Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronic Science, and State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, Hunan 410082, P. R. China.
Nanoscale. 2017 Jun 1;9(21):7235-7241. doi: 10.1039/c7nr01345k.
Recombination dynamics during photoluminescence (PL) in two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) are complicated and can be easily affected by the surroundings because of their atomically thin structures. Herein, we studied the excitation power and temperature dependence of the recombination dynamics on the chemical vapor deposition-grown monolayer WSvia a combination of Raman, PL, and time-resolved PL spectroscopies. We found a red shift and parabolic intensity increase in the PL emission of the monolayer WS with the increasing excitation power and the decay time constants corresponding to the recombination of trions and excitons from transient PL dynamics. We attributed the abovementioned nonlinear changes in the PL peak positions and intensities to the combination of increasing carrier interaction and band structure renormalization rather than to the thermal effect from a laser. Furthermore, the excitation power-dependent Raman measurements support our conclusion. These findings and understanding will provide important information for the development of TMD-based optoelectronics and photonics.
二维（2D）半导体过渡金属二卤化物（TMD）中光致发光（PL）过程中的复合动力学较为复杂，由于其原子层状结构，很容易受到周围环境的影响。在此，我们通过拉曼、PL 和时间分辨 PL 光谱学的组合，研究了在化学气相沉积生长的单层 WS 上的复合动力学对激发功率和温度的依赖关系。我们发现随着激发功率的增加，单层 WS 的 PL 发射出现红移和抛物线强度增加，瞬态 PL 动力学对应的三重态和激子复合的衰减时间常数也随之增加。我们将 PL 峰位置和强度的上述非线性变化归因于载流子相互作用的增加和能带结构重整化的组合，而不是来自激光的热效应。此外，依赖于激发功率的 Raman 测量支持我们的结论。这些发现和理解将为基于 TMD 的光电学的发展提供重要信息。
