Formation of Vanadium Oxide Films on Cu3Au(100)

Abstract

The initial growth of VOx has been investigated by low energy ion backscattering (NICISS), scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Direct evaporation of vanadium onto the Cu3Au(100) substrate gives rise to massive surface alloying, consequent oxygen exposure leads to the formation of rough vanadium oxide films of poor quality. A better way has been developed by forming a thin oxygen layer at the clean Cu3Au substrate which acts positively in two ways: firstly, it prevents completely the alloy formation, secondly, a strong surface wetting of the vanadium oxide occurs resulting in two-dimensional layer growth of good quality. Depending on the pre-oxygen content at Cu3Au(100), the amount of V deposition and annealing temperature, different epitaxial layers of vanadium oxides can be prepared. Namely, three VOx species occur separately: an oxide with low oxygen content showing a quadratic crystallographic lattice, probably VO(100), V2O3(0001) with a hexagonal superlattice and finally, domains with a rectangular unit cell and VO2 stoichiometry. As a consequence, oxygen treated Cu3Au(100) is ideally suited as a metal substrate for growing homogeneous 2D epitaxial vanadium metal oxides.