Study of the optical and plasmon features in the reflectance spectra of the silver nanoparticle layers deposited from the AgNO$_{3}$ onto the silicon surface

The reflectance spectra of Ag layers on a silicon substrate are interpreted using the approach based on the calculation of the reflectance $R_{\operatorname{calc}}$ spectra of a thin film with variable thickness, which makes it possible to follow the effect of c-Si substrate critical points in the Brillouin zone and the formation of characteristics of bulk Ag at the edge of interband transitions. The calculated $R_{\operatorname{calc}}$ spectra were compared with the experimental $R_{\operatorname{exp}}$ spectra of the Ag nanoparticle layers with different morphologies measured at the normal and oblique (45$^{\circ}$) angle of incidence of light. For a layer consisting of coarser nanoparticles, one can observe a steep dip in the $R_{\operatorname{exp}}$ spectrum, which almost coincides with the edge of the interband transitions in bulk Ag in the UV range, and a broad dip in the $R_{\operatorname{exp}}$ spectrum with a minimum at $\lambda$ = 382 nm, which demonstrates the maximum absorption of the localized plasmon resonance of Ag nanoparticles. For the samples consisting of finer particles, the dip of the interband transitions in the $R_{\operatorname{exp}}$ spectra is not observed at both angles of incidence, since the deposited Ag nanoparticles did not form a structure with the optical properties of bulk Ag, but the bulk plasmon resonance appeared at $\lambda\sim$ 335 nm in the longitudinal mode at the oblique angle of incidence.