A high-resolution core-level-photoemission investigation of the (100) surface of TiN and TiC is reported. A surface-shifted component is revealed in both the N 1s level on TiN and in the C 1s level on TiC.Using a curve-fitting procedure a surface shift of -0.57 eV is extracted for the N 1s component on TiN and a shift of -0.26 eV for the C 1s component on TiC. No surface-shifted Ti 2p level could be revealed on either TiN or TiC. These results do not agree with earlier calculated results for TiC which predicted no surface shift in the C 1s level but a small positive shift in the Ti s levels. Using a thermochemical model and accounting only for the loss of coordination at the surface, a shift of -0.07 eV is estimated both for the N 1s level in TiN and for the C 1s level in TiC.

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Scanning tunneling microscopy has been performed on the reconstructed polar surface of substoichiometric VC08O(111). A mixture of (8X1) and (&3X&3)R30' reconstructed areas was found. The (8X1) periodicity could be determined to be the result of a square-lattice surface layer superimposed on the hexagonal substrate. As this square lattice must have its origin in strong and directed in-0 plane bonds with the relatively large length of about 2.9 A, it can be deduced to consist of vanadium atoms. Lateral positions of these vanadium surface atoms with respect to the substrate are suggested from the measured surface corrugation. The (&3X&3)R30' structure was found in small triangular areas which can, due to the measured step heights between the two reconstructions, be believed to be carbon terminated. The occurrence of a reconstructed surface with a reduced atomic concentration is in contrast to what is known for TiC(111) and NbC (111), both having stable (1X1) surfaces. A qualitative explanation for this difference is suggested.

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