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, Bi 3 O 2.5 Se 2 , a 2D bismuth oxyselenide semiconductor with non-neutral layered crystal structure is discovered. Ultrathin Bi 3 O 2.5 Se 2 films are readily synthesized by chemical vapor deposition, displaying tunable band gaps and high room-temperature field-effect mobility of >220 cm 2 V -1 s -1 . Moreover, the as-synthesized Bi 3 O 2.5 Se 2 nanoplates were fabricated into top-gated transistors with a simple device configuration, whose carrier density can be reversibly regulated in the range of 10 14 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.