ZA-derived phonons in the Raman spectra of single-walled carbon nanotubes
We report the observation of four Raman modes in individual, aligned single-walled carbon nanotubes, with frequencies between the RBM and D modes, and above the G± modes. By studying the diameter and excitation-energy dependence, we find that these strongly dispersive and comparatively intense modes...
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| Main Authors: | , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
2 March 2017
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| In: |
Carbon
Year: 2017, Volume: 117, Pages: 360-366 |
| ISSN: | 1873-3891 |
| DOI: | 10.1016/j.carbon.2017.02.101 |
| Online Access: | Verlag, Volltext: http://dx.doi.org/10.1016/j.carbon.2017.02.101 Verlag, Volltext: http://www.sciencedirect.com/science/article/pii/S0008622317302300 
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| Author Notes: | Asmus Vierck, Florentina Gannott, Manuel Schweiger, Jana Zaumseil, Janina Maultzsch |
| Summary: | We report the observation of four Raman modes in individual, aligned single-walled carbon nanotubes, with frequencies between the RBM and D modes, and above the G± modes. By studying the diameter and excitation-energy dependence, we find that these strongly dispersive and comparatively intense modes share the lowest-frequency helical phonon branch as the origin, which can be derived from the out-of-plane acoustic (ZA) phonon branch of graphene. This ZA phonon is observed due to a defect-assisted, double-resonant process, similar to the D mode; its two-phonon overtones and combinations with transverse optical (TO) phonons do not require defects. Our assignment is supported by a theoretical model based on sixth-nearest neighbour tight-binding and a force-constant approach. We present a complete theoretical evaluation of the diameter and excitation-energy dependence of the ZA, 2ZA, and TO±ZA modes, which fits very well to our experimental results and previous studies of the so-called region of intermediate frequency modes. |
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| Item Description: | Gesehen am 17.09.2018 |
| Physical Description: | Online Resource |
| ISSN: | 1873-3891 |
| DOI: | 10.1016/j.carbon.2017.02.101 |