Impedance Spectroscopy of Vanadium Pentoxide Thin Films

V2O5 thin films have been deposited onto an insulating support by radiofrequency (rf) reactive sputtering from a metallic vanadium target at controlled flow rates of argon-oxygen gas mixture. Glancing-incidence x-ray diffraction (GIXD) analysis and scanning electron microscopy (SEM) were used for structural and phase characterization of the obtained materials. The as-sputtered thin films were found to consist of orthorhombic V2O5 phase. Electrical properties were determined by electrochemical impedance spectroscopy (EIS) conducted over the frequency range of 0.1Hz to 1.4MHz and temperatures ranging from room temperature (RT) to 773K. Between RT and 528K, the recorded impedance spectra were interpreted in terms of an equivalent circuit composed of a resistor and non-Debye constant-phase element (CPE) connected in parallel. In this temperature range, the material exhibited n-type extrinsic conductivity. The activation energy of electrical conductivity was 0.243 +/- 0.023eV. At 528K, an abrupt change in resistivity was observed, interpreted as a metal-insulator transition (MIT). Above 528K, the equivalent circuit was composed of a resistor (R) and inductor (L) connected in series, typical of materials exhibiting metallic properties.