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Thin oxide films; Epitaxy; Niobia; Scanning tunneling microscopy; Photoelectron spectroscopy; Density functional theory
Abstract:
Combining low energy electron diffraction, scanning tunneling microscopy, angular resolved photoelectron spectroscopy using synchrotron radiation and density functional theory calculations, we have studied the structure of thin niobia films grown on a Cu3Au(1 0 0) substrate. Nb deposition onto oxygen implanted Cu3Au(1 0 0) and subsequent oxidation results in a flat, well-ordered thin niobia film of hexagonal symmetry. The results suggest that the film consists of 2/3 ML of Nb between two hexagonal O-layers, where Nb5+ cations occupy the threefold hollow sites. This leads to a (√3 x √3)R30° structure with respect to the underlying close packed O layer, which in turn forms a (2 x 7) coincidence structure with the metal substrate. The defect structure includes reflection domain boundaries and vacancies.
