Antibonding surface state band of the Ge(111)2 × 1 surface

The unoccupied surface electronic structure of cleaved Ge(111)2 × 1 surfaces has been investigated with k-resolved inverse photoemission spectroscopy. A prominent empty surface state is detected, which exhibits a large dispersion in good agreement with the antibonding band calculated for the π-bonded chain model. Identical dispersions are obtained for undoped and highly n-doped crystals, which together with photoemission results indicate that no band gap narrowing or shift of the energy levels occurs for highly n-doped crystals as suggested recently from a theoretical model. © 1989.