At-wavelength metrology on Sc-based multilayers for the UV and water window

Abstract

Due to the unusual behavior of its optical constants the first transition element Sc with atomic configuration (3p⁶4s²3d) is a very attractive candidate for multilayer coatings optimized for the anomalous dispersion region of the 3p-3d transition around 28 eV (45 nm) and for the vicinity of the 2p absorption edge at 398 eV (3.12 nm), respectively. New normal incidence reflectivity data for Sc/Si at Sc 3p are shown with peak values up to 54% and for Cr/Sc at Sc 2p with peak values up to 17% are presented. The influence of optical performance on multilayer growth conditions and parameters are discussed in detail and the necessity of at-wavelength metrology for the final characterization is demonstrated. The results encourage e.g. applications for normal incidence optics used for high-power pulsed UV and x-ray laser systems and for x-ray microscopes operated in the water window.