Lateral force microscopy of multiwalled carbon nanotubes

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Atomic Force Microscopy (AFM) is commonly used for imaging carbon nanotubes (CNTs).
• Non-contact mode is typical, but contact mode is crucial for mechanical and elasticity studies.
• Forces in contact mode, particularly lateral forces on CNTs, are not fully understood.

Purpose of the Study:

• To measure lateral forces acting on an AFM tip during contact mode imaging of a carbon nanotube.
• To investigate the dependence of these lateral forces on normal force and the ratio of nanotube diameter to tip radius.

Main Methods:

• Contact mode Atomic Force Microscopy (AFM) was employed.
• Lateral forces were measured during scanning across a carbon nanotube.
• A geometrical model was used to analyze the force data.

Main Results:

• Lateral force magnitude and sign were independent of scan direction.
• Lateral forces were attributed to the AFM tip slipping on the carbon nanotube's edges.
• A simple geometrical model successfully explained the lateral force signal for small nanotube diameter to tip radius ratios.

Conclusions:

• Lateral forces in AFM contact mode imaging of CNTs are primarily due to tip-edge interactions.
• The observed forces are predictable using a geometrical model under specific conditions.
• Understanding these forces is critical for accurate mechanical characterization of carbon nanotubes.