Planje, Inco 
ORCID: 0000-0003-2188-8611
(2020)
Junction design strategies in molecular electronics.
PhD thesis, University of Liverpool.
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Abstract
The field of molecular electronics ultimately aims to develop electronic devices using single molecules as building blocks. To achieve this goal, a thorough understanding of the structure-property relationships in molecular architectures is crucial. The past few decades have seen an explosive number of studies in this emerging field, establishing a solid foundation for electronic interactions at the nanoscale. Despite this progress, the route to genuinely stable and reproducible devices still faces many challenges. This work contributes to tackling some of these challenges by studying the effects of manipulating components of a nanoscale junction on its electronic transport properties. Scanning tunnelling microscopy techniques are employed to fabricate junctions and measure the current through them. Firstly, the influence of junction design on electron transport is studied by inserting platinum or ruthenium metal atoms in the molecular bridge. These organometallic wires generally have a higher conductance than their organic counterparts due to a smaller gap between highest occupied and lowest unoccupied molecular orbitals. However, in the thioether induced midgap wires studied here, only the ruthenium wires show an increased conductance. This is a result of a stronger coupling between molecule and metal, and a better distribution of orbitals along the entire junction, which is not the case for the platinum wires. In the second part, one of the two metal electrodes is replaced by transparent indium tin oxide for future optoelectronic studies and applications. New anchoring groups for binding to this semiconductor electrode are designed and show promising results, including one group that only binds to this indium tin oxide electrode. Moderate rectification is also observed for these metal-molecule-semiconductor junctions. In the third and last part, three junction designs for studying complex effects in molecular structures are discussed. The first is a three-dimensional metal complex, designed to study supramolecular lateral effects, where the metal does not seem to participate in the transport pathway. The second contains a metallic anchoring group, which does not seem to be suitable for forming junctions using the dynamic scanning tunnelling microscopy break-junction technique. Finally, a molecular wire that is designed for optical switching shows a curious inverse correlation of conductance with applied bias voltage. The results presented here confirm yet again that there is a complex interplay between several key parameters, which together dictate the electrical behaviour of nanoscale junctions.
| Item Type: | Thesis (PhD) |
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| Divisions: | Faculty of Science and Engineering > School of Physical Sciences > Chemistry |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 15 Jan 2021 16:09 |
| Last Modified: | 18 Jan 2023 23:29 |
| DOI: | 10.17638/03104055 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3104055 |
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