A High‐Entropy‐Oxides‐Based Memristor: Outstanding Resistive Switching Performance and Mechanisms in Atomic Structural Evolution

Abstract The application of high‐entropy oxide (HEO) has attracted significant attention in recent years owing to their unique structural characteristics, such as excellent electrochemical properties and long‐term cycling stability. However, the application of resistive random‐access memory (RRAM) has not been extensively studied, and the switching mechanism of HEO‐based RRAM has yet to be thoroughly investigated. In this study, HEO (Cr, Mn, Fe, Co, Ni)₃O₄ with a spinel structure is epitaxially grown on a Nb:STO conductive substrate, and Pt metal is deposited as the top electrode. After the resistive‐switching operation, some regions of the spinel structure are transformed into a rock‐salt structure and analyzed using advanced transmission electron microscopy and scanning transmission electron microscopy. From the results of X‐ray photoelectron spectroscopy and electron energy loss spectroscopy, only specific elements would change their valence state, which results in excellent resistive‐switching properties with a high on/off ratio on the order of 10⁵, outstanding endurance (>4550 cycles), long retention time (>10⁴ s), and high stability, which suggests that HEO is a promising RRAM material.