Laser-induced structural modifications in nanocrystalline silicon/amorphous silicon dioxide superlattices

摘要

We calculate and experimentally detect the laser melting threshold in nanocrystalline Si/amorphous SiO_2 superlattices. Using laser energy density slightly above the melting threshold, we observe two types of laser-induced structural modifications: (ⅰ) disappearance of nanocrystalline Si phase in the samples with thin (～2 nm) SiO_2 layers and (ⅱ) amorphization of Si nanocrystals in the samples with thicker ( ≥ 5 nm) SiO_2 layers. The observed Si nanocrystal amorphization increases optical absorption and intensity of visible photoluminescence in nanocrystalline Si/amorphous SiO_2 superlattices.