Abstract
We report resonant photoemission measurements across the Fe 3p→3d photoabsorption threshold from the (110) surface of cleaved single-crystal Fe3O4 using synchrotron radiation. The resonant enhancement effect is used to distinguish the Fe 3d-derived states from the overlapping O 2p states in the valence band. The Fe 3d-derived states are found to extend about 18 eV below the Fermi level. Constant-initial-state spectroscopy across the Fe 3p excitation threshold reveals that this large valence bandwidth is due to a significant amount of cation–ligand hybridization; this result is in accord with recent configuration interaction cluster calculations of the photoemission final states in iron oxides reported by Fujimori et al. The electronic levels that are primarily associated with the different Fe2+ and Fe3+ cation environments in Fe3O4 are identified based on a comparison with photoemission spectra measured from cleaved FexO (x≂0.945) and α-Fe2O3 single crystals. Upon O2 adsorption, the Fe3O4(110) surface is rapidly oxidized, as evidenced by a decrease in the photoemission features associated with the Fe2+ valence state.
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More From: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films
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