Atomistic Features of the Amorphous-Crystal Interface in Silicon

Abstract

We simulate the amorphous-crystal interface in silicon using a combination of interatomic potential molecular-dynamics and tight-binding conjugate-gradient relaxation. The samples we create have high quality crystalline and amorphous portions. We develop some localized measures of order to characterize the interface, including a missing neighbor vector and the bond angle deviation. We find that the measures of order interpolate smoothly from a bulk crystal value to a bulk amorphous value across a 7A thick interface region. The interface structures exhibit a number of interesting features. The crystal planes near the interface are nearly perfect, with a few dimer defects similar to the Si(100) 2 x 1 reconstruction. Interfaces produced with one constant temperature simulation method are rough, with several layers of atoms forming <110> chains and (111) facets. A different simulation method produces more planar interfaces with only a few <110> chains.