Scalable High‐Performance Nanolaminated SERS Substrates Based on Multistack Vertically Oriented Plasmonic Nanogaps

Abstract Metallic nanogap structures can support gap surface plasmon modes and strongly concentrate optical fields to enable surface‐enhanced Raman spectroscopy (SERS) for label‐free biochemical analysis down to single molecule level. However, current scalable SERS substrates based on horizontally oriented plasmonic nanogaps still face challenges for accurate sub‐10 nm control of in‐plane nanostructures. Here, we report a new type of scalable high‐performance SERS substrate based on multistack vertically oriented nanogap hotspots in metal–insulator–metal nanolaminated plasmonic crystals. In contrast to horizontally oriented nanogaps, vertically oriented plasmonic nanogaps can be controlled at subnanometer resolution in the multilayered thin‐film deposition process. After a partial etching of dielectric layers, embedded nanogap hotspots in nanolaminated SERS substrates can be exposed to further increase SERS enhancement factors (EFs) by over one order of magnitude from ≈1 × 10 7 to ≈1.6 × 10 8 . Moreover, oxygen plasma can be used to regenerate clean nanogap hotspots for repeated SERS measurements with maintained high SERS EFs (>1 × 10 8 ). Therefore, this work presents a novel out‐of‐plane plasmonic engineering approach to design and manufacture scalable high‐performance reusable SERS substrates for various biochemical analysis applications that prefer high spatial‐temporal resolution and good hotspot uniformity.