Luminescence of er doped ZnS quantum dots excited by infrared lasers |
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Authors: | Zhang Xiaosong Li Lan Huang Qingsong Zhang Zhongpeng Xi Qun Dong Xiaoyi Liu Yange Ji Ting |
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Affiliation: | Institute of Material Physics, Tianjin University of Technology, Tianjin 300191, People's Republic of China. |
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Abstract: | ZnS:Er quantum dots were prepared in aqueous medium from readily available precursors. The construction, morphology and luminescence properties of the ZnS:Er quantum dots were evaluated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence spectra. The average particle size was calculated using the Scherrer formula to be 4 nm, which is also observed from high resolution transmission electron microscopy (HRTEM) image. Different laser wavelengths at 976 +/- 2 nm and 1480 nm were utilized as the excitation source. ZnS:Er quantum dots had a fluorescence spectrum in 1550 nm region through the 4I13/2 --> 4I15/2 transition. Furthermore, intensity increased with increasing excitation intensity and dopant concentration. The reason for the photoluminescence spectra broadening is discussed. It is because the energy levels of Er3+ are split by a coulombic interaction between electrons, including spin correction and spin-orbit coupling, and eventually by the Stark effect due to ZnS QDs crystal field and local coordination. |
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