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Title:Scanning tunneling microscopy investigation of atomically precise graphene nanoribbons
Author(s):Radocea, Adrian
Director of Research:Lyding, Joseph W.
Doctoral Committee Chair(s):Lyding, Joseph W.
Doctoral Committee Member(s):Girolami, Gregory; Shim, Moonsub; Huang, Pinshane; Schleife, André
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Graphene Nanoribbons
Scanning tunneling microscopy
Scanning tunneling spectroscopy
10,10′-dibromo-9,9′-bianthracene (DBBA)
Abstract:This dissertation demonstrates the dry contact transfer of atomically precise graphene nanoribbons onto H:Si(100) under ultra-high vacuum, detailed electronic characterization, and electron-mediated polymerization of graphene nanoribbon precursors into polyanthrylene. Detailed scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) measurements provided high-resolution imaging and reveal a 2.76 eV bandgap for chevron graphene nanoribbons. It was also discovered that tunneling to the substrate influenced STS measurements. STM and STS studies of two additional GNR geometries, the extended chevron GNR (eGNR) and the hybrid GNR (hGNR) elucidate how structural modification alters the bandgaps of GNRs. The increased lateral extension of the eGNR was found to result in a bandgap of 2.66 eV. The hGNR bandgap was found to be 1.8 eV, in agreement with computational modeling. The hypothesis that positional control over graphene nanoribbon synthesis could be achieved by tip-induced polymerization was explored. While the thermal self-assembly of 10,10′-dibromo-9,9′-bianthracene (DBBA) into N=7 armchair GNRs was previously demonstrated, the electron-mediated formation of polyanthrylene (GNR intermediate) formation was not previously shown. The STM experiments suggest that when the DBBA is thermally annealed to form a close-packed zigzag structure, an STM tip can be used to drive a de-bromination reaction which is followed by polyanthrylene formation, demonstrating a key step towards positional control over GNR synthesis.
Issue Date:2017-06-26
Rights Information:Copyright 2017 Adrian Radocea
Date Available in IDEALS:2017-09-29
Date Deposited:2017-08

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