Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions

Among recently discovered ferroelectricity-related phenomena, the tunnelling electroresistance (TER) effect in ferroelectric tunnel junctions (FTJs) has been attracting rapidly increasing attention owing to the emerging possibilities of non-volatile memory, logic and neuromorphic computing applications of these quantum nanostructures. Despite recent advances in experimental and theoretical studies of FTJs, many questions concerning their electrical behaviour still remain open. In particular, the role of ferroelectric/electrode interfaces and the separation of the ferroelectric-driven TER effect from electrochemical ('redox'-based) resistance-switching effects have to be clarified. Here we report the results of a comprehensive study of epitaxial junctions comprising BaTiO3 barrier, La0.7Sr0.3MnO3 bottom electrode and Au or Cu top electrodes. Our results demonstrate a giant electrode effect on the TER of these asymmetric FTJs. The revealed phenomena are attributed to the microscopic interfacial effect of ferroelectric origin, which is supported by the observation of redox-based resistance switching at much higher voltages.Financial support by the Deutsche Forschungsgemeinschaft through the SFB 855 01/10 entitled 'Magnetoelectric Composites-Future Biomagnetic Interfaces' is acknowledged. The financial support provided via ERA.Net RUS project NANO-C entitled 'Artificial Multiferroic Nanocomposites: Towards Magnetoelectric Materials-by-Design' (01DJ13019) is gratefully acknowledged. This work was also supported by the Deutsche Forschungsgemeinschaft (DFG) via the Research-Group grant FOR 2093. D.S.J. acknowledges a Korea Institute of Science and Technology grant (grant number 2Z04030). The work at the Ioffe Physical-Technical Institute was supported by the Government of the Russian Federation through the programme P220 (project 14.B25.31.0025)