TIME-RESOLVED IMAGING OF GAS-PHASE NANOPARTICLE SYNTHESIS BY LASER-ABLATION

The dynamics of nanoparticle formation, transport, and deposition by p ulsed laser ablation of c-Si into 1-10 Torr He and Ar gases are reveal ed by imaging laser-induced photoluminescence and Rayleigh-scattered l ight from gas-suspended 1-10 nm SiOx particles. Two sets of dynamic ph enomena are presented for times up to 15 s after KrF-laser ablation. A blation of Si into heavier Ar results in a uniform, stationary plume o f nanoparticles, while Si ablation into lighter He results in a turbul ent ring of particles which propagates forward at 10 m/s. Nanoparticle s unambiguously formed in the gas phase were collected on transmission electron microscope grids for Z-contrast imaging and electron energy loss spectroscopy analysis. The effects of gas flow on nanoparticle fo rmation, photoluminescence, and collection are described. (C) 1998 Ame rican Institute of Physics.