Size-dependent optical properties of Si nanocrystals embedded in a silica matrix

We report on a numerical investigation of the size distribution effect on the optical properties of Si nanocrystals embedded in a silica matrix. Firstly, the dielectric function of the composite film is accurately evaluated. Next, a modified version of the Maxwell-Garnett theory is introduced. This model allows the consideration of the size distribution of the Si nanocrystals. We show that a small change in the size dispersion value may induce a sensitive modification in the line shape of the dielectric function. Our results can be used to explain the divergences observed in the literature regarding the dielectric function of Si nanocrystals.