The paper reports on the use of the Lorentz-Drude model to investigate the optical behavior of a novel multilayer localized surface plasmon resonance (LSPR) interface. The plasmonic interface consists of a random array of gold nanostructures (Au NSs) formed by thermal deposition of a 4 nm thick gold film on glass, postannealed at 500 °C for 1 min, and coated with two different dielectric layers, silicon dioxide (SiO x ) and silicon nitride (Si 3 N 4 ), of varying thickness. Atomic force microscopy and scanning electron microscopy were used to determine the average size, height, and particle density. The influence of the morphology and interparticle distance on the LSPR characteristics of a glass/Au NSs interface with a constant thickness of a SiO x overcoating was investigated through the calculation of theoretical transmission spectra. Ajusting the theoretical curve to experimental LSPR spectra allowed the geometry of the plasmonic interface to be fixed and evaluation of the change in the wavelength at maximum absorption (λ max ) as a function of the SiO x overlayers thickness. The theoretical data were compared with experimental results obtained on glass/Au NSs/SiO x and glass/Au NSs/ Si 3 N 4 interfaces.

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