Alloy-ceramic oxide multilayer mirrors for water-window soft x rays

Alloy-ceramic oxide multilayers of Ni(80)Nb(20)- MgO with 3.56-nm period have been made by use of the pulsed-laser deposition technique and characterized by means of grazing-incidence x-ray reflectivity. The interface roughness was found to be only ~0.35 nm at the two interfaces, Ni(80)Nb(20)- MgO and MgO-Ni(80)Nb(20), leading to a peak reflectivity of ~38% at the first order. The atomic structure in the two individual layers, Ni(80)Nb(20) and MgO, is found to be amorphous, in agreement with the deposition conditions. These multilayers can be used as mirrors for soft x rays in the angular range 18 degrees to 39 degrees , depending on the actual wavelength of radiation in the water-window region.