Study On The Properties And Infrared Optical Applications Of YO_xN_y Thin Flims Growed By Reactive Sputtering Methods

Multispectral ZnS can achieve high optical transmission from medium wave infrared to far wave infrared.So it is the first chioce of the infrared windows and domes in aircraft.However,ZnS is soft in texture,brittle,it is difficult to resist the impact damage of solid particles such as sand,hail and raindrops in the atmosphere when the aircraft flying at high speed.It must be coated with antireflective protective film.Moreover,the hardness of traditional thin film materials can no longer meet the requirements.So it is necessary to develop superhard antireflective protective thin films.Transition metal nitride thin films have received extensive attention due to their similar high hardness,good thermal stability,good diffusion barrier,oxidation resistance,wear resistance and corrosion resistance.However,due to the strong binding energy between metal elements and nitrogen element,the hardness of the films is increased while the infrared transmission is decreased.Considering the excellent infrared antireflective properties of metal oxides,oxygen is added into nitride film.In this paper,with quartz and silicon as the substrate,the effects of substrate temperature on the properties of yttrium nitride films and the effects of oxygen flow rate on the properties of yttrium oxynitride films were investigated by RF reactive magnetron sputtering methods.Atomic force microscope,X-ray diffraction,photoelectron spectroscopy,ellipsometer,UV-Vis spectrophotometer and nanoindentation were used to analyze the structure,optical and mechanical characteristics of the films.According to the results of the test,yttrium nitride and yttrium oxynitride films were deposited on ZnS substrates at appropriate temperature and oxygen flow rate.And the transmittance of the films in infrared range was measured by Fourier transform infrared spectroscopy.Research results show that the substrate temperature has a great influence on the properties of yttrium nitride film.Substrate temperature has little effect on the deposition rate of the thin films.With the increase of temperature,the surface roughness of the films decreased.XRD results show that the crystalline phase is yttrium nitride in the range of room temperature to 500°C.With the increase of temperature,the crystallinity first decreases and then increases.At 600°C,the crystalline phase in the film becomes yttrium oxide.XPS results show that the increase of substrate temperature increases the content of bonding oxygen in the films,which leads to the crystalline phase changing to yttrium oxide at higher temperatures.Ellipsometric results show that yttrium nitride is an anomalous dispersion material.With the increase of substrate temperature,the refractive index of the films first decreases and then increases,and the extinction coefficient is maintained at a small value.The optical band gap of yttrium nitride films increases with the increase of temperature,but the change is not obvious.The optical band gap values of yttrium nitride films are about 2.2eV.The hardness of the films have changed a lot,and the increase of temperature has led to a significant increase in the hardness of the films.The oxygen flow has little effect on the properties of yttrium oxynitride film.With the increase of oxygen flow rate,the deposition rate of the films decreased gradually.Surface roughness of the film decreased.XRD results show that the film is cubic yttrium oxide structure,and nitrogen element exists in a form of interstitial atoms,and the crystallinity decreases with the increase of oxygen flow rate.XPS results showed that the content of oxygen element in the film increased significantly with the increase of oxygen flow rate.The ellipsometric results proved that the yttrium oxynitride film was a normal dispersion material.With the increase of oxygen flow rate,the optical band gap of the films increases,and all of them are larger than that of YN and smaller than that of Y₂O₃,indicating that the incorporation of oxygen increases the optical properties of the film.The hardness of the films do not change significantly.Yttrium nitride and yttrium oxynitride thin films were deposited on ZnS substrates,separately.The maximum transmittance of yttrium nitride thin film is 75%.And the transmittance is improved in the near wave infrared and medium wave infrared.The yttrium oxynitride film has a transmittance up to 88%and is greatly improved in the near wave infrared,medium wave infrared and far wave infrared.The transmittance of after deposited yttrium nitride and yttrium oxynitride films is higher than 70%of the ZnS substrate.Further,the maximum hardness of the yttrium nitride film is 8.5 GPa,which can synthesize the high hardness of the yttrium nitride thin film and the high transmittance of the yttrium oxynitride thin film.According to the theory of film system design,the composite film can be prepared to achieve the effect of infrared antireflective and protection.