Improved Physical Properties of Green Fabricated ZnO Thin Films by Annealing Temperature

Abstract

AbstractZnO thin films were prepared by sol‐gel spin coating on a glass substrate via green synthesis using Uncaria gambir leaf extract. The deposited films were characterized for structural, morphological, and optical properties at various annealing temperatures (400, 500, and 600 °C). The ZnO film without annealing shows an amorphous structure, and after annealing, it shows a hexagonal wurtzite structure with a dominant (101) peak. The crystallinity of the films increases up to 500 °C. The crystallite size shows a maximum value (27 nm) at 500 °C. Also, a flat, smooth, uniform wrinkle and the homogenous surface of ZnO thin films are shown at 500 °C. The gambir extract prevents the segregation of crystallites until 500 °C. The transparency was over 80 % in the visual region for all annealed films, and the energy bandgap decreased to 3.81 eV with increasing the annealing temperature up to 500 °C.