Theoretical analysis of optically selective imaging in photoinduced force microscopy

Area of Science:

• Nanoscience
• Spectroscopy
• Materials Science

Background:

• Photoinduced Force Microscopy (PiFM) is a powerful technique for nanoscale imaging.
• Understanding the electric field interactions in composite molecular systems is crucial for advanced material characterization.

Purpose of the Study:

• To theoretically investigate the sensitivity and capabilities of PiFM for composite molecular systems.
• To explore the potential of PiFM for observing forbidden optical electronic transitions and resolving nanoscale features.

Main Methods:

• Utilized discrete dipole approximation to calculate the self-consistent response electric field.
• Modeled the PiFM tip, substrate, and composite molecules interactions.
• Investigated wavelength dependence of PiFM for dimer molecules.

Main Results:

• Demonstrated significantly higher PiFM sensitivity on resonant molecules due to localized electric field enhancement.
• Achieved high-resolution observation of forbidden optical electronic transitions in dimer molecules.
• Revealed drastic changes in PiFM images with incident light wavelength, correlating with electric field structures.

Conclusions:

• PiFM exhibits enhanced sensitivity beyond the traditional z^-4 dependence for resonant molecules.
• PiFM provides multifaceted information on nanomaterials by probing microscopic light-matter interactions.
• This study highlights PiFM's capability to resolve features beyond optical diffraction limits, including forbidden transitions.