Contradictory ageing behaviour and optical property of iodine doped and H2SO4 doped pulsed DC plasma polymerized aniline thin films

Polymerization of aniline in the presence of H2SO4 and iodine vapour is carried out using pulsed DC glow discharge plasma. The as prepared iodine doped plasma polymerized aniline films are found to be highly crystalline due to some crystal structure formed by the iodine incorporated into the film and the ex-situ H2SO4 doped films are found to be amorphous. However, the structure of the iodine doped films transforms to amorphous one while that of the ex-situ H2SO4 doped films transforms to crystalline one due to the effect of ageing. The optical band gap of the samples decreases depending upon the level of doping and annealing, having minimum optical band gap for iodine doped plasma polymerized aniline. Due to ageing, the optical property of the H2SO4 doped film is found to become superior while for iodine doped films a negligible change of the optical property has been noticed even after six months of ageing. (c) 2013 Elsevier Masson SAS. All rights reserved.