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Radiative Versus Nonradiative Decay Processes in Germanium Nanocrystals Probed by Time-resolved Photoluminescence Spectroscopy

Published online by Cambridge University Press:  01 February 2011

P. K. Giri
Affiliation:
Department of Physics, Indian Institute of Technology Guwahati, Guwahati 781039, India
R. Kesavamoorthy
Affiliation:
Materials Science Division, Indira Gandhi Center for Atomic Research, Kalpakkam 603102, India
B. K. Panigrahi
Affiliation:
Materials Science Division, Indira Gandhi Center for Atomic Research, Kalpakkam 603102, India
K.G.M. Nair
Affiliation:
Materials Science Division, Indira Gandhi Center for Atomic Research, Kalpakkam 603102, India
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Abstract

Ge nanocrystals (NCs) of diameter 4–13 nm are grown embedded in a thermally grown SiO2 layer by Ge ion implantation and subsequent annealing. Steady state and time-resolved photoluminescence (PL) studies are performed on these embedded Ge nanocrystals to understand the origin of the PL emission at room temperature. Steady state PL spectra show a broad peak consisting of a peak at ∼2.1 eV originating from Ge NCs and another peak at ∼2.3 eV arising from ion-beam induced defects in the Ge/SiO2 interface. Time-resolved PL studies reveal double exponential decay dynamics of the PL emission on the nanoseconds time scale. The faster component of the decay with large amplitude and having a time constant τ1∼3.1 ns is attributed to the nonradiative lifetime, since the time constant reduces with increasing defect density. The slower component with time constant τ2∼10 ns is attributed to radiative recombination at the Ge NCs. These results are in close agreement with the theoretically predicted radiative lifetime for small Ge NCs.

Type
Research Article
Copyright
Copyright © Materials Research Society 2005

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