Background Pressure Induced Structural and Chemical Change in NiV/B4C Multilayers Prepared by Magnetron Sputtering

NiV/B 4 C 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/B 4 C 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/B 4 C multilayers when background pressure is high. The electron dispersive x-ray spectroscopy (EDX) of NiV/B 4 C 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/B 4 C multilayers, NiV coating, and B 4 C 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/B 4 C multilayers, the background pressure needs lower than 1 × 10 −4 Pa.