In this paper, the effect of dewetted gold nanoparticles (AuNPs) on hexagonal boron nitride (hBN) is discussed along with the changes in surface plasmon resonance (SPR). Au is sputtered on monolayer hBN/SiO2/Si substrate for a varied duration and subjected to thermal annealing. Monolayer hBN is verified by spectroscopic ellipsometry using the Tauc–Lorentz model, while the AuNPs are modeled using a combination of Gauss, Cody–Lorentz, and Tanguy dispersion laws. Sputtering of Au on hBN/SiO2/Si results in a film-like layer compared to the one on SiO2/Si. Before annealing, the improved uniformity of Au on hBN/SiO2/Si diminished the SPR wavelength, λspr, when the sputter duration exceeded 30 s, much sooner compared to 120 s from the one on SiO2/Si. After annealing, the λspr is vibrant for all samples around 2.3 eV. Au dewetted more on hBN due to higher surface tension. Large dewetted AuNPs supported by hBN result in higher photon extinction at λspr. The longest sputter duration of 120 s on hBN/SiO2/Si (mean size 53 nm) exhibited an 11.2% higher extinction coefficient compared to the one on SiO2/Si (mean size 39.6 nm). Findings support the advantages of preparing plasmonic AuNPs by dewetting on monolayer hBN.
