In the research reported here, a two-dimensional Ising-type model was used to study the tracer diffusion coefficients of oxygen ions in YBa2Cu307-x (YBCO) for various values of oxygen concentration and temperature. The first chapter provides a brief introduction to the problem considered in this thesis. This is followed by a short review of superconductivity, with particular reference to the experimental and theoretical aspects of high-temperature superconductivity and its applications. The structure of YBCO is then presented, with emphasis on its behaviour for various values of oxygen concentration and temperature. The model used in the simulations and the results for tracer diffusion coefficients and related quantities obtained by previous workers concludes the chapter. Results from other theoretical models are also included. In the second chapter a theoretical background for the Monte Carlo simulations employed in the present investigation is discussed. This chapter includes a short account on how these numerical methods evolved. The Monte Carlo approach to numerical evaluation of integrals is described. Then the idea of Markov sampling for obtaining members of the canonical ensemble is presented, and the Metropolis algorithm is described. In particular, convergence and the detailed balance condition are discussed. The consequence of starting from an arbitrary initial state when evaluating an observable of interest, and the effect on the reliability of the values of observables, are analysed. The chapter closes with a discussion of Monte Carlo methods applied to a lattice model in statistical mechanics. In chapter three results for the oxygen distribution produced by the diffusion of oxygen in YBCO are presented. These results were obtained from Monte Carlo simulations of the anti-symmetric nextto- nearest neighbour Ising (ASYNNNI) model. In addition to the uniform equilibrium distributions obtained by previous workers, it is found that this model also possesses nonuniform equilibrium oxygen distributions. The nonuniform distributions show a rich phase structure, and some preliminary results for this structure are presented. Results for the tracer diffusion coefficients in the nonuniform equilibrium distributions are given in the last chapter. Both local and global tracer diffusion coefficients for nonuniform equilibrium configurations are presented. Results obtained for uniform and nonuniform equilibrium configurations are compared. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

The class of high Tc superconductors share one common structural aspect, the existence of planes of copper and oxygen ions. These planes are thought to be the source of the superconducting behaviour. They can be represented as a two-dimensional lattice of ions, which facilitates their study using numerical models. One such model is the t − J model. In most studies utilising numerical models, the planes have been considered isotropic. However, recent analysis of cuprate structure has illustrated that this may not be representative of the copper oxide planes. A number of cuprate structures exhibit different phases in which the planes are not isotropic, such as the low temperature orthorhombic and low temperature tetragonal phases. This work will examine the effects of introducing anisotropy into the t − J model in order to understand how these phases affect the results gained from numerical studies. / x, 89 leaves : ill. ; 29 cm.

No description available.

This poster was presented in the Materials for Advanced Metallization (MAM) 2014 Conference in Chemnitz, Germany. Abstract: Atomic Layer Deposition (ALD) has emerged as an ubiquitous method for the deposition of conformal and homogeneous ultra-thin films on complex topographies and large substrates in microelectronics. Electrochemical deposition (ECD) is the first choice for the deposition of copper (Cu) into the trenches and vias of the interconnect system for ULSI circuits. The ECD of Cu necessitates an electrically conductive seed layer for filling the interconnect structures. ALD is now considered as a solution for conformal deposition of Cu seed layers on very high aspect ratio (AR) structures also for technology nodes below 20 nm, since physical vapor deposition is not applicable for structures with high AR. Cu seed layer deposition by the reduction of Cu2O, which has been deposited from the Cu(I) β-diketonate precursor [(nBu3P)2Cu(acac)], has been successfully carried out on different substrates like Ta, TaN, SiO2, and Ru [1, 2]. However, still many questions are unanswered regarding the underlying surface chemistry of the precursor on many substrates, leading to different growth modes during ALD. In this work, the surface chemistry of [(nBu3P)2Cu(acac)] on SiO2 substrate is investigated by in-situ X-ray photoelectron spectroscopy (XPS), reporting vital information about the oxidation state and the atomic concentration after chemisorption on the substrates kept at different temperatures. The aim of the investigation is to understand the stepwise change in the precursor oxidation state with increasing substrate temperature and to identify the temperature limit for the thermal ALD with this Cu precursor on SiO2. For the experiments, the Cu precursor was evaporated on SiO2 substrates kept at temperatures between 22 °C and 300 °C. The measured C/Cu and P/Cu concentration indicated that most of the nBu3P ligands were released either in the gas phase or during adsorption (Fig. 1a). No disproportionation was observed for the Cu precursor in the temperature range between 22 °C and 145 °C. Similarly, in this temperature range the Auger parameter calculated from Cu 2p3/2 and Cu L3VV spectra was found to be 360.0±0.2 eV, comparable to Cu(I) oxidation state [3]. However, disproportionation of the Cu precursor was observed above 200 °C, since C/Cu concentration ratio decreased and substantial metallic Cu was present on the substrate. Hence, 145 °C is the temperature limit for the ALD of Cu2O from this precursor, as the precursor must not alter its chemical state after chemisorption on the substrate. 500 ALD cycles with the probed Cu precursor and wet O2 as co reactant were carried out on SiO2 at 145 °C. After ALD, in situ XPS analysis confirmed the presence of Cu2O on the substrate. Ex-situ spectroscopic ellipsometry indicated an average film thickness of 2.5 nm of Cu2O deposited with a growth per cycle of 0.05 Å/cycle, comparable to previous experiments. References: [1] T. Waechtler, S. Oswald, N. Roth, A. Jakob, H. Lang, R. Ecke, S. E. Schulz, T. Gessner, A. Moskvinova, S. Schulze, M. Hietschold, J. Electrochem. Soc., 156 (6), H453 (2009). [2] T. Waechtler, S. -F. Ding, L. Hofmann, R. Mothes, Q. Xie, S. Oswald, C. Detavernier, S. E. Schulz, X. -P. Qu, H. Lang, T. Gessner, Microelectron. Eng., 88, 684 (2011). [3] J. P. Espinós, J. Morales, A. Barranco, A. Caballero, J. P. Holgado, A. R. González Elipe, J. Phys. Chem. B, 106, 6921 (2002).

