Nucleation and growth mechanism of polycarbazole deposited by electrochemistry

Abstract

Polycarbazole (PCz) thin films have been deposited by electro-oxidation of carbazole in LiCIO, + anhydrous acetonitrile onto SnO2 coated glass substrates, by potentiostatic method and the nucleation and growth mechanism (NGM) were studied. The obtained current time transients (j-t) were fitted using a mathematical equation with three contributions: instantaneous nucleation with two-dimensional (IN2D) or three-dimensional (IN3D) growth, and also a progressive nucleation with three dimensional (PN3D) growth. At the beginning, the IN2D contribution is predominant but, quickly the IN3D processes become more important. At a deposition time t >= 17 s the IN3D corresponds to 80 % of the total current. The visualization by scanning electron microscopy of the surface morphology of the PCz films is in agreement with the NGM proposed by the mathematical method. The film covers very rapidly the SnO2 under layer related to the 2D process, even if some heterogeneities randomly distributed in the films, issued from the 3D processes, are also visible. After two minutes of deposition, the roughness of the whole surface of the films corroborates the 3D processes domination. Therefore, the information directly obtained from the (j-t) transients is a suitable and very useful tool to predict the working conditions in order to control the type of morphology of the film prepared by electropolymerization.