Vacancies on the Si(001) c(4 × 2) surface

Abstract

We have employed a parametrized tight-binding molecular-dynamics scheme in the study of the phenomenon of vacancies on the Si(001) c(4 × 2) surface. Simulated annealing is performed with a 'fictitious-Lagrangian' procedure to determine the optimal structures of a single and a dimer vacancy on this surface. A monovacancy is found to be less stable than a dimer vacancy, which agrees with experimental observations. We also show that there is a possible anisotropy in the surface migration of a dimer vacancy on the surface. The calculated activation energy for dimer-vacancy diffusion is 0.6 eV higher than that estimated experimentally at high temperatures.