Origin of Visible Photoluminescence of ZnO Quantum Dots: Defect-Dependent and Size-Dependent

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• 作者：Luyuan Zhang ; Longwei Yin ; Chengxiang Wang ; Ning lun ; Yongxin Qi ; Dong Xiang
• 刊名：Journal of Physical Chemistry C
• 出版年：2010
• 出版时间：June 3, 2010
• 年：2010
• 卷：114
• 期：21
• 页码：9651-9658
• 全文大小：427K
• 年卷期：v.114,no.21(June 3, 2010)
• ISSN：1932-7455

文摘

To get a real understanding on the complexity of origin and mechanism of visible emission for ZnO quantum dots (QDs), we systematically property of visible emission of ZnO QDs with tunable diameters in a range of 2.2−7.8 nm synthesized via a sol−gel route using self-made zinc−oleate complex as a precursor. It is indicated that the visible emission of ZnO QDs can be ascribed to singly ionized oxygen vacancies, which is associated with the paramagnetic centers with electron paramagnetic resonance (EPR) value of g = 2.0056. The visible emission property of the ZnO QDs displays highly size-dependent behavior. With ZnO QDs size decreasing, the visible emission peaks blue-shift to the positions with shorter wavelength due to quantum size effect, however, is different from that of band gap. Quantitative investigation shows that the visible emission can correspond to a transition of holes from the valence band to the preexisting deep donor energy level, which is different from the well-known conclusion that the visible emission is due to the transition of an electron from the conduction band to a deep trap. Two important points can be obtained: the defects of singly ionized oxygen vacancies determine the origin and intensity of visible emission of ZnO QDs; and the visible emission peak position of ZnO QDs is decided by their size, and a transition of holes from the valence band to the preexisting deep donor energy level is responsible for the visible emission of the ZnO QDs.