Revealing Resistive Switching Mechanism in CaFeO _x Perovskite System with Electroforming‐Free and Reset Voltage‐Controlled Multilevel Resistance Characteristics

Recently, perovskite (PV) oxides with ABO structures have attracted considerable interest from scientists owing to their functionality. In this study, CaFeO is introduced to reveal the resistive switching properties and mechanism of oxygen vacancy transition in PV and brownmillerite (BM) structures. BM-CaFeO is grown on an Nb-STO conductive substrate epitaxially. CaFeO exhibits excellent endurance and reliability. In addition, the CaFeO also demonstrates an electroforming-free characteristic and multilevel resistance properties. To construct the switching mechanism, high-resolution transmission electron microscopy is used to observe the topotactic phase change in CaFeO . In addition, scanning TEM and electron energy loss spectroscopy show the structural evolution and valence state variation of CaFeO after the switching behavior. This study not only reveals the switching mechanism of CaFeO , but also provides a PV oxide option for the dielectric material in resistive random-access memory (RRAM) devices.