Novel Materials Proper to Liquid Process
In this chapter, novel oxide materials, which are special for liquid processes, are introduced. In the liquid process, a final solid oxide is formed by the decomposition of a metal–organic compound and by the subsequent growth of metal oxide, which proceed simultaneously in a pyrolysis reaction. Because of their nature, the organic elements remain until a certain stage during the conversion process from liquid to solid. Carbon atoms thus remaining in the system strongly affect the properties of the solid oxide formed and also affect the gel-to-solid conversion. The complete elimination of carbon from the system generally requires a temperature greater than 1000 °C. Accordingly, carbon should remain in the system when annealing is conducted at 500 °C or 600 °C. In most cases, the remaining carbon tends to degrade the properties of the formed solid. In the case of an ITO film, for example, the resistivity of an ITO film prepared by the vacuum process is typically 1 × 10−4 Ωcm, whereas it increases to 1 × 10−3 Ωcm in the case of a film prepared using the liquid process. This degradation is regrettably common in liquid-processed oxide materials and has been a large drawback of the liquid process compared to the vacuum process.