Thin films are an enabling technology for a wide range of applications, from microprocessors to diffusion barriers. Nanolaminate thin films combine two (or more) materials in a layered structure to achieve performance that neither film could provide on its own. Atomic layer deposition (ALD) is a chemical vapor deposition technique in which film growth occurs through self limiting surface reactions. The atomic scale control of ALD is well suited for producing nanolaminate thin films. In this thesis, ALD of two nanolaminate systems will be investigated: Al₂O₃-Ta₂O₅ and ZnO-SnO₂. Al₂O₃ and Ta₂O₅ are high κ dielectrics that find application as gate oxides for field effect devices such as metal oxide semiconductor field effect transistors and thin film transistors. Al₂O₃-Ta₂O₅ nanolaminate films of a fixed composition and total thickness, but with varied laminate structures, were produced to explore the influence of layer thickness on dielectric behavior. Layer thickness was found to have little impact on the dielectric constant but a strong impact on the leakage current. Thick layered nanolaminates (with 2.5 to 10 nm layers) performed better than either pure material. Showing structure provides a means of tailoring nanolaminate properties. ZnSnO is an amorphous oxide semiconductor used to make transparent TFTs. Although ALD is naturally suited to the production of nanolaminates, the deposition of homogenous ternary compounds is still uncommon. For very thin depositions, nucleation behavior can dominate, resulting in ALD growth rates different than for thicker films. Initial work on ALD of the ZnO-SnO₂ system is presented, focusing on nucleation and growth of each material on the other. It was found that both ZnO and SnO₂ inhibit the growth of one another and a method was developed to characterize the average growth rate for few cycle depositions. / Graduation date: 2011

Metal and oxide interactions are of broad scientific and technological interest in areas such as heterogeneous catalysis, microelectronics, composite materials, and corrosion. In the real world, such interactions are often complicated by the presence of interfacial impurities and/or high electric fields that may change the thermodynamic and kinetic behaviors of the metal/oxide interfaces. This research includes: (1) the surface hydroxylation effects on the aluminum oxide interactions with copper adlayers, and (2) effects of high electric fields on the interface of thin aluminum oxide films and Ni3Al substrate. X-ray photoelectron spectroscopy (XPS) studies and first principles calculations have been carried out to compare copper adsorption on heavily hydroxylated a- Al2O3(0001) with dehydroxylated surfaces produced by Argon ion sputtering followed by annealing in oxygen. For a heavily hydroxylated surface with OH coverage of 0.47 monolayer (ML), sputter deposition of copper at 300 K results in a maximum Cu(I) coverage of ~0.35 ML, in agreement with theoretical predictions. Maximum Cu(I) coverage at 300 K decreases with decreasing surface hydroxylation. Exposure of a partially dehydroxylated a-Al2O3(0001) surface to either air or 2 Torr water vapor results in recovery of surface hydroxylation, which in turn increases the maximum Cu(I) coverage. The ability of surface hydroxyl groups to enhance copper binding suggests a reason for contradictory experimental results reported in the literature for copper wetting of aluminum oxide. Scanning tunneling microscopy (STM) was used to study the high electric field effects on thermally grown ultrathin Al2O3 and the interface of Al2O3 and Ni3Al substrate. Under STM induced high electric fields, dielectric breakdown of thin Al2O3 occurs at 12.3 } 1.0 MV/cm. At lower electric fields, small voids that are 2-8 A deep are initiated at the oxide/metal interface and grow wider and deeper into the metal substrate, which eventually leads to either physical collapse or dielectric breakdown of the oxide film on top.

