Ultrafast Dynamics of Defect-Assisted Electron鈥揌ole Recombination in Monolayer MoS2

详细信息    查看全文

• 作者：Haining Wang ; Changjian Zhang ; Farhan Rana
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：January 14, 2015
• 年：2015
• 卷：15
• 期：1
• 页码：339-345
• 全文大小：426K
• ISSN：1530-6992

文摘

In this Letter, we present nondegenerate ultrafast optical pump鈥損robe 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 鈭? ps and a slow time scale that lasts longer than 鈭?00 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 electron鈥揾ole 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.