Phonon Transport in Suspended Single Layer Graphene

TL;DR

This study measures how heat is conducted by phonons in suspended single-layer graphene across a wide temperature range, revealing a peak near 280K and highlighting the role of flexural phonons.

Contribution

First temperature-dependent phonon transport measurements in suspended Cu-CVD graphene from 15K to 380K, clarifying thermal conductance behavior and phonon contributions.

Findings

Thermal conductance peaks near 280K due to Umklapp process.

At low T, thermal conductivity scales as T^{1.5}.

Thermal conductance approaches ballistic limit for graphene.

Abstract

We report the first temperature dependent phonon transport measurements in suspended Cu-CVD single layer graphene (SLG) from 15K to 380K using microfabricated suspended devices. The thermal conductance per unit cross section $\sigma$/A increases with temperature and exhibits a peak near T~280K ($\pm$10K) due to the Umklapp process. At low temperatures (T<140K), the temperature dependent thermal conductivity scales as ~T^{1.5}, suggesting that the main contribution to thermal conductance arises from flexural acoustic (ZA) phonons in suspended SLG. The $\sigma$/A reaches a high value of 1.7$\times10^5 T^{1.5}$ W/m^2K, which is approaching the expected ballistic phonon thermal conductance for two-dimensional graphene sheets. Our results not only clarify the ambiguity in the thermal conductance, but also demonstrate the potential of Cu-CVD graphene for heat related applications.