Nature of the valence states in silicon transition metal interfaces

Photoemission spectroscopy using synchrotron radiation and excitation energies around the Cooper minimum have been applied to studies of the nature of the bonding in SiPd and SiPt interfaces. Evidence is presented that breaking of the tetrahedral coordination in Si and the Si-metal interaction introduces new valence states in the interface region. The energy positron and the orbital character of these Si-metal mixed valence states are determined. A suggestion is made how these results can be generalized to other Si-transition metal interfaces.