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Absorption and Photoluminescence Study of Cds Quantum Dots: The Role of Host Matrix and Nanocrystal Size and Density

Published online by Cambridge University Press:  10 February 2011

Yu.P. Rakovich
Affiliation:
Departamento de Fisica, Universidade do Minho, 4709-320 Braga, Portugal Department of Physics, Brest Polytechnic Institute, Brest, Belarus
A.G. Rolo
Affiliation:
Departamento de Fisica, Universidade do Minho, 4709-320 Braga, Portugal, E-mail: arolo@a fisica.uminho.pt
M.V. Stepikhova
Affiliation:
Department of Physics, Brest Polytechnic Institute, Brest, Belarus Institute for Physics of Microstructures, RAS, Nizhni Novgorod, Russia
M.I. Vasilevskiy
Affiliation:
Departamento de Fisica, Universidade do Minho, 4709-320 Braga, Portugal
M.J.M. Gomes
Affiliation:
Department of Physics, Brest Polytechnic Institute, Brest, Belarus
M.V. Artemyev
Affiliation:
Physico-Chemical Research Institute, Belarussian State University, Minsk, Belarus
W. Jantsch
Affiliation:
Institute for Semiconductor & Solid State Physics, J. Kepler University, Linz, Austria
W. Heiss
Affiliation:
Institute for Semiconductor & Solid State Physics, J. Kepler University, Linz, Austria
G. Prechtl
Affiliation:
Institute for Semiconductor & Solid State Physics, J. Kepler University, Linz, Austria
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Abstract

In this paper we present results of the absorption and photoluminescence (PL) of CdSdoped Si02 films fabricated by RF co-sputtering (semiconductor volume fraction f=1–15%, nano-crystallite's mean size 5–7nm) and matrix-free films of close-packed CdS nanocrystallites (f∼30%, size 2–5nm) produced by an original chemical method. The absorption spectra have been modelled using the modified Maxwell-Garnett model. This gives the e-h pair state energies and evidence of a strong absorption in the glass matrix containing CdS. The temperature dependence of the spectral position and broadening of the PL peak is analysed. It is concluded that a photo-generated hole is captured on an acceptor-type trap before the radiative recombination with a confined electron. The excitation of this ‘band-edge’ PL occurs through some states in the matrix and directly in the CdS crystallites for the two kinds of samples, respectively. The temperature coefficients of the optical transition energies for the nearly matrix-free films are similar to those of bulk CdS, while for the CdS/glass films they are smaller. This may be because of the different boundary conditions for the thermal expansion of CdS crystallites.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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References

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