This thesis deals with the analysis of nano-structured layers deposited by high-frequency magnetron sputtering on the monocrystalline silicon surface. The content of the work focuses on the magnetron sputtering application as an alternative method for passivation and antireflection layers deposition of silicon solar cells. The procedure of pre-deposite silicon surface cleaning by plasma etching in the Ar/H2 gas mixture atmosphere is suggested. In the next step the silicon nitride and aluminum nitride layers with hydrogen content in Ar/N2/H2 gas mixture by magnetron sputtering are deposited. One part of the thesis describes an experimental pseudo-carbide films deposition from a silicon target in the atmosphere of acetylene (C2H2). An emphasis is placed on the research of sputtered layers properties and on the conditions on the silicon-layer interface with the help of the standard as well as special measurement methods. Sputtered layers structure is analyzed by modern X-ray spectroscopy (XPS) and by Fourier infrared spectroscopy (FTIR). Optical ellipsometry and spectrophotometry is used for the diagnostic of the layers optical properties depending upon the wavelength of incident light. A special method of determining the surface lay-out of the charge´s carrier life in the volume and on the surface of silicon is employed to investigate the passivating effects of the sputtered layers.

Ce travail se place dans le contexte des recherches sur les mémoires quantiques pour la lumière. L’information quantique est stockée dans un état de superposition atomique, dont la durée de vie détermine le temps maximum de stockage.On s’intéresse particulièrement aux matériaux capables de capturer la lumière par excitation résonnante d’une raie d’absorption, puis de conserver l’information quantique dans un état de superposition du fondamental électronique.Dans Tm3+:YAG, l’information est enregistrée dans un état de spin nucléaire. Cependant le champ magnétique qui lève la dégénérescence nucléaire entraîne les différents spins à des vitesses de précession différentes, ce qui tend à détruire l’aimantation initiale, porteuse de l’information.Une étude quantique du cristal est réalisée lors du premier chapitre de ce manuscrit. Les trois chapitres suivants traitent des différents mécanismes conduisant au déphasage des spins nucléaires. On y trouvera différente analyses théoriques qui seront confirmées par un ensemble de résultats expérimentaux, ainsi qu’une description détaillée du dispositif expérimental. Enfin le dernier chapitre, prospectif, exploite les outils développés au cours de la thèse pour préserver les cohérences optiques. Il présente quelques résultats expérimentaux prometteurs sur l’allongement du temps de vie de ces cohérences optiques. / This work takes place in the context of research about quantum memories for light. The quantum information is stored in an atomic superposition state whose lifetime sets the maximum storage time. We are particularly interested in materials which are able to hold the light by resonant excitation of an absorption line, preserving the quantum information in a superposition state of the electronicfundamental.n Tm3+:YAG the information is stored in a nuclear spin state. However, the magnetic field which lifts the nuclear degeneracy generates different precession speeds of the spins. This destroys theinitial magnetization carrier of the information.In the first chapter of this thesis, a quantum analysis of the crystal is done. The following three chapters are devoted to different mechanisms to control the nuclear spins dephasing. There it ispossible to find different theoretical analysis which will be confirmed by a series of experimental measurements, including an extended description of the set-up. Finally, the last chapter presentsthe different techniques used to preserve the optical coherence. Promising experimental measurements are presented to extend the life time of the optical coherences.

