Realization of volatile and non-volatile resistive switching with N-TiO2 nanorod arrays based memristive devices through compositional control

It is attractive to manipulate the volatile and non-volatile resistive switching behaviors of memristors to create genuine neuromorphic systems such as artificial neural networks (ANNs) and spiking neural networks (SNNs). To investigate the above behaviors, nitrogen has been introduced into TiO2 nanorod arrays (TiO2 NRAs) by hydrothermal processing. X-ray photoelectron spectroscopy (XPS) analysis shows that both lattice and interstitial nitrogen are incorporated into the TiO2 NRAs. Nitrogen doped TiO2 NRAs (N-TiO2 NRAs) based memristive devices with different contents of lattice nitrogen were investigated systematically. The results show that non-volatile restive switching is achieved at up to a relative lattice nitrogen content of 21%, with volatile switching behavior above this value. The volatile memristive devices show similar spiking and decay features to the Leaky Integrate-and-Fire (LIF) model. The lifetime of the decay process of the volatile devices rang from 0.029 to 1.835 s. The longest lifetime is obtained when the relative content of lattice nitrogen is about 70%. The volatile behavior is related to the large defect concentration, caused by nitrogen doping. The proposed nitrogen engineered memristive devices could pave the way to achieving a physical neuromorphic system.