Annealing effects on the structural and optical properties of HfO2 thin films deposited by thermal evaporation technique

Hafnium oxide (HfO₂) thin films has been prepared on glass substrates at room temperature by thermal evaporation technique using HfO₂ powders (99% purity) and then are annealed at different temperatures ranging from 150° to 450° for 24 hours in air. The effects of the annealing temperatures on the structural and optical properties of the HfO₂ thin films were studied. Amorphous structures of the HfO₂ films were researched by XRD technology. The results of the study show that the state of the HfO₂ film changes from amorphous to polycrystalline with the increase of heat treatment temperature and the the stress is released. Besides, the refractive index of the films decreases and the band energy changes significantly. Therefore, the heat treatment can effectively change the film properties and it is necessary to comprehensively select the optimal heat treatment temperature according to the specific application of the HfO₂ thin films.