Switchable Optically Active Schottky Barrier in La0.7Sr0.3MnO3/BaTiO3/ITO Ferroelectric Tunnel Junction

Abstract

One of the most desirable attributes of non-volatile memories and memristors is a fast and non-destructive read out of their resistive state. Prototypical ferroelectric (FE) memories use the bulk photovoltaic response associated to the polarization of FE films to address this requirement by optically sensing binary memory cells. A more advanced type of non-volatile memories is FE tunnel junctions (FTJs). They feature resistive state ratios RHigh/RLow up to 106, with a continuum of resistive states accessible, making them promising candidates for neuromorphic computing applications. A novel approach is presented to achieve the optical sensing of the resistive state in a La0.7Sr0.3MnO3/BaTiO3/ITO FTJ, by using the Schottky barrier forming in the La0.7Sr0.3MnO3/BaTiO3 interface to dramatically enhance the optical response of the 5 nm BaTiO3 (BTO) barrier. Illumination with UV light exceeding the BTO bandgap through the top transparent ITO electrode generates a photovoltaic response in the RHigh state, with an open circuit voltage Voc of 400 mV at 20 K, enabling the optical sensing of the resistive state. In the RLow state, the Schottky barrier is removed and the photoresponse disappears.