Publication Date

12-2012

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Materials Science and Engineering

Department

Materials Science and Engineering

Supervisory Committee Chair

Megan Frary

Abstract

The structural and electronic properties of pure and Cs-doped cubic zinc-blende silicon carbide (3C-SiC) were modeled by density functional theory in the plane-wave pseudo-potential formalism as implemented in the Quantum-ESPRESSO package. The equilibrium properties including lattice constant, bulk modulus, cohesive energy, and the indirect band gap energy were calculated for pure 3C-SiC. These values were compared with the experimental and theoretical values reported in the literature, and there was generally excellent agreement.

The influence of Cs on SiC in two structural configurations were modeled, including bulk SiC and a Σ3 grain boundary. The present investigation mainly focused on the neutral defects. To understand the stability of Cs in bulk SiC, the formation energies of isolated Cs defects and vacancy clusters were calculated. For the study of Cs in the grain boundary of SiC, only isolated Cs defects were modeled. Following the charge density and density of states calculations, the electronic structure of isolated Cs defects in bulk SiC was investigated. Relevant intrinsic SiC defect formation energies were also calculated. From the defect formation energies, it was predicted that the most probable stable state for neutral Cs in bulk SiC is for Cs to substitute for a Si atom with an associated C vacancy, CsSi-VC. In the case of Cs migrating to a Σ3 grain boundary in SiC, it is predicted that the most probable state for neutral Cs is for Cs to sit on a Si site at the boundary without an associated defect.

Download

Share

COinS