Physical properties of indium and fluorine codoped zinc oxide thin films deposited by chemical spray

Indium and fluorine codoped zinc oxide (ZnO:In + F) thin films were deposited on glass substrates by the chemical spray technique. The effect of the dopant concentration ratio in the starting solution, as well as the substrate temperature on the electrical, morphological, structural, and optical properties of ZnO:In + F thin films was studied. A minimum electrical resistivity, in the order of 3.4 × 10−3 Ω cm, for as-grown films deposited at 475 °C from a starting solution containing [In]/[Zn] = 3 and [F]/[Zn] = 20 at.%, was obtained. All the films were polycrystalline, and some differences in the intensity of the peaks and preferential growth, depending on the doping ratios, were observed. The deposited ZnO:In + F thin films showed an average optical transmittance in the order of 85%, in the visible region (400–700 nm). The band gap values oscillated around 3.35 and 3.39 eV, and a shift towards higher values with the increase of the dopant concentration was observed. The surface morphology of the films was also strongly affected by the dopant concentration ratio, since a variation in both geometry and grain size was observed.