Advanced multilayer Laue lens fabrication at NSLS-II

In an ongoing effort to advance the state of the art in x-ray nanofocusing optics [1], multilayer Laue lens (MLL) [2,3] fabrication at NSLS-II has matured to include multi-gas reactive sputtering for stress and interfacial roughness reduction, which has recently led to a 70 micron thick single-growth MLL. Reactive sputtering was found to produce WSi2/Si multilayers with an accumulated film stress significantly lower than Ar-only deposition with identical growth conditions. Significant effort has been focused on the achievement of highly-stable gas mixing and process gas pressure measurement for multilayer growth and the problems faced along with implemented solutions will be discussed in detail. Proper layer thickness and placement throughout the stack presents a major obstacle to the fabrication of high-quality nanofocusing MLLs. Initial metrology of extremely thick MLLs by stitching many scanning electron microscope images was found to be greatly simplified by inclusion of marker labels within the stack.