The role of local fields in the optical properties of silicon nanocrystals

In this paper we discuss the role of local fields in the optical properties of silicon nanocrystals. Using a semiempirical tight binding approach, local field effects are included into the linear response theory, going beyond the standard independent particle approximation. The results show that local field effects give an important contribution to the optical properties of silicon nanocrystals, leading to a strong suppression of the absorption in the visible spectral range. This effect is attributed to the classical surface polarization contribution. A comparison between the atomistic tight binding approach and a classical dielectric model shows that the dielectric model gives reasonable results not only for large, but even for small silicon nanocrystals.