Browsing by Author "Kuku, T.A"

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    Electrical properties of vacuum evaporated PbSnS 3 thin films
    (International Journal of Materials Science, 2006-02) Kuku, T.A; Osasona, O.; Azi, Samuel
    Electrical conduction of evaporated PbSnS3 films of thickness ranging between 0.1 and 2.0 μm were studied by measuring the dc current in both parallel (planar) and transverse (cross plane) directions to the substrate surface. Conduction mechanisms relevant to various regions of the current-voltage characteristics are discussed. The obtained film conductivities were of the order 10−5 S cm−1 at room temperature and increased exponentially with increasing temperature. No consistent modification of the conductivity values and nature were observed when the films are doped with CdCl2, PbCl2 and CuI impurities. While planar conductivity activation energies were constant with voltage and increased slightly with deposition temperature, the cross plane values were found to depend on both voltage and film deposition temperature.
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    Ion transport studies on vacuum deposited PbSnI 4 thin films
    (Thin Solid Films, 1999) Kuku, T.A
    Thin films of the material PbSnI4 have been deposited by vacuum evaporation. The electrical conductivity, its activation energy and dielectric breakdown strength have been found to be film thickness dependent for films ≤5000 Å. Conductivity is by anionic defect motion with an activation energy of 0.320 eV and ionic transference number of 0.995 at room temperature. The ionic transport has been independently verified by an electrochemical cell potential method with the use of the material in an all thin film solid state battery of the configuration M/PbSnI4/(AgI,Ag), (M=Sn,Pb), giving OCV values close to the thermodynamic theoretical maximum for the formation of MI2 at the anode.
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    Optical properties of evaporated PbSnS3 thin films
    (Kluwer Academic Publishers, 1998-06) Kuku, T.A; Azi, Samuel
    PbSnS3 is a ternary sulfide semiconductor material which has been relatively little studied in the literature. Thin films of this material were deposited on glass substrates by a thermal evaporation process and their optical properties investigated. The optical parameters were determined from the analysis of measured transmission spectra, at normal incidence, from 400–1500 nm, at room temperature. The fundamental absorption edge is placed at 1.04±0.05 eV and is forbidden in nature. Other absorption edges are obtained at 1.44 and 1.55±0.05 eV, with a nearby direct one at 1.68±0.05 eV. The peaks at 1.44 and 1.55 eV have been independently confirmed by the spectral photocurrent response of the films. © 1998 Kluwer Academic Publishers
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    Structural and ionic transport properties of some A2BX4 (A=Cu, B=Pb, Sn, X=Br, I) compounds.
    (1990) Kuku, T.A; Erharhine, P.O; Chiodelli, G.; Akande, A.R.
    The compounds Cu2PbBr4, Cu2SnI4, and Cu2PbI4 have been synthesized as stable phases in the CuBr-PbBr2, CuI-SnI2, or CuI-PbI2 binary systems. Cu2PbBr4 is cubic (a0=9.170 A ̊), whereas Cu2SnI4 and Cu2PbI4 are hexagonal with a=9.050, c =9.706 A ̊, and a=8.064, c=15.128 A ̊, respectively. These materials are characterized mainly by a rather high anionic defect conductivity over the temperature range 20-270°C. The activation energy for the ionic defect mobility is 0.27 eV for Cu2PbBr4, 0.28 eV for Cu2SnI4 and 0.31 eV for Cu2PbI4