Molecular dynamics simulation of the surface reconstruction and strain relief in Si1-xGex/Si(100) heterostructures

Abstract

The structure of a variety of Si1-xGex/Si heterostructures, as well as bulk Si(100) and Ge(100) modelled by the Stillinger-Weber potential, have been simulated by molecular dynamics to investigate the surface reconstruction and strain relief in the SiGe thin films. It was found that the strain in SiGe/Si(100) thin films was relaxed by the segregation of Ge to the surface. Rebonding of sub-surface atoms into dimers in the presence of a vacancy or cluster of vacancies above them was observed in the ensuing surface reconstruction. For SiGe/Si, the amount of 'rebonded missing dimers' in the surface increased with increasing Ge composition. However, for Ge/Si(100), a V-shaped defect was observed in the Ge thin film. For bulk Si, several rebonded missing dimers were found at the surface, while for bulk Ge(100) the surface showed a typical 2*1 reconstruction. All these findings corroborate recent related experimental studies and theoretical predictions.