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 performed at room temperature, as a function of coverage. The simultaneous quenching of the S-1 and S-2 silicon surface states upon adsorption shows that ethylene adsorbs in a molecular form, on a bridging site between a silicon adatom and rest atom. An electron donation from silicon to ethylene, which indicates a rather strong Si-C bond, induces an upward shift of the shallower molecular orbitals. The C-G double bond is stretched and becomes intermediate between single and double bond.