Different valence Sn doping – A simple way to detect oxygen concentration variation of ZnO quantum dots synthesized under ultrasonic irradiation

Abstract

An ultrasonic method is employed to synthesize the Sn doped Zn0.95Sn0.05O quantum dots with green light emission. Sn2+ and Sn4+ ions are used to create different optical defects inside Zn0.95Sn0.05O quantum dots and the changing trend of oxygen concentration under different ultrasonic irradiation power are investigated. The photoluminescence spectra are employed to characterize the optical defects of Zn0.95Sn0.05O quantum dots. The UV–vis spectra are used to study the band gap of Zn0.95Sn0.05O quantum dots, which is influenced by their sizes. The results indicate that ultrasonic power would influence the size of Zn0.95Sn0.05O quantum dots as well as the type and quantity of defects in ZnO quantum dots. Changing trends in size of Sn2+ and Sn4+ doped Zn0.95Sn0.05O quantum dots are quite similar with each other, while the changing trends in optical defects types and concentration of Sn2+ and Sn4+ doped Zn0.95Sn0.05O quantum dots are different. The difference of the optical defects concentration changing between Sn2+ doped Zn0.95Sn0.05O quantum dots (VO defects) and Sn4+ doped Zn0.95Sn0.05O quantum dots (OZn and Oi defects) shows that the formation process of ZnO under ultrasonic irradiation wiped oxygen out.