Current-Voltage and Differential Conductivity-Voltage Measurements in Au/PI/1-Layer Organic Film/Pb Junctions

Using polyimide (PI) Langmuir-Blodgett (LB) films as a tunneling barrier, current-voltage (I-V) and differential conductivity-voltage (d2I/dV2-V) characteristics of the junctions incorporating 1-layer organic films were investigated. The I-V characteristics exhibited a typical I-V characteristic of ideal tunnel junctions with a noble metal/tunnel barrier/superconductor structure even when the number of deposited PI LB films was less than 10. Several peaks originating in the vibrational modes of the constituent molecules of the 1-layer films were clearly observed in the d2V/dI2-V curves. The I-V and d2V/dI2-V characteristics of the junctions incorporating a heterostructured film were also examined.