Carbon Material with a Highly Ordered Linear-Chain Structure - Polyynes: Synthesis, Properties, and Applications - page 215

FIGURE 11.2 TEM image of oriented carbon film with a single crystal on it
( 10,000) and its electron diffraction pattern (a), Raman spectrum of the same
film (b).

substrate temperature of 180 C [11]. The electron diffraction patterns from
the film, shown in Figure 11.2(a) indicate that the carbon film consists of
two phases. The first phase gives a diffraction pattern with six reflections

similar to that shown in Figure 11.1(a) and corresponding to the inter-

plane spacing of 0.439 nm. This structure is believed to correspond to close-
packed carbon chains with cylindrical symmetry. The second phase shown
in Figure 11.2(a) consists of well-faceted hexagonal crystals corresponding
to a hexagonal lattice with the same interplanar spacing of 0.439 nm. The
Raman spectrum of the film is shown in Figure 11.2(b). As can be seen, a
wide band with a maximum at 1580 cm 1 and very strong peak at 2070 cm 1
are presented in the Raman spectrum. The later peak is related to the
presence of vibrations of cumulene carbon chains

. So there
is clear evidence for the formation of polymer carbon chains characterized
by sp 1

¼ C ¼ C ¼ C ¼ C ¼

hybridization of electron orbitals and possessing a specific electron
diffraction described earlier (Figure 11.1).

The electron band structure of the Tetracarbon TM films was found to be
quite different from that of diamond, graphite and all other known forms of
carbon and was consistent with linear chains as a basic element of the
atomic structure; this was clearly shown by electron spectroscopy meas-
urements with electron excitations [1,2]. In the present work this fact was