Optical properties of hexagonally arranged triangular arrays of Au-Ag nanoparticles

Optical properties of hexagonally arranged triangular arrays of Au-Ag nanoparticles are systematically investigated. A gold thin film is deposited on top of the silver nanoparticles supported with substrate. The hybrid nanoparticles can prevent pure silver nanoparticles from oxidation and the stability of the hybrid Au-Ag nanoparticles compared with pure silver nanoparticles has been verified. Influence of the particle thickness on the extinction spectrum is studied and optimized through discrete dipole approximation (DDA) method and nanosphere lithography (NSL). Considering the nano-fabrication condition, 40 nm thickness is selected and the array is fabricated. The experimental results demonstrate that the measured spectrums are basically in agreement with the theoretical spectrums derived by the DDA calculation.