Electric polarization and diode-like conduction in hydrothermally grown BiFeO₃ thin films

We report the successful synthesis of high-quality BiFeO₃ thin films on a SrRuO₃/SrTiO₃ substrate using hydrothermal methods, and their structural, ferroelectric, and electrical properties. Using a low precursor concentration, we obtained compressively strained BiFeO₃ thin films (thickness: 60 nm) with smooth surface (roughness: 4.2 nm). The ferroelectric polarization of the BFO thin films was parallel with respect to the normal to the substrate and changed direction by 180° under the application of electric field. The current flowed unidirectionally; such rectifying behavior was attributed to Schottky barrier modulation by oxygen vacancies and ferroelectric polarization. Our results provide an important step in the applications of hydrothermally grown BiFeO₃ thin films like a large-area and low-cost photovoltaic device.