Improvement Of Synaptic Properties In Oxygen-Based Synaptic Transistors Due To The Accelerated Ion Migration In Sub-Stoichiometric Channels

The oxygen ion-based synaptic transistor (OIST) is a promising candidate for next-generation synaptic devices for neuromorphic computing. However, the key process parameters that control synaptic characteristics have not yet been studied. In this study, the authors report near-ideal synaptic characteristics by adopting oxygen-deficient transition metal-oxide (TMO) channels and yttria-stabilized zirconia electrolytes. With decreasing oxygen stoichiometry in the TMO channel by controlling the O-2 flow rate during reactive sputtering, the oxygen ion supply and migration are accelerated by lowering the migration barrier. The reduced barrier energy and improved ion diffusivity characteristic in the oxygen-deficient TMO channels are confirmed experimentally through cyclic voltammetry analysis. As a result, improved weight-update linearity and wide conductance range can be achieved in OIST devices with an oxygen-deficient TMO (WO2.7, TiO1.7) channel. The authors confirm the excellent pattern recognition accuracy, which can be explained by the improved synaptic characteristics of the OIST synapse array.