Epitaxial Stabilization of the Superionic Cu_2−xSe Phase at Room Temperature for Memristive Neuromorphic Function

Materials that exhibit resistive switching are of great interest for applications in neuromorphic computing and energy-efficient switching devices. Here we demonstrate that epitaxially grown Cu₂₋ₓSe thin films on Al₂O₃, prepared by molecular beam epitaxy, can stabilize the superionic phase of copper selenide—normally observed only above ~400 K—at room temperature. Current–voltage (I–V) measurements at room temperature reveal memristive switching with ON/OFF ratios up to five orders of magnitude. In addition to resistive switching, these devices display plasticity features including short- to long-term memory transitions, directly emulating synaptic learning rules. These results establish Cu₂₋ₓSe as a versatile platform for nanoscale switching, combining low leakage currents, high ON/OFF ratios, and neuromorphic functionality, with potential applications in brain-inspired computing.