Surface electronic structure of pure and oxidized non-epitaxial Mg2Si layers on Si(111)

Non-epitaxial magnesium silicide (Mg2Si) films of 100 Angstrom thickness were grown on Si(111). The formation of Mg2Si is identified by characteristic shifts uf the Mg 2p and Si 2p peaks in X-ray photoelectron spectroscopy (XPS). Information on the electronic structure of this surface is obtained by metastable impact electron spectroscopy (MIES). The surface density of stales obtained with MIES is dominated by strong emission below the Fermi level (E-F) displaying a characteristic double peak structure. The oxidation of these silicide surfaces is performed at room temperature. The electronic structure of these surfaces is investigated with MIES, UPS (HeI) and XPS. From the comparison with oxidized Mg films it is concluded. that the surface is terminated by an insulating MgO layer. Subsurface oxidation of the silicide does not take place. Furthermore, no formation of silicon oxides is observed. (C) 1998 Elsevier Science B.V.