Improved synaptic functionalities of Li-based nano-ionic synaptic transistor with ultralow conductance enabled by Al <sub>2</sub> O <sub>3</sub> barrier layer
Kyumin Lee, Myounghoon Kwak, Wooseok Choi, Chuljun Lee, Jongwon Lee, Sujung Noh, Jisung Lee, Hansaem Lee, Hyunsang Hwang
Abstract
Abstract In this study, we investigated the effect of an Al 2 O 3 barrier layer in an all-solid-state inorganic Li-based nano-ionic synaptic transistor (LST) with Li 3 PO 4 electrolyte/WO x 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) Al 2 O 3 interfacial layer. A trade-off relationship between the weight update linearity and on/off ratio with varying Al 2 O 3 layer thickness was also observed. To determine the origin of the Al 2 O 3 barrier 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 Al 2 O 3 barrier. Finally, a highly improved pattern recognition accuracy (83.13%) was achieved using the LST with an Al 2 O 3 barrier of optimal thickness.