Carbon Material with a Highly Ordered Linear-Chain Structure - Polyynes: Synthesis, Properties, and Applications - page 224

FIGURE 11.10 EELS spectrum taken from sp 1 oriented carbon films (a), real and
imaginary part of dielectric function (b).

band. The very narrow peak at 1.6 eV corresponds to exciton. The
p -plasmon excitation occurs at

" 1 (E) ¼

the energy where 0, i.e.at

E p ¼ 3.7 eV and is smaller than in graphite (E p ¼

6 eV). It should be noted
that similar features in the EELS spectra are observed in polyacetylene
[15], which also comprises sp 1 -hybridized triple -C C- bonds in the carbon

skeleton. In spite of that, the p -plasmon energy of polyacetylene is higher
than that obtained in the present study (4.9 eV).
As was shown for polydiacetylene [15] the presence of the exciton peak
at the energy of 1.6 eV provides evidence for the high degree of ordering of
carbon chains in the film. Therefore we can conclude that the sp 1 -hybridized
carbon films also consist of a very highly ordered material.

11.4.3 R AMAN S PECTROSCOPY

The Raman spectrum of an sp 1 -hybridized carbon-chain film with thickness

of 50 nm shown in Figure 11.11(a) consists of two broad maximums at