Effect of solvents and stabilizers on sol–gel deposition of Ga-doped zinc oxide TCO films

Gallium-doped zinc oxide spin-coated thin films have been prepared by the sol–gel method. The influence of two solvents, isopropanol and 2-methoxyethanol (2-ME), and two chelating agents, monoethanolamine (MEA) and diethanolamine (DEA), was investigated. X-ray diffraction shows preferential (002)c-axis orientation of the crystallites influenced by the doping content and starting solution composition. Better orientation was obtained with 2-ME as a solvent because of a slower evaporation rate during the spin coating. Better orientation was also obtained using MEA as a stabilizer due to the weaker bonds formed with the Zn2+ions. Typical film thickness was 550 nm. The transparency of the films was greater than 85% in the entire visible range. A sheet resistance of 68 Ω/□ was obtained for the ZnO film doped with 2 at.% of Ga using 2-ME and MEA as a solvent and stabilizer, respectively. The results show that the denser packing created using a high boiling temperature solvent and a low organic content stabilizer improved the layer’s electrical and optical properties.