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Computer simulation of the STM imaging of nanometric 3D objects on a support: carbon nanotubes

Géza I. Márk, László P. Biró and Joseph Gyulai

February 26, 1998

Laboratory for Nanostructure Research
Research Institute for Technical Physics and Materials Science, H-1525 Budapest, P.O.Box 49, Hungary
Tel.: +36-1-392-2681
Fax: +36-1-392-2226

Electronic Properties of Novel Materials -- Progress in Molecular Nanostructures
28 February - 3. March 1998, Kirchberg, Austria,
Vol. 442, AIP Conference Proceedings, Vol. 442. edited by Kuzmany, Hans; Fink, Jörg; Mehring, Michael; Roth, Siegmar (American Institute of Physics,Woodbury, New York,1998) , p. 164.


Till now STM and AFM are the only tools able to probe in the same time the physical properties and able to give information on the geometric parameters (diameter, length) of an individual nanotube. However, tunneling through a nanotube is a much more complex phenomenon than STM imaging of an atomically flat crystalline surface. Besides geometric convolution effects[1], and the resonant tunneling through the two tunneling gaps: STM tip-nanotube, and nanotube-substrate[2], differences in the electronic properties of the nanotube and of the support may play a major role. We used a method based on the wave-packet dynamical calculation of time dependent tunneling current density in the STM tip-nanotube-support system in order to separate the distortion arising in the STM image formation process in pure geometric and electronic effects. The simulated line cuts for the case of a nanotube on a support with similar electronic structure, and for the case of a nanotube on a support with different electonic structure are coincident with experimental data. Out results show that the interpretation of scanning tunneling spectroscopy data of carbon nanotubes has to be done with lots of precautions.
1. L. P. Biró et al., Phys. Rev. B56(1997)12490.
2. L. P. Biró et al., Carbon, in press.

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Last updated: Oct 1, 2002 Géza I. Márk