Photoemission study of the surface and bulk electronic structures of Si(111)7×7 and Si(111)≤3¯×≤3¯:Al

Angle-resolved photoelectron spectroscopy has been used to study the surface and bulk electronic structures of Si(111)7×{}7 and Si(111){}3 ×{} {}3 :Al. For the Si(111)7×{}7 surface we find three surface states at {}-0.2 (S₁), {}-0.8 (S₂), and {}-1.8 (S₃) eV. The S₃ surface state shows dispersion along the {Γ}{}--K{} and {Γ}{}--M{} lines in the 1×{}1 surface Brillouin zone, with a bandwidth of {}0.3 eV. For Si(111){}3 ×{} {}3 :Al we find two surface-state structures A₁ and A₃ which are similar to the S₁ and S₃ structures for the 7×{}7 surface. Structures due to direct transitions from the uppermost two valence bands are also identified in the spectra. Initial energy versus wave vector parallel to the surface, Eᵢ(kₚₐᵣₐ), dispersions are presented along the [112{}], [2 1{} 1{}], and [101{}] azimuthal directions. The experimental dispersions for the direct transitions are in good agreement with calculated dispersions using a free-electron final band.