Bimodal Phonon Scattering in Graphene Grain Boundaries

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Graphene's electrical and mechanical properties concerning grain boundaries (GBs) are well-studied.
• Direct measurements correlating thermal transport with graphene GBs have been lacking.

Purpose of the Study:

• To experimentally measure and compare thermal transport in supported single crystalline graphene with that across individual graphene GBs.
• To investigate the underlying mechanisms responsible for thermal resistance at graphene GBs.

Main Methods:

• Simultaneous comparison of thermal transport in supported single crystalline graphene and across an individual graphene GB.
• Boltzmann transport modeling to analyze phonon scattering phenomena.
• Nonequilibrium molecular dynamics simulations to assess GB disorder.

Main Results:

• Thermal conductance across isolated graphene GBs was found to be up to an order of magnitude lower than theoretical predictions.
• A novel bimodal phonon scattering mechanism was identified, influenced by GB structure and mismatch.
• Boundary roughness scattering dominates low-mismatch GBs, while disordered regions impede transport in higher-mismatch GBs.

Conclusions:

• Graphene GBs significantly impede thermal transport, with thermal conductance values lower than anticipated.
• The study reveals a new phonon scattering phenomenon at GBs, crucial for understanding thermal transport in 2D materials.
• GB disorder is identified as a key factor determining thermal resistance across these boundaries.