Electronic structure and absorption spectra of silicon nanocrystals with a halogen (Br, Cl) coating

Ab initio calculations of the electronic structure and frequency dependence of the imaginary part of the dielectric function for 1-2 nm silicon nanocrystals with the surface fully passivated with Cl or Br halogen atoms have been performed. According to these calculations, passivation with halogens results in the strong localization of valence electrons near the surface. As a result, the width of the band gap of a nanocrystal is noticeably narrowed and its absorptance decreases as compared to the case of hydrogen passivation. These effects are more pronounced in bromine-passivated nanocrystals.