Nanosecond Laser Nanopatterning of Highly Ordered Nanodot Arrays on Silicon Surface: Breaking the Monopoly of Femtosecond Lasers

Laser nanopatterning is an effective strategy to manipulate the surface properties of materials. One of the glaring restrictions is that the fabrication of long-range ordered nanostructures typically relies on ultrafast lasers, especially femtosecond lasers, while the insurmountable thermal effects associated with the longer pulse durations of nanosecond lasers are deeply considered to be the nemesis of this scenario. Herein, for the first time, a nanosecond laser-based nanopatterning technique for fabricating highly ordered nanodot arrays on the monocrystalline silicon surface through a remarkably straightforward process is proposed. The mechanism involves Marangoni flow-assisted low-threshold oxidation of monocrystalline silicon induced by nanosecond laser, along with a domino-like growth process of nanodots driven by optical near-field enhancement. Finite-difference-time-domain (FDTD) simulations provide insight into the underlying origin of nanosecond laser-induced nanodot arrays. The prepared large-area nanodot arrays demonstrate a range of functionalities, including the manipulation of light reflection and diffraction, structural color, and surface-enhanced Raman scattering (SERS). The present study challenges the established view that the pronounced thermal effects associated with the long pulse durations of nanosecond lasers are incompatible with high-precision nanopatterning, which opens new avenues for research into laser-matter interactions.