The influence of ion flux during plasma-enhanced chemical vapor deposition on the sp3/sp2 ratio of diamond-like carbon deposited on alumina particles

To meet the demands of high-voltage power electronics, this study elucidates the role of ion flux in plasma-enhanced chemical vapor deposition in governing the sp3/sp2 ratio of diamond-like carbon (DLC) films on alumina particles, which is believed to have the potential to improve the interface between epoxy and filler particles. Independent control of ion flux revealed a non-monotonic trend in the sp3/sp2 ratio: it initially increases due to suppressed carbon relaxation at moderate flux, then decreases beyond a critical threshold due to thermal graphitization from excessive energy deposition. By integrating the subplantation model with energy analysis, this study clarifies the competition between kinetic stabilization and thermal degradation. This work provides a mechanistic understanding and a practical guideline for optimizing DLC-coated fillers in high-performance composites.