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

ABSTRACT

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.

keywords:

• multiferroic
• BiFeO₃
• thin film

ACKNOWLEDGMENT

The authors acknowledge Prof. Tomoji Kawai (The institute of scientific and industrial research, Osaka University) and Prof. Hitoshi Tabata (University of Tokyo) for the magnetic measurement.