Topological size effect in tin-dioxide cluster films produced by reactive sputtering

The optical properties of tin-dioxide nanofilms produced by reactive sputtering are studied by the internal reflection technique and modulation polarimetry. The angular and spectral characteristics of the reflection coefficients R _s ² and R _p ² are studied for linear-polarized radiations, for which the wave electric field is, correspondingly, orthogonal and parallel to the plane of incidence. The characteristics of the physical difference between the reflection coefficients, ρ = R _s ² -R _p ² , are studied as well. From the experimental results, it follows that (i) the doping-induced finite conductivity of the film brings about the appearance of surface plasmon resonance; (ii) the shape of the spectral and angular characteristics of the parameter ρ is indicative of the cluster structure of the film, which is in agreement with the phase topology data obtained by atomic force microscopy; and (iii) the nonspherical shape of the clusters is responsible for the splitting of resonances and for the dependence of their parameters on the angle of incidence, which defines the topological size effect.