Quenching of Si nanocrystal photoluminescence by doping with gold or phosphorous

Si nanocrystals embedded in SiO2 doped with P and Au at concentrations in the range of 1x1018-3x1020 cm-3 exhibit photoluminescence quenching. Upon increasing the Au concentration, a gradual decrease in nanocrystal photoluminescence intensity is observed. Using a statistical model for luminescence quenching, we derive a typical radius of ∼3 nm for nanocrystals luminescing around 800 nm. Au doping also leads to a luminescence lifetime reduction, which is attributed to energy transfer between adjacent Si nanocrystals, possibly mediated by the presence of Au in the form of ions or nanocrystals. Doping with P at concentrations up to 3x1019 cm-3 leads to a luminescence enhancement, most likely due to passivation of the nanocrystal-SiO2 interfaces. Upon further P doping the nanocrystal luminescence gradually decreases, with little change in luminescence lifetime