Abstract:
The Raman spectra of polyacetylene films doped with electron acceptors (I/sub 2/, BF/sub 3/, SO/sub 3/, etc.) at several doping levels have been measured at room temperat...Show MoreMetadata
Abstract:
The Raman spectra of polyacetylene films doped with electron acceptors (I/sub 2/, BF/sub 3/, SO/sub 3/, etc.) at several doping levels have been measured at room temperature with excitation wavelengths between 457.9 and 1064 nm on a polychromator equipped with a multichannel detector or a Fourier transform spectrophotometer. The observed Raman spectra have been compared with those of the polyacetylene film doped heavily with electron donor (Na). The observed Raman bands of heavily doped samples are attributed to positively charged domains created by acceptor-doping. On the other hand, at low or medium dopant contents, the observed bands are ascribed to the neutral parts remaining the doped films. Since the cross sections of the Raman bands arising from the charged domains are much smaller than those arising, from the neutral polyene parts, the Raman bands of charged domains are observed only at heavy doping levels. The Raman bands of the charged domains are classified into four regions: v/sub 1/, 1560-1470 cm/sup -1/; v/sub 2/, 1300 cm/sup -1/; v/sub 3/, 1180-1100 cm /sup -1/; v4, 990 cm/sup -1/. The v/sub 1/ bands are assigned to the C=C stretching vibrations. The high wavenumbers of the v/sub 1/ bands suggest that bond alternation persists in the charged domains. Significant differences are observed between acceptor-doping and donor-doping. For example, in the 1064-nm excited Fourier-transform Raman spectrum of a heavily iodine-doped polyacetylene film, the wavenumber of the v/sub 1/ band, 1490 cm/sub -1/ , is about 20 cm/sub -1/ lower than that of the Na-doped polyacetylene, the v/sub 2/ wavenumber, 1295 cm/sub -1/, is about 40 cm/sub -1/ higher than that of the Na-doped one, the peak at about 1130 cm/sub -1/ and the shoulder at about 1175 cm/sub -1/ are observed though two peaks are observed at 1165 and 1113 cm/sub -1/ for Na-doping. These observations indicate that geometrical chan-es induced by acceptor-doping are different from those induced by donor-doping.
Date of Conference: 24-29 July 1994
Date Added to IEEE Xplore: 06 August 2002