Study on leakage current, ferroelectric and dielectric properties of BFMO thin films with different bismuth contents

Bi_(1+x)Fe_0.95Mn_0.05O₃ thin films with different bismuth contents (abbreviated as B_1+xFMO, x = − 0.05, 0, 0.05, 0.1) were fabricated by chemical solution deposition on ITO/glass substrates. The effects of Bi nonstoichiometry on the microstructure, leakage current, ferroelectric and dielectric properties of BFMO films are investigated. The B_1.05FMO and B_1.1FMO thin films possess single perovskite structure, while the secondary phase of Bi₂Fe₄O₉ can be observed in BFMO and B_0.95FMO thin films. Compared with the other three samples in this work, drastically reduced leakage current can be found in B_1.05FMO. For each film, the dominant conduction mechanisms are the Ohmic conduction and the space charge limited conduction at lower electric fields and the interface-limited Fowler–Nordheim tunneling at higher electric regions, respectively. Among the B_1+xFMO films (x = − 0.05, 0, 0.05, 0.1), the B_1.05FMO film possesses significantly improved electrical properties, reflected by a large remanent polarization (P_r ~ 68.3 µC/cm²), lower dielectric loss (tanδ ~ 0.02), large dielectric constant (ε_r ~ 210) and high tunability (88%). These results suggest that the 5 mol% excess of Bi is the prior content to get better insulation, optimize ferroelectric as well as dielectric properties of BiFeO₃ film, giving reference to modify electrical performances of ferroelectric materials through regulation of volatile element.