Thermo-physical parameters and characteristics of self-organized nanogratings induced by femtosecond laser

Self-organized nanoripples are induced on bulk metal Cu and Ag by femtosecond laser, and the influence of number of shots on nanostructure formation has been investigated. The AFM images show that obtained grooves on Cu are about 50 nm deep, and have an average spacing of 481.41 nm, which is smaller compared to the incident radiation wavelength (800 nm). Arrays of ablated craters are machined on Cu and Ag surfaces by femtosecond laser in order to determine the optical characteristics of laser irradiated surface. Compared with that of untreated sample, the locations of maximum absorption wavelength of laser treated samples are not shifted, while average absorbance intensities are enhanced both for modified Ag and Cu surfaces. Finally, the effects of thermal conductivity, dielectric function as well as electron–phonon coupling coefficient on nanograting morphology induced by femtosecond laser are discussed qualitatively.

► Defect-free surfaces seems not necessary to limit the risk of structures formation induced by surface defects seeding in femtosecond laser ablation. ► Compared with those of untreated samples, average absorbance intensities are enhanced for laser-modified surfaces. ► Dielectric function of target is found to affect the interspacing of induced nanogratings. ► The larger the electron–phonon coupling coefficient, the higher the clearness gratings induced.