The impact and influence of global socio-economy on the clerical ministry in the Evangelical Lutheran Church in Tanzania (ELCT)

Master's thesis in global studies. School of Mission and Theology, May 200

Effects of target composition on the optical constants of DC sputtered ZnO: Al thin films

Al-doped ZnO thin films were deposited from ZnO:Al ceramic and Zn:Al metal alloy targets in Ar and Ar + O2 atmospheres respectively, using Direct Current (DC) magnetron sputtering. The samples exhibited transmittance T > 80% in visible region with good NIR shielding. The results indicated that, band gap energy ranged from 3.34 to 3.44 eV and 3.39 to 3.46 eV for films prepared from alloy and ceramic targets, respectively. Films obtained from alloy target at a substrate temperature of 200 oC showed low electrical sheet resistance of 10 Ω/sq, and highest values of mobility (15.9 cm2/Vs) and carrier concentration (2.98 × 1021 cm-3). However, films prepared from ceramic target at a substrate temperature of 300 oC revealed the highest sheet resistance of 32 Ω/sq, with lower values of mobility (14.1 cm2/Vs) and carrier concentration (1.92 × 1020 cm-3). The increase in sheet resistance and decrease in mobility as well as carrier concentration might be due to increased scattering centers for carriers, resulting to increased sheet resistance. Optical spectra of the films were fitted to SCOUT software in order to determine the refractive index, n and extinction coefficient, k. Generally, the calculated n and k in the visible part of the solar spectrum for different samples, ranged from 1.59 to 2.2 and 0.00013 to 0.0194 respectively, which are in agreement with results obtained using other methods. In general, the findings of this study shows that alloy target is suitable for deposition of ZnO:Althin films for devices/applications where low deposition temperature is required.Keywords: DC Magnetron Sputtering, Optical Constants, Transparent Conducting Oxides (TCO

Luminous transmittance and phase transition temperature of VO2:Ce thin films prepared by DC reactive magnetron sputtering

Vanadium dioxide (VO2) and cerium-doped vanadium dioxide (VO2:Ce) thin films were prepared by DC reactive magnetron sputtering from vanadium metallic target and V-Ce alloy targets. Luminous transmittance and phase transition temperatures of the films were studied. The Shimadzu SOLIDSPEC-3700 DUV-VIS-NIR spectrophotometer was used to measure the transmittance and reflectance of the films. The phase transition temperature (τc) of the films was obtained from both the transmittance and sheet resistance against temperature curves. A change in sheet resistance of 2 to 3 orders of magnitude was observed for both undoped and Ce-doped VO2 films. Comparison between undoped and doped VO2 films revealed that cerium inclusion altered both the visible and infrared transmittance of VO2 thin films. Luminous transmittance was slightly enhanced while τc was slightly depressed by cerium inclusion in VO2. A two-step increase in transmittance observed in the cooling loop in pure VO2 was found to be suppressed by cerium inclusion.Keywords: vanadium dioxide, luminous transmittance, phase transition temperatur

Hall Effect Parameters of Aluminium and Tungsten Co-Doped VO2 Thin Films

The Hall Effect parameters of Al and W co-doped VO2 thin films were studied in order to explain the effect of co-doping on the electrical properties of thermochromic VO2 films. The carrier concentrations and conductivity of the films were found to increase with increase in temperature while carrier mobility decreased reaching a minimum around the transition temperature then slightly rose and became stable at high temperatures. Tungsten doped films displayed higher carrier concentrations and conductivity on both sides of the metal insulator transition and lower mobility compared to undoped and Al and W co-doped VO2 thin films.Keywords: Vanadium dioxide; Hall effect; Career concentration; career mobilit

Effects of Aluminium and Tungsten Co-Doping on the Optical Properties of VO2 Based Thin Films

