Improvement of high energy X-ray optical performance of W/Si supermirror by optimizing interface compounds using ultra-thin buffer layer

• Published in: Applied surface science 2024-06, Vol.657, p.159736, Article 159736
• Main Authors: Atwal, Simran, Sarkar, P., Bhattacharyya, K., Rao, P.N., Rai, S., Ghorai, Gurupada, Sahoo, P.K., Ghosh, S.K., Bhattacharyya, D., Biswas, A.
• Format: Article
• Language: English
• Subjects: Buffer layer; Interface compound; Interface diffusion; W/Si supermirror
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2024.159736

[Display omitted] •W/Si X-ray supermirror has been designed by block method and fabricated by IBS technique.•Improvement of X-ray optical property of W/Si periodic multilayer has been found by applying C buffer layer.•XPS measurement reveals drastic variation of chemical nature of interface when C buffer layer is applied.•High energy X-ray reflectivity of 36-layer W/Si supermirror also shows improvement using C buffer layer.•TEM measurement of supermirror confirms reduction of interface diffusion. The high energy spectral properties of X-ray supermirrors are governed mainly by the interface diffusion and compound formation at the interfaces. Using ion beam sputtering technique, a set of W/Si periodic multilayers with C buffer layer (BL) and without C BL have been prepared and the effect of BL has been studied by grazing incidence specular X-ray reflectivity, diffused X-ray scattering and X-ray photoelectron spectroscopy. Using C BL at the W-on-Si interfaces, reduction of interface diffusion and minimization of WSix formation at the interfaces has been observed though signature of carbide formation has been noticed. Using the results an interface diffusion model has been proposed explaining the effect of C BL. Block method of X-ray supermirror design has been effectively used for reducing the number of layers of W/Si supermirror targeting the improvement of the performance. Finally, 36-layer W/Si supermirror with C BL and without C BL have been fabricated and the performance evaluated by reflectivity measurement using 25 keV synchrotron X-rays and cross sectional TEM measurements. This study has both technological implication in X-ray optical devices and also offers atomistic insight into the mechanism of improvement of the interface quality by application of ultra-thin buffer layer.