Electronic structure of the prototypical As:Si(111)-1 x 1 surface investigated by inverse-photoemission spectroscopy.

Angle-resolved inverse-photoemission spectra have been measured on the nonreconstructed As:Si(111)-1\ifmmode\times\else\texttimes\fi{}1 surface along the two main directions \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{}K\ifmmode\bar\else\textasciimacron\fi{} and \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{}M\ifmmode\bar\else\textasciimacron\fi{} of the surface Brillouin zone. We observed three empty bands, the lower one of which is characteristic of a surface state partly resonant with bulk states in good agreement with theoretical calculations. We also observed a marked asymmetry in the dispersion along the M\ifmmode\bar\else\textasciimacron\fi{}'\ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{}M\ifmmode\bar\else\textasciimacron\fi{} direction.