Effect of Al doping on the properties of electrodeposited ZnO nanostructures

In this study, Al-doped zinc oxide (AZO) nanostructures are prepared on polycrystalline fluorine-doped tin oxide (FTO)-coated conducting glass substrates from nitrates baths by the electrodeposition process at 70 °C. The electrochemical, morphological, structural and optical properties of the AZO nanostructures were investigated in terms of different Al concentration in the starting solution. It was found from the Mott–Schottky (M-S) plot that the carrier density of AZO nanostructures varied between 3.111020 to 5.561020 cm-3 when the Al concentration was between 0 and 5 mM. Atomic force microscopie (FM) images reveal that the concentration of Al has a very significant influence on the surface morphology and roughness of AZO thin films. X-ray diffraction (XRD) patterns demonstrate preferential (002) crystallographic orientation having c-axis perpendicular to the surface of the substrate and average crystallites size of the films was about 23–36 nm. As compared to pure ZnO, Al-doped ZnO exhibited lower crystallinity and there is a shift in the (002) diffraction peak to higher angles. ZnO nanostructures were found to be highly transparent and had an average transmittance of 80 % in the visible range of the spectrum. After the incorporation of Al content into ZnO the average transmittance increased and the band-gap tuning was also achieved (from 3.22 to 3.47 eV).

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