Study On Epitaxial Growth Of Gem-quality Single Crystal Diamond

Diamond has excellent optical,acoustic,thermal,mec hanical and electrical properties,and has a wide range of applications.It is one of the most promising materials in the 21st century.The huge market demand and prospects have promoted the vigorous development of synthetic diamond.Microwave plasma chemical vapor deposition?microwave plasma chemical vapor deposition,MPCVD?has been recognized as the best method for artificially synthesizing high quality diamond from the beginning to the present.For the MPCVD method,the core of the technology is to stably stimulate the plasma sphere with high energy density.The high energy density is the key to the high quality deposition of diamond.By increasing the microwave power,the above conditions can be effectively realized.In this paper,a 10k W high-power loop antenna type MPCVD device was built in the laboratory.Mainly made research on the preparation of gem-quality single crystal diamond and the study of mass deposition of high quality single crystal diamond.The main work is as follows:1.The preparation process of gem-quality single crystal diamond was studied on a laboratory-made MPCVD equipment.The relationship between vacuum degree and diamond quality was discussed.It was found that the higher the grade,the higher the vacuum performance of the single crystal diamond.The pretreatment process is stabilized.First,the seed crystal growth surface is polished,and then the seed crystal is subjected to heating acid treatment in a strong acid mixed solution by an oil bath method to remove surface metal and organic residues,after acid treatment.The seed crystals were ultrasonically cleaned with acetone,absolute ethanol and deionized water respectively to ensure the cleanliness of the surface of the seed crystal,and then the seed crystal was placed in the cavity for hydrogen-oxygen plasma etching.The process parameters of depositing high quality single crystal diamond were obtained:methane concentration at 8%deposition temperature from 900°C to 1000°C is the best process parameters for depositing gem grade single crystal diamond.2.The intensity and distribution of microwave electric field in 10k W device under high microwave power were studied by computer simulation technology.The analysis results show that under the alternating electric field formed by the superposition of TM₀₁and TM₀₂ modes,The strong electromagnetic field is stable in the area of the substrate directly above the diameter of about 60 mm,and with the increase of microwave power,the electric field intensity is gradually increased from 1.0×10⁵ V·m^-1 to 1.6×10⁵ V·m^-1.The range has also increased from 30 mm to 60 mm.At the same time,the plasma distribution state of the MPCVD equipment was simulated by computer simulation.The simulation results show that the plasma density is concentrated in the range of about 60mm in diameter,which is more suitable for the batch growth of single crystal diamond.The experimental results show that the area that can be used to deposit single crystal diamond is slightly smaller than the actual size of the plasma sphere because the energy density at the edge of the plasma sphere is low enough to sufficiently dissociate the gas source molecules,resulting in the inability to deposit single crystal diamond.In this study,15single crystal diamonds were grown in batches at a power of 6 k W and a pressure of 11k Pa.3.Batch growth of single crystal diamond under high power conditions using a 10 k W device.The experiments found that the problems in batch growth of single crystal diamond mainly include:the sliding of the diamond substrate,the existence of a large amount of thermal stress inside the diamond,and the crack angle of the single crystal diamond polishing,by engraving the corresponding shallow on the substrate table.The method of the groove solves the problem of the sliding of the diamond substrate;the high temperature annealing can release part of the thermal stress in the single crystal diamond substrate,and the polishing crack angle can be effectively performed under the process condition of the methane concentration of 8%and the deposition temperature of 950°C.The single crystal diamond was subjected to substrate repair.