Resonant Tunneling Peaks Appeared in the Current: Voltage Characteristics for Polymeric Thin Films

Current-voltage characteristics measured with conductive-atomic force microscopy for polymeric ultrathin films are examined. The polymeric films were prepared with uv-irradiation onto Langmuir-Blodgett films deposited two layers on glass or silicon substrates. The conjugated backbone chains with alkyl side-chains are regularly arranged on the substrate surface. Anomalous current peaks were observed for many samples; and appearance depends on the film structure and interfacial properties between molecules and electrodes. In addition, the steep increase in current occurred at higher applied voltages; values of the threshold electric field were estimated from Fowler-Nordheim plot. Furthermore the resistance between the electrodes decreased with increase in the effective film thickness.