AFM-based nanoplowing lithography for fabricating plasmonic gaps enabling enhanced light-matter interactions

Plasmonic gaps on a visible-wavelength scale are promising structures for enhancing the interaction between terahertz (THz) and visible light with materials within the gaps. However, conventional lithography techniques, such as electron beam lithography and photolithography, are inefficient for fabricating plasmonic gap structures at the visible wavelength scale. In this study, we demonstrate a simple and efficient approach for fabricating plasmonic gold (Au) gap structures on a visible wavelength scale using atomic force microscopy (AFM) nanoplowing lithography. The gap width can be precisely controlled by adjusting the contact force and macroscopically manipulated through variations in Au etching time. In addition, the parallel patterning of lines using a 12-pens system significantly enhances the yield compared to conventional AFM-based lithography techniques for gap structure fabrication. The resulting rectangular-shaped Au gap structure exhibited a nearly uniform near-field THz signal, independent of the position of the internal probe within the antenna. These structures achieved a peak transmission of approximately 80%, demonstrating their strong potential for next-generation contactless, high-sensitivity near-field sensing applications. Moreover, the Au gap structures serve as effective templates for enhancing light-matter interactions to improve Raman and fluorescence signals in quantum materials with low light absorption, such as two-dimensional semiconductors.