Nonvolatile resistive switching memories-characteristics, mechanisms and challenges

This review presents a summary of current understanding of the resistive switching materials and devices which have inspired extraordinary interest all over the world. Although various switching behaviors and different conductive mechanisms are involved in the field, the resistive switching effects can be roughly classified into filament type and interface type according to their conducting behavior in low resistance state. For those filament based systems, the migration of metallic cations and oxygen vacancies, characterization of the filament as well as the role of Joule heating effects are discussed in detail. As to the interface based system, we describe the methods of modulating interface barrier height such as using different electrodes, inserting a tunnel layer. It is demonstrated that the switching mechanism can transform from one to another along the change of some specific conditions. We also give an overview on the latest developments in multilevel storage and the resistive switching in organic materials. In this paper, the solutions to address the sneak current problems in crossbar structure are discussed.