Research On Irradiation Effect Of SiO₂ Laser Antireflection Films

Sol-gel silica films has the characteristics of excellent optical performance,high resistance to laser damage,good dielectric properties,easy coating and low manufacturing costs.Therefore,it is widely used in microelectronic devices,solar cells,and coating of optical elements.In the current research on inertial confinement fusion,sol-gel SiO₂ films are widely used in the coating of optical elements in high power solid laser device to improve the transmittance of optical elements such as fused silica and reduce the energy loss of laser light in the transmission process to extend the life of the optical components and increase the output power of the laser device.However,during the fusion reaction,the SiO₂ film will be irradiated not only by laser beam and highly penetrating?-rays,neutrons,but also may be irradiated with ion beams,electron beams,etc.Irradiation may cause defects in the SiO₂ film,change the microstructure and surface morphology of the film,and thus reduce the optical performance of the film,which will have an important impact on the use of optical components and the stability of high-power solid laser devices.Therefore,in this thesis,the effects of?-rays and helium ions radiation on the SiO₂ thin film were experimentally studied.The main research contents are as follows:?1?The SiO₂ films were irradiated with?-rays with different doses,and the surface morphology,roughness,microstructure and optical properties of the films with different irradiation doses were analyzed.The results show that the porosity of the film surface is increase and many cracks appear on the surface.With the increase of the irradiation doses,the number of cracks gradually increases and the width of cracks gradually increases.The surface roughness of the film measured by atomic force microscope slightly decreases with the increase of radiation doses,and the measurement results of the contact angle also proved it.In addition,the transmittance of the films gradually decreases with the increase of the radiation doses in the ultraviolet region of 200⁴00 nm.When the irradiation dose is greater than 100 kGy,there was an obvious new absorption peak at 215 nm,and the intensity of the absorption peak increases with the increase of the irradiation doses,indicating that the gamma-ray irradiation caused defects and the accumulation of defects.?2?The effects of different fluences of helium ions on the surface morphology,film thickness,microstructure,internal defects and optical properties of sol-gel SiO₂ films were studied.The results show that the sputtering effect of helium ion implantation causes the thickness of the film gradually decrease with the increase of the implantation fluence.The implantation of helium ions caused cracks on the surface of the film,and the cracks became longer and wider with the increase of the implantation fluence,so that the width was too large to expose the substrate,and the interconnected cracks split the film into many blocks.Meanwhile,the size of pores on the surface of the thin film gradually increase with the increase of the implantation fluence.The implantation of helium ions changed the size of nanoparticles in the film.The larger the implantation fluence,the smaller the particle diameter.In addition,as the implantation fluence increases,the Si-O-Si bond angle in the film becomes smaller,the bond length becomes shorter,and the film becomes denser.The E'center defects was generated in the film by helium ion implantation,and the defects reached saturation at a fluence of 5×10¹66 ions/cm²,and were transformed into the oxygen vacancy center defects as the implantation fluence increased.Due to helium ion implantation,defects in the thin film,denseness of the thin film,and surface morphology of the thin film are changed,resulting in a gradual increase in the absorbance of the thin film with the implanted fluence.The generation of defects,the compactness of the film,and the change of surface morphology cause the absorption rate of the film to increase with the implantation fluence.