Locally excited surface plasmon polaritons (SPPs) induced scanning near-field optical lithography on Ag nano-film

Scanning near-field optical lithography (SNOL) has been considered an outstanding technique for sub-diffraction-limit nanofabrication since the advantages of low-cost and stability. Here, we report the SNOL on Ag nano-film to generate high-accuracy groove and pattern features controllably, using a cantilevered scanning near-field optical microscopy (SNOM) tip and nanosecond laser. The morphology and element analysis of fabricated features indicate that the melting and reshaping of the surface materials are the mechanism of SNOL on Ag nano-film. The electromagnetic filed and thermal field distributions are calculated via a multi-physics model by finite element method (FEM). The simulation reveals that the locally excited surface plasmon polaritons (SPPs) induce the near-field enhancement of light field and produce elliptical hot spot confined in the tip aperture. Single pulse energy and polarization of the incident laser are demonstrated to be essential parameters in lithography. The theoretical influential mechanism of these parameters to the feature width is consistent with experimental results. Due to the hot spot effect with extremely small range and high instantaneous energy underneath the tip aperture, this technology has immense potential in nanostructure processing and nano-welding in the future.