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Enhanced thermoelectric performance of rough silicon nanowires

Nature 451, 163–167 (10 January 2008) | Download Citation

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Abstract

Approximately 90 per cent of the world’s power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30–40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent1. While nanostructured thermoelectric materials can increase ZT > 1 (refs 2–4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20–300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

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Acknowledgements

We thank T.-J. King-Liu and C. Hu for discussions and J. Goldberger for TEM analysis. We acknowledge the support of the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, DOE. A.I.H. and R.C. thank the NSF-IGERT and ITRI-Taiwan programs, respectively, for fellowship support. We also thank the National Center for Electron Microscopy and the UC Berkeley Microlab for the use of their facilities. R.D.D. thanks the GenCat/Fulbright programme for support.

Author information

    • Allon I. Hochbaum
    •  & Renkun Chen

    These authors contributed equally to this work.

Affiliations

  1. Department of Chemistry,

    • Allon I. Hochbaum
    • , Raul Diaz Delgado
    • , Wenjie Liang
    • , Erik C. Garnett
    •  & Peidong Yang

  2. Department of Mechanical Engineering,

    • Renkun Chen
    •  & Arun Majumdar

  3. Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA

    • Mark Najarian
    • , Arun Majumdar
    •  & Peidong Yang

  4. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

    • Arun Majumdar
    •  & Peidong Yang

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Corresponding authors

Correspondence to Arun Majumdar or Peidong Yang.

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    Supplementary Information

    The file contains Supplementary Methods and Discussion; and Supplementary Figures S1-S4 with Legends.

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https://doi.org/10.1038/nature06381

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