Superfícies de silício (100) foram inicialmente pré-ativadas em uma solução diluída de ácido fluorídrico contendo PdCl2. Após essa etapa, filmes finos de Cu-Ni-P foram quimicamente depositados utilizando-se um banho químico contendo 15g/l NiSO4.6H2O; 0.2 g/l CuSO4.5H2O; 15 g/l Na2HPO2.H2O e 60 g/l Na3C6H5O7.2H2O na temperatura de 80ºC onde foi adicionado NH4OH até que o pH da solução atingisse 8,0. Foi observado que as porcentagens estequiométricas de Ni e Cu variaram substancialmente no intervalo de 1 a 3min, e se tornaram praticamente estáveis em 50% e 35%, respectivamente, quando o tempo de deposição foi superior a 3min. Além disso, a porcentagem de P permaneceu quase constante em torno de 17-18% para todos os tempos de deposição. A distribuição de alturas nas imagens FE-SEM resultou bimodal para tempos na faixa de 1 e 3min onde a predominância do modo de maior altura aumentou substancialmente para o tempo de 3min. Tal fato serviu para corroborar a evolução da morfologia superficial de grãos menores com diâmetros na faixa de 0,02 a 0,1µm, predominantemente compostos de Ni, para grãos maiores, na faixa de 0,1 a 0,3µm e predominantemente compostos de Cu. Após um recozimento a 100oC durante 10min em ambiente 20%O2+80%N2, observou-se uma mudança na morfologia superficial em que os aglomerados de fósforo (Po) desapareceram enquanto que os grãos que compunham a imagem não mudaram substancialmente de tamanho após o recozimento. Apesar do desaparecimento dos aglomerados, a concentração de fósforo ainda apresentou valor semelhante ao valor de antes do recozimento (~17-18%). As análises de difração de raios X (XRD) indicaram o aparecimento de um pico de difração alargado ao redor de 22,6º característico de óxido de fósforo (P2O5) com estrutura vítrea amorfa significando que o fósforo em estado puro foi transformado na sua forma oxidada. Por outro lado, picos substancialmente menos intensos de NiO, Ni3P e Si5P6O25 foram observados. Verificou-se também para os filmes recozidos em N2+O2 que a resistividade aumentou para todos os tempos de deposição e o poder termoelétrico medido resultou quase independente do tempo de deposição e, portanto, foi quase independente da espessura do filme para as diferentes temperaturas medidas na faixa de 40 a 120ºC. / Silicon surfaces (100) were initially pre-activated in a diluted hydrofluoric acid solution containing PdCl2. After this step, Cu-Ni-P thin films were chemically deposited using a chemical bath containing 15g/l NiSO4.6H2O; 0.2 g/l CuSO4.5H2O; 15 g/l Na2HPO2.H2O e 60 g/l Na3C6H5O7.2H2O at the temperature of 80°C where NH4OH was added until the pH of the solution reached 8.0. It was observed that the stoichiometric percentages of Ni and Cu varied substantially for deposition time in the range of 1 to 3min, and became practically invariant at 50% and 35%, respectively, when the deposition time was greater than 3min. In addition, the percentage of P remained almost constant at around 17-18% for all the deposition times. The distribution of heights in the FE-SEM images resulted bimodal for times in the range of 1 and 3min where the predominance of the higher average height mode increased substantially for the time of 3min. This fact allowed one to corroborate the superficial morphology passing from smaller grains with diameters in the range of 0.02 to 0.1µm, predominantly composed of Ni to larger grains in the range of 0.1 to 0.3µm with Cu predominant composition. After an annealing at 100°C for 10min in a 20%O2+80%N2 environment, the phosphorus (Po) agglomerates disappeared while the size of the grains did not change substantially after the annealing. Despite the disappearance of the agglomerates, the phosphorus concentration still remained unchanged (~ 17-18%). X-ray diffraction (XRD) analysis showed a broad diffraction peak around 22.6º, which is characteristic of an amorphous vitreous structure (P2O5). In addition, substantially less intense peaks showing small amounts of NiO, Ni3P and Si5P6O25 were observed. It was also verified for the N2+O2 annealed films that the resistivity increased for practically all the deposition times and the measured thermoelectric power was almost independent of the deposition time and, therefore, was also independent of the film thickness for the various temperatures in the range from 40 to 120ºC.

