Determination of optical constants of vacuum annealed ZnO thin films using Wemple Di Domenico model, Sellmier's model and Miller's generalized rules

Thin films of zinc oxide (ZnO) were coated by a spin coater on the glass substrate and are annealed at 300 degrees C and 500 degrees C under the reduced atmosphere of 10-3 mbar. The structural properties were examined by X-ray dif-fractogram (XRD), atomic force microscopy (AFM), and optical study of ZnO thin films by UV-Vis spectropho-tometer. The XRD study showed that the films had a preferred orientation towards the c-axis, and the AFM study revealed a columnar growth. Optical parameters such as band gap, Urbach energy, electron-phonon interaction strength, refractive index, carrier concentration to the effective mass (N/m*) ratio, carrier concentration, and plasma frequency were extracted from transmittance and absorption curves by using Wemple Di Domenico and Sellmier's models. The non-linear optical parameters such as susceptibility and refractive index are obtained from Miller's generalized rules. The optical bandgap was found to decrease with an increase in dopant con-centrations and also with annealing temperature but for 0.5 M bandgap increase at 300 degrees C. The Urbach energy follows the increasing trend for both increase in concentration and annealing temperature. This indicates vacuum annealing induces defect sites in the material under investigation.

Automated summary

Thin films of zinc oxide (ZnO) were coated on glass substrates using a spin coater and annealed at different temperatures in a reduced atmosphere. The structural properties of the films were analyzed using XRD and AFM, and the optical properties were studied using UV-Vis spectrophotometer. The results showed preferred orientation towards the c-axis and columnar growth in the films. Various optical parameters such as band gap, Urbach energy, refractive index, and carrier concentration were determined. Non-linear optical parameters were obtained using Miller's generalized rules. The band gap was found to decrease with dopant concentration and annealing temperature, except for a slight increase at 300°C. The Urbach energy increased with both dopant concentration and annealing temperature, indicating the presence of defect sites in the material.