Abstract
An imaging ellipsometer technique on internal reflection geometry that can measure the thickness distribution of a thin film possessing an assumed refractive index is described. Because a prism is used for the internal reflection geometry, it was theoretically predicted that angular derivation from the normal incidence on the prism surface affects only the Ψ value by a factor of 0.97 at maximum. Measurements were carried out for an optical system of silica substrate–TiO2 layer–silica layer–protein film–air, with a thin-film array of dried protein as the sample film. Thickness of the protein films was two-dimensionally estimated only from the measured map of the Δ value by use of the simulated relationship between the thickness and the Δ value. The thickness map obtained was coincident on the whole with the results according to a mechanical scanning. The detection limit was approximately ±0.2 nm. These findings validate the optical effect of a high-index additional layer to improve the sensitivity and precision of thickness measurements of the sample film on transparent substrates.
© 2005 Optical Society of America
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