Thermal expansion coefficient and lattice anharmonicity of cubic boron arsenide

TL;DR

This study measures and calculates the thermal expansion coefficient and Grüneisen parameter of cubic boron arsenide, confirming its promising thermal management properties and better lattice anharmonicity understanding.

Contribution

The paper provides the first experimental measurement of BAs's thermal expansion coefficient and validates ab initio calculations, resolving previous theoretical inconsistencies.

Findings

Measured thermal expansion coefficient from 300 K to 773 K.

Grüneisen parameter of 0.84 at 300 K, aligning with first-principles calculations.

BAs exhibits a better thermal expansion match with common semiconductors.

Abstract

Recent measurements of an unusual high thermal conductivity of around 1000 W m-1 K-1 at room temperature in cubic boron arsenide (BAs) confirm predictions from theory and suggest potential applications of this semiconductor compound for thermal management applications. Knowledge of the thermal expansion coefficient and Gr\"uneisen parameter of a material contributes both to the fundamental understanding of its lattice anharmonicity and to assessing its utility as a thermal-management material. However, previous theoretical calculations of the thermal expansion coefficient and Gr\"uneisen parameter of BAs yield inconsistent results. Here we report the linear thermal expansion coefficient of BAs obtained from the X-ray diffraction measurements from 300 K to 773 K. The measurement results are in good agreement with our ab initio calculations that account for atomic interactions up to fifth nearest neighbours. With the measured thermal expansion coefficient and specific heat, a Gr\"uneisen parameter of BAs of 0.84 +/- 0.09 is obtained at 300 K, in excellent agreement with the value of 0.82 calculated from first principles and much lower than prior theoretical results. Our results confirm that BAs exhibits a better thermal expansion coefficient match with commonly used semiconductors than other high-thermal conductivity materials such as diamond and cubic boron nitride.