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    Considerations about the determination of optical bandgap from diffuse reflectance spectroscopy using the tauc plot
    (Springer India, 2024) Jubu, Peverga R.; Obaseki, O. S.; Ajayi, D. I.; Danladi, E.; Chahrour, Khaled M.; Muhammad, A.; Landi Jr, S.
    The optical diffuse reflectance data of a semiconductor material is usually converted into the Kubelka-Munk function before proceeding to process the conventional Tauc's plot from which optical bandgap energy can be determined. Firstly, it is conventional/ customary to convert the percentage reflectance (R-infinity(%)) data, which is obtained from UV-vis measurement into an equivalent reflectance (R-infinity) that range between 0 and 1 before processing the Tauc's plot. Secondly, the Kubelka-Munk function is usually multiplied by the incident photon energy, h nu, to produce an all-elements/ comprehensive Tauc's plot. Literature is scarce to convincingly demonstrate that a correct bandgap value can, alternatively be obtained from the Tauc's plot that is derived directly from the (R-infinity(%) data without having to convert to R-infinity. Also, publication is rarely available to demonstrate that a proper bandgap value can be determined without having to multiply the Kubelka-Munk function by the term h nu. The present investigation shows diminutive differences in the bandgap values estimated from the R-infinity(%)-based Tauc's plots and the equivalent R-infinity-based Tauc's plots. This suggests that either of the methods can be employed for a precise bandgap estimate. A comparison between the magnitudes of the bandgap energies determined from the comprehensive Tauc's plot and when the Kubelka-Munk function is not multiplied by h nu reveals insignificant differences in the estimated values. This suggests that either of the two methods can be employed to obtain a reliable bandgap for direct and indirect optical gap semiconductors.
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    Photoanodic properties of In/ß-Ga2O3 nanostructures fabricated under hydrogen reducing ambient by the vapour-phase growth method
    (Elsevier, 2023) Jubu, Peverga R.; Danladi, E.; Chahul, H. F.; Aldayyat, A.; Yusof, Y.; Chahrour, Khaled M.; Kyesmen, P. I.
    A great deal of efforts have been dedicated to reduce carrier recombination problem in ss-Ga2O3 using strategies, such as doping, compositing, and interfacing with different materials to enhance device performance. However, reports are rarely available for integrating In with ss-Ga2O3 for photoelectrochemical applications. Herein, we reports the effect of In addition in ss-Ga2O3 to produce In/ ss-Ga2O3 nanocomposite for photoelectrocatalysis. The intrinsic sample exhited mixed-phase (a-ss)-Ga2O3, whereas the composite showed a mixed-phase ss-Ga2O3-in-dium. A significant amount of In was detected on the heterogenous film, suggesting that doping was exceeded. A significant bandgap narrowing was observed from 4.79 to 4.45 eV upon In incorporation. The presence of In in ss-Ga2O3 resulted in a shift in photoluminescence emission from violet to green light. Photoelectrochemical measurements in 0.1 M KOH solution demonstrated a relatively high photocurrent density of 1.720 mA/cm2 at 1.0 V vs. Ag/AgCl for the In/ ss-Ga2O3 heterogeneous film.