abstract: The research of this dissertation has involved the nanoscale quantitative characterization of patterned magnetic nanostructures and devices using off-axis electron holography and Lorentz microscopy. The investigation focused on different materials of interest, including monolayer Co nanorings, multilayer Co/Cu/Py (Permalloy, Ni81Fe19) spin-valve nanorings, and notched Py nanowires, which were fabricated via a standard electron-beam lithography (EBL) and lift-off process. Magnetization configurations and reversal processes of Co nanorings, with and without slots, were observed. Vortex-controlled switching behavior with stepped hysteresis loops was identified, with clearly defined onion states, vortex states, flux-closure (FC) states, and Omega states. Two distinct switching mechanisms for the slotted nanorings, depending on applied field directions relative to the slot orientations, were attributed to the vortex chirality and shape anisotropy. Micromagnetic simulations were in good agreement with electron holography observations of the Co nanorings, also confirming the switching field of 700-800 Oe. Co/Cu/Py spin-valve slotted nanorings exhibited different remanent states and switching behavior as a function of the different directions of the applied field relative to the slots. At remanent state, the magnetizations of Co and Py layers were preferentially aligned in antiparallel coupled configuration, with predominant configurations in FC or onion states. Two-step and three-step hysteresis loops were quantitatively determined for nanorings with slots perpendicular, or parallel to the applied field direction, respectively, due to the intrinsic coercivity difference and interlayer magnetic coupling between Co and Py layers. The field to reverse both layers was on the order of ~800 Oe. Domain-wall (DW) motion within Py nanowires (NWs) driven by an in situ magnetic field was visualized and quantified. Different aspects of DW behavior, including nucleation, injection, pinning, depinning, relaxation, and annihilation, occurred depending on applied field strength. A unique asymmetrical DW pinning behavior was recognized, depending on DW chirality relative to the sense of rotation around the notch. The transverse DWs relaxed into vortex DWs, followed by annihilation in a reversed field, which was in agreement with micromagnetic simulations. Overall, the success of these studies demonstrated the capability of off-axis electron holography to provide valuable insights for understanding magnetic behavior on the nanoscale. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2010

Les contraintes font maintenant partie des “ boosters ” de la microélectronique au même titre que le SOI (silicium sur isolant) ou le couple grille métallique / diélectrique haute permittivité. Appliquer une contrainte au niveau du canal des transistors MOSFETs (transistors à effet de champ à structure métal-oxyde-semiconducteur) permet d'augmenter de façon significative la mobilité des porteurs de charge. Il y a par conséquent un besoin de caractériser les déformations induites par ces contraintes à l'échelle nanométrique. L'holographie électronique en champ sombre est une technique de MET (Microscopie Électronique en Transmission) inventée en 2008 qui permet d'effectuer des cartographies quantitatives de déformation avec une résolution spatiale nanométrique et un champ de vue micrométrique. Dans cette thèse, la technique a été développée sur le microscope Titan du CEA. Différentes expériences ont été réalisées afin d'optimiser la préparation d'échantillon, les conditions d'illumination, d'acquisition et de reconstruction des hologrammes. La sensibilité et la justesse de mesure de la technique ont été évaluées en caractérisant des couches minces épitaxiées de Si_{1-x}Ge_{x}/Si et en effectuant des comparaisons avec des simulations mécaniques par éléments finis. Par la suite, la technique a été appliquée à la caractérisation de réseaux recuits de SiGe(C)/Si utilisés dans la conception de nouveaux transistors multi-canaux ou multi-fils. L'influence des phénomènes de relaxation, tels que l'interdiffusion du Ge et la formation des clusters de β-SiC a été étudiée. Enfin, l'holographie en champ sombre a été appliquée sur des transistors pMOS placés en déformation uniaxiale par des films stresseurs de SiN et des sources/drains de SiGe. Les mesures ont notamment permis