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

Abstract

Cleaved Si(111)2\ifmmode\times\else\texttimes\fi{}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 J\ifmmode\bar\else\textasciimacron\fi{} points in the 2\ifmmode\times\else\texttimes\fi{}1 surface Brillouin zone. The observed emission corresponds to the dispersion minimum of the antibonding band in the \ensuremath{\pi}-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.