The $(\sqrt{3}\times\sqrt{3}){\rm R}30^{\circ}$-Reconstructed 6H–SiC(0001): A Semiconducting Surface

Abstract

k//-resolved inverse-photoemission spectroscopy of the [Formula: see text] reconstruction of 6H–SiC(0001) reveals a sharp surface state U located 1.10±0.05 eV above the Fermi level at the center of the surface Brillouin zone with a total bandwidth of 0.34±0.05 eV. This value is in good agreement with recent LDA calculations which predict an adatom-induced surface state Σ1 which should be half-filled. In this model, the adatoms are Si atoms occupying the T 4 site above a compact SiC(0001) (Si) termination. In contrast to the predicted metallic behavior, the U state remains completely unoccupied throughout the whole Brillouin zone, and the surface is semiconducting. We propose that some charge transfer from the Si adatoms towards subsituted C atoms in the terminating bilayer stabilizes the reconstruction by moving up the Σ1 state away from the Fermi level.