Electrical properties of Langmuir-Blodgett films of a Ni(dmit)2 charge-transfer complex

Abstract Multilayer structures of a (N-octadecylpyridinium)2-Ni(dmit)2 charge-transfer complex (H2dmit = 4,5-dimercapto-1,3-dithiole-2-thione) have been deposited onto glass substrates by the Langmuir-Blodgett technique. Electrical measurements have been made over the temperature range 100–300 K in the as-deposited state and after chemical doping with iodine. Room temperature in-plane conductivities were 6 × 10−6 S cm−1 and 0.2−0.8 S cm−1 for films as-deposited and after iodine doping, respectively. As-doposited, a linear current versus voltage characteristic was observed and a plot of log (current) versus reciprocal temperature was found to consist of more than one straight line section. Activation energies of 0.59 eV, 0.32 eV and 0.14 eV were measured over different parts of the temperature range studied. After doping with iodine, a current versus voltage plot with a “super-Ohmic” section was noted. In this case, two different activation energies were found; 0.17 ± 0.2 eV at low bias and 0.09 eV for higher applied voltages. A study of the stability of conductivity with time has also been undertaken; films were found to be stable for a period of at least 1 month.