Two different Sb-induced phases have been found upon annealing on fres
hly evaporated Si(100)2 x 1 surfaces. The surface electronic structure
s of the two phases (1 x 1-Sb and 2 x 1-Sb) have been studied with sur
face differential reflectivity (SDR) and angle-resolved photoelectron
spectroscopy (ARUPS). Both techniques show the existence of a gap of a
pproximately 1.6 and 1.4 eV for the two phases, with the empty state l
ocated near the Fermi level.