Les boites quantiques de semiconducteurs représentent une voie attractive pour la réalisation de sources de photon efficaces pour le transfert quantique de l’information, avec un fort potentiel de miniaturisation et d’intégration. Dans ce travail, les paires de photons intriqués sont générées via le déclin radiatif de bi-excitons, à partir de boite quantiques d’InAs auto-assemblées placé dans une jonction p-i-n. Dans une première série d’expérience d’interférence à deux photons, nous avons démontré des corrélations de polarisation non classiques et la capacité de deux photons à interférer. L’intrication a été démontrée avec une fidélité de 0.87±0.04, et une visibilité des interférences de 0.60±0.05. Nous avons ensuite réalisé le premier téléporteur injecté électriquement dans un circuit à fibre monomode. Une fidélité moyenne de 0.704±0.016 a été mesurée pour 6 états distribués symétriquement sur la sphère de Poincaré, ce qui supérieur à la limite classique de 2/3 et prouve la téléportation. Un dispositif modifié de téléportation permettant d’injecter des photons à partir d’un laser continu indépendant a été développé. L’interférence à deux photons entre sources différentes a été démontrée et des battements quantiques observés. La téléportation quantique des états de polarisation portés par les photons a été obtenue avec une fidélité moyenne 0.76±0.012. Le contrôle du spin des charges confinés dans les nanostructures tels que les boites quantiques requiert une compréhension profonde de la physique des matériaux constituant, y compris au niveau nucléaire. Ainsi, nous avons démontré le contrôle électrique de l’interaction hyperfine entre les spins électroniques et nucléaires en utilisant un composant à charge ajustable. La modélisation suggère que le mécanisme est contrôlé par le temps de corrélation hyperfine de l’électron et le temps de dépolarisation du noyau. / Semiconductor quantum dots offer an attractive route towards efficient and high-quality photon sources for optical quantum information applications, with potential for miniaturization and integration on chip. Here, entangled photon pairs are generated in the biexcitonic radiative cascade resulting from electrical excitation of InAs self-assembled quantum dots placed in a p-i-n diode. In a first set of experiments the non-classical polarisation correlations and the ability to interfere the photons in two-photon interference experiments was verified, finding entanglement fidelities of up to 0.87±0.04 and interference visibilities up to 0.60±0.05. Encouraged by the two-photon interference experiments, the first directly electrically driven teleporter was implemented in a single-mode fibre circuit. An average fidelity of 0.704±0.016 was achieved for six states symmetrically distributed on the Poincaré sphere, beating the classical limit of 2/3 and proving that quantum teleportation is taking place. A modified teleportation setup allowed for the accommodation of input photons from an independent CW laser. Two-photon interference between the dissimilar light sources was demonstrated and quantum beats could be observed. Quantum teleportation of polarisation states carried by laser photons was then performed with average fidelity 0.76±0.012. Controlling confined charge carriers in nano-scale systems such as quantum dots requires a deep understanding of the underlying material physics, even on the nuclear level. Voltage control of electron-nuclear hyperfine spin interactions was demonstrated using a charge-tuneable device. Modelling suggests that the mechanism is controlled mainly via the electron hyperfine correlation time and the nuclear depolarisation time.

No description available.

This thesis deals with the main aspects in chemical vapordeposition (CVD) of silicon (Si) and silicon-germanium (Si1-xGex) films for high-speed bipolar transistors.In situdoping of polycrystalline silicon (poly-Si)using phosphine (PH3) and disilane (Si2H6) in a low-pressure CVD reactor was investigated toestablish a poly-Si emitter fabrication process. The growthkinetics and P incorporation was studied for amorphous Si filmgrowth. Hydrogen (H) incorporated in the as-deposited films wasrelated to growth kinetics and the energy for H2desorption was extracted. Film properties such asresistivity, mobility, carrier concentration and grain growthwere studied after crystallization using either furnaceannealing or rapid thermal annealing (RTA). In order tointegrate an epitaxial base, non-selective epitaxial growth(NSEG) of Si and SiGe in a lamp-heated single-waferreduced-pressure CVD reactor was examined. The growth kineticsfor Si epitaxy and poly-Si deposition showed a differentdependence on the deposition conditions i.e. temperature andpressure. The growth rate difference was mainly due to growthkinetics rather than wafer surface emissivity effects. However,it was observed that the growth rate for Si epitaxy and poly-Sideposition was varying during growth and the time-dependencewas attributed to wafer surface emissivity variations. A modelto describe the emissivity effects was established, taking intoconsideration kinetics and the reactor heating mechanisms suchas heat absorption, emission andconduction. Growth ratevariations in opening of different sizes (local loading) andfor different oxide surface coverage (global loading) wereinvestigated. No local loading effects were observed, whileglobal loading effects were attributed to chemical as well astemperature effects. Finally, misfit dislocations formed in theSiGe epitaxy during NSEG were found to originate from theinterface between the epitaxial and polycrystalline regions.The dislocations tended to propagate across the activearea. <b>Keywords:</b>chemical vapor deposition (CVD), bipolarjunction transistor (BJT), heterojunction bipolar transistor(HBT), silicon-germanium (SiGe), epitaxy, poly-Si emitter,in situdoping, non-selective epitaxy (NSEG), loadingeffect, emissivity effect

