Chemical stability the magnetic oxide EuO directly on silicon observed by hard x-ray photoemission spectroscopy

We present a detailed study of the electronic structure and chemical state of high-quality stoichiometric EuO and O-rich Eu1O1+x thin films grown directly on silicon without any buffer layer using hard x-ray photoemission spectroscopy (HAXPES). We determine the EuO oxidation state from a consistent quantitative peak analysis of 4f valence band and 3d core-level spectra. The results prove that nearly ideal, stoichiometric, and homogeneous EuO thin films can be grown on silicon, with a uniform depth distribution of divalent Eu cations. Furthermore, we identify the chemical stability of the EuO/silicon interface from Si 2p core-level photoemission. This work clearly demonstrates the successful integration of high-quality EuO thin films directly on silicon, opening up the pathway for the future incorporation of this functional magnetic oxide into silicon-based spintronic devices