Investigation of Carbon Nanotube Properties and Applications at Microwave and THz Frequencies

Persistent Link:
http://hdl.handle.net/10150/195098
Title:
Investigation of Carbon Nanotube Properties and Applications at Microwave and THz Frequencies
Author:
Wang, Lu
Issue Date:
2010
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This dissertation presents research on synthesis, high-power microwave post-synthetic purification and high frequency characterization of Carbon Nanotubes (CNT). First, CNTs are synthesized using a Chemical Vapor Deposition system. The impact of substrate and methane flow rate on CNT growth is studied using Scanning Electron Microscopy, Transmission Electron Microscopy and Raman microscopy. Second, the microwave irradiation effects on purified HiPCO and CoMoCat Single-Walled CNT thin films are investigated. The measured drastic THz power transmission increase (>10 times) indicates a significant metallic content reduction after the irradiation. The Raman spectra also confirm the metallic-to-semiconducting ratio of Raman-active CNTs decreases by up to 33.3%. The observed microwave-induced effects may potentially lead to a convenient scheme for CNT demetalization. Third, Multi-Walled CNT papers are characterized from 8 to 50 GHz by rectangular waveguide measurements using a vector network analyzer. A rigorous algorithm is developed to extract the samples' effective complex permittivity and permeability from the measured S-parameters. Unlike other reported work, this method does not impose the unity permeability assumption. The algorithm is verified by finite-element simulations and the uncertainties for the characterization method are analyzed. The effective medium theory is then applied to obtain the intrinsic CNT properties. Furthermore, Terahertz Time-Domain Spectroscopy is used to characterize the samples from 50 to 370 GHz. Both transmission and reflection experiments are performed to simultaneously extract the permittivity and permeability. The extracted permittivity is fitted with a Drude-Lorentz model from 8 to 370 GHz. Finally, individual CNT characterizations at microwave frequency are studied. The impacts from impedance mismatching and parasitics on measurement sensitivity are systematically studied, revealing that the parasitic effect is possibly dominant above 10 GHz. A tapered coplanar waveguide test fixture is designed using Advanced Design System (ADS) to improve the impedance mismatching and minimize the test fixture parasitics, therefore optimize the measurement sensitivity. A de-embedding procedure to obtain the CNT's intrinsic electrical properties is presented and demonstrated with ADS simulations. In addition, the test fixture fabrication process is discussed, which is an ongoing research work. At the end, the conclusions of this dissertation are drawn and possible future works are discussed.
Type:
text; Electronic Dissertation
Keywords:
Carbon Nanotube; Microwave; RF; Terahertz
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Physics; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Xin, Hao
Committee Chair:
Xin, Hao

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleInvestigation of Carbon Nanotube Properties and Applications at Microwave and THz Frequenciesen_US
dc.creatorWang, Luen_US
dc.contributor.authorWang, Luen_US
dc.date.issued2010en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis dissertation presents research on synthesis, high-power microwave post-synthetic purification and high frequency characterization of Carbon Nanotubes (CNT). First, CNTs are synthesized using a Chemical Vapor Deposition system. The impact of substrate and methane flow rate on CNT growth is studied using Scanning Electron Microscopy, Transmission Electron Microscopy and Raman microscopy. Second, the microwave irradiation effects on purified HiPCO and CoMoCat Single-Walled CNT thin films are investigated. The measured drastic THz power transmission increase (>10 times) indicates a significant metallic content reduction after the irradiation. The Raman spectra also confirm the metallic-to-semiconducting ratio of Raman-active CNTs decreases by up to 33.3%. The observed microwave-induced effects may potentially lead to a convenient scheme for CNT demetalization. Third, Multi-Walled CNT papers are characterized from 8 to 50 GHz by rectangular waveguide measurements using a vector network analyzer. A rigorous algorithm is developed to extract the samples' effective complex permittivity and permeability from the measured S-parameters. Unlike other reported work, this method does not impose the unity permeability assumption. The algorithm is verified by finite-element simulations and the uncertainties for the characterization method are analyzed. The effective medium theory is then applied to obtain the intrinsic CNT properties. Furthermore, Terahertz Time-Domain Spectroscopy is used to characterize the samples from 50 to 370 GHz. Both transmission and reflection experiments are performed to simultaneously extract the permittivity and permeability. The extracted permittivity is fitted with a Drude-Lorentz model from 8 to 370 GHz. Finally, individual CNT characterizations at microwave frequency are studied. The impacts from impedance mismatching and parasitics on measurement sensitivity are systematically studied, revealing that the parasitic effect is possibly dominant above 10 GHz. A tapered coplanar waveguide test fixture is designed using Advanced Design System (ADS) to improve the impedance mismatching and minimize the test fixture parasitics, therefore optimize the measurement sensitivity. A de-embedding procedure to obtain the CNT's intrinsic electrical properties is presented and demonstrated with ADS simulations. In addition, the test fixture fabrication process is discussed, which is an ongoing research work. At the end, the conclusions of this dissertation are drawn and possible future works are discussed.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectCarbon Nanotubeen_US
dc.subjectMicrowaveen_US
dc.subjectRFen_US
dc.subjectTerahertzen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorXin, Haoen_US
dc.contributor.chairXin, Haoen_US
dc.contributor.committeememberHsieh, Ke Chiangen_US
dc.contributor.committeememberLeroy, Brianen_US
dc.contributor.committeememberMelia, Fulvioen_US
dc.contributor.committeememberShupe, Michaelen_US
dc.identifier.proquest10920en_US
dc.identifier.oclc659754817en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.