Ballistic Transport Enhanced Heat Convection at Nanoscale Hotspots

TL;DR

This study experimentally investigates nanoscale heat convection at hotspots generated by plasmonic heating in graphene supported by gold nanorods, revealing convection's significant role in thermal management of miniaturized devices.

Contribution

First experimental measurement of convective heat transfer coefficient at nanoscale hotspots, highlighting the role of ballistic convection and plasmonic heating in heat dissipation.

Findings

Convective heat transfer coefficient is about 1000 times higher than natural convection.

Heat convection accounts for over half of the total heat transfer at the interface.

Ballistic gas molecule convection and plasmonic hotspots significantly enhance heat dissipation.

Abstract

Along with device miniaturization, severe heat accumulation at unexpected nanoscale hotspots attracts wide attentions and urges efficient thermal management. Heat convection is one of the important heat dissipating paths but its mechanism at nanoscale hotspots is still unclear. Here shows the first experimental investigation of the convective heat transfer coefficient at size-controllable nanoscale hotspots. A specially designed structure of a single layer graphene supported by gold nanorods (AuNRs) is proposed, in which the AuNRs generate plasmonic heating sources of the order of hundreds of nanometers under laser irradiation and the graphene layer works as a temperature probe in Raman thermometry. The determined convective heat transfer coefficient is found to be about three orders of magnitude higher than that of nature convection, when the simultaneous interfacial heat conduction and radiation are carefully evaluated. Heat convection thus accounts to more than half of the total energy transferred across the graphene/AuNRs interface. Both the plasmonic heating induced nanoscale hotspots and ballistic convection of gas molecules contribute to the enhanced heat convection. This work reveals the importance of heat convection at nanoscale hotspots to the accurate thermal design of miniaturized electronics, and further offers a new way to evaluate the convective heat transfer coefficient at nanoscale hotspots.