O estudo teve o objetivo de avaliar a resistência adesiva e a degradação da interface entre uma cerâmica tratada com laser e cimentos resinosos. Sessenta e quatro blocos cerâmicos foram distribuídos em 16 grupos distribuídos de acordo com os fatores em estudo: tratamento da superfície interna da cerâmica: Oxido de Alumínio (Ox), Rocatec (R), Laser de Nd:YAG 141,54 J/cm2 (Nd) e Laser de Nd:YAG + Rocatec (NdR); cimentos resinosos: Panavia F (Kuraray) e Relyx Unicem (3M ESPE); e método de envelhecimento: água destilada (W) e hipoclorito de sódio 10% (H). Após os procedimentos de cimentação e corte dos blocos, metade dos palitos foi armazenada em solução de hipoclorito de sódio 10% para simular envelhecimento in vitro. A resistência de união foi avaliada através do ensaio de microtração (0,5 mm/min) e os padrões de fratura foram classificados em adesivo, coesivo ou misto. Blocos cerâmicos adionciais foram confeccionados e analisados em Microscopia Eletrônica de Varredura e em Microscópio de Força Atômica para verificação dos padrões gerados pelos tratamentos. Os grupos tratados com laser de Nd:YAG apresentaram os maiores valores de resistência de união. Para os grupos cimentados com Panavia F, os valores de resistência de união foram: OxW: 27,71±6,3; RW: 35,67±5,13; NdW: 42,49±6,8; NdRW: 37,41±4,76; OxH: 22,27±6,05; RH: 27,49±8,83; NdH: 32,24±6,94; NdRH: 31,75±7,77. Para os grupos com RelyX Unicem: OxW: 26,74±6,34; RW: 35,07±6,02; NdW: 41,05±7,71; NdRW: 33,85±6,03; OxH: 22,77±7,37; RH: 27,84±6,26; NdH: 36,42±5,08; NdRH: 27,6±5,8. Pode-se concluir que o laser de Nd:YAG foi o tratamento mais efetivo, seguido da associação entre o laser de Nd:YAG+Rocatec, Rocatec e jateamento com Al2O3. Os cimentos testados apresentam comportamentos similares. O envelhecimento in vitro com hipoclorito de sódio diminuiu os valores de resistência de união. / The aim of this study was to evaluate the influence of different surface treatments on resistance to degradation between In-Ceram Alumina and two resin-based cements. Sixteen experimental groups were formed according to ceramic treatment: Sandblasting (S), Rocatec System (R), Nd:YAG Laser (Nd), Nd:YAG Laser plus Rocatec System (NR); luting cement: Panavia F (Kuraray) or Relyx Unicem (3M ESPE); and aging method: water (W) or sodium hypochlorite (H). Sixty four In-Ceram Alumina blocks (10x10x6mm) received four surface treatments: Al2O3 sandblasting; Al2O3 sandblasting + Rocatec Plus; Al2O3 sandblasting + Nd:YAG Lase; Al2O3 sandblasting + Nd:YAG Laser + Rocatec Plus. Each conditioned ceramic block was bonded to a composite block using a resin cement system. After 24h storage time, the blocks were sectioned to obtain sticks with cross-sectional area of 1.0mm2. The specimens were loaded to failure in a universal testing machine at a crosshead speed of 0.5mm/min. The fractured surface morphology of the debonded specimens was observed (40X) to evaluate the fracture pattern. Failure modes were classified as adhesive, cohesive in ceramic, cohesive in resin cement and mixed. The ceramic treatment and the aging method significantly affected the microtensile bond strength. Nd:YAG surface treatment resulted in the best bond strength values. To groups luted with Panavia F cement the microtensile bond strength values were: SW: 27,71±6,3; RW: 35,67±5,13; NdW: 42,49±6,8; NdRW: 37,41±4,76; SH: 22,27±6,05; RH: 27,49±8,83; NdH: 32,24±6,94; NdRH: 31,75±7,77. To groups luted with RelyX cement: SW: 26,74±6,34; RW: 35,07±6,02; NdW: 41,05±7,71; NdRW: 33,85±6,03; SH: 22,77±7,37; RH: 27,84±6,26; NdH: 36,42±5,08; NdRH: 27,6±5,8. Nd:YAG laser was the most effective surface treatment, followed by Nd:YAG+Rocatec, Rocatec and Al2O3 sandblasting. Resin cements presented similar behaviors in spite of aging. NaOCl 12h-immersion decreased Bond strength values.

