A robust AFM-based method for locally measuring the elasticity of samples

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Local sample elasticity investigation is crucial across scientific disciplines.
• Previous work by Herruzo et al. (2014) established a method using frequency-modulation atomic force microscopy (FM-AFM) to determine local elasticity.
• The FM-AFM method demonstrated a linear relationship between the first and second flexural mode frequency shifts (Δf1 and Δf2^2).

Purpose of the Study:

• To propose and validate a novel method for determining sample elastic modulus using contact mode atomic force microscopy (C-AFM).
• To investigate the linear relationship between cantilever frequency shifts and applied load in C-AFM.
• To assess the elastic and plastic deformation behavior of various materials under C-AFM probing.

Main Methods:

• Utilized contact mode atomic force microscopy (C-AFM) to probe sample elasticity.
• Recorded cantilever first (Δf1) and second (Δf2) flexural mode frequency shifts as a function of Z-displacement (piezoelectric scanner).
• Applied a controlled load (F) to induce deformation and analyzed the resulting frequency shifts.

Main Results:

• A linear relationship was observed between Δf1 and Δf2^2 under a specific applied load (F) in C-AFM, similar to FM-AFM findings.
• The study identified and explained the occurrence of plastic deformation followed by elastic deformation during indentation.
• The method successfully determined the elastic modulus for polymers (polystyrene, polypropylene, LLDPE) and a self-assembled monolayer (FDTS).

Conclusions:

• The proposed C-AFM method provides a reliable approach for quantifying local sample elasticity.
• The established linear relation allows for accurate determination of the elastic modulus by analyzing frequency shifts and applied load.
• This technique offers a valuable tool for characterizing the mechanical properties of diverse materials at the nanoscale.