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Title: Molecular electronic properties of porphyrin nanowires
Author: Bennett, Neil
ISNI:       0000 0004 2750 126X
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2010
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Single porphyrin molecules and porphyrins isolated in a matrix of alkanethiols were probed by I-V spectroscopy. Repeated I-V measurements on individual molecules showed evidence of temporal fluctuations and changes of the coupling asymmetry in the molecular junctions. Analysis using the transition voltage spectroscopy technique revealed fluctuations in the voltage minimum Vm, which we suggest is due to the changing nature of the single molecule contact, and this provides estimates of the degree of contact asymmetry. Statistical analysis suggests more than one preferred value of Vm and a molecular energy level alignment to the Fermi energy of E FϵHOMO & 0.4 eV. The behaviour contrasts strongly with results from measurements over the alkanethiol matrix and over porphyrin monolayers, where such fluctuations are absent, in general agreement with previously reported studies. The results can be understood using a simple molecular model of coherent tunnelling and we conclude the electrical properties of single molecular junctions are highly sensitive to the microscopic details of the contacts and molecular conformations or configurations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available