Ultraviolet laser damage properties of single-layer SiO2 film grown by atomic layer deposition

Optical properties and ultraviolet laser damage of single-layer atomic layer deposition (ALD) SiO 2 films were investigated. ALD SiO 2 films of high transparency shows weak absorption at 355nm. The absorption at 355 nm measured by laser calorimeter varies linearly with the film thickness with absorption coefficient of ∼0.76 ppm/nm. Such absorption is considered originating from various point defects in ALD SiO 2 film. Fourier transform infrared (FTIR) spectra confirm the presence of point defects in ALD SiO 2 films including non-bridging oxygen atoms and residual OH groups. Nanosecond laser-induced damage of ALD SiO 2 film at 355 nm was investigated. The damage threshold and damage morphology suggest that laser-induced damage of ALD film is associated with point defect clusters which can absorb enough laser energy to initiate micro-explosion in ALD films. Furthermore, the ALD films were conditioned with sub-nanosecond ultraviolet laser. Significant improvement in damage resistance has been demonstrated after sub-nanosecond laser conditioning. After laser conditioning to 3 J/cm 2 , the damage threshold of 535 nm thick ALD film increased from 5.5 J/cm 2 to 14.9 J/cm 2 and improved about 170%. Annealing of point defects by sub-nanosecond ultraviolet laser is supposed to be the reason for the improvement of the damage resistance.