Research On Key Techniques Of Application Of Optical Grade Thick Diamond Films In Infrared Windows

CVD (Chemical Vapor Deposition) optical grade thick diamond films have wide application prospects in many high-tech fields owing to its extremely high hardness, excellent wear resistance and high thermal conductivity and high Infrared transmittivity. In order to explore the key techniques in infrared windows of application of optical grade thick diamond films, study is carried out in this dissertation. The growth process, polishing technology and anti-reflective coating, surface appearance, microstructure and IR transmittivity of the optical grade thick diamond films prepared by DC PJCVD (Direct Current arc Plasma Jet CVD) are investigated in detail. The main research work done and the results obtained in this dissertation are as follows:1. The heat exchange of DC PJCVD system was analyzed in detail, and the substrate and the three-dimensional atmosphere temperature field models were set up by FLUENT 6.3 and GAMBIT acted as pretreatment software to investigate the process of the plasma discharge. The results indicated that the distribution of plasma flow, velocity field, temperature field and pressure field of the substrate system were asymmetrical and some optimal parameters were obtained. A detailed analysis of the reasons for the error of simulation was done. These can provide the important theoretical foundation for preparing the thick high quality optical-grand diamond films.2. The optical grade thick diamond films were successfully prepared with orthogonal experiment processes in 30kW high power DC PJCVD system. An in-depth study of the technical parameters of the main concentrations of methane, substrate temperature, gas pressure and input power of the thick-film quality, grain size and growth rate of the law was achieved. SEM,AFM,Raman,XRD results showed that the diamond films obtained had even grain sizes, compact column crystals and high quality, which provided the better basis for the IR transmittivity.3. Thick diamond films in the process of preparation showed that the application of a good heat transfer performance of Sn-Pb alloy wire pad put in the interface of the substrate and stage the effective thermal conductivity, and solid-phase contact area rate of 60%, The temperature range of the substrate surface stability, to meet the growth of thick-film optical-level requirements; if at the same time using coaxial central location, can be avoided due to temperature and substrate deformation caused by the "deep-fried film", the stability of the growth of thick-film technology is of great significance.4. The optical grade thick diamond films were polished on two sides by EDM (Electron Discharge Machining) together with mechanical method. The IR transmittivity of the nucleus diamond films was improved from 56.2% to 68.13% after the polishing at 10μm central wavelength; or increased by 11.93%; and from 52.41% to 65.73% at 8～14μm wave-band, or by 13.32%, the process of polishing the thick-film improved IR transmittivity performance.5. The first analysis of the triangle-wave, half wave and the wave of rectangular surface, and so on a different surface topography and the surface polishing steps, holes, cracks, structural defects such as groove on the infrared transmission rate of the law, and through temperature laser Raman mapping analysis to verify when the temperature inside the thick-film diamond stress on the distribution of infrared transmission rate of the law, the study of thick-film diamond-class optical-infrared waves through the window mechanism is of great significance.6. The optical thin film software Macleod and TFC were used to simulate the different refractive index of coating antireflection infrared system, the choice of Y2O3 antireflective materials was a result and in-depth study of Y2O3 by the reflection coating uniformity, density and stress as well as the adhesion of the coating, physical and chemical properties of heat was achieved. The performance for optical-class diamond thick films used in the actual infrared window provides a reliable application of basic research.7. The infrared transmittivity of Y2O3/Diamond films were investigated in detail. The results indicated that the average infrared transmittivity was improved from 68.82% to 82.42% after the deposition of Y2O3 at 10μm central wavelength; or increased by 13.6%; and from 67.98% to 82.45% at 8～12μm wave-band, or by 14.47%, The coated films can meet the demands of infrared window application.