Structural and electronic properties of thermally evaporated V2O5 epitaxial thin films

• V2O5 film of 50 nm thickness on c-plane sapphire was made by thermal evaporation.
• Epitaxial thin film had a smooth surface with 1.5 Å root mean square roughness.
• X-ray spectroscopy probes the electronic structure of the V2O5 film.
• X-ray spectroscopy also shows the molecular geometry and purity of the film.

This study investigated the physicochemical properties of a V2O5 thin film deposited on c-plane sapphire through thermal evaporation at a relatively high pressure. Using atomic force microscopy (AFM), X-ray diffraction (XRD) and a suite of X-ray spectroscopic techniques, it was shown that a high quality epitaxial V2O5 thin film was achieved. AFM step height analysis demonstrated that the film thickness was ~ 50 nm with a surface roughness of 1.5 Å, as determined by root mean square roughness measurements. XRD analysis verified that the film was highly crystalline with a (0001) orientation on the substrate. Vanadium was predominantly in the 5 + oxidation state, with contributions from V4 + states at the surface, shown by X-ray photoemission spectroscopy analysis X-ray absorption spectroscopy further confirmed the predominant presence of V5 + in an octahedral crystal field. The existence with bulk V4 + states was shown through V L-edge X-ray emission spectroscopy which demonstrated the presence of d-d crystal field transitions in an otherwise d0 transition metal oxide. The data suggests that by increasing the partial pressure of oxygen in the vacuum chamber during growth, thermal evaporation can be used as a cheap and efficient way of growing stoichiometric V2O5 thin films.