title: Understanding the effects of dielectric medium, substrate, and depth on electric fields and SERS of quasi-3D plasmonic nanostructures.
abstract: The local electric field distribution and the effect of surface-enhanced Raman spectroscopy (SERS) were investigated on the quasi-3D (Q3D) plasmonic nanostructures formed by gold nanohole and nanodisc array layers physically separated by a dielectric medium. The local electric fields at the top gold nanoholes and bottom gold nanodiscs as a function of the dielectric medium, substrate, and depth of Q3D plasmonic nanostructures upon the irradiation of a 785 nm laser were calculated using the three-dimensional finite-difference time-domain (3D-FDTD) method. The intensity of the maximum local electric fields was shown to oscillate with the depth and the stronger local electric fields occurring at the top or bottom gold layer strongly depend on the dielectric medium, substrate, and depth of the nanostructure. This phenomenon was determined to be related to the Fabry-Pérot interference effect and the interaction of localized surface plasmons (LSPs). The enhancement factors (EFs) of SERS obtained from the 3D-FDTD simulations were compared to those calculated from the SERS experiments conducted on the Q3D plasmonic nanostructures fabricated on silicon and ITO coated glass substrates with different depths. The same trend was obtained from both methods. The capabilities of tuning not only the intensity but also the location of the maximum local electric fields by varying the depth, dielectric medium, and substrate make Q3D plasmonic nanostructures well suited for highly sensitive and reproducible SERS detection and analysis.
authors: Department of Chemical Engineering, University of Washington, Seattle, WA 98195, USA.
authors: Jiajie
authors: J
authors: Xu
authors: Pavel
authors: P
authors: Kvasnička
authors: Matthew
authors: M
authors: Idso
authors: Roger W
authors: RW
authors: Jordan
authors: Heng
authors: H
authors: Gong
authors: Jiří
authors: J
authors: Homola
authors: Qiuming
authors: Q
authors: Yu
mesh_terms: D015374:Biosensing Techniques; D003198:Computer Simulation; D004560:Electricity; D004867:Equipment Design; D006046:Gold / Q000737:chemistry; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D055095:Optics and Photonics; D009991:Oscillometry / Q000379:methods; D012825:Silicon / Q000737:chemistry
chemical_list: D006046:Gold; D012825:Silicon