Optical Models for the Characterization of Silica Nanosphere Monolayers Prepared by the Langmuir?Blodgett Method Using Ellipsometry in the Quasistatic Regime

摘要

We investigated different optical models (one-layer, multilayer, parametric multilayer, and statistical parametric) for the ellipsometric characterization of thin films made of silica spheres in the diameter (D) range of 90?450 nm prepared by the Langmuir?Blodgett (LB) technique. As a continuation of a previous work (Nagy, N., et al. Langmuir 2006, 22, 8416) in terms of threshold wavelength determination and optical models, we investigated the wavelength range of the quasistatic limit (requirement for the effective medium approximation) depending on D. We compared the above models in the aspect of fit quality, stability, uncertainty of parameters, and the amount of information that can be obtained from the evaluation. Besides fundamental properties like diameter, coverage, or packing density, using sophisticated models we can also determine the size distribution of the particles. The ellipsometric results were compared with the results of dynamic light scattering and of scanning electron microscopy.