de vérifier l'additivité des deux procédés de déformation. / Strain engineering is now considered as one of the most important boosters of microelectronics among other technologies such as SOI (Silicon On Insulator) and high-κ metal gates. By applying a stress in the channel of MOSFET (Metal Oxyde Semiconductor Field Effect Transistor) devices, the charge carriers mobility can be significantly increased. Consequently, there is now a need for a strain metrology at the nanometer scale. Dark-field electron holography is a TEM (Transmission Electron Microscopy) technique invented in 2008 that allows to map strain with micrometer field-of-view and nanometer spatial resolution. In this thesis, the technique was developed on the CEA Titan microscope. First, different developements were carried out concerning the sample preparation, the illumination/acquisition conditions and the reconstruction of the holograms. The sensitivity and the accuracy of the technique were evaluated through the characterization of Si_{1-x}Ge_{x} layers epitaxied on Si and by comparing the results with mechanical finite element simulations. Then, the technique was applied to the study of annealed SiGe(C)/Si superlattices that are used in the construction of new 3D architectures such as multichannel or multiwires transistors. The influence of the different relaxation mechanisms on the strain especially Ge interdiffusion and β-SiC clusters formation was investigated. Finally, dark-field electron holography was applied to the characterization of uniaxially strained pMOS transistors by SiN liners and recessed SiGe sources and drains. The measurements allowed to confirm the strain additivity of the two processes.

Three aluminium alloys from AA3003 series modified by zirconium were pre- pared by twin-roll casting. The role of composition, heat treatment and deforma- tion by cold-rolling or equal channel angular pressing on evolution of microstruc- ture and mechanical properties were studied. High density of α-Al(Mn,Fe)Si pre- cipitates formed during annealing between 300 ◦ C and 500 ◦ C. Coherent Al3Zr particles precipitated during annealing at 450 ◦ C with slow heating rate. Recrys- tallization resistance of deformed alloys was enhanced by either Al3Zr precipitates formed before deformation or by α-Al(Mn,Fe)Si particles nucleating simultane- ously with recrystallization. 1

O objetivo desse estudo foi comparar o desempenho de ligaduras ortodônticas estéticas de 4 marcas comerciais, após 30 dias na cavidade bucal, com o uso de dentifrício clareador e convencional para avaliar: alteração de cor por meio da espectrofotometria; a ultraestrutura da superfície por meio da Microscopia Eletrônica de Varredura (MEV); propriedade elástica por meio do teste de tração. Foram avaliadas as ligaduras seguintes marcas comerciais: American Orthodontics, 3M Unitek, Orthotechnology e Morelli Ortodontia. Foram selecionados, após o cálculo amostral, 20 pacientes que atenderam aos critérios de inclusão. Os pacientes receberam, de forma aleatória, com o auxílio do acessório Shooter (TP Orthodontics, La Porte, IN, EUA) ligaduras nos elementos 13, 23, 33 e 43; 32, 31, 41 e 42. No mesmo dia receberam dentifrício clareador Colgate Luminous White (Colgate-Palmolive Indústria e Comércio, São Bernardo do Campo, SP, Brasil) que foi usado por 30 dias (grupo experimental). Após esse período as ligaduras foram removidas, armazenadas (em saliva artificial) e, imediatamente submetidas aos testes. Os pacientes receberam, então, dentifrício convencional Colgate Máxima Proteção Anti-cáries (Colgate-Palmolive Indústria e Comércio, São Bernardo do Campo, SP, Brasil) (grupo controle). Após 30 dias, foram removidas, armazenadas e submetidas aos ensaios. As ligaduras inseridas nos bráquetes dos caninos foram avaliadas para alteração de cor pelo espectrofotômetro (Vita Easyshade Zahnfabrik, Bad Säckingen, Alemanha). Em seguida, as ligaduras, de cada marca, que apresentaram maior e menor variação de cor com o dentifrício clareador e convencional, bem como ligaduras novas, foram submetidas à avaliação qualitativa com a visualização pelo Microscópio Eletrônico de Varredura (EVO 50, Carl Zeiss, Cambridge, Inglaterra). As ligaduras que estavam inseridas nos bráquetes incisivos inferiores foram submetidas ao teste de tração pela Máquina de Ensaio Mecânico Universal (EMIC DL 2000, São José dos Pinhais, PR, Brasil). Os achados