Giant tunnel resistance effect in (SrTiO3)2/(BaTiO3)4/(CaTiO3)2 asymmetric superlattice with enhanced polarization

Abstract

In this work, we report the effectively enhanced tunneling electroresistance effect in Au/(SrTiO₃)₂/(BaTiO₃)₄/(CaTiO₃)₂/Nb:SrTiO₃ superlattice ferroelectric tunnel junction (FTJ). The stable polarization switching and enhanced ferroelectricity were achieved in the nanoscale thickness high-quality epitaxial superlattice. A high ON/OFF current ratio of more than 10⁵ was obtained at room temperature, which is an order of magnitude larger than the BaTiO₃ FTJ with the same structure. Nonvolatile resistance switching controlled by nonvolatile polarization switching was observed in the superlattice FTJ. Driven by increased polarization and intrinsic asymmetric ferroelectricity, a highly asymmetric depolarization field is generated compared with the Au/BaTiO₃/Nb:SrTiO₃ FTJ, resulting in an enhanced tunneling electroresistance effect. These results provide a potential way to construct FTJ memory devices by constructing asymmetric three-component ferroelectric superlattices.