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Abstract:
Transition metal oxides are important materials in heterogenous catalysis, as supporting materials as well as active components. The catalytic activity of Cr2O3 for IE polymerization of olefines or hydrogenation of alkenes is well known and rather high. Therefore, it is important to get information on the surface electronic structure of Cr2O3. Here we report high resolution XPS measurements of a thin epitaxial Cr2O3(111) film grown on Cr(110). The oxide films have been prepared by in situ oxidation of a Cr(110) single crystal disk (12 mm diameter, 1.5 mm thickness, purity 5n) at elevated temperatures (540 K to 780 K) in an atmosphere of 10−6 mbar of O2. The oxygen doses have been typically in the range of a few thousand Langmuirs. Under these conditions a Cr2O3(111) layer [Cr2O3(0001) orientation in hexagonal notation] forms on the surface as confirmed via low energy electron diffraction IV analysis. The film thickness ranges from about 2.5 nm to 8.0 nm under the chosen preparation conditions, allowing electron spectroscopy to be performed without charge compensation. The studies of Cr2O3(111) have been performed as part of a project aimed at investigating idealized catalytic systems under ultrahigh vacuum conditions.
