ATOMIC-STRUCTURE OF THE GE/SI(100)-(2X1) SURFACE

We have determined the atomic structure of the Ge-covered Si(100) surface in one-monolayer coverage using the pseudopotential density-functional total-energy calculation scheme. We find that the asymmetric Ge dimer structure is energetically favored over the symmetric one with a stabilization energy of 0.35 eV/dimer: at equilibrium, the dimer bond length is 2.39 angstrom and the dimer axis tilts 16.3-degrees. The present result confirms the experimental observations of the asymmetric dimers on this surface, but the calculated dimer bond length differs from a recent x-ray standing-wave measurement.