Document Type

Theses, Ph.D


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Publication Details

Successfully submitted for the award of Doctor of Philosophy (Ph.D) to the Technological University Dublin, 2008


The aim of this project is to investigate the effect of bulk structural modification on the electronic properties of fullerene systems as measured using electronic and Electroabsorption (EA) spectroscopy. The existence of a unique solid state feature in C60 is the first indication that the material’s electronic properties may be influenced by its crystalline environment and as such merits investigation. The nature and extent of these interactions in the solid state is still unclear, in particular whether the molecular electrons remain located on the individual molecules or whether they are delocalised across the solid. The extent of these interactions has major repercussions for any proposed electronic or optical applications for fullerenes e.g. in optical switches of luminescent displays. This work presents the effect of structurally altering fullerene films using systematic thermal treatments. A dramatic irreversible effect is observed in the absorption spectrum of C60 as the sample is annealed, indicating a reduction in the charge transfer (CT) processes associated with these transitions. This reduction can be attributed to a closer packing of the molecules in the solid state phase. Data obtained form EA spectroscopy confirms the reduction oscillator strength of the mode at 2.43eV normally associated with the off diagonal CT state again supporting the notion of a closer packed lattice. Analysis of C70 fullerene films also shows an associated increase in oscillator strength of the CT integrals as a result of the thermal treatment process, highlighting the importance of the material’s crystalline environment in determining the material’s electronic properties


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