Abstract
NiV/B4C multilayers with a small d-spacing are suitable for multilayer monochromator working at a photon energy region from 5 to 8 keV, or photon energy region from 10 to 100 keV. To investigate the influence of background pressure during fabrication, NiV/B4C multilayers with a d-spacing of 3.0 nm were fabricated by magnetron sputtering with different background pressures. The grazing incidence x-ray reflectivity (GIXR) and transmission electron microscopy (TEM) measurement illustrated the structural change that happened in NiV/B4C multilayers when background pressure is high. The electron dispersive x-ray spectroscopy (EDX) of NiV/B4C multilayer deposited with a high background pressure suggests a gradient distribution of oxygen, which corresponds to the gradient thickness change. The detailed x-ray absorption near edge spectroscopy (XANES) comparison of NiV/B4C multilayers, NiV coating, and B4C coating showed the chemical state change induced by background pressure. We concluded that during the deposition, vanadium oxide promoted the oxidation of boron. In order to fabricate a good performance of NiV/B4C multilayers, the background pressure needs lower than 1 × 10−4 Pa.
Highlights
Multilayer interference coating is an important optics in the hard x-ray region, which enables the reflection of the short-wavelength light beyond the total external reflection region, and chooses a narrow-band spectrum from the white light radiation
With the background pressure decreasing from 4 × 10−4 to 1 × 10−4 Pa, the grazing angles of Bragg peaks kept increasing, which means the d-spacing of multilayer becomes thinner
The fitted curve matched very well with grazing incidence x-ray reflectivity (GIXR) measurement result, which means the fitted model is in agreement with the deposited layer structure, and the bandwidth of the measured Bragg peaks is similar with the fitted curve, which indicates the good uniformity of 60 bilayers
Summary
Multilayer interference coating is an important optics in the hard x-ray region, which enables the reflection of the short-wavelength light beyond the total external reflection region, and chooses a narrow-band spectrum from the white light radiation. As photon energy requirement of synchrotron radiation facilities and space telescopes extends to several tens of kiloelectron volts, the multilayer working at such wavelength region requires an extremely small d-spacing which is less than 3.0 nm [4–7] This makes the x-ray reflectance very sensitive to the interface and surface quality of the multilayer, which needs the more precise control of fabrication and the more suitable selection of materials. Nickel is one of the ideal absorption materials in the whole hard x-ray region, except for 8.3 keV (Ni K-edge) [12, 13], but nickel is a magnetic material, which is not compatible with magnetron sputtering for small d-spacing multilayers For solving this problem, a nonmagnetic alloy was made up of 93% nickel, and 7% vanadium has been proposed (in the following article, we will use NiV instead of the more correct Ni93V7). Apart from that, the detailed studies on NiV/B4C multilayers were really limited, especially on how to fabricate this promising X-ray multilayer mirror
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