foram submetidos à análise estatística ANOVA e ao teste complementar de Duncan em um nível de significância de 5%. Os resultados mostraram que o dentifrício clareador não conseguiu efetivamente manter a estabilidade de cor das ligaduras ortodônticas estéticas. O valor final para o ΔE (variação total de cor) para todas as marcas foi > 3,3 o que indica uma alteração clinicamente perceptível pelo olho humano e que sinaliza a reposição do material por razões estéticas. Em relação à MEV as imagens obtidas foram heterogêneas e não permitiram caracterizar um padrão para um ou outro dentifrício. No que se refere ao teste de tração, houve melhor desempenho para as marcas 3M Unitek e American Orthodontics. O tipo de dentifrício, clareador ou convencional, não alterou a propriedade elástica entre as marcas estudadas. Pode-se concluir, pela presente pesquisa, que o dentifrício clareador não foi capaz de alterar a estabilidade de cor nas 4 marcas avaliadas por um período de 30 dias. A avaliação qualitativa pela MEV não permitiu concluir se a abrasividade do dentifrício clareador trouxe danos ou injurias à superfície das ligaduras. Apesar disso, o seu uso não alterou a propriedade elástica das mesmas. / The objective of this study was to compare the performance of aesthetic orthodontic ligatures/modules of 4 commercial brands, after 30 days in the oral cavity, with the use of conventional and whitening dentifrice to evaluate: color change by spectrophotometry; the ultrastructure of the surface by Scanning Electron Microscopy (SEM); elastic property by the tensile test. The following brands were evaluated: American Orthodontics, 3M Unitek, Orthotechnology and Morelli Orthodontics. Twenty patients who were included in the inclusion criteria were selected after sample calculation. Patients received, at random, with the aid of the Shooter accessory (TP Orthodontics, La Porte, IN, USA) ligatures on elements 13, 23, 33, 43, 32, 31, 41 e 42 and whitening dentifrice Colgate Luminous White (Colgate-Palmolive Indústria e Comércio, São Bernardo do Campo, SP, Brazil), which was used for 30 days (test group). After this period, the ligatures were removed, stored (in artificial saliva) and immediately submitted to the tests. Patients were then given conventional toothpaste Colgate Maximum Anti-caries Protection (Colgate-Palmolive Indústria e Comércio, São Bernardo do Campo, SP, Brazil). This was the control group. Once again, after 30 days, the modules were removed, stored and submitted to assays. Ligatures inserted into the canine brackets were evaluated by the spectrophotometer (Vita Easyshade Zahnfabrik, Bad Säckingen, Germany) to evaluate the color change. After this step, the ligatures of each brand, which presented greater and lesser color variation, both with the whitening dentifrice as well as the conventional one, and new ligatures, were selected for qualitative evaluation with the visualization by the Scanning Electron Microscope (EVO 50, Carl Zeiss, Cambridge, England). The ligatures that were inserted in the lower incisor brackets were subjected to the tensile test by the Universal Mechanical Testing Machine (EMIC DL 2000, São José dos Pinhais, PR, Brazil). The findings were submitted to ANOVA statistical analysis and Duncan\'s complementary test at a significance level of 5%. The results showed that the whitening dentifrice failed to effectively improve the color stability of aesthetic orthodontic ligatures. The final value for ΔE (total color change) for all brands was > 3.3 which indicates a change clinically perceptible by the human eye and signaling the replacement of the material for aesthetic reasons. In relation to the SEM the images obtained were heterogeneous and did not allow to characterize a standard for one or the other dentifrice. Regarding the tensile test, there was better performance for the brands 3M Unitek and American Orthodontics. The type of dentifrice, whitening or conventional did not alter the elastic property between the brands studied. It can be concluded from the present research that the whitening dentifrice was not able to change the color stability in the 4 brands evaluated for a period of 30 days. The qualitative evaluation by SEM did not allow the conclusion that the abrasiveness of the whitening dentifrice caused damage to the surface of the ligatures. Despite this, their use did not alter their elastic property.

