Preparation of conducting and transparent indium-doped ZnO thin films by chemical spray

Transparent conducting indium-doped zinc oxide thin films were prepared on soda-lime glass substrates by the spray pyrolysis technique. The dependence of the electrical, structural, morphological and optical properties on the preparation conditions has been studied. Two main variables, substrate temperature and molar concentration, were varied in the ranges of 425–525 °C and 0.05–0.5 M, respectively, in order to obtain films with low electrical resistivity and high optical transparency in the visible region. A minimum resistivity value around of 3×10−3 Ω cm was obtained for films deposited from highly concentrated starting solutions, 0.4 and 0.5 M. The values of the free-carrier concentration and the electronic mobility were estimated by Hall effect measurements. X-ray diffraction spectra evidenced a preferential orientation along the (1 0 1) direction. The surface morphology was clearly affected with the molar concentration variation, leading to a smoother appearance as the zinc concentration in the starting solution is increased. Typical optical transmittance values in the order of 85% were obtained in all the films.