Experimental study of Cr∕Sc multilayer mirrors for the nitrogen Kα-emission line

The authors present an experimental study of Cr∕Sc multilayer mirrors optimized for the detection of the nitrogen Kα-emission line (λ=3.16nm) at a grazing incidence around 23°, for electron probe microanalysis applications. The multilayers were deposited onto silicon substrates using a dc magnetron sputtering system. They were characterized with grazing incidence copper Kα x-ray reflectometry and atomic force microscopy, as well as with at-wavelength reflectometry using synchrotron radiation. These various characterization methods pointed out that the interfacial roughness of these multilayers increases drastically with the number of bilayers. Growth parameters were then optimized, and it is shown that the structure and reflectivity of such multilayers can be considerably improved by optimizing the sputter gas pressure during the deposition process. Reflectivity higher than 37% were measured at 22.3° grazing angle for the nitrogen Kα-emission line.