The surface band gaps of Ge(001) 2×1

Applying in-situ combination of angle-resolved photoemission and inverse photoemission spectroscopy on clean Ge(001)2×1 surfaces we determined the binding energies of occupied and unoccupied surface states associated with the surface dimer of the 2×1 reconstruction at the high symmetric points, Γ, J, J′, 12JK and K of the surface Brillouin zone. Together with the experimentally determined valence band maximum the results will be compared on an absolute energy scale with recent surface band structure calculations