Anomalous conduction currents and TSCs in LB films adsorbing dyes

The conduction currents and TSCs are investigated for the phosphatidic acid (PA) LB films and the azobenzen (Az) LB films, adsorbing the cyanine dyes (NK-3), with the sandwich electrodes. The LB films adsorbing the dyes are fabricated using the diffusion-adsorption method, that is, the Langmuir films of PA or Az at the air-water interface adsorb the water-soluble NK-3 dyes and the LB films containing the dyes are deposited on substrates. The conduction currents and the TSCs increase with the amount of the dyes adsorbed in the LB films. Anomalous large conduction currents and TSCs are observed for the Az LB devices containing the dyes. The conduction currents at room temperature follow the Poole conduction above about 3×10⁷ V/m for the PA LB and Az LB devices. A remarkable increase of the conduction currents is also observed for the devices having the Au upper electrode. Therefore, it is estimated that the conduction is caused by the composite mechanisms in the LB films and at the interface. TSCs of the PA LB devices are caused by the distributed dipolar polarizations. Furthermore, it is tentatively considered that the anomalous large TSCs for the Az LB devices are caused by the charge displacement with long distances. The properties are of great interest for developing ultrathin LB devices