Angle-resolved inverse photoemission of H-etched 6H-SiC (0001)

摘要

We present results of angle-resolved inverse photoemission measurements of the ex-situ hydrogen-etched 6H-SiC(0001) surfaces. The etching process leads to an ordered silicate adlayer exhibiting a (3~(1/3) × 3~(1/3)) R30°-reconstructed surface as confirmed by low-energy electron diffraction. Three distinct states at E = 2.6 eV, 5.2 eV, and 7.8 eV above the Fermi level, respectively, are observed whereas no unoccupied Mott-Hubbard surface state is detected. All three states show only a weak dispersion in the ΓM- and ΓK-directions of the (1×1) surface Brillouin zone. A considerable band bending of about 1 eV is found at the SiC/SiO_2 interface. The experimental results are compared to band-structure calculations for an ideally oxidized surface with terminating hydroxyl groups and hydrogen atoms, respectively.