Les outillages de mise en forme à chaud sont soumis à des sollicitations thermomécaniques transitoires. Ils sont donc confrontés à la fissuration par fatigue. Le but de ce travail est d'étudier le comportement et la durée de vie en fatigue des aciers d'outillage, notamment leurs résistances à la propagation de fissure. Dans un premier temps, les chargements thermiques imposés aux outillages de fonderie sous pression de magnésium et d'emboutissage à chaud ont été évalués. Ensuite, le comportement et la durée de vie de l'acier à haute conductivité thermique HDC1 ont été étudiés et comparés à l'acier AISI H11 (acier de référence) en fonction de la température. L'acier HDC1 présente un adoucissement cyclique stable à 20°C et 300°C. Par contre, l'intensité d'adoucissement est plus importante à hautes températures. La durée de vie a été étudiée en utilisant les lois de Manson-Coffin et de Basquin. A hautes températures, l'oxydation devient un mécanisme d'endommagement primordial pour l'acier HDC1 et provoque des durées de vie plus courtes que celles observées sur l'acier AISI H11. La résistance à la propagation de fissure de fatigue a été déterminée dans des aciers à la température ambiante par le biais de critères : l'amplitude de facteur d'intensité de contrainte (∆K) et l'amplitude d'ouverture en pointe de fissure (∆CTOD). La méthode de corrélation d'images a permis de mesurer (∆COD) et d'évaluer (∆CTOD). L'ensemble de ces résultats a permis de mettre en évidence l'effet de fermeture de fissure et le comportement plastique en pointe de fissure. ∆CTOD présente un bon critère pour rationaliser la propagation de fissure dans les aciers étudiés.Enfin, la simulation numérique de la propagation de fissure en fatigue a été menée dans l'acier AISI H11 à 600°C par la méthode de relâchement des nœuds en éléments finis. L'effet des modèles de comportement monotone (élastoplastique) et cyclique (élastoviscoplastique) a été étudié sur le calcul de l'ouverture de fissure et la plasticité en pointe de fissure. L'influence du modèle de comportement est faible sur le calcul de l'amplitude d'ouverture de fissure ∆COD, du fait d'une plasticité confinée en pointe de fissure. Alors que, le modèle de comportement cyclique est mieux adapté pour décrire la plasticité en pointe de fissure. / Hot metal forming tools are subjected to cyclic thermomechanical loading and damage by complex fatigue/wear/oxidation interactions. Thermal solicitations were measured on high pressure die casting and hot stamping processes. Based on thermal measurements, the isothermal fatigue behaviour and lifetime of a new high conductivity steel HDC1 were investigated at different temperatures and strain amplitude then compared to AISI H11 steel. As AISI H11, continue cyclic softening was observed in HDC1 at all temperatures. The Manson-Coffin and Basquin laws were used for life prediction models under different temperatures. It was observed that the fatigue/oxidation interaction was a principal damage mechanism of the HDC1 steel at high temperature. Fatigue crack propagation in steels was investigated at room temperature in SENT specimens. A digital image correlation technique was used to evaluate crack opening (∆COD) and crack tip opening displacement (∆CTOD) ranges. Crack growth rate were investigated using ∆K (Paris law) and ∆CTOD criteria. It was observed that the cyclic crack tip plasticity control the crack propagation resistance. Crack closure could be evaluated by ∆CTOD.Finite element method by debond technique was used to model the crack propagation of AISI H11 at 600°C using both monotonic elasto-plastic (EP) and cyclic elasto-viscoplastic (EVP) constitutive laws materials. The comparison of ∆COD calculated and measured had shown that monotonic EP and cyclic EVP had no significant effect on the ∆COD, mainly due to the small-scale yielding conditions. It is however observed that the cyclic constitutive law was the best suitable model for the crack tip plasticity effect.

Rieck & Nedelman (1991) propuseram um modelo de regressão log-linear tendo como base a distribuição Birnbaum-Saunders (Birnbaum & Saunders, 1969a). O modelo proposto pelos autores vem sendo bastante explorado e tem se mostrado uma ótima alternativa a outros modelos propostos na literatura, como por exemplo, os modelos de regressão Weibull, gama e lognormal. No entanto, até o presente momento, não existe nenhum estudo tratando de refinamentos para as estatísticas da razão de verossimilhanças e escore nesta classe de modelos de regressão. Assim, um dos objetivos desta tese é obter um fator de correção de Bartlett para a estatística da razão de verossimilhanças e um fator de correção tipo-Bartlett para a estatística escore nesse modelo. Estes ajustes melhoram a aproximação da distribuição nula destas estatísticas pela distribuição qui-quadrado de referência. Adicionalmente, objetiva-se obter ajustes para a estatística da razão de verossimilhanças sinalizada. Tais ajustes melhoram a aproximação desta estatística pela distribuição normal padrão. Recentemente, uma nova estatística de teste foi proposta por Terrell (2002), a qual o autor denomina estatística gradiente. Esta estatística foi derivada a partir da estatística escore e da estatística de Wald modificada (Hayakawa & Puri, 1985). A combinação daquelas duas estatísticas resulta em uma estatística muito simples de ser calculada, não envolvendo, por exemplo, nenhum cálculo matricial como produto e inversa de matrizes. Esta estatística foi recentemente citada por Rao (2005): \"The suggestion by Terrell is attractive as it is simple to compute. It would be of interest to investigate the performance of the [gradient] statistic.\" Caminhando na direção da sugestão de Rao, outro objetivo da tese é obter uma expansão assintótica para a distribuição da estatística gradiente sob uma sequência de alternativas de Pitman convergindo para a hipótese nula a uma taxa de convergência de n^{-1/2} utilizando a metodologia desenvolvida por Peers (1971) e Hayakawa (1975). Em particular, mostramos que, até ordem n^{-1/2}, a estatística gradiente segue distribuição qui-quadrado central sob a hipótese nula e distribuição qui-quadrado não central sob a hipótese alternativa. Também temos como objetivo comparar o poder local deste teste com o poder local dos testes da razão de verossimilhanças, de Wald e escore. Finalmente, aplicaremos a expansão assintótica derivada na tese em algumas classes particulares de modelos. / The Birnbaum-Saunders regression model is commonly used in reliability studies.We address the issue of performing inference in this class of models when the number of observations is small. Our simulation results suggest that the likelihood ratio and score tests tend to be liberal when the sample size is small. We derive Bartlett and Bartlett-type correction factors which reduce the size distortion of the tests. Additionally, we also consider modified signed log-likelihood ratio statistics in this class of models. Finally, the asymptotic expansion of the distribution of the gradient test statistic is derived for a composite hypothesis under a sequence of Pitman alternative hypotheses converging to the null hypothesis at rate n^{-1/2}, n being the sample size. Comparisons of the local powers of the gradient, likelihood ratio, Wald and score tests reveal no uniform superiority property.

