ELECTROCHEMICAL CONTROL OF THE FILM FORMA TION OF POLY(3-ALKYLTHIOPHENE)S AND DEVELOPMENT OF THE MEASUREMENT METHOD OF THE FILM THICKNESS

The thickness control and thickness measurement with a surface roughne ssmeter were discussed for poly(3-methylthiophene) (P3MT) and poly(3-h exylthiophene) (P3HT) prepared by electrochemical polymerizations. Aft er the polymerization, aluminum was deposited uniformly on the film. T he metal-coated surface was then traced with a surface roughnessmeter, and the film thickness was determined from the level difference. The relationships between the thickness and the amount of passed charges w ere linear below 3 C/cm(2) of passed charges for P3MT and below 1 C/cm (2) of passed charges for P3HT. The film margin was found to be thicke r. This was corresponded to the SEM observation that the polymer on th e electrode edge grew three-dimensionally, while the other part two-di mensionally. The difference in thickness depending on the places was e xplained in terms of the strength of the electric field; at a high ele ctric field, three-dimensional growth of P3MT was promoted. The conduc tivity of P3MT increased significantly with the decreased thickness in the 0.62 similar to 2.9 mu m range.