First principle simulations of the surface diffusion of Si and Me adatoms on the Si(111) Al, Ga, In, Pb

The intriguing but yet still unexplained experimental results of Hibino and Ogino [Phys. Rev. B 54, 5763 (1996); Surf. Sci. 328, L547 (1995)], who have observed single defect movement on an Me induced Si(111) 3 × 3 surface, have been revived and theoretically analysed. Using Nudged Elastic Band (NEB) optimization, the minimal energy path for an Si adatom moving on the ideal and vacancy defected surfaces has been obtained and the most probable mechanism of the vacancy mediated single defect diffusion has been established. This mechanism is shown to be responsible for the experimentally observed Si adatom movement and predicts a far easier movement of the Me adatom on vacancy defected Me induced Si(111) 3 × 3 surfaces.