Structure of Vanadium Oxide (V2O3) Grown on Cu3Au(100)

Abstract

The epitaxial growth of vanadium oxide (V2O3) has been investigated by scanning tunneling microscopy (STM), low energy ion back-scattering (ISS) and low energy electron diffraction (LEED). Direct evaporation of vanadium onto metal surfaces (Cu, Au or Cu3Au) gives rise to massive surface alloying. The attempt to oxidize the vanadium film by consequent oxygen exposure leads to the formation of rough VO x films of poor quality and mixed valency. A new way of oxide formation has been developed by preoxidation of a Cu3Au substrate, which acts positively in two ways since it prevents completely alloy formation and also forces strong surface wetting of the vanadium oxide. As a result, two-dimensional layer growth of good quality has been achieved. Depending on the preoxygen content at Cu3Au(100), the amount of V deposition and annealing temperature, different epitaxial layers of vanadium oxides can be prepared. In particular, the surface structure of V2O3(0001) was investigated. The surface structure appears completely different from the half layer metal termination at Cr2O3(0001). Specifically, the full vanadium layer stabilized by one third of an oxygen layer located in pseudo bridge positions close to regular oxygen positions of a next layer. Close to defects the full vanadium layer appears also without oxygen stabilization.