Areal inhomogeneities in vapor doped polyaniline films

The conductivity of an initially insulating emeraldine base film can be controlled by adjusting its time of exposure to the vapor of a dopant solution. Before saturation doping is achieved, however, large nonuniformities in resistivity are measured in a spatial pattern related to the geometry of the sample and its support fixtures. Comparison of the spatial measurements to a gas-phase mass-transport analysis finds that the nonuniformity is attributable to a spatially varying flux of dopant incident on the sample from the vapor. The nonuniform flux is caused by diffusion-limited gas-transport of dopant vapor in response to uptake by the sample.