Cu-filled carbon nanotubes by simultaneous plasma-assisted copper incorporation

Carbon nanotubes are filled with copper by means of chemical vapor deposition. Control of the density of copper in the plasma is crucial and is accomplished by adjusting the length of the copper electrodes that are exposed to the tungsten heating filament. Both simple and branched Cu-filled nanotubes were grown. Most of the branched nanotubes branch only once to form a regular trilateral starburst structure; others branch repeatedly in simple dendritic patterns. A model to account for the filling and growth characteristics is proposed based on observations made with a high-resolution transmission electron microscope and selected area electron diffraction.