Determination of the region where Si nanoparticles form during pulsed laser ablation

In vacuum environment, the nano-crystalline silicon films were prepared by pulsed laser ablation at high temperature and room temperature respectively. The amorphous films prepared under normal temperature were thermal-annealed, which leads to crystallization. The morphology and compositon etc. of the samples were characterized by scanning electron microscopy, Raman scattering and X-ray diffraction. The results showed that the temperature threshold of Si nanoparticles formation was 700 ℃ and 850 ℃ respectively. The nucleation energy of the nanoparticles was obtained by quantitative calculation, and the reason of difference between the temperature threshold was discussed from the point of view of energy.

Comparison of nucleation energy of nanoparticles Si formation in substrate heating and subsequent thermal annealing

Ze-Chao¹,

Luo²,

Li-Zhi³

et al. 2010

The extended inertia fluid model to interpret the size distribution of Si nanoparticles prepared by pulsed laser ablation

Fu¹,

Xue-Cheng²,

Rui-Qiang³

et al. 2011

The inertia fluid model proposed by Yoshida et al. can only interpret the influence of ambient pressure on the average size of nanoparticles prepared by pulsed laser ablation. Basing on the model, the Maxwell velocity distribution of the initial ablated particles is considered, a new analytic expression of the size-distribution of nanoparticles is obtained. The simulation results are consistent with the statistic data from Yoshidas experiments under different He pressures. Additionally, the size-distribution of nanoparticles is simulated using the modified model under different ambient gases (He, Ne and Ar),the simulation results coincide with experimental data. The conclusions may serve as the basis for realizing the uniformity and controllability of Si nanoparticles.

Pressure threshold and dynamics of nucleation for Si nano-crystal grains prepared by pulsed laser ablation

Ze-Chao¹,

Luo²,

Ding³

et al. 2011

Si nano-crystal grains are prepared by pulsed laser ablation in low pressure Ar at room temperature through changing the gas pressure and the distance between target and substrate. The morphologies and compositions of samples are characterized by scanning electron microscopy images, Raman scattering spectra and X-ray diffraction spectra.The pressure threshold for Si grain formation is obtained to be 0.6 Pa at a laser fluence of 4 J/cm2, distance between target and substarate of 3 cm, and room temperature.Combining the fluid mechanics model and the nucleation division model, the dynamics process of nucleation is analyzed.The Monte Carlo simulation shows that the nucleation of nano-crystal grains is determined jointly by temperature and supersaturated density.