Influence of aluminum concentration and substrate temperature on the physical characteristics of chemically sprayed ZnO: Al thin solid films deposited from zinc pentanedionate and aluminum pentanedionate

Abstract

In this work, we prepared chemically sprayed aluminum-doped zinc oxide thin films (ZnO:Al) on soda-lime glass substrates. The films were deposited from a starting solution containing zinc pentanedionate and aluminum pentanedionate. The influence of both the dopant concentration in the starting solution and the substrate temperature on the composition, morphology, and transport properties of the ZnO:Al thin films were studied. The structure of all the ZnO:Al thin films was polycrystalline, and a variation in the preferential growth with the aluminum content in the solution was observed: from an initial (0 0 2) growth in films with low Al content (1–3 at%), switching to a predominance of (1 0 1) planes for heavily dopant regime (5 at%). The crystallite size was found to decrease with doping concentration and ranges from 33 to 20 nm. First-order Raman scattering measurements prove the wurtzite structure C 6 ν 4 in the ZnO:Al films deposited. The assignments of the E 2 mode in ZnO:Al differ from previous investigations. The thin solid film composition, and hence, the dopant concentration were determined by Auger Electron Spectroscopy (AES); these results showed that the films are almost stoichiometric ZnO. The optimal deposition conditions leading to conductive and transparent ZnO:Al thin films were also found. In this way a resistivity of 3.0×10 −2 Ωcm with a (0 0 2) preferential growth, were obtained in optimized ZnO:Al thin films.