Atomic force microscopic study on the molecular arrangement of highly conductive LB films of metal(DMIT) 2

Abstract

The atomic force microscope (AFM) was used to obtain the images of the LB film of tridecylmethylammonium-Au(dmit) 2 complex mixed with icosanoic acid. A single-layered sample of the as-deposited LB film revealed a heterogeneous structure with very thin plate-like crystallites of the order of μm distributed in the film surface. The height of the crystalline was about 18 nm measured from the planar region in which a monolayer of icosanoic acid was assumed to be present. This thickness corresponded to a stacking of ca. 10 molecules of Au(dmit) 2 with each of the molecular plane almost parallel to the film surface, taking into account the molecular arrangement in a single crystal. No epitaxial deposition was observed for a multilayered sample, which was shown by the almost random stacking of the plate-like crystallites. The AFM image changed with the electrochemical oxidation that was necessary to make the film conductive. The blurring of the outline of the plate-like crystallites was observed, suggesting a structural change of the crystallites accompanied by the electrochemical oxidation.