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Nanostructured, porous materials offer great promise for application in areas such as energy storage, photovoltaics, and catalysis. These materials are often difficult to characterize because they are structurally and compositionally inhomogeneous, and disordered with features to small to be resolved by scanning probe techniques such as atomic force microscopy (AFM) and scanning electron microscopy (SEM). These shortcomings require that new techniques be developed that can be applied to real world systems to elucidate how the interplay of material composition and structure alters their performance. Towards this end, the development of a hybrid quartz crystal microbalance/ ellipsometric porosimetry (QCM/EP) technique is being pursued to facilitate the determination of a number of material parameters such as porosity, pore size distribution, and surface area. Additionally, the use of adsorbate probe molecules of varying polarity gives further information about adsorbate-surface interactions and surface chemistry characteristics. Simultaneous acquisition of both mass-based and refractive index based adsorption isotherms fosters mechanistic understanding about the behavior of adsorbates confined in mesopores while at the same time reducing the uncertainty in the analysis of the optical parameters acquired via ellipsometry. To highlight the power of this approach, studies of TiO₂ and TiC, electrode materials as model systems will be presented that have helped us validate measurement and modeling protocols for extracting physical properties. / text

abstract: A new nanoparticle deposition technique, Aerosol Impaction-Driven Assembly (AIDA), was extensively characterized for material structures and properties. Aerogel films can be deposited directly onto a substrate with AIDA without the long aging and drying steps in the sol-gel method. Electron microscopy, pore size analysis, thermal conductivity, and optical measurements show the nanoparticle (NP) films to be similar to typical silica aerogel. Haze of nanoparticle films modeled as scattering sites correlates strongly with pore size distribution. Supporting evidence was obtained from particle sizes and aggregates using electron microscopy and small-angle X-ray scattering. NP films showed interlayers of higher porosity and large aggregates formed by tensile film stress. To better understand film stress and NP adhesion, chemical bonding analyses were performed for samples annealed up to 900 °C. Analysis revealed that about 50% of the NP surfaces are functionalized by hydroxyl (-OH) groups, providing for hydrogen bonding. Ellipsometric porosimetry was used to further understand the mechanical properties by providing a measure of strain upon capillary pressure from filling pores. Upon annealing to 200 °C, the films lost water resulting in closer bonding of NPs and higher Young’s modulus. Upon further annealing up to 900 °C, the films lost hydroxyl bonds while gaining siloxane bonds, reducing Young’s modulus. The application of ellipsometric porosimetry to hydrophilic coatings brings into question the validity of pore size distribution calculations for materials that hold onto water molecules and result in generally smaller calculated pore sizes. Doped hydrogenated microcrystalline silicon was grown on crystalline silicon NPs, as a test case of an application for NP films to reduce parasitic absorption in silicon heterojunction solar cells. Parasitic absorption of blue light could be reduced because microcrystalline silicon has a mix of direct and indirect bandgap, giving lower blue absorption than amorphous silicon. Using Ultraviolet Raman spectroscopy, the crystallinity of films as thin as 13 nm was determined rapidly (in 1 minute) and non-destructively. A mono-layer of nanocrystals was applied as seeds for p-doped microcrystalline silicon growth and resulted in higher crystallinity films. Applications of the method could be explored for other nanocrystalline materials. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2020

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

La microscopie SEEC (Surface Enhanced Ellipsometric Contrast) est une technique inventée au mans, il y a une dizaine d’années. Elle permet de visualiser des objets de taille nanoscopique entre polariseur et analyseur croisés en utilisant les propriétés non dépolarisantes de surfaces multicouches. Jusqu’au début de la thèse, seules des observations à l’air étaient possibles. Le but de cette thèse a consisté à adapter cette technique à l’observation in-situ d’objets en immersion dans l’eau.Pour cela, il a fallu inventer de nouvelles surfaces propres à ce nouveau milieu. Les calculs ont montrés que des surfaces fines d’or révélaient un bon contraste pour des objets de 1 nm en immersion dans l’eau. Expérimentalement, nous avons montré que pour exploiter au maximum le contraste SEEC, il est nécessaire de modifier l’éclairage. En parallèle de ces travaux expérimentaux, de nouveaux calculs ont montrés que l’utilisation d’épaisseurs encore plus fines permettait de visualiser ces objets avec un bon contraste et sans aucune modification de l’éclairage. Nous avons appelé cette nouvelle technique : la microscopie CONE. Nous avons découvert deux modes de mesure. Après avoir réalisé des fonctionnalisations homogènes et hétérogènes des surfaces d’or. Ces surfaces ont été utilisées en résonance plasmonique de surface (SPR) pour l’étude de fixation de protéine (adsorption et immobilisation) puis d’interaction protéine/protéine. Ces expériences ont ensuite servies de référence pour évaluer les microscopies SEEC et CONE. Par cela, nous avons prouvé que ces microscopies présentent de forts intérêts pour la détection in-situ de protéines avec un faible coût. / This thesis was supported by National Agency for Research with the project: ANR PNANO-07 SEEC. The Surface Enhanced Ellipsometric Contrast (SEEC) microscopy has invented in 2000 at Le Mans (France). This technique allows the visualization of nanoscopic object between crossed analyzer and polarizer. It’s possible if some special multilayer surfaces are used. There surfaces must have the particularity to not change the polarization of light during the reflection. Until the beginning of the project the SEEC microscopy was useful only for air observations. The goal of the thesis was to adapt this technique to observe on gold surfaces immerged in water and to compare the performance of the SEEC microscopy with Surface Plasmonique Resonance (SPR) in that configuration. The SPR is a biomolecular interaction study reference technique. SEEC microscopy lateral resolution was evaluate by fluorescence microscopy. Next, we realize two model experiments monitor in parallel by SEEC microscopy and by SPR: BSA immobilization and biotinylated IgG fixation by immobilized streptavidine. To compare measurements efficiently we did a huge preparation work (surface functionalizations and microfluidic) to have exactly same conditions in both techniques.Our results show SEEC microscopy cannot replace SPR for biomolecular interaction studies but it can be used as cheap immunological diagnostic technique. This work gives the path to follow on that direction.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.