INVERSE-PHOTOEMISSION STUDY OF NON-RECONSTRUCTED SI(111) SURFACES - ACOMPARISON BETWEEN H-SI(111)1X1 AND AS-SI(111)1X1

The lower conduction-band states of Si(111) have been measured by k(pa rallel to)-resolved inverse photoelectron spectroscopy (KRIPES) on non -reconstructed surfaces obtained either by saturating the dangling bon ds with atomic hydrogen or by replacing the Si surface atoms with As a toms. On the H-Si(111)1 x 1 surface, two conduction bands are measured whose asymmetry in the Gamma-($) over bar M direction reveals their b ulk character. The same conduction band states are also measured on th e As:Si(111)1 x 1 surface, however at lower energies as a result of th e higher electronegativity of the As atoms. These latter data are in e xcellent agreement with recent calculations using the quasi-particle f ormalism.