Local-fields effects in silicon nanoclusters

The effect of the local fields on the absorption spectra of silicon nanoclusters (NCs), freestanding or embeddedin SiO2, is investigated in the DFT-RPA framework for different size and amorphization of the samples.We showthat local field effects have a great influence on the optical absorption of the NCs. Their effect can be described bytwo separate contributions, both arising from polarization effects at the NC interface. First, local fields producea reduction of the absorption that is stronger in the low energy limit. This contribution is a direct consequence ofthe screening induced by polarization effects on the incoming field. Secondly, local fields cause a blue shift onthe main absorption peak that has been explained in terms of perturbation of the absorption resonance conditions.Both contributions do not depend either on the NC diameter nor on its amorphization degree, while showing ahigh sensitivity to the environment enclosing the NCs.