Origin of micrometer-scale propagation lengths of heat-carrying acoustic excitations in amorphous silicon
- Creators
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Kim, Taeyong
- Moon, Jaeyun
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Minnich, Austin J.
Abstract
The heat-carrying acoustic excitations of amorphous silicon are of interest because their mean free paths may approach micron scales at room temperature. Despite extensive investigation, the origin of the weak acoustic scattering in the heat-carrying frequencies remains a topic of debate. Here, we report measurements of the thermal conductivity mean free path accumulation function in amorphous silicon thin films from 60 to 315 K using transient grating spectroscopy. With additional picosecond acoustics measurements and considering the power-law frequency dependence of scattering mechanisms in glasses, we reconstruct the mean free paths from ∼0.1–3 THz. The mean free paths are independent of temperature and exhibit a Rayleigh scattering trend over most of this frequency range. The observed trend is inconsistent with the predictions of numerical studies based on normal mode analysis but agrees with diverse measurements on other glasses. The micron-scale MFPs in amorphous Si arise from the absence of anharmonic or thermally activated relaxation damping in the sub-THz frequencies, leading to heat-carrying acoustic excitations with room-temperature MFPs comparable to those of other glasses at cryogenic temperatures.
Additional Information
© 2021 American Physical Society. Received 22 July 2020; revised 5 March 2021; accepted 27 April 2021; published 9 June 2021. The authors acknowledge discussions with A. B. Robbins and B. C. Daly. This work was supported by the 2018 GIST-Caltech Research Collaboration.Attached Files
Published - PhysRevMaterials.5.065602.pdf
Submitted - 2007.15777.pdf
Supplemental Material - SI_PRM.pdf
Files
Additional details
- Alternative title
- Origin of micron-scale propagation lengths of heat-carrying acoustic excitations in amorphous silicon
- Eprint ID
- 105081
- Resolver ID
- CaltechAUTHORS:20200824-140943584
- GIST-Caltech Research Collaboration
- Created
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2020-08-24Created from EPrint's datestamp field
- Updated
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2021-06-09Created from EPrint's last_modified field