Low-frequency current noise and resistance fluctuations in multiwalled carbon nanotubes

We have measured low-frequency current noise of arc-discharge-grown multiwalled carbon nanotube samples. At room temperature, the noise spectrum displays a regular const/fβ dependence with β∼1 and a noise current close to 10pA/Hz at 100 nA and 100 Hz. The noise power decreases by 1-2 orders of magnitude when cooling down to 4.2 K. Due to the two-probe measurement, contacts are a likely source of the noise. At 4.2 K and below, we observe noise spectra consisting of a few Lorentzian line shapes, each of which arises due to fluctuations between two current values. The switching rates depend on the bias and they are asymmetric with respect to the direction of the current.