Far-field femtosecond laser-driven λ/73 super-resolution fabrication of 2D van der Waals NbOI₂ nanostructures in ambient air

The design and fabrication of ultrafine nanostructures in two-dimensional (2D) van der Waals materials are crucial for the functionalization of electronic devices. Here, we report the utilization of far-field femtosecond laser patterning to fabricate super-resolution nano-groove array (NGA) structures in 2D multilayer NbOI₂ in ambient air, achieving groove widths as low as ~14.5 nm (~λ/73). The NGA structures maintain a well-defined single-crystal NbOI₂ with amorphous Nb₂O₅ edges as narrow as 3.2 nm. The formation mechanism of NGA structure is confirmed to be associated with the coupled field of surface plasmon polariton periodic field and nano-groove-induced local near-field induced by femtosecond laser irradiation. Furthermore, the NGA-NbOI₂ gas sensor exhibits NO₂ sensing performance, with a rapid response time (5.1 s), which is attributed to the existence of abundant NbOI₂-Nb₂O₅ heterojunctions. This approach will propel the further development of nano-lithography techniques for functional device applications of 2D materials.