Alors que nous approchons des nœuds technologiques ultimes dans le domaine de la logique numérique, la réduction de leurs dimensions est d’avantage impactée sur la longueur de leurs contacts plutôt que sur leur grille. Dès lors, il apparait nécessaire de réduire significativement la résistivité de ces contacts afin de ne pas dégrader les performances des futurs nœuds technologiques.Cependant, à cause de l’ancrage du niveau de Fermi, la plupart des métaux utilisés dans la micro-électronique présentent un travail de sortie effectif très éloigné de sa valeur théorique lorsque mis en contact avec du silicium. Prévenant toute modification de la hauteur de barrière Schottky à l’interface, ce phénomène empêche l’optimisation de la résistivité de contact. Afin de l’endiguer, une approche récente consiste à insérer une couche de diélectrique au sein du contact formant ainsi une jonction Métal/Isolant/Semi-conducteur (MIS). Néanmoins, la plupart des études présentées dans l’état de l’art ont été réalisées dans des environnements non-industriels, visant d’avantage à l’obtention de preuves de concept plutôt qu’à l’intégration de contacts MIS dans des produits manufacturés.Ce travail de thèse consiste donc à i) analyser le schéma optimal d’intégration de contacts MIS simultanément sur substrats n et p présentant des concentrations de dopants relativement élevées ; ii) Evaluer l’impact de tels contacts sur les performances des nœuds avancés ; iii) Fabriquer des contacts MIS dans un environnement semi-industriel en utilisant les matériaux conventionnement utilisés en micro-électronique avancée ; iv) Evaluer les propriétés effectives des contacts MIS ainsi fabriqués. / As we reach the ultimately scaled digital logic CMOS nodes, the scaling is more and more reflected on the contact length decrease rather than on that of the gate length in order to preserve well-behaved MOSFET characteristics. As a consequence, meeting the performance requirements for the upcoming devices generations implies to drastically decrease the contact resistivity value.However, due to Fermi level pinning, most of the metals used in the microelectronics today feature an effective metal work function almost independent from their reference value when contacted to silicon. This phenomenon hinders the optimization of the Schottky barrier height at the interface and thus of the contact resistivity. An innovative approach consists in inserting a dielectric layer between the metal and the semiconductor of the contacts thus forming Metal/Insulator/Semiconductor (MIS) junctions. Recently, studies of sub-nanometric TiOx insertions have shown promising results on n-type Si. Nevertheless, most of the studies of the state-of-the-art were performed in a non-industrial environment and were more focused on achieving a proof of concept rather than implementing MIS contacts in existing manufactured products with all their constraints. The work of this thesis consists in i) analyzing the optimal co-integration scheme of MIS contacts on n- and p-type semiconductors presenting relatively high doping concentration; ii) Evaluating the impact of such contacts on advanced MOSFETs nodes; iii) Implementing MIS contacts in a semi-industrial environment using the materials commonly found in advanced microelectronics; iv) Gauging the effective electrical properties of MIS contacts.

A contact structure is a maximally non-integrable hyperplane field $\xi$ on an odd-dimensional manifold $M$. In $3$-dimensional contact geometry, there is a fundamental dichotomy, where a contact structure is either tight or overtwisted. Making use of Giroux's correspondence between contact structures and open books for $3$-dimensional manifolds, Honda, Kazez, and Mat\'{i}c proved that verifying whether a mapping class is right-veering or not gives a way of detecting tightness of the compatible contact structure. As a counter-part to right-veering mapping classes, right-veering closed braids have been studied by Baldwin and others. Ito and Kawamuro have shown how various results on open books can be translated to results on closed braids; introducing the notion of quasi right-veering closed braids to provide a sufficient condition which guarantees tightness. We use the related concept of $P$-bigon right-veeringness for closed braids to show that given a $3$-dimensional contact manifold $(M, \xi)$ supported by an open book $(S, \phi)$, if $L \subset (M, \xi)$ is a non-$P$-bigon right-veering transverse link in pure braid position with respect to $(S, \phi)$, performing $0$-surgery along $L$ produces an overtwisted contact manifold $(M', \xi')$. Furthermore, if we suppose $L \subset (M, \xi)$ is a pure and non-quasi right-veering braid with respect to $(S, \phi)$, performing $p$-surgery along $L$, for $p \geq 0$, gives rise to an open book $(S', \phi')$ which supports an overtwisted contact manifold $(M', \xi')$.

We begin with a rapid introduction to the theory of contact topology, first spending more time than you would probably want on developing the notion of contact manifold before launching right into the thick of the theory. The tools of characteristic foliations and convex surfaces are introduced next, concluding with an overview of Legendrian knots in contact 3-manifolds. Next, we develop a number of lemmas as tools for dealing with characteristic foliations, concluding with some sightseeing with regards to the theory of so-called "movies", allowing a glimpse into the workings of a theorem due to Colin: Two smoothly isotopic embeddings of S^2 into a tight contact 3-manifold inducing the same characteristic foliation are necessarily contact isotopic. We finish with an original observation that Colin’s theorem can be used to replace a key step in Eliashberg and Fraser’s classification of topologically trivial knots, thus providing an alternate proof of that result and thereby highlighting the power of the aforementioned theorem. We provide a simplification of this proof using intermediate results we encountered along the way.

