Time optimized cobalt-doped zinc selenide thin films have been successfully electrodeposited on fluorine-doped tin oxide substrates. The films were deposited at the varying time of 1 min, 3 mins, and 5 mins respectively. Film thickness, optical, structural, electrical, and morphological properties of the deposited thin films were evaluated. Film thickness estimated using the gravimetric method increased from 294.35 nm to 399.62 nm as deposition time increased. Optical properties showed that the absorbance of the films ranged from 13.58% to 83.15% and was found to increase as deposition time increased. Transmittance ranged from 24.40% to 73.15% and was found to decrease as deposition time increased. The reflectance of the films was found to be low while the energy band gap ranged between 2.10 eV and 2.85 eV. Structural properties confirmed the deposition of ZnSe thin film with crystallite size values that fall between 14.68 nm and 18.60 nm. Dislocation density is ranged from 4.66 × 1015 lines/m2 to 2.97 × 1015 lines/m2 while microstrain ranged between 8.53 × 10-3 and 5.83 × 10-3. Crystallite sizes of the films were found to increase as deposition time increased while dislocation density and microstrain were found to decrease as deposition time increased. Electrical properties showed that the deposited films are semiconducting films with electrical resistivity values of 1.54 × 105 Ω cm-1.83 × 104 Ω cm and electrical conductivity values of 6.30 × 10-6 S/cm-5.47 × 10-5 S/cm. The micrograph of the films showed that the films were made up of nanoparticles and nanofibres of different dimensions. Energy-Dispersive X-Ray Spectroscopy (EDS) spectra of the films confirmed the presence of cobalt, zinc, and selenium.

Semiconductor thin films of CuMnS have been deposited onto conductive fluorine-doped tin oxide (FTO) glass substrate using an electrodeposition method to investigate their properties for possible applications. Copper sulfate, manganese sulfate and Thiourea were precursors used for sources of copper, manganese and sulphur ions respectively. The concentration of manganese ions was varied while keeping deposition voltage and time constant at 0.6 and 100 s, respectively. The films were characterized for optical, structural and morphological properties. The results obtained showed that the absorbance of the films is high in the visible (VIS) and near-infrared (NIR) regions but decreases towards NIR. The films transmittance is low in the VIS but increased in the NIR regions. The extinction coefficient is low in the VIS and NIR regions and decreases as concentration of manganese ion increased. The refractive index is high and initially increased slightly from 4.49 to 4.68 in the mid-VIS region while manganese concentration increased from 0.05 to 0.15 M and then decreased to the value of 2.73 as concentration of manganese ion increased further. The optical conductivity is high throughout the VIS and NIR regions while the optical bandgap energy is in the range of 1.5 to 2.05 eV and increases as manganese ion concentration increased. The XRD analysis showed that the deposited thin films of CuMnS are crystalline with average crystallite size and micro-strain in the range of 15.86 - 24. 45 nm and 3.97×10–3 - 6.13×10–3, respectively. The SEM results showed that the films are composed of particle sizes that are spherical in shape, uniform in sizes and densely packed together and consequently make the film surface rough. These properties exhibited by the films make them good materials for applications in photovoltaic calls, solar control coatings, photothermal applications and many other electronic devices that require high temperatures. HIGHLIGHTS This paper focused on the study of the effect of manganese ion concentration on the chalcogenide semiconductor thin films of CuMnS for possible device applications Electrodeposition method was used to fabricate the semiconductor thin films of CuMnS Optical, Structural and morphological properties of the thin films were characterized The deposited thin films of CuMnS were found to have good applications for photovoltaic cells and other optoelectronic device fabrications GRAPHICAL ABSTRACT

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This research presents the estimation of the hydropower potential of River Otamiri through the hydrological analysis of the elements of climate as it affects its catchment area (section passing through the Federal University of Technology Owerri). The study involves the estimation of maximum design floods for the watershed using the Gumbels Probability Distribution Method for various return periods (T r ) with the development of unit hydrograph, storm hydrograph, runoff hydrograph and flood duration curve for the catchment area of the river. In addition watershed parameters like peak flow (Q p ), lag time (T l ), time of concentration (T c ) and rainfall intensity (I c ) were determined using the soil conservation service method and other empirical formulas. In order to determine the available flow for power generation, the stage/head of the river was estimated from records provided by the River Basin Development Authority (R.B.D.A) and flow duration analyses were carried out. The analysis revealed that for time flows of 50, 75 and 100% the following energy values were obtained 34.5 MW, 11.3 MW and 1.5 MW, respectively.

Undoped and cobalt doped copper selenide thin films have been successfully prepared unto fluorine tin oxide (FTO) substrates by electrodeposition method using copper acetate, cobalt nitrate and selenium (IV) oxide as precursors for copper, cobalt and selenium ions respectively. Deposited thin films were subjected to optical, structural, morphological, compositional and electrical analysis using spectrophotometer, x-ray diffractometer, scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDS) and 4-point probe. Optical results observed between the wavelength range of 300 nm and 1,000 nm showed that the films have good optical responses. Absorbance values ranged between 0.1 and 0.81 while transmittance lies between 15.59 and 78.68 %. Energy band gap of the films was found to vary from 2.10 to 2.28 eV. These results showed that cobalt as a dopant could be used to modify properties of copper selenide thin films. Structural analysis showed that the deposited films are polycrystalline in nature with hexagonal structural phase. Crystallite sizes of range 27.56 to 34.27 nm were obtained while dislocation density lied between  and . Microstrain ranged between and . Micrograph images showed flake-like particles that increased in size as percentage of cobalt increased. Energy dispersive spectroscope (EDS) results confirmed the incorporation of cobalt on the deposited copper selenide films. Electrical resistivity of the films increased from  to  while conductivity decreased from  to  as a result of variation in cobalt ion concentration. These properties of the deposited thin films positioned them for solar cell and optoelectronics device applications. HIGHLIGHTS Energy band gap of electrosynthesized cobalt doped copper selenide ranged from 2.10 to 2.28 eV Film thickness values ranged from 48.41 and 176.79 nm. Thickness values of the films were found to increase as concentration of cobalt increase Increase in dopant concentration resulted to shift in diffraction peaks towards larger angles Increase in crystallite size from 27.56 - 34.27 nm was observed as dopant concentration increases SEM images of the films revealed flake - like particles of different sizes GRAPHICAL ABSTRACT