Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 87-94). Also available in electronic format on the Internet.

Made available in DSpace on 2014-06-11T19:23:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-24Bitstream added on 2014-06-13T20:50:23Z : No. of bitstreams: 1 santos_jc_me_bauru.pdf: 1909289 bytes, checksum: 46f1166eec4b53fcdc6e5fe6a3b31b70 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Neste trabalho foi realizada a deposição através da técnica de evaporação resistiva, de filmes finos de GaAs (arseneto de gálio) e de Al (alumínio) com posterior oxidação deste último, formando 'Al IND. 2''O IND. 3' (óxido de alumínio ou alumina) e a caracterização dos filmes de GaAs e da heteroestrutura formada por 'Al IND. 2''O IND. 3' e GaAs. A confecção do dispositivo combinando estes compostos serviu para a investigação das características relevantes do sistema para potencial aplicação em transistores. O trabalho compreendeu investigação sobre as condições de deposição, e foram avaliadas principalmente as características elétricas dos filmes produzidos individualmente. Os resultados apresentados incluem: resistividade em função da temperatura, corrente-voltagem em função da temperatura, difração de raios-X e transmitância na região do infravermelho. Para caracterização do desempenho do sistema 'Al IND. 2''O IND. 3'/GaAs, um transistor simples foi construído sob um substrato de vidro borossilicato com uma camada de GaAs e outra de 'Al IND. 2''O IND. 3'. Os contatos de fonte, dreno e gate foram feitos de In. Essa estrutura permite a medida da corrente de fuga e a avaliação de outras características do sistema. Neste dispositivo foram avaliadas as características corrente-voltagem em função da temperatura, e também a interação com luz, já que GaAs, por apresentar gap direto, torna-se atraente para aplicações opto-eletrônicas. Assim medidas de elétricas foto-induzidas foram realizadas com excitação com fontes de luz branca. Com o intuito de se avaliar a qualidade dos filmes de GaAs obtidos pela evaporação resistiva, tanto a caracterização estrutural quando elétrica também foram feitas em filmes finos de GaAs depositados por sputtering, de modo a se ter um padrão de comparação. / In this work, the deposition of GaAs (gallium arsenide) and Al (aluminum) thin films is carried out by the resistive evaporation technique. In the latter case, an oxidation of the film is accomplished, leading to 'Al IND. 2''O IND. 3' (alumina) formation. The characterization of GaAs thin films and the heterostructure formed by 'Al IND. 2''O IND. 3' and GaAs is also carried out. The elaboration of the device combining these compounds allows investigating the relevant characteristics of this system to potential application in transistors. The work evolved investigation on the deposition conditions, and the electrical characteristics of the films were also evaluated separately. Results includes: resistivity as function of temperature, X-ray diffraction and near infrared transmittance. For characterization of the performance of the 'Al IND. 2''O IND. 3'/GaAs system, a simple transistor was built on a borosilicate glass substrate, with a 'Al IND. 2''O IND. 3' layer on top of a GaAs layer. The contacts of source, drain and gate were done using In. This structure allows evaluating the leak current and other characteristics of this system. In this device, it was evaluated the current - voltage characteristics and the interaction with light, because GaAs, due to its direct bandgap, become very attractive for opto-electronic applications. The, the photo-induced electrical measurements were done under excitation with white light. Aiming the evaluation of the quality of films deposited by the resistive evaporation technique, electrical as well as structural characterization were also carried out for GaAs thin films deposited by sputtering, in order to have a comparing parameter.

