A core level and valence band photoemission study of 6H-SIC(000(1)over-bar)

The results of a photoemission study of the C terminated 6H-SiC(000 (1) over bar) surface, prepared by ex-situ chemical treatment and in-situ beatings. are presented and discussed. The as-introduced unreconstructed 1 x 1 surface shows strong oxygen-derived features that persist up to a heating temperature of about 950 degrees C. After heating at 1050 degrees C a. 3 x 3 reconstructed surface is formed, and the valence band spectra show the two subbands in the density of states of SiC. This surface shows a semiconducting behavior since no or very little emission is observed close to or at the Fermi level. Recorded high-resolution C1s and Si2p spectra show the presence of one type of Si sites and at least three different C sites in the surface region, Two of these C1s components are clearly surface related, and the 3 x 3 reconstruction is therefore suggested to originate from at least two carbon layers on top of a bulk truncated crystal. Heating at 1200 degrees C. is shown to result in a strong enrichment of carbon in the surface region. Recorded core level spectra then show the presence of a graphite C1s peak but also of other shifted components. which suggest quite large compositional modifications in the surface region, (C) 1998 Elsevier Science B.V. All rights reserved.