DFT simulation of the extra Me adatom diffusion on the Ge(111) √3×√3 1/3 ML Me induced surfaces

摘要

A first-principle simulation of the surface diffusion of an extra metal (Me) adatom on the corresponding 1/3 monolayer (ML) Ge(111) √3×√3 Me induced surfaces has been performed. Using the Nudged Elastic Band (NEB) optimization method, the minimum energy paths and activation energy barrier profiles for all known Me inducing √3×√3 reconstruction on a Ge(111) surface have been obtained. The value of the activation barrier is shown to depend on the adatom formation energies and the atomic radius of the diffusing metal: 0.33 eV for Pb and 0.25 eV for Sn. The Arrhenius pre-exponential factors that were obtained in the harmonic approximation are as large as 10~(11-12) Hz for all of the investigated surfaces, which supports the single-atomic diffusion model considered here.