Photoemission studies of intrinsic surface states on Si(100)

Abstract

We have determined the energy vs. k∥ dispersion of intrinsic surface states on Si(100) (2×1) by means of angle-resolved photoemission with synchrotron radiation. For k∥=0, there is a very pronounced surface state 0.7 eV below EF(i.e.,∠0.4 eV below the top of the valence band) which disperses downwards with increasing k∥. At J′ on the boundary of the surface Brillouin zone, we find two states with binding energies of 0.7 and 1.2 eV with respect to EF. A number of geometrical models and their corresponding theoretical surface state bands have recently been published for Si(100) (2×1). Our results disagree qualitatively with all surface state dispersions calculated up to date, i.e., the ideal surface, the vacancy model, the pairing model, and the zig-zag-chain model. Namely, we observed semiconducting surface state bands with a low state density at EF while all models calculated to date yield metallic surface states with a large state density at EF.