Preparation of Al Doped ZnO transparent conductive films by ultrasonic spray pyrolysis

The ZnO:Al thin films with different Al doping concentrations were fabricated on glass substrates by ultrasonic spray pyrolysis method. The morphologies, crystal structures and optical properties were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), reflection spectra (Res), and four-point probe, respectively. The SEM results indicate that the amount of hole on the surface increases and the surface soomthness decreases as Al concentration increasing. The XRD patterns demonstrate that when the molar ratio of Zn to Al is 100:5, the AZO thin films have wurtzite structure with a preferential c-axis orientation. The PL spectra reveal that the NBE-peaks and DLE-peaks are observed in the AZO films with different Al doping concentration. The NBE-peaks show first blue-moved to a later red-shift as Al doping concentration increasing. Reflection spectra showed that all the samples had low reflectivity in visible region. Square resistance results indicate the AZO thin films have good electrical conductivity when the molar ration of Zn to Al is 100:5.