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 spectroscopy (TDS), infrared reflection absorption spectroscopy (IRAS), electron energy loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS). On the clean Cr2O3(0001) surface a weakly chemisorbed and a physisorbed state of ethene may be identified via TDS, IRAS and electron spectroscopies. Under ultrahigh vacuum conditions adsorption and desorption of ethene is fully reversible for both, the clean and the oxygen precovered chromiumoxide surface with peak maxima below room temperature. If the sample, however. is heated to above room temperature under 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 reaction of ethene on the oxide surface. Polymerization is discussed in the context of the mechanism of low pressure polymerization with the Phillips process.