Electrical properties of polyimide Langmuir-Blodgett films sandwiched between metal and superconducting electrodes

The electrical properties of thermally stable multilayer Langmuir-Blodgett (LB) films of polyimide (PI) were examined for cases of Al/PI/Al, Au/PI/Au and Au/PI/(Pb-Bi) junctions. The monolayer thickness of the multilayer PI LB films was about 0.4 nm, and Pb-Bi is a superconducting electrode. The authors also fabricated Nb/Au/PI/(Pb-Bi) Josephson junctions, and examined the electrical properties of the junctions at a temperature of 4.2 K. For Nb/Au/PI/(Pb-Bi) junctions, the typical I-V characteristic for a weakly coupled superconductor was seen. For Au/PI/Au junctions, it was concluded that PI LB layers become good electrically insulating barriers when the number of deposited layers is greater than about 30. For Al/PI/Al junctions, it is shown that an aluminum native oxide layer formed on the base Al electrode makes a significant contribution to the electrical conduction through the PI layer.<
>