The effect of polarization fatigue process and light illumination on the transport behavior of Bi_0.9La_0.1FeO₃ sandwiched capacitor

In this paper, Ag/Bi_0.9La_0.1FeO₃ (BLFO)/La_0.7Sr_0.3MnO₃ sandwich structure was grown epitaxially on SrTiO₃ substrates using pulsed laser deposition. Short-circuit photocurrent (I_short) and frequency dependence of the capacitance were investigated. It reveals that this heterostructure exhibits strong photocurrent responses, the orientation of I_short depends strongly on the polarization orientations, and it varies monotonically from one orientation to the other as the polarization orientation switching gradually from upward (downward) to downward (upward), the I_short value becomes zero when the film is in zero polarization states. The intensity of the I _short can be strengthened by several times after thousands of bipolar electric pulses. Moreover, after polarization fatigue process of bipolar electric pulses or under light illumination, the capacitance of this sandwich structure is always bigger than the original state. However, the magnifying ratio of the capacitance after and before polarization fatigue process or under light illumination decrease with increasing the frequency in the C-f curves. These results suggest that polarization induced surface charge combined with migration of oxygen vacancies is the primary driving force for the varying of interfacial barriers and the oxygen vacancies density near the interface, which in turn leads to different orientations and values of I_short as well as the differential interfacial capacitance. Our results indicate that the photovoltaic response in ferroelectric BLFO thin films could be further explored for solar light photovoltaic and other capacitor devices applications.