An electron momentum spectrometer at the Australian National University has been used to study various aspects of different solid state systems. EMS is a transmission mode technique and involves the collision of the incident electron with a bound electron, after which both electrons are ejected and measured in coincidence. Through well defined reaction kinematics the complete valence spectral momentum density A(ɛ,q) can be measured. The spectrometer has been used to measure the spectral momentum densities (spectral functions) of single crystal targets, as well as targets in disordered states. A new spin polarised electron source was constructed and implemented in the ANU spectrometer, which was used to measure spin dependent features of ferromagnetic samples.¶ This thesis is divided into seven chapters, the first chapter is an introduction into the field of electron momentum spectroscopy, highlighting what has been measured before and how the technique has progressed to its present state. Some comparisons to other experimental techniques will be made.¶ The second chapter describes the ANU EMS spectrometer in detail. The technique requires some technical and advanced equipment that is often used in novel ways. The production of thin (20 nm) free standing targets will be detailed, along with the experimental chamber and electronics used to run the apparatus and collect data. The determination of the energy and momentum resolution of the experiment is also described.¶ The third chapter will detail the design and construction of the new spin polarised electron source. The results of commissioning and characterizing the new source will be presented.¶ Chapters four through six will present the measured results. The fourth chapter will detail the single crystalline measurements for the group eleven noble metals (Cu, Ag and Au). Each sample was measured along three high symmetry directions and compared to a DFT calculation using the LDA and a FP-LMTO basis. The fifth chapter will include the results from samples that were in disordered states, a measurement which is unique to the EMS technique. The polycrystalline and amorphous states of the Si and Ge semiconductors are presented and conclusions are made to the degree of difference in the results and to which theoretical approach to the unique amorphous state of the semiconductors best matches the EMS results. The sixth chapter includes results of ferromagnetic iron, measured using the spin polarised electron source. The spectrometer was used to measure spin-polarised electron-energy-loss-spectroscopy (SPEELS) and magnetic electron-Compton profiles. A theoretical investigation is also presented in chapter six which details the advancements required in the spin polarised electron gun to measure an accurate spin-polarised EMS spectra of a ferromagnetic Fe sample.¶ Chapter 7 includes the summary of all the results presented and conclusions reached from the comparison of the measured EMS spectra and various theoretical calculations. A discussion is presented about the future directions and possibilities of the EMS technique.

Ces travaux contribuent à l'amélioration du procédé de synthèse de dispositifs photovoltaïques en couches minces à base d'alliage Cu(In, Ga)(S, Se)2. Dans cette étude, l'étape d'électrodépôt de Cu-In-Se a été étudiée. Le principal enjeux de cette thèse était l'optimisation de la distribution de courant pendant le procédé d'électrodépôt. La distribution de courant, principalement contrôlée par les conditions hydrodynamiques, est optimisée pour deux types d'électrolyseurs : l'électrolyseur à peigne, qui est le système d'agitation standard à l'IRDEP, et un électrolyseur alternatif à jets. Pour l'optimisation des conditions d'agitations, un système électrochimique (Cu-Ni) a été développé et utilisé pour modéliser les phénomènes de transport de matière pendant le procédé d'électrodépôt de Cu-In-Se. Pour les deux systèmes, l'effet de la variation des paramètres géométriques des électrolyseurs a été étudié, et un paramètre de contrôle a été développé. Le contrôle des conditions hydrodynamiques par le biais de ce paramètre permet d'augmenter l'homogénéité des électrodépôts.

Les techniques d'élaboration par déformation plastique intense permettent d'obtenir des matériaux nanostructurés à l'état massif. La grande quantité de défauts (dislocations, lacunes,...) peut donner lieur à des transformations de phases hors équilibre. L'objectif de ce travail à été de produire par HPT (high pressure torsion) une solution solide hors équilibre à partir du système modèle Cu-Fe et de comprendre les mécanismes physiques à l'origine de sa formation. Le matériau initial est un nanocomposite filamentaire Cu-cfc/Fe-α. Des tranches de ce composite ont été déformées par HPT pour une large gamme de taux de déformation. Le matériau obtenu a été caractérisé par DRX, spectroscopie Mössbauer, MET et sonde atomique tomographique. Les filaments de ferrite sont dans une premier temps amincis jusqu'à environ 5nm. Le mélange forcé commence alors par diffusion de Fe dans Cu-cfc pour enfin aboutir à une solution solide homogène de Fe dans Cu-cfc. A la vue des données, les dislocations et le cisaillement répété des interfaces ne peuvent pas expliquer la formation du mélange forcé. Celle-ci est attribuée à la diffusion accélérée par les lacunes en excès.

