Time-domain control of conductive LB films based on alkylammonium-metal(dmit)2

The conductive Langmuir–Blodgett (LB) films based on dioctadecyldimethylammonium-Au(dmit)2 salt were studied. ‘Waiting time (Tw)’, which is defined as the time between the application of the salts on the water surface and the onset of the compression, was introduced as a film-forming parameter. The film quality at the air/water interface was greatly improved by changing Tw. Furthermore, the atomic force microscope (AFM) images of the LB film indicated that the film forms quasi-three-dimensional (Q-3D) structure in case Tw=5 min but the structure tends to be two-dimensional (2D) with increasing Tw. The resultant conductivity of the LB film also depends on the Tw and the highest conductivity was obtained in case Tw=90 min. The IR absorption spectra suggest that the driving force of the morphological improvement is the oxidation of the Au(dmit)2 moiety proceeding at the air/water interface before the onset of compression.