| 초록 |
ZnO thin films have attracted a great interest as a transparent conductor. ZnO is an n-type wide bandgap semiconductor (Eg = 3.3 eV). Its electrical conductivity is increased by excess zinc at the interstitial positions and by doping with Al. Heat treatment in a mixture of nitrogen and hydrogen gas also increases the electrical conductivity. Typically, hydrated zinc acetate hydrate (Zn(CH3COO)2◦ 2H2O) is used to make ZnO thin films. It is believed that the presence of H2O is essential in the process of hydrolysis and condensation during ZnO fabrication. In this work, anhydrous zinc acetate (Zn(CH3COO)2) was first dissolved in a mixture of anhydrous 2-methoxyethanol, monoethanol amine (MEA), and AlCl3 (1 at% to Zn2+ ) at room temperature. The molar ratio of MEA to zinc acetate was maintained at 1.0 and the concentration of zinc acetate solution was 0.4 M. Anhydrous solution was boiled for inducing ZnO particle growth (stirring at 120℃ for 20 min). For stability, the coating solution was usually used one day after the solution was prepared. The solution was dropped on a 7059 Corning glass substrate, which was spun at 3000 rpm for 20 s. After the spin coating, the films were dried for 10 min on a hot plate at 350℃ to evaporate the solvent and remove organic residuals. The procedures from coating to drying were repeated six times. The films were then fired at 500℃ for 1h in nitrogen with 10% hydrogen. The ZnO films obtained with anhydrous solution were compared with the films made by conventional method. The films seemingly have better characteristics such as surface morphology, electrical and optical characteristics. |
