Plasma treatment effects on surface morphology and field emission characteristics of carbon nanotubes

In this study, electron field-emission properties of carbon nanotube films (CNTs) grown on silicon substrate before and after tetrafluoromethane (CF4), hydrogen (H2) and argon (Ar) plasma etchings were investigated. The CNTs were synthesized by thermal decomposition of methane in the presence of nickel catalyst. Our research results reveal that plasma treatment can modify the surface morphology and enhance the field-emission characteristics of CNTs regardless of the plasma used. The CNTs treated by both non-reactive and reactive plasmas have a higher density of defect and a smaller average diameter reflecting the etching effects of plasma treatments. In addition, higher emission currents and lower turn-on electric fields are also obtained for the CNTs after plasma treatment. As expected, reactive plasma treatment has a more pronounced effect on the surface morphology and field-emission characteristics of the synthesized CNTs than non-reactive plasma treatment. In particular, a huge increase in emission current (more than three orders of magnitude at high electric fields) and a substantial lower turn-on electric field are found for the CNTs after H2 plasma treatment. This huge increase in the emitted current is primarily caused by the increase in the density of field-emission sites resulting from the change of surface morphology and the –CHx nanoparticles redeposited on the CNTs.