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

Abstract

Optical properties and ultraviolet laser damage of single-layer atomic layer deposition (ALD) SiO2 films were investigated. ALD SiO2 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 SiO2 film. Fourier transform infrared (FTIR) spectra confirm the presence of point defects in ALD SiO2 films including non-bridging oxygen atoms and residual OH groups. Nanosecond laser-induced damage of ALD SiO2 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/cm2, the damage threshold of 535 nm thick ALD film increased from 5.5 J/cm2 to 14.9 J/cm2 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.