Photoenhanced Electroresistance at Dislocation-Mediated Phase Boundary

Ferroelectric tunneling junctions have attracted intensive research interest due to their potential applications in high-density data storage and neural network computing. However, the prerequisite of an ultrathin ferroelectric tunneling barrier makes it a great challenge to simultaneously implement the robust polarization and negligible leakage current in a ferroelectric thin film, both of which are significant for ferroelectric tunneling junctions with reliable operating performance. Here, we observe a large tunneling electroresistance effect of -1.0 x 104% across the BiFeO3 nanoisland edge, where the intrinsic ferroelectric polarization of the nanoisland makes a major contribution to tuning the barrier height. This phenomenon is beneficial from the artificially designed tunneling barrier between the nanoscale top electrode and the inclined conducting phase boundary, which is located between the rhombohedral-island and tetragonal-film matrix and arranged with the dislocation array. More significantly, the tunneling electroresistance effect is further improved to -1.6 x 104% by the introduction of photoinduced carriers, which are separated by the flexoelectric field arising from the dislocations. KEYWORDS: ferroelectric tunneling junction, tunneling electroresistance effect, BiFeO3 nanoislands, dislocations, flexoelectric effect