ATOMIC-FORCE MICROSCOPY AND KELVIN PROBE FORCE MICROSCOPY EVIDENCE OFLOCAL STRUCTURAL INHOMOGENEITY AND NONUNIFORM DOPANT DISTRIBUTION IN CONDUCTING POLYBITHIOPHENE

Direct evidence of local structural inhomogeneity and nonuniform dopin g-level distribution in conducting polymer film has been obtained usin g Kelvin probe force microscopy (KFM) and atomic force microscopy (AFM ). The KFM data suggests that the polymer consists of grains that cons tantly differ in work function and thus in the dopant concentration fr om the grain peripheral regions. For the as-grown polymer, most of the doping charge is located at the grain tops, whereas the electrochemic ally doped polymer features relatively higher doped grain periphery an d less doped grain tons. The AFM study reveals two different kinds of the polymer molecular structure dependent on whether the image was tak en at the top of a grain or the grain periphery. This result confirms the inherent inhomogeneity of conducting polymers demonstrated with KF M.