In this thesis, new methods that address some current limitations in nanoelectrospray mass spectrometry (nESI-MS) analysis are presented. One of the major objectives is the potential gain in sensitivity that can be obtained when employing the proposed techniques. In the first part of this thesis, a new emitter, based on the generation of electrospray from a spray orifice with variable size, is presented. Electrospray is generated from an open gap between the edges of two individually mounted, pointed tips. The fabrication and evaluation of two different types of such emitters is presented; an ESI emitter fabricated from polyethylene terephtalate (Paper I), and a high-precision silicon device (Paper II). Both emitters were surface-treated in a selective way for an improved wetting of the gap and to confine the sample solution into the gap. In the second part of this thesis, different methods for improved sensitivity of nESI-MS analysis have been developed. In Paper III, a method for nESI-MS analysis from discrete sample volumes down to 1.5 nL is presented, using commercially available nESI needles. When analyzing attomole amounts of analyte in such a small volume of sample, an increased sensitivity was obtained, compared to when analyzing equal amounts in conventional nESI-MS analysis. To be able to analyze smaller sample volumes, needles with a narrower orifice and a higher flow resistance were needed. This triggered the development of a new method for fabrication of fused silica nESI needles (Paper IV). The fabrication is based on melting of a fused silica capillary by means of a rotating plasma, prior to pulling the capillary into a fine tip. Using the described technique, needles with sub-micrometer orifices could be fabricated. Such needles enabled the analysis of sample volumes down to 275 pL, and a further improvement of the sensitivity was obtained. In a final project (Paper V), nESI-MS was used to study the aggregation behavior of Aβ peptides, related to Alzheimer’s disease. An immunoprecipitation followed by nESI-MS was employed. This technique was also utilized to study the selectivity of the antibodies utilized. / QC 20101112

No description available.

<p>This thesis deals with the main aspects in chemical vapordeposition (CVD) of silicon (Si) and silicon-germanium (Si_1-xGe_x) films for high-speed bipolar transistors.<i>In situ</i>doping of polycrystalline silicon (poly-Si)using phosphine (PH₃) and disilane (Si₂H₆) in a low-pressure CVD reactor was investigated toestablish a poly-Si emitter fabrication process. The growthkinetics and P incorporation was studied for amorphous Si filmgrowth. Hydrogen (H) incorporated in the as-deposited films wasrelated to growth kinetics and the energy for H₂desorption was extracted. Film properties such asresistivity, mobility, carrier concentration and grain growthwere studied after crystallization using either furnaceannealing or rapid thermal annealing (RTA). In order tointegrate an epitaxial base, non-selective epitaxial growth(NSEG) of Si and SiGe in a lamp-heated single-waferreduced-pressure CVD reactor was examined. The growth kineticsfor Si epitaxy and poly-Si deposition showed a differentdependence on the deposition conditions i.e. temperature andpressure. The growth rate difference was mainly due to growthkinetics rather than wafer surface emissivity effects. However,it was observed that the growth rate for Si epitaxy and poly-Sideposition was varying during growth and the time-dependencewas attributed to wafer surface emissivity variations. A modelto describe the emissivity effects was established, taking intoconsideration kinetics and the reactor heating mechanisms suchas heat absorption, emission andconduction. Growth ratevariations in opening of different sizes (local loading) andfor different oxide surface coverage (global loading) wereinvestigated. No local loading effects were observed, whileglobal loading effects were attributed to chemical as well astemperature effects. Finally, misfit dislocations formed in theSiGe epitaxy during NSEG were found to originate from theinterface between the epitaxial and polycrystalline regions.The dislocations tended to propagate across the activearea.</p><p><b>Keywords:</b>chemical vapor deposition (CVD), bipolarjunction transistor (BJT), heterojunction bipolar transistor(HBT), silicon-germanium (SiGe), epitaxy, poly-Si emitter,<i>in situ</i>doping, non-selective epitaxy (NSEG), loadingeffect, emissivity effect</p>

