Solid-state graphitization mechanisms of silicon carbide 6H-SiC polar faces

Due to the higher vapour pressure of silicon, silicon carbide surfaces anne aled at high temperature under vacuum tend to graphitize. The comparison of graphite formation on the silicon and carbon terminations of 6H-SiC reveal s significant differences in the graphitization mechanisms involved. The co nduction-band structure of these interfaces has been determined by angle-re solved inverse photoemission spectroscopy (KRIPES). Although the graphite l ayers grown on the C face are essentially polycrystalline, a small fraction of the film keeps a preferred orientation, where the graphite lattice basi s vectors are rotated by 30 degrees with respect to the basis vectors of th e SiC lattice as in the case of the Si face. This in-plane disorder is in c ontrast with the growth of graphite on the Si face that takes place on a "p assivated" adatom-terminated surface, leading to single-crystalline, hetero epitaxial graphite growth. The observation of unshifted pi* states indicate s a very small interaction of the first graphite monolayer with the Si face . In contrast, KRIPES reveals that the first graphite layer is strongly bou nd to the C face. A rehybridization of the graphite pi* states with occupie d orbitals of the substrate: is inferred from an observed increase in the d ensity of states in the vicinity of the Fermi level. (C) 2000 Elsevier Scie nce B.V. All rights reserved.