▎ 摘　　要

The catalytic activity of nanoparticles to form either crystallographically oriented etch tracks or carbon nanotubes on top of few-layer graphene is tuned through the application of a methane feedstock gas. The catalytic activity for these two processes is found to vary at different rates as a function of the amount of applied feedstock gas. These differences provide a window of growth parameters in which nanotubes can be grown on the surface of few-layer graphene without significant formation of etch tracks. Since this surface growth results in nanotubes which can be crystallographically aligned to the underlying graphene layers, this development could lead to improved electrical interfaces between nanotubes and graphene without the deleterious consequences of catalytic etching. Such improved interfaces could prove to be useful in applications benefiting from low interfacial electrical resistances between one-dimensional and two-dimensional materials, such as in supercapacitor applications. (C) 2014 Elsevier Ltd. All rights reserved.