Silicon nanowires (SiNWs) are promising materials for the realization of highly-efficient and cost effective thermoelectric devices. Reduction of the thermal conductivity of such materials is a necessary and viable pathway to achieve sufficiently high thermoelectric efficiencies, which are inversely proportional to the thermal conductivity. In this article, vertically aligned forests of SiNW and germanium (Ge)-doped SiNW with diameters around 100 nm have been fabricated, and their thermal conductivity has been measured. The results show that discrete surface doping of Ge on SiNW arrays can lead to 23% reduction in thermal conductivity at room temperature compared to uncoated SiNWs. Such reduction can be further enhanced to 44% following a thermal annealing step. By analyzing the binding energy changes of Ge-3d and Si-2p using X-ray photoelectron spectroscopy, we demonstrate that surface doped Ge interacts strongly with Si, enhancing phonon scattering at the Si-Ge interface as has also been shown in non-equilibrium molecular dynamics studies of single nanowires. Overall, our results suggest a viable pathway to improve the energy conversion efficiency of nanowire-forest thermoelectric nanomaterials.
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2 March 2015
Research Article|
March 02 2015
Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium
Ying Pan
;
Ying Pan
1Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering,
ETH Zurich
, Sonneggstrasse 3, 8092 Zurich, Switzerland
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Guo Hong;
Guo Hong
1Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering,
ETH Zurich
, Sonneggstrasse 3, 8092 Zurich, Switzerland
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Shyamprasad N. Raja;
Shyamprasad N. Raja
1Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering,
ETH Zurich
, Sonneggstrasse 3, 8092 Zurich, Switzerland
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Severin Zimmermann;
Severin Zimmermann
1Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering,
ETH Zurich
, Sonneggstrasse 3, 8092 Zurich, Switzerland
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Manish K. Tiwari;
Manish K. Tiwari
2Department of Mechanical Engineering,
University College London
, London, WC1E 7JE, United Kingdom
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Dimos Poulikakos
Dimos Poulikakos
a)
1Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering,
ETH Zurich
, Sonneggstrasse 3, 8092 Zurich, Switzerland
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a)
Author to whom correspondence should be addressed. Electronic mail: [email protected]
Appl. Phys. Lett. 106, 093102 (2015)
Article history
Received:
October 30 2014
Accepted:
February 18 2015
Citation
Ying Pan, Guo Hong, Shyamprasad N. Raja, Severin Zimmermann, Manish K. Tiwari, Dimos Poulikakos; Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium. Appl. Phys. Lett. 2 March 2015; 106 (9): 093102. https://doi.org/10.1063/1.4913879
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