Sümeyra Vural Kaymaz1,2,Hasan Sarigül2,Caner Soylukan2,Selim Tanriseven2,Hasan Kurt3,Meral Yuce2
Sabanci University1,SUNUM Nanotechnology Research and Application Center, Sabanci University2,Imperial College London3
Sümeyra Vural Kaymaz1,2,Hasan Sarigül2,Caner Soylukan2,Selim Tanriseven2,Hasan Kurt3,Meral Yuce2
Sabanci University1,SUNUM Nanotechnology Research and Application Center, Sabanci University2,Imperial College London3
Surface plasmons in metal/dielectric interfaces provide significant levels of electric field enhancements in the subwavelength resolution, enabling a wide range of applications. One such application is surface-enhanced Raman scattering (SERS), a powerful analytical method for label-free molecular fingerprinting of various analytes. A careful design and nanofabrication of SERS substrates with a considerable Raman enhancement factor (EF) at the wavelength of interest are imperative for SERS applications. SERS substrates based on noble metal colloids, roughened nanosurfaces, nanospheres, and nanotips have been previously reported. Nevertheless, the low reproducibility of electric field hot spots has limited the utilization of these inherently random structures with high EF. The period arrays of plasmonic nanostructures offer the potential for generating reproducible SERS substrates. Specifically, metal-insulator-metal (MIM) based nanostructures exhibit substantial gap resonance due to the coupling of localized fields between two metal layers underlying the dielectric layer. By adjusting the geometric parameters of metal nanostructures and dielectric layer thickness, gap resonance can be tuned for application-specific requirements. In this work, we investigated the performance of gold (Au) bow-tie antenna arrays on insulator-metal substrates for SERS applications. The Finite-difference time-domain (FDTD) method was used to simulate the effects of parameters such as bow-tie apex angle, gap size, length, and dielectric layer thickness. We achieved an electric field enhancement of up to 630 times the incoming electric field intensity, corresponding to a SERS EF factor improvement of ~3.9×10<sup>5</sup> in our final optimized design at an excitation wavelength of 785 nm. Later, we fabricated Au MIM bow-tie antenna arrays using electron beam lithography and investigated their optical characteristics with an in-house modular reflection/transmission-based Microspectroscopy system.