Design and simulate the properties of triangular periodic nanoparticle arrays with the structure of bi-layer hexagonal lattice

Abstract

In this study, the discrete dipole approximation (DDA) method was used to simulate the hybrid bi-layer hexagonal lattice of triangular periodic nanoparticle arrays (PNAs). The PNAs nanophotonic devices could be fabricated with pure silver, but their performances would be easily degenerated because of the oxidation (forming Ag2O) and sulfuration (forming Ag2S). Theoretical results show that the oxidation and sulfuration of Ag thin film lead to a significant red shift in the wavelength to reveal the maximum extinction efficiency (λmax) and to a significant decrease in the maximum peak value of localized surface plasmon resonances (LSPRs). The structures with the bi-layer materials of Ag2O–Ag and Ag2S–Ag were used to prove the degeneration of the properties in the extinction spectra of the LSPRs by using DDA method for simulation. We would find that the maximum peak value of the wavelength of the extinction efficiency spectra critically decreased and λmax had a red shift as the thicknesses of Ag2O and Ag2S increased. The structures with the bi-layer materials of Au–Ag and TiO2–Ag were also used to investigate their extinction spectra of the LSPRs. The simulation results of DDA method found that the maximum peak value of the wavelength of the extinction efficiency spectra slightly decreased as the thicknesses Au and TiO2 increased. Based on the Ag triangular nanostructure, the use of Au and TiO2 to form hybrid Au–Ag and TiO2–Ag triangular nanostructure cannot only be used to put forth of preventing oxidation and sulfuration but have a better performance than the Ag2O–Ag and Ag2S–Ag hybrid triangular nanostructures. Meanwhile, the thicknesses of TiO2 or Au layers could be used to decide the refractive index sensitivity (RIS) and figure of merit (FOM) of the hybrid Au–Ag and TiO2–Ag PNAs.