Während über hexagonales (alpha) GaN zum ersten Mal 1932 berichtet wurde, gelang erst 1989 die Synthese einer mit Molekularstrahlepitaxie (MBE) auf 3C-SiC epitaktisch gewachsenen, metastabilen kubischen (eta) GaN Schicht. Die vorliegende Arbeit befaßt sich mit der Herstellung der Verbindungen eta-(In,Ga,Al)N mittels RF-Plasma unterstützter MBE auf GaAs(001) und den mikrostrukturellen sowie optischen Eigenschaften dieses neuartigen Materialsystems. Im Vergleich zur hexagonalen bietet die kubische Kristallstruktur auf Grund ihrer höheren Symmetrie potentielle Vorteile für die Anwendung in optischen und elektronischen Bauelementen. Viele wichtige Materialgrößen der kubischen Nitride sind jedoch noch gänzlich unbekannt, da sich die Synthese einkristalliner Schichten als sehr schwierig erweist. Das Ziel dieser Arbeit ist es daher erstens, die technologischen Grenzen der Herstellung von bauelementrelevanten kubischen (In,Ga,Al)N Heterostrukturen auszuweiten und zweitens, einen Beitrag zur Aufklärung der bis dato wenig bekannten optischen und elektronischen Eigenschaften des GaN und der Mischkristalle In GaN zu leisten. Zunächst wird ein optimierter MBE Prozess unter Einsatz einer Plasmaquelle hohen Stickstofflusses vorgestellt, welcher nicht nur die reproduzierbare Epitaxie glatter, einphasiger GaN Nukleationsschichten auf GaAs ermöglicht. Vielmehr können damit auch dicke GaN. Schichten mit glatter Oberflächenmorphologie hergestellt werden, welche die Grundlage komplizierterer eta-(In,Ga,Al)N Strukturen bilden. An einer solchen GaN Schicht mit einer mittleren Rauhigkeit von nur 1.5 nm werden dann temperaturabhängige Reflexions- und Transmissionsmessungen durchgeführt. Zur Auswertung der Daten wird ein numerisches Verfahren entwickelt, welches die Berechnung des kompletten Satzes von optischen Konstanten im Spektralgebiet 2.0 = 0.4 wären grün-gelbe Laserdioden. Zusammenfassung in PostScript / While the earliest report on wurtzite (alpha) GaN dates back to 1932, it was not until 1989 that the first epitaxial layer of metastable zincblende (eta) GaN has been synthesized by molecular beam epitaxy (MBE) on a 3C-SiC substrate. The present work focuses on radio frequency (RF) plasma-assisted MBE growth, microstructure, and optical properties of the eta-(In,Ga,Al)N material system on GaAs(001). Due to their higher crystal symmetry, these cubic nitrides are expected to be intrinsically superior for (opto-) electronic applications than the widely employed wurtzite counterparts. Owing to the difficulties of obtaining single-phase crystals, many important material constants are essentially unknown for the cubic nitrides. The aim of this work is therefore, first, to push the technological limits of synthesizing device-relevant zincblende (In,Ga,Al)N heterostructures and, second, to determine the basic optical and electronic properties of GaN as well as to investigate the hardly explored alloy InGaN. An optimized MBE growth process is presented which allows not only the reproducible nucleation of smooth, monocrystalline GaN layers on GaAs using a high-nitrogen-flow RF plasma source. In particular, thick single-phase GaN layers with smooth surface morphology are obtained being a prerequisite for the synthesis of ternary eta-(Ga,In,Al)N structures. Temperature dependent reflectance and transmittance measurements are carried out on such a GaN film having a RMS surface roughness as little as 1.5 nm. A numerical method is developed which allows to extract from these data the complete set of optical constants for photon energies covering the transparent as well as the strongly absorbing spectral range (2.0 -- 3.8 eV). Inhomogeneities in the refractive index leading to finite coherence effects are quantitatively analyzed by means of Monte Carlo simulations. The fundamental band gap EG(T) of GaN is determined for 5 < T < 300 K and the room temperature density of states is investigated. Systematic studies of the band edge photoluminescence (PL) in terms of transition energies, lineshapes, linewidths, and intensities are carried out for both alpha- and GaN as a function of temperature. Average phonon energies and coupling constants, activation energies for thermal broadening and quenching are determined. Excitation density dependent PL measurements are carried out for both phases in order to study the impact of nonradiative recombination processes at 300 K. A recombination model is applied to estimate the internal quantum efficiency, the (non)radiative lifetimes, as well as the ratio of the electron to hole capture coefficients for both polytypes. It is seen that the dominant nonradiative centers in the n-type material investigated act as hole traps which, however, can be saturated at already modest carrier injection rates. In summary, despite large defect densities in GaN due to highly mismatched heteroepitaxy on