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We examine the effect of van der Waals (vdW) interactions between atomic force microscope tips and individual carbon nanotubes (CNTs) supported on SiO2. Molecular dynamics (MD) simulations reveal how CNTs deform during atomic force microscopy (AFM) measurement, irrespective of the AFM tip material. The apparent height of a single-(double-) walled CNT can be used to estimate its diameter up to ~2 nm (~3 nm), but for larger diameters the CNT cross-section is no longer circular. Our simulations were compared against CNT dimensions obtained from AFM measurements and resonant Raman spectroscopy, with good agreement for the smaller CNT diameters. In general, AFM measurements of large-diameter CNTs must be interpreted with care, but the reliability of the approach is improved if knowledge of the number of CNT walls is available, or if additional verification (e.g., by optical techniques) can be obtained.

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Publication history
Copyright
Acknowledgements

Publication history

Received: 07 October 2011
Revised: 09 January 2012
Accepted: 21 January 2012
Published: 11 March 2012
Issue date: April 2012

Copyright

© Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2012

Acknowledgements

Acknowledgements

This work was supported by the National Science Foundation (NSF) grants CMMI 0952565 and CMMI 1029221 (R.A. and K.J.H.) and NSF award CAREER ECCS 0954423 (E.P.), the Nanoelectronics Research Initiative (NRI) Coufal Fellowship (A.L.) and the Marco MSD Center (F.X.). The authors thank T. DeBorde and E.D. Minot for the helpful discussion on the technique to estimate the compressive force on CNTs.

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