Electric field enhancement in Au and Ag nanodisks-based photonic crystals: Relevant design insights for efficient SERS substrates

Abstract

In recent years, noble metal nanoparticle-based periodic nanoarrays (photonic crystals) have received special attention due to their gross potential toachieve exceptionally high Electric-Near Field Enhancement (ENFE) factors for visible light and their prospects as candidates for the fabrication of ultrasensitive Surface-Enhanced Raman Spectroscopy (SERS) substrates. In this work, we report a simple but exhaustive theoretical analysis of the ENFE in Auand Ag nanodisks-based photonic crystals by Finite-Difference Time-Domain (FDTD) method. Nanostructures with arrays periodicities from 200 to 1000 [nm], nanodisks diameters from 100 to 500 [nm] and thicknesses from 20 to 200 [nm] were studied. Results show that the ENFE is strongly dependent on each one of these geometrical parameters, observing | 𝐸𝐸| 2 factors that can reach up to 1200 for the visible light spectrum. The effects of nanodisks surface curvature-based defects on the ENFE were also analyzed. This kind of defects seem to be also relevant to maximize the ENFE effects, observing that higher surface curvatures tend to attenuate considerably the electric field amplification. Our research provides relevant insights on the design optimization of this kind of photonic crystals to maximize the ENFE effects, which is a critical issue to assess the future fabrication conditions of efficient SERS substrates.