Medidas de Termoluminescência (TL), Luminescência Opticamente Estimulada (LOE), EPR (Ressonância Paramagnética de Elétron) e RL (Radioluminescência) foram obtidas de amostras de óxido de alumínio e óxido de alumínio dopado com magnésio. As amostras foram calcinadas em três diferentes temperaturas (1100, 1350 e 1600°C) para observar a variação do comportamento das propriedades luminescentes. Ao final, constatou-se que a temperatura de calcinação é um parâmetro de grande importância para a produção de materiais dosimétricos, pois a amostra com melhores resultados LOE foi o material sem dopante tratada a 1600°C. Em trabalhos anteriores, a composição de óxido de alumínio dopado com magnésio havia apresentado nanoestruturas de aluminato de magnésio, observadas através de Microscopia Eletrônica de Transmissão (MET), que influenciaram a sensibilidade do material à radiação. Amostras de aluminato de magnésio puro e dopado com terras raras foram obtidas na forma de pó e calcinadas a 1100, 1350 e 1600°C. Medidas de TL e LOE de amostras irradiadas com fonte de partículas foram analisadas e comparadas com resultados de EPR e Difração de Raios-X (DRX). Como resultado, foi concluído que, nas condições trabalhadas, somente o elemento gadolínio proporcionou aumento de emissão LOE e TL no espectro visível. DRX indicou a formação dos compostos Al5Er3O12 e Al5Yb3O12; gadolínio e európio também formaram estruturas secundárias que não puderam ser determinadas. A partir do óxido de alumínio em pó, foram produzidos alvos para deposição de filmes finos empregando um sistema de sputtering magnetron e lâminas de silício monocristalino (100) tipo P para substrato. Parâmetros de deposição e de tratamento térmico foram variados de modo a produzir amostras com diferentes características. Curvas de TL foram levantadas e analisadas com relação aos resultados de DRX. Imagens de Microscopia Eletrônica de Varredura (MEV) foram obtidas de algumas amostras para visualizar o estado dos filmes depositados após tratamentos térmicos de 500 e 1100°C. Resultados mostraram a formação de picos de difração de a-Al2O3 em algumas das amostras espessas. Medidas de TL de amostras expostas à radiação ambiente exibiram picos de emissão em posições que variaram de acordo com a composição e espessura do filme depositado. / Thermoluminecent (TL), Optically Stimulated Luminescence (OSL), EPR (Electron spin Resonance) and Radioluminescence (RL) measurements were obtained from aluminum oxide and magnesium doped aluminum oxide samples. The samples were calcinated at three different temperatures (1100, 1350 and 1600°C) in order to observe variation of luminescent properties. As results, it was found that the calcination temperature is of great importance in the production of dosimetric materials, since the undoped sample calcinated at 1600°C showed the highest sensibility. In early works, magnesium doped aluminum oxide samples exhibited the formation of nanostructured layer composed by magnesium aluminate, observed using Transmission Electron Microscopy (TEM), which induced an increase of the luminescent properties. Samples of undoped and rare-earths doped magnesium aluminate, calcinated at 1100, 1350 and 1600°C, were produced. TL and OSL measurements were obtained from irradiated aliquots, analyzed and compared to EPR and XRD results. Results showed that, under the parameters used in this work, only gadolinium doped samples exhibited increase in TL and OSL emissions. XRD indicated the formation of Al5Er3O12 and Al5Yb3O12 structures in doped samples; gadolinium and europium doped samples also showed new structures, which couldnt be identified. Powder aluminum oxide was used to produce deposition targets, which were employed in the deposition of thin films over P type monocrystalline silicon (100) wafers. Variations of deposition parameters and heat treatment induced the formation of thin films with different characteristics, observed by XRD and luminescent analysis (TL). XRD results indicated the occurrence of alpha-Al2O3 in some of the thick films. Samples exposed to natural radiation produced TL emission in the visible spectrum.

