Comparison of fitting procedures in the study of plasma‐induced defect formation in carbon nanotubes

We have adopted different fitting procedures to study the Raman dispersion behavior of the G ′ band in plasma‐treated multi‐walled carbon nanotubes (MWCNTs). Our analysis shows that the trend of the G ′ band dispersion is related to the presence of defects in the MWCNTs. The intensity ratio dispersions involving the $G'_{21} $ , $G'_{32} $ , $G'_{41} $ , and $G'_{42} $ components of the G band behave in a similar way to the well known D to G band ratio ( $D/G$ ), which is a good criterion for estimating the defect content in MWCNTs. The $G'_{21} $ , $G'_{32} $ , $G'_{41} $ , and $G'_{42} $ peaks are shown to belong to the lower‐frequency components of the G ′ band by using two‐, three‐, and four‐peak fitting procedures. Conversely, the higher‐frequency components $G'_{22} $ , $G'_{33} $ , $G'_{43} $ , and $G'_{44} $ behave like the G band and are related to the non‐defect content. Consequently, the intensity ratios $G'_{21} /G'_{22} $ , $G'_{32} /G'_{33} $ , and $G'_{41 + 42} /G'_{43 + 44} $ show the same dispersion behavior as that of $D/G$ . The difference of band position between the high and low frequency G ′ band components is found to be sensitive to plasma treatment.