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Title: Control of surface morphology and crystal structure of silicon nanowires and their coherent phonon transport characteristics
Authors: Lee, S.-Y.
Kim, G.-S.
Lim, J.
Han, S.
Li, B. 
Thong, J.T.L. 
Yoon, Y.-G.
Lee, S.-K.
Keywords: Coherent phonon transport
Phonon boundary scattering
Silicon nanowires
Stacking fault
Thermal conductivity
Issue Date: Feb-2014
Citation: Lee, S.-Y., Kim, G.-S., Lim, J., Han, S., Li, B., Thong, J.T.L., Yoon, Y.-G., Lee, S.-K. (2014-02). Control of surface morphology and crystal structure of silicon nanowires and their coherent phonon transport characteristics. Acta Materialia 64 : 62-71. ScholarBank@NUS Repository.
Abstract: We report on the first experimental observation of coherent phonon transport characteristics in silicon nanowires (SiNWs) synthesized by a one-step surface reconstruction growth mechanism. As-grown SiNWs taper down along the growth direction alongside a decrease in both roughness and stacking fault density. Furthermore, by systematically measuring the temperature-dependent thermal conductivity using a conventional thermal bridge method, we found that the measured thermal conductivity values of surface-reconstructed (SR)-SiNWs (13-20 W m-1 K-1) at room temperature are markedly lower than that predicted from the conventional diffuse phonon transport model for given NW diameters. We also observed that the thermal conductivities of SR-SiNWs exhibit an unexpected power law of ∼Tα (1.6 ≤ α ≤ 1.9) in the temperature range of 25-60 K, which cannot be explained by the typical Debye ∼ T3 behavior. Interestingly, our experimental results are consistent with a frequency-dependent model, which can be induced by coherence in the diffuse reflection and backscattering of phonons at the rough surface and stacking faults on SR-SiNWs, resulting in the suppressed thermal conductivity. Therefore, the demonstrated rational synthesis model and measurement technique promise great potential for improving the performance of a wide range of one-dimensional NW-based thermoelectric devices. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Source Title: Acta Materialia
ISSN: 13596454
DOI: 10.1016/j.actamat.2013.11.042
Appears in Collections:Staff Publications

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