O óxido de alumínio foi um dos primeiros compostos investigados, com vista a detectar e medir a radiação por meio da termoluminescência (TL). Comumente referido como \"alumina\", o óxido de alumínio tem características interessantes para o desenvolvimento de materiais para a dosimetria. Seu número atômico efetivo é intermediário entre o do osso e do tecido mole do corpo. Pode ser transformado em material termoluminescente pela inserção de elementos químicos em sua estrutura cristalina. Além da TL, a alumina pode apresentar luminescência opticamente estimulada (OSL), fenômeno que também pode ser usado para determinar a dose de radiação. Neste estudo, dois métodos foram investigados para inserir íons metálicos na alumina. O primeiro método foi baseado na capacidade de adsorção da alumina e o segundo denominado método da coprecipitação foi baseado na formação simultânea de compostos insolúveis. As amostras obtidas por adsorção de íons Cu2+ e Mn2+ não mostraram resultados satisfatórios. No entanto, as pastilhas de óxido de alumínio impurificado com Tm3+ via coprecipitação mostraram sinais de TL e OSL. Foi verificado também que a alumina eletrofundida disponível comercialmente é um material que apresenta resposta TL e OSL. Este material que contém diversos íons metálicos em sua estrutura foi transformado em pastilhas por sinterização com vidro. As curvas da resposta TL em função da temperatura e da resposta TL e OSL em função da dose foram determinadas. Os resultados obtidos indicam que estudos mais aprofundados das pastilhas desenvolvidas podem melhorar suas características para que sejam aplicadas em dosimetria. / The aluminum oxide was one of the former compounds investigated with a view to detecting and measuring radiation by means of the thermoluminescence (TL). Commonly referred to as \"alumina\", aluminum oxide has interesting features for the development of materials for dosimetry. Its effective atomic number has an intermediate value between the bone and soft tissue of the body. It can be transformed into TL material by the insertion of chemical elements in its crystal structure. In addition to the TL, the alumina can provide optically stimulated luminescence (OSL) which can also be used to determine the radiation dose. In this study, two methods were investigated in order to insert metal ions in alumina. The first method was based on the adsorption capacity of alumina and the second named coprecipitation method was based on the simultaneous formation of insoluble compounds. The samples obtained by adsorption of Cu2+ and Mn2+ ions did not show satisfactory results. However, the aluminum oxide impurified with Tm3+ by coprecipitation showed TL and OSL signals. It was also found that the commercially available electrofused alumina is a material that exhibits TL and OSL. This material that contains various metal ions in its structure was made into pellets by sintering with glass. The TL response curves as a function of temperature and the TL and OSL responses as a function of the dose were determined. The obtained results indicate that further studies of the developed pellets can improve the characteristics in order to be applied in dosimetry.

O óxido de alumínio foi um dos primeiros compostos investigados, com vista a detectar e medir a radiação por meio da termoluminescência (TL). Comumente referido como \"alumina\", o óxido de alumínio tem características interessantes para o desenvolvimento de materiais para a dosimetria. Seu número atômico efetivo é intermediário entre o do osso e do tecido mole do corpo. Pode ser transformado em material termoluminescente pela inserção de elementos químicos em sua estrutura cristalina. Além da TL, a alumina pode apresentar luminescência opticamente estimulada (OSL), fenômeno que também pode ser usado para determinar a dose de radiação. Neste estudo, dois métodos foram investigados para inserir íons metálicos na alumina. O primeiro método foi baseado na capacidade de adsorção da alumina e o segundo denominado método da coprecipitação foi baseado na formação simultânea de compostos insolúveis. As amostras obtidas por adsorção de íons Cu2+ e Mn2+ não mostraram resultados satisfatórios. No entanto, as pastilhas de óxido de alumínio impurificado com Tm3+ via coprecipitação mostraram sinais de TL e OSL. Foi verificado também que a alumina eletrofundida disponível comercialmente é um material que apresenta resposta TL e OSL. Este material que contém diversos íons metálicos em sua estrutura foi transformado em pastilhas por sinterização com vidro. As curvas da resposta TL em função da temperatura e da resposta TL e OSL em função da dose foram determinadas. Os resultados obtidos indicam que estudos mais aprofundados das pastilhas desenvolvidas podem melhorar suas características para que sejam aplicadas em dosimetria. / The aluminum oxide was one of the former compounds investigated with a view to detecting and measuring radiation by means of the thermoluminescence (TL). Commonly referred to as \"alumina\", aluminum oxide has interesting features for the development of materials for dosimetry. Its effective atomic number has an intermediate value between the bone and soft tissue of the body. It can be transformed into TL material by the insertion of chemical elements in its crystal structure. In addition to the TL, the alumina can provide optically stimulated luminescence (OSL) which can also be used to determine the radiation dose. In this study, two methods were investigated in order to insert metal ions in alumina. The first method was based on the adsorption capacity of alumina and the second named coprecipitation method was based on the simultaneous formation of insoluble compounds. The samples obtained by adsorption of Cu2+ and Mn2+ ions did not show satisfactory results. However, the aluminum oxide impurified with Tm3+ by coprecipitation showed TL and OSL signals. It was also found that the commercially available electrofused alumina is a material that exhibits TL and OSL. This material that contains various metal ions in its structure was made into pellets by sintering with glass. The TL response curves as a function of temperature and the TL and OSL responses as a function of the dose were determined. The obtained results indicate that further studies of the developed pellets can improve the characteristics in order to be applied in dosimetry.

