An auger and eels study of iron sulfide (FeS 2, F 7S 8 and FeS) surfaces

Abstract

Auger and electron energy loss spectroscopy (EELS) were used to study the iron sulfide (FeS 2, Fe 7S 8 and FeS) surfaces. A characteristic M 2.3VV Auger doublet with a separation of 5.0 eV was observed on the Sulfides. An assignment of the electron energy loss peaks was made based on the energy dependence of the loss peaks and previous photoemission results. In addition to interband transitions and core level excitations, two volume plasmons and two surface plasmons were tentatively identified. The effect of argon ion bombardment was studied by monitoring the changes observed in the EELS spectra with sputtering time. Peaks with strong iron and sulfur character were observed. Heating the damaged sulfides results in reconstruction of the sulfide surfaces through migration of sulfur. For the undamaged sulfides, changes in the EELS spectra are due to variations in surface composition and crystallographic structure. For all the sulfides under study, some evidence of sulfur segregation to the surface was observed. Finally, the reactions of the sulfides with simple gases, such as H 2, CO and O 2 were studied. Heating with H 2 results in removal of elemental sulfur from the surface. CO reacts with Fe on the damage FeS 2 and Fe 7S 8 surfaces. The reaction products can be removed with H 2. All the sulfides are easily oxidized by oxygen to form α-Fe 2O 3. The reactions of H 2S and CO with clean Fe surfaces were also studied using EELS.