Anomalous reduction of thermal conductivity in coherent nanocrystal architecture for silicon thermoelectric material
Reduction of thermal conductivity κ while preserving high electrical conductivity σ in materials continues to be a vital goal in thermoelectric study for the reuse of exhaust heat energy. In the use of an eco-friendly and ubiquitous element, Si as thermoelectric material, high κ value in bulk Si is...
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Published in | Nano energy Vol. 12; pp. 845 - 851 |
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Main Authors | , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier Ltd
01.03.2015
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Subjects | |
Online Access | Get full text |
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Summary: | Reduction of thermal conductivity κ while preserving high electrical conductivity σ in materials continues to be a vital goal in thermoelectric study for the reuse of exhaust heat energy. In the use of an eco-friendly and ubiquitous element, Si as thermoelectric material, high κ value in bulk Si is the essential bottleneck to achieve high dimensionless figure of merit. This is a motivation for many recent studies on reducing κ in Si, by nanostructuring, e.g., using grains/wires with size smaller than the phonon mean free path. However, κ reduction that can be achieved tends to be saturated presumably due to an amorphous limit. Here, we present a nanoarchitecture for defeating the κ amorphous limit while preserving bulk-like σ. This new nanoarchitecture is an assembly of Si nanocrystals with oriented crystals separated by a 1-monolayer amorphous layer with well-controlled nanoscale shaped interfaces. At these interfaces, novel phonon scattering occurs resulting in κ reduction below the amorphous limit. Preservation of bulk-like σ results from the coherency of the carrier wavefunctions among the oriented nanocrystals separated by the ultrathin amorphous layer. The results will bring environmentally-friendly and low-cost thermoelectric Si material compatible with mature LSI process technology and represent guidelines for optimized thermoelectric nanostructures.
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ISSN: | 2211-2855 |
DOI: | 10.1016/j.nanoen.2014.11.029 |