Atomic and electronic structures of heat treated 6H-SiC surface

We have studied heat-treated (950-1300 degrees C) 6H-SiC(0001)Si and (000 (1) over bar)C face with photoemission spectroscopy using synchrotron radiation (SR-PES) and low energy electron diffraction (LEED). We observed LEED patterns of SiC 1 x 1, root 3 x root 3, root 3 x root 3 + 6 root 3 x 6 root 3 and graphite 1 x 1 sequentially with increasing heating temperature for (0001)Si face and SiC 1 x 1 for (000 (1) over bar)C face, respectively. We have measured Si(2p) spectra and valence band energy distribution curves (VB-EDCs). The trend of sublimation of Si atoms from surface is different between Si- and C-face. root 3 x root 3 superstructure must be Si-derived. The 6 root 3 x 6 root 3 structure could be explained as a moire pattern caused by monolayer-graphite sitting on SiC surface. Si Ss-derived state of SiC 1 x 1 is different between SiC 1 x 1 for Si- and C-face. It is suggested that a single crystal graphite layer grows on Si-face and a polycrystalline graphite is formed on C-face for heated specimens above 1150 degrees C. (C) 1998 Elsevier Science B.V. All rights reserved.