Papers by Bolutife Olofinjana
Journal of Materials Science and Engineering B, 2015
The single solid source precursors, bis-(morpholinodithioato-s,s')-Pb and bis-(morpholinodithioat... more The single solid source precursors, bis-(morpholinodithioato-s,s')-Pb and bis-(morpholinodithioato-s,s')-Pb-Cd were prepared by direct reaction of metal chloride solution and ammonium morpholinodithiocarbamate. Lead sulphide and lead cadmium sulphide thin films were deposited on sodalime glass substrates using Metal Organic Chemical Vapour Deposition (MOCVD) technique. Preparation of the films was achieved by the pyrolysis of the prepared precursors at 400 °C with a flow rate of 2.5 dm 3 /min for 2 hours deposition period. The deposited films were characterized using Ultraviolet-Visible spectroscopy, X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). A direct optical band gap of 0.46 eV was obtained from the analysis of the absorption spectrum for lead sulphide and 2.17 eV for lead cadmium sulphide thin films. XRD revealed that both films are polycrystalline in nature, with face-centred cubic phase in PbS film and the presence of cubic and hexagonal phases of CdS and cubic phase of PbS in the PbCdS film. SEM micrographs also revealed polycrystalline nature with uniformly distributed grain estimated to be less than 1 µm in size for both films. It also showed that both films have textured surfaces. The EDX showed that both deposited films are nonstoichiometric and are cation deficient.
The single solid source precursor, cobalt (II) acetylacetonate was prepared and characterized by ... more The single solid source precursor, cobalt (II) acetylacetonate was prepared and characterized by infrared spectroscopy. Thin films of cobalt oxide were deposited on soda lime glass substrates through the pyrolysis (metal organic chemical vapour deposition (MOCVD)) of single solid source precursor, cobalt acetylacetonate, Co[C 5 H 7 O 2 ] 2 at a temperature of 420 • C. The compositional characterization carried out by rutherford backscattering spectroscopy and X-ray diffraction (XRD), showed that the films have a stoichiometry of Co 2 O 3 and an average thickness of 227±0.2 nm. A direct energy gap of 2.15±0.01 eV was calculated by the data obtained by optical absorption spectroscopy. The morphology of the films obtained by scanning electron microscopy, showed that the grains were continuous and uniformly distributed at various magnifications, while the average grain size was less than 1 micron for the deposited thin films of cobalt oxide.
MRS Proceedings, 2012
The Single Solid Source precursor Cadmium Acetylacetonate, Cd[C 5 H 7 O 2 ] 2 was prepared and Ca... more The Single Solid Source precursor Cadmium Acetylacetonate, Cd[C 5 H 7 O 2 ] 2 was prepared and Cadmium Oxide thin films were deposited on Sodalime glass substrate using Metal Organic Chemical Vapour Deposition (MOCVD) technique at deposition temperature of 420 o C The films were characterized using Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX) facility attached to it, X-Ray Diffractometry (XRD) and UV-visible spectrometry. SEM micrographs showed the formation of textured surface with identifiable cubic and hexagonal structures, having average grain size greater than 1 µm. XRD studies indicated the formation of polycrystalline cubic CdO phase with preferred orientation in (111) plane. A direct optical band gap of 2.10 eV was obtained from the analysis of the UV-visible spectrum with an enhanced light absorption in 750 -1000 nm spectrum range. This enhancement is as a result of light trapping by the textured crystalline structure.
Journal of Materials Science & Technology, 2010
Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxys... more Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxysulphide thin films which were deposited on sodalime glass substrates using metal organic chemical vapour deposition (MOCVD) technique at a temperature of 420 • C. Rutherford backscattering spectroscopy (RBS) was used to determine the elemental composition of the film which showed that the films contained large amounts of oxygen. The large amount of oxygen was attributed to the large abundance of oxygen in the starting material. A direct optical energy gap of 3.31 eV was obtained from the analysis of the absorption spectrum. The scanning electron microscopy (SEM) micrographs of the films showed that the films were continuous and porous. An estimated average size of the grains was below 5 µm. X-ray diffraction (XRD) showed that the deposited films were crystalline in nature.
