The Research Of The Preparation Of Large Area Optical Nanocrystally Diamond Films

The excellent physical and chemical properties of nano-diamond have wide application prospect.Especially in the field of vacuum window has a strong advantage.Nano-diamond film not only has good optical properties,but also has a relatively smooth surface without further polishing.Therefore,the research on the preparation of optical nano-diamond film has always been an important direction in diamond field.At present,the most effective method for preparing large-area optical grade nano-diamond film is microwave plasma chemical vapor deposition,but the key lies in the stable optimization of nano-diamond film deposition environment to realize the preparation of large-area nano-diamond films.By using 1 kw quartz clock bell type MPCVD device,Korea Woosinent company R2.0-MPCVD equipment and more 75kw 915 Hz cylindrical cavity type MPCVD device,this paper systematically research the deposition environment and the large area deposition conditions of nano-diamond film.The main work is as follows:1.Influence of gas pressure,power and carbon source on plasma discharge state is study by using emission spectrum under high pressure.The results show that C₂ is the main sedimentary group in plasma under high pressure.As the air pressure rises,when the pressure increases to 20kPa,although the electronic temperature decreases,but the strength of the C₂ group increases with the maximum density of H_?,CH,and C₃,and the electron density is highest.It is shown that increasing the pressure to20kPa can increase the deposition rate effectively.As the power goes up,the density of the electron and the temperature of the electron goes up,and the concentration of the C₂ is much higher than that of the H_?and the CH.It shows that the increase of power can increase deposition rate rapidly but the quality of deposition film will decrease,so need to reduce the concentration of carbon source to reduce the deposition rate.In high pressure conditions,the increase in methane concentration increases the intensity of the h-alpha group more than the C₂ group,It is shown that the increase of methane can promote the decrease of grain size and improve the deposition rate and quality,and because the H alpha etching ability has a critical value,therefore,increasing the concentration of methane in excess of certain methane concentration will reduce the deposition quality.2.The effect of nucleation density on the structure and stress of deposited nano-diamond films was studied in the self-made 1kW quartz clock mask MPCVD device.The results show that the film has a high degree of flatness and a smaller grain size,and a high degree of stress uniformity,and the mainly oriented is<220>.The growth structure of nano-diamond film and the regulation of transmittance were studied by using the Korean Woosinent R2.0-mpcvd device.The results show that the increase of pressure and decrease of carbon source can improve the film quality and deposition rate.It is found that the increase of pressure to 20kPa and the decrease of carbon to 0.5%could obtain the best film quality.The study of the influence of air source on transmittance showed that When the concentration of H2 was too high,the content of sp³CH_x in the film increased significantly,so when H₂ concentration was less than 10%,the optical properties of the films were the best.The influence of the power and carbon source on the light transmittance indicates that the carbon source can reduce the content of sp³CH₂ and unsaturated carbon-carbon bondsthe,so increase of power and decrease of carbon source can increase the transmittance of the film.Finally,at 830W,0.5%carbon concentration,obtain the 30mm diameter and 3?m thickness and 96.4%transmittance nano-diamond coating.3.Using homemade 75 kw,915 Hz multimode cavity MPCVD device,under the condition of high pressure and using 100?silicon as the substrate research the influence of oxygen concentration of nano-diamond film deposition area.The results showed that when the oxygen concentration was lower than 0.65%,the results showed that when oxygen concentration was lower than 0.65%,the increase of oxygen concentration could promote the secondary nucleation and promote the growth of<220>oriented grain,at the same time,the ratio of sp³/sp² is reduced,so the mechanical properties of the films are enhanced.When the oxygen concentration exceeds 0.65%,the increase of oxygen concentration makes the etching phenomenon further enhanced,which inhibits nucleation and promote grains growth and promotes grain growth of<111>orientation,In addition,In addition,the sp³/sp²ratio decreased,so that the mechanical properties of the films are weakened.