Inhibitory Synaptic Supercapacitor With Bidirectional and Tunable Plasticity

Artificial synapse with bidirectional inhibitory plasticity is critical for neuromorphic engineering. However, conventional synaptic devices, such as memristors and transistors, typically exhibit only unidirectional inhibitory plasticity. Herein, we present an inhibitory synaptic supercapacitor based on a Pt/lithium phosphorus oxynitride (LiPON)/Pt architecture, leveraging the electric double-layer (EDL) charge-storage mechanism for bidirectional operation across positive and negative voltage regions. This synaptic supercapacitor successfully mimics key inhibitory synaptic characteristics, including inhibitory postsynaptic current (IPSC), paired pulse depression (PPD), and spike rate-dependent plasticity (SRDP), enabled by controllable EDL formation and dissipation. In addition, the device also exhibits excellent cycling stability. Moreover, a unique pre-voltage modulation method is demonstrated to achieve tunable synaptic plasticity, where the applied pre-voltage regulates the concentration of Li+ gathered at the Pt/LiPON interfaces, thereby tuning the postsynaptic current of the device. Remarkably, the device exhibits zero readout power consumption due to its intrinsic charge-storage property, which enables operation at zero bias voltage during readout. These results highlight the potential of the synaptic supercapacitor as a promising candidate for future neuromorphic engineering.