Date of Award

5-1-2015

Degree Name

Master of Science

Department

Physics

First Advisor

Jayasekera, Thushari

Abstract

The major objective of this thesis is to systematically investigate the effect of hexagonal BN (h-BN) islands on electronic and vibrational properties of single wall carbon Nanotubes. All our investigation are based on first principle Density Functional Theory (DFT) calculations. Our study is motivated by interesting metal-semiconductor transition recently found in periodically patterned graphene with h-BN islands. After reproducing the electronic band structure for pristine single wall zigzag carbon nanotubes (which shows metallic or semiconducting properties depending on their chirality), we investigated their electronic band structure in the presence of h-BN islands. The band structure depends not only on the defect concentration, but also on the pattern of the defect atoms. Our results also suggest that, if we start with a metallic /semiconducting mixture of ZSWCNTs, upon h-BN addition, the sample converts to fully semiconducting. This is a promising result for applications of CNTs in molecular electronics. Fundamental understanding of vibrational properties of nano electronics component is equally important in their applications especially in thermal management and thermoelectric applications. Defect engineering is one of the potential approach for tuning nanoelectronic devices for optimal thermal management and thermoelectric devices. In this work, I present a systematic investigation on how the group velocity and frequency of different phonon modes depend on various h-BN defect concentrations and defect patterns in ZSWCNTs. The study was extended to investigate the effect of hexagonal-C defects on the electronic and vibrational properties of zigzag single wall Boron Nitride nanotubes (ZSWBNNTs).

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