Prof. Jin Kuijuan’s group (Institute of Physics, CAS) proposed series of electrolyte-gated synaptic devices based on the SrFeO_x (SFO) and SrCoO_x (SCO) films, and first successfully demonstrated their artificial neutral functions such as the long-term potentiation and depression of synaptic weight, spike-timing-dependent plasticity, as well as spiking logic operations. By virtue of NEXAFS, XRD and STEM characterizations, the researchers revealed the structural transition mechanism of the SFO and SCO topotactic oxide films, in which reversible transitions between the brownmillerite and perovskite phases through controlling the insertion and extraction of oxygen ions with electrolyte gating governs the multilevel conduction states. These results provide an alternative avenue for future neuromorphic devices via electrolyte-gated transistors with oxygen ions [Advanced Materials 31(19):1900379(2019); Advanced Functional Materials 29(29):1902702(2019)].

The schematic illustration of the transistor structure and measurement setup. Sheet conductance G versus time (Above); Evolution of the structural phase via electrolyte gating and X-ray absorption spectra of the O–K edges (Below)