No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第22708号 / 人博第958号 / 新制||人||227(附属図書館) / 2020||人博||958(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 高木 紀明, 教授 中村 敏浩 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

Ce travail est consacré à l’étude de la diffraction d’atomes rapides (d’énergie cinétiquede l’ordre du keV) en incidence rasante (angles d’incidence ~ 1°) le long ou proche d’unedirection principale d’une surface cristalline. Cette géométrie en incidence rasante permet de(i) récolter, en quelques secondes, la totalité du cliché de diffraction sur un détecteur sensible enposition ; (ii) préserver la cohérence de l’onde de matière en réduisant les sources de décohérencecomme l’excitation électronique et l’agitation thermique. La grande sensibilité des atomes àla forme de la densité électronique de surface (partie répulsive) et au puits attractif de Vander Waals révèle les résonances de Fano et démontre que l’atome voyage, piégé au-dessus de lasurface, de façon cohérente, sur une distance de 0.2μm. Il est également montré que la diffractiond’atomes rapides est une technique robuste pour suivre la dynamique de croissance de semiconducteurs(GaAs) par épitaxie (reconstructions, transitions de phase). Enfin, l’observationde la diffraction sur une feuille de graphène déposé sur 6H-SiC(0001) suggère l’utilisation desatomes rapides comme outil de diagnostic pour le suivi et la caractérisation en temps réel dela croissance du graphène dont les propriétés exceptionnelles dépendent beaucoup des défautsde surface. / This work was devoted to the study of fast atom diffraction (energies in the keV range)at grazing incidence angles (~ 1°) along or close to a low indexed direction of crystalline surfaces.This specific scattering geometry bears two advantages : (i) the diffraction pattern as a wholeis collected within seconds on a position sensitive detector ; (ii) the low energy associated to themotion normal to the surface quenches decoherence due to electronic excitations and stronglyreduces decoherence due to thermal vibrations. The high sensitivity of probe atoms to thesurface electron density (repulsive part) and to the Van der Waals attractive well reveals Fanoresonances where the trapped atoms preserve their coherence over distances as long as 0.2μm.As a complement to these fundamental studies, fast atom diffraction has been proved to be arobust mean to probe the dynamics of epitaxial growth of semiconductors (GaAs). Finally, workperformed on monolayer graphene grown on 6H-SiC(0001) suggest the possibility to use fastatoms to monitor graphene growth in real time, a key process to measure the level of alterationof the intrinsic graphene electronic structure.

This dissertation is related to the understanding of catalytic reactions of metal oxides. For several decades, the surfaces and bulk of materials have been probed to determine additional properties that relate to photocatalytic applications. This investigation furthers these efforts by the (a) modification of a metal oxide surface to isolate known influences of chemical properties and (b) proposing and utilizing a novel methodology for attribution of photocatalytic activity to a discernable influence. For the first effort, by effectively utilizing a known technique for a new application on a metal oxide, such isolations can be made despite unfavorable states. For the second effort, a reduction in the influence of surface states for metal oxides is effectively performed, providing the isolation of influences originating from the bulk. The challenge with such a proposal is verifying such bulk states have been adequately isolated as external influences would obviously distort any conclusions. Thus, techniques to both create such bulk states and eliminate unwanted combinations thereof are additionally required and must be provided for. Lastly, a determination of the photocatalytic activity is made to these states and results are provided.

Grazing incidence pumping (GRIP) is a scheme to produce x-ray lasers and extreme ultraviolet lithography is a means of lithographic production which requires soft x-rays with a bandwidth of 2% centred at 13,5 nm. In this work firstly a grazing incidence pumping of Ni-like Mo and Ne-like Ti x-ray laser media were simulated by using EHYBRID and a post-processor code coupled to it. The required atomic data were obtained from the Cowan code. Besides, the timing issue needed for amplification purpose in a Ti:Sapphire laser system has been described theoretically. Afterwards, in order to produce soft x-ray lasers for extreme ultraviolet lithographic applications, emission of soft x-rays in the 2% bandwidth centred at 13.5 nm emitted from Sn XII and Sn XIII ions were simulated by using the EHYBRID code for a laser operating at 1064 nm with 1 J of pulse energy and 6 ns of pulse duration. The intensity range that has been investigated is between 1-5 x 1012 W/cm2. Ion fractions of tin ions and line intensities corresponding to different electron temperatures were calculated by using the collisional radiative code NeF.

