Nickel Overlayers Modify Precursor Gases to Pattern Forests of Carbon Nanotubes

We analyzed the effect of nickel overlayers positioned in close proximity (bridges) or in contact (stencils) with the catalytic layer on the growth of vertically aligned carbon nanotubes (VACNTs) using thermal chemical vapor deposition (CVD). We studied the physical-chemical mechanisms, namely, the interaction of the overlayer with the gases and with the catalyst. We demonstrate that nickel inhibits CNT growth by adsorbing carbon to form graphene and by interacting with the gas precursors, leading to their modification into species that do not nucleate and grow CNTs. We demonstrate that the effect of the nickel bridge extends to the length of its boundary layer. We tested overlayer patterns and showed that the patterns were replicated during CNT growth. This facile method is a valid alternative to pattern CNT forests without the need for complex lithography and lift-off of the catalyst in applications where lithographic precision is not required.