Abstract
Characterization of an α-(Fe0.75,Cr0.25)2O3(0001) mixed oxide single crystal surface was conducted using X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), low-energy electron diffraction (LEED), and temperature-programmed desorption (TPD). After sputter/anneal cleaning in ultrahigh vacuum (UHV), the mixed oxide surface became terminated with a magnetite-like (111) structure based on the presence of (2 × 2) spots in LEED and Fe2+ in XPS. The composition of the surface was close to that of M3O4 based on XPS, with the metal (M) content ratio of Fe2+/3+ and Cr3+ being close to 1.4:1, despite the film’s bulk being prepared with a 3:1 ratio of these cations. Enrichment of the surface with Cr was not altered by high temperature oxidation in UHV but could be partially reversed by exposure to air. Adsorption of various probe molecules (NO, O2, CO2, and H2O) was used in an effort to identify the active cation sites present on the (Fe,Cr)3O4(111)-terminated surface. Although both XPS an...
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