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Title:Selective metallization and electronic self-healing for high performance carbon-based nanoelectronics
Author(s):Do, Jae Won
Director of Research:Lyding, Joseph W.
Doctoral Committee Chair(s):Lyding, Joseph W.
Doctoral Committee Member(s):Rogers, John A.; Girolami, Gregory S.; Li, Xiuling
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Carbon Nanotube (CNT)
intertube junction
electrical resistance
thermal resistance
solution deposition
covalent bonding
local chemical vapor deposition (CVD)
Abstract:Carbon-based nanomaterials have great potential to be used in future nanoelectronics due to their unique combinations of electrical, thermal, and mechanical properties. Specifically, carbon nanotubes (CNTs) and graphene have attracted great interest over the past decade in both the scientific and industrial communities for a variety of applications including high-performance thin-film transistors (TFTs) and conductive electrodes on transparent and flexible substrates, heat spreaders, and high-strength applications utilizing CNT macrostructures, such as CNT yarns and sheets. However, presently realized applications usually suffer from the high junction resistances between individual CNTs and graphene grains, which cause the performance and reliability of such applications to be significantly lower than those of individual CNTs and graphene. In this dissertation work, we study novel techniques that take advantage of such high resistances in order to enable selective metallization and self-healing in CNT and graphene based devices. First, we investigate a method to reduce the high CNT junction resistance through a nanoscale chemical vapor deposition (CVD) process. We show that by passing current through the CNT devices in the presence of CVD precursor, localized Joule heating induced at the CNT junctions stimulates selective and self-limiting deposition of metallic nanosolder. We also show that the effectiveness of this nanosoldering process depends on the work function of the deposited metal, which can improve the on/off current ratio of CNT devices by nearly an order of magnitude when the right metal (Pd) is chosen. Then, we introduce a different route to carry out the nanosoldering process by applying the metal precursor using a solution-mediated technique. The new process not only facilitates the selective metallization of Pd nanoparticles at the CNT junctions to improve the device performance, but it also enables a multitude of different precursors to be used to deposit a variety of materials. With the enhanced solution-mediated application technique, we then study the versatility of our nanosoldering process by applying it to graphene devices. We show that the grain boundaries (GBs) formed between individual grains act similarly to CNT junctions by heating up during device operation. We also show that the local temperature increases at the GBs trigger the thermal decomposition of metal precursor to deposit Pd selectively at the GBs, which can result in improvement in the overall resistance of the graphene device as well as redistribution of the temperature. Lastly, the nanosoldering process is investigated with an organic-based precursor to bring about further improvement in the CNT devices. The organic-based precursor composed of halogenated aromatic hydrocarbons can undergo dehalogenation and dehydrogenation processes upon heat treatment, resulting in two-dimensional covalent networks of carbon atoms. Our results from combining our nanosoldering technique with the organic-based precursor show significant improvements in the device performance, suggesting that even better connection is achieved at the CNT junctions, possibly by depositing covalent networks of carbon atoms and/or covalently linking individual CNTs at the junctions. Overall, the research described in this dissertation represents a novel technique, which can be used to realize significant improvements in CNT and graphene based devices through electronic self-healing. The nanosoldering technique potentially could also be applied to other device types where nanoscale resistance components limit overall device performance and reliability by improving their electrical, thermal, and mechanical properties.
Issue Date:2015-04-22
Rights Information:Copyright 2015 Jae Won Do
Date Available in IDEALS:2015-07-22
Date Deposited:May 2015

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