Surface plasmons interference nanogratings: wafer-scale laser direct structuring in seconds

It is always a great challenge to bridge the nano- and macro-worlds in nanoscience, for instance, manufacturing uniform nanogratings on a whole wafer in seconds instead of hours even days. Here, we demonstrate a single-step while extremely high-throughput femtosecond laser scanning technique to obtain wafer-scale, highly regular nanogratings on semiconductor-on-metal thin films. Our technique takes advantage of long-range surface plasmons-laser interference, which is regulated by a self-initiated seed. By controlling the scanning speed, two types of nanogratings are readily manufactured, which are produced by either oxidation or ablation. We achieve a record manufacturing speed (>1 cm² s^-1), with tunable periodicity of Λ < 1 µm. The fractional variation of their periodicity is evaluated to be as low as ∆Λ/Λ ≈ 0.5%. Furthermore, by utilizing the semiconductor-on-metal film-endowed interference effects, an extremely high energy efficiency is achieved via suppressing light reflection during femtosecond laser nano-processing. As the fabricated nanogratings exhibit multi-functionality, we exemplify their practical applications in highly sensitive refractive index sensing, vivid structural colors, and durable superhydrophilicity.