Dr Kevin Donovan Project Abstracts
BSc Project Abstracts and MSci Research/Investigative Project Abstracts
Induced Optical Anisotropy in Carbon Nanotube Suspensions
Single and multi-walled carbon nanotubes in suspension will, under the influence of a pulsed electric field align in that field. This alignment may be observed in real time by observing the temporal growth of induced optical birefringence and or dichroism. This project will use the induced optical birefringence to measure the polarisability of the nanotubes along with their average length and their effect on the viscosity of the suspending medium as their concentration is increased.
The Length Distribution of Single Walled Carbon Nanotubes
Single walled carbon nanotubes, SWCNTs, in suspension will, under the influence of a pulsed electric field align in that field. Once the field is switched off the nanotubes will slowly return to their state of random orientation. The randomisation over time may be followed by observing the change in optical anisotropy of the suspension. The rate at which this randomisation occurs will depend on the length of the SWCNT and therefore it should be possible to infer the length of the nanotubes from the decay. This project will involve using the fitting of such decays to find the length distribution of the SWCNTs. A good knowledge of Mathematica, Matlab and/or C++ would be useful to carry out the fitting.
Drift Velocity of Solectrons on One Dimensional Molecular Wires
Charge carriers (electrons or holes) in one dimensional, 1D, semiconductors will strongly interact with the 1D lattice vibrations or phonons forming an electron plus lattice deformation, the composite object being called a Solectron. A remarkable property of the Solectron is that the charge will travel at the velocity of sound (a relatively low velocity) but will achieve this velocity at very low electric fields entailing an ultra-high mobility. Such a 1D semiconductor is provided by single crystal polydiacetylenes, PDAs, and the properties of the Solectron may be studied through the photoconductive properties of the PDA following excitation by a rapid laser pulse. The object of this project is to measure the transient photocurrent and the total photocharge created by such a laser pulse and thus deduce the drift velocity of carriers on PDA chains and how it varies with applied electric field.
The Polydiacetylene Solectron Field Effect Transistor.
Charge carriers travelling on polydiacetylenes, a unique polymer obtainable as large single crystals, have been demonstrated to distort the polymer chain, travelling on the polymer backbone together with this distortion. This collective entity, the Solectron, suffers very little dissipation as it travels offering the possibility of low power consumption devices. The ambition of this project is to employ the Solectron as the means of charge transport in a Field Effect Transistor, using polydiacetylene molecular wires to replace silicon as the semiconducting channel. The intrinsically low dissipation of the Solectron allows operation of a transistor with very low power consumption compared with silicon devices.
