Bulk and surface electronic structures of Si(111)2×1 and Si(111)7×7 studied by angle-resolved photoelectron spectroscopy

By using polarization-dependent angle-resolved photoemission bulk direct transitions from the uppermost two valence bands have been identified in spectra for both Si(111)2×{}1 and Si(111)7×{}7. The experimental initial-energy versus kₚₐᵣₐ dispersions for these transitions obtained in the (11{}0) mirror plane, are in good agreement with calculated dispersions for transitions to a free-electron final band in the photon-energy range 10.2--17.0 eV investigated. The surface electronic structure of cleaved Si(111)2×{}1 is compared with that of the Si(111)7×{}7 surface obtained both by annealing a cleaved sample and by sputtering and annealing a polished sample. The two ways of preparing the 7×{}7 surface result in essentially identical surface electronic structures.