Electronic structure of the 6H–SiC(0001)-3×3 surface studied with angle-resolved inverse and direct photoemission

We have investigated the 3×3 reconstruction of the 6H–SiC(0001) surface with angle-resolved direct and inverse photoemission (ARUPS and IPES). The surface was prepared by heating the sample in a Si flux and showed an excellent 3×3 LEED pattern. In the ARUPS spectra, three occupied surface states were found at the energies 0.5 eV, 1.5 eV and 1.9 eV below EF. In the IPES spectra, an unoccupied dispersionless surface state was observed at 0.5 eV above EF. Thereby, the reconstruction has a semiconducting character with a surface bandgap of 1.0 eV. This result agrees well with recent theoretical results that predict strong electron-correlation effects, leading to a Mott–Hubbard ground state.