Role of remote interfacial phonon (RIP) scattering in heat transport across graphene/SiO2 interfaces

TL;DR

This study introduces a new measurement technique, VMTR, to quantify heat transfer at graphene/SiO2 interfaces, revealing that remote interfacial phonon scattering contributes less than 2% to interfacial heat transfer even at high carrier densities.

Contribution

The paper develops VMTR, a novel pump-probe method, to measure electrostatically modulated interfacial thermal conductance, providing new insights into RIP scattering's role in heat transfer.

Findings

Interfacial thermal conductance increases by up to 0.8 MW/m^2K under electrostatic fields.

RIP scattering accounts for less than 2% of heat transfer at the interface.

Electrostatic pressure may improve interface conformity, affecting heat transfer.

Abstract

Heat transfer across interfaces of graphene and polar dielectrics (e.g. SiO2) could be mediated by direct phonon coupling, as well as electronic coupling with remote interfacial phonons (RIPs). To understand the relative contribution of each component, we develop a new pump-probe technique, called voltage-modulated thermoreflectance (VMTR), to accurately measure the change of interfacial thermal conductance under an electrostatic field. We employed VMTR on top gates of graphene field-effect transistors and find that the thermal conductance of SiO2/graphene/SiO2 interfaces increases by up to {\Delta}G=0.8 MW m-2 K-1 under electrostatic fields of <0.2 V nm-1 . We propose two possible explanations for the observed {\Delta}G. First, since the applied electrostatic field induces charge carriers in graphene, our VMTR measurements could originate from heat transfer between the charge carriers in graphene and RIPs in SiO2. Second, the increase in heat conduction could be caused by better conformity of graphene interfaces un-der electrostatic pressure exerted by the induced charge carriers. Regardless of the origins of the observed {\Delta}G, our VMTR measurements establish an upper limit for heat transfer from unbiased graphene to SiO2 substrates via RIP scattering; i.e., only <2 % of the interfacial heat transport is facilitated by RIP scattering even at a carrier concentration of 4x10^12 cm-2.