Implementation of Synaptic Device Using Ultraviolet Ozone Treated Water-in-Bisalt/Polymer Electrolyte-Gated Transistor

Electrolyte-gated transistors (EGTs) have been extensively studied as a next-generation neuromorphic device mimicking the biological ionic flux in synapses. However, its long-term plasticity characteristic lasts only for few seconds because of the rapid self-discharge of electrical double layer. Here, ultraviolet ozone (UVO) treated water-in-bisalt (WiBS)/polymer electrolyte-gated synaptic transistor (WEST) which excellently implements multiple synaptic functions is proposed. Ultraviolet (UV) light and reactive oxygen radicals generated during UVO treatment form trap sites on the surface of active layer, causing lithium cations in the WiBS/polymer electrolyte to be captured at the electrolyte/active layer interface. The UVO treated WEST shows enhanced nonvolatile memory performance for 10 000 s, up to 1186 times longer than that of the untreated WEST. Also, near-ideal weight update over 10 000 cycle tests with 0.32 and -0.55 nonlinearities of long-term potentiation and depression is acquired with a ten times improved symmetricity. These results confirm that the surface engineering is a key technique for sophisticated ion transport, and demonstrate various applicability of EGTs as a neuromorphic device.