Fabrication thermal stability and reflectivity measurements of Mo/Si multilayers as x-ray mirrors and other optical components

摘要

Abstract: For the wavelength region above the Si-L edge normalincidence soft x-ray mirrors are produced with peakreflectivities around 55%. The Mo/Si multilayer systemsare fabricated by electron beam evaporation inultrahigh vacuum. Analysis of the quality of the stackis made by using an in situ monitoring system measuringthe reflection of the C-K line and ex situ grazingx-ray reflection of the Cu-K$-$alpha$/ line. Asmoothing of the boundaries and thereby a drasticenhancement of the reflectivity can be obtained bythermal treatment of the multilayer system duringgrowth. The microstructure of the multilayer systems isinvestigated by means of Rutherford Backscatteringspectroscopy (RBS) and Sputter/AES technique. Bakingthe final stack after deposition up to 900$DGR@C isapplied to study the thermal stability of the soft x-ray mirror. Near normal incidence mirrors even forshort wavelengths, e.g. the water window (2.4 - 4.4nm), are produced with a Mo/Si bilayer thickness of 2.6nm. An improvement in the quality of the interfaces forsuch ultrathin multilayer systems can be obtained bybombardment of the deposited layers with Ar$+$PLU$/ions as well as by thermal treatment of the multilayersystem and mixing of Mo and Si in the absorber layerduring the deposition run. We report on reflectivitymeasurements of the mirrors and their behavior aspolarizers and analyzers and on the diffractionefficiencies of laterally structured multilayer systemsas gratings.!11