Oxygen vacancy dynamics in redox-based interfaces: tailoring the memristive response

Abstract

Redox-based memristive devices are among the alternatives for the next generation of non-volatile memories, but are also candidates for emulating the behavior of synapses in neuromorphic computing devices. Nowadays it is well established that the motion of oxygen vacancies at the nanoscale is the key mechanism for reversible switching of metal/insulator/metal structures from insulating to conducting, i.e. to accomplish the resistive switching effect. The control of oxygen vacancy dynamics has a direct effect on the resistance changes, and therefore on different properties of memristive devices such as switching speed, retention, endurance and energy consumption. Advances in this direction demand not only experimental techniques that allow the measurement of oxygen vacancy profiles but also theoretical studies that shed light on the mechanisms involved. With these goals in mind we analyze the oxygen vacancy dynamics in redox interfaces formed when an oxidizable metallic electrode is in contact with the insulating oxide. We show how the transfer of oxygen vacancies can be manipulated by the use of different electrical stimulus protocols that allow optimization of device figures such as the ON/OFF ratio or writing energy dissipation. Analytical expressions for both high- and low-resistance states are derived in terms of total oxygen vacancies transferred at the interface. Our predictions are validated with experiments performed in Ti/La1/3Ca2/3MnO3 redox memristive devices.