Interface-Engineered Resistive Switching: CeO₂ Nanocubes as High-Performance Memory Cells

We reported a novel and facile approach to fabricate self-assembled CeO₂ nanocube-based resistive-switching memory device. The device was found to exhibit excellent bipolar resistive-switching characteristics with a high resistance state (HRS/OFF) to low resistance state (LRS/ON) ratio of 10⁴, better uniformity, and stability up to 480 K. The presence of oxygen vacancies and their role was discussed to explain the resistive-switching phenomenon in the fabricated devices. Further, the effect of the film thickness on carrier concentrations and estimated electric field strength with the switching (OFF/ON) ratio were also discussed

Interfacial Redox Reactions Associated Ionic Transport in Oxide-Based Memories

As an alternative to transistor-based flash memories, redox reactions mediated resistive switches are considered as the most promising next-generation nonvolatile memories that combine the advantages of a simple metal/​solid electrolyte (insulator)/​metal structure, high scalability, low power consumption, and fast processing. For cation-based memories, the unavailability of in-built mobile cations in many solid electrolytes/​insulators (e.g., Ta₂O₅, SiO₂, etc.) instigates the essential role of absorbed water in films to keep electroneutrality for redox reactions at counter electrodes. Herein, we demonstrate electrochemical characteristics (oxidation/​reduction reactions) of active electrodes (Ag and Cu) at the electrode/​electrolyte interface and their subsequent ions transportation in Fe₃O₄ film by means of cyclic voltammetry measurements. By posing positive potentials on Ag/Cu active electrodes, Ag preferentially oxidized to Ag⁺, while Cu prefers to oxidize into Cu²⁺ first, followed by Cu/Cu⁺ oxidation. By sweeping the reverse potential, the oxidized ions can be subsequently reduced at the counter electrode. The results presented here provide a detailed understanding of the resistive switching phenomenon in Fe₃O₄-based memory cells. The results were further discussed on the basis of electrochemically assisted cations diffusions in the presence of absorbed surface water molecules in the film

High-Performance Nanocomposite Based Memristor with Controlled Quantum Dots as Charge Traps

We report a novel approach to improve the resistive switching performance of semiconductor nanorod (NR) arrays, by introducing ceria (CeO₂) quantum dots (QDs) as surface charge trappers. The vertically aligned zinc oxide (ZnO) (NR) arrays were grown on transparent conductive glass by electrochemical deposition while CeO₂ QDs were prepared by a solvothermal method. Subsequently, the as-prepared CeO₂ QDs were embedded into a ZnO NR array by dip coating to obtain a CeO₂–ZnO nanocomposite. Interestingly, such a device exhibits excellent resistive switching properties with much higher ON/OFF ratios, better uniformity, and stability over the pure ZnO and CeO₂ nanostructures. The origin of resistive switching was studied and the role of heterointerface was discussed

Interface Thermodynamic State-Induced High-Performance Memristors

A new class of memristors based on long-range-ordered CeO₂ nanocubes with a controlled degree of self-assembly is presented, in which the regularity and range of the nanocubes can be greatly improved with a highly concentrated dispersed surfactant. The magnitudes of the hydrophobicity and surface energy components as functions of surfactant concentration were also investigated. The self-assembled nanostructure was found to demonstrate excellent degradation in device threshold voltage with excellent uniformity in resistive switching parameters, particularly a set voltage distribution of ∼0.2 V over 30 successive cycles and a fast response time for writing (0.2 μs) and erasing (1 μs) operations, thus offering great potential for nonvolatile memory applications with high performance at low cost