The effects of Eu^(3+) doping on the epitaxial growth and photovoltaic properties of BiFeO_(3) thin films

Nowadays,photovoltaic effect has been widely studied in various ferroelectric materials due to its ap-plications as optoelectronic devices.In this work,with BiFeO_(3)(BFO)films as the photovoltaic materials,we report the effects of Eu^(3+)doping content on the phase structure,ferroelectric and optical properties of BFO films grown on Ca_(0.96) Ce_(0.04) MnO_(3)/YAlO_(3)(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 Eu^(3+)doping and the breaking of surface terrace structure induced by Ca_(0.96) Ce_(0.04) MnO_(3) 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/Eu_(x) Bi_(1-x) FeO_(3)/Ca_(0.96) Ce_(0.04) MnO_(3) vertical capacitors.It is found that the short-circuit current density(J_(sc))decreases with increasing Eu^(3+)doping,whereas the open-circuit voltage(V_(oc))first increases to a level of 0.1 V and then decreases with further Eu^(3+)doping.This could be explained by the combined ef-fect of Schottky-junction and depolarization field on the photovoltaic process.Our research suggests that a moderate Eu^(3+)doping is helpful for enhancing the photovoltaic effect of BFO thin film devices.