Ultraviolet photon absorption in single- and double-wall carbon nanotubes and peapods: Heating-induced phonon line broadening, wall coupling, and transformation

Abstract

Research and Development, Hoge Wei 33 B, B-1930 Zaventem, Belgium Ultraviolet photon absorption has been used to heat single-and double-wall carbon nanotubes and peapods in vacuum. By increasing the laser intensity up to 500 mW, a downshift and a broadening of the optical phonons are observed corresponding to a temperature of 1000°C. The UV Raman measurements are free of blackbody radiation. We find that the linewidth changes for the G + and G − bands differ considerably in single-wall carbon nanotubes. This gives evidence that the phonon decay process is different in axial and radial tube directions. We observe the same intrinsic linewidths of graphite ͑highly oriented pyrolytic graphite͒ for the G band in single-and double-wall carbon nanotubes. With increasing temperature, the interaction between the walls is modified for double-wall carbon nanotubes. Ultraviolet photon induced transformations of peapods are found to be different on silica and diamond substrates.

RamanGband in double-wall carbon nanotubes combiningpdoping and high pressure

“…In this section, we use the parameters deduced here and from previous studies 27 on CCVD grown DWs to fit G-band spectra as a function of temperature. TABLE I. Spectral G-band positions of inner and outer tubes of DWs, corresponding pressure coefficients, relative intensities, and spectral positions of the shoulder for four different pressure transmitting media ͑excitation wavelength, 633 nm͒ ͑i: inner tube; o, outer tube; EI, electronic interwall͒.…”

Studies of Fe‐binding sites within multiwall carbon nanotubes using Mössbauer spectroscopy

“…Numerous studies performed on carbon nanotubes (CNTs) have focused on their unusual electrical, mechanical and optical properties 1–5, which can be modified due to the occurrence of defects. Deformations, such as bends and nanotube junctions or defects caused by impurities that appear during or after the nanotube growth may seriously influence properties of CNTs 6–10.…”

Thermal transfer in SWNTs and peapods under UV‐irradiation

“…The structural modification is however slight since the spectral features typical of SWNTs remain unchanged. Interestingly, the band broadening phenomena may also provide a temperature measurement [4,5], however with a different behaviour and reliability for the G+ band with respect to the G-band whose reasons are still a matter of debate [5].…”

“…Both shifting and broadening phenomena reveal a temperature increase due to the enhancement of anharmonic effects, which include all the related physical events such as the effect of thermal expansion, and goes with the decay of one optical phonon into two acoustic phonons with half the initial energy (and opposed linear momentum) [5]. The related temperature increase can be calculated from G+ or Gband shift (dw), using the expression dw = -0.022 K/cm -1…”