On the Raman Spectrum of Nanobundles of Single Wall Carbon Nanotubes
- PDF / 2,789,453 Bytes
- 6 Pages / 415.8 x 637.2 pts Page_size
- 66 Downloads / 247 Views
(Spectra physics 2017) in the back scattering geometry on a Jobin-Yvon T64000 spectrometer equipped with a liquid nitrogen cooled CCD detector. RESULTS Neutron diffraction The profile of the neutron diffraction spectrum is found to be technique-dependent (figure 1).
Sample
SEA
0
0.5
1
1.5
LA Sample
2
2.
0
Q (A'.1)
0.5
1
1.5
2
2.5
Q (A"_')
Figure 1 : Typical neutron diffraction spectra for EA and LA samples. For LA samples, the main peak corresponding to the (10) Bragg reflexion of the hexagonal 2-D lattice is measured between 0.32 and 0.35 A-' while for EA samples the main peak is located in the range 0.42-0.45 A-'. Diferences in the spectra are also observed in the range 0. 51.8 A': well defined peaks for EA samples vs broad structure for LA samples. Calculations of the diffraction spectra of SWNT samples have been reported elsewhere [9]. The position and width of the (10) peak as well as the general profile of the spectrum are very sensitive to the distribution of tube diameters and to the diameter of the bundles. Using this approach, the diffraction data of figure I correspond to samples with an average tube diameter around 1.4 nm for both samples and with a diameter distribution (assumed to be Gaussian) narrower for the EA samples than for the LA samples (full width at half maximum about 0.3 and I nm,4 respectively). The shift to, low-Q of the (10) peak for LA samples is the signature of the presence of a significant amount of tubes with large diameters (up to 2 nmn) [9]. The Radial breathing mode range The frequency of the Atg RBM is very sensitive to the tube diameter. The frequency of the RBM in an isolated tube was estimated by several groups in the framework of different models [10, and references therein]. However the relation between the RBM frequency and the tube diameter is model dependent (see for example figure 2.a). The calculated RBM frequencies of (10, 10) tube was calculated at 165 cmf in Ref. 11, 175 cmqf in Ref. 10 and 195 cmqf in Ref. 12.
108
That emphasizes the difficulty to derive properly the diameters of tubes from the experimental RBM frequencies. SWNT self-assemblate into bundles. Consequently, all the Raman experiments are performed on bundles and not on isolated tube. Due to its radial character, the RBM is likely to be much influenced by the nanotube packing. So, in order to obtain more reliable theoretical relation between the RBM frequency and the tube diameter, it is necessary to take into account the intertube coupling. 240 E o 0
220
240 -
-
E
L
220
0
r
oBundles-
°
>200
,
200- -
o :
0 180
180
-I
-o'
160 LIS
120
0.5
- --
11
•
Isolated
140•'
140
0.6
0.7
0.8
.
0.9
12 0
1
0.5
.•.•.
0.6
0.7
0.8
0.9
1
lid (nm")
lid (nm")
Figure 2.b : Comparison between the RBM frequency in isolated tube and in bundle
Figure 2.a RBM frequency in isolated tube from Ref. 10 (x) and from Ref. 11 (o)
We calculated the RBM frequency of an infinite crystal of identical nanotubes by taking into account the van der Waals interaction between the t
Data Loading...
