Shape-Dependent Conduction Regime in Self-Doped Polyaniline

Conductive polymers are key building blocks for the construction of molecular devices, and it is crucial to elucidate the conduction properties in microscale-shaped nanometer-thickness thin films in which the number of conduction paths is limited. In this study, we describe the effect of chemical doping and spatial limitation on the electrical conduction properties of sulfonated polyaniline (SPAN) strips with nanometer thickness fabricated by fountain-pen lithography and consider their electrical conduction mechanism. Raman spectroscopy indicated that the polarons in the SPAN strips decreased with increasing pH of the SPAN solution. According to the electrical measurements, the current–voltage (I–V) characteristics switched from linear to nonlinear by reducing the polarons and the conducting paths in thin strips. The results suggest that the nonlinear properties arise from the reduction of effective hopping barriers between a small number of conductive regions applied with localized electric field in the bottleneck region.