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Ultrafast Photoluminescence Spectroscopy of Silicon Nanocrystals Open Access


Other title
time correlated single photon counting
silicon nanocrystals
time-resolved photoluminescence
silicon nanocrystal films
charge transfer state
blue-emitting silicon nanocrystals
charge transfer state emission
ultrafast near-field scanning optical microscopy
oxygen-related defects
Type of item
Degree grantor
University of Alberta
Author or creator
De los Reyes, Glenda B
Supervisor and department
Frank A. Hegmann, Department of Physics
Examining committee member and department
Robert Wolkow, Department of Physics
Darren Grant, Department of Physics
Andrew Knights, Department of Engineering Physics McMaster University
Alkiviathes Meldrum, Department of Physics
Raymond Decorby, Department of Electrical and Computer Engineering
Department of Physics

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Ultrafast carrier dynamics in silicon nanocrystals (Si NCs) is explored using time-integrated photoluminescence, time-resolved photoluminescence and pump-probe transient absorption spectroscopies. The role of surface oxygen in the optical emission dynamics of dodecyl functionalized Si NCs is explored. Significant surface oxidation results in a photoluminescence blue shift and an observation of sub-10 ns recombination lifetime. In addition, surface oxidation improves the absolute quantum yield of dodecyl functionalized Si NCs. This study also shows that surface passivation plays an important role in the emission dynamics of functionalized Si NCs. It is shown that photoluminescence in silicon nanocrystals can be tuned by changing the surface passivation alone. Tunable surface-related emissions are significantly blue shifted compared to quantum confinement predictions and exhibit a faster recombination rate similar to that for direct bandgap semiconductors. Furthermore, the photoluminescence quantum yields of these silicon nanocrystals are higher than those that exhibit quantum core state emission. On the other hand, detailed time-resolved photoluminescence studies reveal that the origin of the size-independent blue emission in dodecylamine and ammonia functionalized Si NCs originates from charge transfer states located at the silicon-silicon oxynitride interface. Time-integrated photoluminescence spectroscopy revealed that Si NCs with silicon volume filling fraction below the percolation threshold exhibit strong size-dependent emission in the infrared region. The carrier dynamics of these Si NCs are explored using pump-probe transient absorption spectroscopy with sub-picosecond resolution and time-resolved photoluminescence spectroscopy in the nanosecond and microsecond time scales. Si NC films exhibit sub-picosecond, sub-nanosecond and microsecond lifetimes attributed to carrier trapping at the oxygen-related defects, carrier recombination at the trap states and carrier recombination via the silicon core state, respectively. The results of this study will hopefully contribute to the understanding of the role of oxygen in the optical emission properties of functionalized Si NCs. In addition, the blue emission observed in dodecylamine and ammonia functionalized Si NCs will impact applications in optoelectronic devices. Finally, 800 nm, 65 fs laser pulses is coupled to near-field scanning optical microscopy using single mode fiber. The newly developed ultrafast NSOM is suitable for studying spatially-resolved PL emission in semiconductor nanostructures.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Zhenyu Yang, Glenda B. De los Reyes, Lyubov V. Titova, Ilya Sychugov, Mita Dasog, Jan Linnros, Frank A. Hegmann, and Jonathan G. C. Veinot, ACS Photonics 2015, 2, 595- 605.Mita Dasog, Glenda B. De los Reyes, Lyubov V. Titova, Frank A. Hegmann, Jonathan G.C. Veinot, ACS Nano 2014, 8(9), 9636-9648.Glenda B. De los Reyes, Mita Dasog, MengXing Na, Lyubov V. Titova, Jonathan G. C. Veinot, and Frank A. Hegmann, “Charge transfer state emission dynamics of blue-emitting functionalized silicon nanocrystals”, Physical Chemistry Chemical Physics Manuscript ID CP-ART-08-2015-004819

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