The field of X-ray astronomy is only forty (43) years old, and grazing incidence X-ray telescopes have only been conceived and designed for a little over fifty (50) years. The Wolter Type I design is particularly well suited for stellar astronomical telescopes (very small field-of-view). The first orbiting X-ray observatory, HEAO-1 was launched in 1977, a mere twenty-eight (28) years ago. Since that time large nested Wolter Type I X-ray telescopes have been designed, build, and launched by the European Space Agency (ROSAT) and NASA (the Chandra Observatory). Several smaller grazing incidence telescopes have been launched for making solar observations (SOHO, HESP, SXI). These grazing incidence designs tend to suffer from severe aberrations and at these very short wavelengths scattering effects from residual optical fabrication errors are another major source of image degradation. The fabrication of precision optical surfaces for grazing incidence X-ray telescopes thus poses a great technological challenge. Both the residual "figure" errors and the residual microroughness or "finish" of the manufactured mirrors must be precisely measured, and the image degradation due to these fabrication errors must be accurately modeled in order to predict the final optical performance of the as manufactured telescope. The fabrication process thus consists of a series of polishing and testing cycles with the predictions from the metrology data of each cycle indicating the strategy for the next polishing cycle. Most commercially available optical design and analysis software analyzes the image degradation effects of diffraction and aberrations, but does not adequately model the image degradation effects of surface scatter or the effects of state-of-the-art mosaic detectors. The work presented in this dissertation is in support of the Solar X-ray Imager (SXI) program. We have developed a rigorous procedure by which to analyze detector effects in systems which exhibit severe field-dependent aberrations (conventional transfer function analysis is not applicable). Furthermore, we developed a technique to balance detector effects with geometrical aberrations, during the design process, for wide-field applications. We then included these detector effects in a complete systems engineering analysis (including the effects of diffraction, geometrical aberrations, surface scatter effects, the mirror manufacturer error budget tree, and detector effects) of image quality for the five SXI telescopes being fabricated for NOAA's next generation GOES weather satellites. In addition we have re-optimized the remaining optical design parameters after the grazing incidence SXI mirrors have been imperfectly fabricated. This ability depends critically upon the adoption of an image quality criterion, or merit function, appropriate for the specific application. In particular, we discuss in detail how the focal plane position can be adjusted to optimize the optical performance of the telescope to best compensate for optical figure and/or finish errors resulting from the optical fabrication process. Our systems engineering analysis was then used to predict the increase in performance achieved by the re-optimization procedure. The image quality predictions are also compared with real X-ray test data from the SXI program to experimentally validate our system engineering analysis capability.

yes / Controlling polymer thin-film morphology and crystallinity is crucial for a wide range of applications, particularly in thin-film organic electronic devices. In this work, the crystallization behavior of a model polymer, poly(ethylene oxide) (PEO), during spincoating is studied. PEO films were spun-cast from solvents possessing different polarities (chloroform, THF and methanol) and probed via in situ grazing incidence wide angle x-ray scattering. The crystallization behavior was found to follow the solvent polarity order (where chloroform < THF < methanol) rather than the solubility order (where THF > chloroform > methanol). When spun-cast from non-polar chloroform, crystallization largely followed Avrami kinetics, resulting in the formation of morphologies comprising large spherulites. PEO solutions cast from more polar solvents (THF and methanol) do not form well-defined highly crystalline morphologies and are largely amorphous with the presence of small crystalline regions. The difference in morphological development of PEO spun-cast from polar solvents is attributed to clustering phenomena that inhibit polymer crystallization. This work highlights the importance of considering individual components of polymer solubility, rather than simple total solubility, when designing processing routes for the generation of morphologies with optimum crystallinities or morphologies.

Filmes finos magnéticos têm grande apelo em mídias de gravação com alta densidade de dados. As propriedades magnéticas desses filmes, que dependem da estrutura atômica do material, podem ser modificadas ou induzidas pela presença de interfaces internas. Para o entendimento e melhoramento dessas propriedades, torna-se necessário o uso de técnicas capazes de fornecer informações seletivamente em profundidade. Neste trabalho, acoplamos a espectroscopia de absorção de raios X (XAS) à uma geometria de incidência rasante, e assim usamos a variação da penetração dos raios X dentro do material em torno do ângulo crítico de reflexão total para obter informações resolvidas em profundidade sobre a ordem estrutural e magnética local. Desenvolvemos uma metodologia de medidas e de análise desta informação. Esta metodologia foi aplicada em filmes de FePt e CoPt que produzimos pela técnica de deposição catódica. Em filmes de FePt, uma análise quantitativa completa nos permitiu caracterizar a camada de oxidação da superfície. Em filmes de CoPt, observamos que a ordem química, responsável pela anisotropia perpendicular é parcialmente perdida em grandes profundidades além da superfície para filmes de espessura superior a 50 nm. A presença desta camada desordenada, confirmada por espalhamento ressonante de raios X, explica a incomum dependência em espessura das propriedades magnéticas do sistema estudado. / Magnetic thin films have great appeal in recording media with high data density. The magnetic properties of these films, depending on the material atomic structure, may be modified or induced by the presence of intern interfaces. For the understanding and improving of these properties, becomes necessary the use of techniques able to provide in depth selective information. In this work, we put together the X-ray absorption spectroscopy (XAS) to a grazing incidence setup, and then we use the variation of X-ray penetration inside the material around the critical angle to get depth resolved information about the structural and magnetic local order. We developed a measurements and analysis methodology of this information. This methodology were applied in FePt and CoPt films which we produced by the magnetron sputtering technique In FePt films, a complete quantitative analysis allowed us characterize a surface oxidized layer. In CoPt films, we observed the chemical order, responsible for the perpendicular anisotropy, is partially lost in high depths away from the surface for films thicker than 50 nm. The presence of this disordered layer, confirmed by resonant magnetic X-ray scattering, explains the unconventional in depth dependence of the studied system magnetic properties.

