Evaluation of structural and mechanical properties of amorphous silicon surfaces by a combination approach of Ab-initio and classical molecular dynamics

Abstract

In this study, we use a combiend method of a classical molecular dynamics with the Tersoff potential and an ab-initio calculation based on density functional theory. This combination method can provide quantitative evaluation of the surface energy and surface stress of well-relaxed amorphous silicon in addition to its structure. Using this method, a surface energy of 1.05 ± 0.14 J/m2 and a surface stress of 1.5 ± 1.2N/m was obtained. This calculation also led to a new discovery of the microscopic characteristic of a-Si surfaces, which was not revealed through the use of an empirical potential. It was shown that there are two types of threefold coordinated atoms at the surface region; one with p3-like bonding and the other with sp2-like bonding. In addition, the investigation indicated that the microstructures of these coordination defects were different from those of threefold coordinated atoms observed in the bulk region.