Influence of Thermal Annealing on Mechanical and Optical Property of SiO2 Film Produced by ALD

Abstract

The application range of fused silica optical components can be expanded and the cost of fused silica components can be reduced by depositing the same material film on fused silica substrate. However, due to the different manufacturing process, the performance of ALD SiO2 film is lower than that of fused silica substrate, which also limits the use of this process. In this paper, ALD SiO2 film with different thicknesses were deposited, and then the structure and properties were tested. Finally, the ALD SiO2 film was treated via the annealing process. Transmission electron microscopy (TEM) showed that the ALD SiO2 film had good compactness and substrate adhesion. The Raman spectra showed that the ALD SiO2 film and substrate had the same structure, with only slight differences. The XRD pattern showed that ALD-fused silica did not crystallize before or after annealing. The infrared spectra showed that there was an obvious Si-OH defect in the ALD SiO2 film. The laser damage showed that the ALD SiO2 film had a much lower damage threshold than the fused silica substrate. The nanoindentation showed that the mechanical properties of the ALD SiO2 film were much lower than those of the fused silica substrate. After a low-temperature annealing treatment, the ALD SiO2 film Si-OH defect was reduced, the ALD SiO2 film four-member ring content was increased, the elastic modulus of the ALD SiO2 film was increased from 45.025 GPa to 68.025 GPa, the hardness was increased from 5.240 GPa to 9.528 GPa, and the ALD SiO2 film damage threshold was decreased from 5.5 J/cm2 to 1.3 J/cm2.