Large-scale and uniform Raman substrate of coupled Ag grating with Ag triangle arrays

Vertically coupled plasmonic structures have been widely used in optical applications due to its enhanced electromagnetic fields in the gaps between metallic nanostructures. In this paper, a large-scale vertically coupled structure composed of the Ag triangle array (AgTA) on Ag grating separated by a nanometric dielectric layer is fabricated by nanosphere lithography incorporated with photolithography. Thanks to the effective surface plasmon polaritons excitation on the Ag grating, a significant surface enhanced Raman spectroscopy (SERS) effect arises from a strongly enhanced local electric field within the tiny gaps between the AgTA and Ag grating, which is verified by experiment and theoretical simulations. The as-proposed SERS substrate exhibits a nice uniformity with the relative standard deviation of about 10.5%, leading to excellent reliability for Raman detection. The simple fabrication of the large-area, productive, and inexpensive vertically coupled plasmonic structure can be a potential candidate for SERS applications.