Impact of capillarity forces on the steady-state self-organization in the thin chromium film on glass under laser irradiation

• The model of steady-state self-organization in molten metal was developed.
• The Marangoni convection pushes liquid metal from the hotter to cooler area.
• The capillarity force pushes liquid metal because of gradient in curvature radius.
• Shear stresses of thermal and radius of curvature gradients are equally important.

Metal films on transparent substrates are widely used for mask production in lithography, and lasers are frequently applied for their patterning. Steady self-organization of a chromium thin film on the glass substrate to parallel metal lines under irradiation with partially overlapping highly astigmatic nanosecond laser pulses above the ablation threshold has been observed. Transformations in a chromium film were investigated experimentally and numerically. The theoretical model of the steady self-organization is presented and discussed. It was demonstrated that the capillarity convection force was responsible for the transformation process in the molten metal. It was shown that the thermo-capillarity (Marangoni) shear stress and the stress originating from a variation in the radius of curvature along the structure were equally important in the case of the steady self-organization process.