The purpose of the present work is to obtain thin films of molecular superconductors, represented by k-(BEDT-TTF)_2Cu(NCS)_2 salt, by an electrochemical method. For fundamental knowledge, in addition, mechanisms of electrodepositionof some ion radial salts are tried to clarify.
Electrodeposition of (BEDT-TTF)_2Cu(NCS)_2 salt has been attempted. Althrough a film containing k-type crystals can be easily obtained, it was too difficult to obtain a good film in which k-type crystals were densely packed and highly oriented. Morphology of the films strongly dependson both the current density and the special arrangement of the electrodes.
In order to clarify the nucleation and growth processes in electrodeposition of (BEDT-TTF)_2Cu(NCS)_2 films, in situ microscopic images were observed and recorded with a video recording system. FOr optical observation, a homogeneous solution (BEDT-TTF/CuSCN/KSCN/18-crown-6/1, 1, 2-trichloroethane) was used instead of heterogeneous suspension, which had been used for the lelectrodeposition. When a high potential, 3.0 V vs. Ag, was applied for short period, followed by applying 2.0 V, the nucleation density was enhanged : innumerable small, invisible nuclei were generated. But some of the nuclie began and continued to grow, taking other surrounding nuclei. This is an example of "Ostwald ripening".
In order to accumulate knowledge of electrodeposition and properties of ion radical salts to establish "science of electrocrystallization of molecular compounds", the following compounds were investigated : (1) the physical properties of ion radical salts of aromatic diamines, (2) a new, electrochemical method to prepare quinhydrone crystal.