Controllable anisotropic wetting characteristics on silicon patterned by slit-based spatial focusing of femtosecond laser

We propose a promising method to fabricate controllable anisotropic morphologies in which the slit-based spatial focusing of femtosecond laser is used to create an elliptical-shaped intensity distribution at focal plane, inducing elliptical-shaped morphology with micro/nano-dual-scale structures. Our study shows that 1) by increasing slit width, minor axis increases while major axis and axial ratio decrease; 2) with fixed slit width and laser fluence above the threshold, axial ratio is independent of irradiation pulse number; and 3) when polarization direction is changed from 0° to 90°, the axial ratio of anisotropic morphology declines. As a case study, large-area periodic anisotropic hierarchical structures are fabricated with the bidirectional anisotropic wetting.