Dans cette thèse, nous abordons les défis rencontrés lors de la caractérisation des mémoires non volatiles par microscopie en transmission in situ. Les innovations récentes menées sur les porte-objets de TEM in situ basés sur l'utilisation de puces en silicium apportent de grands avantages comparée aux précédents modèles. Cependant, cette technique reste complexe et les expériences de MET in situ sont difficiles à mener à terme. Ce manuscrit tente d'apporter de nouvelles solutions pour permettre l'observation à l'échelle atomique pendant le recuit, ou la polarisation d'un échantillon dans le MET. Ce projet a été mené à travers plusieurs améliorations effectuées au cours des différentes étapes des expériences de MET in situ. Cette thèse se focalise plus particulièrement sur les problèmes rencontrés lors de la polarisation de dispositifs de mémoires résistives de taille nanométrique. Ces travaux furent conduits à travers une étude des instruments utilisés, le développement de nouvelles méthodes de préparation d'échantillons, et une analyse de l'impact de l'imagerie électronique sur le fonctionnement d'un dispositif dans le MET.Tout d’abord, une nouvelle méthode est développée spécifiquement pour les expériences de MET in situ en température. Grâce à ces développements, la cristallisation de mémoires à changement de phase en GeTe est observée en temps réel. Ces résultats ont notamment permis d'obtenir des informations utiles pour le développement de mémoires à changement de phase de type chalcogénure. Ensuite, de nouvelles puces en silicium dédiées à la polarisation in situ sont développées et produites. Une étude est ensuite menée sur la préparation d'échantillons par FIB afin d'améliorer la qualité des contacts électriques pour la polarisation in situ, ainsi que la technique de préparation elle-même. La qualité de cette méthode est ensuite démontrée à travers des mesures quantitatives obtenues pendant la polarisation in situ d'un échantillon de référence de type jonction PN. Ces développements sont ensuite appliqués afin d’observer des dispositifs de mémoires résistives de type CBRAM en fonctionnement dans le microscope électronique en transmission. Ces résultats ont permis d'apporter de nouvelles informations sur les mécanismes de fonctionnement des mémoires résistives, ainsi que sur la technique de polarisation in situ. / In this work, we address the current challenges encountered during in situ Transmission Electron Microscopy characterization of emerging non volatile data storage technologies. Recent innovation on in situ TEM holders based on silicon micro chips have led to great improvements compared to previous technologies. Still, in situ is a particularly complicated technique and experiments are extremely difficult to implement. This work provides new solutions to perform live observations at the atomic scale during both heating and biasing of a specimen inside the TEM. This was made possible through several improvements performed at different stages of the in situ TEM experiments. The main focus of this PhD concerned the issues faced during in situ biasing of a nanometer size resistive memory device. This was made possible through hardware investigation, sample preparation method developments, and in situ biasing TEM experiments.First, a new sample preparation method has been developed specifically to perform in situ heating experiments. Through this work, live crystallization of a GeTe phase change Memory Material is observed in the TEM. This allowed to obtain valuable information for the development of chalcogenide based Phase Change Resistive Memories. Then, new chips dedicated to in situ biasing experiments have been developed and manufactured. The FIB sample preparation is studied in order to improve electrical operation in the TEM. Quantitative TEM measurements are then performed on a reference PN junction to demonstrate the capabilities of this new in situ biasing experimental setup. By implementing these improvements performed on the TEM in situ biasing technique, results are obtained during live operation of a Conductive Bridge Resistive Memory device. This allowed to present new information on the resistive memories functioning mechanisms, as well as the in situ TEM characterization technique itself.

