Electronic structure ofErSi2andYSi2

We present a theoretical and experimental study of erbium and yttrium disilicides. These materials are representative of the trivalent heavy-rare-earth disilicides that can be epitaxially grown on Si(111). The densities of states are obtained using the augmented-plane-wave method. They are used to calculate the Auger Si LVV spectra. For the measurements, we used x-ray photoemission and Auger electron spectroscopy on monocrystalline ${\mathrm{ErSi}}_{1.7}$. Theoretical and experimental results are compared and show structures due to Er-Si hybridization. Although the valence-band results are in qualitative agreement, we find significant differences that could be related to effects due to silicon vacancies.