Ab initio calculations, based on pseudopotentials and the density functional theory, have been made to investigate the equilibrium atomic geometry, electronic states, and bonding of the ${\mathrm{H}}_2\mathrm{S}$ molecule on the Si(001) and Ge(001) surfaces within two dissociative adsorption geometries. First we consider adsorption of partially dissociated species $(\mathrm{SH}{)}^{-}$ and ${\mathrm{H}}^{+}$ onto the Si or Ge dimer with a $(1\mathrm{}\times 2)$ surface periodicity. Secondly, we consider adsorption of fully dissociated species S and 2H on the surface with a $(1\mathrm{}\times 2)$ periodicity but without dimer formation. In general, the adsorption of ${\mathrm{H}}_2\mathrm{S}$ on the Si(001) and Ge(001) surfaces shows similar behavior. For both geometries studied here, the fundamental band gap is free of surface states, with the highest occupied state lying below the valence band maximum.

• Received 7 October 1998

DOI:https://doi.org/10.1103/PhysRevB.60.5497