Unoccupied electronic states of the FeS 2(100) surface studied by inverse photoemission

Abstract

Inverse photoemission spectra have been measured to study unoccupied electronic states from an FeS 2(100) single crystal along the Γ-X symmetry line with normal incidence electrons at energies between 20 and 40 eV. Two main features of the spectra are found, corresponding to direct bulk transitions into unoccupied iron 3d(e g) and sulphur 3p(σ∗) states, respectively, followed by a prominent minimum and a onset of a band with a wide structure due to mainly transitions into Fe 4sp-S 3d bands. These peaks are located at 1.4 and 3.0 eV above the Fermi level for an initial electron energy of 19.8 eV. They disperse according to band-structure calculations. The onset of the Fe 4sp-S 3d bands is about 5.0 eV above the Fermi level. The experimental results obtained here are in a reasonable agreement with band-structure calculations for FeS 2, and with previous results of optical, BIS and XAS measurements.