Physical properties of Al-doped ZnS thin films prepared by ultrasonic spray technique

The objective of this work is study the effect of Al doping on physical properties of ZnS thin films. Undoped and Al-doped ZnS films were deposited by ultrasonic spray method using atomizer on glass substrates at 500 degrees C. The films were synthesized with different Al doping ratio ranged from 0 to 6 %. The films structure and morphology were studied by means of X-ray diffraction (XRD), scanning electron microscopy. The films optical and electrical properties were studied by UV-VIS spectrophotometer and four probes method. The structural analysis indicated that the doped ZnS films have a hexagonal structure with strong preferred orientation (002) direction for all Al concentration. The (SEM) images revealed a dense surface, highly homogeneous and better adherent to the substrate surface. The average crystallites size increases from 32 nm to 43.8 nm with increasing of Al concentrations. UV-vis-NIR spectro-photometric measurements showed that the films were good transparent (60-73%) in the visible region. The films band gap is ranged from 3.7 eV to 3.9 eV. The performed electrical measurements indicate that the films electrical resistivity depends on the doping ratio. The latter was decreases with increasing the Al concentration from 8 x 10(4) to 3.35 x 10(4)Omega.cm.