We have developed continuous random network (CRN) model based Metropolis Monte Carlo simulation tools which are capable of predicting the structural properties of amorphous semiconductor and oxide materials as well as their interface. To bolster the reliability of the CRN model, we have developed force fields based on gradient corrected density functional theory (DFT) calculations. Our in-house CRN-MMC tools have been massively parallelized, which allows us to create fairly large model structures within a reasonable computational time. Using the integrated CRN-MMC tools, we have elucidated the complex growth and structure of self-interstitial and vacancy clusters in silicon and the effect of strain on the structure and stability of the defect clusters. Our work for vacancy clusters suggests that small vacancy defects exclusively favor fourfold-coordination thermodynamically with no significant kinetic limitation rather than void-like structure formation, which has widely been adapted to explain the behavior and properties of vacancy defects. Our results also highlight the identification of stable high-symmetry fourfold-coordinated V₁₂ and V₃₂ clusters that could be expected to exist to a large extent in a vacancy rich region although its direct characterization appears impractical at present. Our work for self-interstitial clusters provides the first theoretical support for earlier experiments which suggest a shape transition from compact to elongated structures around n = 10. When the cluster size is smaller than 10, the stable I₄ and I₈ compact clusters are found to inhibit the formation of elongated defects, whereas the newly discovered fourfold-coordinated I₁₂ state is found to serve as an effective nucleation center for large extended defects. Our CRN-MMC approach also enabled us to elucidate the underlying mechanisms of synthesis and manipulation of Si rich insulators as well as the fundamental understanding of the relationship between the atomic structure and properties. We developed a valence force field based on a modified Keating model for the structure and energetics of amorphous Si rich oxide materials. In particular, our work emphasizes the importance of correctly describing the wide Si-O-Si angle distribution. Our work also suggests that the relative rigidity between Si and SiO₂ matrices is critical in determination of the Si/SiO₂ interface structure. The present potential model coupled with the CRN-MMC method can be used to create structural models (free of coordination defects) for complex a-SiO[subscript x]-based materials, which will further allow thorough studies of the properties of these materials. / text

It is my hope that this thesis may serve as a guide for future students wishing to build a microscope from scratch. The design and construction of a scanning, confocal fluorescence microscope equipped with shaped microwave excitation is detailed. The use of the microscope is demonstrated by coherently manipulating single Nitrogen-Vacancy centres in diamond. Further the instrument is used to investigate a dual Halbach array magnet system.

Doctor of Philosophy(PhD) / This project focuses on the examination of the structures of lanthanide containing double perovskites of the type Ba2LnB'O6-d (Ln = lanthanide or Y3+ and B' = Nb5+, Ta5+, Sb5+ and/or Sn4+) using synchrotron X-ray and neutron powder diffraction. The first part of this project examined the relative stability of R3 rhombohedral and I4/m tetragonal structures as the intermediate phase adopted by the series Ba2LnB'O6 (Ln = lanthanide (III) or Y3+ and B' = Nb5+, Ta5+ or Sb5+). It was found that I4/m tetragonal symmetry was favoured when B' was a transition metal with a small number of d electrons, such as Nb5+ or Ta5+. This is due to the presence of p-bonding in these compounds. In the Ba2LnNbO6 and Ba2LnTaO6 series R3 rhombohedral symmetry was, however, favoured over I4/m tetragonal symmetry when Ln = La3+ or Pr3+ due to the larger ionic radius of these cations. The incompatibility of the d0 and d10 B'-site cations in this family of compounds was indicated by significant regions of phase segregation in the two series Ba2Eu1-xPrxNb1-xSbxO6 and Ba2NdNb1-xSbxO6. In the second part of this project the compounds in the series Ba2LnSnxB'1-xO6-d (Ln = Pr, Nd or Tb and B' = Nb5+ or Sb5+) were examined to understand the relative stability of oxygen vacancies in these materials compared to the oxidation of the lanthanide cations and to determine if any oxygen vacancy ordering occurred. It was found, using a combination of structural characterisation, X ray Absorption Near Edge Structure and Ultra-Violet, Visible and Near Infrared spectroscopies, that with Ln = Pr or Tb increased Sn4+ doping results in a change in the oxidation state of the Ln3+ cations to Ln4+. This leads to those series containing little or no oxygen vacancies. A loss of B site cation ordering was found to accompany this oxidation state change and phase segregation was found to occur in the Ba2PrSnxSb1-xO6-d series most likely due to the Pr3+ and Pr4+ cations segregating into different phases. The Nd3+ cations in the series Ba2NdSnxSb1-xO6-d, however, can not oxidise to the tetravalent state so the number of oxygen vacancies rises with increasing x. It was found that oxygen vacancies concentrate onto the axial site of the compounds with x = 0.6 and 0.8 at ambient temperature. In Ba2Sn0.6Sb0.4O5.7 the oxygen vacancies were found to change to concentrating on the equatorial site at higher temperatures and it is suggested that this oxygen vacancy ordering plays a role in the adoption of I2/m monoclinic symmetry.

