Enabling next-generation multilayer technology for high-energy x-ray telescopes

Résumé fourni par la source

NiCu/SiNₓ multilayers deposited by reactive magnetron sputtering from a novel split NiCu target are demonstrated as a viable route to broadband hard X-ray telescope optics beyond the 79 keV NuSTAR limit. The split target, equal areas of pure Ni and pure Cu, enables alloy co-sputtering without a pre-alloyed target, yielding amorphous, smooth films with interfacial roughness of 0.51–0.53 nm independent of thickness. A critical NiCu layer threshold of ~2.5 nm is identified, below which interface width rises to 0.75 nm. Four power-law depth-graded stacks (200 and 205 periods) were characterized by XRR at 8.048 keV and synchrotron reflectometry (3.4–10 keV, BESSY II). HAADF-STEM confirms well-ordered bilayers across the full ~1.2 µm depth (σ = 0.35–0.70 nm); EDS reveals ~69 at.% Cu / 31 at.% Ni from differential sputtering yields. Simulated reflectance exceeds 95% to ~55–75 keV, with interference fringes visible to 200 keV.

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