XXIX Symposium "Nanophysics and Nanoelectronics" in Nizhny Novgorod, March 10-14, 2025
Photonics

Applicability of white light interferometers for measuring the roughness of X-ray optical elements

M. M. Barysheva^ab, N. I. Chkhalo^ab, Yu. A. Vainer^a, M. V. Zorina^a, M. S. Mikhailenko^a, R. M. Smertin<sup>a

a</sup> Institute for Physics of Microstructures, Russian Academy of Sciences, Nizhnii Novgorod
^b National Research Lobachevsky State University of Nizhny Novgorod

Abstract: This study demonstrates the capability of modern white-light interferometry for reliable characterization of ultra-smooth silicon substrates with subnanometer surface roughness. To validate the accuracy of interference microscopy measurements in the mid-frequency spatial range, PSD functions of the substrate surface were analyzed using objectives with different magnifications. The results were cross-verified with atomic force microscopy and X-ray diffuse scattering with synchrotron source. The measured surface roughness was consistently determined to be 0.8 nm within the spatial frequency range of 1.5 $\times$ 10$^{-3}$–64 $\mu$m$^{-1}$, confirming the high precision of the applied interferometric techniques.

Keywords: surface roughness, white-light interferometry (WLI), power spectral density function (PSD), ultra-smooth surfaces, atomic force microscopy (AFM), X-ray diffuse scattering, mid-spatial frequencies.

Received: 02.06.2025
Revised: 02.06.2025
Accepted: 02.06.2025

DOI: 10.61011/JTF.2025.10.61342.141-25

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