Semiconductive metal oxides are of great importance in environmental remediation and electronics because of their ability to generate charge carriers when excited with appropriate energy. The electronic structure, light absorption and charge transport properties have made the transition metal oxides an attractive material as photocatalyst. Recently, facet-engineering by morphology control has been intensively studied as an efficient approach to further enhance their photocatalytic performance. However, various processing steps and post-treatments used in the preparation of facet-engineered particles may generate different surface active sites which may affect their photocatalysis. Moreover, many traditional techniques (PL, EPR and XPS) used for materials characterization (oxygen vacancy, hydroxyl group, cation, etc.) are not truly surface specific but analyzing a range from surface few layers to bulk. Accordingly, they can only provide very limited information on chemical states of the surface active features and their distribution among facets, causing difficulties to unambiguously correlate facet-dependent results with activity. As a result, this often leads to different interpretations amongst researchers during the past decades. As the publications of titanium and zinc ranked top two among studies of first row of transition oxides in the past decades, this thesis will firstly review on the disagreements generated among researchers when they correlated the performance of ZnO and TiO₂ with their facet activities based on traditional techniques. As there are shortcomings of these techniques in producing truly facet-dependent features, some results can be misleading and with no cross-literature comparison. To address these issues, we have developed a new technique "probe-molecule-assisted NMR" which allows a genuine differentiation of surface active sites from various facets. This surface-fingerprint technique has been demonstrated to provide both qualitative (chemical shift) and quantitative (peak intensity) information on the concentration and distribution of truly surface features among facets. In light of the new technique, this thesis will revisit the facet-dependent photocatalytic properties and shed light on these issues.

Este trabalho estuda a presença acentuada da vacância imobiliária e suas relações com a dinâmica urbana na área central de São Paulo. Para tanto, são verificadas as diversas formas de tratamento da vacância. A análise é completada com um breve histórico do desenvolvimento urbano da cidade. O cenário atual o cenário atual da área central é descrito através das características específicas do mercado imobiliário, da demanda, da atuação dos diversos agentes urbanos e da presença das ocupações organizadas. A metodologia utilizada inclui entrevistas com agentes ligados ao mercado imobiliário, e uma pesquisa de campo, apoiada em um plano amostral estratificado, por meio da qual se obtém a estimativa da vacância para os distritos Sé e República. Como resultado final do estudo, apontam-se os fatores do crescimento e permanência dos espaços edificados vazios na cidade de São Paulo. / This work studies the excess vacancy and its relations to the urban dynamics in downtown São Paulo. Several forms of dealing with the problem of vacancy are explored, and analysed within the context of a brief historical description of the urban development of the city. The present scenario of the central urban area is described, showing the characteristics of the real estate market, the demand on buildings, the performance of different urban agents, and the organized occupation of housing spaces. The methodology used includes interviews with agents related to the real estate market, and a survey based on a stratified sampling technique, to estimate vacancies in the districts of Sé and República. Finally, the factors leading to the uprising and persistence of vacant buildings in the central area of São Paulo are pointed out.

