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High Pressure Studies of the Raman‐Active Phonons in Carbon Nanotubes
Author(s) -
Venkateswaran U.D.,
Brandsen E.A.,
Schlecht U.,
Rao A.M.,
Richter E.,
Loa I.,
Syassen K.,
Eklund P.C.
Publication year - 2001
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/1521-3951(200101)223:1<225::aid-pssb225>3.0.co;2-6
Subject(s) - carbon nanotube , raman spectroscopy , van der waals force , phonon , g band , materials science , tube (container) , molecular physics , dispersion (optics) , condensed matter physics , drop (telecommunication) , chemical physics , nanotechnology , chemistry , optics , composite material , molecule , telecommunications , physics , organic chemistry , computer science
We report high pressure Raman studies on as‐prepared, purified, and solubilized single‐walled and aligned multi‐walled carbon nanotubes. The pressure dependence of radial (R) and tangential (T) vibrational bands in these samples is measured and compared with the results from other studies. In single‐walled nanotubes, an abrupt drop in the intensity of these bands is seen near 2 GPa, indicative of a phase transition. Experiments on single (unbundled) tubes reveal a ≈10 cm —1 upshift of the R band relative to its frequency in bundled tubes. This is opposite to the predictions of calculations that include the intertube van der Waals interaction only and is explained by the changes in the electronic band dispersion driven by tube–tube interactions. Surprisingly, the pressure dependence of the R and T bands in unbundled tubes is very similar to that seen in bundled tubes, which indicates that the changes in the electronic band structure might significantly influence the pressure dependence.