Angular distribution of photoelectrons from (111) silicon surface states

Abstract
Photoelectron energy spectra were obtained as a function of angle of emission from the cleaved face of lightly−doped p−type silicon using 10.2 eV normal incidence radiation. Measurements were taken in a previously described apparatus on samples prepared under conditions known to produce the 2×1 LEED pattern. A peak in the spectra due to emission from the surface state near the top of the valence bands was quite prominent between 20° and 30° from the [111] surface normal. The variation of the peak’s intensity with azimuthal angle displayed three strong lobes centered about the 〈2̄11〉 directions. Since a dangling−bond surface state of primarily pz character is almost azimuthally isotropic, we attribute the anisotropies observed either to final−state effects on the emission probabilities, or to an unexpectedly large transverse−orbital (S2) content in the initial surface state itself.