Ce travail a pour objectif la fabrication, en épitaxie par jets moléculaires, de nanofils coeurcoquilleà base de GaAs et AlGaAs déposés sur des substrats Si(111), en vue de réaliser desréseaux de fils pour de nouvelles cellules solaires, et pour des fils photoniques permettant uneapproche bottom-up d’émetteurs de photons uniques.La première partie de ce travail est une étude systématique des paramètres clés qui contrôlent lacroissance uni-dimensionnelle de fils GaAs élaborés par un mécanisme vapeur-liquide-solideauto-catalysé, à savoir le rapport des flux As/Ga, la température du substrat, et la vitesse decroissance.La seconde partie se concentre sur la croissance et la caractérisation de fils GaAs recouvertsd’une coquille d’alliages AlGaAs (35% Al) afin de s’affranchir des recombinaisons de surface.Ces coquillesde AlGaAs sont fabriquées en conditions riche-As (rapport As/Ga > 10) afin deconsommer les gouttes de catalyseur gallium et de promouvoir une croissance radiale (le taux decroissance maximal axial/radial est égal à 6). Diverses caractérisations optiques sont réalisées àbasse température sur ces ensembles de fils : cathodoluminescence, photoluminescence etspectroscopie résolue en temps. L’intensité de luminescence et la durée de vie des porteursaugmentent fortement avec la présence de la coquille : une épaisseur de 7 nm de cette dernièreest suffisante pour optimiser la passivation des nanofils et supprimer les recombinaisons liéesaux états de surface. Une fine couche extérieure de GaAs est nécessaire pour éviter touteoxydation de la coquille d’alliage AlGaAs.De plus, grâce à des mesures de CL résolues spatialement, les longueurs de diffusion desexcitons dans ces fils ont été obtenues, allant de 0.7 μm à 1.5 μm pour des épaisseurs decoquilles comprises entre 20 et 50 nm. Des valeurs plus petites sont mesurées pour des coquillesplus épaisses, ce qui tend à montrer l’introduction de défauts dans l’alliage qui pourraientlimiter la qualité de l’interface. Le décalage en énergie de l’émission fournit des informationssur la génération de contraintes dans ces fils coeur-coquille et sur le champ piézo-électrique quien découle. / This report focuses on the fabrication of GaAs nanowires and GaAs/AlGaAs core-shellstructures by molecular beam epitaxy, deposited on Si (111) substrates in order to providearrays of wires for innovative solar cells and bottom-up photonic wires for efficient singlephoton emitters.The first part of this work is a systematic study of the key parameters which control the onedimensionalgrowth of bare GaAs NWs with a self-assisted vapor-liquid-solid growth process,namely the As-to-Ga flux ratio, the substrate temperature, and the deposition rate.The second part concentrates on the growth and characterization of GaAs wires covered with ashell of AlGaAs alloy (35 % Al) in order to get rid of the surface recombinations. These shellswere fabricated under As-rich condition with ratio As/Ga >10 in order to consume the Gadropletscompletely and to promote a radial growth. The obtained axial-to-radial growth ratio is6. The optical characterizations on ensemble were carried out at low temperature via thecathodoluminescence (CL), photoluminescence (PL), and time-resolved PL measurements. Theresults show that the lifetime of carriers and luminescence intensity increase significantly withshell coverage. About 7 nm thick shell is enough to optimize the passivation and suppress thesurface state recombination. A thin outer cap of GaAs is required in order to prevent someoxidation of the AlGaAs alloy shell.In addition, the exciton diffusion lengths of these NWs, studied via the spatially resolved CL,are in the range of 0.7 - 1.5 μm for NWs with shell thicknesses between 20 - 50 nm. Thesevalues are smaller for thicker shells due to the defect formation, leading to limit the quality ofcore-shell interface. The shift in optical emission experiments provides the information of thestrain generation of core-shell when we vary the shell thickness. The piezoelectric field wasnoticed in these samples.

