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;

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

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

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