Structural and electronic properties of thermally evaporated V2O5 epitaxial thin films

Abstract This study investigated the physicochemical properties of a V 2 O 5 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 V 2 O 5 thin film was achieved. AFM step height analysis demonstrated that the film thickness was ~ 50 nm with a surface roughness of 1.5 A, 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 V 4 + states at the surface, shown by X-ray photoemission spectroscopy analysis X-ray absorption spectroscopy further confirmed the predominant presence of V 5 + in an octahedral crystal field. The existence with bulk V 4 + states was shown through V L -edge X-ray emission spectroscopy which demonstrated the presence of d-d crystal field transitions in an otherwise d 0 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 V 2 O 5 thin films.