Extra metal adatom surface diffusion simulation on 1/3 ML Si(111) √3 × √3 metal-induced surfaces

摘要

A first-principle simulation of the surface diffusion of an extra metal (Me) adatom has been performed on the corresponding 1/3 monolayer (ML) Si(111) Me-induced surfaces. Using the nudged elastic band (NEB) optimization method, the minimum energy paths and the activation energy barrier profiles for all known Me-inducing reconstruction on an Si(111) surface at the 1/3 ML coverage have been obtained and compared with the available experimental data. The activation barrier is shown to depend on the atomic size of the diffusing adatom: the barrier has the highest value for the largest Me adatom, Pb (0.44 eV); lower values for the smaller Me adatoms, Sn (0.36 eV), In (0.22 eV) and Ga (0.13 eV); and the lowest value for the smallest Me adatom, Al (0.08 eV). The Arrhenius pre-exponential factors that were obtained in the harmonic approximation are as large as ～10~(11-13) Hz for all of the investigated surfaces, which supports the single-adatom diffusion model considered here.