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A systematic investigation of the dispersion of carbon nanotubes (CNTs), 1-6 nm in diameter and a few microns in length, in a bisphenol F-based epoxy resin has been presented. Several dispersing techniques including high-speed dissolver, ultrasonic bath/horn, 3-roll mill, etc. have been employed. Optical microscopy has been extensively used to systematically characterise the state of CNT dispersion in the epoxy resin during the entire processing cycle from mixing CNT with resin to adding and curing with hardener. Complimentary viscosity measurements were also performed at various stages of nanocomposite processing. A method to produce a good CNT dispersion in resin was established, but the state of CNT dispersion was found to be extremely sensitive to its physical and chemical environments. The cured nanocomposites were further tested for their thermo-mechanical properties by dynamic mechanical thermal analysis (DMTA), and for flexural and compressive mechanical properties. The measured properties of various nanocomposite plates were then discussed in view of the corresponding CNT dispersion.

Iodinated single-walled carbon nanotubes, with iodine covalently bound to the nanotube surface, have been synthesized by oxidation of the carbon nanotubes followed by a modified Hunsdiecker reaction using elemental iodine and iodosobenzene diacetate (IBDA). High-resolution transmission electron microscopy (HRTEM) images show small high-contrast spots which are stable to the electron beam and are assigned to iodine atoms bonded to the surface of the nanotube. Importantly, the electronic properties of the nanotubes were found to be largely intact after functionalization. The iodinated carbon nanotubes were fully characterized using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV−vis−NIR spectroscopy, and thermogravimetric analysis−mass spectrometry (TGA-MS).

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Resonant inelastic x-ray scattering (RIXS), x-ray absorption spectroscopy and x-ray excited optical luminescence (XEOL) have been used to measure element specific filled and empty electronic states over the Si L(2,3) edge of passivated Si nanocrystals of narrow size distribution (diameter 2.2 ± 0.4 nm). These techniques have been employed to directly measure absorption and luminescence specific to the local Si nanocrystal core. Profound changes occur in the absorption spectrum of the nanocrystals compared with bulk Si, and new features are observed in the nanocrystal RIXS. Clear signatures of core and valence band exciton formation, promoted by the spatial confinement of electrons and holes within the nanocrystals, are observed, together with band narrowing due to quantum confinement. XEOL at 12 K shows an extremely sharp feature at the threshold of orange luminescence (i.e., at ∼1.56 eV (792 nm)) which we attribute to recombination of valence excitons, providing a lower limit to the nanocrystal band gap.

The TiO2∕SiO2 gate dielectric stack on 4H-SiC substrate has been studied as a high-κ gate dielectric for metal-oxide semiconductor devices. X-ray photoelectron spectroscopy confirmed the formation of stoichiometric TiO2 films. The leakage current through the stack layer was investigated and it has been shown to be a double conduction mechanism. At low fields, the current is governed by properties of the interfacial layer with a hopping like conduction mechanism, while at relatively high electric field, carriers are modulated by a trap assisted tunneling mechanism through traps located below the conduction band of TiO2. The current-voltage characteristics, time evolution of charge transport, and capacitance-voltage behaviors under constant voltage stressing suggest the composite effect of electron trapping and positive charge generation in the dielectric stack layer.