Since a decade, spintronics and related physics have attracted considerable attention due to the massive research conducted in these areas. The main reason for growing interest in these fields is the expectation to use the electrons spin instead of or in addition to the charge for the applications in spin-based electronics, quantum information, and quantum computation. A prime concern for these spins to be possible candidates for carrying information is the ability to coherently control them on the time scales much faster than the decoherence times. This thesis reports on the spin dynamics in two-dimensional electron gases hosted in artificially grown III-V semiconductor quantum wells. Here we present a series of experiments utilizing the techniques to optically control the spin polarization triggered by either optical or electrical methods i.e. well known pump-probe technique and current-induced spin polarization. We investigated the spin coherence in high mobility dense two-dimensional electron gas confined in GaAs/AlGaAs double and triple quantum wells, and, it\'s dephasing on the experimental parameters like applied magnetic field, optical power, pump-probe delay and excitation wavelength. We have also studied the large spin relaxation anisotropy and the influence of sample temperature on the long-lived spin coherence in triple quantum well structure. The anisotropy was studied as a function sample temperature, pump-probe delay time, and excitation power, where, the coherent spin dynamics was measured in a broad range of temperature from 5 K up to 250 K using time-resolved Kerr rotation and resonant spin amplification. Additionally, the influence of Al concentration on the spin dynamics of AlGaAs/AlAs QWs was studied. Where, the composition engineering in the studied structures allows tuning of the spin dephasing time and electron g-factor. Finally, we studied the macroscopic transverse drift of long current-induced spin coherence using non-local Kerr rotation measurements, based on the optical resonant amplification of the electrically-induced polarization. Significant spatial variation of the electron g-factor and the coherence times in the nanosecond scale transported away half-millimeter distances in a direction transverse to the applied electric field was observed. / Há uma década, a spintrônica e outras áreas relacionadas vêm atraindo considerável atenção, devido a enorme quantidade de pesquisa conduzidas por elas. A principal razão para o crescente interesse neste campo é a expectativa da aplicação do controle do spin do elétron no lugar ou em adição à carga, em dispositivos eletrônicos e informação e computação quânticas. A possibilidade destes spins carregarem informação depende, primeiramente, da habilidade de controlá-los coerentemente, em uma escala de tempo muito mais rápida do que o tempo de decoerência. Esta tese trata da dinâmica de spins em gases de elétrons bidimensionais, em poços quânticos de semicondutores III-V, crescidos artificialmente. Nós apresentamos uma série de experimentos, utilizando técnicas para o controle ótico da polarização de spin, desencadeadas por métodos óticos ou eletrônicos, ou seja, técnicas conhecidas de bombeio e prova e polarização de spin induzida por corrente. Nós investigamos a coerência de spin em gases bidimensionais, confinados em poços quânticos duplos e triplos de GaAs/AlGaAs e a dependência da defasagem com parâmetros experimentais, como campo magnético externo, potência ótica, tempo entre os pulsos de bombeio e prova e comprimento de onda da excitação. Também estudamos a grande anisotropia de relaxação de spin como função da temperatura da amostra, potência de excitação e defasagem entre bombeio e prova, medidos para uma vasta gama de temperatura, entre 5K e 250K, usando Rotação de Kerr com Resolução Temporal (TRKR) e Amplificação Ressonante de Spin (RSA). Além disso estudamos a influência da concentração de Al na dinâmica dos poços de AlGaAs/AlAs, para o qual a engenharia da composição da estrutura permite sintonizar o tempo de defasagem de spin e o fator $ g $ do elétron. Por fim, estudamos a deriva transversal macroscópica da longa coerência de spin induzida por corrente, através de medidas de Rotação de Kerr não-locais, baseadas na amplificação ressonante ótica da polarização eletricamente induzida. Observamos uma variação espacial significante do fator $ g $ e do tempo de vida da coerência, na escala de nanosegundos, deslocada distâncias de meio milímetro na direção transversa ao campo magnético aplicado.

