Multiple Si=O bonds at the silicon cluster surface

A first-principle investigation of the effects of multiple Si=O bonds at the surface of silicon-based clusters with different sizes has been carried out. Total-energy pseudopotential calculations within density functional theory have been applied varying systematically the number of Si=O bonds at the clusters surface. A nonlinear reduction of the energy gap with the Si=O bond number is found. A sort of saturation limit is displayed, providing a consistent interpretation of the photoluminescence redshift observed in oxidized porous silicon samples. Moreover, our results help to clarify the very recent findings on the single silicon quantum dot photoluminescence bandwidth. (C) 2003 American Institute of Physics.