Photoelectron spectroscopic investigations of thin FexSi100−x films

Photoelectron spectroscopic methods (UPS, XPS) were employed to study the electronic properties of FexSi100−x films (0 ≤ x ≤ 75) in the amorphous and polycrystalline state. The amorphous samples were prepared by vapour condensation on sapphire substrates held at room temperature (RT). The polycrystalline samples were obtained by annealing the amorphous films at 950 K. An insulator-to-metal transition in the amorphous films has been detected for Fe content between 10 and 20 at%, as indicated by the development of a step-like photoelectron intensity at the Fermi level. The semiconducting β-FeSi2 phase is observable in the polycrystalline films, as seen by the disappearance of the step-like Fermi edge in the UPS spectra. A line shape analysis of the Fe 2p core levels is used to obtain additional information about the electronic structure of the different phases. Our results will be compared to data taken on FeSi interface layers by other authors.