All-Solid-State Synaptic Transistors with High-Temperature Stability Using Proton Pump Gating of Strongly Correlated Materials.

Designing energy-efficient artificial synapses with adaptive and programmable electronic signals is essential to effectively mimic synaptic functions for brain-inspired computing systems. Here, we report all-solid-state three-terminal artificial synapses that exploit proton-doped metal-insulator transition in a correlated oxide NdNiO (NNO) channel by proton (H) injection/extraction in response to gate voltage. Gate voltage reversibly controls the H concentration in the NNO channel with facile H transport from a H-containing porous silica electrolyte. Gate-induced H intercalation in the NNO gives rise to nonvolatile multilevel analogue states due to H-induced conductance modulation, accompanied by significant modulation of the out-of-plane lattice parameters. This correlated transistor operated by a proton pump shows synaptic characteristics such as long-term potentiation and depression, with nonvolatile and distinct multilevel conductance switching by a low voltage pulse (≥ 50 mV), with high energy efficiency (∼1 pJ) and tolerance to heat (≤150 °C). These results will guide the development of scalable, thermally-stable solid-state electronic synapses that operate at low voltage.