The effects of Eu3+ doping on the epitaxial growth and photovoltaic properties of BiFeO3 thin films

Abstract Nowadays, photovoltaic effect has been widely studied in various ferroelectric materials due to its applications as optoelectronic devices. In this work, with BiFeO3 (BFO) films as the photovoltaic materials, we report the effects of Eu3+ doping content on the phase structure, ferroelectric and optical properties of BFO films grown on Ca0.96Ce0.04MnO3/YAlO3 (001) substrate. We found that a small doping level of 0.05 could induce a phase change of BFO from tetragonal to rhombohedral, due to the shrinking of the lattice upon Eu3+ doping and the breaking of surface terrace structure induced by Ca0.96Ce0.04MnO3 layer. This results in a sharp band gap reduction from 3.30 eV to 2.60 eV, and a decrease in the coercivity of ferroelectric polarization switching. Based on these findings, we investigate the photovoltaic effects of ITO/EuxBi1-xFeO3/Ca0.96Ce0.04MnO3 vertical capacitors. It is found that the short-circuit current density (Jsc) decreases with increasing Eu3+ doping, whereas the open-circuit voltage (Voc) first increases to a level of 0.1 V and then decreases with further Eu3+ doping. This could be explained by the combined effect of Schottky-junction and depolarization field on the photovoltaic process. Our research suggests that a moderate Eu3+ doping is helpful for enhancing the photovoltaic effect of BFO thin film devices.