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arXiv · 2305.17031

Calibration method for complex permittivity measurements using s-SNOM combining multiple tapping harmonics

Dario Siebenkotten·Bernd Kaestner·Arne Hoehl·Shuhei Amakawa
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Abstract

Scattering-type scanning near-field optical microscopy (s-SNOM) enables sub-diffraction spectroscopy, featuring high sensitivity to small spatial permittivity variations of the sample surface. However, due to the near-field probe-sample interaction, the quantitative extraction of the complex permittivity leads to a computationally demanding inverse problem, requiring further approximation of the system to an invertible model. Black-box calibration methods, similar to those applied to microwave vector network analysers, allow the extraction of the permittivity without detailed electromagnetic modelling of the probe-sample interaction. These methods, however, are typically designed for stationary setups. In contrast, the distance between the sample and the probe tip of the s-SNOM is slowly modulated, which is required for the lock-in detection used to extract the near-field interaction buried in the far-field background. Here we propose an improved calibration method that explicitly takes probe tapping into account. We validate our method for an s-SNOM operating in a mid-infrared spectral range by applying it to measurements of silicon microstructures of different but well characterised doping.

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Dario Siebenkotten, Bernd Kaestner, Arne Hoehl, Shuhei Amakawa. 2023-05-26. Calibration method for complex permittivity measurements using s-SNOM combining multiple tapping harmonics. https://arxiv.org/abs/2305.17031

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