Growth of V₂O₃ thin films on a-plane (110) and c-plane (001) sapphire via pulsed-laser deposition

We report the direct deposition of epitaxial 215-nm-thick vanadium sesquioxide (V₂O₃) films on a- and c-plane sapphire substrates from powder-pressed V₂O₃ targets via pulsed-laser deposition (PLD) in an evacuated deposition chamber devoid of O₂. The films were characterized using x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS), x-ray absorption fine structure (XAFS) spectroscopy, and atomic force microscopy (AFM). XPS measurements confirmed that the stoichiometry of the powder was conserved in the films. XRD patterns together with XAFS measurements proved that V₂O₃ was epitaxial on the a-sapphire substrate with epitaxial relation (110)_film// (110)_substrate, and the results are consistent with the epitaxy on the c-plane substrate as well. The room-temperature resistivities of V₂O₃ films on a- and c-plane substrates were 1.49 × 10^-4 and 3.00 × 10^-5 Ω m, respectively. The higher resistivities of the films compared to bulk V₂O₃ might be attributed to thermal stresses resulting from difference in thermal expansion coefficients (TECs) of the films and the substrates.