Thermal oxidation of silicon belongs to the most decisive steps in microelectronic fabrication because it allows creating electrically insulating areas which enclose electrically conductive devices and device areas, respectively. Deal and Grove developed the first model (DG-model) for the thermal oxidation of silicon describing the oxide thickness versus oxidation time relationship with very good agreement for oxide thicknesses of more than 23 nm. Their approach named as general relationship is the basis of many similar investigations. However, measurement results show that the DG-model does not apply to very thin oxides in the range of a few nm. Additionally, it is inherently not self-consistent. The aim of this paper is to develop a self-consistent model that is based on the continuity equation instead of Fick’s law as the DG-model is. As literature data show, the relationship between silicon oxide thickness and oxidation time is governed—down to oxide thicknesses of just a few nm—by a power-of-time law. Given by the time-independent surface concentration of oxidants at the oxide surface, Fickian diffusion seems to be neglectable for oxidant migration. The oxidant flux has been revealed to be carried by non-Fickian flux processes depending on sites being able to lodge dopants (oxidants), the so-called DOCC-sites, as well as on the dopant jump rate.

Advances in computing capabilities have facilitated the application of quantum mechanical methods to increasingly larger and more complex chemical systems, including weakly interacting and biologically relevant species. One such ab initio-based composite methodology, the correlation consistent composite approach (ccCA), has been shown to be reliable for the prediction of enthalpies of formation and reaction energies of main group species in the gas phase to within 1 kcal mol-1, on average, of well-established experiment, without dependence on experimental parameterization or empirical corrections. In this collection of work, ccCA has been utilized to determine the proton affinities of deoxyribonucleosides within an ONIOM framework (ONIOM-ccCA) and to predict accurate enthalpies of formation for organophosphorus compounds. Despite the complexity of these systems, ccCA is shown to result in enthalpies of formation to within ~2 kcal mol-1 of experiment and predict reliable reaction energies for systems with little to no experimental data. New applications for the ccCA method have also been introduced, expanding the utility of ccCA to solvated systems and complexes with significant noncovalent interactions. By incorporating the SMD solvation model into the ccCA formulation, the Solv-ccCA method is able to predict the pKa values of nitrogen systems to within 0.7 pKa unit (less than 1.0 kcal mol-1), overall. A hydrogen bonding constant has also been developed for use with weakly interacting dimers and small cluster compounds, resulting in ccCA interaction energies for water clusters and dimers of the S66 set to within 1.0 kcal mol-1 of well-established theoretical values.

While the spin trapping properties of thiols have been investigated through EPR analysis and kinetics studies, few groups have studied these properties using strictly computational methods. In particular, α-lipoic acid (ALA) and its reduced form, dihydrolipoic acid (DHLA), one of the strongest endogenously produced antioxidants, show potential for being effective, naturally occurring spin traps for the trapping of reactive oxygen species. This research covers electronic structure calculations of ALA, DHLA, and their corresponding hydroxyl radical spin adducts, performed at the cc-pVDZ/B3LYP/DFT level of theory. The effects on DHLA introduced by other radicals such as ·OOH, ·OCH3, and ·OOCH3 are reported. Explicit solvation was carried out using open-source molecular packing software and was studied using MOPAC PM6 semi-empirical geometry optimizations. Complete Basis Set (CBS) limit extrapolations were performed using cc-pVXZ (X = D, T, Q) Dunning basis sets under the DFT/B3LYP level of theory, and results are compared to the literature.

No description available.

<div> Challenges in the semiconductor industry have resulted in the discovery of a plethora of promising materials and devices such as the III-Vs (InGaAs, GaSb, GaN/InGaN) and 2D materials (Transition-metal dichalcogenides [TMDs]) with wide-ranging applications from logic devices, optoelectronics to biomedical devices. Performance of these devices suffer significantly from scattering processes such as polar-optical phonons (POP), charged impurities and remote phonon scattering. These scattering mechanisms are long-ranged, and a quantitative description of such devices require non-local scattering calculations that are computationally expensive. Though there have been extensive studies on coherent transport in these materials, simulations are scarce with scattering and virtually non-existent with non-local scattering. </div><div> </div><div>In this work, these scattering mechanisms with full non-locality are treated rigorously within the Non-Equilibrium Green's function (NEGF) formalism. Impact of non-locality on charge transport is assessed for GaSb/InAs nanowire TFETs highlighting the underestimation of scattering with local approximations. Phonon, impurity scattering, and structural disorders lead to exponentially decaying density of states known as Urbach tails/band tails. Impact of such scattering mechanisms on the band tail is studied in detail for several bulk and confined III-V devices (GaAs, InAs, GaSb and GaN) showing good agreement with existing experimental data. A systematic study of the dependence of Urbach tails with dielectric environment (oxides, charged impurities) is performed for single and multilayered 2D TMDs (MoS2, WS2 and WSe2) providing guideline values for researchers. </div><div><br></div><div>Often, empirical local approximations (ELA) are used in the literature to capture these non-local scattering processes. A comparison against ELA highlight the need for non-local scattering. A physics-based local approximation model is developed that captures the essential physics and is computationally feasible.</div>

A polymer brush is formed by densely grafting the chain ends of polymers onto a surface. This tethering of the long macromolecules has considerable influence on the surface properties, which can be additionally modified by changing the environmental conditions. In this context it is of special interest to understand and control the behavior of the grafted layer and to create surfaces that display a desired response to external stimulation. The present work studies densely grafted polymer brushes and the effects that such an environment imposes on an individual chain molecule in the grafted layer. For this purpose we developed a new self-consistent field approach to describe mixtures of heterogeneous chains comprised of differently sized hard spheres. Applying this method to the case of polymer brushes we consider a fraction of grafted molecules to be different from the majority brush chains. The modification of these chains includes a variation in the degree of polymerization, a different solvent selectivity behavior and a variable size of the free end-monomer. Due to the computational efficiency of the present approach, as compared for example to direct simulation methods, we can study the conformations of the modified 'guest' chains systematically in dependence of the relevant parameters. With respect to brush profile and the distribution of the free chain ends the new method shows very good quantitative agreement with corresponding simulation results. We also confirm the observation that these 'guest' chains can undergo a conformational transition depending on the type of modification and the solvent quality. For the cases studied in the present work we analyze the conditions to achieve a most sensitive behavior of this conformational switching. In addition, an analytical model is proposed to describe this effect. We compare its predictions to the numerical results and find good agreement.

