Review of mechanisms proposed for redox based resistive switching structures

Mechanisms proposed for redox-based memristors are reviewed. Emphasis is given on MIM (metal/insulator/metal) devices of the type MOM where the insulator is an oxide. The oxide conducts oxygen via oxygen vacancies. MOM devices in which the insulator conducts intercalated cations are analogous to the ones with mobile oxygen vacancies. Switching, memory and short term hysteresis are three independent phenomena governed by different mechanisms. A necessary condition for memory is presented. Electroforming, filament formation and alteration and I-V curve crossing are discussed. A new mechanism for unipolar switching is suggested. The metal electrodes are sorted into four types according to the nature of their oxygen transfer. The effect of humidity in the ambient is discussed.