Nanoelectronic Properties of a Model System and of a Conjugated Polymer: A Study by Kelvin Probe Force Microscopy and Scanning Conductive Torsion Mode Microscopy

The sub-100 nm morphology of those conjugated polymers that already found their way into electronic industry applications is known to heavily influence the electromechanical properties and the performance of those materials. Properties we are talking about are charge injection, transport, recombination, trapping, and the phase behavior and mechanical robustness of the polymer blend. Of paramount importance is also the analysis of the stability of these properties over time. Electrical atomic force microscopy is an ideal tool to measure simultaneously electronic properties, surface morphology, and mechanical properties of thin films of conjugated polymers. Here we present a combined topography, Kelvin probe force microscopy (KPFM), and the recently presented scanning conductive torsion mode microscopy (SCTMM) study on a gold/polystyrene model system. Conductive gold nanoparticles are embedded into a nonconductive thin polystyrene film. This system is a mimic for conjugated polymer compounds where conductive domains are embedded in a nonconductive matrix, like for PEDOT:PSS or PPy:PSS. We control the nanoscale morphology of the model by varying the distribution of gold nanoparticles inside the polystyrene film. We study the influence of the morphology on the surface potential by KPFM and on the conductivity by SCTMM. By the knowledge we gain from the model we are able to predict the structure of a homemade PPy:PSS compound.