Rational Design on Polymorphous Phase Switching in Molybdenum Diselenide-Based Memristor Assisted by All-Solid-State Reversible Intercalation toward Neuromorphic Application.

In this work, a low-power memristor based on vertically stacked two-dimensional (2D) layered materials, achieved by plasma-assisted vapor reaction, as the switching material, with which the copper and gold metals as electrodes featured by reversible polymorphous phase changes from a conducting 1T-phase to a semiconducting 2H-one once copper cations interacted between vertical lamellar layers and vice versa, was demonstrated. Here, molybdenum diselenide was chosen as the switching material, and the reversible polymorphous phase changes activated by the intercalation of Cu cations were confirmed by pseudo-operando Raman scattering, transmission electron microscopy, and scanning photoelectron microscopy under high and low resistance states, respectively. The switching can be activated at about ±1 V with critical currents less than 10 µA with an on/off ratio approaching 100 after 100 cycles and low power consumption of ∼0.1 microwatt as well as linear weight updates controlled by the amount of intercalation. The work provides alternative feasibility of reversible and all-solid-state metal interactions, which benefits monolithic integrations of 2D materials into operative electronic circuits.

In Situ Current-Accelerated Phase Cycling with Metallic and Semiconducting Switching in Copper Nanobelts at Room Temperature.

Here, a current-accelerated phase cycling by an in situ current-induced oxidation process was demonstrated to reversibly switch the local metallic Cu and semiconducting Cu2O phases of patterned polycrystalline copper nanobelts. Once the Cu nanobelts were applied by a direct-current bias of ∼0.5 to 1 V in air with opposite polarities, the resistance between several hundred ohms and more than MΩ can be manipulated. In practice, the thickness of 60 nm with a moderate grain size inhibiting both electromigration and permanent oxidation is the optimized condition for reversible switching when the oxygen supply is sufficient. More than 40% of the copper localized beneath the positively biased electrode was oxidized assisted by the Joule heating, blocking the current flow. On the contrary, the reduction reaction of Cu2O was activated by the thermally assisted electromigration of Cu atoms penetrating the interlayer at the reverse bias. Finally, based on a high on/off ratio, the fast switching and the scalable production, reusable feasibility based on copper nanobelts such as the memristor array was demonstrated.