Spontaneous evolution of nanotips on silicon surface below the laser ablation threshold

► Spontaneous evolution of 2D array of Si nanotips under laser irradiation of silicon surface. ► The equidistant nanotips are organized into a square, and the “V”-shaped patterns. ► The nanotips evolve from the nonlinear flow instability of molten Si layer. ► These localized structures may be identified as the lump solitons.