Influence of oxygen on electrical conductance and local structural properties of BiFeO3 thin films

The effect of oxygen on the electrical conductance and local structural properties of BiFeO3 (BFO) thin films on SiO2/Si substrates grown by RF magnetron sputtering was investigated. The conductivities of BFO were studied in a planar electrode with blue light irradiation. The BFO films grown with oxygen (BFO-O2) show a large conductivity increase, which is 12.66 times more than the BFO grown without oxygen (BFO), and the conductivity change is entirely caused by the BFO thin films. To explain the mechanism of increased electrical conductance, the local structure at the Fe K-edge was investigated by using time-resolved x-ray absorption spectroscopy (TRXAS). The applied voltage and blue light exposure affected the Fe–O bond, while the valence states of Fe atoms in BFO thin films remained unchanged. When the BFO films were irradiated, the bonding distance of the Fe–O bond was deviated, resulting in an oxygen vacancy. These findings imply that BFO thin films with more oxygen components exhibit higher electrical conductivity when exposed to blue light. The results of this research should pave the way for optoelectronic applications to modulate the electrical conductivity driven by oxygen and blue light.