A first-principles study of defects and adatoms on silicon carbide honetcomb structures

Abstract

In this thesis a study of electronic and magnetic properties of two dimensional (2D), single layer of silicon carbide (SiC) in hexagonal structure and its quasi 1D armchair nanoribbons are presented by using first-principles plane wave method. In order to reveal dimensionality effects, a brief study of 3D bulk and 1D atomic chain of SiC are also included. The stability analysis based on the calculation of phonon mode frequencies are carried out for different dimensionalities. It is found that 2D single layer SiC in honeycomb structure and its bare and hydrogen passivated nanoribbons are ionic, non magnetic, wide band gap semiconductors. The band gap further increases upon self-energy corrections. Upon passivation of Si and C atoms at the edges of nanoribbon with hydrogen atoms, the edge states are discarded and the band gap increases. The effect of various vacancy defects, adatoms and substitutional impurities on electronic and magnetic properties in 2D single layer SiC and in its armchair nanoribbons are also investigated. Some of these vacancy defects and impurities, which are found to influence physical properties and attain magnetic moments, can be used to functionalize SiC honeycomb structures for novel applications.