X-ray broadband Ni/SiC multilayers: improvement with W barrier layers

Abstract

We present an experimental study and performance improvement of periodic and aperiodic Ni/SiC multilayer coatings. Periodic Ni/SiC multilayer mirrors have been coated and characterized by grazing incidence X-ray reflectometry at 8.048 keV (Cu Kα radiation) and by measurements at 3 keV and 5 keV on synchrotron radiation facilities. An interdiffusion effect is found between Ni and SiC layers. A two-material model, Ni(x)Si(y)/SiC, using a silicide instead of Ni, was used to fit the measurements. The addition of 0.6 nm W barrier layers at the interfaces allows a significant reduction of the interdiffusion between Ni and SiC. In order to obtain a specific reflectivity profile in the 2 - 8 keV energy range, we have designed and coated aperiodic multilayer mirrors by using Ni/SiC with and without W barrier layers. The experimental reflectivity profiles as a function of the photon energy were measured on a synchrotron radiation facility in both cases. Adding W barrier layers in Ni/SiC multilayers provides a better precision on the layer thicknesses and a very good agreement between the experimental data and the targeted spectral profile.

Investigation of NiV-based multilayers for the high energy x-ray probe

“…In the pure Ar coatings, the Si layer density is fixed to that of the nominal density of silicon in the LLNL database (2.33 g/cm 3 ). The NiV layers density are allowed to vary for all measurements, but expect to be near nominal density (8.79 g/cm 3 ), though B. Emprin et al 14 has reported Ni densities at 7.2 g/cm 3 at 8.0 keV. The silicon that is sputtered in a reactive Ar/N 2 atmosphere is varied, since it is reported to chemically change to silicon nitride which has a nominal density a 3.17 g/cm 3 .…”

Assessment of Potential of the High-Voltage Anodic Plasma Source to Deposit Multilayer Structures Relevant to X-ray Mirror Applications

“…The current literature presents several material pairs investigated for applications in X-ray optics, including W/Si [4], Pt/C [5], Ni/SiC [6], Ir/B 4 C [7], W/B 4 C [8], and W/Sc [9]. Many authors observed interlayer mixing between the used pair materials, and have therefore involved separation/barrier layers from low-segregation materials.…”

“…Many authors observed interlayer mixing between the used pair materials, and have therefore involved separation/barrier layers from low-segregation materials. Emprin et al [6] used W to improve the X-ray reflectivity (XRR) of Ni/SiC multilayers. Although multilayer performance was not improved by the addition of W barrier layers, the authors showed very good agreement between modelled and experiment XRR results.…”