Epitaxial Cu₂₋ₓSe Thin Films Exhibiting Memristive and AntiferroelectricSwitching for Neuromorphic Function

Materials exhibiting resistive switching are of great interest for applications in neuromorphic

computing and energy-efficient electronic devices. Here, we demonstrate that epitaxial Cu₂₋ₓSe

thin films grown on Al₂O₃ substrates by molecular beam epitaxy can stabilize the superionic

phase of copper selenide—normally observed only above ~400 K—at room temperature. By

precisely tuning the growth conditions, we control the stoichiometry and thereby induce either

the superionic or the antiferroelectric phase. Room-temperature current–voltage (I–V)

measurements reveal memristive switching with ON/OFF ratios exceeding five orders of

magnitude and antiferroelectric switching with ratios up to three orders of magnitude. We further

demonstrate how the memristive and antiferroelectric behaviors can serve as building blocks for

artificial neuron architectures. Moreover, the memristive devices exhibit plasticity features,

including short-term memory transitions, emulating synaptic learning rules. These findings

establish Cu₂₋ₓSe as a versatile platform for nanoscale switching that combines low leakage

current, large ON/OFF ratios, and neuromorphic functionality—positioning it as a promising

candidate for bio-inspired and reconfigurable electronic systems.