Switchable photovoltaic properties in PZT epitaxial thin films

Ferroelectric thin films are investigated for their potential in photovoltaic applications, due to large open-circuit voltage and switchable photovoltaic effect. The photocurrent can be controlled by the direction of the ferroelectric polarization, allowing in theory to achieve a 100% switchability of the photocurrent with the polarization, which is of great interest for potential photoferroelectric memory devices. However, it is not always achievable in capacitor devices. In this work, a careful study of the switchability of the PV properties of epitaxial lead zirconate titanate thin films has been conducted in order to investigate the role played by the ferroelectric polarization. 100 nm thick PZT films were grown using pulsed laser deposition and integrated into capacitor geometry between SrRuO3 bottom and Pt top electrodes and the photoinduced current in the PZT devices was studied under UV illumination, in different polarization states. A voltage pulse protocol was used to pole the device under increasing electric fields to reach different electrical states while measuring their polarization value. These results revealed the critical role of the depolarizing field as the driving force for the photocurrent and allowed us to extract the screening efficiency of electrodes.