Processing Technology And Film Properties Of Indium Tim Oxide Thin Film

Indium tin oxide (ITO) thin films were widely utilized in liquid critical displays (LCD), energy-saving windows for construction, solar cells, Car windshields, electromagnetic shielding, and so on due to their unique characteristics such as high conductivity, excellent transparency to visible light, and strong reflectivity to infrared light. In this case, ITO precursor slurries were prepared by organic and inorganic sol-gel methods using metal indium and tin salt as raw materials. A dip-coating process was performed to deposit ITO precursor slurry on the substrate. After heat-treatment the ITO thin films were obtained.In order to increase photoelectric properties of ITO thin film the kind of organic system and hydrolysis catalysts were discussed in the precursor slurry preparation. Also, the concentration of the In³⁺ that was in the precursor slurry was adjusted. Silane coupling agents were used to enhance the adhesion of ITO thin films on glass substrate and the working principle was investigated. Besides, it had been studied that the influences of dip-coating times and speed, heat-treatment time and atmosphere on the film electric properties.The film sheet resistance was measured by four-point probe method. The microstructure was studied under a scanning electron microscope (SEM) and a transmission electric microscope (TEM). The film adhesion was measured by a nano-scratching test using a nano indenter. The optical characteristics of the ITO thin films were tested through the UV-vis spectrophotometer. The crystalline phases of the ITO thin films were analyzed using X-ray diffraction (XRD).The results indicated that homogeneously dispersed ITO precursor slurry was prepared using acetylacetone system and acetic acid as a hydrolysis catalyst without drying in vacuum. The film resistance decreased when the concentration of the In³⁺ was increased. It is because of the function of coupling agent that indium tin oxide particles adhered to the glass substrate by the O-Si-O band. That is to say coupling agent changed the connection between the film and substrate from simply physical absorption to more firm chemical absorption, thus enhancing the film adhesion. By introducing the coupling agent into the ITO film system did not change the film crystal structure. The film's preferred orientation was (222) plant. The film's average transmittance rose from 78.9% to 83.6% in 390nm-780nm range of visible light wavelength. Compared with different adopting methods of the coupling agent, adding the coupling agent into the ITO precursor slurry was more effective in increasing film adhesion than using it pretreated substrate. According to a nano-scratching test, the film critical share stress when the film peeled from the substrate increased 49%. In addition, the film resistance tended to deceased when the dip-coating times and speed grew.