Selective synthesis of carbon nanotubes and multi-layer graphene by controlling catalyst thickness

► Selective synthesis of CNTs and multi-layer graphene was demonstrated. ► This method was performed just by changing the Fe thickness under the same condition. ► Only CNTs were obtained with Fe films of 5 nm and less. ► Multi-layer graphene was formed with those of 20 nm and more. ►The thickness of graphene can be also controlled by the Fe thickness further.