Browsing by Author "Todd, M. A."

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    Comparative studies of PST thin films as prepared by Sol-Gel, LDCVD and sputtering techniques
    (Taylor and Francis, 2002) Huang, Zhaorong; Donohue, P. P.; Zhang, Qi; Williams, D.; Anthony, C. J.; Todd, M. A.; Whatmore, Roger W.
    Lead scandium tantalate (PST) thin films for pyroelectric applications have been deposited by using liquid delivery chemical vaporise deposition (LDCVD), sputtering and sol-gel techniques. These films were annealed by using rapid thermal annealing to improve their electrical properties. Their microstructures and electrical properties such as permittivity εr, dielectric loss tanδ, pyroelectric coefficient p, and thermal detection figure of merit Fd were studied. It is suggested to use a combination of methods to depositing films and then use rapid thermal annealing to produce high quality PST thin films.
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    Kinetics of phase transformations in lead scandium tantalate thin films
    (Taylor and Francis, 2004) Battat, J.; Huang, Zhaorong; Donohue, P. P.; Todd, M. A.; Whatmore, Roger W.
    The phase transformations from amorphous to pyrochlore to perovskite in lead scandium tantalate (PST) thin films during rapid thermal annealing process (RTA) have been studied. Volume fractions for pyrochlore and perovskite were obtained from their respective X-ray diffraction intensities. Two models assuming the starting phase being pure amorphous or pyrochlore were analysed in detail. Equations have been derived and numerical calculation used to simulate the volume fractions for each phase as functions of annealing time. Transformation parameters k and n were obtained by comparing experiment with simulation using a least-squares curve fitting technique.
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    Pulse-extended excimer laser crystallisation of Pb(Zr,Ti)O 3 thin films for integration on low thermal budget substrates
    (Taylor and Francis, 2003-06) Donohue, P. P.; Todd, M. A.; Huang, Zhaorong
    Excimer laser annealing has been used to convert low temperature (non-ferroelectric) deposited lead zirconate titanate (PZT) to the perovskite phase without significantly heating underlying layers. A pulse-extension technique has been used to lengthen the laser pulse duration from 25 ns to 374 ns, lowering the surface temperature and improving the heat distribution in the PZT, as compared to the non-extended case, but still not significantly heating the substrate. Initial experiments are reported which have shown the technique to be capable of crystallising over half a 500 nm thick PZT film to perovskite although a melting effect limited the converted thickness. The thickness crystallised is however of the order of that used in FeRAM devices and modelled temperature profiles suggest that the technique provides a tractable solution for high temperature processing of ferroelectric thin films of thickness 200-300 nm on low thermal budget substrates.