Atomic-force-microscopy-based time-domain two-dimensional infrared nanospectroscopy

Area of Science:

• Spectroscopy
• Nanotechnology
• Materials Science

Background:

• Infrared (IR) spectroscopy advances spatial resolution and spectroscopic information.
• Atomic force microscopy (AFM) offers sub-10 nm spatial resolution, overcoming diffraction limits.
• 2D IR spectroscopy provides insights into molecular structures, coupling, and energy transfer.

Purpose of the Study:

• To integrate AFM's spatial precision with 2D IR spectroscopy's analytical power.
• To develop a novel nanospectroscopy technique for advanced material analysis.
• To investigate vibrational dynamics at the nanoscale.

Main Methods:

• Developed AFM-2DIR nanospectroscopy by combining AFM and 2D IR spectroscopy.
• Mechanically detected photothermal responses to tip-enhanced femtosecond IR pulses.
• Utilized Fourier Transforms (FFTs) to extract spatially resolved spectroscopic data.

Main Results:

• Elucidated vibrational anharmonicity in a carbonyl mode.
• Probed hyperbolic phonon polaritons in h¹⁰BN using tip-enhanced near-field photons.
• Observed energy transfer between phonon polaritons and phonons, and among polariton modes.

Conclusions:

• AFM-2DIR nanospectroscopy enables in situ investigation of vibrational anharmonicity, coupling, and energy transfer in nanostructures.
• The technique is suitable for unraveling relaxation processes in 2D materials at IR frequencies.
• This method bridges the gap between high-resolution imaging and detailed molecular spectroscopy.