Thermal Conductivity and Thermal Rectification in Graphene Nanoribbons: a Molecular Dynamics Study

TL;DR

This study uses molecular dynamics to analyze thermal conductivity and rectification in graphene nanoribbons, revealing edge effects, defect impacts, and significant rectification in asymmetric structures.

Contribution

It provides detailed molecular dynamics insights into how edge chirality, shape, and defects influence thermal properties and rectification in graphene nanoribbons.

Findings

Zigzag edges have higher thermal conductivity than armchair edges.

Asymmetric nanoribbons exhibit significant thermal rectification.

Defects reduce thermal conductivity but not rectification.

Abstract

We have used molecular dynamics to calculate the thermal conductivity of symmetric and asymmetric graphene nanoribbons (GNRs) of several nanometers in size (up to ~4 nm wide and ~10 nm long). For symmetric nanoribbons, the calculated thermal conductivity (e.g. ~2000 W/m-K @400K for a 1.5 nm {\times} 5.7 nm zigzag GNR) is on the similar order of magnitude of the experimentally measured value for graphene. We have investigated the effects of edge chirality and found that nanoribbons with zigzag edges have appreciably larger thermal conductivity than nanoribbons with armchair edges. For asymmetric nanoribbons, we have found significant thermal rectification. Among various triangularly-shaped GNRs we investigated, the GNR with armchair bottom edge and a vertex angle of 30{\deg} gives the maximal thermal rectification. We also studied the effect of defects and found that vacancies and edge roughness in the nanoribbons can significantly decrease the thermal conductivity. However, substantial thermal rectification is observed even in the presence of edge roughness.