Formation mechanism and properties of nanorod-structured ZnO films prepared by pyrolysis of Zn acetate films

Nanorod-structured ZnO (NR-ZnO) films were formed on glass substrates by thermal treatment of Zn acetate films in a closed-type tube furnace. The formation mechanism of the NR-ZnO films is proposed as follows: the volatile Zn acetate was vaporized from the top region of the Zn acetate films; the mixture of ZnO and Zn acetate groups in the intermediate region acted as a seed layer; and ZnO NRs were grown in the intermediate region via the vapor-solid process of the volatile groups. The as-formed NR-ZnO films exhibited a wurtzite crystal structure with strong c-axis orientation. The optical bandgap of the film was ∼3.27 eV, and photoluminescence emissions centered at 3.10, 2.98, and 2.81 eV were observed. The diffuse and specular transmittance values of the film were ∼95% and 59% at 550 nm, respectively. This difference originated from the structure of the NRs, which increased the light path length in the films.