Preparation And Characterization Of Zno Films Coated On The Glass Substrates By Spray Pyrolysis Method

ZnO is a wide band gap semiconductor with a band gap value-3.3 eV at room temperature, would appear to be an excellent candidate for a conducting transparent oxide. The conductive and transparent ZnO thin films is a n-type semiconductor, the combination of Zn/O atomic ratio do not follow the stoichiometric ratio, and obtain the vacancies followed by oxygen evvolution from the ZnO crystals. The properties of ZnO thin fims could be controled by the process, for different functions. In addition,the doping technique, using reative donors (Al, In, F), is proposed to further increase the conductivity. The ZnO:Al (AZO) thin films is one of the promising materials for fabrication of optelectronic devices, due to its excellent optical and electical properties。Transparent conducting doped ZnO thin films have been prepared on the preheated glass substrates by a spray pyrolysis technique using zinc acetate as precursors, aluminum chloride and indium chloride as dopant precurors. The effect of incorporation of Al and In in the starting solution has been studied. The process parameters have been optimized to prepare the ZnO thin films for thin films solar cells. The spray pyrolysis equipment has been improved to face the industrial needs.The transmission was detected by Uv-Vis and the optical constants are deduced from the fringe pattern of the transmission. The surface topography of the films were analyzed by hign resolution microscopes. The sheet resistance was investigated by the means of four probe method. The crystal structure of the ZnO films coated on glass substrates was analyzed by X-ray diffraction (XRD). The obtained results are as follow:(1) The obtained results revealed that the structures and properties of the films were greatly affected by substrate temperature. The lowest resistivity of 3.5×10-3Ωm was obtained with optical transmittance up to 80% in visible region and a band gap of 3.24 eV at room temperature.(2) The ZnO films prepared are polycrystalline but retain hexagonal wurtzite structure with preferred orientations of (002) plane. The crystal structure transition from hexagonal system to diagonal hexagonal system has happen with the increase of In concentration in the starting solution, but the films maintain preferred orientations of (002) plane, the new structure (InAlO3(ZnO)17) was observed at the In dopant upper to 1%.(3) The electrical resistivity of ZnO films was greatly improved by annealing in a vacuum. The minimum electrical resistivity was obtained in the In-doped film annealed at 300 and its value was 8.25×10-5Ωm, which close to the TCO properties indexes; the resistivity of Al-doped film was also decreased(the minimum up to 3.05×10-3Ωm)...