Thinning strategy of substrates for diamond growth with reduced PCD rim: Design and experiments

The appearance of polycrystalline diamond (PCD) at the edges of deposited layers is a major obstacle in MPCVD diamond growth process. In this work, diamond growth states with various substrate thicknesses were simulated to obtain the distribution of electric field intensity, electron density and temperature on the substrate surface. The simulation results indicate that the distribution of surface plasma can be controlled by the design of substrate thickness, thus affecting the growth of diamond. Three samples with different substrate thicknesses were grown and the variation of crystal quality from the edges to the centers was analyzed by Raman spectroscopy. The growth results showed that as the thickness of the substrate decreased, the formation of PCD rim was inhibited. One reason for this phenomenon is that the plasma density at the edges and corners decreases when a thinner substrate is used, which suppresses the probability of two-dimensional nucleation and defect formation.