SOFT-X-RAY EMISSION AND AUGER-ELECTRON SPECTROSCOPIC STUDY OF FES, FE0.875S, AND FE0.5S

Soft x-ray emission spectra are obtained of sulfur in FeS, Fe 0.9S, Fe0.875S, and Fe0.5S. The structure in the Kβ emission spectra is consistent with recent SCF-Xα calculations for ferrous iron in an octahedral crystal field. Broadening in the Kβ emission spectra with decrease in the Fe-S bond distance is in agreement with the trends predicted by the SCF-Xα calculations. The charge on the sulfur ions is calculated from the shifts of the K α emission lines. Calculated charges on FeS and Fe 0.5S are in good agreement with previous LCAO calculations and photoemission data. Shifts in the Kα line positions for Fe 0.9S and Fe0.875S indicate that electroneutrality is satisfied by a reduction in charge on sulfur rather than the coexistence of ferrous and ferric iron. The Auger spectra of sulfur show sharp structure for FeS which gradually disappears as the sulfides become more cation deficient. The Auger data is discussed in terms of changes in the electronic density of states in the valence band as predicted by the SCF-Xα calculations.