Exploring Electron Transport and Memristive Switching in Nanoscale Au/WOx/W Multijunctions Based on Anodically Oxidized Al/W Metal Layers

Abstract

An array of semiconducting tungsten-oxide (WOx) nanorods, 100 nm wide and 700 nm long, is synthesized via the porous-anodic-alumina-assisted anodization of tungsten on a substrate and is modified by annealing in air and vacuum. The rods buried in the alumina nanopores are self-anchored to the tungsten layer while their tops are interconnected via gold electrodeposited inside and over the pores. Thus formed metal/semiconductor/metal microdevices are used for studying electron transport within the nanorods and across the multiplied nanoscale Au/WOx and W/WOx interfaces. The dominating effect of a Schottky junction that forms at the Au/WOx interface is justified for the as-anodized and air-annealed nanorods tested at room temperature, which transforms into an ohmic contact at elevated temperature, whereas the bottom W/WOx interface turns out to be Schottky-like and govern the electron transport, giving a higher barrier and a set of pronounced diode-like characteristics in the as-anodized nanoarrays. The amorphous nanorods reveal bipolar resistive switching with a gradual reset due to the field-driven movement of oxygen vacancies and induced modifications of the Au/WOx Schottky interface. The unique electrical and interfacial properties of the nanoscale Au/WOx/W multijunctions form a basis for their application in emerging resistive random access memories or 3D gas-sensing nanodevices.

An array of semiconducting tungsten-oxide (WOx) nanorods, 100 nm wide and 700 nm long, is synthesized via the porous-anodic-alumina-assisted anodization of tungsten on a substrate and is modified by annealing in air and vacuum. The rods buried in the alumina nanopores are self-anchored to the tungsten layer while their tops are interconnected via gold electrodeposited inside and over the pores. Thus formed metal/semiconductor/metal microdevices are used for studying electron transport within the nanorods and across the multiplied nanoscale Au/WOx and W/WOx interfaces. The dominating effect of a Schottky junction that forms at the Au/WOx interface is justified for the as-anodized and air-annealed nanorods tested at room temperature, which transforms into an ohmic contact at elevated temperature, whereas the bottom W/WOx interface turns out to be Schottky-like and govern the electron transport, giving a higher barrier and a set of pronounced diode-like characteristics in the as-anodized nanoarrays. The amorphous nanorods reveal bipolar resistive switching with a gradual reset due to the field-driven movement of oxygen vacancies and induced modifications of the Au/WOx Schottky interface. The unique electrical and interfacial properties of the nanoscale Au/WOx/W multijunctions form a basis for their application in emerging resistive random access memories or 3D gas-sensing nanodevices.