2007 Fiscal Year Final Research Report Summary
Spectroscopic Study on Inverse Auger Effect of Semiconductor Quantum Dots
| Project/Area Number |
18550024
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | Kwansei Gakuin University |
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Principal Investigator |
TAMAI Naoto Kwansei Gakuin University, Department of Chemistry, School of Science and Technology, Professor (60163664)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Inverse Auger Effect / Semiconductor Quantum Dots / Single-Photon Timing / Auger Effect / Transient Absorption Spectroscopy / Single Particle Spectroscopy |
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| Research Abstract |
Various sized CdTe QDs were synthesized in organic and water solvents, and the precursors were removed by several methods. Steady-state luminescence spectra were examined as a function of excitation wavelength, and the spectral shape of QDs was found to be independent of the wavelength, suggesting the free from an impurity. The second (400nm) and third (266nm) harmonics of femtosecond Ti:sapphire laser were used as excitation pulse to measure the luminescence decay and analyze inverse Auger effect.
By using various sized CdTe QDs, we found that inverse Auger effect was observed when ω/Eg is larger than 2.5, in which the lifetime becomes shorter and multicarriers are formed in single CdTe QDs. For 5.4nm sized CdTe QDs (Eg=1.73 eV), the quantum efficiency of inverse Auger effect was 190%. In addition, the effective mass of the electron and hole may play an important role on the threshold energy of 2.5Eg for inverse Auger effect of CdTe QDs. Excitation intensity dependence of transient absorption dynamics was also examined to reveal Auger effect of CdTe QDs that is due to the interaction of muliticarriers generated by inverse Auger effect. The Auger effects of CdTe QDs and nanowires can be analyzed by the time-dependent recombination rate by Global analysis and the Auger recombination rate of nanowires was found to be larger than that of QDs. Furthermore, the excitation intensity dependence in single particle spectroscopy revealed that the Auger ionization plays an dominant role for the blinking dynamics of CdTe QDs.
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