É feito um resumo dos principais modelos criados para se explicar as intrigantes propriedades do centro DX e atualizar o problema. O decaimento da fotocondutividade persistente (PPC) é medido em AlxGa1-x As dopado com Si e se discute a validade dos modelos em função da cinética de captura dos elétrons pelos centros DX. Boa concordância com o modelo de Chadi e Chang é encontrada desde que se postule a existência de um nível doador mais raso. O crescimento por MBE assim como todo o processamento de amostras para os experimentos realizados é descrito sinteticamente. É discutido também o problema dos contatos a baixa temperatura e a possível influência dos centros DX nos desvios do comportamento ôhmico observados. Inclui-se também a descoberta da. fotocondutividade persistente em AlxGa1-xAs dopado com Pb, que também é relacionado à existência dos centros DX. / A short discussion about the main models created to explain the striking properties of the DX center is done in order to bring the problem up-to-date. The decay of persistent photoconductivity is measured and it is analyzed as a function of the kinetics of electron trapping by DX centers in Si-doped AlxGa1-xAs, according to these models. Good agreement with Chadi and Chang\'s model is found as long as we postulate the existence of a shallower donor. The M.B.E. growth as well as the whole sample processing is shortly described. It in siso diacussed the problem of low temperature contacts and the possible influence of DX centers in the deviation from ohmic behavior. Persistent Photoconductivity has been found in Pb-doped AlxGa1-xAs and it is also related to the DX center existence.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / An experimental synovitis model of the radio-carpal joint was induced in 8 male intact ponies with an intra-articular injection of 0.25ml of Freund s complete adjuvant. Four ponies had the affected joint irradiated with a 4J/cm2 of laser in a cranio-caudal direction. The control group received the same technique with the device turned off. The heart rate was lower (p<0.05) in the treated group (37±6.9) than in the control group (41.2±5.7). The carpal angle of maximum flexion was significantly (p <0.05) lower in the treated group (94.4±27.2) than in the control group (125.6±5.3). The results of this study show that treatment with laser of gallium arsenide, in the dose of 4J/cm2, presented analgesic effect and improved joint movement in this model of Freund s adjuvant induced acute synovitis. / Um modelo experimental de sinovite aguda rádio-carpiana foi induzido em oito pôneis machos adultos com uma injeção intra-articular de 0,25 ml de adjuvante completo de Freund para avaliar o efeito da terapia laser nesta lesão. Um grupo (n= 4) teve a articulação afetada tratada com laser de arseneto de gálio na dose diária de 4J/cm2 na incidência crânio-caudal por 15 sessões. O grupo controle (n= 4) não foi tratado. A freqüência cardíaca foi estatisticamente (p<0,05) menor no grupo tratado (37±6,9) do que no grupo controle (41,2±5,7). O ângulo de flexão carpal máximo foi significativamente (p<0,05) menor no grupo tratado (94,4±27,2) do que no grupo controle (125,6±5,3). Os resultados deste estudo mostram que a terapia com laser de arseneto de gálio na dose de 4J/cm2 apresentou efeito analgésico e melhorou a mobilidade do membro afetado pela sinovite aguda induzida por Adjuvante Completo de Freund.

Cette thèse porte sur l'élaboration d'un biocapteur, à bas coût, pour la détection de pathogènes dans les secteurs de l'agroalimentaire et de l'environnement. Le modèle visé est la bactérie Escherichia coli, dont les souches pathogènes sont responsables, chaque année, de plusieurs crises sanitaires. L'utilisation de biocapteurs pour une détection rapide, sensible et sélective de pathogènes répond ainsi aux inquiétudes quant aux risques d'infection pour la population. Le capteur est constitué d'une fine membrane en arsénieure de gallium (GaAs) vibrant sur des modes de cisaillement d'épaisseur générés par champ électrique latéral via ses propriétés piézoélectriques. Nous montrons dans ce travail que la GaAs offre des possibilités de microfabrication, de biofonctionnalisation et de régénération intéressantes pour la conception d'un dispositif à bas coût. Nous avons mis en parallèle deux méthodes d'usinage de membranes minces : par voie chimique et par plasma, avec pour objectif, l'obtention de structures planes et lisse. Nous nous sommes intéressés à la réalisation d'une interface de bioreconnaissance. La caractérisation de celle-ci, par les techniques de spectroscope infrarouge à transformée de Fourier, nous a fait progresser sur a compréhension du phénomène d'auto-assemblage de molécules sur GaAs et nous a permis de développer des interfaces à haute densité. Nous avons étudié sa régénération et la photo-oxydation par UV a démontré un fort potentiel pour des applications de capteurs réutilisables. Enfin à travers des caractérisations électriques du transducteur, nous avons mis en avant l'impact de différents paramètres de l'environnement sur la réponse du dispositif. / This thesis addresses the development of a potentially low cost sensor dedicated for detection of pathogens in food industry processing and environment sectors. Such a sensor could serve detection of Escherichia coli bacteria whose pathogenic strains are the source of foodborne illnesses encountered worldwide every year. Hence, biosensor devices are needed for a rapid, sensitive and selective detection of pathogens to prevent outbreak risks. The design of the sensor consists of a resonant membrane fabricated in gallium arsenide (GaAs) crystal that operates at shear modes of bulk acoustic waves generated by lateral field excitation. In addition to its piezoelectric properties, as shown in this work, fabrication of a GaAs-based biosensor benefits from a well-developed technology of microfabrication and biofunctionalization and the possibility of regeneration that should result in cost savings of used devices. The transducer was fabricated by using typical clean room fabrication techniques. Plasma and wet etching were investigated and compared for achieving thin membranes with high quality surface morphology. Extensive research was carried out by Fourier transform infrared spectroscopy to determine optimum conditions for biofunctionalization of the GaAs surface. This activity allowed to advance the fundamental knowledge of self-assembly formation and, consequently, fabrication of high density biointerfaces. Among different biochip regeneration methods, it has been demonstrated that liquid UV photooxidation has a great potential for re-usable devices. Finally, operation of the transducer device was evaluated in various medium, simulating real conditions for detection.

