Engineering the tube size for an inner surface modification by plasma-based ion implantation

► Critical radius of tube characterizes the size of inner surface modification by PBII. ► Temporal sheath dynamics demonstrated the effective range of process parameters. ► Plasma density and steady pulse voltage were two main effect factors. ► Optimum process parameters bounded by ion implantation dose and processing time. ► Critical radius of tube was determined in grid-enhanced PBII technique.