Electronic structure of the annealed Ge(111) and Si(111) surfaces: Similarities in local bonding

We have studied the valence-band and surface-core-level states for thermally annealed Ge(111)-(2 ×{} 8) and Si(111)-(7 ×{} 7) and laser-annealed Ge(111)-(1 ×{} 1) and Si(111)-(1 ×{} 1) surfaces with high-resolution photoelectron spectroscopy using synchrotron radiation. We find two surface states near the top of the valence band which exhibit characteristic emission patterns within the hexagonal 1 ×{} 1 surface Brillouin zone as well as characteristic surface-core-level spectra which indicate the existence of a common local bonding geometry for all these surfaces.