Carbon nanotube growth enhanced by nitrogen incorporation

It is well known that the growth of carbon nanotubes (CNTs) by chemical vapor deposition using a transition metal catalyst is greatly enhanced in a nitrogen environment. We show here that the enhanced growth is closely related to nitrogen incorporation into the CNT wall and cap during growth. This behavior is consistent with theoretical calculations of CNx thin films, showing that nitrogen incorporation to the graphitic basal plane reduces the elastic strain energy for curving the graphitic layer. Enhanced CNT growth by nitrogen incorporation is thus due to a decrease in the activation energies required for nucleation and growth of the tubular graphitic layer.