Cu–Ni composition gradient for the catalytic synthesis of vertically aligned carbon nanofibers

The influence of catalyst alloy composition on the growth of vertically aligned carbon nanofibers was studied using Cu–Ni thin films. Metals were co-sputtered onto a substrate to form a thin film alloy with a wide compositional gradient, as determined by Auger analysis. Carbon nanofibers were then grown from the gradient catalyst film by plasma enhanced chemical vapor deposition. The alloy composition produced substantial differences in the resulting nanofibers, which varied from branched structures at 81%Ni–19%Cu to high aspect ratio nanocones at 80%Cu–20%Ni. Electron microscopy and spectroscopy techniques also revealed segregation of the initial alloy catalyst particles at certain concentrations.