Thickness Mapping and Layer Number Identification of Exfoliated van der Waals Materials by Fourier Imaging Micro-Ellipsometry

Ralfy Kenaz; Saptarshi Ghosh; Pradheesh Ramachandran; Kenji Watanabe; Takashi Taniguchi; Hadar Steinberg; Ronen Rapaport

doi:10.1021/acsnano.2c12773

論文 Thickness Mapping and Layer Number Identification of Exfoliated van der Waals Materials by Fourier Imaging Micro-Ellipsometry

Ralfy Kenaz ; Saptarshi Ghosh ; Pradheesh Ramachandran ; Kenji Watanabe (National Institute for Materials Science) ; Takashi Taniguchi (National Institute for Materials Science) ; Hadar Steinberg ; Ronen Rapaport

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Ralfy Kenaz, Saptarshi Ghosh, Pradheesh Ramachandran, Kenji Watanabe, Takashi Taniguchi, Hadar Steinberg, Ronen Rapaport. Thickness Mapping and Layer Number Identification of Exfoliated van der Waals Materials by Fourier Imaging Micro-Ellipsometry. ACS Nano. 2023, 17 (10), 9188-9196. https://doi.org/10.1021/acsnano.2c12773

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(abstract)

As properties of mono- to few layers of exfoliated van der Waals heterostructures are heavily dependent on their thicknesses, accurate thickness measurement becomes imperative in their study. Commonly used atomic force microscopy and Raman spectroscopy techniques may be invasive and produce inconclusive results. Alternatively, spectroscopic ellipsometry is limited by tens-of-microns lateral resolution and/or low data acquisition rates, inhibiting its utilization for micro-scale exfoliated flakes. In this work, we demonstrate a Fourier imaging spectroscopic micro-ellipsometer with sub-5 microns lateral resolution along with fast data acquisition rate and present angstrom-level accurate and consistent thickness mapping on mono-, bi- and trilayers of graphene, hexagonal boron nitride and transition metal dichalcogenide (MoS2, WS2, MoSe2, WSe2) flakes. We show that the optical microscope integrated ellipsometer can also map minute thickness variations over a micro-scale flake. In addition, our system addresses the pertinent issue of identifying monolayer thick hBN

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