<p>In this thesis the magnetic and structural properties of ultra-thin 3d transition metals films have been investigated, in particular Fe, Ni and Co films. X-ray Magnetic Circular Dichroism (XMCD) has provided element specific spin (m_s ) and orbital (m_l ) moments per atom by utilizing the magneto optic sum-rules. Element specific hysteresis curves have been measured by means of X-ray Resonant Magnetic Scattering (XRMS), and the local crystallographic structure has been investigated using Extended X-ray Absorption Fine Structure (EXAFS). </p><p>By performing XMCD on Fe/Ag(100) we observe a spin reorientation from in-plane to out-of-plane as the Fe thickness is lowered. At temperatures below 300K it occurs around 5-7 mono layers (ML) of Fe. While reorienting the magnetization out-of-plane the orbital moment increases with 125% but only a minor increase (5%) of the spin moment is observed. Extended X-ray Absorption Fine Structure (EXAFS) measurements indicate that films 6 ML and thicker have a bulk-like bcc structure. For the thin out-of-plane films, the local crystallographic structure is more complicated. </p><p>The spin reorientation of the Au/Co/Au tri-layer system has been studied as a function of temperature, Co layer and Au cap thickness. An unexpected behavior of the orbital moment upon spin reorientation is found in these systems. An ex-situ prepared sample shows a smooth spin reorientation from an in-plane to an out-of-plane easy magnetization direction as the temperature is lowered from 300K to 200K. In-situ prepared samples have also been investigated and a novel phase diagram has been identified. The Au/Co interface has been explored during the Au capping by means of photoemission measurements. </p><p>In the bi- and tri-layer system of Fe and Ni we have been able to manipulate the spin reorientation by varying the Fe and Ni thickness. A novel non-collinear interlayer exchange interaction for 3d ferro magnets in direct contact has been discovered for a set of samples. This exchange interaction is found to be strongly dependant on the preparation conditions.</p>

Résumé: Parmi les aspects les plus passionnants de l'étude du développement dans les sociétés modernes on trouve celui de la dimension culturelle de la modernité et, plus spécialement, les différents courants et les propositions élaborées sur le terrain conflictuel des relations interethniques. Historiquement les sociétés latino-américaines ont vécu une relation complexe, tendue et irrésolue à l'égard de leurs populations indigènes. D'innombrables courants idéologiques et politiques se sont succédé à travers le temps sans résoudre cette tension, résultat de l'intégration de différentes cultures dans un projet de développement social commun. Même en tenant compte de la grande variété des réalités sociales, démographiques, économiques et politiques que la population indigène a expérimentées dans cette région, l'on constate une sorte de résurgence générale de l'identité indigène dans le milieu urbain, ce qui est mis en évidence tant au travers de données de type quantitatif que qualitatif. Ce processus de ré articulation indigène dans la ville a stimulé un nouveau débat ainsi qu'une série de questionnements à l'égard des processus identitaires émergeant au sein de ces sociétés. Partant de cette constatation empirique, ce travail a été orienté vers la recherche de certaines réponses à ces questions, analysant les éléments théoriques relevant du thème central de cette étude, c'est-à-dire, l'identité ethnique dans le cas des indigènes mapuche du Chili. Resumen: Entre los procesos más interesantes del estudio del desarrollo en las sociedades modernas se encuentra el de la dimension cultural de la modernidad, y más especificamente, el terreno conflictivo de las relaciones inter éntnicas. Históricamente, las sociedades latinoamericanas han vivido una relación compleja, tensa e irresuelta frente a sus poblaciones indígenas. Numerosas corrientes ideológicas y políticas se han sudedido a través del tiempo sin lograr resolver satisfactoriamente dicha tensión, resultado, entre otros factores, de la integración forzada de diferentes culturas en un proyecto de desarrollo social comun. Incluso considerando la gran variedad de realidades sociales, demográficas, económicas y políticas que la población indígena presenta en la región, se puede constatar en el último tiempo una suerte de resurgimiento general de la identidad indígena en el medio urbano, evidenciado tanto por datos cuantitativos, como cualitativos. Partiendo de esta constatación empírica, este documento se orienta a la búsqueda de respuestas a dichos procesos, analizando elementos teóricos relevantes y pertinentes al tema central y profundizando con el estudio de casos propuesto, es decir, la identidad étnica de los indígenas mapuche en Chile. Summary: Among the most interesting processes in developmental studies of modern societies we find the cultural dimension of modernity and, more specifically, the conflictive domain of inter ethnical relations. Latin American societies have historically lived a very complex, tense and unresolved relation with their indigenous peoples. Uncountable ideological and political schools of thought have tried to resolve this tension, consequence of the imposition of a common social project, without success. Even considering the vast variety of social, demographic, economic and political realities the indigenous peoples present in the region, lately a sort of re emergency of the indigenous identity in urban areas has taken place. Starting from this empirical evidence, this document searches for answers to explain such identity processes through a rich articulation between the analysis of relevant theoretic elements and the in-depth study case proposed which is the mapuche indigenous population in Chile.

