Analyzing SERS reproducibility and performance: the role of illumination area

Surface-enhanced Raman Spectroscopy (SERS) is a powerful optical sensing technique widely used in fields like medicine, microbiology, and environmental analysis. Planar SERS substrates are preferred for their ease of integration into lab-on-chip systems and superior reproducibility. Substrate performance is assessed using metrics like enhancement factor, sensitivity, and reproducibility. Many experimental and post-processing factors can influence these metrics and their interpretations, with one of the most critical being the illumination area-essentially, the number of hotspots generating the signal. We investigated with Raman mapping the impact of the illumination area on 5 SERS substrates showing that a larger illumination area improves reproducibility on random structures, while it sacrifices resolution. Furthermore, a larger illumination area leads to more stable signals, particularly in irregular nanostructures, yielding higher sensitivity. In conclusion, choosing a SERS substrate should consider the trade-off between uniformity for resolution and larger illumination area for signal reproducibility.