Nanoscale self-assembled surface structures of silicon at femtosecond excitation

The results are presented for single picosecond and femtosecond pulse ablation of silicon which creates a continuum of the dominant filament structures with periods as small as 200 nm. It is assumed that the instability of the capillary waves is responsible for the phenomenon observed. Also it is shown that for single pulse femtosecond excitation the filament structure formation is accompanied by a fine substructure generation with a period of 60 nm. The mechanism of this substructure remains obscure.