First-principles calculation on diffusion of Si adatoms on H/Si(001)-(2×1) surface

We report the result of first-principles calculations on the Si adsorption on the monohydride terminated Si(001)-(2×1) surface. It is found that the Si adatom spontaneously segregates one H atom from a surface Si dimer during adsorption, and further captures the remaining H atom of the same Si dimer during surface migration, leading to the most stable adsorption geometry. The Si adatom diffusion process on the hydrogenated Si(001) surface is complicated by the transfer of H atoms between the adatom and the Si dimer atoms. The migration of the Si adatom is extremely reduced compared with that on the bare Si(001) surface.