VACANCY-INDUCED ELECTRONIC STATES IN ERSI1.7(0001)

The physical origin of bulk related features observed by angle-resolve d photoelectron spectroscopy for an ordered 2ML root 3 x root 3R30 deg rees ErSi1.7 silicide on Si(111) has been investigated by means of ban d structure calculations. The photoemission data are well explained wi th the defected Er silicide model, i.e. the prominent peaks related to bulk states are consistent with the presence of a defected Si graphit e-like plane. More specifically, the calculations clearly predict a ne arly flat non-bonding pi band near the Fermi level that is observed ex perimentally and directly reflects the ordered root 3 array of Si vaca ncies. (C) 1997 Elsevier Science Ltd.