Comparative Study of Pd/B4C X-ray Multilayer Mirrors Fabricated by Magnetron Sputtering with Kr and Ar Gas

• Published in: Materials Vol. 13; no. 20; p. 4504
• Main Authors: Ni, Hangjian, Huang, Qiushi, Liu, Genchang, Qi, Runze, Zhang, Zhong, Li, Xiuhong, Li, Zhongliang, Wang, Jie, Wang, Zhanshan
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 11.10.2020; MDPI
• Subjects: Boron carbide; Comparative studies; Energy; Gases; hard X-ray; heavy noble gas; interface quality; Interface roughness; Interfaces; Magnetron sputtering; Morphology; multilayer; Multilayers; Pd/B4C; Radiation; Rare gases; Space telescopes; Spectrum analysis; X ray mirrors
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma13204504

Ultrathin Pd/B4C multilayers are suitable X-ray mirrors working at the photon energy region of 7–20 keV. To further improve the layer structure, Pd/B4C multilayers with a d-spacing of 2.5 nm were fabricated by magnetron sputtering using the heavy noble gas Kr and compared with the conventional ones fabricated by Ar. Although the Kr-sputtering process can work at a lower pressure, the interface width—especially the interface roughness—is a little larger than that made by Ar. A stronger polycrystallization and a lower content of sputter gas atoms were found in the Kr-made sample, which can be explained by the joint effect from less recoiled particles and lower sputtering pressure. A good reflectance of 68% of the Kr made multilayer was measured at 10 keV, which is only slightly lower than that of the Ar made sample (71%).