2007 年 32 巻 2 号 p. 337-340
The ditetradecyldimethylammoniuim-Au(dmit)2 (2C14-Au(dmit)2) salt can be transferred onto solid substrates reproducibly up to 160 layers. The conductance of the 2C14-Au(dmit)2 film of single layer does not increase by the electrochemical oxidation and is less than 10-7 S. As for the samples with thickness more than two layers, the conductance increases with increasing the time of the electrochemical oxidation (Tox) reaching the maximum conductance, Gmax, and, then, decreases gradually. The Gmax increases from 10-6 S up to 10-3 S with increasing the thickness in the range of 2-4 layers obeying Gmax proportional to N7.9. We postulate that the macroscopic conduction paths are formed by the accumulation of the molecular layer in the thickness range of 2-4 layers. In the thickness range of 4-40 layers, the Gmax is approximately proportional to N (the least-square fitting gives Gmax proportional to N1.3), indicating that the molecular layers can be oxidized uniformly to give a uniform conductivity. In the range of 40-160 layers, however, Gmax is almost constant with the average value of 2.04 x 10-2 S, indicating that the surface layers cannot be oxidized effectively and do not contribute to the macroscopic conduction significantly if the total number of layers is more than ca. 40.
