High reflectivity Co/Mg multilayer working in the broad soft x-ray range of 350-770 eV

A Co/Mg multilayer was proposed and optimized to work in the broad soft x-ray range of 350-770 eV. The multilayers with a d-spacing of 6.0 nm showed large interface widths of 1.95-1.07 nm which were significantly improved to 0.65-0.62 nm by using a higher Co sputtering power. Grazing incidence x-ray reflectometry, atomic force microscopy, transmission electron microscopy and x-ray diffraction measurements were used to study the multilayer structure and a more ordered polycrystalline structure was found in the multilayers deposited with higher Co power, which can explain the great improvement. The effect of Ar sputtering pressure on the layer structure was also studied. The measured soft x-ray reflectivity results indicated a high reflectivity of 18%-27.5% at 400-700 eV can be reached if a saturated number of bilayers of 50 were deposited.

Automated summary

A Co/Mg multilayer with optimized composition and structure was developed for high reflectivity in the broad soft x-ray range. The interface widths and ordered polycrystalline structure of the multilayers were significantly improved by using a higher Co sputtering power.