Experimental Investigation of Size Effects on the Thermal Conductivity of Silicon-Germanium Alloy Thin Films
Name
Cheaito-2012-Experimental investigation of size effects on the thermal.pdf
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Author(s)
Cheaito, Ramez
Duda, John C.
Beechem, Thomas E.
Hattar, Khalid
Ihlefeld, Jon F.
Medlin, Douglas L.
Rodriguez, Mark A.
Campion, Michael John
Piekos, Edward S.
Hopkins, Patrick E.
Date Issued
November 2012
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Cheaito, Ramez et al. “Experimental Investigation of Size Effects on the Thermal Conductivity of Silicon-Germanium Alloy Thin Films.” Physical Review Letters 109.19 (2012). © 2012 American Physical Society
Version
Final published version
Abstract
We experimentally investigate the role of size effects and boundary scattering on the thermal conductivity of silicon-germanium alloys. The thermal conductivities of a series of epitaxially grown Si[subscript 1-x] Ge[subscript x] thin films with varying thicknesses and compositions were measured with time-domain thermoreflectance. The resulting conductivities are found to be 3 to 5 times less than bulk values and vary strongly with film thickness. By examining these measured thermal conductivities in the context of a previously established model, it is shown that long wavelength phonons, known to be the dominant heat carriers in alloy films, are strongly scattered by the film boundaries, thereby inducing the observed reductions in heat transport. These results are then generalized to silicon-germanium systems of various thicknesses and compositions; we find that the thermal conductivities of Si[subscript 1-x]Ge[subscript x] superlattices are ultimately limited by finite size effects and sample size rather than periodicity or alloying. This demonstrates the strong influence of sample size in alloyed nanosystems. Therefore, if a comparison is to be made between the thermal conductivities of superlattices and alloys, the total sample thicknesses of each must be considered.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1103/PhysRevLett.109.195901
