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Ultrafast Dynamics of Defect-Assisted Carrier Capture in MoS2 Nanodots Investigated by Transient Absorption Spectroscopy
Da Ke1,2, Lai-zhi Sui1,2,3, Dun-li Liu1,2, Jian-qiu Cui4, Yun-feng Zhang1,2, Qing-yi Li1,2, Su-yu Li1,2, Yuan-fei Jiang1,2, An-min Chen1,2, Jun-ling Song4, Ming-xing Jin1,2
1.Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China;2.Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy, Jilin University, Changchun 130012, China;3.State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Dalian 116023, China;4.School of Chemical & Material Engineering, Jiangnan University, Wuxi 214122, China
Abstract:
MoS2 nanodots are emerging as promising semiconductor materials for optoelectronic devices. However, most of the recent attention is focused on the fabrication of MoS2 nanodots, and the survey for exciton dynamics of MoS2 nanodots remains less explored. Herein, we use femtosecond transient absorption spectroscopy to investigate the carrier dynamics of MoS2 nanodots. Our results show that defect-assisted carrier recombination processes are well consistent with the observed dynamics. The photo-excited carriers are captured by defects with at least two different capture rates via Auger scattering. Four processes are deemed to take part in the carrier relaxation. After photoexcitation, carrier cooling occurs instantly within ~0.5 ps. Then most of carriers are fast captured by the defects, and the corresponding time constant increases from ~4.9 ps to ~9.2 ps with increasing pump fluence, which may be interpreted by saturation of the defect states. Next a small quantity of carriers is captured by the other kinds of defects with a relatively slow carrier capture time within ~65 ps. Finally, the remaining small fraction of carriers relaxes via direct interband electron-hole recombination within ~1 ns. Our results may lead to deep insight into the fundamentals of carrier dynamics in MoS2 nanodots, paving the way for their further applications.
Key words:  MoS2  Transient absorption spectroscopy  Defect-assisted carrier capture
FundProject:This work was supported by the National Natural Science Foundation of China (No.11674128, No.21403232, No.11474129, and No.11504129), the Jilin Province Scientific and Technological Development Program, China (Grant No. 20170101063JC), the Thirteenth Five-Year Scientific and Technological Research Project of the Education Department of Jilin Province, China (2016, No. 400).
二硫化钼纳米点中的缺陷辅助载流子俘获超快动力学
柯达1,2, 隋来志1,2,3, 刘敦利1,2, 崔建秋4, 张云峰1,2, 李庆仪1,2, 李苏宇1,2, 姜远飞1,2, 陈安民1,2, 宋俊玲4, 金明星1,2
1.吉林大学, 原子与分子物理研究所, 长春 130012;2.吉林省应用原子分子光谱重点实验室, 长春 130012;3.中国科学院大连化学物理研究所, 分子反应动力学国家重点实验室, 大连 116023;4.江南大学, 化学与材料工程学院, 无锡 214122
摘要:
二硫化钼纳米点正在成为有潜质的半导体材料用于光电设备的应用.然而,关于对其中激子动力学的研究却很少.本文利用飞秒瞬态吸收光谱学来研究二硫化钼纳米点的载流子动力学.结果显示,缺陷辅助的载流子再复合过程与观测到的动力学相符,通过俄歇散射对光激载流子进行俘获至少存在两种不同俘获速率的缺陷.四个过程参与了载流子驰豫,在受到光激发后,立即在~0.5 ps内载流子冷却,然后大部分载流子被缺陷快速俘获,随着泵浦能量的增加,该过程对应的时间从~4.9 ps增加到~9.2 ps,这可以用缺陷态的饱和来解释.接下来,拥有相对慢的载流子俘获速率的其它类型缺陷对小部分载流子进行俘获,该过程约65 ps.最后,剩余的少量载流子通过直接带间跃迁发生电子-空穴再复合,时间约为1 ns.研究结果可以深入了解二硫化钼纳米点中的载流子动力学基本原理,引导其更多的应用.
关键词:  二硫化钼  瞬态吸收光谱  缺陷辅助的载流子俘获
DOI:10.1063/1674-0068/31/cjcp1802018
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