Si-rich SiC(111)/(0001)3x3 and √3x√3 surfaces:: A Mott-Hubbard picture

The electronic structures of Si-rich reconstructions of SiC surfaces oriented parallel to the c axis are studied by means of first-principles calculations and angle-resolved photoemission spectroscopy (ARUPS). Independent of the reconstruction model, but in particular for the most favorable Si adtetramer-adlayer and T-4-site Si adatom models, the density-functional theory gives rise to half-filled pronounced dangling bond bands within the fundamental gap clearly indicating metallic surfaces. In contrast to theory, ARUPS observes only Wry occupied surface-state bands but no density of states at the Fermi energy. The explanation of the discrepancies within a Mott-Hubbard picture allows a reliable description of the details of the surface band structure.[S0163-1829(98)03444-4].