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Light-Emission Performance of Silicon Nanocrystals Deduced from Single Quantum Dot Spectroscopy

Authors

  • Jan Valenta,

    1. Department of Chemical Physics and Optics, Faculty of Mathematics and Physics Charles University, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic)
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  • Anna Fucikova,

    1. Department of Chemical Physics and Optics, Faculty of Mathematics and Physics Charles University, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic)
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  • František Vácha,

    1. Institute of Physical Biology, University of South Bohemia and Institute of Plant Molecular Biology, Academy of Sciences of the Czech Republic, Budweis (Czech Republic)
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  • František Adamec,

    1. Institute of Physical Biology, University of South Bohemia and Institute of Plant Molecular Biology, Academy of Sciences of the Czech Republic, Budweis (Czech Republic)
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  • Jana Humpolíčková,

    1. J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, v.v.i., Prague 8 (Czech Republic)
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  • Martin Hof,

    1. J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, v.v.i., Prague 8 (Czech Republic)
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  • Ivan Pelant,

    1. Institute of Physics of the Academy of Sciences of the Czech Republic v.v.i., Prague 6 (Czech Republic)
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  • Kateřina Kůsová,

    1. Institute of Physics of the Academy of Sciences of the Czech Republic v.v.i., Prague 6 (Czech Republic)
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  • Kateřina Dohnalová,

    1. Institute of Physics of the Academy of Sciences of the Czech Republic v.v.i., Prague 6 (Czech Republic)
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  • Jan Linnros

    Corresponding author
    1. Department of Microelectronics and Applied Physics, Royal Institute of Technology Electrum 229, 164 21 Kista-Stockholm (Sweden)
    • Department of Chemical Physics and Optics, Faculty of Mathematics and Physics Charles University, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic).
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  • This work was supported by the Czech Ministry of Education, Youth and Sports through the research centers LC510, LC06063 and the research plan MSM0021620835, by the project 202/07/0818 of the GACR, the project IAA101120804 of the GAAV, and the Institutional Research Plan (IP) AV0Z 10100521 and by (JL) the National Swedish Research Council (VR). The authors thank S. Bakardjieva for the HR-TEM measurements.

Abstract

Spectra of individual silicon nanocrystals within porous Si grains are studied by the wide-field imaging microspectroscopy and their ONOFF blinking is detected by the confocal single-photon-counting microscopy. Observed spectral and blinking properties comprise all features reported before in differently prepared single Si nanocrystals (SiNCs). Former apparently contradictory results are shown to be due to different experimental conditions. When the effect of dark periods (OFF switching) is removed the common ultimate photoluminescence properties of SiO2 passivated SiNCs are found, namely the quantum efficiency (QE) of about 10–20% up to the pumping rate corresponding to one exciton average excitation per quantum dot. At higher pump rates the QE is slowly decreasing as the 0.7th power of excitation. This is most likely due to Auger recombination which, however, seems to be weakened compared with measurements of nanocrystal assemblies. We conclude that SiNCs may be pumped above one exciton occupancy to yield a higher light emission, being advantageous for applications.

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