Force Volume Atomic Force Microscopy-Infrared for Simultaneous Nanoscale Chemical and Mechanical Spectromicroscopy

Area of Science:

• Nanotechnology
• Spectroscopy
• Materials Science

Background:

• Photothermal atomic force microscopy-infrared (AFM-IR) integrates AFM's spatial resolution with IR spectroscopy's chemical identification.
• Existing AFM-IR modes (contact, tapping, peak force tapping) have limitations regarding tip wear, sample damage, or spatial resolution.

Purpose of the Study:

• Introduce a novel force volume AFM-IR variant.
• Overcome limitations of existing AFM-IR techniques.
• Enhance nanoscale chemical imaging and material property sensing.

Main Methods:

• Developed a force volume AFM-IR mode with engage, hold, and retract segments per pixel.
• Utilized IR laser pulsing during the constant-force hold segment for resonance-enhanced detection.
• Incorporated infrared laser repetition rate sweeping for contact resonance curves and Q-factor analysis.
• Enabled variable probing depth control and surface-sensitive detection.

Main Results:

• Achieved sub-10 nm spatial chemical resolution with monolayer sensitivity.
• Demonstrated simultaneous nanomechanical property sensing and precise force control.
• Eliminated lateral forces, reducing tip wear and sample damage compared to contact mode.
• Provided alternative to conventional frequency tracking by analyzing contact resonance curves.

Conclusions:

• Force volume AFM-IR offers a valuable new approach for nanoscale chemical and mechanical characterization.
• The technique integrates high resolution, sensitivity, and reduced sample interaction.
• This method is poised to become a significant addition to established AFM-IR modalities.