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Importance of frequency-dependent grain boundary scattering in nanocrystalline silicon and silicon-germanium thermoelectrics

Hua, Chengyun and Minnich, Austin J. (2014) Importance of frequency-dependent grain boundary scattering in nanocrystalline silicon and silicon-germanium thermoelectrics. Semiconductor Science and Technology, 29 (12). Art. No. 124004. ISSN 0268-1242. http://resolver.caltech.edu/CaltechAUTHORS:20140512-105243137

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Abstract

Nanocrystalline silicon and silicon-germanium alloys are promising thermoelectric materials that have achieved substantially improved figure of merits compared to their bulk counterparts. This enhancement is typically attributed to a reduction in lattice thermal conductivity by phonon scattering at grain boundaries. However, further improvements are difficult to achieve because grain boundary scattering is poorly understood, with recent experimental observations suggesting that the phonon transmissivity may depend on phonon frequency rather than being constant as in the commonly used gray model. Here, we examine the impact of frequency-dependent grain boundary scattering in nanocrystalline silicon and silicon-germanium alloys in a realistic 3D geometry using frequency-dependent variance-reduced Monte Carlo simulations. We find that the grain boundary may not be as effective as predicted by the gray model in scattering certain phonons, with a substantial amount of heat being carried by low frequency phonons with mean free paths longer than the grain size. Our result will help guide the design of more efficient thermoelectrics.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0268-1242/29/12/124004DOIArticle
http://iopscience.iop.org/0268-1242/29/12/124004/PublisherArticle
http://arxiv.org/abs/1404.7847arXivDiscussion Paper
Additional Information:© 2014 IOP Publishing Ltd. Received 30 April 2014, revised 30 June 2014. Accepted for publication 24 July 2014. Published 14 November 2014. The authors thank J.P. Peraud and N.G. Hadjicontantinou for useful discussions. This work was sponsored in part by Robert Bosch LLC through Bosch Energy Research Network Grant no. 13.01.CC11, by the National Science Foundation under Grant no. CBET CAREER 1254213, and by Boeing under the Boeing-Caltech Strategic Research & Development Relationship Agreement.
Funders:
Funding AgencyGrant Number
Bosch Energy Research Network13.01.CC11
NSFCBET CAREER 1254213
Boeing-Caltech Strategic Research & Development Relationship AgreementUNSPECIFIED
Subject Keywords:grain boundary scattering, Monte Carlo simulations, nanocrystalline thermoelectrics
Classification Code:PACS: 61.72.Mn, 73.63.Bd, 63.22.-m, 61.46.Hk
Record Number:CaltechAUTHORS:20140512-105243137
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140512-105243137
Official Citation:Importance of frequency-dependent grain boundary scattering in nanocrystalline silicon and silicon–germanium thermoelectrics Chengyun Hua and Austin J Minnich 2014 Semicond. Sci. Technol. 29 124004
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45678
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:12 May 2014 20:23
Last Modified:06 Jan 2015 18:15

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