Dynamic Mechanical Analyzer (DMA) was used to study the frequency dependence of storage and loss modulus of amorphous Pd₄₀Ni₁₀Cu₃₀P₂₀ alloy over a broad frequency range around its glass transition temperature. The amorphous samples were subjected to two testing conditions: constant frequency with continuous heating and isothermal with frequency sweep. The storage modulus E′ exhibited a sigmoidal change from about 90 GPa to a low value of about 0 GPa over the glass transition region. The loss modulus, E″, was characterized by an asymmetrical peak with a smaller slope at the low temperature side than at the high temperature side upon heating. These changes in moduli were associated with mechanical relaxation due to atomic motion. Similar results were also obtained under isothermal condition. The Kohrausch-Williams-Watts function was used to fit the data obtained under the isothermal condition. The peak frequencies obtained were then fitted to the VFT equation and the scaling law equation. / Singapore-MIT Alliance (SMA)

The use of solar cells for energy production has indeed a bright future. Reduction of cost for fabrication along with increased efficiency are key features for a market boom, both achieved as a result of increased knowledge of the technology. Especially the thin film solar cell technology with absorbers made of Cu(In,Ga)Se2 (CIGS) is promising since it has proven high power conversion efficiency in combination with a true potential for low cost fabrication. In this thesis different recipes for fabrication of the Cu(In,Ga)Se2 absorber layer have been studied. The deposition technique used has been co-evaporation from elemental sources. For all depositions the substrate has been heated to a constant temperature of 500 ºC in order for the growing absorber to form a chalcopyrite phase, necessary for the photovoltaic functionality. The selenium has been evaporated such to always be in excess during depositions whereas the metal ratio Cu/(In+Ga) has been varied according to different recipes but always to be less than one at the end of the process. In the work emphasis has been on the radiative properties of the CIGS film during growth. The substrate heater has been temperature controlled to maintain the constant set temperature of the substrate, regardless of varying emitted power caused by changing surface emissivity. Depending on the growth conditions the emissivity of the growing film is changing, leading to a readable variation in the electrical power to the substrate heater. Since the thermal radiation from the substrate during growth has been of central focus, this has been studied in detail. For this reason the substrate has been treated as an optical stack composed of glass/Mo/Cu(In,Ga)Se2/CuxSe which determine the thermally radiated power by its emissivity. An optical model has been adopted to simulate the emissivity of the stack. In order to use the model, the optical constants for Cu(In,Ga)Se2 and CuxSe have been derived for the wavelength interval 2 μm to 20 μm. The simulation of the emissivity of the stack during CIGS growth agreed well with what has been seen for actual growth. Features of the OP-signal could hereby be explained as a result of film thickness of Cu(In,Ga)Se2 and CuxSe respectively. This is an important knowledge for an efficient fabrication in large scale.

No description available.

Processing of nanostructured WC-Co and W-Co powders,modelling of Fe-Mn-Si alloy, swelling of Fe-Cu alloy, andmechanical properties and sintering of Fe-Mn-Si steels havebeen studied in the present thesis. W-Co precursors made by chemical synthesis were used toproduce nanostructured WCCo and W-Co powders by calcination,reduction and carburization. The phase constituents in thecalcined powders depend on temperature and atmospheres. Cobaltcan accelerate the reduction rate of the W-Co precursors as acatalyst, and cobalt influences the formation of intermediatephases during the reduction of the precursors. The ratio of carbon monoxide to carbon dioxide controlscarburization process, gives different intermediate phases andcarburization rates. There exist several intermediate phases: W6Co6C, W3Co3C, W2C due to varying carbon monoxide content in thecarburization gases. Nanostructured WC-Co powders with aparticle size of 20-50 nm have been obtained. The effect of silicon content on the particle sizedistribution of milled Fe-Mn-Si master alloy powders is muchmore significant than that of manganese content. A finer finalparticle size can be obtained in the alloy powders with highersilicon compositions. Long time milling results in theagglomeration of small particles. The grinding process can bedescribed using classic batch grinding equation based on thepopulation balance model. A swelling model for Fe-Cu alloyssintered at the temperatures above the melting point of copperhas been established based on the penetration mechanism. In themodel, the particle coordination number and heating rate wereused to express the porosity and the thickness of the diffusionlayers between iron and copper particles respectively. The effects of sintering temperature and time on theproperties of sintered steels have been studied. Fe-Mn-Simaster alloys made by cast-milling, atomizing, and acombination of atomization and milling have been covered. Themilled, and atomizationmilled alloy steels showed goodmechanical properties with small dimensional change. Transientliquid phase of the Fe-Mn-Si alloys accelerates densification,and offer fast diffusion of alloying elements. The addition ofa small amount of Fe-Mn-Si master alloy to Astaloy 85Mo powdercan lead to high strength with zero dimensional change. <b>Key words:</b>Processing; Modelling; Nanostructured powder;WC-Co; W-Co; Calcination; Reduction; Carburization; Particlesize; Sintered steel; Fe-Cu alloy; Swelling; Fe-Mn-Si masteralloy; Mechanical properties; Sintering parameters.