Chemically sprayed ZnO:F thin films deposited from diluted solutions: Effect of the time of aging on physical characteristics

Transparent and conductive fluorine-doped zinc oxide (ZnO:F) thin films were deposited on glass substrates by the chemical-spray technique starting from a diluted solution of zinc acetate and hydrofluoric acid. The effect of the aging time of the starting solution on the electrical, structural, morphological and optical characteristics of ZnO:F thin films was observed and analyzed. The resistivity of the ZnO:F thin films decreases as a more aged solution is used, reaching a saturation value of 6×10⁻² Ω cm. X-ray diffraction reveals that the films are polycrystalline in nature with a (1 0 0) preferential growth in almost all the cases. High-resolution scanning electron microscopy clearly reveals that the films are composed of nanoparticles of spherical shape, whose average diameter is in the order of 15 nm that matches well with the crystallite size calculated from X-ray diffraction. This result shows that fluorine incorporation effectively inhibits grain growth. This, in turn, produces a porous structure. Also, the increase in the time of aging enhances slightly the transmittance of the films.