Fast formation of hybrid periodic surface structures on Hf thin-film by focused femtosecond laser beam

We present the results of high-ordered periodic surface structure formation by femtosecond laser pulses (λ = 1026 nm, τ = 232 fs) using an astigmatic Gaussian beam with a diameter of ≈100 μm on the surface of metal films (thickness of 15 nm and 150 nm) of Hf sputtered on the glass substrate. Continuous and uniform structures with a period of ≈700 nm are formed at a scanning speed up to 2000 μm/s on the film with a thickness of 15 nm. In addition, the formation of ablative periodic substructures with a period of about 160 nm oriented perpendicularly to the main ones was observed on the oxide protrusions. In the case of 150 nm thick film, defects, cracks and phase shifts accompanied a uniform structure with a period of ≈940 nm formed at a speed up to 500 μm/s.