Optical properties of granular tin films from 022 to 10 μm

The optical properties of granular tin films were investigated in the spectral region from 0.22 to 1.0 microm. As the particles forming the films increased in size (from ~43.0 to 70.0 nm) the peak observed in the reflectance was shifted to longer wavelengths. Parameters such as the film thickness and the filling factor have been determined and served for the calculation of reflectance using the well-known Maxwell-Garnett approach. An extension of this theory was also used to characterize the granular films. The revised dipole theory that includes frequency-dependent terms neglected in the static approximation seems to give a better description of the optical behavior of granular surfaces.