SCANNING-TUNNELING-MICROSCOPY AND SPECTROSCOPY OF POLYANILINE - EVIDENCE FOR CHAIN-FOLDED LAMELLAE WITH ANOMALOUS DEFORMABILITY

Scanning tunneling microscopy reveals a distinct lamellar morphology o n the surfaces of emeraldine base (EB-II) and its protonated salt (ES- II) films. From this, we derived a chain-folded lamella structural mod el that may help reconcile the ''3D granular metal'' with the ''quasi- 1D metallic chain'' conduction models developed for this class of cond ucting polymers. Current-voltage tunneling spectroscopy (TS) experimen ts show a finite density of states at the Fermi energy for all the sam ples, indicating the importance of tunneling to disordered surface sta tes. Current-tip-displacement TS experiments reveal an anomalous slow current decay for samples protonated beyond the insulator-metal percol ation transition. We related this to significant tip intrusion into th e film surface owing to high elasticity in the c axis of the protonate d lattice. We also briefly highlighted the importance of tunneling res istance set point, and the roles of surface mobility and deformability , in relation to tunneling to and from these organic polymer surfaces. [S0163-1829(97)00847-3].