High thermal conductivity of high-quality monolayer boron nitride and its thermal expansion

TL;DR

This study demonstrates that high-quality monolayer boron nitride exhibits exceptionally high thermal conductivity, making it a promising material for heat dissipation in flexible electronics, with detailed theoretical and experimental analysis of its thermal properties.

Contribution

The paper provides the first comprehensive measurement and theoretical analysis of the thermal conductivity and expansion of monolayer boron nitride, highlighting its potential for thermal management applications.

Findings

Monolayer BN has a thermal conductivity of 751 W/mK at room temperature.

Thermal conductivity decreases with increasing thickness of BN layers.

Theoretical calculations accurately reproduce the experimental thermal expansion coefficients.

Abstract

Heat management becomes more and more critical, especially in miniaturized modern devices, so the exploration of highly thermally conductive materials with electrical insulation and favorable mechanical properties is of great importance. Here, we report that high-quality monolayer boron nitride (BN) has a thermal conductivity (\k{appa}) of 751 W/mK at room temperature. Though smaller than that of graphene, this value is larger than that of cubic boron nitride (cBN) and only second to those of diamond and lately discovered cubic boron arsenide (BAs). Monolayer BN has the second largest \k{appa} per unit weight among all semiconductors and insulators, just behind diamond, if density is considered. The \k{appa} of atomically thin BN decreases with increased thickness. Our large-scale molecular dynamic simulations using Green-Kubo formalism accurately reproduce this trend, and the density functional theory (DFT) calculations reveal the main scattering mechanism. The thermal expansion coefficients (TECs) of monolayer to trilayer BN at 300-400 K are also experimentally measured, and the results are comparable to atomistic ab initio DFT calculations in a wider range of temperatures. Thanks to its wide bandgap, high thermal conductivity, outstanding strength, good flexibility, and excellent thermal and chemical stability, atomically thin BN is a strong candidate for heat dissipation applications, especially in the next generation of flexible electronic devices.