Development of Highly Conductive Langmuir-Blodgett Films: From Metallic toward Superconducting Properties

Studies on highly conductive LB films based on ditetradecyldimethylammonium-Au(dmit)2 [2C14-Au(dmit)2] salt have been reviewed. The room temperature conductivity of the 2C14-Au(dmit)2 LB film is as high as 40 S/cm after electro-oxidation. The resistance vs. temperature plot depends on the gap distance for the measurement. A weak metallic behavior is seen from room temperature down to 210-250 K, when the gap distance is 500 μm, while it extends down to 56-106 K, when the gap distance is 5 μm, indicating that the disorders in the film are important limiting factors for the macroscopic resistance. The data of the complex magnetic susceptibility (χ’ + iχ”) suggest the existence of the Meissner state below 3.9 K. Although some samples show resistance drop on cooling below 4 K, the typical resistance behaviors are of activation type at the lower temperature. We consider that disorders such as grain boundaries and/or defects are important limiting factors that should be solved to improve the electrical conduction toward the realization of global superconductivity.