British Journal of Applied Science & Technology, 2016
The prevalent problem of air pollution in Nigeria is attributable to the country’s huge populatio... more The prevalent problem of air pollution in Nigeria is attributable to the country’s huge population, put in excess 160 million and the trend of industrial growth. In 2010, the country witnessed a rare occurrence of 9-day period of heavy dust episode (HDE). The dust reduced visibility to < 1 km, causing cancellation of several flights. The aim of this study is to assess the level of aerosol mass loadings and, nature and sources of the HDE aerosols. Two fractions of particulate matter (PM) were collected for about two months including the period of the HDE. Samples were collected on Whatman polycarbonate filters using low-volume GENT sampler equipped with a stacked filter unit (SFU) to hold two 47 mm filters. 7-day back trajectory analysis was performed using UGAMP trajectory model driven by ECMWF wind analyses data. Morphological analysis of the PM was done using Scanning Electron Microscopy (SEM), chemical compositions determined with Energy Dispersive X-ray (EDX) and particle number per unit area of filter (particle density) was estimated using optical microscopy. The range of mass concentration of PM2.5, PM2.5-10 and PM10 are 1.24 – 58.7, 5.1 – 354.9 and 8.33 – 379.2 μg m-3, respectively. EDX detected twelve (12) elements: Fe, Na, Mg, Al, Si, S, K, P, Cl, Ca, Mo and O. Elements of crustal origin (Si, Al, Fe, Ca and Mg) account for a high percentage of the elemental composition of the PM. Four distinct classes of particles - mineral dust, NaCl containing agglomerate, Calcium-rich dust and alumina-silicate – were identified from the morphological and compositional analysis of the PM. From the backward trajectory analyses, most of the crustal components of the HDE dust can be attributed to long range dust transport from North Africa and the Sahel region, while maritime aerosols are attributable to the marine environment in the Atlantic, down South.
Journal of Materials Science and Engineering B, 2015
Single solid source precursors, Manganese acetylacetonate (Mn[C 5 H 7 O 2 ] 2 ) and Lithium manga... more Single solid source precursors, Manganese acetylacetonate (Mn[C 5 H 7 O 2 ] 2 ) and Lithium manganese acetylacetonate (Li-Mn[C 5 H 7 O 2 ] 3 ) were prepared and thin films of Mn-O and Li-Mn-O were deposited on sodalime glass substrates using MOCVD (Metal organic chemical vapour deposition) technique by pyrolysing Mn[C 5 H 7 O 2 ] 2 and Li-Mn[C 5 H 7 O 2 ] 3 respectively at a temperature of 420 °C for approximately 2 h. The films were characterized using RBS (Rutherford backscattering spectroscopy), SEM (Scanning electron microscopy), XRD (X-ray diffraction), van der Pauw method and Ultraviolet-Visible Spectroscopy. The compositional analysis showed that the Mn:O ratio is 0.2:0.8 while that of Li:Mn:O was found to be 0.47:0.24:0.29. SEM micrograph showed that Mn-O film is composed of hollow needle-like rods with coarse, continuous and uniformly distributed polycrystalline grains rod-like, having average grain size estimated to be below 10µm while those of Li-Mn-O showed that the film is dendritic and polycrystalline in which some of the grains were found to lump together. XRD also showed the polycrystalline nature of the films with orthorhombic MnO 2 and orthorhombic Li 3 MnO 4 structures for Mn-O and Li-Mn-O thin films respectively. Results of characterization also showed that the films are semiconducting, highly absorbing in the visible region with absorption edges observed at wavelengths of 525 nm and 550 nm, corresponding to direct optical band gaps of 2.36 eV and 2.25eV for Mn-O and Li-Mn-O thin films respectively.
