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

Photoluminescence from silicon nanocrystals in nc-Si/SiO2 multilayers has b een investigated by time-resolved measurements. The photoluminescence (PL) decay is fitted by two exponentials with relaxation times of the order of s imilar to 25-30 and similar to 80-100 mum at room temperature which are ind ependent of the emission wavelength. The experimental data are interpreted by considering two light emission mechanisms with closely similar wavelengt hs, both involving localized states and corresponding to two coupled subsys tems. One involves localized states related to Si=O bonds, and the other se lf-trapped excitons. In the case of light emission from self-trapped excito n annihilation, PL was not limited by Auger recombination in the regime of multiple excitation of silicon nanocrystals. (C) 2001 American Institute of Physics.