  Carbon nanotubes are a good realization of one-dimensional crystals where
basic science and potential nanodevice applications merge. Defects are known to
modify the electrical resistance of carbon nanotubes. They can be present in
as-grown carbon nanotubes, but controlling externally their density opens a
path towards the tuning of the nanotube electronic characteristics. In this
work consecutive Ar+ irradiation doses are applied to single-walled nanotubes
(SWNTs) producing a uniform density of defects. After each dose, the room
temperature resistance versus SWNT-length [R(L)] along the nanotube is
measured. Our data show an exponential dependence of R(L) indicating that the
system is within the strong Anderson localization regime. Theoretical
simulations demonstrate that mainly di-vacancies contribute to the resistance
increase induced by irradiation and that just a 0.03% of di-vacancies produces
an increase of three orders of magnitude in the resistance of a 400 nm SWNT
length.
