Silicon is rather inefficient light emitter due to the indirect-band gap electronic structure, requiring a phonon to balance electron momentum during interband transition. Fortunately, momentum requirements are relaxed in 1-5 nm dia Si crystals as a result of quantum confinement effects and bright photoluminescence in the UV/VIS range is achieved. Photoluminescent Si nanocrystals along with C and SiC based nanoparticles are considered bio-inert and may lead to the development of biocompatible and smaller probes than metal chalcogenide based quantum dots. Published Si nanocrystal production procedures typically do not allow for the fine control of the particle size. In this study, we offer an efficient way to reduce H-terminated Si nanocrystal diameter and narrow size distribution through photo-catalyzed dissolution in the HF/HNO3 acid mixture. Si particles were produced using lateral etching of Si wafer in HF/EtOH/H20 bath followed by sonication in a deaerated methanol. We show that Si nanoparticle dissolution follows the shrinking core model that accounts for the etching rate variation with the particle size. Significant improvement in PL quantum yield is observed following acid treatment suggesting improvement in the dangling bond passivation.
Pub Type: Journals
absorbance, particle etching, photoluminescence, silicon nanocrystal