Les critiques littéraires estiment qu’il existe une certaine relation entre Robbe-Grillet et Echenoz, entre le Nouveau Roman et les jeunes écrivains de chez Minuit. Mais jusqu’à nos jours, il n’existe pas encore de recherches systématiques sur leur filiation dans les aspects divergents et convergents, notamment sur les différences et les ressemblances dans le récit. Dans cette étude, en interprétant l’obscurité du miroir non seulement comme fragmentation en multiples reflets mais aussi comme inversion du vide, nous apercevons que chez les deux écrivains, le sujet unit vainement en lui le même et l’autre en raison d’une crise identitaire. À travers un ailleurs en antithèse de l’ici, les auteurs dressent une typologie spatiale dominée par le vide et l’ouverture. Concernant la structure narrative, il existe aussi des voies différentes de reflets du miroir au sein du texte et entre les textes. D’ailleurs, les deux écrivains produisent par eux-mêmes des images spéculaires, qui se superposent et s’excluent, lorsque nous les envisageons au reflet du discours critique, ou dans le miroir de leur groupe respectif. / The literary critics have found the relation between Robbe-Grillet and Echenoz and that between New Novel and young writers at Midnight. However, in terms of their filiation, there is no systematic research related to the convergent and divergent aspects so far, especially the differences and similarities in the narration. By interpreting the obscurity of the mirror as the fragmentation of multiple reflections and the inversion of the vacancy as well, this dissertation finds that the subject in their writings incorporates both the self and the other to itself in vain because of the identity crisis. Based on the antithesis between here and there, both authors provide a typology space dominated by vacancy and openness. Regarding the narrative structure, there are different ways to mirror reflections within a text and between the texts. Moreover, from the perspective of the critical discourses, or in the mirror of their respective groups, both writers form some overlapped and inter-excluded specular images.

CuNi nanoparticles were synthesized using a new polyol synthesis method. Three different CuxNi1-x catalysts were synthesized where x = 20, 50 and 80. The nanoparticles were deposited on carbon, C, gamma-alumina, γ-Al2O3, yttria-stabilized zirconia, YSZ, and samariumdoped ceria, SDC. Each set of catalysts was tested using the Reverse Water Gas Shift, RWGS, reaction under atmospheric pressure and at temperatures ranging from 400°C-700°C. The experiments were repeated 3 times to ensure stability and reproducibility. Platinum nanoparticles were also deposited on the same supports and tested for the RWGS reaction at the same conditions. The CuNi nanoparticles were characterized using a variety of different techniques. Xray diffraction, XRD, measurements demonstrate the resence of two CuNi solid solutions: one Cu rich solid solution, and the other a Ni rich solid solution. X-ray photo electron spectroscopy, XPS, measurements show Cu enrichment on all catalytic surfaces. Scanning electron microscopy, SEM, measurements show CuNi nanoparticles ranging in size from 4 nm to 100 nm. Some agglomeration was observed. SDC showed the best yield with all catalysts. Furthermore, high oxygen vacancy content was shown to increase yield of CO for the RWGS reaction. Cu50Ni50/SDC shows the combination of highest yield of CO and the best stability among CuNi catalysts. It also has similar yields (39.8%) as Pt/SDC at 700°C, which achieved the equilibrium yield at that temperature (43.9%). The catalyst was stable for 48 hours when exposed to high temperatures (600-700°C). There was no CH4 observed during any of the experiments when the partial pressure of the reactant gases was fed stoichiometrically. Partial pressure variation experiments demonstrated the presence of CH4 when the partial pressure of hydrogen was increased to twice the value of the partial pressure of CO2.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22159号 / 工博第4663号 / 新制||工||1727(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 田中 功, 教授 中村 裕之, 教授 邑瀬 邦明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

