Effect of temperature on the deposition of ZnO thin films by successive ionic layer adsorption and reaction

In this study, ZnO thin films were deposited on glass substrates by the successive ionic layer adsorption and reaction (SILAR) method, and the effect of the temperature treatment in ethylene glycol on the crystal structure, surface morphology, and optical properties of the films were investigated. When the temperature was below 85 °C, the ZnO films showed poor optical transmission and had a rough surface crystal structure. As the temperature was increased, dense polycrystalline films with uniform ZnO grain distribution were obtained. The optical transmittance of the ZnO thin films fabricated at temperatures greater than 95 °C was very high (90%) in the visible-light region. Therefore, it could be concluded that increasing the temperature of treatment in ethylene glycol helps in obtaining fine-grained ZnO films with a high growth rate and a low concentration of oxygen vacancies. However, temperatures greater than 145 °C led to shedding of ZnO from the surface and a reduction in the growth rate. Thus, temperature treatment was confirmed to play an important role in ZnO film deposition instead of post thermal annealing after the film growth.