Position of the empty surface-state band on Si(111) 2×1

The cleaved silicon surface of a highly n-type doped crystal has been studied with k-resolved inverse-photoemission spectroscopy (KRIPES). The dispersion of the unoccupied electronic surface-state band of a single-domain 2×1 reconstruction was found to be very similar to p-type doped samples. The band minimum at point J¯ occurs at the same energy value with similar intensity as for p-type doped samples. Comparison of the present results with scanning tunneling microscopy (STM) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS), on similar samples, indicates that the empty band observed in KRIPES differs from that seen at the Fermi level by STM and ARUPS. An explanation in terms of either many-body effects in KRIPES or of strong electron-phonon interactions in the different techniques is suggested.