Thin polypyrrole films formed on mica and alumina with and without surfactant present: characterization by scanning probe and optical microscopy

Chemical deposition of electrically conducting polypyrrole (PPy) thin films on mica and alumina was carried out in aqueous solutions with and without surfactant. Examination of film morphology and thickness by atomic force microscopy (AFM) indicated a strong dependence of structure on the method of preparation. Films grown in the absence of surfactant were thicker than 150 nm with wrinkles present, indicating the overcoming of film–substrate adhesion by internal film cohesion. Oxidative polymerization with surfactant allowed reproducible synthesis of very thin films (50 nm thickness) with improved adhesion and suppressed formation of wrinkles. Experimental results are discussed within the context of a Stranski–Krastanov model of film growth. Film thickness and surface fractal dimensions were derived from AFM. Fractal analysis of PPy films on alumina helped discern their presence on the microscopically rough substrate and quantitatively expressed the changes in sample color by surface roughness.