Fig. 6.

(a)-(d) Corresponding normal-incidence absorption spectra of monolayer graphene with the thickness of the SiO₂ spacer increased from 25 to 40 nm in steps of 5 nm. The diameters of the Ag nanodisks are d₁ = 140 nm, d₂ = 120 nm, d₃ = 100 nm, d₄ = 80 nm, and the other parameters are the same as those in Fig. 2