  Single walled carbon nanotubes with Pd ohmic contacts and lengths ranging
from several microns down to 10 nm are investigated by electron transport
experiments and theory. The mean free path (mfp) for acoustic phonon scattering
is estimated to be lap~300 nm, and that for optical phonon scattering is lop~15
nm. Transport through very short (~10 nm) nanotubes is free of significant
acoustic and optical phonon scattering and thus ballistic and quasi-ballistic
at the low and high bias voltage limits respectively. High currents of up to 70
uA can flow through a short nanotube. Possible mechanisms for the eventual
electrical breakdown of short nanotubes at high fields are discussed. The
results presented here have important implications to high performance nanotube
transistors and interconnects.
