Ultrafast-Laser-Induced Nanostructures with Continuously Tunable Period on Au Surface for Photoluminescence Control in Monolayer MoS₂

Nanostructures of noble metal offer an exciting opportunity to tune photoluminescence (PL) in 2D materials, which has shown promise for applications in plasmonic devices. However, an efficient, designable, residue-free nanofabrication method remains challenging. Herein, a one-step ultrafast laser nanofabrication method is performed in fabrication of laser induced periodic surface structure (LIPSS) with continuously tunable periods over a wide range (from 439 to 2086 nm) on Au. The process of LIPSS imprinting is revealed at different time scales: periodical energy deposition within hundreds of femtoseconds, phase transition after 10 ps, and resolidification after 200 ps. Furthermore, the intensity and peak shift of PL in monolayer MoS₂ (1L-MoS₂) can be tuned by LIPSS, 11-fold enhancement resulting from nanoscale confinement of the incident laser and exciton-trion localized interconversion emanating from hot electron transfer and tensile strain. The results are promising for 2D-materials/metal heterostructures to applications in plasmonic devices and nanophotonic integrated circuits.