The influence of conjugation in molecular tunneling junctions and nanofabrication

Yanxi Zhang

Research output: ThesisThesis fully internal (DIV)

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The goal of this thesis is to investigate the tunneling properties of large-area molecular junctions comprising self-assembled monolayers (SAMs) of conjugated, organic molecules with different conjugation patterns and to incorporate them into three-terminal junctions to modulate the tunneling charge transport via gating with electric fields. In Molecular Electronics, it is crucial to understand how the conjugation patterns influence the tunneling charge transport. First, we studied the properties of SAMs comprising quaterthiophene with a flexible butanethiol chain using CP-AFM and EGaIn as the top contacts. We found the SAM is mechanically and electrically robust. Next, we designed and synthesized three benzodithiophenes based molecular wires with different conjugation patterns. Then we studied the tunneling charge transport of the large-area molecular junctions comprising these molecules and compared the results to a well-known anthraquinone. We found that the quinone functional group doesn’t only introduce cross conjugation but also suppresses tunneling transport due to its electronegativity. Later we tried to incorporate organic molecules into nano-gap tunneling junctions using nanoskiving, that we call SAM-templated addressable nanogap electrodes (STANs). We discussed our efforts to fabricate the solid-state devices comprising molecular tunneling junctions. In the last part, we fabricated the ultra-long, free-standing gold nanowires using nanoskiving. We demonstrated two applications of the suspended gold nanowires in the microfluidic channels: One acts as a hot-wire anemometer that measures the flow by a change in resistance across the Au nanowire; and the other is that stretching DNA molecules in the stream to visualize them by single-molecule fluorescence imaging.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University of Groningen
  • Chiechi, Ryan, Supervisor
  • Hummelen, Kees, Supervisor
  • Hong, W., Assessment committee, External person
  • Pchenitchnikov, Maxim, Assessment committee
  • van der Giessen, Erik, Assessment committee
Award date26-Oct-2018
Place of Publication[Groningen]
Print ISBNs978-94-034-1101-9
Electronic ISBNs978-94-034-1100-2
Publication statusPublished - 2018

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