Growth and field emission of coiled carbon nanotubes by plasma-enhanced chemical vapor deposition

Plasma-enhanced chemical vapor deposition (PECVD) was used to grow Fe-catalyzed carbon nanotubes (CNTs). The coiled CNTs were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanotubes were about 10-50 nm in diameter and well beyond 2 μm in length. Field emission properties showed that the turn-on emission threshold field was about 2.5 V/μm with a current density of 0.1 μA/cm2 and the maximal current density reached about 15 μA/cm2 at the electric field of 6.75 V/μm. The FN plots revealed that the field emission of the CNTs followed Fowler-Nordheim behavior. For the work function of CNTs to be 5.0 eV, the field enhancement factor calculated from the slopes of the FN plots was about 7600.