Browsing by Author "Mainwaring, DE"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Electron transport properties of irradiated polyimide thin films in single track regime
    (American Institute of Physics, 2009-03-23) Murugaraj, P; Mainwaring, DE; Siegele, R
    We have prepared a suite of polyimide thin films containing spatially separated one-dimensional conductive-nanowires by ion-beam irradiation exhibiting temperature dependent electrical resistance consistent with thermally activated electron hopping with activation energies about 1 eV arising from localized states spatially distributed along the ion tracks. Dielectric measurements showed the formation of high dielectric constant interphase regions surrounding each ion track generated during the irradiation process, responsible for space-charge accumulation which influences electron transport within the ion tracks. This behavior suggests a role for space-charge effects and dielectric properties in this interphase region in the control of electron transport within single track nanowires. © 2009, American Institute of Physics
  • No Thumbnail Available
    Item
    Formation of energetic heavy ion tracks in polyimide thin films
    (Elsevier, 2013-11-01) Deslandes, A; Murugaraj, P; Mainwaring, DE; Ionescu, M; Cohen, DD; Siegele, R
    Polyimide thin films have been irradiated with a high energy beam of heavy ions to a fluence of approximately 4 × 1013 ions/cm2. Proton backscattering spectroscopy was used to measure the composition of the films, which showed that oxygen was the element that exhibited the most rapid loss from the film. The gases evolved from the film during polymer modification were monitored using a quadrupole mass spectrometer for residual gas analysis (RGA). The fluence dependence of RGA signals were indicative of multi-step processes of gas release, whereby the passage of an ion through a region of pristine film changes the local molecular structure to one that will more readily form volatile species when subsequent ions pass. © 2013, Elsevier B.V.
  • No Thumbnail Available
    Item
    Improved electromechanical sensitivity of polymer thin films containing carbon clusters produced in situ by irradiation with metal ions
    (Elsevier, 2010-12) Murugaraj, P; Mainwaring, DE; Khelil, NA; Peng, JL; Siegele, R; Sawant, P
    Greatly enhanced electromechanical sensitivities were observed in ion beam irradiated polyimide films, where high resolution transmission electron microscopy and atomic force microscopy studies showed that 5.5 MeV Cu3+ ions produce randomly dispersed and highly oriented conducting nanochannels containing carbon clusters in polyimide with considerable overlap and narrow tunnel gap distributions between neighbouring nanochannels. Selected area electron diffraction studies confirmed the graphitic structure of these carbon clusters and also showed that the graphitic layers had preferential orientation parallel to the ion beam direction arising from relaxation of the graphitic layers within the nanochannels relieving local surface stresses in the polyimide matrix generated during irradiation as well as alignment of graphitic basal layers by volatile gases formed during irradiation escaping to the surface minimising resistance to gas flow. Electron energy loss spectroscopy also confirmed the graphitic structure of these carbon clusters within the nanochannels. Film electrical resistance increased exponentially with applied strain demonstrating the dominant role of tunnel gap modulation under strain. Gauge factors >1000 were achieved in these films at >3000 μstrains. Narrow distribution of tunnel gaps between the overlapping nanochannels is responsible for the high electromechanical sensitivities observed in these films compared to carbon nanotube–polymer (50) films. © 2010, Elsevier Ltd.
  • No Thumbnail Available
    Item
    Probing the structure of nanochannal arrays by electrostatic force microscopy
    (World Scientific Publishing Co., 2011-04-01) Murugaraj, P; Kumar, N; Jakubov, T; Mainwaring, DE; Siegele, R
    Electrostatic force microscopy (EFM) represents a versitile tool for the characterisation of electric and dielectric structures at nanoscale which can be employed to provide charge distributions associated with such nanotopologies. EFM-phase profiles show only the variation of electrostatic force which is strongly influenced by the surface conductivity of nanostructured arrays providing improved definition compared to conventional AFM. Here we apply it to carbon nanochannel arrays embedded within polyimide dielectric matrices. © 2012 World Scientific Publishing Co.