Numerical simulation and experiment of uniform growth of MPCVD diamond coating

Abstract

Based on the microwave plasma module of multiphysics simulation software COMSOL Multiphysics, a numerical model of hydrogen plasma inside a MPCVD reactor was built. The effect of different height differences Δh between the circular molybdenum support added on the outer side of the substrate and the substrate on the plasma distribution at the surface of the substrate was investigated. The uniformity of plasma distribution was quantitatively analyzed by coefficient of variation, and the microstructure of diamond coating surface was characterized by SEM. The results show that when Δh=0 mm, the uniformity of plasma distribution is the best, the coefficient of variation is 3.998%, and the uniformity of grain distribution and size of diamond coating is significantly improved compared with that without molybdenum support. When Δh0 mm, the uniformity of plasma distribution does not increased but decreases, and the coefficient of variation increases to 10.048%. In addition, when Δh=−2.0 mm, the plasma density on the substrate surface decreases by about 20%, which is not conducive to the growth of diamond coating.

Keywords

• diamond coating
• uniformity
• microwave plasma
• numerical simulation