Transport and tunneling in multiwalled carbon nanotubes

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.

Department dc:contributor.department

Department of Engineering Physics and Mathematics

Grantor dc:publisher

Helsinki University of Technology

Year dc:date.issued

2005

Author dc:creator

• Tarkiainen, Reeta

Contributors dc:contributor

• Aalto-yliopisto
• Aalto University

Language dc:language.iso

en

Repository record dc:identifier.uri

https://aaltodoc.aalto.fi/handle/123456789/2578

OAI record oai:identifier

https://aaltodoc.aalto.fi/server/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Aaaltodoc.aalto.fi%3A123456789%2F2578