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

Abstract

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 ($S_1$), ≊-0.8 ($S_2$), and ≊-1.8 ($S_3$) eV. The $S_3$ 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 $A_1$ and $A_3$ which are similar to the $S_1$ and $S_3$ 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, $E_i$(k${¯}_{\mathrm{para}}$), 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.