Journal
NANO LETTERS
Volume 20, Issue 11, Pages 8384-8391Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.0c03590
Keywords
phonons; thermal transport; alloys; nanowires; first-principles; virtual crystal approximation
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Funding
- National Science Foundation (NSF) [EEC-1160494]
- NSF [DMR-1507654]
- NSF NNCI Award [1542159]
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Accurate measurements of the size-dependent lattice thermal conductivity (kappa(1)) of alloy nanostructures are challenging but help to address outstanding questions on the effects of atomic disorder and surface roughness on low-frequency vibrational modes in functional materials. Here, we report sensitive kappa(1) measurements of multiple segments of the same individual SiGe nanowires. In contrast to a previous report of ballistic thermal transport over several microns in SiGe nanowires, the obtained kappa(1) are nearly independent of the segment length from 2 to 10 mu m and the temperature between 150 and 300 K. The results are in agreement with a theoretical calculation based on the virtual crystal approximation of the vibrational modes as phonons with mean free paths suppressed by purely diffuse surface scattering. The findings inform continuing theoretical efforts for understanding the roles of different types of vibrational modes in thermal transport in disordered thermoelectric and electronic materials.
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