abstract: The scaling of transistors has numerous advantages such as increased memory density, less power consumption and better performance; but on the other hand, they also give rise to many reliability issues. One of the major reliability issue is the hot carrier injection and the effect it has on device degradation over time which causes serious circuit malfunctions. Hot carrier injection has been studied from early 1980's and a lot of research has been done on the various hot carrier injection mechanisms and how the devices get damaged due to this effect. However, most of the existing hot carrier degradation models do not consider the physics involved in the degradation process and they just calculate the change in threshold voltage for different stress voltages and time. Based on this, an analytical expression is formulated that predicts the device lifetime. This thesis starts by discussing various hot carrier injection mechanisms and the effects it has on the device. Studies have shown charges getting trapped in gate oxide and interface trap generation are two mechanisms for device degradation. How various device parameters get affected due to these traps is discussed here. The physics based models such as lucky hot electron model and substrate current model are presented and gives an idea how the gate current and substrate current can be related to hot carrier injection and density of traps created. Devices are stressed under various voltages and from the experimental data obtained, the density of trapped charges and interface traps are calculated using mid-gap technique. In this thesis, a simple analytical model based on substrate current is used to calculate the density of trapped charges in oxide and interface traps generated and it is a function of stress voltage and stress time. The model is verified against the data and the TCAD simulations. Finally, the analytical model is incorporated in a Verilog-A model and based on the surface potential method, the threshold voltage shift due to hot carrier stress is calculated. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

<div>Computational Chemistry has proven to be an effective means of solving chemical problems. The two main tools of Computational Chemistry - quantum mechanics and molecular mechanics, have provided viable avenues to probe such chemical problems at an electronic or molecular level, with varying levels of accuracy and speed. In this work, attempts have been made to combine the speed of molecular mechanics and the accuracy of quantum mechanics to work across multiples scales of time and length, effectively resulting in simulations of large chemical systems without compromising the accuracy.</div><div><br></div><div>The primary tool utilized for methods development and application in this work is the Effective Fragment Potential (EFP) method. The EFP method is a computational technique for studying non-covalent interactions in complex systems. EFP is an accurate \textit{ab initio} force field, with accuracy comparable to many Density Functional Theory (DFT) methods, at significantly lower computational cost. EFP decomposes intermolecular interactions into contributions from four terms: electrostatics, polarization, exchange-repulsion and dispersion.</div><div><br></div><div>In the first chapter, the possibility of applying EFP method to study large radical-water clusters is probed. An approximate theoretical model in which the transition dipole moments of excitations are computed using the information from the ground state orbitals is implemented.</div><div><br></div><div>A major challenge to broaden the scope of EFP is to overcome its limitation in describing only small and rigid molecules such as water, acetone, etc. In the second chapter, the extension of EFP method to large covalently bound biomolecules and polymers such as proteins, lipids etc., is described. Using this new method, referred to as BioEFP/mEFP, it is shown that the effect of polarization is non-negligible and must be accounted for when modeling photochemical and electron-transfer processes in photoactive proteins.</div><div><br></div><div>Another area of interest is the development of novel drug-target binding models, in which a chemically active part of the ligand is modified via functional group modification, while the rest of the system remains intact. In the third chapter, the development and application of a drug-target binding model is explained.<br></div><div><br></div><div><div>Lastly, in the fourth and final chapter, we show the derivation for working equations corresponding to the coupling gradient term describing the dispersion interactions between quantum mechanical and effective fragment potential regions.</div><div><br></div><div>The primary focus of this work is to explore and expand the boundaries of multiscale QM/MM simulations applied to chemical and biomolecular systems. We believe that the work described here leads to exciting pathways in the future in terms of modeling novel systems and processes such as heterogeneous catalysis, QSAR, crystal structure prediction, etc.</div></div>

