Characterisation of the topography and surface potential of electrodeposited conducting polymer films using atomic force and electric force microscopies

Atomic force and electric force microscopies (AFM/EFM) have been used to characterise simultaneously the surface morphology and the surface potential (work function) of conducting polymer films. The technique is most valuable in allowing the local variations of surface potential to he mapped in the nanometer scale. Studies of electrochemically prepared polypyrrole films have shown that the work function in the grains is higher than it is in the surrounding areas suggesting a higher dopant concentration in the grains. The effect of polymer film thickness and polymerisation method on the surface potential was investigated. Electrochemical treatment of the polymer films did not change the topography but always changed the surface potential, although the magnitude and direction of the change depended on the polymer and experimental conditions. The surface potential distribution across the sample surface was similar for all cases investigated with the exception of polypyrrole/dodecylsulphate which exhibited changes in surface potential distribution when treated in a solution of its own dopant. In general, the magnitude of the surface potential changes appear to be due to a complex interplay of effects arising from the chemical nature of the dopant ion and the polymer. (C) 2000 Elsevier Science Ltd. All rights reserved.