Title: Thickness-Dependent Cross-Plane Thermal Conductivity Measurements of Exfoliated Hexagonal Boron Nitride

Abstract

Submicrometer-thick layers of hexagonal boron nitride (hBN) exhibit high in-plane thermal conductivity and useful optical properties, and serve as dielectric encapsulation layers with low electrostatic inhomogeneity for graphene devices. Despite the promising applications of hBN as a heat spreader, the thickness dependence of its cross-plane thermal conductivity is not known, and the cross-plane phonon mean free paths (MFPs) have not been measured. We measure the cross-plane thermal conductivity of hBN flakes exfoliated from bulk crystals. We find that submicrometer thick flakes exhibit thermal conductivities up to 8.1 ± 0.5 W m^–1 K^–1 at 295 K, which exceeds previously reported bulk values by more than 60%. Surprisingly, the average phonon mean free path is found to be several hundred nanometers at room temperature, a factor of 5 larger than previous predictions. When planar twist interfaces are introduced into the crystal by mechanically stacking multiple thin flakes, the cross-plane thermal conductivity of the stack is found to be a factor of 7 below that of individual flakes with similar total thickness, thus providing strong evidence that phonon scattering at twist boundaries limits the maximum phonon MFPs. These results have important implications for hBN integration in nanoelectronics and improve our understanding of thermalmore » transport in twodimensional materials.« less

Authors:

Jaffe, Gabriel R.  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-2672-0375"

Smith, Keenan J. ^[1]; Watanabe, Kenji  ^[2];

• Search DOE PAGES for author "Watanabe, Kenji"
• Search DOE PAGES for ORCID "0000-0003-3701-8119"

Taniguchi, Takashi  ^[3];

• Search DOE PAGES for author "Taniguchi, Takashi"
• Search DOE PAGES for ORCID "0000-0002-1467-3105"

Lagally, Max G. ^[4]; Eriksson, Mark A. ^[1]; Brar, Victor W. ^[1]

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+ Show Author Affiliations

1. Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
2. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
3. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
4. Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States

Publication Date:

Mon Feb 27 00:00:00 EST 2023

Research Org.:

Univ. of Wisconsin, Madison, WI (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); JSPS KAKENHI

OSTI Identifier:

1958926

Alternate Identifier(s):

OSTI ID: 1960362

Grant/Contract Number:  

FG02-03ER46028; SC0020313; 19H05790; 20H00354; 21H05233

Resource Type:

Published Article

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Name: ACS Applied Materials and Interfaces Journal Volume: 15 Journal Issue: 9; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; phonon; mean free path; hBN; cross-plane; thermal conductivity; twist interface; interfaces; thickness; wires