A Kelvin probe force microscopic study of the local dopant distribution in conducting polybithiophene

Local dopant distribution in electrochemically deposited polybithiophene films as well as the effect of the electrochemical treatment were studied ex situ using the technique of Kelvin probe force microscopy (KFM). The doping-level distribution was found to be directly related to the polymer surface morphology. For the as-grown polymer, most of the doping anodic charge was found to be located at the grain tops. The polymer that was further electrochemically doped featured relatively higher doped grain periphery and less doped grain tops. On the contrary, undoping of the polymer resulted in no pronounced change in the dopant distribution pattern. The effect of the pretreatment of the HOPG support on the properties of the polymer films is also discussed. A model is proposed that relates the observed inhomogeneity to the lateral distribution of the primary polymer nuclei formed during the initial steps of the polymer deposition process. The results suggest that the KFM is a powerful tool for studying dopant distribution in conducting polymers.