The Discovery of a High-Mobility Two-Dimensional Bismuth Oxyselenide Semiconductor and Its Application in Nonvolatile Neuromorphic Devices

The development of two-dimensional (2D) electronics is always accompanied by the discovery of 2D semiconductors with high mobility and specific crystal structures, which may bring revolutionary breakthrough on proof-of-concept devices and physics. Here, Bi₃O_2.5Se₂, a 2D bismuth oxyselenide semiconductor with non-neutral layered crystal structure is discovered. Ultrathin Bi₃O_2.5Se₂ films are readily synthesized by chemical vapor deposition, displaying tunable band gaps and high room-temperature field-effect mobility of >220 cm² V^-1 s^-1. Moreover, the as-synthesized Bi₃O_2.5Se₂ nanoplates were fabricated into top-gated transistors with a simple device configuration, whose carrier density can be reversibly regulated in the range of 10¹⁴ cm^-2 just by a facile method of electrostatic doping at room temperature. These features enable it to be functionalized into nonvolatile synaptic transistors with ultralow operating energy consumption (∼0.5 fJ), high repeatability, low operating voltage (0.1 V), and long retention time. Our work extends the family of bismuth oxyselenide 2D semicondutors.