Velocity-dependent friction enhances tribomechanical differences between monolayer and multilayer graphene

Area of Science:

• Materials Science
• Nanotechnology
• Tribology

Background:

• Understanding nanoscale friction is crucial for designing advanced materials and devices.
• Graphene's unique properties make it a promising material for micro/nanoelectromechanical systems (MEMS/NEMS).
• The relationship between sliding speed and friction at the nanoscale is complex and not fully understood.

Purpose of the Study:

• To investigate the influence of sliding speed on nanoscale friction forces between a silicon tip and graphene.
• To explore the layer-dependent behavior of friction in monolayer and multilayer graphene.
• To model and explain the observed friction dynamics using a theoretical framework.

Main Methods:

• Utilized Atomic Force Microscopy (AFM) to measure nanoscale friction forces.
• Experimentally varied sliding speeds to observe changes in friction.
• Employed the thermally activated Prandtl-Tomlinson model for theoretical analysis.

Main Results:

• Friction forces exhibit a linear increase with the logarithm of sliding speed.
• This velocity dependence is significantly amplified in monolayer graphene compared to multilayers.
• The amplification is attributed to tip-induced corrugation in the interaction potential, affecting atomic hopping dynamics.
• The Prandtl-Tomlinson model successfully explained experimental observations and allowed parameter extraction.

Conclusions:

• Sliding speed has a pronounced, layer-dependent effect on nanoscale graphene friction.
• Thermally activated processes and tip-induced surface dynamics play a key role in friction at the nanoscale.
• Contact stiffness is a dominant factor in slip event frequencies, independent of graphene layer count.