Browsing by Author "F.O. OGUNDARE"

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    He+ induced changes in the surface structure and optical properties of RF-sputtered amorphous alumina thin films
    (ELSEVIER, 2016) F.O. OGUNDARE; OLARINOYE, OYELEKE
    High quality 50 nmthickstoichiometric amorphous aluminium oxide films were reactively sputtered on micro scope glass slide substrates. The films were exposed to energetic (2.20 MeV) He+ at different ion fluences of 6×1012 ion/cm2;1×1013 ion/cm2;2×1013 ion/cm2;3×1013 ion/cm2; and 4 × 1013 ion/cm2. The effect of the ion irradiation on the optical, structural phase and surface properties of the alumina films was investigated via UV–VIS–NIRspectroscopy,X-raydiffraction analysis and theatomicforcemicroscopyrespectively. Thetrans missionandabsorptionspectraoftheirradiatedfilmsshowedvariationthatdependedonionfluence.Therefrac tive index, extinction coefficient, optical conductivity, dielectric constant and energy loss functions of the films were also affected by He+ irradiation. Optical band gap and films' structural phase were however not altered bytheionirradiation. The variation in optical constants induced by radiation was attributed to electronic excita tion and increase in surface roughness of the films
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    Improving the stoichiometry of RF-sputtered amorphous aluminathin films by thermal annealing
    (2015) OLARINOYE, OYELEKE; F.O. OGUNDARE
    High quality alumina thin films weredeposited on glass substrate by reactive radio-frequency sputtering. The de position process and rate were controlled by radio-frequency power and reactive gas (oxygen) flow rate. The re lationships between O/Al ratio contents and the structural, electrical resistivity and optical parameters of the films were investigated. The O/Al of the films varied with change in oxygen flow ratio, power density and post deposition annealing. The structure and phase of the filmswere unaltered as the deposition parameters and post depositionannealing up to 573 Kwerevaried. O/Al of 1.5 was obtained at oxygen flow ratio of 11%, radio-frequency power of 250 W and post deposition annealing of 573 K. The sheet resistance of the films were all very high but the same within experimental uncertainties. The optical parameters (transmittance, refractive index and extinction coefficient) of the films varied considerably and dependedonthe films’ stoichiometry
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