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

We have investigated the 3 x 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 x 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 E-F. In the IPES spectra, an unoccupied dispersionless surface state was observed at 0.5 eV above E-F. 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. (C) 2000 Elsevier Science B.V. All rights reserved.