Unoccupied surface state on the (√3 × √3) R30° of 6H-SiC(0001)

Abstract

Applying k-resolved inverse photoemission (KRIPES) to the √3×√3 R30°-reconstructed 6H-SiC(0001) face, we have observed a sharp surface state U located at 1.10 ± 0.05 eV above the Fermi level at the centre of the surface Brillouin zone. Its bandwidth of 0.34 ± 0.05 eV is in good agreement with the 0.35 eV predicted by first-principle calculations based on a Si-adatom model. However, LDA calculations predict a half-filled Σ1 state and a metallic character for this reconstruction. Together with recent ARUPS data, our results reveal that the one-electron band Σ1 is split into two bands, giving a semiconducting surface with a reduced indirect bandgap around 2.0 eV at the ' point. Many-body correlation effects may give rise, in the limit of strong localization, to this bandgap opening.