The use of fly ash as a supplementary cementitious material (SCM) has increased in the last century due to its various environmental benefits as a recycled product. Within the last 60 years, it has been found that it can be used to effectively control damage induced by Alkali-Silica Reaction. However, it is not completely understood how to properly assign a dosage of fly ash to control the reaction. This depends greatly on the fly ash characteristics (e.g. composition, particle size, and reactivity), the reactivity of the aggregate (e.g. high to low reactivity level) and the environmental exposure conditions. The characteristics of the fly ash depend on the coal source being burned and the burning conditions that result in the fly ash formation. A major concern when supplementing cement with fly ash for ASR mitigation is the effect of the alkali contribution of the fly ash to the concrete pore solution. Current test methods cannot accurately determine the alkali contribution of fly ashes and there is no standardized test method to doing so. When contributed by the implementation of a SCM, alumina has been found to play a role in the ability of an SCM to mitigate ASR-induced damage. It has been observed that fly ashes containing higher levels of alumina (18-25%) tend to improve concrete durabilty more effectively when compared to fly ashes with lower levels of alumina. Additionally, the use of metakaolin, which is composed of 45-50% alumina, has been found to lessen expansion with a lower percentage of cement replacement than would be required if fly ash is used. Furthermore, the use of fly ash with another SCM material, a high quality ultra-fine fly ash or alumino-siliceous metakaolin, in ternary blends may improve the performance of fly ash resulting in a broadening of the spectrum of SCMs usable for ASR mitigation. For successful use of SCMs, it is important to develop an understanding of the alkalisilica reaction and the ability of such SCMs to control expansion. This report provides an overview of alkali-silica reaction and the use of fly ash and metakaolin as SCMs to mitigate expansion due to the reaction, with an emphasis on the role of alumina when contributed from the two materials. / Graduation date: 2012

GaN nanopore arrays with pore diameters of approximately 75 nm were fabricated by inductively coupled plasma etching (ICP) using anodic aluminum oxide (AAO) films as etch masks. Nanoporous AAO films were formed on the GaN surface by evaporating an Al film onto a GaN epilayer and subsequently anodizing the aluminum. To minimize plasma-induced damage, the template was exposed to CF4-based plasma conditions. Scanning electron microscopy (SEM) analysis shows that the diameter and the periodicity of the nanopores in the GaN were directly transferred from the original anodic alumina template. The pore diameter in the AAO film can be easily controlled by tuning the anodization conditions. Atomic force microscopy (AFM), photoluminescence (PL) and micro-Raman techniques were employed to assess the quality of the etched GaN nanopore surface. Such a cost-effective method to produce nano-patterned GaN template would be useful for growth and fabrication of III-Nitrides based nanostructures and photonic band gap materials. / Singapore-MIT Alliance (SMA)

Selbstreinigende, ultrahydrophobe Oberflächen lassen sich in der Technik vielfältig einsetzen. Das ultrahydrophobe Verhalten beruht einerseits auf einer Rauigkeit im μm-Bereich und andererseits auf der chemischen Zusammensetzung der Oberfläche. Durch den gegebenen Oberflächenaufbau sind derartige Materialien jedoch empfindlich gegen Verschleiß. In diesem Beitrag wird ein Schichtverbund bestehend aus Aluminiumoxid und zwei polymeren Komponenten vorgestellt. Die Aluminiumoxidschicht wird auf dem Wege der anodischen Oxidation erzeugt. Dieses seit langem bekannte Verfahren ermöglicht nicht nur die Oxidation der Aluminiumoberfläche, sondern gestattet es, auch, definierte Oberflächenprofile einzustellen. Durch den gezielten Einbau des hochmolekularen Polymers Chitosan in die mikroprofilierte Aluminiumoxidschicht wurde eine mechanische Stabilisierung der Schicht im Sinne eines anorganisch-organischen Composites erreicht. Außerdem dienten die Amino-Seitengruppen des Chitosans als reaktives Interface für die notwendige chemische Hydrophobierung und als Reaktionszentrum für Vernetzungen, wodurch eine weitere mechanische Stabilisierung bewirkt wird. Der Schichtaufbau hat wesentlichen

