Comparison of laser-induced damage of monolayer ZrO2 films preparated by PVD and sol-gel methods

The monolayer zirconia PVD and sol-gel films deposited on K9 glass substrates were prepared with electron beam evaporation method and spin method respectively. Both the films have similar optical thickness. The laser-induced damage threshold (LIDT) of the two kinds of films was measured. The thermal absorption, porous ratio and the surface morphologies of the films were investigated by Stanford photo-thermal solutions, ellipsometer and atomic force microscopy, respectively. Optical microscopy was used to characterize the defects and impurities of the films before laser irradiation and damage morphology after laser irradiation. The experimental results showed that the different damage morphologies of the two kinds of films were relative to their thermal absorption and microstructure. The zirconia PVD film had a dense and compact structure and much defects or impurities. The zirconia sol-gel film had a porous structure and less defects or impurities, and its LIDT was 26.9 J/cm2. Therefore the zirconia PVD film had larger absorption (115.10 × 10-6) and smaller porous ratio (0.20), and it had smaller LIDT (18.8 J/cm2). For the zirconia PVD film, the damage morphology was a combination of sputter and stress rupture. While for the zirconia sol-gel film, the damage morphology was mostly delamination. Explanation was presented theoretically at last.