Optical contrast and refractive index of natural van der Waals heterostructure nanosheets of franckeite

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Patricia Gant ; Foad Ghasemi ; David Maeso ; Carmen Munuera ; Elena López-Elvira ; Riccardo Frisenda ; David Pérez De Lara ; Gabino Rubio-Bollinger ; Mar Garcia-Hernandez ; Andres Castellanos-Gomez (2017)
  • Publisher: Beilstein-Institut
  • Journal: Beilstein Journal of Nanotechnology, volume 8, pages 2,357-2,362 (issn: 2190-4286, eissn: 2190-4286)
  • Related identifiers: doi: 10.3762/bjnano.8.235, pmc: PMC5687002
  • Subject: TP1-1185 | Nanoscience | complex refractive index | franckeite | Technology | optical identification | Full Research Paper | Q | T | Science | Physics | Nanotechnology | Chemical technology | van der Waals heterostructure | QC1-999 | optical contrast

We study mechanically exfoliated nanosheets of franckeite by quantitative optical microscopy. The analysis of transmission-mode and epi-illumination-mode optical microscopy images provides a rapid method to estimate the thickness of the exfoliated flakes at first glance. A quantitative analysis of the optical contrast spectra by means of micro-reflectance allows one to determine the refractive index of franckeite over a broad range of the visible spectrum through a fit of the acquired spectra to a model based on the Fresnel law.
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