Study On High Quality Diamond Prepared By High Pressure MPCVD

CVD diamond has excellent physical and chemical properties and therefore has a wide range of applications in many fields.Compared with other deposition methods,microwave plasma chemical vapor deposition(MPCVD)has the advantages of providing a pure deposition environment and a high-density plasma,and thus is the preferred method for preparing high-quality diamond.In the deposition process of CVD diamond,increasing the deposition pressure can increase the active group concentration and plasma density,which is conducive to the growth of high quality diamond.In this experiment,a self-made multimode MPCVD device was used to study the growth of high-quality CVD diamond under high deposition pressure and microwave power.The specific work is as follows:1)Using a laboratory-made 10kW non-cylindrical multi-mode resonant cavity MPCVD apparatus to perform experiments in a deposition environment with a microwave power of5kW and a methane concentration of 0.7%,and using the CH4/H2 mixture gas as the working gas,plasma simulation and emission were performed.The simulation results show that the plasma density is higher and the activity is stronger under high deposition pressure.The results of the emission spectra show that increasing the gas pressure is beneficial to increase the strength of the main active groups in the plasma,such as CH,H_?,and so on.In the early stage of pressure increase,the electron temperature rises with the increase of the pressure.When the deposition pressure is higher than 17 kPa,the electron temperature begins to decrease with the increase of the pressure.From this,it can be seen that an appropriate increase in the deposition pressure is beneficial to increase the plasma activity and is beneficial to the growth of high-quality CVD diamond.2)Using a 10kW non-cylindrical multimode resonant cavity MPCVD device made in the laboratory,the deposition of polycrystalline diamond films was performed in the air pressure range of 8-20 kPa.The research shows that when the temperature is increased from 8kPa to 14kPa at a temperature of 850?,the uniformity of the diamond film surface becomes better and the growth quality is improved.When the deposition pressure is higher than 17kPa,the defects in the deposited diamond begin to increase,and the temperature is at 1150?.The surface morphology of SEM has the same trend of change,indicating that proper increase of the deposition pressure to a certain range is conducive to the high quality diamond film growth.The obtained regulation rule indicates that diamond film with good surface quality can be grown within the high pressure deposition range of 14kPa to17kPa.This result is also consistent with the results from the emission spectrum analysis.3)The epitaxial growth of single crystal diamond was studied in a laboratory with a 10kW non-cylindrical resonant cavity MPCVD apparatus under a power of 4500W methane concentration of 8%.The results show that single crystal diamond after plasma etching can effectively inhibit the emergence of growth defects.In epitaxial growth,the change of deposition temperature will have a significant effect on the quality of epitaxial single crystals.If the deposition temperature is too low,the growth rate will be too slow.If the deposition temperature is too high,growth defects will occur.Through research,the growth of high-quality single-crystal diamond was finally achieved at a power of 4.5 kW,a methane concentration of 8%,and a deposition temperature of 1000?.