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Optical Studies of Silicon Nanocrystals in Colloidal and Sol-Gel Matrices

Published online by Cambridge University Press:  15 February 2011

Howard W. H. Lee
Affiliation:
Lawrence Livermore National Laboratory Livermore, CA 94550
Jeffrey E. Davis
Affiliation:
Department of Applied Science, University of California, Livermore, CA 94550
Margaret L. Olsen
Affiliation:
Lawrence Livermore National Laboratory Livermore, CA 94550
Susan M. Kauzlarich
Affiliation:
Department of Chemistry, University of California, Davis, CA 95616
Richard A. Bley
Affiliation:
Department of Chemistry, University of California, Davis, CA 95616
Subhash H. Risbud
Affiliation:
Division of Materials Science and Engineering, University of California, Davis, CA 95616
David J. Duval
Affiliation:
Division of Materials Science and Engineering, University of California, Davis, CA 95616
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Abstract

We studied the optical properties of silicon nanocrystals incorporated into colloidal and solgel matrices. The silicon nanocrystals are produced by ultrasonic dispersion of porous silicon layers. We report results on the dependence of the photoluminescence (PL) spectra with excitation intensity. The PL shows a blue peak (at ∼ 415-460 nm.) and a red peak (at ∼ 680 nm). This PL spectrum shows a remarkable dependence on the excitation intensity. As the intensity is increased, the blue peak grows at the expense of the red. A model is suggested for this behavior. We also report on the excitation intensity dependence and the emission wavelength dependence of the PL decay at low (1 kHz) and high (82 MHz) repetition rates of optical excitation. When low repetition rate excitation is used, the PL decay times are all exponential, short (ns), and appear to vary little with emission wavelength. This sharply contrasts with what is observed in porous silicon. With high repetition rate excitation, both red and blue peaks show long (100's ns) and short (ps-ns) lifetime components. We contrast the different optical properties of these silicon nanocrystals with that observed in porous silicon.

Type
Research Article
Copyright
Copyright © Materials Research Society 1994

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References

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