Improved synaptic functionalities of Li-based nano-ionic synaptic transistor with ultralow conductance enabled by Al ₂ O ₃ barrier layer

Abstract

In this study, we investigated the effect of an Al₂O₃barrier layer in an all-solid-state inorganic Li-based nano-ionic synaptic transistor (LST) with Li₃PO₄electrolyte/WO<i>_x</i>channel structure. Near-ideal synaptic behavior in the ultralow conductance range (∼50 nS) was obtained by controlling the abrupt ion migration through the introduction of a sputter-deposited thin (∼3 nm) Al₂O₃interfacial layer. A trade-off relationship between the weight update linearity and on/off ratio with varying Al₂O₃layer thickness was also observed. To determine the origin of the Al₂O₃barrier layer effects, cyclic voltammetry analysis was conducted, and the optimal ionic diffusivity and mobility were found to be key parameters in achieving ideal synaptic behavior. Owing to the controlled ion migration, the retention characteristics were considerably improved by the Al₂O₃barrier. Finally, a highly improved pattern recognition accuracy (83.13%) was achieved using the LST with an Al₂O₃barrier of optimal thickness.