Origin of discrete resistive switching in chemically heterogeneous vanadium oxide crystals

Phase changes in oxide materials such as VO₂ offer a foundational platform for designing novel solid-state devices. Tuning the V : O stoichiometry offers a vast electronic phase space with non-trivial collective properties. Here, we report the observation of discrete threshold switching voltages (V_th) with constant ΔV_th between cycles in vanadium oxide crystals. The observed threshold fields over 10 000 cycles are ∼100× lower than that noted for stoichiometric VO₂ and show unique discrete behaviour with constant ΔV_th. We correlate the observed discrete memristor behaviour with the valence change mechanism and fluctuations in the chemical composition of spatially distributed VO₂-VO₂ complex oxide phases that can synergistically co-operate with the insulator-metal transition resulting in sharp current jumps. The design of chemical heterogeneity in oxide crystals, therefore, offers an intriguing path to realizing low-energy neuromorphic devices.