Ultrafast large-area micropattern generation in nonabsorbing polymer thin films by pulsed laser diffraction.

An ultrafast, parallel, and beyond-the-master micropatterning technique for ultrathin (30-400 nm) nonabsorbing polymer films by diffraction of laser light through a 2D periodic aperture is reported. The redistribution of laser energy absorbed by the substrate causes self-organization of polymer thin films in the form of wrinklelike surface relief structures caused by localized melting and freezing of the thin film. Unlike conventional laser ablation and laser writing processes, low laser fluence is employed to only passively swell the polymer as a pre-ablative process without loss of material, and without absorption/reaction with incident radiation. Self-organization in the thin polymer film, aided by the diffraction pattern, produces microstructures made up of thin raised lines. These regular microstructures have far more complex morphologies than the mask geometry and very narrow line widths that can be an order of magnitude smaller than the openings in the mask. The microstructure morphology is easily modulated by changing the film thickness, aperture size, and geometry, and by changing the diffraction pattern.