Implementing 0.1 nm B4C barriers in ultrashort period 1.0 nm W/Si multilayers for increased soft x-ray reflectance

Dennis IJpes*, Andrey Yakshin, J.M. Sturm, Marcelo Ackermann

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)
26 Downloads (Pure)


Ultrashort period 1.0 nm W/Si multilayers have potential as dispersive Bragg reflectors in high-resolution x-ray fluorescence. However, formation of WSix leads to poor optical performance. To address this, we introduce ultrathin 0.1 nm B4C diffusion barriers in sputter-deposited 1.0 nm W/Si, inhibiting W–Si interaction. We demonstrate that the peak reflectance at a wavelength of 0.834 nm increased with a factor of 3.4 compared to W/Si. Diffuse scattering measurements reveal no change in interfacial roughness when applying B4C barriers compared to W/Si. X-ray reflectivity analysis shows a substantial increase in optical contrast between Si and W as well as sharper transitions between the layers. Chemical analysis suggests that the B4C barrier reduces formation of WSix through partial substitution of W-silicide bonds with
W-carbide/boride bonds, leading to an increase in optical contrast. The resulting structure of W/Si with B4C barriers offers a compelling alternative to the more established W/B4C multilayer at the ultrashort scale due to its superior soft- and hard x-ray reflectance.
Original languageEnglish
Article number245301
Number of pages9
JournalJournal of Applied Physics
Issue number24
Publication statusPublished - 28 Jun 2023


  • Multilayer
  • Reflectance
  • UT-Hybrid-D


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