Optical properties and structural characterization of bias sputtered ZrO₂ films

The zirconia (ZrO₂) thin films were synthesized using the RF reactive sputtering method at various dc negative bias. The effect of deposition temperature and post-annealing process on the structure and optical properties of ZrO₂ were investigated. It was found that the films deposited on silicon would develop a highly monoclinic phase (over(1, ̄) 1 1) with preferential orientation using the bias sputtering at a high substrate temperature, whereas tetragonal zirconia was formed on glass under the same condition. The dispersion curve of the films rose up after post-annealing, especially for the films deposited at a higher bias. The refractive index of ZrO₂ films increased to 2.17 (at 550 nm) by applying an appropriate bias, while the band gap energy decreased to 5.65 eV correspondingly. The dependence of the optical properties on the structure of films was educed consequently.