A simple combinatorial method to discover Co–Mo binary catalysts that grow vertically aligned single-walled carbon nanotubes

A simple yet versatile combinatorial method to discover binary metal nanoparticle catalysts was developed. In this method, the nominal thickness of component metals can be independently screened for a wide range by simply setting a mask with a slit above a substrate during sputter-deposition. Using this method, we prepared a catalyst library with Mo (0.2–4 nm) and Co (0.2–8 nm) thickness profiles on a SiO2/Si wafer and discovered active catalysts that grow vertically aligned single-walled carbon nanotubes by alcohol catalytic chemical vapor deposition.