The design and fabrication of the metallic nano-annular aperture structure on the glass and the study of its optical property

Abstract

The concentrated local electric field on a substrate surface is very helpful to enhance the signal for surface-enhanced Raman scattering (SERS) and surface plasmon resonance (SPR) techniques. In this research, the metallic nano-cylinder, the nano-hole, and nano-annular aperture structures on the glass have been simulated by the finite difference time domain method (FDTD) first to understand the localized surface plasmon resonance (LSP) of them. The simulations for different inner diameters, outer diameters and thickness of the gold film have been done and the better dimension and film thickness which can induce the largest electric field concentration have been chosen. We coated 2 nm and 5 nm thick chromium(Cr), and 50nm and 60nm thick gold(Au) films on SF2 glass substrate, respectively. The different nanoannular aperture structures were successfully patterned on them by using focus ion beam (FIB) to etching gold film surface. Using the OB Morph measurement to observe the structure caused by the SPR shifted. The transmission spectrometer has been adapted to measurement the substrate to observe the spectrum of them. Different concentrations of sodium chloride(NaCl) solutions also have been measured on the different substrates, and the shift of the transmission light wave peak was detected.