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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.
Himpsel et al. (Wed,) studied this question.