We present electron transport experiments on single walled carbon nanotubes (SWNTs). By measuring the linear scaling of resistance with length, we determine an unusually long mean free path of Lm ∼1 μm at room temperature. From the temperature dependence of the mean free path for over 10 samples we show that inelastic scattering with acoustic phonons are the main source of scattering at room temperature and experimentally determine the electron-acoustic phonon strength. Disorder ultimately limits the low temperature mean free path (Lm ∼10 μm), which we show by employing scanning gate microscopy. We analyze the non-linear scaling of resistance with length and temperature to further elucidate the nature of this disorder. In general, we find that transport in 1-dimension is dominated by the strongest defect along the channel. For larger source-drain voltage (VSD > 0.2 V), we show that L m is significantly reduced in both metallic and semiconducting SWNTs, due to electrons scattering with the higher energy phonons. In semiconducting samples, when the Fermi energy is close to the energy band gap, we observe an anomalous conductance dip. Finally, we utilize locally controlled gate structures to fabricate a series of tunable barriers to form a superlattice and observe its mini-band structure superimposed on that of the nanotubes.
|Subjects||Condensed matter physics|
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