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Ultralow-voltage field-ionization discharge on whiskered silicon nanowires for gas-sensing applications

A Corrigendum to this article was published on 21 February 2011

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Several hundred million volts per centimetre of electric-field strength are required to field-ionize gas species. Such fields are produced on sharp metallic tips under a bias of a few kilovolts. Here, we show that field ionization is possible at dramatically lower fields on semiconductor nanomaterials containing surface states, particularly with metal-catalysed whiskers grown on silicon nanowires. The low-voltage field-ionization phenomena observed here cannot be explained solely on the basis of the large field-amplification effect of suspended gold nanoparticles present on the whisker tips. We postulate that field penetration causes upward band-bending at the surface of exposed silicon containing surface states in the vicinity of the catalyst. Band-bending enables the valence electron to tunnel into the surface states at reduced fields. This work provides a basis for development of low-voltage ionization sensors. Although demonstrated on silicon, low-voltage field ionization can be detected on any sharp semiconductor tip containing proper surface states.

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Figure 1: Field ionization dynamics.
Figure 2: Nanowires used to measure anomalous semiconductor-assisted gas ionization.
Figure 3: Current–voltage curves.
Figure 4: Energy-band diagrams for FI on a semiconductor surface.
Figure 5: Sensitivity and the effect of gas admixtures on the low-voltage field-ion current.

Change history

  • 01 February 2011

    In the version of this Article originally published, the corresponding author and the Acknowledgements were incorrect. These errors have now been corrected in the HTML and PDF versions of the text.


  1. Li, F., Xie, Z., Schmidt, H., Sielemann, S. & Baumbach, J. I. Ion mobility spectrometer for online monitoring of trace compounds. Spectrochim. Acta B 57, 1563–1574 (2002).

    Article  Google Scholar 

  2. Riley, D. J. et al. Helium detection via field ionization from carbon nanotubes. Nano Lett. 3, 1455–1458 (2003).

    Article  CAS  Google Scholar 

  3. Modi, A., Koratkar, N., Lass, E., Wei, B. & Ajayan, P. M. Miniaturized gas ionization sensors using carbon nanotubes. Nature 424, 171–174 (2003).

    Article  CAS  Google Scholar 

  4. Velasquez-Garcia, L. F. & Akinwande, A. I. Micro Electro Mechanical Systems. IEEE 21st International Conference on, 2008, 742–745 (2008).

  5. Gomer, R. Field Emission and Field Ionization (Harvard Univ. Press, 1961).

    Google Scholar 

  6. Miller, M. K., Cerezo, A., Hetherington, M. G. & Smith, G. D. W. Atom Probe Field Ion Microscopy (Oxford University Press, 1996).

    Google Scholar 

  7. Liu, X. & Orloff, J. Analytical model of a gas phase field ionization source. J. Vac. Sci. Technol. B 23, 2816–2820 (2005).

    Article  CAS  Google Scholar 

  8. Doerk, G. S., Ferralis, N., Carraro, C. & Maboudian, R. Growth of branching Si nanowires seeded by Au–Si surface migration. J. Mater. Chem. 18, 5376–5381 (2008).

    Article  CAS  Google Scholar 

  9. Müller, E. W. & Tsong, T. T. Field Ion Microscopy; Principles and Applications (American Elsevier Pub., 1969).

    Book  Google Scholar 

  10. Forbes, R. G., Edgcombe, C. J. & Valdre, U. Some comments on models for field enhancement. Ultramicroscopy 95, 57–65 (2003).

    Article  CAS  Google Scholar 

  11. Read, F. H. & Bowring, N. J. Field enhancement factors of random arrays of carbon nanotubes. Nucl. Instrum. Methods Phys. Res. 519, 305–314 (2004).

    Article  CAS  Google Scholar 

  12. Banan-Sadeghian, R. & Kahrizi, M. COMSOL Multiphysics Conf. 251–254 (2005).

  13. Willardson, R. K. & Beer, A. C. Semiconductors and Semimetals: Injection Phenomena (Academic, 1970).

    Google Scholar 

  14. Ohno, Y., Nakamura, S. & Kuroda, T. Mechanisms of field ionization and field evaporation on semiconductor surfaces. Jpn. J. Appl. Phys. 17, 2013–2022 (1978).

    Article  CAS  Google Scholar 

  15. Banan-Sadeghian, R. & Kahrizi, M. A novel gas sensor based on tunneling-field-ionization on whisker-covered gold nanowires. IEEE Sensors J. 8, 161–169 (2008).

    Article  Google Scholar 

  16. Singh, J. P., Karabacak, T., Lu, T. M., Wang, G. C. & Koratkar, N. Field ionization of argon using β-phase W nanorods. Appl. Phys. Lett. 85, 3226–3228 (2004).

    Article  CAS  Google Scholar 

  17. Garnett, E. C. et al. Dopant profiling and surface analysis of silicon nanowires using capacitance–voltage measurements. Nature Nanotech. 4, 311–314 (2009).

    Article  CAS  Google Scholar 

  18. Ohno, Y., Nakamura, S., Adachi, T. & Kuroda, T. Field-ion microscopy of GaAs and GaP. Surf. Sci. 69, 521–532 (1977).

    Article  CAS  Google Scholar 

  19. Gao, K., Yan, M., Feng, M. & Zhu, X. Measurement of charge-transfer rate coefficients between Co3+ and Ar, N2 at electron-volt energy. J. Phys. B 35, 233–240 (2002).

    Article  CAS  Google Scholar 

  20. Orloff, J. H. & Swanson, L. W. Study of a field-ionization source for microprobe applications. J. Vac. Sci. Technol. 12, 1209–1213 (1975).

    Article  CAS  Google Scholar 

  21. Ernst, L. & Block, J. H. Field ion microscopy of germanium: Field ionization and surface states. Surf. Sci. 49, 293–309 (1975).

    Article  CAS  Google Scholar 

  22. Müller, E. W. & Bahadur, K. Field ionization of gases at a metal surface and the resolution of the field ion microscope. Phys. Rev. 102, 624–634 (1956).

    Article  Google Scholar 

  23. Moh’d, R., Jason, P. & Robert, W. Tungsten nanotip fabrication by spatially controlled field-assisted reaction with nitrogen. J. Chem. Phys. 124, 204716 (2006).

    Article  Google Scholar 

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The work reported herein was partially supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada, a University of California CITRIS research grant funded by Hewlett Packard Labs, NSF grant 0547679 and an Army Research Office (ARO) research grant 55176-EL-DRP. R.B.S. would like to thank J. Y. Oh for help with nanowire synthesis, Logeeswaran VJ for help with the vacuum chamber set-up and A. Ghogha for help with statistical analysis.

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R.B.S. designed and carried out experiments, analysed data and wrote the manuscript. M.S.I. supervised the project, analysed data and edited the manuscript. Both authors discussed the results, and commented on the manuscript.

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Correspondence to M. Saif Islam.

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The authors declare no competing financial interests.

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Banan Sadeghian, R., Saif Islam, M. Ultralow-voltage field-ionization discharge on whiskered silicon nanowires for gas-sensing applications. Nature Mater 10, 135–140 (2011).

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