AC impedance of multi-walled carbon nanotubes

Abstract

We have placed a multi-walled carbon nanotube (MWNT) on a pair of nano-gapped electrodes and measured its AC impedance at room temperature for frequencies up to 200 kHz. The real part of the impedance ReZ displayed no characteristic features while the imaginary part ImZ exhibited a transition from capacitive to inductive behaviors around 50 kHz. Both ReZ and ImZ spectra show no substantial changes with varying the electrode gap distance and changing the atmosphere from air to vacuum. On the other hand, upon increasing the DC bias. the whole ImZ spectral curve shifts upward to higher impedances while ReZ displays little bias dependence. We found that the inductive behavior of ImZ above 100 kHz has a negative correlation with the low-bias DC conductance of MWNTs, which approximately represents the contact conductance between MWNTs and the electrodes. This result indicates that the MWNT-electrode interface determines the inductive part of ImZ. [DOI: 10.1380/ejssnt.2007.12]