Raman spectra of misoriented bilayer graphene

We compare the main feature of the measured Raman scattering spectra from single layer graphene with a bilayer in which the two layers are arbitrarily misoriented. The profiles of the 2D bands are very similar having only one component, contrary to the four found for commensurate Bernal bilayers. These results agree with recent theoretical calculations and point to the similarity of the electronic structures of single layer graphene and misoriented bilayer graphene. Another new aspect is that the dependance of the 2D frequency on the laser excitation energy is different in these two latter systems

Use of resonance Raman spectroscopy to study the phase diagram of PbZr0.52Ti0.48O3

Evidence is presented for the first time that the sharp and continuous spectral changes observed in PbZr0.52Ti0.48O3 (PZT) between 350 and 10 K with the 647.1 nm wavelength are due to a resonance Raman effect. Such a phenomenon can be explained by means of a self-trapped exciton emission oxygen deficient complex (TiTi' - VO-) of PZT powder whose energy is close to the radiation line of the laser. This kind of approach should also be very useful to distinguish the phase transition sequence for other related ferro/ piezoelectric systems

Raman spectroscopy of iodine-doped double-walled carbon nanotubes

We present a Raman spectroscopy study of iodine-intercalated (p-type-doped) double-walled carbon nanotubes. Double-walled carbon nanotubes (DWCNTs) are synthesized by catalytic chemical vapor deposition and characterized by Raman spectroscopy. The assignment of the radial breathing modes and the tangential modes of pristine DWCNTs is done in the framework of the bond polarization theory, using the spectral moment method. The changes in the Raman spectrum upon iodine doping are analyzed. Poly-iodine anions are identi- fied, and the Raman spectra reveal that the charge transfer between iodine and DWCNTs only involves the outer tubes

Evidence of 1D behaviour of He4^4 confined within carbon-nanotube bundles

We present the first low-temperature thermodynamic investigation of the controlled physisorption of He$^{4}$ gas in carbon single-wall nanotube (SWNT) samples. The vibrational specific heat measured between 100 mK and 6 K demonstrates an extreme sensitivity to outgassing conditions. For bundles with a few number of NTs the extra contribution to the specific heat, C$_{ads}$, originating from adsorbed He$^{4}$ at very low density displays 1D behavior, typical for He atoms localized within linear channels as grooves and interstitials, for the first time evidenced. For larger bundles, C$_{ads}$ recovers the 2D behaviour akin to the case of He$^{4}$ films on planar substrates (grafoil).Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

Structural selective charge transfer in iodine-doped carbon nanotubes

We have investigated iodine intercalated carbon nanostructures by extended X-ray absorption fine structure (EXAFS) and Raman spectroscopies. We discuss here the charge transfer and the iodine–carbon interaction as a function of the carbon nanostructures (graphite, multi-walled, double-walled and single walled nanotubes). The results show that iodine is weakly adsorbed on the surface of all multi-walled nanotubes. By contrast, a charge transfer between iodine and single walled nanotubes is evidenced

Raman-Active modes in Homogeneous and Inhomogeneous Bundle of Single-Walled Carbon Nanotubes

In the present work, the non-resonant Raman active modes were calculated for several diameters, chiralities and sizes for homogeneous and inhomogeneous bundles of single-walled carbon nanotubes (BSWCNT's), using the spectral moment’s method (SMM). Additional intense Raman active modes are present in the breathing-like modes (BLM) spectra of these systems in comparison with a single fully symmetric A1g mode characteristic of isolated nanotubes (SWCNT's). The dependence of the frequency of these modes in terms of diameters, lengths and number of tubes is investigated. We find that for finite bundle, additional breathing-like modes (BLM's) appear as a specific signature. Finally, the effects of the inhomogeneous bundles on the Raman spectra were studied.In the present work, the non-resonant Raman active modes were calculated for several diameters, chiralities and sizes for homogeneous and inhomogeneous bundles of single-walled carbon nanotubes (BSWCNT's), using the spectral moment’s method (SMM). Additional intense Raman active modes are present in the breathing-like modes (BLM) spectra of these systems in comparison with a single fully symmetric A1g mode characteristic of isolated nanotubes (SWCNT's). The dependence of the frequency of these modes in terms of diameters, lengths and number of tubes is investigated. We find that for finite bundle, additional breathing-like modes (BLM's) appear as a specific signature. Finally, the effects of the inhomogeneous bundles on the Raman spectra were studied

Size And Chirality Effects On Raman Spectrum Of Double-Wall Carbon Nanotube Bundle

We study the tube size and bundling effects on Raman active breathing-like phonon modes (BLM) and tangential-like phonon mode (TLM) of double-walled carbon nanotubes (DWCNT) in the framework of the bond polarization theory, and use the spectral moment’s method. The Raman active modes are calculated for different diameter and chirality of the inner and outer DWCNT tubes. The dependence of the Raman spectrum of bundles of identical DWCNTs as a function of the size of the bundle is analysed and additional breathing-like modes are predicted in DWCNT bundle of finite size.We study the tube size and bundling effects on Raman active breathing-like phonon modes (BLM) and tangential-like phonon mode (TLM) of double-walled carbon nanotubes (DWCNT) in the framework of the bond polarization theory, and use the spectral moment’s method. The Raman active modes are calculated for different diameter and chirality of the inner and outer DWCNT tubes. The dependence of the Raman spectrum of bundles of identical DWCNTs as a function of the size of the bundle is analysed and additional breathing-like modes are predicted in DWCNT bundle of finite size

Modelling and simulation of vibrationnal properties of carbon nanotubes and derivatives

The aim of the present paper is to identify the main Raman vibrational features of carbon nanotubes and derivatives. In this goal, Raman active mode calculations have been performed on different single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as well as peapods. The comparison between the calculations performed on these different systems allows us to identify the Raman-active modes of each carbon nanomaterials. In SWCNTs, the tangential modes are located around 1590 cm-1 and the radial breathing mode follows A/D law. This latter law is modified in bundle of SWCNTs, DWCNTs or peapods.The aim of the present paper is to identify the main Raman vibrational features of carbon nanotubes and derivatives. In this goal, Raman active mode calculations have been performed on different single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as well as peapods. The comparison between the calculations performed on these different systems allows us to identify the Raman-active modes of each carbon nanomaterials. In SWCNTs, the tangential modes are located around 1590 cm-1 and the radial breathing mode follows A/D law. This latter law is modified in bundle of SWCNTs, DWCNTs or peapods

Nonresonant Raman spectrum of C60 nanopeapod: C60 polymerization effects

We present a force constants model for the vibrational modes in C60 dimer and polymer phases. The results of this model are used to calculate the nonresonant Raman spectra of infinitely long isolated C60 dimer and polymer peapod in the framework of bond-polarization theory by using the spectral moment’s method. The changes of the Raman spectrum in terms of the structure of the C60 molecules inside the nanotubes are identified. We show that the lowest Raman frequency region of the nanotube is more affected by the C60 chain insertion in comparison with the higher one.We present a force constants model for the vibrational modes in C60 dimer and polymer phases. The results of this model are used to calculate the nonresonant Raman spectra of infinitely long isolated C60 dimer and polymer peapod in the framework of bond-polarization theory by using the spectral moment’s method. The changes of the Raman spectrum in terms of the structure of the C60 molecules inside the nanotubes are identified. We show that the lowest Raman frequency region of the nanotube is more affected by the C60 chain insertion in comparison with the higher one