Formation of Vanadium Oxide Films on Cu3Au(100)

Abstract

The initial growth of VO x 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 Cu 3 Au(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 Cu 3 Au 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 Cu 3 Au(100), the amount of V deposition and annealing temperature, different epitaxial layers of vanadium oxides can be prepared. Namely, three VO x species occur separately: an oxide with low oxygen content showing a quadratic crystallographic lattice, probably VO(100), V 2 O 3 (0001) with a hexagonal superlattice and finally, domains with a rectangular unit cell and VO 2 stoichiometry. As a consequence, oxygen treated Cu 3 Au(100) is ideally suited as a metal substrate for growing homogeneous 2D epitaxial vanadium metal oxides.