Abstract Isopropyl alcohol¡]IPA¡^and toluene are extensively used in industry as solvents. They are all highly toxic to animals and humans. Accordingly, IPA and toluene are strongly associated with problems of VOCs. In first step catalytic incineration was adopted to decompose IPA and toluene in laboratory, and the second step for a pilot-scale regenerative catalytic oxidizer ¡]RCO¡^were adopted to decompose mixture VOCs in real soil herein. The screening test of catalytic activity and the influences of the operational parameters on IPA and toluene removal efficiencies were widely discussed through catalytic incinerations of IPA and toluene in laboratory. The more effective and cheaper catalysts through above discussions of catalytic incineration were selected. And they were utilized in an pilot scale RCO as follows to investigate their performance in VOCs oxidation and RCO operations in THC removal of contamination soils. The achievements of this study are summarized as follows: ¡]1¡^Cu/Mn and Cu/Co gravel catalytic incinerations of isopropyl alcohol The results demonstrated that 10 wt% Cu0.6Co0.4 catalyst was the most effective because the CO2 yield reached 95 % under the following operating conditions; a temperature of 425oC, an inlet IPA concentration of 2500 ppm, an oxygen concentration of 21%, and a space velocity of 13500 hr-1. Additionally, the stability test results indicated that the 10 wt% Cu0.6Co0.4 catalyst exhibited excellent stability at both low and high conversion of IPA. ¡]2¡^20% Cu/Mn aluminum oxide catalytic incinerations of toluene The conversion for toluene reached 95% when the Cu/Mn catalyst was used with a metal ratio of 1:1 and 20% loading at 350¢XC, an influent toluene concentration of 1000 ppm, oxygen concentration of 21%, a space velocity of 12000 hr-1, and relative humidity of 26%. The long-term test was proceeded for seven days at a constant influent toluene concentration of 1000 ppm, constant oxygen concentration of 21%, constant space velocity of 12000 hr-1 and constant relative humidity of 26%. The SEM results indicated the Cu/Mn catalyst was quite stable at 350¢J. ¡]3¡^RCO testing for a copper/manganese catalyst of gaseous toluene The Cu/Mn (20wt%) catalyst was selected as the best one, because it converted 95% of the toluene at 400¢J. The results also indicating that the Cu/Mn catalyst was quite stable at 400¢J. (4) RTO treatment of VOCs with SVE system The conversion for VOCs reached 80% at 900¢XC, an influent VOCs concentration of 450-2000 ppm and a gas flow rate of 0.5 m3/min.The Thermal Recovery Efficiency¡]TRE¡^was approximately 86-90% in a RTO operated at 800-900¢J. (5)RCO treatment of VOCs with SVE system¡]10 wt% Cu0.6Co0.4 gravel catalyst¡^ The 10 wt% Cu0.6Co0.4 gravel catalyst was the poverty active, because it converted 65% of the VOCs by SVE system operated at 650¢J. (6)RCO treatment of VOCs with SVE system¡]20% Cu/Mn aluminum oxide catalytst¡^ The 20% Cu/Mn aluminum oxide catalytic was the best choice, because it converted 95% of the VOCs at 650¢J, an influent VOCs concentration of 450-10000 ppm and a gas flow rate of 0.5-1.5 m3/min. The SEM results indicated that the conversion of VOCs decay did not clearly vary at 650¢J, also indicating that the Cu/Mn catalyst selected was quite stable. The TRE was approximately 90% in a RCO¡]20% Cu/Mn aluminum oxide catalytic¡^operated at 650¢J. (7)RCO treatment of VOCs with SVE system¡]20% Cu/Mn gravel catalytst¡^ The 20% Cu/Mn gravel catalytst was the best selection , because it converted 95% of the VOCs at 600¢J, an influent VOCs concentration of 450-10000 ppm and a gas flow rate of 0.5-1.5 m3/min. The SEM results indicated that the conversion of VOCs decay did not clearly vary at 600¢J, also indicating that the Cu/Mn catalyst selected was quite stable. The TRE was approximately 90% in a RCO¡]20% Cu/Mn gravel catalytic¡^operated at 600¢J.