Confirming the key role of Ar ion bombardment in the growth feature of nanostructured carbon materials by PECVD.

In order to confirm the key role of Ar ion bombardment in the growth feature of nanostructured carbon materials (NCMs), here we report a novel strategy to create different Ar ion states in situ in plasma enhanced chemical vapor deposition (PECVD) by separating catalyst film from the substrate. Different bombardment environments on either side of the catalyst film were created simultaneously to achieve multi-layered structural NCMs. Results showed that Ar ion bombardment is crucial and complex for the growth of NCMs. Firstly, Ar ion bombardment has both positive and negative effects on carbon nanotubes (CNTs). On one hand, Ar ions can break up the graphic structure of CNTs and suppress thin CNT nucleation and growth. On the other hand, Ar ion bombardment can remove redundant carbon layers on the surface of large catalyst particles which is essential for thick CNTs. As a result, the diameter of the CNTs depends on the Ar ion state. As for vertically oriented few-layer graphene (VFG), Ar ions are essential and can even convert the CNTs into VFG. Therefore, by combining with the catalyst separation method, specific or multi-layered structural NCMs can be obtained by PECVD only by changing the intensity of Ar ion bombardment, and these special NCMs are promising in many fields.