Plasmonic signal enhancements using randomly distributed nanoparticles on a stochastic nanostructure substrate

The surface-enhanced Raman spectrum was investigated through a numerical model and experiments constructed based on the stochastic Ag nanoislands (AgNIs) substrate. By a rigorous coupled-wave analysis (RCWA) method, the basic properties of electric field were calculated for numerical analysis. The plasmonic coupling between Au nanoparticles (AuNPs) and AgNI substrate was optimized by changing the position of AuNPs on the Ag nanostructured substrate. Furthermore, we experimentally confirmed that AgNIs substrate enable that the intensity of Raman spectra were dramatically improved up to ∼20-fold compared to that of a silver thin film as we expected in numerical calculations. The results gained in this work suggest that we could significantly enhance the Raman signal using easily fabricable AgNI substrates, and can provide the potential applications, such as food, pharmaceutical, and security inspections.