Elementary processes during low-energy self-bombardment of Si(100) 2 × 2 a molecular dynamics study

Abstract

The properties of the Si(100)-(2 × 2) surface are investigated with respect to low-energy silicon impact by molecular dynamics (MD) simulations. Special attention is paid to the effects of penetration. The total energy and forces are calculated by means of a density-functional non-orthogonal tight-binding scheme, which recently has been successfully applied to various covalent systems (C, BN, CN, Si). Within this framework the bulk displacement energy along the [100] direction is determined at a value of 23 eV, while the surface displacement threshold is slightly lower at 18 eV. The energetic analysis of trajectories of impinging atoms yields the penetration thresholds and cross sections for different low energy entries within the surface unit cell. The penetration threshold was obtained at a value of 8 ± 2 eV. The results will be discussed with regard to experimental findings in silicon homoepitaxy using low-energy ion beam deposition.

Key Words:

• Subplantation
• Silicon
• Ion beam deposition
• Molecular dynamics