Characterization of Carbon Nanotubes and Nanowires and Their Applications

Kim, Ki Chul

Graduate Thesis Or Dissertation

Characterization of Carbon Nanotubes and Nanowires and Their Applications Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/ft848q847

Abstract

This thesis establishes comprehensive methodology for characterization of metallic nanowires (NWs) and carbon nanotubes (CNTs), and evaluation of their performance for interconnect applications at microwave/ mm-wave/THz frequencies. The research focus is on the development of modeling and measurement methods to determine constitutive material parameters, i.e. conductivity, and contact resistance of platinum (Pt) NWs, as well as on the development of modeling approaches to evaluate characteristic parameters for antennas, nano-coaxial lines, and single wire transmission lines composed of CNTs. Applicability of traditional two-port measurements is investigated for accurate determination of material parameters for Pt NWs over a broad frequency range. Two test-setups are developed. First, several configurations with directly contacted Pt NWs to a host coplanar waveguide (CPW) structure are designed and realized to determine the conductivity and contact resistance. Full-wave finite element and circuit models are used to determine the two parameters by fitting simulations to measurements. It is found that the single measurement setup with direct contacts cannot determine the two parameters simultaneously. To solve this problem, two approaches based on transmission line and lumped element models for Pt NWs are developed. Both approaches employ a set of two NWs with different lengths. The feasibility of both approaches is thoroughly studied and relevant conclusions are made. An approach based on lumped element models is validated experimentally, and it is shown that the contact resistance and conductivity of 300 nm diameter Pt NWs are about 50 W and 0.013sbulk, respectively. In the second setup, the capacitive coupling contact between the Pt NWs and the CPW structure is exploited to determine the NW’s conductivity. Two variations of this setup, specifically in-slot and on-dielectric configurations, are developed. Full-wave finite-element models are utilized to demonstrate suitability of the two configurations and to determine the conductivity of Pt NWs by fitting to measurements. Structural and elemental analyses of fabricated devices are conducted to assess fabrication and measurement issues. Full-wave modeling for individual CNTs and CNT bundles is performed by the use of method of moments and finite element method codes in order to CNTs as antennas, nano-coaxial lines, and single wire transmission lines. Characteristic parameters, such as impedance, gain, efficiency, and line loss for each interconnect are evaluated and compared to those of their copper-based counterparts. Results show better performance of CNTs over conventional metals at microwave frequencies. The extension of modeling and metrology for semiconducting NWs and CNTs, and the study of graphene at microwave frequencies are proposed as directions for future work.

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