Nanoscale cavitation instability of the surface melt along the grooves of one-dimensional nanorelief gratings on an aluminum surface

Femtosecond laser nanostructuring at low fluences produces a onedimensional quasiperiodic grating of grooves on an aluminum surface with a period (≈0.5 μm) that is determined by the length of a surface elec� tromagnetic wave. The structure of the grooves of the surface nanograting is formed by regular nanopeaks fol� lowing with a period of about 200 nm. Some nanopeaks manifest craters at their tops. It is suggested that nanopeaks are formed due to the frozen nanoscale spallative ablation of a nanolayer of an aluminum melt in quasiperiodic regions corresponding to interference maxima of the laser radiation with the surface electro� magnetic wave. The periodicity of the appearance of nanopeaks along grooves is due to the previously pre� dicted mechanism of cavitation deformation of the melt surface in the process of macroscopic spallation ablation. However, in this case, cavitation is coherent (similar to a nearcritical spinodal decay) rather than spontaneous. DOI: 10.1134/S0021364011160065