PHONON ENGINEERING OF SILICON NANOWIRES BY CONTROL DOPING, FIRST PRINCIPLE APPROACH

Author

Masoud Babaeian, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2012

Degree Name

Master of Science

Department

Physics

First Advisor

Jayasekera, Thushari

Abstract

In this study, we have investigated the electronic and dynamical properties of several semiconductor nanowires with different diameters in the presence of impurities along the [111] direction. All of the nanowires are hydrogen-passivated and we have considered Germanium impurities with different patterns and concentration. The electronic structure calculations were carried out within Density Functional Theory, DFT, and the lattice dynamical properties were evaluated using Density Functional Perturbation Theory, DFPT, as it is implemented in the Quantum ESPRESSO package. The transmission coefficients of phonons along the nanowires were calculated using Green's Function technique. The interatomic force constants, which are input for the Green's function technique, were obtained from DFPT. Finally, the Landauer formalism was used to evaluate the thermal conductance of Silicon nanowires, SiNWs. A thorough analysis of the data suggested that doping of SiNWs with Germanium atoms has small effect on the electronic structure. A layered Germanium configuration is found to substantially decrease the thermal conductance of SiNWs, suggesting that doped SiNWs are potential materials for thermo-electronic applications.