Resistive switching behavior of hexagonal sodium tungsten bronze nanowire

Highly purified hexagonal sodium tungsten bronze nanowires, with diameters of 100-400 nm and lengths of 7-10 μm, have been synthesized via a hydrothermal method. Energy-dispersive X-ray Spectrometer quantitative analysis demonstrated directly that sodium ions can be drived to transport along the nanowire by the applied bias voltage. The current-voltage measurement results show that the Au/NaxWO3 nanowire/Au device exhibit different resistive switching behaviors under small and large bias voltage. The drift of sodium ions under a relatively large bias voltage might induce distinct changes in its concentrations near the junctions between NaxWO3 nanowire and Au electrodes, which will change the heights of these two Schottky barriers and switch this device to high or low resistance state accordingly. The existence of sodium ions also might induce strong disorder in WO3 lattice, which will lead to the localization of states in the conduction band tail. The localized states can be filled or drained under a relatively small bias voltage, which will also switch the device to high or low resistance state. These two resistive switching mechanisms compete with each other, which endows the Au/NaxWO3 nanowire/Au system with more abundant resistive switching properties.