Tunable Raman spectroscopy study of CVD and peapod-derived bundled and individual double-wall carbon nanotubes

Abstract

We use 40 laser excitation energies to analyze the differences in the Raman spectra from chemical vapor deposition-derived double-wall carbon nanotube ͑CVD-DWNT͒ bundles, fullerene-derived DWNT bundles ͑C 60 -DWNTs͒, and individual fullerene-derived DWNTs with inner type-I and type-II semiconducting tubes paired with outer metallic tubes. For the radial breathing mode ͑RBM͒ of SWNTs, an experimental RBM vs d t relationship of the form RBM = A / d t + B is obtained for the inner tubes of DWNT bundles where the A and B constants are found to be close to those obtained by elasticity theory when modeling the elastic properties of graphite. A similar change in RBM is observed for an inner type-II semiconducting ͑6,5͒ tube and a type-I ͑9,1͒ tube when inside various metallic outer tubes. The G-band frequency is observed to upshift when switching the laser resonance from DWNTs with semiconducting inner tubes to DWNTs with metallic inner tubes. Finally, we measure the GЈ feature from C 60 -DWNTs and note a downshift in frequency with respect to that of CVD-DWNTs.

G′band in double- and triple-walled carbon nanotubes: A Raman study

“…Such G band dependencies on E laser are expected for this doubleresonance Raman feature [22,37]. We observe similarities in the dispersions of the G bands and we note that the inner nanotubes show a clear frequency difference due to nanotube diameter differences.…”

“…At this point, it is important to remember that the RBMs of the inner nanotubes from bundled DWNTs consist of clusters of narrow peaks in comparison to the single-peak characteristics of bundled SWNTs [34]. Several Raman studies have discussed the G bands of bundled DWNTs, for example, the frequency shifts and intensity changes associated with the ω G dependence on E laser , as well as on the growth method or the amount of dopants [22,[35][36][37][38][39]. The present work brings out a new discussion of the annealing temperature dependence of the G band for DWNTs.…”

“…This finding tells us how strongly the M18 family contributes to the observed G band intensity, and this is confirmed by the facts that the intensity ratio I The E laser vs ω G relations of the inner (lower four relations) and the outer (upper four relations) nanotube from bundled DWNTs are presented. The blue and black lines are, respectively, the fitted linear relations for fullerene-peapod derived DWNTs [22] and for CVD DWNTs [37]. The red lines are adapted from the Raman results for the bundled DWNTs produced with 1500 and 2000…”

Interwall screening and excitons in double-wall carbon nanotubes

“…[16][17][18][19] Double-wall tubes are the simplest systems of multiwall carbon nanotubes and thus are suited for studying the interactions between different walls. [20][21][22][23][24][25][26][27][28] In this work we examine effects of screening by the interwall Coulomb interaction on excitons and optical spectra in double-wall tubes based on the effective-mass theory and a static screened Hartree-Fock approximation. We shall focus on excitons in a semiconducting nanotube surrounded by or containing another coaxial semiconducting or metallic nanotube.…”

Cross-polarized excitons in double-wall carbon nanotubes

“…[15][16][17][18] Double-wall tubes are the simplest systems of multiwall carbon nanotubes and are suitable for studying the interactions between different walls. [19][20][21][22][23][24][25][26] In a previous paper, 27 we have shown that the excitons in double-wall carbon nanotubes show a red shift caused by the interwall screening.…”