Femtosecond laser-induced melting and shaping of indium nanostructures on silicon wafers

We study the modification of indium semi-spherical nanostructures with radii of around 175 nm on silicon wafers into linear microstructures more than 2 μm long in the direction of polarization of laser pulses (1.56 μm, 150 fs, up to 7.5 nJ and 30 000 laser pulses with 8 MHz repetition rate). The experimental results and a rudimentary analysis confirm that melting occurs from intense laser pulses. In short, we demonstrate that melting of the indium droplet followed by trapping in high spatial frequency laser induced periodic surface structures on a silicon substrate cause nanostructure modification. The understanding of the modification process, melting, and moving in the nano-grating structured field, pave the way to design nanostructures of arbitrary shapes at the sub-wavelength scale.