Ultrafast Dynamics of Defect-Assisted Electron Hole Recombination in Mono layer MoS2
Ultrafast Dynamics of Defect-Assisted Electron Hole Recombination in Mono layer MoS2
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DOI：
10.1021/nl503636c
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发表时间：
2015-01-01
期刊：
影响因子：
10.8
通讯作者：
Rana, Farhan
中科院分区：
文献类型：
--
作者：
Wang, Haining;Zhang, Changjian;Rana, Farhan
在这封信中，我们提出了非简并的超快光泵浦探测研究的载流子复合动力学的二硫化钼单层。通过将探针调谐到比激子线长得多的波长，我们使探针透射对光激发电子和空穴的总布居敏感。我们的测量揭示了两个不同的时间尺度上的光激发的电子和空穴重组;一个快速的时间尺度，持续类似于2 ps和一个缓慢的时间尺度，持续时间超过类似于100 ps。所观察到的载流子动力学的温度和泵浦能量密度的依赖性是一致的缺陷辅助复合作为电子空穴复合的主导机制，其中电子和空穴被捕获的缺陷通过俄歇过程。二维原子材料中的强库仑相互作用，以及二维金属二硫属化物中的强电子和空穴相关性，使得俄歇过程对于缺陷捕获载流子特别有效。我们提出了一个载流子复合动力学模型，定量地解释了我们的数据为不同的温度和泵注量的所有功能。俄歇载流子俘获速率常数的理论估计值与实验测定值吻合得很好。我们的研究结果强调了俄歇过程在二维原子材料中所起的重要作用。
In this Letter, we present nondegenerate ultrafast optical pumpprobe studies of the carrier recombination dynamics in MoS2 monolayers. By tuning the probe to wavelengths much longer than the exciton line, we make the probe transmission sensitive to the total population of photoexcited electrons and holes. Our measurement reveals two distinct time scales over which the photoexcited electrons and holes recombine; a fast time scale that lasts similar to 2 ps and a slow time scale that lasts longer than similar to 100 ps. The temperature and the pump fluence dependence of the observed carrier dynamics are consistent with defect-assisted recombination as being the dominant mechanism for electronhole recombination in which the electrons and holes are captured by defects via Auger processes. Strong Coulomb interactions in two-dimensional atomic materials, together with strong electron and hole correlations in two-dimensional metal dichalcogenides, make Auger processes particularly effective for carrier capture by defects. We present a model for carrier recombination dynamics that quantitatively explains all features of our data for different temperatures and pump fluences. The theoretical estimates for the rate constants for Auger carrier capture are in good agreement with the experimentally determined values. Our results underscore the important role played by Auger processes in two-dimensional atomic materials.