Thesis (Ph.D.)--McMaster University (Canada), 1992. / Source: Dissertation Abstracts International, Volume: 54-08, Section: B, page: 4182. Adviser: J. E. Greedan.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Cette thèse s’intéresse à l’exaltation du signal Raman sur des nanomatériaux cuivrés. Des couches minces d’épaisseur de cuivre variable ont été préparées et étudiées avant et après oxydation dans l’air à des températures inférieures à 200°C. Leur microstructure a été caractérisée par microscopies MEB et AFM. L’épaisseur des couches de cuivre et d’oxyde cuivreux a été mesurée localement par ces techniques, et comparée aux résultats d’études spectroscopiques par ellipsométrie et absorption UV-visible. Une modélisation des spectres d’absorption UV-visible, basée sur des calculs d’interférences à partir des équations de Fresnel, permet de déterminer à la fois les épaisseurs des couches et leurs indices de réfraction. L’étude Raman de ces échantillons permet de discuter et de quantifier le phénomène d’exaltation Raman par interférences (IERS). D’autres échantillons nanostructurés à base de cuivre, recouverts de graphène monofeuillet, ont été étudiés. Les variations d’intensité Raman du graphène sont discutées en termes d’IERS. La dernière partie du manuscrit est consacrée à l’étude du signal SERS de molécules déposées sur des substrats commerciaux nanostructurés d’or, et à leur évolution après avoir recouvert ces substrats d’une couche mince de cuivre. / This thesis studies the enhanced Raman signatures on copper based materials. Thin copper films were prepared and studied before and after thermal oxidation in air, under 200 °C. Their microstructure has been characterized by SEM and AFM. The thickness of the copper and cuprous oxide films have been characterized locally by those techniques, and by ellipsometry and UV-visible absorption spectroscopic techniques. A modeling of the UV-visible spectra has been performed based on interference calculations using Fresnel equations, allowing the determination of both the thicknesses and the refractive indices of the films. Raman study of these samples allows a quantification of the interference enhanced Raman phenomenon (IERS). Other copper nanostructured samples covered with single layer graphene (SLG) have been studied, and The Raman intensity of SLG discussed in terms of IERS. The last part of the manuscript is dedicated to SERS studies of molecules deposited on nanostructured golden commercial substrates and to the evolution of the Raman the signal after covering these substrates with a thin copper layer.

