MoS2-based multiterminal ionic transistor with orientation-dependent STDP learning rules

Synaptic devices with dynamic properties are essential for constructing a neuromorphic system. In this paper, a multiterminal in-plane-gate ionic MoS2 transistor with dynamic synaptic characteristics is demonstrated by using poly (vinyl alcohol) as the laterally coupled proton-conducting electrolyte. The device can be regulated at a low operating voltage of 2 V due to the significant electric-double-layer effect. Typical synaptic behaviors such as excitatory postsynaptic current, inhibitory postsynaptic current, paired-pulse facilitation, and dynamic filtering are successfully mimicked. The ability of multiterminal coplanar transistor to regulate synaptic weights depending on spatial orientation is also demonstrated in this device. More importantly, orientation-dependent spike-timing-dependent plasticity learning rules can be successfully realized through this multiterminal ionic transistor. Such device may provide a promising way to construct spatiotemporally-correlated neuromorphic systems.