Photoemission study of the antibonding surface-state band on Si(111)2×1

Abstract
Cleaved Si(111)2×1 surfaces of a heavily n-doped crystal have been studied with angle-resolved photoemission. A new surface state is observed at the Fermi level, only appearing close to the points in the 2×1 surface Brillouin zone. The observed emission corresponds to the dispersion minimum of the antibonding band in the π-bonded chain model. The direct surface-state band gap is found to be 0.45 eV, in good agreement with results from absorption measurements. This indicates that excitonic effects are small in those measurements.