Determination of the source of two extra components in Si 2p photoelectron spectra of the SiO2/Si(1 0 0 ) interface

Ultrathin silicon oxide films were thermally grown on Si(100). High resolution photoelectron spectra of the Si 2p core--level were recorded at a photon energy of 180eV. Applying a fitting procedure to these spectra allows to separate various components. The line--shape consists of seven resolved components, which correspond to the electron signals of unoxidized Si(0)and the various different oxidation states of silicon (Si(1)(+), Si(2)(+), Si(3)(+), Si(4)(+)). The Si(0)--signal was composed of the bulk signal (B) and two extra components (Si(alpha), Si(beta). In order to determine the origin of these extra components a photoelectron diffraction analysis was performed. A model for the atomic structure at the interface is proposed. Within this model the Si(alpha) and Si(beta) signal are assigned to specific atom positions.