Impact of Bi Deficiencies on Ferroelectric Resistive Switching Characteristics Observed at p-Type Schottky-Like Pt/Bi1-dFeO3 Interfaces

This work reports a resistive switching effect observed at rectifying Pt/Bi1dFeO3 interfaces and the impact of Bi deficiencies on its characteristics. Since Bi deficiencies provide hole carriers in BiFeO3, Bi-deficient Bi1dFeO3 films act as a p-type semiconductor. As the Bi deficiency increased, a leakage current at Pt/Bi1dFeO3 interfaces tended to increase, and finally, rectifying and hysteretic currentvoltage (IV) characteristics were observed. In IV characteristics measured at a voltage-sweep frequency of 1 kHz, positive and negative current peaks originating from ferroelectric displacement current were observed under forward and reverse bias prior to set and reset switching processes, respectively, suggesting that polarization reversal is involved in the resistive switching effect. The resistive switching measurements in a pulse-voltage mode revealed that the switching speed and switching ratio can be improved by controlling the Bi deficiency. The resistive switching devices showed endurance of >105 cycles and data retention of >105 s at room temperature. Moreover, unlike conventional resistive switching devices made of metal oxides, no forming process is needed to obtain a stable resistive switching effect in the ferroelectric resistive switching devices. These results demonstrate promising prospects for application of the ferroelectric resistive switching effect at Pt/Bi1dFeO3 interfaces to nonvolatile memory.