ADSORPTION OF ETHYLENE ON SI(111)7X7 BY SYNCHROTRON-RADIATION PHOTOEMISSION

Ethylene adsorption on Si(111)7x7 was studied by valence band and Si2p core line synchrotron radiation photoemission. Experiments were perfo rmed at room temperature, as a function of coverage. The simultaneous quenching of the S-1 and S-2 silicon surface states upon adsorption sh ows that ethylene adsorbs in a molecular form, on a bridging site betw een a silicon adatom and rest atom. An electron donation from silicon to ethylene, which indicates a rather strong Si-C bond, induces an upw ard shift of the shallower molecular orbitals. The C-G double bond is stretched and becomes intermediate between single and double bond.