Abstract:
In this paper, the characteristics of a multilayer NiMo/C system, promising for Göebel-type mirrors, are investigated. The structures were synthesized by reactive magnetron sputtering in argon with pulsed nitrogen supply, the percentage of which in the chamber was equal to 15 and 30% of the total pressure of the working gas. The periods of multilayer structures $d\approx$ 41.5 and 33.5 $\mathring{\mathrm{A}}$ are calculated based on the actual systems of collimation and focusing of hard X-ray radiation in diffractometers of the DRON type (St. Petersburg). The effect of annealing at maximum temperatures of 250 and 320$^\circ$C on the reflective and structural properties of multilayer NiMo/C structures was studied. Based on the results of small-angle X-ray reflectometry at a wavelength of $\lambda$ = 0.154 nm, the structural parameters of NiMo/C were determined. It is shown that the values of the transition regions on the C and NiMo layers are in the range of 4–7 $\mathring{\mathrm{A}}$ and generally tend to decrease or fluctuate slightly after annealing. After annealing, the NiMo/C samples synthesized with a nitrogen content of 15% had reflection coefficients in the first order of $R$ = 78.8–76.1% for periods $d\approx$ 41.5–33.5 $\mathring{\mathrm{A}}$, respectively. For structures synthesized with 30% nitrogen content, $R$ = 81.4–77.4%. The high reflectivity of the multilayer NiMo/C structures allowed us to assert that it is a good alternative to the Göebel-type mirrors based on a pair of W/Si materials widely used in technology.
Keywords:multilayer X-ray mirrors, reactive magnetron sputtering, Göebel type mirrors.
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