Ion Irradiation of Solid Carbons - Polyynes: Synthesis, Properties, and Applications - page 266

FIGURE 13.1 (left panel) Transmission electron microscopy (TEM) of a cluster of
assembled carbon thin films deposited by low energy cluster beam deposition
(LECBD). The image shows the porous structure consisting of closed graphite
particles and graphene foils embedded in a not well resolved amorphous matrix;
(right panel) Typical mass distribution of the cluster beam— it is representative of
a large variety of sizes and bonding.
Raman spectra have been obtained with a Jobin Yvon single monochro-
mator equipped with a notch filter and a CCD detector cooled at liquid
nitrogen temperature. Raman scattering has been excited through a He-Ne
laser (632.8 nm) at low power (6mW) to avoid heating effects. Spectra have
been taken both in situ, that is during and after the deposition in an ultra
high vacuum (UHV) chamber, and ex situ after the exposition of the
deposited film to atmosphere.
Figure 13.2 shows some Raman spectra taken under different experi-
mental conditions. According to several pieces of literature data, it is possi-
ble to assign the Raman features observed in all of the reported spectra
to different bonding configurations. Features located between 1000 and
2000 cm 1 are due to the presence of sp 2 components in the film. In many
cases, this is the most relevant part of the spectrum and a huge amount of
literature has been published to account for the correlation between these
features and the atomic and electronic structure of the investigated samples
(see e.g. Ferrari and Robertson [ 12 ] ). In that spectral region two structures
appear around 1330-1380 cm 1 (D line) and 1550-1500 cm 1 (G line). The
position, width and intensity of the two lines are strongly dependent on the
structure of the obtained carbon particles. However, it was clearly pointed
out by a series of experiments (e.g. Ferrari and Robertson [13]) that the