The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Transport and Tunneling in Multiwalled Carbon Nanotubes

Reeta Tarkiainen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics for public examination and debate in Auditorium F1 at Helsinki University of Technology (Espoo, Finland) on the 3rd of June, 2005, at 12 noon.

Overview in PDF format (ISBN 951-22-7701-8)   [1458 KB]
Dissertation is also available in print (ISBN 951-22-7700-X)

Abstract

Carbon nanotubes are promising new candidates for the construction of molecular-scale electronic circuits. However, the widely varying quality of the material, synthesized using different methods, results in large variation in electronic transport properties. In this Thesis, electronic transport in both disordered and good-quality multiwalled carbon nanotubes was studied. The transport in disordered samples, synthesized using chemical vapor deposition method, was studied to this extent for the first time.

The transport in disordered samples was found to be diffusive. The mean free path is so short that the quantum corrections to conductivity, the weak localization correction and the interaction correction, are best described using the theory for a two-dimensional conductor. The samples are found to be close to the strong localization limit, and the electron dephasing cannot be fully accounted for using the standard electron-electron scattering only. An additional dephasing mechanism is required, such as magnetic impurities. As bias voltage is increased the sample resistance was observed to change in accordance with an electron heating model.

The tunneling conductivity of both disordered and good-quality samples was measured, and a zero bias anomaly was discovered in both cases. However, the results differ due to the larger resistivity of the disordered samples. In the disordered case, the functional form of the anomaly was successfully compared with the non-perturbative theory of electron tunneling into a disordered 1D electrode. In the good-quality samples, the anomaly obeyed a power law, which can result from both environmental quantum fluctuation theory for ultra-small junctions and the Luttinger model. At high voltages the predictions differ, and better agreement with the environmental quantum fluctuation theory was found.

Construction of single-electron transistors, with good charge sensitivity, was demonstrated. Current fluctuations were observed to originate both from background charge fluctuations and resistance fluctuations of the device itself.

This thesis consists of an overview and of the following 9 publications:

  1. R. Tarkiainen, M. Ahlskog, A. Zyuzin, P. Hakonen, and M. Paalanen. 2004. Transport in strongly disordered multiwalled carbon nanotubes. Physical Review B 69, 033402.
  2. R. Tarkiainen, M. Ahlskog, P. Hakonen, and M. Paalanen. 2003. Transport in disordered carbon nanotubes. Physica E 18, pages 206-207. © 2003 Elsevier Science. By permission.
  3. R. Tarkiainen, M. Ahlskog, P. Hakonen, and M. Paalanen. 2003. Electron heating effects in disordered carbon nanotubes. In: Proceedings of the International Conference on Quantum Transport and Quantum Coherence. Journal of the Physical Society of Japan 72, Supplement A, pages 100-101.
  4. R. Tarkiainen, M. Ahlskog, M. Paalanen, A. Zyuzin, and P. Hakonen. 2005. Tunneling spectroscopy of disordered multiwalled carbon nanotubes. Physical Review B 71, 125425.
  5. R. Tarkiainen, M. Ahlskog, J. Penttilä, L. Roschier, P. Hakonen, M. Paalanen, and E. Sonin. 2001. Multiwalled carbon nanotube: Luttinger versus Fermi liquid. Physical Review B 64, 195412.
  6. M. Ahlskog, P. Hakonen, M. Paalanen, L. Roschier, and R. Tarkiainen. 2001. Multiwalled carbon nanotubes as building blocks in nanoelectronics. Journal of Low Temperature Physics 124, pages 335-352.
  7. M. Ahlskog, R. Tarkiainen, L. Roschier, and P. Hakonen. 2000. Single-electron transistor made of two crossing multiwalled carbon nanotubes and its noise properties. Applied Physics Letters 77, pages 4037-4039.
  8. L. Roschier, R. Tarkiainen, M. Ahlskog, M. Paalanen, and P. Hakonen. 2001. Multiwalled carbon nanotubes as ultrasensitive electrometers. Applied Physics Letters 78, pages 3295-3297.
  9. R. Tarkiainen, L. Roschier, M. Ahlskog, M. Paalanen, and P. Hakonen. 2005. Low-frequency current noise and resistance fluctuations in multiwalled carbon nanotubes. Physica E 28, pages 57-65. © 2005 Elsevier Science. By permission.

Errata of publication 3

Keywords: carbon nanotubes, electron transport, mesoscopic systems

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© 2005 Helsinki University of Technology

Last update 2011-05-26