Angle-resolved ultraviolet-photoelectron-spectroscopy study of theSi(111)3×3-Al surface

Angle-resolved ultraviolet-photoelectron spectra have been measured for the $\mathrm{Si}\mathrm{}\left(111\right)\mathrm{}\sqrt{3}\times \sqrt{3}$-Al surface. Two surface-state bands have been found at $E_b=\sim 1.3-1.9$ eV below the Fermi level which disperse in accordance with the $\sqrt{3}\times \sqrt{3}$ surface Brillouin zone. It is suggested that a nondispersive surface-state band found at $E_b\approx 0.3$ eV is extrinsic to the $\sqrt{3}\times \sqrt{3}$ surface. The two dispersive bands are in qualitative agreement with those calculated for threefold-hollow adatom models.