Photoemission study of the silicate adlayer reconstruction on Si-terminated 6H-SiC (0001)

We present a photoemission study of a highly ordered silicate adlayer structure on Si-terminated 6H-SiC showing a (root 3x root3)R30 degrees LEED pattern. The adlayer has a nominal stoichiometry of SiO2 and forms during the preparation of 6H-SiC (0001) at 1000 degreesC in 5.10(4) Pa of hydrogen. The binding energy signature of the Si 2p (three components), C Is tone component) and O Is tone component) core level spectra is compatible with a structural model of the adlayer as derived from a previously published LEED analysis. Angle resolved valence band spectra show a surface state in the ionic gap of SiC assigned to Si-O bonding states. A silicon dangling bond state that is expected on the basis of the structural model for the adlayer is not observed. An analysis of the relative intensities of the three Si 2p components indicates that the dangling bond is initially hydrogen terminated and transforms into a Si-O bond above 500 degreesC.