Spatially localized electronic structure in polyaniline by scanning tunneling spectroscopy

Variations of local electronic structure of fully and partially protonated emeraldine hydrochloride films, as determined by tunneling spectroscopy in a scanning tunneling microscope, are compared. Two types of electronic structure predominate, a highly conductive metallic-like, and a less conductive semiconductor-like structure. These variations were observed on length scales of tens of nanometers. Additionally, some measurements provide evidence for the existence of regions with a locally stable bipolaron configuration. Implications of these first observations of spatial variations of electronic structure in an amorphous organic material to the conduction mechanisms proposed for polyaniline are discussed. © 1989.