Reliable Resistive Switching and Synaptic Behaviors Based on a TiO x -Doped N Memristor for Information Storage and Neuromorphic Computing

Bipolar resistive switching (RS) and synaptic behaviors of resistive random access memory (RRAM) based on TiO x are demonstrated. RS uniformity is improved by introducing nitrogen into the RS layer using radio frequency sputtering in the reactive Ar/N-2 ambient. The conductive mechanism is in good agreement with the space-charge-limited conduction model. The activation energy fit by the Arrhenius equation and conductive atomic force microscopy results indicate that the conductive filaments are formed by oxygen vacancies. More importantly, reliable multilevel RRAM can be achieved by tuning the compliance current, which enables the achievement of distinguishable resistance states. Furthermore, multilevel RRAM enables the simulation of synaptic functions, such as learning-forgetting-relearning, habituation, and spike-timing-dependent plasticity (STDP). Image pattern recognition based on STDP learning rules using a digital memristor is demonstrated. The findings may offer a route to the development of future storage and neuromorphic computing.