Increased Phonon Scattering by Nanograins and Point Defects in Nanostructured Silicon with a Low Concentration of Germanium
Author(s)Zhu, G. H.; Lan, Y. C.; Wang, X. W.; Joshi, G.; Wang, D. Z.; Yang, J.; Vashaee, D.; Guilbert, H.; Pillitteri, A.; Chen, Gang; Ren, Z. F.; Lee, H.; Dresselhaus, Mildred; ... Show more Show less
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The mechanism for phonon scattering by nanostructures and by point defects in nanostructured silicon (Si) and the silicon germanium (Ge) alloy and their thermoelectric properties are investigated. We found that the thermal conductivity is reduced by a factor of 10 in nanostructured Si in comparison with bulk crystalline Si. However, nanosize interfaces are not as effective as point defects in scattering phonons with wavelengths shorter than 1 nm. We further found that a 5 at. % Ge replacing Si is very efficient in scattering phonons shorter than 1 nm, resulting in a further thermal conductivity reduction by a factor of 2, thereby leading to a thermoelectric figure of merit 0.95 for Si[subscript 95]Ge[subscript 5], similar to that of large grained Si[subscript 80]Ge[subscript 20] alloys.
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science; Massachusetts Institute of Technology. Department of Mechanical Engineering
Physical Review Letters
American Physical Society
Zhu, G. H. et al. “Increased Phonon Scattering by Nanograins and Point Defects in Nanostructured Silicon with a Low Concentration of Germanium.” Physical Review Letters 102.19 (2009): 196803.
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