Effect of coupling crater structure and Ag nanoparticles on SERS enhancement

This study was aimed at enhancing surface plasmon resonance through a combination of Ag nanoparticles (NPs) and an asymmetric crater structure capable of concentrating light. The crater structure was fabricated via wet-chemical etching of a GaAs(100) wafer, after which an Ag film was deposited inside, and subjected to rapid thermal annealing to form NPs. The results were analysed in terms of the magnitude of the Raman intensity, from which an optimal combination of annealing temperature and film thickness was determined. Ag nanowires (NWs) were also spray-coated onto the AgNPs to elucidate the effect of coupling the NPs with the NWs. The Raman intensity was 22 times higher inside the crater with AgNPs and NWs than on a flat area without NPs; however, further increases in the amount of AgNWs resulted in greater coverage of the AgNPs, which reduced the Raman intensity. We expect the proposed method for Raman signal enhancement to promote further development and applications of surface-enhanced Raman scattering (SERS) spectroscopy.