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In this work, we have prepared the undoped and Al-doped ZnO thin films by a homemade spray pyrolysis method at 450°C onto glass substrates. The X-ray diffraction patterns of undoped ZnO and aluminized zinc-oxide (AZO) thin films exhibit hexagonal wurtzite crystal structure with high crystalline quality, the crystallite size is nanometric. The morphology of the undoped and Al-doped ZnO thin films also indicate that all samples have a nanoscale grain size around 50 nm, and the microstructure of ZnO films is highly influenced by the aluminum doping. The two films are characterized by UV-visible spectrophotometry showing that the films have a whole optical transmission above 85% in the visible range. The composition of our films is obtained by energy dispersive spectrum, confirmed by Auger electron spectroscopy (AES) and by Rutherford back-scattering spectrometry (RBS) techniques. [ABSTRACT FROM AUTHOR]

Undoped ZnO thin films have been prepared on glass substrates at different substrate temperatures by spray pyrolysis method. The effect of temperature on the structural, morphological and optical properties of n-type ZnO films was studied. The X-ray diffraction (XRD) results confirmed that the ZnO thin films were polycrystalline with wurtzite structure. Scanning electron microscopy (SEM) measurements showed that the surface morphology of the films changed with temperature. The studies demonstrated that the ZnO film had a transmission of about 85 % and energy gap of 3.28 eV at 450 °C. The RBS measurements revealed that ZnO layers with a thickness up to 200 nm had a good stoichiometry. [ABSTRACT FROM AUTHOR]

Pure and Al-doped Zin Oxide ZnO (AZO) thin films with different aluminum (Al) concentrations (0.5, 1, 2, and 3 at.%) were prepared on glass substrates by a dip-coating technique using different Zn and Al precursors. The structural, morphological, optical and electrical properties of these films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Atomic force electron microscopy, ultraviolet–visible spectrophotometry, photoluminescence (PL) spectroscopy and four-point probe technique. XRD results showed that the obtained AZO thin films were polycrystalline with a highly c-axis preferred (002) orientation, and the average crystallites size decreased from 29 to 25 nm with the increase in Al doping concentration. EDS microanalysis confirmed the presence of Zn, O and Al elements in the prepared films as expected. The optical study demonstrated that the ZnO thin film had a good transparency in the visible range with a maximum transmittance of 90% and the band gaps varied from 3.16 to 3.26 eV by Al doping. SEM micrographs showed a wrinkles-like morphology of the thin films that changed in density with the increase of Al concentrations. The PL emission spectra indicated that except the thin film doped with 1 at.%, other films exhibited high emission intensities under an excitation of 325 nm which allows to apply them as downconversion layers for solar cell applications. [ABSTRACT FROM AUTHOR]

Abstract: This work presents the effect of postdeposition annealing on the structural, electrical and optical properties of undoped ZnO (zinc oxide) thin films, prepared by radio-frequency sputtering method. Two samples, 0.17 and 0.32 µm-thick, were annealed in vacuum from room temperature to 350 °C while another 0.32 µm-thick sample was annealed in air at 300 °C for 1 h. X-ray diffraction analysis revealed that all the films had a c-axis orientation of the wurtzite structure normal to the substrate. Electrical measurements showed that the resistivity of samples annealed in vacuum decreased gradually with the increase of annealing temperature. For the 0.32 µm-thick sample, the gradual decrease of the resistivity was essentially due to a gradual increase in the mobility. On the other hand, the resistivity of the sample annealed in air increased strongly. The average transmission within the visible wavelength region for all films was higher than 80%. The band gap of samples annealed in vacuum increased whereas the band gap of the one annealed in air decreased. The main changes observed in all samples of this study were explained in terms of the effect of oxygen chemisorption and microstructural properties. [Copyright &y& Elsevier]