Aluminium and tungsten co-doped vanadium dioxide (VO2:W:Al) thin films were deposited by DC reactive magnetron sputtering technique. In this work we report on the effects of aluminium and tungsten co–doping on the optical properties of vanadium dioxide (VO2) based thin films with a view of combining both increased luminous transmittance (Tlum) and lowered transition temperature (τc). The effect of aluminium and tungsten co-doping on semiconductor-metal transition of vanadium dioxide films was investigated and compared with tungsten doped and undopedVO2films. Spectral transmittances of the films were obtained using Shimadzu SolidSpec-3700 DUV UV-VIS-NIR spectrophotometer. The results revealed that the transmittance of tungsten and aluminium co–doped vanadium dioxide using two Al pellets showed a peak at about 54% in the visible spectral range with fairly good switching characteristics and a transition temperature of 61 oC.Keywords: Transition temperature, luminous transmittance; tungsten-aluminium co-doping; vanadium dioxid;

Subcritical water extraction of bioactive compounds from dry loquat (Eriobotrya japonica) leaves and characterization of triterpenes in the extracts

Medicinal properties of loquat leaf extracts (LLEs) are associated with their constituents of phenolic compounds and triterpenes. In this study, the efficacy of subcritical water extraction (SWE) technique was assessed by comparing with conventional solid-liquid extraction (CE) and Soxhlet extraction (SE). Results showed that the highest yields of total polyphenols were 82.7 ± 1.5 mgGAE/g leaf weight (LW), total flavonoids (54.1 ± 4.1 mgQE/g LW) and total triterpenoids (37.5 ± 3.2 mgUAE/g LW) were obtained by SWE compared to total polyphenols (61.8 ± 3.3 mgGAE/g LW), total flavonoids (43.2 ± 0.6 mgQE/g LW) and total triterpenoids (28.7 ± 2.3 mgUAE/g LW) extracted by SE and total polyphenols (50.3 ± 1.8 mgGAE/g LW), total flavonoids (40.4 ± 2.1 mgQE/g LW) and total triterpenoids (22.9 ± 3.2 mgUAE/g LW) obtained by CE. The extraction efficiency of triterpenes using SWE was about 1.7 times higher than those obtained using traditional extraction methods, and their main structural pattern of the cured extracts was comparable to the extracts obtained using traditional extraction methods.The infrared spectra obtained from the three extraction techniques appeared identical, but the variation in the intensity of the peak of absorption was visible among the three extraction techniques. The similarity of the infrared spectral pattern (peak coincided peak by peak) implies that the triterpenes in the extract obtained by the three techniques were identical by LC/MS. The findings of this study have demonstrated that SWE can be employed as an alternative green extraction technology to get important phytochemicals from plant sources.Keywords: Chinese loquat leaf, Eriobotrya japonica, subcritical water extraction, triterpen

Effects of rapid thermal annealing on the properties of room-temperature oxygenated DC sputtered zinc thin films for CZTS solar cells application

This work investigated the potential to achieve zinc oxide (ZnO) films for Cu2ZnSnS4 (CZTS) solar cells window layer at controlled annealing conditions as a potential approach to address elemental inter-diffusion in CZTS solar cells. This involved rapid thermal annealing (RTA) of room-temperature oxygenated DC sputtered zinc thin films in an ambient of nitrogen gas at different temperatures. Structural, morphological, optical, and electrical properties of these films were determined by X-ray diffractometer, Scanning Electron Microscopy, Ultraviolet-visible-near infrared spectrophotometer, and Hall Effect measurement, respectively. ZnO phases were observed after annealing the films over 150 °C. The films’ grains sizes improved with increasing RTA temperature. An exponential decrease in these films’ resistivity was observed with increasing RTA temperature attaining the lowest value at 300 °C. The bandgap and average solar transmittance of the films increased with increasing RTA temperature achieving values that are potential for applications in CZTS solar cells window layer at RTA temperatures beyond 200 °C. Keywords: Sputtering; Rapid thermal annealing; Zinc oxide; Structural; Opt-electrica

