Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium

Journal Article · Mon Mar 02 00:00:00 EST 2015 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4913879· OSTI ID:22412767

Pan, Ying; Hong, Guo; Raja, Shyamprasad N.; Zimmermann, Severin; Poulikakos, Dimos ^[1]; Tiwari, Manish K. ^[2]

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1. Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092 Zurich (Switzerland)
2. Department of Mechanical Engineering, University College London, London, WC1E 7JE (United Kingdom)

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.

• OSTI ID: 22412767
• Journal Information: Applied Physics Letters, Vol. 106, Issue 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
77 NANOSCIENCE AND NANOTECHNOLOGY
ANNEALING
BINDING ENERGY
COMPARATIVE EVALUATIONS
DOPED MATERIALS
ENERGY CONVERSION
GERMANIUM
INTERFACES
MOLECULAR DYNAMICS METHOD
NANOMATERIALS
NANOWIRES
PHONONS
SILICON
SURFACES
TEMPERATURE RANGE 0273-0400 K
THERMAL CONDUCTIVITY
X-RAY PHOTOELECTRON SPECTROSCOPY