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Thermal conductivity in porous silicon nanowire arrays

Jeffrey M Weisse1, Amy M Marconnet1, Dong Rip Kim1, Pratap M Rao1, Matthew A Panzer2, Kenneth E Goodson1 and Xiaolin Zheng1*

Author affiliations

1 Department of Mechanical Engineering, Stanford University, Stanford, CA, 94305, USA

2 KLA-Tencor Corporation, Milpitas, CA, 95035, USA

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Citation and License

Nanoscale Research Letters 2012, 7:554  doi:10.1186/1556-276X-7-554

Published: 6 October 2012

Abstract

The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

Keywords:
Thermal conductivity; Silicon nanowires; Porous silicon; Thermoreflectance