  The field emission properties of ion irradiated multiwalled carbon nanotubes
(MWCNTs) and doublewalled carbon nanotubes (DWCNTs) have been studied. The
carbon nanotubes synthesized by a chemical vapor deposition method were
irradiated by high energy (90 MeV) Au ions with different ion fluence from
4x1011 to 1x1013 ions/cm2 . After ion irradiation, the field emission
properties of MWCNTs and DWCNTs were greatly influenced. The change in the
emission characteristics is due to structural defects caused by the high energy
ion irradiation. The emission characteristic of MWCNTs was improved and turn-on
field decreased from 5.43 to 3.10 V/m by ion irradiation. Noticeable
improvement in emission characteristics of MWCNTs was observed at a fluence of
1x 10 13 ions/cm2. The emission characteristics of DWCNTs deteriorated and the
turn-on field was increased from 2.44 to 7.76 V/m. This results show the
distinctly different behavior of ion irradiated MWCNTs and DWCNTs.
