Effect of reaction temperature and reaction time on the sizes and defects of Sn doped ZnO quantum dots synthesized under ultrasonic irradiation

Abstract

Sn doped Zn0.95Sn0.05O quantum dots were synthesized via an ultrasonic method under different reaction time and reaction temperature. Optical defects of these Zn0.95Sn0.05O quantum dots were controlled by tuning the valence states of the dopants (Sn2+ or Sn4+). For Sn2+ doped Zn0.95Sn0.05O quantum dots, main optical defects were \({V}_{{O}}^{ \cdot }\) defects. While for Sn4+ doped Zn0.95Sn0.05O quantum dots, main optical defects were \({{O}_{Zn}}\) and \({{O}_i}\) defects. UV–Vis spectra were employed to investigate the energy gap of these quantum dots. Photoluminescence properties were measured to discuss the optical defect types and concentrations in these quantum dots. It was found that the reaction condition played an important role in controlling the particle sizes and optical defects of Zn0.95Sn0.05O quantum dots. Moreover, with reaction temperature or reaction time increasing, for both Sn2+ and Sn4+ doped Zn0.95Sn0.05O quantum dots, changing trends of their particle sizes were almost same. While changing trends of their optical defect types and concentrations were different. The results indicate that, oxygen in Sn doped Zn0.95Sn0.05O quantum dots died out much more completely under the ultrasonic reaction with higher reaction temperature and longer reaction time.