Research On Synthesis Of Mechanical Grade Single Crystal Diamond By MPCVD

Owing excellent properties such as high hardness, high Elasticity Modulus, high heat conductivity, high wear-resistance and corrosion resistance that make single crystal diamonds（SCDs） a potential material in cutting tools fabrication especially ultra-precision machining. Microwave plasma chemical vapor deposition（MPCVD） is one of the best methods for diamond synthesizing at present. The technology has been used for SCDs low-volume production by some enterprises abroad. By contrast, hindering by poor equipment and technique, our country remains the laboratory research stage so far.In this study, a homemade 5k W MPCVD equipment has been used for research of single crystal diamond growing. Main contents of this research: 1. Effect of methane concentration, deposition temperature and gas pressure on growth of SCDs have been studied respectively using CH₄/H₂ gases. 2. Effects of N₂, O₂, Ar addition CH₄/H₂ mixtures growth of SCDs have been studied respectively. 3. On the basis of above research, a large SCD have been synthesized successfully. Raman spectroscopy, X-ray diffraction and infrared absorption spectrum have been used for SCDs characterization.High performance device is the guarantee of high quality single crystal diamond synthesis, but the optimization of process conditions is also important. Though the performance of homemade MPCVD device can’t compare with advanced foreign devices, based on study of synthetic process of SCDs and parameters optimization, we can still synthesize a large SCD with a considerable growth rate（56.0 μm/h） and acceptable quality. Size of the CVD diamond seed we used is 7.0×7.0×0.3 mm³, the size of the as grown SCD is 8.3×8.3×2.0 mm³. XRD rocking curve showed that quality of the as grown SCD is close to that of the mechanical grade seed.