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 polythiophene derivative thin films was found to change substantially after exposure to I2 vapor. Small PT bundles with an average dimension of 400 إ were observed in films prior to oxidation (doping) by I2, using the technique of scanning probe microscopy. However, upon doping by I2, the bundles in the same film were replaced by much larger units with a range of different sizes. The oxidation process was instantaneous, and all the derivative films behaved in a qualitatively identical fashion. The change in morphology is concluded to be due to aggregation of the polymer chains, which is caused by charge species introduced through oxidation by I2.