Department of Chemistry

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Browsing Department of Chemistry by Author "Ketchemen, Kevin IY"

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    CdS thin films deposition by AACVD: effect of precursor type, decomposition temperature and solvent.
    (Journal of Materials Science: Materials in Electronics, 2018-09) Ketchemen, Kevin IY; Mlowe, Sixberth; Nyamen, Linda D; Ndifon, Peter T; O'Brien, Paul; Revaprasadu, Neerish
    ABSTRACT Hexagonal cadmium sulfide (CdS) thin films were deposited on glass substrates by Aerosol Assisted Chemical Vapour Deposition (AACVD) using cadmium(II) dithiocarbamate and xanthate complexes in tetrahydrofuran (THF) and mixed solvents (THF+ chloroform) at 400 and 450 oC. The surface morphology and size of the CdS films determined using scanning electron microscopy (SEM), showed the formation of films of various morphologies depending on the precursor, the deposition temperature and solvent used. An increase in temperature resulted in an increase in particle size and a change in morphology with the formation of CdS films with distorted structures. The CdS films showed an overall blue shift in their absorption band edge (2.35 – 2.49 eV) compared to the bulk CdS. In dithiocarbamates, a slight blue shift was observed with a shift to high wavelengths with the reduction of the carbon chain of the dithiocarbamate and an increase in temperature; while in xanthate, a strong blue shift was observed at both deposition temperatures. The use of mixed THF + chloroform solvent at 450 oC showed the formation of films with irregular structures compared to those deposited using THF solvent alone, indicating the role of the solvent in the shape direction of the films formation. The elemental composition determined by energy dispersive X-ray spectroscopy (EDX) measurements revealed the 1:1 (Cd:S) ratio in all the samples confirming the stoichiometry of the CdS films.
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    Heterocyclic lead(II) thioureato complexes as single-source precursors for the aerosol assisted chemical vapour deposition of PbS thin films
    (Inorganica Chimica Acta, 2018) Ketchemen, Kevin IY; Mlowe, Sixberth; Nyamen, Linda D; Aboud, Ahmed A; Akerman, Matthew P; Ndifon, Peter T; O'Brien, Paul; Revaprasadu, Neerish
    The lead N’-benzoylthioureato complexes of N-morpholine (1) and N-pyrrolidine (2) were synthesized and characterized by elemental analysis, Fourier Transform Infra-Red (FT-IR) spectroscopy, proton nuclear magnetic resonance (1H nmr) and thermogravimetric analyses (TGA). The X-ray single crystal structure of complex (1) was determined. The compounds were both used as single source precursors to deposit PbS films on glass substrates at 350, 400 and 450 °C using aerosol assisted chemical vapour deposition (AACVD) The surface morphology of PbS films were determined by scanning electron microscopy (SEM), the crystalline phases established by powder X-ray diffraction (p-XRD) analyses and composition by energy dispersive X-ray spectroscopy (EDX). The particle sizes were found to range between 82 and 85 nm from complex (1) and 70–105 nm for (2) The PbS films were studied by Near Infra-red (NIR) UV–Vis spectroscopy, band gap ranging from 1.46 to 1.55 eV were observed.
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    Tailoring Shape and Crystallographic Phase of Copper Sulfide Nanostructures Using Novel Thiourea Complexes as Single Source Precursors
    (Journal of Inorganic and Organometallic Polymers and Materials, 2019-05) Ketchemen, Kevin IY; Khan, Malik D; Mlowe, Sixberth; Nyamen, Linda D; Ndifon, Peter T; O'Brien, Paul; Revaprasadu, Neerish
    Copper sulfide thin films and nanoparticles have been prepared via aerosol assisted chemical vapour deposition and solvothermal hot injection routes, respectively. Both routes employed heterocyclic amine based benzoylthioureato-copper(II) complexes as single source precursors. Copper sulfide thin films of diverse morphologies ranging from cubic to snowy or irregular crystallites depending on the deposition temperature were observed. Powder X-ray diffraction studies of the as deposited thin films have indicated the formation of hexagonal and cubic phases of copper sulfide. In the case of the nanoparticles, Roxbyite (Cu1.75S) phase was obtained in dodecanethiol at temperatures of 150, 190 and 230 °C. However, a preferred growth of nanoparticles was observed in the presence of oleylamine whereas the roxbyite phase was obtained at temperatures of 150, 200 and 250 °C. Also transmission electron microscopy showed the formation of close to spherical, hexagonal nano-disk and rod shaped nanoparticles.