Grazing incidence mirrors with enhanced reflectance in the soft X-ray region

•Low-Z material on top improves the reflectivity of grazing incidence X-ray mirrors.•The experiment has confirmed the theory.•The best bilayer systems for the spectral range of 0.8–18 nm have been found.

A design strategy for the fabrication broadband grazing incidence mirrors in the wavelength range of 0.8–18 nm is proposed. Instead of high-density materials, we propose a bilayer coating consisting of the high-density material most suitable for the task coated with a thin film of low-density material. In the wavelength range of 4–18 nm, an increase of the reflection coefficients of such coatings by 10–20% compared with the single high-density layers traditionally used is theoretically expected. We also present an experimental demonstration of such advantageous properties based on a Cr-C bilayer film.