Highly reflective Ru Y multilayer mirrors for the spectral range of 9 11 nm

The results of the investigation of the reflective characteristics of multilayer mirrors based on Ru Y are presented. Reflection coefficients at the level of 38.5 at an operating wavelength of 9.4 nm. It is shown that the deposition of B4C barrier layers onto Y layers makes it possible to significantly increase the reflection coefficient compared to structures without barrier layers. A reflectance of 54 was obtained for mirrors optimized for 11.4 nm, which is close to the theoretical limit for these material