Electronic and structural properties of the 6H-SiC(0001) surfaces

The atomic and electronic structures of clean 6H-SiC(0001) surfaces have been investigated by means of LEED and photoelectron spectroscopies (XPS, XAES and UPS). First a clean surface having the (3 x 3) structure has been obtained by heating the sample at 800 degrees C under a low Si flux. Successive annealings in UHV have produced two other stable reconstructions, namely the (root 3 x root 3)R30 degrees and the (6 root 3 x 6 root 3)R30 degrees. The various surface structures show distinctive core-level and Auger line shapes, which are characteristic of the composition of the surface layer, as checked by the XPS intensities by two different excitation sources (Mg K alpha and Zr M zeta), while UPS spectra show sizeable differences in the character of the valence bands. The evaluation of the atomic composition is able to sort between different models proposed in the literature.