Table 1: Evaluation of the complex refractive index ( , ) of NPs multilayer structure and a thermally evaporated Au film by ellipsometry.

Refractive index Extinction coefficient

Au evaporated film 30 nm0.488−2.4
5 nm Au colloidal 1 layer equivalent to 5 nm3.814−0.896
5 nm Au colloidal 4 layers equivalent to 20 nm3.014−1.664
15 nm Au colloidal 4 layers equivalent to 60 nm3.045−1.522