Anisotropic thermal transport in bulk hexagonal boron nitride

Journal Article · Tue Jun 26 00:00:00 EDT 2018 · Physical Review Materials

DOI:https://doi.org/10.1103/PhysRevMaterials.2.064005· OSTI ID:1458358

Jiang, Puqing ^[1]; Qian, Xin ^[1]; Yang, Ronggui ^[1]; Lindsay, Lucas ^[2]

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1. Univ. of Colorado, Boulder, CO (United States). Dept. of Mechanical Engineering
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division

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 × 50 μm² 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. Here, this article 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.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC05-00OR22725; 1511195; AR0000743
• OSTI ID: 1458358
• Alternate ID(s): OSTI ID: 1457208
• Journal Information: Physical Review Materials, Vol. 2, Issue 6; ISSN 2475-9953
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY