### Abstract

We report on the surface nanostructuring of silicon wafer by self-organization of redeposited Si nanoparticles, at various energy levels, in the vaporization regime of laser-matter interaction. By using the semiconfined configuration, a quasi-two-dimensional turbulent Si vapor field with gradients of pressure and temperature is formed. The turbulent field evolves into point vortices which condense into Si nanodroplets. At a low laser energy of ∼1.2 J (0.23 GW/ cm^{2}), the inertial instability of nanodroplets under gradients of pressure and temperature, cause their intermittent accumulation in the low-pressure regions of turbulent field. The solidification of Si nanodroplets into particles and their redeposition, cause a simple two-dimensional low density nanostructuring of Si wafer in the near periphery region, and a high density nanostructuring in the periphery region of the spot. The pattern of redeposited Si nanoparticles in these regions is equivalent to the pattern of point vortices in a two-dimensional turbulent field. Such a pattern of point vortices is obtained by numerical simulation from the two-dimensional Navier-Stokes equation for forced turbulence. The self-organization of the coherent point vortex pattern is generated by numerical simulation of the solitary turbulence model based on the nonlinear Schrödinger equation. At the high laser energy of ∼1.5 and ∼2.0 J (∼0.42 and ∼0.52 GW/ cm^{2}, respectively), the transition from simple intermittent two-dimensional nanoparticle organization into a continuous and more complex one takes place. The nanostructured pattern shows a continuous distribution of Si particles, whose size increases from the periphery toward the center without spatial intermittency, showing a gradient of particle size. In addition, the open and closed loops chain clusters appear, with morphology and fractal dimension similar to the chain clusters which grow according to the Meakin-Jullien model of cluster-cluster aggregation. At the higher power density of ∼0.52 GW/ cm^{2}, the chain clusters become connected and tend to compactification. They form a network similar to the one obtained by numerical simulation of two-dimensional turbulence at small Stokes numbers. The silicon surface nanostructured by recondensation in this case comprises only the nanometer sized particles.

Original language | English |
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Article number | 114308 |

Journal | Journal of Applied Physics |

Volume | 106 |

Issue number | 11 |

DOIs | |

Publication status | Published - Dec 28 2009 |

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### ASJC Scopus subject areas

- Physics and Astronomy(all)

### Cite this

*Journal of Applied Physics*,

*106*(11), [114308]. https://doi.org/10.1063/1.3266003