Atomic and electronic structures of the group-IV elements on Si(111)-(√3 × √3) surface

Abstract

We have examined the Si(111) surface with 1/3 monolayer of group-IV elements within the ab initio density functional theory. We have considered two possible threefold-coordinated sites for the atom adsorption: (i) H3 site (this site is directly above a fourth-layer Si atom and (ii) T4 site (directly above a second-layer Si atom). For the atoms Ge, Sn, and Pb, the T4 position always gives the most stable configuration, comparing with the H3 site. The calculated energy difference between T4 and H3 for Pb, Ge, and Sn, is 0.32 eV, 0.59 eV, and 0.41 eV, respectively. We have also presented electronic band structure and orbital character of the surface states of the Sn/Si(111)-(√3 × √3) surface.