Raman scattering in carbon nanotubes
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Date
2009-03-13T11:25:55Z
Authors
Shiri, Pricciard Roy
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Abstract
Analysis of peak shifts of Raman vibrational modes in single-walled carbon nan-
otubes (SWCNTs) gives important information about the vibrational properties of
SWCNTs, which in turn gives a deeper understanding of the physical, electronic
and thermal properties of SWCNTs.
In this work, the temperature dependence of the frequencies and linewidths of
the vibrational modes of semi-conducting and metallic nanotubes were studied using
Raman spectroscopy. The SWCNTs used here were synthesized using the electric-
arc discharge method. Two laser lines, the 514.5 nm and 488.0 nm were used to
exploit the resonances of the semi-conducting tubes and the 647.1 nm was used to
excite metallic SWCNTs.
The radial breathing mode (RBM) peak positions of semi-conducting and metal-
lic tubes were observed to decrease at di®erent rates with increasing temperatures.
The line shapes of the RBMs also change signi¯cantly with changes in temperatures.
The G+ and G¡ peaks of the tangential modes (G-band) of semi-conducting and
metallic nanotubes also decrease at di®erent rates with increasing temperatures.
A comparison of the rates of change of mode frequency of the G+ and G¡ modes
in metallic and semi-conducting nanotubes gives more insight into the role played
by electron-phonon coupling and plasmon-phonon coupling in each case. It gives
a deeper insight into the contentious issue of mode assignment of the G+ and G¡-modes of metallic SWCNTs.