Interference effects in molecular nanojunctions



Ferri, N
(2019) Interference effects in molecular nanojunctions. PhD thesis, University of Liverpool.

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Abstract

Nicolò Ferri: Interference effects in molecular nanojunctions From the earliest theoretical investigation of the possibility of single molecule conductance, to today where single molecule conductance techniques are becoming routine operations, the field of molecular electronics has grown exponentially, becoming an important research topic with possible future applications. Understanding electron transport in nanojunctions has lately been a hot topic and represents a fundamental step for the advancement of molecular electronics. This thesis aims at unravelling some of the mysteries and mechanisms that revolve around the behaviour of some molecular wires. This thesis focusses its attention towards interference effects in organic molecular wires: in this thesis two main types of interferences are studied: one located on the contacts of a series of molecular wires and one regarding the structure-property relationships within molecular wires. The novelty of this work lies in the synthesis of new molecular wires and their conductance studies with STM-based techniques. The first project demonstrated the existence of strong interactions between thiol contacts and gold electrodes (so-called ‘gateway states’) that were interfering with the conductance decay of a series of double barrier tunnelling molecular wires of increasing length by suppressing the attenuation of their conductance over their length. A simple experiment supported by theoretical calculations featuring the synthesis of molecular wires with thiols replaced by thioether contacts demonstrated the existence of these interactions by cancelling their effects. The second project was focussed on the study of interference effects in thiophene-based molecular wires. Several series of molecular wires were synthesized in multiple subprojects to gain a better understanding of these effects by finely tuning the molecular wires structures such as the introduction of heteroatom bridges and the insertion of carbonyl moieties as cross conjugation points within the backbone of a molecular wire. On this project some unusual switching properties of some of the wires were discovered and investigated. Finally, this study managed to shed some light on the behaviour of all the bithiophene-based molecular wires analysed and the information discovered will be useful in the tool-box for finely tuning properties of molecular wires.

Item Type: Thesis (PhD)
Divisions: Fac of Science & Engineering > School of Chemistry
Depositing User: Symplectic Admin
Date Deposited: 26 Mar 2019 11:23
Last Modified: 03 Mar 2021 17:05
DOI: 10.17638/03031638
Supervisors:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3031638