Broadband SERS substrates by oblique angle deposition method

Strong electric field enhancement can be achieved in metal-insulator-metal (MIM) configuration where a thin dielectric layer is in between two metal layers. Here MIM nanostructures with intrinsic electromagnetic hot spots accessible for analytes are fabricated by oblique angle deposition (OAD). Firstly, silver nanoparticles are produced by OAD on a flat silver mirror with a thin dielectric over-layer. The broadband absorption peak of this particle-on-film system can be tuned by varying the particle size in order to fit a given excitation laser source for SERS (surface-enhanced Raman scattering). Then we deposit MIM nanoparticles on three-dimensionally structured silicon by an equivalent OAD method. By two-photon induced luminescence imaging and Raman measurements, we demonstrate strong and uniform field enhancement over the proposed substrate which is a good candidate for SERS application.