SOL-GEL PREPARATION AND CHARACTERIZATION OF MULTIFERROIC BiFeO3 THIN FILMS WITH VARIOUS BI/FE RATIO

BiFeO3 thin films have been prepared on Pt/TiO2/SiO2/Si substrates by sol-gel method using precursor solutions of various elemental ratio (Bi:Fe = 1.1:1.0, 1.0:1.0, and 1.0:1.1). The θ < eqid2 > 2θ scan XRD patterns show all the films consist mainly of polycrystalline perovskite and the crystallinity of Bi:Fe = 1.1:1.0 is better than the others. SEM and AFM images show all BiFeO3 film have rosette structures, which consist of perovskite phase and matrix phase. The leakage current density measured at the temperature of 80 K is lower than 10−4 A/cm2 in all the films when the electric field reaches 1.6 MV/cm. The leakage mechanism of BiFeO3 thin film is dominated by Schottky conduction at 80 K. At 80 K, the remanent polarizations at maximum applied voltage of 2.8 MV/cm are 100, 49, and 44 μC/cm2 for the ratio of Bi:Fe = 1.1:1.0, 1.0:1.0, and 1.0:1.1, respectively. The saturated magnetization of BiFeO3 thin films at 80 K were found to be 14, 22.5, 15 emu/cm3 for the ratio of Bi:Fe = 1.1:1.0, 1.0:1.0, and 1.0:1.1, respectively. Among these ratio, BiFeO3 thin film deposited from precursor of Bi:Fe = 1. 1:1.0 gives the best ferroelectric property.