We have advanced the state-of-the-art for nano-fabrication of carbon nanotube (CNT) based field emission devices, and have conducted experimental and theoretical investigations to better understand the reasons for the high reduced brightness achieved. We have demonstrated that once the CNT emitter failure modes are better understood and resolved, such CNT emitters can easily reach reduced brightness on the order of 10⁹ A m⁻² sr⁻¹ V⁻¹ and noise levels of about 1%. These results are about 10% better than the best brightness results from a nanotip emitter archived to date. Our CNT emitters have order of magnitude better reduced brightness than state-of-the-art commercial Schottky emitters. Our analytical models of field emission matched our experimental results well. The CNT emitter was utilized in a modified commercial scanning electron microscope (SEM) and briefly operated to image a sample. We also report a successful emission from a lateral CNT emitter element having a single suspended CNT, where the electron emission is from the CNT sidewall. The lateral CNT emitters have reduced brightness on the order of 10⁸ A m⁻² sr⁻¹ V⁻¹, about 10X less than the vertical CNT emitters we fabricated and analyzed. The characteristics of the lateral field emitter were analyzed for manually fabricated and directly grown CNT emitters. There was no significant difference in performance based on the way the CNT emitter was fabricated. We showed that the fabrication technique for making a single CNT emitter element can be scaled to an array of elements, with potential density of 10⁶-10⁷ CNT emitters per cm². We also report a new localized, site selective technique for editing carbon nanotubes using water vapor and a focused electron beam. We have demonstrated the use of this technique to cut CNTs to length with 10s of nanometers precision and to etch selected areas from CNTs with 10s of nanometers precision. The use of this technique was demonstrated by editing a lateral CNT emitter. We have conducted investigations to demonstrate the effects of higher local water pressure on the CNT etching efficiency. This was achieved by developing a new method of localized gas delivery with a nano-manipulator. / text

Cette thèse se propose d’étudier les procédés de dopage et de recuit laser comme outils permettant la réalisation de cellules photovoltaïques au silicium cristallin. Des émetteurs dopés ou recuits par laser sont tout d’abord réalisés à l’aide de trois lasers et de différentes sources dopantes. Les lasers utilisés sont un laser vert nanoseconde, un laser excimère et un laser ultraviolet à haute cadence. Comme sources dopantes nous avons utilisé le verre de phosphore, des couches de nitrures de silicium dopées au bore ou au phosphore, ou encore des implantations ioniques de bore ou de phosphore. Des dopages très efficaces sont obtenus avec chaque couple laser/source dopante. En particulier, de faibles valeurs de résistances carrées et de densités de courant de saturation sont obtenues. Ces procédés laser sont ensuite appliqués à la réalisation de cellules à émetteur sélectif et à champ arrière au bore. Les cellules à émetteur sélectif dopé par laser (en utilisant le verre de phosphore comme source dopante) atteignent un rendement de 18,3 %, ce qui représente un gain total de 0,6 %abs comparé aux cellules standard à émetteur homogène. Les cellules à champ arrière au bore recuit par laser (à partir d’une implantation ionique de bore) montrent quant à elles un gain de 0,3 %abs par rapport aux cellules à champ arrière à l’aluminium, offrant ainsi un rendement de 16,7 %. / This study aims at investigating laser doping and laser annealing for crystalline silicon solar cells processing. Laser-processed emitters are firstly realized using three lasers and different dopants sources. The lasers are a nanosecond green laser, an excimer laser and a high-frequency ultraviolet laser. As dopants sources we used either phosphosilicate glass, phosphorus and boron-doped silicon nitrides, or phosphorus and boron ion implantation. Efficient phosphorus and boron doping are obtained using any of these laser/sources couple. In particular, low sheet resistances and low emitter saturation current densities are obtained. These laser processes are then applied to selective emitter and boron back-surface-field solar cells. Laser-doped selective emitter solar cells (using phosphosilicate glass as a dopants source) reach 18.3 % efficiency. This represents an overall gain of 0.6 %abs when compared to standard homogeneous emitter. On the other hand, laserannealed boron back-surface-field solar cells (using implanted boron as a dopants source) feature an overall gain of 0.3 %abs when compared to standard aluminium back-surface-field solar cells, thus yielding an efficiency of 16.7 %.

