Control of oxygen vacancy concentration in ZnO nanowires containing sulfur as a reducing agent

Light illumination influences the electrical characteristics and stability of oxide nanowire transistors. In this study, transistor characteristics of oxygen-vacancy-rich ZnO nanowires under illumination were investigated. In order to control the oxygen vacancies on the surface of ZnO, sulfur was used as a reducing agent during nanowire growth. Unlike pure nanowires, ZnO nanowires with sulfur as a reducing agent exhibited a dramatically enhanced green emission peak at around 520 nm in the photoluminescence spectrum, which is primarily generated under oxygen-deficient ambient conditions. The threshold voltage of a nanowire transistor using ZnO with sulfur showed no significant change under illumination. In contrast, the threshold voltage of pure ZnO shifted significantly in the negative direction under illumination. This phenomenon may arise from the fact that light illumination on the channel region of ZnO reduced with sulfur cannot generate additional oxygen vacancies on the nanowire surface because oxygen vacancies were created almost to the saturation point during nanowire growth.