A Tight-Binding Molecular-Dynamics Approach to Structural and Electronic Properties of a-SiC

Abstract

There have been a few theoretical studies addressing the topological structure, electronic distribution in amorphous silicon carbide (a-SiC) [1, 2, 3, 4, 5, 6]. These studies have involved molecular dynamics (MD) simulations in combination with an ab initio pseudo-potential approach (PA) in the local density approximation (LDA) for exchange and correlation interactions among valence electrons [1, 2, 3], Monte Carlo calculations within the Tersoff empirical potential (TEP) formalism [4, 5] and MD simulations based on the TEP [6]. The densities of states (DOS), computed for small super-cells using the PA, do not show a distinct semiconducting band gap (BG), though the DOS of the 54-atom sample [1] has the distinct dip demonstrating the trend towards gap formation. Electronic states in large sized a-SiC samples were carefully investigated in the framework of a sp3s* tight-binding (TB) scheme [6]. However, the latter investigation is inconsistent, since by generating a-SiC samples the scheme was not involved. The first-principles PA makes it possible to obtain accurately the atomic distribution in a-SiC but electronic states are computed incorrectly, since the LDA is known to underestimate the BG [2,7]. Therefore, it is rewarding to study both the atomic and electronic structures of a-SiC using another procedures capable to provide the appropriate atomic distribution and to describe the electronic states in the BG region in the framework of the same approach.