des modifications structurales localisées. De plus, nous avons démontré que la formation d’un plasma entre l’anode et le verre pouvait être à l’origine de phénomènes d'échanges ioniques conduisant notamment à la formation d’entités azotées NO2/N2O4 piégées dans le verre. Par la suite, une étude des propriétés physico-chimiques des surfaces polarisées a été conduite. Les résultats préliminaires obtenus concernent l'influence de la charge d'espace sur (i) la mouillabilité, (ii) la chimie de surface et (iii) les réponses optiques de molécules adsorbées. / The purpose of this work is to control physicochemical properties of glasses surfaces using a thermal polarization treatment. For this, the implementation of a space charge layer has been characterized for various silicates and borosilicates glasses. These comparative studies have shown that cations depletion from anode toward cathode induces both an electric field and structural local changes. To go further, we demonstrated that there is a plasma formation between anode and glass surfaces which could be the cause of ionic exchange phenomena leading to the formation of nitrogen NO2/N2O4 entities entrapped inside glass network. Subsequently, physicochemical properties studies of polarized surfaces were performed. Preliminary results concerning the space charge influence on (i) surface wettability, (ii) surface chemistry and (iii) optical responses of adsorbed molecules on poled glass surface have been obtained.