Si nanoparticles fabricated from Si swarf by photochemical etching method

Si nanoparticles are produced from Si swarf which is a waste during slicing Si ingots to produce Si wafers for solar cell use. The beads mill method produces flake-like Si with scores of nanometers width from Si swarf. Subsequent photochemical dissolution with light longer than 560 nm wavelength in a 0.5 % HF solution results in sphere-shaped Si nanoparticles of 1–7 nm diameter. Si nanoparticles dispersed in ethanol show blue photoluminescence at ~400 nm (3.1 eV) under UV irradiation, indicating band-gap widening due to the quantum confinement effect. The band-gap energy of most of the Si nanoparticles is estimated to be 2.5–3.3 eV from the PL spectra, corresponding to the Si nanoparticle size of 1.9–3.2 nm. On the other hand, Si nanoparticles produced by immersion in the HF solution in the dark show much weaker blue photoluminescence. These results demonstrate that the Si dissolution reaction is greatly enhanced by photo-generated holes.