No description available.

La recherche de biomarqueurs pour le dépistage, le diagnostique ou le traitement de maladie requiert le développement de dispositifs hautement sensibles alliant un faible coût d’analyse, un faible encombrement et une réponse rapide. Dans ce cadre, nous développons un biocapteur acoustique utilisant des ondes de volume pour permettre la détection d’analyte particulière dans un milieu biologique complexe. La géométrie retenue est une membrane résonante à excitation et détection piézoélectriques intégrées vibrant sur un mode de cisaillement d’épaisseur généré par un champ latéral. Le transducteur utilise les propriétés particulières de l’arséniure de gallium pour assurer une détection sensible et sélective, aussi bien grâce à ses propriétés piézoélectriques que ses possibilités de microfabrication ou de biofonctionnalisation. Dans un premier temps, nous avons dimensionné le dispositif et modélisé son comportement. Une sensibilité à un ajout de masse a pu être estimée à environ 0.1 ng.Hz-1. Nous avons ensuite envisagé la microfabrication du capteur en utilisant uniquement des techniques de microfabrication à faible coût (gravure humide et photolithogravure). Ceci a permis d’obtenir des membranes épaisses (50 μm) de géométrie et d’état de surface maitrisés. Nous avons ensuite envisagé la réalisation de la biointerface grâce au développement d’une interface chimique spécifique permettant d’immobiliser covalemment une monocouche dense de protéine à la surface du GaAs. Cette monocouche a été caractérisée par une analyse originale couplant la microscopie à force atomique (AFM) et la spectrométrie de masse MALDI-TOF. Enfin, les interfaces fluidiques et électriques ont été mises au point et ont permis de tester le dispositif par une mesure d’impédance. / The biomarkers detection for screening, diagnosis or treatment of disease requires the development of highly sensitive devices combining low cost of analysis, a small size and quick responses. In this context, we develop a biosensor using bulk acoustic wave to allow the detection of specific analyte in a complex biological medium. The geometry used is a piezoelectric resonant membrane using shear mode vibration excited by lateral field. The transducer uses the specific properties of gallium arsenide to provide a highly sensitive and selective detection thanks to its piezoelectric properties and also its microfabrication or biofonctionnalisation facilities. First, we dimensioned the device and modeled it behavior. A sensitivity to adding mass has been estimated at 0.1 ng.Hz-1. Then, we considered the sensor microfabrication using only low cost process (photolithography and wet etching). Through these processes, we obtained well formed thick membranes (50μm) with specific surface properties and microstructuration. Next, we realize the biointerface through the development of a specific chemical interface in order to immobilize a dense protein monolayer covalently attached to the GaAs surface. This monolayer was characterized by an original analysis coupling the atomic force microscopy and the mass spectroscopy MALDI-TOF. Finally, fluid and electrical interfaces have been developed and we tested the device by impedance measurements

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18780号 / 理博第4038号 / 新制||理||1581(附属図書館) / 31731 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 戸塚 圭介, 教授 川上 則雄, 教授 佐々 真一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM