Self-trapped excitons in silicon nanocrystals with sizes below 1.5 nm in Si/SiO2 multilayers

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Abstract
Photoluminescence from silicon nanocrystals in nc-Si/SiO2 multilayers has been investigated by time-resolved measurements. The photoluminescence (PL) decay is fitted by two exponentials with relaxation times of the order of ∼25–30 and ∼80–100 μm at room temperature which are independent of the emission wavelength. The experimental data are interpreted by considering two light emission mechanisms with closely similar wavelengths, both involving localized states and corresponding to two coupled subsystems. One involves localized states related to Si=O bonds, and the other self-trapped excitons. In the case of light emission from self-trapped exciton annihilation, PL was not limited by Auger recombination in the regime of multiple excitation of silicon nanocrystals.