Abstract
We have studied the correlation between the conductance and Fourier transform-infrared (FT-IR) spectra of the Langmuir-Blodgett (LB) film based on ditetradecyldimethylamrnonium-Au(dmit)2 [2C14-Au(dmit)2] salt. The 2CI4-Au(dmit)2 salt was transferred onto a CaF2 substrate and was electrochemically oxidized using a constant current of 0.8 micro A in an aqueous solution of LiClO4. The conductance and the FT-IR spectra were measured using a slit between the electrodes by taking out the samples from the electrolyte and dried by nitrogen gas every thirty minutes. We have already reported that the conductance gradually increases with time of the oxidation up to 150 min but it turns to decrease modestly later. Accompanied by the oxidation, a broad band appears in a wide range of 850-7000 cm-1 and the peak shifts from 2000 cm-1 down to 1630 cm·1 in the first 120 min and it turns to be constant later. The area change of the IR spectra, which is proportional to the oscillator strength, is in close agreement with the conductance behavior. These results strongly indicate that the broad absorption is of charge transfer (CT) band and the conducting properties can be controlled precisely by monitoring the CT band together with the CH2 symmetric, CH2 antisymmetric and C=S stretching bands located at around 2850 cm·1, 2920 cm-1 and 1055 cm-1, respectively.
