Physics Advanced Laboratory

Garki, Nigeria

Physics Advanced Laboratory

Garki, Nigeria
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Fashina A.A.,African University of Science and Technology | Adama K.K.,Physics Advanced Laboratory | Oyewole O.K.,African University of Science and Technology | Oyewole O.K.,Kwara State University | And 9 more authors.
Journal of Renewable and Sustainable Energy | Year: 2015

This paper presents the results of an experimental study of the effects of surface texture on the optical and light trapping properties of silicon wafers. Surface texture is controlled by anisotropic etching with potassium hydroxide (KOH) and isopropyl alcohol (IPA) solutions. The anisotropic etching of (001) crystalline silicon wafers is shown to result in the formation of {111} pyramidal facets on the surfaces of the wafers. A combination of profilometry, optical microscopy, scanning electron microscopy, and atomic force microscopy is used to study the effects of KOH/IPA etching on the morphology and roughness of the textured surfaces. The results show that IPA concentration has the strongest effect on the surface roughness of (001)-single crystal crystals at temperatures up to 80 °C. Above this value, evidence of temperature-induced cracking was revealed on the silicon substrate. The best volume concentration ratio of KOH:IPA is also found to be 2:4. The implications of the study are discussed for the design of light trapping in silicon solar cells. © 2015 AIP Publishing LLC.


Mustapha K.,African University of Science and Technology | Mustapha K.,Kwara State University | Annan E.,African University of Science and Technology | Azeko S.T.,African University of Science and Technology | And 4 more authors.
Journal of Composite Materials | Year: 2016

This paper presents the results of a combined experimental and theoretical study of the strength, fracture toughness, and resistance-curve behavior of natural fiber-reinforced earth-based composite materials. The composites, which consist of mixtures of laterite, clay, and straw, are stabilized with controlled levels of Ordinary Portland cement. The compositional dependence of compressive, flexural/bend strength, and fracture toughness are explored for different proportions of the constituent materials using composites and crack-tip shielding models. The underlying crack-microstructure interactions associated with resistance-curve behavior were also studied using in situ/ex situ optical microscopy. This revealed evidence of crack bridging by the straw fibers. The measured resistance-curve behavior is also shown to be consistent with predictions from small- and large-scale bridging models. The implications of the results are then discussed for potential applications in the design of robust earth-based building materials for sustainable eco-friendly homes. © SAGE Publications.


Rwenyagila E.R.,African University of Science and Technology | Rwenyagila E.R.,University of Dar es Salaam | Agyei-Tuffour B.,African University of Science and Technology | Zebaze Kana M.G.,Physics Advanced Laboratory | And 4 more authors.
Journal of Materials Research | Year: 2014

This study presents the optical properties of layered ZnO/Al/ZnO composite thin films that are being explored for potential applications in solar cells and light emitting devices. The composite thin films are explored as alternatives to ZnO thin films. They are produced via radio frequency magnetron sputtering. The study clarifies the role of the aluminum mid-layer in a ZnO (25 nm)/Al/ZnO (25 nm) film structure. Multilayers with low resistivity ∼362 Ω cm and average transmittances between ∼85 and 90% (in the visible region of the solar spectrum) are produced. The highest Haacke figure of merit of 4.72 × 10-3 Ω-1 was obtained in a multilayer with mid-layer Al thickness of 8 nm. The combined optical band gap energy of the multilayered films increased by ∼0.60 eV for mid-layer Al thicknesses between ∼1 and 10 nm. The observed shifts in the optical absorption edges to shorter wave lengths of the spectrum are shown to be in agreement with the Moss-Burstein effect. Copyright © 2014 Materials Research Society.


Rwenyagila E.R.,African University of Science and Technology | Rwenyagila E.R.,University of Dar es Salaam | Agyei-Tuffour B.,African University of Science and Technology | Zebaze Kana M.G.,Physics Advanced Laboratory | And 4 more authors.
Journal of Materials Research | Year: 2014

This study presents the optical properties of layered ZnO/Al/ZnO composite thin films that are being explored for potential applications in solar cells and light emitting devices. The composite thin films are explored as alternatives to ZnO thin films. They are produced via radio frequency magnetron sputtering. The study clarifies the role of the aluminum mid-layer in a ZnO (25 nm)/Al/ZnO (25 nm) film structure. Multilayers with low resistivity ∼362 Ω cm and average transmittances between ∼85 and 90% (in the visible region of the solar spectrum) are produced. The highest Haacke figure of merit of 4.72 × 10-3 Ω-1 was obtained in a multilayer with mid-layer Al thickness of 8 nm. The combined optical band gap energy of the multilayered films increased by ∼0.60 eV for mid-layer Al thicknesses between ∼1 and 10 nm. The observed shifts in the optical absorption edges to shorter wave lengths of the spectrum are shown to be in agreement with the Moss-Burstein effect. Copyright © 2014 Materials Research Society.


Fashina A.A.,African University of Science and Technology | Zebaze Kana M.G.,African University of Science and Technology | Zebaze Kana M.G.,Physics Advanced Laboratory | Soboyejo W.O.,African University of Science and Technology | And 3 more authors.
Journal of Materials Research | Year: 2015

This study presents an analytical model of the reflectance of flat and textured silicon substrates. The model was used to study the reflection behavior of textured silicon surfaces under non-normal incidence. By characterizing the incident light and facets of the silicon wafer with vector geometry, dot products and Phong's reflection model (https://cs.oberlin.edu/bob/cs357.08/VectorGeometry/VectorGeometry.pdf) were used to determine the reflection angles between incident light rays and pyramidal facets. The possible optical interactions are considered for a wide range of pyramidal geometries and light incidence angles that are relevant to the exposure of textured silicon surfaces to incident sunlight. Furthermore, the model was used to investigate the possibility of secondary reflection, for the full range of incidence angles to the substrate. The textured silicon surfaces were found to reduce the reflection angles more effectively than flat substrates at lower angles of incidence. Secondary reflection was also found to be experienced or guaranteed, for all pyramid heights, when the angle of incidence to the substrate was less than 19.4°. The predictions are validated with experimental measurements of reflectance from (001)-textured silicon surfaces. The implications of the results are then discussed for the development of micropyramids for improved photoconversion in silicon solar cells. Copyright © Materials Research Society 2015.