The purpose of this thesis was to investigate age related variations in anterior ocular characteristics and their effect on the response to short-term (one-hour) open eye orthokeratology (OK) lens wear and overnight hydrogel lens wear. Sixty-three volunteer subjects were divided into three groups comprising children (Group I), young adults (Group II) and older adults (Group III). Anterior ocular characteristics that were measured included corneal topography with the Medmont corneal topographer, total, stromal and epithelial thickness with the Holden-Payor optical pachometer, microscopic cell characteristics with the confocal microscope, corneal aesthesiometry, corneal modulus of elasticity, and tear film, palpebral and eyelid characteristics. The older cornea was found to be more spherical in shape (asphericity Q = -0.24 ?? 0.07 in group III compared to -0.34 ?? 0.09 and -0.32 ?? 0.17 in groups I and II respectively) and showed a tendency from with-the-rule to against-the-rule astigmatism. Older subjects also had a decreased endothelial cell density (2596 ?? 111 cells/mm2 in group III compared to 2793 ?? 138 cells/mm2 in group II) and reduced eyelid tension compared to the younger groups. Children were found to have lower blink rates than adults. It was concluded that these changes might have a significant impact on contact lens wear. The responses to two contact lens based techniques, orthokeratology (OK) and hydrogel overnight wear (ON), were studied. Sixty subjects (20 per group) wore reverse-geometry lenses (BE, Ultravison Aust Pty Ltd) of Boston XO material in one eye under open eye conditions for one hour in one eye only. Changes in unaided visual acuity, corneal curvature, corneal thickness and confocal microscopic variables were measured after OK lens wear. All subject groups showed statistically significant improvements (p &lt 0.05) in unaided visual acuity, a trend for more positive (less prolate) corneal asphericity, increase in apical corneal radius and decrease in central total corneal thickness, after OK lens wear. When the groups were stratified, statistical significance was obtained between the older group and the other two younger groups for change in apical corneal radius (0.23 ?? 0.01 mm in group I, 0.15 ?? 0.01 mm for group II, 0.06 ?? 0.33 for group III). The change in asphericity also showed significant differences between the older age group (0.10 ?? 0.08 mm) and the young adult group (0.21 ?? 0.13). Central corneal thinning obtained after one hour of OK lens wear revealed significant differences between the older adult group (-1.9 ?? 3.2 ??m) and the other two groups (-5.0 ?? 5.9 ??m in group I, -5.0 ?? 2.0 ??m for group II). Sixty subjects wore hydrogel lenses (One-Day Acuvue, Johnson and Johnson Visioncare Pty Ltd) made of etafilcon A in one eye only overnight during sleep at their home. Changes in unaided visual acuity, corneal curvature, corneal thickness, confocal microscopic variables and slitlamp variables were measured after ON lens wear. All subjects showed significant thickening (p &lt 0.05) of the cornea with ON wear, more in the lens-wearing eye. This study reported that the edema response induced by Acuvue contact lenses is stromal in origin. The edema response of the older group (33.9 ?? 11.5 ??m) was lower than the other two groups as demonstrated by the difference in the change in central stromal thickness (49.3 ?? 20.3 ??m for group I and 51.0 ?? 20.0 ??m for group II). However, a statistically significant difference in the change in thickness was not reached either for the central total corneal thickness or for other topographic locations. Corneal and visual changes found in this study confirm previous reports of the effects of short term OK and hydrogel ON lens wear. Older lens wearers showed a reduced or delayed response to short-term lens wear. Studies investigating the effects of age with long lens-wearing durations are warranted to quantify these effects further.

In this thesis, an adapted form of dynamic Electrostatic Force Microscopy is presented as an alternative technique for non-contact dynamic characterization of beam resonators. The actuation of the test resonant beam was accomplished by applying a modulated signal to a probe cantilever that was positioned closely above the resonant beam. The frequency response of the coupled electrostatic interaction between the conductive beams was studied close to the resonance of the test beams. Modulation of the input signal allowed the test resonator to be actuated without requiring on-chip circuitry, and the probing frequency range kept independent of the resonant frequency of the probe cantilever. The resonant response of three test cantilever beams were experimentally characterized using two softer probe cantilevers. A model was constructed to describe the coupled electrostatic interaction and simulations were performed to compare predictions from the model to experimental data. The amplitude response shape, resonant frequency and quality factor from the model fit well with experimental results, showing that the resonant response of a resonator can be characterized using this technique. However, the phase and voltage variation responses were not well characterized, indicating further work to develop the force expressions in the model is needed. / October 2006

Abstract The theme of this thesis is the MBE growth of doped arsenide compound semiconductor layers including uniformly doped layers and a modulation-doped heterostructure. The Hall measurement system has been set up to measure the carrier concentration and mobility of these samples. We have also studied the ohmic contacts on epitaxial InGaAs layers by TLM method. For uniformly doped samples, the experimental relation between doping concentration and MBE cell temperature have been established, and are in good agreement with reported results. In the experiment on GaAs/AlGaAs modulation-doped heterostructure, an electron mobility of 27000[cm2/(V•s)] was obtained by cooling the sample down to 170K with liquid nitrogen. This result is consistent with published results. For P-type ohmic contacts on InGaAs, a comparison between two metal layer compositions of Cr+Zn+Au and Cr+Zn+Cr+Au was made. The Cr+Zn+Cr+Au layer gave a lowest specific contact resistance of 3.38¡Ñ10-6(ohm•cm2) at an annealing temperature of 360¢J. A N-type ohmic contact of Au+Ge+Au was also investigated. This metal layer has a lowest specific contact resistance of 9.75¡Ñ10-7(ohm•cm2) without annealing.

Extr. de: Diss.--Physique--Berlin--University of Regensburg, 1998. / Notes Bibliogr.

Diss.--Bayreuth, 2000. / Bibliogr. p. 155-165.

Dissertation--Kiel, 2006.

Thèse de doctorat : Génie Mécanique : Villeurbanne, INSA : 2002. Thèse de doctorat : Génie Mécanique : Université des Sciences Techniques et Economique de Budapest : 2002. / Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. p.113-116.