Diameter Increase in Millimeter-Tall Vertically Aligned Single-Walled Carbon Nanotubes during Growth

Diameter increase was found during the rapid, vertically aligned growth of millimeter-long single-walled carbon nanotubes (SWCNTs). The diameters continuously increased on average from 1.7 nm at the top to 3.7 nm at the bottom of vertically aligned SWCNTs. The SWCNT structures ranged from straight and bundled at the top to bent and isolated and even collapsed at the bottom. Our findings show the importance of suppressing catalyst coarsening to obtain thin SWCNTs, as well as a potential production route of thick SWCNTs and edgeless bilayer graphene ribbons.