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Caracterization of the electronic and structural properties of a Ca_xMg_[1-x]Te alloy

Authors: Ana Matilde Alçada

Supervisors: Pedro Borlido; José António Paixão

MSc thesis, UC - Dissertações de Mestrado (Supervisores: Pedro Borlido, José António Paixão) (2025)

Abstract: With the continued demand for smaller, faster and more potent electronic devices,the search of new compounds to lengthen the physical limits of conventional materials and optimize the transistor-making process has become critical. In the case of Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), the optimal choices for gate dielectrics must possess specific characteristics, such as a high valued dielectric constant, a sufficiently large energy gap and interface stability. In this Thesis, we aim to study the electronic component of the dielectric constant for a new family of materials --- the Ca_{1-x}Mg_xTe alloy, in the R-3m rhombohedral phase --- and comment on its success as a high-k compound in the next generation of gate dielectrics. For this purpose, we employed Density Functional Theory (DFT), utilizing the Quantum ESPRESSO computational code to construct a model of our target alloy and evaluate several of its most pertinent quantities by carrying out first-principle calculations. Furthermore, beyond our explicitly calculated set of structures, we constructed a cluster expansion to predict the same properties for higher-order configurations and generated Special Quasirandom Structures (SQS’s) to identify representative configurations and better grasp the disordered nature of the alloy. Additionally, to complement the computational work, this thesis also features a small experimental component where synthesis of this alloy was attempted for some values of concentration x.