Soft X-ray reflectivity and structure evaluation of Ni/C/Ti/C multilayer X-ray mirrors for water-window region

A Ni/Ti-based multilayer with thin interleaved carbon layers (Ni/C/Ti/C multilayer) has been designed and fabricated for the reflection coating of a grazing-incident-angle reflector in the water-window region for use in X-ray photoemission spectroscopy. It was found to be a highly reflective mirror at wavelengths just above the Ti absorption edge (around 2.73 nm), as designed. A Ni/C/Ti/C multilayer with 0.2-nm-thick interleaved carbon layers was fabricated by magnetron sputtering. The measured reflectivity was 40% at a wavelength of 2.76 nm and an incident angle of 9.5°. This value is a little bit higher than that for a Ni/Ti multilayer with almost the same layer structure. Furthermore, the addition of thin carbon layers was found to significantly improve the heat resistance of a multilayer.