Plasmonic Moiré Superlattices for Robust Nanogap Cluster Formation

Plasmonic nanogaps are of great interest due to their ability to enhance optical fields and support quantum optical effects, making them essential for applications such as sensing and spectroscopy. However, developing a reliable and straightforward method to generate sub-10 nm gaps remains a significant challenge. Here, we propose an efficient strategy for creating plasmonic nanogap clusters based on moiré superlattice structures. This geometry-driven approach yields nanogaps substantially smaller than the feature dimensions of the individual periodic arrays and robustly generates nanogap clusters despite typical fabrication errors. Voltage-contrast scanning electron microscopy confirms the formation of well-defined sub-10 nm gaps, which are critical for nanogap-enabled applications. Building upon this validated concept, we further introduce elevated plasmonic moiré superlattices and demonstrate their consistently high sensitivity against fabrication-induced variations via surface-enhanced Raman spectroscopy. Notably, the proposed strategy is scalable, as it can be implemented using conventional large-area lithography techniques. Taken together, this work provides a promising and broadly accessible platform for future research in nanophotonics, quantum optics, and advanced sensing.