Saturation of luminescence from Si nanocrystals embedded in SiO <inf>2</inf>

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Journal Article
Physica Status Solidi (A) Applications and Materials Science, 2010, 207 (1), pp. 183 - 187
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We present a photoluminescence excitation study of silicon nanocrystals in a SiO 2 matrix. We show that although the excitation cross-section is wavelength-dependent and increases for shorter excitation wavelengths, the maximum time-integrated photoluminescence signal for a given sample saturates atthesamelevelindependentofexcitationwavelength or amount of generated electron-hole pairs per nanocrystal after a laser pulse. We demonstrate explicitly that saturation is achieved when every nanocrystal has absorbed at least one photon. In nanocrystals where several electron-hole pairs have been created during the excitation pulse, fast non-radiative recombinations reduce their number, leading to the situation that only a single electron-hole pair per nanocrystal can recombine radiatively, producing a photon and contributing to the photoluminescence. In this way a natural limit is set for photoluminescence intensity from an ensemble of Si nanocrystals excited with a laser pulse with a short duration in comparison with the radiative recombination time. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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