Ion implantation is used to grow nanotubes out of carbon and other materials. Catalytic material is placed on or in a membrane that physically and possibly environmentally separates an implantation chamber or region from a growth chamber or region. High-energy ions are implanted into the catalytic material from one side to grow nanotubes on an exposed surface in the growth chamber. Ion implantation via the membrane provides for greater flexibility to separate and independently control the implantation and growth processes.