Interface engineered ultrashort period soft X-ray multilayers: Growth, characterization, and optical response

Dennis IJpes

Research output: ThesisPhD Thesis - Research UT, graduation UT

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Soft X-ray mirrors play a crucial role as optical components in various industrial and research applications, spanning from space astronomy and X-ray fluorescence (XRF) to synchrotron research. In all these applications, high reflectance of the mirror is critical in order to improve the performance of the optical system. These mirrors, technically known as multilayers, need to be extremely thin to efficiently reflect incident soft X-ray radiation. This requires a period of the multilayer on the order of 1-3 nanometers (nm). At this scale, the individual layers are only a few tenths of nm thick, approaching the limit of layers to grow a closed and continuous film.

The research described in this thesis aims to increase the reflectance of soft X-ray multilayers with periods from 2.5 nm down to 1.0 nm by gaining a deeper understanding of how these ultra-thin layers grow and interact. This involves using a combination of cutting-edge analytical techniques to obtain reliable information about the internal structure of these nanoscale multilayers. Additionally, the study uses techniques collectively referred to as "interface engineering" to reach a reflectance which is state-of-the-art. These techniques include the use of diffusion barrier layers, ion beam polishing, and seed layers.

The practical application of these techniques resulted in a substantial increase in reflectance for tungsten/silicon (W/Si), tungsten/boron carbide (W/B4C), and tungsten/aluminium (W/Al) soft X-ray multilayers. The investigation of the internal structure of these ultrathin multilayers contributed to an increased understanding of thin-film growth and layer interaction at the atomic scale. This thesis serves as a foundation for further studies on ultrashort period multilayers and offers a blueprint for scientists and engineers involved in the design and fabrication of soft X-ray optics.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Twente
  • Ackermann, Marcel David, Supervisor
  • Yakshin, Andrey, Co-Supervisor
Award date13 Dec 2023
Place of PublicationEnschede
Print ISBNs978-90-365-5926-3
Electronic ISBNs978-90-365-5927-0
Publication statusPublished - 13 Dec 2023


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