Low temperature growth of highly crystallized ZnO:Al films by ultrasonic spray pyrolysis from acetylacetone salt

High-quality ZnO:Al films were deposited on glass substrates at a relatively low temperature of 300 °C by ultrasonic spray pyrolysis. Zn(acac)2 and Al(acac)3 acted as zinc and aluminum source, which dissolved in ethanol–water solution. The influences of aluminum concentration and vacuum annealing on microstructure, electrical and optical properties were investigated by XRD, SEM, EDS, four-point probe and visible spectroscopy. The experimental results shown that ZnO:Al films exhibit stronger (1 0 1) preferred orientation and have lenticular-like grain morphology. The resistivity as low as 4.3 × 10−1 Ω cm for as-deposited films was obtained at the 4 at.% doping concentration, which can be decreased to 10−2 Ω cm level by post-deposited vacuum annealing. The average transmittance of as-deposited films was nearly 80% in the visible range, and that of 4 at.% doped ZnO films reduced to 60% after vacuum annealing at 550–600 °C.