Optimized Strategy for Fabricating High-Aspect-Ratio Periodic Structures Over Large Areas Using ps-Direct Laser Interference Patterning

This work addresses the fabrication of large area high-aspect-ratio micropatterns on stainless steel by means of direct laser interference patterning (DLIP). For this purpose, a novel fabrication strategy is employed, based on multiple over-scans coupled with advanced two-beam interference optics. Periodic line- and cross-like DLIP patterns are fabricated with different aspect ratios (AR) having spatial periods (Λ) of 6.0, 10.0, and 30.0 μm. By varying process parameters, including laser fluence, pulse-to-pulse overlap, and the number of scans, ARs up to 2.4 are achieved. Furthermore, laser-induced periodic surface structures result from the laser treatment, obtaining multiscaled patterns. The effect of the processing parameters on the morphology of the produced patterns is investigated by means of white light interferometry, scanning electron microscopy, 2D fast Fourier transformation, and focused ion beam. Particularly for the multiscan approach, the redeposition of ablated material significantly contributes to structure formation process and shows a strong dependency on the number of applied scans.