The present paper is devoted to the influence of the growth temperature of multi-walled carbon nanotubes (MWCNTs) on their defective structure. The MWCNTs obtained within the range of 610–750 °C have been studied using two methods: Raman spectroscopy and the analysis of the temperature dependence of conductivity. This approach allows us to obtain independent data on the concentration of the defects within the MWCNTs via the intensity ratio of 2D and D bands, on one hand, and charge carrier concentration, on the other hand. The results obtained using Raman spectroscopy and the analysis of the conductivity have provided asymptotic and volcano-like curves, respectively, of defect concentration within the temperature range studied. This can be attributed to the difference in the probing depth of each method (∼50 nm for Raman spectroscopy, and ∼2–3 nm for conductivity measurements) providing different sensitivity to surface impurities or defects. The secondary factors (the size of the active component, the amount of the lateral carbon deposits) have been shown to mask the influence of the growth temperature. Nevertheless, as these secondary factors and the synthesis temperature independently affect the effective nanotube defectiveness, we have shown the defect concentration to fall with increasing MWCNT growth temperature.
- multi-walled carbon nanotubes
- Raman spectroscopy