Recent advances in development of Cr/Sc based reflective multilayer coatings for x-ray applications - Institut d'Optique Graduate School Access content directly
Conference Papers Year : 2018

Recent advances in development of Cr/Sc based reflective multilayer coatings for x-ray applications

Abstract

Many scientific and industrial applications in x-ray range require the use of reflective multilayer coatings with a good efficiency and stability and often of a particular spectral band width. Here we report on recent advances in optimization of Cr/Sc-based multilayer systems for various x-ray applications. We have investigated and developed several approaches to design periodic and aperiodic multilayer mirrors using as a base the Cr/Sc pair of materials. A method to characterize sub-nanometric layers based on grazing incidence X-ray reflectometry has been proposed and tested experimentally. We have elaborated a certain number of periodic and large-band aperiodic multilayer mirrors for plasma diagnostics at grazing incidence in the hard x-ray range between 2 to 10 keV [1]. The development of efficient normal incidence optics in the soft x-ray range remains quite a challenge. Proposed more than 20 years ago as a most promising system for the water- window range, the Cr/Sc multilayer could provide about 60% peak theoretical reflectance at near-normal incidence around the Sc L2,3 edge at 397 eV. However, the values of measured reflectance of Cr/Sc multilayers achieved so far are much lower than predicted because of a number of reasons. Apart of the problem of stability while depositing several hundreds of sub-nanometer layers, the most significant reflectivity loss is caused by formation of a rough interface as a result of the material interdiffusion. We studied an influence of boron carbide (B4C) introduced in the multilayer structure as a barrier layer or a third material and an effect of nitridation of chrome layers during deposition on optical and structural properties of the Cr/Sc reflective coatings with the aim to improve the performance of multilayer mirrors in the water-window range. Several sets of Cr/Sc-based multilayer mirrors were deposited by magnetron sputtering and characterized by using both soft and hard x-ray reflectivity techniques. Complementary analysis of the structural parameters was performed by using the x-ray reflectivity and standing waves enhanced x-ray fluorescence techniques later on [2]. The normal incidence reflectivity was measured at the metrology beamline of Soleil synchrotron [3]. We will demonstrate that combining both effects (the nitridation of Cr and the use of B4C barrier layers), we have been able to produce a new multilayer system (CrNx∕B4C∕Sc) with the peak reflectance as high as 23% measured at near normal incidence of 85.7° around the photon energy of 397 eV.
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Dates and versions

hal-04549859 , version 1 (17-04-2024)

Identifiers

  • HAL Id : hal-04549859 , version 1

Cite

Evgueni Meltchakov, Catherine Burcklen, Sébastien de Rossi, Charles Bourassin-Bouchet, Jennifer Rebellato, et al.. Recent advances in development of Cr/Sc based reflective multilayer coatings for x-ray applications. PXRNMS (Physics of X-ray and Neutron Multilayer Structures) 2018, Laboratoire Charles Fabry, Institut d'Optique Graduate School, Université Paris-Saclay; Laboratoire de Chimie Physique Matière et Rayonnement, Sorbonne Université; CNRS, Nov 2018, Palaiseau, France. ⟨hal-04549859⟩
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