Vertical Graphene Tunneling Heterostructure with Ultrathin Ferroelectric BaTiO₃ Film as a Tunnel Barrier

Ferroelectric tunnel junctions (FTJs) have attracted enormous interests as one of the promising candidates for next-generation non-volatile resistance memories. In this work, we report a novel FTJ employing both two-dimensional material and semiconductor electrode, in the graphene/BaTiO₃/Nb:SrTiO₃ heterostructure, yielding an interesting tunneling electroresistance (TER) effect. We investigate the TER dependence on Nb doping concentrations from 0.1 to 1.0 wt% in the semiconductor electrode. In addition to modulating barrier height by ferroelectric polarization reversal, the ON/OFF resistance ratio can be tuned by adjusting Nb doping concentrations due to further modulation of barrier width. An optimized ON/OFF ratio above 10³ of the device is observed when introducing 0.1 wt% Nb concentration at room temperature. Furthermore, good retention property and switching reproducibility can be achieved in the devices. The results provide a novel pathway to design the graphene-based FTJ at the nanoscale, which is useful for developing non-volatile memory devices with enhanced performance.