Abstract

Heterostructures composed of bismuth ferrite, BiFeO3, and vanadium dioxide, VO2, films were successfully grown by means of the radio-frequency and DC sputtering on sapphire substrates. The X-ray diffraction (XRD) patterns showed that both films were polycrystalline in nature. The XRD data revealed the formation of the monoclinic VO2 (M) phase. The bottom VO2 exhibited a sharp metal-insulator transition (MIT) at 327 K with a variation in the value of the resistance of two orders of magnitude. Measurements of the electric polarization (P) versus the electric field (E) of the top BiFeO3 showed closed loops, although visually distinct from those of a true ferroelectric. In spite of the well-defined MIT of VO2, the effect of the structural change associated with the transition on the ferroelectric properties of BiFeO3 was masked by the large leakage currents. The probably perturbation of the ferroelectric order in the BiFeO3 , associated with the structural changes through the MIT of VO2 was investigated by measuring the P-E dependence at temperatures below and above the MIT of VO2 . Although round-shaped hysteresis were obtained, a small but sizeable difference in the values of the apparent remnant P at the temperatures of interest was observed. By the same token, the transition of VO2 seemed to influence the possible magneto-electric coupling in the BiFeO3 layer.