Application of contact-resonance AFM methods to polymer samples

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Contact-resonance Atomic Force Microscopy (CR-AFM) is utilized for measuring mechanical properties of stiff materials.
• CR-AFM offers significantly shorter acquisition times compared to techniques like force-distance curves.
• Existing CR-AFM data analysis involves tip positioning, normalized contact stiffness calculation, and calibration samples.

Purpose of the Study:

• To propose and validate an alternative CR-AFM data analysis procedure for determining elastic modulus.
• To investigate the suitability of CR-AFM for polymer sample analysis.
• To identify limitations and drawbacks of CR-AFM for specific material types.

Main Methods:

• Developed an alternative CR-AFM data analysis method based on fitting CR frequency versus load approximations.
• Evaluated CR-AFM's impact on sample surface, including wear and roughness changes.
• Performed point CR measurements on bulk and thin-film polymer samples.

Main Results:

• The proposed fitting method successfully determined the elastic modulus of bulk polystyrene and poly(methyl methacrylate).
• CR-AFM scanning under continuous contact was found to cause sample wear and surface alteration.
• CR-AFM exhibited poor resolution for moduli below approximately 10 GPa.

Conclusions:

• CR-AFM is not appropriate for polymer sample analysis due to limitations in resolution and a lack of comprehensive physical models.
• The developed analysis method provides an alternative for elastic modulus determination in CR-AFM.
• Further research is needed to address the dynamic response complexities of cantilevers in contact with samples.