中国物理B ›› 2008, Vol. 17 ›› Issue (4): 1280-1285.doi: 10.1088/1674-1056/17/4/022

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Size-dependent optical properties and carriers dynamics in CdSe/ZnS quantum dots

马红1, 马国宏1, 马洪良2, 王文军3, 高学喜3   

  1. (1)Department of Physics, Shanghai University, Shanghai 200444, China; (2)Instrumental Analysis and Research Center, Shanghai University, Shanghai 200444, China; (3)School of Physics Science and Information Engineering, Liaocheng University, Liaocheng 252059, China
  • 收稿日期:2007-06-22 修回日期:2007-10-22 出版日期:2008-04-20 发布日期:2008-04-20
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No 10774099), Science and Technology Commission of Shanghai Municipal (Grant No 06PJ14042), Shanghai Municipal Education Commission (Grant No 06AZ089), and the Shanghai Leading A

Size-dependent optical properties and carriers dynamics in CdSe/ZnS quantum dots

Ma Hong(马红)a), Ma Guo-Hong(马国宏)a)†, Wang Wen-Jun(王文军)b), Gao Xue-Xi(高学喜)b), and Ma Hong-Liang(马洪良)c)   

  1. a Department of Physics, Shanghai University, Shanghai 200444, China; b School of Physics Science and Information Engineering, Liaocheng University, Liaocheng 252059, China; c Instrumental Analysis and Research Center, Shanghai University, Shanghai 200444, China
  • Received:2007-06-22 Revised:2007-10-22 Online:2008-04-20 Published:2008-04-20
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No 10774099), Science and Technology Commission of Shanghai Municipal (Grant No 06PJ14042), Shanghai Municipal Education Commission (Grant No 06AZ089), and the Shanghai Leading A

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摘要： Size-dependence of optical properties and energy relaxation in CdSe/ZnS quantum dots (QDs) were investigated by two-colour femtosecond (fs) pump--probe (400/800 nm) and picosecond time-resolved photoluminescence (ps TRPL) experiments. Pump--probe measurement results show that there are two components for the excited carriers relaxation, the fast one with a time constant of several ps arises from the Auger-type recombination, which shows almost particle size-independence. The slow relaxation component with a time constant of several decades of ns can be clearly determined with ps TRPL spectroscopy in which the slow relaxation process shows strong particle size-dependence. The decay time constants increase from 21 to 34 ns with the decrease of particle size from 3.2 to 2.1 nm. The room-temperature decay lifetime is due to the thermal mixing of bright and dark excitons, and the size-dependence of slow relaxation process can be explained very well in terms of simple three-level model.

关键词: semiconductor quantum dots, Auger-type recombination, time-resolved spectroscopy

Abstract: Size-dependence of optical properties and energy relaxation in CdSe/ZnS quantum dots (QDs) were investigated by two-colour femtosecond (fs) pump--probe (400/800 nm) and picosecond time-resolved photoluminescence (ps TRPL) experiments. Pump--probe measurement results show that there are two components for the excited carriers relaxation, the fast one with a time constant of several ps arises from the Auger-type recombination, which shows almost particle size-independence. The slow relaxation component with a time constant of several decades of ns can be clearly determined with ps TRPL spectroscopy in which the slow relaxation process shows strong particle size-dependence. The decay time constants increase from 21 to 34 ns with the decrease of particle size from 3.2 to 2.1 nm. The room-temperature decay lifetime is due to the thermal mixing of bright and dark excitons, and the size-dependence of slow relaxation process can be explained very well in terms of simple three-level model.

Key words: semiconductor quantum dots, Auger-type recombination, time-resolved spectroscopy

中图分类号:  (Excitons and related phenomena)

  • 71.35.-y
78.47.-p (Spectroscopy of solid state dynamics) 78.55.Et (II-VI semiconductors) 78.67.Hc (Quantum dots) 79.20.Fv (Electron impact: Auger emission)