Stress Properties Of Ta₂O₅/SiO₂ Coatings Prepared By Ion Beam Sputtering

Stress existed in almost all the thin film systems.In the regular optical coating process,thin film stress could bend the optical substrate.Even stronger stress could make the thin film crack or peel.Higher order aberration would appear after the deformable mirror coating process due to its special structure on the back side,which would badly influence the performance of the adaptive optical system.In COIL laser system,the coatings of deformable mirrors were prepared by ion beam sputtering technology,due to its lower scattering and absorption,higher reflectivity,and lower deposition temperature.But stronger compressive stress could be caused,which would make it harder to adjust.So the compressive stress could only be decreased by adjusting the deposition parameters.In this thesis,Ta₂O₅ ? SiO₂ single layer and Ta₂O₅/SiO₂ multi-layers were prepared by ion beam sputtering under different deposition conditions.The spectrum properties were measured by Lambda 1050 spectrophotometer,and the optical constant and thickness were calculated by software Essential Macleod.Stoney formula was used to calculate the stress from the curvature data measured by K-Space thin film stress measurement system.The thin films were annealed by high-low temperature circulation to release the stress.Finally,coatings of two different deposition parameters were deposited on two simplified ?220mm DM samples,and the measured properties were compared with finite element analysis results.The experimental results show that the thin film prepared by ion beam sputtering generally got high compressive stress.Ta₂O₅ monolayer stress increases with the increase of ion beam voltage,and decreases with the increase of oxygen partial first then increases with the increases of oxygen partial pressure.The stress of SiO₂ monolayer decreases with the increase of the ion beam voltage,and then increases with the increase of the ion beam voltage,and increases with the increase of oxygen partial pressure in a certain range.The heating of substrate has a certain influence on the stress of two kinds of materials.The stress can be released by high and low temperature impact.The stress variation of multilayer films is consistent with that of single layer films,which can be used to predict the trend of multilayer films.