Figure 2. Nanoparticle generation and launch.

(a) An SEM image shows a typical silicon nanoparticle that is released by laser-induced thermo-mechanical stress ablation from a pure silicon (111) surface. Particles in the size range from below 100 nm to beyond 1,000 nm have been observed, with a variation of shapes. Although a full model of the release mechanism is still subject to future research, the cracks and defects on the front side of the back-irradiated silicon wafer (b) corroborate the hypothesis that micro cracks are the emission sites of nanosilicon. Energy-dispersive X-ray spectroscopy on the ejected nanomaterial allows us to identify silicon as the principal element, with oxygen as an occasional contaminant in some particles. Scale bar in (a) is 300 nm and in (b) is 1,000 nm.