Le thermo-photovoltaïque (TPV), conversion du rayonnement thermique par des cellules photovoltaïques (PV), est un dispositif qui a suscité un intérêt croissant depuis deux décennies, notamment pour son efficacité supérieure à celle de la conversion photovoltaïque classique. Ceci est essentiellement dû à l'accord entre le spectre du rayonnement de la source thermique et le spectre de conversion de la cellule PV. Les rendements maximaux sont obtenus pour des sources thermiques cohérentes, émettant dans une gamme spectrale étroite, énergétiquement au-dessus de l'énergie de la bande interdite de la cellule PV. On propose dans ce travail d'appliquer une méthode d'optimisation stochastique, en l'occurrence l'optimisation par essaims de particules, pour concevoir et optimiser de telles sources. On aboutit alors à des structures unidimensionnelles simples, à base de films minces de diélectriques, métaux et de semi-conducteurs. Les propriétés radiatives de ces sources, stables pour des températures allant jusqu'à 1000 K, sont aisément contrôlables à l'aide de paramètres simples comme les épaisseurs des films ou la concentration de dopage. Finalement, on propose une étude d'optimisation paramétrique des propriétés optiques des matériaux susceptibles de maximiser l'échange radiatif en champ proche entre deux milieux plans semi-infinis. Cette étude aboutit à un outil pratique, sous forme d'abaques, permettant de guider le choix des matériaux pertinents afin de maximiser les puissances au même temps que l'efficacité des systèmes TPV nanométriques. / Thermo-photovoltaic conversion of thermal radiation is a concept that has been thoroughly investigated during the two last decades because of its high efficiency when compared to classical photovoltaics (PV). These high performances are mainly due to the good-matching between the thermal source radiation spectrum and the PV cell conversion spectrum. Maximal efficiencies areobtained with coherent sources that emit in narrow spectral bands, just above the band gap energy of the cell. In this report, a stochastic method to design and optimize such sources, the particle swarm optimization in this case, is firstly presented. This method leads to simple one-dimensional structures, composed of thin films of dielectrics, metals and semiconductors. The radiativeproperties of these sources are easily tunable with control parameters as simple as films thicknesses and doping concentrations. They are stable at high temperatures up to 1000 K. Second, a parametric optimization study of usual materials optical properties models (Drude and Lorentz) is presented in order to maximize radiative heat transfer between semi-infinite planes separated by nanometric gaps. This leads to a simple tool in the form of abacuses which would guide the choice of relevant materials to maximize the output power of nano thermo-photovoltaic devices.

Cette thèse a pour but d'étudier le dopage par implantation ionique pour la réalisation des différentes zones dopées des cellules solaires en silicium cristallin (émetteur, champ arrière...). L'avantage de l'implantation ionique, par rapport à la diffusion gazeuse, est de pouvoir contrôler le profil des dopants implantés ainsi que de simplifier les procédés de fabrication des cellules. Deux techniques d'implantation ionique ont été utilisées dans ces travaux, l'implantation classique par faisceau d'ions et l'implantation par immersion plasma. Des dopages au phosphore, au bore et à l'arsenic ont été réalisés par cette technique d'implantation avec une activation par recuit thermique. L'importance de la température de recuit, des doses d'implantation et des couches de passivation sur la qualité électrique des jonctions formées a été mise en évidence. Des jonctions à faible courant de saturation ont pu être obtenues pour les différentes sources dopantes. Ces dopages par implantation ont ensuite été appliqués à la réalisation de cellules solaires en silicium sur substrat de type p (avec un émetteur dopé au phosphore) et sur substrat de type n (avec un émetteur dopé au bore et un champ arrière dopé au phosphore). L'utilisation de l'implantation ionique a permis d'atteindre un rendement de 19,1 % sur les cellules de type p soit un gain de 0,6 %abs par rapport au dopage par diffusion gazeuse, ainsi qu'un rendement de 20,2 % sur les cellules de type n. / This study aims at investigating the use of ion implantation doping for the realization of emitters and back surface fields of silicon solar cells. The benefits of using ion implantation instead of high temperature gaseous diffusion are the possibility to precisely control the dopant concentration profiles as well as to simplify the solar cells fabrication process. Beam line ion implantation and plasma immersion ion implantation techniques have been used and compared during this work. Phosphorus, boron and arsenic have been implanted and activated by thermal annealing to form the various doping layers. The influences of the annealing temperature, of the implantation doses and of the passivation layers on the junction electrical quality have been studied. Low emitter saturation current densities were reached for each dopant. The implanted doped regions were then integrated in p-type silicon solar cell structure (including a phosphorus doped emitter) and in n-type PERT bifacial solar cell structure (including a boron doped emitter and a phosphorus doped back surface field). With the use of ion implantation, efficiency of 19,1 % was reached for the p-type solar cells corresponding to an overall gain of 0,6 %abs as compared to the gaseous diffusion doping, while 20,2 % of efficiency were measured on the n-type bifacial silicon solar cells.