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Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model
Published on: August 22, 2015
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Switching-on quantum size effects in silicon nanocrystals
Wei Sun1, Chenxi Qian, Liwei Wang
1Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada.
Advanced Materials (Deerfield Beach, Fla.)
|December 5, 2014
Summary
Silicon nanocrystal luminescence quantum yield shows a "volcano" trend with size. Below 5 nm, quantum confinement enhances light emission, but smaller sizes increase non-radiative recombination, reducing yield.
Area of Science:
- Materials Science
- Nanotechnology
- Solid-State Physics
Background:
- Silicon's unique quantum confinement effects are crucial for its optical properties.
- Understanding luminescence quantum yield in silicon nanocrystals is key to developing new optoelectronic devices.
Purpose of the Study:
- To investigate the absolute luminescence quantum yield (LQE) of size-separated silicon nanocrystals.
- To elucidate the relationship between silicon nanocrystal size and their emissive properties.
Main Methods:
- Size-separation of silicon nanocrystals.
- Measurement of absolute luminescence quantum yield across different sizes.
Main Results:
- A distinct "volcano" behavior was observed in the luminescence quantum yield as a function of silicon nanocrystal size.
- The "volcano" behavior shows a transition around 5 nm, a peak yield at 3.7-3.9 nm, and a subsequent decrease.
- Three distinct size-dependent regions were identified, corresponding to bulk transition, enhanced radiative recombination, and increased non-radiative recombination.
Conclusions:
- Silicon nanocrystal size critically dictates luminescence quantum yield.
- Quantum confinement plays a dual role, enhancing emission up to a point, after which non-radiative pathways dominate.
- The observed "volcano" behavior provides a roadmap for optimizing silicon nanocrystals for light-emitting applications.
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