resistiveswitching

Resistive switching is the reversible alteration of the electrical resistance of a material or device in response to an electrical stimulus, typically between a high-resistance state (HRS) and a low-resistance state (LRS). This switching is the basis for resistive random-access memory (ReRAM), a nonvolatile memory technology that aims to supplement or replace conventional flash memory in future storage and computing systems.

Two broad mechanisms are recognized. Filamentary switching involves the formation and dissolution of a conductive filament within the switching layer, commonly produced by the movement of metal cations or oxygen vacancies. Valence-change or interface switching involves modulation of the oxide's electronic structure and defect chemistry near an interface, changing the conductivity without a fully developed filament.

Switching can be unipolar or bipolar. In unipolar devices, SET and RESET operations can occur with the same polarity but at different voltages or currents, often driven by joule heating. In bipolar devices, SET and RESET require opposite polarities, aligning with ion migration and filament formation/dissolution controlled by the direction of the electric field.

Materials and structures: common switching layers include metal oxides such as TiO2, HfOx, TaOx, NiO, and Al2O3, as well as chalcogenides, perovskites, and certain polymers. Devices are typically metal-insulator-metal stacks or crossbar structures, where the switching layer is sandwiched between electrodes.

Advantages include nonvolatility, scalability, and fast switching; challenges include device-to-device variability, endurance, retention, and the need for an initial forming step in many devices. Ongoing research seeks materials engineering, device architectures, and circuit techniques to improve reliability and energy efficiency.