Influence of oxygen on optical properties of Si nanocrystallites

摘要

The influence of oxygen on optical absorption spectra, radiative lifetimes, and localization of states is analyzed within the quasiparticle formalism based on the GW approximation for defect-free Si nanocrystallites. Passivation with hydroxyls and oxide coverage have significant influence on the spatial distribution of the highest-occupied and lowest-unoccupied molecular orbitals as well as on the radiative lifetimes. Oxidation blueshifts the onset of absorption, whereas oxide coverage and passivation with hydroxyls tend to redshift it. The indirect-gap nature of the optical transitions in Si bulk is transferred to the Si nanocrystallites independently of the oxygen contents.