Étude de phase des systèmes Ni/Si-endommagé et Ni/a-Si, par XRD résolue en temps et nanocalorimétrie

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

Le test de concordance de script (TCS) explore-t-il des processus de raisonnement clinique différents de ceux du QCM à contexte riche (basés sur des cas cliniques) ? : et si oui, quels sont-ils ?

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

Et si on normalisait la folie?: Démarche de conscientisation face à la stigmatisation par le biais d'une intervention de groupe avec des individus vivant avec le trouble de personnalité limite.

Essai critique présenté à la Faculté des études supérieures en vue de l’obtention du grade de M.Sc. en service social

Caratérisation de la surface d’énergie potentielle des matériaux complexes et son application sur la cinétique du SiO2/Si

Dans ce rapport de mémoire, nous avons utilisé les méthodes numériques telles que la dynamique moléculaire (code de Lammps) et ART-cinétique. Ce dernier est un algorithme de Monte Carlo cinétique hors réseau avec construction du catalogue d'événements à la volée qui incorpore exactement tous les effets élastiques. Dans la première partie, nous avons comparé et évalué des divers algorithmes de la recherche du minimum global sur une surface d'énergie potentielle des matériaux complexes. Ces divers algorithmes choisis sont essentiellement ceux qui utilisent le principe Bell-Evans-Polanyi pour explorer la surface d'énergie potentielle. Cette étude nous a permis de comprendre d'une part, les étapes nécessaires pour un matériau complexe d'échapper d'un minimum local vers un autre et d'autre part de contrôler les recherches pour vite trouver le minimum global. En plus, ces travaux nous ont amené à comprendre la force de ces méthodes sur la cinétique de l'évolution structurale de ces matériaux complexes. Dans la deuxième partie, nous avons mis en place un outil de simulation (le potentiel ReaxFF couplé avec ART-cinétique) capable d'étudier les étapes et les processus d'oxydation du silicium pendant des temps long comparable expérimentalement. Pour valider le système mis en place, nous avons effectué des tests sur les premières étapes d'oxydation du silicium. Les résultats obtenus sont en accord avec la littérature. Cet outil va être utilisé pour comprendre les vrais processus de l'oxydation et les transitions possibles des atomes d'oxygène à la surface du silicium associée avec les énergies de barrière, des questions qui sont des défis pour l'industrie micro-électronique.

Electrical Characteristics of n-ZnO/p-Si Heterojunction Diodes Grown by Pulsed Laser Deposition at Different Oxygen Pressures

Heterojunction diodes of n-type ZnO/p-type silicon (100) were fabricated by 12 pulsed laser deposition of ZnO films on p-Si substrates in oxygen ambient at 13 different pressures. These heterojunctions were found to be rectifying with a 14 maximum forward-to-reverse current ratio of about 1,000 in the applied 15 voltage range of -5 V to +5 V. The turn-on voltage of the heterojunctions was 16 found to depend on the ambient oxygen pressure during the growth of the ZnO 17 film. The current density–voltage characteristics and the variation of the 18 series resistance of the n-ZnO/p-Si heterojunctions were found to be in line 19 with the Anderson model and Burstein-Moss (BM) shift.

Photoacoustic investigation of intrinsic and extrinsic Si

An open-cell configuration of the photoacoustic (PA) technique is employed to determine the thermal and transport properties of intrinsic Si and Si doped with B (p-type) and P (n-type). The experimentally obtained phase of the PA signal under heat transmission configuration is fitted to that of theoretical model by taking thermal and transport properties, namely, thermal diffusivity, diffusion coefficient, and surface recombination velocity, as adjustable parameters. It is seen from the analysis that doping and also the nature of dopant have a strong influence on the thermal and transport properties of semiconductors. The results are interpreted in terms of the carrier-assisted and phonon-assisted heat transfer mechanisms in semiconductors as well as the various scattering processes occurring in the propagation of heat carriers.

Influence of Si, Sb and Sr Additions on the Microstructure, Mechanical Properties and Corrosion Behavior of AZ91 Magnesium Alloy

All the exciting work on developing new and better alloys has led older alloys, such as AZ9l , being abandoned by researchers. lt is believed that the full potential of AZ9l in automotive design has not been realized. Whatever works have been carried out on AZ9lalloy to improve its mechanical properties are insufficient in terms of its potential usage in auto industries. Due to the fact that AZ91 offers high room temperature mechanical properties and good castability, still this alloy is a primary choice for the auto component manufactures. Small improvement in its creep properties will have a huge impact in the transportation industries. Hence, in the present work, “Influence of Si, Sb and Sr Additions on the Microstructure, Mechanical Properties and Corrosion Behavior of AZ91 Magnesium Alloy”, an attempt has been made to improve the creep properties of AZ9l alloy through minor alloying elemental additions and to understand its strengthening mechanisms. The effect of alloying additions on the ageing and tensile properties of AZ9l is also studied. In addition to that, role of various intermetallics formed due to the alloying additions on the corrosion properties of AZ9l alloy is investigated.

Calorimetry of hydrogen desorption from a-Si nanoparticles

The process of hydrogen desorption from amorphous silicon (a-Si) nanoparticles grown by plasma-enhanced chemical vapor deposition (PECVD) has been analyzed by differential scanning calorimetry (DSC), mass spectrometry, and infrared spectroscopy, with the aim of quantifying the energy exchanged. Two exothermic peaks centered at 330 and 410 C have been detected with energies per H atom of about 50 meV. This value has been compared with the results of theoretical calculations and is found to agree with the dissociation energy of Si-H groups of about 3.25 eV per H atom, provided that the formation energy per dangling bond in a-Si is about 1.15 eV. It is shown that this result is valid for a-Si:H films, too.

Performance of correlation functionals in ab initio chemisorption cluster-model calculations: Alkali metals on Si(111)

The performance of different correlation functionals has been tested for alkali metals, Li to Cs, interacting with cluster models simulating different active sites of the Si(111) surface. In all cases, the ab initio Hartree-Fock density has been obtained and used as a starting point. The electronic correlation energy is then introduced as an a posteriori correction to the Hartree-Fock energy using different correlation functionals. By making use of the ionic nature of the interaction and of different dissociation limits we have been able to prove that all functionals tested introduce the right correlation energy, although to a different extent. Hence, correlation functionals appear as an effective and easy way to introduce electronic correlation in the ab initio Hartree-Fock description of the chemisorption bond in complex systems where conventional configuration interaction techniques cannot be used. However, the calculated energies may differ by some tens of eV. Therefore, these methods can be employed to get a qualitative idea of how important correlation effects are, but they have some limitations if accurate binding energies are to be obtained.

Studies on the optical band gap and cluster size of the polyaniline thin films irradiated with swift heavy Si ions

Polyaniline thin films prepared by RF plasma polymerisation were irradiated with 92MeV Si ions for various fluences of 1 1011, 1 1012 and 1 1013 ions/cm2. FTIR and UV–vis–NIR measurements were carried out on the pristine and Si ion irradiated polyaniline thin films for structural evaluation and optical band gap determination. The effect of swift heavy ions on the structural and optical properties of plasma-polymerised aniline thin film is investigated. Their properties are compared with that of the pristine sample. The FTIR spectrum indicates that the structure of the irradiated sample is altered. The optical studies show that the band gap of irradiated thin film has been considerably modified. This has been attributed to the rearrangement in the ring structure and the formation of CRC terminals. This results in extended conjugated structure causing reduction in optical band gap