Sm, Nd doped BiFeO₃epitaxial film for photodetector with extremely large on-off current ratio

BiFeO₃is one of the star materials in the field of ferroelectric photovoltaic for its relatively narrow bandgap (2.2-2.7 eV) and better visible light absorption. However, a high temperature over 600 °C is indispensable in the usual BiFeO₃growth process, which may lead to impure phase, interdiffusion of components near the interface, oxygen vacancy and ferrous iron ions, which will result in large leakage current and greatly aggravate the ferroelectricity and photoelectric response. Here we prepared Sm, Nd doped epitaxial BiFeO₃film via a rapid microwave assisted hydrothermal process at low temperature. The Bi_0.9Sm_0.5Nd_0.5FeO₃film exhibits narrow bandgap (1.35 eV) and photo response to red light, the on-off current ratio reaches over 10⁵. The decrease in band gap and +2/+3 variable element doping are responsible for the excellent photo response. The excellent photo response performances are much better than any previously reported BiFeO₃films, which has great potential for applications in photodetection, ferroelectric photovoltaic and optoelectronic devices.