Electrostatic force microscopy evaluation of the conductivity of individual multiwalled carbon nanotubes

The electric conductivity of individual multiwalled carbon nanotubes (CNTs) doped with nitrogen has been studied in as-synthesized, heat-treated, and argon-ion-irradiated states by the method of electrostatic force microscopy (EFM). Modelling of transverse cross-section profiles of EFM images were used to determine the potential difference across the probe tip–CNT gap $(U_{\operatorname{tip-CNT}})$, which is a parameter related to the conductivity of CNTs. A strong correlation between the specific volume conductivity of a CNT layer and average $U_{\operatorname{tip-CNT}}$ value has been found for all types of samples. It is established that a change in the conductivity of N-doped CNTs upon thermal annealing and argon-ion irradiation is caused by modification of the composition and/or concentration of defects in CNT walls.