Wear, 2015
ABSTRACT Surface texturing or topographical design is one of the primary techniques to control fr... more ABSTRACT Surface texturing or topographical design is one of the primary techniques to control friction and wear performance of surfaces in tribological contact. Laser surface texturing (LST), whereby a laser beam is used to produce regular arrays of dimples on a surface, has been demonstrated to reduce friction in conformal lubricated contacts. Friction and wear behavior under boundary lubrication is also known to be dependent on the formation and durability of the tribochemical film formed from lubricant additives. In this paper, the effects of LST on the formation and durability of tribochemical films and its consequent impacts on friction and wear behavior in various lubrication regimes were evaluated. Friction and wear tests that cycled through different lubrication regimes were conducted with both polished and LST treated surfaces using a synthetic lubricant with and without model additives of ZDDP and MoDTC mixture. In the base oil without additives, LST produced noticeable reduction in friction in all lubrication regimes. However, with low-friction model additives, friction was higher in tests with LST due to significant differences in the tribochemical film formation in the polished and LST surfaces, as well as the sliding counterface. Continuous tribo-films were formed on ball conterface rubbed against polished surfaces while the films were streaky and discontinuous in ball rubbed against LST surfaces. LST produced more wear on the ball counterface in both base and additized oils. No measurable wear was observed in both the polished and LST flat specimens.
The precursor bis-(morpholinodithioato-s,s')-Cd-Hg was prepared and the thin films of mercury... more The precursor bis-(morpholinodithioato-s,s')-Cd-Hg was prepared and the thin films of mercury cadmium sulphide were deposited on sodalime glass substrate by Metallorganic Chemical Vapour Deposition (MOCVD) technique. The surface morphology was obtained using Stereoscan 430i LEICA Scanning Electron Microscope. The elemental analysis was carried out using Energy Disperse X-ray (EDX). The ratio of the elements in the prepared films obtained from the EDX was found to be Hg:Cd:S = 17.55:38.12:44.32, giving a stoichiometry of Hg x Cd (1-x) S (1-δ) , δ = 0.20. . A direct band gap of 2.36 eV was obtained from the analysis of the absorption spectrum. Electrical characterization was carried out both in the dark and normal room illumination. The dark and room illumination conductivities were found to be of the same order (10 -6 Ω -1 cm -1) and the activation energy for both conditions are 0.12 eV and 0.19 eV respectively. The conductivity type was found to be p-type using the hot probe met...
Journal of Modern Physics, 2011
A single solid source precursor bis-(morpholinodithioato-s,s')-Mo was prepared and molybdenum sul... more A single solid source precursor bis-(morpholinodithioato-s,s')-Mo was prepared and molybdenum sulphide thin film was deposited on sodalime glass using Metal Organic Chemical Vapour Deposition (MOCVD) technique at deposition temperature of 420˚C. The film was characterized using Rutherford Backscattering Spectroscopy (RBS), Ultraviolet-Visible Spectroscopy, Four-point Probe technique, Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD) and Atomic Force Microscopy (AFM). A direct optical band gap of 1.77 eV was obtained from the analysis of the absorption spectrum. The sheet resistance was found to be of the order of 10 -5 Ω -1 ·cm -1 . SEM micrographs of the films showed the layered structure of the film with an estimated grain size that is less than 2 µm while XRD indicates parallel orientation of the basal plane to the substrate surface.
