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. Author manuscript; available in PMC: 2020 Nov 19.
Published in final edited form as: Chem Soc Rev. 2020 May 19;49(11):3315–3347. doi: 10.1039/c8cs00916c

Fig. 6.

Fig. 6

(a) AFM topography of five representative hexagonal boron-nitride (hBN) frustums with different aspect ratio (Ar = d/t). All the frustums have a height of 256 nm ± 4 nm. Scale bars 300 nm. (b) AFM-IR absorption spectra (p-polarization) obtained by positioning the AFM tip at the center of representative frustums, as indicated in panel-a. The schematic of the incident polarization used for the measurements, along with the depiction of the quantities t and d, are provided as an inset. (c) AFM-IR maps (scale bars 200 nm) at selected wavelengths highlighting near-field patterns of the hBN polaritons for the Ar = 2.34 frustum.63 These AFM-IR experiments were obtained in ringdown mode. Adapted with permission from L. V. Brown, Nano Lett., 2018, 18, 1628–1636. Copyright (2018) American Chemical Society. The AFM-IR images at 1408 cm−1 and 1464 cm−1 are from the same dataset reported by Brown et al. but have not been published previously.