?/20 surface nanostructuring of ZnO by mask-less ultrafast laser processing

Fabrication of nanostructures with a feature size much smaller than the laser wavelength is challenging due to the optical diffraction limit. It's well known that the irradiation of polarized ultrafast laser generates periodic nanostructures, so called laser-induced periodic sur -face structures (LIPSS). Owing to the modulated field, the surface is periodically ablated to form specific patterns, which can be used for some photonic applications including surface-enhanced Raman scattering (SERS). In this paper, we investigate the morphologies of LIPSS on ZnO substrates by mask-less ultrafast laser processing. By adjusting the laser processing parameters, including fluence, pulse number, polarization, and pulse duration, the homogenous nanos-trip array and nanopillar array are created. Furthermore, by adjusting the laser fluence, a single nanogroove with a width of similar to 20 nm and a single nanocavity with a diameter of similar to 24 nm are created. The gold nanoparticles are then coated on the ZnO nanopillar array for SERS application. We found that the concentration of defects in ZnO substrate is increased by the laser irradiation, which is beneficial for SERS performances to achieve an enhancement factor of SERS as high as 2.28 x 10(7).

Automated summary

Uniform nanotriplet arrays and nanopillar arrays, as well as single nanogrooves and nanocavities, can be created on zinc oxide (ZnO) substrates by mask-less ultrafast laser processing. Coating gold nanoparticles on the ZnO nanopillar array enables surface-enhanced Raman scattering (SERS) application, with a SERS enhancement factor as high as 2.28 x 10(7). Laser irradiation increases the concentration of defects in the ZnO substrate, which is beneficial for achieving high SERS performance.