Low-energy ion polishing of Si in W/Si soft X-ray multilayer structures

R. V. Medvedev*, K. V. Nikolaev, A. A. Zameshin, D. Ijpes, I. A. Makhotkin, S. N. Yakunin, A. E. Yakshin, F. Bijkerk

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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The effect of ion polishing in sputter deposited W/Si multilayer mirrors with a d-spacing of 2.5 nm was studied. 0.1 to 0.5 nm of Si were etched with 100 eV Ar+ ions. This process resulted in a pronounced reduction in diffused scattering, measured at wavelengths about 0.1 nm. However, CuKa X-ray specular reflectivity and AFM showed only a marginal reduction of the roughness amplitude in the systems. Furthermore, the soft X-ray reflectivity at 0.84 and 2.4 nm did not show any changes after the ion polishing as compared to the nonpolished structures. Grazing incidence X-ray reflectivity (GIXR) analysis revealed that there was no pure W present in the deposited multilayers, with WSi2 being formed instead. As a result, it was concluded that the initial roughness in W/Si multilayers grown by magnetron sputtering is not the major factor in the reflectivity deviation from the calculated value for an ideal system. Nevertheless, the grazing incidence small-Angle X-ray scattering (GISAXS) analysis revealed that ion polishing reduces the vertical propagation of roughness from layer to layer by a factor of two, as well as favorably affecting the lateral correlation length and Hurst parameter. These improvements explain the reduction of diffused X-ray scattering at 0.1 nm by more than an order of magnitude, which is relevant for applications like high resolution XRD analysis.

Original languageEnglish
Article number045302
JournalJournal of Applied Physics
Issue number4
Early online date25 Jul 2019
Publication statusPublished - 28 Jul 2019


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