L'introduction d'une contrainte mécanique dans le canal de MOSFETs sur SOI est indispensable pour les noeuds technologiques sub-22 nm. Son efficacité dépend de la géométrie et des règles de dessin du dispositif. L'impact des étapes du procédé de fabrication des transistors (gravure des zones actives, formation de la grille métallique, implantation des Source/Drain (S/D)) sur la contrainte du silicium contraint sur isolant (sSOI) a été mesuré par diffraction des rayons X en incidence rasante (GIXRD). Parallèlement, le gain en performances de MOSFETs sur sSOI a été quantifié par rapport au SOI (100% de gain en mobilité pour des nMOS longs et larges (L=W=10 μm), 35% de gain en courant de drain à saturation (IDsat) pour des nMOS courts et étroits (L=25 nm, W=77 nm)). Des structures contraintes innovantes ont aussi été étudiées. Un gain en IDsat de 37% (18%) pour des pMOS sur SOI (sSOI) avec des S/D en SiGe est démontré par rapport au sSOI avec des S/D en Si, pour une longueur de grille de 60 nm et des films de 15 nm d'épaisseur. Des mesures GIXRD, couplées à des simulations mécaniques, ont permis d'étudier et d'optimiser des structures originales avec transfert de contrainte d'une couche enterrée précontrainte (en SiGe ou en nitrure) vers le canal.

The objective of this thesis is to improve understanding of the development of corrosion products (scales) that form on the inner walls of carbon steel pipelines in CO2-rich (sweet) oilfield environments. If well adherent to the carbon steel surface, such scales can significantly reduce the metal’s rate of corrosion. Typically, the open literature labels sweet corrosion scale as ferrous (II) carbonate (FeCO3) or siderite, although this may not always be the case. For example, Fe2(OH)2CO3 (chukanovite) and Fe3O4 (magnetite) are known to modify the protective character of a sweet corrosion product scale. Practical electrochemical methods for the assessment of substrate corrosion, and electron/photon-based characterisation techniques for investigating scale structure and composition, have revealed interesting aspects of the nature of sweet corrosion scale development on model high purity Fe and real-world pipeline steel surfaces. Concerning scale development on model Fe substrates immersed in CO2-saturated deionised water (buffered to pH = 6.8, T = 80°C, Ptotal = 1 bar), electrochemical data supplemented by grazing incidence x-ray diffraction (GIXRD) and scanning electron microscopy (SEM) show that a semi-protective mixed corrosion scale comprising siderite and chukanovite becomes a highly protective siderite scale with longer exposure time. The introduction of sodium chloride to the CO2-saturated solution (T = 80°C, pH = 6.8, Ptotal = 1 bar) impedes the rate of scale formation. Increasing [NaCl] from the start of experiment is suspected to limit the precipitation kinetics of sweet corrosion scale crystals, since chukanovite is no longer observed, and siderite formation is somewhat slowed as well. SEM imaging, using an electronic workfunction-sensitive detector (in lens), reveals nanoscale deposits on the corroded Fe surface in regions that are devoid of µm-scale crystals. With the Raman spectra from these regions considered, it is interpreted that the nanoscale deposits are likely amorphous iron carbonate, albeit oxidised to a significant extent. Moving to real-world carbon steel immersion in sweet solutions, a scale comprising predominantly chukanovite is observed (using GIXRD and SEM) on the 1% Ni weld zone (WZ) surface of a pipeline weld-joint, but not on adjacent, distinct regions (heat affected zones (HAZ) and base metal (BM)). This selective scaling is suggested to be due to some initial corrosion of the weld-joint, which generates sufficient [Fe2+(aq)], and a macro-galvanic effect across the weld, i.e. WZ is cathodic to HAZ and BM. Further, to gain mechanistic insight into compositional changes during sweet corrosion scale growth, an electrochemical cell for in situ GIXRD (named E-cell) has been developed and commissioned. Diffraction patterns acquired using synchrotron radiation, from a pipeline steel surface, reveal the formation and temporal evolution of a multicomponent corrosion scale. Accompanying electrochemical data suggest that the scale is quite protective.

Organic semiconductors show promise to yield a novel class of bendable electronic devices, and much research efforts have focused on the optimization of these films for device performance. It is well known that the structure of organic films has a large influence over the electronic properties. In particular, the carrier mobility is often highly anisotropic, and domain boundaries have a detrimental effect on charge transport. Therefore the domain structure and lattice orientation are of particular interest. However, little is known about the domain structure of organic films, and techniques to study these properties have only begun to emerge in recent years. In this thesis, we apply two experimental techniques, Grazing-Incidence X-ray Diffraction (GIXD) and Lateral Force Microscopy (LFM), toward studying the lattice and domain structure of tetracene films grown on the silicon(001)-monohydride surface. We describe the necessary steps toward optimizing the sensitivity of these techniques to the domain structure. Results show that the crystalline tetracene films form a layered morphology in which the a-b plane lies parallel to the substrate surface. The film lattice structure is similar to bulk tetracene, and the lattice is confined to two orthogonal orientations, forming a partially-commensurate relationship with the substrate surface lattice along the film 'a' axis. LFM images reveal two types of polycrystalline domains. The first type ("major domains") are tens of microns in size, and are classified by their lattice orientation. They are subdivided into the second type ("sub-domains"), which range from 0.1 to 5um in size, and are argued to represent regions of uniform molecular tilt direction. The GIXD data show that the single-crystal domains which comprise these two larger domain types are anisotropic in size, being up to two times longer along the film 'b' axis than along 'a'. The single-crystal domains range from 0.05 to 0.2um in size, depending on lattice orientation and film thickness. The mathematical basis for these single-crystal domain size calculations is presented. The single-crystal domain sizes are thickness-dependent, and are two orders of magnitude smaller than a typical surface island observed in atomic-force microscopy (AFM) topographs. Substrate steps can also significantly influence the film structure by inducing boundaries in the single-crystal domains and sub-domains, but not in the major domains. This detailed knowledge of the domain structure of organic thin-films may assist in our understanding of the factors which affect charge transport in thin films, and may help to direct research efforts in optimizing the film structure for device performance. / Natural Sciences and Engineering Research Council (NSERC), Canadian Foundation for Innovation (CFI), Ontario Innovation Trust (OIT).

