Browsing by Author "Maloda, Elisante M"

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    Optical and electrical properties of dc magnetron sputtered multi-layered ZnO: Ga thin films prepared from alloy and ceramic targets
    (University of Dar es Salaam, 2014) Maloda, Elisante M
    Transparent conducting oxides (TCos) are semiconductor materials that have high carrier concentrations, high electrical conductivity as well as high transmittance of bean light in the visible and near infrared regions. TCOs are used in PV cells, display devices, touch screen and LED application as well. Based on PV cell applications, TCO layer where it can be converted to electrical energy ready for use. Therefore, it is important to have a superior TCO layer in PV cells. Thus, TCOs based on ZnO: Ga films were prepared by DC magnetron sputtering technique. The films are multilayer prepared from alloy and ceramic targets with gallium composition of 3 wt % and 4 wt% respectively. The optical transmittance and electrical property of multi-layered films were studied by using the UV-VIS spectrophotometer and Ecopia HMS-3000 Hall Effect measurement respectively. The band gaps and extinction coefficients of multi-layered films were computed empirically. Film refractive indices were calculated by Swanepoels method which is based on the use of extremes of the interference fringes spectra. The films deposited at substrate temperature of 270֯c and argon/oxygen gas ratio of 1.36 showed the best desired results. The films have optical transmittance over 91% in the wavelength range of 451 nm to 599nm and the lowest resistivity of 1.794̽*10¯⁴ Ωcm corresponding with sheet resistance of 20.8 ohms/square. Moreover, the highest carrier concentration of 4.756*10²ˈ cm¯ and mobility of 7.530cm²/vs. were obtained. Also, the films have band gaps and refractive indices in the range of 3.30 eV to 3.56 Ev and 1.59 to 1.75 respectively.