Silicon Nanocrystals Prepared by Femtosecond Laser Ablation in solution under different ablation time

Spherical silicon (Si) nano-crystals (NCs) were prepared through pulsed femtosecond laser ablating of porous silicon power immersed in 1-hexene. Compared to bulk Si, Raman spectra of Si NCs show a redshift and an asymmetrical broadening. High resolution transmission electron microscopy measurements show that Si particles were dispersed uniformly in 1-hexene. FTIR spectra showed that the Si nanoparticles were passivated by organic molecules. Based on the room temperature photoluminescence (PL) excitation and PL decay curves, we assign blue PL to localized excitons through oxygen associated surface states from the colloids Si NCs. Because of the good surface passivation for colloidal silicon NCs, the quantum yield increases with extending ablation time.