First-principles and empirical modeling of scintillator materials, silicon nano-bridges and MuGFETs

This dissertation presents work done as part of three different application areas, viz. (a) electronic structure calculations within the density functional theory (DFT) for Cerium (Ce) and Europium (Eu) doped inorganic scintillator materials, (b) empirical model to extract the specific contact resistance of silicon (Si) nanobridges based on device measurements, and (c) simulation of current-voltage characteristics of multiple-gate field effect transistor (MuGFET) using a finite element based software.;First-principles DFT calculations are used to study Ce and Eu doped scintillators and non-scintillators. A theoretical criterion is presented and is employed for prediction of new bright scintillators. A few predictions have been successfully validated by experimental synthesis and measurements. Trends in families of Ce (and Eu) doped compounds are studied using ab initio calculations. DFT calculations are used to identify a closely related family of Ce-doped non-scintillating compounds. It has been shown that first-principles calculations can contribute meaningfully towards development of new bright scintillators with applications such as gamma-ray detectors for homeland security.;Empirical modeling is used to determine the contact resistance of Si nano-bridges. Predicted value of specific contact resistance is consistent with the epitaxial growth of these nanowires. Finally, TCAD simulations are used to study the deleterious effect of gate misalignment arising out of lithography errors for multiple-gate FETs (MuGFETs).