Fig. 5

Multimodal capability of PF-SNOM with correlative mechanical, electrical, and optical near-field measurements. a Topography of a multi-layer hyperbolic boron nitride (h-BN) on an Si substrate. The scale bar is 400 nm and is the same for b−f. b Logarithmic modulus map of h-BN and Si surface. c Map of adhesion between the tip and the sample surface. d Electrical contact current between the tip and the sample surface measured in the peak force tapping (PFT) operation. e−f Peak force scattering-type scanning near-field optical microscopy (PF-SNOM) images at 1530 and 1560 cm⁻¹ infrared frequencies. Phonon polaritons of h-BN are revealed. Every pixel in the PF-SNOM images is an averaged signal of 150 PFT cycles. g Profiles of topography (black) overlaid with electrical current (red), the profile is averaged across the interface between h-BN and Si from an area shown as a white dashed box in e. h Average profiles of PF-SNOM responses of 1530 cm⁻¹ (red) and 1560 cm⁻¹ (blue) from the white dashed box in e. The spatial periods of polaritonic patterns of h-BN are found to be 128 nm for 1530 cm⁻¹ and 104 nm for 1560 cm⁻¹, which correspond to the half wavelength of phonon polariton wave in h-BN