Preparation of ITO Thin Films by Sol-Gel Process and Their Characterizations

Indium-tin-oxide (ITO) has attracted intense interest due to some of its unique characteristics; it has high optical transmittance in the visible region, low electric resistivity, and chemical stability. Therefore, ITO thin films have been found to play an important role in opto-electronic applications. In this work, uniform and transparent ITO films were deposited onto glass substrates using a sol-gel process. The initial sols were prepared by mixing solutions of indium nitrate prepared in anhydrous ethanol with tin chloride and mechanically stirring the resultant mixture until a clear and sticky coating sol was obtained. The glass substrates were dip-coated and annealed at 550 °C. Because annealing conditions affect the microstructures, the properties of the resultant ITO films can be controlled. Depending on annealing time and film thickness, the electrical resistivity of the ITO coating varied from 27000 to 1400 Ω/□ for 8% by wt. Sn-content The optical transmittance of 200 nm thick ITO film was more than 80% in the visible region. The surface morphology examined by SEM appears to be uniform over large surface areas. Possible correlations among the film properties and film preparation conditions are discussed.