Surface character in the experimental Fermi surface of epitaxialErSi1.7s(0001) by photoemission spectroscopy

Abstract

The electronic structure of erbium silicide, ${\mathrm{ErSi}}_{1.7}$ (0001), 100-\AA{}-thick films epitaxially grown on Si(111), has been measured by angular-resolved ultraviolet photoemission (ARUPS) using synchrotron radiation. Valence-band spectra for different collection angles along the \ensuremath{\Gamma}M\ensuremath{\Gamma} and \ensuremath{\Gamma}KM directions of the substrate Si(111)-(1\ifmmode\times\else\texttimes\fi{}1) surface Brillouin zone (SBZ) and different Fermi-surface maps have been measured by the photoemission technique using photon energies of 21.2, 33, and 55 eV. The Fermi surface is characterized by hole and electron pockets at particular high-symmetry points in the SBZ. In opposition to what was expected considering both the crystallographic structure and calculated band structure, the shape of the Fermi-surface maps obtained for different photon energies are very similar. Moreover, the photoemission spectra using different photon energies show a very weak dispersion as a function of the k wave vector perpendicular to the surface (${\mathbf{k}}_{\mathrm{\ensuremath{\perp}}}$ ). All these findings suggest that the electronic states which contribute to the experimentally determined Fermi surface have a strong bidimensional character. No noticeable effect of the light polarization on the valence-band curves is observed indicating a hybrid nature of the involved orbitals.