The development of InGaN quantum dots (QDs) is both scientifically challenging and promising for applications in visible spectrum LEDs, lasers, detectors, electroabsorption modulators and photovoltaics. Such QDs are typically grown using the Stranski-Krastanov (SK) growth mode, in which accumulated in-plane compressive strain induces a transition from 2D to 3D growth. This method has a number of inherent limitations, including the unavoidable formation of a 2D wetting layer and the difficulty of controlling the composition, areal density, and size of the dots. In this research, I have developed InGaN QDs by two methods using a plasma-assisted molecular beam epitaxy reactor. In the first method, InGaN QDs were formed by SK growth mode on (0001) GaN/sapphire. In the second, I have addressed the limitations of the SK growth of InGaN QDs by developing a novel alternative method, which was utilized to grow on both (0001) GaN/sapphire and AlN/sapphire. This method relies upon the ability to form thermodynamically stable In-Ga liquid solutions throughout the entire compositional range at relatively low temperatures. Upon simultaneous or sequential deposition of In and Ga on a substrate, the adatoms form a liquid solution, whose composition is controlled by the ratio of the fluxes of the two constituents FIn/(FIn+FGa). Depending on the interfacial free energy between the liquid deposit and substrate, the liquid deposit and vapor, and the vapor and substrate, the liquid deposit forms Inx-Ga1−x nano-droplets on the substrate. These nano-droplets convert into InxGa1−xN QDs upon exposure to nitrogen RF plasma. InGaN QDs produced by both methods were investigated in-situ by reflection high-energy electron diffraction and ex-situ by atomic force microscopy, field emission scanning electron microscopy, transmission electron microscopy, high resolution x-ray diffraction, and grazing incidence small angle x-ray scattering. The optical activity and device potential of the QDs were investigated by photoluminescence measurements and the formation and evaluation of PIN devices (in which the intrinsic region contains QDs embedded within a higher bandgap matrix). InGaN QDs with areal densities ranging from 109 to 1011 cm−2 and diameters ranging from 11 to 39 nm were achieved.

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Orientador: Elson Longo da Silva / Coorientador: Marcelo Ornaghi Orlandi / Banca: José maria Corrêa Bueno / Banca: Daniela Coelho de Oliveira / Banca: Reginaldo Muccillo / Banca: Juan Andrés / Resumo: O trabalho que se apresenta centra-se no estudo investigativo do crescimento de cristais de óxido de cobre (II), CuO, com cristais organizados em diferentes formas semelhantes à ouriços-do-mar, fibras, e nanobastões, com controle fino da morfologia e cristalizados pelo método hidrotérmico assistido por micro-ondas. Esses materiais foram previamente caracterizados por difração de raios X (DRX), medida de área de superfície específica, espectroscopia de fotoelétrons excitados por raios X, microscopia eletrônica de varredura de alta resolução e de transmissão, além de espectroscopia de absorção de raios X próxima à borda de absorção (XANES), e outras. Pelas técnicas de microscopia combinadas foi possível caracterizar detalhadamente os materiais sintetizados, como sua estrutura, forma, tamanho, composição química, direção de crescimento, etc. Os óxidos obtidos foram testados quanto suas propriedades catalíticas na reação de desidrogenação do etanol - atividade, seletividade, frequência de reação. A originalidade do trabalho é que ao compreender as relações entre a morfologia do cristal e a estrutura da superfície dos óxidos nanoestruturados será possível obter catalisadores mais sensíveis, seletivos e com maior atividade catalítica. Ademais, foram realizados experimentos in situ de redução e reoxidação a temperatura programada, monitorada por XANES e DRX, resolvidos no tempo e na temperatura. Assim obteve-se uma projeção semiquantitativa de diferentes espécies de clusters de cobre (Cu2+, Cu+, e/ou Cu0). Esses resultados sugerem particularidades intrínsecas devido às diferentes morfologias no estado ativo nas cinéticas de redução e reoxidação. Em suma, foi desenvolvida uma rota sintética rápida e eficaz para sintetizar estruturas de CuO com diversas morfologias. Os materiais foram ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The