GaAs, band edge luminescence is observed up to 500 K with intensities comparable to those of state-of-the-art alpha-GaN. For the first time, thick InGaN films are fabricated on which blue and green luminescence can be observed up to 400 K for x=0.17 and x=0.4, respectively. Apart from bulk-like InGaN films, the first coherently strained InGaN/GaN (multi) quantum wells with In contents as high as 50 % and abrupt interfaces are grown. This achievement shows that a ternary alloy can be synthesized in a metastable crystal structure far beyond the miscibility limit of its binary constituents despite the handicap of highly lattice mismatched heteroepitaxy. The well widths of these structures range between 4 and 7 nm and are thus beyond the theoretically expected critical thickness for the strain values observed. It is to be expected that even higher In contents can be reached for film thicknesses below 5 nm. The potential application of such InGaN/GaN multi quantum wells with x >= 0.4 would thus be diode lasers operating in the green-yellow range. abstract in PostScript

Elektrische und magnetische Emitter können zur Erforschung unterschiedlicher plasmonischer Nanostrukturen genutzt werden. Indem wir die Änderung der Abstrahldynamik und in der Lebensdauer bestimmen, detektieren wir die photonische lokale Zustandsdichte. Diese Zustandsdichte, die eine Eigenschaft der Umgebung ist, ermöglicht uns nicht nur Rückschlüsse auf die elektronischen und andere physikalische Eigenschaften dieser zu treffen sondern auch die allgemeinen Eigenschaften der plasmonischen Nanostruktur im Bezug auf Licht-Materie Kopplung zu bestimmen. Eine starke Licht-Materie-Kopplung ist für die zukünftige Anwendung im Bereich der Quantentechnologien wichtig. Wenn Emitter hierbei mit plasmonischen Nanostrukturen koppeln, fokussieren letztere nicht nur das emittierte Lichts an der Oberfläche im Subwellenlängenbereich sondern ermöglichen durch die Feldüberhöhung an der Oberfläche auch eine starke Licht-Materie-Kopplung. In der Arbeit konzentrieren wir uns auf zwei grundlegend unterschiedliche plasmonische Systeme: zunächst untersuchen wir analytisch den Einfluss von Graphen auf elektrische und magnetische Emitter und diskutieren dann die Lebensdaueränderungen und Strahlungsdynamiken in der Nähe von Silber- und Goldnanostrukturen. Im ersten Teil der Arbeit analysieren wir den Einfluss von Graphen mit einer Bandlücke auf den Emitter und zeigen Möglichkeiten zur experimentellen Bestimmung der Bandlücke auf. Im zweiten Teil modellieren wir die Propagation elektromagnetischer Felder im dreidimensionalen Raum mit Hilfe der Diskontinuierlichen Galerkin Zeitraum Methode mit erweiterten Funktionalitäten. Diese verwenden wir sowohl zur theoretischen Modellierung des ersten dreidimensionalen Fluoreszenlebensdauerabbildungsmikroskopie mit einem einzelnen Quantenemitter als auch zur selbstkonsistent Beschreibung von Emittern in der Nähe eines Goldpentamers. Die Kombination der Studien betont die Stärke von Emittern elektrische, optische und magnetische Eigenschaften zu detektieren. / Electric and magnetic emitters can be used to probe different plasmonic nanostructures. By determining the modification of the radiation dynamics and the lifetimes, we can measure the photonic local density of states. This, being a property of the enviroment, does not only allow us to draw conclusions regarding the electronic and other physical properties of the latter but also regarding the general light-matter coupling properties of the plasmonic nanostructure. A strong light-matter coupling is important for future applications in quantum technology. If emitters couple specifically to plasmonic nanostructure, the latter do not only focus the emitted light at the sub-wavelength scale at the surface of the structure but also allow for such a strong light-matter coupling due to the field enhancement at the surface. In this work, we focus on two different basic plasmonic systems: first, we study analytically the influence of graphene on electric and magnetic emitters, and second we discuss lifetime modifications and radiation dynamics close to silver and gold nanostructures. In the first part of this work, we specifically focus on the influence of graphene exhibiting a finite band gap on the emitter. In the second part, we model the propagation of electromagnetic fields in three-dimensional space making use of the discontinuous Galerkin time-domain method with extended functionalities. This framework we apply to model the first three-dimensional scanning-probe fluorescence-lifetime imaging microscopy by use of a single quantum-emitter as well as for a self-consistent description of emitters in the proximity of a gold pentamer. The combination of these studies stress that the strength of emitters lies in the detection of electronic, optical and magnetic properties.

