Electronic Structure of β-NaxV2O5 (x ≈ 0.33) Polycrystalline Films: Growth, Spectroscopy, and Theory

We present a detailed study of the microstructure and electronic structure of β-NaxV2O5 (x ≈ 0.33) polycrystalline films, combining film growth, X-ray spectroscopies, and first-principles calculations. High-quality crystalline and stoichiometric V2O5 and β-Na0.33V2O5 films were grown by a sol–gel process, spin-coating, and rapid thermal annealing. The V2O5 film, which exhibits a rough surface, is preferentially oriented in the (001) direction perpendicular to the surface, whereas the b-axis of β-Na0.33V2O5 is oriented in the substrate plane. The β-Na0.33V2O5 film consists of a nested layered structure composed of single-crystalline rods of a few hundred nanometers in diameter and a few micrometers in length. Photoemission and X-ray absorption measurements of β-Na0.33V2O5 confirm the Na incorporation and the presence of mixed V5+ and V4+ species and weakly occupied V 3d states. At the V L-edge, X-ray absorption and resonant inelastic X-ray measurements suggest a larger crystal field for β-Na0.33V2O5 compar...