{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/24221"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/24221","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Charging and defects in single-walled carbon nanotubes","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.","abstract_html":"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.","abstract_has_math":false,"creators":["Nguyen, Khoi T."],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Materials Science & Engr","degree_department":null,"school":null,"contributors":["Shim, Moonsub","Abelson, John R.","Lyding, Joseph W.","Rockett, Angus A."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-25T15:04:57Z","date_published":"2011-05-25T15:04:57Z","updated_at":"2026-07-22T22:25:23Z","subjects":["Carbon Nanotubes","Graphene","Raman spectroscopy","Electron-phonon coupling."],"languages":["en"],"rights":["Copyright 2011 Khoi T. Nguyen"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/24221","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Shim, Moonsub","Abelson, John R.","Lyding, Joseph W.","Rockett, Angus A."]},{"key":"dc:creator","label":"Author","values":["Nguyen, Khoi T."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-25T15:04:57Z","2011-05"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Materials Science & Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Carbon Nanotubes","Graphene","Raman spectroscopy","Electron-phonon coupling."]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2011 Khoi T. Nguyen"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/24221"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["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.","Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2011-04-12T17:16:55Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Nguyen_Khoi.pdf: 2095854 bytes, checksum: e7350756d6abba252e715139d5231cd2 (MD5)","Made available in DSpace on 2011-05-25T15:04:57Z (GMT). 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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.","Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2011-04-12T17:16:55Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Nguyen_Khoi.pdf: 2095854 bytes, checksum: e7350756d6abba252e715139d5231cd2 (MD5)","Made available in DSpace on 2011-05-25T15:04:57Z (GMT). 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