Scientists use single-step laser ablation to fabricate ultra-uniform structures smaller than 50 nanometers

Researchers at Sun Yat-sen University (SYSU) have developed a new single-step laser ablation technique capable of fabricating ultra-uniform surface structures with features smaller than 50 nanometers—almost a thousand times thinner than a human hair.

The work, published in the International Journal of Extreme Manufacturing, used a carefully tuned femtosecond laser under water immersion to etch nanogratings just 46 nanometers apart with groove widths near 13 nanometers onto highly oriented pyrolytic graphite (HOPG). It addresses a long-standing challenge: fabricating uniform structures smaller than 100 nanometers.

"Laser ablation is usually a violent process that disrupts surface uniformity at these scales," explained Assoc. Prof. Huang Min, corresponding author of the study. "What we discovered is a way to tame this process—turning it into a precise, controlled tool for directly fabricating nanostructures that were once achievable only through complex, multi-step nanofabrication techniques."

Approaching the scale of 100 nanometers, traditional femtosecond laser ablation tends to produce chaotic, nonuniform morphologies due to inherent thermal and mechanical effects. By carefully tuning the laser fluence and scanning speed under water, the SYSU team identified a "sweet spot" that significantly reduced those disruptive effects.

Their result is amazing: fabricating long-range, perfectly aligned nanogratings with remarkable flatness and structural integrity in a single pass. In some cases, grooves reached depths of 560 nm with aspect ratios of 43, a feat attributed to the excitation of quasistatic surface plasmon polaritons at the damage-threshold regime.

Beyond this, their technology can also scale to larger two-dimensional surfaces without losing uniformity through a careful stitching process. That makes it promising for industrial production of large-area nanograting metasurfaces with highly anisotropic optical properties.

"The greatest advantage is simplicity," said Assoc. Prof. Huang. "Unlike conventional nanofabrication, which requires complex lithography and high-cost processing, this method can produce deep-subwavelength gratings directly, efficiently, and at nanoscale."

Looking ahead, the researchers see potential applications ranging from extreme ultraviolet (EUV) and X-ray optics to graphene nanostructures, since the graphite used in this study can serve as a direct source for graphene.

The SYSU team is now exploring whether the mild ablation process can be extended to other solid materials, potentially broadening its industrial relevance. If successful, this work could mark the beginning of a new era in nanomanufacturing—where ultrafine structures are no longer confined to costly cleanrooms, but crafted directly and efficiently with light in water.

International Journal of Extreme Manufacturing (IJEM, IF: 21.3) is dedicated to publishing the best advanced manufacturing research with extreme dimensions to address both the fundamental scientific challenges and significant engineering needs.

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