Plasmonic Nanolamination for High-Performance SERS Substrates Based on Vertically Stacked 3D Multiple Nanogaps

While surface-enhanced Raman spectroscopy (SERS) offers ultrasensitive detection performance, achieving signal reproducibility remains a key challenge due to nanoscale geometrical variations in plasmonic hotspots. Top-down fabrication strategies have been employed to improve uniformity and reproducibility; however, the current horizontally oriented nanogaps are limited in achieving precise control at sub-10 nm scales, restricting the achievement of a high density of hotspots. In this work, we report a high-performance silver-based nanolaminate SERS substrate based on vertically stacked 3D multiple nanogaps, providing uniform and densely packed hotspots. By selectively etching the dielectric layers, nanogap hotspots are exposed to analyte molecules, resulting in a significant increase in the SERS enhancement factor, reaching up to 1.75 x 108. We also demonstrate that plasmonic nanolamination reveals great uniformity with a relative standard deviation value of 11% over a large area (400 pixels) and quantitatively confirms substrate reproducibility. Furthermore, the high-throughput nanoimprint lithography to fabricate high-performance nanolaminate SERS substrates allows the fabrication of large-scale devices (similar to 16 cm2) cost-effectively. Therefore, this work presents that the silver-based nanolaminate SERS substrate is highly suitable for various practical SERS applications due to its uniformity, reproducibility, and high sensitivity.