Preparation and characterization of well-ordered MoOx films on Cu3Au(1 0 0)–oxygen substrate (CAOS)

The goal of this work is to prepare well-ordered molybdenum oxide films using oxygen implanted Cu3Au(1 0 0) substrate (CAOS, Cu3Au–Oxygen Substrate) and identify the structure of the different oxide phases. Those films were grown on an UHV chamber (2 × 10−10 mbar background pressure) and prepared by electron beam deposition. The structure of the films was studied using low energy electron diffraction (LEED), scanning tunnelling microscopy (STM), and X-ray photoelectron spectroscopy (XPS). The ultra thin molybdenum film shows the formation of an oxide layer with hexagonal symmetry plus a square lattice. The hexagonal mesh units are rotated by 90° (or 30°) with respect to one another. Based on XPS data, the Mo cations are in an oxidation state that ranges from 4+ to 6+. STM results show the presence of hexagonal islands formed over a square symmetry phase.