Momodu D.Y.,African University of Science and Technology | Tong T.,Princeton University | Zebaze Kana M.G.,Physics Advanced Laboratory | Zebaze Kana M.G.,Kwara State University | And 3 more authors.
Journal of Applied Physics | Year: 2014

This paper presents the results of a combined analytical, computational, and experimental study of adhesion and degradation of Organic Light Emitting Devices (OLEDs). The adhesion between layers that are relevant to OLEDs is studied using an atomic force microscopy technique. The interfacial failure mechanisms associated with blister formation in OLEDs and those due to the addition of TiO2 nanoparticles into the active regions are then elucidated using a combination of fracture mechanics, finite element modeling and experiments. The blisters observed in the models are shown to be consistent with the results from adhesion, interfacial fracture mechanics models, and prior reports of diffusion-assisted phenomena. The implications of the work are then discussed for the design of OLED structures with improved lifetimes and robustness. © 2014 AIP Publishing LLC.


Isah K.U.,Minna Federal University Of Technology | Ahmadu U.,Minna Federal University Of Technology | Idris A.,Minna Federal University Of Technology | Kimpa M.I.,Minna Federal University Of Technology | And 3 more authors.
Materials for Renewable and Sustainable Energy | Year: 2015

Dye-sensitized solar cells (DSSC) were fabricated using red bougainvillea glabra flower dye extracts as natural dye sensitizers at three dye pH values of 1.23, 3.0, and 5.7. Water was used as dye-extracting solvent. DSSCs from dye extract of pH 3.0 had the highest photocurrent density J sc of 3.72 mA/cm2 and fill factor FF of 0.59. While the DSSCs from dye sensitizer pHs of 1.23 and 5.7 had J sc of 1.13 and 2.27 mA/cm2, and fill factors of 0.43 and 0.61, respectively. The maximum powers P max of the DSSCs were 0.50, 1.64, and 0.94 mW/cm2 for dye sensitizer pH of 1.2, 3.0, and 5.7, respectively. © 2014 The Author(s).


Kana M.G.Z.,Physics Advanced Laboratory | Oberafo A.A.,Physics Advanced Laboratory | Odunaike R.K.,Olabisi Onabanjo University
Journal of Engineering and Applied Sciences | Year: 2010

Investigations have been carried out at temperatures between 123 and 300 K on as deposited, vacuum evaporated Al-Ge-Au sandwich structure samples fabricated on Al support discs. The sandwiched, evaporated Ge layers were vacuum-deposited in either one or two steps and of various thicknesses while the Al and Au contacts on either side were each vacuum-deposited in one step. Furthermore for the two-step Ge depositions, the first Ge layer was exposed to air at room temperature for an hour before the second layer was deposited. All the samples showed good ohmic behaviour. The specific resistance (R s) of the Al-Ge-Au layers increased as the thickness of the sandwiched Ge layer increased but decreased as the temperature increased. The dependence of R s on the temperature indicated semiconducting behaviour in the Ge layer. It was also found that for a given overall thickness, R s increased as the mnnber of steps increased while there was no significant change in R s for samples of same overall Ge thickness deposited in the same nwnber of steps. © Medwell Journals, 2010.


Isa M.T.,Ahmadu Bello University | Ameh A.O.,Ahmadu Bello University | Gabriel J.O.,Ahmadu Bello University | Adama K.K.,Physics Advanced Laboratory
Leonardo Electronic Journal of Practices and Technologies | Year: 2012

The extraction and characterization of chitin from four sources of Nigerian origin was investigated. Chemical demineralization and deproteinization was done to obtain the chitin. Proximate analysis, XRD and SEM analysis were conducted on obtained chitins. The investigation revealed that the shrimp had the highest yield of chitin of 8.15%, crab, crayfish and periwinkle had yields of 7.8%, 2.88% and 0.44% respectively. The proximate analysis showed that chitin from shrimp had highest moisture and protein content of 8.70% and 4.16% respectively. Crayfish had the highest ash and fiber content of 7.20% and 6.98% respectively. Crab has the highest lipid content of 1.70%. The SEM analysis showed very uniform structure with a lamellar organization and less dense structure for chitin from shrimp and the surface of chitin from crayfish consists of fibers that form parallel thread networks. XRD analysis showed that chitin from shrimp was more crystalline than others.


Agbo P.E.,Ebonyi State University | Nnabuchi M.N.,Ebonyi State University | Onogu K.O.,Physics Advanced Laboratory
Journal of Ovonic Research | Year: 2012

Novel TiO 2/MnO core-shell thin film has been deposited onto a glass substrate by the chemical bath deposition technique. The films were annealed at temperatures of 373K and 673K in order to investigate the effect of annealing on the optical bandgap and thickness of the film. The films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Rutherford backscattering (RBS) and spectrophotometer. Our results showed that there is more crystallization and more orientation of the crystal growth with increase in temperature. The results also revealed that most of the optical properties were significantly affected by the annealing process. The calculated thickness shows that the films are nanocrystalline in nature and temperature dependent. The optical band gaps decreased with increase in temperature and are in the range of 3. 21eV- 3. 89eV.

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