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D. Feiertag, C. Eisenmenger-Sittner, H. Mahr:
"Fast Determination Of The Optical Properties Of Metallic And Dielectric Thin Films";
Poster: Joint Vacuum Conference 14 (JVC-14), Dubrovnik, Kroatien; 04.06.2012 - 08.06.2012.

The optical properties of thin films such as extinction coefficient and refractive index are important input data for e.g. thickness determination or for the design of advanced optical components. In many cases they may deviate from well known values of bulk materials and may have to be assessed experimentally.
In this paper a fast and efficient method is presented to determine the optical properties of a thin film. Coatings with a linear thickness gradient were deposited on transparent substrates. The thickness gradient is generated by using a stepper motor which moves a shutter over the substrate with constant velocity at constant deposition rate. By means of these wedge shaped samples it was possible to determine quantities like extinction coefficients or refractive indices in dependence on the wavelength by simple optical spectrometry.
The measured optical constants were compared to literature values for well known metals (Ag, Au, Cu, Mo) and for dielectric substances (Alumina or MgF2). Excellent correspondence to the values in literature was found.
Going further, the same sample geometry was applied to less common materials like mixtures of dielectrics and metals. It was possible to extract extinction coefficients and refractive indices for these unknown materials with ease.
Finally, the obtained data were compared to transmission measurements with a commercially available optical scanner. It was found that even measurements with the scanner yielded reliable results. Therefore, transmission scanners may also be used as devices for the determination of optical constants and, in turn, for quantitative film thickness measurements with high spatial resolution once the optical constants are known.

This work was supported by the Austrian Science Fund (FWF), project "T-scan", grant number TRP-6