The nucleation and growth of Si nanoparticle produced by pulsed laser ablation in helium gas ambient is investigated via direct simulation Monte Carlo method with a real physical scale of target-substrate configuration. The nucleation area is important for the formation of Si nanoparticles, and the average size and size distribution of Si nanoparticles formed in this region depend on its range. The narrower the nucleation area and, therefore, the less the maximum times of collisions between Si atoms in the region, the smaller and the more uniform the Si nanoparticles. A nucleation and growth process is clearly observed. It is shown that the nucleation region and the nucleation growth internal is changing with time. The ambient gas pressure is important to nucleation region. The suitable pressure range under certain conditions is given and our simulated results are approximately in agreement with the previous experimental data.
The single crystalline Si target with high resistivity was ablated by a XeCl excimer laser (wavelength 308nm) in pure Ar
gas under the ambient pressure of 10 Pa. The mask with a 1-10 mm diameter hole in the center was placed at a distance
of 1.5 cm to the Si target. The Si nanocrystalline films were systemically deposited on a glass or single crystalline Si
substrate placed behind the mask parallelly with a distance of 1.0 cm. The Raman and X-ray diffraction spectra indicate
that the films were nanocrystalline. Scanning electron microscope images of the films showed that the diameter of the
hole affected on the quantity and distributed range of Si nanoparticles on the substrate. It was obtained that the average
size of Si nanoparticles decreasing with the diameter of the hole increasing, the quantity of Si nanoparticles was
proportional to the power of 1.5 of the hole diameter. It is the nonlinear dynamic process to lead to the experimental
result.
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