Local-field effects in silicon nanoclusters

TL;DR

This study investigates how local electromagnetic fields influence the optical absorption spectra of silicon nanoclusters, revealing significant effects that depend on the environment but are independent of size and amorphization.

Contribution

It provides a detailed analysis of local field effects on silicon nanoclusters' optical properties within the DFT-RPA framework, highlighting environmental sensitivity.

Findings

Local fields significantly alter absorption spectra.

Two main contributions: absorption reduction and blue shift.

Effects depend on environment, not on size or amorphization.

Abstract

The effect of the local fields on the absorption spectra of silicon nanoclusters (NCs), freestanding or embedded in SiO2, is investigated in the DFT-RPA framework for different size and amorphization of the samples. We show that local field effects have a great influence on the optical absorption of the NCs. Their effect can be described by two separate contributions, both arising from polarization effects at the NC interface. First, local fields produce a reduction of the absorption that is stronger in the low energy limit. This contribution is a direct consequence of the screening induced by polarization effects on the incoming field. Secondly, local fields cause a blue shift on the 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 a high sensitivity to the environment enclosing the NCs.