Binding and diffusion of an al adatom on the hydrogen-terminated si(100) surface

We studied the initial stage of the adsorption of Al on the hydrogen-terminated Si(100)2 × 1 surface using first-principles calculations with norm-conserving pseudopotentials. By mapping out the adsorption energy of a single Al adatom on the hydrogen-terminated Si surface, we obtain a binding energy of 1.8 eV and an activation energy of 0.6 eV for diffusion both parallel and perpendicular to the Si-dimer rows. We find that the adsorption energy per adatom increases when the number of Al adatoms increases to two or more. We think that the adatoms form clusters, considering the low activation energy and the behavior of the adsorption energy.