Polymer self-assembled nano-structures and surface relief gratings induced with laser at 157 nm

Surface relief gratings (SRG) and self-organized nano-structures induced by laser light at 157 nm on the fluoropolymer poly(2,2,2- trifluoroethyl methacrylate) (PTFEMA), films were obtained under well-controlled light exposure conditions. Regular and semi-regular spaced self-organized grating-like structures were created on polymeric films for 7.5–100 mJ/cm2 laser energy fluence. For lower laser fluence, the surface morphology of light exposed/non-exposed areas exhibited irregular-like structure morphologies, while polymer surface irradiation with energy fluence higher than 150 mJ/cm2 causes progressively fading out of the regular patterns. Under the specific experimental conditions, the SRG and self-organization patterning have their origin in the development of a surface thermal instability (Rayleigh’s instability), which is resolved itself into regular patterns on the surface of the fluoropolymer film. The thermal instability is due to the explosive polymer surface photodissociation at 157 nm and the build up of longitudinal and periodic surface stress, which eventually create the SRG and the self-assembled structures on the polymer