Diamond nucleation behavior influenced by pretreatment on 4H-SiC substrates

In this study, we investigated the nucleation and growth behavior of diamond on 4H-SiC Si-face and C-face substrates using the microwave plasma chemical vapor deposition (MPCVD) method, following ultrasonic surface pretreatment. A mixture of diamond powder and ethanol was utilized during the pretreatment, and the nucleation characteristics were analyzed by varying the pretreatment time (30, 60, and 90 min). The results revealed that diamond nucleation density and mechanism were strongly influenced by the surface orientation and pretreatment duration. On the Si-face (0001), nucleation initially followed an island-growth mode but became more uniform with increased pretreatment time, resulting in enhanced nucleation density and reduced grain size. Conversely, the C-face (000–1) achieved uniform nucleation at shorter pretreatment durations (30 min), but prolonged pretreatment led to grain overgrowth and a reduction in nucleation density. TEM analysis showed a rough and non-uniform SiC–diamond interface on the Si-face, attributed to thermal expansion mismatch and residual tensile stress. In contrast, the C-face exhibited a smoother and more uniform interface structure without intermediate layers. These findings highlight the critical role of substrate polarity and optimized pretreatment conditions in achieving high-quality diamond nucleation and growth on 4H-SiC substrates.