Depth-graded Mo/Si multilayer coatings for hard x-rays.

This manuscript presents the first systematic study of non-periodic, broadband Mo/Si multilayer coatings with and without B4C interface barrier layers for hard x-ray applications with large field of view. The photon energy of operation in this work is 17.4 keV, the Mo K alpha emission line. The coatings involve layers with varying thicknesses in the nanometer scale and the behavior at the layer interfaces plays a crucial role in their performance. Reflectivity measurements and modeling at 8.05 keV and 17.4 keV, Transmission Electron Microscopy (TEM), as well as thin film stress measurements, are employed to examine and optimize the reflective performance of these coatings and the physics of their constituent layers and interfaces. Mo/Si with B4C barrier layers on the Mo-on-Si interface is shown to produce the highest reflectivity among all design configurations considered in this work. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement