| This work includes two main parts:1) The study of the preparation, the morphologies and structural, electrical and optical properties of ITO thin films with sol-gel methodTransparent conductive indium tin oxide (ITO) thin films have been deposited by the spin-coating process on common glass substrate using solutions of acetyl acetone, ethanol, indium and tin salts with sol-gel method. The surface and cross-sectional morphologies and structural, electrical and optical properties of the ITO films are investigated by SEM, Raman Spectrum, XRD, four-point probe method and UV/VIS/NIR spectrometer, respectively. Firstly, the influence of different annealing temperatures on the crystallinity of the ITO films is investigated. The XRD results show that at 300℃the film is polycrystalline with cubic bixbyite In2O3 structure which is gradually decomposed from InOCl primitive orthorhombic structures of as spin-coated films, so we choose 300℃as the lowest annealing temperature in this experiment. At this temperature the influence of different technological conditions (spin-coating times, annealing times, Sn4+ dopant concentrations, and In3+ sol concentrations) on the properties of ITO films have been investigated in detail. The experimental results are discussed and the experimental conditions are optimized.The highly conductive and transparent ITO thin film has been obtained by the sol-gel spin-coating method with low temperature annealing treatment. With the increase of annealing time, a surface morphology changes from flaky structure into globular structure with an average crystalline size of about 20nm after 22 hours annealing at 300℃. No peaks of Sn and Sn compound (SnO or SnO2) have been observed in the XRD results, and all the peaks are verified to be of In2O3. Besides the change of Sn4+ dopant concentration from 5wt% to 20wt% doesn't change the structure of the ITO film. While with the increase of the In3+ sol concentration up to 0.51M, deficiencies and interstices in ITO thin films decrease significantly, and the surface becomes smoother. The sheet resistance and the transmittance in visible range of ITO thin films are strongly dependent on annealing time at 300℃annealing temperature. The sheet resistance of the films decrease and the transmittance in visible range increase with the increasing annealing time up to 22 hours. The sheet resistance shows a minimum value of approximately 1500Ω/□and the transmittance in visible range shows a maximum value of approximately 73% for ITO film annealed at 300℃for 22 hours. Additionally, the sheet resistance and the transmittance in visible range decrease with the increase of spin-coating times and In3+ sol concentrations. Furthermore, the sheet resistance reaches a minimum value with 10wt% Sn dopant content; however, the dopant content of Sn has little influence on the transmittance in visible range.In summary, the optimized preparation conditions are: 0.17M In3+ sol concentration, 10wt% Sn dopant content, 10 times for spin-coating, 300℃annealing temperature, 22 hours annealing time. The thickness of the ITO film is about 345nm, the grain size is about 20nm, the sheet resistance shows a value of 1500Ω/□, and the transmittance in visible range shows a value about 83% by contrast with bare glass substrate.2) The influence of temperature-humidity treatment on amorphous ITO filmsAmorphous indium tin oxide (ITO) thin films have been deposited on silicon and Corning 7059 glass substrates at room temperature (RT) and at 75℃by direct-current magnetron sputtering method. After exposure of the two kinds of samples to the temperature-humidity (T-H) test, two different types of circular structures are formed on the surface of ITO film. One is composed of granules, and the other one is composed of several concentric circular. The EDS analysis displays that the Sn and In concentration is different from center to the edge. Metallic ion concentration corrosion cells are used to explain the phenomena. The reflectivity and resistivity do not show distinguish degradation with the temperature-humidity treatment. |
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