ZnO:F thin films deposited by chemical spray: effect of the fluorine concentration in the starting solution

Conductive and transparent fluorine-doped zinc oxide, ZnO:F, thin films were deposited at 500°C on glass substrates by the chemical spray technique. Two sets of samples were deposited, based on a fresh and a two-day old starting solution prepared from zinc acetyl acetonate and ammonium fluoride dissolved in a mixture of water and alcohol. The electrical, structural, morphological and optical characteristics of the films as a function of the fluorine concentration in the starting solution were studied. Films with a resistivity as low as 2×10−2 Ω cm, mobility up to 5 cm2/(V s), carrier concentration in the range 1.5–5.7×1020 cm−3 and a transmittance in the range 75–90% were achieved with the old solution. Films were polycrystalline, growing preferentially along the (0 0 2) and (1 0 0) directions, depending on the fluorine concentration in the starting solution.