Field emission characteristics of multiwalled carbon nanotubes grown at low temperatures using electron cyclotron resonance chemical vapor deposition

摘要

Vertically aligned multiwailed carbon nanotubes were synthesized by electron cyclotron resonance chemical vapor deposition on Ni-coated glass substrates at temperatures as low as 400℃. Negative self-biases were induced to the substrates by radio frequency plasma to give ion bombardment to the growing surface. An increase of self-bias voltages from -50 to -200 V resulted in an evolution of the microstructures from amorphous carbon to nanorods, subsequently to nanotubes. Nanotubes grown above -150 V were more straight in morphology and better in crystallinity than nanorods grown at -100 V. In the field emission (FE) measurements, the electric fields to obtain 1 μA/cm~2 were 4.6 and 11.1 V/μm for the nanorods and nanotubes grown at -100 and -200 V, respectively. The emission areas, calculated from the Fowler-Nordheim plots, were much larger in the nanorods than the nanotubes. It is considered that a larger amount of crystalline defects in nanorods plays a major role in improving their FE characteristics.