Paper
5 October 2005 Determination of complex optical indices in the 80-140nm VUV wavelength region from reflectivity measurements under normal incidence: application to ZnSe
F. Bridou, M. Cuniot-Ponsard, J. M. Desvignes
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Abstract
The observation of hot plasmas in the interstellar medium requires efficient mirrors in the 80-120 nm wavelength range. Contrary to that of most metals, the high reflectivity of pure aluminum is maintained close to 80% in this range. Unfortunately, it is drastically reduced to values lower than 10% by the strongly absorbing thin alumina layer which spontaneously forms upon air contact. We report here the results obtained with a capper layer of ZnSe. The optical indices given for this material by Palik's tables lead to predict a resulting high reflectivity, provided the layer prevents oxidization of underlying Al. The measured reflectivity does not agree with theory. The reasons for this inconsistency are examined. It is shown that complex indices of ZnSe in the wavelength region between 80 and 140 nm can be extracted. from the reflectivity measurements obtained with different ZnSe thicknesses on Al. The imaginary part of the index is then found to differ strongly from Palik's tables value.
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F. Bridou, M. Cuniot-Ponsard, and J. M. Desvignes "Determination of complex optical indices in the 80-140nm VUV wavelength region from reflectivity measurements under normal incidence: application to ZnSe", Proc. SPIE 5963, Advances in Optical Thin Films II, 59631S (5 October 2005); https://doi.org/10.1117/12.624848
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KEYWORDS
Reflectivity

Aluminum

Vacuum ultraviolet

Mirrors

Absorption

Reflectometry

Solar energy

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