Heat-activated structural evolution of sol-gel-derived ZnO thin films

Zinc oxide (ZnO) thin films were prepared by a sol–gel dip coating process. The present work focuses on the crystallization behavior of these films during heating. In particular, the cases of (a) change of heating temperature and (b) change of heating time are studied. The characterization of the films by various analytical methods shows a correlation between heating temperature and film structure. At lower heating temperatures, granular structure dominates the films, while the films feature a columnar grain growth at higher-heating temperatures. The transition from granular to columnar structure is studied by the variation of heating times at a fixed-heating temperature. The evolution mechanism of the microstructure has been discussed in terms of continuous growth of the grains aided by an enhanced diffusion process.