Optical properties of Ag-doped polyvinyl alcohol nanocomposites: a statistical analysis of the film thickness effect on the resonance parameters

Abstract

Nanocomposites made of polymer films embedding silver nanoparticles were prepared by thermal annealing of poly-(vinyl) alcohol films containing AgNO3. Low (2.5% w:w) and high (25% w:w) doping concentration of silver nitrate were considered as well as their effect on the optical properties of thin (30 nm) and thick (300 nm and more) films. The topography and the optical properties (refractive index $n$ and extinction coefficient $k$) of such films were studied by atomic force microscopy and spectroscopic ellipsometry. For a given doping level, the parameters of the surface plasmon-polariton resonance (amplitude, position and width) were shown to be thickness-dependent. Multivariate statistical analysis techniques (principal component analysis and support vector machines) were used to explain the differences in the optical behavior of the thick and thin films.