Les méthodes géophysiques non intrusives sont requises pour caractériser la zone vadose, les réservoirs d’hydrocarbures, ou les sites de stockages de CO₂. Nous analysons l’impact d’une injection de CO₂ gazeux sur la conductivité électrique et les propriétés électrocinétiques des roches carbonatées partiellement ou totalement saturées grâce aux méthodes de polarisations provoquée et spontanée. Les données sont analysées au regard au regard de mesures effectuées sur une roche chimiquement neutre, vis-à-vis du CO₂, c’est-à-dire , un grès de Fontainebleau. Nous comparons également nos résultats aux données de la littérature. Le coefficient de couplage électrocinétique est un paramètre clé, dont nous allons étudier la dépendance vis-à-vis de la saturation, sujet hautement débattu de nos jours. En utilisant la méthode de polarisation spontanée, nous étudions les relations entre le coefficient de couplage électrocinétique, la pression capillaire ainsi que la perméabilité relative au sein des roches carbonatées. Un système expérimental a été élaboré pour mesurer simultanément la perméabilité relative, l’indice de resistivité et le coefficient de couplage électrocinétique en écoulement diphasique de type eau-gaz, en fonction de la saturation en azote ou en dioxyde de carbone. Les résultats sont comparés à des modèles théoriques basés sur les approches de Brooks et Corey et van Genuchten, dont les exposants nous permettent d’ajuster les données avec les modèles de pression capillaire avec succès. Les échantillons sont saturés avec des saumures de différentes compositions, dont les ions sont mono- ou divalents et pour lesquelles la force ionique est comprise entre 10⁻⁴ et 10⁰ Mol L⁻¹. La valeur absolue du coefficient de couplage électrocinétique augmente lorsque la force ionique de la solution diminue, ce qui a déjà été observé dans les roches gréseuses. Le potentiel zêta a été calculé en utilisant une version modifiée de l’équation d’Helmholtz-Smoluchowski, qui prend en compte les effets liés à la conductivité de surface. Comme pour le coefficient de couplage, la valeur absolue du potentiel zêta chute lorsque la force ionique augmente. Nous nous intéressons également aux effets liés à une injection de CO₂ et à la dissolution de la calcite sur la valeur de ce potentiel zêta. Enfin, nous utilisons la méthode de polarisation provoquée pour déterminer l’influence de conductivité de l’eau porale sur la conductivité électrique complexe, la chargeabilité normalisée ainsi que le temps de relaxation en milieu carbonaté non saturé. Nous montrons que ces paramètres peuvent être considérés comme des paramètres de polarisation de la double couche électrique lorsque la conductivité de l’eau porale est comprise entre 10⁻³ et 10⁰ S m⁻¹. / Minimally intrusive geophysical methods are required to characterize both the vadose zone of the Earth, hydrocarbon reservoirs and CO₂ sequestration. We investigate the impact of gaseous CO₂ on both electrical conductivity and electrokinetic properties of limestones under saturated and unsaturated conditions, using the spectral induced polarization and the self-potential methods. These data are contrasted with measurements performed on a Fontainebleau sandstone and data from the literature. That said, the dependence of a key parameter, the streaming coupling coefficient, with the saturation remains highly debated. Using the self-potential method, we explore the relationship between the streaming potential coupling coefficient, the capillary pressure curves and the permeability in carbonate rocks characterized by distinct textures. A new core flooding system is used to measure simultaneously both the relative permeability, the resistivity index and the streaming potential coupling coefficient in steady-state two-phase flow conditions as a function of the saturation with CO₂ or N₂. The results are compared with a recently developed theoretical model, which can accommodate either the Brooks and Corey or the van Genuchten models for the capillary pressure curves. Saturation was achieved with monovalent and divalent brines with ionic strength ranging from 1x10⁻³ Mol L⁻¹ to 1x10⁰ Mol L⁻¹. The magnitude of the coupling coefficient increases with decreasing ionic strength similarly to the trend observed for sandstones. The zeta potential has been calculated at full saturation using a modified version of the Helmholtz-Smoluchowski equation that accounts for surface electrical conductivity. Under atmospheric conditions, the magnitude of the zeta potential is decreasing with the increase of the ionic strength. We also investigate the effects of a CO₂ release and the calcite dissolution on the magnitude of the zeta potential. Finally, we use the spectral induced polarization method to determine the pore water conductivity effects on the complex electrical conductivity, the normalized chargeability and the main relaxation time during drainage in a clay free limestone. We also show evidences that these parameters could be considered as polarization parameters of the electrical double layer in the pore water conductivity range 10⁻³ - 10⁰ S m⁻¹.

The generalized radiation conditions at infinity of Sommerfeld-Kupradze type are established in the theory of thermoelasticity of anisotropic bodies. Applying the potential method and the theory of pseudodifferential equations on manifolds the uniqueness and existence theorems of solutions to the basic three-dimensional exterior boundary value problems are proved and representation formulas of solutions by potential type integrals are obtained.

The generalized radiation conditions at infinity of Sommerfeld-Kupradze type are established in the theory of thermoelasticity of anisotropic bodies. Applying the potential method and the theory of pseudodifferential equations on manifolds the uniqueness and existence theorems of solutions to the basic three-dimensional exterior boundary value problems are proved and representation formulas of solutions by potential type integrals are obtained.