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18. Iron oxide model catalysts: Preparation and characterization
Abstract:
In an attempt to introduce steps in oxide surfaces in a controlled way, different iron oxide phases were grown on an atomically stepped Pt(9 11 11) surface. For low coverages, wetting FeO(111) films are formed which induce step bunching with doubled and tripled terrace widths. Further Fe deposition and oxidation results in formation of Fe3O4(111) islands in a similar Stranski-Krastanov growth mode as on the basal Pt(111) surface. However, restricted diffusion across the step bunches results in a high concentration of comparatively flat elongated Fe3O4 islands which form a closed coalesced film at relatively low overall deposition. High pressure oxidation of coalesced Fe3O4 films results in poorly defined Fe2O3(0001). The FeO films grown on vicinal Pt substrates may serve as model systems for systematic studies of well-defined defective oxide surfaces, but the catalytically more relevant Fe3O4 and Fe2O3 phases can not be obtained reproducibly with a well-defined step structure.