Boron Doped ZnO Films Deposited by DC Reactive Sputtering Using Zn:B Target: Influence of the Deposition Temperature on the Structural, Electrical and Optical Properties

ZnO-based transparent and conducting oxides (TCOs) are commonly used as a window layer in thin-film solar cells. However, TCOs with high transparency in the visible and near-infrared parts of the electromagnetic spectrum, plus excellent electrical properties are required in this application. In this study, TCOs based on ZnO:B films deposited by DC reactive sputtering using Zn:B alloy target were investigated. The impact of deposition temperature on the growth and physical properties of the films was examined. Structural, optical and electrical properties of these films were investigated by means of x-ray diffraction (XRD), Ultraviolet-Visible-Near Infrared (UV-VIS-NIR) spectroscopy, and Hall effect measurement, respectively. The XRD analysis revealed that all films are of hexagonal wurtzite structures, with a preferred orientation along the c-axis. The optical spectroscopy results indicated that all the ZnO:B films had optical transparency above 90% in the visible region which then slightly decreased in the near-infrared region. The highest carrier concentration, conductivity, and mobility were obtained at the deposition temperature of 300 °C–due to improvement in crystal growth–while higher temperatures slightly deteriorated the electrical properties, possibly due to a slight decrease in the crystallite size. Keywords: ZnO; Transparent and conducting oxides; ZnO:B, DC reactive sputtering; deposition temperatur

The Quest for Teacher Job Satisfaction –Job Performance Relationship in Tanzania’s Public Primary Schools: The Case of Iringa Region

This study attempted to assess job satisfaction- job performance relationship as distinct work-related attitudes among teachers in public primary schools. The main aim was to establish the validity of the relationship based on the Tanzanian work setting in education. The study was based in Iringa Region as a case study area. Forty two (42) public primary schools were randomly selected for the study from all the districts of the region. Sampling procedure used the principle of purposive, stratified and simple random samplings. Data was collected using observations, individual interviews, documentary review and structured questionnaires. Closed ended questions were used as survey instruments. In addition to using SPSS for data analysis, content and normal regression analyses were also employed. Generally, the study substantiated that there is a statistical significant relationship between teachers’ job satisfaction and job performance.The regression results, further, indicated that living and working conditions as well as supervision such as by school heads have greater influence on teachers’ job performance than the other predictors. The results are contrary to studies which indicate that there is no relationship between employee job satisfaction and job performance. From policy and practical points of view, the study concluded that there is a need for serious measures to address teachers’ claims and demands related to their professional duties and responsibilities. The Tanzania’s education and employment policies should provide for teachers’ social recognition and value in society. The study also suggested areas for further research

Effects of Multilayer Structure on the Microstructure and Optical Properties of the DC Sputtered Chromium Thin Films for Selective Solar Absorber Applications

Chromium thin films exhibit several properties that make them potential for solar thermal applications. In this work the effect of film thickness and sputtering power based multilayer structure on the optical properties of DC sputtered chromium thin films is reported. The structural, topological, and optical properties of these films were determined by X-ray diffractometer, Atomic Force Microscopy, and Ultraviolet-Visible-Near Infrared spectrophotometer, respectively. XRD spectra revealed a single peak with preferential orientation of (200) and (210) for single layer and multilayer chromium films, respectively. The grain size and roughness were relatively higher for the multilayer compared to single layer Chromium films. Spectral transmittance showed very high sensitivity to film thickness with average peak of 69% and 5% at a wavelength range of 250-2500 nm for the film thickness of 12 nm and 94 nm, respectively. Spectral transmittance was also found to be higher in single layered films than multi-layered films. Findings from this study suggest that multilayer structure have the potential of tuning the microstructure and optical properties of low thickness Cr films, hence, extending its potential applications in selective solar absorber applications. Keywords: Multilayer, Chromium, Sputtering, Optical constants &nbsp