REFLECTANCE DIFFERENCE SPECTROSCOPY SPECTRA OF CLEAN (3X2), (2X1), AND C(2X2) 3C-SIC(001) SURFACES - NEW EVIDENCE FOR SURFACE-STATE CONTRIBUTIONS TO OPTICAL ANISOTROPY SPECTRA

In this study we applied the surface sensitive optical method reflecta nce difference spectroscopy to investigate the optical response of cle an cubic 3 C-SiC(001) surfaces. The main reconstructions, the Si-rich (3 x 2) and (2 x 1) as well as the C-rich c(2 x 2) were prepared by an nealing in Si flux. For (3 x 2) we find a strong spectral feature at 4 .2 eV that is not observed for the other two reconstructions. Since th e direct gap of 3 C-SiC is at higher photon energies the 4.2 eV featur e must be related to the surface. Angle resolved ultraviolet photoelec tron spectroscopy measurements indicate surface states around the (X) over bar point of the unreconstructed surface Brillouin zone. We concl ude that the 4.2 eV feature is associated with this surface state and suggest that it is linked to the E-2 gap of bulk Si at 4.2 eV. (C) 199 8 American Vacuum Society.