Optical and electrical properties of multiferroic bismuth ferrite thin films fabricated by sol-gel technique

Single-phase multiferroic BiFeO₃ thin films have been prepared on LaNiO₃/Si(100) and Si(100) wafer via sol-gel technique. The films are polycrystalline with preferring orientation of (101). The film has a conspicuous absorption in the blue and green light region, and band gap of 2.74 eV. The refractive index and the extinction coefficient of the film is about 2.36 and 0.06 at 600 nm, 2.26 and close to zero in the range of 800-1200 nm, respectively. The films also exhibit favorable ferroelectric and dielectric properties. A large photo induced open-circuit voltage was observed, indicating that the film exhibits photovoltaic behaviours.