ADSORPTION AND REACTION OF ETHENE ON CR2O3(0001) CR(110)/

Adsorption of Ethene on a clean and oxygen precovered Cr2O3(0001) film , grown on a Cr(110) surface, is studied via thermal desorption spectr oscopy (TDS), infrared reflection absorption spectroscopy (IRAS), elec tron energy loss spectroscopy (EELS) and X-ray photoelectron spectrosc opy (XPS). On the clean Cr2O3(0001) surface a weakly chemisorbed and a physisorbed state of ethene may be identified via TDS, IRAS and elect ron spectroscopies. Under ultrahigh vacuum conditions adsorption and d esorption of ethene is fully reversible for both, the clean and the ox ygen precovered chromiumoxide surface with peak maxima below room temp erature. If the sample, however. is heated to above room temperature u nder a background pressure of ethene, the formation of hydrocarbons on the surface is observed which may be only removed from the surface by applying higher temperatures coupled with sputter anneal treatments. We interpret these findings as the consequence of a polymerization rea ction of ethene on the oxide surface. Polymerization is discussed in t he context of the mechanism of low pressure polymerization with the Ph illips process.