High-resolution core-level study of hexagonal WC(0001)

Abstract

Results from a high-resolution core-level-photoemission investigation of the (0001) surface of a WC single crystal using synchrotron radiation are reported. Surface-shifted components were identified in both the C 1s and the W 4f levels. A surface C 1s core-level shift of -0.66 eV and a surface W 4f core-level shift of -0.38 eV were determined using a curve-fitting procedure. When using a thermochemical model and accounting only for the loss of coordination at the surface a shift of -0.62 eV was predicted for the carbon level and -0.39 eV for the tungsten level. Oxygen exposures were made for aiding in the assignment of surface-shifted features but also for investigating the initial oxidation behavior. Two chemically shifted W 4f components, having shifts of +0.29 and +0.66 eV, could be identified after oxygen exposures in the 30--300-L range.