Abstract
Carbon nanotubes are known to be synthesized by catalytic chemical vapor deposition (CCVD). Catalysts, e.g., Fe, Ni, Co, etc. play an important role in the process of synthesizing. Other elements, e.g., Cu, though showing no effect on the growth, have been used to enhance the catalytic effect of Ni by alloying it with Ni. In this study, microwave plasma enhanced chemical vapor deposition (MPECVD) was used to grow one -dimensional carbon nanostructured materials on silicon. The results showed that the increase of Cu from 20 at% to 40 at% changes the morphology of carbon from tubules to filaments, and the tangled conditions are less observed in this Ni-Cu alloy range. Straight carbon nanotubes were effectively catalyzed at Cu< 40 at%, and interestingly enough the occurrence of spiral carbon nanofibers(~100 nm) at Cu > 60 at%. Therefore, it is not surprising that Ni is a typically effective catalyst for carbon nanotubes. The catalytic effect of Cu-Ni alloys is prominent at Cu<60 at%, where d-band is unfilled and favors the catalysis of carbon nanotubes. Above 60 at% Cu, the filled d-band is less favorable for the growth of one–dimensional carbon nanostructured materials.