Quantitative Nanoinfrared Spectroscopy of Anisotropic van der Waals Materials

Francesco L. Ruta, Aaron J. Sternbach, Adji B. Dieng, Alexander S. McLeod, D. N. Basov

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Anisotropic dielectric tensors of uniaxial van der Waals (vdW) materials are difficult to investigate at infrared frequencies. The small dimensions of high-quality exfoliated crystals prevent the use of diffraction-limited spectroscopies. Near-field microscopes coupled to broadband lasers can function as Fourier transform infrared spectrometers with nanometric spatial resolution (nano-FTIR). Although dielectric functions of isotropic materials can be readily extracted from nano-FTIR spectra, the in-and out-of-plane permittivities of anisotropic vdW crystals cannot be easily distinguished. For thin vdW crystals residing on a substrate, nano-FTIR spectroscopy probes a combination of sample and substrate responses. We exploit the information in the screening of substrate resonances by vdW crystals to demonstrate that both the in-and out-of-plane dielectric permittivities are identifiable for realistic spectra. This novel method for the quantitative nanoresolved characterization of optical anisotropy was used to determine the dielectric tensor of a bulk 2H-WSe2microcrystal in the mid-infrared.

Original languageEnglish (US)
Pages (from-to)7933-7940
Number of pages8
JournalNano Letters
Volume20
Issue number11
DOIs
StatePublished - Nov 11 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

Keywords

  • dielectric
  • identifiability
  • optics
  • SNOM
  • van der Waals
  • WSe

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