O trabalho realizado nesta tese esteve apoiado em dois objetivos principais. O primeiro centrado na otimização das etapas e processos de fabricação de células solares de silício de alto rendimento envolvendo redução de custos. O segundo objetivo foi direcionado na implementação de células solares eficientes e não dependentes do armadilhamento de impurezas através da difusão de alumínio. Para levar a cabo estes objetivos de forma planejada, o trabalho dividiu-se em otimizações teóricas e implementações experimentais. As otimizações teóricas foram realizadas utilizando dois programas: um programa desenvolvido (simulacell.pas) e implementado no próprio LME (versão 2), e o outro adquirido comercialmente, PC1D. De acordo com os resultados obtidos em estruturas completas n+p e n++n+p foi possível concluir que tanto as estruturas formadas através de emissores homogêneos como as obtidas utilizando emissores duplamente difundidos permitem alcançar eficiências elevadas, 25,5% a 26,0%, respectivamente, em um amplo intervalo de espessuras e concentrações superficiais de dopantes. No que tange aos desenvolvimentos experimentais, este trabalho se inicia com o desenvolvimento de um processo simplificado de baixo custo, em células solares de silício Cz de baixa resistividade com estrutura n+pp+, tipo \"mesa\". Este processo simplificado também está baseado na difusão de fósforo e alumínio (P/Al), utilizando gases industriais e reagentes químicos de grau \"para análise\", como uma transposição do processo de fabricação anteriormente desenvolvido no LME-EPUSP em substratos de silício FZ utilizando tecnologia planar. A célula solar mais representativa do processo implementado, A-16-1, permitiu atingir eficiências no entorno de 17%. As implementações experimentais visaram inicialmente o desenvolvimento de um procedimento visando à qualificação de materiais de partida (silício), utilizando a técnica de decaimento fotocondutivo (PCD) através de dois procedimentos de passivação de superfícies; oxidações térmicas e difusões suaves de fósforo. Posteriormente, utilizando o sistema PCD, novas otimizações dos emissores de tipo n+ homogêneos e regiões de tipo p foram realizadas, seguidos por oxidações térmicas passivadoras hidrogenadas, preservando-se o tempo de vida do volume em valores elevados (aproximadamente 1ms, após a realização de todas as etapas térmicas). Estes resultados qualificam o silício e os materiais de consumo utilizados, assim como, o novo processo de fabricação desenvolvido. Esta técnica também permitiu qualificar os emissores com perfil Gaussianos processados, atingindo valores da ordem de 45fA/cm2 para densidades de recombinação em estruturas n+pn+. Desenvolveram-se também estruturas n+p em materiais Cz de baixa resistividade 2-3W.cm de dois diferentes fabricantes, e silício FZ com 0,5W.cm. Pôde ser comprovada a qualidade das etapas que compõem o processo completo otimizado tendo-se obtido tensões de circuito aberto-implícitas de 652,4mV (Si-Cz fabricante 1) e 662,6mV (Si-Cz fabricante 2), e 670,8mV (FZ). De acordo com simulações realizadas utilizando parâmetros habituais de dispositivos do próprio LME, estas tensões, quando associadas a um conjunto óptico frontal típico das células solares de alto rendimento do LME (texturização química aleatória e filme de SiO2), permitirão atingir valores entre 19% - 20%. Entretanto, utilizando texturização e camada dupla torna-se plausível atingir o marco de 21% de rendimento, ultrapassando assim a barreira dos 17% (recorde nacional), e comprovando a potencialidade da infra-estrutura deste laboratório para o desenvolvimento de células solares não dependentes do efeito do armadilhamento de impurezas através da difusão de alumínio. / The work developed at this thesis has been based on two main objectives. First, it was focused on the optimization of the steps and processes for the fabrication of high efficiency solar cells, reducing production costs. The latter objective was directed to develop solar cells that were efficient and non-dependent on impurities gettering performed through the aluminum diffusion. In order to attend the planned objectives the work was divided into the theoretical objectives and experimental developments. The theoretical optimizations were performed using two different program codes: one was developed at LME (simulacell.pas), being upgraded afterwards (version 2); and the other was acquired commercially, the PC1D. According to the obtained results in complete structures n+p and n++n+p, it was possible to conclude that the homogeneous and double diffused emitter structures can provide high efficiencies, from 25,5% to 26,0%, respectively, for a wide range of thicknesses and surface doping levels. Concerning the experimental developments, this work starts with a low cost simplified process, using Cz silicon solar cells with low base resistivity and the structure n+pp+, \"mesa\" type. This simplified process was also