Will Polycrystalline Platinum Tip Sliding on a Gold(111) Surface Produce Regular Stick-Slip Friction?

Area of Science:

• Tribology
• Materials Science
• Nanotechnology

Background:

• Atomic Force Microscopy (AFM) commonly exhibits stick-slip friction signals at the atomic scale.
• AFM metal tips are typically polycrystalline, influencing friction behavior on metal surfaces.

Purpose of the Study:

• To investigate the effect of polycrystalline tip geometry on friction using molecular dynamics (MD) simulations.
• To understand how tip microstructure influences stick-slip friction and substrate deformation.

Main Methods:

• Detailed molecular dynamics (MD) simulations were performed.
• Simulations modeled a polycrystalline platinum (Pt) tip sliding on a gold (Au(111)) surface.

Main Results:

• Polycrystalline Pt tips with multiple grains induced plastic deformation in the Au substrate, resulting in irregular stick-slip friction.
• A single-crystalline tip apex was necessary for clear, single atomic slip stick-slip friction.
• The single-crystalline tip showed tolerance to gold atom adhesion due to metal bonding.

Conclusions:

• Tip apex microstructure is critical for achieving atomic-scale stick-slip friction.
• Plastic deformation from polycrystalline tips disrupts regular friction signals.
• Tip mass also influences friction regime transitions, consistent with the Prandtl-Tomlinson model.