Orientador: Wilson de Figueiredo Jardim / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-16T20:28:08Z (GMT). No. of bitstreams: 1 Paschoalino_MatheusPaes_D.pdf: 18936349 bytes, checksum: 14276ac91e3b802b1f9fb8852267885f (MD5) Previous issue date: 2010 / Resumo: A fotocatálise heterogênea é uma técnica com grande aplicabilidade comercial quando o fotocatalisador encontra-se na forma suportada. O semicondutor mais estudado como fotocatalisador é o TiO2, principalmente o P25 (Degussa) devido suas excelentes propriedades físicoquímicas e fotocatalíticas. Além do TiO2, óxidos como ZnO e SiO2 também foram amplamente avaliados, enquanto que outros como CuO e Ga2O3 foram muito pouco estudados. Trabalhos recentes mostraram que a eficiência dos fotocatalisadores pode ser prejudicada em função do tipo de suporte ou substrato a que estes são fixados, devido a fatores como ligação catalisadorsuporte ineficiente, além de possíveis alterações morfológicas durante a deposição. Dentro deste contexto os objetivos deste trabalho foram: (a) desenvolver um suporte nanoestruturado ideal para o P25, composto por TiO2/SiO2, que possibilite sua fixação simples e rápida sobre superfícies de vidro e (b) avaliar a eficiência de CuO com alta área superficial na inativação fotocatalítica de E. coli e analisar a atividade fotocatalítica de b-Ga2O3 na degradação de compostos orgânicos. Como resultados obtiveram-se suportes nanoestruturados (100 a 315 m g) com alta adesão em vidro, suportando o P25 eficientemente para degradação de compostos emergentes (hormônios e antibióticos) em diferentes tipos de reatores sob iluminação natural e artificial. Óxidos de cobre com altas áreas superficiais (> 40 m g) mostraram-se eficientes na inativação de E. coli (10 UFC mL) após 1 ou 4 h de irradiação (l > 360 nm). O b-Ga2O3 (1 g L) apresentou-se seletivo para degradação de BTEX (4 mg L) utilizando-se uma lâmpada germicida como fonte de fótons. / Abstract: Heterogeneous photocatalysis is a technique with high commercial applicability when the photocatalyst is supported onto a substrate. The most studied semiconductor used as photocatalyst is the P25 TiO2 (Degussa) due to its excellent physiochemical and photocatalytic properties. Besides TiO2, other oxides such as ZnO and SiO2 were also studied, while CuO and Ga2O3 did not receive similar interest. Recent publications showed that photocatalyst efficiency could be impaired depending of the nature of the support or the substrate used, due to factors like inefficient catalyst-support bond and morphological alterations that can occur during deposition process. In this context, the purposes of this work were: (a) to develop a nanosupport for the P25, synthetizing a TiO2/SiO2 composite capable of fixing it over glass surfaces; (b) to evaluate the high surface area CuO efficiency on the photocatalytical inactivation of E. coli, and (c) to evaluate the photocatalatyc activity of b-Ga2O3 on the degradation of organic compounds. Nanostructured supports were obtained (100 to 315 m g) with high adhesion over glass, supporting P25 efficiently and allowing the degradation of emerging compounds (hormones and antibiotics) using different reactors under natural and artificial ilumination. Copper oxides with high surface area (> 40 m g) showed to be efficient on the E. coli inactivation (10 CFU mL) after 1 or 4 h irradiation (l > 360 nm). b-Ga2O3 (1 g L) was selective for BTEX degradation (4 mg L) using a germicidal lamp as photons source. / Doutorado / Quimica Analitica / Doutor em Ciências

The thesis is focused on the investigation of fundamental catalytic properties of two model catalysts-CeOx/Cu(111) and CuOx/Cu(111)-by means of advanced surface science techniques. The investigations performed on CeOx are devoted to the study of the relationship between the surface structure and the surface activity of ceria. We develop the preparation method leading to growth of epitaxial CeOx(111) thin films with the adjustable morphological parameters-the step density and the ordering of surface oxygen vacancies. By using the CeOx(111) films with precisely controlled structure we identify the role of the step edges and of the oxygen vacancies in the interaction of water with ceria. The investigation performed on CuOx is focused on the microscopic characterization of the reduction process of Cu2O(111) on the molecular level directly under a near ambient pressure of CO. In direct microscopic study we identify the active initiation centers, the intermediate oxide phases, and the kinetics of the reduction reaction of Cu2O(111).

A field trial was conducted to test the anthelmintic effect of a single dose of 4g of copper oxide wire particles (COWP) in bolus form in indigenous goats belonging to small scale communal farmers in three areas in the Bergville district of Kwa-Zulu Natal Province, South Africa namely Dukuza, Ogade and Hoffenthal. Faecal egg counts (FECs) determined by both the McMaster and Pitchford–Visser methods, FAMACHA / Dissertation (MSc (Veterinary Tropical Diseases))--University of Pretoria, 2009. / Veterinary Tropical Diseases / unrestricted