Dimer charge asymmetry determined by photoemission from epitaxial Ge on Si(100)-(2×1)

The charge asymmetry between the up and down atoms of an asymmetric dimer on Si(100)-(2×1) or Ge(100)-(2×1) is tied to the core-level energy splitting. Previous studies of the surface components in the core-level photoemission spectra disagreed on the assignments of the atomic origins, resulting in a disagreement on the charge asymmetry. The present core-level study of the growth of Ge on Si(100) shows clearly that the dimers are essentially covalent.