Thermal Conductivity and Phonon Transport in Suspended Few-Layer Hexagonal Boron Nitride

TL;DR

This study measures the thermal conductivity of suspended few-layer hexagonal boron nitride, revealing high values close to bulk material and showing how surface residues impact heat transport at room temperature.

Contribution

It provides direct measurements of thermal conductivity in suspended few-layer h-BN and examines the effects of polymer residue on phonon transport.

Findings

Thermal conductivity of 11-layer h-BN is about 360 W/mK at room temperature.

Polymer residue reduces thermal conductivity to about 250 W/mK in 5-layer h-BN.

Thermal conductivities decrease at low temperatures, indicating increased phonon scattering.

Abstract

The thermal conductivity of suspended few-layer hexagonal boron nitride (h-BN) was measured using a micro-bridge device with built-in resistance thermometers. Based on the measured thermal resistance values of 11-12 atomic layer h-BN samples with suspended length ranging between 3 and 7.5 um, the room-temperature thermal conductivity of a 11-layer sample was found to be about 360 Wm-1K-1, approaching the basal plane value reported for bulk h-BN. The presence of a polymer residue layer on the sample surface was found to decrease the thermal conductivity of a 5-layer h-BN sample to be about 250 Wm-1K-1 at 300 K. Thermal conductivities for both the 5 layer and the 11 layer samples are suppressed at low temperatures, suggesting increasing scattering of low frequency phonons in thin h-BN samples by polymer residue.