Evolution of visible photoluminescence of Si quantum dots embedded in silicon oxide matrix

Photoluminescence properties of nc-Si/SiOx nanocomposites produced by pressing the mixture of the silica aerogel powder with the porous silicon have been studied. The transformation of emission spectra of Si quantum dots, its quantum yield and emission kinetics during the long time (few months) aging in ambient conditions and formation conditions (external pressure) were observed. The different behavior of short and long wave range emission of Si quantum dots embedded in silicon oxide matrix has been obtained. The observed blue-shifting (from 2.02 to 2.05 eV) of emission peak associated with the free exciton recombination in Si quantum dots at forming pressure increasing is explained by the reduction of average Si quantum dot dimension due to the breaking away the surface irregularities and smoothing of the Si nanoparticles surface. Effect of a strong increase in intensity (more than 1 order) and blue shifting of emission of Si quantum dots were discovered in nc-Si/SiOx nanocomposites at few months' storage in ambient conditions. Such effects were explained in terms of both surface passivation and the carrier confinement. It was also confirmed by the fact that for aged composites the photoluminescence kinetics transforms by adding the stretched exponential term to the single exponential low.