SURFACE-MORPHOLOGY CHANGES IN POLYTHIOPHENE AND POLYTHIOPHENE DERIVATIVE FILMS AFTER BEING OXIDIZED WITH IODINE - A SCANNING PROBE MICROSCOPY STUDY

The nanometer-scale surface morphology of polythiophene (PT) and polyt hiophene derivative thin films was found to change substantially after exposure to I-2 vapor. Small PT bundles with an average dimension of 400 Angstrom were observed in films prior to oxidation (doping) by I-2 , using the technique of scanning probe microscopy. However, upon dopi ng by I-2, the bundles in the same film were replaced by much larger u nits with a range of different sizes. The oxidation process was instan taneous, and ail the derivative films behaved in a qualitatively ident ical fashion. The change in morphology is concluded to be due to aggre gation of the polymer chains, which is caused by charge species introd uced through oxidation by I-2.