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

The epitaxial growth of vanadium oxide (V 2 O 3 ) 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 Cu 3 Au) 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 Cu 3 Au 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 Cu 3 Au(100), the amount of V deposition and annealing temperature, different epitaxial layers of vanadium oxides can be prepared. In particular, the surface structure of V 2 O 3 (0001) was investigated. The surface structure appears completely different from the half layer metal termination at Cr 2 O 3 (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.