X-Ray Photoelectron Spectroscopic Study of Highly Conductive Bromine-doped Polyacetylene

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Abstract
The bromine-doped polyacetylenes were studied by X-ray photoelectron spectroscopy. The IR, Raman, and mass spectra were also measured. We find that below the doping content at which the electrical conductivity shows the maximum, bromine content is higher in the surface region than in the bulk. The C ls peak of X-ray photoelectron spectrum is composed of at least two components with the splitting of about 1.7 eV. The relative intensities of two components change with bromine content. The higher-binding-energy component of C ls peak is attributed to positively charged carbon atoms in the metallic domains where dopant is highly concentrated, and the lower-binding-energy component to carbon atoms in the undoped low-conductive domains. The amount of charge transfer in the metallic domain is estimated to be about 0.3|e| per carbon atom. A possible reaction mechanism of bromine with polyacetylene is discussed.