Abstract
Arrays of gold quasi-3D nanoholes were proposed and fabricated as substrates for surface-enhanced Raman scattering (SERS). By detecting rhodamine 6G (R6G) molecules, the gold quasi-3D nanoholes demonstrated an SERS intensity that was 25-62 times higher than that of two-dimensional nanoholes with the same geometrical shapes and periodicities. The larger SERS enhancement of the quasi-3D nanoholes is attributed to the enhanced electromagnetic field on the top-layer nanohole, the bottom nanodiscs and the field coupling between the two layers. In addition, the investigation of the shape dependence of the SERS on the quasi-3D nanoholes demonstrated that the quadratic, circular, triangular and rhombic holes exhibited different SERS properties. Numerical simulations of the electromagnetic properties on the nanostructures were performed with CST Microwave Studio, and the results agree with the experimental observations.