Enhanced photovoltaic effects and switchable conduction behavior in BiFe_0.6Sc_0.4O₃ thin films

Enhanced photovoltaic effects are demonstrated in an In₂O₃-SnO₂/BiFe_0.6Sc_0.4O₃/LaNiO₃ (ITO/BFSO/LNO) ferroelectric thin film heterostructure. The Sc-substitution greatly improves the bulk conductivity of BiFeO₃ (BFO) and modifies the energy band alignment in the ITO/BFSO/LNO capacitor structure, where a tunable Schottky-to-Ohmic contact at the BFSO/LNO interface and an Ohmic ITO/BFSO contact are purposely established. In negatively poled BFSO films, constructive photovoltaic effects at both the bulk and the BFSO/LNO interface lead to a large V_oc up to 0.6 V and a 5-fold enhancement in efficiency compared with conventional BFO films. In addition, ferroelectric polarization modulation of the Schottky barrier height at the BFSO/LNO interface results in a conversion between Schottky and Ohmic conduction, which gives rise to switchable high- and low-resistance states. The present work demonstrates a strategy effective to realize ferroelectric-based thin film structure with enhanced photovoltaic effects and memory function.