Nanotube Coalescence-Inducing Mode: A Novel Vibrational Mode in Carbon Systems


  • We are grateful to J. C. Charlier, A. Jorio, X. Zhao, H. Kataura, Y. Ando, and H. Terrones for helpful and encouraging discussions. This work was supported by the CLUSTER of Ministry of Education, Culture, Sports, Science and Technology. The MIT authors acknowledge support under NSF DMR 04-05538. M.T. thanks CONACYT-Mexico for grants 37589-U and 411464-Inter American Collaboration. R.S. acknowledges MEXT Grant (No. 16076201). This work made use of the MRSEC Shared Experimental Facilities at MIT, supported by the National Science Foundation under award number DMR-02-13282.


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A resonant Raman mode located at 1855 cm−1 is related to vibrations of linear carbon chains and observed as a precursor to the merging of highly purified double-walled carbon nanotubes (DWNTs, see figure). This mode, termed the “coalescence-inducing mode” (CIM), which initiates the coalescence process, is induced by thermal annealing and its effect is enhanced by boron doping. The CIM mode arises from the generation of short 1D carbon chains (e.g., 3–7 atoms long) established covalently between adjacent tubes.