Study On The Preparation And Properties Of ZnO Transparent Conductive Oxide Films

ZnO transparent conductive oxide thin films doped with suitable dopants have more excellent optical and electrical properties, and are applied widely to various electrical and optical devices including liquid crystal display, solar cell and so on, as transparent and conductive oxide electrodes. In this paper, influence of dopant style and dopant concentration, low temperature synthesis, low-dimension polycrystical structure on electirical and optical properties of ZnO films were investigated.ZnO thin films doped with A13+,F- were deposited on substrates by sol-gel method from 2-methoxyethanol solutions prepared by Zincacetate as precursor, MEA as stabilizer. Homogenous transparent ZnO thin films were formed finally by dipping, drying, pre-heat treatment in air and annealing in different atmospheres. XRD, FESEM, XPS, UV-VIS-NIR and Four-Point probe method were used to charicterize chemical components, microstructure, optical and electrical properties of ZnO based thin films.The result showed that dopant concentration, annealing temperature, the number of coatings, sol concentration and atmosphere had influence in various degree on the photoelectric performance of the ZnO based thin films. Increasing the dopant concentration and the annealing temperature could reduce resistivity of thin films, but over high dopant concentration and annealing temperature would increase the resistivity of thin films instead. The transmittance of thin films within the range of visible light was not impacted basically.by different dopant concentrations and atmospheres, but high annealing temperature increased the transmittance of films. Increasing sol concentration and the number of coatings could increase the thickness of thin films, which would reduce the resistivity of the thin films and the transmittance within the range of visible light. The resistivity of the film annealed in air atmosphere was high and decreased sharply by heat treatment in Ar at 550℃and H2 above 300℃. Homogenous, dense thin films with grain size of 20nm were obtained after annealing at 400℃in H2 for 1h and grain growth strongly preferred orientation of C-axis perpendicular to the substract surface.The optimum technological parameters for ZnO based thin films are that the sol concentration is 0.6 mol/L, the dopant concentration of AlF3 is 1at%, the number of coatings is 15,the pre-heat treatment temperature is 450℃, the annealing temperature is 550℃in air, 550℃in Ar and 400℃in H2 for 1h. The transmittance of the thin films within the range of visible light is about 90%, the lowest sheet resistance is 10?/□, close to ITO conductive films.