The single solid source precursors, bis-(morpholinodithioato-s,s')-Pb and bis-(morpholinodithioat... more The single solid source precursors, bis-(morpholinodithioato-s,s')-Pb and bis-(morpholinodithioato-s,s')-Pb-Cd were prepared by direct reaction of metal chloride solution and ammonium morpholinodithiocarbamate. Lead sulphide and lead cadmium sulphide thin films were deposited on sodalime glass substrates using Metal Organic Chemical Vapour Deposition (MOCVD) technique. Preparation of the films was achieved by the pyrolysis of the prepared precursors at 400 °C with a flow rate of 2.5 dm 3 /min for 2 hours deposition period. The deposited films were characterized using Ultraviolet-Visible spectroscopy, X-ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). A direct optical band gap of 0.46 eV was obtained from the analysis of the absorption spectrum for lead sulphide and 2.17 eV for lead cadmium sulphide thin films. XRD revealed that both films are polycrystalline in nature, with face-centred cubic phase in PbS film and the presence of cubic and hexagonal phases of CdS and cubic phase of PbS in the PbCdS film. SEM micrographs also revealed polycrystalline nature with uniformly distributed grain estimated to be less than 1 µm in size for both films. It also showed that both films have textured surfaces. The EDX showed that both deposited films are nonstoichiometric and are cation deficient.
Journal of Modern Physics, 2013
Thin films of copper titanium oxide were deposited by metal organic chemical vapour deposition te... more Thin films of copper titanium oxide were deposited by metal organic chemical vapour deposition technique from the synthesized single solid source precursor, copper titanium acetylacatonate Cu [Ti(C 5 H 7 O 2 ) 3 ] at the deposition temperature of 420˚C. The deposited films were characterized using Rutherford Backscattering Spectroscopy, Scanning Electron Microscopy with Energy Dispersive X-Ray facility attached to it, X-Ray Diffractometry, UV-Visible Spectrometry and van-der Pauw Conductivity measurement. Results show that the thickness of the prepared film is determined as 101.236 nm and the film is amorphous in structure, having average grain size of approximately 1 µm. The optical behaviour showed that the absorption edge of the film was at 918 nm near infrared with corresponding direct energy band gap of 1.35 eV. The electrical characterization of the film gave the values of resistivity, sheet resistance and conductivity of the film as 3.43 × 10 −1 Ω-cm, 3.39 × 10 6 Ω/square and 2.91 (Ω-cm) −1 respectively.
Journal of Materials Science & Technology, 2010
Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxys... more Molybdenum oxodithiocarbamate was prepared as a single solid source precursor for molybdenum oxysulphide thin films which were deposited on sodalime glass substrates using metal organic chemical vapour deposition (MOCVD) technique at a temperature of 420 • C. Rutherford backscattering spectroscopy (RBS) was used to determine the elemental composition of the film which showed that the films contained large amounts of oxygen. The large amount of oxygen was attributed to the large abundance of oxygen in the starting material. A direct optical energy gap of 3.31 eV was obtained from the analysis of the absorption spectrum. The scanning electron microscopy (SEM) micrographs of the films showed that the films were continuous and porous. An estimated average size of the grains was below 5 µm. X-ray diffraction (XRD) showed that the deposited films were crystalline in nature.
MRS Proceedings, 2012
The Single Solid Source precursor Cadmium Acetylacetonate, Cd[C 5 H 7 O 2 ] 2 was prepared and Ca... more The Single Solid Source precursor Cadmium Acetylacetonate, Cd[C 5 H 7 O 2 ] 2 was prepared and Cadmium Oxide thin films were deposited on Sodalime glass substrate using Metal Organic Chemical Vapour Deposition (MOCVD) technique at deposition temperature of 420 o C The films were characterized using Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray (EDX) facility attached to it, X-Ray Diffractometry (XRD) and UV-visible spectrometry. SEM micrographs showed the formation of textured surface with identifiable cubic and hexagonal structures, having average grain size greater than 1 µm. XRD studies indicated the formation of polycrystalline cubic CdO phase with preferred orientation in (111) plane. A direct optical band gap of 2.10 eV was obtained from the analysis of the UV-visible spectrum with an enhanced light absorption in 750 -1000 nm spectrum range. This enhancement is as a result of light trapping by the textured crystalline structure.
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Papers by Bolutife Olofinjana