Solution-processed metal oxide synaptic transistor with bilayer Li-ion-conducting gate dielectric

Abstract

This study presents a cost-effective, solution-processable approach to emulating synaptic plasticity using a solution-processed metal oxide thin-film transistor (TFT) with a bilayer Li-ion-conducting gate dielectric of Li₅AlO₄ and Li₄Ti₅O₁₂. This bilayer gate dielectric configuration reduces the DC conductivity of the Li₅AlO₄ film by three orders of magnitude, effectively reducing the gate leakage current of the transistor by similar orders. Additionally, the fabricated TFT demonstrates an ON/OFF ratio of 7.1 × 10³ with a saturation carrier mobility of 0.62 cm² V⁻¹ s⁻¹ and a subthreshold swing of 242 mV decade⁻¹. Additionally, this TFT shows high endurance in transfer characteristics over 100 consecutive cycles. Synaptic testing reveals that the device can successfully mimic short-term plasticity by applying various gate signals. Furthermore, paired pulse facilitation (PPF) is observed, fitting well with a double-exponential decay function. The transition from short-term plasticity (STP) to long-term plasticity (LTP) is also demonstrated, alongside potentiation-depression events. These potentiation-depression data are then used for artificial neural network simulations. Using a simple feed-forward neural network, the device achieves a pattern recognition accuracy of 92% with a mean loss of 0.3. A confusion matrix for numbers 0–9 further confirms the high accuracy of the device in recognizing these digits with the highest probability.