In order to realize future nanotube electronics, it is not only necessary
to thoroughly understand their transport properties, but also to be able to
fabricate devices possessing the desirable qualities. While the latter goal
is still distant, the transport in single-walled nanotubes is already
understood quite well.
With multiwalled carbon nanotubes the situation is more
complicated. Room temperature ballistic transport has been reported, but in
the typical configuration with MWNTs on an insulating substrate, diffusive
transport behaviour is mainly observed: interference effects are found to be
significant, either in 1D or 2D depending on the electron mean free path.
We have investigated electron transport in extremely disordered MWNTs as
a function of magnetic field and temperature. Our AFM studies reveal that
the curvature of CVD tubes is intrinsic, and due to a high concentration of
structural defects
. We find that in our CVD grown tubes the electron mean
free path $\ell$ and phase coherence length $L_{\phi}$ are very short. In
fact, $\ell$ turns out to be so short that our nanotube samples are near the
strong localization regime.