present work goal the crystal growth of copper (II) oxide (II), CuO, with in different particles assembly. Herein, we report results of three distinct controlled CuO morphologies, urchin-like, fiber-like and nanorods, with fine control of morphology and crystallized by microwave assisted hydrothermal method. These materials were previously characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, surface area determination, scanning electron microscopy high-resolution and transmission electron microscopy, and absorption spectroscopy, X-ray absorption near edge (XANES), and others. The entire sequence of the crystallization procedure of CuO was monitored by field emission scanning electron microscopy in combination with transmission electron microscopy combined was possible to characterize in detail the materials synthesized, and its structure, shape, size, chemical composition, direction of growth, etc. The oxides obtained were tested for their catalytic properties in the reaction of dehydrogenation of ethanol - activity, selectivity, turnover frequency. The originality of this work is that by understanding the relationships between morphology and crystal structure of the surface oxides of nanostructured catalysts will be possible to obtain more sensitive and more selective catalytic activity. Copper-based catalysts obtained by microwave-assisted morphosynthesis were correlated with the dehydrogenation of ethanol. The degree of reduction and reoxidation was monitored using time-resolved in situ XANES and XRD during TPR under H2 and TPO under O2. A semiquantitative estimation of the different chemical forms (Cu2+, Cu+, and/or Cu0) was obtained. The results suggest intrinsic particularities due to different morphologies at the active state in reduction kinetics. In summary, we developed a rapid... (Complete abstract click electronic access below) / Doutor

[pt] Nesta tese de doutoramento apresentamos a técnica de microscopia de feixe duplo (MEV e FIB) como uma ferramenta modificadora das propriedades físico-química dos semicondutores orgânicos, a qual pode ser eficaz para alterar e controlar a mobilidade dos portadores de carga nestes materiais semicondutores. Neste caso, filmes finos e dispositivos orgânicos, principalmente à base de tiofeno, foram bombardeados com diferentes doses de íons de Ga com objetivo de induzir modificações na estrutura polimérica a partir das diversas interações entre o íon e o polímero. As propriedades dos filmes finos e dos dispositivos bombardeados foram caracterizadas através das técnicas de UV-Vis, Espectroscopia Raman e CELIV, as quais indicaram a existência de dois regimes de comportamentos governados pela dose de íons empregada. Técnicas avançadas de microscopia eletrônica indicaram a formação de uma estrutura tipo grafítica, em torno de 50 nm da superfície do bombardeamento, decorrente da interação entre os íons de gálio e a camada polimérica. A possibilidade de construir dispositivos orgânicos intercalados com camadas grafíticas pode ser explorada de forma a construir arquiteturas mais eficientes, explorando a alta resolução espacial que a técnica FIB proporciona. / [en] In this doctoral thesis we presented the dual-beam microscopy (SEM and FIB) technique as a modifier tool of physicochemical properties of the organic semiconductors, which it can be effective to change and control the charge carrier mobility into these semiconductor materials. In this case, organic devices and thin films, especially at thiophene base, were bombarded with different Ga ion doses in order to induce modification in the polymeric structure from the various interactions between the ion and the polymer. The bombarded thin films and devices properties were characterized by UV-Vis, Raman spectroscopy and CELIV techniques, which indicated the existence of two behavior regimes governed by the ion dose employed. Advanced electron microscopy techniques indicated the formation of a graphitic structure, around 50 nm from the surface bombardment, resulting of the interaction between the gallium ions and the polymer layer. The possibility to fabricate organic devices interspersed with graphitic layers can be exploited in order to construct more efficient architectures, using the high spatial resolution of the FIB technique.

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