Several fungal endophytes (C. protuberata, F. culmorum, and C. magna) confer stress tolerance to plants in the presence of certain pressures. This relationship is known as habitat-adapted symbiosis; its mechanism is currently unknown. Here, sFTIR, FTIR coupled to an FPA detector, and Raman spectromicroscopy are used to examine whether any biochemical differences exist between different isolates of the same species: one that can confer stress tolerance to plants and the other that cannot. No major differences have been observed in spectra that can differentiate between those endophytes that confer stress tolerance and those that do not. However, some hy-phae from both isolates of C. protuberata have been found to contain mannitol; its pres-ence may be more common in geothermal rather than non-geothermal isolates. Mannitol is a compound involved in providing stress tolerance to fungi. Any role that it may have in the mechanism of habitat-adapted symbiosis will need further investigation.

Several fungal endophytes (C. protuberata, F. culmorum, and C. magna) confer stress tolerance to plants in the presence of certain pressures. This relationship is known as habitat-adapted symbiosis; its mechanism is currently unknown. Here, sFTIR, FTIR coupled to an FPA detector, and Raman spectromicroscopy are used to examine whether any biochemical differences exist between different isolates of the same species: one that can confer stress tolerance to plants and the other that cannot. No major differences have been observed in spectra that can differentiate between those endophytes that confer stress tolerance and those that do not. However, some hy-phae from both isolates of C. protuberata have been found to contain mannitol; its pres-ence may be more common in geothermal rather than non-geothermal isolates. Mannitol is a compound involved in providing stress tolerance to fungi. Any role that it may have in the mechanism of habitat-adapted symbiosis will need further investigation.

Langmuir-Blodgett (LB) organic monomolecular (monolayer) films containing fatty acids and their perfluorinated counterparts separate into phases under certain conditions. These perfluorinated surfactant containing mixed-phase systems have been shown to exhibit many favourable attributes in comparison to non- perfluorinated surfactant monolayers. In this thesis project, two of these films were investigated. One film is a 2:1 ratio mixture of arachidic acid (C19H39COOH AA) to perfluorotetradecanoic acid (C13F27COOH PA), which phase-separates into hexagonal domains ~6 ìm large (2:1 ratio of AA to PA 2AA1PA). The other film is a 2:1 mixture of stearic acid (C17H35COOH - SA) to PA, which phase-separates into linear domains ~300 nm wide (2:1 ratio of SA to PA 2SA1PA).<p> Through the use of atomic force microscopy (AFM), and various synchrotron photoemission electron microscopy-based (PEEM) techniques, the films were characterized. As properties such as molecular organization, and dispersion of the molecules in the film, affect film function, it is necessary to use a variety of techniques to better understand order and composition in the films.<p> First, the well-known and previously-studied film, 2AA1PA, was used to better understand contrast mechanisms in the energy filtered x-ray photoemission electron microscope (X-PEEM) at the CLS. Through the use of techniques such as secondary electron emission microscopy (SEEM), ultraviolet photoelectron spectroscopy (UPS), and x-ray linear dichroism microscopy (XLDM), the effects of secondary electrons, valence character, and polarization dependence were studied so as to better understand their contribution to contrast in energy-filtered PEEM-based spectromicroscopy.<p> Second, the composition and organization of a novel system (2SA1PA), was characterized using traditional near-edge x-ray absorption fine-structure (NEXAFS) spectroscopy. As the size of the domains in the 2SA1PA system are below the spatial resolution limit of PEEM spectromicroscopy, methods involving selective phase dissolution, and spectrum subtraction, were used to acquire phase composition and molecular order information.<p> The high lateral and vertical spatial resolution of AFM allowed physical imaging and confirmation of sample structure, as well as very accurate domain height determination. X-PEEM supplements this with chemical sensitivity using high spatial resolution spectromicroscopy. Therefore, using AFM and X-PEEM as complimentary techniques, it is possible to physically and chemically characterize phase-separated monolayer films.

