Large electroresistance and tunable photovoltaic properties of ferroelectric nanoscale capacitors based on ultrathin super-tetragonal BiFeO3 films

Ferroelectric nanocapacitors with simultaneously tunable resistance and photovoltaic effect have great potential for realizing high-density non-volatile memories and multifunctional opto-electronic nanodevices. Here, using a polystyrene sphere template method, we developed well-ordered Au nanoelectrode arrays on super-tetragonal BiFeO3 (T-BFO)/La0.7Sr0.3MnO3 (LSMO) epitaxial thin films, forming Au/T-BFO/LSMO nanocapacitors. The nanocapacitors exhibited switchable resistance states and photovoltaic responses, controllable by the ferroelectric polarization of T-BFO. Owing to the giant polarization of T-BFO, both giant electroresistance (ON/OFF current ratio >20 000) and noticeable photovoltage (∼0.4 V) were achieved in the Au/T-BFO/LSMO nanocapacitors. These results demonstrate that the T-BFO-based nanocapacitors are promising for applications in high-density memories with multiple routes for non-destructive readout, as well as other multifunctional nanodevices.