Long-term performance and durability of Ir/B4C multilayer x-ray mirrors: focusing on composition, structure, and reflectivity properties

Reflecting optics with multilayer (ML) thin-film coatings, using various nanostructures and materials, are employed in various applications, including EUV lithography,1 synchrotron radiation beamlines,2,3 x-ray free-electron lasers,4 and astronomical optics.5,6 In order to enhance the performance of x-ray observatory telescopes, which detect x-ray emission in the universe (including clusters of galaxies, neutron stars, and black holes), further developments in these optical systems are required. The most important element in x-ray optics is the mirror system, which tunes the reflectivity range and the effective area. Missions, such as NASA’s Chandra or ESA’s XMM-Newton telescope launched in 1999, detect extreme objects that emit x-rays up to ∼10 keV by utilizing iridium single layer x-ray mirror coatings in grazing incidence angle geometry.7,8