Ultrafast laser-induced sub-100 nm structures on tungsten surfaces. Stretched liquid dynamics insights

The origin of high-spatial-frequency laser-induced periodic surface structures, known as HSFLs, has always been a controversial topic. HSFLs of sub-100 nm periodicity and sub-20 nm amplitude are generated on tungsten by Ti:sapphire femtosecond laser irradiation under four different processing environments (ambient, air at 10 mbar, Ar at 10 mbar, and vacuum at 10${}^{-7}$ mbar). The topography and subtopography analysis together with two-temperature model-molecular dynamics simulations reveal that HSFLs formation originates from laser-induced thermal stresses, implying both surface tension and tensile forces are involved. The experimental observation of subsurface cavitation confirms a hydrodynamics-based origin for these nanostructures. (© 2023 The Authors. physica status solidi (a) applications and materials science published by Wiley‐VCH GmbH)