<div>Optical signals are a necessary tool for quantum technologies to carry information both for long-range and on-chip application. The scope of their use is determined by their ability to effectively interact with qubits. The deep-subwavelength interaction volume demands the understanding of the properties of optical fields in the near-field and light-matter interaction in this regime. Recent studies have unraveled the rich characteristics in the physical quantity known as the near-field photonic spin density (PSD). Photonic spin density is the spatial distribution of light's spin angular momentum. It is characterized by the degree of circular polarization of an optical field in deep-subwavelength volumes. In this thesis we study the properties of PSD in the near-field regime and demonstrate a platform for coherent light-spin-qubit interaction based on PSD. We show that nitrogen-vacancy (NV) centers in diamond can coherently interact with an optical beam where the interaction strength is determined by PSD in the nanoscale. To understand the near-field characteristics of PSD we study the evanescent waves and spin-momentum locking of light.</div><div><br></div><div>Evanescent electromagnetic waves possess spin-momentum locking, where the direction of propagation (momentum) is locked to the inherent polarization of the wave (transverse spin). We study the optical forces arising from this universal phenomenon and show that the fundamental origin of recently reported optical chiral forces is spin-momentum locking. For evanescent waves, we show that the direction of energy flow, direction of decay, and direction of spin follow a right hand rule for three different cases of total internal reflection, surface plasmon polaritons, and HE₁₁ mode of an optical fiber.</div><div>Furthermore, we explain how the recently reported phenomena of lateral optical force on chiral and achiral particles is caused by the transverse spin of the evanescent field and the spin-momentum locking phenomenon. Our work presents a unified view on spin-momentum locking and how it affects optical forces on chiral and achiral particles. </div><div><br></div><div>To probe the near-field properties of PSD, we propose and employ a single NV center in diamond as a nanoscale sensor. NV centers have emerged as promising room-temperature quantum sensors for probing condensed matter phenomena ranging from spin liquids, two-dimensional (2D) magnetic materials, and magnons to hydrodynamic flow of current. Here, we demonstrate that the NV center in diamond can be used as a quantum sensor for detecting the photonic spin density. We exploit a single spin qubit on an atomic force microscope tip to probe the spinning field of an incident Gaussian light beam. The spinning field of light induces an effective static magnetic field in the single spin qubit probe. We perform room-temperature sensing using Bloch sphere operations driven by a microwave field (XY8 protocol). This nanoscale quantum magnetometer can measure the local polarization of light in ultra-sub-wavelength volumes. We also put forth a rigorous theory of the experimentally measured phase change using the NV center Hamiltonian and perturbation theory involving only virtual photon transitions. </div><div><br></div><div>In order to study the wavelength dependence of the optically induced magnetic field, we demonstrate this effect for an ensemble of NV centers. We characterize the wavelength dependence of the effective static magnetic field caused by the interaction of PSD and the spin qubit. We show that the strength of the field is inversely dependent on the detuning between the frequency of the optical beam and the optical transition of the NV centers. We show an optically induced rotation of over 10 degrees in the spin qubit of NV centers at room temperature. The direct detection of the photonic spin density at the nanoscale using NV centers in diamond opens interesting quantum metrological avenues for studying exotic phases of photons, nanoscale properties of structured light as well as future on-chip applications. </div><div><br></div>

The correlation of vacancy concentration with microhardness of Fe-Al alloys was studied on samples quenched from 1000 řC and subsequently annealed at lower temperatures. Using X-ray diffraction the lattice parameter and crystal structure were determined for samples of Fe-Al alloys. By measurements of positron lifetime was revealed the high concentration of vacancies in quenched samples and subsequent annealing caused significant decrease in vacancy concentration while in samples with Al content above 39% also the decrease of microhardness was measured. Measurements of coincidence Doppler broadening of annihilation peak helped to distinguish the annihilations coming from positron trapped or delocalized annihilated by electrons of both atoms, Fe and Al. Comparison of measured results with theoretical quantum-mechanics calculations performed in this diploma thesis determined the most probable defect type as a vacancy on A-sublatice of B2 structure.