ADSORPTION OF ETHYLENE ON THE SI(100)-(2X1) SURFACE

The adsorption of ethylene on Si(100)-(2 x 1) has been studied using h igh-resolution electron energy loss spectroscopy. Upon adsorption, the ethylene molecule rehybridizes from sp2 to sp3 and forms a di-sigma b onded structure to the surface. However, the bonding of the surface si licon atoms - whether or not the Si-Si dimer bond remains - cannot be derived from just a study of ethylene adsorption. With low exposures o f atomic hydrogen on the ethylene-saturated Si(100) surface, we observ ed an additional Si-H vibrational mode and no significant change in th e chemisorbed ethylene spectrum. This result leads to the conclusion t hat the surface dangling bonds still exist after ethylene adsorption, and they are accessible to atomic hydrogen. Consequently, the adsorpti on of ethylene must be accompanied by cleavage of the original Si-Si d imer bonds on the surface.