title: Broadband infrared vibrational nano-spectroscopy using thermal blackbody radiation.
abstract: Infrared vibrational nano-spectroscopy based on scattering scanning near-field optical microscopy (s-SNOM) provides intrinsic chemical specificity with nanometer spatial resolution. Here we use incoherent infrared radiation from a 1400 K thermal blackbody emitter for broadband infrared (IR) nano-spectroscopy. With optimized interferometric heterodyne signal amplification we achieve few-monolayer sensitivity in phonon polariton spectroscopy and attomolar molecular vibrational spectroscopy. Near-field localization and nanoscale spatial resolution is demonstrated in imaging flakes of hexagonal boron nitride (hBN) and determination of its phonon polariton dispersion relation. The signal-to-noise ratio calculations and analysis for different samples and illumination sources provide a reference for irradiance requirements and the attainable near-field signal levels in s-SNOM in general. The use of a thermal emitter as an IR source thus opens s-SNOM for routine chemical FTIR nano-spectroscopy.
authors.forename: Brian T
authors.initials: BT
authors.lastname: O'Callahan
authors.forename: William E
authors.initials: WE
authors.lastname: Lewis
authors.forename: Silke
authors.initials: S
authors.lastname: Möbius
authors.forename: Jared C
authors.initials: JC
authors.lastname: Stanley
authors.forename: Eric A
authors.initials: EA
authors.lastname: Muller
authors.forename: Markus B
authors.initials: MB
authors.lastname: Raschke