Anisotropic thermal transport in bulk hexagonal boron nitride

Puqing Jiang, Xin Qian, Ronggui Yang, Lucas Lindsay

Research output: Contribution to journalArticlepeer-review

115 Scopus citations

Abstract

Hexagonal boron nitride (h-BN) has received great interest in recent years as a wide band-gap analog of graphene-derived systems along with its potential in a wide range of applications, for example, as the dielectric layer for graphene devices. However, the thermal transport properties of h-BN, which can be critical for device reliability and functionality, are little studied both experimentally and theoretically. The primary challenge in the experimental measurements of the anisotropic thermal conductivity of h-BN is that typically the sample size of h-BN single crystals is too small for conventional measurement techniques, as state-of-the-art technologies synthesize h-BN single crystals with lateral sizes only up to 2.5 mm and thicknesses up to 200 μm. Recently developed time-domain thermoreflectance (TDTR) techniques are suitable to measure the anisotropic thermal conductivity of such small samples, as it only requires a small area of 50×50μm2 for the measurements. Accurate atomistic modeling of thermal transport in bulk h-BN is also challenging due to the highly anisotropic layered structure. Here we conduct an integrated experimental and theoretical study on the anisotropic thermal conductivity of bulk h-BN single crystals over the temperature range of 100-500 K using TDTR measurements with multiple modulation frequencies and a full-scale numerical calculation of the phonon Boltzmann transport equation starting from first principles. Our experimental and numerical results compare favorably for both the in-plane and the through-plane thermal conductivities. We observe unusual temperature dependence and phonon-isotope scattering in the through-plane thermal conductivity of h-BN and elucidate their origins. This paper not only provides an important benchmark of the anisotropic thermal conductivity of h-BN, but also develops fundamental insight into the nature of phonon transport in this highly anisotropic layered material.

Original languageEnglish
Article number064005
JournalPhysical Review Materials
Volume2
Issue number6
DOIs
StatePublished - Jun 26 2018

Funding

P.J., X.Q., and R.Y. acknowledge support from NSF Grant No. 1511195 and DOE Grant No. DE-AR0000743. L. L. acknowledges support from the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.

FundersFunder number
Office of Basic Energy Sciences
U. S. Department of Energy
National Science Foundation1511195
U.S. Department of Energy
Office of Science
Division of Materials Sciences and Engineering

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