Optical absorption cross sections of Si nanocrystals

Using the photoluminescence Auger saturation phenomenon, we deduce the valu es of the absorption cross section of silicon nanocrystals in a wide range of energies. The very large variation of their values versus energy of the absorbed light is attributed to the enhanced optical transition oscillator strength but reduced density of electronic states towards higher confinemen t energies. The overall spectral behavior of the absorption cross section r eflects the indirect-gap nature of silicon nanocrystals.