Recent progress in redox-based resistive switching

Recent advancements in resistive switching cell are based on three conduction mechanisms - electrochemical (ECM), Valence-change (VCM) and thermo-chemical (TCM). In the ECM type cells, migration of anions, typically oxygen ions, towards the anode, and reduction of the cation sublattice provide either metallically or semiconducting phases and triggers a bipolar memory operation. The major factors determining the functionality of the ECM cells are the electrode reaction and the transport kinetics. The VCM type switching is generally observed in metal oxides. Finally, the resistive switching based on the TCM mechanism is discussed. Whenever, this thermo-chemical effect dominates over the electrochemical effect, a unipolar switching behavior is observed. Conductive filament formed during the electroforming process is interpreted as a sequence of threshold switching and subsequent Joule heating, which triggers local redox reactions.