Raman spectroscopy study of heat-treated and boron- doped double wall carbon nanotubes

Citation Villalpando-Paez, F. et al. " Raman spectroscopy study of heat-treated and boron-doped double wall carbon nanotubes. Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. We performed Raman spectroscopy experiments on undoped and boron-doped double walled carbon nano-tubes ͑DWNTs͒ that exhibit the " coalescence inducing mode " as these DWNTs are heat treated to temperatures between 1200 ° C and 2000 ° C. The fact that boron doping promotes DWNT coalescence at lower temperatures allowed us to study in greater detail the behavior of first-and second-order Raman modes as a function of temperature with regard to the coalescence process. Furthermore, by using various excitation laser energies we probed DWNTs with different metallic ͑M͒ and semiconducting ͑S͒ inner and outer tubes. We find that regardless of their M and S configurations, the smaller diameter nanotubes disappear at a faster rate than their larger diameter counterparts as the heat treatment temperature is increased. We also observe that the frequency of the G band is mostly determined by the diameter of the semiconducting layer of those DWNTs that are in resonance with the laser excitation energy. Finally, we explain the contributions to the GЈ band from the inner and outer layers of a DWNT.