Large area nanopatterning of silicon surface by chemical assisted laser processing using near-field enhancement by particle-lens arrays

Nanopattering of silicon substrates using near-field enhancement by particle-lens arrays in a chemical solution is presented for the first time. Both experimental and theoretical investigations have been carried out to understand the properties of the nanopatterns produced. The obtained results proved that the developed nanofabrication technique is a flexible method for precise surface nanopatterning over large area surface. Novel nanostructures such as nano-bump and ring arrays, that previously not possible to be produed using the particle-lens arrays, have been demonstrated using this technique. A close-packed monolayer of SiO₂ spheres (r= 250 nm) was directly formed onto the silicon surface by self-assembly, and a 248nm wavelength KrF excimer laser was used to irradiate the samples. The theoretical modeling of the optical near-field is based on extended Mie theory. The effect of the laser fluence and assisted chemicals is studied. Due to the focusing of the particle lens, a reaction between the chemical solution and substrate can be induced in the locally high energy region. As a result, a lower laser fluence than the ablation threshold of bulk silicon can be used to generate nano-scale features.