Competition and cooperation between lattice-oriented growth and step-templated growth of aligned carbon nanotubes on sapphire

The authors study the growth mechanism of single-walled carbon nanotubes (SWNTs) horizontally aligned on A-plane single crystal sapphire (112¯0) by making the controlled step/terrace structure. SWNT growth direction was sensitive to the surface geometry of the sapphire, and there was competition between two growth modes, lattice-oriented growth and step-templated growth. On the substrate with single-atomic steps, SWNTs aligned parallel to the [11¯00] direction as dominated by the lattice-oriented growth mode, while SWNTs aligned along the step edges when the double-atomic or higher steps were formed. Our findings have potential for the fabrication of designed architecture of SWNTs by combining these two growth modes.