Resistive Switching in 2D Bismuth Oxyhalide Nanosheets for Nonvolatile Memory and Emulation of Leaky Integrate-and-fire Functions

The resistive switching (RS) behaviors have been widely studied in a large number of two-dimensional (2D) materials. Bismuth oxyhalides have emerged as a typical ternary 2D layered material recently. However, the studies focusing on the RS behaviors in 2D bismuth oxyhalides are still limited. Herein, the RS behaviors in 2D BiOX (X = Cl, Br and Cl + Br) nanosheets have been systematically studied. 2D BiOX nanosheets are exfoliated from their bulk materials which are synthesized by a hydrothermal method. Vertical memristors with Pt/BiOX/Pt sandwiched structures have been fabricated for RS measurements. Among them, 2D BiOCl nanosheet has no RS behaviors. BiOBr nanosheet demonstrates non-volatile bipolar RS behaviors with a large ON/OFF ratio (∼105), long time retention (104 s) and good endurance (280 cycles) as well as good environmental stability, suggesting potential applications in non-volatile memory. Furthermore, BiOBr0.7Cl0.3 nanosheet shows volatile threshold switching (TS) behaviors with the ON/OFF ratio up to 105. The device with TS behaviors can be utilized to emulate the leaky integrate-and-fire (LIF) functions in biological synapses. This work demonstrates a new material with non-volatile or volatile RS behaviors, providing a new TS device for emulation of LIF activity.