based on the phosphorus/ aluminum diffusion (P/Al), using industrial gases and for analysis grade chemical reagents, as a fabrication process transposition of the process previously developed at LME-EPUSP using silicon substrates with planar technology. The most representative solar cells of the implemented process, A-16-1, provided about a 17% efficiency. The experimental implementations aimed the development of procedure for starting material (silicon) qualification, by using the photoconductive decay technique (PCD) with two surface passivation procedures: thermal oxidation and light phosphorus diffusion. Later, using PCD system, new optimizations of n+ homogeneous emitters and p-type region were performed, followed by passivating thermal oxidations with hydrogenation, maintaining the volume lifetime at high values (approximately 1ms, after each thermal step). These results qualified the used silicon and the consumer materials, as well the new fabrication process developed. This technique has also allowed qualifying the processed Gaussian profile emitters, providing values about 45fA/cm2 for the recombination current density in n+pp+ structures. N+p structures were also developed using Cz silicon with low resistivity 2- 3W.cm of two different manufacturers and FZ with 0.5W.cm. It could be proved the quality of the steps of a complete optimized process resulting implicit open circuit voltages of 652.4mV (Cz silicon - manufacturer type 1), 662.6mV (Cz silicon - manufacturer type 2), and 670.8mV (FZ silicon). According to the theoretical simulations performed using the usual parameters of devices processed at LME (random chemical texturization and SiO2 film), efficiencies between 19%-20% can be reached. However, using a random texturization and a double layer anti-reflection system, a 21% efficiency becomes possible, surpassing the 17% barrier (national record), and proving the potentiality of this laboratory facility for the development of solar cells non-dependent on impurity gettering through the aluminum diffusion.

This thesis represents a comprehensive examination of the phonotactic behaviour (i.e. attraction to sound) of the female Gryllus bimaculatus under laboratory conditions. Chapter 2 is the first study to analyze the effect of substrate texture on walking performance in crickets. Substrate texture is found to play an essential role in the phonotactic responses of G. bimaculatus. Smooth substrate texture has a detrimental effect due to slipping, whereas a rough texture results in optimal walking performance due to the friction with the walking legs. Chapter 3 represents the first detailed lifetime study analysing phonotaxis in crickets. My results demonstrate that the optimal age to test phonotaxis in G. bimaculatus females is from day 7 to 24 after the final moult. I also found that selectiveness was persistent with age. These findings contradict the female choosiness hypothesis. This study is also the first to describe the effect of senescence on phonotaxis in insects, as responsiveness decreases with age. Chapter 4 compares the phonotactic behaviour of female crickets from different laboratory-bred colonies. From six tested cricket lab colonies, I found three groups statistically different from each other. Females raised under laboratory conditions at the University of Cambridge and Anglia Ruskin University were most reponsive at a frequency of 4.5 kHz, whereas females bred in Tokushima University in Japan were tuned towards a higher frequency of 5 kHz. These results suggest a degree of artificial allopatric speciation. Comparisons with crickets bred under low-quality conditions in a local pet shop demonstrate a loss of responsiveness, indicating that breeding conditions have a direct effect on phonotactic responsivity. Chapter 5 is the first study to report the presence of phonotaxis in males of G. bimaculatus. Previously it was unknown if G. bimaculatus males were able to perform phonotaxis, given that they were only recognised as endurance signal producers. In the present study, only 20% of the studied males (N=70) performed a weak phonotactic response. This finding has potential ecological implications in terms of male cricket territory establishment, and male-male interactions in the wild, which are discussed. Chapter 6 explores the song pattern recognition of the female G. bimaculatus by changing the duration of either the first, second or third pulse of the chirps. A long first pulse decreased the phonotactic response whereas phonotaxis remained strong when the third pulse was long. Chirps with three pulses of increasing duration of 5, 20 and 50 ms elicited phonotaxis, but the chirps were not attractive when played in reverse order. The data are in agreement with a mechanism in which processing of a sound pulse has an effect on the processing of the subsequent pulse, as outlined in the flow of activity in a delay-line and coincidence-detector circuit.