Filmes finos magnéticos têm grande apelo em mídias de gravação com alta densidade de dados. As propriedades magnéticas desses filmes, que dependem da estrutura atômica do material, podem ser modificadas ou induzidas pela presença de interfaces internas. Para o entendimento e melhoramento dessas propriedades, torna-se necessário o uso de técnicas capazes de fornecer informações seletivamente em profundidade. Neste trabalho, acoplamos a espectroscopia de absorção de raios X (XAS) à uma geometria de incidência rasante, e assim usamos a variação da penetração dos raios X dentro do material em torno do ângulo crítico de reflexão total para obter informações resolvidas em profundidade sobre a ordem estrutural e magnética local. Desenvolvemos uma metodologia de medidas e de análise desta informação. Esta metodologia foi aplicada em filmes de FePt e CoPt que produzimos pela técnica de deposição catódica. Em filmes de FePt, uma análise quantitativa completa nos permitiu caracterizar a camada de oxidação da superfície. Em filmes de CoPt, observamos que a ordem química, responsável pela anisotropia perpendicular é parcialmente perdida em grandes profundidades além da superfície para filmes de espessura superior a 50 nm. A presença desta camada desordenada, confirmada por espalhamento ressonante de raios X, explica a incomum dependência em espessura das propriedades magnéticas do sistema estudado. / Magnetic thin films have great appeal in recording media with high data density. The magnetic properties of these films, depending on the material atomic structure, may be modified or induced by the presence of intern interfaces. For the understanding and improving of these properties, becomes necessary the use of techniques able to provide in depth selective information. In this work, we put together the X-ray absorption spectroscopy (XAS) to a grazing incidence setup, and then we use the variation of X-ray penetration inside the material around the critical angle to get depth resolved information about the structural and magnetic local order. We developed a measurements and analysis methodology of this information. This methodology were applied in FePt and CoPt films which we produced by the magnetron sputtering technique In FePt films, a complete quantitative analysis allowed us characterize a surface oxidized layer. In CoPt films, we observed the chemical order, responsible for the perpendicular anisotropy, is partially lost in high depths away from the surface for films thicker than 50 nm. The presence of this disordered layer, confirmed by resonant magnetic X-ray scattering, explains the unconventional in depth dependence of the studied system magnetic properties.

Ce travail de thèse décrit l’alignement par pulvérisation de nanofils d'argent (AgNWs) aux interfaces solides sous la forme de films mono- et multicouches. Cette technique permet de contrôler la densité de nanofils dans le plan sur des zones macroscopiques avec des paramètres d'ordre nématique atteignant des valeurs > 0,90 dans les films monocouches. La répétition des cycles de dépôt en utilisant l’assemblage couche-par-couche produit des films multicouches dans lesquels par exemple des superstructures uniaxiales ou hélicoïdales peuvent être préparées en choisissant les directions de pulvérisation appropriées pour chaque monocouche individuelle. Les systèmes uniaxiaux sont des polariseurs fortement dépendant de la longueur d'onde (en raison de l'orthogonalité des plasmons transversaux et longitudinaux des AgNWs) et montrent une conductivité anisotrope dans le plan. Les systèmes hélicoïdaux montrent un dichroïsme circulaire très élevé qui peut être ajusté par exemple par le biais de la densité des AgNWs dans le plan ou de la distance entre les monocouches individuelles. Les mesures de la matrice Müller confirment que le dichroïsme circulaire observé découle de la superstructure hélicoïdale des multicouches à base d’AgNWs. / This thesis work describes the spray-alignment of silver nanowires (AgNWs) at solid interfaces in the form of mono- and multilayer films. The technique allows to control the in-plane density of nanowires over macroscopic areas with the best nematic order parameters reaching > 0.90 in monolayer films. Repeated deposition cycles using layer-by-layer assembly yield multilayer films in which for example uniaxial or helically twisted superstructures can be prepared by choosing appropriate spraying directions for each individual monolayer. Uniaxial systems are strong wavelength dependent polarizers (due to the orthogonality of the transversal and longitudinal plasmons of the AgNWs) and they show anisotropic in-plane conductivitiy. Helically twisted systems show very high circular dichroism which can be tuned for example through the in-plane density of AgNWs or through the distance between individual monolayers. Müller Matrix measurements confirm that the observed circular dichroism arises from the helically twisted superstructure of the AgNW multilayers.