Charging and defects in single-walled carbon nanotubes

Nguyen, Khoi T.

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https://hdl.handle.net/2142/24221 Copy

Description

Title

Charging and defects in single-walled carbon nanotubes

Author(s)

Nguyen, Khoi T.

Issue Date

2011-05-25T15:04:57Z

Director of Research (if dissertation) or Advisor (if thesis)

Shim, Moonsub

Doctoral Committee Chair(s)

Shim, Moonsub

Committee Member(s)

• Abelson, John R.
• Lyding, Joseph W.
• Rockett, Angus A.

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Carbon Nanotubes
• Graphene
• Raman spectroscopy
• Electron-phonon coupling.

Abstract

Single-Walled Carbon Nanotubes (SWCNTs) have been one of the most intensively studied materials. Because of their single-atomic-layer structure, SWCNTs are extremely sensitive to environmental interactions, in which charge transfer and defect formation are the most notable effects. Among a number of microscopic and spectroscopic methods, Raman spectroscopy is a widely used technique to characterize physics and chemistry of CNTs. By utilizing simultaneous Raman and electron transport measurements along with polymer electrolyte gating, this dissertation focuses on studying charging and defects in SWCNTs at single nanotube level and in single layer graphene, the building block of SWCNTs. By controllably charging metallic SWCNTs (m-CNTs), the intrinsic nature of the broad and asymmetric Fano lineshape in Raman G band of m-CNTs was first time evidenced. The observation that Fano component is most broadened and downshifted when Fermi level is close to the Dirac point (DP) reveals its origin as the consequence of coupling of phonon to vertical electronic transitions. Furthermore, we have systematically introduced covalent defects to m-CNTs to study how phonon softening and electrical characteristics are affected by disorders. In addition to decreasing electrical conductance with increasing on/off current ratio eventually leading to semiconducting behavior, adding covalent defects reduces the degree of softening and broadening of longitudinal optical (LO) phonon mode but enhances the softening of transverse optical (TO) mode of the G-band near the DP. Charging and defect effects in semiconducting SWCNTs and single layer graphene, a closely related material to SWCNTs, have also been discussed.

Graduation Semester

2011-05

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http://hdl.handle.net/2142/24221

Copyright and License Information

Copyright 2011 Khoi T. Nguyen

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