Research Of Optical Grade Diamond Deposition By MPCVD

Because of its unique physical and Chemical properties,Chemical Vapor Deposition(Chemical Vapor Deposition,CVD)diamond can meet the strict requirements of abrasive resistance,thermal conductivity,light transmittance,etc,in the field of the mechanism,thermotics,microelectronics,optics and so on,which has received extensive attention of scientific researchers.in the field of many.In much method of CVD for the preparation of diamond,Microwave Plasma CVD(Microwave Plasma CVD,MPCVD)possess many other advantages such as non-pollution,which is an ideal method to obtain high quality of diamond.This research work is finished at the home-made MPCVD device,and in microwave discharge process,the pattern of the microwave cavity mainly has two kinds of TM01 and TM02,which formed electric field enhanced region above the substrate table that inspired work gas to produce large size plasma ball.At the same time,the input of high microwave power can be carried out,in oder to ensure the high energy density of the plasma and improve the quality of diamond.The research of the optical grade CVD diamond film and homogeneous epitaxial monocrystalline diamond was carried out using the microwave plasma device.In the process of the research of optical grade diamond film,it was studied that the local vacuum and air leakage rate,concentration of carbon source,substrate temperature,deposition pressure,maicrowave power and other factors to impact on the the quality of the diamond film.Studies have shown that air leakage rate is higher,the quality of the diamond film is worse,which is related to the number of N atoms that is come from the air into the vacuum system.When local vacuum is less than 1 Pa,and the bottom vacuum leak rate is less than 0.3 Pa/min,it is beneficial to prepare high quality CVD diamond film;as the concentration of methane increases,the grain size size and mass of the diamond film will decrease significantly.There is a link between deposition temperature and secondary nucleation of diamond,lower temperature will enhance secondary nucleation of diamond film and is not good for the preparation of high quality diamond film.In case that the water cooling system and the substrate structure remain unchanged,microwave power and working pressure coupling degree is the direct factors influencing the substratetemperature,and the higher the microwave power,the greater working pressure,the substrate temperature is higher,and the higher the energy density of the plasma ball,the stronger the working gas ionization degree,the quality of the diamond film is better.Under the conditions of the microwave power of 4700 W and the working pressure of 5.0 kPa,the self-supporting diamond film with a diameter of 50 mm was successfully prepared,and the optical transmission rate was 50%.In study of the growth of homogeneous epitaxial single-crystal diamond,was mainly discussed the pretreatment of the substrate,hydrogen and oxygen plasma etching pretreatment,and the influence of growth temperature on single crystal epitaxial growth,and the quality of sample surface morphology and the crystal was analyzed in the result.The study found that the suitable hydrogen plasma etching pretreatment,to a certain extent,can reduce the macroscopic defects on the surface of the single crystal substrate,within 30 minutes of etching time the effect is good;the law of substrate temperature influence on diamond is that substrate temperature is higher,the epitaxial growth rate of single crystal diamond is faster,but will speed up the growth rate of defects caused by the substrate surface impurities;The substrate temperature is controleed at 960 ~ 1050 ? is beneficial to improve the quality of crystal growth,the single crystal samples infrared transmittance is up to 65%.