Investigation of phonon coherence and backscattering using silicon nanomeshes

Jaeho Lee, Woochul Lee, Geoff Wehmeyer, Scott Dhuey, Deirdre L. Olynick, Stefano Cabrini, Chris Dames (), Jeffrey J. Urban () and Peidong Yang ()
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Jaeho Lee: University of California
Woochul Lee: University of California
Geoff Wehmeyer: University of California
Scott Dhuey: Molecular Foundry, Lawrence Berkeley National Laboratory
Deirdre L. Olynick: Molecular Foundry, Lawrence Berkeley National Laboratory
Stefano Cabrini: Molecular Foundry, Lawrence Berkeley National Laboratory
Chris Dames: University of California
Jeffrey J. Urban: Molecular Foundry, Lawrence Berkeley National Laboratory
Peidong Yang: University of California

Nature Communications, 2017, vol. 8, issue 1, 1-8

Abstract: Abstract Phonons can display both wave-like and particle-like behaviour during thermal transport. While thermal transport in silicon nanomeshes has been previously interpreted by phonon wave effects due to interference with periodic structures, as well as phonon particle effects including backscattering, the dominant mechanism responsible for thermal conductivity reductions below classical predictions still remains unclear. Here we isolate the wave-related coherence effects by comparing periodic and aperiodic nanomeshes, and quantify the backscattering effect by comparing variable-pitch nanomeshes. We measure identical (within 6% uncertainty) thermal conductivities for periodic and aperiodic nanomeshes of the same average pitch, and reduced thermal conductivities for nanomeshes with smaller pitches. Ray tracing simulations support the measurement results. We conclude phonon coherence is unimportant for thermal transport in silicon nanomeshes with periodicities of 100 nm and higher and temperatures above 14 K, and phonon backscattering, as manifested in the classical size effect, is responsible for the thermal conductivity reduction.

Date: 2017
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Persistent link: https://EconPapers.repec.org/RePEc:nat:natcom:v:8:y:2017:i:1:d:10.1038_ncomms14054

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DOI: 10.1038/ncomms14054

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