Well unipolar resistive switching (RS) behaviors were observed from Ag/ZnO single-microwire/Ag memristors. The reset voltages were larger than the set voltages, and all of them were less than 1 V. The resistance ratios of high-resistance state (HRS) to low-resistance state (LRS) reached 10³. The bistable RS behaviors were entirely reversible and steady within 100 cycles. It was found that the dominant conduction mechanisms in LRS and HRS were ohmic behavior and space-charge-limited current (SCLC), respectively.

The advent of memristors and the continuing research and development in the field of brain-inspired computing could allow realization of a veritable “thinking machine”. In this study, ZnO-based memristors were fabricated using a radio frequency magnetron sputtering method. The ZnO oxide layer was prepared by incorporating silver nanocrystals (NCs). Several synaptic functions, i.e. nonlinear transmission characteristics, short-term potentiation, long-term potentiation/depression, and pair-pulse facilitation, were imitated in the memristor successfully. Furthermore, the transition from synaptic behaviors to bipolar resistive switching behaviors of the device was also observed under repeated stimulus. It is speculated that the switching mechanism is due to the formation and rupture of the conductive Ag filaments and the corresponding electrochemical metallization. The experimental results demonstrate that the Ag/Ag:ZnO/Pt memristor with resistive switching and several synaptic behaviors has a potential application in neuromorphic computing and data storage systems.

The rapid expansion of data information has necessitated higher requirements for the operational speed, low energy consumption and high density integration. Resistive random access memory (RRAM), which can realize all of the mentioned advantages, has the potential to be the next-generation nonvolatile memory device. However, it is not easy to design an RRAM device with both high performance and stability. Herein, we improve the performance of the RRAM devices by incorporating Cu nanocrystals (NCs) into the ZnO oxide layer. Afterwards, many resistive parameters of the NC-RRAM devices are markedly improved, such as longer retention time over 10 ⁶ s, with consecutive 10 ³ switching cycles. It is inferred that the switching mechanism is due to the migration of Cu cations and the corresponding electrochemical metallization, and the Cu NCs enhance the electric field intensity, which boosts the formation and rupture of the conductive filaments.