Scan direction of circularly polarized laser beam determines the orientation of laser-induced periodic surface structures (LIPSSs) on silicon

Upon irradiation of a silicon surface with circularly polarized green nanosecond laser pulses, the formation of linear periodic nanostructures is observed. Due to the lack of inherent directional anisotropy by the laser polarization, no 1D-laser-induced periodic surface structures (LIPSSs) formation is expected. The orientation of the formed surface modulation depends on the laser scan direction. Silicon wafers, which are often used in LIPSS studies, are commonly considered inert substrates. This assumption needs to be reconsidered. Our finding is not explained by the current LIPSS theories.