Si nanocrystal grains were prepared by pulsed laser ablation with different laser fluence in Ar gas of 10 Pa at room temperature.\nThe as-formed grains in the space deposited on the substrates and distributed in a certain range apart from target. According to\nthe depositing position and radius of grains, the nucleation locations of grains in the space were roughly calculated. The results\nindicated that the width of nucleation region broadened with increasing of ion densities diagnosed by Langmuir probe, which\nincreased with laser fluence from 2 J/cm2 to 6 J/cm2; that is, width of nucleation region broadened with addition of laser fluence.\nAt the same time, the width broadened with the terminal formation position moving backward and the initial formation position\nof grains moving toward ablated spot.The experimental results were explained reasonably by nucleation thermokinetic theory.
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