Article Identification of the monolayer thickness difference in a mechanically exfoliated thick flake of hexagonal boron nitride and graphite for van der Waals heterostructures

Yoshiaki Hattori ; Takashi Taniguchi SAMURAI ORCID (National Institute for Materials Science) ; Kenji Watanabe SAMURAI ORCID (National Institute for Materials Science) ; Masatoshi Kitamura

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Yoshiaki Hattori, Takashi Taniguchi, Kenji Watanabe, Masatoshi Kitamura. Identification of the monolayer thickness difference in a mechanically exfoliated thick flake of hexagonal boron nitride and graphite for van der Waals heterostructures. Nanotechnology. 2023, 34 (29), 295701. https://doi.org/10.1088/1361-6528/accf23
SAMURAI

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(abstract)

Exfoliated flakes of layered materials, such as hexagonal boron nitride (hBN) and graphite with a thickness of several tens of nanometers, are used to construct van der Waals heterostructures. A flake with a desirable thickness, size, and shape is often selected from many exfoliated flakes placed randomly on a substrate using an optical microscope. This study examined the visualization of thick hBN and graphite flakes on SiO2/Si substrates through calculations and experiments. In particular, the study analyzed areas with different atomic layer thicknesses in a flake. For visualization, the SiO2 thickness was optimized based on the calculation. As an experimental result, the area with different thicknesses in a hBN flake showed different brightness in the image obtained using an optical microscope with a narrow band-pass filter. The maximum contrast was 12% with respect to the difference of one atomic layer thickness. In addition, hBN and graphite flakes were observed by differential interference contrast (DIC) microscopy. In the observation, the area with different thicknesses exhibited different brightnesses and colors. Adjusting the DIC bias had a similar effect to selecting a wavelength using a narrow band-pass filter.

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Keyword: Hexagonal boron nitride, van der Waals heterostructures, optical microscope

Date published: 2023-07-16

Publisher: IOP Publishing

Journal:

  • Nanotechnology (ISSN: 13616528) vol. 34 issue. 29 295701

Funding:

  • Chubei Itoh Foundation
  • Kansai Research Foundation
  • Japan Society for the Promotion of Science 21H04655
  • Hyogo Science and Technology Association
  • Iketani Science and Technology Foundation

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1088/1361-6528/accf23

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Updated at: 2025-02-15 12:30:44 +0900

Published on MDR: 2025-02-15 12:30:44 +0900

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