| SiO2thin film has vitreous or amorphous structure, also with ring structure of long range disorder and short range order on the molecule scale, so it has outstanding optical properties and thermal stability, chemical stability, anti-heat impact. So far, SiO2thin film is the best choice for low index thin film material in the range from ultraviolet to near infrared. It is important for scientific meaning and practical value to research the optical properties, mechanics properties, structure characteristic and relationship of the ion beam sputtering (IBS) SiO2thin film.In order to systematically research the basic propertics of IBS-SiO2thin film and its applications in the multilayer coatings. First of all, the characteristic, statue and trend of ion beam sputtering technology are introduced. Second, the statue and trend of the properties, relationship between the properties and deposition technology and the properties in working circumstance of IBS-SiO2thin film are also introduced and analysed. Third, list the measuing and analysing method of the optical properties of SiO2thin film, and the stoken methods of the stress and thermodynamics are also reached.The optical properties are the important basic performance of SiO2thin film, in here, the model of the interface and index-grade is established, the relationship between the index and annealing tempetature is researched and analysed, following the rule: with temperature growing up, the index decreases and then increases, has turning point at550℃. The refractive index and physical thickness of SiO2thin film has the following aging effects: index with one-direction and0.003unit increasing, thickness stable; the index-grade has the strong relationship with the surface quality and the substrate material, also the different combination of substrate-film has the totally different properties: SiO2thin film-fused silica has the minus grade and aging convergence, SiO2thin film-Silica has the positive grade and aging stable.Thermodynamical properties is the important performance of SiO2thin film also, in here, the stress, density, mass, modulus of elasticity, hardness, poisson ratio and thermal expansion coefficient of SiO2thin film are analysed and measured. The stress of IBS-SiO2thin film mainly suffers from the inner stress, is about-800MPa, and rapidly come down to-66MPa with450℃annealing, so annealing is the effective method to adjust the film stress. It has the high correlation between the trend of the stress, density and index with annealing, the correlation coefficient is about0.9. The modulus of elasticity, hardness and Young’s modulus grow up with annealing temperature rising, the thermal eapansion coefficient reach at minimum 5.2210-7℃-1at550℃.Microstucture is another important property of SiO2thin film. The rms of SiO2thin film keeps consistant with annealing, the trend of the microstructure of SiO2thin film with annealing by the peak decomposition of IR absorption spectrum were studied; when annealing temperature increasing, the microstructure of SiO2thin film come to cristobalite, the bond-angle is near to12, SRO(short range order) grow up and reach the maximum at550℃, and it can be approved by XRD. The H2O and OH in the film disappear when the annealing temperature reached over450℃.Finally, the applications of SiO2thin film as low index material in AR and HR multilayer were studied. Annealing can move the transmittance spectrum, loss, phase shift of HR, but almost cannot affect the scatter and rms. It has aging-effect of AR, residual reflectance can decrease from45ppm to24ppm in several tens day. The on-line measuring system of low loss film were self-designed and builded. Annealing has positve effects on the ring laser syeterm, the sysytem reach the most stability when the film is annealed at550℃, the output of laser only decline to90.5%after working230hr. |
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