Laser‐Induced Reversible and Irreversible Surface Nanostructuring

Abstract Harnessing the 4D transmission electron microscopy (4D‐TEM) technique capable of in situ study of light‐material interactions with high spatiotemporal resolution, the authors are able to demonstrate the formation of a reversible laser‐induced periodic surface structure (RLIPSS) on the top few‐nanometer surface of free‐standing amorphous thin films of silicon nitride and silicon dioxide. Compared with commonly reported permanent laser‐induced periodic surface structures (LIPSS) grown on thermal ablation of materials, highly ordered RLIPSS here develop in a nonthermal manner by femtosecond laser irradiation with unprecedented low intensity down to 10 000 times lower than their reported ablation thresholds. This reversible structure can undergo a transition to permanent structure with increasing laser intensity and number of laser shots. The orientation of the RLIPSS exhibits an unexpected memory of laser polarization, making it a potential candidate for future ultrafast rewritable photo‐image recording. These experimental results exclude the widely accepted formation mechanism of LIPSS based on the interference between the incident light with the surface scattering waves or the surface plasmon polaritons, and suggest a novel mechanism for surface laser micromachining, relevant to the laser‐induced production of charged point defects and the polarization‐dependent generation of tensile stress induced by electrostatic repulsion.