Role of Ammonia on the Growth Mechanism of ZnO Films Deposited at Ambient Temperature

Zinc oxide (ZnO) was synthesized by chemical bath deposition (CBD) technique at room temperature. The species distribution diagrams, and the solubility curves were used for determining the better chemical conditions required to evaluate the ammonia role for obtaining high quality ZnO films. ZnSO4, NH4NO3, and KOH were the chemical reagents used for the bath. Three different pH zones between 9 and 13 were selected to synthesize the films. X-ray diffraction analysis showed that the pH value of the chemical bath and the ammonia concentration influences on the structure crystalline of the deposited films. Three different surface morphologies were obtained according to the pH of the solution. The bandgap energy values measured in the deposited films range from 3.52 eV to 3.77 eV. The estimated Urbach's tails energy values confirmed that samples exhibited high crystallinity. By controlling the ammonia concentration and pH, deposition of high quality ZnO films can be obtained at room temperature.