Interfacial Redox Reactions Associated Ionic Transport in Oxide-Based Memories

Abstract

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., TaO, SiO, 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 FeO 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 Cu 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 FeO-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.

Facilitate Measurement of Electrochemical Reactions in Redox‐Based Memristors by Simply Thickening the Electrolyte Layer

“…Mechanism of resistive switching in ECM systems is well understood under the oxidation of active electrode, migration of the mobile ions in solid electrolyte and their reduction at inert electrode which finally results in formation of a conductive filament between the two electrodes. Rupture and formation of this conductive filament under bias voltage is the major key in resistance switching . Therefore Redox reactions at the interface of solid electrolyte and metal electrodes play a vital role in ECMs.…”

“…Another study in Cu,Ag/Ta 2 O 5 /Pt cell has shown that using CV curves could reveal the effect of density on diffusion and filament growth of Ag and Cu. Also the effects originating from environmental condition, like moisture in the air, can be revealed using CV curves . Ag is the most promising candidate for use in ECM cells because of its high ion mobility and desirable electrochemical properties.…”

“…. For example the reduction of water at the interface of Pt counter electrode with solid electrolyte has been considered as follows: …”

“…Rupture and formation of this conductive filament under bias voltage is the major key in resistance switching. [10][11][12] Therefore Redox reactions at the interface of solid electrolyte and metal electrodes play a vital role in ECMs. Electrochemistry at the nanoscale has inspired the research toward understanding the mechanisms engaged in the resistance switching of memristors.…”

“…Also the effects originating from environmental condition, like moisture in the air, can be revealed using CV curves. [10,12,18,19] Ag is the most promising candidate for use in ECM cells because of its high ion mobility and desirable electrochemical properties. Because of this, Ag is extensively studied using CV curves to reveal the nature of its redox reactions in memristors.…”