ZnO films fabricated by chemical bath deposition from zinc nitrate and ammonium citrate tribasic solution

Zinc oxide (ZnO) films were prepared on glass substrates by chemical bath deposition at 50 °C. A solution of zinc nitrate, ammonium citrate tribasic and sodium hydroxide was used, and various deposition conditions were investigated. The optimal ratio of [Zn(NO3)2]:[(NH4)3C6H5O7]:[NaOH] was 10.0:4.0:4.3, and the optimal annealing temperature was 400 °C. X-ray diffraction patterns showed that the annealed films prepared at the optimal ratio have a wurtzite structure. Scanning electron micrograph showed that the film consists of nanoparticles with a size of several decade nanometers. Transmittance spectra showed high optical absorption below 380 nm and transmittance over 80% in the range of 400-900 nm. The optical band gap of the film annealed at 400 °C was 3.26 eV, and the dark electrical resistivity was with an order of 103 Ωcm at room temperature.