Preparation and characterization of well-ordered, thin niobia films on a metal substrate

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 Cu 3Au(1 0 0) substrate. Nb deposition onto oxygen implanted Cu 3Au(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 Nb 5+ cations occupy the threefold hollow sites. This leads to a ( 3 × 3 ) R30° structure with respect to the underlying close packed O layer, which in turn forms a (2 × 7) coincidence structure with the metal substrate. The defect structure includes reflection domain boundaries and vacancies.