Thin films of bismuth vanadates with modifiable conduction properties

Thin films of bismuth vanadates are deposited by chemical vapor deposition (CVD) on alpha-Al2O3 substrates using an O2 atmosphere and vanadyl(IV) acetylacetonate and triphenylbismuth as precursors. The microstructure of the samples is studied by XRD and Raman spectroscopy and their chemical composition is investigated by XPS and SIMS. AFM is used to analyze the surface morphology of the samples. All the samples show a nonohmic behavior beyond a threshold voltage, Vth, which is linearly dependent on the V4+/V5+ ratio. Impedance spectroscopy measurements indicate that the obtained samples are oxide ion conductors at room temperature and that the mechanism of ion conduction occurs by means of hopping between vacancies. Furthermore, ferroelectric-paraelectric transitions take place in the materials at low temperatures.