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Nano Wall Growth and Structural, Electro-Optical Characterization of Spray Pyrolytic Cobalt Oxide Thin Films. |
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PP: 51-58 |
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Author(s) |
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M. M. Islam,
M. G. M. Choudhury,
M. M. Rahman,
M. K. R. Khan,
M. Shahjahan,
K. Uddin,
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Abstract |
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| Cobalt oxide thin films were deposited by spray pyrolysis method onto a glass substrate at 300ºC substrate temperature. Structural, optical and electrical properties of the films were studied. The crystal structure of as-deposited and annealed samples was determined by X-ray diffraction (XRD) analysis. The structure of cobalt oxide was found to be cubic with lattice constant is a ~ 0.4 nm. The spectral absorption coefficient () at the fundamental absorption region was determined using the spectral data of transmittance and reflectance. The band gap energies were determined depending on the film thickness and the values obtained were vary from 1.357 eV to 1.440 eV for CoO phase and 1.474 eV to 1.516 eV for Co3O4 phase, respectively depending on film thickness. The refractive index and dielectric constant were calculated from reflectance and transmittance data. Refractive index varies from 1 to 2.8. From the thermal emf measurements the thermoelectric power S, the scattering factor A, low temperature activation energy E0 and coefficient of activation energy have also been calculated. The values of A lies between 1.1 to 1.28 suggesting that the scattering is due to lattice vibration and the position of Fermi energy at low temperature, E0 (~ 0.0002 eV) suggests that Fermi level is just on the top edge of valance band. At room temperature activation energy becomes ~ 0.29 eV, which indicates that the Fermi level is inside the forbidden energy gap. |
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