Structural, electrical, and optical properties of polycrystalline (1−x)BiFeO₃-xBi_0.5K_0.5TiO₃ thin films

The effects of multiferroic (1 − x)BiFeO₃-xBi_0.5K_0.5TiO₃ (BFO-xBKT, x = 0, 0.1, 0.2, 0.3, and 0.4) thin films on the structural, electrical, and optical properties had been investigated. The phases of all the films corresponded to a perovskite structure according to the X-ray diffraction patterns and the Raman shift measurements. Meanwhile, the merging of (104) and (110) peaks of the BFO-xBKT thin films revealed the phase transition from a rhombohedral structure to a tetragonal structure. The atomic force microscope showed that the BFO-xBKT thin films had uniform morphology and the grain size of the BFO-xBKT thin films became smaller when the Bi_0.5K_0.5TiO₃ content increased. The maximum remnant polarization 2P_r = 17.1 μC/cm² and lowest leakage current of 3.07×10⁻⁷ A/cm² were observed in the BFO−0.3BKT thin film. The leakage current conduction mechanism displayed Ohmic conduction in the low electric field region and in the high electric field region, the mechanism was dominated by the Fowler−Nordheim tunneling for BFO-xBKT (x = 0.1, 0.2, 0.3, and 0.4) thin films. The absorption edges of BFO-xBKT were blue-shifted with the increasing of the x value.