Browsing by Author "Lambi, John Ngolui"

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    Compositional studies of various metal oxide coatings on glass
    (Thin Solid Films, 9019-02) Ajayi, E.O.B; Akanni, M.S; Lambi, John Ngolui; Jeynes, Chris
    Oxide films were deposited on soda-lime glass substrates by pyrolysis of indium, copper, chromium and aluminium acetylacetonates. Ion beam analysis and X-ray photoelectron spectroscopy were performed showing that the appropriate metal oxides were deposited. The indium and chromium oxide films appeared to be quite clean but the copper and aluminium oxide films were porous and had very high concentrations of carbon with associated oxygen. The copper film also had significant free copper near the surface. Significant leaching of sodium and potassium from the substrate in these two latter films was also observed. Promising optical absorbance was observed for the chromium film
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    Preparation and Characterisation of Pyrolytically-Deposited Thin Oxide Films from Metal-Organic Compounds
    (Obafemi Awolowo University, 1987) Lambi, John Ngolui; Ajayi, O.B.; Akanni, M.S.
    A simple and versatile pyrolytic method of preparing thin metal oxide films that is based on the Metal Organic Chemical Vapour Deposition (MOCVD) technique and that is operative at relatively low temperatures (420°C) has been utilised to prepare the thin metal oxide films of indium, zinc, aluminium and copper from the appropriate metal acetylacetonate or carboxylate. To fully understand the pyrolytic route leading to film formation, the thermal decomposition of some of the starting materials was investigated in detail at 420°C in air and N,, using separately, a Muffle furnace and a flow system. The identities of the products as determined by a combination of techniques are Cu, CO2, a carboxylic acid and an odd chain-length alkene, in the case of the copper(II) soaps; ZnO, CO2 and a ketone for the zinc soaps; and a mixture of Cu, Cu20 and CuO in the case of the copper(II) acetylacetonate. While mechanisms have been proposed to account for the degradative routes of the soaps, which of the metal acetylacetonates is still inconclusive. A combination of Ion Beam, X-ray and optical absorption studies have shown that the oxide films of indium, zinc and aluminium are, of the expected stoichiometry, while that of copper is of mixed composition (CuO/Cu2O/Cu). It is not immediately clear why carbon and alkali metal contamination was observed for the Al2O3 and CuO/Cu2O/Cu films but not for the In2O 3 film. Scanning Electron Microscopy (SEM) has shown the films to be polycrystalline. The observed optical characteristics (high transmittances, T = 75-90%; moderate reflectances, R < 21%; low absorbances, A < 8%; high refractive indices, nf > 1.5 and low extinction coefficients, k < 0.4) are as expected for these thin films. Potential uses of these thin layers based on their observed properties are also discussed.