L'obbiettivo di questa tesi è di investigare il ruolo della formazione delle aspettative nei modelli macroeconomici basati su agenti e stock-flussi coerenti. Mentre ci sono stati notevoli passi avanti nello sviluppo di tali modelli, la ricerca sulla formazione e sul ruolo delle aspettative in essi rimane ancora poco sviluppato. La tesi è composta da tre articoli, ognuno dei quali si focalizza sulla formazione delle aspettative in un settore economico speci co e presenta una serie di esperimenti riguardanti la variazione dei meccanismi di formazione delle aspetta- tive, dinamiche di opinioni e sentimenti, così come le applicazioni delle politiche economiche. La tesi dimostra l'influenza potenzialmente forte delle aspettative dei agenti sulla volatilità macroeconomica e mostra che, dipendendo dalla loro speci cazione e l'ambiente economico, le aspettative possono essere sia un elemento stabilizzante che un elemento destabilizzante. Inoltre, attraverso l'ampia gamma di esperimenti politici condotti, serve a sottolineare il ruolo importante delle politiche stabilizzanti nei sistemi che esibiscono fluttuazioni endogene, e il capitolo 4 in particolare mette in evidenza la potenziale dipendenza dell'efficacia delle politiche economiche dalle aspettative. Allo stesso tempo, alcuni dei risultati ottenuti avvertono che nei sistemi complessi, gli interventi politici devono essere calibrati attentamente affinché non diventino essi stessi fonte di instabilità. / The purpose of this thesis is to investigate the role of expectations formation in agent-based and stock-flow consistent macroeconomic models. While there have been considerable advances in the development of such models, research on the formation and role of beliefs and expectations within them remains underdeveloped. The thesis consists of three papers, each of which focuses on expectations formation in one particular economic sector and presents a range of experiments concerning the variation of expectations formation mechanisms, belief and sentiment dynamics, as well as policy applications. The thesis demonstrates the potentially strong influence of agents' expectations on macroeconomic volatility and shows that depending on their specification as well as the economic environment, expectations can be both a stabilising and destabilising factor. Moreover, through the wide range of policy experiments conducted, it serves to emphasise the important role of stabilisation policies in systems exhibiting endogenous fluctuations and chapter 4 in particular highlights the potential dependence of policy effectiveness on expectations. At the same time, some of the obtained results caution that in complex systems, policy interventions must be carefully calibrated lest they themselves become a source of instability.

Por medio del Decreto Supremo Nº 410-2015-EF, el cual aprobó el Reglamento del Decreto Legislativo Nº 1224, Decreto Legislativo que regula la Promoción de la Inversión Privada mediante Asociaciones Público-Privadas (en adelante, las APP’s) y Proyectos en Activos (actualmente derogado) se incorporó a las optimizaciones en el marco normativo nacional referido a la ejecución de contrato de APP. El mencionado mecanismo ha vuelto a ser considerado dentro del Decreto Legislativo N° 1362 y su reglamento aprobado por Decreto Supremo N° 240-2018-EF. Así, las optimizaciones se incorporaron como un mecanismo para realizar cambios a determinadas obligaciones establecidas en los contratos de APP. No obstante, se ha apreciado que dichas optimizaciones presentan una regulación confusa, la cual ha generado confusiones y discordancias respecto de en su correcta ejecución y, por ende, el desarrollo de las obligaciones establecidas en los contratos; ello se aprecia por ejemplo en el caso específico del Contrato de Concesión de la Línea 2 del Metro de Lima. Por lo tanto, por medio del presente trabajo de investigación se planteará una propuesta de regulación de las optimizaciones, la cual tiene por finalidad que estas se vuelvan una herramienta que permita mejorar su aplicación en los contratos de APP. / Through the promulgation of Supreme Decree 410-2015-EF, which approved the Regulation of Legislative Decree No. 1224, Legislative Decree that regulates the Promotion of Private Investment through Public-Private Partnerships and Projects in Assets was incorporated into the optimizations in the national regulatory framework referred to the execution of the PPP contract. The mentioned mechanism has been considered again in Legislative Decree No. 1362 and its regulations approved through Supreme Decree No. 240-2018-EF. Thus, the optimizations were incorporated as a mechanism to make changes to certain obligations established in the PPP contracts. However, it has been appreciated that these present incoherent regulations, which damages their correct execution and, therefore, the development of the established obligations; This has been seen in the specific case of the Concession Contract for Line 2 of the Lima Metro. Therefore, by means of this research work, a proposal for the regulation of optimizations will be proposed, it is intended that they become a tool to improve their application in PPP contracts. / Tesis

No description available.

This thesis presents a means of enhancing the iterative calculation techniques used in electronic structure calculations, particularly Kohn-Sham DFT. Based on the subspace iteration method of the FEAST eigenvalue solving algorithm, this nonlinear FEAST algorithm (NLFEAST) improves the convergence rate of traditional iterative methods and dramatically improves their robustness. A description of the algorithm is given, along with the results of numerical experiments that demonstrate its effectiveness and offer insight into the factors that determine how well it performs.