Rolled-Up Ag-SiO_x Hyperbolic Metamaterials for Surface-Enhanced Raman Scattering

A convenient technique is reported to fabricate Ag-SiO_x hyperbolic metamaterials (HMMs) as robust surface-enhanced Raman scattering (SERS) substrates based on roll-up nanotechnology. As an illustration, dramatic enhancement is achieved using Rhodamine 6G as a molecular probe, which indicates that a larger plasmonic density of states exist, leading to a greatly enhanced local electromagnetic (EM) field when the sample is irradiated with a laser beam. Optimized results are obtained by controlling the thickness of alumina coating onto Ag-SiO_x HMMs using atomic layer deposition. Finite-difference time-domain simulations further illustrate the excitation of localized surface plasmon modes by calculating the EM field properties on the surface of Ag-SiO_x HMMs. This efficient method of producing Ag-SiO_x HMMs with highly SERS-active properties could spur expanding applications in metamaterials and bioanalysis.