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Fresnel transmission coefficients for thermal phonons at solid interfaces

Hua, Chengyun and Chen, Xiangwen and Ravichandran, Navaneetha K. and Minnich, Austin J. (2015) Fresnel transmission coefficients for thermal phonons at solid interfaces. . (Unpublished)

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Interfaces play an essential role in phonon-mediated heat conduction in solids, impacting applications ranging from thermoelectric waste heat recovery to heat dissipation in electronics. From a microscopic perspective, interfacial phonon transport is described by transmission and reflection coefficients, analogous to the well-known Fresnel coefficients for light. However, these coefficients have never been directly measured, and thermal transport processes at interfaces remain poorly understood despite considerable effort. Here, we report the first measurements of the Fresnel transmission coefficients for thermal phonons at a metal-semiconductor interface using ab-initio phonon transport modeling and a thermal characterization technique, time-domain thermoreflectance. Our measurements show that interfaces act as thermal phonon filters that transmit primarily low frequency phonons, leading to these phonons being the dominant energy carriers across the interface despite the larger density of states of high frequency phonons. Our work realizes the long-standing goal of directly measuring thermal phonon transmission coefficients and demonstrates a general route to study microscopic processes governing interfacial heat conduction.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Hua, Chengyun0000-0003-3587-8342
Minnich, Austin J.0000-0002-9671-9540
Additional Information:The authors thank J. Carrete and N. Mingo for providing the first-principles calculations for silicon, Prof. Nathan Lewis group for the access to the ellipsometer, and the Kavli Nanoscience Institute (KNI) at Caltech for the availability of critical cleanroom facilities. X. C. thanks Melissa A. Melendes, Matthew H. Sullivan and Carol M. Garland from the KNI for fabrication assistance, and Victoria W. Dix from the Lewis group at Caltech for the help with the ellipsometer measurements. This work was sponsored in part by the National Science Foundation under Grant no. CBET 1254213, and by Boeing under the Boeing-Caltech Strategic Research & Development Relationship Agreement.
Group:Kavli Nanoscience Institute
Funding AgencyGrant Number
Boeing-Caltech Strategic Research & Development Relationship AgreementUNSPECIFIED
Record Number:CaltechAUTHORS:20201028-142023904
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106335
Deposited By: Tony Diaz
Deposited On:29 Oct 2020 16:00
Last Modified:29 Oct 2020 16:00

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