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A New Family of Light Emitting Si Nanoparticles

Published online by Cambridge University Press:  28 May 2012

Naoto Shirahata
Naoto Shirahata*
Affiliation:
Nanoarchitectonics Research Center (WPI-MANA), National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, 305-0047, Japan
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Abstract

Color-tuning of UV luminescent silicon nanocrystals (Si NCs) was successfully achieved by precise size control of non-oxidized NCs. The alkoxy-capped Si NCs was synthesized via sodium biphenylide reduction of SiCl4 encapsulated with inverse micelles, and subsequent alkoxylation of surface Si-Cl bonds. Due to the high molecular packing density of alkoxy monolayers, outermost surface of the NCs was completely protected from oxidation even under ambient conditions. Interestingly, the optical absorption and emission spectra were blueshifted with reduction of non-oxidized NC size, and we found strong light emission in the UV range when the NCs were smaller than 2.5 nm. More than 20% of PL quantum efficiencies (QYs) were estimated from those UV luminescent NCs. Monodispersed NCs without oxide can provided narrow PL spectra with 35-40 nm of line-widths, while the presence of oxidized surface region of NCs led to the broad PL spectra. In addition, the redshift of PL spectra were observed from the partially-oxidized NCs which were formed due to the lower surface molecular coverage, suggesting the significant difference in optical transition of photogenerated carriers between the non-oxidized and the partially-oxidized NCs. This can be well-illustrated by comparing decay profiles of the carriers for each sample through the time-resolved PL spectroscopic observation.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1437: Symposium L – Group IV Photonics for Sensing and Imaging , 2012 , mrss12-1437-l05-04
Copyright
Copyright © Materials Research Society 2012

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References

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