Oxidation of silicon nanoparticles produced by ns laser ablation in liquids

The investigation of nanoparticles produced by ns pulsed Nd:YAG laser ablation of silicon in liquids is reported. Combined characterization by morphological and structural techniques shows that these nanoparticles have a mean diameter of ~3 nm and a core-shell structure consisting of a Si-nanocrystal surrounded by a layer of oxidized Si. Time resolved luminescence spectra evidence visible and UV emissions: a broad band around 1.9 eV originates from Si-nanocrystals, while two bands centered at 2.7 eV and 4.4 eV are associated with oxygen deficient centers in the SiO2 shell.