Self-rectifying and artificial synaptic characteristics of amorphous Ta2O5 thin film grown on two-dimensional metal-oxide nanosheet

Abstract

Amorphous Ta2O5 (ATa2O5) films were grown on Sr2Nb3O10/TiN/SiO2/Si (SN-TSS) at room temperature. Sr2Nb3O10 (SN) metal-oxide nanosheets were used as a tunneling barrier to induce self-rectifying properties in ATa2O5 memristors. An ATa2O5 thin film grown on one SN monolayer exhibited a typical bipolar switching curve without any self-rectifying property, indicating that one SN monolayer cannot function as a tunneling barrier. This ATa2O5 thin film showed switching behavior owing to the formation and breakage of oxygen vacancy (OV) filaments. Self-rectifying characteristics were observed in an ATa2O5 thin film grown on two SN monolayers, which behaved as a tunneling barrier in the Pt/ATa2O5/SN-TSS memristor. The current conduction of this ATa2O5 thin film in the high-resistance state (HRS) is explained by Schottky emission, direct tunneling, and Fowler–Nordheim (FN) tunneling. In the low-resistance state (LRS), this ATa2O5 thin film shows insulating behavior, indicating that OV filaments were not formed. The current conduction of this ATa2O5 thin film in the LRS was attributed to direct tunneling and FN tunneling. Moreover, ATa2O5 thin films grown on two SN monolayers exhibited artificial synaptic properties. Therefore, the ATa2O5 thin film can be used as an artificial synapse with a cross-sectional array structure.