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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Nitrogen-Doped Single-Walled Carbon Nanotube Thin Films

Toma Susi

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Science for public examination and debate in Auditorium T2 at the Aalto University School of Science (Espoo, Finland) on the 20th of May 2011 at 12 noon.

Overview in PDF format (ISBN 978-952-60-4124-7)   [27845 KB]
Dissertation is also available in print (ISBN 978-952-60-4123-0)

Abstract

Carbon nanotubes are one of the most exciting materials for emerging practical nanotechnologies. However, a significant issue for applications is the mixture of semiconducting and metallic tubes in all typical samples. One of the proposed solutions for this problem is to tailor the electronic structure by doping the lattice with heteroatoms, most notably nitrogen.

In this thesis, nitrogen-doped single-walled carbon nanotubes (N-SWCNTs) were synthesized using an ambient pressure floating catalyst chemical vapor deposition method. A novel combination of precursors was used, with carbon monoxide (CO) acting as the carbon source and ammonia (NH3) as the nitrogen source. Experiments were conducted with two reactor setups, both utilizing iron nanoparticles as the catalysts. The material was deposited as grown directly from the gas phase as films on various substrates and subsequently characterized by a variety of microscopic and spectroscopic methods, as well as sheet resistance measurements.

The sheet resistance measurements of the thin film samples revealed that the doped films had unexpectedly high resistances. To understand this effect, a resistor network model was developed, which allowed the disentanglement of the contribution of bundle–bundle contacts when combined with data for undoped films. Assuming doping does not significantly change the contacts, the increased resistances of the doped films are likely due to enhanced carrier scattering by defect sites in the nanotubes. This work represents the first experimental report on macroscopic N-SWCNT thin films.

Finally, the mechanism of the initial stages of N-SWCNT growth was studied for the first time by tandem infrared and mass spectrometry gas measurements and first principles electronic-structure calculations. We investigated the bonding and chemistry of CO, NH3, and their fragments on a model Fe55 icosahedral cluster. A possible dissociation path for NH3 to atomic nitrogen and hydrogen was identified, with a reaction barrier consistent with an experimentally determined value. Both C–C and C–N bond formation reactions were found to be barrierless and exothermic, while a parasitic reaction of hydrogen cyanide formation had a large barrier of over 1 eV.

This thesis consists of an overview and of the following 7 publications:

  1. Susi, T., Nasibulin, A.G., Ayala, P., Tian, Y., Zhu, Z., Jiang, H., Roquelet, C., Garrot, D., Lauret, J-S., Kauppinen, E.I., 2009. High quality SWCNT synthesis in the presence of NH3 using a vertical flow aerosol reactor, Physica Status Solidi B 246, 2507-2510, doi: 10.1002/pssb.200982338.
  2. Zhu, Z., Jiang, H., Susi, T., Nasibulin, A.G., and Kauppinen, E.I., 2010. The Use of NH3 to Promote the Production of Large-Diameter Single-Walled Carbon Nanotubes with a Narrow (n,m) Distribution, Journal of the American Chemical Society 133, 1224-1227, doi: 10.1021/ja1087634.
  3. Susi, T., Zhu, Z., Ruiz-Soria, G., Arenal, R., Ayala, P., Nasibulin, A.G., Lin, H., Jiang, H., Stephan, O., Pichler, T., Loiseau, A., and Kauppinen, E.I., 2010. Nitrogen-doped SWCNT synthesis using ammonia and carbon monoxide, Physica Status Solidi B 247, 2726-2729, doi: 10.1002/pssb.201000312.
  4. Susi, T., Kaskela, A., Zhu, Z., Ayala, P., Arenal, R., Tian, Y., Laiho, P., Mali, J., Nasibulin, A.G., Jiang, H., Lanzani, G., Stephan, O., Laasonen, K., Pichler, T., Loiseau, A., Kauppinen, E.I., 2011. Nitrogen-doped Single-Walled Carbon Nanotube Thin Films Exhibiting Anomalous Sheet Resistances, Chemistry of Materials 23, 2201-2208, doi: 10.1021/cm200111b.
  5. Mudimela, P.R., Nasibulin, A.G., Jiang, H., Susi, T., Chassaing, D., and Kauppinen, E.I., 2009. Incremental Variation in the Number of Carbon Nanotube Walls with Growth Temperature. The Journal of Physical Chemistry C, 113, 2212-2218, doi: 10.1021/jp808316p.
  6. Lanzani, G., Susi, T., Ayala, P., Jiang, T., Nasibulin, A.G., Bligaard, T., Laasonen, K., and Kauppinen, E.I., 2010. Mechanism study of floating catalyst CVD synthesis of SWCNTs, Physica Status Solidi B 247, 2708-2712, doi: 10.1002/pssb.201000226.
  7. Susi, T., Lanzani, G., Nasibulin, A.G., Ayala, P., Jiang, T., Bligaard, T., Laasonen, K., and Kauppinen, E.I., 2011. Mechanism of the initial stages of nitrogen-doped single-walled carbon nanotube growth, Physical Chemistry Chemical Physics (in press), doi: 10.1039/c1cp20454h.

Keywords: nitrogen doping, SWCNT, chirality control, electrode, growth mechanism

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© 2011 Aalto University

Last update 2011-07-04