Effect of oxygen vacancies on the resistive switching behavior of hexagonal WO3 nanowire

Abstract

The concentration of oxygen vacancies in hexagonal WO3 nanowires has been well regulated after being reduced in H2 environment at different temperatures. The current-voltage characteristics based on the Au/WO3 nanowire/Au device reveal that the conduction mechanism is converted from a bulk-limited type (space-charge-limited conduction) to an electrode-limited type (Schottky emission) with the increase of oxygen vacancy concentration and bias voltage. Ultraviolet photoelectron spectra of WO3 nanowires indicate that the defect states of oxygen vacancy approach the Fermi level gradually as the concentration of oxygen vacancies increasing. These defect states are always localized owing to the disordered distribution of oxygen vacancies, and then the space-charge-limited conduction and the transport of electrons are suppressed gradually. Under larger bias voltage, more localized states will be filled, which enhances the space-charge-limited conduction in WO3 nanowire. In the meantime, it will enhance the height of the interfacial barrier and turn the Ohmic contact into Schottky type. Therefore, it is possible to regulate the resistive switching behaviors of WO3 nanowire by adjusting the concentration of oxygen vacancies and even bias sweeping range.