Langmuir-Blodgett (LB) organic monomolecular (monolayer) films containing fatty acids and their perfluorinated counterparts separate into phases under certain conditions. These perfluorinated surfactant containing mixed-phase systems have been shown to exhibit many favourable attributes in comparison to non- perfluorinated surfactant monolayers. In this thesis project, two of these films were investigated. One film is a 2:1 ratio mixture of arachidic acid (C19H39COOH AA) to perfluorotetradecanoic acid (C13F27COOH PA), which phase-separates into hexagonal domains ~6 ìm large (2:1 ratio of AA to PA 2AA1PA). The other film is a 2:1 mixture of stearic acid (C17H35COOH - SA) to PA, which phase-separates into linear domains ~300 nm wide (2:1 ratio of SA to PA 2SA1PA).<p> Through the use of atomic force microscopy (AFM), and various synchrotron photoemission electron microscopy-based (PEEM) techniques, the films were characterized. As properties such as molecular organization, and dispersion of the molecules in the film, affect film function, it is necessary to use a variety of techniques to better understand order and composition in the films.<p> First, the well-known and previously-studied film, 2AA1PA, was used to better understand contrast mechanisms in the energy filtered x-ray photoemission electron microscope (X-PEEM) at the CLS. Through the use of techniques such as secondary electron emission microscopy (SEEM), ultraviolet photoelectron spectroscopy (UPS), and x-ray linear dichroism microscopy (XLDM), the effects of secondary electrons, valence character, and polarization dependence were studied so as to better understand their contribution to contrast in energy-filtered PEEM-based spectromicroscopy.<p> Second, the composition and organization of a novel system (2SA1PA), was characterized using traditional near-edge x-ray absorption fine-structure (NEXAFS) spectroscopy. As the size of the domains in the 2SA1PA system are below the spatial resolution limit of PEEM spectromicroscopy, methods involving selective phase dissolution, and spectrum subtraction, were used to acquire phase composition and molecular order information.<p> The high lateral and vertical spatial resolution of AFM allowed physical imaging and confirmation of sample structure, as well as very accurate domain height determination. X-PEEM supplements this with chemical sensitivity using high spatial resolution spectromicroscopy. Therefore, using AFM and X-PEEM as complimentary techniques, it is possible to physically and chemically characterize phase-separated monolayer films.

No description available.

Ce mémoire de thèse traite de l'étude de jonctions pn silicium planaires, réalisées par épitaxie localisée, avec un nouveau type de microscopie à émission de photoélectrons (XPEEM) filtré en énergie. L'objectif est d'améliorer notre compréhension des facteurs influençant l'imagerie XPEEM de jonctions modèles avec une perspective à plus long terme d'application de cette technique aux cas réels.Sur les trois types de jonction réalisées présentant des champs électriques variables (P+/P, N+/P, P+/N), nous avons d'abord mis en œuvre un procédé de passivation en trois étapes afin de se rapprocher de conditions en bandes plates en surface. Ce procédé nous a permis d'étudier la position des niveaux électroniques de part et d'autre des jonctions grâce à une imagerie en XPEEM spectroscopique avec électrons secondaires (travail de sortie local), électrons de cœur Si 2p et bande de valence, avec à la fois avec des sources X de laboratoire et le rayonnement synchrotron. Un mécanisme de contraste des images en électrons de cœur dû à la toute première couche atomique de surface a été montré. Ensuite, nous avons mis en évidence le rôle du champ électrique au niveau de la zone de déplétion des jonctions qui décale la position apparente de cette dernière dans l'image XPEEM. Nous avons comparé les résultats expérimentaux avec des simulations (logiciel SIMION) afin d'estimer son influence sur les conditions d'imagerie. Enfin, nous avons étudié l'impact de la technique d'imagerie en champ sombre sur la localisation de la jonction réelle au niveau de la surface de l'échantillon. / This thesis addresses the problem of imaging of model systems planar silicon pn junctions, fabricated by localized epitaxy, using the novel energy-filtered X-ray PhotoElectron Emission Microscope (XPEEM). The objective is to improve the understanding of the phenomena influencing the XPEEM images of the junctions, with as long-term perspective, a possible application of this method in a complementary way to existing techniques of 2D dopant mapping.The studies were carried out over three types of junction realized to this purpose and presenting variable electrical field (P+/P, N+/P, P+/N). We firstly developed and optimized a passivation protocol in three-steps which yielded a surface close to flat band conditions. This process allowed us to deduce band alignments as a function of doping level and type on both side of the junction thanks to spectroscopic XPEEM imaging of secondary electrons (to determine local work function), Si 2p core-level and valence band with both laboratory photon sources and synchrotron radiation. Contrast in core-level imaging due to the first atomic layer of the surface was also shown.Then, we highlighted the role of the lateral electric field across the depletion zone of a pn junction which shifts the apparent position of the latter in PEEM imaging. We compared experimental results and simulations performed with SIMION software to estimate the influence of pn junctions on PEEM imaging. Dark field imaging of the junction was also simulated. Comparison with the experimental results showed that it can be used to localize the real junction.

No description available.