Improvement in conductance modulation linearity of artificial synapses based on NaNbO3 memristor

Abstract

A crystalline NaNbO3 (NN) film was deposited on the TiN/SiO2/Si (T-S) substrate at 300 °C by using the pulsed laser deposition method. The NN film that was annealed at 300 °C under 5 Torr O2 atmosphere displays a typical bipolar switching curve. Growth and dissociation of the oxygen vacancy filament is responsible for the switching property of this NN memristor. This NN memristor shows good biological synaptic properties, but displays a non-linear conductance modulation with the application of an identical pulse. The non-linear conductance modulation is related to the non-linear growth of the oxygen vacancy filament that is controlled by two growth mechanisms (the fast redox process and the slow oxygen ion diffusion process) with different growth rates. The NN memristor was annealed under 10 Torr N2 atmosphere to increase the number of oxygen vacancies, and it displayed improved conductance modulation linearity. The filament in this NN film can be grown linearly and the redox process became the main growth mechanism. Therefore, the conductance modulation linearity can be improved by increasing the number of oxygen vacancies, and this method can be applied to other memristors.