Thin films of bismuth vanadates with modifiable conduction properties

Thin films of bismuth vanadates are deposited by chemical vapor deposition (OVD) on alpha-Al2O3 substrates using an O-2 atmosphere and vanadyl(IV) ace tylacetonate and triphenyl-bismuth as precursors. The microstructure of the samples is studied by XRD and Raman spectroscopy and their chemical compos ition is investigated by XPS and SIMS. AFM is used to analyze the surface m orphology of the samples. All the samples show a nonohmic behavior beyond a threshold voltage, V-th, 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 con duction occurs by means of hopping between vacancies. Furthermore, ferroele ctric-paraelectric transitions take place in the materials at low temperatu res.