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Étude de la croissance et des propriétés d'émission dans le visible de nanograins de silicium dans une matrice de silice amorphe : analyse quantitative par ellipsométrie spectroscopique

Abstract : This work deals with the growth and the study of visible photoluminescence properties of thin silica (SiO2) layers containing silicon (Si) nanograins, prepared by magnetron sputtering. A thermal annealing at a temperature exceeding 900°C is needed for the emission of visible photoluminescence at room temperature whose efficiency has been correlated, according to infrared absorption measurements, to the degree of phase separation between Si and SiO2 as well as to the decrease of the structural disorder. Raman scattering and transmission electron microscopy techniques have shown the formation of Si nanocrystals in the Si-rich samples. The rate of Si incorporation was found to be dependant of both sputtering area ratio Si/SiO2 and substrate temperature : a maximum of Si was introduced during the deposition achieved at 400-500°C, where a maximum photoluminescence intensity has been detected. The peak position of the photoluminescence spectra was found to vary decreases from 1.65 to 1.35 eV when the excess of Si in the silica is enhanced, i.e. when mean size of Si inclusions is increased. These results support an origin of the luminescence lying in the quantum confinement of carriers within the Si nanograins than can be either crystallized or amorphous. The evolution of the infrared spectra together with the comparative studies performed on samples obtained by Si implantation in thermal silica or porous silicon, have shown that an abrupt interface between the Si nanostructures and the surrounding medium greatly improves the photoluminescence efficiency through the decrease of the density of defects (dangling bonds). By means of modeling of ellipsometric spectra, a quantitative analysis made has been carried out for the first time, aiming at determining the excess of Si in the silica matrix and also the dielectric function of the Si inclusions. This approach, which is fully detailed, is relatively accurate and presents the great advantage to be a non destructive tool. The decrease of the photoluminescence energy versus the excess of Si is increased is pointed out, whatever the deposition conditions used. This strongly supports the role of quantum confinement in the photoluminescence process.
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https://tel.archives-ouvertes.fr/tel-00004183
Contributor : Stéphane Charvet <>
Submitted on : Thursday, January 15, 2004 - 4:10:12 PM
Last modification on : Friday, April 19, 2019 - 1:49:31 AM
Long-term archiving on: : Friday, April 2, 2010 - 7:34:42 PM

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  • HAL Id : tel-00004183, version 1

Citation

Stéphane Charvet. Étude de la croissance et des propriétés d'émission dans le visible de nanograins de silicium dans une matrice de silice amorphe : analyse quantitative par ellipsométrie spectroscopique. Matière Condensée [cond-mat]. Université de Caen, 1999. Français. ⟨tel-00004183⟩

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