Discrete memristive levels and logic gate applications of Nb2O5 devices

Controlled resistive switching behavior has shown potential for brain-inspired functionalities and feasibility for multi-functional photelectric sensors. For the first time, bias-polarity dependent switching characteristic is observed in forming-free W/Nb2O5/(Pt, ITO) sandwiched structures. When voltage bias was applied to the W electrode, a multi-level cell (MLC) with more than two switching states was observed while a single-level (SLC) with binary switching states was observed with Pt or ITO biasing electrode. Moreover, devices with Pt electrodes exhibit higher SET voltages (>1) while devices with ITO electrodes exhibit lower SET voltages (<1) owing to mobile Sn4+ ions in the ITO electrodes which would absorb some oxygen ions and speed up the oxidation process during filament formation. Here MLC is attributed to the formation probability of multiple tiny filaments within interfacial layers arising from the interfacial oxygen ion migration between the W top electrode and Nb2O5 films. Moreover, implementation of Boolean logic functions using Nb2O5 films paves step towards commercialization of related logic circuits. (c) 2021 Elsevier B.V. All rights reserved.