Adsorption of partially and fully dissociated H2S molecules on the Si(001)and Ge(001) surfaces

Ab initio calculations, based on pseudopotentials and the density functiona l theory, have been made to investigate the equilibrium atomic geometry, el ectronic states, and bonding of the H2S molecule on the Si(001) and Ge(001) surfaces within two dissociative adsorption geometries. First we consider adsorption of partially dissociated species (SH)(-) and H+ onto the Si or G e dimer with a(1x2) surface periodicity. Secondly, we consider adsorption o f fully dissociated species S and 2H on the surface with a (1 x 2) periodic ity but without dimer formation. In general, the adsorption of H2S on the S i(001) and Ge(001) surfaces shows similar behavior. For both geometries stu died here, the fundamental band gap is free of surface states, with the hig hest occupied state lying below the valence band maximum. [S0163-1829(99)14 531-4].