Large Area Superhydrophilic Silicon Surface Texturing using Nanosecond Laser Pulses

We report experimental investigations of large area laser micro/nano texturing of silicon (100) targets by Nd: YAG laser pulses (λ=532 nm, τ =7 ns) addressing the wetting behavior of processed silicon surface. In particular, ns laser surface processing is used to develop hierarchical surface structures by the line scanning method to create parallel micro-channels with proper overlap between the lines at different laser pulse fluence ranging from 2 J/cm² to 4 J/cm². We observe that the bottom of craters formed due to single and multipulse laser irradiations are rather flat, but some concentric nano-ripple features are present along the rim of the craters, resulting in the formation of multiscale surface morphology. The topography of the samples is investigated using AFM and SEM, whereas the wetting property is measured through sessile drop contact angle measurements. The combination of microscale channels written by parallel line scan, with self-organized surface patterns and random nanoparticles decoration, formed on the surface allow developing highly hydrophilic silicon surfaces with contact angle values reaching around 5°, presenting potential interest for superwetting applications.