La toxine bactérienne de Shiga se lie au glycosphingolipide (GSL) globotriaosylcéramide (Gb3) afin d’entrer par endocytose dans les cellules en utilisant une voie dépendante et indépendante de la clathrine. Dans la voie indépendante de la clathrine, la toxine de Shiga réorganise les lipides de la membrane de façon à imposer une contrainte mécanique sur la bicouche, conduisant ainsi à la formation de pic d’invagination d'endocytose profonds et étroits. Mécaniquement ce phénomène n’est pas encore compris, notamment il reste énigmatique, comment se traduisent les propriétés géométriques de l’agrégation des glycosphingolipides GSLS et de la toxine. Dans mon travail de thèse, via l’utilisation de la sous-unité B de la toxine de Shiga (STxB) comme un modèle, différentes espèces moléculaires de son récepteur Gb3 ont été synthétisés avec des structures délibérément choisis. Les études réalisées par imagerie de haute résolution et par la modélisation informatique ont permis d’élucider les contraintes mécano-chimique sous-jacente conduisant à une réorganisation efficace qui a pour résultat l’agrégation de la toxine et la réorganisation des lipides. En combinant des expériences de simulation sur ordinateur de dynamique des particules dissipatives (DPD) et des expériences sur des modèles de membranes cellulaires, nous avons fourni la preuve de l’induction d’une force de fluctuation-membrane, de type « force de Casimir », conduisant à l'agrégation des molécules de toxines associées à la membrane à des échelles de longueur mésoscoiques. Nous avons observé et mesuré, en outre la condensation lipidique induite par la toxine, quantitativement sur des monocouches de Langmuir en utilisant la réflectivité des rayons X (XR) et par la mesure de la diffraction des rayons X par incidence rasante (GIXD), fournissant ainsi une preuve directe de l'hypothèse que la toxine a le potentiel de réduire de façon asymétrique la surface moléculaire sur la partie membranaire exoplasmique, ce qui conduit à une déformation locale de la membrane. Durant ma thèse, nos efforts ont été consacrés à la réalisation de nouveaux glycosphinolipides (GSL) comme outils chimiques à visée biologique. Par ailleurs, une nouvelle stratégie de reconstitution de GSL fonctionnels sur la membrane cellulaire, basée sur une réaction de ligation de type « click » entre un glycosyl-cyclooctyne et un azido-sphingosine a été étudiée. Les résultats obtenus sur les cellules se sont avérés beaucoup moins efficace que ceux in vitro. Une poursuite de l'optimisation de cette méthodologie est actuellement en cours. Une sonde fluorescente du glycosphinolipide Gb3, marquée à l’Alexa Fluor 568 lui-même lié par l'intermédiaire d'un bras PEG-α à la position de la chaîne acyle, a été synthétisée. Cette sonde se lie à la STxB sur couche mince de TLC, mais pas sur des membranes modèles. D'autres améliorations sont discutées. / Bacterial Shiga toxins bind to the glycosphingolipid (GSL) globotriaosylceramide (Gb3) to enter cells by clathrin-dependent and independent endocytosis. In the clathrin-independent pathway, Shiga toxin reorganizes membrane lipids in a way such as to impose mechanical strain onto the bilayer, thus leading to the formation of deep and narrow endocytic pits. Mechanistically how this occurs is not yet understood, and notably how the geometric properties of toxin-GSLs complexes translate into function has remained enigmatic. In my thesis work, using the B-subunit of Shiga toxin (STxB) as a model, different molecular species of its receptor Gb3 have been synthesized with deliberately chosen structures, coupled with high resolution imaging and computational modeling, to understand the underlying mechano-chemical constraints leading to efficient toxin clustering and lipids reorganization. By combining dissipative particle dynamics (DPD) computer simulation and experiments on cell and model membranes, we provided evidence that a membrane fluctuation-induced force, termed Casimir-like force, drives the aggregation of tightly membrane-associated toxin molecules at mesoscopic length scales. Furthermore, toxin-induced lipid condensation was observed and measured quantitatively on Langmuir monolayers using X-ray reflectivity (XR) and grazing incidence x-ray diffraction (GIXD), thereby providing direct evidence for the hypothesis that the toxin has the potential to asymmetrically reduce the molecular area of the exoplasmic membrane leaflet, leading to local membrane deformation. During my PhD, effort was also invested to develop new GSL tools applied to the biological setting. A novel strategy based on the Cu-free click reaction between glycosyl-cyclooctyne and azido-sphingosine was designed with the goal to functionally incorporate GSLs into cellular membranes. Following the synthesis work, click reactions have been performed in solution and on cells. Compared to the former, results on cells were far less efficient. Further optimization is currently ongoing. A fluorescently labeled Gb3 probe with Alexa Fluor 568 coupled via a PEG linker to the α-position of the acyl chain, was synthesized, to which STxB bound on TLCs, but not on model membranes. Further improvements are discussed.