Vertically aligned carbon nanotubes produced by radio-frequency plasma-enhanced chemical vapor deposition at low temperature and their growth mechanism

Vertically aligned carbon nanotubes (CNTs) were produced at a low temperature (<500 °C) by radio-frequency plasma-enhanced chemical vapor deposition. The CNTs formed by the direct current-biased C2H2/H2 plasma process were stacked in cup-like graphite layers and contained a catalyst particle on their top. Raman spectrum showed the features of a graphene sheet-type structure formed by this plasma process. In this reaction, the direct current bias voltage was a crucial factor for efficient CNT production. Attack of carbonic cations by a moderate kinetic energy against a substrate induced the growth of vertically aligned CNTs. The growth process is discussed in terms of the dissolution/diffusion/precipitation mechanism.