Lateral Ionic-Gated Graphene Synaptic Transistor with Transition from Paired-Pulse Facilitation to Depression for Filtering and Image Recognition

The transition from paired-pulse facilitation to paired-pulse depression is of significant importance for regulating biologic neural network. Here, we fabricate and investigate a lateral ionic-gated graphene synaptic transistor (GST) with short gate length. We control the channel current via e-field-dependent movement and diffusion of ions for realizing the transition from paired-pulse facilitation to depression. This phenomenon comes from the over-diffusion and trapping of a finite number of ions and the short ion-diffusion length under large negative gate pulse stimuli. This device successfully emulates facilitation and depression synaptic functions, for leveraging the accumulation, migration and diffusion of ions. Moreover, enhanced high-pass filtering and conversion from long-term depression to long-term potentiation are achieved by changing pulses time interval. Our results indicate that our device possesses excellent frequency-dependent synaptic plasticity, making it highly suitable for information filtering up to 33 Hz in neuromorphic systems, and image edge enhancement for neural image processing. In additional, a simulated artificial neural network built on lateral ionic-gated GSTs for handwritten digit recognition can achieve a learning accuracy of 82.4%.