Formation mechanism of compositional defects in SiC coatings on large-size batch-produced graphite substrates

In our previous work, we optimized the temperature field and gas flow field of CVD SiC and identified favorable process conditions for large-size batch deposition. However, the formation mechanism of compositional defects under these process conditions remains unclear. This study shifts the focus from forward process optimization to a defect-oriented mechanistic investigation: compositional defects are classified into crystal-structure-related defects and impurity-related defects, and their formation mechanisms under varying deposition temperatures, deposition pressures, and H₂/MTS molar ratios are revealed by combining MD simulation, FEM simulation, and experimental characterization. As an extension, the interfacial thermal stress of the SiC/GaN/graphite system during MOCVD service was briefly evaluated to assess the potential risk of crack initiation and spalling. These findings provide a theoretical basis for defect suppression in large-scale batch production of SiC coatings.