The Ta/Cr/Pt three-layer system can be used as a planar x-ray waveguide, that is to say it can guide an x-ray beam inside its chromium layer. This property comes from the difference in density and hence in optical index between the two “heavy” or cladding tantalum and platinum layers and the “light” or guiding chromium layer. The waveguide will be efficient provided the layers are a few nanometers thick and that the interfaces are as sharp as possible. To control the quality of the stack, we combine grazing incidence x-ray fluorescence (GIXRF) and x-ray reflectivity (XRR) measurements on a series of Ta/Cr/Pt samples, whose only difference is the thickness of the Cr layer. The three considered samples have been deposited by magnetron sputtering and their designed structures are: Ta (8 nm)/Cr (5, 10, and 15 nm)/Pt (14 nm)/Si substrate. The combination of XRR and GIXRF tightens constraints on the parameters used to simulate the stack: thickness, roughness, composition, and density of the layers and their interlayers. For each sample we used six GIXRF curves obtained from three different characteristic x-ray lines (Ta Lα, Cr Kα, and Pt Lβ_2,15) excited at three different incident photons energies (6.25, 10, and 12 keV) as well as one XRR curve obtained at 6.25 keV. The XRR-GIXRF combined analysis demonstrates that the Ta/Cr/Pt structure is too simplistic and that it is necessary to introduce some interlayers at the top and bottom of the stacks to obtain a reliable agreement between the experimental and simulated GIXRF and XRR curves.

中文翻译：

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Ta/Cr/Pt 薄膜叠层的 X 射线反射率和掠入射 X 射线荧光联合研究

Ta/Cr/Pt三层系统可以用作平面X射线波导，也就是说它可以在其铬层内部引导X射线束。该特性来自于两个“重”或包覆钽和铂层与“轻”或引导铬层之间的密度差异以及光学指数的差异。如果层的厚度为几纳米并且界面尽可能尖锐，则波导将是高效的。为了控制叠层的质量，我们对一系列 Ta/Cr/Pt 样品进行掠入射 X 射线荧光 (GIXRF) 和 X 射线反射率 (XRR) 测量，其唯一的区别是 Cr 层的厚度。所考虑的三个样品是通过磁控溅射沉积的，其设计结构为：Ta (8 nm)/Cr (5、10 和 15 nm)/Pt (14 nm)/Si 基底。XRR 和 GIXRF 的结合加强了对用于模拟堆叠的参数的约束：层及其夹层的厚度、粗糙度、成分和密度。对于每个样品，我们使用从三种不同的特征 X 射线线（Ta Lα、Cr Kα 和 Pt Lβ _2,15）获得的 6 条 GIXRF 曲线，这些特征 X 射线线在三种不同的入射光子能量（6.25、10 和 12 keV）以及一条在 6.25 keV 处获得的 XRR 曲线。XRR-GIXRF 组合分析表明，Ta/Cr/Pt 结构过于简单，有必要在堆叠的顶部和底部引入一些中间层，以获得实验和模拟的 GIXRF 和 XRR 曲线之间的可靠一致性。