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Nanostructuring of a silicon surface by laser redeposition of Si vapor
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 o...
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| Published in: | Journal of applied physics 2009-12, Vol.106 (11), p.114308-114308-14 |
|---|---|
| Main Authors: | , , , |
| Format: | Article |
| Language: | English |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | 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. |
|---|---|
| ISSN: | 0021-8979 1089-7550 |
| DOI: | 10.1063/1.3266003 |