Role of the interface region on the optoelectronic properties of silicon nanocrystals embedded in SiO2.

Light-emitting silicon nanocrystals embedded in SiO2 have been investigated by x-ray absorption measurements in total electron and photoluminescence yields, by energy filtered transmission electron microscopy and by ab initio total energy calculations. Both experimental and theoretical results show that the interface between the silicon nanocrystals and the surrounding SiO2 is not sharp: an intermediate region of amorphous nature and variable composition links the crystalline Si with the amorphous stoichiometric SiO2. This region plays an active role in the light-emission process.