Ensemble Effects in the Temperature-Dependent Photoluminescence of Silicon Nanocrystals |
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Authors: | Matthias Jakob Morteza Javadi Jonathan G. C. Veinot Al Meldrum Aras Kartouzian Ulrich Heiz |
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Affiliation: | 1. Chair of Physical Chemistry, Technical University of Munich, Lichtenbergstrasse 4, 85748 Garching, Germany;2. Department of Chemistry, University of Alberta, T6G 2R3 Edmonton, Alberta, Canada;3. Department of Physics, University of Alberta, T6G 2E1 Edmonton, Alberta, Canada |
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Abstract: | In this work the temperature-dependent photoluminescence of alkyl-capped silicon nanocrystals with mean diameters of between 3 and 9 nm has been investigated. The nanocrystals were characterized extensively by FTIR, TEM, powder XRD, and X-ray photoelectron spectroscopy prior to low-temperature and time-resolved photoluminescence spectroscopy experiments. The photoluminescence (PL) properties were evaluated in the temperature range of 41–300 K. We found that the well-known temperature-dependent blueshift of the PL maximum decreases with increasing nanocrystal diameter and eventually becomes a redshift for nanocrystal diameters larger than 6 nm. This implies that the observed shifts cannot be explained solely by band-gap widening, as is commonly assumed. We propose that the luminescence of drop-cast silicon nanocrystals is affected by particle ensemble effects, which can explain the otherwise surprising temperature dependence of the luminescence peak. |
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Keywords: | ensemble effects luminescence nanocrystals silicon time-resolved spectroscopy |
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