Development of Al-based multilayer optics for EUV

We report on the development of multilayer optics for the extreme ultra-violet (EUV) range. The optical performance of Al-based multilayer mirrors is discussed with regard to promising reflectivity and selectivity characteristics and the problems of the interfacial roughness for this type of multilayers. We demonstrate a possibility to reduce the average roughness by introducing additional metal layer (W or Mo) rather than depositing a buffer layer at each interface. We have prepared and tested Al/SiC, Al/W/SiC and Al/Mo/SiC multilayers of various periods for the spectral range from 15 to 40 nm, which is the range of increasing interest for high-order harmonic generation, synchrotron radiation and astrophysics. The structure of the three-component systems has been optimized in order to obtain the best reflectivity for each wavelength within the spectral range. We have shown that introduction of refractory metal in Al-based periodic stack can improve the optical performance of multilayer reflecting coatings designed for the EUV applications. PACS 42.70.-a · 61.05.Cm · 68.35.Ct · 78.67.Pt · 81.07.-b E. Meltchakov ( ) · C. Hecquet · S. De Rossi · Y. Menesguen · A. Jérome · F. Bridou · F. Varniere · M.-F. Ravet-Krill · F. Delmotte Laboratoire Charles Fabry, Institut d’Optique Graduate School, 91127 Palaiseau, France e-mail: [email protected] Fax: +33-169-358807 M. Roulliay Laboratoire d’Interaction du rayonnement X avec la Matière (LIXAM), 91403 Orsay, France