Free-Form Laser Nano-Patterning of Silicon with Subsurface-Seeding

Direct-laser-writing enables two- and three-dimensional (2D and 3D) nano-structuring of materials with significant advantages in simplicity, speed and maskless fabrication. In order to achive surface nano-patterning, the two major directions are (i) ablating the surface and (ii) laser-induced-periodic-surface structuring (LIPSS). Here, we introduce another yet approach based on subsurface seeding. We recently demonstrated 3D laser nano-structuring of silicon using spatial beam modulation [1]. Here, we advance this paradigm to enable controlled surface nano-patterning (Fig. 1). By using subsurface modifications as seeds (“in-chip” preforms) and propagating these to the surface, we achieve direct nano-patterning. Unlike traditional approaches, we achieve free-form nano-structuring, including curved nano-patterns (Fig. 1 c), and ultra-fine structures with features down to 400 nm.