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Eu3+ -doped Si/SiO2 nanocomposites were successfully prepared by Ar sputtering deposition on quartz substrates. The optical properties were studied using time-resolved photoluminescence spectroscopy. Excited by intense picosecond laser pulses with energy greater than1GW/cm2 and wavelength at 532nm the observed photoluminescence consists of a rapidly decaying component with life time of ∼1 s and a slowly component with life time of ∼ 2 ms. The former was recognized as coming from Si/SiO2 nanostructures matrix while the latter as coming from the impurity Eu3+ ions. Using the intense laser excitation a two-photon absorption by silicon matrix occurred, resulting in photo-induced carriers produced in conduction band. A direct recombination from Si/SiO2 nanostructure host gives a weak but fast emission, and creates a large number of nonequilibrium phonon. For Eu3+ emission a set of 5D0 to 7F multiplet transitions were identified. In addition to the direct excitation by 532nm the excited state 5D0 of Eu3+ ions was also found to be populated due to energy transfer from silicon matrix. The mechanism of phonon-assisted energy transfer is discussed.
The combinatorial fabrication of nanocrystalline Si particles embedded in a SiO2 matrix (nc-Si:SiO2) by RF co-sputtering of Si and SiO2 targets is described. The peak of the photoluminescence (PL) spectra of the films varies systematically from 760 to 600 nm, consistent with the presumed systematic variation in the size distribution of the embedded Si particles. The correlation between the optical properties of the samples and the formation parameters is also analyzed.
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