Multiferroic and photovoltaic current properties of tetragonally strained BiFeO3 thin films

Abstract

Mn (5%) doped BiFeO3 (MBFO) thin films were epitaxially grown on La2/3Sr1/3MnO3/LaAlO3 substrates via pulsed laser deposition. The MBFO thin film was confirmed to be an epitaxial thin film having a (001) orientation crystal structure by X-ray diffraction experiments. Compared to the BiFeO3 (BFO) thin film, the MBFO thin films have a shrunk a-axis lattice constant and a significantly elongated c-axis lattice constant, showing a c/a ratio of 1.15, and exhibiting high tetragonal strain. Due to the high tetragonal strain, the MBFO thin film exhibited higher polarization, magnetization, and d33 values than the BiFeO3 (BFO) thin film, resulting in enhanced multiferroic properties. From the results of the study on the relationship between the ferroelectric domain structure and the thickness observed by piezoresponse force microscope, it was confirmed that the domain wall energies of the MBFO thin films were larger than those of the BFO thin films. In addition, the I-V curves (photovoltaic current) showed that the MBFO thin films had the open-circuit voltages and photovoltaic currents higher than that of the BFO thin films due to its higher ferroelectric polarization and smaller band gap than those of the BFO thin films.