Shi S L, Li G Q, Xu S J, Zhao Y, Chen G H
Department of Physics and HKU-CAS Joint Laboratory on New Materials, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
J Phys Chem B. 2006 Jun 1;110(21):10475-8. doi: 10.1021/jp0610968.
The green emission band of ZnO has been investigated by both experimental and theoretical means. Two sets of equally separated fine structures with the same periodicity (close to the longitudinal optical (LO) phonon energy of ZnO) are well resolved in the low-temperature broad green emission spectra. As the temperature increases, the fine structures gradually fade out and the whole green emission band becomes smooth at room temperature. An attempt to quantitatively reproduce the variable-temperature green emission spectra using the underdamped multimode Brownian oscillator model taking into account the quantum dissipation effect of the phonon bath is done. Results show that the two electronic transitions strongly coupled to lattice vibrations of ZnO lead to the observed broad emission band with fine structures. Excellent agreement between theory and experiment for the entire temperature range enables us to determine the dimensionless Huang-Rhys factor characterizing the strength of electron-LO phonon coupling and the coupling coefficient of the LO and bath modes.
通过实验和理论手段对ZnO的绿色发射带进行了研究。在低温宽绿色发射光谱中，两组具有相同周期性（接近ZnO的纵向光学（LO）声子能量）的等间隔精细结构得到了很好的分辨。随着温度升高，精细结构逐渐消失，在室温下整个绿色发射带变得平滑。尝试使用考虑声子浴量子耗散效应的欠阻尼多模布朗振子模型定量再现变温绿色发射光谱。结果表明，与ZnO晶格振动强烈耦合的两个电子跃迁导致了观察到的具有精细结构的宽发射带。在整个温度范围内理论与实验的出色吻合使我们能够确定表征电子-LO声子耦合强度的无量纲黄-里斯因子以及LO与浴模的耦合系数。
