The Wettability and Diffusion of Al Droplets on the C- and Si-Terminated 4H-SiC Surfaces: A Classic Molecular Dynamics Study

Unique physical characteristics make AlSiC an important packaging material for power electronics devices such as insulated-gate bipolar transistors (IGBTs). In the present study, we performed classical molecular dynamics simulations to investigate the effect of the 4H-SiC surface termination characteristics on the wettability of molten Al droplets. This result has considerable significance for improving the wettability between a matrix and reinforcing particles, which is required to prepare AlSiC composites by the casting method. Density profile analysis was adopted to calculate the contact angles theta of Al droplets on a surface of SiC, including Si- and C-terminated surfaces. The calculated angles theta were 99.8 degrees and 81.7 degrees, respectively. The stratification of the droplet density in the C-terminated system depended strongly on the terminated characteristics of the SiC surface and helped increase the wettability of droplets in this system. In addition, droplet diffusion on the Si-terminated surface was obviously slower than that on the C-terminated surface. The wetting characteristic of molten Al droplets depended strongly on the interaction energy, indicating that the surface terminated characteristics had a strong effect on the wettability of the SiC surface. Compared to the results for the Si-terminated surface, the molten Al droplet had a considerably smaller contact angle and the C-terminated surface showed a higher wettability.