High-Field Quasiballistic Transport in Short Carbon Nanotubes

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 $l_{\mathrm{ap}}\sim 300\mathrm{nm}$, and that for optical phonon scattering is $l_{\mathrm{op}}\sim 15\mathrm{nm}$. Transport through very short ($\sim 10\mathrm{nm}$) nanotubes is free of significant acoustic and optical phonon scattering and thus ballistic and quasiballistic at the low- and high-bias voltage limits, respectively. High currents of up to $70\mu \mathrm{A}$ 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.