Surface-enhanced Raman scattering from semiconductor and graphene quantum dots coupled to metallic-film-on-nanosphere substrates

In this article, we perform surface-enhanced Raman scattering (SERS) with a periodically corrugated metallic substrate obtained by evaporating an Ag film onto an artificial opal crystal, which is a self-assembled lattice of SiO(2)600-nm spheres. These metallic-film-on-nanosphere (MFON) surfaces are characterized by scanning electron microscopy for different Ag film thicknesses ranging from 44 to 620nm. Raman scattering spectra are measured for two different types of quantum dots, CdTeSe quantum dots (QDs) and graphene quantum dots (GQDs). We are able to show that enhancement of the Raman spectra can be obtained for all MFON substrates and for both types of QDs. For both CdTeSe and graphene quantum dots, the strongest SERS effect was observed in samples with 135nm Ag thickness. This is attributed to the formation of hot spots in the nanogap dips of the Ag film.