With the miniaturisation of silicon based technology approaching its fundamental physical limit, molecular electronic components are considered an alternative route to prolong the lifetime of integrated circuit technology. In order to realise this technology, the fundamental physical and electronic properties of such nanoscopic materials and devices must be fully understood.
This thesis reports the successful formation and characterisation of a series of novel molecular wires on both planar and nanoparticulate surfaces, from which two papers have been published. Formation of these wires was achieved using the reproducible chemical self-assembly method often utilised in bottom-up molecular electronics. After the initial chemisorption of a functional headgroup to a suitable substrate, subsequent layers were chemically reacted by means of an imine bond formation. This allowed multilayer donor-π-bridge-acceptor systems of up to ca. 10.4 nm in length to be constructed. Not only does this
method allow the formation of reasonably complex systems, it also enables functionality to be incorporated into the wire. The assembly characteristics of various wires have been characterised using Quartz Crystal Microbalance and X-ray Photoelectron Spectroscopy, and in the case of those on TiO₂ nanoparticles, with Infrared Spectroscopy. Furthermore, an investigation into the factors affecting the formation of upright, homogeneous monolayers was carried out on a set of related compounds, revealing the importance of molecule-molecule
and molecule-substrate interactions.
Multiple molecular wires were also characterised with respect to their electrical properties which show symmetrical or asymmetrical current-voltage curves. This was done using Scanning Tunnelling Spectroscopy to obtain current-voltage characteristics, as well as the so called current jump method to measure single molecule current or that of small clusters of molecules. The effect of increasing molecular length and steric hindrance on molecular current rectification was examined, as well as the effect of increasing length on single molecule conductance.