Crystallization-dependent 100-nm periodic structures on gold and graphene based on femtosecond laser irradiation

Laser-induced periodic surface structures (LIPSS), particularly those exhibiting high-spatial frequency LIPSS (HSFL), hold paramount significance in precision manufacturing due to their capacity for rapid nanostructure generation. However, in the case of Au, a material widely employed in micro-nano applications, the manifestation of HSFL remains predominantly elusive. This study successfully fabricated HSFL with a periodicity of 100 nm on Au, leveraging the crystallization induced by a 520-nm femtosecond laser (fs-laser). The fundamental element for instigating HSFL formation resides in exploiting "amorphous Au" with disordered lattice structures coupled with the fs-laser-induced crystallization. The disordered lattice structures facilitated the dominance of electron-phonon coupling in the thermal transport, suppressing the hot-electron diffusion effect-a prerequisite for HSFL formation. The crystallization controlled the conversion of "amorphous Au" into the typical crystalline state of Au while also enabling period multiplication contingent on the number of fs-laser pulses. It ultimately facilitated the formation of a 100-nm HSFL on crystalline Au. Furthermore, the versatility of Au HSFL was demonstrated through its application in periodic nanopatterning (i.e., HSFL) on single-layer graphene. Therefore, besides unveiling novel physical mechanisms underpinning the formation of metal HSFL, the attainment of Au HSFL undoubtedly promises significant advancements in nanoelectronics and nanophotonics.