L'existence de noyaux triaxiaux a fait l'objet d'un débat de longue date. La possibilité de la triaxialité mole et rigide a été proposée très tôt, et de nombreuses études théoriques et expérimentales ont été consacrées à ce phénomène intrigant. Plus récemment, deux marqueurs uniques de la triaxialité dans les noyaux ont été intensivement étudiés : le mouvement d'oscillation de l'axe de rotation (wobbling) et la chiralité dynamique. Ces types exotiques de mouvement ont été observées dans des régions spécifiques du tableau nucléaire : le mouvement d'oscillation dans les noyaux de Lu impair-pair avec A ~ 160, la chiralité principalement dans les noyaux impair-impair et pair-impair avec A ~ 130. Nous avons récemment étudié les noyaux de Nd à très hauts spins et identifié plusieurs bandes, qui ont été interprétées comme la manifestation de divers types de mouvement collectif : rotation suivant un axe incliné, rotation suivant les axes longs et courts, mouvement de wobbling et bandes chirales. Un autre phénomène révélé par nos résultats récents sur les noyaux de Nd avec seulement quelques trous neutroniques par rapport à la fermeture de couche N = 82, est la coexistence de forme. En effet, ces noyaux sont prévus pour avoir des isomères de hauts spins construis sur une forme sphérique, coexistant avec des bandes triaxiales, ou des formes très voire super-déformées . Ma thèse se compose de deux expériences. Tout d'abord, j'ai préparé, exécuté et analysé une expérience réalisée au « Research Center of Nuclear Physics » (RCNP) de l' Université d'Osaka . Cette expérience visait à étudier les isomères de hauts spins et à développer les schémas de niveaux des noyaux de 135La, 136La et 136Ba. Nous avons utilisé un faisceau radioactif de 17N de 80 MeV créé par la réaction directe de 18O sur une cible 9Be et sélectionné à l'aide d'un spectromètre achromatique. Le faisceau radioactif de 17N bombardait une cible de 124Sn de 20 mg/cm2 d'épaisseur pour produire les noyaux d'intérêt par une réaction de fusion-évaporation. Cette thèse présente les résultats obtenus pour le 135La, qui comprennent la construction et la discussion du schéma de niveau et la mesure de la durée de vie de deux isomères connus. La deuxième partie de la thèse consiste en l'analyse de deux expériences différentes réalisée en utilisant la même combinaison de faisceau-cible 48Ca + 96Zr à une énergie légèrement différentes et deux dispositifs expérimentaux différents, EUROBALL et JUROGAM II + RITU + GREAT, pour étudier les isotopes du néodyme de 138Nd à 141Nd. Mon travail a été axé sur les noyaux pair-pair de 138Nd et 140Nd, avec un accent particulier sur le 140Nd. La multitude de bandes de spin élevé observées dans ce noyau sont discutées dans le cadre du modèle « Cranked Nilsson - Strutinsky » (CNS) et du modèle « Tilted Axis Cranking » (TAC). Les bandes de hauts spins observées dans les noyaux de 138-141Nd sont toutes interprétées comme basées sur un minimum d'énergie associé à une déformation triaxiale. Elles représentent donc un fort soutien à l'existence de la forme nucléaire triaxiale stable à hauts spins. L'isomère de haut spin 27– a également été identifié dans le 140Nd qui, combinée avec l'isomère 20+ précédemment connu dans le même noyau va permettre d'extraire pour la première fois une valeur expérimentale de la différence d'énergie entre les orbitales πh11/2 et π(d5/2g7/2) à hauts spins. / The existence of triaxial nuclei has been the subject of a long standing debate. The possibility of soft and rigid triaxiality has been proposed very early, and many theoretical and experimental studies have been devoted to this intriguing phenomenon since then. More recently two unique fingerprints of triaxiality in nuclei have been intensively studied : the wobbling motion and the dynamic chirality. These exotic types of motion were observed in specific regions of the nuclear chart : the wobbling motion in the odd-even Lu nuclei with A ∼ 160, the chirality primarily in the odd-odd and odd-even nuclei with A ∼ 130 nuclei. We have recently studied the Nd nuclei up to very high spins and identified several bands, which were interpreted as the manifestation of various types of collective motion : tilted axis rotation, principal axis rotation along the short and long axes, wobbling motion and chiral bands. Another phenomenon revealed by our recent results on the Nd nuclei with neutron numbers just below the N=82 shell closure, is the shape coexistence. In fact, these nuclei are predicted to have high-spin seniority isomers built on a spherical shape, coexisting