Molecular electronics involves 1) the use of the novel combinations of macroscopy properties offered by organic molecular materials in electronic and optoelectronic devices, and 2) the study of systems at the molecular scale in order to determine their potential as components of molecular scale devices. Conjugated, conductive polymers offer good prospects for mid-term application, but still require basic studies to underpin the development of materials suitable for use in practical devices. Molecular-scale electronics is a much longer term target which, at present, lacks a strong fundamental scientific base. Both aspects of molecular electronics will be addressed in the TOPFIT project.
Conjugated oligomers and polymers with precise structure and molecular weight are being prepared for basic scientific studies of macroscopic and microscopic chemical, electronic and optical properties.
Model polymers and oligomers have been prepared and preliminary samples of end functionalized polyene oligomers are available. Laser apparatus for photophysical studies is being assembled and tested on known samples. Theoretical calculation of the band gaps of a series of model polymers is providing guidelines for synthesis. The characterization of conductive polymer layers for capacitors has been completed ahead of schedule. An evaluation procedure has been developed to evaluate the potential of materials for field effect transistors (FET) etc. Initial studies of sensors utilizing enzymes incorporated in conductive polymers are underway. Scanning tunnelling microscopy (STM) studies of materials on graphite substrates have revealed extreme sensitivity of the formation of stable, imageable layers to molecular structure. Modelling of molecule substrate interactions together with studies of specifically prepared molecules and a range of substrates are being undertaken to elucidate this effect. Software for image analysis has been tested on STM images of monolayers.
APPROACH AND METHODS
Oligomers and polymers will be synthesised with precise stereochemistry, molecular weight and chemical structures chosen to give controlled energy gaps between valence and conduction bands. Experimental and theoretical studies will be directed to providing an understanding of the conduction processes; the measurement of the evolution of properties as a function of chain length will underpin this effort. The mid- and long-term application of these materials as the active components in capacitors, FETs, etc. will be explored in collaboration with the industrial partner.
Scanning tunnelling microscopy (STM) observations indicate that highly ordered monolayers require molecular structures similar to those of conductive materials. Methods for the reproducible preparation of ordered monolayers of specifically synthesised molecules on solid surfaces will be explored and their structure, physical and chemical properties studied. The aim will be to obtain monolayers that can be manipulated to provide elementary data storage and processing functions.
Parallel work in computational science will be initiated in order to provide a broad, well-balanced basis for future developments beyond the lifetime of this project.
Since the physics of semiconductive polymers is different from that of conventional semiconductors, the development of stable, processable materials offers prospects for both improvements of currently available components and totally new devices. Investigations conducted at the molecular scale will enable the long term prospects for molecular scale devices to be evaluated on a firm scientific basis.
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