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Tight-binding calculations of electron scattering rates in semiconducting zigzag carbon nanotubes
Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. (Electronics design division)
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The technological interest in a material depends very much on its electrical, magnetic, optical and/or mechanical properties. In carbon nanotubes the atoms form a cylindrical structure with a diameter of the order 1 nm, but the nanotubes can be up to several hundred micrometers in length. This makes carbon nanotubes a remarkable model for one-dimensional systems. A lot of efforts have been dedicated to manufacturing carbon nanotubes, which is expected to be the material for the next generation of devices. Despite all the attention that carbon nanotubes have received from the scientific community, only rather limited progress has been made in the theoretical understanding of their physical properties. In this work, we attempt to provide an understanding of the electron-phonon and electron-defect interactions in semiconducting zigzag carbon nanotubes using a tight-binding approach. The electronic energy dispersion relations are calculated by applying the zone-folding technique to the dispersion relations of graphene. A fourth-nearest-neighbour force constant model has been applied to study the vibrational modes in the carbon nanotubes. Both the electron-phonon interaction and the electron-defect interaction are formulated within the tight-binding approximation, and analyzed in terms of their quantum mechanical scattering rates. Apart from the scattering rates, their components in terms of phonon absorption, phonon emission, backscattering and forward scattering have been determined and analyzed. The scattering rates for (5,0), (7,0), (10,0), (13,0) and (25,0) carbon nanotubes at room temperature and at 10K are presented and discussed. The phonon scattering rate is dependent on the lattice temperature in the interval 0-0.17 eV. We find that backscattering and phonon emission are dominant over forward scattering and phonon absorption in most of the energy interval. However, forward scattering and phonon absorption can be comparable to backscattering and phonon emission in limited energy intervals. The phonon modes associated with each peak in the electron-phonon scattering rates have been identified, and the similarities in the phonon scattering rates between different nanotubes are discussed. The dependence of the defect scattering rate on the tube diameter is similar to that of the phonon scattering rate. Both the phonon and the defect scattering rates show strong dependence on the tube diameter (i.e., the scattering rate decreases as a function of the index of the nanotube). It is observed that the backscattering and forward scattering for electrons interacting with defects occur with same frequency at all energies, in sharp contrast to the situation for phonon scattering. It is demonstrated that the differences in the scattering rate between different tubes are mainly due to the differences in their band structures.

 

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2011. , p. 94
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 55
Keywords [en]
Tight-binding, carbon nanotubes, electron-phonon scattering, backscattering, forward scattering
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:miun:diva-13162Local ID: STCISBN: 978-91-86694-15-9 (print)OAI: oai:DiVA.org:miun-13162DiVA, id: diva2:392422
Presentation
2011-01-19, O111, Mid Sweden University, Sundsvall, 13:15 (English)
Opponent
Supervisors
Available from: 2011-01-28 Created: 2011-01-27 Last updated: 2016-10-19Bibliographically approved
List of papers
1. Electron-phonon scattering rates in semiconducting zigzag carbon nanotubes
Open this publication in new window or tab >>Electron-phonon scattering rates in semiconducting zigzag carbon nanotubes
2011 (English)In: Journal of Computational and Theoretical Nanoscience, ISSN 1546-1955, Vol. 8, no 9, p. 1694-1702Article in journal (Refereed) Published
Abstract [en]

The energy dependence of the scattering rate for electrons interacting with phonons in semiconducting zig-zag carbon nanotubes has been investigated using a tight-binding method. Apart from the scattering rates, their components in terms of phonon emission, phonon absorption, backscattering and forward scattering have been determined. Results for (7, 0), (10, 0), (13, 0) and (25, 0) nanotubes at both room temperature and at 10K are presented and discussed. It is demonstrated that backscattering of the electron generally is more likely than forward scattering, and that phonon absorption can be comparable to, or even more important than, phonon emission in limited energy intervals. Furthermore, the phonons responsible for the main features in the scattering rates have been identified, and the similarities in the scattering rates between different nanotubes are clarified.

Keywords
Carbon Nanotubes; Electron-Phonon Scattering; Scattering Rates; Backscattering
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:miun:diva-12152 (URN)10.1166/jctn.2011.1868 (DOI)000298514100009 ()2-s2.0-84856886654 (Scopus ID)STC (Local ID)STC (Archive number)STC (OAI)
Available from: 2010-10-22 Created: 2010-10-22 Last updated: 2016-10-14Bibliographically approved
2. Electron-phonon and electron-defect scattering rates in semiconducting zigzag carbon nanotubes
Open this publication in new window or tab >>Electron-phonon and electron-defect scattering rates in semiconducting zigzag carbon nanotubes
2010 (English)In: Proceedings - 2010 8th International Vacuum Electron Sources Conference and Nanocarbon, IVESC 2010 and NANOcarbon 2010, IEEE conference proceedings, 2010, p. 282-283Conference paper, Published paper (Refereed)
Abstract [en]

The electron transport properties of single walled carbon nanotubes are of fundamental importance for the development of carbon based nanotechnology. Carbon nanotubes can display both chemical and structural defects, which affect electronic states near the Fermi level. This is further complicated by the fact that the concentration of defects depends upon the method of synthesis. In this work, we have investigated both electron-phonon and electron-defect scattering in semiconducting zigzag carbon nanotubes by calculating and analyzing the quantum-mechanical scattering rates for these processes. One objective of this work is to give a theoretical limit for the concentration of defects at which electron-defect scattering rates would be comparable to the electron-phonon scattering rates.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2010
Keywords
carbon nanotubes; electron-phonon scattering; electron-defect scattering rate; tight-binding approximation
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:miun:diva-12153 (URN)10.1109/IVESC.2010.5644235 (DOI)2-s2.0-78650663872 (Scopus ID)978-142446642-9 (ISBN)
Conference
8th International Vacuum Electron Sources Conference, IVESC 2010 and NANOcarbon 2010; Nanjing; 14 October 2010 through 16 October 2010
Available from: 2010-10-22 Created: 2010-10-22 Last updated: 2013-03-20Bibliographically approved

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Thiagarajan, Kannan: Tight-binding calculations of electron scattering rates in semiconductiong zigzag carbon nanotubes. 2011(1589 kB)2446 downloads
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