Effect of the oxygen partial pressure on the toughness of tetragonal zirconia thin films for optical applications

The zirconia thin films (80–120 nm thick) were deposited on (1 0 0) silicon substrate using metal organic chemical vapor deposition. The effect of oxygen partial pressure during the process and post annealing step on the structure, microstructure and mechanical properties were investigated. Under peculiar experimental conditions, nano-crystallized tetragonal thin films were obtained. The film structure was stable when annealed and some of the films exhibited large toughness values, up to 3.9 MPa m1/2. This high toughness value is interesting to use this material as a protect layer for optical applications as this zirconia layer displays a minimum reflectance in the near infrared window. This minimum reflectance could be shifted depending on the thickness of the films.