ADSORPTION OF WATER ON TIC(100) - EVIDENCE FOR COMPLEX-REACTION AND DESORPTION PATHWAYS

The interaction of water with the nonpolar TiC(100) face has been prob ed as a function of surface temperature over the range 98-773 K. Tempe rature-programmed desorption (TPD) has been used to monitor the desorp tion products as a function of coverage while high-resolution electron energy loss spectroscopy (HREELS) has been used to probe the nature o f adsorbed species as a function of surface temperature. Together, the se molecularly specific probes reveal the presence of both molecularly and dissociatively adsorbed water in the monolayer regime at cryogeni c temperatures. Furthermore, both Ti and C surface atoms participate i n the dissociation of water and lead to the production of a complex ar ray of surface species. With increasing surface temperature, the desor ption species D2O, CO, CO2, and D-2 are observed over a broad temperat ure range. The desorption of CO and CO2 demonstrates the consumption o f carbon from the TiC surface while the desorption of D-2 is thought t o be related to presence of carbon vacancies known to exist within thi s and other metal carbides.