with bands built on either triaxial, highly or even superdeformed shapes.My PhD consists of two experiments. Firstly I have prepared, performed and analysed an experiment realized at the Research Center of Nuclear Physics (RCNP) of the Osaka University. This experiment was performed to study the isomeric states and to develop the level schemes of the 135La, 136La and 136Ba nuclei. We have used a radioactive 17N beam of 80 MeV created by the stripping reaction of 18O on a 9Be target and selected using an achromatic spectrometer. The 17N radioactive beam bombarded a 20 mg/cm2 124Sn target to produce the nuclei of interest by a fusion-evaporation reaction. The present thesis presents the results obtained for 135La, which include the construction and discussion of the level scheme and the measurement of the lifetime of two known isomers. The second part of the thesis consists in the analysis of two different experiments performed using the same beam-target combination 48Ca + 96Zr at slightly different beam energies and two different settups, EUROBALL and JUROGAM II + RITU + GREAT, to study the neodymium isotopes from 138Nd to 141Nd. My work was focused on the even-even 138Nd and 140Nd nuclei, with special emphasis on 140Nd, which is discussed in the present thesis. The multitude of high-spin bands observed in this nucleus are discussed in the framework of Cranked Nilsson-Strutinsky (CNS) and Tilted Axis Cranking (TAC) models. The observed high-spin bands in 138−141Nd which are consistently interpreted as based on an energy minimum at triaxial deformation, represent a strong support for the existence of stable triaxial nuclear shapes at high spins. A 27– high-spin isomer has also been identified in 140Nd, which combined with the previous known 20+ isomer in the same nucleus allow to extract for the first time an experimental value for the energy difference between the πh11/2 and π(d5/2g7/2) orbitals at high spins.

The goal of this project is to study novel nanoscale excitation volumes, sensitive enoughto study individual chromophores and go on to study new and exciting self assemblyapproaches to this problem. Small excitation volumes may be engineered using light con-finement inside apertures in metal films. These apertures enhance fluorescence emissionrates, quantum yields, decrease fluorescence quenching, enable higher signal-to-noiseratios and allow higher concentration single chromophore fluorescence, to be studied byrestricting this excitation volume. Excitation volumes are reported on using the chro-mophore's fluorescence by utilising fluorescence correlation spectroscopy, which monitorsfluctuations in fluorescence intensity. From the correlation in time, we can find the res-idence time, the number of chromophores, the volume in which they are diffusing andtherefore the fluorescence emission efficiency. Fluorescence properties are a probe ofthe local environment, a particularly powerful tool due to the high brightness (quantumyield) fluorescent dyes and sensitive photo-detection equipment both of which are readilyavailable, (such as avalanche photodiodes and photomultiplier tubes). Novel materialscombining the properties of conducting and non-conducting materials at scales muchsmaller than the incident wavelength are known as meta-materials. These allow combi-nations of properties not usually possible in natural materials at optical frequencies. Theproperties reported so far include; negative refraction, negative phase velocity, fluorescenceemission enhancement, lensing and therefore light confinement has also been proposed tobe possible. Instead of expensive and slow lithography methods many of these materialsmay be fabricated with self assembly techniques, which are truly nanoscopic and otherwiseinaccessible with even the most sophisticated equipment. It was found that nanoscaled volumes from ZMW and HMMs based on NW arrays wereall inefficient at enhancing fluorescence. The primary cause was the reduced fluorescencelifetime reducing the fluorescence efficiency, which runs contrary to some commentatorsin the literature. NW based lensing was found to possible in the blue region of the opticalspectrum in a HMM, without the background fluorescence normally associated with a PAAtemplate. This was achieved using a pseudo-ordered array of relatively large nanowireswith a period just smaller than lambda / 2 which minimised losses. Nanowires in the traditionalregime lambda / 10 produced significant scattering and lead to diffraction, such that they werewholly unsuitable for an optical lensing application.