Amorphous Ta2O5 memristor with excellent self-selective and artificial synaptic properties for artificial neural networks

Abstract

An amorphous Ta₂O₅ (ATO) thin film grown on a TiN/SiO₂/Si (TS) substrate at room temperature exhibited a bipolar switching I–V curve owing to the formation and destruction of conductive oxygen vacancy filaments. However, ATO films do not exhibit self-selective properties. An insulating ATO (IATO) thin film was deposited on the TS substrate to form a tunneling barrier, which induced self-selective properties in the ATO memristor. The ATO thin film grown on the IATO/TS substrate exhibited excellent self-selective properties with large nonlinearity and on/off ratios and good endurance and retention characteristics. Schottky emission, direct tunneling (DT), and Fowler–Nordheim tunneling (FNT) are responsible for the current conduction in the Pt/ATO/IATO/TS memristor in the high-resistance state. Moreover, current conduction in the low-resistance state can be explained by DT and FNT. The Pt/ATO/IATO/TS memristor exhibited synaptic properties; thus, it can imitate biological synapses. Therefore, the ATO memristor can be used as an artificial synapse with a cross-point array structure in artificial neural networks.