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Temperature-Dependent Mean Free Path Spectra of Thermal Phonons Along the c-Axis of Graphite

Zhang, Hang and Chen, Xiangwen and Jho, Young-Dahl and Minnich, Austin J. (2016) Temperature-Dependent Mean Free Path Spectra of Thermal Phonons Along the c-Axis of Graphite. Nano Letters, 16 (3). pp. 1643-1649. ISSN 1530-6984.

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Heat conduction in graphite has been studied for decades because of its exceptionally large thermal anisotropy. While the bulk thermal conductivities along the in-plane and cross-plane directions are well-known, less understood are the microscopic properties of the thermal phonons responsible for heat conduction. In particular, recent experimental and computational works indicate that the average phonon mean free path (MFP) along the c-axis is considerably larger than that estimated by kinetic theory, but the distribution of MFPs remains unknown. Here, we report the first quantitative measurements of c-axis phonon MFP spectra in graphite at a variety of temperatures using time-domain thermoreflectance measurements of graphite flakes with variable thickness. Our results indicate that c-axis phonon MFPs have values of a few hundred nanometers at room temperature and a much narrower distribution than in isotropic crystals. At low temperatures, phonon scattering is dominated by grain boundaries separating crystalline regions of different rotational orientation. Our study provides important new insights into heat transport and phonon scattering mechanisms in graphite and other anisotropic van der Waals solids.

Item Type:Article
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URLURL TypeDescription Information Paper
Minnich, Austin J.0000-0002-9671-9540
Additional Information:© 2016 American Chemical Society. Received: November 4, 2015; Revised: February 2, 2016; Publication Date (Web): February 3, 2016. The authors are grateful to the Kavli Nanoscience Institute at Caltech for the availability of critical cleanroom facilities and to the Lewis Group at Caltech for use of certain facilities. The authors also thank Matthew H. Sullivan for FIB assistance and Carol M. Garland for TEM assistance. This work was supported by a start-up fund from the California Institute of Technology and by the National Science Foundation under CAREER Grant CBET 1254213. H.Z. also gratefully acknowledges the financial support of the CAS Pioneer Hundred Talents Program. H.Z. and X.C. contributed equally to this work. The authors declare no competing financial interest.
Group:Kavli Nanoscience Institute
Funding AgencyGrant Number
NSFCBET 1254213
Chinese Academy of SciencesUNSPECIFIED
Subject Keywords:Mean free path, graphite, phonon, cross-plane, thermal conductivity, thickness dependent
Issue or Number:3
Record Number:CaltechAUTHORS:20160222-135642950
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Official Citation:Temperature-Dependent Mean Free Path Spectra of Thermal Phonons Along the c-Axis of Graphite Hang Zhang, Xiangwen Chen, Young-Dahl Jho, and Austin J. Minnich Nano Letters 2016 16 (3), 1643-1649 DOI: 10.1021/acs.nanolett.5b04499
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64639
Deposited By: Tony Diaz
Deposited On:23 Feb 2016 00:15
Last Modified:09 Mar 2020 13:19

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