The Effect of Li on the Spectrum of Er3+ in Li- and Er-Codoped ZnO Nanocrystals

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• 作者：Yunfeng Bai ; Yuxiao Wang ; Kun Yang ; Xueru Zhang ; Guanya Peng ; Yinglin SongZhiyun PanChin Hsien Wang
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：August 14, 2008
• 年：2008
• 卷：112
• 期：32
• 页码：12259-12263
• 全文大小：229K
• 年卷期：v.112,no.32(August 14, 2008)
• ISSN：1932-7455

文摘

Infrared-to-visible upconversion emission intensities are investigated in Li⁺ and Er³⁺ codoped ZnO nanocrystals. Li⁺ ions doped in ZnO/Er³⁺ nanocrystals can greatly enhance the upconversion emission intensity of Er³⁺ ions. The extended X-ray absorption fine structure spectroscopy data show that both the Er−O bond length and coordination number of the Er−Er bond have been altered by introducing Li⁺ ions in the ZnO/Er³⁺ nanocrystals. The variation of Er−O bond length leads to the change in the local asymmetry around Er³⁺ ions. Meanwhile, the greater coordination number of the Er−Er bond causes stronger interaction between neighboring Er³⁺ ions and, hence, strengthens the reaction Er³⁺ (⁴F_7/2) + Er³⁺ (⁴I_11/2) → 2Er³⁺ (⁴F_9/2). In this process, the ⁴F_9/2 state is a metastable state that could be excited to the ²H_9/2 state by absorbing one photon at high excitation power. Li⁺ ions also can reduce the OH groups in specimen, which is the other reason for enhancing the upconversion emission intensities.