Surface Charge Transfer Doping Enabled Large Hysteresis in van der Waals Heterostructures for Artificial Synapse

Exploitation of the I–V hysteresis property in a van der Waals heterostructure is significant to modulate its electronic properties and develop unique applications. In this work, we report a two-terminal MoS2 floating-gate (FG) artificial synaptic device, the surface of which was functionalized by an ultrathin deposition (0.1 nm) of MoO3 on the channel region. The surface functionalization together with the FG field effect greatly enhance hysteresis of the device, resulting in a significantly expanded memory window (from 6 to 14.8 V) and a remarkably increased ON/OFF current ratio (from 10 to 107). In addition, essential synaptic functions were successfully emulated in this synaptic two-terminal device, including transition from short-term to long-term potentiation, paired-pulse facilitation/depression, and spike timing-dependent plasticity. These findings promise surface charge transfer doping as an effective method to broaden the functionality of two-dimensional transition metal dichalcogenides-based electronic devices and provide a platform for the development of electric-modulated neuromorphic architectures.