Macroscopic field emission properties of aligned carbon nanotubes array and randomly oriented carbon nanotubes layer

Abstract

Aligned carbon nanotubes (CNTs) array was synthesized using r.f. plasma-enhanced chemical vapor deposition on iron-coated silicon substrates from an acetylene and hydrogen mixture. The macroscopic field emission properties of the aligned CNTs array and randomly oriented CNTs layer were studied by means of a vacuum field emission system, which permits integrated field emission using an ITO/glass or a phosphor/ITO/glass screen. After field emission measurements with the applied electric field of <8 V/μm, there was no obvious change in the alignment of the CNTs array, but the formation of tower-like structure on the top of CNTs was observed, indicating that nearly all the CNTs of aligned CNTs array were involved in field emission, and every field emission site (tower-like structure) actually consists of some carbon nanotube tips. At high electric field, some of the aligned CNTs were pulled off due to the weak adhesion between the CNTs and the substrate. We also found that randomly oriented CNTs layer could have similar field emission property as aligned CNTs array. An inhomogeneous field emission and enhanced emission effect from the array sides were observed by using a phosphor screen. For a macroscopic scale area, a homogenous and stable emission was difficult to obtain from the directly synthesized aligned CNTs array or randomly oriented CNTs layer on catalyst coated substrates.