SERS-active substrates based on embedded Ag nanoparticles in $c$-Si: modeling, technology, application

A simple method for obtaining SiO$_2$ : Ag : Si and Ag : Si hybrid nanostructures is presented. High-temperature annealing of an Ag island film on the surface of $c$-Si makes it possible to preserve the plasmonic properties of Ag nanoparticles and protect them from external influences by coating them with a thermally grown layer of SiO$_2$. The calculation of the electric field strength distribution in the structure with embedded Ag nanoparticles in $c$-Si demonstrates the presence of intrinsic “hot spots” at the corners of the nanoparticles, which leads to a maximum enhancement factor ($\sim$10$^6$) of Raman scattering. A numerical calculation of the dependence of the spectral position of a localized plasmon resonance on the geometry of structures can serve as a basis for their design in the future. Surface-enhanced Raman scattering showed reliable detection of the methyl orange from an aqueous solution at a concentration of $<$ 10$^{-5}$ M.